Effects of vitamin D supplementation on fasting glucose, dyslipidemia, blood pressure, and abdominal obesity among patients with metabolic syndrome: a protocol for systematic review and meta-analysis of randomized controlled trials

Abstract

Background Vitamin D deficiency can play a role in extraskeletal functions that are involved with a set of risk factors associated with metabolic syndrome (MetS). The purpose of this review is to investigate the impact of vitamin D supplementation on fasting glucose, dyslipidemia, blood pressure, and abdominal obesity among patients with MetS. Methods EMBASE, Medline, Web of Science, Lilacs, the Cochrane Central Register of Controlled Trials, clinicaltrials.gov databases, and grey literature will be systematically searched for randomized controlled trials (RCTs) of vitamin D supplementation compared with placebo, through December 2020. We will include in the study patients with MetS diagnosed by the criteria set forth by the National Cholesterol Education Program Adult Treatment Panel III or the International Diabetes Federation. The effect of oral vitamin D supplementation on lipid profile improvement (triglycerides, high-density lipoprotein cholesterol—HDL-C) is this review’s primary outcome. The systematic review will be performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The study screening, data extraction, and quality assessment will be fulfilled by two independent reviewers according to the Cochrane Risk of Bias tool (RoB 2.0). The results of the systematic review will be provided according to the type of intervention, characteristics of the target population, the methods of measurement of vitamin D, the calculated vitamin D concentrations, types of biological samples, and types of outcomes. Meta-analyses will be conducted where appropriate. The Cochran’s Q test and the I 2 -heterogeneity test will be used to assess the presence of heterogeneity and whether the fixed or the random-effects model would be appropriate for combining study results using the inverse variance method or the DerSimonian-Lair method, respectively. Publication bias will be evaluated using funnel plots and Egger’s and Begg’s tests. The strength of the evidence will be assessed according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Discussion This systematic review will assess the effects of vitamin D supplementation on fasting glucose and triglyceride levels, waist circumference and mean blood pressure, and HDL-C among individuals with MetS. These findings may assist with decision-making within a clinical setting. Systematic review registration PROSPERO registration number CRD42019123212

Effects of Vitamin D Supplementation on Lipid Profile in Adults with the Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

“…Accordingly, correcting vitamin D deficiency through VDS was suggested to alleviate MetS, specifically the atherogenic dyslipidemia component of this syndrome [11]. This topic is gaining attention in the research world and is of clinical relevance [41].…”

Unravelling the relationship between serum 25-hydroxyvitamin D levels and trabecular bone score in U.S. adults

“…A recently developed analytical tool, TBS, has rarely been used in the assessment and management of the impact of serum 25(OH)D levels on bone microarchitecture. In studies of adult individuals, the preservation of bone mass and microarchitecture at the spine has been reported with combined calcium and vitamin D supplementation [19]; however, correction of vitamin D insufficiency (reference range, ≥30 ng/mL) in postmenopausal women showed no clinically meaningful beneficial effects on BMD [20]. One study reported that TBS did not differ by vitamin D level in patients with primary hyperparathyroidism (reference range, 14 to 65 pg/ml) [21].…”

Relationships among Vitamin D Insufficiency, Health belief, Quality of Life and Metabolic Syndrome in Northeastern Taiwanese Adults: A Cross-sectional Community-based Cohort Study

“…The VDI is associated with several components of MetS [10]. The inverse correlation between Vitamin D concentration and the development of MetS could be explained by the dependence of insulin production in pancreatic β cells on Vitamin D and its receptor interaction [11], obesity resulting in more sequestration of vitamin D in adipose tissue, and greater volumetric dilution of serum 25(OH)D level, less sun exposure, poor dietary habits, and varied genetic expression of enzymes involving vitamin D metabolism [17,42].…”

“…Vitamin D levels are also in uenced by age, sex, smoking, sedentary lifestyle, poor dietary habits, sun exposure, sun-protective behavior, latitude of residence, differences in gene expression of vitamin D-metabolizing enzymes, and impaired hepatic 25-hydroxylation [5][6][7][8]. Decreased 25(OH)D levels are closely associated with a variety of illnesses including bone metabolic disorders, tumors, cardiovascular diseases, diabetes mellitus, arterial hypertension, heart failure, peripheral arterial disease, acute myocardial infarction, various types of cancers, autoimmune and in ammatory diseases, decreased immune defenses and increased mortality [9,10]. The vitamin D receptor was found in β cells in the pancreas, adipose, and musculoskeletal tissues and vitamin D inadequacy could compromise the capacity of β cells to convert pro-insulin into insulin [4].…”