title: Effect of weight loss on muscle fiber type, fiber size, capillarity, and succinate dehydrogenase activity in humans.
abstract: 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.
authors.affiliation: 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
authors.forename: P A
authors.initials: PA
authors.lastname: Kern
authors.forename: R B
authors.initials: RB
authors.lastname: Simsolo
authors.forename: M
authors.initials: M
authors.lastname: Fournier
mesh_terms: 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
chemical_list: D013385:Succinate Dehydrogenase