Acute and chronic changes in rat soleus muscle after high-fat high-sucrose diet

Abstract

The effects of obesity on different musculoskeletal tissues are not well understood. The glycolytic quadriceps muscles are compromised with obesity, but due to its high oxidative capacity, the soleus muscle may be protected against obesity‐induced muscle damage. To determine the time–course relationship between a high‐fat/high‐sucrose (HFS) metabolic challenge and soleus muscle integrity, defined as intramuscular fat invasion, fibrosis and molecular alterations over six time points. Male Sprague‐Dawley rats were fed a HFS diet (n = 64) and killed at serial short‐term (3 days, 1 week, 2 weeks, 4 weeks) and long‐term (12 weeks, 28 weeks) time points. Chow‐fed controls (n = 21) were killed at 4, 12, and 28 weeks. At sacrifice, animals were weighed, body composition was calculated (DXA), and soleus muscles were harvested and flash‐frozen. Cytokine and adipokine mRNA levels for soleus muscles were assessed, using RT‐qPCR. Histological assessment of muscle fibrosis and intramuscular fat was conducted, CD68+ cell number was determined using immunohistochemistry, and fiber typing was assessed using myosin heavy chain protein analysis. HFS animals demonstrated significant increases in body fat by 1 week, and this increase in body fat was sustained through 28 weeks on the HFS diet. Short‐term time‐point soleus muscles demonstrated up‐regulated mRNA levels for inflammation, atrophy, and oxidative stress molecules. However, intramuscular fat, fibrosis, and CD68+ cell number were similar to their respective control group at all time points evaluated. Therefore, the oxidative capacity of the soleus may be protective against diet‐induced alterations to muscle integrity. Increasing oxidative capacity of muscles using aerobic exercise may be a beneficial strategy for mitigating obesity‐induced muscle damage, and its consequences.

Mechanical adaptations of skinned cardiac muscle in response to dietary-induced obesity during adolescence in rats

“…As previously shown using the same diets (Collins et al 2016, Collins et al 2017Rios et al 2019), animals in the high-fat high-sucrose group reached significantly greater body mass and percentage body fat compared to control group animals, indicating the presence of obesity. The high-fat high-sucrose diet did not affect lean body mass development but rather, led to greater fat content.…”

“…For the first 7 weeks, animals in the dietary-induced obesity group (n=8) were fed a high-fat high-sucrose diet (Dyets 103915) consisting of 24% protein, 20% fat, and 45% protein, and for the second half of the study weeks 8-14) the diet (Dyets 102412) was comprised of 15-20% protein, 40% fat, and 40-45% carbohydrates (>97% of carbohydrates from sucrose). Obesity was induced over a fourteen week period, a time frame that has been shown previously to result in obesity in adult rats (Collins et al 2016, Collins et al 2017Rios et al 2019). The diet began at weaning and was maintained through adolescence and into adulthood.…”

Obesity, Metabolic Syndrome, and Musculoskeletal Disease: Common Inflammatory Pathways Suggest a Central Role for Loss of Muscle Integrity

“…Also, there is a lack of data describing the effect of obesity on muscle integrity, and a lack of consistent protocols to assess muscle strength (Tomlinson et al, 2016 ). However, data from our lab (Collins et al, 2016a , c , 2017b ) and others, in rodents (Ciapaite et al, 2015 ) and large mammals (Clark et al, 2011 ), have demonstrated deleterious alterations in muscle structural integrity with metabolic disturbance. Computational approaches modeling the gastrocnemius muscle have demonstrated that whole-muscle force is dependent on muscle integrity, specifically regarding reductions of muscle force due to intramuscular lipid (Rahemi et al, 2015 ).…”

“…Work from our laboratory has demonstrated that the oxidative soleus muscle is protected against HFS-induced damage over short-term and long-term exposures in a rat model (Collins et al, 2017b ; Figure 4 ). By 3-days on HFS, dynamic increases in mRNA levels for superoxide dismutase (SOD2) in HFS animals implicate compensatory oxidative stress scavenging in the soleus muscle compared to control animals.…”

The effect of high‐fat diet on the morphological properties of the forelimb musculature in hypertrophic myostatin null mice

“…In this respect, a study using mixed high‐fat and sucrose diet in rats to evaluate muscle performance in obesity, showed that even though the quadriceps muscle was functionally attenuated, the slow twitch soleus muscle was resistant to diet‐based muscle alteration (Collins et al. ). The alteration of CSA of type IIB and IIX fibers on HFD seems to be of relevance to the muscle phenotype as well as to its metabolic activity.…”