Brown Adipose Tissue Volume in Healthy Lean South Asian Adults Compared With White Caucasians: A Prospective, Case-Controlled Observational Study
Does volume and activity of brown adipose tissue contribute to the difference in incidence of type 2 diabetes between ethnic groups?
Data from a cohort of Dutch nationals with south Asian ancestry were matched to Caucasian participants. Eligible participants were healthy lean men ages 18-28 years. Body mass index (BMI) was matched between the two groups. Brown adipose tissue was measured for volume and activity with cold-induced 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography computed tomography scans, and assessed using resting energy expenditure, nonshivering thermogenesis, and serum parameters.
A total of 12 participants were enrolled in each group. Compared with Caucasian participants, south Asian participants did not differ in age (mean 23.6 years for south Asians vs. 24.6 years for Caucasians) or BMI (21.5 kg/m2 vs. 22.0 kg/m2), but were shorter and lighter. Thermoneutral resting energy expenditure was 1,297 kcal per day in south Asian participants compared with 1,689 kcal per day in white Caucasian participants. On cold exposure, shiver temperature of south Asians was 2.0°C higher than Caucasians, and nonshivering thermogenesis was increased by 20% in white Caucasians, but was not increased in south Asians. Although the maximum and mean standardized uptake values of 18F-FDG in brown adipose tissue did not differ between groups, total brown adipose tissue volume was lower in south Asians (188 ml [standard deviation 81]) than it was in Caucasians (287 ml ; difference –34%, p = 0.04). Overall, brown adipose tissue volume correlated positively with basal resting energy expenditure in all assessable individuals (β = 0.44, p = 0.04).
The investigators concluded that lower resting energy expenditure, nonshivering thermogenesis, and brown adipose tissue volumes in south Asian populations might underlie their high susceptibility to metabolic disturbances, such as obesity and type 2 diabetes. Development of strategies to increase brown adipose tissue volume and activity might help prevent and treat such disorders, particularly in south Asian individuals.
This study provides an interesting hypothesis for the increased risk of diabetes among Asian populations. Given the small sample size, larger studies are warranted.
Keywords: Risk, Tomography, X-Ray Computed, Diabetes Mellitus, Type 2, European Continental Ancestry Group, Adipose Tissue, Brown, Cold Temperature, Positron-Emission Tomography, Asian Continental Ancestry Group, Fluorodeoxyglucose F18, Case-Control Studies, Body Mass Index, Thermogenesis, Cardiovascular Diseases, Obesity, Energy Metabolism, Diabetes Mellitus
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