Mechanistic Effects of Vitamin D Supplementation on Metabolic Syndrome Components in Patients with or without Vitamin D Deficiency

Relationship between Circulating 25-Hydroxyvitamin D and Metabolic Syndrome in Chinese Adults: A Large Nationwide Longitudinal Study

OBJECTIVE

This study investigated the association of circulating levels of 25-hydroxyvitamin D (25[OH]D) with the risk of metabolic syndrome (MetS) and its components in adults.

METHODS

This nationwide cohort involved 23,810 Chinese adults attending annual health evaluations. Serum 25(OH)D levels, MetS status, and covariates were determined at each examination. Among them, 8146, 3310, and 1971 completed two, three, and more than three evaluations, respectively. A hybrid mixed-effects and Cox regression model was employed to determine the cross-sectional and longitudinal relationships.

RESULTS

The odds ratios (ORs) and 95% confidence intervals (CIs) of MetS were significantly lower in individuals within quartile 4 (vs. 1) of serum 25(OH)D for both between-individual (0.43 [0.35, 0.52]) and within-individual comparisons (0.60 [0.50, 0.73]), respectively (all p-trends < 0.001). Among the MetS components, the corresponding ORs (95% CI) in between- and within-individual comparisons were 0.40 (0.29, 0.54) and 0.26 (0.19, 0.36) for abdominal obesity, 0.49 (0.41, 0.58) and 0.78 (0.66, 0.93) for high triglycerides, 0.70 (0.59, 0.82) and 0.75 (0.64, 0.87) for hypertriglyceridemia, 0.48 (0.39, 0.59) and 0.87 (0.71, 1.07) for low HDL cholesterol, and 0.92 (0.76, 1.12) and 0.49 (0.41, 0.59) for hypertension, respectively. Decreased hazard ratios (95% CIs) in quartile 4 (vs. 1) of 25(OH)D were found for MetS (0.80 [0.65, 1.00]), high triglycerides (0.76 [0.62, 0.92]), abdominal obesity (0.77 [0.63, 0.96]), and low HDL cholesterol (0.64 [0.50, 0.81]).

CONCLUSIONS

Decreased concentrations of serum 25(OH)D correlate significantly to a heightened MetS risk and specific components. Our findings underscore the potential preventive function of circulating vitamin D concerning metabolic disorders.

Effect of oral versus parenteral vitamin D3 supplementation on nuclear factor-κB and platelet aggregation in type 2 diabetic patients

Platelet hyperactivity is one of the key factors implicated in the development and progression of diabetic vascular complications. Activated platelets mediate leukocyte recruitment that further enhances inflammatory responses in vascular wall ultimately resulting in atherosclerotic complications. Since vitamin D insufficiency is highly prevalent in diabetics, we aimed to evaluate the effect of three dosage forms of vitamin D supplementation on lipid profile, NF-κB, platelet aggregation, and platelet calcium content in type 2 diabetic patients. Type 2 diabetic patients were randomized to receive daily (4000 IU/day) or weekly (50 000 IU/week) oral vitamin D3 for 3 months. Another group received a single parenteral dose (300 000 IU) of vitamin D3, whereas the control group received their antidiabetic drug(s) alone. Serum 25(OH)D, total cholesterol, triglycerides, high- and low-density lipoprotein cholesterol, NF-κB, and platelet aggregation were measured at the beginning and 3 months after vitamin D supplementation. Platelet calcium content was evaluated by measuring the fluorescence intensity of Rhod-2-stained platelets by confocal fluorescence microscopy. Results showed that serum 25(OH)D3 levels significantly increased in all vitamin D3-treated groups. However, the mean level for parenteral treated group was significantly lower than oral-treated groups. Oral and parenteral treatment were also able to decrease NF-κB level, platelet aggregation, and platelet calcium content. However, both oral doses of vitamin D3 were superior to the single parenteral dose. In conclusion, restoring normal levels of vitamin D is an important determinant to maintain normal platelet function and reduce inflammation. Nevertheless, further long-term studies are still needed.

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.

The Role of Vitamin D and Its Molecular Bases in Insulin Resistance, Diabetes, Metabolic Syndrome, and Cardiovascular Disease: State of the Art

In the last decade, an increasing awareness was directed to the role of Vitamin D in non-skeletal and preventive roles for chronic diseases. Vitamin D is an essential hormone in regulating calcium/phosphorous balance and in the pathogenesis of inflammation, insulin resistance, and obesity. The main forms of vitamin D, Cholecalciferol (Vitamin D3) and Ergocalciferol (Vitamin D2) are converted into the active form (1,25-dihydroxyvitamin D) thanks to two hydroxylations in the liver, kidney, pancreas, and immune cells. Some anti-inflammatory cytokines are produced at higher levels by vitamin D, while some pro-inflammatory cytokines are released at lower levels. Toll-Like Receptor (TLR) expression is increased, and a pro-inflammatory state is also linked to low levels of vitamin D. Regardless of how it affects inflammation, various pathways suggest that vitamin D directly improves insulin sensitivity and secretion. The level of vitamin D in the body may change the ratio of pro- to anti-inflammatory cytokines, which would impact insulin action, lipid metabolism, and the development and function of adipose tissue. Many studies have demonstrated an inverse relationship between vitamin D concentrations and pro-inflammatory markers, insulin resistance, glucose intolerance, metabolic syndrome, obesity, and cardiovascular disease. It is interesting to note that several long-term studies also revealed an inverse correlation between vitamin D levels and the occurrence of diabetes mellitus. Vitamin D supplementation in people has controversial effects. While some studies demonstrated improvements in insulin sensitivity, glucose, and lipid metabolism, others revealed no significant effect on glycemic homeostasis and inflammation. This review aims to provide insight into the molecular basis of the relationship between vitamin D, insulin resistance, metabolic syndrome, type 1 and 2 diabetes, gestational diabetes, and cardiovascular diseases.

A causal relationship between antioxidants, minerals and vitamins and metabolic syndrome traits: a Mendelian randomization study

BACKGROUND

The available evidence regarding the association of antioxidants, minerals, and vitamins with the risk of metabolic syndrome (MetS) traits is currently limited and inconsistent. Therefore, the purpose of this Mendelian randomization (MR) study was to investigate the potential causal relationship between genetically predicted antioxidants, minerals, and vitamins, and MetS.

METHODS

In this study, we utilized genetic variation as instrumental variable (IV) to capture exposure data related to commonly consumed dietary nutrients, including antioxidants (β-carotene, lycopene, and uric acid), minerals (copper, calcium, iron, magnesium, phosphorus, zinc, and selenium), and vitamins (folate, vitamin A, B6, B12, C, D, E, and K1). The outcomes of interest, namely MetS (n = 291,107), waist circumference (n = 462,166), hypertension (n = 463,010), fasting blood glucose (FBG) (n = 281,416), triglycerides (n = 441,016), and high-density lipoprotein cholesterol (HDL-C) (n = 403,943), were assessed using pooled data obtained from the most comprehensive genome-wide association study (GWAS) available. Finally, we applied the inverse variance weighting method as the result and conducted a sensitivity analysis for further validation.

RESULTS

Genetically predicted higher iron (OR = 1.070, 95% CI 1.037-1.105, P = 2.91E-05) and magnesium levels (OR = 1.130, 95% CI 1.058-1.208, P = 2.80E-04) were positively associated with increased risk of MetS. For each component of MetS, higher level of genetically predicted selenium (OR = 0.971, 95% CI 0.957-0.986, P = 1.09E-04) was negatively correlated with HDL-C levels, while vitamin K1 (OR = 1.023, 95% CI 1.012-1.033, P = 2.90E-05) was positively correlated with HDL-C levels. Moreover, genetically predicted vitamin D (OR = 0.985, 95% CI 0.978-0.992, P = 5.51E-5) had a protective effect on FBG levels. Genetically predicted iron level (OR = 1.043, 95% CI 1.022-1.064, P = 4.33E-05) had a risk effect on TG level.

CONCLUSIONS

Our study provides evidence that genetically predicted some specific, but not all, antioxidants, minerals, and vitamins may be causally related to the development of MetS traits.

Vitamin D3 alleviates nonalcoholic fatty liver disease in rats by inhibiting hepatic oxidative stress and inflammation via the SREBP-1-c/ PPARα-NF-κB/IR-S2 signaling pathway

Introduction: Nonalcoholic fatty liver disease (NAFLD) is a chronic disease characterized by fat deposits in liver cells, which can lead to hepatitis and fibrosis. This study attempted to explore the protective effect of vitamin D3 (VitD) against NAFLD. Methods: Adult male albino rats were randomized into four separate groups: the negative control group was fed a standard rat chow; the positive group received a high-fat diet (20%) and 25% fructose water (NAFLD); the VitD control group was intramuscularly treated with VitD (1,000 IU/kg BW) 3 days per week for 10 weeks; and the NAFLD group was treated with VitD therapy. Biochemical and hepatic histological analyses were performed. Hepatic oxidative stress and inflammatory conditions were also studied. Hepatic expression of sterol regulatory element-binding protein 1-c (SREBP-1-c), peroxisome proliferator-activated receptor alpha (PPAR-α), and insulin receptor substrate-2 was analyzed by quantitative real-time polymerase chain reaction. Results and discussion: The NAFLD rats exhibited elevated terminal body weight, hepatic injury markers, dyslipidemia, glucose intolerance, and insulin resistance. Moreover, the NAFLD rats had increased SREBP-1-c expression and reduced PPAR-α and IRS-2 expressions. Histological analysis showed hepatic steatosis and inflammation in the NAFLD group. In contrast, VitD administration improved the serum biochemical parameters and hepatic redox status in NAFLD rats. Also, VitD treatment ameliorated hepatic inflammation and steatosis in the NAFLD group by decreasing the expression of SREBP-1-c and increasing the expression of PPAR-α. Overall, these results suggest that VitD could have a protective effect against NAFLD and its associated complication.

The Impact of Vitamin D Deficiency and Insufficiency on the Outcome of Type 2 Diabetes Mellitus Patients: A Systematic Review

Vitamin D deficiency and insufficiency are public health concerns that have contributed to multiple negative health outcomes. Recent studies have revealed that vitamin D deficiency and insufficiency influence glycaemic control and the development of diabetes complications. The goal of this systematic review is to summarise the latest evidence on the impact of vitamin D deficiency and insufficiency on the outcome of Type 2 Diabetes Mellitus (T2DM) patients. In this PRISMA-guided systematic review, articles were sourced from three databases, namely, PubMed, Scopus, and Web of Science. The review only included literature published from 2012 until 2022, and 33 eligible studies met the inclusion criteria for this review. The included articles were critically appraised using the Mixed Method Appraisal Tool (MMAT). According to our findings, vitamin D deficiency or insufficiency is associated with mental health status, macrovascular and microvascular complications of T2DM, metabolic syndrome, increased risk of obesity, increased blood pressure, dyslipidaemia, glycaemic control, nerve-related disease, musculoskeletal-related complications, and reduced quality of life. Due to the diverse implications of vitamin D deficiency and insufficiency, screening for vitamin D levels in T2DM patients may be beneficial.

Effects of Vitamin D supplementation or deficiency on metabolic phenotypes in mice of different sexes

Vitamin D is a steroid hormone precursor that was initially recognized for its important roles in calcium-phosphate homeostasis and bone health. However, the resent prevalence of vitamin D deficiency has highlighted its non-skeletal function, such as its important role in regulating endogenous metabolism. The aim of the present study was to examine the roles of vitamin D supplementation or deficiency on metabolic phenotypes in both male and female mice by using targeted metabolomics analysis. Six weeks old C57BL/6 mice of different sexes were fed with standard chow diet (1000 IU/kg vitamin D3 contained), vitamin D deficient diet (0 IU/kg vitamin D3 contained), or vitamin D enriched diet (10,000 IU/kg vitamin D3 contained) for a total of 14 weeks. Liver pathological analysis showed that vitamin D deficiency caused significant fat deposition in both male and female mice. While vitamin D supplementation was found to improve the accumulation of fat in the liver tissue. Metabolomics analysis indicated that metabolic perturbation related to vitamin D regulation in male mice mainly involved in tricarboxylic acid cycle, fatty acylcarnitine and fatty acid metabolism, sugar metabolism, glutathione metabolism, steroid hormone and pyrimidine metabolism. Based on the criteria of VIP> 1 in OPLS-DA analysis and P < 0.05 in hypothesis test, a total of 62 metabolites and 78 metabolites were found to be significantly changed in VD-deficiency group and VD-supplement group compared with the control group, respectively. While for female mice, the metabolites disturbance mainly involved in fatty acylcarnitine and fatty acid metabolism, TCA, sugar metabolism, folate cycle, methionine cycle, and purine metabolism. A total of 38 and 57 metabolites were found to be significantly changed (VIP>1 and P < 0.05) in VD-deficiency group and VD-supplement group compared with the control group, respectively. Energy metabolism was the most relevant metabolic pathway for vitamin D regulation in both male and female mice. Sex-specific changes of fatty acyl carnitines and dehydroepiandrosterone were observed in the vitamin D supplementation groups. However, most of the energy metabolism related compounds exhibited the same trend in vitamin D supplementation groups of different sexes. Pearson's correlation analysis indicated that vitamin D was significantly correlated (P < 0.05) with the levels of D-fructose 6-phosphate, D-glucose 1-phosphate, D-glucose 6-phosphate, DL-pyroglutamic acid, 2-oxoglutarate, L-glutamic acid, and fumarate, which were all involved in the sugar metabolism pathway. The results achieved in this study demonstrated that vitamin D significantly regulated the metabolism of lipid and sugar, and the regulation showed a certain sex specificity.

Effects of vitamin D supplementation on the regulation of blood lipid levels in prediabetic subjects: A meta-analysis

This meta-analysis aimed to systematically investigate whether vitamin D supplementation reduces blood lipid—total cholesterol (TC), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), and triglyceride (TG)—levels in prediabetic individuals. Pubmed, Web of Science, Cochrane Library, Embase, CNKI, and WANFANG databases were searched for studies published before 13 February 2022 (including 13 February 2022). Five articles were included. The results showed that vitamin D intervention led to a significant reduction in TG compared with control or placebo treatment (−0.42 [−0.59, −0.25], P &lt; 0.001). Subgroup analyses showed that this effect was particularly significant among the studies that included obese subjects (−0.46 [−0.65, −0.28], P &lt; 0.001), the studies that also included men (not only women) (−0.56 [−0.78, −0.34], P &lt; 0.001), and the studies with intervention durations longer than 1 year (−0.46 [−0.65, −0.28], P &lt; 0.001). Both relatively low doses of 2,857 IU/day (−0.65 [−0.92, −0.38], P &lt; 0.001) and relatively high doses of 8,571 IU/day (−0.28 [−0.54, −0.02] P = 0.04) of vitamin D supplementation reduced TG levels, and the effect was observed both in Northern Europe (−0.65 [−0.92, −0.38], P &lt; 0.001) and Asian (−0.25 [−0.48, −0.03], P = 0.03) country subgroups. No significant effects on TC, HDL-C, and LDL-C were shown. In conclusion, vitamin D supplementation might beneficially affect TG levels in individuals with prediabetes. Particularly longer durations of treatment, more than 1 year, with doses that correct vitamin deficiency/insufficiency, can have a beneficial effect. This meta-analysis was registered at www.crd.york.ac.uk/prospero (CRD42020160780).

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.

Vitamin D insufficiency is associated with inflammation and deregulation of adipokines in patients with metabolic syndrome

BACKGROUND

Previous studies have been reported that vitamin D deficiency increased the risk of metabolic syndrome (MetS). Nonetheless, the exact mechanisms underlying this association is unclear. Besides, inflammation and deregulation of adipokines secretion have been recognized as pivotal factors that contribute to the pathogenesis of these conditions. Therefore, we assessed whether serum vitamin D status is associated with serum levels of adipokines and inflammatory markers in these patients.

METHODS

This case-control study was carried out among 65 patients with MetS who had vitamin D insufficiency (cases) and 130 MetS patients who had vitamin D sufficiency (controls). Cases and controls were recruited from among those referred to health centers in Zabol County, Iran. Vitamin D insufficiency was regarded as a serum 25-hydroxyvitamin D [25(OH)D] concentration below 30 ng/ml. Serum concentrations of leptin, adiponectin, visfatin, and resistin and also adiponectin/leptin ratio along with serum levels of interleukin 6 (IL-6), IL-10 and tumor necrosis factor-alpha (TNF-α), were evaluated.

RESULTS

Serum levels of leptin, resistin, and TNF-α were significantly higher, whereas, serum adiponectin and adiponectin/leptin ratio were significantly lower in cases than the controls. There was no significant difference in serum visfatin, IL-6, and IL-10 between the groups. Serum levels of 25(OH)D were inversely correlated with leptin, resistin, and TNF-α in both unadjusted models and after adjustment for potential confounders.

CONCLUSION

Our findings indicated that vitamin D insufficiency in MetS patients is associated with increased inflammation and serum adipokine abnormalities which may be associated with developing metabolic complications in these patients.

Nutritional Therapy in Persons Suffering from Psoriasis

Psoriasis is a chronic inflammatory skin disease. Immunological, genetic, and environmental factors, including diet, play a part in the pathogenesis of psoriasis. Metabolic syndrome or its components are frequent co-morbidities in persons with psoriasis. A change of eating habits can improve the quality of life of patients by relieving skin lesions and by reducing the risk of other diseases. A low-energy diet is recommended for patients with excess body weight. Persons suffering from psoriasis should limit the intake of saturated fatty acids and replace them with polyunsaturated fatty acids from the omega-3 family, which have an anti-inflammatory effect. In diet therapy for persons with psoriasis, the introduction of antioxidants such as vitamin A, vitamin C, vitamin E, carotenoids, flavonoids, and selenium is extremely important. Vitamin D supplementation is also recommended. Some authors suggest that alternative diets have a positive effect on the course of psoriasis. These diets include: a gluten-free diet, a vegetarian diet, and a Mediterranean diet. Diet therapy for patients with psoriasis should also be tailored to pharmacological treatment. For instance, folic acid supplementation is introduced in persons taking methotrexate. The purpose of this paper is to discuss in detail the nutritional recommendations for persons with psoriasis.

Role of Vitamin D in the Metabolic Syndrome

The prevalence of hypovitaminosis D has risen in developed countries over the past few years in association with lifestyle changes and an increase in unhealthy habits. Vitamin D deficiency has been implicated in various diseases, including metabolic syndrome (MetS), which is clinically defined by a set of metabolic and vascular disorders. The objective of this study was to review scientific evidence on the relationship between MetS and vitamin D deficiency to support the development of prevention strategies and health education programs. An inverse relationship has been reported between plasma vitamin D concentrations and the features that define MetS, i.e., elevated serum concentrations of glucose, total cholesterol, low-density lipoproteins, triglycerides, glycosylated hemoglobin, and a high body mass index. Numerous studies have described the benefits of vitamin D supplementation to improve outcomes in individuals with MetS. Interventions to maintain optimal vitamin D concentrations are proposed as a preventive strategy against MetS.

Serum 25-Hydroxyvitamin D Concentrations and Cardiometabolic Biomarkers in Chinese Rural Population

There is a paucity of data on the relation between serum 25-hydroxyvitamin D [25(OH)D] concentration and cardiometabolic biomarkers in the Chinese population. To comprehensively and quantitatively examine the association of 25(OH)D and cardiometabolic traits, we conducted a cross-sectional study in the Chinese rural population. Serum 25(OH)D and eight cardiometabolic biomarkers were measured in 1714 individuals from Henan province, China. Scatter plot was used to visualize the distribution and correlation of 25(OH)D and cardiometabolic indicators. Moreover, multivariate linear regressions and restricted cubic spline (RCS) functions were performed to examine the quantitative association between the serum 25(OH)D and cardiometabolic parameters. The median serum 25(OH)D level was 19.94 ng/ml in all participants, with an estimated 50.12% presenting vitamin D deficiency. Serum 25(OH)D level showed significantly modest association with cardiometabolic parameters (p<0.05) except for diastolic blood pressure (r=0.03, p=0.22). Multiple linear regression models showed that 25(OH)D concentration was positively associated with high-density lipoprotein cholesterol (HDL-C) and negatively associated with low-density lipoprotein cholesterol (LDL-C) and fasting serum glucose (GLU). The results of restricted cubic spline models indicated a positively linear association of 25(OH)D with HDL-C (p for overall<0.001, p for nonlinearity=0.191) and a negatively linear association with GLU (p for overall=0.024, p for nonlinearity=0.095). Overall, vitamin D deficiency was very common among Chinese rural population living near the 34 degrees north latitude. Besides, there were significant association between 25(OH)D concentrations and cardiometabolic biomarkers including HDL-C and GLU levels. Future longitudinal studies and randomized trials are warranted to clarify the causal relationship.