Introduction
Diabetes Mellitus in Migrant South Asians
Aetiology of Diabetes and Cardiovascular Risk in South Asians
Mechanism | Evidence |
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Adiposity | At a given BMI, South Asians have a higher fat mass and a larger proportion of fat in deep abdominal subcutaneous and visceral deposits compared to white Europeans. There is also some evidence for greater liver fat. Such findings are in keeping with greater insulin resistance in South Asians |
Lean body mass | South Asians have less lean tissue than white Europeans for any given BMI. This relative lack of skeletal muscle and capacity for glucose disposal contributes to greater insulin resistance and diabetes risk |
ß-cell function | Compared to white Europeans, South Asians have greater ß-cell function until adulthood but earlier and more rapid decline in insulin production beyond middle age. Such evidence requires verification using robust measures of beta-cell function |
Fitness and skeletal muscle function | South Asians obtain a lower level of cardiorespiratory fitness than white Europeans for the same level of physical activity and have evidence of reduced fat oxidation (indicative of impaired muscle metabolism) during submaximal exercise compared with BMI-matched white Europeans. Once again, studies using more robust measures of muscle function are required to verify these findings |
Lifestyle | South Asians are less physically active than white Europeans. There is no consistent evidence linking South Asian dietary patterns to increased diabetes risk; however, short term overfeeding may have greater adverse effects in South Asians |
Genetic factors | There is some evidence that epigenetic signals may contribute to the increased risk of diabetes in South Asians. These signals appear to relate mostly to impaired beta-cell function. Genetic risk factors for diabetes do not appear to significantly differ between South Asians and white Europeans |
Foetal programming | There is little robust evidence for foetal programming underlying the excess risk of diabetes in South Asians; observational data suggests that increased maternal fasting blood glucose levels mediate the relationship between South Asian ethnicity and greater fat mass in offspring but the long-term implications of this finding is not clear |