A Single-Dose of a Polyphenol-Rich Fucus Vesiculosus Extract is Insufficient to Blunt the Elevated Postprandial Blood Glucose Responses Exhibited by Healthy Adults in the Evening: A Randomised Crossover Trial.

Margaret Murray,Lisa Ryan,Maxine Bonham,Aimee Dordevic

doi:10.3390/antiox8020049

Margaret Murray, Lisa Ryan + Show 2 more

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https://doi.org/10.3390/antiox8020049

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Abstract

When healthy adults consume carbohydrates at night, postprandial blood glucose responses are elevated and prolonged compared to daytime.Extended postprandial hyperglycaemia is a risk factor for type 2 diabetes. Polyphenols are bioactive secondary metabolites of plants and algae with potential to moderate postprandial glycaemia. This study investigated whether a polyphenol-rich alga (Fucus vesiculosus) extract moderated postprandial glycaemia in the evening in healthy adults. In a double blind, placebo-controlled, randomised three-way crossover trial, 18 participants consumed a polyphenol-rich extract, a cellulose placebo and rice flour placebo (7:15 p.m.) prior to 50 g available carbohydrate from bread (7:45 p.m.), followed by three hours of blood sampling to assess glucose and insulin. A subset of participants (n = 8) completed the same protocol once in the morning with only the cellulose placebo (7:15 a.m.). No effect of the polyphenol-rich extract was observed on postprandial glycaemia in the evening, compared with placebos, in the group as a whole. However, in females only, peak blood glucose concentration was reduced following the polyphenol-rich extract. In the subset analysis, as expected, participants exhibited elevated postprandial blood glucose in the evening compared with the morning following the cellulose placebo. This was the first study to investigate whether a polyphenol intervention moderated evening postprandial hyperglycaemia. The lowering effect observed in females suggests that this warrants further investigation.

Highlights

Postprandial hyperglycaemia is characteristic of type 2 diabetes mellitus (T2DM), it is often present prior to clinical diagnosis and this is known as impaired glucose tolerance (IGT) or pre-diabetes [1,2]
While it is well understood that insulin sensitivity decreases throughout the day and into the evening [25,55,56], these findings suggest that this may be exaggerated among Asian individuals, resulting in highly elevated postprandial insulin responses and 2-h glucose concentrations within the range for IGT in the evening among healthy individuals
In line with the literature, an elevated postprandial blood glucose response was observed in healthy individuals when carbohydrates were consumed in the evening compared with the morning

Summary

Introduction

Postprandial hyperglycaemia is characteristic of type 2 diabetes mellitus (T2DM), it is often present prior to clinical diagnosis and this is known as impaired glucose tolerance (IGT) or pre-diabetes [1,2]. Marine algae contain bioactive polyphenolic molecules with capacity to moderate postprandial hyperglycaemia, including phlorotannins, which are unique to marine algae [4]. Antioxidants 2019, 8, 49 α-glucosidase, as demonstrated in chemical assay [4] and the alteration of hepatic enzyme (inhibiting glucose-6-phosphatase and phosphoenolpyruvate carboxykinase) to promote glycogen production and the removal of glucose from the blood, as demonstrated in a diabetic mouse model [7]. Marine algal polyphenols (MAPs) have been shown to upregulate phosphorylation of AMPK (adenosine monophosphate-activated protein kinase), ACC (acetyl-CoA carboxylase) and Akt (a serine/threonine protein kinase) in diabetic mouse and rat models to increase the number of GLUT4 (glucose transporter 4) transporters at the cell membrane and increase glucose uptake at a cellular level [8,9]

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