Comparison of Different Sources and Degrees of Hydrolysis of Dietary Protein: Effect on Plasma Amino Acids, Dipeptides, and Insulin Responses in Human Subjects

Abstract

The effect of protein fractionation on the bioavailability of amino acids and peptides and insulin response and whether the protein source influences these effects in humans are poorly understood. This study compared the effects of different sources and degrees of hydrolysis of dietary protein, independent of carbohydrate, on plasma amino acid and dipeptide levels and insulin responses in humans. Ten subjects were enrolled in the study, with five subjects participating in trials on either soy or whey protein and their hydrolysates. Protein hydrolysates were absorbed more rapidly as plasma amino acids compared to nonhydrolyzed protein. Whey protein also caused more rapid increases in indispensable amino acid and branched-chain amino acid concentrations than soy protein. In addition, protein hydrolysates caused significant increases in Val-Leu and Ile-Leu concentrations compared to nonhydrolyzed protein. Whey protein hydrolysates also induced significantly greater stimulation of insulin release than the other proteins. Taken together, these results demonstrate whey protein hydrolysates cause significantly greater increases in the plasma concentrations of amino acids, dipeptides, and insulin.

Tryptophan-containing milk protein-derived dipeptides inhibit xanthine oxidase

“…In addition, side effects associated with drugs such as Allopurinol should not occur with food-derived protein hydrolyzates. It has been demonstrated that protein breakdown following enzyme hydrolysis results in a greater increase in plasma amino acids and di-peptides compared to unhydrolyzed proteins in vivo [61,88]. In addition, amino acid uptake decreases with hydrolyzates containing higher peptide chain length [30].…”

“…These include the management of cardiovascular disease with angiotensin converting enzyme (ACE) inhibitory, antithrombotic, anti-inflammatory, mineral binding and 4 anti-oxidant peptide activities [6,12,23,49]. Milk proteins, peptide sequences encrypted within the primary structures of the milk proteins and amino acids have also been associated with the regulation of postprandial glycaemia and insulin secretion in normoglycaemic and type 2 diabetic subjects [24,26,56,57,61,72]. Different studies have demonstrated the anti-oxidative role of milk proteins and peptides [19,53,70,75,83].…”

Can milk proteins be a useful tool in the management of cardiometabolic health? An updated review of human intervention trials

“…Milk proteins have been extensively investigated for their insulinotropic and glucose-lowering effects in healthy subjects (73,75,82,83,(90)(91)(92)(93)(94)(95)(96)(97)(98)(99) and to a limited extent in individuals with suboptimal glucose control (100)(101)(102)(103)(104)(105)(106) . The dose varied significantly between studies from as little as 10 g (92,105,106) -51 g (91) .…”

Protein hydrolysates and tissue repair

“…It is generally accepted that protein hydrolysates are absorbed faster and utilised more effectively than intact proteins (6,7,9,10,36 -38) . A number of studies have shown that the same N load is absorbed faster when delivered as hydrolysed protein, or di-and tri-peptides rather than as whole protein or free amino acids (37 -39) and this results in significantly greater increases in plasma concentrations of amino acids and dipeptides (39) . These greater increases in absorption and appearance of amino acids in plasma have also been associated with greater incorporation of N into protein, with a number of studies demonstrating greater N incorporation into tissue protein in animals fed hydrolysed whey peptides compared with intact protein (10,40) .…”