Whey Protein Effect on Glycaemic and Appetite Responses in T2D

The current study will investigate the effect if whey protein on postprandial glycaemia and appetite in type II diabetics, assessing incretin (GLP-1, GIP), insulin, and appetite control (leptin, PYY3-36) hormone responses.

Whey protein accounts of ~20% of whole milk protein. Ingestion of whey protein at meal times generates insulinotrophic/β-cell stimulation via amino acid absorption and the bioactive peptides generated during gastrointestinal digestion, resulting in attenuation of postprandial blood glucose. The bioactive peptides stimulate the release of incretin hormone, GLP-1, and inhibit DPP-IV activity potentially decreasing the rate of GLP-1 degradation. The current study will employ a randomised, double-blind, counter-balanced, cross-over design, whereby participants will each complete three trials; a) whey protein, b) hydrolysed protein, and c) placebo intervention. Hydrolysed protein provides amino acid content, without bioactive peptides associated with incretin release, therefore, demonstrating insulinotrophic properties, only. Many studies within the literature are limited for practical reasons, such as investigating high dosages (30-50 g) of whey protein, or high glycaemic index meal types which would be unlikely to form part of habitual dietary activity of type II diabetics. Therefore, the current study will objectively measure postprandial glycaemic and appetite responses following the ingestion of whey/hydrolysed protein, whilst ensuring ecological validity, dosages (18 g) and test meals applicable to everyday life, and true clinical utility for managing type-II diabetes by integrating interventions into the habitual lives of type-II diabetic individuals.

Capillary glucose concentrations are monitored for 6 hours/wk following breakfast (09:00-12:00) and lunch (12:15-15:15).

PYY3-36 will be measured from blood collection tubes containing EDTA, aprotinin, and DPPIV inhibitor.

Insulin will be measured from blood collection tubes containing EDTA, aprotinin, and DPPIV inhibitor.

Visual Analogue Scales (VAS) will be used to assess self reported feelings of appetite sensations (i.e. hunger, satiety, prospective food intake).

Interstitial glucose is measured from 36 h prior to the trial, until 24 h following the trial, each week for three weeks.

Inclusion Criteria: Type II diabetic males aged 18-65 years old. Treated with metformin, or diet and lifestyle modification, only. BMI < 40 kg/m2. Stable physical activity pattern during the three months immediately preceding study. Exclusion Criteria: Not treated with insulin. No metabolic disease other than diabetes.

King DG, Walker M, Campbell MD, Breen L, Stevenson EJ, West DJ. A small dose of whey protein co-ingested with mixed-macronutrient breakfast and lunch meals improves postprandial glycemia and suppresses appetite in men with type 2 diabetes: a randomized controlled trial. Am J Clin Nutr. 2018 Apr 1;107(4):550-557. doi: 10.1093/ajcn/nqy019.