Comprehensive assessment of insulin resistance in non‐obese Asian Indian and Chinese men

Abstract

Aims/IntroductionIndian individuals are more insulin resistant (IR) than Chinese individuals, even among those with a non‐obese body mass index (BMI). However, BMI often underestimates body fat in Indian individuals, and it remains unclear whether Indians would remain more IR than Chinese individuals when both BMI and body fat are equally matched.Materials and MethodsUsing the hyperinsulinemic‐euglycemic clamp with stable‐isotope infusion, we comprehensively assessed IR between 13 non‐obese Indian men with 13 Chinese men matched for age, BMI and body fat. We further compared the differences in insulin metabolic clearance rate (MCR) between the two groups and its relationship with various metabolic parameters. The response of lipid and amino acid metabolism to insulin stimulation was also evaluated using metabolomic profiling.ResultsThe rates of endogenous glucose production during fasting were similar, and endogenous glucose production was completely suppressed during insulin clamp for both ethnic groups. Glucose disappearance during insulin clamp was also similar between the two groups, even after accounting for differences in insulin concentration. Metabolomic profiles of amino acids and various acylcarnitines were similar during both fasting and insulin clamp. However, plasma insulin during clamp was significantly higher in Indian men, indicating that insulin MCR was lower. Insulin MCR correlated significantly with total adiposity and skeletal muscle insulin sensitivity.ConclusionWhen equally matched for body fat, non‐obese Indian men had similar skeletal muscle insulin sensitivity and endogenous glucose production to Chinese men. The effects of insulin on lipid and amino acid metabolism were also similar. Low insulin MCR is associated with greater adiposity and lower skeletal muscle insulin sensitivity.

Differences in type 2 diabetes risk between East, South, and Southeast Asians living in Singapore: the multi-ethnic cohort

“…Consistent with our study, other authors also reported higher insulin resistance in ethnic Indians than Chinese or Malays8–13 21 25 and Europeans,9 22 23 26 28 31 even after adjustments for BMI or waist circumference 21–23. In a study conducted in Singapore where body fat and insulin sensitivity were directly measured, Indians were also more insulin resistant than Chinese, independent of adiposity 24.…”

“…In a study conducted in Singapore where body fat and insulin sensitivity were directly measured, Indians were also more insulin resistant than Chinese, independent of adiposity 24. However, this was not observed in two other studies conducted in Canada and Singapore when matched for body fat 9 11. In a study that examined the skeletal muscle transcriptome in Chinese, Malays, and Indians, the expression of SNRK and AMPKα2 genes involved in glucose uptake was lowest in Indians 25.…”

“…To our knowledge, this is the first study that evaluated potential mediators of differences in T2D risk in major Asian ethnic groups using a prospective design. Previous studies have either been cross-sectional6 or focused only on ethnic differences in T2D risk factors rather than the incidence of T2D 7–13 21–25…”

“…Several reasons may explain the differences in susceptibility to T2D between these Asian ethnic groups. Results from previous studies indicate that ethnic Indians are more abdominally obese and insulin resistant than ethnic Chinese individuals 7–11. Differences in adiponectin levels8 12 13 and inflammation12 13 between Asian ethnic groups have also been reported.…”

Clinical Determinants of Diabetes Progression in Multiethnic Asians with Type 2 Diabetes – A 3-Year Prospective Cohort Study

“…It is reasonable to postulate that these traditional risk factors may at least partly contribute to the accelerated diabetes progression in Malays with T2DM. Although several studies have examined ethnic differences in insulin resistance among the 3 ethnic groups in Singapore, 20,21 studies comparing beta cell function across ethnic groups are relatively scarce. One early study showed that healthy and lean Malay males exhibited a lower insulin secretory capacity that was accompanied by a higher glucose excursion in response to mixed-meal tolerance test as compared to their Chinese and Indian counterparts.…”