Birth weight relates to blood pressure and microvascular function in normal subjects

OBJECTIVE: The relationship between low birth weight and elevated blood pressure in adult life is well established but presently unexplained. Both microvascular dysfunction and insulin resistance have been proposed as a possible explanation. We have examined the relation between birth weight and blood pressure in 30 healthy subjects exhibiting a wide range of insulin sensitivity, and assessed whether microvascular function and/or insulin resistance may underlie this relationship. METHODS: Birth weight data were obtained from birth announcements. Blood pressure was measured with an ambulatory blood pressure monitor and insulin sensitivity was assessed by the hyperinsulinaemic, euglycaemic clamp technique. Microvascular function, i.e. capillary recruitment and endothelium-dependent and -independent vasodilatation in the skin, was evaluated by videomicroscopy and iontophoresis of acetylcholine and sodium nitroprusside. RESULTS: Birth weight was significantly associated with blood pressure (r= -0.50; P< 0.05), capillary recruitment (r= +0.52; P< 0.05), acetylcholine-mediated vasodilatation (r= +0.40; P< 0.05), insulin sensitivity (r= +0.62; P< 0.01) and waist-to-hip ratio (r= -0.42; P< 0.05). Regression analysis showed a significant association of birth weight with 24 h systolic blood pressure (regression coefficient: -7.6 mmHg/kg; 95% confidence interval: -13.0 to -1.0). Adjustment for capillary recruitment and waist-to-hip ratio decreased the regression coefficient by 39 and 41%, respectively. The results were similar after adjustment for age, sex or body mass index. CONCLUSION: These results suggest that capillary recruitment and body fat distribution may partly explain the relationship between birth weight and blood pressure.     

Comparison of insulin sensitivity,clearance, and secretion estimates using euglycemic and hyperglycemic clamps in children

The euglycemic clamp is the gold standard for estimating insulin sensitivity. The hyperglycemic clamp is easier to perform and is the gold standard for estimating beta-cell secretion. Reports in adults suggest that hyperglycemic clamps can estimate insulin sensitivity with results equivalent to euglycemic clamps. We investigated whether insulin sensitivity measures from both clamps are equivalent in children. Thirty-one lean and obese children (mean body mass index, 25.1 +/- 4.9 kg/m(2); mean age, 8.7 +/- 1.4 yr; 15 girls and 16 boys; 12 black and 19 white) were studied. All subjects underwent hyperglycemic clamps, then euglycemic clamps 2-6 wk later. Body composition was estimated by dual energy x-ray absorptiometry. Visceral and sc abdominal fat was estimated by abdominal magnetic resonance imaging. Whole-body glucose disposal and insulin sensitivity (SI clamp) derived from both clamps and normalized for total or visceral fat and lean mass were significantly correlated (r, 0.45-0.65; P < 0.05). However, absolute SI clamp values were not equivalent. Bland-Altman comparisons found that SI clamp estimates from hyperglycemic clamps became less precise as SI clamp increased. There were significant correlations between indices of beta-cell secretion from the hyperglycemic clamp and mean C-peptide values from the euglycemic clamp (P < 0.05). However, no correlation was found between measures of total insulin clearance (derived from the euglycemic clamp) and surrogates of hepatic insulin clearance (derived from the hyperglycemic clamp). In this cohort of diverse children, SI clamp values from euglycemic and hyperglycemic clamps were significantly correlated but were not equivalent, whereas the insulin clearance measures were not correlated. It cannot be assumed that the hyperglycemic clamp obviates the need for euglycemic clamp studies to accurately estimate insulin sensitivity in children.     

Relationships between changes in abdominal fat distribution and insulin sensitivity during a very low calorie diet in abdominally obese men and women

BACKGROUND AND AIM: Little is known about the association between abdominal obesity and insulin sensitivity during rapid weight loss. We assessed the role of visceral and subcutaneous fat as determinants of insulin sensitivity during rapid weight loss in obese persons with the metabolic syndrome. METHODS AND RESULTS: Twenty abdominally obese individuals [11 women and 9 men, body mass index (BMI) 35.8+/-3.5 kg/m2] with the metabolic syndrome underwent a very-low-calorie diet (VLCD) for nine weeks. At baseline, the computed tomography (CT) measured area of total (r=-0.50, p=0.033) and visceral fat tissue (r=-0.48, p=0.043), but not that of subcutaneous fat tissue (r=-0.34, p=0.17), correlated with insulin sensitivity as assessed by the quantitative insulin sensitivity check index after adjusting for sex and age. The 18 subjects who completed the study lost 14.8 kg during the VLCD. Total, visceral and subcutaneous abdominal fat tissue decreased by 22%, 29% and 17%, respectively. The decrease in total (r=-0.51, p=0.035) and subcutaneous abdominal fat (r=-0.57, p=0.017), but not visceral fat (r=0.11, p=0.68), correlated with the increase in insulin sensitivity. Waist circumference did not offer any additional information concerning abdominal fat distribution or insulin sensitivity compared with that provided by BMI at baseline or after weight loss. The waist/hip ratio was not associated with the CT measures of abdominal fat distribution or insulin sensitivity. CONCLUSIONS: Total abdominal fat may be more important than its compartmentalisation in abdominally obese individuals with the metabolic syndrome. In this subgroup of individuals with obesity, the measurement of waist circumference and the waist/hip ratio offered little additional information over that provided by BMI at baseline or after weight loss.     

Growth hormone treatment reduces abdominal visceral fat in postmenopausal women with abdominal obesity: a 12-month placebo-controlled trial

Abdominal obesity is associated with blunted GH secretion and a cluster of cardiovascular risk factors that characterize the metabolic syndrome. GH treatment in abdominally obese men reduces visceral adipose tissue and has beneficial effects on the metabolic profile. There are no long-term data on the effects of GH treatment on postmenopausal women with abdominal obesity. Forty postmenopausal women with abdominal obesity participated in a randomized, double-blind, placebo-controlled, 12-month trial with GH (0.67 mg/d). The primary aim was to study the effect of GH treatment on insulin sensitivity. Measurements of glucose disposal rate (GDR) using a euglycemic, hyperinsulinemic glucose clamp; abdominal fat, hepatic fat content, and thigh muscle area using computed tomography; and total body fat and fat-free mass derived from (40)K measurements were performed at baseline and at 6 and 12 months. GH treatment reduced visceral fat mass, increased thigh muscle area, and reduced total and low-density lipoprotein cholesterol compared with placebo. Insulin sensitivity was increased at 12 months compared with baseline values in the GH-treated group. In the GH-treated group only, a low baseline GDR was correlated with a more marked improvement in insulin sensitivity (r = -0.68; P < 0.001). A positive correlation was found between changes in GDR and liver attenuation as a measure of hepatic fat content between baseline and 12 months (r = 0.7; P < 0.001) in the GH-treated group. In postmenopausal women with abdominal obesity, 1 yr of GH treatment improved insulin sensitivity and reduced abdominal visceral fat and total and low-density lipoprotein cholesterol concentrations. The improvement in insulin sensitivity was associated with reduced hepatic fat content.     

What are the physical characteristics associated with a normal metabolic profile despite a high level of obesity in postmenopausal women?

Although obesity is often associated with insulin resistance and a cluster of metabolic disturbances, the existence of a subgroup of healthy but obese individuals has been postulated. It is unclear why some obese individuals fail to show traditional risk factors associated with the insulin resistance syndrome despite having a very high accumulation of body fat. To address this issue, we identified and studied a subgroup of metabolically normal but obese (MNO) postmenopausal women to gain insight into potential physiological factors that may protect them against the development of obesity-related comorbidities. We carefully examined the metabolic characteristics of 43 obese, sedentary postmenopausal women (mean +/- SD, 58.0 +/- 6.0 yr). Subjects were classified as MNO or as metabolically abnormal obese (MAO) based on an accepted cut-point for insulin sensitivity (measured by the hyperinsulinemic/euglycemic clamp technique). Thereafter, we determined 1) body composition (fat mass and lean body mass), 2) body fat distribution (abdominal visceral and sc adipose tissue areas, midthigh sc adipose tissue and muscle attenuation), 3) plasma lipid-lipoprotein levels, 4) plasma glucose and insulin concentrations, 5) resting blood pressure, 6) peak oxygen consumption, 7) physical activity energy expenditure, and 8) age-related onset of obesity with a questionnaire as potential modulators of differences in the risk profile. We identified 17 MNO subjects who displayed high insulin sensitivity (11.2 +/- 2.6 mg/min.kg lean body mass) and 26 MAO subjects with lower insulin sensitivity (5.7 +/- 1.1 mg/min.kg lean body mass). Despite comparable total body fatness between groups (45.2 +/- 5.3% vs. 44.8 +/- 6.6%; P: = NS), MNO individuals had 49% less visceral adipose tissue than MAO subjects (141 +/- 53 vs. 211 +/- 85 cm(2); P: < 0.01). No difference was noted between groups for abdominal sc adipose tissue (453 +/- 126 vs. 442 +/- 144 cm(2); P: = NS), total fat mass (38.1 +/- 10.6 vs. 40.0 +/- 11.8 kg), muscle attenuation (42.2 +/- 2.6 vs. 43.6 +/- 4.8 Houndsfield units), and physical activity energy expenditure (1060 +/- 323 vs. 1045 +/- 331 Cal/day). MNO subjects had lower fasting plasma glucose and insulin concentrations and lower insulin levels during the oral glucose tolerance test (P: values ranging between 0.01-0.001). No difference was observed between groups for 2-h glucose levels and glucose area during the oral glucose tolerance test. MNO subjects showed lower plasma triglycerides and higher high density lipoprotein cholesterol concentrations than MAO individuals (P: < 0.01 in both cases). Results from the questionnaire indicated that 48% of the MNO women presented an early onset of obesity (<20 yr old) compared with 29% of the MAO subjects (P: = 0.09). Stepwise regression analysis showed that visceral adipose tissue and the age-related onset of obesity explained 22% and 13%, respectively, of the variance observed in insulin sensitivity (total r(2) = 0.35; P: < 0.05 in both cases). Our results support the existence of a subgroup of obese but metabolically normal postmenopausal women who display high levels of insulin sensitivity despite having a high accumulation of body fat. This metabolically normal profile is associated with a lower accumulation of visceral adipose tissue and an earlier age-related onset of obesity.     

Oxidative stress is associated with adiposity and insulin resistance in men

To investigate the direct relationship of oxidative stress with obesity and insulin resistance in men, we measured the plasma levels of 8-epi-prostaglandin F2alpha (PGF2alpha) in 14 obese and 17 nonobese men and evaluated their relationship with body mass index; body fat weight; visceral, sc, and total fat areas, measured by computed tomography; and glucose infusion rate during a euglycemic hyperinsulinemic clamp study. Obese men had significantly higher plasma concentrations of 8-epi-PGF2alpha than nonobese men (P < 0.05). The plasma levels of 8-epi-PGF2alpha were significantly correlated with body mass index (r = 0.408; P < 0.05), body fat weight (r = 0.467; P < 0.05), visceral (r = 0.387; P < 0.05) and total fat area (r = 0.359; P < 0.05) in all (obese and nonobese) men. There was also a significant correlation between the plasma levels of 8-epi-PGF2alpha and glucose infusion rate in obese men (r = -0.552; P < 0.05) and all men (r = -0.668; P < 0.01). In all subjects, the plasma levels of 8-epi-PGF2alpha were significantly correlated with fasting serum levels of insulin (r = 0.487; P < 0.01). In brief, these findings showed that the circulating levels of 8-epi-PGF2alpha are related to adiposity and insulin resistance in men. Although correlation does not prove causation, the results of this study suggest that obesity is an important factor for enhanced oxidative stress and that this oxidative stress triggers the development of insulin resistance in men.     

Elevated plasma levels of alpha-melanocyte stimulating hormone (alpha-MSH) are correlated with insulin resistance in obese men

OBJECTIVE: The role of alpha-melanocyte stimulating hormone (MSH) in obesity has been well-documented. However, circulating alpha-MSH concentrations in obese men and their relationship with clinical indicators of obesity and glucose metabolism have not as yet been evaluated. METHODS: We measured the plasma concentrations of alpha-MSH in 15 obese and 15 non-obese male subjects. The relationship of the plasma concentrations of alpha-MSH with body mass index (BMI), body fat mass (measured by bioelectric impedance), body fat distribution (measured by computed tomography), insulin levels, insulin resistance (assessed by the glucose infusion rate (GIR) during an euglycemic hyperinsulinemic clamp study) and with the serum concentrations of leptin and TNF-alpha were also evaluated. RESULTS: In obese men, the plasma alpha-MSH concentrations were significantly increased compared with those in non-obese men (P< 0.02). The plasma levels of alpha-MSH were positively correlated with BMI (r= 0.560, P< 0.05), fasting insulin levels (r=0.528, P< 0.05) and with visceral fat area (r=0.716, P<0.01), but negatively correlated with GIR (r= -0.625, P< 0.02) in obese male subjects. There were significant correlations between plasma concentrations of alpha-MSH and visceral fat area (r=0.631, P< 0.02), and GIR (r = -0.549, P< 0.05) in non-obese male subjects. Circulating concentrations of alpha-MSH were not significantly correlated with the serum concentrations of leptin and TNF-alpha in both obese and non-obese men. CONCLUSION: Circulating concentrations of alpha-MSH are significantly increased and correlated with insulin resistance in obese men.     

The interrelation of birth weight and regional lipid deposition: a twins study

This study examined the hypothesis that low birth weight is associated with changes in regional lipid deposition as well as insulin sensitivity in adult twins. Eleven adult female twin pairs were studied by magnetic resonance to determine regional adiposity. Their insulin sensitivity was assessed by the homeostasis model assessment. There were significant associations between birth weight and current homeostasis model assessment value (r=-0.528, P=.012), abdominal visceral (r=-0.581, P=.005), and subcutaneous fat volumes (r=-0.638, P=.001) if the group of 22 subjects were analyzed as individuals. There were no significant associations of the intratwin pair difference in birth weight and differences between adult twins in these same variables possibly because of limited patient numbers. Reduced birth weight does confer an increased risk of abdominal adiposity as well as insulin resistance in twin populations as it does in the general population.     

Quantitative insulin sensitivity check index is a useful indicator of insulin resistance in Japanese metabolically obese, normal-weight subjects with normal glucose tolerance

To clarify whether quantitative insulin sensitivity check index (QUICKI) is useful as an indicator of insulin resistance in Japanese metabolically obese, normal-weight (MONW, body mass index (BMI) <25 and visceral fat area (VFA) > or = 100 cm2 by abdominal computed tomography scanning) subjects with normal glucose tolerance (NGT). Insulin resistance was measured by QUICKI and euglycemic hyperinsulinemic clamp study (clamp IR) in 27 MONW and 27 normal subjects (BMI <25 and visceral fat area <100 cm2). QUICKI (P<0.01) and clamp IR (p<0.01) were significantly decreased in MONW subjects compared with normal subjects. QUICKI was significantly associated with VFA [MONW subjects: r = -0.459, p<0.02; all (MONW and normal) subjects: r = -0.506, p<0.0001] and with the serum levels of triglycerides (MONW subjects: r = -0.386, p<0.05; all subjects: r = -0.505, p<0.001) in MONW and all subjects. There were significant correlations between clamp IR and VFA (MONW subjects: r = -0.562, p<0.01; all subjects: r = -0.575, p<0.0001), fasting serum levels of insulin (MONW subjects: r = -0.673, p<0.001; all subjects: r = -0.619, p<0.0001) or serum levels of triglycerides (MONW subjects: r = -0.485, p<0.02; all subjects: r = -0.565, p<0.0001) in MONW and all subjects. QUICKI was significantly correlated with clamp IR in MONW (r = 0.754, p<0.0001) and in all subjects (r = 0.568, p<0.0001). QUICKI may be an useful method for assessing insulin resistance in Japanese MONW subjects with NGT.     

Peripheral blood mitochondrial DNA content is inversely correlated with insulin secretion during hyperglycemic clamp studies in healthy young men

Abnormalities in mitochondrial DNA(mtDNA) have been implicated in the pathogenesis of diabetes mellitus. We recently reported that decreased mtDNA content precedes the development of diabetes mellitus and is associated with parameters of insulin resistance. In this study, we examined whether there is any relation between mtDNA content and insulin secretion. We compared the mtDNA content of peripheral blood leukocytes with the parameters of insulin secretion measured by hyperglycemic clamp in a group of healthy young men. There were statistically significant correlations between mtDNA content in peripheral blood and fasting plasma insulin (r=-0.43, P<0.05) and C-peptide levels (r=-0.44, P<0.05). MtDNA content also correlated negatively with acute insulin response(r=-0.48, P<0.05), late insulin response (r=-0.50, P<0.05) during hyperglycemic clamp and insulin secretion after glucagon stimulation (r=-0.60, P<0.01). mtDNA content in peripheral blood correlated negatively with homeostasis model (HOMA) insulin resistance (r=-0.45, P<0.05) although it did not correlate with the insulin insensitivity index (M/I) during hyperglycemic clamp. In summary, the mtDNA content of peripheral blood correlated negatively with indices of insulin resistance and insulin secretion in healthy young men. The compensatory response of pancreas beta cells to insulin resistance might contribute in part to increased insulin secretion in these subjects.     

Relationship between serum resistin concentrations and insulin resistance in nonobese, obese, and obese diabetic subjects

Early reports suggested that resistin is associated with obesity and insulin resistance in rodents. However, subsequent studies have not supported these findings. To our knowledge, the present study is the first assessment in human subjects of serum resistin and insulin sensitivity by the insulin clamp technique. Thirty-eight nonobese subjects [age, 23 +/- 4 yr; body mass index (BMI), 25.4 +/- 4.3 kg/m(2)], 12 obese subjects (age, 54 +/- 8 yr; BMI, 33.0 +/- 2.5 kg/m(2)), and 22 obese subjects with type 2 diabetes (age, 59 +/- 7 yr; BMI, 34.0 +/- 2.4 kg/m(2)) were studied. Serum resistin concentrations were not different among nonobese (4.1 +/- 1.7 ng/ml), obese (4.2 +/- 1.6 ng/ml), and obese diabetic subjects (3.7 +/- 1.2 ng/ml), and were not significantly correlated to glucose disposal rate during a hyperinsulinemic glucose clamp across groups. Serum resistin was, however, inversely related to insulin sensitivity in nonobese subjects only (r = -0.35; P = 0.05), although this association was lost after adjusting for percent body fat. Serum resistin was not related to percent fat, BMI, or fat cell size. A strong correlation was observed between serum resistin and resistin mRNA expression from abdominal sc adipose tissue in a separate group of obese subjects (r = 0.62; P < 0.01; n = 56). Although the exact function of resistin is unknown, we demonstrated only a weak relationship between resistin and insulin sensitivity in nonobese subjects, indicating that resistin is unlikely to be a major link between obesity and insulin resistance in humans.     

Circulating levels of active ghrelin is associated with abdominal adiposity, hyperinsulinemia and insulin resistance in patients with type 2 diabetes mellitus

OBJECTIVE: To investigate the relationship between the circulating level of active ghrelin and abdominal adiposity, serum levels of insulin or insulin resistance in patients with type 2 diabetes mellitus. DESIGN: We measured the plasma levels of the active form of ghrelin in 18 obese and 18 nonobese patients with type 2 diabetes mellitus using a radioimmunoassay (RIA) kit. Body fat accumulation was measured by computed tomography (CT) and insulin resistance by the glucose infusion rate (GIR) during an euglycemic hyperinsulinemic clamp study. RESULTS: Plasma levels of ghrelin in obese patients with type 2 diabetes mellitus were significantly decreased compared with nonobese patients. There were significant correlations between the plasma levels of ghrelin and BMI (r=-0.505, P<0.01), visceral (r=-0.444, P<0.01), subcutaneous (r=-0.506, P<0.01) and total (r=-0.534, P<0.01) fat area, serum levels of insulin (r=-0.513, P<0.01) or GIR (r=0.478, P<0.01) in type 2 diabetic patients. The plasma level of ghrelin was significantly associated with serum levels of insulin (F=8.468, P<0.05) or GIR (F=8.522, P<0.05) after adjustment for BMI in patients with type 2 diabetes mellitus. CONCLUSIONS: Decreased plasma levels of active ghrelin are significantly associated with abdominal adiposity, hyperinsulinemia and insulin resistance in type 2 diabetic patients. Hyperinsulinemia associated with insulin resistance may suppress plasma levels of active ghrelin in patients with type 2 diabetes mellitus.     

Pubertal alterations in growth and body composition. VI. Pubertal insulin resistance: relation to adiposity, body fat distribution and hormone release

OBJECTIVE: To investigate the independent influence of alterations in fat mass, body fat distribution and hormone release on pubertal increases in fasting serum insulin concentrations and on insulin resistance assessed by the homeostasis model (HOMA). DESIGN AND SUBJECTS: Cross-sectional investigation of pre- (n=11, n=8), mid- (n=10, n=11), and late-pubertal (n=10, n=11) boys and girls with normal body weight and growth velocity. MEASUREMENTS: Body composition (by a four-compartment model), abdominal fat distribution and mid-thigh interfascicular plus intermuscle (extramyocellular) fat (by magnetic resonance imaging), total body subcutaneous fat (by skinfolds), mean nocturnal growth hormone (GH) release and 06:00 h samples of serum insulin, sex steroids, leptin and insulin-like growth factor-I (IGF-I). RESULTS: Pubertal insulin resistance was suggested by greater (P<0.001) fasting serum insulin concentrations in the late-pubertal than pre- and mid-pubertal groups while serum glucose concentrations were unchanged and greater (P<0.001) HOMA values in late-pubertal than pre- and mid-pubertal youth. From univariate correlation fat mass was most related to HOMA (r=0.59, P<0.001). Two hierarchical regression models were developed to predict HOMA. In one approach, subject differences in sex, pubertal maturation, height and weight were held constant by adding these variables as a block in the first step of the model (r(2)=0.36). Sequential addition of fat mass (FM) increased r(2) (r(2)((inc)remental)=0.08, r(2)=0.44, P<0.05) as did the subsequent addition of a block of fat distribution variables (extramyocellular fat, abdominal visceral fat, and sum of skinfolds; r(2)(inc)=0.11, r(2)=0.55, P<0.05). Sequential addition of a block of hormone variables (serum IGF-I and log((10)) leptin concentrations; r(2)(inc)=0.04, P>0.05) did not reliably improve r(2) beyond the physical characteristic and adiposity variables. In a second model, differences in sex and pubertal maturation were again held constant (r(2)=0.25), but body size differences were accounted for using percentage fat data. Sequential addition of percentage body fat (r(2)((inc)remental)=0.11, r(2)=0.36, P<0.05), then a block of fat distribution variables (percentage extramyocellular fat, percentage abdominal visceral fat, and percentage abdominal subcutaneous fat; r(2)(inc)=0.08, r(2)=0.44, P=0.058), and then a block of serum IGF-I and log((10)) leptin concentrations (r(2)(inc)=0.07, r(2)=0.51, P<0.05) increased r(2). Mean nocturnal GH release was not related to HOMA (r=-0.04, P=0.75) and therefore was not included in the hierarchical regression models. CONCLUSION: Increases in insulin resistance at puberty were most related to FM. Accumulation of fat in the abdominal visceral, subcutaneous and muscular compartments may increase insulin resistance at puberty beyond that due to total body fat. Serum concentrations of leptin and IGF-I may further modulate HOMA beyond the effects of adiposity and fat distribution. However, the results are limited by the cross-sectional design and the use of HOMA rather than a criterion measure of insulin resistance.     

Effect of pioglitazone on abdominal fat distribution and insulin sensitivity in type 2 diabetic patients

We examined the effect of pioglitazone on abdominal fat distribution to elucidate the mechanisms via which pioglitazone improves insulin resistance in patients with type 2 diabetes mellitus. Thirteen type 2 diabetic patients (nine men and four women; age, 52 +/- 3 yr; body mass index, 29.0 +/- 1.1 kg/m(2)), who were being treated with a stable dose of sulfonylurea (n = 7) or with diet alone (n = 6), received pioglitazone (45 mg/d) for 16 wk. Before and after pioglitazone treatment, subjects underwent a 75-g oral glucose tolerance test (OGTT) and two-step euglycemic insulin clamp (insulin infusion rates, 40 and 160 mU/m(2).min) with [(3)H]glucose. Abdominal fat distribution was evaluated using magnetic resonance imaging at L4-5. After 16 wk of pioglitazone treatment, fasting plasma glucose (179 +/- 10 to 140 +/- 10 mg/dl; P < 0.01), mean plasma glucose during OGTT (295 +/- 13 to 233 +/- 14 mg/dl; P < 0.01), and hemoglobin A(1c) (8.6 +/- 0.4% to 7.2 +/- 0.5%; P < 0.01) decreased without a change in fasting or post-OGTT insulin levels. Fasting plasma FFA (674 +/- 38 to 569 +/- 31 microEq/liter; P < 0.05) and mean plasma FFA (539 +/- 20 to 396 +/- 29 microEq/liter; P < 0.01) during OGTT decreased after pioglitazone. In the postabsorptive state, hepatic insulin resistance [basal endogenous glucose production (EGP) x basal plasma insulin concentration] decreased from 41 +/- 7 to 25 +/- 3 mg/kg fat-free mass (FFM).min x microU/ml; P < 0.05) and suppression of EGP during the first insulin clamp step (1.1 +/- 0.1 to 0.6 +/- 0.2 mg/kg FFM.min; P < 0.05) improved after pioglitazone treatment. The total body glucose MCR during the first and second insulin clamp steps increased after pioglitazone treatment [first MCR, 3.5 +/- 0.5 to 4.4 +/- 0.4 ml/kg FFM.min (P < 0.05); second MCR, 8.7 +/- 1.0 to 11.3 +/- 1.1 ml/kg FFM(.)min (P < 0.01)]. The improvement in hepatic and peripheral tissue insulin sensitivity occurred despite increases in body weight (82 +/- 4 to 85 +/- 4 kg; P < 0.05) and fat mass (27 +/- 2 to 30 +/- 3 kg; P < 0.05). After pioglitazone treatment, sc fat area at L4-5 (301 +/- 44 to 342 +/- 44 cm(2); P < 0.01) increased, whereas visceral fat area at L4-5 (144 +/- 13 to 131 +/- 16 cm(2); P < 0.05) and the ratio of visceral to sc fat (0.59 +/- 0.08 to 0.44 +/- 0.06; P < 0.01) decreased. In the postabsorptive state hepatic insulin resistance (basal EGP x basal immunoreactive insulin) correlated positively with visceral fat area (r = 0.55; P < 0.01). The glucose MCRs during the first (r = -0.45; P < 0.05) and second (r = -0.44; P < 0.05) insulin clamp steps were negatively correlated with the visceral fat area. These results demonstrate that a shift of fat distribution from visceral to sc adipose depots after pioglitazone treatment is associated with improvements in hepatic and peripheral tissue sensitivity to insulin.     

Abdominal obesity,muscle composition,and insulin resistance in premenopausal women

The independent relationships between visceral and abdominal sc adipose tissue (AT) depots, muscle composition, and insulin sensitivity were examined in 40 abdominally obese, premenopausal women. Measurements included glucose disposal by euglycemic clamp, muscle composition by computed tomography, abdominal and nonabdominal (e.g. leg) AT by magnetic resonance imaging and cardiovascular fitness. Glucose disposal rates were negatively related to visceral AT mass (r = -0.42, P < 0.01). These observations remained significant (P < 0.01) after control for nonabdominal and abdominal sc AT, muscle attenuation, and peak oxygen uptake. Total, abdominal, or leg sc AT or muscle attenuation was not significantly (P > 0.10) related to glucose disposal. Subdivision of abdominal sc AT into anterior and posterior depots did not alter the observed relationships. Further analysis matched two groups of women for abdominal sc AT but with low and high visceral AT. Women with high visceral AT had lower glucose disposal rates compared with those with low visceral AT (P < 0.05). A similar analysis performed on two groups of women matched for visceral AT but high and low abdominal sc AT revealed no statistically different values for insulin sensitivity (P > 0.10). In conclusion, visceral AT alone is a strong correlate of insulin resistance independent of nonabdominal, abdominal sc AT, muscle composition, and cardiovascular fitness. Subdivision of abdominal sc AT did not provide additional insight into the relationship between abdominal obesity and metabolic risk.     

Evidence of increased visceral obesity and reduced physical fitness in healthy insulin-resistant first-degree relatives of type 2 diabetic patients

OBJECTIVE: First-degree relatives (FDR) of type 2 diabetic patients are often insulin resistant. Visceral obesity is closely linked to both insulin resistance and type 2 diabetes. We therefore hypothesized that the inheritance of an increased tendency to store fat in visceral fat depots may be a characteristic phenotypic feature in FDR contributing to their insulin resistance. DESIGN AND METHODS: We measured fat distribution in 20 FDR and 14 age-, gender- and body mass index (BMI)-matched controls employing dual energy X-ray absorbtiometry (DEXA)- and computed tomography (CT)-scanning. Insulin-stimulated glucose uptake (ISGU) was determined by a hyperinsulinemic clamp and maximal aerobic work capacity (VO2 max) by a bicycle ergometer test. Baseline lipolysis was measured using [3H]palmitate. The activity level of the hypothalamic-pituitary-adrenal axis was assessed as the 24 h urinary (u)-cortisol/creatinine ratio. RESULTS: All subjects had a normal oral glucose tolerance test (OGTT), but FDR were insulin resistant (ISGU: 6.64+/-0.48 vs 9.12+/-0.98 mg/kg ffm/min, P=0.01). Despite similar BMI (25.2+/-0.5 vs 24.8+/-0.7 kg/m2, P=0.61) and overall fat mass (26.4+/-1.6 vs 24.2+/-2.1%, P=0.41) in FDR vs controls, the amount of visceral adipose tissue was substantially increased (65.9+/-10.0 vs 40.1+/-11.3 cm2, P<0.05) and VO2 max was reduced (52.2+/-3.1 vs 63.3+/-3.9 ml/kg ffm/min, P<0.05) in FDR. Visceral adiposity was inversely correlated with ISGU (FDR: r=-0.52, P<0.05; controls: r=-0.65, P<0.01) and in multiple regression analysis visceral adiposity (P<0.01), VO2 max (P<0.001) and a family history of type 2 diabetes (P<0.05) (r2=0.64) all significantly and independently contributed to the level of ISGU. Baseline palmitate appearance (145+/-10 vs 139+/-15 micromol/min, P=0.74) and the 24 h u-cortisol/creatinine ratio ((24.9+/-1.3 vs 27.4+/-2.0).10(-6), P=0.28) were both comparable in the two groups. CONCLUSION: Healthy but insulin-resistant FDR have enhanced visceral obesity and reduced VO2 max compared with people without a family history of diabetes, despite similar BMI and overall fat mass. Both the visceral adiposity and reduced aerobic fitness are strongly associated with and may contribute to their insulin resistance.     

Abdominal visceral fat reduction is associated with favorable changes of serum retinol binding protein-4 in nondiabetic subjects

The adipocytokine retinol binding protein-4 (RBP4) has recently been shown to link obesity and insulin resistance, although their relationship remains controversial in human studies. The influence of weight reduction with changes of fat distribution on serum RBP4 concentration in nondiabetics is also unknown. We assessed the effect of weight reduction (especially abdominal visceral fat loss) on serum RBP4 levels after a structuralized weight-reduction program. We conducted a prospective intervention study consisting of a 16-week weight reduction program, including lifestyle modification and adjuvant appetite suppressants. A total of 52 nondiabetic subjects aged 37.4 +/- 11 years with a body mass index of 27.4 +/- 4 kg/m (2) were included. Serum RBP4 concentrations with other metabolic parameters and abdominal adipose tissue areas as determined by computed tomography scan were measured both before and 16 weeks after the weight reduction program. Subjects had a 10.9% loss of body weight accompanied by a 25.5% decrease in serum RBP4 levels, with improved ( ) insulin sensitivity after the program. The changes in RBP4 levels were significantly correlated with the amounts of abdominal visceral fat loss (r = 0.38, p<0.01) but were not associated with the amount of total body fat loss or abdominal subcutaneous fat loss. Weight reduction, especially the loss of abdominal visceral fat, lowers serum RBP4 concentrations in nondiabetic subjects. The relationship between individual changes in RBP4 and abdominal visceral fat indicated that RBP4 may be involved in the beneficial effect of visceral fat reduction on the improvement of insulin resistance and metabolic syndrome.     

Changes in plasma leptin and insulin action with resistive training in postmenopausal women

OBJECTIVE: To determine the effects of 16 weeks of resistive training alone (RT) and with weight loss (RT+WL) on insulin action, plasma leptin concentrations and leptin's relationship to beta-cell sensitivity to glucose, resting metabolic rate (RMR), and plasma catecholamines in older women. SUBJECTS: Fifteen obese postmenopausal women aged 50-69 y. MEASUREMENTS: Body composition (by dual-energy X-ray absorptiometry), RMR (by indirect calorimetry), insulin action (by 2 h hyperglycemic clamps; 7.9 mmol/l above basal plasma glucose levels), plasma leptin and insulin (by RIA), and plasma catecholamines (by enzymatic methods). RESULTS: RT and RT+WL resulted in significant improvements in muscular strength (P<0.01) with no changes in maximal oxygen consumption. Body weight, fat mass and percent body fat did not change with RT, but decreased with RT+WL (P<0.001). Fat-free mass and RMR increased after training when both groups were combined (P<0.05). The insulin response during the last 20 min of the 2 h hyperglycemic clamps decreased 16% after RT (P=0.05), 43% after RT+WL (P<0.05), and 29% in the entire group (P<0. 01) without any changes in glucose utilization. Plasma leptin levels did not change after RT, but decreased by 36% after RT+WL (P<0.05). Baseline leptin levels correlated with body weight (r=0.68, P<0.01), body fat mass (r=0.77, P<0.001), and RMR (kcal/d; (r=0.69, P<0.005), but not with baseline norepinephrine or epinephrine levels. Plasma leptin levels correlated with basal insulin (r=0.73, P<0.005), and approached significance with the 0-10 min and 100-120 min insulin response to hyperglycemia before training (both r=0.51, P=0.07). In the entire group, the change in insulin response from 100-120 min during the clamp correlated with the change in leptin levels (r=0.60, P<0.05), but this was not independent of changes in fat mass. CONCLUSIONS: Although changes in leptin levels were not related to changes in RMR or plasma catecholamines after RT with and without weight loss, the increase in insulin action after training and weight loss may be related to the decrease in leptin levels that were mediated by the loss of body fat in the obese, postmenopausal women. International Journal of Obesity (2000)24, 27-32     

Adiponectin, insulin resistance, and C-reactive protein in postpubertal Asian Indian adolescents

High-sensitivity C-reactive protein (hs-CRP) levels are closely associated with adiposity and predict coronary heart disease and type 2 diabetes mellitus. However, relationships of CRP to adiponectin and other markers of insulin resistance have been inadequately researched in children. We measured fasting serum levels of adiponectin, insulin, hs-CRP, and lipoproteins, and recorded the anthropometric profile and percentage of body fat (%BF; bioimpedance method) in 62 (36 normal weight, 26 overweight) healthy, urban, postpubertal Asian Indian males (aged 14 to 18 years). Serum levels of adiponectin were lower (P = not significant [NS]), whereas those of fasting insulin (P = .01) and hs-CRP (P = .02) were higher in overweight subjects. Adiponectin levels inversely correlated with body mass index (BMI; r = -0.26, P < .05), %BF (r = -0.24, P < .05), fasting insulin (r = -0.32, P < .05) and insulin resistance measured by the homeostasis model of assessment (HOMA-IR; r = -0.31, P < .05), but not with hs-CRP levels. Fasting insulin and hs-CRP levels correlated significantly with BMI, %BF, waist circumference (WC), waist-to-hip circumference ratio (W-HR), and triceps and subscapular skinfold thickness. The correlation of adiponectin with insulin sensitivity was independent of abdominal obesity, but became nonsignificant after controlling for BMI and %BF. Further, BMI was an independent predictor of adiponectin levels and the ratio of adiponectin and %BF was an independent predictor of fasting insulin levels. Although adiponectin levels did not correlate with hs-CRP levels, we observed dichotomous relationships of adiponectin and hs-CRP levels with generalized and abdominal obesity, respectively. We conclude that generalized obesity affects the adiponectin-insulin relationship in postpubertal Asian Indian males; however, the relationship of adiponectin with hs-CRP needs further evaluation.     

女性肥胖和2型糖尿病患者高葡萄糖钳夹过程中胰岛素原的分泌和释放

目的 探讨女性肥胖和2型糖尿病患者在持续高糖情况下胰岛素原分泌和释放的变化.方法 12例肥胖、7例2型糖尿病和9例正常对照组,行150分钟高葡萄糖钳夹试验,用酶联免疫法测定各时点胰岛素原.结果 肥胖组和2型糖尿病组空腹胰岛素原(PI)水平高于对照组.2型糖尿病组在10～150分钟期间胰岛素原/胰岛素比值高于肥胖组和对照组.Spearman相关分析显示,PI与胰岛素原分泌第一时相(FPPR)(r=0.464,P=0.026)和内脏脂肪(VA)(r=0.447,P=0.033)呈正相关;与葡萄糖代谢清除率(GDR)(r=-0.533,P=0.009)呈负相关.结论 胰岛素原分泌与胰岛素抵抗密切相关.持续高糖情况下肥胖患者由于胰岛素抵抗代偿性高分泌胰岛素原,2型糖尿病患者存在胰岛功能损害,胰岛素原分泌降低,而且胰岛素原转换胰岛素过程中存在缺陷.