Effect of combined vitamin D administration plus dietary intervention on oxidative stress markers in patients with metabolic syndrome: A pilot randomized study

Effects of vitamin D supplementation on cardiometabolic parameters among patients with metabolic syndrome: A systematic review and GRADE evidence synthesis of randomized controlled trials

Various pathophysiologic mechanisms were proposed to underlie the effect of vitamin D on MetS components. In this systematic review, we reviewed randomized control clinical trials to verify whether vitamin D supplementation (VDS) at different doses is effective concomitantly in controlling high-density lipoprotein cholesterol (HDL-c), triglycerides (TG), fasting glucose level, blood pressure, and central obesity in adults diagnosed with MetS. The following scientific databases were searched from 1998 until April 2023: EMBASE, MEDLINE (PubMed), Web of Science, Latin American and Caribbean Health Sciences Literature (Lilacs), the Cochrane Central Register of Controlled Trials, clinicaltrial.gov, and Google Scholar. No language restrictions were applied. Seven studies were included, and they showed a high level of heterogeneity. All studies reported a significant increase in serum 25(OH)D levels in the intervention groups. Of these, only two noted a significant decrease in triglyceride (TG) level and waist circumference. However, the certainty levels of the evidence rating were very low and low for triglyceride (TG) level and waist circumference, respectively, and moderate for fasting glucose level, blood pressure, and HDL-c. In conclusion, despite these benefits, considering the low certainty, the evidence does not support that VDS decreases triglyceride (TG) level and waist circumference in adults with MetS.

Insight into the Interaction Mechanism of Vitamin D against Metabolic Syndrome: A Meta-Analysis and In Silico Study

As a dietary supplement or functional food additive, vitamin D (VD) deficiency may impact extra-skeletal functions associated with metabolic syndrome (MetS) risk factors. However, the precise effects and mechanisms of VD supplementation on dyslipidemia and insulin resistance in MetS subjects remain controversial. Here, we investigate potential therapeutic targets, pathways and mechanisms of VD against MetS through a comprehensive strategy including meta-analysis, network pharmacology analysis, molecular docking, dynamics simulations, and quantum chemical calculations. Our results reveal that VD supplementation significantly reduces triglyceride levels, fasting glucose, and insulin concentrations in subjects, thereby improving insulin homeostasis to some extent. We theoretically identify 14 core MetS-associated targets. Notably, VD exhibits substantial interactions with three targets (PPARγ, FABP4, and HMGCR) in the PPAR signaling pathway, indicating that VD can modulate this pathway. Van der Waals forces predominantly stabilize the complexes formed between VD and the three targets. Nonetheless, to provide valuable insights for personalized MetS management, further research is necessary to confirm our findings, emphasizing the importance of exploring genetic variability in VD response. In conclusion, our study contributes insights into the mechanisms of VD in preventing and treating MetS through dietary supplementation, promoting the development of VD-based functional foods or nutritious diets.

Nutritional supplements improve cardiovascular risk factors in overweight and obese patients: A Bayesian network meta-analysis

Background

Overweight and obesity are considered as one of the major risk factors for cardiovascular diseases (CVD). At present, many studies have proved that multiple nutritional supplements play an active role in metabolic diseases. However, the comparative efficacy of different nutritional supplements in improving indicators of cardiometabolic risk in obese and overweight patients is uncertain.

Methods

Cochrane Library, PubMed, Embase, and Web of Science were searched for the period from January 1990 to March 2022. A random-effect model was built in the Bayesian network meta-analysis. The surface under the cumulative ranking analysis (SUCRA) and clustering rank analysis was performed for ranking the effects.

Results

The study included 65 RCTs with 4,241 patients. In terms of glucose control, probiotic was more conductive to improve FBG (MD: -0.90; 95%CrI: -1.41 to -0.38), FINS (MD: -2.05; 95%CrI: -4.27 to -0.02), HOMA-IR (MD: -2.59; 95%CI -3.42 to -1.76). Probiotic (MD: -11.15, 95%CrI -22.16 to -1.26), omega-3 (MD: -9.45; 95%CrI: -20.69 to -0.93), VD (MD: -17.86; 95%CrI: -35.53 to -0.27), and probiotic +omega-3 (MD: 5.24; 95%CrI: 0.78 to 9.63) were beneficial to the improvement of TGs, TC and HDL-C, respectively. The SUCRA revealed that probiotic might be the best intervention to reduce FBG, FINS, HOMA-IR; Simultaneously, α-lipoic acid, VD, and probiotic + omega-3 might be the best intervention to improve TGs, TC, and HDL-C, respectively. Cluster-rank results revealed probiotic had the best comprehensive improvement effect on glucose metabolism, and probiotic + omega-3 may have a better comprehensive improvement effect on lipid metabolism (cluster-rank value for FBG and FINS: 3290.50 and for TGs and HDL-C: 2117.61).

Conclusion

Nutritional supplementation is effective on CVD risk factors in overweight and obese patients. Probiotic supplementation might be the best intervention for blood glucose control; VD, probiotic + omega-3 have a better impact on improving lipid metabolism. Further studies are required to verify the current findings.

The impacts of vitamin D supplementation in adults with metabolic syndrome: A systematic review and meta-analysis of randomized controlled trials

Background: Studies have shown the association of vitamin D status with the development of metabolic syndrome (MetS), which has attracted an extensive research interest with inconsistent results. Therefore, we hypothesized that vitamin D supplementation (VDS) will benefit adults with MetS.

Aims: To test our hypothesis, we performed a meta-analysis to evaluate the effect of VDS on MetS in adults using relevant biomarkers such as anthropometric parameters, blood pressure, blood lipid profile, glycemia, oxidative stress and vitamin D toxicity (VDT).

Methods: Randomized controlled trials published in PubMed, Web of Science, embase and the Cochrane Library between 2012 and 2022 on the effect of VDS on MetS in adults were searched. The language was limited to English. A meta-analysis performed using RevMan 5.4 and Stata 14.0 software, sensitivity analysis, and evaluation of the risk of bias and general quality of the resulting evidence were conducted.

Results: Eventually, 13 articles were included in this meta-analysis. Overall, VDS significantly increased the endline serum 25-hydroxyvitamin D levels as compared to the control [MD:17.41, 95% CI (14.09, 20.73), p < 0.00001]. VDS did not affect waist circumference, body mass index, body fat percentage and VDT biomarkers, but decreased waist-to-hip ratio and blood pressure (p < 0.01). VDS significantly decreased fasting plasma glucose (FPG) [MD: 3.78; 95% CI (−6.52, −1.03), p = 0.007], but did not affect the levels of blood high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglyceride (TG). Pooled estimate of nine papers indicated a significant reduction of fasting insulin (FI) (p = 0.006), and homeostasis model assessment of insulin resistance (p = 0.0001). The quantitative insulin check index levels were moderately increased (p = 0.007) without any impact on the glycosylated hemoglobin type A1C (HbA1c). For the oxidative stress parameters, VDS significantly lowered the levels of malondialdehyde and hypersensitive C-reactive protein (p < 0.05).

Conclusion: Results of this meta-analysis demonstrate that VDS only reduces insulin resistance and hypertension but not the blood lipid profile and HbA1c. It appears that the evidence for the benefit of VDS in adults with MetS is inconclusive. Further clinical studies are still needed.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

Effect of Vitamin D on Paraxonase-1, Total Antioxidant Capacity, and 8-Isoprostan in Children with Attention Deficit Hyperactivity Disorder

METHOD

In this double-blind, randomized, placebo-controlled trial, 75 children (aged 6-12) diagnosed with ADHD were randomly assigned into two groups. The supplementation group received vitamin D3 (2000 IU), and the control group received a placebo for 3 months. Blood samples were collected at baseline and after intervention to analyze the 25(OH)D, paraxonase-1 activity (PON-1), Total Antioxidant Capacity (TAC), and 8-isoprostan levels.

RESULTS

A significant rise in circulating 25(OH)D was observed in the vitamin D group versus the placebo group at the end of the study. There was no reduction in 8-isoprostan levels in the vitamin D group compared to the placebo group. Serum paraxonase-1 and TAC concentration decreased in both groups, but these alterations were not statistically significant in the treatment group versus the placebo group at the end of the intervention.

CONCLUSION

Vitamin D supplementation for 3 months did not have beneficial effects on biomarkers of oxidative stress status. To confirm these findings, further studies on children are suggested.

Circulating serum vitamin D levels in relation to metabolic syndrome in children: A systematic review and dose-response meta-analysis of epidemiologic studies

Findings from epidemiologic studies that evaluated the relationship between serum vitamin D levels and metabolic syndrome (MetS) in children were contradictory. We conducted a systematic review and meta-analysis on the relation of serum 25(OH)D levels and MetS in children. A comprehensive search was conducted in electronic databases, up to November 2020. Eleven cross-sectional studies that reported the link between circulating vitamin D levels and MetS in children were included in the analysis. Combining 11 effect sizes from 11 cross-sectional studies with 22,196 participants revealed that highest versus lowest serum vitamin D concentration was significantly associated with a 50% reduced odds of MetS in children (OR: 0.50; 95%CI: 0.39, 0.64). Subgroup analysis by study location revealed decreased odds of MetS in both non-Asian (OR: 0.45; 95%CI: 0.33, 0.63) and Asian countries (OR: 0.54; 95%CI: 0.39, 0.76) with no heterogeneity in these subgroups. When we confined the studies to those with representative populations (n = 21,611), a significant inverse association was found between highest versus lowest circulating vitamin D level and MetS (OR: 0.55; 95%CI: 0.42, 0.71). Dose-response analysis showed that each 10 ng/ml (or 25 nmol/L) in serum vitamin D was linearly related to a 12% reduced odds of MetS (OR: 0.88; 95%CI: 0.78, 0.99) in children. A nonlinear association was also detected between serum 25(OH)D and MetS. This meta-analysis revealed that circulating vitamin D concentration was inversely associated with odds of MetS in children, in a dose-response fashion. The same finding was found in the studies with representative populations.

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

BACKGROUND

Metabolic syndrome (MetS) increases the risk of cardiovascular disease, with atherogenic dyslipidemia being a major contributing factor.

METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to assess whether vitamin D supplementation (VDS) alleviates dyslipidemia in adults with MetS. Scientific databases (PUBMED, MEDLINE, CINAHL, EMBASE, Cochrane Library, ClinicalTrials.gov, International Clinical Trials Registry Platform) and the gray literature were searched for randomized controlled trials of VDS, reporting on blood lipids. A narrative review, meta-analyses, sensitivity analyses, and appraisal of the risk of bias and overall quality of evidence produced were conducted.

RESULTS

Seven studies were included, and four were meta-analyzed. The risk of bias was generally low, and the final quality of evidence was low or very low. VDS, whether in high or low dose, significantly increased endline vitamin D blood levels; did not affect total, low-density, high-density cholesterol levels, and novel lipid-related biomarkers; yet, significantly increased triglycerides (TG) levels compared with placebo (MD: 30.67 (95%CI: 4.89-56.45) mg/dL; p = 0.02 for low-dose VDS; and MD: 27.33 (95%CI: 2.06-52.59) mg/dL; p = 0.03 for high-dose VDS). Pertaining heterogeneity was high (I² = 86%; and I² = 51%, respectively), and some included studies had significantly higher baseline TG in the intervention arm. The sensitivity analyses revealed robust results.

CONCLUSION

VDS seems not to affect blood lipids in adults with MetS.

Relationship of oxidative stress to visceral adiposity in youth and role played by vitamin D

BACKGROUND

Visceral adipose tissue (VAT) accumulation is a major cardiometabolic risk factor, associated with increased inflammation. Oxidative stress (OS) is also associated with inflammation and cardiometabolic issues, yet mainly through general obesity. Both OS and obesity were linked to vitamin D deficiency.

OBJECTIVES

To investigate whether OS increase is associated with VAT accumulation in youth, and whether in the presence of VAT accumulation, a higher vitamin D status is associated with lower OS.

METHODS

One hundred and fifty-eight youth with overweight/obesity, 7 to 17 years old, were recruited (Pediatric Clinic, Luxembourg). We assessed visceral and subcutaneous abdominal adipose tissues by magnetic resonance imaging, OS by DNA/RNA oxidative damage with ELISA and vitamin D by high-performance liquid chromatography.

RESULTS

VAT was the body fat compartment the most strongly associated with OS (R_Pearson : 0.298; P < 10^-4 ). The general linear (GLM) models assessing the relationship between OS, VAT and vitamin D concentrations showed that "Log₁₀ OS = (0.003 × VAT) + 3.911 (R²_adjusted : 0.083; P-value < 10^-4 )"; "Log₁₀ OS = (0.003 × VAT) - (0.156 × log₁₀ vitamin D) + 4.110 (R²_adjusted : 0.101; P-value < 10^-4 )". After back-transformation of the log-values into normal values, the GLM showed that, for a person with an average value of VAT (40.7 cm² ), a 10 cm² increase in VAT would increase OS by approx. 771.833 pg/mL, after age, gender, Tanner stage and physical activity adjustment. An approximate increase of 9 ng/mL of vitamin D would counterbalance this negative effect of increased VAT.

CONCLUSION

Dietary strategies improving vitamin D status should be investigated to tackle VAT and OS increase.