Specific insulin and proinsulin concentrations in nondiabetic South Indians

Increased β-Cell Workload Modulates Proinsulin-to-Insulin Ratio in Humans

Increased proinsulin secretion, which characterizes type 2 diabetes and insulin resistance, may be due to an intrinsic, primitive defect in proinsulin processing or be secondary to increased demand on β-cells (hyperinsulinemia secondary to insulin resistance). An alternative way to investigate the relation between relative hyperproinsulinemia and increased secretory demand is to study the dynamic changes in the proinsulin-to-insulin ratio after partial pancreatectomy, a model of acute increased β-cell workload on the remaining pancreas. To pursue this aim, patients without diabetes, scheduled for partial pancreatectomy, underwent 4-h mixed-meal tests and hyperinsulinemic-euglycemic clamps before and after surgery. After acute β-cell mass reduction, no changes were observed in the fasting proinsulin-to-insulin ratio, whereas the fold change in the proinsulin-to-insulin ratio significantly increased over time after the meal. Further, our data demonstrate that whole-body insulin resistance is associated with underlying defects in proinsulin secretion, which become detectable only in the presence of increased insulin secretion demand.

Increased carotid intimal media thickness precedes albuminuria in South Indian type 2 diabetic subjects

Introduction Intimal media thickness (IMT) of common carotid artery (CCA) is used as an index of atherosclerosis. IMT is increased in subjects with diabetes and also with diabetic nephropathy.

Aim The study was undertaken in South Indian type 2 diabetic patients with different degrees of albuminuria to see whether albuminuria worsened IMT.

Material and methods IMT was measured by ultrasonography in 273 diabetic subjects with normoalbuminuria (n=91), microalbuminuria (n=92), clinical proteinuria (Prot) (n=90) and in age-matched non-diabetic subjects (n=99). The diabetic subjects were older than the non-diabetic subjects hence IMT was age-adjusted using a linear regression formula.

Results Age-adjusted IMT value in diabetic subjects was significantly higher (0.88±0.3 mm) than in non-diabetic subjects (0.57±0.34 mm) (p<0.001). Mean IMT in normoalbuminuria (0.87±0.26 mm), microalbuminuria (0.90± 0.33 mm) and Prot (0.86±0.39 mm) patients were not significantly different from each other. Male gender, age, diabetes and total cholesterol were independently associated with IMT, while duration of diabetes, hypertension and HbA1C were not.

Conclusion Increased carotid IMT occurred in type 2 diabetes prior to the presence of albuminuria. Further deterioration in IMT did not occur with the presence of albuminuria.

Plasma adiponectin does not correlate with insulin resistance and cardiometabolic variables in nondiabetic Asian Indian teenagers

OBJECTIVE

The objectives of this study were to determine age- and sex-specific concentrations of adiponectin in Asian Indian teenagers and adults and to assess whether its blood levels correlated with insulin resistance and other cardiometabolic parameters.

RESEARCH DESIGN AND METHODS

We studied 196 teenagers (94 boys, 102 girls) 12-18 years of age, selected from a cohort of 2,640 individuals from a cross-sectional school-based survey in Chennai, India. For comparison, adiponectin and plasma insulin were measured in 84 healthy adults. Correlation of adiponectin with plasma levels of insulin, proinsulin, insulin resistance, anthropometry, and family history of diabetes were studied.

RESULTS

Adiponectin showed a sex dimorphism, with girls having higher values (in microg/ml) (10.3 +/- 5.0) than boys (8.4 +/- 3.5) (P < 0.0001), and it showed a positive correlation with HDL cholesterol in boys only and not with other lipid parameters, insulin resistance, proinsulin, anthropometry, and family history of diabetes. In the adults, adiponectin correlated with fasting glucose and inversely with triglycerides.

CONCLUSIONS

In Asian Indian adults and teenagers, adiponectin did not correlate directly with measures of insulin sensitivity, overweight, and other cardiometabolic variables. This was at variance with several reports in other populations showing an inverse association of adiponectin with insulin resistance, proinsulin, and BMI, suggesting ethnic differences in the relationship of adiponectin with insulin sensitivity. The role of adiponectin in relation to action of insulin needs more detailed studies in Asian Indians.

A cellular assay for measuring the modulation of glucose production in H4IIE cells

Type II diabetes and its associated complications are a major health concern of the developed world. One of the hallmarks of diabetes is insulin resistance, where secreted insulin no longer has any effect on its target tissues, namely, liver, muscle, and fat. An important therapeutic strategy is to modulate blood glucose levels using pharmacological agents. Glycogen synthase kinase-3 (GSK3) is a serine-threonine protein kinase that plays important roles in regulating glucose metabolism. It is a key negative regulator of insulin action and is an important contributing factor to insulin resistance in liver, muscle, and adipose tissue. We describe the development of a cell-based assay designed to measure glucose production in rat hepatoma cell line H4IIE liver cells in response to treatment with small molecule inhibitors, including GSK3 inhibitors. The assay is set up in a 96-well format, and glucose production is assessed using a convenient fluorescence-based readout. This disease-relevant cellular assay is a valuable tool for the progression of small molecules that modulate glucose production.

Diabetes and cardiovascular disease among Asian Indians in the United States

CONTEXT

Studies, mostly from outside the United States, have found high prevalence of diabetes, coronary heart disease (CHD), and hypertension among Asian Indians, despite low rates of associated risk factors.

OBJECTIVE

To analyze the prevalence of obesity, diabetes, CHD, hypertension, and other associated risk factors among Asian Indians in the United States compared to non-Hispanic whites.

DESIGN, SETTING, AND SUBJECTS

Cross-sectional study using data from the National Health Interview Survey (NHIS) for 1997, 1998, 1999, and 2000. We analyzed 87,846 non-Hispanic whites and 555 Asian Indians.

MAIN OUTCOME MEASURES

Whether a subject reported having diabetes, CHD, or hypertension.

RESULTS

Asian Indians had lower average body mass indices (BMIs) than non-Hispanic whites and lower rates of tobacco use, but were less physically active. In multivariate analysis controlling for age and BMI, Asian Indians had significantly higher odds of borderline or overt diabetes (adjusted OR [AOR], 2.70; 95% confidence interval [CI], 1.72 to 4.23). Multivariate analysis also showed that Asian Indians had nonsignificantly lower odds ratios for CHD (AOR, 0.58; 95% CI, 0.25 to 1.35) and significantly lower odds of reporting hypertension (AOR, 0.58; 95% CI, 0.42 to 0.82) compared to non-Hispanic whites.

CONCLUSION

Asian Indians in the United States have higher odds of being diabetic despite lower rates of obesity. Unlike studies on Asian Indians in India and the United Kingdom, we found no evidence of an elevated risk of CHD or hypertension. We need more reliable national data on Asian Indians to understand their particular health behaviors and cardiovascular risks. Research and preventive efforts should focus on reducing diabetes among Asian Indians.

Markers of endothelial dysfunction in hyperglycaemic Asian Indian subjects

OBJECTIVE

The aims of this study were the following: (1). to determine the levels of endothelin-1(ET1), soluble adhesion molecules like intracellular adhesion molecule-1 (sICAM-1), and vascular cell adhesion molecule-1 (sVCAM-1) in different stages of glucose intolerance and to identify a suitable marker of endothelial dysfunction and (2). to determine the possible association of these biochemical parameters with diabetic complications and with impaired glucose tolerance (IGT).

RESEARCH DESIGN AND METHODS

In this cross-sectional study, plasma ET1, sICAM-1, and sVCAM-1 were measured by enzyme-linked immunosorbent assay (ELISA) in 20 nondiabetic subjects, in 15 subjects with IGT, in 21 Type 2 diabetic subjects without any complication, and in 21 Type 2 diabetic patients with nephropathy and retinopathy.

RESULTS

Median ET1 levels were significantly elevated (P=.004) in IGT subjects (0.31 fmol/ml) when compared with the nondiabetic subjects (0.11 fmol/ml). Subjects with nephropathy (0.50 fmol/ml) had significantly higher (P=.002) ET1 values when compared with those without complications (0.40 fmol/ml). The levels of sICAM-1 and sVCAM-1 did not show any significant difference among the groups. ET1 showed correlation with age, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting plasma glucose (FPG), 2 h post glucose (2hPG), waist-to-hip ratio (WHR), total white blood corpuscles count, glycosylated haemoglobin (HbA1c), triglycerides (TG), very-low-density lipoprotein cholesterol (VLDLc), and hypertension (HTN). In the multiple linear regression analysis, plasma ET1 was significantly associated with the presence of Type 2 diabetes either with or without complications (P<.0001 and P=.0098, respectively), WHR (P=.0063), and sVCAM-1 (P=.0051). The total variance explained by the above-mentioned parameters was 55%.

CONCLUSION

Elevated levels of ET1 were present in subjects with IGT and in Type 2 diabetic subjects. Such associations with sICAM-1 or sVCAM-1 in these subjects were not seen. ET1 could be an early marker of endothelial dysfunction, which appeared to occur even in the subclinical stages of hyperglycaemia.

Insulin secretion and action show differences in impaired fasting glucose and in impaired glucose tolerance in Asian Indians

BACKGROUND

The aim of the study was to compare the abnormalities in insulin secretion and insulin sensitivity in impaired fasting glucose (IFG) and in impaired glucose tolerance (IGT).

METHODS

Glucose tolerance was determined by oral glucose tolerance test in 289 non-diabetic subjects selected for this study (M : F, 160 : 129, mean age 42.2 +/- 11.0 (SD) years, mean body mass index (BMI) 24.9 +/- 4.2 kg/m(2)). Diabetic subjects were excluded from the study. The association of insulin resistance and beta-cell function (calculated by HOMA model) with IFG and IGT was studied using linear and multiple logistic regression analyses. Subjects with normoglycaemia (NGT) were used as controls.

RESULTS

Insulin resistance was significantly more in IFG and in IGT than in NGT. beta-cell dysfunction was significantly higher in IFG than in IGT. IFG was associated with both insulin resistance (OR = 9.11, p < 0.001) and beta-cell dysfunction (inverse correlation, OR = 0.103, p < 0.001), while only insulin resistance was significantly associated with IGT (OR = 1.24, p = 0.005).

CONCLUSIONS

In urban South Asian Indians, IFG differed from IGT in having combined insulin resistance and beta-cell dysfunction, while IGT was associated only with insulin resistance.

Diminution of early insulin response to glucose in subjects with normal but minimally elevated fasting plasma glucose. Evidence for early beta-cell dysfunction

AIM

Systematic analysis of beta-cell function in Japanese health examinees.

METHODS

In 938 Japanese health examinees (627 men and 311 women, mean age and body mass index, 54.0 years and 23.6 kg/m2, respectively), plasma specific insulin was measured at fasting and during a 75-g oral glucose tolerance test. The subjects were stratified into six groups based on fasting plasma glucose < or = 5.1 mmol/l, 5.2-6.0 mmol/l, 6.1-6.9 mmol/l, 7.0-7.8 mmol/l, 7.9-8.7 mmol/l, and > or = 8.8 mmol/l as the 1st, 2nd, 3rd, 4th, 5th and 6th groups, respectively.

RESULTS

Distribution of fasting insulin showed a very modest 'inverted U' shape, with the peak in the 5th group. Progressive increase from the 1st toward the 5th group was significant. In contrast, the ratio of change in insulin to change in glucose from 0 to 30 min during the glucose tolerance test was greatest in the 1st group and progressively declined in the groups with higher fasting glycaemia. Difference in the ratio was most striking and highly significant between the 1st and 2nd groups. Distribution of the insulin to glucose ratio of subjects with normal glucose tolerance significantly overlapped with that of untreated patients with diabetes.

CONCLUSIONS

In a Japanese population, (i) beta-cell starts to deteriorate during normoglycaemia with a minimal elevation of fasting plasma glucose, and (ii) there are glucose-tolerant subjects with beta-cell dysfunction.

Association of proinsulin and insulin resistance with coronary artery disease in non-diabetic south Indian men

AIMS

To evaluate the association of plasma proinsulin and insulin resistance (IR) with coronary artery disease (CAD) in non-diabetic subjects.

METHODS

In this case control study, 41 normoglycaemic men with angiographic evidence of CAD were compared with 41 control men matched for age and glycaemia and with no history or evidence of cardiac diseases. Estimations of plasma glucose, lipids, fasting plasma specific insulin (SI) and proinsulin (PI) were performed. IR was calculated by the homeostasis model assessment (HOMA) method. Multiple logistic regression analysis was performed to test the association of the variables with the prevalence of CAD.

RESULTS

Subjects with CAD had a higher body mass index (BMI) (25.4 +/- 4.3 vs. 22.9 +/- 3.2 kg/m2, P = 0.003) and waist to hip ratio (WHR) (0.95 +/- 0.05 vs. 0.89 +/- 0.09, P = 0.001) and a lower high-density lipoprotein (HDL) cholesterol level (0.97 +/- 0.2 vs. 1.1 +/- 0.2 mmol/l, P = 0.002). They also had higher mean SI values (107.5 vs. 62.3 pmol/l, P = 0.002), PI values (19.3 vs. 5.7 pmol/l, P < 0.0001), PI/SI ratios (21.4 vs. 10.3, P < 0.0001) and HOMA IR (4.2 vs. 2.4, P = 0.004) compared with non-CAD subjects. These variables were associated with CAD in the unadjusted multiple regression analysis. In the multiple regression with the forward entry of the variables, WHR and PI only showed independent association with CAD.

CONCLUSIONS

Subjects with CAD had higher levels of obesity and WHR. CAD showed an association with low HDL cholesterol, circulating PI, PI/SI ratios and IR.

Diagnosing insulin resistance in the general population

OBJECTIVE

Difficulties in measuring insulin sensitivity prevent the identification of insulin-resistant individuals in the general population. Therefore, we compared fasting insulin, homeostasis model assessment (HOMA), insulin-to-glucose ratio, Bennett index, and a score based on weighted combinations of fasting insulin, BMI, and fasting triglycerides with the euglycemic insulin clamp to determine the most appropriate method for assessing insulin resistance in the general population.

RESEARCH DESIGN AND METHODS

Family history of diabetes, BMI, blood pressure, waist and hip circumference, fasting lipids, glucose, insulin, liver enzymes, and insulin sensitivity index (ISI) using the euglycemic insulin clamp were obtained for 178 normoglycemic individuals aged 25-68 years. Product-moment correlations were used to examine the association between ISI and various surrogate measurements of insulin sensitivity. Regression models were used to devise weights for each variable and to identify cutoff points for individual components of the score. A bootstrap procedure was used to identify the most useful predictors of ISI.

RESULTS

Correlation coefficients between ISI and fasting insulin, HOMA, insulin-to-glucose ratio, and the Bennett index were similar in magnitude. The variables that best predicted insulin sensitivity were fasting insulin and fasting triglycerides. The use of a score based on Mffm/I = exp[2.63 - 0.28ln(insulin) - 0.31ln(TAG)] rather than the use of fasting insulin alone resulted in a higher sensitivity and a maintained specificity when predicting insulin sensitivity.

CONCLUSIONS

A weighted combination of two routine laboratory measurements, i.e., fasting insulin and triglycerides, provides a simple means of screening for insulin resistance in the general population.

Insulin resistance alone does not explain the clustering of cardiovascular risk factors in southern India

AIMS

To determine whether insulin resistance (IR calculated using the HOMA model) has a dominant role in the clustering of cardiovascular risk factors in the Asian Indian population.

METHODS

A total of 654 non-diabetic subjects aged > or =40 years (male 396: female 258) were selected from a population survey. They had estimates of fasting and 2 h plasma glucose, insulin levels, body mass index (BMI), waist-to-hip ratio (WHR) and blood pressure. Factor analysis was carried out using the principle components analysis (PCA) with varimax orthogonal rotation of continuously distributed variables, considered to represent the components of insulin resistance syndrome including the calculated IR.

RESULTS

There were three major clusters of cardiovascular disease (CVD) risk variables in men and four clusters in women. Insulin resistance, 2 h plasma glucose, insulin and obesity aggregated as the major domain. Insulin resistance was not linked with hypertension. BMI was a common link for all the three factors in men, and for three of the four in women.

CONCLUSIONS

Insulin resistance is not the only underlying factor for the clustering of CVD risk factors in south Indians. These findings are consistent with the presence of several distinct physiological domains, as shown in other ethnic groups.

Insulin secretion and action in different stages of glucose tolerance in Asian Indians

AIMS

To evaluate the sequence of changes in insulin secretion and action in different stages of glucose tolerance and the effect of obesity on insulin profile in South Indian adults. Blood samples from 260 consecutive cases with no known history of diabetes were collected. Plasma insulin levels were measured during a 75-g oral glucose tolerance test. Insulin resistance (IR) was calculated, using the homeostasis model assessment (HOMA). An index of insulin secretion was derived as the ratio of incremental insulin at 30 min divided by 30 minute plasma glucose (delta I/G).

RESULTS

Normoglycaemia was present in 164, impaired glucose tolerance (IGT) in 60 and diabetes in 36 subjects. Fasting and 2 h insulin secretion showed bell shaped curves with increasing plasma glucose. The peak values corresponded to the cut-off values used for the diagnosis of clinical diabetes. IR was higher in obese than in nonobese, nondiabetic subjects but the effect of obesity on IR was not found in subjects with diabetes. IGT was associated with higher IR, but not with evidence of a beta-cell defect.

CONCLUSIONS

Evaluation of insulin resistance and beta-cell function in different stages of glucose tolerance indicate that insulin resistance is manifested in the early stage of glucose intolerance in South Indians, i.e. IGT. A beta-cell defect was mostly found in people with diabetes. The beta-cell defect is more common in diabetes among the nonobese.