Impact of heat therapy on body composition and skeletal muscle function in a model of peripheral artery disease
Authors: Kim Kyoungrae , Roseguini Bruno T. 
Published: June 2021

IntroductionPatients with symptomatic peripheral artery disease (PAD) have a profound limitation in exercise performance that is partly caused by ischemia‐related skeletal muscle abnormalities, including reduced muscle mass and strength. Current medical therapy for the exercise limitation in PAD is limited. We recently reported that exposure to leg heat therapy (HT) causes a marked increase in leg blood flow in patients with PAD. In this study, we used a model of diet‐induced obesity and peripheral arterial insufficiency to examine the effects of repeated treatment with HT on body composition and skeletal contractile function.MethodsMale 32‐week‐old C57Bl/6 mice were fed 60% high‐fat diet for 10 weeks. At 42 weeks of age, the animals underwent bilateral ligation of the femoral artery to induce hindlimb ischemia. After two weeks of recovery, the animals were randomly assigned to receive HT or a control intervention. Heat therapy was applied by placing the animal in a flat bottom restrainer and immersing the lower half of the body in a glass container filled with water at 39°C (n=7) for 30 min daily over 3 consecutive weeks. Animals assigned to the control group (n=8) were also restrained, but were placed in an empty container. Rectal temperature was measured before and during exposure to a single session of HT or the control intervention (n=3/group). Body composition was assessed prior to the onset of the treatment and then once a week throughout the intervention. Forty‐eight hours following the last treatment session, the animals were anesthetized and the soleus and extensor digitorum longus (EDL) muscles were harvested for the assessment of contractile function.ResultsRectal temperature increased during acute exposure to HT from a baseline of 35.1±0.4°C to 38.3±0.2°C. In the control group, rectal temperature remained at baseline levels throughout the treatment session (35.4±0.3°C). At baseline, fat mass (Control: 17.2±0.7 g vs. 16.0±0.8 g, p=0.51) and lean mass (Control: 28.4 g vs. HT: 28.4 g, p=0.7) were not different between groups. However, fat mass was significantly lower in the group exposed to HT at week 2 (Control: 19.6 g vs. HT: 14.72 g, p=0.03) and week 3 (Control: 20.32 g vs. HT: 14.54 g, p=0.01), while there was no difference between groups in lean mass throughout the intervention period (p>0.05). Muscle mass relative to body mass was significantly higher in animals exposed to HT as compared to the control group in the EDL muscle (Control: 0.33±0.01 mg/g vs. HT: 0.38±0.01 mg/g, p=0.003). Maximal absolute force of the EDL muscle was also higher in animals treated with HT when compared to the control group (Control: 488.5±12.4 mN, HT: 529.5±14.5 mN, p=0.05). There were no differences between groups in relative muscle mass and maximal force development of the soleus muscle (p>0.05).ConclusionThese findings indicate that repeated exposure to HT has positive effects on body composition and improves skeletal muscle function in a mouse model of diet‐induced obesity and PAD. This new therapeutic tool might be a practical alternative for PAD patients with restricted locomotion and multiple comorbidities, including diabetes and obesity.Support or Funding InformationFunding: Ralph W. and Grace M. Showalter Research Trust AwardThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.