Tryptophan supplementation and high-intensity interval training prevent muscle atrophy and adipose tissue inflammation in high-fat-fed aged rats

PURPOSE: The lowering of tryptophan amino acid levels and physical inactivity are associated with the age-related deterioration of muscle mass and physical performance. This study aims to investigate the effects of high-intensity interval training (HIIT) and tryptophan supplementation on muscle atrophy markers and inflammation in rats. METHODS: Thirty-five 20-month-old male Wistar rats were randomly split into five groups: normal diet (ND), high-fat diet (HFD), HFD plus tryptophan supplementation, HFD plus HIIT, and HFD plus both tryptophan supplementation and HIIT. HIIT was comprised of seven 1-min sets (12-52 m/min) separated by active recovery for eight weeks (3 times/week). The groups receiving tryptophan supplementation were also administered orally with a daily dosage of 100 mg/kg body weight. Mesenteric adipose tissue, muscle tissue, and blood samples were used to analyze the variables. RESULTS: An HFD resulted in substantial elevations in the muscle atrogin-1 gene levels, the mammalian target of rapamycin (mTOR) gene expression levels, and mTORC1 and atrogin-1 protein levels in the muscle. It also increased TNF-α concentrations and decreased interleukin-10 within the adipose tissue. Tryptophan supplementation and HIIT restored the HFD-induced adipose tissue and muscle dysfunction. The integration of HIIT and tryptophan supplementation improved muscle atrophy and reduced inflammation in adipose tissue. Subsequent analysis indicated that HIIT and tryptophan supplementation improved glucose levels, significantly correlating with decreased atrogin-1 and mTORC1 protein content in muscle and decreasing TNF-α levels in adipose tissue. CONCLUSION: Tryptophan supplementation, HIIT, and their combination similarly can influence muscle atrophy markers and adipose tissue inflammation in aging during HFD feeding.