Slow versus fast proteins in the stimulation of beta-cell response and the activation of the entero-insular axis in type 2 diabetes

Background We tested whether ingestion of whey protein can induce greater post-prandial amino acid (AA) levels in the plasma and a higher beta-cell response than casein ingestion in type 2 diabetes mellitus patients. Methods The study was designed as a double-blind, randomized, and controlled cross-over clinical trial. Twelve post-absorptive type 2 diabetic subjects who were withdrawn from their usual hypoglycemic therapy were studied. A medium calorie (approximate to 6 kca/kg BW), high protein (approximate to 50% of total kcal) mixed meal, containing whey protein, casein, or a free amino acid (FREE AA) mixture matching the casein AA composition, was randomly administered on three different occasions. Results Following ingestion of whey protein, plasma concentrations of total, branched chain, and essential AA were 25-50% greater than after ingestion of casein (p < 0.0001), and were similar to those observed after the FREE AA meal. With whey protein, C-peptide, insulin, and pro-insulin concentrations were greater by 12-40% (p < 0.02 or less) than with casein, and similar to those with FREE AA. Glucagon-like polypeptide 1 (GLP-1) response tended to be lower with casein than with whey protein. Glucose-dependent insulinotropic polypeptide (GIP) response was greater with either whey protein or casein than with FREE AA. Post-prandial glucose concentrations were similar after whey protein and casein ingestion, but lower after the FREE AA meal. Conclusions In type 2 diabetes, the ingestion of a fast-absorbable protein results in a greater post-prandial aminoacidemia and a higher beta-cell secretion than the ingestion of a 'slow' protein. Whether these changes can be maintained chronically in combination with hypoglycemic therapy, possibly also resulting in better glycemic control, remains to be established. Copyright (c) 2006 John Wiley & Sons, Ltd.