Effect of Weight Loss on Muscle Fiber Type, Fiber Size, Capillarity, and Succinate Dehydrogenase Activity in Humans

To determine the level of coordination in succinate dehydrogenase (SDH) activity between plantaris motoneurons and muscle fibers, the soleus and gastrocnemius muscles were bilaterally excised in four cats to subject the plantaris to functional overload (FO). Five normal cats served as controls. Twelve weeks after surgery the right plantaris in each cat was injected with horseradish peroxidase to identify plantaris motoneurons. SDH activity then was measured in a population of plantaris motoneurons and muscle fibers in each cat. Control motoneurons and muscle fibers had similar mean SDH activities and a similar relationship between cell size and SDH activity. After FO, muscle fiber size doubled and mean muscle fiber SDH activity halved. Motoneuron mean SDH activity and size were unaffected by FO. Total SDH activity was unchanged in both the motoneurons and muscle fibers after FO. These changes suggest a selective increase in contractile proteins with little or no modulation of mitochondrial proteins in the muscle fibers, because total SDH activity was unchanged in muscle fibers after FO. These data demonstrate that although mean SDH activities were similar in control motoneurons and muscle fibers, mean SDH activities in these two cell types can change independently.

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Muscle fiber type composition and fiber size in successfully and unsuccessfully endurance-raced horses

Journal of Applied Physiology ◽

10.1152/jappl.1993.75.4.1758 ◽

1993 ◽

Vol 75 (4) ◽

pp. 1758-1766 ◽

Cited By ~ 47

Author(s):

J. L. Rivero ◽

A. L. Serrano ◽

P. Henckel ◽

E. Aguera

Keyword(s):

Muscle Fiber ◽

Fiber Type ◽

Reductase Activity ◽

Muscle Fiber Type ◽

Lower Percentage ◽

Type I ◽

Fiber Type Composition ◽

Type Composition ◽

Fiber Size ◽

Muscle Fiber Type Composition

Triplicate biopsies from three different depths of the gluteus medius muscle were obtained in 36 endurance-raced horses, aged 8.42 +/- 2.85 yr. Twenty of the horses were considered excellent endurance performers according to the mean speed of their three fastest records in endurance events for the past 2 or 3 years, whereas 16 were moderate performers, with a mean racing speed < 12.5 km/h (in 120- to 180-km endurance rides), < 14 km/h (in 80- to 120-km endurance rides), or < 13.5 km/h (in 40- to 60-km endurance rides). Significant differences in muscle fiber type composition and fiber size were recorded; excellent performers had a higher percentage and a larger size of type I and type IIa fibers (high and low myosin adenosinetriphosphatase activity at pH 4.5, respectively) and a lower percentage of type IIb fibers (moderate myosin adenosinetriphosphatase activity at pH 4.5), including both type IIb oxidative (moderate to high NADH-tetrazolium reductase activity) and IIb nonoxidative (low NADH-tetrazolium reductase activity). The differences in distribution of myofiber types and in fiber sizes were more marked in the deeper parts compared with the superficial regions of muscle. Our results also imply a greater homogeneity among the fiber type sizes across the muscle in horses with a superior endurance performance than in horses that had been poorly or moderately endurance raced. Thus the results show that fiber type proportions and fiber size in equine skeletal muscle are directly related to the athletic ability of the horse for endurance events.

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Aging reduces succinate dehydrogenase activity in rat type IIx/IIb diaphragm muscle fibers

Journal of Applied Physiology ◽

10.1152/japplphysiol.00644.2019 ◽

2020 ◽

Vol 128 (1) ◽

pp. 70-77 ◽

Cited By ~ 2

Author(s):

Matthew J. Fogarty ◽

Natalia Marin Mathieu ◽

Carlos B. Mantilla ◽

Gary C. Sieck

Keyword(s):

Succinate Dehydrogenase ◽

Dehydrogenase Activity ◽

Fiber Type ◽

Oxidative Capacity ◽

Diaphragm Muscle ◽

Type I ◽

Specific Force ◽

Succinate Dehydrogenase Activity ◽

Cross Sectional ◽

Fresh Frozen

In aged rats, diaphragm muscle (DIAm) reduced specific force and fiber cross-sectional area, sarcopenia, is selective for vulnerable type IIx and/or IIb DIAm fibers, with type I and IIa fibers being resilient. In humans, the oxidative capacity [as measured by maximum succinate dehydrogenase (SDHmax) activity] of fast-type muscle is reduced with aging, with slow-type muscle being unaffected. We hypothesized that in aged Fischer rat DIAm exhibiting sarcopenia, reduced SDHmax activity would occur in type IIx and/or IIb fibers. Rats obtained from the NIA colony (6, 18, and 24 mo old) were euthanized, and ~2-mm-wide DIAm strips were obtained. For SDHmax and fiber type assessments, DIAm strips were stretched (approximately optimal length), fresh frozen in isopentane, and sectioned on a cryostat at 6 μm. SDHmax, quantified by intensity of nitroblue tetrazolium diformazan precipitation, was assessed in a fiber type-specific manner by comparing serial sections labeled with myosin heavy chain (MyHC) antibodies differentiating type I (MyHCSlow), IIa (MyHC2A), and IIx and/or IIb fibers. Isometric DIAm force and fatigue were assessed in DIAm strips by muscle stimulation with supramaximal pulses at a variety of frequencies (5–100 Hz) delivered in 1-s trains. By 24 mo, DIAm sarcopenia was apparent and SDHmax in type IIx and/or IIb fibers activity was reduced ~35% compared with 6-mo-old control DIAm. These results underscore the remarkable fiber type selectivity of type IIx and/or IIb fibers to age-associated perturbations and suggest that reduced mitochondrial oxidative capacity is associated with DIAm sarcopenia. NEW & NOTEWORTHY We examined the oxidative capacity as measured by maximum succinate dehydrogenase activity in older (18 or 24 mo old) Fischer 344 rat diaphragm muscle (DIAm) compared with young rats (6 mo old). In 24-mo-old rats, SDH activity was reduced in type IIx/b DIAm fibers. These SDH changes were concomitant with sarcopenia (reduced specific force and atrophy of type IIx/b DIAm fibers) at 24 mo old. At 18 mo old, there was no change in SDH activity and no evidence of sarcopenia.

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