Postprandial hyperglycaemia can lead to adverse modifications to functional proteins within the body and eventually lead to the development of type 2 diabetes. Previous research by this group has shown that an apple polyphenol extract reduced hyperglycaemia following a high-carbohydrate meal. The aim of this study is to investigate the effects of lower doses of the apple extract on postprandial glycaemia, insulinaemia and plasma gastric inhibitory polypeptide concentrations following a mixed carbohydrate test meal.
Introduction: Sharp peaks in blood glucose levels can lead to adverse modifications to functional proteins, oxidative stress and pancreatic beta cell dysfunction. It is therefore desirable to consume a diet that will allow more gradual rises in blood glucose levels after meals. Fruit polyphenols may help to limit the glucose excursion following a high carbohydrate meal. Previous research by this research group has demonstrated that 1200 mg of apple polyphenols (Appl'In™) inhibited the average incremental area under the curve (T+0 to T+30 min) of plasma glucose by 54% relative to placebo. Possible mechanisms include inhibition of intestinal enzymes and inhibition of intestinal glucose absorption by decreasing SGLT1/GLUT2 transport activity. The literature also suggests that foods rich in polyphenols exert beneficial effects on risk factors of cardiovascular disease such as hypertension, lipid metabolism and vascular function. Study design: A randomised, controlled, double-blind, cross-over study will be conducted. Four matched test drinks will be consumed in random order on separate study visits immediately before a mixed-carbohydrate test meal, containing either: 1) 1.2 g, 2) 0.9 g 3). 0.6 g of apple polyphenols, or 4). placebo. Postprandial changes in plasma glucose, insulin, NEFA, GIP, GLP-1 concentrations as well as changes in vascular function will be measured. Twenty-four hour urine samples will be collected for analysis of urinary polyphenol metabolites and glucose. In a sub sample of participants, a paracetamol absorption test will be incorporated via addition of 1.5 g paracetamol into the test drink.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
34
Drinks will be delivered in random order at 4 separate study visits immediately before a high-carbohydrate meal. Seven days wash-out period will be required between study days.
Metabolic Research Unit at King's College London
Waterloo Campus, London, United Kingdom
Postprandial Glycaemia
Primary outcome: Area over baseline t+0-30 min for plasma glucose
Time frame: 30 min following the test drink
Postprandial Insulinaemia
Peak postprandial insulin concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial Glucose-dependent Insulinotropic Polypeptide (GIP) Concentrations
Peak postprandial GIP concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial Glucagon-like Peptide-1 (GLP-1) Concentrations
Peak postprandial GLP-1 concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial C-peptide Concentrations
Peak postprandial C-peptide concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial Non-esterified Fatty Acid (NEFA) Concentrations
Peak postprandial NEFA concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
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Postprandial Triglyceride (TAG) Concentrations
Peak postprandial TAG concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial Paracetamol Concentrations
Peak postprandial paracetamol concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min (1.5 g paracetamol will be added to all test drinks in a sub-group of participants).
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Postprandial Polyphenol Metabolite Concentrations
Peak postprandial polyphenol metabolites concentrations (Cmax) t +0-30 min and change from baseline data and areas over baseline t+0-30 min and t+0-240 min.
Time frame: baseline and 10, 20, 30, 45, 60, 75, 90, 120, 150, 180, 240 min following the test drink
Vascular Endothelial Function by Flow-mediated Dilation (FMD)
Change in FMD after the consumption of test drink.
Time frame: baseline and 120, 240, 300 min following the test drink
Vascular Function (Arteriograph Measurement)
Change in augmentation index following the test drink.
Time frame: Baseline and 60, 90, 120, 180, 240 min following the test drink
Blood Pressure
Change in blood pressure following the test drink.
Time frame: Baseline and 60, 90, 120, 180, 240 min following the test drink
Urinary Polyphenol Metabolites
Change in urinary polyphenol metabolite concentration following the test drink.
Time frame: 0-4 h, 4-8 h, 8-24 h following the test drink
Urinary Glucose
Change in urinary glucose concentration following the test drink.
Time frame: 0-4 h, 4-8 h, 8-24 h following the test drink