Diagnosing insulin resistance in the general population

Elevated fasting triglycerides predict impaired glucose tolerance in adolescents at risk for type 2 diabetes

OBJECTIVE

The aim of this study was to evaluate whether fasting laboratory values can predict impaired glucose tolerance (IGT) in adolescents who are at risk for developing type 2 diabetes mellitus (T2DM).

HYPOTHESIS

Elevated fasting triglycerides, a marker for worsening insulin resistance, predict risk for IGT.

DESIGN

Following a fast of at least 9 h, laboratory measures, body mass index (BMI), and demographic information were obtained. The subjects then underwent a 75-g oral glucose challenge with a 2-h postchallenge glucose determination.

SUBJECTS

Eighty-four adolescents aged 12-20 yr with at least two risk factors for developing T2DM (obesity, family history of T2DM, or acanthosis nigricans) and with either a fasting insulin level > or =25 microU/mL or a homeostasis model assessment of insulin resistance (HOMA-IR) > or =3.5 were recruited for the study.

RESULTS

Ten subjects (12%) had IGT [2-h glucose > or =140 mg/dL (7.77 mmol/L)], and 10 subjects (12%) had impaired fasting glucose [IFG; fasting glucose > or =100 mg/dL (5.55 mmol/L)]. However, only three (30%) subjects with IGT had IFG, though all subjects with IGT had a fasting triglyceride level > or =150 mg/dL (1.70 mmol/L). Of those subjects with elevated triglycerides, 29% had IGT. As a screening test to predict risk for IGT, elevated triglycerides >150 mg/dL had a sensitivity of 100% and a specificity of 68%. The positive predictive value was 29%, and the negative predictive value was 100%.

CONCLUSIONS

Screening with fasting glucose alone would have missed 70% of subjects with IGT in this population of insulin-resistant adolescents. However, a fasting triglyceride level > or =150 mg/dL was strongly associated with IGT and may help to identify at-risk adolescents who should undergo formal glucose tolerance testing.

Molecular mechanisms of insulin resistance and associated diseases

Insulin resistance is a state in which higher than normal concentrations of insulin are required for normal response. The most common underlying cause is central obesity, although primary insulin resistance in normal-weight individuals is also possible. Excess abdominal adipose tissue has been shown to release increased amounts of free fatty acids which directly affect insulin signalling, diminish glucose uptake in muscle, drive exaggerated triglyceride synthesis and induce gluconeogenesis in the liver. Other factors presumed to play the role in insulin resistance are tumour necrosis factor alpha, adiponectin, leptin, IL-6 and some other adipokines. Hyperinsulinaemia which accompanies insulin resistance may be implicated in the development of many pathological states, such as hypertension and hyperandrogenaemia. Insulin resistance underlies metabolic syndrome and is further associated with polycystic ovary syndrome and lipodystrophies. When beta-cells fail to secrete the excess insulin needed, diabetes mellitus type 2 emerges, which is, besides coronary heart disease, the main complication of insulin resistance and associated diseases.

Fasting-based estimates of insulin sensitivity in overweight and obesity: a critical appraisal

OBJECTIVE

To identify simple methods to estimate the degree of insulin resistance.

RESEARCH METHODS AND PROCEDURES

The performance of a wide range of fasting-based index estimates of insulin sensitivity was compared by receiver operating characteristic analysis (area under curves and their 95% confidence intervals) against the M value from euglycemic insulin clamp studies collected in the San Antonio (non-Hispanic whites and Hispanic residents of San Antonio, TX) and European Group for the Study of Insulin Resistance (non-diabetic white Europeans) databases (n = 638).

RESULTS

Insulin resistance differed substantially between lean (BMI < 25 kg/m2), overweight or obese (BMI > or = 25 kg/m2), and type 2 diabetic individuals. Estimates of insulin resistance were, therefore, assessed in each group separately. In the overweight and obese subgroup (n = 302), the receiver operating characteristic performance of fasting-based indices varied from 0.72 (0.62 to 0.82), in the case of the insulin/glucose ratio, to 0.80 (0.72 to 0.88) in the case of Belfiore free fatty acids. One superior method could not be identified; the confidence intervals overlapped, and no statistically significant differences emerged. All indices performed better when using the whole study population, with fasting plasma insulin, homeostatic model assessment, insulin/glucose ratio, quantitative insulin sensitivity check index, glucose/insulin ratio, Belfiore glycemia, revised quantitative insulin sensitivity check index, McAuley index, and Belfiore free fatty acids showing area under curves of 0.83, 0.90, 0.66, 0.90, 0.66, 0.90, 0.85, 0.83, and 0.86, respectively, because of the inclusion of very insulin sensitive (lean) and very insulin resistant cases (diabetic subjects).

DISCUSSION

In conclusion, a superior fasting-based index estimate to distinguish between the presence and absence of insulin resistance in overweight and obesity could not be identified despite the use of the large datasets.

Transient and steady-state euglycemic clamp validation of a model for glycemic control and insulin sensitivity testing

BACKGROUND

There is an urgent need for a simple and accurate measure of insulin sensitivity to diagnose insulin resistance in the general population and quantify changes due to clinical intervention. A new physiological control model of glucose and insulin metabolism is validated with the euglycemic-hyperinsulinemic clamp during steady and transient states.

METHODS

The data consist of n = 60 (15 lean, 15 overweight, 15 obese, and 15 morbidly obese) euglycemic-hyperinsulinemic clamp trials performed on normoglycemic insulin-resistant individuals. The glucose and insulin model is fitted using an integral-based method. Correlations between clamp-derived insulin sensitivity index (ISI) and the model's insulin sensitivity parameter (SI) are obtained during steady and transient states. Results are compared with log-homeostasis model assessment (HOMA), a widely used fasting surrogate for insulin sensitivity.

RESULTS

Correlation between model-based insulin sensitivity, SI, and ISIG (ISI normalized by steady-state glucose) is r = 0.99 (n = 60) at steady state and r = 0.97 at transient state, respectively. Correlations did not significantly change across subgroups, with narrow 95% confidence intervals. Log-HOMA correlations are r=-0.72 to SI and r=-0.71 to ISIG for the overall population but are significantly lower in the subgroups, with wide 95% confidence intervals.

CONCLUSIONS

The model-based insulin sensitivity parameter, SI, highly correlates to ISIG in all subgroups, even when only considering a transient state. The high correlation of SI offers the potential for a short, simple yet highly correlated, model-based assessment of insulin sensitivity that is not currently available.

Association of insulin resistance and hematologic parameters: study of a middle-aged and elderly Chinese population in Taiwan

BACKGROUND

Chronic inflammation is a common feature related to changes in hematologic parameters in insulin resistance. The aims of this study were to explore the relationship between hematologic parameters and insulin resistance, and to establish a gerontologic profile for following studies.

METHODS

Residents aged over 40 years in 3 major townships in I-Lan County participating in the Adult Health Examination were invited for the study. Diagnosis of diabetes mellitus (DM) was done according to American Diabetes Association criteria. Insulin resistance was measured by homeostasis model assessment (HOMA-IR), and subjects with the highest tertile of HOMA-IR were defined as being insulin resistant. Hematologic parameters including white blood cell (WBC) count, red blood cell (RBC) count, hemoglobin, and platelet count were measured for comparisons.

RESULTS

A total of 857 subjects (mean age, 64.6 +/- 11.2 years; male/female, 373/484) participated in this study. Their mean body mass index (BMI) was 24.5 +/- 3.7 kg/m2, and 42.4% of them were obese and 21.8% were overweight. The overall prevalence of DM was 15.4% (7.7% were previously diagnosed and 7.7% were newly diagnosed), and impaired fasting glucose was 7.2%. Trend analyses confirmed that age, BMI, HOMA-IR, WBC and platelet counts were significantly increased as glycemic metabolism exacerbated (p = 0.007, < 0.001, < 0.001, < 0.001 and 0.025, respectively). Compared with insulin-sensitive subjects, insulin-resistant subjects were more likely to be females (70.2% vs. 49.7%, p < 0.001), and had significantly higher BMI (26.2 +/- 3.9 kg/m2 vs. 23.7 +/- 3.3 kg/m2, p < 0.001), HOMA-IR (3.6 +/- 3.5 vs. 0.7 +/- 0.3, p < 0.001), WBC count (6686.9 +/- 1889.2/mm3 vs. 5942.9 +/- 1740.4/mm3, p < 0.001), and platelet count (243.5 +/- 70.9 x 10(3)/mm3 vs. 231.0 +/- 62.2 x 10(3)/mm3, p = 0.011), but not age (64.5 +/- 11.0 years vs. 64.6 +/- 11.4 years, p = 0.93) or RBC count (4.6 +/- 0.6 M/mm3 vs. 4.6 +/- 0.6 M/mm3, p = 0.76). When age and sex were controlled, HOMA-IR significantly correlated with WBC count (gamma = 0.23, p < 0.001) and platelet count (gamma = 0.09, p = 0.007). However, by multiple logistic regression, female gender, overweight and obesity, and elevated WBC count were all found to be independent risk factors of insulin resistance, but age, RBC and platelet counts were not.

CONCLUSION

Elevated WBC count but not RBC count was significantly associated with insulin resistance and glycemic metabolism. The relationship between platelet count and insulin resistance deserves further investigations.

[Evaluation of microalbuminuria in non-diabetic individuals]

AIM

To evaluate the presence of microalbuminuria in non-diabetic subjects, associating it to the presence of cardiovascular risk factors like hypertension, smoking, dislipidemia and obesity. The urinary albumin excretion rate (UAE) was also evaluated regarding to insulin secretion and resistance indices.

DESIGN AND METHODS

105 subjects aged 33.4 +/- 1.4 years (57.1% women), received 75 g dextrose for an OGTT, and the following variables were evaluated for glucose and insulin curves: basal and 2 hours values, peak values (PV) and area under the curves (AUC). To evaluate insulin secretion and resistance, we used the insulinogenic, delta, HOMA, QUICKI, glucose to insulin ratio and the relation between insulinogenic and HOMA indices. A urine sample was collected overnight for albuminuria. Individuals were allocated in two groups: 1) normal, and 2) altered glucose metabolism.

RESULTS

The two groups differed in age, BMI, BP, abdominal circumference (AC), WHR, cholesterol, triglycerides (TG), glycemias (basal and 2h), AUCg, HOMA and QUICKI indices and the relation between insulinogenic and HOMA. Mean UAE was 4.28 +/- 2.73 microg/mL, correlating to DBP, glycemias, AUCg, GPV, HOMA, 2h insulin, IPV e AUCi. By stepwise multiple-regression analysis, only AUCg was predictive of UAE. By comparing interquartile intervals of UAE, we found statistical significance between the 1st and 4th quartile for: BMI, SBP, DBP, AC, waist, 2h glucose, TG, LDL, AUCg, AUCi, GPV and HOMA and QUICKI indices.

CONCLUSION

Although in the absence of microalbuminuric individuals, we found differences among UAE in individuals across a range of glucose tolerance and differences between clinical and laboratorial variables in the interquartile analysis. Our findings suggest that in non-diabetic individuals, UAE is associated to some characteristics of the metabolic syndrome, probably predisposing to greater atherogenic susceptibility.

Metabolic syndrome throughout the menopausal transition: influence of age and menopausal status

OBJECTIVE

To assess the relationship between the main components of both the metabolic syndrome and insulin resistance and menopausal status in the menopausal transition.

METHODS

A total of 124 healthy women were divided into four groups according to their menstrual status: the first group consisted of 35 women in menopausal transition with menstrual bleeding (MTM) and with cycles between 35 and 80 days; the second group was composed of 29 women in menopausal transition with 3-6 months of amenorrhea (MTA). The third group consisted of 31 postmenopausal women (PostM) and the fourth group of 29 premenopausal women (PreM) with regular cycles. The metabolic syndrome was evaluated following the ATP III criteria. Evaluation of insulin resistance was made through the HOMA, QUICKI and McAuley indices and the triglycerides/high density lipoprotein (HDL) cholesterol ratio.

RESULTS

The triglycerides/HDL cholesterol ratio increased in MTM, MTA and PostM women in comparison with PreM women. A slight decrease in the QUIKI index (p = 0.06) and a decrease in the McAuley index (p < 0.001) were observed in MTM, MTA and PostM women in comparison to PreM women. The relative frequencies of metabolic syndrome in the four groups were: PreM, 0%; MTM, 20%; MTA, 21%; and PostM, 22% (p = 0.0001). The most frequent markers of the metabolic syndrome were increased waist circumference, low HDL cholesterol levels and hypertension. Linear regression between menopausal status and metabolic syndrome was lost when age was added to the model.

CONCLUSIONS

The frequency of metabolic syndrome increased from the time of the menopausal transition to the postmenopause. Abdominal obesity was the most frequent feature observed. Nevertheless, aging erased the effect of the menopause on the metabolic syndrome. In order to prevent cardiovascular disease, the metabolic syndrome must be evaluated from the time of the menopausal transition.

Correlations between measures of insulin sensitivity and weight loss

OBJECTIVE

Many formulas have been proposed to calculate insulin sensitivity and studies have shown their effectiveness. However, few studies have been done to compare formulas.

METHODS

Seventy-two obese participants completed a randomized weight loss study. Weight loss, change in body fat and change in waist circumference were used as surrogates for change in insulin sensitivity. Correlation coefficients were calculated for each of these surrogates with proposed formulas for insulin sensitivity found in the literature.

RESULTS

The change in insulin sensitivity using the formula proposed by McAuley (exp(2.63-0.28 x ln(fasting insulin)-0.31 x ln(fasting triglyceride in mmol/l)) showed the greatest correlation with weight loss (r=-0.59, p<0.0001) and was statistically superior to change in fasting glucose, fasting insulin and homeostasis model assessment (HOMA).

CONCLUSIONS

The insulin sensitivity formula proposed by McAuley provides an accurate means of detecting insulin resistance. As it does not require a glucose tolerance test, it is also easier and less expensive than most other formulas. Use of this formula rather than fasting glucose would detect many more patients with insulin resistance who are at risk for subsequent diabetes and other complications.

Insulin resistance and impaired glucose metabolism in a predominantly Maori community

We sought to identify lifestyle behaviours which influence risk of impaired glucose metabolism, IGM (newly diagnosed type 2 diabetes, impaired glucose tolerance [IGT] or impaired fasting glycemia [IFG]) or insulin resistance (IR) in a predominantly Maori community, and applied the McAuley formula to determine whether it predicts high risk individuals amongst this community. Three hundred and seventy one participants completed a lifestyle and dietary behaviour questionnaire and oral glucose tolerance test. Clinical variables, microalbuminuria, fasting glucose, insulin and lipids were measured. Diabetes, IFG and IGT were defined according to WHO criteria. IR was defined using the McAuley formula. Those with IGM and those with IR showed similar risk factor attributes. Odds ratios (95% CI) for development of IGM and IR were 0.43 (0.21-0.88) and 0.51 (0.33-0.80), respectively, for regular physical activity, and 0.55 (0.26-1.15) and 0.59 (0.37-0.96), respectively, for two or more dietary behaviours characterized by a high intake of fibre. Regular physical activity and a diet characterized by a high intake of dietary fibre were found to reduce risk of newly diagnosed IGM or IR. The McAuley formula appears to predict high-risk individuals in a predominantly Maori population as it does in European populations.

Hypoadiponectinemia is associated with insulin resistance and glucose intolerance after renal transplantation: impact of immunosuppressive and antihypertensive drug therapy

The objectives of this analysis were (1) to assess whether low serum adiponectin concentrations are associated with insulin resistance, metabolic syndrome, and new-onset posttransplantation diabetes mellitus (PTDM) and (2) to examine the possible effects of immunosuppressive and antihypertensive therapies on circulating adiponectin levels after renal transplantation. A total of 172 consecutive previously nondiabetic renal transplant recipients were examined 3 mo after transplantation, the majority (n = 167) with an oral glucose tolerance test. Serum adiponectin was measured by an in-house time-resolved immunofluorometric assay. Insulin secretion and insulin sensitivity were estimated by previously validated oral glucose tolerance test-derived indexes. One- and 6-yr follow-up data were available in subgroups of patients. Lower adiponectin levels were significantly associated with insulin resistance but not with insulinopenia. Patients with low adiponectin levels (first quartile) had significantly higher odds of PTDM (odds ratio [OR] 3.6; 95% confidence interval [CI] 1.1 to 12.7; P = 0.049) and metabolic syndrome (OR 3.9; 95% CI 1.6 to 9.5; P = 0.003) than patients in the upper (fourth) quartile. The increased risk for PTDM in patients with low adiponectin levels remained significant after adjustment for age, steroid dose, and family history of diabetes. Treatment with beta blockers was independently associated with lower serum adiponectin levels, and total steroid dose was associated with higher serum adiponectin levels. Low baseline adiponectin levels were also associated with significantly higher odds of PTDM at 6 yr (OR 6.9; 95% CI = 1.1 to 41.8; P = 0.037). Serum adiponectin levels correlate with posttransplantation insulin sensitivity and glucose tolerance. Glucocorticoids and beta blockers seem to have opposite effects on circulating adiponectin levels.

Hyperinsulinemia and dyslipidemia in non-diabetic benign prostatic hyperplasia

BACKGROUND

BPH is a multifactorial disease. Several studies have elucidated the role of hormones and growth factors in its etiology. Insulin is a growth-stimulating hormone. Previous studies have reported the association between hyperinsulinemia, dyslipidemia and BPH in patients with metabolic disorders like diabetes. We evaluated insulin and lipid profile parameters in non-diabetic BPH cases and correlated it with prostate size.

METHODS

50 symptomatic BPH cases and 38 controls were included in this study. Fasting serum insulin concentrations were measured by radioimmunoassay. Insulin resistance was assessed by HOMA. Fasting glucose, total cholesterol and triglycerides were quantified by enzymatic methods. HDL-cholesterol was quantified by phosphotungstate magnesium chloride method. LDL-cholesterol was calculated by Friedwald's formula.

RESULTS

Fasting serum insulin, HOMA, total cholesterol, and LDL-cholesterol were significantly higher and HDL-cholesterol was significantly lower in cases as compared to controls. Insulin was significantly associated with prostate size, cholesterol, triglycerides, VLDL-cholesterol and LDL-cholesterol in BPH cases. Stepwise regression analysis showed insulin as an independent risk factor in the development of BPH.

CONCLUSIONS

Hyperinsulinemia associated with insulin resistance is an independent risk factor in the development of BPH.

Influence of obesity and insulin resistance on left atrial size in children

BACKGROUND

Left atrial (LA) enlargement has been linked to obesity and insulin resistance in adults.

OBJECTIVE

The purpose of this study was to determine the association in children between LA area and: (i) different components of the metabolic syndrome including obesity (OB), measures of body mass index (BMI) and waist circumference (WC), homeostasis model assessment-insulin resistance (HOMA-IR, proinsulin), and blood pressure (BP); and (ii) left ventricular mass (LVM) and diastolic function, measured using echo Doppler.

METHODS AND RESULTS

Eighty-four (44 females) subjects, [40 OB (BMI>95%), 28 overweight (BMI>85%)], 16 non-OB (BMI<85%)] aged 9+/-2.24 yrs were matched for sex and age. BMI, WC, BP, Tanner stage, and Mode M, 2-dimensional and Doppler transmitral echocardiography were assessed. A standard oral glucose tolerance test (OGTT) was done, measuring glucose, insulin, and proinsulin concentrations. Hypertension was only present in OB subjects (25%). Significant univariate association (p<0.001) was found between LA area and height (r=0.52), age (r=0.45), Tanner stage (r=0.45), BMI (r=0.66), WC (r=0.70), systolic BP (r=0.52), diastolic BP (r=0.53), proinsulin (r=0.36), and HOMA-IR (r=0.36). In the multivariate regression analysis, independent variables were entered in a stepwise fashion: initially, gender (p=0.006) and Tanner stage (p=0.011) were still significant independent correlates of LA area after adjusting for age, gender, and Tanner stage. Subsequently, incorporation of WC showed that WC (p=0.018) was a significant independent correlate of LA area. A larger model constructed to test the significance of adjustment factors, including WC, BP, LVM, and HOMA-IR showed that WC (p<0.001) was the only significant independent variable.

CONCLUSION

LA enlargement is present in childhood and is related to abdominal OB and insulin resistance, suggesting that children with central OB are at increased risk for cardiovascular disease.

Postprandial Adiponectin Levels Are Unlikely to Contribute to the Pathogenesis of Obesity in Prader-Willi Syndrome

AIM

To investigate fasting and postprandial adiponectin levels in PWS patients as compared to obese and lean subjects and whether they could contribute to the pathogenesis of obesity in this syndrome.

METHODS

We studied 7 patients with PWS, 16 obese patients and 42 lean subjects for the fasting study. From this group, we evaluated 7 patients with PWS, 7 age-sex-BMI-matched obese non-PWS patients and 7 age-sex-matched lean subjects before and after the administration of 3,139.5 kJ (750 kcal) of a standard liquid meal (53.2% carbohydrate, 30% fat, 16.7% protein) after an overnight fast. Blood samples were obtained every 15 min for the first hour and every 30 min thereafter until 6 h. Adiponectin, IGF-I, glucose, triglycerides, cholesterol, and insulin were measured.

RESULTS

Fasting plasma adiponectin levels were lower in PWS than in lean subjects (5.24+/-2.56 vs. 8.28+/-4.63 microg/ml, p=0.041) but higher than in obese patients (4.01+/-1.27 microg/ml, p=0.047). After the meal, adiponectin concentrations mildly decreased in PWS at time point 240 min, while in obese and lean subjects no changes were observed. However, 6-hour postprandial AUC for adiponectin was similar in all three groups.

CONCLUSION

Fasting adiponectin levels are low in PWS, but they are so mildly modulated postprandially that these changes do not seem significant for the pathogenesis of obesity in this syndrome.

Simple fasting methods to assess insulin sensitivity in childhood

The 'gold standard' techniques used to measure insulin sensitivity in children are the hyperinsulinaemic-euglycaemic clamp and Bergman's minimal model. Although precise, these techniques are complex, invasive and time consuming. Alternative indirect measures of insulin sensitivity have been developed that utilize fasting glucose and insulin data in algorithms or computer programs. These methods include homeostatic model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI) and the glucose to insulin ratio (G:I). Each of these three fasting techniques has been developed and validated in adults, with little or no validation in children. Increasingly, HOMA and QUICKI are being used in childhood studies to assess insulin sensitivity. In a group of 79 pre-pubertal children, we found that the correlation between the minimal model and RHOMA (r = -0.4) was no better than that between the minimal model and fasting insulin (r = 0.4), with an even weaker correlation between the minimal model and QUICKI (r = 0.2). In addition, neither HOMA nor QUICKI were able to detect a reduction in insulin sensitivity with obesity or during growth hormone therapy, unlike the minimal model. In children with normal glucose levels, neither HOMA nor QUICKI was superior to fasting insulin. Validation of the derivation formulae for these methods in children is needed before they are more widely used. The potential benefits of these simple fasting techniques is that they are useful in large field studies. However, if the study groups are small or longitudinal changes in insulin sensitivity are sought, more precise techniques such as the clamp or minimal model should be used.

An insulin-sensing sugar-based fluorescent hydrogel

We have prepared a small library of amphiphiles, each comprising a polar carbohydrate head group attached through an N-terminal amino acid to a nonpolar pyrene tail group. One of these derivatives is sensitive to the presence of insulin in aqueous media.

Diagnosis of insulin resistance and associated syndromes: the spectrum from the metabolic syndrome to type 2 diabetes mellitus

Insulin resistance is a common underlying physiologic abnormality associated with central obesity, type 2 diabetes and cardiovascular disease. Clinically, its hallmark markers of hypertension, glucose intolerance and dyslipidemia have been grouped into associated syndromes of insulin resistance. Insulin resistance is now considered a useful marker of clinical risk and a target for therapeutic intervention. While the criteria for diagnosis of syndromes related to insulin resistance have been established, the clinical diagnosis of insulin resistance remains a significant challenge. As more clinicians focus on the management of insulin resistance in patients with cardiovascular disease, type 2 diabetes and other syndromes of insulin resistance, its diagnosis will take on increasing importance. This review focuses on the current definition and diagnosis of insulin resistance and associated syndromes.

Differences in cardiovascular risk factors, insulin resistance, and insulin secretion in individuals with normal glucose tolerance and in subjects with impaired glucose regulation: the Telde Study

OBJECTIVE

To assess the cardiovascular risk profile, the degree of insulin resistance, and beta-cell secretion in a cohort of subjects with different categories of impaired glucose regulation (IGR): impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and combined IFG/IGT.

RESEARCH DESIGN AND METHODS

We studied 902 nondiabetic subjects between 30 and 80 years of age, recruited from a cross-sectional population-based study in Telde, Gran Canaria Island, Spain. Categories of glucose tolerance were defined according to 2003 modified American Diabetes Association criteria. Risk factors for cardiovascular disease, the presence of the metabolic syndrome, and indirect measures of both insulin resistance and beta-cell function were analyzed.

RESULTS

A total of 132 (14.6%) participants had isolated IFG, 59 (6.5%) isolated IGT, and 48 (5.3%) combined IFG/IGT. Groups with normal glucose tolerance (NGT) and combined IFG/IGT had, respectively, the most favorable and unfavorable levels of cardiovascular risk factors, metabolic syndrome rates, and measures of insulin resistance. Subjects with IFG and IGT showed an intermediate profile between NGT and IFG/IGT categories. We found no significant differences between IFG and IGT in cardiovascular risk factors, metabolic syndrome prevalence, or insulin resistance. The IFG group exhibited a more impaired insulin secretion than those with IGT or IFG/IGT.

CONCLUSIONS

Individuals with IGR, especially those with IFG/IGT, have increased values of cardiovascular risk factors and higher indexes of insulin resistance. Groups with isolated IFG and isolated IGT present similar cardiovascular risk profiles. Subjects with IFG are characterized by more defective beta-cell function than other forms of IGR.

Validation of insulin resistance indexes in a stable renal transplant population

OBJECTIVE

The purpose of this study was to investigate the validity of established insulin resistance indexes, based on fasting blood parameters, in a stable renal transplant population.

RESEARCH DESIGN AND METHODS

Fasting insulin, homeostasis model assessment (HOMA), the quantitative insulin sensitivity check index (QUICKI), and McAuley's index were assessed for correlation and agreement with whole-body glucose uptake (M value) divided by prevailing serum insulin concentrations (I value) assessed during a hyperinsulinemic-euglycemic clamp in 51 stable renal transplant recipients, who were at a median of 7.5 years after transplant. Multivariate linear regression analyses were used to determine independent risk factors for insulin resistance.

RESULTS

The M/I value correlated with fasting insulin concentration (r = -0.56), HOMA (r = -0.53), QUICKI (r = 0.52), and McAuley's index (r = 0.61) (all P < 0.01). Linear regression showed agreement between all indexes and insulin resistance. However, McAuley's index showed the strongest agreement irrespective of age, sex, renal allograft function, and obesity. In multivariate analysis, fasting insulin concentration (beta = -0.59, P = 0.002), fasting triglyceride concentration (beta = -0.33, P = 0.04), and BMI (beta = -1.22, P = 0.05) were independently associated with the M/I value.

CONCLUSIONS

All investigated insulin resistance indexes were valid estimates of insulin resistance in the long-term stable renal transplant population. However, correlation and agreement were strongest for McAuley's index. In addition to fasting insulin and triglyceride concentrations, of which McAuley's index is composed, only BMI seemed to be independently associated with insulin resistance in this population.

The effects of 24 weeks of moderate- or high-intensity exercise on insulin resistance

This study was designed to investigate the effect of exercise intensity on insulin resistance by comparing moderate- and high-intensity interventions of equal energy cost. Maximum oxygen consumption (VO(2max)), insulin, glucose and triglycerides were measured in 64 sedentary men before random allocation to a non-exercise control group, a moderate-intensity exercise group (three 400-kcal sessions per week at 60% of VO(2max)) or a high-intensity exercise group (three 400-kcal sessions per week at 80% of VO(2max)). An insulin sensitivity score was derived from fasting concentrations of insulin and triglycerides, and insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). Data were available for 36 men who finished the study. After 24 weeks, insulin concentration decreased by 2.54+/-4.09 and 2.37+/-3.35 mU l(-1), insulin sensitivity score increased by 0.91+/-1.52 and 0.79+/-1.37, and HOMA-IR decreased by -0.6+/-0.8 and -0.5+/-0.8 in the moderate- and high-intensity exercise groups, respectively. When data from the exercise groups were combined, one-way analysis of variance with one-tailed post hoc comparisons indicated that these changes were significantly greater than those observed in the control group (all P<0.05). Twenty-four week changes in insulin concentration, insulin sensitivity score and HOMA-IR were not significantly different between the exercise groups. These data suggest that exercise training is accompanied by a significant reduction in insulin resistance, as indicated by well-validated surrogate measures. These data also suggest that moderate-intensity exercise is as effective as high-intensity exercise when 400 kcal are expended per session.

Tesaglitazar, a novel dual peroxisome proliferator-activated receptor alpha/gamma agonist, dose-dependently improves the metabolic abnormalities associated with insulin resistance in a non-diabetic population

AIMS/HYPOTHESIS

Insulin resistance is associated with abnormalities in lipid and glucose metabolism, which are major components of metabolic syndrome and risk factors for vascular disease. This study examined the effect of tesaglitazar (Galida), a novel, dual-acting peroxisome proliferator-activated receptor alpha/gamma agonist, on lipid and glucose metabolism in patients with evidence of insulin resistance.

METHODS

A 12-week, multicentre, randomised, double-blind, placebo-controlled, dose-finding study compared the efficacy and safety of oral tesaglitazar (0.1, 0.25, 0.5 and 1.0 mg/day) and placebo in 390 non-diabetic patients with hypertriglyceridaemia (plasma triglyceride concentration >1.7 mmol/l) and abdominal obesity (waist-to-hip ratio >0.90 for men and >0.85 for women).

RESULTS

A 1.0-mg dose of tesaglitazar reduced fasting triglycerides (the primary endpoint) by 37% (95% CI: -43% to -30%; p<0.0001), non-HDL-cholesterol by 15% (95% CI: -20% to -10%; p<0.0001) and NEFA by 40% (95% CI: -51% to -27%; p<0.0001), and increased HDL-cholesterol by 16% (95% CI: 8 to -24%; p<0.0001). At the end of treatment there was a dose-dependent increase in patients with pattern A LDL particle diameter (40% at baseline vs 87% at 12 weeks for tesaglitazar 1.0 mg). Tesaglitazar produced significant reductions in fasting insulin concentration (-35%; p<0.0001) and plasma glucose concentration (-0.47 mmol/l; p<0.0001). Respiratory infection and gastrointestinal symptoms were the most common adverse events and were similarly frequent in all groups.

CONCLUSIONS/INTERPRETATION

Tesaglitazar was well tolerated and produced significant, dose-dependent improvements in lipid and glucose metabolism and insulin sensitivity. Tesaglitazar may have the potential to prevent vascular complications and delay progression to diabetes in these patients.

An exploratory analysis of criteria for the metabolic syndrome and its prediction of long-term cardiovascular outcomes: the Hoorn study

Studies have shown an increased risk of cardiovascular outcomes with the metabolic syndrome, but information on predictive properties of the National Cholesterol Education Program Adult Treatment Panel 3 (NCEP) criteria is sparse. The authors used data from the Hoorn population-based study in the Netherlands including 2,484 participants aged 50-75 years examined in 1989 and followed for cardiovascular morbidity and mortality through 2000 to assess NCEP criteria, excluding known diabetes or cardiovascular disease. Cluster analyses explored whether NCEP identifies a mixture of heterogeneous groups. For each gender, participants meeting NCEP criteria seemed to be divided into clusters distinguished primarily by triglycerides or high density lipoprotein cholesterol. Cutpoints for components predicting cardiovascular events using classification and survival tree methodology varied by endpoint and gender, but Cox model hazards ratios were relatively comparable regardless of cutpoints (range: 1.3-2.5). Clear gradation in risk of cardiovascular outcomes was evident with increasing number of components, with statistically elevated risk for >or=3 (NCEP) components in men but for >or=2 components in women. Exploratory analyses of alternative metabolic syndrome criteria suggest cardiovascular risk estimates comparable to those derived by using NCEP, but criteria evaluating risk on more of a continuum would potentially allow consideration of alternative definitions by gender or for patients with other risk factors.

Ultrasonography for the evaluation of visceral fat and the metabolic syndrome

Association between abdominal obesity and cardiovascular disease has been related with visceral adiposity, through the predisposition of developing type 2 diabetes mellitus and metabolic syndrome (MS). Sonography is a simple and reliable method to measure both subcutaneous and visceral fat. To analyze the relationship of anthropometric measurements with abdominal adiposity measured by sonography and to analyze the utility of sonography in the prediction of insulin resistance (IR) and the other components of MS. Visceral fat measurements by sonography correlated better with components of MS than did subcutaneous fat measurements. Preperitoneal circumference (PC) was strongly correlated with all components of MS and with IR expressed as a homeostasis model assessment (HOMA) index for IR. PC was better than waist circumference (WC) in predicting triglyceride levels, apolipoprotein B levels, and HOMA index, but WC was better than PC in predicting high-density lipoprotein cholesterol levels. The area under the receiver operating characteristic curve was 0.699 for PC and 0.684 for WC, in subjects with body mass index 25 kg/m2 or greater (P=.024 and .015, respectively). PC and WC showed good correlation with HOMA index (Spearman correlation coefficient=0.306, P<.001 and .206, P<.001, respectively). Abdominal visceral fat is better correlated with MS than subcutaneous fat; sonography is a useful method to evaluate the abdominal fat; PC is the best sonography parameter correlated with components of MS, and in overweight and obese subjects, PC is better than WC at predicting components of the MS.

Elevated intraocular pressure is associated with insulin resistance and metabolic syndrome

BACKGROUND AND AIM

Elevated intraocular pressure (IOP), a well-known risk factor for glaucoma, has recently been shown to be associated with some metabolic complications and obesity. We investigated the link between IOP and metabolic disturbances, focusing especially on metabolic syndrome and insulin resistance.

METHODS

Eye examinations, including IOP measurement, were conducted on 943 subjects (533 men and 410 women). Body mass index (BMI), percent body fat, waist circumference, systolic and diastolic pressure, fasting insulin, glucose, lipids, and other metabolic parameters were measured. The homeostasis model assessment (HOMA) score and McAuley index were calculated to assess whole-body insulin resistance.

RESULTS

Both of these insulin resistance indices showed positive associations with IOP (p < 0.05), even after statistical adjustment for other risk factors. IOP was higher in participants with metabolic syndrome, as compared to those who did not have metabolic syndrome. The mean IOP tended to increase linearly with the presence of increasing numbers of components for metabolic syndrome.

CONCLUSIONS

These results suggest that insulin resistance might contribute to an explanation that would account for many previous findings concerning the association between IOP and obesity, hypertension, and diabetes.

Are ethnic differences in insulin sensitivity explained by variation in carbohydrate intake?

AIMS/HYPOTHESIS

Minority populations are disproportionately affected by diabetes. This health disparity may be due to less healthy diets and/or heritable factors in minority populations. These factors must be assessed concurrently to better appreciate their contribution to insulin sensitivity.

METHODS

We analysed overweight, healthy adults using the National Health and Nutrition Examination Survey 1999-2000. Means for dietary intake variables and insulin sensitivity were calculated by ethnicity. Linear regressions were performed to evaluate the association between ethnicity, dietary variables, dietary glycaemic index and insulin sensitivity. Fasting insulin was used to characterise insulin sensitivity.

RESULTS

Non-Hispanic whites have higher energy and fat intake, while Hispanics have higher carbohydrate intake and African-Americans have lower fibre intake. In unadjusted analyses both Hispanics and African-Americans have lower insulin sensitivity, but only Hispanics are more likely to have lower insulin sensitivity after controlling for dietary variables and BMI.

CONCLUSIONS/INTERPRETATION

Ethnic differences in insulin sensitivity remain after controlling for dietary differences and other factors, suggesting that inherent metabolic differences exist. Further studies are needed to define inherent metabolic factors, as well as other non-dietary factors that affect insulin sensitivity.

Comparison of Hormone and Glucose Responses of Overweight Women to Barley and Oats

OBJECTIVE

To determine the effect of particle size (flour vs. flakes) on glycemic responses after oats and barley (Prowashonupana cultivar), which contain high amounts of soluble fiber, are consumed by overweight women.

DESIGN

Ten women, average age 50 years and body mass index 30, consumed glucose (1 g/kg body weight) and four test meals (1 g carbohydrate/kg body weight; 2/3 of the carbohydrate from oat flour, oatmeal, barley flour, or barley flakes and 1/3 from pudding) in a Latin square design after consuming controlled diets for 2 days. Blood samples were collected at fasting and periodically after each meal.

RESULTS

Peak glucose and insulin levels after barley were significantly lower than those after glucose or oats. Glucose areas under the curve (AUCs) after test meals compared with AUCs after glucose were reduced after both oats and barley (29-36% by oats and 59-65% by barley) (p < 0.002). Insulin AUCs after test meals compared with glucose AUCs were significantly reduced only by barley (44-56%) (p < 0.005). Indexes for insulin resistance (HOMA, MFFM, Cederholm) after the oat and barley meals were not different from indexes after the glucose meal. Glucagon and leptin responses did not significantly differ for the carbohydrates tested.

CONCLUSIONS

Particle size of the oats or barley had little effect on the glycemic responses. Both oat and barley meals reduced glycemic responses; the high soluble fiber content of this barley appeared to be a factor in the greater reduction observed.

Insulin sensitivity at diagnosis of Type 2 diabetes is not associated with subsequent cardiovascular disease (UKPDS 67)

AIMS

Insulin resistance is common in Type 2 diabetes which, in turn, is associated with a markedly increased risk of cardiovascular disease. Whether insulin sensitivity measured after diagnosis of diabetes is associated with incident cardiovascular disease was evaluated in this prospective study.

METHODS

Three thousand five hundred and eighty-two subjects with newly diagnosed diabetes, recruited to the UK Prospective Diabetes Study (UKPDS), free of cardiovascular disease, and with complete information on insulin sensitivity and potential confounders, were followed prospectively to the first occurrence of (i) fatal or non-fatal myocardial infarction, MI (ii) fatal or non-fatal stroke, and (iii) coronary heart disease, CHD (fatal or non-fatal MI, sudden death or ischaemic heart disease). Insulin sensitivity was measured by Homeostatic Model Assessment (HOMA).

RESULTS

Insulin sensitivity as measured by HOMA was not associated with subsequent MI, stroke, or CHD in univariate or multivariate models controlling for age, sex, ethnicity, HbA(1c), body mass index, plasma triglycerides, cholesterol and smoking. The hazard ratio associated with a doubling of insulin sensitivity with fatal or non-fatal MI in a multivariate model was 0.92 (95% confidence interval, CI, 0.80-1.05). These results were not changed by the exclusion of overweight patients randomized to metformin.

DISCUSSION

Estimation of insulin sensitivity provides no additional useful information with respect to the risk of the first occurrence of cardiovascular disease in patients with newly diagnosed Type 2 diabetes. Among patients with Type 2 diabetes, insulin resistance is not a risk factor for cardiovascular disease.

Assessment of insulin sensitivity from measurements in the fasting state and during an oral glucose tolerance test in polycystic ovary syndrome and menopausal patients

BACKGROUND

Polycystic ovary syndrome (PCOS) and menopausal subjects are characterized by an increased cardiovascular and type 2 diabetes mellitus risk, at least partially related to insulin disturbances. The evaluation of insulin resistance in these patients could be useful as primary prevention. The aim of the study was to verify the validity of several indexes of insulin sensitivity in PCOS and menopausal subjects by comparing the data obtained by these indexes to those of euglycemic-hyperinsulinemic clamp studies.

METHODS

One hundred PCOS and 110 menopausal subjects were analyzed; all subjects underwent an oral glucose tolerance test (75 g) and euglycemic-hyperinsulinemic clamp study. Seven PCOS patients and 13 menopausal subjects had impaired glucose tolerance or type 2 diabetes mellitus and were excluded from the study. After analysis of correlation coefficients between the evaluated indexes and the clamp studies, the sensitivity and specificity of different cut-off values for each parameter were analyzed by receiver operating characteristic (ROC) curves.

RESULTS

The best correlation coefficients with clamp studies were obtained with the Avignon insulin sensitivity index (SiM) (R(s) = 0.7812) in PCOS patients and the Matsuda and De Fronzo index (R(s) = 0.6178) in menopausal patients. The best predictive index of insulin resistance in PCOS was a Avignon insulin sensitivity basal index (SibB) value of 62 or less (78% sensitivity, 95% specificity) and an insulin area under the curve (AUC) of 7,000 microIU/ml or more (>/=50,225 pmol/liter) x 120 min (83% sensitivity, 90% specificity). In the menopausal population, the best predictive performance was obtained by an insulin AUC of 10,000 microIU/ml or more (>/=71,750 pmol/liter) x 240 min (70% sensitivity, 88% specificity).

CONCLUSIONS

The presence of high correlation coefficients does not necessarily mean that the indexes of insulin resistance have an optimal predictive performance; this is probably due to the presence of many borderline values. The simple evaluation of insulin AUC seems to effectively replace the euglycemic-hyperinsulinemic clamp in routine clinical practice, allowing results superimposable to those obtained by minimal model analysis.

Effect of behavioral interventions on insulin sensitivity and atherosclerosis in the Watanabe heritable hyperlipidemic rabbit

OBJECTIVE

A previous study suggested that insulin metabolic variables play a role in the progression of atherosclerosis in Watanabe heritable hyperlipidemic (WHHL) rabbits. The present study sought to determine: 1) if young, individually caged WHHLs are insulin-resistant relative to New Zealand white (NZW) rabbits and 2) whether dietary or exercise interventions can improve insulin sensitivity and slow the development of atherosclerosis in these animals.

METHODS

Forty-two WHHLs were assigned to a dietary, exercise, or control condition, and 12 NZWs were used as a comparison control group. The intervention ran from 3 to 7 months of age, and all animals received an intravenous glucose tolerance test at the beginning and end of the intervention.

RESULTS

WHHLs were insulin-resistant relative to NZWs at 3 months of age. Whereas the dietary intervention was effective in controlling insulin resistance, WHHLs in the exercise group without dietary restriction and the control group exhibited significant increases in insulin resistance. No intervention significantly influenced the progression of atherosclerosis.

CONCLUSIONS

Young WHHLs are insulin-resistant during an early period when atherosclerosis is developing rapidly. Dietary restriction, but not exercise without weight control, is effective in controlling insulin metabolic variables in the WHHL model. Although dietary intervention can reduce cardiovascular risk factors such as insulin resistance, it is not effective in slowing the development of atherosclerosis in these genetically dyslipidemic animals. Similarly, exercise training, without dietary control, does not influence the progression of disease in WHHLs.

Limited accuracy of surrogates of insulin resistance during puberty in obese and lean children at risk for altered glucoregulation

This study evaluated the accuracy of surrogate indexes of insulin sensitivity (SI) in children. Surrogates (homeostasis model assessment index of insulin resistance, quick insulin sensitivity index, and 40/insulin ratio index) were cross-sectionally investigated in 66 obese and lean children (17 Tanner stage I, 19 Tanner stage II-III, and 30 Tanner stage IV-V) as indexes of insulin resistance in comparison with the minimal model. The pubertal decrease in SI was found with the minimal model (-47%; P = 0.01), but not with surrogates, which were not correlated to SI. Baseline insulin (Ib) did not mirror the decrease in SI, did not significantly change when plotted against pubertal stage or age, and was not correlated to SI. Ib and surrogates were positively correlated with the body mass index. The disposition index, which quantifies the feedback between SI and insulin release, was widely scattered and decreased during puberty (P = 0.05). The specificity and sensitivity of surrogates as predictors of insulin resistance were poor (e.g. 81.1% and 30.7%, respectively, for the homeostasis model assessment index of insulin resistance). Thus, during puberty, surrogates are not accurate predictors of insulin resistance. Because reference methods are rather expensive and invasive, additional studies of alternative techniques for evaluating SI are needed to allow accurate measurement of insulin resistance in children.

Post-Transplantation Diabetes Mellitus

Post-transplantation diabetes mellitus (PTDM) is defined as sustained hyperglycemia developing in any patient without history of diabetes before transplantation, that meets the current diagnostic criteria by the American Diabetes Association or the World Health Organization. Several risk factors have been identified: age, nonwhite ethnicity, and glucocorticoid therapy for rejection and chronic immunosuppression with cyclosporine and especially tacrolimus. The pathophysiology of this condition resembles that of type 2 diabetes mellitus: pretransplantation end-stage liver/renal and heart disease are insulin-resistant states, and after transplantation, glucocorticoids induce further peripheral insulin insensitivity. The "second hit" appears to be an acquired (yet reversible) insulin secretion defect resulting from the calcineurin inhibitors cyclosporine and tacrolimus. An international panel of experts has recently published the proceeding of a Consensus Conference proposing strategies for the screening, prevention and management of PTDM. Future directions include pre- and post-transplantation glucose load testing for high-risk individuals and pharmacological agents to decrease insulin resistance and to preserve beta-cell function.

Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women

AIMS/HYPOTHESIS

A diet low in saturated fatty acids and rich in wholegrains, vegetables and fruit is recommended in order to reduce the risk of obesity, cardiovascular disease and type 2 diabetes mellitus. However there is widespread interest in high-fat ("Atkins Diet") and high-protein ("Zone Diet") alternatives to the conventional high-carbohydrate, high-fibre approach. We report on a randomised trial that compared these two alternative approaches with a conventional diet in overweight insulin-resistant women.

METHODS

Ninety-six normoglycaemic, insulin-resistant women (BMI >27 kg/m(2)) were randomised to one of three dietary interventions: a high-carbohydrate, high-fibre (HC) diet, the high-fat (HF) Atkins Diet, or the high-protein (HP) Zone Diet. The experimental approach was designed to mimic what might be achieved in clinical practice: the recommendations involved advice concerning food choices and were not prescriptive in terms of total energy. There were supervised weight loss and weight maintenance phases (8 weeks each), but there was no contact between the research team and the participants during the final 8 weeks of the study. Outcome was assessed in terms of body composition and indicators of cardiovascular and diabetes risk.

RESULTS

Body weight, waist circumference, triglycerides and insulin levels decreased with all three diets but, apart from insulin, the reductions were significantly greater in the HF and HP groups than in the HC group. These observations suggest that the popular diets reduced insulin resistance to a greater extent than the standard dietary advice did. When compared with the HC diet, the HF and HP diets were shown to produce significantly (p<0.01) greater reductions in several parameters, including weight loss (HF -2.8 kg, HP -2.7 kg), waist circumference (HF -3.5 cm, HP -2.7 cm) and triglycerides (HF -0.30 mmol/l, HP [corrected] -0.22 mmol/l). LDL cholesterol decreased in individuals on the HC and HP diets, but tended to fluctuate in those on the HF diet to the extent that overall levels were significantly lower in the HP group than in the HF group (-0.28 mmol/l, 95% CI 0.04-0.52, p=0.02). Of those on the HF diet, 25% showed a >10% increase in LDL cholesterol, whereas this occurred in only 13% of subjects on the HC diet and 3% of those on the HP diet.

CONCLUSIONS/INTERPRETATION

In routine practice a reduced-carbohydrate, higher protein diet may be the most appropriate overall approach to reducing the risk of cardiovascular disease and type 2 diabetes. To achieve similar benefits on a HC diet, it may be necessary to increase fibre-rich wholegrains, legumes, vegetables and fruits, and to reduce saturated fatty acids to a greater extent than appears to be achieved by implementing current guidelines. The HF approach appears successful for weight loss in the short term, but lipid levels should be monitored. The potential deleterious effects of the diet in the long term remain a concern.

Pubertal changes in HOMA and QUICKI: relationship to hepatic and peripheral insulin sensitivity

BACKGROUND

Homeostasis model assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI) are measures of insulin resistance and insulin sensitivity derived from fasting glucose (FG) and insulin levels. They thus should reflect, in principle, insulin action on both the liver and the periphery.

METHODS

Twenty-three prepubertal and early pubertal adolescents were studied at baseline and after 6 months, using the frequently sampled intravenous glucose tolerance test (IVGTT) with labeled glucose. Total body insulin sensitivity (SI) was calculated using the minimal model and total glucose concentrations. Peripheral insulin sensitivity (SI*) was calculated from labeled glucose concentrations. Hepatic insulin resistance (HIR) was calculated by multiplying glucose production over the last hour by the average insulin level. HOMA and QUICKI were calculated from the fasting glucose and insulin values.

RESULTS

HOMA, QUICKI fasting insulin, and glucose to insulin ratio were all significantly related to SI (p <0.05) but were not independently related to SI* or HIR. Multiple linear regression analysis revealed that both SI* and HIR independently predicted HOMA and fasting glucose (p <0.1). QUICKI, fasting insulin, and glucose to insulin ratio were not independently related to SI, SI*, or HIR.

CONCLUSIONS

HOMA and fasting insulin reflect total body insulin sensitivity and HIR but not peripheral insulin sensitivity in prepubertal and early pubertal adolescents.

Dietary PUFA and the metabolic syndrome in Indian Asians living in the UK

Indian Asians living in the UK have a 50% higher CHD mortality rate compared with the indigenous Caucasian population, which cannot be attributed to traditional risk factors. Instead, features of the metabolic syndrome, including raised plasma triacylglycerol, reduced HDL-cholesterol (HDL-C) and an increased proportion of small dense LDL particles, together with insulin resistance and central obesity, are prevalent among this population. The present review examines evidence to support the hypothesis that an imbalance in dietary PUFA intake, specifically a higher intake of n-6 PUFA in combination with the lower intake of the long-chain (LC) n-3 PUFA, plays an important role in the prevalence of the metabolic syndrome observed in Indian Asians. Data are presented to illustrate the impact of manipulation of the background n-6 PUFA intake (moderate or high n-6 PUFA) and the subsequent response to supplementation with LC n-3 PUFA on blood lipids and insulin action in a group of Indian Asian volunteers. The results demonstrate that supplementation with LC n-3 PUFA had no impact on insulin action in those subjects consuming either the moderate- or high-n-6 PUFA diet. In the postprandial phase reductions in plasma triacylglycerol concentrations were greater in those consuming the high-n-6 PUFA background diet subsequent to fish oil supplementation. The present study concludes that, contrary to the central hypothesis, the prevalence of metabolic abnormalities in Indian Asians compared with Caucasians may not be attributable to differences in intakes of n-6 and n-3 PUFA.

Plasma insulin and cardiovascular mortality in non-diabetic European men and women: a meta-analysis of data from eleven prospective studies

AIMS/HYPOTHESIS

We examined the association between plasma insulin and cardiovascular mortality in non-diabetic European men and women based on data from eleven prospective studies.

METHODS

The study population comprised 6156 men and 5351 women aged 30-89 years. Baseline measurements included oral glucose tolerance test, fasting and 2-h plasma insulin, and conventional risk factors. Cox models were used to calculate hazard ratios (HRs) and their 95% confidence intervals, and overall HRs were assessed by meta-analyses.

RESULTS

During the 8.8-year follow-up, 362 men and 70 women died from cardiovascular disease. The age- and smoking-adjusted overall HR of cardiovascular mortality for the highest vs the lower quartiles of fasting insulin was 1.58 (95% CI: 1.26-1.97) in men and 2.64 (1.54-4.51) in women. Adjusting for other risk factors in addition, the HR was 1.54 (1.16-2.03) in men and 2.66 (1.45-4.90) in women. For 2-h insulin these HRs were 1.28 (0.99-1.66), 1.87 (0.87-4.02), and 0.85 (0.60-1.21), 1.36 (0.53-3.45). The overall HRs for interquartile ranges for fasting and 2-h insulin, with full adjustment, were 1.13 (1.05-1.22) and 1.11 (1.01-1.23) in men, and 1.25 (1.08-1.45) and 1.11 (0.91-1.36) in women.

CONCLUSIONS/INTERPRETATION

Hyperinsulinaemia, defined by the highest quartile cut-off for fasting insulin, was significantly associated with cardiovascular mortality in both men and women independently of other risk factors. Associations between high 2-h insulin and cardiovascular mortality were weaker and non-significant. Weak positive associations of fasting and 2-h insulin with cardiovascular mortality over interquartile ranges were, however, more similar.

Insulin resistance syndrome in children

The insulin resistance syndrome (syndrome X, metabolic syndrome) has become the major health problem of our times. Associated obesity, dyslipidemia, atherosclerosis, hypertension, and type 2 diabetes conspire to shorten life spans, while hyperandrogenism with polycystic ovarian syndrome affect the quality of life and fertility of increasing numbers of women. Whereas a growing number of single genetic diseases affecting satiety or energy metabolism have been found to produce the clinical phenotype, strong familial occurrences, especially in racially prone groups such as those from the Indian subcontinent, or individuals of African, Hispanic, and American Indian descents, together with emerging genetic findings, are revealing the polygenetic nature of the syndrome. However, the strong lifestyle factors of excessive carbohydrate and fat consumption and lack of exercise are important keys to the phenotypic expression of the syndrome. The natural history includes small for gestational age birth weight, excessive weight gains during childhood, premature pubarche, an allergic diathesis, acanthosis nigricans, striae compounded by gynecomastia, hypertriglyceridemia, hepatic steatosis, premature atherosclerosis, hypertension, polycystic ovarian syndrome, and focal glomerulonephritis appearing increasingly through adolescence into adulthood. Type 2 diabetes, which develops because of an inherent and/or an acquired failure of an insulin compensatory response, is increasingly seen from early puberty onward, as is atheromatous disease leading to coronary heart disease and stroke. A predisposition to certain cancers and Alzheimer's disease is also now recognized. The looming tragedy from growing numbers of individuals affected by obesity/insulin resistance syndrome requires urgent public health approaches directed at their early identification and intervention during childhood. Such measures include educating the public on the topic, limiting the consumption of sucrose-containing drinks and foods with high carbohydrate and fat contents, and promoting exercise programs in our nation's homes and schools.

Type 2 diabetes mellitus in children--an increasing health problem in Mexico

The incidence of type 2 diabetes mellitus (DM2) in children has increased worldwide and is commonly associated with overweight. Forty-four children with DM2 were studied by clinical histories, anthropometric measurements, and biochemical analysis. Homeostasis model assessment (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were determined to evaluate insulin resistance. Only five patients presented normal body mass index (BMI); the remainder were overweight, and 76% had acanthosis nigricans. Laboratory results yielded hyperglycemia, elevated glycosylated hemoglobin, insulin and C-peptide. Elevated HOMA-IR and decreased QUICKI values suggest insulin resistance. No significant difference was found between sexes, although overweight in girls had more influence over blood pressure and lipid levels (p <0.05). Time from diagnosis and HOMA-IR yielded relevant values (p = 0.010). Laboratory results, QUICKI, and HOMA-IR values suggested that these patients present DM2 and decreased insulin sensitivity. We recommend prevention of overweight and sedentary life-style.

Glucose metabolism and visceral fat in GH deficient adults: 1 year of GH replacement

The aim of the current study is to evaluate the effects of 12-month growth hormone (GH) replacement on glucose metabolism and visceral fat in 24 adults with GH deficiency (11 men, 13 women, age 41+/-1.9 year, BMI 27+/-1.2 kg/m2. Glucose metabolism was measured in the fasting state by the homeostatic model assessment (HOMA) insulin resistance index and during a standard oral glucose tolerance test (OGTT). Data were analyzed by HOMA and the insulin sensitivity index (ISI)-composite derived from the OGTT. Visceral fat was evaluated by CT scan. GH-deficient adults had increased visceral fat (P=0.029) with lower fasting glucose levels (P=0.004) than the control group on baseline evaluation. GH replacement induced deterioration in glucose metabolism, with progressive increment in fasting insulin levels at 6 and 12 months (P=0.024) and in 2-h-OGTT insulin levels at 3, 6 and 12 months (P=0.001). Plasma glucose levels did not change during the study. There was a deterioration in insulin sensitivity index observed by an increase in HOMA-IR (P=0.049) and a reduction in the ISI-composite (P=0.028), both at 12 months of replacement. Visceral fat and waist-to-hip-ratio (WHR) reduced not only at month 6 but also at month 12 (P=0.0001 and 0.023, respectively). In conclusion, 12 months of GH replacement seem to impair glucose homeostasis, despite favorable alterations in body composition.

Revised QUICKI provides a strong surrogate estimate of insulin sensitivity when compared with the minimal model

OBJECTIVE

To compare insulin sensitivity (Si) from a frequently sampled intravenous glucose tolerance test (FSIGT) and subsequent minimal model analyses with surrogate measures of insulin sensitivity and resistance and to compare features of the metabolic syndrome between Caucasians and Indian Asians living in the UK.

SUBJECTS

In all, 27 healthy male volunteers (14 UK Caucasians and 13 UK Indian Asians), with a mean age of 51.2+/-1.5 y, BMI of 25.8+/-0.6 kg/m(2) and Si of 2.85+/-0.37.

MEASUREMENTS

Si was determined from an FSIGT with subsequent minimal model analysis. The concentrations of insulin, glucose and nonesterified fatty acids (NEFA) were analysed in fasting plasma and used to calculate surrogate measure of insulin sensitivity (quantitative insulin sensitivity check index (QUICKI), revised QUICKI) and resistance (homeostasis for insulin resistance (HOMA IR), fasting insulin resistance index (FIRI), Bennetts index, fasting insulin, insulin-to-glucose ratio). Plasma concentrations of triacylglycerol (TAG), total cholesterol, high density cholesterol, (HDL-C) and low density cholesterol, (LDL-C) were also measured in the fasted state. Anthropometric measurements were conducted to determine body-fat distribution.

RESULTS

Correlation analysis identified the strongest relationship between Si and the revised QUICKI (r=0.67; P=0.000). Significant associations were also observed between Si and QUICKI (r=0.51; P=0.007), HOMA IR (r=-0.50; P=0.009), FIRI and fasting insulin. The Indian Asian group had lower HDL-C (P=0.001), a higher waist-hip ratio (P=0.01) and were significantly less insulin sensitive (Si) than the Caucasian group (P=0.02).

CONCLUSION

The revised QUICKI demonstrated a statistically strong relationship with the minimal model. However, it was unable to differentiate between insulin-sensitive and -resistant groups in this study. Future larger studies in population groups with varying degrees of insulin sensitivity are recommended to investigate the general applicability of the revised QUICKI surrogate technique.

The prevalence of the metabolic syndrome among arab americans

OBJECTIVE

To estimate the prevalence of the metabolic syndrome in Arab Americans by age, sex, and BMI and to examine the association between insulin resistance and each of the components of the metabolic syndrome.

RESEARCH DESIGN AND METHODS

We studied a representative, cross-sectional, population-based sample of 542 Arab Americans aged 20-75 years. The metabolic syndrome was defined by Adult Treatment Panel III (ATP III) and World Health Organization (WHO) diagnostic criteria. Insulin resistance was estimated by homeostasis model assessment (HOMA-IR).

RESULTS

The age-adjusted prevalence of the metabolic syndrome was 23% (95% CI 19-26%) by the ATP III definition and 28% (24-32%) by the WHO definition. Although the prevalence increased significantly with age and BMI in both sexes by both definitions, differences in estimates were noted. With ATP III, the age-specific rates were similar for men and women aged 20-49 years but were significantly higher for women aged >/=50 years. With WHO, rates were higher for men than women aged 20-49 years and similar for those aged >/=50 years. The most common component of the metabolic syndrome in men and women was low HDL cholesterol with the ATP III and the presence of glucose intolerance and HOMA-IR with the WHO. Strong associations between HOMA-IR and individual components of the metabolic syndrome were observed. After fitting a model with HOMA-IR as the outcome, waist circumference, triglyceride level, and fasting plasma glucose level were significantly associated with HOMA-IR.

CONCLUSIONS

The metabolic syndrome is common among Arab Americans and is related to modifiable risk factors.

Glucose metabolism and visceral fat in GH deficient adults: two years of GH-replacement

The aim of this study was to evaluate the effect of 24 months of growth hormone (GH) replacement on glucose metabolism and visceral fat in 17 adults with GH deficiency: 9 men and 8 women; age 40 +/- 1.8 yr. [range 20-61] and body mass index 25 +/- 0.8 Kg/m2. Glucose metabolism was evaluated by a standard oral glucose tolerance test (OGTT), by the homeostatic model assessment (HOMA) insulin resistance index and by the insulin sensitivity index (ISI)-composite derived from the OGTT. Visceral fat was evaluated by CT scan.Twenty-four months of GH replacement induced an increase in the prevalence of abnormal glucose tolerance, with significant progressive increment in 2h-OGTT insulin levels at 3, 12 and 24 months (p = 0.005). Plasma glucose levels and ISI-composite did not alter during the study. HOMA-IR index increased only in the group of patients (n = 8) who had abnormal OGTT at 24 months (p = 0.012). Visceral fat reduced at month 12 and remained decreased until the end of the study (p = 0.009). In conclusion, the present study suggests that adults with GH deficiency after twenty-four months of GH replacement developed abnormal glucose tolerance, probably due to an increase in insulin resistance, associated with higher insulin levels, despite favorable alterations in body composition.

In overweight patients with chronic hepatitis C, circulating insulin is associated with hepatic fibrosis: implications for therapy

BACKGROUND/AIMS

Host factors such as increased body mass index (BMI) and genotype-specific viral factors contribute to the development of steatosis in patients with chronic hepatitis C (HCV). We hypothesized that host metabolic factors associated with increased BMI may play a role in disease progression.

METHODS

Fasting serum was collected from 160 patients with chronic HCV at the time of liver biopsy and 45 age, gender and BMI matched controls, and assessed for levels of insulin, c-peptide and leptin.

RESULTS

Patients with viral genotype 3 had more severe steatosis (P=0.0001) and developed stages 1 and 2 fibrosis at a younger age (P<0.05) than patients with genotype 1. For both genotypes, overweight patients had significantly more steatosis and increased insulin and leptin levels. In contrast to lean patients, there was a statistically significant increase in circulating insulin levels with increasing fibrosis in overweight patients with chronic HCV (P=0.03). Following multivariate analysis, insulin was independently associated with fibrosis (P=0.046) but not inflammation (P=0.83). There was no association between serum leptin levels and stage of fibrosis.

CONCLUSIONS

Increasing circulating insulin levels may be a factor responsible for the association between BMI and fibrosis in patients with HCV, irrespective of viral genotype.

Diagnosing insulin resistance by simple quantitative methods in subjects with normal glucose metabolism

OBJECTIVE

To identify a reliable yet simple indirect method for detection of insulin resistance (IR).

RESEARCH DESIGN AND METHODS

A total of 65 subjects (44 men and 21 women aged 30-60 years) were selected by a simple random sampling method. Inclusion criteria were voluntary participation from staff and hospital personnel, absence of abnormal glucose tolerance, and normal results of lipid profile and basic blood chemistry. A blood sample was taken after a 12-h overnight fast to determine plasma lipid, glucose, and insulin levels. An intravenous glucose tolerance test with administration of insulin after 20 min and extraction of multiple blood samples for glucose and insulin measurements and calculation of the minimal model approximation of the metabolism of glucose (MMAMG) S(i) value were performed. Three indirect indexes used to predict insulin sensitivity or IR were calculated, and metabolic syndrome was diagnosed using the Adult Treatment Panel III (ATP III) criteria. All results were correlated with those of the MMAMG.

RESULTS

The 75th percentile value as the cutoff point to define IR corresponded with a fasting plasma glucose level of 12 mU/l, a homeostasis model assessment of 2.6, a 25th percentile for S(i) value of 21, and QUICKI (quantitative insulin sensitivity check index) and McAuley indexes of 0.33 and 5.8, respectively. The S(i) index correlated (P < 0.001) with all the indirect indexes and parameters of the metabolic syndrome.

CONCLUSIONS

When compared with the S(i) index, the most sensitive and specific indirect method was the score proposed by McAuley et al. (specificity 0.91, sensitivity 0.75, 9.2 probability ratio of a positive test), followed by the existence of metabolic syndrome (specificity 0.91, sensitivity 0.66, 7.8 probability ratio of a positive test).

Evaluation of HOMA and QUICKI as measures of insulin sensitivity in prepubertal children

BACKGROUND

Simple fasting sample methods to measure insulin sensitivity (SI) such as homeostasis model assessment (HOMA) and quantitative insulin-sensitivity check index (QUICKI) have been widely promoted in adult studies but have not been formally evaluated in children. The aim of this study was to compare HOMA and QUICKI to the minimal model as measures of SI in prepubertal children.

METHOD

The study population consisted of twins (n = 44), premature (n = 17), small for gestational age (SGA) (15), and normal (n = 3) prepubertal children. The insulin-sensitivity index derived by the minimal model (SIMM) was calculated by the minimal model with plasma glucose and insulin data from a 90-min frequently sampled intravenous glucose test with tolbutamide. The HOMA resistance index (RHOMA) and QUICKI were calculated from fasting plasma glucose and insulin values.

RESULTS

The correlation between RHOMA and SIMM (r = -0.4, p < 0.001) was no better than that between fasting insulin and SIMM (r = -0.4, p < 0.001). QUICKI was poorly correlated with SIMM (r = 0.2, p = 0.02). The correlation between SIMM and RHOMA is largely confined to low SI values (< 10 x 10(-4)/min microU/mL.) In seven SGA subjects, the introduction of growth hormone treatment led to an expected fall in SIMM by 8.2 +/- 2.8 x 10(-4)/min microU/mL (p = 0.02) that was not detected by either RHOMA (p = 0.1) or QUICKI (p = 0.2). Similarly, SIMM values were lower in obese (n = 9) compared to non-obese subjects (p = 0.04); however, no difference was found between these two groups with either RHOMA (p = 0.21) or QUICKI (p = 0.8).

CONCLUSION

As measures of SI in prepubertal children, RHOMA is no better than fasting insulin and QUICKI, a poor measure. Neither RHOMA nor QUICKI was able to detect changes in SI induced by either obesity or growth hormone therapy.

Weight, adiposity, and physical activity as determinants of an insulin sensitivity index in pima Indian children

OBJECTIVE

To determine whether measures of physical activity are related to an insulin sensitivity index ([ISI] 10(4)/fasting insulin x glucose) independent of weight or adiposity in children.

RESEARCH DESIGN AND METHODS

We conducted a longitudinal study of 90 Pima Indian children (39 boys and 51 girls) at 5 and 10 years of age measuring adiposity (dual-energy X-ray absorptiometry), physical activity behavior (questionnaire: number of activities per week [ACT], average hours per week [TIME]), and energy expenditure (doubly labeled water: physical activity level [PAL]).

RESULTS

In cross-sectional analyses, ACT was correlated with ISI at 5 years of age (r = 0.24, P = 0.02) and at 10 years of age (r = 0.21, P = 0.05), but these relationships were not independent of weight or adiposity. PAL was correlated with ISI at 10 years of age (r = 0.39, P = 0.03) but was not independent of weight or adiposity. Longitudinally, ISI decreased from 5 to 10 years of age, and increases in weight and adiposity were associated with decreases in ISI (r = -0.51 and -0.41, respectively; both P < 0.0001). ACT decreased from 5 to 10 years of age, but children who had smaller decreases in ACT had smaller decreases in ISI, independent of increases in weight or adiposity (partial r = 0.22, P = 0.04 adjusted for either weight or adiposity).

CONCLUSIONS

These data suggest that early establishment and maintenance of an active lifestyle can have a beneficial effect on ISI that is partially independent of changes in weight or adiposity. This is particularly relevant considering the current epidemics of both obesity and type 2 diabetes in children.