Gestational weight gain and the risk of offspring obesity at 10 and 16 years: a prospective cohort study in low-income women.

OBJECTIVE: To study the association between gestational weight gain (GWG) and offspring obesity risk at ages chosen to approximate prepuberty (10 years) and postpuberty (16 years). DESIGN: Prospective pregnancy cohort. SETTING: Pittsburgh, PA, USA. SAMPLE: Low-income pregnant women (n = 514) receiving prenatal care at an obstetric residency clinic and their singleton offspring. METHODS: Gestational weight gain was classified based on maternal GWG-for-gestational-age Z-score charts and was modelled using flexible spline terms in modified multivariable Poisson regression models. MAIN OUTCOME MEASURES: Obesity at 10 or 16 years, defined as body mass index (BMI) Z-scores ≥95th centile of the 2000 CDC references, based on measured height and weight. RESULTS: The prevalence of offspring obesity was 20% at 10 years and 22% at 16 years. In the overall sample, the risk of offspring obesity at 10 and 16 years increased when GWG exceeded a GWG Z-score of 0 SD (equivalent to 30 kg at 40 weeks); but for gains below a Z-score of 0 SD there was no relationship with child obesity risk. The association between GWG and offspring obesity varied by prepregnancy BMI. Among mothers with a pregravid BMI <25 kg/m(2) , the risk of offspring obesity increased when GWG Z-score exceeded 0 SD, yet among overweight women (BMI ≥25 kg/m(2) ), there was no association between GWG Z-scores and offspring obesity risk. CONCLUSIONS: Among lean women, higher GWG may have lasting effects on offspring obesity risk.

Effects of acute exercise on postprandial triglyceride response after a high-fat meal in overweight black and white adolescents.

OBJECTIVE: We examined the effects of acute exercise on postprandial triglyceride (TG) metabolism following a high-fat meal in overweight black vs white adolescents. DESIGN AND SUBJECTS: Twenty-one black and 17 white adolescents (12-18 yrs, body mass index 85th percentile) were evaluated twice, during control versus exercise trials, 1-4 weeks apart, in a counterbalanced randomized design. In the control trial, participants performed no exercise on day 1. In the exercise trial, participants performed a single bout of 60-min exercise (50% VO2 peak) on a cycle ergometer on day 1. On day 2 of both trials, participants consumed a high-fat breakfast (70% calories from fat) and blood was sampled for TG concentration in the fasted state and for 6 h postprandially. RESULTS: There was a significant main effect of condition on postprandial peak TG concentration (P=0.01) and TG area under the curve (AUC) (P=0.003), suggesting that independent of race, peak TG and TG-AUC was lower in the exercise trial vs control trial. Including Tanner stage, gender, total fat (kg) and visceral adipose tissue (VAT) as independent variables, stepwise multiple regression analyses revealed that in whites, VAT was the strongest (P<0.05) predictor of postprandial TG-AUC, explaining 56 and 25% of the variances in TG-AUC in the control and exercise trials, respectively. In blacks, VAT was not associated with postprandial TG-AUC, independent of trial. CONCLUSION: A single bout of aerobic exercise preceding a high-fat meal is beneficial to reduce postprandial TG concentrations in overweight white adolescents to a greater extent than black adolescents, particularly those with increased visceral adiposity.

ß-cell autoimmunity in overweight non-diabetic youth: any implications?

BACKGROUND AND OBJECTIVE: The presence of ß-cell antibodies is associated with a high risk of type 1 diabetes. With increasing rates of obesity, the distinction between obese T1DM and T2DM has become difficult. Moreover, increasing body mass index (BMI) in at-risk children has been proposed not only as a possible contributor to T1DM by increasing insulin resistance, but also as exerting an effect via the immunomodulatory properties of certain adipokines. This study aimed to determine prevalence of ß-cell autoantibodies (AA) in overweight non-diabetic children and assess insulin sensitivity and secretion derived from an oral glucose tolerance test (OGTT) in those with vs. without ß-cell AA. RESEARCH DESIGN AND METHODS: A total of 357 overweight (BMI > 85%) youths underwent OGTTs, dual energy X-ray absorptiometry (DEXA) and measurement of GAD65 and IA-2 AA according to the NIDDK harmonization assay. Using the same methodology, AA were measured in 90 normal weight, non-diabetic individuals. RESULTS: About 1.9% of overweight and 4.4% of control normal weight children had evidence of ß-cell autoimmunity, with GAD65 AA detected in all subjects but none with IA-2. Youth with positive vs. those with negative AA had higher leptin/adiponectin ratio, glucose at 60 min and C-peptide at 90 min. CONCLUSIONS: These findings suggest that the prevalence of ß-cell AA in overweight youth may be similar to that in non-overweight children. Further studies using standardized methods are required.

Reproducibility of the oral glucose tolerance test in overweight children.

OBJECTIVE: We examined the reproducibility of the oral glucose tolerance test (OGTT) in overweight children and evaluated distinguishing characteristics between those with concordant vs. discordant results. DESIGN: Sixty overweight youth (8-17 yr old) completed two OGTTs (interval between tests 1-25 d). Insulin sensitivity was assessed by the surrogate measures of fasting glucose to insulin ratio, whole-body insulin sensitivity index, and homeostasis model assessment of insulin resistance, and insulin secretion by the insulinogenic index with calculation of the glucose disposition index (GDI). RESULTS: Of the 10 subjects with impaired glucose tolerance (IGT) during the first OGTT only three (30%) had IGT during the second OGTT. The percent positive agreement between the first and second OGTT was low for both impaired fasting glucose and IGT (22.2 and 27.3%, respectively). Fasting blood glucose had higher reproducibility, compared with the 2-h glucose. Youth with discordant OGTTs, compared with those with concordant results, were more insulin resistant (glucose/insulin 2.7+/-1.4 vs. 4.1+/-1.8, P=0.006, whole-body insulin sensitivity index of 1.3+/-0.6 vs. 2.2+/-1.1, P=0.003, and homeostasis model assessment of insulin resistance 10.6+/-8.1 vs. 5.7+/-2.8, P=0.001), had a lower GDI (0.45+/-0.58 vs. 1.02+/-1.0, P=0.03), and had higher low-density lipoprotein cholesterol (117.7+/-36.6 vs. 89.9+/-20.1, P=0.0005) without differences in physical characteristics. CONCLUSIONS: Our results show poor reproducibility of the OGTT in obese youth, in particular for the 2-h plasma glucose. Obese youth who have discordant OGTT results are more insulin resistant with higher risk of developing type 2 diabetes mellitus, as evidenced by a lower GDI. The implications of this remain to be determined in clinical and research settings.

Cardiorespiratory fitness and abdominal adiposity in youth.

The purpose of this study was to determine whether cardiorespiratory fitness (CRF) is associated with lower abdominal adiposity in youth. Subjects included healthy 61 African-American and 52 white children and adolescents (age: 8-17 years). Body composition was measured by dual-energy X-ray absorptiometry and computed tomography. CRF (VO(2max)) was assessed using a graded maximal treadmill test. CRF was inversely related (P<0.05) to total adiposity, waist circumference, and visceral and abdominal subcutaneous adipose tissue (AT) independent of race. These findings remained significant (P<0.05) after adjusting for age, gender and pubertal status. Multiple regression analyses revealed that CRF is an independent contributor (P<0.05) of waist circumference, and visceral and abdominal subcutaneous AT after accounting for age, pubertal status, gender and body mass index percentile. Our observation suggest that in youth, CRF is associated with lower visceral and abdominal subcutaneous AT, and reinforces the notion that youth should engage in regular physical activity to improve aerobic fitness and reduce abdominal adiposity.

Correlations between fatty acid and glucose metabolism. Potential explanation of insulin resistance of puberty.

In vivo resistance to the action of insulin on glucose uptake has been documented during puberty. To test the hypothesis that the glucose-fatty acid cycle, as proposed by Randle et al. (Randle PJ, Garland PB, Hales CN, Newsholme EA: The glucose fatty-acid cycle: its role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. Lancet 1:785-789, 1963), may be responsible for this phenomenon, we studied nine prepubertal (Tanner I), nine pubertal (Tanner II-IV), and five young adult healthy subjects. The rate of lipolysis was measured with [d-5]glycerol tracer during basal state and during a stepwise hyperinsulinemic (10 and 40 mU.m-2.min-1)-euglycemic clamp. The rates of insulin-stimulated glucose disposal (Rd) were measured during the clamp, whereas glucose and fat oxidation were measured by using indirect respiratory calorimetry. Basal glycerol rate of appearance (Ra; lipolysis) and fat oxidation were similar between prepubertal and pubertal subjects but higher than adults when the data were expressed per kilogram body weight or per kilogram fat-free mass (FFM; glycerol Ra: 2.5 +/- 0.2, 2.6 +/- 0.2 vs. 1.6 +/- 0.2 mumol.min-1.kg FFM-1, P < 0.05; fat oxidation: 4.4 +/- 0.6, 4.8 +/- 0.3 vs. 3.2 +/- 0.6 mumol.min-1.kg FFM-1, P < 0.05). However, when expressed for total body, glycerol Ra and fat oxidation were higher in pubertal versus prepubertal and adult subjects. Insulin-like growth factor I (IGF-I) levels correlated with total-body lipolysis (r = 0.52, P = 0.006) and with total lipid oxidation (r = 0.44, P = 0.016) at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Can clinical factors estimate insulin resistance in type 1 diabetes?

An insulin resistance syndrome (IRS) score was developed based on clinical risk factors in adults with childhood-onset type 1 diabetes in the Epidemiology of Diabetes Complications (EDC) Study and was validated using euglycemic-hyperinsulinemic clamp studies. Hypertension, waist-to-hip ratio (WHR), triglyceride and HDL cholesterol levels, family history of type 2 diabetes, and glycemic control were risk factors used to define the score. A score of 1 (lowest likelihood IRS) to 3 (highest likelihood IRS) was assigned for each risk factor. Eligible subjects (n = 24) were recruited from the EDC cohort based on tertile of IRS score. Subjects received an overnight insulin infusion to normalize glucose levels, then underwent a 3-h euglycemic-hyperinsulinemic (60 mU x m(-2) x min(-1)) clamp. Glucose disposal rate (GDR) was determined during the last 30 min of the clamp. The GDR differed significantly by IRS group (9.65 +/- 2.99, 8.02 +/- 1.39, and 5.68 +/- 2.16 mg x kg(-1) x min(-1), P < 0.01). The GDR was inversely correlated with the IRS score (r = -0.64, P < 0.01). Using linear regression, the combination of risk factors that yielded the highest adjusted r2 value (0.57, P < 0.001) were WHR, hypertension, and HbA1. This study found that clinical risk factors can be used to identify subjects with type 1 diabetes who are insulin resistant, and it provides validation of a score based on clinical factors to determine the extent of insulin resistance in type 1 diabetes. This score will be applied to the entire EDC population in future studies to determine the effect of insulin resistance on complications.

Correlates of insulin antibodies in newly diagnosed children with insulin-dependent diabetes before insulin therapy.

Insulin antibodies, as measured by plasma radiolabeled insulin-binding capacity, were determined in 124 newly diagnosed insulin-dependent diabetic (IDDM) children before and after 1, 3, and 5 days of insulin therapy. Controls were 35 nondiabetic children with plasma insulin binding capacity of 1.0 +/- 0.7%. The patients were divided into three groups according to their plasma insulin-binding capacity. Group 1 (N = 79) had binding within two standard deviations (SD) of the control mean, group 2 (N = 20) had insulin binding 2-6 SD above controls, and group 3 (N = 25) showed insulin-binding capacity of more than 6 SD above the control mean. After exogenous insulin therapy, plasma 125I-insulin-binding capacity dropped significantly in both groups 2 and 3, concurrent with significant increases in plasma insulin levels. The three groups differed from each other in that patients in group 3 were significantly younger than in the other groups and clinically seemed to be more severely dehydrated, as reflected in their higher levels of serum urea nitrogen, plasma glucose, potassium, and elevated pulse rate. The three groups did not differ in respect to sex, HLA-DR antigens, Coxsackie-B antibody titers, islet cell cytoplasmic antibodies, immunoglobulin level, and C-peptide levels. Only two of 446 siblings of IDDM children showed elevated insulin binding, one of whom developed IDDM 6 wk later. The presence of an insulin-binding substance probably representing insulin antibodies in some cases of newly diagnosed IDDM suggests that autoimmunity in this disorder is not limited to the B-cell membrane and cytoplasm and lends further support to the heterogeneity of IDDM.

Insulin secretion, insulin sensitivity and diabetes in black children.

Historically, type 2 diabetes has been considered rare in the pediatric population. However, over the last decade, there has been a disturbing upswing in the rate of non-type 1 diabetes in the pediatric age group, particularly adolescents, with a greater proportion of Black children being affected. In this review, the following questions will be addressed: (1) what are the clinical characteristics of youth-onset atypical diabetes, (2) how common is it, (3) what are the risk factors, and (4) how should it be treated?

The relationship of physical fitness to lipid and lipoprotein(a) levels in adolescents with IDDM.

OBJECTIVE--Increased physical activity and physical fitness are recommended therapeutic modalities in addition to insulin and diet in the management of children with IDDM. The aim of this study was to assess the fitness levels of adolescents with IDDM compared with healthy control subjects and to evaluate the relationship between physical fitness and metabolic control. RESEARCH DESIGN AND METHODS--We studied 59 patients with IDDM, 28 boys and 31 girls, age 15.6 +/- 2.5 yr, duration of diabetes 7.6 +/- 3.5 yr, HbA1 10.6 +/- 2.1% (mean +/- SD), and compared them with 18 healthy, nondiabetic control subjects, 9 boys and 9 girls, matched for age, BMI, and Tanner stage. Physical fitness was measured by VO2max during progressive bicycle ergometry. HbA1 was used to determine glycemic control. Lipid profile included fasting total cholesterol, HDL, LDL, Lp(a), and TG levels. RESULTS--Patients with IDDM had lower VO2max levels than control subjects (33.7 +/- 7.0 vs. 41.0 +/- 10.4 ml.kg-1.min-1, P = 0.001). Males with IDDM had lower VO2max than male control subjects, but diabetic and control females showed no difference. In IDDM patients, VO2max correlated inversely with HbA1, insulin dose, cholesterol, LDL, TGs, and Lp(a), but did not correlate with HDL, which correlated inversely with BMI. CONCLUSIONS--We conclude that the state of physical fitness is an important correlate of lipid levels and Lp(a) in adolescents with IDDM. We speculate that higher physical fitness levels in adolescents with IDDM may decrease the risk of CVD through modulating lipid levels.

Impact of physical fitness and glycemic control on in vivo insulin action in adolescents with IDDM.

The relationship of in vivo insulin-mediated glucose utilization to the state of physical fitness and the degree of glycemic control was examined in 27 adolescents with insulin-dependent diabetes mellitus (IDDM) compared with 10 nondiabetic adolescent control subjects. In vivo total-body insulin-mediated glucose metabolism was evaluated by the hyperinsulinemic-euglycemic clamp. Physical fitness was assessed by maximal oxygen consumption (VO2 max) during cycle ergometry. Patients and control subjects had similar levels of VO2 max (34.9 +/- 8.6 vs. 38.6 +/- 9.9 ml.kg-1.min-1, P = 0.3). Patients had lower total-body insulin-mediated glucose metabolism compared with control subjects (33.9 +/- 14.3 vs. 63.8 +/- 17.2 mumol.kg-1.min-1, P = 0.0002). Among the patients, females had lower total-body insulin-mediated glucose metabolism compared with males (24.2 +/- 2.8 vs. 40.7 +/- 3.4 mumol.kg-1.min-1, P less than 0.001); however, this difference disappeared after correcting for sex differences in fitness levels. Insulin-mediated glucose metabolism correlated with VO2 max in patients and control subjects (r = 0.83, r = 0.81, P less than 0.05). The regression of total-body insulin-mediated glucose metabolism on VO2 max for patients was -2.84 +/- 0.255 VO2 max and for control subjects was 7.12 +/- 0.143 VO2 max, indicating that for similar degrees of physical fitness patients have lower total body insulin-mediated glucose metabolism levels than control subjects. In patients, total-body insulin-mediated glucose metabolism correlated with the degree of glycemic control as assessed by the level of glycosylated hemoglobin (r = -0.63, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin sensitivity in African-American children with and without family history of type 2 diabetes.

OBJECTIVE: African-Americans are at increased risk for type 2 diabetes. We have previously demonstrated that African-American children are hyperinsulinemic and insulin resistant compared with their white American peers. The aim of the present investigation was to assess the impact of family history of type 2 diabetes on insulin sensitivity in African-American children. RESEARCH DESIGN AND METHODS: A total of 13 prepubertal healthy children with negative family history (FH-) and 9 with positive family history (FH+) of type 2 diabetes underwent a 3-h hyperinsulinemic (40 mU x m(-2) x min(-1))-euglycemic clamp study to assess insulin sensitivity. The groups were comparable for age, pubertal status, total body adiposity determined by dual-energy X-ray absorptiometry, abdominal adiposity assessed by computed tomography scan at the level of L4-5 lumbar vertebra, and physical fitness measured by maximal oxygen consumption (VO2max). RESULTS: The FH+, compared with the FH-, group had lower insulin-stimulated glucose disposal (10.9+/-1.2 vs. 14.2+/-0.9 mg x kg(-1) x min(-1), P = 0.035) and lower nonoxidative glucose disposal (5.7+/-0.8 vs. 8.3+/-0.6 mg x kg(-1) x min(-1), P = 0.015), with no differences in rates of glucose oxidation, fat oxidation, or insulin-mediated free fatty acid suppression. Fasting hepatic glucose production assessed with [6,6-2H2]glucose and basal rates of glucose and fat oxidation were not different between the two groups. CONCLUSIONS: These data suggest that in African-American children, family history of type 2 diabetes is a risk factor for insulin resistance. These children manifest important metabolic alterations, including impaired insulin-stimulated total and nonoxidative glucose disposal early in the first decade of life. We propose that this familial tendency, combined with environmental influences, could lead to type 2 diabetes decades later.

Is gestational weight gain associated with offspring obesity at 36 months?

OBJECTIVE: We examined the association between gestational weight gain (GWG) and offspring obesity at age 36 months. METHODS: Mother-infant dyads (n = 609) were followed from a first study visit (mean [standard deviation]: 18.8 [2.7] weeks gestation) to 36 months postpartum. Total GWG over the entire pregnancy was defined as excessive or non-excessive according to the 2009 Institute of Medicine guidelines. Four mutually exclusive categories of excessive or non-excessive GWG across early (conception to first study visit) and late (first study visit to delivery) pregnancy defined GWG pattern. Body mass index (BMI) z-scores ≥95th percentile of the 2000 Centers for Disease Control (CDC) references defined offspring obesity at 36 months. Multivariable log-binomial models adjusted for pre-pregnancy BMI and breastfeeding were used to estimate the association between GWG and childhood obesity risk. RESULTS: Nearly half of the women had total excessive GWG. Of these, 46% gained excessively during both early and late pregnancy while 22% gained excessively early and non-excessively late, and the remaining 32% gained non-excess weight early and excessively later. Thirteen per cent of all children were obese at 36 months. Excessive total GWG was associated with more than twice the risk of child obesity (adjusted risk ratio [95% confidence interval]: 2.20 [1.35, 3.61]) compared with overall non-excessive GWG. Compared with a pattern of non-excessive GWG in both early and late pregnancy, excessive GWG in both periods was associated with an increased risk of obesity (2.39 [1.13, 5.08]). CONCLUSIONS: Excessive GWG is a potentially modifiable factor that may influence obesity development in early childhood.

Insulin sensitivity, lipids, and body composition in childhood: is "syndrome X" present?

Syndrome X, or the syndrome of insulin resistance, is a cluster of related metabolic abnormalities of hyperinsulinemia, glucose intolerance, increased very low density lipoprotein (VLDL), decreased high density lipoprotein (HDL), and hypertension in nonobese adults and plays an important role in the genesis of cardiovascular disease. The aim of the present study was to examine the relationships among insulin sensitivity, plasma lipid levels, and body composition in the pediatric age group to determine whether these associations are present in childhood. Twenty healthy Caucasian Tanner stage I (TI) children (age, 10.7 +/- 0.3 yr; body mass index, 18.9 +/- 0.8 kg/m2) and 22 pubertal Tanner stage II-IV (TII-IV) adolescents (age, 14.0 +/- 0.3 yr; body mass index, 20.0 +/- 0.4 kg/m2) were studied. In vivo insulin-mediated glucose disposal (Rd) was evaluated during a 40 mu/m2. min hyperinsulinemic-euglycemic clamp. Body composition was assessed isotopically by the H218O dilution principle. Fasting blood was obtained for cholesterol, triglyceride (TG), VLDL, low density lipoprotein (LDL), and HDL determinations. In both groups, the strongest correlation of Rd was with percent body fat (%BF) (TI: r = -0.82; P < 0.001; TII-IV: r = -0.73; P < 0.001). In addition, in TI, Rd was correlated with TG (r = 0.64; P = 0.001), VLDL (r = 0.64; P = 0.001), and diastolic blood pressure (r = -0.50; P = 0.01). There were no such correlations in TII-IV. In TI, % BF correlated positively with LDL and negatively with TG and VLDL. In TII-IV, % BF correlated positively with cholesterol and LDL. After correcting for %BF, partial correlation analysis revealed no relationship between Rd and lipid levels in either group. This suggests that the relationship of insulin sensitivity to lipid levels was secondary to the effect of body composition on lipid levels. However, regardless of body composition, the basal insulin level was correlated with TG (r = 0.38; P = 0.04) and VLDL (r = 0.40; P = 0.04) in TII-IV subjects. We conclude that 1) the primary correlate of insulin sensitivity is %BF in both prepubertal and pubertal subjects, with no relationship to plasma lipids; 2) in prepubertal children, diastolic blood pressure is negatively correlated with insulin sensitivity and positively with insulin levels, independent of adiposity; and 3) after the onset of puberty, basal insulin levels are positively correlated with VLDL and TG regardless of the degree of adiposity. This observation could be a very early manifestation of the genesis of syndrome X in childhood.

Testosterone treatment in adolescents with delayed puberty: changes in body composition, protein, fat, and glucose metabolism.

Previously, we demonstrated decreased protein breakdown and insulin resistance in pubertal adolescents compared with prepubertal children. Puberty-related increases in sex steroids and/or GH could be potentially responsible. In the present study, the effects of 4 months of testosterone enanthate (50 mg in every 2 weeks) on body composition, protein, fat, and glucose metabolism and insulin sensitivity were evaluated in adolescents with delayed puberty. Body composition was assessed by H218O-dilution principle. Protein breakdown, oxidation, and synthesis were measured during primed constant infusion of [1-13C]leucine. Whole-body lipolysis was measured during primed constant infusion of [2H5]glycerol. Insulin action in suppressing proteolysis and lipolysis and stimulating glucose disposal was assessed during a stepwise hyperinsulinemic (10 and 40 mU-m2.min) euglycemic clamp. Fat and glucose oxidation rates were calculated from indirect calorimetry measurements. After 4 months of testosterone treatment, height, weight, and fat free mass (FFM) increased and fat mass, percent body fat, plasma cholesterol, high- and low-density lipoproteins, and leptin levels decreased significantly. Whole-body proteolysis and protein oxidation were lower after testosterone treatment (proteolysis, 0.49 +/- 0.03 vs 0.54 +/- 0.04 g.h.kg FFM, P = 0.032; oxidation, 0.05 +/- 0.01 vs. 0.09 +/- 0.01 g.h.kg FFM, P = 0.015). Protein synthesis was not different, and resting energy expenditure was not different. Total body lipolysis was not affected by testosterone treatment, however, fat oxidation was higher after testosterone (pre-: 2.4 +/- 0.7 vs. post-: 3.5 +/- 0.7 mumol.kg.min, P = 0.031). During the 40 mU.m2.min hyperinsulinemia, insulin sensitivity of glucose metabolism was not affected with testosterone therapy (59.1 +/- 8.8 vs. 57.1 +/- 8.2 mumol.kg.min per muU/mL). However, metabolic clearance rate of insulin was higher posttestosterone (13.6 +/- 1.1 vs. 16.7 +/- 0.8 mL.kg.min, P = 0.004). In conclusion, after 4 months of low-dose testosterone treatment in adolescents with delayed puberty 1) FFM increases and fat mass and leptin levels decrease; 2) postabsorptive proteolysis and protein oxidation decrease; 3) fat oxidation increases; and 4) insulin sensitivity in glucose metabolism does not change, whereas insulin clearance increases. These longitudinal observations are in agreement with our previous cross-sectional studies of puberty and demonstrate sparing of protein breakdown of approximately 1.2 g.kg.day FFM, wasting of fat mass, but no change in insulin sensitivity after short periods of low-dose testosterone supplementation.

Insulin secretion and sensitivity in black versus white prepubertal healthy children.

We had previously demonstrated greater insulin secretion and lower insulin sensitivity in black pubertal adolescents compared with whites. This study aimed to investigate whether similar black/white differences are present in the prepubertal period or are characteristics of the pubertal period. Twelve black and 11 white healthy prepubertal children, matched for age, body mass index, and Tanner I pubertal development, underwent a 2-h hyperglycemic clamp (225 mg/dL). Physical fitness was assessed by maximal oxygen consumption (VO2max) measurement during graded bicycle ergometry, and resting energy expenditure was measured by indirect calorimetry after overnight fast. Fasting and first phase insulin concentrations were higher in blacks than in whites [14.7 +/- 1.3 vs. 10.4 +/- 1.2 (P = 0.02) and 76.9 +/- 6.8 vs. 52.1 +/- 6.4 microU/mL (P = 0.016)]. There were no differences in second phase insulin levels and insulin sensitivity index. Both maximal oxygen consumption (VO2max) and resting energy expenditure were lower in black children, whereas insulin-like growth factor I was higher. After controlling for these differences, race contributed significantly to basal insulin, but not to first phase insulin. In summary, previously reported black/white differences in insulin secretion and sensitivity during adolescence may have their origin in early childhood manifested as hyperinsulinemia. However, genetic (race) vs. environmental factors (physical activity/fitness and energy balance) should be carefully scrutinized as potential factors responsible for such differences.

Leptin before and after insulin therapy in children with new-onset type 1 diabetes.

Serum leptin levels reflect the amount of body fat. However, several reports suggest that insulin may also regulate serum leptin levels. This study was aimed at testing whether leptin levels are low in newly diagnosed patients with type 1 diabetes and increase after institution of insulin therapy. Nineteen children with new-onset type 1 diabetes were studied. Serum leptin levels were measured at presentation before insulin therapy was initiated (day 0), 1 day after insulin therapy (day 1), 3-5 days after insulin therapy (day 3-5), and at 3 months of follow-up (3 months). The control group consisted of 19 healthy children matched for age and body mass index. On day 0 leptin levels were lower in the patients compared with those in controls (3.3 +/- 0.2 vs. 6.2 +/- 0.9 ng/mL; P < 0.005). After insulin therapy, leptin levels increased significantly by day 1 without significant weight change and became comparable to control values by days 3-5. Before insulin therapy, leptin did not correlate with weight, body mass index, or hemoglobin A1c. After insulin therapy, leptin levels on days 3-5 correlated with insulin dose (r = 0.43; P = 0.03). The results of this study demonstrate that children with new-onset type 1 diabetes have low leptin levels before insulin therapy. Leptin levels increase within 24 h of insulin therapy and become comparable to nondiabetic levels by 3-5 days. This rapid increase in leptin after 24 h of insulinization is independent of changes in body weight and is postulated to be due to a stimulatory effect of insulin on leptin production, nutritional replenishment, or both factors together.

Glucose intolerance in obese adolescents with polycystic ovary syndrome: roles of insulin resistance and beta-cell dysfunction and risk of cardiovascular disease.

The roles of insulin resistance and insulin secretion in the pathogenesis of glucose intolerance in polycystic ovary syndrome (PCOS) were evaluated in 11 adolescents with impaired glucose tolerance (IGT) and 10 with normal glucose tolerance (NGT). Hepatic glucose production and insulin-stimulated glucose disposal were measured using [6,6-(2)H(2)]glucose and a 3-h hyperinsulinemic (80 mu/m(2).min)-euglycemic clamp. First and second phase insulin secretions were evaluated during a hyperglycemic clamp. Automated blood pressure measurements were made to assess the nocturnal change in blood pressure. Hepatic glucose production was significantly higher in IGT vs. NGT. Insulin-stimulated glucose disposal was not different between the two groups. The first phase insulin level was lower in IGT (207.9 +/- 21.0 vs. 357.0 +/- 62.9 muu/mL; P = 0.025; 1247 +/- 126 vs. 2142 +/- 377 pmol/L) without a difference in second phase insulin. The glucose disposition index (product of insulin sensitivity x first phase insulin) was lower in IGT vs. NGT (278 +/- 40 vs. 567 +/- 119 mg/kg.min; P = 0.023; 1546 +/- 223 vs. 3249 +/- 663 micromol/kg.min). The glucose disposition index correlated inversely with OGTT glucose concentrations at 30, 60, and 120 min. Adolescents with PCOS-IGT lacked the normal nocturnal decline in blood pressure. We conclude that in obese adolescents with PCOS, glucose intolerance is associated with 1) decreased first phase insulin secretion, 2) decreased glucose disposition index, and 3) increased hepatic glucose production. These metabolic abnormalities are precursors of type 2 diabetes and are present early in the course of PCOS. Furthermore, the absence of nocturnal dipping in blood pressure may herald the early expression of cardiovascular disease risk in these adolescents.

Roles of insulin resistance and beta-cell dysfunction in the pathogenesis of glucose intolerance in cystic fibrosis.

The roles of insulin deficiency and insulin resistance in the pathogenesis of glucose intolerance in cystic fibrosis (CF) were evaluated in eight patients (aged 16.5 +/- 1.9 yr), four with normal glucose tolerance (NGT) and four with impaired glucose tolerance (IGT), and in seven healthy control (CN) subjects. First and second phase insulin secretions were evaluated during a hyperglycemic clamp. Hepatic glucose production (HGP) and insulin-stimulated glucose disposal were measured using [6,6-2H2]glucose and a stepwise hyperinsulinemic-euglycemic clamp. First and second phase insulin levels were significantly lower in both groups of CF patients compared with control values. There was an inverse relationship between glycohemoglobin level and first phase insulin (r = -0.81; P = 0.015) and second phase insulin (r = -0.97; P < 0.001). During the hyperglycemic clamp, the insulin sensitivity index was lower in CF-IGT, but not CF-NGT, compared with control values (6.66 +/- 1.79, 12.82 +/- 1.61, and 13.02 +/- 1.78 mumol/kg.min/pmol.L, respectively; P < 0.05). Basal HGP and fasting plasma glucose were higher in CF vs. CN [24.8 +/- 2.9 vs. 16.9 +/- 1.4 mumol/kg.min (P = 0.036) and 5.8 +/- 0.2 vs. 5.4 +/- 0.1 mmol/L (P = 0.035), respectively]. During the hyperinsulinemic euglycemic clamp, insulin-stimulated glucose disposal was significantly lower in CF-IGT (45.68 +/- 4.87 mumol/kg.min) vs. CF-NGT (78.99 +/- 1.34 mumol/kg.min) and CN (71.74 +/- 6.88 mumol/kg.min). Insulin sensitivity was lower in CF-IGT vs. CF-NGT (7.04 +/- 0.86 and 14.38 +/- 0.84 mumol/kg.min/pmol.L; P < 0.05). We conclude that 1) glycohemoglobin is a strong correlate of insulin deficiency in CF; and 2) glucose intolerance in this group of CF patients occurred as a consequence of concomitant insulin deficiency and insulin resistance.

Lipolysis in African-American children: is it a metabolic risk factor predisposing to obesity?

Rates of obesity and type 2 diabetes are higher in African-American (AA), compared with American white (AW), adults and children. It is not known whether biologic and/or environmental differences are responsible for this racial disparity. We and others have demonstrated that AA children are hyperinsulinemic, compared with their AW peers. This investigation tested the hypothesis that hyperinsulinemia in AA children is associated with lower rates of lipolysis, which could be a risk factor for future obesity. Forty prepubertal children (20 AA and 20 AW) with comparable body composition (assessed by dual-energy x-ray absorptiometry) and visceral adiposity (evaluated with computed tomography scan) were studied. Total body lipolysis was measured with [(2)H(5)]glycerol after overnight fasting. Basal lipolysis was approximately 40% lower in AA vs. AW children, whether the data were expressed for total body (85.7 +/- 8.9 vs. 130.3 +/- 14.1 micromol/min, P = 0.011) or per-kilogram BW (2.4 +/- 0.2 vs. 3.8 +/- 0.4 micromol/min.kg, P = 0.002) or per kilogram fat free mass (FFM) (3.3 +/- 0.3 vs. 5.2 +/- 0.5 micromol/min.kg FFM, P = 0.004), or per kg fat mass (FM) (13.7 +/- 1.6 vs. 21.3 +/- 3.3 micromol/min.kg FM, P = 0.046). Fasting insulin levels were higher in AA children (99.6 +/- 7.8 vs. 77.4 +/- 5.9 pmol/L, P = 0.032). Lipolysis correlated positively with fat mass, percent body fat, and abdominal fat mass. However, in multiple-regression analysis models after controlling for insulin and body composition, race remained a significant contributor to the variance in lipolysis. In summary, the present study demonstrates that rates of lipolysis are significantly lower in AA children, compared with their white peers. This may constitute an early metabolic phenotype that may mediate fat trapping and susceptibility to obesity in a specific environmental context of energy excess conducive to fat accretion.