Abstract
PurposeElevated postprandial glycaemia [PPG] increases the risk of cardiometabolic complications in insulin-resistant, centrally obese individuals. Therefore, strategies that improve PPG are of importance for this population. Consuming large doses of whey protein [WP] before meals reduces PPG by delaying gastric emptying and stimulating the secretion of the incretin peptides, glucose-dependent insulinotropic polypeptide [GIP] and glucagon-like peptide 1 [GLP-1]. It is unclear if these effects are observed after smaller amounts of WP and what impact central adiposity has on these gastrointestinal processes.MethodsIn a randomised-crossover design, 12 lean and 12 centrally obese adult males performed two 240 min mixed-meal tests, ~5–10 d apart. After an overnight fast, participants consumed a novel, ready-to-drink WP shot (15 g) or volume-matched water (100 ml; PLA) 10 min before a mixed-nutrient meal. Gastric emptying was estimated by oral acetaminophen absorbance. Interval blood samples were collected to measure glucose, insulin, GIP, GLP-1, and acetaminophen.ResultsWP reduced PPG area under the curve [AUC0–60] by 13 and 18.2% in the centrally obese and lean cohorts, respectively (both p <0.001). In both groups, the reduction in PPG was accompanied by a two-three-fold increase in GLP-1 and delayed gastric emptying. Despite similar GLP-1 responses during PLA, GLP-1 secretion during the WP trial was ~27% lower in centrally obese individuals compared to lean (p = 0.001). In lean participants, WP increased the GLP-1ACTIVE/TOTAL ratio comparative to PLA (p = 0.004), indicative of reduced GLP-1 degradation. Conversely, no treatment effects for GLP-1ACTIVE/TOTAL were seen in obese subjects.ConclusionPre-meal ingestion of a novel, ready-to-drink WP shot containing just 15 g of dietary protein reduced PPG in lean and centrally obese males. However, an attenuated GLP-1 response to mealtime WP and increased incretin degradation might impact the efficacy of nutritional strategies utilising the actions of GLP-1 to regulate PPG in centrally obese populations. Whether these defects are caused by an individual’s insulin resistance, their obese state, or other obesity-related ailments needs further investigation.Clinical Trial RegistrationISRCTN.com, identifier [ISRCTN95281775]. https://www.isrctn.com/.
Highlights
The prevalence of obesity is increasing globally, which poses a significant challenge to health care systems
Fat distribution is a critical determinant of insulin sensitivity [4], when fat is stored around visceral areas [5,6,7], which is associated with hepatic insulin resistance, dyslipidaemia and impairments in insulin-mediated peripheral glucose disposal [8]
In the years that precede the transition from normal glucose tolerance [NGT] to type 2 diabetes (T2D), a progressive decline in both insulin’s action and its secretion occurs augmenting a steady decline in glucose tolerance [9]
Summary
The prevalence of obesity is increasing globally, which poses a significant challenge to health care systems. Obesity is a welldefined risk factor for the development of cardio-metabolic complications such as cardiovascular disease [CVD] and type 2 diabetes [T2D] [1, 2]. Obesity increases the risk of T2D six-fold, irrespective of genetic risk [3]. Not all obese individuals develop T2D or display dysglycaemia. For individuals who develop T2D, evidence suggests that it is the deterioration in postprandial glycaemia [PPG], rather than fasting glycaemia, that precedes the decline to overt dysglycaemia [10]. PPG excursions have been shown to independently predict future cardiovascular morbidity and mortality even when fasting blood glucose concentrations or HbA1c are normalised [11,12,13]. Approaches to minimising PPG are of importance for both patient and nonpatient populations
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