Abstract
The mechanisms accounting for the loss of muscle function with obesity and type 2 diabetes are likely the result of a combination of neural and muscular factors. One muscular factor that is important, yet has received little attention, is the protein machinery involved in longitudinal and lateral force transmission. The purpose of this study was to compare the levels of force transfer and membrane integrity proteins before and after a 12‐week endurance training program in lean, obese, and obese type 2 diabetic adults. Nineteen sedentary subjects (male = 8 and female = 11) were divided into three groups: Lean (n = 7; 50.3 ± 4.1 y; 69.1 ± 7.2 kg); Obese (n = 6; 49.8 ± 4.1 y; 92.9 ± 19.5 kg); and Obese with type 2 diabetes (n = 6; 51.5 ± 7.9 years; 88.9 ± 15.1 kg). Participants trained 150 min/week between 55% and 75% of VO2max for 12 weeks. Skeletal muscle biopsies were taken before and after the training intervention. Baseline dystrophin and muscle LIM protein levels were higher (~50% p < .01) in lean compared to obese and type 2 diabetic adults, while the protein levels of the remaining force transfer and membrane integrity proteins were similar between groups. After training, obese individuals decreased (−53%; p < .01) the levels of the muscle ankyrin repeat protein and lean individuals decreased dystrophin levels (−45%; p = .01), while the levels of the remaining force transfer and membrane integrity proteins were not affected by training. These results suggest that there are modest changes to force transfer and membrane integrity proteins in middle‐aged individuals as a result of 12 weeks of lifestyle and training interventions.
Highlights
Obesity affects approximately 650 million people, accounting for 13% of the world's adult population (World HealthOrganization, 2016)
The major findings of this study were as follows: (1) that dystrophin and muscle LIM protein levels were higher in lean controls compared with obese and type 2 diabetic adults and (2) that a 12-week endurance training program had a small effect on the levels of force transfer and membrane integrity proteins
The muscle ankyrin repeat protein (MARP) and dystrophin levels were altered by training in obese and lean individuals, respectively
Summary
Obesity affects approximately 650 million people, accounting for 13% of the world's adult population (World HealthOrganization, 2016). Obesity and type 2 diabetes have been suggested to accelerate the loss of muscle strength with age (Park et al, 2006) and muscle strength has been acknowledged as the critical factor for determining physical disability and mortality (Manini & Clark, 2012). One muscular factor that is important, yet has received little attention, is the protein machinery involved in longitudinal and lateral force transmission. Force is transmitted both longitudinally, through the Z-lines of sarcomeres in series to the myotendinous junction and on to the tendon, and laterally, from the sarcomeres through the surrounding basal lamina and extracellular matrix (ECM) to the tendon (Hughes, Wallace, & Baar, 2015). The lateral force transmission pathway is composed of costameric proteins and intermediate filaments (Henderson, Gomez, Novak, Mi-Mi, & Gregorio, 2017)
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