Protein ‘pre-loads’ in type 2 diabetes: what do we know and what do we need to find out?
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KeywordsGastric emptying Glucagon-like peptide-1 Incretins Insulin Nutrition Postprandial glycaemia Whey
To the Editor: We read with interest the Short Communication from Jakubowicz et al, published recently in Diabetologia . The authors reported that acute administration of 50 g whey protein, in liquid form, 30 min before a high carbohydrate breakfast, substantially reduced postprandial glycaemia as compared with placebo in patients with type 2 diabetes, and there were concomitant increases in both glucagon-like peptide-1 (GLP-1) and insulin.
These outcomes are consistent with our study, published in 2009, involving a 55 g whey pre-load in type 2 diabetic patients, which adopted a very similar study design , and was cited by Jakubowicz and Froy in a previous review , but to our surprise, not in their paper . Moreover, we showed that the whey pre-load also slowed the emptying of the subsequent meal from the stomach, and stimulated glucose-dependent insulinotropic polypeptide (GIP) and cholecystokinin (CCK), in addition to GLP-1 and insulin. It is now appreciated that slowing gastric emptying represents an important mechanism by which dietary or pharmacological strategies can attenuate postprandial glycaemia ; this includes the ‘short-acting’ GLP-1 receptor agonists . Stimulation of both GLP-1 and CCK are likely to contribute to the slowing of gastric emptying induced by whey protein.
While the impressive effects of such a ‘pre-load’ strategy in the acute setting are now clear, it is important to refine this approach for practical long-term use. Whey protein is relatively expensive, and the cost of such a large dose taken on a regular basis would be prohibitive for many patients. Whey supplements would also incur a substantial burden in energy consumption, unless it were shown that patients compensate by adjusting their overall energy intake. Whey also has the capacity to increase glucagon , which would be counterproductive to glycaemic control. Accordingly, future studies should examine how the dose of whey could be minimised (for example, by combining a pre-load with an inhibitor of dipeptidyl peptidase 4 ) and whether the effects of whey on glycaemia are sustained with long-term use. It would also be important to refine which type 2 diabetic patients should be selected for this therapeutic strategy; probably those with a relatively low HbA1c (~7.5% [58 mmol/mol] or less) would be ideal, given that this is the group in whom postprandial glycaemia, as opposed to preprandial blood glucose, makes the predominant contribution to overall glycaemic control .
The authors’ work in this field has been funded by the National Health and Medical Research Council of Australia.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.
All authors were responsible for the conception and design of the manuscript, drafting the article and revising it critically for important intellectual content. All authors approved the version to be published.