C. Punyadeera et al., Weight-related differences in glucose metabolism and free fatty acid production in two South African population groups, INT J OBES, 25(8), 2001, pp. 1196-1205
OBJECTIVE: The effects of free fatty acids (FFA), leptin, tumour necrosis f
actor (TNF) alpha and body fat distribution on in vivo oxidation of a gluco
se load were studied in two South African ethnic groups.
DESIGN AND MEASUREMENTS: Anthropometric and various metabolic indices were
measured at fasting and during a 7h oral glucose tolerance test (OGTT). Bod
y composition was measured using bioelectrical impedance analysis and subcu
taneous and visceral fat mass was assessed using a five- and two-level CT-s
can respectively. Glucose oxidation was evaluated by measuring the ratio of
(CO2)-C-13 to (CO2)-C-12 in breath following ingestion of 1-C-13-labelled
glucose.
SUBJECTS: Ten lean black women (LBW), ten obese black women (OBW), nine lea
n white women (LWW) and nine obese white women (OWW) were investigated afte
r an overnight fast.
RESULTS: Visceral fat levels were significantly higher (P < 0.01) in obese
white than black women, despite similar body mass indexes (BMIs). There wer
e no ethnic differences in glucose oxidation however; in the lean subjects
of both ethnic groups the area under the curve (AUC) was higher than in obe
se subjects (P < 0.05 for both) and was found to correlate negatively with
weight (r = -0.69, P < 0.01) after correcting for age. Basal TNF alpha conc
entrations were similar in all groups. Percentage suppression of FFAs at 30
min of the OCTT was 24 +/- 12% in OWW and - 38 +/- 23% (P < 0.05) in OBW,
ie the 30 min FFA level was higher than the fasting level in the latter gro
up. AUC for FFAs during the late postprandial period (120 - 420 min) was si
gnificantly higher in OWW than OBW (P < 0.01) and LWW (P < 0.01) and correl
ated positively with visceral fat mass independent of age (r = 0.78, P < 0.
05) in the OWW only. Leptin levels were higher (P < 0.01) both at fasting a
nd during the course of the OCTT in obese women from both ethnic groups com
pared to the lean women.
CONCLUSIONS: Glucose oxidation is reduced in obese subjects of both ethnic
groups; inter- and intra-ethnic differences were observed in visceral fat m
ass and FFA production and it is possible that such differences may play a
role in the differing prevalences of obesity-related disorders that have be
en reported in these two populations.