Vitamin D Levels Decline with Rising Number of Cardiometabolic Risk Factors in Healthy Adults: Association with Adipokines, Inflammation, Oxidative Stress and Advanced Glycation Markers

Vitamin D Determinants, Status, and Antioxidant/Anti-inflammatory-Related Effects in Cardiovascular Risk and Disease: Not the Last Word in the Controversy

Beyond its key role in calcium homeostasis, vitamin D has been found to significantly affect the cardiovascular (CV) system. In fact, low vitamin D levels have been associated with increased CV risk, as well as increased CV morbidity and mortality. The majority of effects of this molecule are related directly or indirectly to its antioxidative and anti-inflammatory properties. Generally, vitamin D insufficiency is considered for 25-hydroxyvitamin D (25(OH)D) levels between 21-29 ng/mL (corresponding to 52.5-72.5 nmol/L), deficiency as 25(OH)D levels less than 20 ng/mL (<50 nmol/L), and extreme deficiency as 25(OH)D less than 10 ng/mL (<25 nmol/L). However, the definition of an optimal vitamin D status, as defined by 25(OH)D, remains controversial for many extra-bone conditions, including CV disease. In this review, confounding factors affecting the 25(OH)D measurement and status will be discussed. In particular, available evidence on the mechanism and role of vitamin D in relation to CV risk and disease through its antioxidant effect will be reported, also facing the aspect regarding the debate on the minimum blood 25(OH)D level required to ensure optimal CV health.

The Association between the Atherogenic Index of Plasma and Cardiometabolic Risk Factors: A Review

Background: Metabolic syndrome (MetS) is a condition caused by a combination of cardiometabolic risk factors (CMR). MetS leads to type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD), both of which place a burden on not only the patients but also the healthcare system. Diagnostic criteria for MetS vary, and there is no universal tool to detect it. Recently, many studies have found positive associations between the atherogenic index of plasma (AIP) and some CMR factors. Therefore, a comprehensive review was needed to recapitulate these studies and qualitatively estimate the likelihood of AIP being associated with CMR. We aimed to review and summarise observational data on AIP and CMR factors and verify their association. Materials and Methods: A review of observational studies was conducted by searching “atherogenic index of plasma” in PubMed, One Search, and the Cochrane library. A total of 2068 articles were screened, and 32 were included after excluding paediatric, non-human and interventional studies, and those carried out on cohorts with conditions unrelated to MetS or on lipid-lowering medication. The Newcastle-Ottawa scale was used to assess their quality. Results: Most studies that reported high waist circumference (WC), triglycerides (TG), insulin resistance (IR) and low high-density lipoprotein cholesterol (HDL-C) concentration, also reported high AIP. Few studies investigated blood pressure (BP) and some discrepancies existed between their results. Conclusion: AIP may be associated with WC, TG, IR, and HDL-C. It is unclear if AIP is associated with BP. The current study’s results should be used to inform futureward a meta-analysis to be seen quantitatively. It is also recommended that more cohort studies stratified by gender and ethnicity be performed to ascertain if AIP can predict MetS before it manifests.

Effect of vitamin D3 supplementation on cardiometabolic disease risk among overweight/obese adult males in the UK: A pilot randomised controlled trial

BACKGROUND

Observational studies suggest links between reduced serum 25(OH)D concentration and increased cardiometabolic disease risk. However, these studies provide limited evidence of causation, with few conclusive randomised controlled trials (RCT) having been carried out to date. This RCT investigated the effect of vitamin D₃ supplementation on vascular function and cardiometabolic disease risk markers, in 55 healthy males aged 18-65 years with plasma 25(OH)D concentration <75 mol L^-1 and body mass index ≥24.9 kg m^-2 .

METHODS

Participants were assigned to consume 125 µg day^-1 (5000 IU day^-1 ) vitamin D₃ or placebo for 8 weeks. Blood samples and vascular function measures were obtained at baseline, as well as at weeks 4 and 8. The primary outcome was arterial stiffness, an indicator of cardiovascular disease (CVD) risk, assessed by pulse wave velocity. Biomarkers of CVD risk, insulin resistance and endothelial function were measured using an enzyme-linked immunosorbent assay.

RESULTS

Daily oral intake of 125 µg supplemental vitamin D₃ led to a significant improvement in plasma 25(OH)D concentrations over the 8-week intervention in the vitamin D group compared to the change in the placebo group (p ˂ 0.001). In the vitamin D group, the baseline mean ± SD 25(OH)D concentration was 38.4 ± 15.9 and this increased to 72.8 ± 16.1 nmol L^-1 after 8 weeks of supplementation. The intervention had no effect on arterial stiffness, as measured by pulse wave velocity, although vitamin D₃ supplementation did lead to a decrease in mean ± SD brachial pulse pressure from baseline to 8 weeks of -2.9 ± 3.4 mmHg (p = 0.027) in the vitamin D group compared to the same period in the placebo group. The intervention had no effect on the remaining cardiometabolic parameters.

CONCLUSIONS

Overall, treatment significantly improved brachial pulse pressure but no other cardiometabolic disease risk markers. To follow on from this pilot RCT, future large-scale clinical trials over longer durations may offer further insights.

Associations between serum vitamin D3, atherogenic indices of plasma and cardiometabolic biomarkers among patients with diabetes in the KERCADR study

BACKGROUND

We sought the association between serum 25-hydroxyvitamin D₃ (25(OH) D₃) levels and atherogenic indices of plasma as novel predictive biomarkers of cardiometabolic disease risk in patients with type 2 diabetes mellitus (T2DM).

METHODS

The present study was a nested case-control study conducted on 252 participants with T2DM and controls from the second phase of the KERCADR cohort study. The participants with a mean (±SD) age of 49.79 ± 5.85 years were randomly selected and allocated into case and control groups. Independent t-test, Hierarchical Linear Regression, Univariate ANOVA, and partial correlation were used for analysis the data. Atherogenic indices of plasma include Castelli Risk Index I (CRI I), Castelli Risk Index II (CRI II), and the novel Atherogenic Index of Plasma (AIP), and Atherogenic Coefficient (AC).

RESULTS

There was a significant difference among case and control groups for AIP in males and females (P < 0.001 and P = 0.007, respectively). The levels of AIP, CRI I, and AC significantly decreased (P = 0.017, P = 0.029, and P = 0.029, respectively) with improved serum vitamin D status only in control male participants. The main effect of BMI and vitamin D status on AIP, CRI I, and AC, and the main effect of BMI on CRI I, CRI II, and AC were significant in control males and females, respectively.

CONCLUSION

We conclude that there is a reverse significant association between AIP and serum vitamin D among healthy males. Low serum level of vitamin D is associated with atherogenic dyslipidemia. Therefore, improving vitamin D status as an important indicator may alleviate AIP as a surrogate marker for predicting the risk of CVD events in healthy men and women with normal BMI.

Vitamin D status and systemic redox biomarkers in adults with obesity

BACKGROUND & AIMS

Vitamin D has been proposed to have a protective role against oxidative stress. The present study was conducted to test the hypothesis that suboptimal levels of 25(OH)D are related to oxidative/antioxidative biomarkers in adults independently of obesity.

METHODS

In this case-control study, 140 subjects with obesity and 90 age- and sex-matched 25(OH)D sufficient normal weight controls were selected. Subjects with obesity were categorized as 25(OH)D sufficient, insufficient, and deficient based on their serum 25(OH)D concentrations. Serum malondialdehyde (MDA), total oxidant status (TOS), and total antioxidant capacity (TAC) as well as erythrocytes superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) along with serum paraoxonase-1 (PON1) and arylesterase (AREase) activities were assessed.

RESULTS

Serum concentrations of 25(OH)D were inversely correlated with BMI, WC, fat mass, and visceral fat. Serum levels of MDA and TOS, and erythrocyte SOD activities were significantly higher, whereas, serum TAC, PON1, and AREase were significantly lower in subjects with obesity compared to the controls (p < 0.0001). 25(OH)D deficient obese subjects exhibited higher serum levels of MDA as well as erythrocyte SOD activity (p < 0.05) and lower serum levels of TAC (p < 0.0001), PON1 (p < 0.05), and AREase (p < 0.0001) compared to obese subjects with 25(OH)D sufficiency and controls even when adjusted for BMI.

CONCLUSIONS

The present findings demonstrated a strong association between the severity of 25(OH)D deficiency and oxidative/antioxidative related parameters independently of obesity.

Relationship between 25 Hydroxyvitamin D, Overweight/Obesity Status, Pro-Inflammatory and Oxidative Stress Markers in Patients with Type 2 Diabetes: A Simplified Empirical Path Model

Vitamin D deficiency is highly prevalent in patients with overweight/obesity and type 2 diabetes (T2DM). Herein, we investigated the relationship between vitamin D status and overweight/obesity status, insulin resistance (IR), systemic inflammation as well as oxidative stress (OS). Anthropometric and laboratory assessments of 25-hydroxyvitamin D (25(OH)D) and glycemic, pro-inflammatory and OS biomarkers were performed in a sample of 47 patients with T2DM who were divided into categories based on overweight and degree of obesity. The main findings were: the overweight/obesity status correlated negatively with the degree of serum 25(OH)D deficiency (ρ = −0.27) with a trend towards statistical significance (p = 0.069); the homeostasis model assessment of insulin resistance (HOMA-IR) was significantly different (p = 0.024) in patients with 25(OH)D deficiency, as was total oxidant status (TOS) and oxidative stress index (OSI) in patients with severe serum 25(OH)D deficiency as compared to those with 25(OH)D over 20 ng/mL (TOS: p = 0.007, OSI: p = 0.008); and 25(OH)D had a negative indirect effect on TOS by body mass index (BMI), but BMI was not a significant mediator of the studied relationship. In a setting of overweight and increasing degree of obesity, patients with T2DM did not display decreasing values of 25(OH)D. Subjects with the lowest values of 25(OH)D presented the highest values of BMI. Patients with 25(OH)D deficiency were more insulin resistant and showed increased OS but no elevated systemic inflammation. The negative effect of 25(OH)D on TOS did not seem to involve BMI as a mediator.

Health implication of vitamin D on the cardiovascular and the renal system

Vitamin D regulates the calcium and phosphorus balance in the body. The activated form of vitamin D (1 α,25-dihydroxyvitamin D) binds to vitamin D receptor which regulates genes that control cell proliferation, differentiation and apoptosis. In the cardiovascular system, the vitamin D receptor is present in cardiomyocytes and the arterial wall. A clear correlation between vitamin D level and cardiovascular diseases is established. Vitamin D deficiency affects the renin-angiotensin system leading to ventricular hypertrophy and eventually to stroke. While clinical trials highlighted the positive effects of vitamin D supplements on cardiovascular disease these still need to be confirmed. This review outlines the association between vitamin D and cardiovascular and renal disease summarising the experimental data of selective cardiovascular disorders.

The relationship between vitamin D deficiency and oxidative stress can be independent of age and gender

Abstract. The active vitamin D (1,25(OH)2D) acts through a nuclear receptor to perform several functions in cellular metabolism. 1,25(OH)2D participates directly in calcium homeostasis, regulates the immune system, nervous system, blood pressure, insulin secretion, among others. Vitamin D deficiency could also be associated with several diseases and increased cellular oxidative damage. The present study aimed to investigate whether lipid peroxidation and/or protein oxidation are affected by vitamin D deficiency and whether sunlight exposure/diet, gender, and age might influence this relationship. Vitamin D concentrations were obtained from the Heart Hospital database and a questionnaire was applied among the 212 participants. We used the inactive vitamin D (25(OH)2) in the analyses since 1,25(OH)2D has a short half-life and a low blood concentration. Lipid peroxidation and protein oxidation analyses were performed using spectrophotometry. Multivariate analyses suggested the participation of vitamin D deficiency (<30 ng/mL) and sunlight/diet in oxidative stress (p <0.05; R2 MDA: 0.562; R2 CG: 0.429). Multiple linear regression test show that the age and gender of patients are not interfering in the analyses (p>0.05). Therefore, we suggest that the relationship between vitamin D deficiency and oxidative stress can be independent of age and gender.

Serum 25-hydroxyvitamin D is associated with insulin resistance independently of obesity in children ages 5-17

AIM

To determine the association of vitamin D with insulin resistance and obesity in children.

METHODS

A total of 92 obese and 58 non-obese children aged 5-17 years were evaluated. Data were collected related to anthropometric (weight, height), and biochemical parameters (fasting plasma glucose, serum insulin, serum 25-hydroxyvitamin D, lipid profile, vitamin B12, parathormone) and physical examination (blood pressure, acanthosis nigricans, stria, lipomastia). Insulin resistance (IR) was calculated using the homeostasis model assessment (HOMA). HOMA-IR = fasting insulin level (μU/ml) × fasting glucose (mg/dL)/405. A HOMA-IR value >2.5 was defined as insulin resistance.

RESULTS

According to the US Endocrine Society classification, vitamin D deficiency (0-20 ng/ml) was determined at significantly higher rates in the obese group than in the control group (p < 0.001). The rate of subjects with a vitamin D level of 20-30 ng/ml was significantly lower in the obese group than in the control group (p < 0.001) Within the obese group a statistically significant difference was determined between the insulin resistant and non-insulin resistant groups in respect of serum 25-hydroxyvitamin D levels (p = 0.001) and vitamin B12 levels (p = 0.001). A significant negative correlation was determined between serum 25-hydroxyvitamin D and HOMA-IR (r=-0.256, p = 0.016) and insulin (r = -0.258, p = 0.015). The systolic blood pressure (p = 0.001) and diastolic blood pressure (p = 0.003) values were significantly different in the control and obese groups. A statistically significant difference was determined between the control and obese groups in terms of the levels of insulin, HOMA-IR, HbA1c, cortisol, LDL, total cholesterol, HDL, triglyceride, hemoglobin, MCV, MPV, and calcium.

CONCLUSION

The prevalence of vitamin D deficiency was higher in obese children compared to normal-weight and overweight children. Serum 25(OH)D levels showed a negative correlation with insulin and HOMA-IR. Serum 25(OH)D is associated with insulin resistance independently of obesity.

Strong association between serum Vitamin D and Vaspin Levels, AIP, VAI and liver enzymes in NAFLD patients

Some studies indicated poor vitamin D level in NAFLD which is independently correlated with severity of steatosis. Low 25(OH) D3 levels are associated with an impaired lipid profile. Impaired levels and function of vaspin and omentin, which are adipokines, have been demonstrated in NAFLD patients. This study determined the relationship between vitamin D and serum liver enzymes, ultrasound findings, some adipokines, atherogenic index of plasma (AIP) and visceral adiposity index (VAI) in patients with NAFLD in a cross-sectional study. This study was a cross-sectional study in eighty-three NAFLD patients (57 males and 26 females). Plasma levels of omentin-1e-1, vaspin were measured. Anthropometric indices metabolic status was assessed. Visceral adiposity index and atherogenic index of plasma were calculated according to suggested formula. Anthropometric indices, lipid profiles, liver enzymes as well as abdominal ultrasonography and the status of vitamin D were assessed. The results showed that aspartate aminotransferase (AST) (44.22 ± 8.5 IU/L vs. 40.19 ± 8.75 IU/L, p-value = 0.039) AIP (0.767 ± 0.142 vs. 0.6417 ± 0.139, p < 0.001) and VAI (9.28 ± 3.25 vs. 7.048 ± 2.415, p = 0.001) were significantly higher in patients with vitamin D deficiency compared to those with vitamin D sufficiency. The positive correlations between Vaspin levels and vitamin D were found to be remarkably significant in both males and females (r = 0.437; P = 0.004; P < 0.001, r = -0.709, respectively. In both males and females serum vitamin D concentrations were negatively associated with AIP. Partial correlations controlling for age and sex showed that vitamin D is significantly and inversely associated with AIP, VAI, AST, and ALT. Additionally, vitamin D levels correlated directly with vaspin.

Relationship of serum Vitamin D concentrations with Adipokines and Cardiometabolic risk among non-Hispanic black type 2 diabetic and non-diabetic subjects: a cross-sectional study

BACKGROUND

To report the association of serum 25-hydroxyvitamin D [25(OH)D] and its association with adipokines and cardiometabolic risk factors in Haitian Americans (HA) and African Americans (AA) by ethnicity and type 2 diabetes (T2D) status.

METHODS

A cross-sectional study in 197 HA (92 with T2D and 102 without T2D) and 200 AA (97 with T2D and 103 without T2D) recruited in South Florida. Serum 25(OH)D concentrations and adipokines were analyzed by ELISA and cardiometabolic risk factors were indexed by obesity, glycemic control, insulin sensitivity, lipid profile, and blood pressure.

RESULTS

Controlling for age, BMI, energy intake, smoking status and HOMA2-IR in multivariate linear regression analyses, serum 25(OH)D concentrations were significantly associated with WC (R² = 0.760, B = - 0.092, P = 0.027), HbA1C (R² = 0.142, B = - 0.012, P = 0.010), and TG (R² = 0.159, B = - 1.192, P = 0.003) in only HA without T2D. While serum 25(OH)D concentrations were significantly associated with TC (R² = 0.168, B = - 0.329, P = 0.040), log leptin (R² = 0.544, B = - 0.007, P = 0.021), and adiponectin (R² = 0.144, B = 0.111, P = 0.033), but slightly associated with LDL-c (R² = 0.133, B = - 0.278, P = 0.064) in only AA without T2D. Among individuals with T2D, serum 25(OH)D concentrations were marginally associated with IL-6 (R² = 0.109, B = 0.076, P = 0.085) in HA with T2D, and there was a trend toward significance with log leptin (R² = 0.393, B = - 0.006, P = 0.075) in AA with T2D in regression analysis.

CONCLUSIONS

The findings that the associations of serum 25(OH)D concentrations with adipokines and cardiometabolic factors differ between HA and AA has clinical and public implications to guide design of T2D preventive strategies that are culturally specific even within the same ethnicity.

Serum 25-hydroxyvitamin D and cardiovascular disease risk factors in women with excessive weight gain during pregnancy and in their offspring at age 5-6 years

BACKGROUND/OBJECTIVE

Low 25-hydroxyvitamin D levels [25(OH)D] may increase the risk for cardiovascular disease (CVD). In pregnant women excessive weight gain and 25(OH)D deficiency are common complications and both could have deleterious consequences on their children. We aimed to study the relationship between serum 25(OH)D and CVD risk factors in pregnant women and in their offspring at school age.

SUBJECTS/METHODS

Fasting serum 25(OH)D and its bioavailable fraction were quantified in 310 healthy pregnant women [with adequate (n = 113), insufficient (n = 113) and excessive (n = 84) weight gain]. A follow-up at 5-6 years was performed in sixty-six children born of these mothers. Lipids, insulin, glucose, and high-sensitivity C-reactive protein (hsCRP) were measured in all subjects. Children's carotid intima-media thickness (cIMT) together with visceral and intra-abdominal fat were measured by ultrasonography.

RESULTS

Lower maternal 25(OH)D concentrations were associated with lower maternal age, and higher body mass index, triglycerides and hsCRP (all p < 0.05). In women with excessive weight gain during gestation, serum 25(OH)D concentrations showed independent associations with maternal hsCRP (β = -0.283 p = 0.03) and triglycerides (β = -0.436, p = 0.005). Maternal serum 25(OH)D concentrations were also independently associated with cIMT (β = -0.288, p = 0.04), visceral fat (β = -0.281, p = 0.01) and intra-abdominal fat (β = -0.248, p = 0.01) in their children at 5-6 years.

CONCLUSIONS

Lower serum 25(OH)D concentrations were related to CVD risk factors in pregnant woman and in their offspring. The cardiometabolic consequences of low 25(OH)D concentrations during pregnancy could be aggravated by excessive weight gain during gestation.

Serum 25(OH)D and adipokines levels in people with abdominal obesity

Abdominal obesity is a risk factor for cardiovascular disease and diabetes mellitus and has been associated with vitamin D deficiency. Some studies have suggested an association between obesity and adipokine levels as well as low serum 25-hydroxyvitamin D (25(OH)D) level but the underlying mechanisms of the interlink between vitamin D status and serum leptin and adiponectin concentrations are still disputed. We included 435 residents (132 males) from St. Petersburg, Russia into this study. All subjects had physical examination and demographics noted. Blood was collected after an overnight fast and plasma glucose, insulin, serum lipids, 25(OH)D and adipokines (adiponectin and leptin) concentrations were determined at baseline in all participants. Abdominal obesity was diagnosed in 310 (71.3%) subjects (251 females and 59 males). Vitamin D insufficiency and deficiency were found in 314 (72.2%) subjects. Mean (95% CI) age, body mass index (BMI) and serum 25(OH)D for the cohort were 47.6±11.3years; 28.7±0.2kg/m² and 62.5±24.3nmol/l respectively. Serum 25(OH)D level inversely correlated with body weight, waist circumference (WC) and BMI in females but not in males, was lower in diabetic than non-diabetic subjects, and was not significantly different in subjects with and without MetS. WC was positively correlated with leptin and negatively correlated with adiponectin. We found correlation between leptin and serum 25(OH)D level (r=-0.15, p=0.01) but this finding was a characteristic seen only in women. Our study showed a high prevalence of abdominal obesity, vitamin D deficiency and insufficiency in residents from North-West region of Russia, close association between adipokine (leptin, adiponectin) concentrations as well as vitamin D status and body composition (WC, BMI). However in our study the interlink between leptin level and 25(OH)D was found only in females. Further investigations are required to study the relationship between serum 25(OH)D level, obesity and serum adipokine levels.

Adiponectin and vitamin D-binding protein are independently associated at birth in both mothers and neonates

CONTEXT

Adult body fat is associated with birth anthropometry, suggesting a role for metabolic regulators including vitamin D and the adipokines-adiponectin and irisin-which have been reported to interact but, as yet, data remain controversial.

OBJECTIVE

To study (i) the relationship between vitamin D, its binding protein (VDBP) and the adipokines, adiponectin, and irisin in mothers and neonates at birth and (ii) their effects on neonate anthropometric outcomes.

DESIGN

Cross-sectional study for healthy mothers with full-term and uncomplicated births.

SETTING

Primary care.

SUBJECTS

Seventy pairs of newly delivered neonates and their mothers.

MAIN OUTCOMES FEATURES

Biochemical markers from maternal and cord: VDBP, adiponectin, irisin, calcium, albumin, parathyroid hormone, 25OHD, 1,25(OH)₂D. Maternal demographic and social characteristics and neonate anthropometric parameters were recorded.

RESULTS

Maternal VDBP levels (364.1 ± 11.9 μg/ml) demonstrated a strong positive correlation with maternal adiponectin (4.4 ± 0.4 μg/ml) and irisin (308.8 ± 50.8 ng/ml) concentrations, which remained significant (p < 0.001 and p < 0.041, respectively) after adjustment with multiple parameters, including weeks of gestation, maternal age, and BMI. The finding of a strong association of VDBP (355.3 ± 29.2 μg/ml) and adiponectin (11.9 ± 2.0 μg/ml) but not irisin (174.4 ± 26.0 ng/ml) was also evident in neonates (p = 0.03 and p = 0.94, respectively). No association was observed in both maternal and neonatal vitamin D, adiponectin, and irisin.

CONCLUSIONS

The main findings of this study are (i) the perspective of a potential independent interaction of VDBP and adiponectin in both mothers and neonates and (ii) the lack of a causative model effect of both maternal/neonatal vitamin D status and adipokine profile on neonatal anthropometry at birth, as a surrogate marker of future metabolic health of the offspring.

Vitamin D deficiency, oxidative stress and antioxidant status: only weak association seen in the absence of advanced age, obesity or pre-existing disease

Vitamin D deficiency (plasma 25-hydroxycholecalciferol (25(OH)D)70 % of participants were vitamin D deficient. No significant correlations and no biomarker differences across 25(OH)D quartiles or groups were seen except for total antioxidant status. A weak direct association (r 0·252, P<0·05) was observed between 25(OH)D and FRAP, and those in the lowest 25(OH)D quartile and group had significantly lower FRAP values. Results did not reveal a clear link between vitamin D status and oxidative stress biomarkers in the absence of advanced age, obesity and disease, though some evidence of depleted antioxidant status in those with vitamin D deficiency was seen. Poor antioxidant status may pre-date increased oxidative stress. Study of effects of correction of deficiency on antioxidant status and oxidative stress in vitamin D-deficient but otherwise healthy subjects is needed.