Sex differences in insulin sensitivity and insulin response with increasing age in black South African men and women. (December 2016)

• Record Type: Journal Article
• Authors: Goedecke, Julia H.; George, Cindy; Veras, Katherine; Peer, Nasheeta; Lombard, Carl; Victor, Hendriena; Steyn, Krisela; Levitt, Naomi S.
• Is Part Of: Diabetes research and clinical practice. Volume 122(2016)
• Page Start: 207
• Page End: 214
• Publication Date: 2016-12
• Subjects: African -- Insulin sensitivity -- Insulin secretion -- Age -- Body fat -- Beta cell function; Diabetes -- Periodicals; Diabetes Mellitus -- Periodicals; 616.462
• DOI: 10.1016/j.diabres.2016.11.005
• Languages: English
• ISSNs: 0168-8227

Abstract

Highlights: African women had lower insulin sensitivity than BMI-matched African men. Insulin sensitivity was more closely associated with BMI in African men than women. β-cell function did not differ in African men and women. Insulin sensitivity did not change with increasing age in African men and women. β-cell function declined similarly with increasing age in African men and women. Abstract: Aims: Black Africans are disproportionally affected by type 2 diabetes, but the pathophysiology is poorly understood. The study aimed to examine the effect of sex and age on insulin sensitivity and insulin response in black South African adults. Methods: This cross-sectional study included a random sample of 179 men and 260 women aged 25–74 years with normal glucose tolerance from 5 peri-urban townships in Cape Town, SA. Insulin sensitivity (insulin sensitivity index, ISI0, 120 ) and response (insulinogenic index, IGI), and the disposition index (DI, ISI0, 120 × IGI), derived from an oral glucose tolerance test, were measured. Results: Although men were older (median [interquartile range]: 39 [30–48] vs. 35 [29–44], P = 0.021) and had significantly lower BMI than women (22.6 [20.0–25.3] vs. 31.0 [25.9–35.7] kg/m 2, P = 0.001), DI was not different ( P = 0.740), but ISI0, 120 was higher ( P = 0.007) and IGI was lower ( P = 0.074) in men than women, adjusting for age and BMI. With increasing age, DI ( β (95%CI): −24.4 (−36.3 to −12.5), P < 0.001) and IGI ( β (95%CI): −4.9 (−7.5 to −2.2), P < 0.001) decreased similarly in both sexes, but ISI0, 120 did not change ( β (95%CI): 0.005 (−0.20 to 0.03), P = 0.675). Conclusion: Black South African women with normal glucose tolerance have lower insulin sensitivity than their male counterparts, but increase their insulin response to maintain normoglycemia. With increasing age, insulin sensitivity remains unchanged, but the insulin response decreases at a similar rate in men and women.