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


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.
Schutte
Aletta E
AE
Hypertension in Africa Research Team, School for Physiology, Nutrition, and Consumer Sciences, North-West University (Potchefstroom Campus), Private Bag X6001, Potchefstroom 2520, South Africa.
Huisman
Hugo W
HW
van Rooyen
Johannes M
JM
Malan
Leoné
L
Malan
Nico T
NT
Fourie
Carla M T
CM
Louw
Roan
R
van der Westhuizen
Francois H
FH
Schutte
Rudolph
R
D000328:Adult; D000368:Aged; D044383:Black People / Q000235:genetics*; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure; D002097:C-Reactive Protein / Q000378:metabolism; D002318:Cardiovascular Diseases / Q000097:blood / Q000453:epidemiology*; D008076:Cholesterol, HDL / Q000097:blood; D003404:Creatinine / Q000378:metabolism; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000453:epidemiology; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000172:deficiency*; D008099:Liver / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D014280:Triglycerides / Q000097:blood; D044465:White People / Q000235:genetics; D055815:Young Adult
D001786:Blood Glucose; D008076:Cholesterol, HDL; D014280:Triglycerides; D007334:Insulin-Like Growth Factor I; D002097:C-Reactive Protein; D003404:Creatinine