Simultaneously aligning with the latest evidence of mitochondrial heterogeneity in adipose tissue, muscle fat infiltration in sarcopenia may stem from the selective atrophy of beige fat mitochondria [111], while SO exhibits typical white fat dysfunction coupled with enhanced FGF21 resistance, leading to a disorder in the capacity of adipose tissue to store and metabolize triglycerides [112]. The gene discussed is FGF21; the disease is sarcopenia.