Relationship between skeletal muscle lipoprotein lipase activity and 24-hour macronutrient oxidation.
A low ratio of whole-body 24-h fat/carbohydrate (CHO) oxidation has been shown to be a predictor of subsequent body weight gain. We tested the hypothesis that the variability of this ratio may be related to differences in skeletal muscle metabolism. Since lipoprotein lipase (LPL) plays a pivotal role in partitioning lipoprotein-borne triglycerides to adipose (storage) and skeletal muscle (mostly oxidation), we postulated that a low ratio of fat/CHO oxidation was associated with a low skeletal muscle LPL (SMLPL) activity. As an index of substrate oxidation, 24-h RQ was measured under sedentary and eucaloric conditions in 16 healthy nondiabetic Pima males. During a 6-h euglycemic, hyperinsulinemic clamp, muscle biopsies were obtained at baseline, 3, and 6 h. Heparin-elutable SMLPL activity was 2.92 +/- 0.56 nmol free fatty acids/g.min (mean +/- SD) at baseline, was unchanged (2.91 +/- 0.51) at the third hour, and increased significantly (P < 0.05) to 3.13 +/- 0.57 at the sixth hour of the clamp. The mean (of baseline and 3-h) SMLPL activity correlated inversely with 24-h RQ (r = 0.57, P < 0.03) but not with body size, body composition, or insulin-mediated glucose uptake. Since SMLPL activity is related to the ratio of whole body fat/CHO oxidation rate, a decreased muscle LPL activity may, therefore, predispose to obesity.
Ferraro
R T
RT
Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, Arizona 85016.
Eckel
R H
RH
Larson
D E
DE
Fontvieille
A M
AM
Rising
R
R
Jensen
D R
DR
Ravussin
E
E
D050260:Carbohydrate Metabolism; D004734:Energy Metabolism; D006801:Humans; D007198:Indians, North American; D007328:Insulin / Q000502:physiology; D050356:Lipid Metabolism; D008071:Lipoprotein Lipase / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000378:metabolism*
D007328:Insulin; D008071:Lipoprotein Lipase