Effect of weight loss on muscle fiber type, fiber size, capillarity, and succinate dehydrogenase activity in humans.
To examine the effects of weight loss on muscle oxidative properties, nine obese subjects (body mass index, 34 +/- 1.5) had muscle biopsies before and after weight loss and weight stabilization. Weight loss ranged from 13-32 kg and represented 20.8 +/- 2.1% of initial weight. After weight loss, there was no change in the proportions of oxidative (type I and type IIa) fibers and also no change in mean fiber cross-sectional area, whereas there was a small, but significant, decrease in the relative interstitial space (P < 0.05). However, weight loss resulted in a 32 +/- 6% (mean +/- SEM) increase in capillary/fiber ratio and a 54% increase in capillary density (P < 0.05). In addition, there was a 41 +/- 13% increase in succinate dehydrogenase (SDH) activity (P < 0.05). This increase in muscle capillarization and SDH activity was seen in all fiber types, even the relatively lower oxidative type IIx fibers. There was a strong correlation between the change in capillary/fiber ratio and the change in SDH activity (r = 0.82; P < 0.02). Thus, weight loss resulted in no change in muscle fiber type or cross-sectional area, but produced increases in capillary/fiber ratio, capillary density, and SDH activity, suggesting an increase in muscle oxidative capacity.
Kern
P A
PA
Department of Medicine, University of Arkansas for Medical Sciences, and The Central Arkansas Veterans Health Care System, Little Rock 72205, USA. kernphilipa@exchange.uams.edu
Simsolo
R B
RB
Fournier
M
M
D000328:Adult; D000368:Aged; D001706:Biopsy; D002196:Capillaries / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018656:Muscle Fibers, Fast-Twitch / Q000201:enzymology / Q000473:pathology; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000473:pathology*; D018657:Muscle Fibers, Slow-Twitch / Q000201:enzymology / Q000473:pathology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000201:enzymology / Q000473:pathology*; D009765:Obesity / Q000201:enzymology / Q000473:pathology / Q000628:therapy*; D010084:Oxidation-Reduction; D013385:Succinate Dehydrogenase / Q000378:metabolism*; D015431:Weight Loss
D013385:Succinate Dehydrogenase