Plasma concentrations of adiponectin, a novel adipose-specific protein with putative antiatherogenic and antiinflammatory effects, were found to be decreased in Japanese individuals with obesity, type 2 diabetes, and cardiovascular disease, conditions commonly associated with insulin resistance and hyperinsulinemia. To further characterize the relationship between adiponectinemia and adiposity, insulin sensitivity, insulinemia, and glucose tolerance, we measured plasma adiponectin concentrations, body composition (dual-energy x-ray absorptiometry), insulin sensitivity (M, hyperinsulinemic clamp), and glucose tolerance (75-g oral glucose tolerance test) in 23 Caucasians and 121 Pima Indians, a population with a high propensity for obesity and type 2 diabetes. Plasma adiponectin concentration was negatively correlated with percent body fat (r = -0.43), waist-to-thigh ratio (r = -0.46), fasting plasma insulin concentration (r = -0.63), and 2-h glucose concentration (r = -0.38), and positively correlated with M (r = 0.59) (all P < 0.001); all relations were evident in both ethnic groups. In a multivariate analysis, fasting plasma insulin concentration, M, and waist-to-thigh ratio, but not percent body fat or 2-h glucose concentration, were significant independent determinates of adiponectinemia, explaining 47% of the variance (r(2) = 0.47). Differences in adiponectinemia between Pima Indians and Caucasians (7.2 +/- 2.6 vs. 10.2 +/- 4.3 microg/ml, P < 0.0001) and between Pima Indians with normal, impaired, and diabetic glucose tolerance (7.5 +/- 2.7, 6.1 +/- 2.0, 5.5 +/- 1.6 microg/ml, P < 0.0001) remained significant after adjustment for adiposity, but not after additional adjustment for M or fasting insulin concentration. These results confirm that obesity and type 2 diabetes are associated with low plasma adiponectin concentrations in different ethnic groups and indicate that the degree of hypoadiponectinemia is more closely related to the degree of insulin resistance and hyperinsulinemia than to the degree of adiposity and glucose intolerance.

Ghrelin is a novel endogenous natural ligand for the growth hormone (GH) secretagogue receptor that has recently been isolated from the rat stomach. Ghrelin administration stimulates GH secretion but also causes weight gain by increasing food intake and reducing fat utilization in rodents. To investigate the possible involvement of ghrelin in the pathogenesis of human obesity, we measured body composition (by dual X-ray absorption) as well as fasting plasma ghrelin concentrations (radioimmunoassay) in 15 Caucasians (8 men and 7 women, 31 ؎ 9 years of age, 92 ؎ 24 kg body wt, and 29؎10% body fat, mean ؎ SD) and 15 Pima Indians (8 men and 7 women, 33 ؎ 5 years of age, 97 ؎ 29 kg body wt, and 30 ؎ 8% body fat). Fasting plasma ghrelin was negatively correlated with percent body fat (r ‫؍‬ -0.45; P ‫؍‬ 0.01), fasting insulin (r ‫؍‬ -0.45; P ‫؍‬ 0.01) and leptin (r ‫؍‬ -0.38; P ‫؍‬ 0.03) concentrations. Plasma ghrelin concentration was decreased in obese Caucasians as compared with lean Caucasians (P < 0.01). Also, fasting plasma ghrelin was lower in Pima Indians, a population with a very high prevalence of obesity, compared with Caucasians (87 ؎ 28 vs. 129 ؎ 34 fmol/ml; P < 0.01). This result did not change after adjustment for fasting plasma insulin concentration. There was no correlation between fasting plasma ghrelin and height. Prospective clinical studies are now needed to establish the role of ghrelin in the pathogenesis of human obesity. Diabetes 50: [707][708][709] 2001 W e recently reported (1) that the gastric hormone ghrelin (2) provides a peripheral signal to the brain that induces adiposity in rodents. To investigate a possible involvement of ghrelin in the pathogenesis of human obesity, we measured endogenous ghrelin concentrations in lean and obese Caucasian and Pima Indian individuals. We hypothesized that 1) obese individuals would present with elevated ghrelin levels that could contribute to the pathogenesis of obesity and 2) Pima Indians, a population with one of the highest reported prevalence rates of obesity and type 2 diabetes in the world, would present with elevated ghrelin levels when compared with Caucasians. RESEARCH DESIGN AND METHODSA total of 15 Caucasian and 15 Pima Indian subjects matched for age, sex, and body weight were divided into lean (n ϭ 7) and obese (n ϭ 8) subgroups (Table 1). Obesity was defined as BMI Ͼ30 kg/m 2 , according to the criteria of both the World Health Organization and the International Obesity Task Force. All participants were between 20 and 50 years of age, nondiabetic according to an oral glucose tolerance test, and healthy according to a physical examination and routine laboratory tests. Subjects were admitted to the research ward of the Clinical Diabetes and Nutrition Section of the National Institutes of Health in Phoenix, Arizona, where they received a weightmaintaining diet (50% carbohydrate, 30% fat, and 20% protein) and abstained from exercise for at least 2 days before the study. The protocol was approved by the Tribal Council of the Gila River In...

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Epidemiological studies have firmly established that obesity is a major risk factor for the development of Type II (non-insulin-dependent) diabetes mellitus [1±4]. Obesity does not, however, invariably result in diabetes and many people who are very obese are able to maintain normal glucose tolerance. The reason why some people with obesity develop Type II diabetes and others do not is largely not known.There is good evidence that differences in body fat distribution play a part [3±9]. A large number of cross-sectional studies have shown that obese people with an abdominal pattern of fat accumulation are Diabetologia (2000) Abstract Aims/hypothesis. Cross-sectional studies indicate that enlarged subcutaneous abdominal adipocyte size is associated with hyperinsulinaemia, insulin resistance and glucose intolerance. To further explore the pathophysiological significance of these associations, we examined prospectively whether enlarged subcutaneous abdominal adipocyte size predicts Type II (non-insulin-dependent) diabetes mellitus. Methods. Body composition (hydrodensitometry), mean subcutaneous abdominal adipocyte size (fat biopsy), insulin sensitivity (hyperinsulinaemic clamp) and the acute insulin secretory response (25-g i. v. GTT) were assessed in 280 Pima Indians with either normal (NGT), impaired (IGT) or diabetic glucose tolerance (75-g OGTT). Subjects with NGT were then followed prospectively. Results. After adjusting for age, sex and per cent body fat, mean subcutaneous abdominal adipocyte size was 19 % and 11 % higher in subjects with diabetes and IGT, compared with those with NGT (p < 0.001). Insulin sensitivity was inversely correlated with mean subcutaneous abdominal adipocyte size (r = ±0.53, p < 0.0001), even after adjusting for per cent body fat (r = ±0.31, p < 0.001). In 108 NGT subjects followed over 9.3 4.1 years (33 of whom developed diabetes), enlarged mean subcutaneous abdominal adipocyte size but not high per cent body fat, was an independent predictor of diabetes, in addition to a low insulin sensitivity and acute insulin secretory response [relative hazard 10 th vs 90 th centile (95 % CI): 5.8 (1.7±19.6), p < 0.005]. In 28 NGT subjects with a 9 % weight gain over 2.7 1.3 years, changes in insulin sensitivity were inversely and independently related to changes in mean subcutaneous abdominal adipocyte size and per cent body fat. Conclusion/interpretation. Although enlarged mean subcutaneous abdominal adipocyte size is associated with insulin resistance cross-sectionally, prospectively, both abnormalities are independent and additive predictors of Type II diabetes. [Diabetologia (2000

and acute insulin response (AIR) (25-g intravenous glucose challenge). Sixty-three subjects developed diabetes over an average follow-up of 6.9 ؎ 4.9 years. In 224 subjects, who remained nondiabetic, follow-up measurements of M and AIR were available. At baseline, ALT, AST, and GGT were related to percent body fat (r ‫؍‬ 0.16, 0.17, and 0.11, respectively), M (r ‫؍‬ ؊0.32, ؊0.28, and ؊0.24), and HGO (r ‫؍‬ 0.27, 0.12, and 0.14; all P < 0.01). In a proportional hazard analysis with adjustment for age, sex, body fat, M, and AIR, higher ALT [relative hazard 90th vs. 10th centiles (95% CI): 1.9 (1.1-3.3), P ‫؍‬ 0.02], but not AST or GGT, predicted diabetes. Elevated ALT at baseline was associated prospectively with an increase in HGO (r ‫؍‬ 0.21, P ‫؍‬ 0.001) but not with changes in M or AIR (both P ‫؍‬ 0.1). Higher ALT concentrations were cross-sectionally associated with obesity and whole-body and hepatic insulin resistance and prospectively associated with a decline in hepatic insulin sensitivity and the development of type 2 diabetes. Our findings indicate that high ALT is a marker of risk for type 2 diabetes and suggest a potential role of the liver in the pathogenesis of type 2 diabetes.

The central role of the hypothalamus in the origination and͞or processing of feeding-related stimuli may be modulated by the activity of other functional areas of the brain including the insular cortex (involved in enteroceptive monitoring) and the prefrontal cortex (involved in the inhibition of inappropriate response tendencies). Regional cerebral blood f low (rCBF), a marker of neuronal activity, was measured in 11 healthy, normal-weight men by using positron emission tomography in a state of hunger (after 36-h fast) and a state of satiation (after a liquid meal). Hunger was associated with significantly increased rCBF in the vicinity of the hypothalamus and insular cortex and in additional paralimbic and limbic areas (orbitofrontal cortex, anterior cingulate cortex, and parahippocampal and hippocampal formation), thalamus, caudate, precuneus, putamen, and cerebellum. Satiation was associated with increased rCBF in the vicinity of the ventromedial prefrontal cortex, dorsolateral prefrontal cortex, and inferior parietal lobule. Changes in plasma insulin concentrations in response to the meal were negatively correlated with changes in rCBF in the insular and orbitofrontal cortex. Changes in plasma free fatty acid concentrations in response to the meal were negatively correlated with changes in rCBF in the anterior cingulate and positively correlated with changes in rCBF in the dorsolateral prefrontal cortex. In conclusion, these findings raise the possibility that several regions of the brain participate in the regulation of hunger and satiation and that insulin and free fatty acids may be metabolic modulators of postprandial brain neuronal events. Although exploratory, the present study provides a foundation for investigating the human brain regions and cognitive operations that respond to nutritional stimuli.

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The intestinal fatty acid binding protein locus (FABP2) was investigated as a possible genetic factor in determining insulin action in the Pima Indian population. A polymorphism at codon 54 of FABP2 was identified that results in an alanineencoding allele (frequency 0.71) and a threonine-encoding allele (frequency 0.29). Pimas who were homozygous or heterozygous for the threonine-encoding allele were found to have a higher mean fasting plasma insulin concentration, a lower mean insulin-stimulated glucose uptake rate, a higher mean insulin response to oral glucose and a mixed meal, and a higher mean fat oxidation rate compared with Pimas who were homozygous for the alanine-encoding allele. Since the FABP2 threonine-encoding allele was found to be associated with insulin resistance and increased fat oxidation in vivo, we further analyzed the FABP2 gene products for potential functional differences. Titration microcalorimetry studies with purified recombinant protein showed that the threonine-containing protein had a twofold greater affinity for long-chain fatty acids than the alanine-containing protein. We conclude that the threonine-containing protein may increase absorption and/or processing of dietary fatty acids by the intestine and thereby increase fat oxidation, which has been shown to reduce insulin action. (J. Clin.