Validity and reproducibility of HOMA-IR, 1/HOMA-IR, QUICKI and McAuley's indices in patients with hypertension and type II diabetes

β-cell dysfunction in adolescents and adults with newly diagnosed type 2 diabetes mellitus

OBJECTIVE

To compare β-cell function in adolescents and adults with newly diagnosed type 2 diabetes (T2DM).

STUDY DESIGN

Thirty-nine adolescents with T2DM, 38 age- and weight-matched control subjects, and 19 adults with T2DM were studied. The adolescent subjects with diabetes were divided on the basis of whether they needed insulin to control their initial hyperglycemia. The primary outcome variable was the disposition index, computed from the acute insulin response to glucose corrected for insulin sensitivity (1/Homeostatic model assessment of insulin resistance).

RESULTS

The disposition index was significantly reduced in all 3 diabetic groups (control n=3360, adolescents with T2DM without insulin n=630, adolescents with T2DM with insulin n=120, adults with T2DM n=200; P<.001), and the adolescents with more severe hyperglycemia at diagnosis had lower disposition index than those with a more modest presentation (P<.05).

CONCLUSION

At the time of diagnosis, adolescents with T2DM have significant β-cell dysfunction, comparable with adults newly diagnosed with T2DM. Thus, severe β-cell impairment can develop within the first two decades of life and is likely to play a central role in the pathogenesis of T2DM in adolescents.

Interaction between physical activity and sleep duration in relation to insulin resistance among non-diabetic Chinese adults

BACKGROUND

It is of a public health interest to explore the relationship between different types of physical activity, sleep duration and diabetes/insulin resistance. However, little is known about such relationship. This study examines the single and joint associations of different types of physical activity, and sleep duration on insulin resistance among non-diabetic Chinese adults.

METHODS

Data was collected from 1124 non-diabetic adults in Jiangsu Province from the China Health and Nutrition Survey (CHNS). Domestic, occupational, transportation and leisure physical activity were assessed in terms of metabolic equivalent (MET)-hours-per-week to account for both intensity and time spent. Sleep duration was categorized into three groups: ≤ 7 hours, 7-9 hours, and ≥ 9 hours. Insulin resistance was evaluated by the homeostasis model of assessment (HOMA) and defined as the highest quartile of HOMA.

RESULTS

Total physical activity was mainly composed of occupational activity (75.1%), followed orderly by domestic, transportation and leisure time activity in both men and women. Total physical activity level was strongly negatively associated with fasting insulin and HOMA (p < 0.001). Among four types of physical activity, occupational activity was significantly negatively associated with HOMA after full adjustment (p < 0.05). Transportation activity was also negatively associated with HOMA when adjusted for age and gender (p = 0.028). Moreover, the combination of low physical activity and short sleep duration was associated with the highest odds of insulin resistance (adjusted OR = 3.26, 95% CI: 1.57-6.78), compared to those with high physical activity and adequate sleep duration.

CONCLUSIONS

Physical activity, mainly occupational physical activity, was negatively associated with insulin resistance in non-diabetic Chinese population, independently of potential confounders. There was a synergic effect of low physical activity and short sleep duration on insulin resistance.

Vascular function is not impaired early in the course of bipolar disorder

OBJECTIVE

Individuals with bipolar disorder face a nearly two-fold increased risk of cardiovascular mortality relative to the general population. Endothelial dysfunction precedes cardiovascular disease and serves as a quantifiable phenotype for vasculopathy. We investigated whether individuals with bipolar disorder had poorer vascular function than controls using a case-control design.

METHODS

The sample of 54 participants included 27 individuals with bipolar disorder and 27 age- and gender-matched controls. Participants underwent an assessment of metabolic (weight, lipids, and insulin resistance) and vascular parameters (endothelial function using flow-mediated dilation; arterial stiffness using pulse wave velocity and estimated aortic pressure).

RESULTS

Participants had a mean age of 32 years and 41% were female. No significant differences were found between groups in endothelial function or arterial stiffness. Individuals with bipolar disorder demonstrated 100% greater insulin resistance.

CONCLUSION

The lack of clinically significant differences in vascular function in this young sample suggests any increased risk either occurs later in the course of illness or is largely due to behavioral risk factors, such as smoking, which was balanced between groups. Substantial insulin resistance is identifiable early in course of illness, perhaps secondary to treatment.

Vasculopathy related to manic/hypomanic symptom burden and first-generation antipsychotics in a sub-sample from the collaborative depression study

BACKGROUND

Mood disorders substantially increase the risk of cardiovascular disease, though the mechanisms are unclear. We assessed for a dose-dependent relationship between course of illness or treatment with vasculopathy in a well-characterized cohort.

METHODS

Participants with mood disorders were recruited for the National Institute of Mental Health Collaborative Depression Study (CDS) and followed prospectively. A cross-sectional metabolic and vascular function evaluation was performed on a sub-sample near completion after a mean follow-up of 27 years.

RESULTS

A total of 35 participants from the University of Iowa (33) and Washington University (2) sites of the CDS consented to a metabolic and vascular function assessment at the Iowa site. In multivariate linear regression, controlling for age, gender, and smoking, manic/hypomanic, but not depressive, symptom burden was associated with lower flow-mediated dilation. Cumulative exposure to antipsychotics and mood stabilizers was associated with elevated augmentation pressure and mean aortic systolic blood pressure. This appeared specifically related to first-generation antipsychotic exposure and mediated by increases in brachial systolic pressure. Although second-generation antipsychotics were associated with dyslipidemia and insulin resistance, they were not associated with vasculopathy.

CONCLUSIONS

These results provide evidence that chronicity of mood symptoms contribute to vasculopathy in a dose-dependent fashion. Patients with more manic/hypomanic symptoms had poorer endothelial function. First-generation antipsychotic exposure was associated with arterial stiffness, evidenced by higher augmentation pressure, perhaps secondary to elevated blood pressure. Vascular phenotyping methods may provide a promising means of elucidating the mechanisms linking mood disorders to vascular disease.

Selection of the appropriate method for the assessment of insulin resistance

Insulin resistance is one of the major aggravating factors for metabolic syndrome. There are many methods available for estimation of insulin resistance which range from complex techniques down to simple indices. For all methods of assessing insulin resistance it is essential that their validity and reliability is established before using them as investigations. The reference techniques of hyperinsulinaemic euglycaemic clamp and its alternative the frequently sampled intravenous glucose tolerance test are the most reliable methods available for estimating insulin resistance. However, many simple methods, from which indices can be derived, have been assessed and validated e.g. homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI). Given the increasing number of simple indices of IR it may be difficult for clinicians and researchers to select the most appropriate index for their studies. This review therefore provides guidelines and advices which must be considered before proceeding with a study.

Comparative effects of rosuvastatin and atorvastatin on glucose metabolism and adipokine levels in non-diabetic patients with dyslipidaemia: a prospective randomised open-label study

AIMS

The impact of statins on glucose metabolism and adipokines remains controversial. We compared the effects of rosuvastatin and atorvastatin on glucose homeostasis, insulin sensitivity (IS), adiponectin and leptin levels as well as systemic inflammation in non-diabetic patients with dyslipidaemia.

METHODS

Thirty-six patients were randomly assigned to 10 mg/day of rosuvastatin (n = 18) or 20 mg/day of atorvastatin (n = 18) for 12 weeks. Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), fasting plasma glucose, insulin, homeostasis model assessment-insulin resistance (HOMA-IR), quantitative IS check index (QUICKI), adiponectin, leptin and high-sensitivity C-reactive protein (hsCRP) were measured at baseline and after 4 and 12 weeks.

RESULTS

Both statins significantly lowered TC, LDL-C, non-HDL-C and TG compared with baseline. Only rosuvastatin caused a significant reduction in insulin and HOMA-IR levels (-35%, p = 0.005 and -33%, p = 0.011 respectively) and a significant increase in QUICKI (+11%, p = 0.003) at 12 weeks. In terms of adipokines and hsCRP, no difference was observed after 4 and 12 weeks of treatment with either statin.

CONCLUSIONS

Rosuvastatin compared with atorvastatin resulted in significant improvements in IS indices. No significant changes in adiponectin, leptin or hsCRP levels were observed at 4 and 12 weeks of treatment with either statin.

A comparison of novel and commonly-used indices of insulin sensitivity in African American chronic hemodialysis patients

BACKGROUND

Insulin resistance (IR) is highly prevalent in chronic hemodialysis (CHD) patients and is associated with poor cardiovascular outcomes. Hyperinsulinemic euglycemic glucose clamp (HEGC) is the gold standard for measuring IR. The comparison of commonly-used indirect indices of IR to HEGC has not been adequately performed in this population. Furthermore, the validity of newly proposed adipokine-based IR indices has not been explored.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This is an observational study performed in a single center, involving 12 prevalent CHD patients (50 ± 9 years old, 100% African American, 33% women, body mass index of 34.4 ± 7.6 kg/m(2)) who were studied three consecutive times. IR was assessed by HEGC (glucose-disposal rate [GDR]), homeostatic model assessment of IR (HOMA-IR), HOMA-IR corrected by adiponectin (HOMA-AD), leptin adiponectin ratio (LAR), QUICKI, and the McAuley's index at each time point.

RESULTS

Eighty-three percent of the subjects displayed either glucose intolerance or overt insulin resistance by HEGC (GDR median, 5.71; interquartile range [IQR], 4.16, 6.81). LAR and HOMA-AD were the best correlates of IR measured by HEGC (r=-0.72, P<0.001, and -0.67, P<0.001), respectively. Fat percentage, interleukin-6, and adipokines (leptin, adiponectin, and resistin) were strongly associated with GDR. HEGC, LAR, and HOMA-AD had the best intraclass correlation coefficients.

CONCLUSION

IR is common in CHD patients. Adipokine-based indices are the best correlates of IR measurements by HEGC. HOMA-IR and QUICKI are reasonable alternatives. Use of these indices may allow better detection of alterations in insulin sensitivity in CHD patients.

Comparison between surrogate indexes of insulin sensitivity/resistance and hyperinsulinemic euglycemic glucose clamps in rhesus monkeys

The euglycemic glucose clamp is the reference method for assessing insulin sensitivity in humans and animals. However, clamps are ill-suited for large studies because of extensive requirements for cost, time, labor, and technical expertise. Simple surrogate indexes of insulin sensitivity/resistance including quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment (HOMA) have been developed and validated in humans. However, validation studies of QUICKI and HOMA in both rats and mice suggest that differences in metabolic physiology between rodents and humans limit their value in rodents. Rhesus monkeys are a species more similar to humans than rodents. Therefore, in the present study, we evaluated data from 199 glucose clamp studies obtained from a large cohort of 86 monkeys with a broad range of insulin sensitivity. Data were used to evaluate simple surrogate indexes of insulin sensitivity/resistance (QUICKI, HOMA, Log HOMA, 1/HOMA, and 1/Fasting insulin) with respect to linear regression, predictive accuracy using a calibration model, and diagnostic performance using receiver operating characteristic. Most surrogates had modest linear correlations with SI(Clamp) (r ≈ 0.4-0.64) with comparable correlation coefficients. Predictive accuracy determined by calibration model analysis demonstrated better predictive accuracy of QUICKI than HOMA and Log HOMA. Receiver operating characteristic analysis showed equivalent sensitivity and specificity of most surrogate indexes to detect insulin resistance. Thus, unlike in rodents but similar to humans, surrogate indexes of insulin sensitivity/resistance including QUICKI and log HOMA may be reasonable to use in large studies of rhesus monkeys where it may be impractical to conduct glucose clamp studies.

Novel adiponectin-resistin (AR) and insulin resistance (IRAR) indexes are useful integrated diagnostic biomarkers for insulin resistance, type 2 diabetes and metabolic syndrome: a case control study

Background

Adiponectin and resistin are adipokines which modulate insulin action, energy, glucose and lipid homeostasis. Meta-analyses showed that hypoadiponectinemia and hyperresistinemia are strongly associated with increased risk of insulin resistance, type 2 diabetes (T2DM), metabolic syndrome (MS) and cardiovascular disease. The aim of this study was to propose a novel adiponectin-resistin (AR) index by taking into account both adiponectin and resistin levels to povide a better indicator of the metabolic homeostasis and metabolic disorders. In addition, a novel insulin resistance (IR_AR) index was proposed by integration of the AR index into an existing insulin resistance index to provide an improved diagnostic biomarker of insulin sensitivity.

Methods

In this case control study, anthropometric clinical and metabolic parameters including fasting serum total adiponectin and resistin levels were determined in 809 Malaysian men (208 controls, 174 MS without T2DM, 171 T2DM without MS, 256 T2DM with MS) whose ages ranged between 40-70 years old. Significant differences in continuous variables among subject groups were confirmed by ANCOVA or MANCOVA test using 1,000 stratified bootstrap samples with bias corrected and accelerated (BCa) 95% CI. Spearman's rho rank correlation test was used to test the correlation between two variables.

Results

The AR index was formulated as 1+log₁₀(R₀)-log₁₀(A₀). The AR index was more strongly associated with increased risk of T2DM and MS than hypoadiponectinemia and hyperresistinemia alone. The AR index was more strongly correlated with the insulin resistance indexes and key metabolic endpoints of T2DM and MS than adiponectin and resistin levels alone. The AR index was also correlated with a higher number of MS components than adiponectin and resistin levels alone. The IR_AR index was formulated as log₁₀(I₀G₀)+log₁₀(I₀G₀)log₁₀(R₀/A₀). The normal reference range of the IR_AR index for insulin sensitive individuals was between 3.265 and 3.538. The minimum cut-off values of the IR_AR index for insulin resistance assessment were between 3.538 and 3.955.

Conclusions

The novel AR and IR_AR indexes are cost-effective, precise, reproducible and reliable integrated diagnostic biomarkers of insulin sensitivity for screening subjects with increased risk of future development of T2DM and MS.

Low density lipoprotein cholesterol is inversely correlated with abdominal visceral fat area: a magnetic resonance imaging study

Background

Visceral Fat Area (VFA) is an independent predictor of coronary disease. While low density lipoprotein cholesterol (LDL-C) is used to determine risk and guide therapy, its accuracy fails in obese patients who may have low LDL-C despite high VFA.

Objective

We sought to describe the relationship between VFA, LDL-C and to describe shifting cholesterol metabolism with increasing VFA.

Methods

42 High-risk vascular patients not on lipid-lowering therapy provided a fasting lipid profile and underwent magnetic resonance imaging (MRI) to quantify VFA and subcutaneous fat area (SFA) at the L4-L5 disc. Comparisons: 1. Correlation between VFA, SFA, LDL-C and the standard lipid panel 2. Correlation between VFA, SFA and markers of cholesterol synthesis (desmosterol, lathosterol) and cholesterol absorption (cholestanol, sitosterol).

Results

VFA was inversely correlated with LDL-C (r = -0.348) indicating potential discordance between cardiovascular risk and LDL-C. However, VFA was appropriately correlated with other markers of increased risk: r = -0.361 with HDL-C, r = 0.503 with VLDL-C, r = 0.499 with TG (all p < 0.05). VFA did not correlate significantly with non-HDL-C. VFA correlated positively with cholesterol synthesis markers (desmosterol, lathosterol) and negatively with an absorption marker (cholestanol).

Conclusions

LDL-C is inversely correlated with VFA and this may explain the loss of the relationship between LDL-C and cardiovascular events in the obese. While Non-HDL-C did not correlate positively with VFA, the absence of a negative correlation suggests that it may be a more appropriate lipid target in an increasingly obese world.

Insulin resistance is independently associated with liver aminotransferases in diabetic patients without ultrasound signs of nonalcoholic fatty liver disease

BACKGROUND

It has been shown that elevated levels of alanine and aspartate aminotransferases (ALT and AST) are associated with insulin resistance and type 2 diabetes mellitus; however, the pattern of this association in diabetic patients with negative or mild steatosis is not well understood. The aim of this study was to assess the association between elevated liver enzymes and insulin resistance in diabetic subjects without ultrasound signs of nonalcoholic fatty liver disease (NAFLD) (i.e., with less than 30% steatosis).

METHODS

In a cross-sectional study, a total of 670 diabetic subjects without established causes of liver injury were included. Patients with evidence of NAFLD in ultrasonography were not included. Fasting blood samples were obtained and plasma glucose, insulin, glycosylated hemoglobin (HbA1c), C-peptide, alkaline phosphatase, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipid profile were measured. Three indices of insulin sensitivity/insensitivity: Homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and McAuley were also calculated.

RESULTS

Elevated ALT was significantly (p < 0.001) correlated with fasting insulin, C-peptide, HOMA-IR, QUICKI, McAuley, and waist circumference. The same correlations were also observed for AST, which in all cases were weaker than ALT. Multivariate regression analysis showed that, among the above-mentioned variables, only HOMA-IR and fasting insulin were independently correlated with both ALT and AST. This correlation was independent of body mass index (BMI) or waist circumference.

CONCLUSION

In type 2 diabetes, in the absence of a detectable steatosis by ultrasonography, ALT and AST are associated with hyperinsulinemia and insulin resistance, independent of obesity. This finding possibly indicates that in diabetes a mild stage of steatosis is sufficient to mediate the association between insulin resistance and aminotransferases.

β-cell function is associated with metabolic syndrome in Mexican subjects

AIMS

The clinical diagnosis of metabolic syndrome does not find any parameters to evaluate the insulin sensitivity (IS) or β-cell function. The evaluation of these parameters would detect early risk of developing metabolic syndrome. The aim of this study is to determine the relationship between β-cell function and presence of metabolic syndrome in Mexican subjects.

MATERIAL AND METHODS

This study is part of the Mexican Survey on the Prevention of Diabetes (MexDiab Study) with headquarters in the city of Puebla, Mexico. The study comprised of 444 subjects of both genders, aged between 18 and 60 years and allocated into two study groups: (1) control group of individuals at metabolic balance without metabolic syndrome and (2) group composed of subjects with metabolic syndrome and diagnosed according to the criteria of the Third Report of the National Cholesterol Education Program Expert Panel on Defection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Anthropometric, biochemical, and clinical assessments were carried out.

RESULTS

Average age of the subjects in the control group (n = 254) was 35.7 ± 11.5 years and 42.0 ± 10.7 years for subjects in the metabolic syndrome group (n = 190). Subjects at metabolic balance without metabolic syndrome showed decreased IS, increased insulin resistance (IR), and altered β-cell function. Individuals with metabolic syndrome showed a high prevalence (P ≤ 0.05) of family history of type 2 diabetes (T2D). This group also showed a significant metabolic imbalance with glucose and insulin levels and lipid profile outside the ranges considered safe to prevent the development of cardiovascular disease and T2D.

CONCLUSION

The main finding in this study was the detection of altered β-cell function, decreased IS, an increased IR in subjects at metabolic balance, and the progressive deterioration of β-cell function and IS in subjects with metabolic syndrome as the number of features of metabolic syndrome increases.

MRI sagittal abdominal diameter is a stronger predictor of metabolic syndrome than visceral fat area or waist circumference in a high-risk vascular cohort

Objective:

To determine whether sagittal abdominal diameter (SAD) is associated with the metabolic syndrome independently of visceral fat area (VFA) and waist circumference (WC).

Methods:

Forty-three high-risk vascular patients were evaluated for metabolic syndrome criteria and underwent magnetic resonance imaging (MRI) to quantify SAD and VFA at the L4–L5 disc.

Comparisons:

1. Baseline differences in patients with and without the metabolic syndrome 2. Forward binary logistic regression analysis of predictors of the metabolic syndrome with SAD, VFA and WC as independents 3. Correlates of SAD.

Results:

Patients with metabolic syndrome had greater SAD, VFA and WC than patients without the metabolic syndrome (P < 0.01). Of SAD, VFA and WC, only SAD was associated with metabolic syndrome on forward binary logistic regression; beta 0.68, Wald’s statistic 10.8 (P = 0.001) and c-statistic 0.89 (P < 0.001). A > 22.7 cm SAD threshold identified metabolic syndrome with a 91% sensitivity and 80% specificity. SAD correlated with waist circumference (r = 0.918), high-density lipoprotein-cholesterol (r = −0.363), triglyceride (r = 0.401), fasting glucose (r = 0.428) and the QUICK index of insulin sensitivity (r = −0.667) (all P < 0.05).

Conclusions:

MRI-measured SAD is associated with the metabolic syndrome and renders the current gold standard of VFA redundant. This measure of obesity-related cardiovascular risk requires validation and evaluation in a prospective cohort.

Liver fat percent is associated with metabolic risk factors and the metabolic syndrome in a high-risk vascular cohort

Objective

To determine whether liver fat percent (LFP) is associated with the metabolic syndrome independently of visceral fat area (VFA).

Methods

43 High-risk vascular patients not on lipid-lowering therapy were evaluated for the Adult Treatment Panel III (ATPIII) metabolic syndrome criteria and underwent magnetic resonance imaging (MRI) to quantify VFA and subcutaneous fat area (SFA) at the L4-L5 disc and liver magnetic resonance spectroscopy (MRS) to quantify LFP. Comparisons: 1. Baseline differences in patients with and without the metabolic syndrome 2. Forward binary logistic regression analysis of predictors of the metabolic syndrome with VFA, SFA and LFP as independents 3. Correlates of LFP.

Results

43 patients were included in analysis. Patients with metabolic syndrome had greater VFA, SFA and LFP than patients without the metabolic syndrome (all p < 0.01). Of VFA, SFA and LFP, only LFP was associated with the diagnosis of the metabolic syndrome on forward binary logistic regression with an OR of 1.17 per 1% increase in LFP (p = 0.015). A 4% LFP threshold identified the metabolic syndrome with 84% sensitivity and 82% specificity. LFP correlated with waist circumference (r = 0.768), HDL-cholesterol (r = -0.342), triglyceride (r = 0.369), fasting glucose (r = 0.584) and the QUICK Index of insulin sensitivity (r = -0.679) (all p < 0.05)

Conclusions

LFP is associated with the metabolic syndrome and renders the current gold standard of VFA redundant in this analysis. This measure of obesity-related cardiovascular risk requires further validation and evaluation in a prospective cohort.

Insulin resistance is associated with increased cholesterol synthesis, decreased cholesterol absorption and enhanced lipid response to statin therapy

OBJECTIVE

Increasing insulin resistance is associated with a shift in cholesterol metabolism to increased synthesis and decreased absorption. Since statins inhibit cholesterol synthesis, we hypothesized that insulin-resistant patients will have greater LDL cholesterol (LDL-C) response to statins than insulin-sensitive patients.

METHODS

High-risk vascular patients not on lipid-lowering therapy were recruited and treated with Atorvastatin 80 mg for 6 weeks. Percent LDL-C response to Atorvastatin was related to insulin sensitivity using the quantitative insulin sensitivity check index (QUICKI). Comparisons: (1) correlation between %LDL-C response and QUICKI. (2) Differences in cholesterol metabolism markers in insulin-resistant (lowest tertile QUICKI) vs insulin-sensitive patients (highest tertile of QUICKI). (3) Correlation of QUICKI with percent LDL-C response after correction for cholesterol metabolism markers.

RESULTS

154 patients were enrolled of which 66 were suitable for this sub-study. Average LDL-C reduction was 57+/-12% (mean+/-SD). QUICKI correlated negatively with percent LDL-C reduction (Pearson's r=-0.258, p=0.037) and on regression analysis explained approximately 7% (R2=0.067) of the variation in percent LDL-C response which approximates that reported by pharmacogenomics. Insulin-resistant patients had higher levels of cholesterol synthesis markers (desmosterol, lathosterol) and lower levels of absorption markers (cholestanol, sitosterol) and the correlation between QUICKI and percent LDL-C response ceased to be significant when these factors were controlled for.

CONCLUSIONS

Insulin-resistant patients have superior LDL-C responses to statin therapy and that this may be related to increased cholesterol synthesis.

BACKGROUND

Patients with features of the metabolic syndrome, e.g. high triglycerides (TG) and low high density lipoprotein cholesterol (HDL-C) may have an enhanced benefit from statin therapy. A retrospective analysis from the 4S investigators where the study population was stratified by HDL-C and TG quartiles revealed variations in statin efficacy. Patients who fell into both the lowest quartile of HDL-C (<39 mg/dl) and highest quartile of TG (>159 mg/dl) had a greater frequency of features of the metabolic syndrome (high BMI, hypertension, diabetes) than the patients in the highest quartile of HDL-C (>52 mg/dl) and lowest quartile of TG (<98 mg/dl). The 4S investigators suggested that patients with low HDL-C and high TG achieved an enhanced clinical benefit from statins compared to patients with high HDL-C and low TG with hazard ratios of 0.48 and 0.86 respectively and a treatment-by-subgroup interaction p value of 0.03 [1]. Since the clinical benefit of statin therapy is directly proportional to achieved percent reduction in low density lipoprotein cholesterol (LDL-C) [2], we hypothesized that insulin-resistant patients would have greater percent decreases in LDL-C with statin therapy.

Impaired glucose metabolism and the exaggerated blood pressure response to exercise treadmill testing in normotensive patients

The authors aimed to investigate the association between glucose metabolism measures and the exaggerated blood pressure response (EXBPR) to exercise testing in normotensive nondiabetic patients. One hundred and forty-two consecutive patients underwent office blood pressure (BP) measurements, 24-hour BP monitoring, echocardiography, and treadmill exercise test according to the Bruce protocol. The population was divided into 2 groups according to EXBPR at a submaximal workload level. Furthermore, blood samples were obtained for fasting glucose (FG), fasting insulin (FI), and lipid profile assessment. Measures of insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR], quantitative insulin sensitivity check index [QUICKI], and McAuley index) were also estimated, and a standardized oral glucose tolerance test was performed to evaluate glucose levels at 120 minutes (G120). Patients with EXBPR (n=40; 27 men) compared with those without EXBPR (n=102; 66 men) were older by 4+/-6 years (P<.001). FG, FI, G120, HOMA-IR, QUICKI, and McAuley index differed in patients with EXBPR compared with those without EXBPR (P<.001 for all). Logistic multivariable regression models revealed that the studied glucose metabolism measures, duration of exercise, and 24-hour systolic BP remained determinants of EXBPR (P<.05 for all) after adjustment. Impaired glucose measures are significant determinants of EXBPR to exercise testing in normotensive nondiabetic patients, suggesting that impaired glucose metabolism may contribute to adverse cardiovascular prognosis including new-onset hypertension.

Association of capillary density and function measures with blood pressure, fasting plasma glucose, and insulin sensitivity

The pathophysiology underlying the association between hypertension and insulin resistance remains unclear. The study purpose was to determine whether reduced capillary density and/or function underlie, and may therefore explain, this association. The study was conducted on 115 black and non-black participants aged 18 to 55 years: 91 with normal blood pressure (systolic blood pressure [SBP] <130 mm Hg) and 24 with mild blood pressure elevation (SBP 130-159 mm Hg). Capillary density and function were quantified using direct capillaroscopy measures. Insulin sensitivity (IS) was estimated using the Quantitative Insulin Sensitivity Check Index (QUICKI). Endothelial function (EF) was measured using strain-gauge plethysmography. Data were analyzed by linear regression adjusted for age, sex, race, and body mass index (BMI). After adjustment for BMI, capillary density and function measures were significant predictors of SBP ( P<.01), fasting plasma glucose (P=.012, P=.03, and P=.004, respectively), and EF (P=.033, P=.001, and P=.009, respectively). However, none of the capillary measures were significant predictors of fasting insulin or IS. These capillaroscopy data demonstrated an association with SBP but not insulin resistance, suggesting that capillary measures are unlikely to explain the association between hypertension and insulin resistance, at least with modest degrees of blood pressure elevation.

Obesity and insulin resistance increase plasma viscosity in young women with polycystic ovary syndrome

OBJECTIVE

To investigate the plasma viscosity in young women with polycystic ovary syndrome (PCOS).

DESIGN

Patients with PCOS and healthy controls were assessed for plasma viscosity. The acquired data were tested for association with hyperandrogenemia, obesity and insulin resistance (IR) in patients with PCOS. Plasma viscosity was determined by a viscometer Type 53610/I SCHOTT-Instruments, Mainz at 37 degrees C.

PATIENTS

The study included 96 young women with PCOS and 72 healthy controls. Main outcome measures. Plasma viscosity and IR.

RESULTS

Plasma viscosity was 1.243 +/- 0.67 mm(2)/s in the control group and 1.252 +/- 0.82 in women with PCOS (p = 0.416). Using multiple regression analysis, total protein (B = 0.348, p = 0.005), area under curve for insulin (B = 0.320, p = 0.011) and BMI (B = 0.315, p = 0.013) were proven to be significantly correlated to plasma viscosity. Plasma viscosity was significantly increased in women with PCOS with IR compared to matched for age and BMI PCOS women without IR (1.300 +/- 0.055 vs. 1.231 +/- 0.049 mm(2)/s) (p = 0.004).

CONCLUSION

Young women with PCOS presented a plasma viscosity that was increased by obesity and IR. Therefore, clinical management of young overweight women with PCOS with IR should always include a serious reduction in body weight and the use of oral contraceptive treatment with cautious.

Eight-month follow-up of physical activity and central adiposity: results from an Internet-delivered randomized control trial intervention

BACKGROUND

Less than half of U.S. adults engage in the recommended amount of physical activity (PA). Internet-delivered PA programs increase short-term PA but long-term adherence is largely equivocal.

PURPOSE

To determine whether increased PA following the 16-week Internet-delivered Active Living Every Day (ALED-I) program is maintained 8 months later in sedentary and overweight rural adults.

METHODS

In our previous randomized controlled trial (N = 32; 18 intent-to-treat controls, 14 ALED-I interventions), the ALED-I group increased PA (+1384 steps/day; E.S. = 0.95) and reduced central adiposity. Nine original intervention participants and ten delayed intent-to-treat control participants completed ALED-I and an 8-month followup. Pedometer-measured PA, anthropometric variables, and cardiometabolic disease risk factors were assessed at baseline, postintervention, and at 8 months.

RESULTS

Control crossover participants increased PA (+1337 steps/ day; P = .04). Eight months following completion of ALED-I (N = 19), PA levels relapsed (-1340 steps/day) and were similar to levels before the intervention (6850 +/- 471 steps/day vs. 6755 +/- 543 steps/day; P = .89). Total cholesterol and triglycerides improved, -9.9% and -18.2%, respectively, and reductions in central adiposity were maintained (97.1 +/- 2.2 cm vs. 97.2 +/- 2.2 cm; P = .66).

CONCLUSIONS

The ALED-I intervention was efficacious in the short-term but did not produce longer-term adherence to PA. Future theory-based internet-delivered interventions that produce habituation of increased PA are warranted.

Internet-delivered lifestyle physical activity intervention: limited inflammation and antioxidant capacity efficacy in overweight adults

Overweight and physical inactivity are associated with elevated reactive oxygen species and chronic low-grade inflammation. Exercise training studies have measured changes in systemic inflammatory and oxidative/antioxidative biomarkers but predominantly at moderate-high intensities. Few low-intensity, lifestyle-based physical activity (PA) studies have been conducted. The purpose of this study was to determine whether improvements in lifestyle-oriented PA resulting from a 16-wk Internet-delivered PA program [Active Living Every Day-Internet (ALED-I)] elicit cardioprotective improvements in measures of inflammation, oxidation, or antioxidant enzyme capacity. Forty-one men and women (age 23-62 yr) were randomized to either the ALED-I intervention [n = 19; age = 40.4 +/- 1.9 yr; body mass index (BMI) = 31.4 +/- 1.1 kg/m(2)] or a delayed intent-to-treat control condition (n = 22; age = 46.6 +/- 1.3 yr; BMI = 31.0 +/- 0.7 kg/m(2)). TNF-alpha, C-reactive protein, myeloperoxidase, superoxide dismutase, catalase, total antioxidative capacity, change in PA, and other cardiometabolic disease risk factors were measured at baseline and postintervention. The ALED-I group increased PA and decreased central adiposity without changes in the control group. There was no change in the control group for any inflammation, oxidation, or antioxidant biomarkers. TNF-alpha decreased (P = 0.01) in the intervention group but was not statistically different from the control group. In conclusion, modest improvements in daily low-intensity ambulatory PA as a result of an Internet-delivered lifestyle PA intervention may be cardioprotective in sedentary and overweight adults through reductions in central adiposity and inflammation. However, the absence of favorable changes in other inflammation, oxidation, and antioxidant biomarkers highlights the need for further attention to the dose response of lifestyle-structured PA promotion strategies for health maintenance/improvement.

The metabolic syndrome, insulin resistance, and its surrogates in African and white subjects with type 2 diabetes in South Africa

BACKGROUND

Coronary heart disease (CHD) is rare in diabetic Africans in South Africa, unlike diabetic African-Americans, despite moderate levels of conventional risk factors, with absence of the usual male predominance. Because the metabolic syndrome and insulin resistance (IR) are associated with CHD, we have analyzed the prevalence and severity of the metabolic syndrome, and IR, in African and white subjects with type 2 diabetes.

METHODS

A total of 500 African and 254 white diabetic patients were evaluated for features of the metabolic syndrome (International Diabetes Federation [IDF] definition); insulin resistance (homeostasis model assessment-insulin resistance [HOMA-IR]) was calculated in subgroups.

RESULTS

In men, Africans had a lower body mass index (BMI) and smaller waists than white subjects (p < 0.0001); the metabolic syndrome was present in 46.5% and 74.1% of African and white patients respectively (p < 0.0001). In women, frequencies of the metabolic syndrome were similar, but severe metabolic syndrome (4 or 5 criteria) was more frequent in the white group (73.1%) than in the Africans (52.9%) (p = 0.0003). The prevalence of hypertriglyceridemia was lower in African men and women (p < 0.0001) and contributed to their lower prevalence of the metabolic syndrome/severe metabolic syndrome. Compared with the white patients, in African subjects HOMA-IR was 40% lower (p < 0.0001), and correlated with the triglyceride:high-density lipoprotein cholesterol ratio (TG:HDL-C) (r = 0.409, p < 0.0001).

CONCLUSIONS

In diabetic Africans, in comparison with white patients, the lower prevalence of the metabolic syndrome in men and severe metabolic syndrome in women, and lesser insulin resistance, might contribute to their lower risk of CHD; the higher prevalence in women might contribute to the reversal of the male:female ratio. The TG:HDL-C ratio appears to be a valid estimate of insulin resistance in diabetic Africans.

Clinical measures of physical fitness predict insulin resistance in people at risk for diabetes

BACKGROUND AND PURPOSE

Physical inactivity has been well documented as a risk factor for type 2 diabetes. Previous studies measured the level of physical activity either with questionnaires or with direct measurements of maximum oxygen uptake. However, questionnaires are patient-report measures, and methods for obtaining direct maximum oxygen uptake measurements often are not available clinically. The purpose of this study was to investigate whether clinical measurement of health-related physical fitness with a simple test battery can predict insulin resistance, a precursor of type 2 diabetes, in people at risk for diabetes.

SUBJECTS AND METHODS

A total of 151 volunteers with at least one diabetes risk factor (overweight, hypertension, dyslipidemia, family history, impaired glucose tolerance, gestational diabetes, or delivering a baby weighing more than 4.0 kg) were recruited. Insulin resistance (as determined with the homeostasis model assessment of insulin resistance [HOMA-IR]), physical fitness (including body composition, as determined with the body mass index and waist circumference), muscle strength (handgrip strength [force-generating capacity]), muscle endurance (sit-up test), flexibility (sit-and-reach test), and cardiorespiratory endurance (step test) were measured, and a physical activity questionnaire was administered. Backward regression analysis was used to build the prediction models for insulin resistance from components of physical fitness and physical activity.

RESULTS

Body mass index, muscle strength, and cardiorespiratory fitness predicted HOMA-IR in men (adjusted R(2)=.264). In women, age, waist circumference, and cardiorespiratory fitness were the predictors of HOMA-IR (adjusted R(2)=.438).

DISCUSSION AND CONCLUSION

Clinical measures of physical fitness can predict insulin resistance in people at risk for diabetes. The findings support the validity of clinical measures of physical fitness for predicting insulin resistance in people at risk for diabetes.

Internet-delivered behavior change program increases physical activity and improves cardiometabolic disease risk factors in sedentary adults: results of a randomized controlled trial

OBJECTIVES

To determine whether the Active Living Every Day (ALED-I) internet-delivered theory-based physical activity (PA) behavior change program increases PA and improves cardiometabolic disease risk factors (CDRF) in sedentary overweight adults.

METHODS

The study was a randomized control trial that took place in southern Wyoming and northern Colorado from 2005-2007. Thirty-two men and women (21-65 years) were randomized to a 16-week ALED-I intervention (n=14; age=41.4+/-3.7 years; BMI=32.3+/-1.3 kg/m(2)) or a delayed intent-to-treat control condition (n=18; age=49.4+/-1.7 years; BMI=30.6+/-0.8 kg/m(2)). At baseline and post-intervention, PA by pedometer and CDRFs were measured.

RESULTS

Both groups had similar baseline PA levels. ALED-I increased PA by an average of 1384 steps/day (p=0.03) compared to 816 steps/day (p=0.14) for the control group. Waist circumference (100.6+/-2.4 vs. 96.6+/-2.7 cm) and Coronary Risk Ratio (5.1+/-0.3 vs. 4.7+/-0.3) decreased in the ALED-I group and did not change in the control group (99.2+/-2.2 vs.99.8+/-2.1 cm) and (3.7+/-0.1 vs. 3.7+/-0.1), respectively.

CONCLUSIONS

The internet-delivered ALED program increased PA and improved some CDRFs in sedentary overweight/obese adults. To our knowledge, this is the first efficacy trial of the internet-delivered ALED program. Further studies are warranted due to the reach and cost-effectiveness of internet-delivered PA programs.

Preserving insulin secretion in Type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a complex disease characterized by insulin resistance and a progressive decline in β-cell function and mass. Current evidence suggests that β-cell dysfunction is present early in the course of the disease and that this dysfunction, rather than insulin resistance, is primarily responsible for the progression of T2DM. β-cell dysfunction can be accelerated by glucose toxicity, lipotoxicity, oxidative stress, chronic increases in inflammatory mediators and, potentially, the use of sulfonylureas. This review suggests that future efforts to limit the impact of T2DM must focus on strategies to preserve β-cell function. Several interventions have shown promise in this regard, including lifestyle modifications, thiazolidinediones, potassium channel openers, incretin mimetics, cytokine antagonists, bariatric surgery and dipeptidyl peptidase IV inhibitors, although therapeutic insulin remains the most robust and physiological approach.

Associations between physical activity, body fat, and insulin resistance (homeostasis model assessment) in adolescents: the European Youth Heart Study

BACKGROUND

More and better data are needed to understand the action of physical activity (PA) on insulin resistance and the concomitant relation with body fat in adolescence.

OBJECTIVE

We examined the relation between total PA and intensity levels with insulin resistance under special consideration of waist circumference and skinfold thickness.

DESIGN

This was a cross-sectional study of 613 adolescents (352 girls, 261 boys) with a mean (+/-SD) age of 15.5 +/- 0.5 y from Sweden and Estonia. Total, low, moderate, and vigorous PA was measured by accelerometry. Body fat estimators included waist circumference and the sum of 5 skinfold thicknesses. Fasting insulin and glucose were measured, and insulin resistance was calculated according to the homeostasis model assessment (HOMA). Linear regression analysis and analysis of covariance were used to determine the association between PA and insulin resistance while considering body fat. All estimates were adjusted for sex, country, pubertal status, and indicators of body fat when applicable.

RESULTS

Total, moderate, and vigorous PA were inversely correlated with HOMA. Body fat estimators were positively correlated with HOMA. Significant contrasts in HOMA concentrations were seen when comparing the lower 2 tertiles with the upper tertile of PA indicators. Repeating the analysis with body fat estimators showed significant contrasts in HOMA concentrations when comparing the lower tertiles with the upper tertile.

CONCLUSION

In view of an increase in obesity in young people, the results accentuate the role of PA in sustaining metabolic balance in adolescence and the potential benefit of an increase of time spent at higher PA levels for youth with relatively elevated amounts of body fat.

Acute sex steroid withdrawal reduces insulin sensitivity in healthy men with idiopathic hypogonadotropic hypogonadism

CONTEXT

Evidence suggests that testosterone (T) influences insulin sensitivity in men. The mechanism of this effect is unclear but is thought to involve changes in body composition.

OBJECTIVE

The aim of this study was to determine whether acute sex steroid withdrawal decreases insulin sensitivity in young, healthy men with idiopathic hypogonadotropic hypogonadism (IHH).

DESIGN

This was a 2-wk prospective study.

SETTING

The study was conducted at a General Clinical Research Center.

PATIENTS

Twelve men with IHH (age 40.8 +/- 2.8 yr) were studied: 1) on hormone replacement with normal T levels and 2) 2 wk after discontinuing therapy.

MAIN OUTCOME MEASURES

Each evaluation comprised a 75-g oral glucose tolerance test with assessment of insulin sensitivity (fasting insulin levels, homeostatic model assessment for insulin resistance, and Matsuda insulin sensitivity index) and insulin secretion (corrected insulin response). Serum cortisol, leptin, adiponectin, free fatty acids, IL-6, C-reactive protein, and TNF-alpha levels were also measured.

RESULTS

Body mass index was unchanged (27.1 +/- 1.1 to 27.2 +/- 1.1 kg/m(2)). Serum T levels decreased from 529 +/- 65 to 28 +/- 8 ng/dl (P < 0.00005). Fasting insulin levels increased from 4.9 +/- 0.7 to 6.2 +/- 0.6 microU/ml (P = 0.005), homeostatic model assessment of insulin resistance increased from 1.07 +/- 0.2 to 1.4 +/- 1.01 (P < 0.005), and insulin sensitivity index decreased from 11.0 +/- 2.3 to 7.5 +/- 0.7 (P < 0.05). There was a trend for fasting glucose levels to increase, 86.7 +/- 1.3 to 90.8 +/- 1.7 mg/dl (P = 0.09). IL-6 levels increased from 1.2 +/- 0.2 to 2.4 +/- 0.5 pg/ml (P < 0.01), whereas TNF-alpha levels decreased from 1.0 +/- 0.1 to 0.6 +/- 0.1 pg/ml (P < 0.05). No other significant changes were observed.

CONCLUSIONS

1) Acute sex steroid withdrawal reduces insulin sensitivity in young healthy IHH men. 2) The acuity of the hypogonadism and absence of changes in body mass index or leptin levels suggest that sex steroids modulate insulin sensitivity in the absence of apparent or detectable changes in body composition.