Dietetics, Nutrition and Biological Sciences
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Item Effects of oat β-glucan consumption at breakfast on ad libitum eating, appetite, glycemia, insulinemia and GLP-1 concentrations in healthy subjects.(2018-06-18) Zaremba, Suzanne; Gow, Iain F.; Drummond, Sandra; McCluskey, Jane T.; Steinert, Robert E.There is evidence that oat β-glucan lowers appetite and ad libitum eating; however, not all studies are consistent, and the underpinning mechanisms are not entirely understood. We investigated the effects of 4 g high molecular weight (MW) oat β-glucan on ad libitum eating, subjective appetite, glycemia, insulinemia and plasma GLP-1 responses in 33 normal-weight subjects (22 female/11 male, mean age (y): 26.9 ± 1.0, BMI (kg/m ): 23.5 ± 0.4). The study followed a randomised double-blind, cross-over design with subjects fed two test breakfasts with and without oat β-glucan followed by an ad libitum test meal on two different days. Blood samples and ratings for subjective appetite were collected postprandially at regular time intervals. Oat β-glucan increased feelings of fullness (p = 0.048) and satiety (p = 0.034), but did not affect energy and amount eaten at the ad libitum test meal. There was a treatment by time interaction for plasma GLP-1, plasma insulin and blood glucose. GLP-1 was significantly reduced at 90 min (p = 0.021), blood glucose at 30 min (p = 0.008) and plasma insulin at 30 and 60 min (p = 0.002 and 0.017, respectively) following the oat β-glucan breakfast when compared with the control breakfast. Four grams of high MW oat β-glucan lowers appetite but not ad libitum eating and beneficially modulates postprandial glycaemia, it does however, not increase plasma GLP-1 secretion. [Abstract copyright: Copyright © 2018 Elsevier Ltd. All rights reserved.]Item Infusion of Mg in Humans Acutely Reduces Serum Insulin Levels: a Pilot Study(John Libbey Eurotext, 2011-12) Gow, Iain F.; O'Donnell, M.; O'Donnell, L.; Flapan, A.Background: infusion of Mg for therapeutic purposes is still a matter for debate. Dosages vary considerably, yet subclinical effects on normal physiology are largely ignored. In human and animal models, interactions between Mg and insulin exist, thus we have investigated the effect of infusing Mg on serum insulin, ionised Mg (Mg2+) and Ca (Ca2+) and plasma glucose in human volunteers. Methods: six male volunteers were infused with magnesium sulphate (MgSO4) dissolved in normal saline, using a high-dose loading- bolus, followed by a lower-level maintenance- period. Findings: serum Mg2+ rose rapidly throughout the bolus infusion, declined during the maintenance phase, but remained higher than pre-infusion levels throughout the experimental period; serum Ca2+ rose when serum Mg2+ was highest. Infusion of MgSO4 had no effect on heart rate or blood pressure, but caused a rapid, pronounced drop in circulating fasting insulin (p < 0.0005), which slowly recovered to basal values during the course of the maintenance infusion. A slight, transient rise in plasma glucose (p < 0.05) concomitant with the decline in serum insulin was also observed. Interpretation: it is possible that the effect of Mg2+ on insulin may have been due to antagonism of Ca2+ entry in pancreatic beta-cells, the insulin decline causing a subsequent rise in circulating glucose levels. We suggest that these effects of MgSO4 infusions should be considered where the aim is to achieve high doses of blood Mg2+ levels by clinical intervention.