Myosteatosis and myofibrosis: Relationship with aging, inflammation and insulin resistance

Abstract

The mechanisms impairing muscle quality and leading to myofibrosis (MF) and myosteatosis (MS), are incompletely known. In biopsies of paraspinous muscle (PM) of 16 healthy elderly men undergoing elective vertebral surgery, we histologically determined the area of MF and MS expressed as muscle quality index (MQI), in order to investigate the relation between them, as well as the main predictors of muscle quality. Total PM muscle area and intermuscular adipose tissue (IMAT) were evaluated by MRI and body composition by DXA. Circulating fasting glucose, insulin, hs-CRP, leptin, adiponectin and IL-6 were measured and HOMA index calculated. Quantification of gene expression in PM and in subcutaneous adipose tissue (SAT) overlying the muscle was performed by real time-PCR. The degree of MS and MF were significantly and positively related to each other and positively associated with BMI, waist circumference, FM and FM% as well as with the amount of IMAT. Leptin levels were positively associated with MF and MS, whereas hs-CRP was significantly related only to MF. In backward regression analyses, larger waist circumference and smaller PM muscle area explained 90% of MF variance, whereas leptin predicted about 80% of MS variance. IL-6 expression in SAT was significantly higher in participants with higher MQI values. In PM biopsies we found significantly higher expression of SOCS-3 and a trend toward higher expression of myostatin with greater degrees of MQI. MS and MF are related phenomena that concur to alter muscle quality with aging and both should be considered in the evolution of sarcopenia.

Current Status of Sarcopenia in Korea: A Focus on Korean Geripausal Women

“…The degree of myofibrosis and myosteatosis that are the main predictors of quality of muscles is associated with aging and a pattern of increased adiposity. 41) Aging of skeletal muscle is associated not only with muscle atrophy and replacement of muscle by adipose tissue but also with an increase in fibrous connective tissue; similar results have been observed in obese condition. 41) In general, patients with sarcopenia have low weight and low BMI.…”

“…41) Aging of skeletal muscle is associated not only with muscle atrophy and replacement of muscle by adipose tissue but also with an increase in fibrous connective tissue; similar results have been observed in obese condition. 41) In general, patients with sarcopenia have low weight and low BMI. In contrast, patients with SO have high weight, low lean body mass, and high BMI.…”

Impact of preoperative quality as well as quantity of skeletal muscle on survival after resection of pancreatic cancer

“…Furthermore, the associations among immunity, inflammation, and adipocytokines have recently been emphasized as key mechanisms by which sarcopenia affects patient survival. 17,26 We currently are implementing preoperative and postoperative nutritional and exercise therapeutic protocols, especially for patients with sarcopenia or with poor nutritional status. Although the ideal period of these perioperative therapies before and after operation is not established, in our opinion, at least 1 month before operation and a few months after operation are required to improve sarcopenia.…”

“…Several studies have shown that loss of muscle tissue in sarcopenia is accompanied by infiltration with fat and connective tissue, a condition known as myosteatosis. 17 Assessments of skeletal muscle quality and intramuscular fat infiltration are therefore crucial for considering sarcopenia.…”

The pathogenetic bases of sarcopenia

“…Moreover, skeletal muscle aging is associated with myofibrosis and myosteatosis and to gradual fibrous replacement in the muscle (29). In addition, recent histological studies have shown that high values of serum CRP seem to be related with reduced protein synthesis and increased protein catabolism (30).…”