Reverse fiber type disproportion: A distinct metabolic myopathy.

Introduction: In this investigation we characterized the physiological and metabolic responses to incremental exercise in 13 subjects with a predominance of type II fibers on muscle biopsy.

Methods: Subjects underwent incremental exercise testing with measures of maximum oxygen uptake ( V˙O2 max), maximum heart rate (fc max), chronotropic index (fc / V˙O2 slope), maximum ventilation ( V˙emax), blood lactate, ammonia, and creatine kinase (CK) levels. Muscle fiber type was determined by myosin ATPase histochemistry.

Lipin-1 regulates autophagy clearance and intersects with statin drug effects in skeletal muscle.

LPIN1 encodes lipin-1, a phosphatidic acid phosphatase (PAP) enzyme that catalyzes the dephosphorylation of phosphatidic acid to form diacylglycerol. Homozygous LPIN1 gene mutations cause severe rhabdomyolysis, and heterozygous LPIN1 missense mutations may promote statin-induced myopathy. We demonstrate that lipin-1-related myopathy in the mouse is associated with a blockade in autophagic flux and accumulation of aberrant mitochondria.

Intact skeletal muscle mitochondrial enzyme activity but diminished exercise capacity in advanced heart failure patients on optimal medical and device therapy.

Background: A skeletal myopathy, perhaps attributable to neuro-endocrine excitation or disuse, has been described in heart failure (HF) patients, and is thought to contribute to their exercise limitation. Our purpose was to assess biochemical and morphometric characteristics of skeletal muscles of HF patients on optimal HF therapy. A secondary purpose was to explore the effects of clonidine, which interrupts the neuro-endocrine excitation, on these same muscle characteristics.

Abnormalities of calcium handling proteins in skeletal muscle mirror those of the heart in humans with heart failure: a shared mechanism?

Background: In the failing human heart, abnormalities of Ca(2+) cycling have been described, but there is scant knowledge about Ca(2+) handling in the skeletal muscle of humans with heart failure (HF). We tested the hypothesis that in humans with HF, Ca(2+) cycling proteins in skeletal muscle are abnormal.

Methods And Results: Ten advanced HF patients (50.

Nicotinamide adenine dinucleotide tetrazolium reductase identifies microvasculature activation in muscle from adult patients with dermatomyositis.

Objective: Previous work has suggested involvement of the muscle microvasculature in the pathogenesis of dermatomyositis (DM). Our study evaluates whether standard histochemical reactions can identify microvascular changes in muscle biopsies from patients with DM compared to myopathic and nonmyopathic controls.

Methods: Muscle biopsies were obtained from 111 patients, including 45 patients with DM.