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Kelly West Award lecturer highlights underpinnings of South Asian phenotype of type 2 diabetes


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South Asians—people from or with ancestral lineage from one of the eight countries in the Indian subcontinent—account for a quarter of the world’s population. Members of this diverse group are also up to four times more likely to have type 2 diabetes than people of other ethnicities.

Viswanathan Mohan, MD, PhD, DSc, FRCP, FNA, FACE, MACP, FRSE

The recipient of the 2024 Kelly West Award for Outstanding Achievement in Epidemiology, V. Mohan, MD, PhD, DSc, FRCP, FNA, FACE, MACP, FRSE, Director of the Madras Diabetes Research Foundation in Chennai, India, shared remarkable findings on the epidemiology and endotype of type 2 diabetes in South Asians residing in the Indian subcontinent and in Western countries in “Lessons Learnt from Epidemiology of Diabetes in South Asians—The Kelly West Lecture 2024,” held on Sunday, June 23.

The Kelly West Award for Outstanding Achievement in Epidemiology Lecture can be viewed on-demand by registered meeting participants on the virtual meeting platform. If you haven’t registered for the 84th Scientific Sessions, register today to access the valuable meeting content through Aug. 26.

Dr. Mohan highlighted the dramatic increase in type 2 diabetes prevalence among Asian Indians, concomitant with the socioeconomic growth fostered by the liberalization and globalization of India in the 1980s. While type 2 diabetes was a “migrant Indian condition” in earlier decades—with higher prevalence in Indians who had migrated to more affluent world regions than those in India—this no longer holds true.

An estimated 101 million people in India have diabetes, with 136 million more projected to have prediabetes, according to the Indian Council of Medical Research–India Diabetes (ICMR-INDIAB) cross-sectional population-based study conducted by Dr. Mohan and colleagues. Dr. Mohan described this study, with a sample size over 113,000, as perhaps the most ambitious epidemiological study ever done, given the sheer size and complexity of the population.

In addition to the increasing prevalence of type 2 diabetes, Dr. Mohan said, “We are finding some startling things.”

Type 2 diabetes in South Asians occurs at least 10 years earlier than in white Europeans. Moreover, it occurs at much lower BMI levels, with a sharp increase in prevalence at BMIs as low as 18­–20.

These epidemiological differences, along with differences in disease-specific features such as hyperinsulinemia, rapid development of insulin deficiency, low high-density cholesterol levels, and low vitamin B12 levels characterize what Dr. Mohan referred to as the “South Asian Phenotype” of type 2 diabetes.

Dr. Mohan expounded further on the earlier age of onset of type diabetes in South Asians, sharing striking data indicating that the South Asian phenotype is present at birth and continues through childhood and adolescence.

“South Asians/Indians exhibit greater insulin resistance at earlier stages in the natural history of type 2 diabetes compared to white Europeans, driven mainly by ectopic liver fat,” he noted.

Dr. Mohan reviewed a study of metabolic differences between Pima and Asian Indians to illustrate how two ethnic populations with high prevalence of type 2 diabetes nevertheless have distinct pathophysiologic drivers—insulin resistance in Pima Indians and insulin deficiency in Asian Indians.

Dr. Mohan and colleagues subclassified the South Asian type 2 diabetes phenotype into four subgroups. In addition to subgroups described in studies of other ethnic populations, such as severe insulin-deficient and insulin-resistant obese diabetes, Dr. Mohan said, “There is this unique combined insulin-resistant and -deficient diabetes in South Asians, which incidentally is more prone to retinopathy and nephropathy.”

In recent and ongoing research, Dr. Mohan and colleagues have sought to delineate the genetic and environmental factors that underpin the South Asian type 2 diabetes phenotype. One of their key findings is that higher consumption of white rice is associated with new onset diabetes in South Asians. They are also identifying new and unexpected risk factors associated with type 2 diabetes, such as exposure to air pollution.

Given the multifactorial causes—ethnic/genetic/intrauterine parameters, lifestyle factors, and other risk factors such as air pollution—that contribute to the South Asian phenotype, Dr. Mohan said that the solutions need to be multi-pronged.

“I think [the increasing prevalence of type 2 diabetes in South Asians] is not going to end unless we take this up on a war footing,” he said.

The Kelly West Award is given in memory of Kelly M. West, widely regarded as the “father of diabetes epidemiology.”

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