Dependency of the metabolic effect of sc-injected human regular insulin on intra-abdominal fat in patients with type 2 diabetes.

Ten patients with type 2 diabetes were enrolled in an isoglycemic glucose clamp study to determine the impact of intra-abdominal fat, subcutaneous abdominal fat and total abdominal fat on the metabolic effect of a single bolus (0.2 IU/kg) of sc-injected human regular insulin. The maximum metabolic effect associated highly and negatively with intra-abdominal fat (r = - 0.72, p < 0.02) and with the homeostasis model assessment insulin resistance score (HOMA, r = - 0.71, p < 0.03). Likewise, the total metabolic effect of sc-injected insulin correlated strongly and negatively with intra-abdominal fat (r = - 0.77, p < 0.01), HOMA (r = - 0.74, p < 0.02) and HbA (1c) (r = - 0.70, p < 0.03). Stepwise multiple regression analyses showed that the highest metabolic effect was only significantly predicted by intra-abdominal fat, indicating a high negative correlation with the maximum effect (beta = - 0.72) whereas time to maximum metabolic effect showed a strong (beta = 0.72) and positive correlation with HOMA. In combination with the HOMA, it is intra-abdominal fat, and not subcutaneous abdominal fat, which explains 50 - 75 % of the variability of the effect of sc human regular insulin in patients with type 2 diabetes.     

Serum alanine aminotransferase is associated with serum adiponectin, C-reactive protein and apolipoprotein B in young healthy men.

Several studies have reported an association between markers of liver injury, including elevated concentrations of alanine aminotransferase (ALT) aspartate aminotransferase (AST), and prospective risk of type 2 diabetes. We therefore examined the relationship between ALT and AST on the one hand, and serum adiponectin and highly sensitive CRP on the other, both of which have been reported to be associated with prospective risk of type 2 diabetes; we also tested for variable components of metabolic syndrome in 198 male college students aged 18-20 years. ALT showed a positive relationship with percentage body fat (r = 0.19, p = 0.02), serum leptin (r = 0.21, p = 0.01), LDL cholesterol (r = 0.29, p = 0.0003), triglyceride (r = 0.28, p = 0.0004) and apolipoprotein B (r = 0.35, p < 0.0001) even after adjustment for body mass index (BMI). Although there was a significant relationship with serum insulin, adiponectin (inversely), homeostasis model assessment of insulin resistance, systolic and diastolic blood pressure, HDL cholesterol (inversely) and LDL particle diameter in simple regression analysis, significance disappeared after adjustment for BMI. In contrast, CRP (r = 0.16, p = 0.04) was associated with ALT after adjustment for BMI, although simple regression analysis revealed no association between the two. Relationships were smaller for AST, and significance disappeared after adjustment for BMI. Multiple regression analysis excluding lipid variables revealed significant and independent associations of ALT with adiponectin and percentage body fat. In a model including lipid variables, apolipoprotein B emerged as an independent predictor of ALT in addition to adiponectin and percentage body fat. These variables explained 29 % of ALT variability. In conclusion, serum ALT levels were associated with leptin and CRP as well as many components of the insulin resistance syndrome in young healthy men. Adiponectin, apolipoprotein B and percentage body fat emerged as significant and independent predictors of ALT. Since adiponectin and chronic subclinical inflammation have been reported to predict the development of type 2 diabetes and since abnormalities in apolipoprotein B metabolism occur in the early course of insulin resistance, these findings may be compatible with the association between liver markers and risk of diabetes.     

The Visceral Adiposity Syndrome in Japanese-American Men

Japanese-Americans have an increased prevalence of non-insulin-dependent diabetes mellitus and coronary heart disease when compared to native Japanese. This increase has been associated with fasting hyperinsulinemia, hypertriglyceridemia, and low plasma levels of high-density lipoprotein (HDL) cholesterol. The purpose of this study was to examine the relationship of both visceral adiposity and insulin resistance to this metabolic syndrome and to the presence of a predominance of small, dense low-density lipoprotein (LDL) particles (LDL subclass phenotype B) that has been associated with increased atherogenic risk. Six Japanese-American men with non-insulin-dependent diabetes, each receiving an oral sulfonylurea, were selected. One or 2 nondiabetic Japanese-American men, matched by age and body mass index, were selected for each diabetic subject, giving a total of 9 nondiabetic men. Diabetic subjects had significantly higher fasting plasma glucose (p=0.0007) and lower insulin sensitivity (S_I, p=0.018) using the minimal model technique than nondiabetic subjects matched for body mass index. Six men (2 with diabetes) had LDL phenotype A and 8 (4 with diabetes) had phenotype B. One nondiabetic subject had an intermediate low-density lipoprotein pattern. Significantly greater amounts of intra-abdominal fat (p=0.045) measured by computed tomography were found in the men with phenotype B while fasting insulin (p=0.070) and triglycerides (p=0.051) tended to be higher. Intra-abdominal fat was significantly correlated with S_I (r=-0.559), plasma triglycerides (r=0.541), plasma free fatty acids (r=0.677), LDL density (relative flotation rate, r=-0.803), and plasma HDL-cholesterol (r=-0.717). S_I was significantly correlated only with plasma free fatty acids (r=-0.546) and tended to be correlated with hepatic lipase activity (r=-0.512, p=0.061). In conclusion, these observations indicate that in non-obese Japanese-American men, the metabolic features of the so-called insulin resistance syndrome, including LDL phenotype B, are more strongly correlated with visceral adiposity than with S_I. It may therefore be more appropriate to call this the visceral adiposity syndrome. Although questions concerning mechanisms still remain, we postulate that visceral adiposity plays a central role in the development of many of the metabolic abnormalities, including LDL subclass phenotype B, that occur in this metabolic syndrome.     

Differences in the Serum Nonesterified Fatty Acid Profile of Young Women Associated with a Recent History of Gestational Diabetes and Overweight/Obesity

BackgroundNonesterified fatty acids (NEFA) play pathophysiological roles in metabolic syndrome and type 2 diabetes (T2D). In this study, we analyzed the fasting NEFA profiles of normoglycemic individuals at risk for T2D (women with a recent history of gestational diabetes (GDM)) in comparison to controls (women after a normoglycemic pregnancy). We also examined the associations of NEFA species with overweight/obesity, body fat distribution and insulin sensitivity.ResultsWomen after GDM had a lower molar percentage of total saturated fatty acids (SFA; 38.55% vs. 40.32%, p = 0.0002) than controls. At an explorative level of significance several NEFA species were associated with post-GDM status (with and without adjustment for body mass index (BMI) and HbA1c): The molar percentages of 14:0, 16:0, 18:0 and 18:4 were reduced, whereas those of 18:1, 18:2, 20:2, 24:4, monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and total n-6 NEFA were increased. BMI and the amount of body fat correlated inversely with several SFA and MUFA and positively with various PUFA species over the whole study cohort (abs(ρ)≥0.3 for all). 14:0 was inversely and BMI-independently associated with abdominal visceral adiposity. We saw no correlations of NEFA species with insulin sensitivity and the total NEFA concentration was similar in the post-GDM and the control group.ConclusionIn conclusion, we found alterations in the fasting NEFA profile associated with a recent history of gestational diabetes, a risk marker for T2D. NEFA composition also varied with overweight/obesity and with body fat distribution, but not with insulin sensitivity.     

Normal insulin sensitivity and IMCL content in overweight humans are associated with higher fasting lipid oxidation

Intramyocellular lipid (IMCL) storage is considered a local marker of whole body insulin resistance; because increments of body weight are supposed to impair insulin sensitivity, this study was designed to assess IMCL content, lipid oxidation, and insulin action in individuals with a moderate increment of body fat mass and no family history of diabetes. We studied 14 young, nonobese women with body fat <30% (n = 7) or >30% (n = 7) and 14 young, nonobese men with body fat <25% (n = 7) or >25% (n = 7) by means of the euglycemic-insulin clamp to assess whole body glucose metabolism, with indirect calorimetry to assess lipid oxidation, by localized (1)H NMR spectroscopy of the calf muscles to assess IMCL content, and with dual-energy X-ray absorptiometry to assess body composition. Subjects with higher body fat had normal insulin-stimulated glucose disposal (P = 0.80), IMCL content in both soleus (P = 0.22) and tibialis anterior (P = 0.75) muscles, and plasma free fatty acid levels (P = 0.075) compared with leaner subjects in association with increased lipid oxidation (P < 0.05), resting energy expenditure (P = 0.046), resting oxygen consumption (P = 0.049), and plasma leptin levels (P < 0.01) in the postabsorptive condition. In conclusion, in overweight subjects, preservation of insulin sensitivity was combined with increased lipid oxidation and maintenance of normal IMCL content, suggesting that abnormalities of these factors may mutually determine the development of insulin resistance associated with weight gain.     

Effects of a combination of rhGH and metformin on adiponectin levels in patients with metabolic syndrome.

Adiponectin is a recently discovered adipocytokine that correlates negatively with body mass index and body fat. In patients with GH deficiency, treatment with recombinant human growth hormone (rhGH) reduces body fat mass and thus may also have a favorable effect in patients with metabolic syndrome, and would also be expected to increase adiponectin levels. However, due to its diabetogenic effect, rhGH treatment also bears an increased risk for the development of type 2 diabetes mellitus. We conducted a 18-month randomized, double-blind, placebo-controlled study to assess the effect of rhGH in combination with metformin (MGH) in 14 obese men (7 MGH; 7 Metformin+Placebo, 54 +/- 2 years, BMI 33.0 +/- 1.2 kg/m(2)) with mildly elevated fasting plasma glucose (FPG) at screening (6.1-8.0 mmol/l). All patients received metformin (850 mg twice daily) for treatment of type 2 diabetes mellitus/impaired glucose tolerance, either alone or in combination with rhGH (daily dose 9.5 mug/kg body weight). Glucose disposal rate (GDR) was measured using the euglycemic hyperinsulinemic clamp technique, and body composition was measured by DEXA at 0 and 18 months. After 18 months, the mean adiponectin concentration increased by 32 +/- 11 % (p = 0.018) in the MGH group and did not change in the MP group (- 10 +/- 13 %; p = n. s.). The difference in relative changes in adiponectin levels between the two groups after 18 months was statistically significant (p = 0.026). Improvement in insulin sensitivity (GDR) correlated positively with adiponectin levels (r = 0.73; p = 0.004). In conclusion, the additional administration of rhGH increased adiponectin levels in patients with metabolic syndrome, indicating its potential role in adiponectin-associated insulin sensitivity alterations.     

Effect of Chronic Athletic Activity on Brown Fat in Young Women

BackgroundThe effect of chronic exercise activity on brown adipose tissue (BAT) is not clear, with some studies showing positive and others showing negative associations. Chronic exercise is associated with increased resting energy expenditure (REE) secondary to increased lean mass and a probable increase in BAT. Many athletes are in a state of relative energy deficit suggested by lower fat mass and hypothalamic amenorrhea. States of severe energy deficit such as anorexia nervosa are associated with reduced BAT. There are no data regarding the impact of chronic exercise activity on BAT volume or activity in young women and it is unclear whether relative energy deficiency modifies the effects of exercise on BAT.PurposeWe assessed cold induced BAT volume and activity in young female athletes compared with non-athletes, and further evaluated associations of BAT with measures of REE, body composition and menstrual status.MethodsThe protocol was approved by our Institutional Review Board. Written informed consent was obtained from all participants prior to study initiation. This was a cross-sectional study of 24 women (16 athletes and8 non-athletes) between 18–25 years of age. Athletes were either oligo-amenorrheic (n = 8) or eumenorrheic (n = 8).We used PET/CT scans to determine cold induced BAT activity, VMAX Encore 29 metabolic cart to obtain measures of REE, and DXA for body composition.ResultsAthletes and non-athletes did not differ for age or BMI. Compared with non-athletes, athletes had lower percent body fat (p = 0.002), higher percent lean mass (p = 0.01) and trended higher in REE (p = 0.09). BAT volume and activity in athletes trended lower than in non-athletes (p = 0.06; p = 0.07, respectively). We found negative associations of BAT activity with duration of amenorrhea (r = -0.46, p = 0.02).BAT volume correlated inversely with lean mass (r = -0.46, p = 0.02), and positively with percent body fat, irisin and thyroid hormones.ConclusionsOur study shows a trend for lower BAT in young female athletes compared with non-athletes, and shows associations of brown fat with menstrual status and body composition. Brown fat may undergo adaptive reductions with increasing energy deficit.     

Pre-Pubertal Children Born Post-Term Have Reduced Insulin Sensitivity and Other Markers of the Metabolic Syndrome

Background

There are no data on the metabolic consequences of post-term birth (≥42 weeks gestation). We hypothesized that post-term birth would adversely affect insulin sensitivity, as well as other metabolic parameters and body composition in childhood.

Methods

77 healthy pre-pubertal children, born appropriate-for-gestational-age were studied in Auckland, New Zealand: 36 born post-term (18 boys) and 41 (27 boys) born at term (38–40 weeks gestation). Primary outcome was insulin sensitivity measured using intravenous glucose tolerance tests and Bergman’s minimal model. Other assessments included fasting hormone concentrations and lipid profiles, body composition from whole-body dual-energy X-ray absorptiometry, 24-hour ambulatory blood pressure monitoring, and inflammatory markers.

Results

Insulin sensitivity was 34% lower in post-term than in term children (7.7 vs. 11.6 x10^-4·min^-1·(mU/l); p<0.0001). There was a compensatory increase in acute insulin response among post-term children (418 vs 304 mU/l; p=0.037), who also displayed lower glucose effectiveness than those born at term (2.25 vs 3.11 x10^-2·min^-1; p=0.047). Post-term children not only had more body fat (p=0.014) and less fat-free mass (p=0.014), but also had increased central adiposity with more truncal fat (p=0.017) and greater android to gynoid fat ratio (p=0.007) compared to term controls. Further, post-term children displayed other markers of the metabolic syndrome: lower normal nocturnal systolic blood pressure dipping (p=0.027), lower adiponectin concentrations (p=0.005), as well as higher leptin (p=0.008) and uric acid (p=0.033) concentrations. Post-term boys (but not girls) also displayed a less favourable lipid profile, with higher total cholesterol (p=0.018) and LDL-C (p=0.006) concentrations, and total cholesterol to HDL-C ratio (p=0.048).

Conclusions

Post-term children have reduced insulin sensitivity and display a number of early markers of the metabolic syndrome. These findings could have important implications for the management of prolonged pregnancies. Future studies need to examine potential impacts later in life, as well as possible underlying mechanisms.     

Circulating Interleukin‐6 in Relation to Adiposity,Insulin Action,and Insulin Secretion

Objective: Plasma concentrations of interleukin‐6 (IL‐6), a proinflammatory cytokine produced and released in part by adipose tissue, are elevated in people with obesity and type 2 diabetes. Because recent studies suggest that markers of inflammation predict the development of type 2 diabetes, we examined whether circulating plasma IL‐6 concentrations were related to direct measures of insulin resistance and insulin secretory dysfunction in Pima Indians, a population with high rates of obesity and type 2 diabetes. Research Methods and Procedures: Fasting plasma IL‐6 concentrations (enzyme‐linked immunosorbent assay), body composition (DXA), insulin action (M; hyperinsulinemic euglycemic clamp), and acute insulin secretory responses to glucose (25 g intravenous glucose tolerance test) were measured in 58 Pima Indians without diabetes (24 women, 34 men). Results: Fasting plasma IL‐6 concentrations were positively correlated with percentage of body fat (r = 0.26, p = 0.049) and negatively correlated with M (r = ?0.28, p = 0.031), but were not related to acute insulin response (r = 0.13, p = 0.339). After adjusting for percentage of body fat, plasma IL‐6 was not related to M (partial r = ?0.23, p = 0.089). Discussion: Fasting plasma IL‐6 concentrations are positively related to adiposity and negatively related to insulin action in Pima Indians. The relationship between IL‐6 and insulin action seems to be mediated through adiposity.     

Liraglutide as Additional Treatment to Insulin in Obese Patients with Type 1 Diabetes Mellitus

ObjectiveBecause approximately 40% of patients with type 1 diabetes have the metabolic syndrome, we tested the hypothesis that addition of liraglutide to insulin in obese patients with type 1 diabetes will result in an improvement in plasma glucose concentrations, a reduction in hemoglobin A1c (HbA1c), a fall in systolic blood pressure, and weight loss.MethodsThis is a retrospective analysis of data obtained from 27 obese patients with type 1 diabetes treated with liraglutide in addition to insulin. Patients were also treated for hypertension. Paired t tests were used to compare the changes in HbA1c, insulin doses, body weight, body mass index, 4-week mean blood glucose concentrations (28-day insulin pump mean blood glucose), blood pressure, and lipid parameters prior to and 180 ± 14 days after liraglutide therapy.ResultsMean glucose concentrations fell from 191 ± 6 to 170 ± 6 mg/dL (P = .002). HbA1c fell from 7.89 ± 0.13% to 7.46 ± 0.13% (P = .001), without an increase in frequency of hypoglycemia. Mean body weight fell from 96.20 ± 3.68 kg to 91.56 ± 3.78 kg (P<.0001). Daily total and bolus doses of insulin fell from 73 ± 6 to 60 ± 4 (P = .008) units and from 40 ± 5 to 29 ± 3 units (P = .011), respectively. Mean systolic blood pressure fell from 130 ± 3 to 120 ± 4 mm Hg (P = .020).ConclusionAddition of liraglutide to insulin in obese patients with type 1 diabetes mellitus leads to improvements in glycemic control and HbA1c and to reductions in insulin dose, systolic blood pressure, and body weight. (Endocr Pract. 2013;19:963-967)     

Body Fat Patterning,Hepatic Fat and Pancreatic Volume of Non-Obese Asian Indians with Type 2 Diabetes in North India: A Case-Control Study

ObjectiveTo evaluate body fat patterning and phenotype including hepatic fat and pancreatic volume of non-obese (BMI: < 25 kg/m²) Asian Indians with type 2 diabetes residing in North India.MethodsNon-obese patients with type 2 diabetes (n = 93) and non-obese, normo-glycemic subjects (n = 40) were recruited. BMI, waist & hip circumferences, skinfold thickness at 8 sites, body fat, lean mass and detailed abdominal fat evaluation [total abdominal fat, total subcutaneous fat (superficial, deep, anterior, and posterior), total intra-abdominal fat (intra-peritoneal, retroperitoneal)], liver span, grades of fatty liver and pancreatic volume were compared.ResultsWaist circumference, subscapular skinfolds and total truncal fat (on DEXA) were higher whereas calf, total peripheral skinfolds and total leg fat (on DEXA) lower in patients. Specifically, the following volumes were higher in cases as compared to controls; total abdominal fat (19.4%), total intra-abdominal fat (49.7%), intra-peritoneal fat (47.7%), retroperitoneal fat (70.7%), pancreatic volume (26.6%), pancreatic volume index (21.3%) and liver span (10.8%). In cases, significant positive correlations were observed for pancreatic volume with BMI, waist and hip circumferences, W-HR, subscapular, abdominal and total truncal skinfolds, truncal, total subcutaneous, total intra-abdominal, intra-peritoneal, retroperitoneal fat depots, liver span and fatty liver.ConclusionsIn non-obese Asian Indians with type 2 diabetes, subcutaneous and intra-abdominal obesity, including fatty liver, and pancreatic volume were higher and peripheral subcutaneous adiposity was lower than BMI matched non-diabetic subjects. Importantly, increased pancreatic volume in patients was highly correlated with multiple measures of abdominal obesity and liver fat.     

Amelioration of hyperlipidemia by low fat diets in chronically streptozotocin-diabetic rats

The effects of reduced dietary fat intake on plasma lipid levels were examined in diabetic rats. One week after induction of diabetes (D) with streptozotocin (65 mg/kg, iv), the animals were fed food pellets consisting of 1.5% (D1.5), 2.5% (D2.5) or 5% (D5) fat for two weeks. Irrespective of the diets, both food and water consumed by untreated diabetic rats were 2- to 5-fold greater respectively compared to normal. Plasma glucose concentrations were also similarly increased. Plasma and skeletal muscle lipid levels were significantly greater than controls in D2.5 and D5, but not in the D1.5 group. Plasma and muscle lipid concentrations correlated directly with fat consumption. In D5 rats receiving insulin treatment, plasma glucose and lipid concentrations were comparable to control values. These findings indicate that the degree of hyperlipidemia in chronically diabetic rats is directly related to dietary fat intake. They also demonstrate that dietary interventions can modulate some of the metabolic abnormalities in diabetes.     

Elevated serum GGT concentrations predict reduced insulin sensitivity and increased intrahepatic lipids.

Elevated serum gamma-glutamyltransferase (GGT) concentrations have been related to features of the metabolic syndrome as well as increased risk of cardiovascular and liver disease. More recently, elevated GGT levels were shown to predict development of type 2 diabetes in a longitudinal study from Korea. The aim of the present study was to test the hypothesis that serum GGT is associated with glucose tolerance, insulin sensitivity and beta-cell function in a healthy, non-diabetic Caucasian population from the Tübingen family study. Insulin sensitivity was estimated by oGTT (n = 850) or measured by hyperinsulinemic euglycemic clamp (n = 245), respectively. A subgroup (n = 70) underwent additional determination of intrahepatic lipid content using 1H magnetic resonance spectroscopy. Serum GGT was positively correlated with two-hour glucose during oGTT (r = 0.15, p < 0.0001) and negatively correlated with insulin sensitivity from oGTT (r = -0.31, p < 0.0001) and clamp (r = -0.27, p < 0.0001). The relationship between GGT and insulin sensitivity remained significant after adjusting for sex, age, BMI, and AST using multivariate regression analysis. Inclusion of serum triglyceride levels as a parameter of lipid metabolism kept the relationship significant in the oGTT group (p < 0.0001), but not in the smaller clamp group (p = 0.11). Additionally, serum GGT was positively correlated with hepatic lipid content (r = 0.49, p < 0.001) independent of sex, age, BMI, AST or serum triglycerides. There was no significant correlation between GGT and the index for beta-cell function after adjusting for age, sex, BMI and insulin sensitivity (p = 0.74). In conclusion, elevated serum GGT levels predict glucose intolerance probably via insulin resistance rather than beta-cell dysfunction. This may be primarily related to hepatic insulin resistance and increased intrahepatic lipids. The association observed between elevated hepatic lipids and reduced insulin sensitivity might explain the increased diabetes risk observed in subjects with elevated serum GGT concentrations. In the absence of overt liver disease, elevated serum GGT concentrations may point the clinician to incipient disturbances in the glucose metabolism.     

Effect of short-term therapy with recombinant human growth hormone (GH) on metabolic parameters and preclinical atherosclerotic markers in hypopituitary patients with growth hormone deficiency.

OBJECTIVE: This study examines the effects of growth hormone replacement on body composition, insulin sensitivity, lipid profile, endothelial dysfunction and carotid intima media thickness in patients with adult-onset growth-hormone (GH) deficiency. METHODS: Twelve patients with severe GH deficiency received GH replacement for one year. In all patients, the following parameters were evaluated before and after six and twelve months of therapy: fasting glucose, insulin levels and lipid profile, bone mineral density and body composition. Carotid intima media thickness and brachial flow-mediated dilatation were also evaluated by arterial ultrasonography at basal condition and after one year of therapy. RESULTS: No significant changes were seen in body weight and blood pressure, total fat and lean mass, or bone mineral density after six months of GH replacement. There was an increase in triglycerides (p = 0.05), while total and HDL cholesterol, blood glucose, insulin levels did not change significantly. After twelve months, an increase in lean mass and a decrease in fat mass (p < 0.01 vs. baseline), a decrease in insulin resistance (p < 0.01 vs. six months; p = 0.01 vs. baseline) and a decrease in triglycerides (p < 0.01) were observed. Intima media thickness was greater in GH deficiency than in controls (p = 0.01) before therapy, and was unchanged after twelve months of therapy, whereas the flow-mediated dilatation tended to improve (p = 0.05). CONCLUSIONS: GH replacement is able to reverse typical metabolic and body composition alterations in patients with adult GH deficiency after twelve months, but it is unable to revert the vascular alteration completely. Flow-mediated dilatation seems to be a more precocious marker of the remission of arterial damage.     

Intramyocellular lipid and insulin resistance: differential relationships in European and African Americans

Insulin resistance has been associated with the accumulation of fat within skeletal muscle fibers as intramyocellular lipid (IMCL). Here, we have examined in a cross-sectional study the interrelationships among IMCL, insulin sensitivity, and adiposity in European Americans (EAs) and African Americans (AAs). In 43 EA and 43 AA subjects, we measured soleus IMCL content with proton-magnetic resonance spectroscopy, insulin sensitivity with hyperinsulinemic-euglycemic clamp, and body composition with dual-energy X-ray absorptiometry. The AA and EA subgroups had similar IMCL content, insulin sensitivity, and percent fat, but only in EA was IMCL correlated with insulin sensitivity (r = -0.47, P < 0.01), BMI (r = 0.56, P < 0.01), percent fat (r = 0.35, P < 0.05), trunk fat (r = 0.47, P < 0.01), leg fat (r = 0.40, P < 0.05), and waist and hip circumferences (r = 0.54 and 0.55, respectively, P < 0.01). In a multiple regression model including IMCL, race, and a race by IMCL interaction, the interaction was found to be a significant predictor (t = 1.69, DF = 1, P = 0.0422). IMCL is related to insulin sensitivity and adiposity in EA but not in AA, suggesting that IMCL may not function as a pathophysiological factor in individuals of African descent. These results highlight ethnic differences in the determinants of insulin sensitivity and in the pathogenesis of the metabolic syndrome trait cluster.     

Increased intramyocellular lipid accumulation in HIV-infected women with fat redistribution.

The human immunodeficiency virus (HIV)-lipodystrophy syndrome is associated with fat redistribution and metabolic abnormalities, including insulin resistance. Increased intramyocellular lipid (IMCL) concentrations are thought to contribute to insulin resistance, being linked to metabolic and body composition variables. We examined 46 women: HIV infected with fat redistribution (n = 25), and age- and body mass index-matched HIV-negative controls (n = 21). IMCL was measured by 1H-magnetic resonance spectroscopy, and body composition was assessed with computed tomography, dual-energy X-ray absorptiometry (DEXA), and magnetic resonance imaging. Plasma lipid profile and markers of glucose homeostasis were obtained. IMCL was significantly increased in tibialis anterior [135.0 +/- 11.5 vs. 85.1 +/- 13.2 institutional units (IU); P = 0.007] and soleus [643.7 +/- 61.0 vs. 443.6 +/- 47.2 IU, P = 0.017] of HIV-infected subjects compared with controls. Among HIV-infected subjects, calf subcutaneous fat area (17.8 +/- 2.3 vs. 35.0 +/- 2.5 cm2, P < 0.0001) and extremity fat by DEXA (11.8 +/- 1.1 vs. 15.6 +/- 1.2 kg, P = 0.024) were reduced, whereas visceral abdominal fat (125.2 +/- 11.3 vs. 74.4 +/- 12.3 cm2, P = 0.004), triglycerides (131.1 +/- 11.0 vs. 66.3 +/- 12.3 mg/dl, P = 0.0003), and fasting insulin (10.8 +/- 0.9 vs. 7.0 +/- 0.9 microIU/ml, P = 0.004) were increased compared with control subjects. Triglycerides (r = 0.39, P = 0.05) and extremity fat as percentage of whole body fat by DEXA (r = -0.51, P = 0.01) correlated significantly with IMCL in the HIV but not the control group. Extremity fat (beta = -633.53, P = 0.03) remained significantly associated with IMCL among HIV-infected patients, controlling for visceral abdominal fat, abdominal subcutaneous fat, and antiretroviral medications in a regression model. These data demonstrate increased IMCL in HIV-infected women with a mixed lipodystrophy pattern, being most significantly associated with reduced extremity fat. Further studies are necessary to determine the relationship between extremity fat loss and increased IMCL in HIV-infected women.     

Exercise and diet enhance fat oxidation and reduce insulin resistance in older obese adults.

Older, obese, and sedentary individuals are at high risk of developing diabetes and cardiovascular disease. Exercise training improves metabolic anomalies associated with such diseases, but the effects of caloric restriction in addition to exercise in such a high-risk group are not known. Changes in body composition and metabolism during a lifestyle intervention were investigated in 23 older, obese men and women (aged 66 +/- 1 yr, body mass index 33.2 +/- 1.4 kg/m(2)) with impaired glucose tolerance. All volunteers undertook 12 wk of aerobic exercise training [5 days/wk for 60 min at 75% maximal oxygen consumption (Vo(2max))] with either normal caloric intake (eucaloric group, 1,901 +/- 277 kcal/day, n = 12) or a reduced-calorie diet (hypocaloric group, 1,307 +/- 70 kcal/day, n = 11), as dictated by nutritional counseling. Body composition (decreased fat mass; maintained fat-free mass), aerobic fitness (Vo(2max)), leptinemia, insulin sensitivity, and intramyocellular lipid accumulation (IMCL) in skeletal muscle improved in both groups (P < 0.05). Improvements in body composition, leptin, and basal fat oxidation were greater in the hypocaloric group. Following the intervention, there was a correlation between the increase in basal fat oxidation and the decrease in IMCL (r = -0.53, P = 0.04). In addition, basal fat oxidation was associated with circulating leptin after (r = 0.65, P = 0.0007) but not before the intervention (r = 0.05, P = 0.84). In conclusion, these data show that exercise training improves resting substrate oxidation and creates a metabolic milieu that appears to promote lipid utilization in skeletal muscle, thus facilitating a reversal of insulin resistance. We also demonstrate that leptin sensitivity is improved but that such a trend may rely on reducing caloric intake in addition to exercise training.     

Effect of Rosiglitazone on Insulin Sensitivity and Body Composition in Type 2 Diabetic Patients

Objective: To investigate the effects of rosiglitazone (RSG) on insulin sensitivity and regional adiposity (including intrahepatic fat) in patients with type 2 diabetes. Research Methods and Procedures: We examined the effect of RSG (8 mg/day, 2 divided doses) compared with placebo on insulin sensitivity and body composition in 33 type 2 diabetic patients. Measurements of insulin sensitivity (euglycemic hyperinsulinemic clamp), body fat (abdominal magnetic resonance imaging and DXA), and liver fat (magnetic resonance spectroscopy) were taken at baseline and repeated after 16 weeks of treatment. Results: There was a significant improvement in glycemic control (glycosylated hemoglobin −0.7 ± 0.7%, p ≤ 0.05) and an 86% increase in insulin sensitivity in the RSG group (glucose-disposal rate change from baseline: 17.5 ± 14.5 μmol glucose/min/kg free fat mass, p < 0.05), but no significant change in the placebo group compared with baseline. Total body weight and fat mass increased (p ≤ 0.05) with RSG (2.1 ± 2.0 kg and 1.4 ± 1.6 kg, respectively) with 95% of the increase in adiposity occurring in nonabdominal regions. In the abdominal region, RSG increased subcutaneous fat area by 8% (25.0 ± 28.7 cm², p = 0.02), did not alter intra-abdominal fat area, and reduced intrahepatic fat levels by 45% (−6.7 ± 9.7%, concentration relative to water). Discussion: Our data indicate that RSG greatly improves insulin sensitivity in patients with type 2 diabetes and is associated with an increase in adiposity in subcutaneous but not visceral body regions.     

Insulin Action,Regional Fat,and Myocyte Lipid: Altered Relationships with Increased Adiposity

Objective: Abdominal fat and myocyte triglyceride levels relate negatively to insulin sensitivity, but their interrelationships are inadequately characterized in the overweight. Using recent methods for measuring intramyocyte triglyceride, these relationships were studied in men with a broad range of adiposity. Research Methods and Procedures: Myocyte triglyceride content (¹H‐magnetic resonance spectroscopy of soleus and tibialis anterior muscles and biochemical assessment of vastus lateralis biopsies), regional fat distribution (DXA and abdominal magnetic resonance imaging), serum lipids, insulin action (euglycemic hyperinsulinemic clamp), and substrate oxidation rates (indirect calorimetry) were measured in 39 nondiabetic men (35.1 ± 7.8 years) with a broad range of adiposity (BMI 28.6 ± 4.1 kg/m², range 20.1 to 37.6 kg/m²). Results: Relationships between insulin‐stimulated glucose disposal and regional body fat depots appeared more appropriately described by nonlinear than linear models. When the group was subdivided using median total body fat as the cut‐point, insulin‐stimulated glucose disposal correlated negatively to all regional body fat measures (all p ≤ 0.004), serum triglycerides and free fatty acids (p < 0.02), and both soleus intramyocellular lipid (p = 0.003) and vastus lateralis triglyceride (p = 0.04) in the normal/less overweight group. In contrast, only visceral abdominal fat showed significant negative correlation with insulin‐stimulated glucose disposal in more overweight men (r = ?0.576, p = 0.01), some of whom surprisingly had lower than expected myocyte lipid levels. These findings persisted when the group was subdivided using different cut‐points or measures of adiposity. Discussion: Interrelationships among body fat depots, myocyte triglyceride, serum lipids, and insulin action are generally absent with increased adiposity. However, visceral abdominal fat, which corresponds less closely to total adiposity, remains an important predictor of insulin resistance in men with both normal and increased adiposity.     

Abdominal adipose tissue cytokine gene expression: relationship to obesity and metabolic risk factors

Adipose tissue is a major source of inflammatory and thrombotic cytokines. This study investigated the relationship of abdominal subcutaneous adipose tissue cytokine gene expression to body composition, fat distribution, and metabolic risk during obesity. We determined body composition, abdominal fat distribution, plasma lipids, and abdominal subcutaneous fat gene expression of leptin, TNF-alpha, IL-6, PAI-1, and adiponectin in 20 obese, middle-aged women (BMI, 32.7 +/- 0.8 kg/m2; age, 57 +/- 1 yr). A subset of these women without diabetes (n = 15) also underwent an OGTT. In all women, visceral fat volume was negatively related to leptin (r = -0.46, P < 0.05) and tended to be negatively related to adiponectin (r = -0.38, P = 0.09) gene expression. Among the nondiabetic women, fasting insulin (r = 0.69, P < 0.01), 2-h insulin (r = 0.56, P < 0.05), and HOMA index (r = 0.59, P < 0.05) correlated positively with TNF-alpha gene expression; fasting insulin (r = 0.54, P < 0.05) was positively related to, and 2-h insulin (r = 0.49, P = 0.06) tended to be positively related to, IL-6 gene expression; and glucose area (r = -0.56, P < 0.05) was negatively related to, and insulin area (r = -0.49, P = 0.06) tended to be negatively related to, adiponectin gene expression. Also, adiponectin gene expression was significantly lower in women with vs. without the metabolic syndrome (adiponectin-beta-actin ratio, 2.26 +/- 0.46 vs. 3.31 +/- 0.33, P < 0.05). We conclude that abdominal subcutaneous adipose tissue expression of inflammatory cytokines is a potential mechanism linking obesity with its metabolic comorbidities.