1 Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226; and 2 Department of Neurology, University of Tennessee Health Sciences Center, Memphis, Tennessee 38163
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Sleep deprivation in rats results in progressive declines in circulating concentrations of both total and free thyroxine (T4) and triiodothyronine (T3) without an expected increase in plasma thyroid-stimulating hormone (TSH). Administration of thyrotropin-releasing hormone (TRH) results in appropriate increases in plasma TSH, free T4, and free T3 across experimental days, suggesting deficient endogenous TRH production and/or release. This study examined transcriptional responses related to TRH regulation following sleep deprivation. In situ hybridization was used to detect and quantitate expression of mRNAs encoding prepro-TRH and 5'-deiodinase type II (5'-DII) in brain sections of six rats sleep deprived for 16-21 days, when there was marked hypothyroxinemia, and in sections from animals yoked to the experimental protocol as well as from sham controls. TRH transcript levels in the paraventricular nucleus (PVN) were essentially unchanged at 15-16 days but increased to about threefold control levels in three of four rats sleep deprived for 20-21 days, a change comparable to that typically found in prolonged experimental hypothyroidism. There was no evidence for suppression of 5'-DII mRNA levels, which would be a sign of T3 feedback downregulation of neurons in the PVN. A failure to increase serum TSH in response to hypothyroxinemia and to increased prepro-TRH mRNA expression indicates that alterations in posttranscriptional stages of TRH synthesis, processing, or release likely mediate the central hypothyroidism induced by sleep deprivation.
central hypothyroidism; preprothyrotropin-releasing hormone messenger ribonucleic acid; paraventricular nucleus; thyroid hormones
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
THERE IS NEAR UNIVERSAL CONCURRENCE that profound and chronic sleep deprivation is a risk factor for illness (1, 2) and that it impairs recovery (5, 14). Although specific physiological changes that may contribute to pathology in the clinical population have yet to be extensively investigated, characteristic findings have emerged from studies in laboratory animals. A typical 3-wk survival period in sleep-deprived rats is marked by hypercatabolism, manifested by increased food intake and loss of body weight without diabetes or malabsorption of calories (8, 22, 27). Body temperature initially increases slightly, by <0.5°C (8). Despite this resemblance to hyperthyroidism, plasma thyroxine (T4) and triiodothyronine (T3) instead decline progressively to very low concentrations (8, 23). Plasma norepinephrine increases (45), whereas plasma corticosteroids remain unchanged (23). Resistance to infectious disease is decreased, revealed by early and continual infection of the mesenteric lymph nodes by bacteria translocated from the intestine, and periodic transient infections of major organs (26). The endocrine changes and the septic state eventuate in an acute condition of advanced morbidity and hypothermia that precede death. Terminal signs and positive blood cultures are consistent with lethal septicemia (21).
The declines in both plasma T4 and T3 in sleep-deprived rats are considered grossly abnormal, not only because of their progressiveness and severity but also because of the apparent lack of pituitary activation. The free forms of T4 and T3 decline in parallel with the total concentrations, indicating that changes in binding characteristics are not responsible for low T4 (23). Plasma reverse T3 concentrations are not increased into a range that would indicate T4 inactivation (23). T4 shows a greater decline than does T3, to 75% below basal concentrations by the onset of advanced morbidity, compared with a 55% decline in T3 (8). The increased T3-to-T4 ratio likely involves local T3 production by brown adipose tissue (BAT), a major T4-to-T3 conversion pathway in the rat, which can contribute 40% or more of circulating T3 (54). Indeed, the T4-to-T3 conversion enzyme, type II 5'-deiodinase, in BAT is increased 100-fold in sleep-deprived rats (6), a level consistent with experimental hypothyroidism (13, 54).
Low plasma T4 is a potent stimulator of thyroid-stimulating hormone (TSH) secretion from the pituitary (61). A previous study in sleep-deprived rats indicated that the plasma TSH concentration remains at basal levels; therefore, TSH is inappropriately low for the amount of circulating T4 (23). However, stimulation tests of the pituitary-thyroid axis by administration of exogenous thyrotropin-releasing hormone (TRH) reveal a normal rise in plasma TSH comparable to control levels, and a subsequent, appropriate rise in plasma free T4 and free T3 throughout the progressive course of hypothyroxinemia (23). This pattern is consistent with central hypothyroidism in humans and experimental animals (47, 52) and points to critical alterations of the thyroidal axis by central mechanisms leading to TRH deficiency.
TRH-containing neurons in the paraventricular nucleus (PVN) of the hypothalamus exert control over the biosynthesis and release of TSH from the pituitary (reviewed in Refs. 15, 31). Experimental hypothyroidism in rats results in a significant increase in prepro-TRH mRNA expression and peptide content in the PVN (35, 53, 57, 63) and hypothalamic TRH release (50). In the present study, we evaluated TRH transcript expression in the PVN by in situ hybridization in sleep-deprived and comparison rats. We also evaluated type II 5'-deiodinase (5'-DII) mRNA expression in the arcuate nucleus and median eminence (ARC-ME), known to be rich in 5'-DII and to show increased expression during thyroidectomy produced by chemicals or surgery (60). The principal finding is that prepro-TRH mRNA levels increase during prolonged sleep deprivation as an apparently appropriate response to decreased circulating thyroid hormone concentration, but expected TSH responses to peripheral hypothyroxinemia and to increased TRH transcript levels do not occur. 5'-DII mRNA expression in the ARC-ME was slightly but insignificantly increased in sleep-deprived animals rather than being suppressed, as would be expected if thyroid hormones were present in sufficient local excess to exert increased negative feedback on the PVN, and thereby contribute to downregulation of the thyroid axis. These findings point to posttranscriptional mechanisms and/or inhibitory factors as responsible for TRH deficiency and resultant hypothyroxinemia induced by sleep deprivation.
![]() |
METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Animals.
All procedures were carried out in accordance with the National
Institutes of Health guidelines on the care and use of animals and with
an animal study protocol approved by the University of Tennessee Animal
Care and Use Committee. Eighteen adult male Sprague-Dawley rats
(Harlan, Indianapolis, IN) weighing 464 ± 33 (±SD) g and aged
24 ± 2.5 wk were surgically prepared, of which six pairs served
as sleep deprived and experimentally yoked animals, respectively, with
six surgical controls. Anesthesia and analgesia were induced by
ketamine · HCl (100 mg/kg ip), xylazine · HCl (2.4 mg/kg im), and atropine sulfate (0.1 mg/kg im). Supplementary doses of
ketamine · HCl (10 mg/kg ip) were provided as needed. A
solution of 1-2% lidocaine · HCl (2.4 mg/kg) was also
administered subcutaneously at an abdominal incision site through which
a low-frequency telemetric transmitter (Barrows, San Jose, CA) was
implanted to detect hypothermia, one indication of advanced morbidity
(9, 21). Cortical and muscle electrodes were implanted for
monitoring sleep and wakefulness. Animals were allowed to recover from
surgery for 7 days.
Animal environmental conditions. Rats were kept under conditions of constant light to diminish the amplitude of the circadian rhythm. This was to avoid the influence of phase of circadian rhythm on dependent variables under study and the influence of sleep deprivation on the phase, which would differ between subject groups. Ambient air temperature was maintained at 28°C, within the thermoneutral zone established for rats (56), with thermostatically controlled heat lamps. Food and water were available ad libitum. Rats were fed a balanced, purified diet that was isocaloric to a normal diet and augmented with protein, as used in previous studies (23, 27).
Procedure for producing sleep-deprived, yoked, and sham control animals. The apparatus and procedures for sleep deprivation are detailed elsewhere (9, 27). In brief, amplitude changes in electroencephalogram (EEG) variables were electronically processed to detect sleep onset in the rat to be sleep deprived, which triggered slow rotation of a platform on which the rats were housed, forcing both the sleep-deprived and the yoked rats to move for several seconds. The yoked rat experienced forced locomotion at the same time as the sleep-deprived rat, but it could sleep whenever the platform was stationary because the sleep-deprived partner was awake. This experimental paradigm results in consistent sleep loss across subject groups (21, 22, 24, 27). During a 7-day baseline period, with 6 s of rotation every hour, rats are awake 47% of the time. Thereafter, sleep-deprived rats are kept awake 90% of total time, and much of the remaining sleep is highly fragmented and/or consists of low-amplitude EEG transitional sleep. Yoked rats are awake 58% of total time, and their sleep is fragmented because of frequent arousals from sleep due to the paired conditions and are thus considered partially sleep deprived. Sham controls are permitted to sleep normally throughout the baseline and experimental periods.
Sleep-deprived rats exhibit a consistent progression of clinical signs, but individual animals do so at different rates (46). The only definitive clinical marker of severity of sleep deprivation is an eventual, acute terminal condition of advanced morbidity and hypothermia. We have used this retrospectively in other studies to determine the temporal course of each animal in proportion to its survival period (9, 22, 27). In the present study, sleep deprivation or control conditions were maintained for 15-21 days, which brackets the final quartile of survival defined in previous studies. We wished to produce sleep deprivation long enough for marked hypothyroxinemia and its sequelae to become manifest but short enough to preclude advanced morbidity and hypothermia. To these ends, food intake, body weight, and 24-h body temperature were monitored daily, as previously described (9, 27). Special food tubes with a waste receptacle afforded accurate measurement of food consumption (9). In four pairs of animals, the deprivation period extended to 20-21 days, by which time the fourth sleep-deprived rat had reached advanced morbidity. The subsequent two pairs of animals were studied after 16 days.Tissue collection and processing.
At the end of the experimental periods, rats were deeply anesthetized
with injectable anesthetics and analgesics, and cardiac puncture was
performed for exsanguination and blood sampling. The brain was removed
and frozen in 40°C hexane. Blood that had been drawn into serum
separator tubes during the cardiac puncture procedure was centrifuged,
and the serum was stored at
80°C for assay of T4,
T3, and TSH.
In situ hybridization. The prepro-TRH oligonucleotide (5'-GTCTTTTTCCTCCTCCTCCCTTTTGCCTGGATGCTG- GCGTTTTGTGAT-3') was a 48-bp sequence used by other investigators (64) complementary to a region of the TRH transcript characterized in rat brain by Lechan et al. (39). The 5'-DII oligonucleotide (5'-GCCATCTGAAGGGTGAGCCTCATCAATGTATACCAACAGG-3') was a 40-mer derived from the sequence published by Croteau et al. (13), complementary to a conserved region of Rattus norvegicus and Rattus rattus type II iodothyronine deiodinase that also has 90 and 88% homology with human and Rana catesbeiana sequences, respectively.
Frozen brain sections (16 µm) were cut on a cryostat atHormone determinations. Serum from unoperated colony rats was assayed for quality control and to provide values for comparison with those of the treatment groups. Serum concentrations of total T4 and total T3 were determined in single-batch radioimmunoassays using commercial kits (Diagnostic Systems Laboratories, Webster, TX). The coefficient of variation with an assay was <3% for T4 and <6% for T3. Serum TSH was determined by immunoassay by AniLytics, (Gaithersburg, MD). The low and high sensitivities were 0.4 and >50 ng/ml, and the coefficient of variation with the assay was <4%.
Data analysis. A one-way analysis of variance (ANOVA) was used to determine a main effect due to treatment. Post hoc comparisons among the individual groups of sleep-deprived, yoked, and sham controls utilized the Bonferroni correction for multiple comparisons. For all analyses, statistical significance was considered when P < 0.05. Variance is given as means ± SD unless specifically noted as means ± SE.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Physiological variables and plasma concentrations of TSH,
T4, and T3.
Sleep-deprived rats were hyperphagic and lost weight. Daily food
consumption averaged +205 ± 21% (range: +187 to +231%) of baseline amounts on each of the last 3 days of each experiment, and
weight loss was 9.5 ± 4.8% (range:
1.0 to
15.3%) of
baseline at the time of tissue collection. Corresponding food
consumption and body weight changes in yoked controls were +148 ± 25% (range: +114 to +174%) and +3.8 ± 1.5% (range: +1.6 to
+5.3%), whereas respective values in sham control rats were +109 ± 10% (range: +100 to +125%) and +5.0 ± 4.0% (range: +1.7 to
+10.7%). Core temperature was assessed for a decline >1°C
below baseline during 24 h, indicative of advanced morbidity,
which occurred in one rat sleep deprived for 21 days.
|
Prepro-TRH and 5'-DII mRNA expression in the sleep-deprived brain.
Representative autoradiographic images in Fig.
2 illustrate the distribution of TRH
transcripts in sham control and sleep-deprived rat brain, showing
strong expression in the hypophysiotropic area of the PVN, as well as
in the LH and Rt. Quantitative hybridization results
demonstrate that prepro-TRH mRNA expression in the Rt and LH did not
differ among sleep-deprived, yoked, and sham control groups. Prepro-TRH
mRNA expression in the PVN showed a significant increase in the
sleep-deprived group vs. sham control (P < 0.02) and a
similar trend that did not reach significance in the yoked group.
|
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Sleep deprivation resulted in the characteristic spectrum of changes observed in previous studies, including weight loss and dramatically increased food consumption (22, 27) and marked hypothyroxinemia (8, 23) (Fig. 1). The progressive decline in circulating total and free T4 and T3 observed in previous studies indicates that the mechanisms responsible for decreased hormone production/release are affected early and persistently. Previous investigations suggested that alterations in central mechanisms regulating TRH synthesis and release may be responsible, since sleep-deprived rats with low thyroid hormone levels and unchanged TSH respond to exogenous TRH administration with an appropriate burst of TSH release and thyroid activation throughout the average 21-day experimental period (23). The stimulated TSH release in sleep-deprived rats is not blunted, which, when it occurs in response to food restriction (49), may be considered part of an adaptive response to lower energy requirements. The thyroid hormone profile of the sleep-deprived rat is consistent with central hypothyroidism in humans (47, 52) and resembles TRH deficiency in rats produced by lesions of the PVN, which results in decreased plasma T4 and T3 (43), decreased plasma TSH response to hypothyroidism (3, 43), but normal TSH secretion in response to exogenous TRH administration (3).
Prepro-TRH mRNA expression in the PVN showed a significant increase in the sleep-deprived group, and a similar trend in the yoked group, relative to the sham control group. TRH transcript levels in the LH and the Rt did not differ among groups (Figs. 2 and 4), consistent with preferential upregulation of TRH biosynthesis in the hypophysiotropic pathway (19, 35, 53, 57). Post hoc evaluation of individual sleep-deprived animals revealed threefold elevations in three of four animals studied at 20-21 days but not in those studied after shorter duration despite nearly comparable hypothyroxinemia. Many days also are required to observe increased prepro-TRH mRNA in experimental models of thyroid hormone depletion. T4 is diminished after chemical or surgical thyroidectomy to a concentration much lower than that observed in sleep-deprived rats within 3-6 days (29, 30, 38) without an appreciable increase in TRH transcript levels in the PVN (38). Thereafter, prepro-TRH mRNA begins to rise (38), concurrent with TRH depletion in the median eminence and much of the hypothalamus (63). In thyroidectomized animals, prepro-TRH mRNA levels reach 155-190% of the euthyroid level by 14 days (38, 42, 63) and 200-250% of euthyroid control by 21 days or longer (11, 12, 34, 38, 53). These peak changes are comparable to those observed in this study, and the lack of accumulation of TRH transcripts in 16-day sleep-deprived animals may be consistent with the more gradual progression to a severely hypothyroxinemic state during sleep deprivation (8, 23) than during experimental hypothyroidism. However, yoked animals tended to show elevated prepro-TRH mRNA expression at 20-21 days despite more moderate decreases in peripheral T4 (Fig. 4) (8, 23), indicating that the duration of hypothyroxinemia may be as important a factor as its severity in triggering this response. TRH transcripts were not elevated in one sleep-deprived rat studied after 21 days, but this was accompanied by advanced morbidity. It remains to be determined whether failure to upregulate TRH expression may result in a more severe pathological course or, conversely, whether an abrupt decline in prepro-TRH mRNA expression may be associated with the terminal phase of sleep deprivation.
A major feature distinguishing thyroidectomy and sleep deprivation is the TSH response. Sleep-deprived animals in the present study showed no change, or only slight increases, in plasma TSH at the end of the deprivation period. This is consistent with a previous study that utilized indwelling catheters for repeated blood sampling that revealed unchanged TSH across experimental days despite progressive hypothyroxinemia (23). In contrast, TSH levels rise during chemical thyroidectomy even before serum T4 or T3 shows a detectable change (40). Modest declines of serum T4 by 11-24% during 4 days of low-dose methylmercaptoimidazole or propylthiouracil treatment, with little or no change in serum T3, are associated with three- to fourfold increases in serum TSH (40). Severalfold increases in TSH occur by 4-6 days after thyroidectomy treatments (29, 30, 38), before any detectable change in prepro-TRH mRNA expression (38). As experimental hypothyroidism is prolonged beyond this initial period, TSH levels increase progressively to more than 10-fold euthyroid levels (29, 30, 38). Maintenance of 50% of normal plasma T4 in thyroidectomized animals by supplementary T4 administration for 14 days is associated with an eight- to ninefold elevation of plasma TSH concentration (16). The blunted TSH response in sleep-deprived animals, therefore, is inappropriate, given both the magnitude and duration of hypothyroxinemia and the above-demonstrated increase in TRH transcripts.
TRH deficiency produced by PVN lesions likewise results in a markedly blunted TSH response to hypothyroidism. Serum TSH concentrations in PVN-lesioned animals show only 30% of the increase seen in thyroidectomized rats with intact PVN (30, 57). This is associated with a dramatically blunted increase in TSH subunit mRNA levels in anterior pituitary in response to hypothyroidism of 2-4 wk duration (57). The threshold for thyroid hormone feedback onto the pituitary adenohypophysis is lowered in PVN-lesioned or deafferented animals (29, 41), such that even small doses of T4 are effective in completely suppressing the marginal increases in serum TSH (41). On the basis of the similarities between sleep-deprived and PVN-lesioned animals, TRH deficiency remains a more compelling explanation for thyroid axis suppression than does primary TSH deficiency, particularly in light of the fact that sleep-deprived rats respond to exogenous TRH administration with an appropriate increase in serum TSH (23). The present results, demonstrating appropriate increases in TRH transcript levels in PVN, direct attention to factors regulating the translation of prepro-TRH mRNA, processing and release of TRH peptide, and/or feedback responsiveness of pituitary thyrotrophs as the foci of altered thyroid hormone regulation in sleep-deprived animals.
An additional comparison between PVN-lesioned and sleep-deprived rats concerns the T4-to-T3 conversion enzyme 5'-DII. This enzyme is upregulated in response to decreased circulating T4, with identical concentration dependence of activities in pituitary, cerebral cortex, and BAT (54, 55). Prolonged experimental hypothyroidism increases pituitary 5'-DII activity to 400-900% of euthyroid levels (13, 48). This response is not reversed by subsequent PVN lesions, but such lesions in euthyroid animals reduce plasma T4 and T3 by 60 and 75%, respectively, yet produce only a moderate 50% elevation of pituitary 5'-DII at 1 wk (43). A previous study of rats sleep deprived for 14 days likewise revealed only a modest, statistically insignificant 40% increase in 5'-DII activity in the pituitary, whereas that in BAT was increased 100-fold (6). Supplemental T4 treatment partially reduced the BAT 5'-DII activation during sleep deprivation (6), indicating a sensitivity to T4 that would predict a larger than observed increase in pituitary 5'-DII activity. The attenuated responsiveness of pituitary 5'-DII activity may be indicative of comparable TRH deficiency in PVN-lesioned and sleep-deprived animals.
Regulation of 5'-DII in responses to changing thyroid hormone status has also been investigated in brain. Studies in cerebral cortex indicate that, although enzyme activity is primarily responsive to T4, 5'-DII mRNA expression is inversely related to T3 levels (10). Local production of T3 from T4 via 5'-DII in astrocytes (17) and tanycytes (60) of the ARC-ME has been proposed to play a specific role in signaling the PVN, which lacks 5'-DII (48). We found moderate increases in 5'-DII mRNA in ARC-ME of two sleep-deprived animals (Fig. 4), consistent with the modest 30-60% elevations observed after hypothyroxinemia resulting from fasting (18) or thyroidectomy (18, 60). The greater difficulty in achieving consistent sample locations in sections through the ARC-ME renders the quantitation of 5'-DII mRNA expression somewhat less reliable than the prepro-TRH measurements. Nevertheless, there was clearly no indication of reduced 5'-DII mRNA in the ARC-ME that might indicate local T3 excess. In comparison, 5'-DII mRNA levels in ARC-ME are decreased in euthyroid animals treated with T4 (18). Feedback action of thyroid hormones exerted at the level of the hypothalamus is considered an important factor affecting TRH release (51) as well as its production. Although we did not specifically evaluate 5'-DII mRNA levels in the periventricular area (PE), there was likewise no indication of the severalfold increase observed in this region that appears uniquely induced by fasting and associated with enhanced feedback downregulation of prepro-TRH expression in the PVN by T3 (18) (see Fig. 3).
Recent reports have described acute upregulation of 5'-DII activity in several brain regions in response to diverse stresses, including a model of forced walking with an eventual period of short-term sleep deprivation (7, 20). In the latter paradigm, increased activity was particularly prominent in frontal cortex. Because enzyme activity and mRNA levels can be regulated independently (see above), it is difficult to relate such observations to the present hybridization results. The levels of 5'-DII mRNA are much lower in cortex than ARC-ME, and we saw no suggestion of a change in transcript levels in cortex. It should be noted that reported increases in enzyme activity were more prominent after 10 h of forced mobility than after the longer intervals that included sleep deprivation (7), further indicating that this is an acute response unlikely to be relevant to the model of prolonged sleep deprivation employed in the present study.
Besides thyroid hormones, several nonthyroidal factors affect TRH translation, production, and release via short and long control loops and therefore have the potential to explain thyroid axis suppression during sleep deprivation. Hypothetically, sustained wakefulness may lead to decreased neuronal stimulation of the PVN by other brain regions. Electrical stimulation, used to mimic neuronal excitation of the PVN, results in increased TRH release through the portal system, resulting in elevated plasma TSH (15). Under certain conditions, such as exposure to cold, ascending noradrenergic and/or adrenergic projections to the PVN (reviewed in Refs. 38, 64) appear to override the normal inhibitory effects of increased T3 and produce increased TRH mRNA expression in the PVN (64). To assess functional activation in the sleep-deprived rat brain, a study of metabolic activity revealed that glucose metabolism is decreased in most hypothalamic structures except the lateral hypothalamic feeding "on" center (24). Although the PVN had not been explicitly quantitated in that study, the particularly low metabolic rates of adjacent structures indicate a decreased metabolic activity that may reflect tonic inhibition in this region. Another candidate factor, dopamine, exerts inhibitory control on TRH at two central levels, affecting both hypothalamic TRH release (4) and pituitary TSH responses to TRH (37). L-Dopa administration to hypothyroid patients lowers elevated TSH levels without changing the response to TRH (reviewed in Ref. 37). Abundant evidence shows that dopamine acts on pituitary thyrotrophs (reviewed in Ref. 37). Recent evidence has also linked dopamine to the regulation of the expression of 5'-DII mRNA in the ARC-ME via a dopamine- and cAMP-regulated phosphoprotein found in tanycytes (28), which may be relevant insofar as 5'-DII mRNA was not found to be robustly increased in this region in the present study.
Several additional nonthyroidal factors are implicated in sleep deprivation-induced hypothyroxinemia by virtue of coexisting metabolic (8, 24, 27) and host defense abnormalities (21, 26). Neuropeptide Y can induce food-seeking behavior and hyperphagia (58), which are prominent features of the sleep deprivation profile. Neuropeptide Y is contained in neurons innervating TRH cells (59) and appears to block catecholaminergic inputs to the PVN (reviewed in Ref. 38). Endotoxin and cytokine exposure, implicated in the hypercatabolic and immune-suppressed state of the sleep-deprived animal (26), produces key characteristics of central hypothyroidism, including low plasma T4 and T3 but inappropriately normal or decreased TSH levels (33, 36, 62). Conversely, thyroid axis suppression by glucocorticoids is not a candidate mechanism, because overactivation of the hypothalamicpituitary-adrenal axis has not been found in this model (23), and the present results provide direct evidence against glucocorticoid-induced reductions in prepro-TRH mRNA expression in PVN (32).
In summary, sleep deprivation produces the paradoxical combination of peripheral hypercatabolism and central hypothyroxinemia. Other clinical states to which sleep deprivation may be typically compared are associated with suppression of TRH mRNA expression in the PVN, which appears to explain suppression of the thyroid axis in these cases. In contrast, increased prepro-TRH mRNA expression was demonstrated in the sleep-deprived brain, consistent with compensatory TRH biosynthesis. These data suggest that the locus of abnormal thyroid hormone regulation lies after prepro-TRH transcription, at steps up to and including release of the mature peptide. Features of the sleep-deprived profile point to nonthyroidal control mechanisms, such as inhibitory neurotransmitters and neuromodulators, including those related to immunity, as potential candidates mediating central hypothyroxinemia induced by sleep deprivation.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank Dr. Qihong Zhou for preparation of frozen sections, and Jason M. Scott for technical assistance.
![]() |
FOOTNOTES |
---|
Research support was provided by the National Institute of Neurological Disorders and Stroke (NS-38733) and the National Heart, Lung, and Blood Institute (HL-59271).
Address for reprint requests and other correspondence: C. A. Everson, MCW Neurology Research 151, VA Medical Center, Bldg. 70, 5000 West National Ave., Milwaukee, WI 53295 (E-mail: ceverson{at}mcw.edu).
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.
March 19, 2002;10.1152/ajpendo.00558.2001
Received 19 December 2001; accepted in final form 8 March 2002.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Anonymous. Treatment of Sleep Disorders of Older
People. NIH Consens Dev Conf Consens Statement, 1990, vol. 8, no.
3.
2.
Anonymous
Wake up America: a national sleep alert.
In: Executive Summary and Executive Report to the United States Congress and to the Secretary of the US Department of Health and Human Services. Washington, DC: National Commission on Sleep Disorders Research, 1993, p. 1-76.
3.
Aizawa, T,
and
Greer MA.
Delineation of the hypothalamic area controlling thyrotropin secretion in the rat.
Endocrinology
109:
1731-1738,
1981[Abstract].
4.
Andersson, K,
and
Eneroth P.
Thyroidectomy and central catecholamine neurons of the male rat. Evidence for the existence of an inhibitory dopaminergic mechanism in the external layer of the median eminence and for a facilitatory noradrenergic mechanism in the paraventricular hypothalamic nucleus regulating TSH secretion.
Neuroendocrinology
45:
14-27,
1987[ISI][Medline].
5.
Aurell, J,
and
Elmqvist D.
Sleep in the surgical intensive care unit: continuous polygraphic recording of sleep in nine patients receiving postoperative care.
Br Med J
290:
1029-1032,
1985[ISI][Medline].
6.
Balzano, S,
Bergmann BM,
Gilliland MA,
Silva JE,
Rechtschaffen A,
and
Refetoff S.
Effect of total sleep deprivation on 5'-deiodinase activity of rat brown adipose tissue.
Endocrinology
127:
882-890,
1990[Abstract].
7.
Baumgartner, A,
Hiedra L,
Pinna G,
Eravci M,
Prengel H,
and
Meinhold H.
Rat brain type II 5'-iodothyronine deiodinase activity is extremely sensitive to stress.
J Neurochem
71:
817-826,
1998[ISI][Medline].
8.
Bergmann, BM,
Everson CA,
Kushida CA,
Fang VS,
Leitch CA,
Schoeller DA,
Refetoff S,
and
Rechtschaffen A.
Sleep deprivation in the rat. V. Energy use and mediation.
Sleep
12:
31-41,
1989[ISI][Medline].
9.
Bergmann, BM,
Kushida CA,
Everson CA,
Gilliland MA,
Obermeyer W,
and
Rechtschaffen A.
Sleep deprivation in the rat. II. Methodology.
Sleep
12:
5-12,
1989[ISI][Medline].
10.
Burmeister, LA,
Pachucki J,
and
St. Germain DL.
Thyroid hormones inhibit type 2 iodothyronine deiodinase in the rat cerebral cortex by both pre- and posttranslational mechanisms.
Endocrinology
138:
5231-5237,
1997
11.
Calza, L,
Aloe L,
and
Giadino L.
Thyroid hormone-induced plasticity in the adult rat brain.
Brain Res Bull
44:
549-557,
1997[ISI][Medline].
12.
Ceccatelli, S,
Giardino L,
and
Calza L.
Response of hypothalamic peptide mRNAs to thyroidectomy.
Neuroendocrinology
56:
694-703,
1992[ISI][Medline].
13.
Croteau, W,
Davey JC,
Galton VA,
and
St. Germain DL.
Cloning of the mammalian type II iodothyronine deiodinase. A selenoprotein differentially expressed and regulated in human and rat brain and other tissues.
J Clin Invest
98:
405-417,
1996
14.
Cureton-Lane, RA,
and
Fontaine DK.
Sleep in the pediatric ICU: an empirical investigation.
Am J Crit Care
6:
56-63,
1997[Medline].
15.
De Greef, WJ,
Rondeel JM,
van Haasteren GA,
Klootwijk W,
and
Visser TJ.
Regulation of hypothalamic TRH production and release in the rat.
Acta Med Austriaca
19, Suppl1:
77-79,
1992.
16.
DeVito, WJ,
Connors JM,
and
Hedge GA.
The pituitary TSH response to TRH is inversely related to the plasma TSH concentration and directly related to the pituitary TSH content during hypothyroidism in the rat.
Acta Endocrinol (Copenh)
114:
27-36,
1987[Medline].
17.
Diano, S,
Naftolin F,
Goglia F,
Csernus V,
and
Horvath TL.
Monosynaptic pathway between the arcuate nucleus expressing glial type II iodothyronine 5'-deiodinase mRNA and the median eminence-projective TRH cells of the rat paraventricular nucleus.
J Neuroendocrinol
10:
731-742,
1998[ISI][Medline].
18.
Diano, S,
Naftolin F,
Goglia F,
and
Horvath TL.
Fasting-induced increase in type II iodothyronine deiodinase activity and messenger ribonucleic acid levels is not reversed by thyroxine in the rat hypothalamus.
Endocrinology
139:
2879-2884,
1998
19.
Dyess, EM,
Segerson TP,
Liposits Z,
Paull WK,
Kaplan MM,
Wu P,
Jackson IM,
and
Lechan RM.
Triiodothyronine exerts direct cell-specific regulation of thyrotropin-releasing hormone gene expression in the hypothalamic paraventricular nucleus.
Endocrinology
123:
2291-2297,
1988[Abstract].
20.
Eravci, M,
Pinna G,
Meinhold H,
and
Baumgartner A.
Effects of pharmacological and nonpharmacological treatments on thyroid hormone metabolism and concentrations in rat brain.
Endocrinology
141:
1027-1040,
2000
21.
Everson, CA.
Sustained sleep deprivation impairs host defense.
Am J Physiol Regulatory Integrative Comp Physiol
265:
R1148-R1154,
1993
22.
Everson, CA,
Bergmann BM,
and
Rechtschaffen A.
Sleep deprivation in the rat. III. Total sleep deprivation.
Sleep
12:
13-21,
1989[ISI][Medline].
23.
Everson, CA,
and
Reed HL.
Pituitary and peripheral thyroid hormone responses to thyrotropin-releasing hormone during sustained sleep deprivation in freely moving rats.
Endocrinology
136:
1426-1434,
1995[Abstract].
24.
Everson, CA,
Smith CB,
and
Sokoloff L.
Effects of prolonged sleep deprivation on local rates of cerebral energy metabolism in freely moving rats.
J Neurosci
14:
6769-6778,
1994[Abstract].
26.
Everson, CA,
and
Toth LA.
Systemic bacterial invasion induced by sleep deprivation.
Am J Physiol Regulatory Integrative Comp Physiol
278:
R905-R916,
2000
27.
Everson, CA,
and
Wehr TA.
Nutritional and metabolic adaptations to prolonged sleep deprivation in the rat.
Am J Physiol Regulatory Integrative Comp Physiol
264:
R376-R387,
1993
28.
Fekete, C,
Mihaly E,
Herscovici S,
Salas J,
Tu H,
Larsen PR,
and
Lechan RM.
DARPP-32 and CREB are present in type 2 iodothyronine deiodinase-producing tanycytes: implications for the regulation of type 2 deiodinase activity.
Brain Res
862:
154-161,
2000[ISI][Medline].
29.
Fukuda, H,
and
Greer MA.
The effect of basal hypothalamic isolation on pituitary-thyroid activity and the response to propylthiouracil.
Endocrinology
100:
911-917,
1977[Abstract].
30.
Greer, MA,
Sato N,
Wang X,
Greer SE,
and
McAdams S.
Evidence that the major physiological role of TRH in the hypothalamic paraventricular nuclei may be to regulate the set-point for thyroid hormone negative feedback on the pituitary thyrotroph.
Neuroendocrinology
57:
569-575,
1993[ISI][Medline].
31.
Joseph-Bravo, P,
Uribe RM,
Vargas MA,
Perez-Martinez L,
Zoeller T,
and
Charli JL.
Multifactorial modulation of TRH metabolism.
Cell Mol Neurobiol
18:
231-247,
1998[ISI][Medline].
32.
Kakucska, I,
Qi Y,
and
Lechan RM.
Changes in adrenal status affect hypothalamic thyrotropin-releasing hormone gene expression in parallel with corticotropin-releasing hormone.
Endocrinology
137:
2795-2802,
1995.
33.
Kakucska, I,
Romero LI,
Clark BD,
Rondeel JM,
Qi Y,
Alex S,
Emerson CH,
and
Lechan RM.
Suppression of thyrotropin-releasing hormone gene expression by interleukin-1-beta in the rat: implications for nonthyroidal illness.
Neuroendocrinology
59:
129-137,
1994[ISI][Medline].
34.
Kim, SY,
Post RM,
and
Rosen JB.
Differential regulation of basal and kindling-induced TRH mRNA expression by thyroid hormone in the hypothalamic and limbic structures.
Neuroendocrinology
63:
297-304,
1996[ISI][Medline].
35.
Koller, KJ,
Wolff RS,
Warden MK,
and
Zoeller RT.
Thyroid hormones regulate levels of thyrotropin-releasing-hormone mRNA in the paraventricular nucleus.
Proc Natl Acad Sci USA
84:
7329-7333,
1987[Abstract].
36.
Kondo, K,
Harbuz MS,
Levy A,
and
Lightman SL.
Inhibition of the hypothalamic-pituitary-thyroid axis in response to lipopolysaccharide is independent of changes in circulating corticosteroids.
Neuroimmunomodulation
4:
188-194,
1997[ISI][Medline].
37.
Krulich, L.
Neurotransmitter control of thyrotropin secretion.
Neuroendocrinology
35:
139-147,
1982[ISI][Medline].
38.
Lechan, RM,
and
Toni R.
Thyrotropin-releasing hormone neuronal systems in the central nervous system.
In: Endocrinology, edited by Nemeroff C. Boca Raton, FL: CRC, 1992, p. 279-330.
39.
Lechan, RM,
Wu P,
Jackson IM,
Wolf H,
Cooperman S,
Mandel G,
and
Goodman RH.
Thyrotropin-releasing hormone precursor: characterization in rat brain.
Science
231:
159-161,
1986[ISI][Medline].
40.
Mannisto, PT,
Ranta T,
and
Leppaluoto J.
Effects of methylmercaptoimidazole (MMI), propylthiouracil (PTU), potassium perchlorate (KClO4) and potassium iodide (KI) on the serum concentrations of thyrotrophin (TSH) and thyroid hormones in the rat.
Acta Endocrinol (Copenh)
91:
271-281,
1979[Medline].
41.
Martin, JB,
Boshans R,
and
Reichlin S.
Feedback regulation of TSH secretion in rats with hypothalamic lesions.
Endocrinology
87:
1032-1040,
1970[ISI][Medline].
42.
Muller, LM,
and
Kennedy JA.
Quantification of rat pre-pro-thyrotropin releasing hormone (TRH) mRNA by reverse transcription-polymerase chain reaction using external and internal standardization.
J Neurosci Methods
68:
269-274,
1996[ISI][Medline].
43.
Murakami, M,
Tanaka K,
Greer MA,
and
Mori M.
Anterior pituitary type II thyroxine 5'-deiodinase activity is not affected by lesions of the hypothalamic paraventricular nucleus which profoundly depress pituitary thyrotropin secretion.
Endocrinology
123:
1676-1681,
1988[Abstract].
44.
Nowak, TS, Jr.
Localization of 70 kDa stress protein mRNA induction in gerbil brain after ischemia.
J Cereb Blood Flow Metab
11:
432-439,
1991[ISI][Medline].
45.
Pilcher, JJ,
Bergmann BM,
Refetoff S,
Fang VS,
and
Rechtschaffen A.
Sleep deprivation in the rat. XIII. The effect of hypothyroidism on sleep deprivation symptoms.
Sleep
14:
201-210,
1991[ISI][Medline].
46.
Rechtschaffen, A,
Bergmann BM,
Everson CA,
Kushida CA,
and
Gilliland MA.
Sleep deprivation in the rat. X. Integration and discussion of the findings.
Sleep
12:
68-87,
1989[ISI][Medline].
47.
Refetoff, S.
Thyroid function tests and effects of drugs on thyroid function.
In: Endocrinology, edited by DeGroot LJ. Philadelphia, PA: Saunders, 1989, p. 590-639.
48.
Riskind, PN,
Kolodny JM,
and
Larsen PR.
The regional hypothalamic distribution of type II 5'-monodeiodinase in euthyroid and hypothyroid rats.
Brain Res
420:
194-198,
1987[ISI][Medline].
49.
Rodriguez, F,
Mellado M,
Montoya E,
and
Jolin T.
Sensitivity of thyrotropin secretion to TSH-releasing hormone in food-restricted rats.
Acta Endocrinol (Copenh)
124:
194-202,
1991[Medline].
50.
Rondeel, JM,
de Greef WJ,
Klootwijk W,
and
Visser TJ.
Effects of hypothyroidism on hypothalamic release of thyrotropin-releasing hormone in rats.
Endocrinology
130:
651-656,
1992[Abstract].
51.
Rondeel, JM,
de Greef WJ,
van der Schoot P,
Karels B,
Klootwijk W,
and
Visser TJ.
Effect of thyroid status and paraventricular area lesions on the release of thyrotropin-releasing hormone and catecholamines into hypophysial portal blood.
Endocrinology
123:
523-527,
1988[Abstract].
52.
Samuels, MH,
and
Ridgway EC.
Central hypothyroidism.
Endocrinol Metab Clin North Am
21:
903-919,
1992[ISI][Medline].
53.
Segerson, TP,
Kauer J,
Wolfe HC,
Mobtaker H,
Wu P,
Jackson IM,
and
Lechan RM.
Thyroid hormone regulates TRH biosynthesis in the paraventricular nucleus of the rat hypothalamus.
Science
238:
78-80,
1987[ISI][Medline].
54.
Silva, JE,
and
Larsen PR.
Interrelationships among thyroxine, growth hormone, and the sympathetic nervous system in the regulation of 5'-iodothyronine deiodinase in rat brown adipose tissue.
J Clin Invest
77:
1214-1223,
1986[ISI][Medline].
55.
Silva, JE,
and
Leonard JL.
Regulation of rat cerebrocortical and adenohypophyseal type II 5'-deiodinase by thyroxine, triiodothyronine, and reverse triiodothyronine.
Endocrinology
116:
1627-1635,
1985[Abstract].
56.
Szymusiak, R,
and
Satinoff E.
Maximal REM sleep time defines a narrower thermoneutral zone than does minimal metabolic rate.
Physiol Behav
26:
687-690,
1981[ISI][Medline].
57.
Taylor, T,
Wondisford FE,
Blaine T,
and
Weintraub BD.
The paraventricular nucleus of the hypothalamus has a major role in thyroid hormone feedback regulation of thyrotropin synthesis and secretion.
Endocrinology
126:
317-324,
1990[Abstract].
58.
Tomaszuk, A,
Simpson C,
and
Williams G.
Neuropeptide Y, the hypothalamus and the regulation of energy homeostasis.
Horm Res
46:
53-58,
1996[ISI][Medline].
59.
Toni, R,
Jackson IM,
and
Lechan RM.
Neuropeptide-Y-immunoreactive innervation of thyrotropin-releasing hormone-synthesizing neurons in the rat hypothalamic paraventricular nucleus.
Endocrinology
126:
2444-2453,
1990[Abstract].
60.
Tu, HM,
Kim SW,
Salvatore D,
Bartha T,
Legradi G,
Larsen PR,
and
Lechan RM.
Regional distribution of type 2 thyroxine deiodinase messenger ribonucleic acid in rat hypothalamus and pituitary and its regulation by thyroid hormone.
Endocrinology
138:
3359-3368,
1997
61.
Utiger, RD.
Thyrotropin-releasing hormone and thyrotropin secretion.
J Lab Clin Med
109:
327-335,
1987[ISI][Medline].
62.
Van Haasteren, GA,
van der Meer MJ,
Hermus AR,
Linkels E,
Klootwijk W,
Kaptein E,
van Toor H,
Sweep CG,
Visser TJ,
and
de Greef WJ.
Different effects of continuous infusion of interleukin-1 and interleukin-6 on the hypothalamic-hypophysial-thyroid axis.
Endocrinology
135:
1336-1345,
1994[Abstract].
63.
Yamada, M,
Satoh T,
Monden T,
Murakami M,
Iriuchijima T,
Wilber JF,
and
Mori M.
Influences of hypothyroidism on TRH concentrations and preproTRH mRNA levels in rat hypothalamus: a simple and reliable method to detect preproTRH mRNA level.
Neuroendocrinology
55:
317-320,
1992[ISI][Medline].
64.
Zoeller, RT,
Kabeer N,
and
Albers HE.
Cold exposure elevates cellular levels of messenger ribonucleic acid encoding thyrotropin-releasing hormone in paraventricular nucleus despite elevated levels of thyroid hormones.
Endocrinology
127:
2955-2962,
1990[Abstract].