Dietary Combination of Sucrose and Linoleic Acid Increases Intramyocellular Lipid and Impairs Muscle Strength in Female Zucker Diabetic Fatty Rats

Sarcopenic obesity is associated with metabolic disorders and physical limitations. Intramyocellular lipid (IMCL) accumulation is a critical factor affecting muscle strength, independent of muscle mass, in obesity. While diet plays an important role in regulating IMCL, the effects of specific dietary combinations remain poorly understood. This study examined the effects of different combinations of dietary carbohydrates and fats on skeletal muscle quality and function in obese rats. Female Zucker diabetic fatty rats were fed diets containing either sucrose or palatinose combined with either oleic or linoleic acid for 12 weeks. Body and muscle weights, IMCL content, and grip strength were measured. C2C12 myotubes were treated in vitro with varying concentrations of glucose or insulin, along with fatty acids (oleic acid or linoleic acid), to mimic the exposure of each diet. The diet combining sucrose and linoleic acid (SL) significantly increased IMCL accumulation in the extensor digitorum longus (EDL) muscle and reduced grip strength. A negative correlation was observed between IMCL and grip strength. Cluster of differentiation 36 (CD36) protein levels tended to increase in the EDL of the SL diet-fed group. In vitro experiments demonstrated that high glucose levels combined with linoleic acid increased IMCL and CD36 expression. In conclusion, diets high in sucrose and linoleic acid exacerbate IMCL accumulation and reduce muscle strength in obese rats through hyperglycemia-induced interaction.