Skeletal Muscle Lipid Content and Oxidative Activity in Relation to Muscle Fiber Type in Aging and Metabolic Syndrome

Abstract

One of the most noticeable effects of aging is the reduction in skeletal muscle mass and strength (sarcopenia). The metabolic syndrome (MS) is also prevalent in old subjects, but its relevance to skeletal muscle characteristics has poorly been investigated. Immunohistochemical studies were performed with muscle biopsies from young (22 years) and old (73 years) men with and without MS to reveal age-dependent and MS-associated modifications of fiber-type characteristics. Atrophy of type II fibers and altered fiber shape characterized muscle aging in lean healthy men. In contrast, increased cross-sectional area of the most abundant type I and type IIA fibers, and reduced cytochrome c oxidase content in all fiber types, characterized MS. Aging and particularly MS were associated with accumulation of intramyocellular lipid droplets. Although lipids mostly accumulated in type I fibers, matrix-assisted laser desorption/ionization-mass spectrometry imaging of intramyocellular lipids did not distinguish fiber types, but clearly separated young, old, and MS subjects. In conclusion, our study suggests that MS in the elderly persons is associated with alterations in skeletal muscle at a fiber-type specific level. Overall, these fiber type-specific modifications may be important both for the age-related loss of muscle mass and strength and for the increased prevalence of MS in elderly subjects.

Frailty and sarcopenia as the basis for the phenotypic manifestation of chronic diseases in older adults

“…In fact, supporting a causal effect of insulin resistance on sarcopenia in the elderly, induction of insulin resistance in old rats by sucrose feeding results in significant loss of lean body mass, increase in fat mass and reduced muscle protein synthesis (Gatineau et al, 2015). The alteration of skeletal muscle by insulin resistance is further suggested by the altered muscle fiber type content and the increased accumulation of intramyocellular lipid droplets in muscle biopsies from elders with metabolic syndrome (Gueugneau et al, 2015).…”

Physiological role of receptor activator nuclear factor-kB (RANK) in denervation-induced muscle atrophy and dysfunction

“…Functional muscle overload causes a gain in muscle mass while prolonged exercise leads to the transformation of pre-existing fast-twitch muscle fibers to a slow-twitch oxidative phenotype. Type IIb fibers, the most powerful fibers, are converted to oxidative phenotype fibers (type I or IIa) and disappear through a necrotic process during myopathies, aging, and glucocorticoid treatments [18, 19] . Intracellular/cytosolic Ca 2+ ([Ca 2+ ] i ) fluctuations play a crucial role in the maintenance and adaptation of muscle phenotypes.…”

A Proof of Concept to Bridge the Gap between Mass Spectrometry Imaging, Protein Identification and Relative Quantitation: MSI~LC-MS/MS-LF

“…Previous investigations based on human biopsies indicated that muscle aging (sarcopenia) is associated with important modifications at the fiber-type level. Specifically, MALDI-MSI provided evidence for aging- and metabolic syndrome-dependent alterations in intra-myofibrillar lipids [2]. Using small human biopsies, MSI of proteins could be less sample-consuming than usual analytical techniques, such as two-dimensional gel electrophoreses [3] or shot-gun proteomics [4].…”