Studies on plasma free fatty acid and ketone bodies in young patients with muscular atrophy

The Interaction of Duchenne Muscular Dystrophy and Insulin Resistance

Duchenne muscular dystrophy (DMD), caused by deficiency of functional dystrophin protein, is a fatal, progressive muscle disease that frequently includes metabolic dysregulation. Herein, we explore the physiologic consequences of dystrophin deficiency within the context of obesity and insulin resistance. We hypothesized that dystrophin deficiency increases the frequency of insulin resistance, and insulin resistance potentiates muscle pathology caused by dystrophin deficiency.

Isolation of Mitochondria-Associated ER Membranes (MAMs), Synaptic MAMs, and Glycosphingolipid Enriched Microdomains (GEMs) from Brain Tissues and Neuronal Cells

Subcellular fractionation is a valuable procedure in cell biology to separate and purify various subcellular constituents from one another, i.e., nucleus, cytosol, membranes/organelles, and cytoskeleton. The procedure relies on the use of differential centrifugation of cell and tissue homogenates. Fractionated subcellular organelles may be subjected to additional purification steps that enable the isolation of specific cellular sub-compartments, including interorganellar membrane contact sites. Here we outline a protocol tailored to the isolation of mitochondria, mitochondria-associated ER membranes (MAMs), and glycosphingolipid enriched microdomains (GEMs) from the adult mouse brain, primary neurospheres, and murine embryonic fibroblasts (MEFs). We also provide a detailed protocol for the purification of synaptosomes and their corresponding MAMs .

Components of energy expenditure in the mdx mouse model of Duchenne muscular dystrophy

Previous observations showing that basal heat production rates and glucose metabolism were reduced in mdx mouse skeletal muscles incubated in vitro led us to study the components of total energy expenditure by open-circuit indirect calorimetry in the intact, free-moving mdx mouse. Our purpose was to verify if the mdx mouse exhibited whole-body alterations in energy metabolism. The results revealed that total and basal energy expenditure, as well as spontaneous activity, energetic cost of activity, and, therefore, energy expended in relation to activity were not significantly different in C57B1/10 (control) and in dystrophic (mdx) mice. In contrast, the thermic effect of food was 32% larger in mdx than in control mice and was accompanied by significant differences in post-prandial glucose and lipid oxidation. The present in vivo study could not show a direct demonstration that impaired glucose metabolism by skeletal muscles participated in this phenomenon. However, since post-prandial glucose metabolism by skeletal muscles contributes a significant part of the thermic effect of food, the present data are in line with previous studies in vitro that show that mdx mouse skeletal muscles probably suffer an impaired control of their energy metabolism.

Glucose, free fatty acid and ketone body metabolism in Duchenne muscular dystrophy

We examined how the substances, especially glucose, free fatty acids (FFA) and ketone bodies, and hormones associated with energy metabolism change with the disease progress in Duchenne muscular dystrophy (DMD). Serum creatine kinase (CK) activity was used as an index of the stage of DMD, because this activity is exponentially decreases with the progress of the disease. The glucose concentration in DMD patients with CK activity of less than 1,000 U/l (low CK) was significantly lower than that in controls, although there was no significant difference between that in DMD patients with CK activity of more than 1,00 U/l (high CK) and that in controls. The FFA concentration in both high CK and low CK patients was significantly higher than that in controls. The FFA concentration in low CK patients tended to be higher than that in high CK patients. The ketone body concentration in low CK patients was significantly higher than that in controls and that in high CK patients. The [glucagon]:[insulin] ratio in low CK patients was significantly higher than that in controls and that in high CK patients. It was also observed in a correlational study that the glucose concentration decreased with the age and the decrease in CK activity, i.e., with the progress of DMD. The FFA and ketone body concentrations increased with the decrease in the glucose concentration. The decrease in the glucose concentration may be due to a caloric shortage and/or degenerated muscle, which cannot supply enough gluconeogenic substrates, such as alanine. The kinetics of insulin and glucagon in DMD may help to maintain the glucose metabolism. Increased concentrations of FFA and ketone bodies may be helpful in the advanced stage of DMD, as energy sources and as substrates, sparing muscle protein.