ABSTRACT
BACKGROUND AND AIMS: Higher fiber intake is associated with increased insulin sensitivity (IS) and reduced glucose-induced insulin secretion (GIIS) during isocaloric-diets; however, its role in hypocaloric-diets is unclear. We examined whether increased fiber intake predicts the amelioration in IS and GIIS following a hypocaloric-diet. METHODS AND RESULTS: This is a post-hoc analysis of 55 adult subjects (BMI > 27 kg/m2) who completed a 6-month hypocaloric-diet (-500 kcal/day). Dietary intake was assessed using 3-day food records at baseline and post-intervention. We evaluated glucose-induced insulin and C-peptide secretions as AUC of plasma insulin and C-peptide during intravenous-glucose-tolerance tests (IVGTT) and IS via hyperinsulinemic-euglycemic clamps. Data analysis employed regression models and 2-way RM ANOVAs. Post-intervention % change in fiber intake was associated positively with ISclamp (r = 0.30) and negatively with % change in total (r = -0.37) and 2nd phase GIISIVGTT (r = -0.44) but not C-peptide secretion. It remained associated with lower 2nd phase GIISIVGTT after adjustment for sex and % changes in BMI and energy-intake, independently of other macronutrients. Subjects who increased fiber intake (to 28.7 ± 9.0 g/day) had a greater decrease in 2nd phase GIISIVGTT, not C-peptide secretion, independently of sex or changes in adiposity or energy-intake compared to subjects who decreased intake (to 20.0 ± 6.8 g/day). CONCLUSION: Higher fiber intake is an independent predictor of reduced 2nd phase glucose-induced hyperinsulinemia after a hypocaloric-diet. It was not associated with plasma C-peptide, suggesting a role in faster insulin clearance rather reduced insulin secretion. Promoting high-fiber intake may increase the effectiveness of hypocaloric-diets in preventing type 2 diabetes. REGISTRATION: ISRCTN14476404, BioMedCentral.com. CLINICAL TRIAL REGISTRATION: This trial was registered at BioMed Central as ISRCTN14476404, on July 28th, 2017.
Subject(s)
Blood Glucose/metabolism , Caloric Restriction , Dietary Fiber/administration & dosage , Hyperinsulinism/prevention & control , Insulin/blood , Obesity/diet therapy , Adiposity , Biomarkers/blood , Caloric Restriction/adverse effects , Female , Humans , Hyperinsulinism/blood , Hyperinsulinism/diagnosis , Hyperinsulinism/etiology , Male , Middle Aged , Obesity/diagnosis , Obesity/physiopathology , Time Factors , Treatment Outcome , Weight LossABSTRACT
BACKGROUND/OBJECTIVE: Plasma apoB predicts the incidence of type 2 diabetes (T2D); however, the link between apoB-linpoproteins and risks for T2D remain unclear. Insulin resistance (IR) and compensatory hyperinsulinemia characterize prediabetes, and the involvement of an activated interleukin-1 (IL-1) family, mainly IL-1ß and its receptor antagonist (IL-Ra), is well documented. ApoB-lipoproteins were reported to promote IL-1ß secretion in immune cells; however, in vivo evidence is lacking. We hypothesized that obese subjects with hyperapoB have an activated IL-1 system that explains hyperinsulinemia and IR in these subjects. SUBJECTS/METHODS: We examined 81 well-characterized normoglycemic men and postmenopausal women (⩾27 kg m(-2), 45-74 years, non-smokers, sedentary, free of chronic disease). Insulin secretion and sensitivity were measured by the gold-standard Botnia clamp, which is a combination of a 1-h intravenous glucose tolerance test (IVGTT) followed by 3-h hyperinsulinemic euglycemic clamp. RESULTS: Plasma IL-1ß was near detection limit (0.071-0.216 pg ml(-1)), while IL-1Ra accumulated at 1000-folds higher (77-1068 pg ml(-1)). Plasma apoB (0.34-1.80 g l(-1)) associated significantly with hypersinsulinemia (totalIVGTT: C-peptide r=0.27, insulin r=0.22), IR (M/I=-0.29) and plasma IL-1Ra (r=0.26) but not with IL-1ß. Plasma IL-1Ra associated with plasma IL-1ß (r=0.40), and more strongly with hyperinsulinemia and IR than apoB, while the association of plasma IL-1ß was limited to second phase and total insulin secretion (r=0.23). Adjusting the association of plasma apoB to hyperinsulinemia and IR for IL-1Ra eliminated these associations. Furthermore, despite equivalent body composition, subjects with hyperapoB (⩾80th percentile, 1.14 g l(-1)) had higher C-peptide secretion and lower insulin sensitivity than those with low plasma apoB (⩽20th percentile, 0.78 g l(-1)). Adjustment for plasma IL-1 Ra eliminated all group differences. CONCLUSION: Plasma apoB is associated with hyperinsulinemia and IR in normoglycemic obese subjects, which is eliminated upon adjustment for plasma IL-1Ra. This may implicate the IL-1 family in elevated risks for T2D in obese subjects with hyperapoB.
