Sarcopenia and Age-Related Endocrine Function

Kunihiro Sakuma,Akihiko Yamaguchi

doi:10.1155/2012/127362

Abstract

Sarcopenia, the age-related loss of skeletal muscle, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, and an increased risk of fall-related injuries. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, numerous targets exist for drug discovery. In this paper, we summarize the current understanding of the endocrine contribution to sarcopenia and provide an update on hormonal intervention to try to improve endocrine defects. Myostatin inhibition seems to be the most interesting strategy for attenuating sarcopenia other than resistance training with amino acid supplementation. Testosterone supplementation in large amounts and at low frequency improves muscle defects with aging but has several side effects. Although IGF-I is a potent regulator of muscle mass, its therapeutic use has not had a positive effect probably due to local IGF-I resistance. Treatment with ghrelin may ameliorate the muscle atrophy elicited by age-dependent decreases in growth hormone. Ghrelin is an interesting candidate because it is orally active, avoiding the need for injections. A more comprehensive knowledge of vitamin-D-related mechanisms is needed to utilize this nutrient to prevent sarcopenia.

Highlights

Age-related declines in muscle mass and strength, known as sarcopenia, are often an important antecedent of the onset of disability in older adulthood
We summarize the current understanding of the endocrine contribution to sarcopenia and provide an update on practical hormonal intervention for the elderly
The same group demonstrated that treatment with human ghrelin (2 μg/Kg twice daily intravenously, 3 weeks) significantly improved several parameters in 10 patients with chronic heart failure [105]

Summary

Introduction

Age-related declines in muscle mass and strength, known as sarcopenia, are often an important antecedent of the onset of disability in older adulthood. The term is applied clinically to denote loss of muscle mass, sarcopenia is often used to describe both a set of cellular processes (denervation, mitochondrial dysfunction, and inflammatory and hormonal changes) and a set of outcomes such as decreased muscle strength, decreased mobility and function [1], increased fatigue, a greater risk of falls [2], and reduced energy needs. The specific contribution of each of these factors is unknown, but there is emerging evidence that the disruption of several positive regulators (Akt and serum response factor) of muscle hypertrophy with age is an important feature in the progression of sarcopenia [8,9,10]. Several lines of evidence point to inflammation being associated with loss of muscle strength and mass with aging [11]. We summarize the current understanding of the endocrine contribution to sarcopenia and provide an update on practical hormonal intervention for the elderly

The Adaptative Changes in Catabolic Mediators

Anabolic Hormones in Sarcopenic Muscle

Findings

Conclusion