Supplementary Material for: Skeletal Muscle Gene Expression Profile Is Modified by Dietary Protein Source and Calcium during Energy Restriction

Background/Aims: The potential of whey protein and calcium to modify skeletal muscle gene expression during energy restriction (ER) was investigated in a model of diet-induced obesity. Methods: Obese C57BL/6J mice received casein (calcium 0.4%) and two different high-calcium (1.8%) whey protein-based [whey protein isolate (WPI) + Ca and α-lactalbumin + Ca] diets for ER. Results: Compared to casein, WPI and α-lactalbumin-based diets altered 208 and 287 genes, respectively, of which 186 genes were common to WPI and α-lactalbumin diets. These genes represented 31 KEGG pathways. The Wnt signaling was the most enriched pathway among the 101 genes regulated by α-lactalbumin only, whereas the 22 genes regulated by WPI only were not associated with KEGG pathways. Unlike casein, WPI and α-lactalbumin diets decreased Aldh1a7, Fasn, leptin, Nr4a3 and Scd1 mRNA expression, indicating dietary protein source-dependent alterations in muscle lipid and fatty acid metabolism. Muscle weight or lean body mass maintenance did not differ between groups although modest changes in hypertrophy/atrophy signaling were found. Conclusion: The skeletal muscle gene expression profile is modified by the dietary protein source and calcium during ER which may explain, at least in part, the greater anti-obesity effect of whey proteins and calcium compared to casein.