Heat therapy improves body composition and muscle function but does not affect capillary or collateral growth in a model of obesity and hindlimb ischemia

Abstract

Heat therapy (HT) has emerged as a potential adjunctive therapy to alleviate the symptoms of peripheral artery disease (PAD), but the mechanisms underlying the positive effects of this treatment modality remain undefined. Using a model of diet-induced obesity (DIO) and ischemia-induced muscle damage, we tested the hypothesis that HT would alter body composition, promote vascular growth and mitochondrial biogenesis, and improve skeletal muscle function. Male DIO C57Bl/6J mice underwent bilateral ligation of the femoral artery and were randomly allocated to receive HT or a control intervention for 30 min daily over 3 weeks. When compared to a group of lean, sham-operated animals, ligated DIO mice exhibited increases in body and fat masses, exercise intolerance and contractile dysfunction of the isolated soleus (SOL) and extensor digitorum longus (EDL) muscles. Repeated HT averted an increase in body mass induced by high-fat feeding due to reduced fat accrual. Fat mass was ~25% and 29% lower in the HT group relative to controls after 2 and 3 weeks of treatment, respectively. Muscle mass relative to body mass and maximal absolute force of the EDL, but not SOL, were higher in animals exposed to HT. There were no group differences in skeletal muscle capillarization, the expression of angiogenic factors, mitochondrial content and the diameter of the gracilis arteries. These findings indicate that HT reduces diet-induced fat accumulation and rescues skeletal muscle contractile dysfunction. This practical treatment may prove useful for diabetic and obese PAD patients who are unable to undergo conventional exercise regimens.

Microvascular Dysfunction in Peripheral Artery Disease: Is Heat Therapy a Viable Treatment?

“…In a similar investigation, Kim et al (2020) found that in addition to preserving muscle mass, heat therapy treatment may also be beneficial for improving body composition in an obese murine model of hindlimb ischemia. However, the authors noted that there were no improvements in capillary or collateral growth in response to the chronic heat therapy [48]. Overall, Kim et al (2019 and2020) revealed that chronic heat therapy may elicit benefits at the muscular level, which may be partially attributed to the increase in core temperature.…”

“…Chronic heat therapies have been used in both animal models of PAD and patients with PAD. Roseguini's group has explored the impacts of chronic heat therapy in murine models of chronic hindlimb ischemia [47,48]. Kim et al (2019) found that muscular mass (+7%) in the ischemic limb was greater following heat therapy compared to control [47].…”

Sympathetic Nerve Activity and Blood Pressure Response to Exercise in Peripheral Artery Disease: From Molecular Mechanisms, Human Studies, to Intervention Strategy Development

“…Meanwhile, heating exposure increases the contraction force of the ischemia-induced damaged skeletal muscle [175]. In a mice obesity model, the heating exposure also decreased the percentage of fat and increase the ratio of muscle mass to body mass even if capillary density and collateral supply diameter was unchanged [176].…”

Skeletal Muscle Mitochondrial Dysfunction and Oxidative Stress in Peripheral Arterial Disease: A Unifying Mechanism and Therapeutic Target

“…Considering the aspects of limited conduit artery blood flow and impaired endothelium-dependent vasodilation during physical activity in this population, there will probably be an increased reliance on the microcirculation to meet the metabolic demands of the contracting muscle. Therefore, novel strategies targeting skeletal muscle myopathy to reverse muscle atrophy [ 66 , 67 ] that can be used in addition to those targeting capillary rarefaction [ 68 , 69 ] hold great potential to produce greater and more sustainable clinical impact.…”