Correlation between the glucose clamp technique and the homeostasis model assessment in hypertension

Effects of Telmisartan and Losartan on Insulin Resistance in Hypertensive Patients with Metabolic Syndrome

Partial peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists are known to decrease insulin resistance. Experimental studies have shown that the angiotensin type 1 receptor blocker (ARB) telmisartan has a PPAR-gamma-activating property, but there does not appear to be a class effect. To test telmisartan's clinical importance, we here investigated its effect on insulin resistance in hypertensive patients with metabolic syndrome (MetS) in comparison with another ARB, losartan. A total of 42 hypertensive MetS patients (29 female, 13 male) were included (mean age: 50+/-9, range: 20-70 years). NCEP-ATP III criteria were used for the diagnosis of MetS. Patients were randomized to receive either telmisartan 80 mg/day (n=21) or losartan 50 mg/day (n=21) for 8 weeks. Biochemical assessments were made at baseline and at the end of the 8 weeks. Insulin resistance was evaluated by using homeostasis model assessment of insulin resistance (HOMA-IR). Both groups had similar reductions in systolic and diastolic pressures (p>0.05). HOMA-IR did not change significantly in either group throughout the study. In the telmisartan group, the mean HOMA-IR at baseline and at the end of the study were 1.9+/-07 and 1.9+/-0.5, respectively. The figures for the losartan group were 1.8+/-0.6 and 1.8+/-0.6, corresponding. In conclusion, in contrast with the reports that telmisartan may decrease insulin resistance by an effect associated with its molecular structure, 8 weeks of telmisartan treatment in the present study had a neutral effect on insulin resistance in hypertensive MetS patients, and similar results were obtained for losartan.

Metabolic syndrome and gender differences in postprandial lipaemia

BACKGROUND

Postprandial hyperlipidaemia may be a predictor of vascular risk.

DESIGN

We evaluated postprandial lipaemia after an oral fat tolerance test (OFTT) in men (n=41) and women (n=21) with metabolic syndrome (MetS).

METHODS

Triglyceride (TG) levels were measured before and 2, 4, 6 and 8 h after the fat load.

RESULTS

Men showed a greater plasma TG response 8 h after the fat load (284+/-117 versus 224+/-126 mg/dl, P=0.029). Only fasting TG levels significantly predicted the TG area under the curve (AUC) and incremental AUC.

CONCLUSIONS

Men had a more pronounced postprandial hypertriglyceridaemia and seem to have delayed TG clearance.

Effect of a diet and exercise intervention on oxidative stress, inflammation and monocyte adhesion in diabetic men

Diabetes increases the risk of coronary artery disease. We examined the effects of lifestyle modification on key contributing factors to atherogenesis, including oxidative stress, inflammation and cell adhesion. Diabetic men (N=13) were placed on a high-fiber, low-fat diet in a 3-week residential program where food was provided ad libitum and daily aerobic exercise was performed. In each subject, pre- and post-intervention fasting blood was drawn for circulating levels of serum lipids, glucose and insulin, oxidative stress marker 8-isoprostaglandin F2alpha (8-iso-PGF2alpha), the inflammatory protein C-reactive protein (CRP), and soluble intracellular adhesion molecule (sICAM)-1 and sE-selectin as indicators of endothelial activation. Using subject sera and human aortic endothelial cell (HAEC) culture systems, serum-induced monocyte adhesion, ICAM-1, vascular cell adhesion molecule-1 (VCAM-1) and cell surface abundance, and monocyte chemotactic protein-1 (MCP-1) production were determined. Nitric oxide (NO), superoxide, and hydrogen peroxide production were measured in vitro by fluorometric detection. After 3 weeks, significant reductions (p<0.05) in BMI, all serum lipids including total cholesterol (pre: 188.9+/-10.1 mg/dL versus post: 146.3+/-3.8 mg/dL) and low-density lipoprotein (103.1+/-10.2 mg/dL versus 76.4+/-4.3 mg/dL), fasting serum glucose (157.5+/-10.1 mg/dL versus 126.7+/-8.7 mg/dL), insulin (33.8+/-4.0 microU/ml versus 23.8+/-3.4 microU/ml), homeostasis model assessment for insulin resistance, 8-iso-PGF2alpha, CRP, sICAM-1, and sE-selectin were noted. In vitro, serum-stimulated monocyte adhesion, cellular ICAM-1 and VCAM-1 expression (p<0.05), and fluorometric detection of superoxide and hydrogen peroxide production decreased, while a concomitant increase in NO production was noted (all p<0.01). A combination of diet and exercise ameliorates oxidative stress, inflammation, and monocyte-endothelial interaction. Intensive lifestyle modification may improve novel CAD risk factors in men with diabetes.

Effect of cholecystokinin on feeding is attenuated in monosodium glutamate obese mice

Treatment of newborn mice with monosodium glutamate (MSG) is neurotoxic for hypothalamic arcuate nucleus (ARC) and causes obesity. In the MSG-treated 16-week-old NMRI mice, we detected specific ablation of ARC neuronal cells, 8 times higher fat to body mass ratio but unchanged body mass compared to controls, advanced hyperglycemia and hyperinsulinemia--both more pronounced in males, and hyperleptinemia--more severe in females. After fasting, the MSG-treated mice showed attenuated food intake compared to controls. Cholecystokinin octapeptide, which decreased food intake in a dose-dependent manner in 24 h fasted controls, did not significantly affect food intake in the MSG-treated animals. We propose that the obesity-related changes in the feeding behavior of the MSG-treated obese mice were the result of missing leptin and insulin receptors in ARC and consequent altered neuropeptide signaling. This makes the MSG model suitable for clarifying generally the central control of food intake.

Effects of amlodipine-atorvastatin combination on inflammation markers and insulin sensitivity in normocholesterolemic obese hypertensive patients

OBJECTIVE

The objective of this study was to assess the effect of amlodipine-atorvastatin combination on plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and insulin sensitivity in normocholesterolemic obese hypertensive patients.

MATERIALS AND METHODS

After a 4-week placebo wash-out period, 50 normocholesterolemic [total cholesterol (TC) <5.2 mmol/L], obese (BMI >/=30 kg/m(2)) hypertensive patients (DBP >90 and <105 mm Hg and SBP >140 and <180 mm Hg) were randomly treated with amlodipine (10 mg) or with amlodipine (10 mg) plus atorvastatin (20 mg) according to a cross-over design; each treatment had a 12-week duration. At the end of the placebo and of each treatment period, blood pressure (BP), TNF-alpha, IL-6, insulin resistance (IR) by homeostasis model assessment of IR index (HOMA-IR) and TC were evaluated.

RESULTS

Amlodipine monotherapy decreased both SBP (-17.1 mm Hg, p=0.008 vs. placebo) and DBP (-14.3 mm Hg, p=0.008) as well as TNF-alpha (from 3.66+/-1.6 to 3.09+/-1.1 pg/ml, p=0.045) and HOMA-IR (from 4.58+/-0.7 to 3.88+/-0.6, p=0.007). The amlodipine-atorvastatin combination produced a decrease in SBP (-22.5 mm Hg, p=0.0007 vs. placebo, p=0.039 vs. amlodipine), DBP (-17.7 mm Hg, p=0.0007 vs. placebo; p=0.04 vs. amlodipine), TNF-alpha (2.59+/-0.9 pg/mL, p=0.007 vs. placebo and p=0.038 vs. amlodipine) and HOMA-IR (2.86+/-0.4, p=0.0008 vs. placebo and p=0.007 vs. amlodipine). The combination reduced IL-6 (from 7.93+/-1.9 to 5.59+/-1.2 pg/mL, p=0.008 vs. placebo and p=0.007 vs. amlodipine) and TC (from 4.3+/-0.5 to 3.6+/-0.4 mmol/L, p=0.008 vs. placebo and vs. amlodipine). HOMA-IR changes significantly correlated with TNF-alpha changes (r=0.38, p<0.05) during combination but not during amlodipine monotherapy. In normocholesterolemic, obese hypertensive patients, the amlodipine-atorvastatin combination decreased inflammatory markers and IR more than amlodipine monotherapy and produced a greater SBP and DBP reduction.

Postprandial lipaemia in menopausal women with metabolic syndrome

BACKGROUND

The metabolic syndrome (MetS) is associated with an increased incidence of coronary heart disease (CHD). Postprandial hypertriglyceridaemia is also associated with CHD. The aim of this study was to evaluate the postprandial lipaemia after an oral fat tolerance test (OFTT) in women with MetS.

METHODS

OFTT, was given to 21 menopausal women with MetS (defined by the Adult Treatment Panel III) and to 12 healthy menopausal women. Triglyceride (TG) levels were measured before and 2, 4, 6 and 8h after the OFTT. The postprandial response was quantified by the areas under the curve (AUC) of TG levels. MetS women were subdivided according to body mass index (BMI) < or > or =30kg/m(2), and to fasting TG levels < or > or =150mg/dl.

RESULTS

The response to the OFTT was significantly higher in the MetS group compared to healthy [AUC(S.D.), in mg/dl/h; 2014(933) versus 732(197), p<0.001]. The subjects with BMI < or > or =30kg/m(2) had similar fasting TG levels [157(60)mg/dl versus 158(67) mg/dl] and AUC [1975(898) versus 2072(1044), respectively]. The MetS women with TG> or =150mg/dl had higher AUC compared to those with TG<150mg/dl [2502(854) versus 1281(441), p=0.002]. In linear regression analysis, where BMI, high-density lipoprotein cholesterol, fasting TG, HOMA-IR and QUICKI were the independent variables, only fasting TGs significantly predicted the AUC (coefficient B=11.866, p=0.008).

CONCLUSIONS

The fasting TG concentration is the main determinant of postprandial lipaemia. The obesity state was not an additional determinant for exaggerated postprandial response in MetS women. The abnormal postprandial lipaemia could be added as an important metabolic disturbance to the MetS.

Increased expression of hypothalamic leptin receptor and adiponectin accompany resistance to dietary-induced obesity and infertility in female C57BL/6J mice

BACKGROUND

Obesity is strongly associated with female infertility, but the mechanisms underlying this relationship are largely unknown.

METHODS

We investigated the effect of increasing dietary fat percentage upon body mass, hypothalamic neuropeptide gene expression, adipose hormone secretion and fertility in females of the inbred mouse strains C57BL/6J and DBA/2J. To assess the effect of obesity independent of dietary influence, we also compared these parameters in wild-type female C57BL/6J mice to those congenic for the obesogenic mutations ob/ob and A(y)/a.

RESULTS

After 24 weeks, rather than exhibiting an obese, leptin-resistant phenotype like their female DBA/2J counterparts, wild-type female C57BL/6J mice remained lean, fertile and manifested increased hypothalamic LEPR-B expression. Although both mutant genotypes were associated with obesity and subfertility, ob/ob mice demonstrated significantly increased hypothalamic LEPR-B expression, whereas A(y)/a mice had a significant reduction. Interestingly, wild-type female C57BL/6J mice were noted to manifest significantly higher and lower levels of adiponectin and tissue plasminogen activator inhibitor-1 (tPAI-1), respectively, than weight-matched wild-type female DBA/2J mice.

CONCLUSIONS

We conclude that (1) resistance to the obese-infertile phenotype in female C57BL/6J mice is associated with increased hypothalamic leptin receptor expression and alterations in adipokine levels consistent with decreased adipose tissue inflammation and (2) that long-standing hyperleptinemic obesity in mice is associated with a downregulation of the hypothalamic leptin receptor.

Effects of a Low-Fat, High-Fiber Diet and Exercise Program on Breast Cancer Risk Factors In Vivo and Tumor Cell Growth and Apoptosis In Vitro

The present study investigated the effects of a diet and exercise intervention on known breast cancer (BCa) risk factors, including estrogen, obesity, insulin, and insulin-like growth factor-I (IGF-I), in overweight/obese, postmenopausal women. In addition, using the subjects' pre- and postintervention serum in vitro, serum-stimulated growth and apoptosis of three estrogen receptor-positive BCa cell lines were studied. The women where placed on a low-fat (10-15% kcal), high-fiber (30-40 g per 1,000 kcal/day) diet and attended daily exercise classes for 2 wk. Serum estradiol was reduced in the women on hormone treatment (HT; n = 28) as well as those not on HT (n = 10). Serum insulin and IGF-I were significantly reduced in all women, whereas IGF binding protein-1 was increased significantly. In vitro growth of the BCa cell lines was reduced by 6.6% for the MCF-7 cells, 9.9% for the ZR-75-1 cells, and 18.5% for the T-47D cells. Apoptosis was increased by 20% in the ZR-75-1 cells, 23% in the MCF-7 cells, and 30% in the T-47D cells (n = 12). These results show that a very-low-fat, high-fiber diet combined with daily exercise results in major reductions in risk factors for BCa while subjects remained overweight/obese. These in vivo serum changes slowed the growth and induced apoptosis in serum-stimulated BCa cell lines in vitro.

Familial factors in diabetic nephropathy: an offspring study

AIMS

Familial clustering of diabetic nephropathy in patients with Type 2 diabetes suggests that inherited factors predispose to diabetic nephropathy, but the nature of these factors is uncertain. The aim of the study was to compare the prevalence of known risk factors for nephropathy in non-diabetic offspring of Type 2 diabetic patients with and without nephropathy and in control subjects.

METHODS

Three groups of patients were recruited with 40 or 41 subjects in each group. These were subjects having one Type 2 diabetic parent with nephropathy (DN); subjects having one parent with Type 2 diabetes without nephropathy (DnoN), and non-diabetic unrelated control subjects with no personal or parental history of diabetes (Control subjects).

RESULTS

The median (interquartile range) albumin/creatinine ratio (ACR) was 1.40 (0.96-2.90) mg/mmol in DN; 0.94 (0.50-1.46) mg/mmol in DnoN and 1.22 (0.66-1.83) mg/mmol in Controls (ANOVA: P = 0.03). ACR was higher in group DN than in DnoN (P < 0.006) and in Control subjects (P < 0.03), but there was no difference between DnoN and Control subjects. Twenty-four-hour ambulatory blood pressure monitoring showed mean daytime systolic blood pressure to be significantly higher in group DN than in DnoN (P < 0.02) or Control subjects (P < 0.01) (ANOVA: P = 0.004). Fasting insulin, HOMA-IR, interleukin-6 (IL-6) and C-reactive protein (CRP) were similar in the three groups.

CONCLUSION

Our data provide further evidence that genetic factors are important in determining urinary albumin excretion and renal disease associated with Type 2 diabetes and suggest that genes that affect systemic arterial blood pressure but not those relating to insulin resistance or inflammation are likely to be implicated.

The Metabolic Syndrome: Recognition and Management

The National Cholesterol Education Program defines the metabolic syndrome as three or more of five abnormalities: waist circumference of >40 in (102 cm) for men or >35 in (88 cm) for women, triglyceride level of > or =150 mg/dL, high-density lipoprotein cholesterol of <40 mg/dL in men or <50 mg/dL in women, blood pressure of > or =130 or > or =85 mm Hg, and fasting glucose of > or =110 mg/dL. It is related to insulin resistance, but the two terms are not synonymous. Both are associated strongly with obesity. The metabolic syndrome is important as an indicator of increased risk of cardiovascular disease (CVD) in patients with and without clinical CVD. The CVD risk of the metabolic syndrome is greater than that conferred by any single CVD risk factor. Since risk factors tend to cluster, if one component of the metabolic syndrome is present, one should assess for other risk factors. The metabolic syndrome is also predictive of new-onset type 2 diabetes. Early diagnosis provides justification for measures that can improve components of the syndrome and reduce CVD risk. The management strategy for metabolic syndrome focuses on overall CVD risk rather than single risk factors; effective therapy includes priority for weight reduction and increased physical activity. Pharmacotherapy is typically needed for control of high blood pressure, hypercoagulability, and increased levels of blood glucose and triglycerides.

Comparison of the effects of valsartan and felodipine on plasma leptin and insulin sensitivity in hypertensive obese patients

Aim of this study was to compare the effect of valsartan and felodipine on blood pressure (BP), plasma leptin (L), insulin sensitivity and plasma norepinephrine (NE) in obese hypertensive patients. Ninty-six obese patients (body mass index [BMI] > or = 30 kg/m2) with mild to moderate essential hypertension (diastolic blood pressure [DBP] > 90 and < 110 mmHg, as evaluated with an appropriately sized cuff) aged 31-60 years, were randomized to a valsartan (80 mg/day for 16 weeks; n = 48) or felodipine (5 mg/day for 16 weeks; n = 48) treatment group after a 2-week wash-out period. After the first 4 weeks of treatment there was a titration with dose-doubling in non responder patients (DBP > 90 mmHg). At the end of the placebo period and of active treatment period, BP and BMI were evaluated and a venous sample was drawn at the same hour in the morning to evaluate plasma L and NE. Insulin resistance index (HOMA-IR) was calculated. No dietary advice was prescribed. Both valsartan and felodipine significantly decreased BP values (-19.3/15 mmHg and -18.9/13.6 mmHg, respectively p < 0.001 vs. placebo), with no difference between treatments. However, felodipine increased plasma NE (+124 pg/ml, +38.2%, p < 0.05 vs. placebo and < 0.01 vs. valsartan) and had no effect on L, body weight and HOMA-IR index, while valsartan did not modify NE and produced a significant reduction in L (-3.7 ng/ml, -10.1%, p < 0.05 vs. placebo), BMI (-1.7 kg/m2, -4.7%, p < 0.01 vs. placebo) and HOMA-IR index (-1.6, -20%, p < 0.05 vs. placebo). These results suggest that in hypertensive obese subjects, treatment with valsartan might offer an advantage over treatment with felodipine, since valsartan may help to improve obesity-related disorders in addition to lowering BP.

Assessing the predictive accuracy of QUICKI as a surrogate index for insulin sensitivity using a calibration model

The quantitative insulin-sensitivity check index (QUICKI) has an excellent linear correlation with the glucose clamp index of insulin sensitivity (SI(Clamp)) that is better than that of many other surrogate indexes. However, correlation between a surrogate and reference standard may improve as variability between subjects in a cohort increases (i.e., with an increased range of values). Correlation may be excellent even when prediction of reference values by the surrogate is poor. Thus, it is important to evaluate the ability of QUICKI to accurately predict insulin sensitivity as determined by the reference glucose clamp method. In the present study, we used a calibration model to compare the ability of QUICKI and other simple surrogates to predict SI(Clamp). Predictive accuracy was evaluated by both root mean squared error of prediction as well as a more robust leave-one-out cross-validation-type root mean squared error of prediction (CVPE). Based on data from 116 glucose clamps obtained from nonobese, obese, type 2 diabetic, and hypertensive subjects, we found that QUICKI and log (homeostasis model assessment [HOMA]) were both excellent at predicting SI(Clamp) (CVPE = 1.45 and 1.51, respectively) and significantly better than HOMA, 1/HOMA, and fasting insulin (CVPE = 3.17, P < 0.001; 1.67, P < 0.02; and 2.85, P < 0.001, respectively). QUICKI and log(HOMA) also had the narrowest distribution of residuals (measured SI(Clamp) - predicted SI(Clamp)). In a subset of subjects (n = 78) who also underwent a frequently sampled intravenous glucose tolerance test with minimal model analysis, QUICKI was significantly better than the minimal model index of insulin sensitivity (SI(MM)) at predicting SI(Clamp) (CVPE = 1.54 vs. 1.98, P = 0.001). We conclude that QUICKI and log(HOMA) are among the most accurate surrogate indexes for determining insulin sensitivity in humans.

Ambulatory blood pressure reduction after rosiglitazone treatment in patients with type 2 diabetes and hypertension correlates with insulin sensitivity increase

BACKGROUND

Within the metabolic syndrome, insulin resistance and compensatory hyperinsulinemia are associated with blood pressure (BP) elevation through various potential mechanisms. Thiazolidinediones are antihyperglycemic agents that decrease insulin resistance.

OBJECTIVE

To determine the effect of the thiazolidinedione rosiglitazone on BP and insulin resistance in patients with type 2 diabetes and hypertension.

METHODS

In 20 subjects (nine men and 11 women) with type 2 diabetes but with a poor glycemic control, and with poorly controlled or newly diagnosed hypertension, rosiglitazone 4 mg daily was added-on therapy for 26 weeks. At baseline and at the end of the treatment period patients underwent ambulatory blood pressure monitoring, a hyperinsulinemic euglycemic clamp, and blood tests for glucose, insulin, HbA1c, lipids, and routine laboratory parameters.

RESULTS

Insulin sensitivity estimated with the clamp significantly increased (Mbw/I index changed from 33.9 +/- 2.6 to 41.9 +/- 3.2 micromol/min per kg per nmol/l, P < 0.001) and the HOMA-IR index significantly decreased (6.34 +/- 0.39 versus 4.40 +/- 0.33, P < 0.001) during rosiglitazone treatment. Ambulatory BP presented small but significant reductions for the total 24-h period (135.3 +/- 1.8 versus 129.9 +/- 1.7 mmHg, P < 0.001 for systolic BP and 76.0 +/- 1.6 versus 71.9 +/- 1.6 mmHg, P < 0.001 for diastolic BP), daytime and night-time. The changes in systolic and diastolic BP correlated with the change in insulin sensitivity (r = -0.78, P < 0.01 and r = -0.68, P < 0.01, respectively). There were also significant reductions in fasting plasma glucose (9.39 +/- 0.41 versus 7.55 +/- 0.31 mmol/l, P < 0.001), insulin (94.0 +/- 0.41 versus 79.5 +/- 5.6 pmol/l, P < 0.01) and HbA1c (8.15 +/- 0.24 versus 7.24 +/- 0.19%, P < 0.001).

CONCLUSIONS

Treatment of type 2 diabetic hypertensive patients with rosiglitazone significantly increased insulin sensitivity and lowered ambulatory BP. These changes were strongly correlated. Thiazolidinediones may thus possess a BP-lowering effect beyond their antihyperglycemic properties.

Impact of degree of obesity on surrogate estimates of insulin resistance

OBJECTIVE

To evaluate the role of adiposity in the relationship between specific and surrogate estimates of insulin-mediated glucose uptake (IMGU) in a large nondiabetic population.

RESEARCH DESIGN AND METHODS

Healthy volunteers were classified by BMI into normal weight (<25.0 kg/m(2), n = 208), overweight (25.0-29.9 kg/m(2), n = 168), and obese (>or=30.0 kg/m(2), n = 109) groups. We then assessed how differences in BMI affect the correlation between steady-state plasma glucose (SSPG) concentration at the end of a 180-min infusion of octreotide, glucose, and insulin (a specific measure of IMGU) and five surrogate estimates: fasting plasma glucose, fasting plasma insulin, homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and area under the curve for insulin in response to oral glucose (I-AUC).

RESULTS

Correlation coefficients (r values) between SSPG and surrogate measures of IMGU were all significant (P < 0.05), but the magnitude varied between BMI groups: normal weight: fasting plasma glucose 0.20, fasting plasma insulin 0.33, HOMA-IR 0.36, QUICKI -0.33, and I-AUC 0.69; overweight: fasting plasma glucose 0.19, fasting plasma insulin 0.55, HOMA-IR 0.55, QUICKI -0.54, and I-AUC 0.72; and obese: fasting plasma glucose 0.40, fasting plasma insulin 0.56, HOMA-IR 0.60, QUICKI -0.61, and I-AUC 0.69.

CONCLUSIONS

The relationship between direct and surrogate estimates of IMGU varies with BMI, with the weakest correlations seen in the normal-weight group and the strongest in the obese group. In general, I-AUC is the most useful surrogate estimate of IMGU in all weight groups. Fasting plasma insulin, HOMA-IR, and QUICKI provide comparable information about IMGU. Surrogate estimates of IMGU based on fasting insulin and glucose account for no more than 13% of the variability in insulin action in the normal-weight group, 30% in the overweight group, and 37% in the obese group.

Effect of diet and exercise intervention on inflammatory and adhesion molecules in postmenopausal women on hormone replacement therapy and at risk for coronary artery disease

Inflammation and the recruitment of monocytes into the artery wall are thought to be important aspects in the initiation and progression of atherosclerosis. The present study was designed to examine the effects of a rigorous diet and exercise intervention on plasma lipids and inflammatory and circulating adhesion molecules. Twenty postmenopausal women at risk for coronary artery disease (CAD) were placed on a high-fiber, low-fat diet, where food was provided ad libitum and daily aerobic exercise, primarily walking, was performed. In each subject, pre- and post-intervention fasting blood was drawn for serum lipid, insulin, glucose, C-reactive protein (CRP), serum amyloid A (SAA), interleukin-6 (IL-6) and both soluble (s) intracellular and vascular adhesion molecule (sICAM-1 and sVCAM-1) were measured. After 2 weeks, significant reductions in body mass index (BMI) (P <.001), glucose (P <.05), insulin (P <.01), all serum lipids, and total cholesterol (total-C):high-density lipoprotein-cholesterol (HDL-C) (P <.01). Reductions in homeostasis model assessment for insulin resistance (HOMA-IR) (P <.01), CRP (P <.01), SAA (P <.01) and sICAM-1 (P <.05) were noted, as well as an increase in the quantitative insulin sensitivity check index (P <.05). Reductions were also noted in 5 women not using hormone replacement therapy (HRT). No significant reductions were found in IL-6 or sVCAM-1 in response to the intervention. Overall, this intervention resulted in improved metabolic and lipid profiles, reduced inflammatory, and cell adhesion molecules in postmenopausal women in the absence of caloric restriction. The rapid improvements may reduce the risk of acute myocardial infarction (MI), and if sustained, these changes may mitigate the risk for atherosclerosis progression and its clinical consequences.

Evaluation of insulin resistance in acromegalic patients before and after treatment with somatostatin analogues

Many studies have recently shown that simple computer-solved indices, based on fasting glucose and insulin levels, closely mirror the euglycemic clamp technique in studying insulin resistance or pancreatic insulin secretion. Few data are at present available on the evaluation of these novel indices in acromegalic patients, known to be GH-dependent insulin-resistant subjects, in particular during medical treatment with somatostatin analogues. Indeed, these drugs are able to inhibit not only GH and IGF-I levels, but also insulin and glucagon pancreatic secretion, with contrasting effects on glucose metabolism. In this study, insulin resistance was evaluated by the homeostasis model assessment (HOMA-IR) and insulin sensitivity by quantitative insulin check index (QUICKI) in 27 normoglycemic acromegalic patients, before and after 6-month therapy with somatostatin analogues (lanreotide-SR 30-60 mg every 7-28 days in 15 and octreotide-LAR 20-30 mg every 28 days in 12). Thirty-five age- and sex-matched healthy subjects and 17 surgically treated acromegalic patients (5 cured and 12 not cured) were studied as control groups. Before medical treatment, HOMA-IR was higher in acromegalic patients than in healthy controls (4 +/- 3 vs 1.7 +/- 0.7, p < 0.05), while QUICKI was lower (0.33 +/- 0.04 vs 0.36 +/- 0.03, p < 0.05). During medical therapy, HOMA-IR decreased to 2.4 +/- 1.6 (p < 0.05) and became similar to that recorded in both healthy subjects and surgically treated patients. However, fasting glucose was increased and fasting insulin was decreased. QUICKI did not significantly change from basal values. No differences were observed between patients who normalized or not hormonal levels. The effects of the 2 drugs, though higher glucose levels were seen in patients treated with octreotide-LAR. In conclusion, this study demonstrates that medical treatment is able to improve insulin resistance, even if only successful surgery is able to completely normalize both HOMA-IR and QUICKI.

Assessment of cardiac autonomic modulation during adolescent obesity

OBJECTIVE

To investigate the cardiovascular autonomic function in pediatric obesity of different duration by using standard time domain, spectral heart rate variability (HRV), and nonlinear methods.

RESEARCH METHODS AND PROCEDURES

Fifty obese children (13.9 +/- 1.7 years) were compared with 12 lean subjects (12.9 +/- 1.6 years). Obese children were classified as recent obese (ROB) (<4 years), intermediate obese (IOB) (4 to 7 years), and long-term obese (OB) (>7 years). In all participants, we performed blood pressure (BP) measurements, laboratory tests, and 24-hour electrocardiogram/ambulatory BP monitoring. The spectral power was quantified in total power, very low-frequency (LF) power, high-frequency (HF) power, and LF to HF ratio. Total, long-term, and short-term time domain HRV were calculated. Poincaré plot and quadrant methods were used as nonlinear techniques.

RESULTS

All obese groups had higher casual and ambulatory BP and higher glucose, homeostasis model assessment, and triglyceride levels. All parameters reflecting parasympathetic tone (HF band, root mean square successive difference, proportion of successive normal-to-normal intervals, and scatterplot width) were significantly and persistently reduced in all obese groups in comparison with lean controls. LF normalized units, LF/HF, and cardiac acceleration (reflecting sympathetic activation) were significantly increased in the ROB group. In IOB and OB groups, LF, but not nonlinear, measures were similar to lean controls, suggesting biphasic behavior of sympathetic tone, whereas nonlinear analysis showed a decreasing trend with the duration of obesity. Long-term HRV measures were significantly reduced in ROB and IOB.

DISCUSSION

Autonomic nervous system changes in adolescent obesity seem to be related to its duration. Nonlinear methods of scatterplot and quadrant analysis permit assessment of autonomic balance, despite measuring different aspects of HRV.

QUICKI is a useful index of insulin sensitivity in subjects with hypertension

Insulin resistance may link disorders of metabolic homeostasis such as diabetes and obesity with disorders of hemodynamic homeostasis such as hypertension. Thus it is of interest to validate simple methods for quantifying insulin sensitivity in hypertensive patients. The quantitative insulin-sensitivity check index (QUICKI) is a novel mathematical transformation of fasting blood glucose and insulin levels. In obese and diabetic subjects, QUICKI has a significantly better linear correlation with glucose clamp determinations of insulin sensitivity than minimal-model estimates. To determine whether QUICKI is also useful in hypertensive subjects, we performed glucose clamps and frequently sampled intravenous glucose tolerance tests (FSIVGTT) on 27 hypertensive subjects taken off antihypertensive medication. Indexes of insulin sensitivity derived from glucose clamp studies (SIClamp) were compared with QUICKI, minimal-model analysis of FSIVGTTs (SIMM), and homeostasis model assessment (HOMA). The correlation between QUICKI and SIClamp ( r = 0.84) was significantly better than that between SIMM and SIClamp( r = 0.65; P < 0.028). The correlation between QUICKI and SIClamp was comparable to that between 1/HOMA and SIClamp ( r = 0.82). When studies were repeated in 14 subjects who had resumed antihypertensive medications, the percent changes in SIClamp for each of these patients were significantly correlated with percent changes in QUICKI ( r = 0.61) and HOMA ( r = −0.54) but not SIMM ( r = −0.18). We conclude that QUICKI is a simple, robust index of insulin sensitivity that is useful for evaluating and following the insulin resistance of hypertensive subjects in both research studies and clinical practice.

Postprandial lipemia in hypertension

OBJECTIVE

Many studies have shown that patients with coronary artery disease have an exaggerated rise and a delayed fall of plasma triglyceride (TG) concentration postprandially. We examined whether patients with essential hypertension have the same response to a fatty meal.

METHODS

A fatty meal (350g per 2 m(2) body surface with 83.5% fat) was given to 25 patients with essential hypertension (H) and to 25 normotensives (N). The two groups were matched for age, body mass index, lipid profile, basal glucose and insulin concentrations, and an index of homeostasis model of insulin resistance (HOMA-IR). A quantitative insulin sensitivity check index (QUICKI) was calculated. Blood samples were taken at 0, 4, 6, and 8 hours after the fatty meal. Lipid variables were measured in all samples. Blood glucose and insulin levels were measured in the fasting state.

RESULTS

Total and high density lipoprotein cholesterol, apolipoprotein A1 and B, lipoprotein (a), HOMA-IR and QUICKI did not differ significantly over time between the groups. The plasma TG concentration (mg/dL) increased significantly after fat loading in H (from 118 +/- 31 to 284 +/- 137 at 4 hours, 327 +/- 93 at 6 hours and 285 +/- 71 at 8 hours) compared to N group (from 105 +/- 29 to 150 +/- 38 at 4 hours, 148 +/- 40 at 6 hours and 115 +/- 34 at 8 hours), p = 0.001, p < 0.001 and p < 0.001, respectively.

CONCLUSION

This study suggests that patients with hypertension have an exaggerated response and delayed clearance of plasma TG concentration after fat loading.

Effects of an oral androgen on muscle and metabolism in older, community-dwelling men

To determine whether oxymetholone increases lean body mass (LBM) and skeletal muscle strength in older persons, 31 men 65-80 yr of age were randomized to placebo (group 1) or 50 mg (group 2) or 100 mg (group 3) daily for 12 wk. For the three groups, total LBM increased by 0.0 +/- 0.6, 3.3 +/- 1.2 (P < 0.001), and 4.2 +/- 2.4 kg (P < 0.001), respectively. Trunk fat decreased by 0.2 +/- 0.4, 1.7 +/- 1.0 (P = 0.018), and 2.2 +/- 0.9 kg (P = 0.005) in groups 1, 2, and 3, respectively. Relative increases in 1-repetition maximum (1-RM) strength for biaxial chest press of 8.2 +/- 9.2 and 13.9 +/- 8.1% in the two active treatment groups were significantly different from the change (-0.8 +/- 4.3%) for the placebo group (P < 0.03). For lat pull-down, 1-RM changed by -0.6 +/- 8.3, 8.8 +/- 15.1, and 18.4 +/- 21.0% for the groups, respectively (1-way ANOVA, P = 0.019). The pattern of changes among the groups for LBM and upper-body strength suggested that changes might be related to dose. Alanine aminotransferase increased by 72 +/- 67 U/l in group 3 (P < 0.001), and HDL-cholesterol decreased by -19 +/- 9 and -23 +/- 18 mg/dl in groups 2 and 3, respectively (P = 0.04 and P = 0.008). Thus oxymetholone improved LBM and maximal voluntary muscle strength and decreased fat mass in older men.

Metabolic effects of nandrolone decanoate and resistance training in men with HIV

Thirty human immunodeficiency virus (HIV)-infected men were randomized to a high dose of nandrolone decanoate weekly (group 1) or nandrolone plus resistance training (group 2) for 12 wk. For the two groups, nandrolone had no significant effects on total cholesterol, LDL cholesterol, LDL phenotype, or fasting triglycerides, although triglycerides decreased by 66 +/- 124 mg/dl for the entire population (P = 0.01). Group 2 subjects had a favorable increase of 5.2 +/- 7.7A in LDL particle size (P = 0.03), whereas there was no change in group 1. Lipoprotein(a) decreased by 7.3 +/- 6.8 mg/dl for group 1 (P = 0.002) and by 6.9 +/- 8.1 for group 2 (P = 0.013). However, HDL cholesterol decreased by 8.7 +/- 7.4 mg/dl for group 1 (P < 0.001) and by 10.6 +/- 5.9 for group 2 (P < 0.001). Percentages of HDL(2b) (9.7-12 nm) and HDL(2a) (8.8-9.7 nm) subfractions decreased similarly for the two groups, whereas HDL(3a) (8.2-8.8 nm) and HDL(3b) (7.8-8.2 nm) increased in the groups during study therapy (P < or = 0.02 for all comparisons). There was no evidence of a decreased insulin sensitivity in either group, whereas fasting glucose, fasting insulin, and homeostasis model assessment improved in group 2 (P < 0.05). These metabolic effects were favorable (other than for HDL), but changes were generally transient (except for HDL in group 2), with measurements returning to baseline 2 mo after the interventions were completed.

Indices of insulin action, disposal, and secretion derived from fasting samples and clamps in normal glucose-tolerant black and white children

OBJECTIVE

To validate fasting indices of insulin sensitivity and secretion in a diverse pediatric population against gold standard estimates from euglycemic and hyperglycemic clamps.

RESEARCH DESIGN AND METHODS

A total of 31 children (mean BMI 25.1 +/- 4.9 kg/m(2), mean age 8.7 +/- 1.4 years, 15 girls and 16 boys, 12 black and 19 white) underwent euglycemic and hyperglycemic clamps 2-6 weeks apart to derive insulin sensitivity indices (SI (Eug clamp) and SI (Hyper clamp)). Fasting samples were used to derive the homeostasis model assessment of insulin resistance index (HOMA-IR), HOMA of percent beta-cell function (HOMA-B%), quantitative insulin sensitivity check index (QUICKI), insulinogenic index, antilipolytic insulin sensitivity index (ISI-FFA), and C-peptide-to-insulin ratio.

RESULTS

The QUICKI correlated best with SI (Eug clamp) (r = 0.69, P < 0.05) and had greater correlations to SI (Eug clamp) than did either SI (Hyper clamp) (r = 0.45, P < 0.05) or the HOMA-IR (r = -0.51, P < 0.05). Both fasting insulin and the insulinogenic index correlated well with first- and steady-phase insulin secretion (r's from 0.79 to 0.86, P < 0.05). HOMA-B% was not as highly correlated (r = 0.69-0.72, P < 0.05). Fasting C-peptide-to-insulin ratio was not significantly correlated with clamp-derived metabolic clearance rate of insulin. ISI-FFA was not correlated with the degree of free fatty acid suppression obtained from the clamps.

CONCLUSIONS

The QUICKI, fasting insulin, and the insulinogenic index all closely correlate with corresponding clamp-derived indices of insulin sensitivity and secretion in this diverse pediatric cohort. These results, if replicated in similarly diverse populations, suggest that estimates based on fasting samples can be used to rank order insulin secretion and sensitivity in pediatric cohorts.

Relationships between left ventricular mass and the renin-angiotensin system, catecholamines, insulin and leptin

OBJECTIVES

Several neurohormonal systems have been suggested to stimulate myocardial cell growth, and thus take part in the development of left ventricular (LV) hypertrophy. We studied associations between LV mass and markers of the renin-angiotensin-aldosterone system (RAAS), the sympathetic nervous system, glucose homeostasis and leptin.

DESIGN

A total of 115 hypertensive patients with LV hypertrophy and two age- and gender-matched control groups consisting of 38 hypertensive patients without LV hypertrophy and 38 normotensive subjects were included. We examined determinants of the RAAS, plasma levels and 24-h urinary excretions of noradrenaline and adrenaline, plasma proinsulin, insulin, glucose, leptin and LV mass by echocardiography.

RESULTS

Plasma renin activity (PRA) and serum aldosterone were higher (both P < 0.001) in the LV hypertrophy group than in patients without LV hypertrophy and normotensive subjects (1.0 +/- 0.8, 0.2 +/- 0.2 and 0.2 +/- 0.2 ng mL(-1) h(-1), and 327 +/- 126, 269 +/- 146 and 221 +/- 80 pmol L(-1), respectively). PRA and aldosterone both related (P < 0.001) to LV mass index (r = 0.44 and 0.27, respectively). Catecholamine levels and excretions were similar in all three groups and did not relate to LV mass index. Proinsulin, insulin and leptin levels were all elevated in the hypertensive patients (P < 0.01), but proinsulin, insulin, insulin sensitivity (by the homeostasis model assessment) and leptin did not relate to LV geometry, when indexed for body size.

CONCLUSIONS

Plasma renin activity and serum aldosterone levels are elevated in hypertensive LV hypertrophy and relate to LV mass index. In addition to blood pressure, activation of the RAAS may be an important nonhaemodynamic mechanism in the control of LV hypertrophy.

Metabolic correlates with obstructive sleep apnea in obese subjects

OBJECTIVE

To examine links between obstructive sleep apnea (OSA), insulin resistance, and dyslipidemia.

STUDY DESIGN

Obese (body mass index [BMI] >95th percentile for age and gender) children who snored (n = 62, 46 males, age 10.89 [5-16 years] underwent polysomnography and metabolic studies.

RESULTS

Respiratory disturbance index (RDI) was 9.23 (0-95), with 23 children (39%) recommended for treatment. Fasting insulin levels were 154.6 pmol/L +/- 79.8 (52-486), and fasting glucose levels were high in 7 children (11%). Fasting insulin levels correlated with sleep variables, including log transformed RDI (log(10)RDI) (P =.01), desaturation events (P =.05), arousal index (P =.01), and sleep-time with oxygen saturation in arterial blood <90% (P =.03) (adjusted r (2) = 0.21, F = 3.9, P =.005), but not with age, or BMI Z score. Log(10)RDI correlated with fasting insulin (P =.001) and BMI Z score (P =.03) (adjusted r (2) = 0.12, F = 3.9, P =.005), but not age or other metabolic variables. The correlation between log(10)RDI and fasting insulin persisted in models combining sleep and metabolic variables: log(10)RDI, adjusted r (2) = 0.75, F = 35.2, P <.001, and for fasting insulin, adjusted r (2) = 0.42, F = 6.1, and P <.001.

CONCLUSIONS

The severity of OSA (log(10)RDI) correlated with fasting insulin levels, independent of BMI. Insulin levels may be further elevated as a consequence of OSA in obese children.

Obstructive sleep apnea is independently associated with insulin resistance

Epidemiological studies have implicated obstructive sleep apnea (OSA) as an independent comorbid factor in cardiovascular and cerebrovascular diseases. It is postulated that recurrent episodes of occlusion of upper airways during sleep result in pathophysiological changes that may predispose to vascular diseases. Insulin resistance is a known risk factor for atherosclerosis, and we postulate that OSA represents a stress that promotes insulin resistance, hence atherogenesis. This study investigated the relationship between sleep-disordered breathing and insulin resistance, indicated by fasting serum insulin level and insulin resistance index based on the homeostasis model assessment method (HOMA-IR). A total of 270 consecutive subjects (197 male) who were referred for polysomnography and who did not have known diabetes mellitus were included, and 185 were documented to have OSA defined as an apnea-hypopnea index (AHI) > or =5. OSA subjects were more insulin resistant, as indicated by higher levels of fasting serum insulin (p = 0.001) and HOMA-IR (p < 0.001); they were also older and more obese. Stepwise multiple linear regression analysis showed that obesity was the major determinant of insulin resistance but sleep-disordered breathing parameters (AHI and minimum oxygen saturation) were also independent determinants of insulin resistance (fasting insulin: AHI, p = 0.02, minimum O(2), p = 0.041; HOMA-IR: AHI, p = 0.044, minimum O(2), p = 0.022); this association between OSA and insulin resistance was seen in both obese and nonobese subjects. Each additional apnea or hypopnea per sleep hour increased the fasting insulin level and HOMA-IR by about 0.5%. Further analysis of the relationship of insulin resistance and hypertension confirmed that insulin resistance was a significant factor for hypertension in this cohort. Our findings suggest that OSA is independently associated with insulin resistance, and its role in the atherogenic potential of sleep disordered breathing is worthy of further exploration.

Quantification of insulin secretion in relation to insulin sensitivity in nondiabetic postmenopausal women

To evaluate mechanisms underlying the close association between insulin secretion and insulin sensitivity, insulin sensitivity was evaluated by the euglycemic-hyperinsulinemic clamp technique (M/I(clamp)) and insulin secretion was determined from the 75-g oral glucose tolerance test (OGTT) and from the glucose-dependent arginine-stimulation test in 81 nondiabetic postmenopausal women, all aged 61 years. M/I(clamp) was normally distributed with mean +/- SD of 69.9 +/- 30.5 nmol glucose center.kg(-1).min(-1)/pmol insulin.l(-1). It was found that the several different measures of insulin secretion from the OGTT and the glucose-dependent arginine-stimulation test were all inversely related to M/I(clamp). However, measures determining the direct insulin responses were more markedly potentiated by low M/I(clamp) than were measures determining glucose potentiation of insulin secretion. Moreover, the product of M/I(clamp) times measures of insulin secretion (disposition index [DI]) was inversely related to the 2-h glucose value. Finally, surrogate insulin sensitivity measures quantified from OGTT and the glucose-dependent arginine-stimulation test only weakly correlated to M/I(clamp) (R(2) approx equal to 0.25). Thus, 1) insulin secretion is adaptively increased when insulin sensitivity is low in nondiabetic postmenopausal women; 2) beta-cell exocytotic ability shows more efficient adaptation than beta-cell glucose recognition to low insulin sensitivity; 3) impaired beta-cell adaptation (i.e., low DI) is associated with higher 2-h glucose values during OGTT, although other regulatory mechanisms also exist; and 4) indirect surrogate measures of insulin sensitivity only weakly correlate to insulin sensitivity as determined by the euglycemic-hyperinsulinemic clamp.

Insulin resistance syndrome in childhood: associations of the euglycemic insulin clamp and fasting insulin with fatness and other risk factors

OBJECTIVE

Our objective was to describe in children the relation of fatness and insulin resistance to the risk factors associated with the insulin resistance syndrome and to compare fasting insulin with the euglycemic insulin clamp as a measure of insulin resistance in children.

STUDY DESIGN

This was a random selection of participants after blood pressure screening of 12,043 students in the fifth through eighth grades. Euglycemic insulin clamp studies with an insulin infusion rate of 1 mU/kg/min and a variable infusion of 20% glucose to maintain euglycemia, that is, plasma glucose at 5.6 mmol/L. Insulin sensitivity (M(lbm)) is defined as the amount of glucose required to maintain euglycemia (milligrams of glucose infused per kilogram lean body mass per minute).

RESULTS

Body mass index was significantly correlated with fasting insulin and significantly inversely correlated with M(lbm). Fasting insulin was significantly correlated with systolic blood pressure in both sexes, all lipids, except high-density lipoprotein-cholesterol in males and triglycerides and high-density lipoprotein-cholesterol in females, but after adjustment was done for body mass index, it was significantly related only to triglycerides. M(lbm) was significantly correlated only with triglycerides and high-density lipoprotein-cholesterol, and this did not change after adjustment was done for body mass index. A clustering effect for the risk factors was seen in children in the lowest quartile of M(lbm) (highest degree of insulin resistance) compared with children in the highest quartile of M(lbm) (lowest degree of insulin resistance).

CONCLUSIONS

As defined by M(lbm), there is an early association of insulin resistance, independent of body fat, with the risk factors. There is a significant relation between fasting insulin, as an estimate of insulin resistance, and the risk factors, but this is significantly influenced by body fatness. The clustering of risk factors according to level of M(lbm) suggests that adult cardiovascular disease is more likely to develop in children with the greatest degree of insulin resistance.