Primary supervisor: Dr Carl Hulston, University of Birmingham

Non-academic partner: Dr Mads Sørensen Larsen, Arla Foods

Project description

Aim

To determine the effectiveness of micellar casein isolate in enhancing postprandial glycaemic control and to identify the underlying mechanisms

Background

An interest in the role of milk proteins in the management of obesity and the metabolic syndrome stems from the association between high dairy consumption and lower body mass. Additionally, experimental trials have shown that milk proteins can improve blood glucose responses and reduce short-term food intake when consumed before/with carbohydrate-rich foods. Milk contains two types of proteins, namely whey and casein (~20% and 80% of total protein content, respectively). Whey protein is characterised as a rapidly digestible protein, with ingestion resulting in a fast but transient postprandial increase in plasma amino acids. In contrast, casein coagulates in the acidic environment of the stomach, which leads to a moderate but more prolonged increase in postprandial amino acids. Research has predominantly focused on whey protein as it is a readily available by-product of cheese making. Acute studies have shown that pre-meal ingestion of whey protein can reduce blood glucose excursions, with the effect being mediated by an enhanced insulin (and incretin) response. Although promising, there is concern that elevated nutrient signalling towards greater insulin secretion could accelerate pancreatic fatigue and failure, potentially worsening glucose tolerance in the long-term. An alternative approach could be to use the slow digestion properties of casein to help manage postprandial glycaemia. Casein has received less research attention, but our recent unpublished data show that micellar casein isolate is just as effective as whey protein at reducing postprandial glycaemia. Moreover, this effect occurred with insulin concentrations approximately half that of an energy-matched whey protein condition, suggesting an alternative mechanism of action (likely reduced glucose absorption). Enhanced glycaemic control alongside more modest insulin secretion represents a healthier metabolic response to feeding. Thus, casein supplementation may have utility in the management of obesity and type 2 diabetes.

Project summary

Metabolic studies will be performed in overweight participants (males and females) as these individuals are at increased risk of developing insulin resistance and type 2 diabetes. Initial studies will optimise the dose/timing of casein ingestion. Later studies will employ dual stable isotope tracer methodology (U-13C-labelled glucose ingestion, 2H2 glucose infusion) to quantify specific components of postprandial glucose flux (i.e., glucose appearance from the gut, endogenous glucose production, and whole-body glucose disposal), thereby determining the mechanism of enhanced glycaemic control. These sophisticated tracer methods are possible in few laboratories worldwide.

Candidates are encouraged to contact Dr Carl Hulston to discuss the project before applying if they wish to.