title: Sex differences in insulin sensitivity and insulin response with increasing age in black South African men and women.
abstract: OBJECTIVE
  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 25-74years 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/m2, P=0.001), DI was not different (P=0.740), but ISI0,120was 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 ISI0,120did not change (β (95%CI): 0.005 (-0.20 to 0.03), P=0.675).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Non-Communicable Disease Research Unit, South African Medical Research Council, Francie van Zijl Drive, Parow Valley, 7505 Cape Town, South Africa; Division of Exercise Science and Sports Medicine, Department of Human Biology, 3rd Floor Sports Science Institute of South Africa, Boundary Road, Newlands 7700, South Africa. Electronic address: julia.goedecke@mrc.ac.za.
authors.forename: Julia H
authors.initials: JH
authors.lastname: Goedecke
authors.affiliation: Non-Communicable Disease Research Unit, South African Medical Research Council, Francie van Zijl Drive, Parow Valley, 7505 Cape Town, South Africa.
authors.forename: Cindy
authors.initials: C
authors.lastname: George
authors.affiliation: Division of Exercise Science and Sports Medicine, Department of Human Biology, 3rd Floor Sports Science Institute of South Africa, Boundary Road, Newlands 7700, South Africa; Department of Physiology and Biophysics, University of São Paulo, São Paulo, Brazil.
authors.forename: Katherine
authors.initials: K
authors.lastname: Veras
authors.affiliation: Non-Communicable Disease Research Unit, South African Medical Research Council, Francie van Zijl Drive, Parow Valley, 7505 Cape Town, South Africa; Division of Diabetes and Endocrinology, Department of Medicine, University of Cape Town, South Africa.
authors.forename: Nasheeta
authors.initials: N
authors.lastname: Peer
authors.affiliation: Biostatistics Unit, South African Medical Research Council, Francie van Zijl Drive, Parow Valley, 7505 Cape Town, South Africa.
authors.forename: Carl
authors.initials: C
authors.lastname: Lombard
authors.affiliation: Division of Exercise Science and Sports Medicine, Department of Human Biology, 3rd Floor Sports Science Institute of South Africa, Boundary Road, Newlands 7700, South Africa.
authors.forename: Hendriena
authors.initials: H
authors.lastname: Victor
authors.affiliation: Division of Diabetes and Endocrinology, Department of Medicine, University of Cape Town, South Africa.
authors.forename: Krisela
authors.initials: K
authors.lastname: Steyn
authors.affiliation: Division of Diabetes and Endocrinology, Department of Medicine, University of Cape Town, South Africa.
authors.forename: Naomi S
authors.initials: NS
authors.lastname: Levitt
mesh_terms: D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy / Q000453:epidemiology*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D015994:Incidence; D007328:Insulin / Q000627:therapeutic use*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D017678:Sex Distribution; D013019:South Africa / Q000453:epidemiology
chemical_list: D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin
keywords: African; Age; Beta cell function; Body fat; Insulin secretion; Insulin sensitivity