Differential effects of leptin administration on the abundance of UCP2 and glucocorticoid action during neonatal development

M. G. Gnanalingham,1 A. Mostyn,1 R. Webb,1 D. H. Keisler,2 N. Raver,3 M. C. Alves-Guerra,4 C. Pecqueur,4 B. Miroux,4 M. E. Symonds,1 and T. Stephenson1

1Centre for Reproduction and Early Life, Institute of Clinical Research, University of Nottingham, Nottingham, United Kingdom; 2Department of Animal Sciences, University of Missouri, Columbia, Missouri; 3Institute of Biochemistry, Food Science and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot, Israel; and 4Faculté de Médecine Necker-Enfants-Malades, Paris, France

Submitted 13 May 2005 ; accepted in final form 1 August 2005


    ABSTRACT
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 ABSTRACT
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
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In the neonate, adipose tissue and the lung both undergo a rapid transition after birth, which results in dramatic changes in uncoupling protein abundance and glucocorticoid action. Leptin potentially mediates some of these adaptations and is known to promote the loss of uncoupling protein (UCP)1, but its effects on other mitochondrial proteins or glucocorticoid action are not known. We therefore determined the effects of acute and chronic administration of ovine recombinant leptin on brown adipose tissue (BAT) and/or lung in neonatal sheep. For the acute study, eight pairs of 1-day-old lambs received, sequentially, 10, 100, and 100 µg of leptin or vehicle before tissue sampling 4 h from the start of the study, whereas in the chronic study, nine pairs of 1-day-old lambs received 100 µg of leptin or vehicle daily for 6 days before tissue sampling on day 7. Acute leptin decreased the abundance of UCP2, glucocorticoid receptor, and 11{beta}-hydroxysteroid dehydrogenase (11{beta}-HSD) type 1 mRNA and increased 11{beta}-HSD type 2 mRNA abundance in BAT, a pattern that was reversed with chronic leptin administration, which also diminished lung UCP2 protein abundance. In BAT, UCP2 mRNA abundance was positively correlated to plasma leptin and nonesterified fatty acids and negatively correlated to mean colonic temperature in the leptin group at 7 days. In conclusion, leptin administration to the neonatal lambs causes differential effects on UCP2 abundance in BAT and lung. These effects may be important in the development of these tissues, thereby optimizing lung function and fat growth.

lung; neonate; mitochondria; uncoupling protein-2


LEPTIN IS A 16-KDA POLYPEPTIDE HORMONE that is principally synthesized and secreted by adipose tissue and acts to regulate energy homeostasis and a range of neuroendocrine and reproductive functions in the adult (1, 23, 62). The role of leptin in the neonate has yet to be fully determined. Plasma leptin concentrations increase with gestational age in conjunction with an increase in fetal adipose tissue deposition, leptin mRNA abundance, and plasma cortisol (10, 76). In the newborn sheep, plasma leptin concentrations decline during the immediate 6 h after birth and then increase up to 7 days of age, whereas plasma cortisol continues to decrease (5). These temporal changes in leptin and cortisol coincide with maturation of the hypothalamic-pituitary-adrenal axis and the rapid activation of uncoupling protein (UCP)1, which is unique to brown adipose tissue (BAT) (13, 57) and is followed by the gradual loss of UCP1 (11). UCP1 has a defined role in nonshivering thermogenesis at birth by its avoidance of adenosine triphosphate (ATP) synthase and its allowance of proton reentry into the mitochondrial matrix, thus creating the proton electrochemical gradient to be dissipated as heat (25). In the neonatal sheep, both acute (1-day) and chronic (6-day) leptin administration result in reduced UCP1 mRNA and protein abundance, in conjunction with maintained colonic temperature and plasma nonesterified fatty acid (NEFA) concentration, therefore not affecting thermogenic potential (43). Similar assessments of leptin administration on physiological function and mitochondrial protein abundance in the lung have not previously been undertaken, even though fetal and adult lungs are leptin responsive (16, 33, 71), and the survival of the neonate is dependent on the extrauterine adaptation of the fetal lung and the establishment of independent ventilation.

The peak in UCP1 abundance at birth is accompanied by parallel increases in other mitochondrial proteins including voltage-dependent anion channel (VDAC), located on the outer mitochondrial membrane, and cytochrome c, present within the intermembrane space (46). VDAC is a component of the mitochondrial permeability pore, which regulates the supply of mitochondrial adenosine diphosphate and ATP and is proposed to have a role in apoptosis (15, 31). Cytochrome c is an essential component of the mitochondrial respiratory chain and is a mobile electron transporter involved in the electron transfer from complex III to complex IV (34, 40). In the lung, the peak in VDAC abundance at 7 days of postnatal age coincides with the maximal abundance of UCP2 protein, which, although undetectable in the fetal lung, follows the peak in UCP2 mRNA at 6 h of age before declining rapidly in postnatal life (29, 46). UCP2, a recently discovered member of the inner mitochondrial membrane carrier subfamily, is highly abundant in the lung (29, 53) and has postulated roles in energy regulation (7, 9), reactive oxygen species production (36, 50), and apoptosis in conjunction with VDAC and cytochrome c proteins (37, 73). UCP2 has also been genetically linked to obesity (22) and may have a limited role in thermogenesis (21). Adult rodent studies have shown that administration of leptin to ob/ob mice, which do not produce leptin and are thus hypothermic, hyperphagic, and obese, restores a normal body temperature despite a 50% reduction in food intake (54). These changes in body temperature have been linked to increased abundance of UCP1 (58) and UCP2 (30) in BAT by some, but not all, studies (42). Moreover, these changes appear to be unique to rodents, as leptin treatment of large mammals, such as sheep and pigs, has been found to have a more limited role in thermogenesis (38, 43). No study to date has previously investigated the effect of leptin administration on the development of neonatal BAT and lung with respect to the abundance of UCP2, VDAC, and cytochrome c proteins that change dramatically over this period (29).

The interaction and increase in plasma concentrations of catecholamines, thyroid hormones, prolactin, cortisol, and leptin are crucial in fetal and neonatal BAT development (67). However, the impact of acute and chronic leptin administration on local glucocorticoid action, as determined by the expression of glucocorticoid receptor (GR, type 2) and isoforms of 11{beta}-hydroxysteroid dehydrogenase (11{beta}-HSD), within neonatal BAT have not been previously examined. In the lung, for example, the peripartum peak in GR and 11{beta}-HSD1 mRNA peak at 140 days gestation (term ~147 days), in conjunction with UCP2, has emphasized the developmental link between UCP2 and cortisol and may aid in the extrauterine adaptation of the fetal lung and in the establishment of independent breathing (29). 11{beta}-HSD1 behaves predominantly as an 11-oxoreductase, catalyzing the conversion of inactive cortisone to active cortisol, thereby amplifying activation of intracellular GR, whereas 11{beta}-HSD2 behaves as an 11-dehydrogenase, catalyzing the inactivation of cortisol to inert cortisone (4, 63). In the developing lung and BAT of the fetus, UCP2, GR, 11{beta}-HSD1, and 11{beta}-HSD2 mRNA are significantly correlated with fetal plasma cortisol and norepinephrine (28). Leptin is a potent stimulator of the sympathetic nervous system (32, 59) and inhibitor of adrenocorticotropic hormone-stimulated glucocorticoid secretion by the adrenal gland (55). A further aim of our study was to examine the effect of leptin administration on local glucocorticoid action within neonatal BAT over the neonatal period, in which there are rapid changes in both UCP1 and cortisol (5, 11).

The aims of this study were thus to determine 1) the effect of acute and chronic leptin administration on the abundance of UCP2, GR, 11{beta}-HSD1, and 11{beta}-HSD2 mRNA in neonatal sheep BAT at 1 and 7 days postnatal age; 2) the effect of chronic leptin administration on the abundance of UCP2, VDAC, and cytochrome c proteins in the neonatal lung as measured at 7 days postnatal age, when maximal mitochondrial protein abundance normally occurs (46); and 3) significant associations between plasma leptin and NEFA concentrations with physiological and molecular variables measured during the study period.


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Animals

Seventeen pairs of triplet lambs, born normally at term to Bluefaced Leicester x Swaledale ewes, were entered into the study. The first eight pairs of lambs were used to determine the effect of acute administration of ovine recombinant leptin (26) on thermoregulation and to establish the required dose of leptin necessary to obtain a 10-fold rise in plasma concentration of leptin. During the course of this study, it was observed that plasma leptin was higher in female than in male lambs (43), thus only female lambs were used in a subsequent study in which the effects of chronic treatments of leptin were examined in nine pairs of lambs. For each ewe, one untreated triplet remained with its mother throughout the study. Full details of materials and methods have been previously published (43). All operative procedures and experimental protocols had the required Home Office approval as designated by the Animals (Scientific Procedures) Act of 1986.

Acute Study

Each lamb remained with its mother until 16 ± 2.5 h after birth, during which time all lambs obtained adequate amounts of colostrum. Pairs of lambs were selected on the basis of matched body weight (±10%) and were then placed in a constant temperature room of 15 (±1)°C, which represents a cool challenge to neonatal lambs (65). A jugular vein catheter was inserted into each animal under local anesthetic (2% xylocaine) to enable vehicle or leptin to be given and blood samples to be taken. In the acute study, one lamb from each pair was randomly assigned (irrespective of sex) to receive recombinant ovine leptin (26). After a 1-h acclimatization period in the calorimeter box, lambs were initially injected intravenously with vehicle (1 ml of sterile water), and 5-ml blood samples were taken ~40–60 min after each injection while the lambs were sleeping. Subsequently, six males and two females were treated with leptin to be compared with four males and four females treated with vehicle alone. One lamb was then injected with 10 µg of leptin in 1 ml of sterile water, and its sibling received water alone. Water rather than saline was used for intravenous injection, since leptin does not dissolve with saline. This procedure was then repeated twice, with the modification that treated lambs were injected with 100 µg of leptin. The rationale for the incremental leptin dosages was to determine a dose-response curve because there were no comparable studies previously undertaken in sheep. Finally, between 70 and 90 min after the final injection, each lamb was humanely euthanized by intravenous administration of barbiturate [100 mg/kg pentobarbital sodium (Euthatal); RMB Animal Health, Essex, UK]. Perirenal adipose tissue depots and all major organs were rapidly removed, placed in liquid nitrogen, and stored at –70°C until subsequent laboratory analysis.

Chronic Study

Pairs of lambs were selected on the basis of matched body weight (±10%), and a jugular vein catheter was inserted into each animal under local anesthetic (2% xylocaine) to enable vehicle or leptin administration and blood sampling. Lambs were entered into the study on day 1 of life and injected daily for 6 days at ~9:30 AM with 100 µg of either leptin or vehicle (sterile water). Body weight was measured daily, and blood samples were taken on each study day before treatment. On day 7, each lamb was humanely euthanized, and tissue was sampled as described previously.

Laboratory Analyses

Protein detection. Mitochondria were prepared from 1 g of frozen lung and BAT (specifically perirenal adipose tissue, which constitutes ~80% of adipose tissue in a newborn sheep) (66), and protein contents of each preparation were determined by the Lowry method (39). Western blotting was utilized to measure the abundance of each protein. Exactly the same amount of protein was loaded onto each gel for every sample. After electroblotting of the polyacrylamide gel onto a nitrocellulose membrane, Ponceau red staining was used to visually confirm that similar amounts of protein had been transferred before subjecting the membranes to immunodetection (46). Abundance of cytochrome c was determined on 10 mg of mitochondrial protein by using an antibody (Santa Cruz, CA) at a dilution of 1:1,000. VDAC abundance was determined using an antibody raised in rabbits to ovine VDAC, purified from the kidney of a newborn lamb as described by Mostyn et al. (46) and used at a dilution of 1:2,000. UCP1 content was measured as described by Schermer et al. (60). Abundance of UCP2 protein was determined using the same antibody as described by Pecqueur et al. (53) at a dilution of 1:10,000, which was raised against human UCP2. A single band was detected at the same molecular mass as the UCP2 peptide in the postnatal tissues (46, 53). Densitometric analysis was performed on each gel, and all values were expressed in densitometric units. Specificity of detection was confirmed using nonimmune rabbit serum. A range of molecular-mass markers was included on all gels. Densitometric analysis was performed using AIDA (version 2.0, Raytest Isotopenmeßgeräte) on each membrane after image detection, using a Fujifilm LAS-1000 cooled charge-coupled device (CCD) camera (Fuji Photo Film, Tokyo, Japan), and all values are expressed in densitometric units. Specificity of detection was confirmed using nonimmune rabbit serum. A range (10–68 kDa) of molecular-mass markers was included on all gels. All gels were run in duplicate, and a reference sample (an appropriate ovine mitochondrial sample) was included on each to allow comparison between gels.

Messenger RNA detection. Total RNA was isolated from BAT using Tri-Reagent (Sigma, Poole, UK) and the expression of UCP2, GR, 11{beta}-HSD1, and 11{beta}-HSD2 mRNA determined by reverse transcriptase-polymerase chain reaction (RT-PCR), as previously described in detail by Gnanalingham and colleagues (28, 29). Briefly, the PCR anaylsis consisted of an initial denaturation [95°C (15 min)], amplification [stage I, 94°C (30 s); stage II, annealing temperature (30 s); stage III, 72°C (60 s)], and final extension [72°C (7 min); 8°C "hold"]. The annealing temperature and cycle number of each primer were optimized and used in the linear range for each tissue. Agrose gel electrophoresis (2.0–2.5%) and ethidium bromide staining confirmed the presence of both the product and 18S at the expected sizes. Densitometric analysis was performed on each gel by image detection, using a Fujifilm LAS-1000 cooled CCD camera, and UCP2, GR, 11{beta}-HSD types 1 and 2, and 18S mRNA abundance were determined. Consistency of lane loading for each sample was verified, and all results are expressed as a ratio of a reference sample to r18S abundance. All analyses and gels were conducted in duplicate with appropriate positive and negative controls and a range of molecular-mass markers. The resultant PCR product was extracted (QIAquick gel extraction kit, Qiagen, catalogue no. 28704) and sequenced, and results were cross-referenced against the GenBank website to determine specificity of the target gene.

Plasma leptin and NEFA determinations. Plasma concentrations of NEFA were measured enzymatically (12) and cortisol by radioimmunoassay, as described by Bispham et al. (6). Plasma leptin concentration was determined using a validated double-antibody radioimmunoassay, as described by Delavaud et al. (19). Plasma concentrations of leptin were assayed in duplicate 200-µl samples with a rabbit anti-ovine leptin primary antibody, iodinated ovine leptin, and sheep anti-rabbit secondary antibody. The leptin intra- and interassay coefficients of variation were 4.2 and 9.1% (n = 5), respectively.

Statistical Analyses

All data are presented as means ± SE. Tests of normality as determined by the Kolmogorov-Smirnoff test revealed that the data were nonparametric. Statistically significant (P < 0.05) differences between values obtained from vehicle-control and leptin-treated groups were determined by Mann-Whitney U-test. Significant correlations (P < 0.05) between fetal plasma leptin concentration, physiological, and molecular indexes were undertaken independently by a two-tailed Spearman’s rank order test (SPSS v. 11.0, SPSS) in vehicle and leptin groups on day 7, after 6 days of intravenous vehicle or leptin (100 µg/day), because this was the last time point when all of the measured parameters were available.


    RESULTS
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Effect of Acute and Chronic Leptin Administration on Plasma Cortisol Concentration in Neonatal Sheep

There was no significant difference in plasma cortisol concentration between vehicle-control and leptin-treated groups following acute leptin administration (data not shown). There was a decline in plasma cortisol concentration between day 1 and day 6 of postnatal life in both vehicle-control and leptin-treated groups (Fig. 1). By day 6 of chronic leptin administration, plasma cortisol concentration was significantly lower in the leptin-treated group compared with vehicle-control (Fig. 1). In the vehicle group, plasma cortisol concentration on day 6 was negatively correlated (R2 = 0.44, P = 0.003) to the mean colonic temperature over 7 days.



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Fig. 1. Effect of chronic daily (6 days) administration of leptin (100 µg/day) on the plasma concentration of cortisol (nmol/l) on days 1, 2, and 6 of treatment in neonatal sheep. Values are means ± SE (n = 7–8 per group). *P < 0.05, mean value significantly different from vehicle-treated group.

 
Effect of Acute and Chronic Leptin Administration on UCP2, GR, and 11{beta}-HSD type 1 and 2 mRNA Abundance in BAT

The abundance of UCP2, GR, and 11{beta}-HSD2 mRNA was decreased (P < 0.01) between 1 and 7 days of postnatal life in BAT, a pattern that was reversed for the abundance of 11{beta}-HSD1 mRNA (Figs. 2 and 3). Acute leptin administration decreased (P < 0.01) the abundance of UCP2, GR, and 11{beta}-HSD1 mRNA and increased (P < 0.01) the abundance of 11{beta}-HSD2 mRNA. This pattern of abundance was reversed with chronic leptin administration. There were no effects of sex on any of the measurements made during the acute leptin study.



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Fig. 2. Effect of acute (2 h) and chronic (6 days) administration of leptin (L; 100 µg/day) on the abundance of uncoupling protein-2 (UCP2) mRNA (A) and glucocorticoid receptor (GR) mRNA (B) in brown adipose tissue of neonatal sheep sampled at 1 and 7 days postnatal age. Examples of gene mRNA expression are given. Values are means ± SE (n = 8–9 per group). **P < 0.01, mean value significantly different from vehicle-treated (V) lambs and between 1 and 7 days postnatal life.

 


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Fig. 3. Effect of acute (2 h) and chronic (6 days) administration of leptin (100 µg/day) on the abundance of 11{beta}-hydroxysteroid dehydrogenase type 1 (11{beta}-HSD1) mRNA (A) and 11{beta}-hydroxysteroid dehydrogenase type 2 (11{beta}-HSD2) mRNA (B) in brown adipose tissue of neonatal sheep sampled at 7 days postnatal age. Examples of gene mRNA expression are given. Values are means ± SE (n = 8–9 per group). **P < 0.01, mean value significantly different from vehicle-treated lambs and between 1 and 7 days postnatal life.

 
A number of significant relationships were observed between plasma leptin and NEFA concentration, for which leptin was persistently raised [e.g., leptin day 6: vehicle, 2.1 ± 0.2; leptin, 17.6 ± 2.7 µg/ml (P < 0.05)], and for physiological and molecular indexes measured during the chronic leptin study in BAT of the vehicle-control and leptin-treated groups at 7 days postnatal life, as outlined in Table 1. UCP2 and GR mRNA were positively correlated with each other in both groups and to 11{beta}-HSD1 mRNA in BAT after leptin administration. In the leptin group, UCP2 mRNA was positively correlated with cytochrome c protein and with plasma leptin and NEFA concentration on day 7. In this group, UCP2 mRNA was also negatively correlated with the mean colonic temperature over the 7-day study period and UCP1 protein as previously published (43). Plasma leptin concentration on day 7 was positively correlated with GR mRNA in the leptin group and with guanosine diphosphate (GDP) binding in the vehicle group, which was also positively correlated with GR in the vehicle group and with 11{beta}-HSD2 mRNA in the leptin group. In the leptin group, 11{beta}-HSD1 mRNA was positively correlated with plasma leptin on day 7 and negatively correlated with 11{beta}-HSD2 mRNA. Similarly, in the leptin group, 11{beta}-HSD2 mRNA was positively correlated with UCP1 mRNA and protein and with the mean colonic temperature on day 7, as previously published (43). In this group, VDAC was positively correlated with the mean colonic temperature over the 7-day study period. Plasma cortisol on day 6 was positively correlated with GR and 11{beta}-HSD1 mRNA and negatively correlated to UCP1 protein and GDP binding in the leptin group.


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Table 1. Significant relationships in brown adipose tissue between plasma leptin concentration and physiological and molecular indexes measured in sheep neonate subjected to intravenous leptin (100 µg/day) or vehicle for 6 days

 
Effect of Chronic Leptin Administration on Mitochondrial Protein Abundance in Neonatal Lung

Chronic leptin administration decreased (P < 0.01) UCP2 protein abundance in the lung (Fig. 4), whereas VDAC and cytochrome c protein abundance were unaffected (data not shown). A number of significant relationships were observed between plasma leptin and NEFA concentration and physiological and molecular indexes measured, as outlined in Table 2. In this regard, mean plasma leptin concentration over 7 days was positively correlated to UCP2 and total lung per kilogram body weight in the leptin group. Plasma leptin on day 7 was negatively correlated to UCP2 in the lungs of controls. Cytochrome c was positively correlated with VDAC protein and with total lung per kilogram body weight in the lungs of the leptin group.



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Fig. 4. Effect of chronic (6 days) administration of leptin (100 µg/day) on abundance of UCP2 protein in the lung of neonatal sheep sampled at 7 days postnatal age. Examples of protein expression are given. Values are means ± SE (n = 8–9 per group). *P < 0.05, mean value significantly different from vehicle-treated lambs.

 

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Table 2. Significant relationships in lung between plasma leptin, and physiological and molecular indexes measured in sheep neonate subjected to intravenous leptin (100 µg/day) or vehicle for 6 days

 

    DISCUSSION
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The exact function and regulation of UCP2 in newborns remain unclear, and this study has highlighted that leptin differentially regulates UCP2 within neonatal BAT and lung, which may be important in the transition from fetal to neonatal life. The observed changes in UCP2 after leptin administration occurred during the decline in plasma cortisol concentration (5) and the establishment of independent ventilation and thermoregulation in the newborn (11). Our findings suggest that leptin has a role in the regulation of UCP2 within neonatal BAT and lung, which may be important in the regulation of lung function in the newborn (29). Clearly, additional studies are warranted to clarify how the present observations directly impact on physiological function and/or regulation.

Leptin and UCP2 in Neonatal BAT

We have shown for the first time that chronic but not acute leptin administration upregulates UCP2 mRNA abundance in neonatal BAT and that this effect may be mediated by an increase in glucocorticoid action and lipolysis. Importantly, these responses were observed in the absence of any effect of leptin on food intake or behavior (43). An increase in UCP2 mRNA in neonatal BAT following chronic leptin administration has not been demonstrated previously. Earlier studies have all examined mice and rats, which are altricial species, immature at birth with undeveloped BAT (45). The upregulation in UCP2 mRNA and loss of UCP1 (43) with chronic leptin administration coincides with the concomitant rise in plasma leptin and leptin mRNA, which is in parallel with increased adipose tissue deposition during the first 7 days of neonatal life in the sheep (5). The rise in leptin during the first week of neonatal life occurs in parallel with an increase in cell volume (72) but no change in adipocyte number (17), a loss of UCP1 and BAT (11), and the increased deposition of white adipose tissue, both around the central body organs and subcutaneously (11). The cellular mechanisms by which leptin promotes UCP2 mRNA abundance, but loss of UCP1 protein in neonatal BAT, remains to be elucidated but might involve apoptosis, which has been linked to the transformation of brown to white adipocytes in the adult mouse (35).

It has been shown that intracerebroventricular leptin administration promotes catabolism of adipocytes by stimulating apoptosis in rats, which is characterized by internucleosomal fragmentation of genomic DNA, elevated levels of DNA strand breaks, and a reduction in total DNA content and cellular volume (56). These findings have led to the "adipocyte apoptosis hypothesis," whereby leptin, acting via brain receptors, causes a hormonal and/or neural signal to be sent to adipose tissue depots (20). Enhanced apoptosis, potentially acting through UCP2, and increased production of reactive oxygen species then lead to increased transcription of endonucleases, proteases, and phospholipases, which ultimately results in apoptotic cell death (20). In vitro studies support a role for UCP2 in adipocyte apoptosis, demonstrating an increased expression of several caspases in preadipocytes overexpressing UCP2 (64). The positive association between UCP2 mRNA and cytochrome c protein noted with raised leptin suggests augmented apoptosis in neonatal BAT following leptin administration (37, 73).

Although the regulation and function of the BAT-specific UCP1 has been well established (13, 44), this is less clear for UCP2 (47). By the ability of UCP2 to uncouple mitochondrial respiration, several rodent studies have implied a role for UCP2 in nonshivering thermogenesis (22, 30), a role well established for UCP1 (13, 48). However, UCP2-null mice maintain their body temperature in a cold environment, in contrast to UCP1-null mice (47, 48). Moreover, we have shown that BAT UCP2 mRNA is negatively correlated with mean colonic temperature over 7 days and with UCP1 protein in the leptin group, supporting studies that dismiss a direct thermogenic role for UCP2 (47, 48). We have also shown that GR and both plasma leptin and NEFA appear to regulate UCP2 mRNA in neonatal BAT, thereby supporting a role for glucocorticoids in regulating UCP2 (29). Although the activity of UCP1 is tightly regulated by plasma NEFA concentration (24), this has not been shown for UCP2, with in vivo physiological and pathological states associated with a two- to threefold elevation in plasma NEFA not affecting UCP2 mRNA abundance in rodent BAT (69). In rodent and human preadipocyte cell lines, however, unsaturated fatty acids have markedly induced UCP2 mRNA (3, 69).

We have also shown differential effects of leptin on the abundance of UCP2 mRNA and on glucocorticoid action in neonatal BAT, because within 4 h of leptin administration, UCP2 mRNA decreased in conjunction with lower 11{beta}-HSD1 and raised 11{beta}-HSD2 mRNA. Surprisingly, this pattern was reversed after 6 days of leptin administration, as the relative mRNA abundance changed with age. One reason for the change in response to increasing age is the gradual decline in plasma cortisol that follows the postpartum surge (5). In the present study, we have shown that chronic leptin administration promotes local glucocorticoid action by increasing GR and 11{beta}-HSD1 mRNA and decreasing 11{beta}-HSD2 mRNA, suggesting that these peripheral leptin effects may be independent of any central effects that leptin potentially has on neonatal BAT. Indeed, these adaptations are accompanied by lower plasma cortisol by 6 days of age. Although there are no comparable in vivo studies in the neonatal period, in vitro studies utilizing adipose tissue biopsies from idiopathic obesity patients showed that leptin mRNA was positively correlated with 11{beta}-HSD1 expression and activity. These were both associated with indexes of obesity such as body mass index and fasting insulin (74). Leptin also increases 11{beta}-HSD1 expression and activity in human adipose stromal cells (70). In addition, transgenic mice overexpressing 11{beta}-HSD1 selectively in adipose tissue are hyperleptinemic (41), paralleling the positive association between 11{beta}-HSD1 mRNA and plasma leptin on day 7 in the present study. Interestingly, we found that 11{beta}-HSD2 mRNA, which was reduced by chronic leptin administration, appeared to have a potential role in neonatal BAT heat production, being positively correlated with UCP1, GDP binding, and the mean colonic temperature on day 7 in the leptin group alone. These associations might be important in maintaining thermoregulation, especially when UCP1 abundance is diminished by chronic leptin administration (43). Although these significant correlations do not necessarily indicate clinically significant effects, they do, however, indicate an association between the parameters examined, suggesting potential means of regulation. Additional studies are needed to determine whether these observations underlie potential clinical effects and physiological regulation, as well as functional changes.

Leptin and UCP2 in the Neonatal Lung

Chronic leptin administration decreased UCP2 protein in the lung, in contrast with the increase in UCP2 mRNA in BAT, for which we were unable to confirm UCP2 protein in BAT because the antibody raised against UCP2 cross-reacts with UCP1 (53). Although, UCP2 is abundant in the neonatal lung (29, 53), its exact role and function have yet to be determined. Cumulative evidence identifies both fetal and adult lungs as leptin responsive (16, 33, 71), and respiratory anomalies that are common with the obese phenotype (tachypnea, decreased lung compliance, and aberrant respiratory muscle adaptations) are attenuated after prolonged leptin administration in the ob/ob mouse (68). This is the first time that the impact of chronic leptin administration on the abundance of UCP2 in the neonatal lung has been examined. UCP2-deficient mice are resistant to infection with Toxoplasma gondii, and their macrophages generate 80% more reactive oxygen species than wild-type mice and have fivefold greater toxoplasmacidal activity in vitro, which is absent in the presence of a quencher of reactive oxygen species (2). This proposed role for UCP2 in macrophage-mediated immunity and limitation of reactive oxygen species has been supported by others (36, 50). It is conceivable that the decreased abundance of UCP2 protein in the lung with chronic leptin administration could promote reactive oxygen species production and maintain host immunity through augmentation of alveolar macrophage phagocytosis and leukotriene synthesis. The impact of a precocious decrease in UCP2 with leptin administration on later lung function has yet to be examined.

Mean plasma leptin over 7 days was positively associated with total lung per kilogram body weight in the leptin group alone, suggesting a potential role for leptin in lung growth. This finding accords with leptin receptor-deficient mice (71) that exhibit a 75% decreased rate of tracheal epithelial proliferation compared with wild-type littermates, emphasizing a potential role for leptin in pulmonary growth. Other studies further suggest a significant impact of leptin on general pulmonary health in rodents both as a growth factor and as a neurohumoral modulator of central respiration (51), as well as on specific respiratory disorders in humans including obesity hypoventilation syndrome and obstructive sleep apnea (52). Although we did not observe a significant association between UCP2 mRNA and NEFA in the leptin group, Xiao et al. (75) proposed that NEFA regulate lung UCP2 mRNA in both neonatal and adult rodents. In this study, calorie restriction caused a rapid increase in NEFA, and lung UCP2 mRNA was increased by NEFA administration to fed animals. In the sheep, we have not found any evidence of a close relationship among maternal nutrient restriction, plasma NEFA, and acute or chronic changes in UCP2 (29), indicating that other mechanisms are involved in UCP2 regulation in large mammals. In addition, the positive association between the apoptotic mitochondrial proteins VDAC and cytochrome c (37, 73) with raised plasma leptin and total lung per kilogram body weight supports a role for apoptosis in neonatal lung development. In accord with the possible leptin-induced apoptotic increase in UCP2 mRNA within BAT as discussed above, apoptotic activity has been observed during all six (embryonic, pseudoglandular, canalicular, saccular, alveolar, and microvascular) stages of fetal lung development, suggesting its important role during this highly orchestrated process (18). After birth, apoptosis also emerges as an important process after extensive proliferation and subsequent transformation of primary saccules into functional alveoli (8, 61) that could be leptin mediated.

In conclusion, we have shown for the first time that leptin administration to the neonate has differential effects on the abundance of UCP2 in BAT and lung. These effects may be important in the development of these tissues, thereby optimizing lung function and fat growth.


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This work was funded in part by the Nottingham University Hospitals Research and Development Directorate, the Special Trustees for Nottingham University Hospitals, and a University of Nottingham scholarship to A. Mostyn.


    FOOTNOTES
 

Address for reprint requests and other correspondence: M. E. Symonds, Academic Division of Child Health, School of Human Development, Queen’s Medical Centre, University Hospital, Nottingham NG7 2UH, UK (e-mail: michael.symonds{at}nottingham.ac.uk)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.


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  1. Ahima RS and Flier JS. Adipose tissue as an endocrine organ. Trends Endocrinol Metab 11: 327–332, 2000.[CrossRef][ISI][Medline]
  2. Arsenijevic D, Onuma H, Pecquer C, Raimbault S, Manning BS, Miroux B, Couplan E, Alves-Guerra MC, Goubern M, Surwit R, Bouillaud F, Richard D, Collins S, and Ricquier D. Disruption of the uncoupling protein-2 gene in mice reveals a role in immunity and reactive oxygen species production. Nat Genet 26: 435–439, 2000.[CrossRef][ISI][Medline]
  3. Aubert J, Champigny O, Saint-Marc P, Negrel R, Collins S, Ricquier D, and Ailhaud G. Up-regulation of UCP-2 gene expression by PPAR agonists in preadipose and adipose csells. Biochem Biophys Res Commun 238: 601–611, 1997.
  4. Bamberger CM, Schulte HM, and Chrousos GP. Molecular determinants of glucocorticoid receptor function and tissue sensitivity to glucocorticoids. Endocr Rev 17: 245–261, 1996.[Abstract]
  5. Bispham J, Budge H, Mostyn A, Dandrea J, Clarke L, Keisler D, Symonds ME, and Stephenson T. Ambient temperature, maternal dexamethasone, and postnatal ontogeny of leptin in the neonatal lamb. Pediatr Res 52: 85–90, 2002.[Abstract/Free Full Text]
  6. Bispham J, Gopalakrishnan GS, Dandrea J, Wilson V, Budge H, Keisler DH, Broughton Pipkin F, Stephenson T, and Symonds ME. Maternal endocrine adaptation throughout pregnancy to nutritional manipulation: consequences for maternal plasma leptin and cortisol and the programming of fetal adipose tissue development. Endocrinology 144: 3575–3585, 2003.[Abstract/Free Full Text]
  7. Boss O, Hagen T, and Lowell BB. Uncoupling proteins 2 and 3, potential regulators of mitochondrial energy metabolism. Diabetes 49: 143–156, 2000.[Abstract]
  8. Bruce MC, Honaker CE, and Cross RJ. Lung fibroblasts undergo apoptosis following alveolarization. Am J Respir Cell Mol Biol 20: 228–236, 1999.[Abstract/Free Full Text]
  9. Buemann B, Schierning B, Toubro S, Bibby BM, Sørensen T, Dalgaard L, Pedersen O, and Astrup A. The association between the val/ala-55 polymorphism of the uncoupling protein 2 gene and exercise efficiency. Int J Obes Relat Metab Disord 25: 467–471, 2001.[CrossRef][Medline]
  10. Cetin I, Morpurgo PS, Radaelli T, Taricco E, Cortelazzi D, Bellotti M, Pardi G, and Beck-Peccoz P. Fetal plasma leptin concentrations: relationship with different intrauterine growth patterns from 19 weeks to term. Pediatr Res 48: 646–651, 2000.[Abstract/Free Full Text]
  11. Clarke L, Buss DS, Juniper DS, Lomax MA, and Symonds ME. Adipose tissue development during early postnatal life in ewe-reared lambs. Exp Physiol 82: 1015–1017, 1997.[Abstract/Free Full Text]
  12. Clarke L, Darby CJ, Lomax MA, and Symonds ME. Effect of ambient temperature during 1st day of life on thermoregulation in lambs delivered by cesarean section. J Appl Physiol 76: 1481–1488, 1994.[Abstract/Free Full Text]
  13. Clarke L, Heasman L, Firth K, and Symonds ME. Influence of route of delivery and ambient temperature on thermoregulation in newborn lambs. Am J Physiol Regul Integr Comp Physiol 272: R1931–R1939, 1997.[Abstract/Free Full Text]
  14. Clarke L, Heasman L, Juniper DT, and Symonds ME. Maternal nutrition in early-mid gestation and placental size in sheep. Br J Nutr 79: 359–364, 1998.[ISI][Medline]
  15. Crompton M. The mitochondrial permeability transition pore and its role in cell death. Biochem J 341: 233–249, 1999.[CrossRef][ISI][Medline]
  16. Dal Farra C, Zsurger N, Vincent JP, and Cupo A. Binding of a pure 125I-monoiodoleptin analog to mouse tissues: a developmental study. Peptides 21: 577–587, 2000.[CrossRef][ISI][Medline]
  17. Darby CJ, Clarke L, Lomax MA, and Symonds ME. Brown adipose tissue and liver development during early postnatal life in hand-reared and ewe-reared lambs. Reprod Fertil Dev 8: 137–145, 1996.[CrossRef][ISI][Medline]
  18. Del Riccio V, Tuyl MV, and Post M. Apoptosis in lung development and neonatal lung injury. Pediatr Res 55: 183–189, 2004.[Abstract/Free Full Text]
  19. Delavaud C, Bocquier F, Chilliard Y, Keisler DH, Gertler A, and Kann G. Plasma leptin determination in ruminants: effect of nutritional status and body fatness on plasma leptin concentration assessed by a specific RIA in sheep. J Endocrinol 165: 519–526, 2000.[Abstract/Free Full Text]
  20. Della-Fera MA, Qian H, and Baile CA. Adipocyte apoptosis in the regulation of body fat mass by leptin. Diabetes Obes Metab 3: 299–310, 2001.[CrossRef][ISI][Medline]
  21. Faggioni R, Shigenaga J, Moser A, Feingold KR, and Grunfeld C. Induction of UCP2 gene expression by LPS: potential mechanism for increased thermogenesis during infection. Biochem Biophys Res Commun 244: 75–78, 1998.[CrossRef][ISI][Medline]
  22. Fleury C, Neverova M, Collins S, Pecquer C, Raimbault S, Champigny O, Meyrueis C, Bouillaud F, Seldin MF, Surwit R, Ricquier D, and Warden C. Uncoupling protein-2: a novel gene linked to obesity and hyperinsulinemia. Nat Genet 15: 269–272, 1997.[CrossRef][ISI][Medline]
  23. Friedman JM and Halaas JL. Leptin and the regulation of body weight in mammals. Nature 395: 736–770, 1998.[CrossRef][Medline]
  24. Garlid KD, Orosz DE, Modriansky M, Vassanelli S, and Jezek P. On the mechanism of fatty acid-induced proton transport by mitochondrial uncoupling protein. J Biol Chem 271: 2615–2620, 1996.[Abstract/Free Full Text]
  25. Garlid KD, Jaburek M, Jezek P, and Varecha M. How do uncoupling proteins uncouple? Biochim Biophys Acta 1459: 383–389, 2000.[ISI][Medline]
  26. Gertler A, Simmons J, and Keisler DH. Large scale preparation of biologically active recombinant ovine obese protein (leptin). FEBS Lett 422: 137–140, 1998.[CrossRef][ISI][Medline]
  27. Giralt M, Martin I, Iglesias R, Vinas O, Villarroya F, and Mampel T. Ontogeny and perinatal modulation of gene expression in rat brown adipose tissue. Eur J Biochem 193: 297–302, 1990.[CrossRef][ISI][Medline]
  28. Gnanalingham MG, Giussani DA, Stephenson T, Symonds ME, and Gardner DS. Chronic umbilical cord compression results in premature maturation of lung and brown adipose tissue in the late gestation ovine fetus. Am J Physiol Endocrinol Metab 289: E456–E465, 2005.[Abstract/Free Full Text]
  29. Gnanalingham MG, Mostyn A, Dandrea J, Yakubu DP, Symonds ME, and Stephenson T. Ontogeny and nutritional programming of uncoupling protein-2 and glucocorticoid receptor mRNA in the ovine lung. J Physiol 565: 159–169, 2005.[Abstract/Free Full Text]
  30. Gong DW, He Y, Karas M, and Reitman M. Uncoupling protein-3 is a mediator of thermogenesis regulated by thyroid hormone, {beta}3-adrenergic agonists, and leptin. J Biol Chem 272: 24129–24132, 1997.[Abstract/Free Full Text]
  31. Gottlieb RA. Mitochondria: execution central. FEBS Lett 482: 6–12, 2000.[CrossRef][ISI][Medline]
  32. Haynes WG, Morgan DA, Walsh SA, Mark AL, and Sivitz WI. Receptor mediated regional sympathetic nerve action by leptin. J Clin Invest 100: 270–278, 1997.[Abstract/Free Full Text]
  33. Henson MC, Swan KF, Edwards DE, Hoyle GW, Purcell J, and Castracane VD. Leptin receptor expression in fetal lung increases in late gestation in the baboon: a model for human pregnancy. Reproduction 127: 87–94, 2004.[Abstract/Free Full Text]
  34. Jiang X and Wang X. Cytochrome-c mediated apoptosis. Annu Rev Biochem 73: 87–106, 2004.[CrossRef][ISI][Medline]
  35. Kim DW, Kim BS, Kwon HS, Kim CG, Lee HW, Choi WH, and Kim CG. Atrophy of brown adipocytes in the adult mouse causes transformation into white adipocyte-like cells. Exp Mol Med 35: 518–526, 2003.[ISI][Medline]
  36. Kizaki T, Suzuki K, Hitomi Y, Taniguchi N, Saitoh D, Watanabe K, Onoe K, Day NK, Good RA, and Ohno H. Uncoupling protein 2 plays an important role in nitric oxide production of lipopolysaccharide-stimulated macrophages. PNAS 99: 9392–9397, 2002.[Abstract/Free Full Text]
  37. Lehninger AL, Nelson DL, and Cox MM. Oxidative phosphorylation and photo phosphorylation. In: Principles of Biochemistry, edited by Geller E. New York: Worth, 1993, p. 542–597.
  38. Litten JC, Mostyn A, Perkins KS, Corson AM, Symonds ME, and Clarke L. The effect of administration of recombinant human leptin during the neonatal period on the plasma concentration and gene expression of leptin in the piglet. Biol Neonate 87: 1–7, 2004.[CrossRef][ISI][Medline]
  39. Lowry OH, Rosenbrough NJ, Farr AL, and Randall RJ. Protein measurement with the Folin phenol reagent. J Biol Chem 193: 265–275, 1951.[Free Full Text]
  40. Ludwig B, Bender E, Arnold S, Huttemann M, Lee I, and Kadenbach B. Cytochrome c oxidase and the regulation of oxidative phosphorylation. Chembiochem 2: 392–403, 2001.[CrossRef][ISI][Medline]
  41. Masuzaki H, Paterson J, Shinyama H, Morton NM, Mullins JJ, Seckl JR, and Flier JS. A transgenic model of visceral obesity and the metabolic syndrome. Science 294: 2166–2170, 2001.[Abstract/Free Full Text]
  42. Memon RA, Hotamisligil GS, Wiesbrock SM, Uysal KT, Faggioni R, Moser AH, Feingold KR, and Grunfeld C. Upregulation of uncoupling protein 2 mRNA in genetic obesity: lack of an essential role for leptin, hyperphagia, increased tissue lipid content, and TNF-alpha. Biochim Biophys Acta 1484: 41–50, 2000.[ISI][Medline]
  43. Mostyn A, Bispham J, Pearce S, Evens Y, Raver N, Keisler DH, Webb R, Stephenson T, and Symonds ME. Differential effects of leptin on thermoregulation and uncoupling protein abundance in the neonatal lamb. FASEB J 16: 1438–1440, 2002.[Abstract/Free Full Text]
  44. Mostyn A, Pearce S, Budge H, Elmes M, Forehead AJ, Fowden AL, Symonds ME, and Stephenson T. Influence of cortisol on adipose tissue development in the fetal sheep during late gestation. J Endocrinol 176: 23–30, 2003.[Abstract/Free Full Text]
  45. Mostyn A, Pearce S, Stephenson T, and Symonds ME. Hormonal and nutritional regulation of adipose tissue mitochondrial development and function in the newborn. Exp Clin Endocrinol Diabetes 112: 2–9, 2004.[CrossRef][ISI][Medline]
  46. Mostyn A, Wilson V, Dandrea J, Yakubu DP, Budge H, Alves-Guerra MC, Pecqueur C, Miroux B, Symonds ME, and Stephenson T. Ontogeny and nutritional manipulation of mitochondrial protein abundance in adipose tissue and the lungs of postnatal sheep. Br J Nutr 90: 323–328, 2003.[CrossRef][ISI][Medline]
  47. Nedergaard J and Cannon B. The "novel" "uncoupling" proteins UCP2 and UCP3: what do they really do? Pros and cons for suggested functions. Exp Physiol 88: 65–84, 2003.[Abstract/Free Full Text]
  48. Nedergaard J, Golozoubova V, Matthias A, Asadi A, Jacobsson A, and Cannon B. UCP1: the only protein able to mediate adaptive non-shivering thermogenesis and metabolic inefficiency. Biochem Biophys Acta 1504: 82–106, 2001.[ISI][Medline]
  49. Nedergaard J, Matthias A, Golozoubova V, Jacobsson A, and Cannon B. UCP1: the original uncoupling protein—and perhaps the only one? New perspectives on UCP1, UCP2, and UCP3 in the light of the bioenergetics of the UCP1-ablated mice. J Bioenerg Biomembr 31: 475–491, 1999.[CrossRef][ISI][Medline]
  50. Negre-Salvayre A, Hirtz C, Carrera G, Cazenave R, Troly M, Salvayre R, Penicaud L, and Casteilla L. A role for uncoupling protein-2 as a regulator of mitochondrial hydrogen peroxide generation. FASEB J 11: 809–815, 1997.[Abstract/Free Full Text]
  51. O’Donnell CP, Schaub CD, Haines AS, Berkowitz DE, Tankersley CG, Schwartz AR, and Smith PL. Leptin prevents respiratory depression in obesity. Am J Respir Crit Care Med 159: 1477–1484, 1999.[Abstract/Free Full Text]
  52. O’Donnell CP, Tankersley CG, Polotsky VP, Schwartz AR, and Smith PL. Leptin, obesity and respiratory function. Respir Physiol 119: 163–170, 2000.[CrossRef][ISI][Medline]
  53. Pecqueur C, Alves-Guerra MC, Gelly C, Lévi-Meyrueis C, Couplan E, Collins S, Ricquier D, Bouillaud F, and Miroux B. Uncoupling protein-2: in vivo distribution, induction upon oxidative stress and evidence for translational regulation. J Biol Chem 276: 8705–8712, 2001.[Abstract/Free Full Text]
  54. Pelleymounter MA, Cullen MJ, Baker MB, Hecht R, Winters D, Boone T, and Collins F. Effects of the obese gene product on body weight regulation in ob/ob mice. Science 269: 540–543, 1995.[ISI][Medline]
  55. Pralong FP, Roduit R, Waeber G, Castillo E, Mosimann F, Thorens B, and Gaillard RC. Leptin inhibits directly glucocorticoid secretion by normal human and rat adrenal gland. Endocrinology 139: 4264–4268, 1998.[Abstract/Free Full Text]
  56. Qian H, Azain MJ, Compton MM, Hartzell DL, Hausman GJ, and Baile CA. Brain administration of leptin causes deletion of adipocytes by apoptosis. Endocrinology 139: 791–794, 1998.[Abstract/Free Full Text]
  57. Ricquier D and Bouillaud F. The uncoupling protein homologues: UCP1, UCP2, UCP3, StUCP and AtUCP. Biochem J 345: 161–179, 2000.[CrossRef][ISI][Medline]
  58. Scarpace P, Matheny M, Pollock B, and Tumer N. Leptin increases uncoupling protein expression and energy expenditure. Am J Physiol Endocrinol Metab 273: E226–E230, 1997.[Abstract/Free Full Text]
  59. Scarpace PJ and Matheny M. Leptin induction of UCP1 gene expression is dependent on sympathetic innervation. Am J Physiol Endocrinol Metab 275: E259–E264, 1998.[Abstract]
  60. Schermer SJ, Bird JA, Lomax MA, Shepherd DA, and Symonds ME. Effect of fetal thyroidectomy on brown adipose tissue and thermoregulation in newborn lambs. Reprod Fertil Dev 8: 995–1002, 1996.[ISI][Medline]
  61. Schittney JC, Djonov V, Fine A, and Burri PH. Programmed cell death contributes to postnatal lung development. Am J Respir Cell Mol Biol 18: 786–793, 1998.[Abstract/Free Full Text]
  62. Schwartz MW, Seeley RJ, Campfield LA, Burn P, and Baskin DG. Identification of targets of leptin action in rat hypothalamus. J Clin Invest 98: 1101–1106, 1996.[Abstract/Free Full Text]
  63. Stewart PM and Krozowski ZS. 11{beta}-Hydroxysteroid dehydrogenase. Vitam Horm 57: 249–324, 1999.[ISI][Medline]
  64. Sun X and Zemel MB. Role of uncoupling protein 2 (UCP2) expression and 1alpha, 25-dihydroxyvitamin D3 in modulating adipocyte apoptosis. FASEB J 18: 1430–1432, 2004.[Abstract/Free Full Text]
  65. Symonds ME, Andrews DC, and Johnson PJ. The control of thermoregulation in the developing lamb during slow wave sleep. J Dev Physiol 11: 289–298, 1989.[ISI][Medline]
  66. Symonds ME, Bryant MJ, Clarke L, Darby CJ, and Lomax MA. Effect of maternal cold exposure on brown adipose tissue and thermogenesis in the neonatal lamb. J Physiol 455: 487–502, 1992.[Abstract]
  67. Symonds ME, Mostyn A, Pearce S, Budge H, and Stephenson T. Endocrine and nutritional regulation of fetal adipose tissue development. J Endocrinol 179: 293–299, 2003.[Abstract/Free Full Text]
  68. Tankersley CG, O’Donnell C, Daood MJ, Watchko JF, Mitzner W, Schwartz A, and Smith P. Leptin attenuates respiratory complications associated with the obese phenotype. J Appl Physiol 85: 2261–2269, 1998.[Abstract/Free Full Text]
  69. Thompson MP and Kim D. Links between fatty acids and expression of UCP2 and UCP3 mRNAs. FEBS Lett 568: 4–9, 2004.[CrossRef][ISI][Medline]
  70. Tomlinson JW, Moore J, Cooper MS, Bujalska I, Shahmanesh M, Burt C, Strain A, Hewison M, and Stewart PM. Regulation of expression of 11{beta}-hydroxysteroid dehydrogenase type 1 in adipose tissue: tissue-specific induction by cytokines. Endocrinology 142: 1982–1989, 2001.[Abstract/Free Full Text]
  71. Tsuchiya T, Shimizu H, Horie T, and Mori M. Expression of leptin receptor in lung: leptin as a growth factor. Eur J Pharmacol 365: 273–279, 1999.[CrossRef][ISI][Medline]
  72. Vernon RG. Development of perirenal adipose tissue in the neonatal lamb: effects of dietary safflower oil. Biol Neonate 32: 15–23, 1977.[ISI][Medline]
  73. Voehringer DW, Hirschberg DL, Xiao J, Lu Q, Roederer M, Lock CB, Herzenberg LA, Steinman L, and Herzenberg LA. Gene microarray identification of redox and mitochondrial elements that control resistance or sensitivity to apoptosis. Proc Natl Acad Sci USA 97: 2680–2685, 2000.[Abstract/Free Full Text]
  74. Wake DJ, Rask E, Livingstone DEW, Soderberg S, Olsson T, and Walker BR. Local and systemic impact of transcriptional up regulation of 11{beta}-hydroxysteroid dehydrogenase type 1 in adipose tissue in human obesity. J Clin Endocrinol Metab 88: 3983–3988, 2003.[Abstract/Free Full Text]
  75. Xiao H, Massaro D, Massaro GD, and Clerch LB. Expression of lung uncoupling protein-2 mRNA is modulated developmentally and by caloric intake. Exp Biol Med 229: 479–485, 2004.[Abstract/Free Full Text]
  76. Yuen BS, McMillen IC, Symonds ME, and Owens PC. Abundance of leptin mRNA in fetal adipose tissue is related to fetal body weight. J Endocrinol 163: R11–R14, 1999.[Abstract/Free Full Text]




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