Beneficial effects of collagen peptide ingestion to reduce serum triacylglycerides have been reported, suggesting that the physiological conditions of adipocytes are modulated following collagen peptide ingestion. In this study, the effects of prolylhydroxyproline, a major digestive product of ingested collagen peptide in the blood, on the differentiation of mouse 3T3-L1 preadipocytes in vitro were investigated. 3T3-L1 preadipocytes were induced to differentiate to adipocytes and treated with

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... olylhydroxyproline, or with an amino acid mixture of proline and hydroxyproline as a control. The amount of lipid was not affected by these treatments. However, the size of the lipid droplet was significantly smaller when treated with prolylhydroxyproline compared to the amino acid mixture or the non-treated control. Proton-coupled oligopeptide transporters were expressed in non-differentiated and/or differentiated 3T3-L1 cells. These results suggest that prolylhydroxyproline might modulate the morphology of lipid droplets by incorporation into adipocytes through the transporters.