ABSTRACT
This study evaluated the effects of an aqueous extract of Caulerpa racemosa (AEC) on cardiometabolic syndrome markers, and the modulation of the gut microbiome in mice administered a cholesterol- and fat-enriched diet (CFED). Four groups of mice received different treatments: normal diet, CFED, and CFED added with AEC extract at 65 and 130 mg/kg body weight (BW). The effective concentration (EC50) values of AEC for 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and lipase inhibition were lower than those of the controls in vitro. In the mice model, the administration of high-dose AEC showed improved lipid and blood glucose profiles and a reduction in endothelial dysfunction markers (PRMT-1 and ADMA). Furthermore, a correlation between specific gut microbiomes and biomarkers associated with cardiometabolic diseases was also observed. In vitro studies highlighted the antioxidant properties of AEC, while in vivo data demonstrated that AEC plays a role in the management of cardiometabolic syndrome via regulation of oxidative stress, inflammation, endothelial function (PRMT-1/DDAH/ADMA pathway), and gut microbiota.
Subject(s)
Caulerpa , Gastrointestinal Microbiome , Metabolic Syndrome , Plant Extracts , Animals , Mice , Arginine/metabolism , Caulerpa/chemistry , Dietary Supplements , Endothelium/metabolism , Plant Extracts/administration & dosageABSTRACT
BACKGROUND: Vitamin D has been suggested to affect peripheral insulin sensitivity. Evidence regarding the effect of vitamin D supplementation on insulin sensitivity is still conflicting. PURPOSE: This meta-analysis aimed to assess the effect of vitamin D supplementation on insulin sensitivity in humans with or at risk for insulin resistance. DATA SOURCES AND STUDY SELECTION: PubMed, Web of Science, Embase, CINAHL, and Cochrane Library were systematically searched for randomized controlled trials (RCTs) from 1980 until 31 December 2018 reporting treatment effects of vitamin D supplementation on insulin sensitivity. DATA EXTRACTION: The main outcome of interest was the change in insulin sensitivity, derived from the gold standard hyperinsulinemic-euglycemic clamp or the Matsuda index derived from the oral glucose tolerance test and insulin sensitivity index from intravenous glucose tolerance test. We extracted data on the standardized mean difference between the vitamin D treatment and placebo groups in change from baseline insulin sensitivity. DATA SYNTHESIS: Eighteen RCTs were included in this meta-analysis comparing vitamin D supplementation (n = 612) with placebo (n = 608). Vitamin D supplementation had no effect on insulin sensitivity (standardized mean difference -0.01, 95% CI -0.12, 0.10; P = 0.87, I 2 = 0%). Visual inspection of funnel plot symmetry did not suggest potential publication bias. LIMITATIONS: The number of individuals who participated in the included studies was relatively small, possibly due to the invasive character of the measurement (e.g., clamp). CONCLUSIONS: This meta-analysis provides no evidence that vitamin D supplementation has a beneficial effect on peripheral insulin sensitivity in people with or at risk for insulin resistance.
Subject(s)
Insulin Resistance , Vitamin D Deficiency/diet therapy , Vitamin D/administration & dosage , Adolescent , Adult , Aged , Dietary Supplements , Female , Glucose Tolerance Test , Humans , Insulin/metabolism , Insulin Secretion/drug effects , Insulin-Secreting Cells/drug effects , Insulin-Secreting Cells/physiology , Male , Middle Aged , Randomized Controlled Trials as Topic/statistics & numerical data , Vitamin D/pharmacology , Vitamin D Deficiency/epidemiology , Vitamin D Deficiency/metabolism , Young AdultABSTRACT
The obese insulin-resistant state is often associated with low circulating concentration of vitamin D 25-hydroxyvitamin D3 [25(OH)D3 ]. Fat sequestration of vitamin D in the expanded obese adipose tissue mass has been pointed out as a plausible explanation for this circulating vitamin D deficiency. However, the putative mechanisms behind this hypovitaminosis D remain to be elucidated. The presence of vitamin D receptor and vitamin D-metabolizing enzymes in insulin-sensitive organs suggests that vitamin D may be involved in glucose and lipid metabolism and may be related to insulin sensitivity. Indeed, mainly in vitro studies support a role of vitamin D in regulating glucose and lipid metabolism in several insulin-sensitive tissues including adipose tissue, skeletal muscle, liver, as well as pancreatic insulin secretion. A potential role of vitamin D in gut barrier function and metabolism has also been suggested. This review summarizes recent knowledge on vitamin D deficiency in the aetiology of obesity-related insulin resistance and discusses potential underlying mechanisms. Finally, the role of vitamin D supplementation on insulin sensitivity and glycaemic control is discussed.