Role of Bioactive Peptide Sequences in the Potential Impact of Dairy Protein Intake on Metabolic Health

For years, there has been an increasing move towards elucidating the complexities of how food can interplay with the signalling networks underlying energy homeostasis and glycaemic control. Dairy foods can be regarded as the greatest source of proteins and peptides with various health benefits and are a well-recognized source of bioactive compounds. A number of dairy protein-derived peptide sequences with the ability to modulate functions related to the control of food intake, body weight gain and glucose homeostasis have been isolated and characterized. Their being active in vivo may be questionable mainly due to expected low bioavailability after ingestion, and hence their real contribution to the metabolic impact of dairy protein intake needs to be discussed. Some reports suggest that the differential effects of dairy proteins-in particular whey proteins-on mechanisms underlying energy balance and glucose-homeostasis may be attributed to their unique amino acid composition and hence the release of free amino acid mixtures enriched in essential amino acids (i.e., branched-chain-amino acids) upon digestion. Actually, the research reports reviewed in this article suggest that, among a number of dairy protein-derived peptides isolated and characterized as bioactive compounds in vitro, some peptides can be active in vivo post-oral administration through a local action in the gut, or, alternatively, a systemic action on specific molecular targets after entering the systemic circulation. Moreover, these studies highlight the importance of the enteroendocrine system in the cross talk between food proteins and the neuroendocrine network regulating energy balance.