Different Molecular and Structural Adaptations with Eccentric and Conventional Strength Training in Elderly Men and Women

Abstract

Reprogramming of gene expression contributes to structural and functional adaptation of muscle tissue in response to altered use. The aim of this study was to investigate mechanisms for observed improvements in leg extension strength, gain in relative thigh muscle mass and loss of body and thigh fat content in response to eccentric and conventional strength training in elderly men (n = 14) and women (n = 14; average age of the men and women: 80.1 ± 3.7 years) by means of structural and molecular analyses. Biopsies were collected from m. vastus lateralis in the resting state before and after 12 weeks of training with two weekly resistance exercise sessions (RET) or eccentric ergometer sessions (EET). Gene expression was analyzed using custom-designed low-density PCR arrays. Muscle ultrastructure was evaluated using EM morphometry. Gain in thigh muscle mass was paralleled by an increase in muscle fiber cross-sectional area (hypertrophy) with RET but not with EET, where muscle growth is likely occurring by the addition of sarcomeres in series or by hyperplasia. The expression of transcripts encoding factors involved in muscle growth, repair and remodeling (e.g., IGF-1, HGF, MYOG, MYH3) was increased to a larger extent after EET than RET. MicroRNA 1 expression was decreased independent of the training modality, and was paralleled by an increased expression of IGF-1 representing a potential target. IGF-1 is a potent promoter of muscle growth, and its regulation by microRNA 1 may have contributed to the gain of muscle mass observed in our subjects. EET depressed genes encoding mitochondrial and metabolic transcripts. The changes of several metabolic and mitochondrial transcripts correlated significantly with changes in mitochondrial volume density. Intramyocellular lipid content was decreased after EET concomitantly with total body fat. Changes in intramyocellular lipid content correlated with changes in body fat content with both RET and EET. In the elderly, RET and EET lead to distinct molecular and structural adaptations which might contribute to the observed small quantitative differences in functional tests and body composition parameters. EET seems to be particularly convenient for the elderly with regard to improvements in body composition and strength but at the expense of reducing muscular oxidative capacity. is likely occurring by the addition of sarcomeres in series or by hyperplasia. The expression of transcripts encoding factors involved in muscle growth, repair and remodeling (e.g. IGF-1, HGF, MYOG, MYH3) was increased to a larger extent after EET than RET. MicroRNA 1 expression was decreased independent of the training modality, and was paralleled by an increased expression of IGF-1 representing a potential target. IGF-1 is a potent promoter of muscle growth, and its regulation by microRNA 1 may have contributed to the gain of muscle mass observed in our subjects. EET depressed genes encoding mitochondrial and metabolic transcripts. The changes of several metabolic and mitochondrial transcript...

Metabolic Exploration of Muscle Biopsy

“…In this study, biopsies of vastus lateralis showed an enhanced expression of transcripts encoding factors involved in muscle growth, repair and remodeling (i.e. IGF-1, HGF, MYOG, MYH3) (Mueller et al, 2011). Of note, eccentric cycle ergometry was observed to depress genes encoding mitochondrial and metabolic transcripts.…”

Circulating MicroRNAs as Potential Biomarkers of Exercise Response

“…A huge number of studies have been focused on their potential as biomarkers for various diseases, particularly for cancer. In a similar manner, physical exercise has been shown to be an activator of gene expression and miRNA levels that vary considerably depending on the mode of exercise [30,59,60,61,62,63,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,117,118,119,120,121,122,123,124,125]. Many studies revealed miRNAs to have a potential as markers of muscle function and exercise adaptation.…”

“…Interestingly, the expression levels of myomiRs were unaffected after this particular resistance training program. In elderly participants, the strength training lasting 12 weeks resulted in downregulation of miR-1 [63]. miRNAs altered by muscle atrophy may play a role in the age-related loss of skeletal muscle [64].…”

Chronic Eccentric Exercise and the Older Adult

“…Detailed descriptions of each of the 14 studies are outlined in Table 1. In cases where multiple publications investigated the same population of subjects, the most appropriate publication was reviewed [22][23][24][25][26][27]. In all tables thereafter (Tables 2, 3, and 4), relative efficacy of eccentric exercise is described using percent change from baseline within groups.…”