A novel Sarcopenic Obesity Rat Model Based on Ageing and High-fat Diet

Background: Sarcopenic obesity (SO) is defined as a combination of obesity and sarcopenia, leading to serious health consequences. However, lack of animal model has hampered research into this disorder. Methods Twelve-months-old male Sprague Dawley(SD) rats were fed a high-fat diet (HFD) from early to late adulthood, and their phenotypes were evaluated by determining age-related changes in muscle mass and strength, histopathology, HFD-induced adiposity, and metabolic parameter disturbances. The experimental animals results were compared with those obtained for two-month-old and twelve-month -old rats who were fed a standard diet. Results Aged non-obese rats (20 months, and fed standard diet) showed a decline in quadriceps cross-sectional area/body weight, forelimb grip strength, myofibre cross-sectional area and number, and intermyofibrillar mitochondria number(IFM), accompanied by increased myocyte apoptosis, without metabolic disorder. However, aged obese rats (20 months, and fed high-fat diet) exhibited increased visceral fat, remarkable glycolipid metabolic disorders, and insulin resistance, a more prominent loss of muscle mass and strength, accompanied with a more pronounced decline in myofibre number, IFM, increase in myocyte apoptosis. Conclusion Taken together, aged non-obese rats showed a typical sarcopenic phenotype with ageing. Obesity concomitant with sarcopenia aggravated the animal condition through visceral fat accumulation and insulin resistance. These results support the idea that the aged obese SD rat model represents certain features common with SO in humans and lays the foundation for further studies into the disorder.