Insulin resistance may be critical type 2 diabetes driver in Chinese people
medwireNews: Insulin resistance may be a more important determinant of type 2 diabetes risk in Chinese people than impaired beta-cell function, show findings from a large population-based study.
The researchers included 94,952 participants (about a third men) from the nationwide study, selecting those who did not have type 2 diabetes, either previously diagnosed or identified at the baseline oral glucose tolerance test (OGTT). Almost 70% of the participants had prediabetes according to their OGGT result.
During a median 3.1 years of follow-up, 6.8% of this cohort developed diabetes, and Weiqing Wang (Shanghai Jiao Tong University School of Medicine, China) and co-researchers found that insulin resistance predicted diabetes more strongly than did impaired beta-cell function. Each standard deviation increase in insulin resistance was associated with a 2.17-fold increased risk for diabetes, and each standard deviation decrease in beta-cell function was associated with a 1.92-fold increase.
The investigators say this contrasts with previous smaller studies showing impaired beta-cell function to be the primary driver of diabetes risk in East Asian people; however, they caution that their indicators of insulin resistance and beta-cell dysfunction – HOMA-IR and HOMA-B – are only surrogate measures.
The authors of a commentary linked to the research article in The Lancet Diabetes & Endocrinology echo this warning, saying that while HOMA-IR is a reliable marker of insulin resistance, HOMA-B “correlates only modestly with dynamic tests of β-cell function” and “cannot be interpreted in isolation without a measure of glucose sensitivity.”
Elaine Chow and Juliana Chan, both from The Chinese University of Hong Kong, also note that isolated impaired glucose tolerance is particularly common in Chinese people, suggesting a critical role for “defective early phase insulin secretion which cannot be fully reflected by an abnormal HOMA-B, the latter being an indicator of basal insulin secretion.”
They say: “As such, the relative contributions of β-cell abnormalities versus insulin resistance along the spectrum from prediabetes to diabetes require further investigation, notably in non-Caucasian populations, hit hardest by this epidemic.”
From the current study findings, Wang and team calculated that 24.4% of incident diabetes in their Chinese cohort was attributable to insulin resistance, and 12.4% to beta-cell dysfunction, with similar proportions seen for people with normal glucose tolerance or with prediabetes at baseline.
However, they also found that the combined effects of insulin resistance and beta-cell dysfunction on diabetes risk were synergistic, that is, greater than the individual effects of each risk factor added together.
Of note, the researchers found that the stronger effect of insulin resistance compared with beta-cell dysfunction on diabetes risk was “more pronounced” among obese people than among those with normal weight, “indicating that obesity might modify the association between insulin resistance and diabetes in the adult population in China.”
They stress that “in East Asians, it does not take much weight gain to cause insulin resistance and increased risk of diabetes,” noting that the per standard deviation risk increase was higher for those with a BMI of 23–24 versus less than 23 kg/m2 (hazard ratios of 1.83 and 1.90, respectively).
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