Lipid accumulation product (LAP) as a potential index to predict risk of insulin resistance in young, non-obese Asian Indian males from Southern India: observations from hyperinsulinemic-euglycemic clamp studies.

INTRODUCTION: We aimed to compare the predictive accuracy of surrogate indices namely the lipid accumulation product (LAP) index, homeostatic model of assessment of insulin resistance (HOMA-IR), fasting glucose-insulin ratio (FG-IR) and the quantitative-insulin sensitivity check index (QUICKI), against the M value of hyperinsulinemic-euglycemic clamp (HEC), and to determine a cut-off value for the LAP index to predict risk of insulin resistance in non-obese (body mass index <21 kg/m2), normoglycemic, Asian Indian males from Southern India. RESEARCH DESIGN AND METHODS: Data of HEC studies performed in 108 non-obese, normoglycemic, Asian Indian males was obtained retrospectively and the M value (a measure of whole-body insulin sensitivity) was calculated. The M value is the rate of whole-body glucose metabolism at the hyperinsulinemic plateau (a measure of insulin sensitivity) and is calculated between 60 and 120 min after the start of the insulin infusion in the HEC procedure. The LAP index, the HOMA-IR, FG-IR and QUICKI were calculated. Spearman's correlation and logistic regression analysis were performed. Cut-off value for the LAP index was obtained using receiver operating characteristics with area under curve (AUC) analysis at 95% CI. P value <0.05 was considered to be statistically significant. RESULTS: Significant negative correlation was observed for the M value with LAP index (r=-0.39, p<0.001) while significant positive correlation was noted with FG-IR (r=0.25; p<0.01) and QUICKI (r=0.22; p<0.01). The LAP index cut-off value ≥33.4 showed 75% sensitivity and 75% specificity with AUC (0.72) to predict risk of insulin resistance in this cohort. CONCLUSION: The LAP index showed higher predictive accuracy for the risk of insulin resistance as compared with HOMA-IR, QUICKI and FG-IR in non-obese, normoglycemic Asian Indian males from Southern India.

The triglyceride/glucose ratio is a reliable index of fasting insulin resistance: Observations from hyperinsulinaemic-euglycaemic clamp studies in young, normoglycaemic males from southern India.

BACKGROUND & AIMS: Non-obese Asians have a high propensity to develop insulin resistance. Therefore, screening such individuals for insulin resistance using simple surrogate indices is important. In this study, we aimed to validate the triglyceride-glucose (Tg/glu) ratio against the M value of hyperinsulinaemic-euglycaemic clamp (HEC) procedure and other surrogate indices of insulin resistance in normoglycaemic Indian males from Southern India. METHODS: A cohort of 105 normoglycaemic males (mean BMI: 19.2 ± 2.6 kg/m2) underwent HEC procedure. Surrogate indices of insulin resistance viz. the triglyceride-glucose (Tg/Glu) ratio, the triglyceride-glucose index, the McAuley's index, the HOMA-IR, the QUICKI, the fasting glucose to insulin ratio (FG-IR), and the fasting C- peptide index were calculated and correlated with the M value. The cut-off value for the Tg/Glu ratio was obtained using the Receiver Operator Characteristics (ROC) with Area under curve (AUC) analysis at 95% confidence interval (CI). The P value < 0.05 was considered statistically significant. RESULTS: The Tg/Glu ratio demonstrated significantly higher AUC (0.81), when compared to the Tg × glu index (0.63), 20/fasting C peptide × fasting plasma glucose index (0.55), HOMA-IR (0.47), QUICKI (0.26), FGIR (0.12) and McAuley's index (0.18). For the Tg/Glu ratio, a cut-off value ≥ 1.19 had high sensitivity (80%) and specificity (79%) values (PPV: 16%; NPV: 98.8%) respectively. CONCLUSION: The Tg/Glu ratio can be used as a reliable surrogate index to screen for risk of insulin resistance in lean, normoglycaemic males from Southern India.

Bioimpedance analysis with a novel predictive equation - A reliable technique to estimate fat free mass in birth weight based cohorts of Asian Indian males.

AIM: To validate bioimpedance based predictive equations for fat free mass (FFM) against DEXA and to derive a novel birth weight based predictive equation for FFM in a birth weight based cohort of healthy Asian Indian men. METHODOLOGY: Whole body composition was done using DEXA and bioimpedance in 117 young Asian Indian men, born of normal birth weight (n = 59, birth weight ≥2.5 kg) or low birth weight (n = 58, birth weight < 2.5 kg). Predictive accuracy of 11 different bioimpedance based equations for FFM was evaluated using Pearson's correlation analysis and the root of mean squared prediction error (RMSE) analysis. RESULTS: The mean FFM (on DEXA) and total lean mass & impedance index (on bioimpedance) were significantly higher in the low birth weight cohort. Significantly higher body fat percentage was noted on bioimpedance, for the normal birth weight cohort, but not on DEXA. In addition, the mean values of predicted FFM were significantly higher in the low birth weight cohort for 9 different predictive equations. Specifically, the mean FFM values obtained using the predictive equations of Schaefer et al., Hoot cooper et al. and Hughes et al. were in close agreement with the actual FFM values on DEXA. A novel predictive equation (CMC equation) for FFM based on birth weight was derived. FFM = 32.637 + (-0.222*age) + (-32.51*waist-to-hip ratio) + (0.33*body mass index) + (1.58 * 1 or 2 (1 = normal birth weight, 2 = low birth weight) + (0.510*waist circumference). CONCLUSIONS: Our study findings substantiate the validity of Bio-impedance analysis (BIA) as a reliable and noninvasive tool for estimating body composition measures in birth-weight based cohorts of Asian Indian males. Further, we have devised a novel BIA-based predictive equation that can be useful in larger epidemiological studies to look at alterations in body fat in this cohort.

Differential performance of surrogate indices of fasting insulin resistance in low-birthweight and normal-birth weight cohorts: Observations from Hyperinsulinaemic-Euglycaemic clamp studies in young, Asian Indian males.

AIM: To evaluate the predictive accuracy of surrogate measures of fasting insulin resistance/sensitivity like the Homeostasis model assessment for insulin resistance (HOMA -IR), Fasting glucose/insulin ratio (FG-IR), Quantitative insulin sensitivity check index (QUICKI), and the 20/fasting C peptide x fasting plasma glucose [20/(FCP × FPG)] index in comparison to M value derived from hyperinsulinaemic-euglycaemic clamp (HEC) studies in two birth weight based cohorts of Asian Indian males. METHODS: HEC studies were performed in non-diabetic Asian Indian males (n = 117), born of normal birth weight (n = 59, birth weight > 2.5 kgs) and low birth weight (n = 58, birth weight < 2.5 kgs). Anthropometry and biochemical analysis were done. Surrogate indices of fasting insulin resistance were calculated and data were analysed by Pearson's correlation and Random calibration model analysis. RESULTS: Amongst surrogate indices of fasting insulin resistance/sensitivity, the mean values for HOMA-IR, QUICKI, FG-IR, 20/(FCP × FPG) index and M value were similar between the two groups. Significant positive correlation was observed for FG-IR and QUICKI with M value (the gold standard measure of insulin sensitivity derived from HEC procedure) in the low birth weight cohort in contrast to the normal birth weight cohort, wherein no significant correlation was observed for any of the indices. Random calibration model analysis showed highest predictive accuracy for QUICKI in both the study groups. CONCLUSION: The QUICKI index showed highest predictive accuracy in the normal birth weight and the low birth weight cohorts of Asian Indian males.