Departments of 1 Biochemistry and 2 Microbiology and Immunology, East Carolina University School of Medicine, Greenville 27834; and 3 IBM Life Sciences, Research Triangle Park, North Carolina 27709
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ABSTRACT |
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Considerable evidence suggests that there are ethnic differences in lipid metabolism between African American and Caucasian women, which may result in increased synthesis of fat in adipose tissue. The purpose of this study was to measure the in vitro rates of [14C]glucose incorporation into the glyceride-glycerol backbone of triglycerides (TG) and diglycerides (DG) in abdominal subcutaneous (SAT) and omental adipose tissue (OAT). Morbidly obese [African American (n = 15): body mass index (BMI) = 45 ± 2.3; Caucasian (n = 18): BMI = 51 ± 2.3] and preobese [African American (n = 7): BMI = 27 ± 1.0; Caucasian (n = 7): BMI = 25 ± 1.0] women were examined in this study. There were no significant differences in the rates of synthesis of either TG or DG in SAT of either preobese or obese women. On the other hand, both preobese and obese African American women had higher rates of synthesis of TG in OAT compared with their Caucasian counterparts. This increase in TG synthesis in OAT was not due to differences in cell size or rates of reesterification. Thus African American woman have an increased capacity to synthesize TG in OAT compared with Caucasian women, which may contribute to the higher prevalence of obesity in African American women.
triglyceride synthesis; obesity and ethnicity
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INTRODUCTION |
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NUMEROUS STUDIES HAVE SHOWN that there are differences in lipid metabolism between African American and Caucasian women. It has been shown that African American women have lower plasma triglyceride (TG) and higher HDL cholesterol levels than Caucasians (24, 30-34). These differences in plasma TG may be due to an increased uptake of TG-rich lipoproteins from circulation that is mediated by lipoprotein lipase (LPL) or a decreased synthesis of VLDL particles in liver. Recently, Friday et al. (15) have shown that lean African American males have a faster rate of clearance of TG from circulation partly due to higher postheparin plasma LPL activity. Despres et al. (8) examined the effects of race on plasma lipids and LPL activity in men and women as part of the HERITAGE Family Study. They found that, irrespective of sex, blacks had higher LPL activity and lower hepatic lipase activity than whites, suggesting that African American women have an increased clearance of TG from circulation. This increased uptake of TG may result in an increased synthesis and storage of fat in African American women, which may in part contribute to the increased weight gain and obesity seen in African American women (13, 14, 19-21).
The purpose of this study was to examine possible differences in the in vitro rates of newly synthesized glycerides in African American and Caucasian women. This was accomplished by measuring the rates of incorporation of [14C]glucose into TG and diglycerides (DG) in abdominal subcutaneous (SAT) and omental adipose tissue (OAT) from African American and Caucasian women. In addition, the rates of reesterification were evaluated in a subset of obese women to determine whether there were differences in the recycling of free fatty acids (FFA).
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METHODS |
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Subjects. Four groups of women participated in this study: preobese [body mass index (BMI) 24.5-28.8] African Americans and Caucasians and morbidly obese (BMI > 35) African Americans and Caucasians. The participants were free of vascular disease, diabetes, cancer, or emotional distress and were not taking medications that might affect carbohydrate or lipid metabolism. The subjects were not taking hormone replacement therapy or birth control pills. The women who participated in this study were recruited consecutively over a period of 18 mo from the Department of Surgery at East Carolina School of Medicine and were divided into groups on the basis of BMI according to the guidelines of the World Health Organization; preobese ranged in BMI from 24.5 to 28.8, and the morbidly obese ranged in BMI from 35 to 70 kg/m2. African American women were included in this study only if their parents and grandparents were of African American descent. Body mass and height were recorded to the nearest 0.1 kg and 0.1 cm, respectively, and BMI was calculated. Waist-to-hip ratio (WHR) was measured only in the preobese subjects due to inherent inaccuracies of waist and hip measurements in morbidly obese subjects. WHR was measured as the ratio of the minimal waist circumference to the maximal circumference of the buttocks. Forty-seven women were recruited for this study: 18 obese Caucasian, 15 obese African American, 7 preobese Caucasian, and 7 preobese African American. SAT and OAT were obtained from these volunteers during abdominal surgery for gastric bypass or total abdominal hysterectomy. Abdominal SAT was dissected from the epigastric region of the abdomen, and abdominal OAT was dissected from the greater omentum. Blood samples were collected 1 wk before surgery, and plasma was analyzed for glucose and insulin concentrations as previously described (24). Written consent was obtained from all of the subjects after they were informed of the nature of the study. The Institutional Review Board for human subject research approved the protocols used in this study.
Plasma analyses.
Blood was collected from the subjects after a 12-h fast, and a
preservative solution containing sodium azide (50 mg/ml) and aprotinin
(1 TIU/ml) was added (2 µl/ml blood). Plasma was prepared by
centrifugation, aliquoted, and stored at 80°C until analyzed. Samples were analyzed spectrophotometrically for glucose (16-UV; Sigma
Chemical, St. Louis, MO) and by microparticle enzyme immunoassay for
insulin (IMX; Abbott Labs, Abbott Park, IL).
Incubations. To measure possible differences in glyceride synthesis between the races, we used the method described by Edens et al. (11). This method gives an accurate assessment of glyceride synthesis with the use of [14C]glucose as a substrate. It has been shown that glucose is incorporated solely into the glyceride-glycerol backbone and that only negligible amounts are incorporated into FFA. With the additional measurements of esterification and lipolysis, the rate of reesterification can be determined to assess the amount of recycling that occurs during synthesis. Human adipose tissue was obtained from surgery and transported to the laboratory immediately in RPMI 1640 (Invitrogen, Frederick, MD). The tissue was washed with phosphate-buffered saline (PBS), cleaned, minced, and preincubated in incubation medium [4% essentially fatty acid-free BSA (Sigma Chemical) and 4 mM glucose in Krebs-Ringer bicarbonate buffer] for 30 min at 37°C in a 95% O2-5% CO2 atmosphere. After incubation, 100-mg pieces were weighed and transferred to the assay tubes containing incubation medium, [preincubation buffer containing 0.5 mM oleic acid and radioactive substrates [14C]glucose (final specific activity 0.4 uCi/µmol) and [3H]oleate (final specific activity 20 µCi/mol)]. Incubations occurred for 1 h at 37°C in a 95% O2-5% CO2 atmosphere. All assays were run in triplicate. After incubation, tissues were washed with PBS to remove unincorporated label, blotted dry, and transferred to a new tube for homogenization. Homogenates were extracted with a 2:1 chloroform-methanol mixture and centrifuged. The organic phase was transferred to a preweighed vial and allowed to evaporate and was then reweighed to determine lipid weight. A known amount of sample was loaded onto silica plates, and the lipids were separated by thin-layer chromatography using heptane-isopropyl ether-acetic acid (60:40:3). Bands corresponding to DG and TG were scraped and counted for radioactivity.
Cell size determination.
Adipocytes were prepared according to the method of Rodbell
(27), and adipocyte cell size was determined according to
the method of Di Girolamo et al. (9). One gram of adipose
tissue was digested, the average diameter of >150 cells was determined by ocular gradient, and total lipid was extracted from a 100-mg piece
of adipose to determine the cell volume. The average cell diameter was
converted to the mean fat cell volume by the equation (V = D3/6) and multiplied by the density of lipid, 0.915 g/ml, to give the mean fat cell TG content. The TG content of tissue
was divided by the mean fat cell TG content to give the number of cells
per gram tissue.
Lipolysis. Glycerol concentration in the medium was determined for the experiments that measured rates of reesterification. Glycerol was determined as described by Boobis and Maughan (5), in which medium from the incubation tubes was removed before termination of the reaction, and the glycerol concentration was determined by measuring the fluorescence at 420 nm.
Reesterification.
The percentage of reesterification was calculated as previously
described by Leibel and Hirsch (22). Reesterification is a
measure of the incorporation of unlabeled fatty acids into newly synthesized glycerides during the incubation. The rate of
reesterification of fatty acids is the difference between esterified
fatty acids accounted for by [3H]oleate and the total
moles of fatty acids that must have been esterified to give
[14C]glyceride formation. First, the rate of unlabeled
FFA must be calculated as: E(U) = {3 · (nmol [14C]TG) nmol
[3H]TG + 2 · (nmol
[14C]DG)
nmol [3H]DG}, where the
3H-labeled glycerides represent the
[3H]oleate esterified to [14C]glucose
backbone. Second, because the rate of glycerol release can be measured
during the incubation, it is then possible to calculate the percentage
of those FFA released by TG hydrolysis (L = 3 · moles of glycerol released) that were
reesterified to newly synthesized TG or DG. Therefore, the percentage
of reesterification %RE = [E(U)/(3 · L)] · 100.
Statistics. To examine significant differences between the races within each group (obese African American vs. obese Caucasian)(preobese African American vs. preobese Caucasian), Student's t-tests were performed, and P < 0.05 implied statistical significance. All analysis was performed on SPSS version 9.0 (SPSS, Chicago, IL).
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RESULTS |
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Table 1 shows the characteristics of
the subjects in this study. There were no significant differences in
age, BMI, glucose, or insulin concentrations between the races in
either the preobese or obese groups. WHR measurements in preobese
subjects were also similar between the races. There were no significant
differences in the average cell diameter of obese women in either SAT
or OAT. Preobese African American women had a larger SAT cell diameter compared with that of preobese Caucasian women (P < 0.05), but there were no differences in OAT cell size.
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The rates of incorporation of [14C]glucose into TG (Fig.
1A) and DG (Fig.
1B) of obese women are shown in Fig. 1. There were no
significant differences in the rates of newly synthesized TG or DG in
SAT between the races. Obese African American women had significantly
higher rates of TG synthesis in OAT compared with obese Caucasian women
(P = 0.003; Fig. 1A). There were no
differences in newly synthesized DG in OAT of the obese women. Similar
to previous reports (11, 12), DG accumulation accounted
for 21-24% in the SAT depending on the group, whereas OAT had a
larger DG accumulation, with 31-41% depending on the group (Fig.
1B).
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The rates of incorporation of [14C]glucose into TG (Fig.
2A) and DG (Fig.
2B) of preobese women are shown in Fig. 2. There were no
significant differences in the rates of newly synthesized TG or DG in
SAT between the races. Preobese African American women had
significantly higher rates of TG synthesis in OAT compared with
preobese Caucasian women (P < 0.001; Fig.
2A). There were no differences in newly synthesized DG in
OAT of the preobese women. DG accumulation accounted for 21-29%
in the SAT depending on the group, whereas OAT had a larger DG
accumulation, with 30-53% depending on the group (Fig.
1B).
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To determine whether the increase in the capacity of OAT was due to an
increase in the recycling of FFA, we measured the rate of
reesterification in a subset of the obese group (Table
2). Basal measurements of lipolysis and
esterification were similar in both groups. There were no statistical
differences found between the races in any of the parameters calculated
for reesterification. The rates of reesterification were 34-37%
in SAT and 26-30% in OAT, depending on the group. Therefore, it
appears that the increased synthesis found in OAT of African American
women was not due to significant differences in reesterification.
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To better evaluate the rates of glyceride synthesis, we examined the
relationship between cell size and the rates of incorporation of
glucose into total lipid (TG + DG) in both adipose tissue depots. As expected, total lipid synthesis from glucose was significantly correlated with cell size in both depots and in both races (Fig. 3, A and B). There
were no significant differences between the slopes of the regression
lines in SAT (P = 0.34) between the races; however, the
slopes of the regression lines were significantly different in OAT
(P < 0.001) between African American and Caucasian women.
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DISCUSSION |
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The novel findings of this study are that African American women have an increased capacity to synthesize TG from glucose in OAT compared with Caucasian women regardless of the presence of obesity. This increase in synthesis is not due to differences in cell size or the rates of reesterification. Also, we confirmed previous reports that larger cells have higher rates of synthesis than smaller cells by showing that the rates of synthesis of glyceride-glycerol correlated with average cell diameter in both adipose tissue depots.
The rates of incorporation of glucose into TG and DG measured in this study are in agreement with previous reports (11, 22), and these results confirm previous reports that obesity is associated with an increase in cell size and a concomitant increase in glyceride synthesis (4, 16, 18, 28, 29), indicating that larger cells synthesize more fat than smaller cells whether they are from an obese or a lean subject. SAT tends to have higher rates of glyceride synthesis than OAT, which is probably due to a larger average cell size in SAT than in OAT, as seen in this study (average obese SAT 123.5 vs. OAT 98.0 µm and average preobese SAT 111.0 vs. OAT 81.7 µm) and in others (11, 25). In addition, SAT had a lower percentage of DG accumulation than OAT (24 vs. 39%, respectively), indicating that the synthesis of TG accounts for the majority of newly synthesized glycerides.
Preobese and obese African American women had a significant increase in the synthesis of glycerides in vitro in OAT compared with their Caucasian counterparts. The increased rate of TG synthesis in OAT tended to reduce the percentage of DG accumulation in OAT, but this decrease was not significantly different. These data suggest that African American women have a higher capacity to acquire the substrates needed for glyceride synthesis compared with Caucasian women, which may suggest that African American women tend to accumulate more visceral fat than Caucasian women. However, the result regarding visceral fat deposition in African American and Caucasian women seems to be inconclusive. Although several studies have reported that African American women have less visceral fat than Caucasian women, in most of these studies the African American women tended to have higher BMIs than Caucasian women. Furthermore, many of these studies reported less visceral adipose tissue relative to total adipose tissue or, after correction for total body fat mass, waist circumference or BMI (2, 7, 8, 17, 23). In addition, some studies even reported that African American women had an increase in SAT compared with Caucasians, which resulted in an overall increase in total adipose tissue (8, 17). Although the amount of visceral fat was not determined in our subjects, the BMI and WHR of the preobese subjects were not significantly different between the races, suggesting that there were no differences in visceral fat deposition between our groups. Because we found that both preobese and obese African American women have increased rates of synthesis in OAT, this may indicate that the OAT of African American women is metabolically more active than the OAT of Caucasian women. However, the rates of lipolysis in our subsets of obese patients were not different, nor were there differences in the rates of reesterification. On the other hand, an important observation in this study is that, although African American women have an increased capacity to synthesize fat in OAT compared with Caucasian women, the correlation of cell size to total lipid synthesis in OAT was stronger in the Caucasian women. This suggests that African American women have a higher and less dramatic increase in synthesis as their fat cells become larger, whereas Caucasian women have a lower but more rapid increase in synthesis as their fat cells become larger. However, because these experiments were carried out under in vitro conditions, the preferential increase in synthesis in OAT in vitro needs to be explored further to determine whether these results play a significant role in vivo.
Surprisingly, there were no differences in the rates of synthesis in SAT between the races in either preobese or obese women. Preobese African American women did have a significantly larger average cell size in SAT; however, the rate of glyceride synthesis was not statistically different. The significance of an increase in SAT cell size in preobese African American women may be linked to the availability of substrates needed for glyceride synthesis. We (6) and others (15) have recently reported that lean African American women have a faster clearance of lipid from circulation after a fat load, due in part to an increase in postheparin LPL activity and expression in SAT. This suggests that, although the capacity to synthesize glycerides in vitro was similar between the races, in vivo, lean and preobese African American women may have an increased availability of substrate to SAT and, therefore, an increased capacity to synthesize fat.
Although the exact mechanisms underlying the preferential increase in glyceride synthesis in OAT of African American women need to be more thoroughly examined in future studies, it seems reasonable to speculate that these differences may be due to increased enzyme activity or increased availability of substrates. To date, there have been no measurements of the activities of the enzymes that are involved in the pathway of glyceride synthesis between the races. Therefore, examination of key enzymes that may influence the regulation of glyceride synthesis, such as phosphofructokinase, glycerol-3-phosphate dehydrogenase, diacylglycerol acyltransferase, and glycerol phosphate acyltransferase, is needed. In addition, the uptake of the substrates needed for TG synthesis, i.e., glucose and FFA, is regulated by distinct processes. Glucose transport into the cell is regulated by glucose transporters, GLUT1 at basal and GLUT4 upon insulin stimulation (26). Our experiments measured rates of glyceride synthesis under basal conditions. This may mean that increased glyceride synthesis would be due to an increase in basal glucose transport, mediated by GLUT1. This suggests that African American women have a higher transport than Caucasian women of glucose uptake that might be related to a higher expression of GLUT1. Therefore, direct measurements of glucose transport and utilization of glucose in adipocytes are needed. Fatty acid transporters have been shown to mediate FFA uptake into adipocytes (1, 3). There has been considerable work on the identification and characterization of FFA transporters, but further work is needed to better understand their role in glyceride synthesis. In vivo, the availability of FFA to the cell is mediated in part by LPL (10). Recent evidence has shown that lean and preobese African Americans have higher postheparin LPL activity than Caucasians (6, 8), suggesting that African Americans have access to an excess of FFA in circulation. The increase in LPL activity found in lean and preobese African Americans may indicate that they have an increased availability of substrate needed for glyceride synthesis, which may accelerate the accumulation of fat and, therefore, the onset of obesity. However, this increased availability of substrate due to LPL is attenuated in the obese African American women, indicating that there must also be an enhanced uptake of FFA in both preobese and obese African American women that helps maintain an increased rate of glyceride synthesis. Therefore, measurements of FFA uptake and incorporation into adipocytes in African Americans are needed.
Taken together, these data suggest that the mechanisms of TG synthesis may be different between African American and Caucasian women. However, it appears as though these differences are manifested primarily in OAT. This suggests that OAT may have an increased ability to acquire substrates from circulation. Because there are no significant differences in the rate of reesterification between the races, perhaps the uptake of glucose, which serves as the backbone of the lipid, may be a key component to the differences seen between these groups. Therefore, future studies should be directed toward examining the uptake of both glucose and FFA into adipocytes, as well as key enzyme activities, to better understand the ethnic differences in glyceride synthesis between African American and Caucasian women.
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ACKNOWLEDGEMENTS |
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We thank Tom Green and Rania Abdel-Rahman for their technical assistance.
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FOOTNOTES |
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This work was supported in part by a grant from the University of North Carolina Institute of Nutrition and by a grant from the American Diabetes Association.
Address for reprint requests and other correspondence: H. A. Barakat, Dept. of Biochemistry, East Carolina Univ. School of Medicine, 600 Moye Blvd., Greenville, NC 27858 (E-mail: barakath{at}mail.ecu.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.
July 30, 2002;10.1152/ajpendo.00225.2002
Received 23 May 2002; accepted in final form 25 July 2002.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Abumrad, N,
Coburn C,
and
Ibrahimi A.
Membrane proteins implicated in long-chain fatty acid uptake by mammalian cells: CD36, FATP and FABPm.
Biochim Biophys Acta
1441:
4-13,
1999[ISI][Medline].
2.
Albu, JB,
Murphy L,
Frager DH,
Johnson JA,
and
Pi-Sunyer FX.
Visceral fat and race-dependent health risks in obese nondiabetic premenopausal women.
Diabetes
46:
456-462,
1997[Abstract].
3.
Berk, PD,
Wada H,
Horio Y,
Potter BJ,
Sorrentino D,
Zhou SL,
Isola LM,
Stump D,
Kiang CL,
and
Thung S.
Plasma membrane fatty acid-binding protein and mitochondrial glutamic-oxaloacetic transaminase of rat liver are related.
Proc Natl Acad Sci USA
87:
3484-3488,
1990[Abstract].
4.
Bjorntorp, P,
and
Karlsson M.
Triglyceride synthesis in human subcutaneous adipose tissue cells of different size.
Eur J Clin Invest
1:
112-117,
1970[ISI][Medline].
5.
Boobis, LH,
and
Maughan RJ.
A simple one-step enzymatic fluorometric method for the determination of glycerol in 20 microliters of plasma.
Clin Chim Acta
132:
173-179,
1983[ISI][Medline].
6.
Bower, JF,
Deshaies Y,
Pfeifer MA,
Tanenberg RJ,
and
Barakat H.
Differences in lipoprotein lipase between African American and Caucasian women (Abstract).
Diabetes
50:
A305,
2001.
7.
Conway, JM,
Yanovski SZ,
Avila NA,
and
Hubbard VS.
Visceral adipose tissue differences in black and white women.
Am J Clin Nutr
61:
765-771,
1995[Abstract].
8.
Despres, JP,
Couillard C,
Gagnon J,
Bergeron J,
Leon AS,
Rao DC,
Skinner JS,
Wilmore JH,
and
Bouchard C.
Race, visceral adipose tissue, plasma lipids, and lipoprotein lipase activity in men and women: the Health, Risk Factors, Exercise Training, and Genetics (HERITAGE) family study.
Arterioscler Thromb Vasc Biol
20:
1932-1938,
2000
9.
Di Girolamo, M,
Mendlinger S,
and
Fertig JW.
A simple method to determine fat cell size and number in four mammalian species.
Am J Physiol
221:
850-858,
1971
10.
Eckel, RH.
Lipoprotein lipase. A multifunctional enzyme relevant to common metabolic diseases.
N Engl J Med
320:
1060-1068,
1989[Abstract].
11.
Edens, NK,
Fried SK,
Kral JG,
Hirsch J,
and
Leibel RL.
In vitro lipid synthesis in human adipose tissue from three abdominal sites.
Am J Physiol Endocrinol Metab
265:
E374-E379,
1993
12.
Edens, NK,
Leibel RL,
and
Hirsch J.
Lipolytic effects on diacylglycerol accumulation in human adipose tissue in vitro.
J Lipid Res
31:
1351-1359,
1990[Abstract].
13.
Flegal, KM.
The obesity epidemic in children and adults: current evidence and research issues.
Med Sci Sports Exerc
31:
S509-S514,
1999[ISI][Medline].
14.
Flegal, KM,
Carroll MD,
Kuczmarski RJ,
and
Johnson CL.
Overweight and obesity in the United States: prevalence and trends, 1960-1994.
Int J Obes Relat Metab Disord
22:
39-47,
1998[Medline].
15.
Friday, KE,
Srinivasan SR,
Elkasabany A,
Dong C,
Wattigney WA,
Dalferes E, Jr,
and
Berenson GS.
Black-white differences in postprandial triglyceride response and postheparin lipoprotein lipase and hepatic triglyceride lipase among young men.
Metabolism
48:
749-754,
1999[ISI][Medline].
16.
Goldrick, RB,
and
McLoughlin GM.
Lipolysis and lipogenesis from glucose in human fat cells of different sizes. Effects of insulin, epinephrine, and theophylline.
J Clin Invest
49:
1213-1223,
1970[ISI][Medline].
17.
Hill, JO,
Sidney S,
Lewis CE,
Tolan K,
Scherzinger AL,
and
Stamm ER.
Racial differences in amounts of visceral adipose tissue in young adults: the CARDIA (Coronary Artery Risk Development in Young Adults) study.
Am J Clin Nutr
69:
381-387,
1999
18.
Horton, ES,
Danforth E, Jr,
Sims EA,
and
Salans LB.
Correlation of forearm muscle and adipose tissue metabolism in obesity before and after weight loss (Abstract).
Clin Res
20:
548,
1972.
19.
Kuczmarski, RJ.
Prevalence of overweight and weight gain in the United States.
Am J Clin Nutr
55:
495S-502S,
1992[Abstract].
20.
Kuczmarski, RJ,
Flegal KM,
Campbell SM,
and
Johnson CL.
Increasing prevalence of overweight among US adults. The National Health and Nutrition Examination Surveys, 1960 to 1991.
JAMA
272:
205-211,
1994[Abstract].
21.
Kumanyaka, SK.
Obesity in minority populations: an epidemiologic assessment.
Obes Res
2:
168-182,
1994.
22.
Leibel, RL,
and
Hirsch J.
A radioisotopic technique for analysis of free fatty acid reesterification in human adipose tissue.
Am J Physiol Endocrinol Metab
248:
E140-E147,
1985
23.
Lovejoy, JC,
de la Bretonne JA,
Klemperer M,
and
Tulley R.
Abdominal fat distribution and metabolic risk factors: effects of race.
Metabolism
45:
1119-1124,
1996[ISI][Medline].
24.
MacLean, PS,
Bower JF,
Vadlamudi S,
Green T,
and
Barakat HA.
Lipoprotein subpopulation distributions in lean, obese, and type 2 diabetic women: a comparison of African and white Americans.
Obes Res
8:
62-70,
2000
25.
Maslowska, MH,
Sniderman AD,
MacLean LD,
and
Cianflone K.
Regional differences in triacylglycerol synthesis in adipose tissue and in cultured preadipocytes.
J Lipid Res
34:
219-228,
1993[Abstract].
26.
Olson, AL,
and
Pessin JE.
Structure, function, and regulation of the mammalian facilitative glucose transporter gene family.
Annu Rev Nutr
16:
235-256,
1996[ISI][Medline].
27.
Rodbell, M.
Metabolism of isolated fat cells. I. Effects of hormones on glucose metabolism and lipolysis.
J Biol Chem
239:
375-380,
1964
28.
Salans, LB,
Bray GA,
Cushman SW,
Danforth E, Jr,
Glennon JA,
Horton ES,
and
Sims EA.
Glucose metabolism and the response to insulin by human adipose tissue in spontaneous and experimental obesity. Effects of dietary composition and adipose cell size.
J Clin Invest
53:
848-856,
1974[ISI][Medline].
29.
Smith, U.
Effect of cell size on lipid synthesis by human adipose tissue in vitro.
J Lipid Res
12:
65-70,
1971
30.
Srinivasan, SR,
Freedman DS,
Sharma C,
Webber LS,
and
Berenson GS.
Serum apolipoproteins A-I and B in 2,854 children from a biracial community: Bogalusa Heart Study.
Pediatrics
78:
189-200,
1986[Abstract].
31.
Srinivasan, SR,
Wattigney W,
Webber LS,
and
Berenson GS.
Race and gender differences in serum lipoproteins of children, adolescents, and young adultsemergence of an adverse lipoprotein pattern in white males: the Bogalusa Heart Study.
Prev Med
20:
671-684,
1991[ISI][Medline].
32.
Sumner, AE,
Kushner H,
Sherif KD,
Tulenko TN,
Falkner B,
and
Marsh JB.
Sex differences in African-Americans regarding sensitivity to insulin's glucoregulatory and antilipolytic actions.
Diabetes Care
22:
71-77,
1999[Abstract].
33.
Tyroler, HA,
Glueck CJ,
Christensen B,
and
Kwiterovich PO, Jr.
Plasma high-density lipoprotein cholesterol comparisons in black and white populations. The Lipid Research Clinics Program Prevalence Study.
Circulation
62:
IV99-IV107,
1980[Medline].
34.
Tyroler, HA,
Hames CG,
Krishan I,
Heyden S,
Cooper G,
and
Cassel JC.
Black-white differences in serum lipids and lipoproteins in Evans County.
Prev Med
4:
541-549,
1975[ISI][Medline].