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...

Type 2 diabetes mellitus is characterized by 4 major metabolic abnormalities: obesity, impaired insulin action, insulin secretory dysfunction, and increased endogenous glucose output (EGO) (1-3). Although there is substantial evidence that the first 3 of these abnormalities are present in most individuals before the onset of diabetes, the sequence with which they develop and their relative contributions to the progression from normal glucose tolerance (NGT) to impaired glucose tolerance (IGT), and ultimately to type 2 diabetes (4-6), remain unknown in the absence of a detailed longitudinal study (7)(8)(9)(10)(11)(12). Current understanding of the pathogenesis of type 2 diabetes is based on a large number of cross-sectional (13-25) and prospective (26-40) studies.In cross-sectional studies, subjects with IGT were on average more obese and more insulin-resistant than those with NGT. Basal EGO, largely reflecting hepatic glucose production, was not increased (3,7,8,(13)(14)(15). Whether insulin secretion is impaired in individuals with IGT is controversial. Some studies have found a lower early insulin secretory response (occurring within minutes of an intravenous or oral glucose load) in individuals with IGT compared with those with . Lower early insulin responses have also been demonstrated in first-degree relatives of individuals with type 2 diabetes, a population at high risk for developing diabetes (20)(21)(22). However, others have reported normal or increased early insulin secretion in both groups of individuals (13,14,23,24). Similarly, both lower (18) and higher (25) late insulin responses (2 hours after an oral glucose load) have been reported in subjects with IGT compared with those with NGT. With respect to the pathogenesis of diabetes, such cross-sectional findings must be interpreted with caution, because many individuals with IGT will never develop diabetes, and their metabolic characteristics may well differ from those who do.In recent years, several prospective studies, in which nondiabetic individuals are metabolically characterized on a single occasion and then followed for several years to determine who develops diabetes, have helped to identify metabolic abnormalities that predispose to diabetes. These studies have shown that obesity (27-29, 33-35, 39) and insulin resistance (30-35) predict the development of diabetes in many populations, whereas basal EGO was not predictive in the only study in which it was measured (30). A low early insulin response predicted diabetes in most (30,(35)(36)(37)(38)(39) but not all (31, 32) studies. Together, these results indicate that defects in both insulin action and insulin secretion predispose some individuals with NGT to diabetes, but they give little information about the time course with which these abnormalities change as glucose tolerance worsens.To determine the natural history of insulin secretory dysfunction and insulin resistance during the development of diabetes, and to understand how these factors interact with one another during the developm...

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.

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

Body weight is regulated by complex neurohormonal interactions between endocrine signals of long-term adiposity (e.g., leptin, a hypothalamic signal) and short-term satiety (e.g., amylin, a hindbrain signal). We report that concurrent peripheral administration of amylin and leptin elicits synergistic, fat-specific weight loss in leptin-resistant, diet-induced obese rats. Weight loss synergy was specific to amylin treatment, compared with other anorexigenic peptides, and dissociable from amylin's effect on food intake. The addition of leptin after amylin pretreatment elicited further weight loss, compared with either monotherapy condition. In a 24-week randomized, double-blind, clinical proof-of-concept study in overweight/obese subjects, coadministration of recombinant human leptin and the amylin analog pramlintide elicited 12.7% mean weight loss, significantly more than was observed with either treatment alone (P < 0.01). In obese rats, amylin pretreatment partially restored hypothalamic leptin signaling (pSTAT3 immunoreactivity) within the ventromedial, but not the arcuate nucleus and up-regulated basal and leptin-stimulated signaling in the hindbrain area postrema. These findings provide both nonclinical and clinical evidence that amylin agonism restored leptin responsiveness in diet-induced obesity, suggesting that integrated neurohormonal approaches to obesity pharmacotherapy may facilitate greater weight loss by harnessing naturally occurring synergies.pramlintide ͉ metreleptin ͉ adiposity ͉ synergy ͉ leptin resistance T he discovery of leptin in 1994 (1) revolutionized our understanding of the biological basis of body-weight regulation and raised hopes that this adipokine could be a breakthrough treatment for obesity. Although leptin plays a pivotal role in regulating energy homeostasis in rodents and humans, its pharmaceutical development as a stand-alone antiobesity agent has proven unsuccessful (2). Although leptin replacement elicits profound weight loss in leptindeficient (Lep ob /Lep ob ) mice and humans (3, 4), even high pharmacological doses elicit only marginal weight loss in non-leptindeficient, diet-induced obese (DIO) rodents and humans (2, 5). The obese state is thus thought to be associated with ''leptin resistance,'' wherein overweight/obese individuals become insensitive to high circulating leptin concentrations (6). The mechanistic basis for leptin resistance is poorly understood, but rodent data implicate leptin transport saturation (7), leptin receptor down-regulation (8), and reduced hypothalamic postreceptor signaling (9, 10).Amylin, a 37-aa peptide hormone cosecreted with insulin from pancreatic ␤-cells (11), binds specific receptors in the hindbrain area postrema (AP) that activate multiple central nervous system (CNS) regions to regulate both glucose and energy homeostasis (12). In obese humans, the amylin analog pramlintide elicited sustained reductions in food intake and body weight (13,14). Amylin-induced weight loss in DIO rats that was observed to be fat-specific with relative...

Chronic low-grade inflammation may be involved in the pathogenesis of insulin resistance and type 2 diabetes. We examined whether a high white blood cell count (WBC), a marker of inflammation, predicts a worsening of insulin action, insulin secretory function, and the development of type 2 diabetes in Pima Indians. We

Adiponectin, the most abundant adipose-specific protein, has been found to be negatively associated with degree of adiposity and positively associated with insulin sensitivity in Pima Indians and other populations. Moreover, adiponectin administration to rodents has been shown to increase insulin-induced tyrosine phosphorylation of the insulin receptor (IR) and also increase whole-body insulin sensitivity. To further characterize the relationship between plasma adiponectin concentration and insulin sensitivity in humans, we examined 1) the cross-sectional association between plasma adiponectin concentration and skeletal muscle IR tyrosine phosphorylation and 2) the prospective effect of plasma adiponectin concentration at baseline on change in insulin sensitivity. Fasting plasma adiponectin concentration, body composition (hydrodensitometry or dual energy X-ray absorptiometry), insulin sensitivity (insulinstimulated glucose disposal, hyperinsulinemic clamp), and glucose tolerance (75-g oral glucose tolerance test) were measured in 55 Pima Indians (47 men and 8 women, aged 31 ؎ 8 years, body fat 29 ؎ 8% [mean ؎ SD]; 50 with normal glucose tolerance, 3 with impaired glucose tolerance, and 2 with diabetes). Group 1 (19 subjects) underwent skeletal muscle biopsies for the measurement of basal and insulin-stimulated tyrosine phosphorylation of the IR (stimulated by 100 nmol/l insulin). The fold increase after insulin stimulation was calculated as the ratio between maximal and basal phosphorylation.Group 2 (38 subjects) had follow-up measurements of insulin-stimulated glucose disposal. Cross-sectionally, plasma adiponectin concentration was positively associated with insulin-stimulated glucose disposal (r ‫؍‬ 0.58, P < 0.0001) and negatively associated with percent body fat (r ‫؍‬ ؊0.62, P < 0.0001) in the whole group. In group 1 plasma adiponectin was negatively associated with the basal (r ‫؍‬ ؊0.65, P ‫؍‬ 0.003) and positively associated with the fold increase in IR tyrosine phosphorylation (r ‫؍‬ 0.69, P ‫؍‬ 0.001) before and after the adjustment for percent body fat (r ‫؍‬ ؊0.58, P ‫؍‬ 0.01 and r ‫؍‬ 0.54, P ‫؍‬ 0.02, respectively). Longitudinally, after adjustment for age, sex, and percent body fat, low plasma adiponectin concentration at baseline was associated with a decrease in insulin sensitivity (P ‫؍‬ 0.04). In conclusion, our cross-sectional data suggest a role of physiological concentration of fasting plasma adiponectin in the regulation of skeletal muscle IR tyrosine phosphorylation. Prospectively, low plasma adiponectin concentration at baseline precedes a decrease in insulin sensitivity. Our data indicate that adiponectin plays an important role in regulation of insulin sensitivity in humans. Diabetes 50:1884 -1888, 2002 A dipose tissue serves not only as an energy storage organ, but also secretes hormones and metabolites that are thought to regulate insulin sensitivity and energy metabolism (1,2). Adiponectin, the most abundant adipose-specific protein, is exclusively expressed in and secreted from a...