A significant decline in IGF-I may predispose young Africans to subsequent cardiometabolic vulnerability

J Clin Endocrinol Metab. 2010 May;95(5):2503-7. doi: 10.1210/jc.2009-2329. Epub 2010 Mar 9.

Abstract

Objectives: Low serum IGF-I is an independent risk factor for diabetes and cardiovascular disease. These noncommunicable diseases are extremely common in urban black South Africans, but their IGF-I concentration is unknown. We aimed to compare serum IGF-I concentrations of African and Caucasian people, investigate their age-related IGF-I decline, and determine whether IGF-I could account, at least in part, for the high prevalence of noncommunicable diseases in black Africans.

Research design and methods: This cross-sectional study involved 211 African and 316 Caucasian men and women (aged 20-70 yr). Fasting glucose, insulin, lipids, albumin, creatinine, liver enzymes, cotinine, high-sensitivity C-reactive protein, reactive oxygen species, IGF-I, blood pressure (BP), and pulse wave velocity were determined.

Results: IGF-I was lower in Africans (P < 0.001) and in both ethnicities declined significantly by age quartiles (P < 0.001). In African men and women, IGF-I declined significantly from age quartile 1 to 2 (r = -0.65, P < 0.001), not seen in young Caucasian men and women (r = -0.08, P = 0.45; r = -0.10, P = 0.34). This was confirmed after adjustment for BP, insulin resistance, high-sensitivity C-reactive protein, cotinine, gamma-glutamyl transferase, and reactive oxygen species. Only young Africans showed significant negative correlations of IGF-I with BP, pulse wave velocity, and high-density lipoprotein cholesterol.

Conclusions: Africans presented lower IGF-I levels than Caucasians due to an accelerated decline in serum IGF-I concentration prior to 40 yr of age. Strong associations of low serum IGF-I with blood pressure and arterial stiffness in young Africans suggest that the loss of cardiometabolic protection by IGF-I could predispose them to earlier disease onset.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • African Continental Ancestry Group / genetics*
  • Aged
  • Blood Glucose / analysis
  • Blood Pressure
  • C-Reactive Protein / metabolism
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / epidemiology*
  • Cholesterol, HDL / blood
  • Creatinine / metabolism
  • Cross-Sectional Studies
  • Diabetes Mellitus / blood
  • Diabetes Mellitus / epidemiology
  • European Continental Ancestry Group / genetics
  • Female
  • Humans
  • Insulin-Like Growth Factor I / deficiency*
  • Liver / enzymology
  • Male
  • Middle Aged
  • Risk Factors
  • South Africa / epidemiology
  • Triglycerides / blood
  • Young Adult

Substances

  • Blood Glucose
  • Cholesterol, HDL
  • Triglycerides
  • Insulin-Like Growth Factor I
  • C-Reactive Protein
  • Creatinine