Is vitamin D deficiency related to accumulation of advanced glycation end products, markers of inflammation, and oxidative stress in diabetic subjects?

Association Between Lower Levels of Vitamin D and Inflammation in the Geriatric Population: A Systematic Review and Meta-Analysis

There have been suggestions that vitamin D has anti-inflammatory effects; however, the variabilities of vitamin D levels among specific groups of patients and its association with these inflammatory events have not been demonstrated. This study aims to study the association between vitamin D levels and vitamin D deficiency and inflammatory events among the elderly population. PubMed, Web of Science, Scopus, Science Direct, and ClinicalKey were systematically searched in December 2023 to include the relevant data. Comprehensive Meta-Analysis (version 3.0, Biostat, Inc., Englewood, NJ) was the software used for data analyses. A total of 12 studies were included in this analysis with 14,717 elderly patients. There was an overall significant decrease in vitamin D levels in elderly patients with high inflammatory markers compared to controls (Hedges' g = -0.221, 95% CI: -0.268, -0.173, P < 0.001), and event of vitamin D deficiency was found to be 0.321 (95% CI: 0.305, 0.337, P < 0.001). There is a significant decrease in vitamin D levels among the elderly with different inflammatory conditions. Future longitudinal studies and well-designed, large, randomized controlled trials are required to study the association between vitamin D deficiency and the incidence of inflammatory events in this specific group of patients.

Vitamin D and biomarkers of inflammation and oxidative stress among pregnant women: a systematic review of observational studies

OBJECTIVE

This systematic review aimed to map the evidence evaluated the relationship between vitamin D and redox and inflammatory status during gestation.

METHODS

Three databases (PubMed/MEDLINE, Scopus, and Web of Science (WoS)) and reference list of included documents were searched for related observational studies published until 2nd October 2023. To determine the quality of the selected observational studies, the Newcastle-Ottawa Scale (NOS) was used.

RESULTS

After a primary search of three databases, 19492records were appeared. When duplicates and irrelevant documents were removed, 14 articles were found to have eligible criteria. The design of the identified studies was cross-sectional, case-control and cohort. Evidence showed an adverse association between 25(OH)D and the biomarkers of inflammation, such as high-sensitivity C-reactive protein (hs-CRP), Interleukin-1beta (IL-1β), Interleukin-6 (IL-6), and tumor necrosis factor- alfa (TNF-α) during pregnancy. On the contrary, some studies represented that 25(OH)D positively correlated with hs-CRP in the cord blood. One study suggested a direct association between serum concentrations of 25(OH)D and Interleukin-8 (IL-8), macrophage inflammatory protein (MIP), and TNF-α levels in mothers with gestational diabetes mellitus (GDM). A case-control study showed that lower serum concentration of 25(OH)D positively correlated with total antioxidant capacity (TAC) levels in participants.

CONCLUSIONS

Evidence confirmed the supposition of the direct relationship between vitamin D levels and biomarkers with anti-inflammatory and anti-oxidative properties. However, the Existence of inconsistent evidence confirms the need for further studies in mothers with GDM and hypertensive disorders.

PROSPERO REGISTRATION CODE

CRD42020202600.

Is skin autofluorescence a novel non-invasive marker in diabetes? A systematic review and meta-analysis of case-control studies

Background

The advanced glycation end product (AGE) is produced from the nonenzymatic reaction between glucose and macromolecules by aging. Accumulation of AGE causes functional and structural changes in body proteins that lead to impairment of tissue protein functions. We aimed to validate AGE measurement by skin autofluorescence (SAF) in diabetes mellitus (DM) compared to the nondiabetes population.

Materials and Methods

We searched the PubMed, Cochrane, and Scopus databases from their inception till September 18, 2022, for casecontrol studies measuring AGE by SAF. Nonhuman studies, as well as review articles, study proposals, editorials, case reports, or congress posters, were excluded. We used a random effects model to assess the standard mean difference (MD) of age, body mass index (BMI), HbA1c, and SAF between diabetes and nondiabetes individuals.

Results

Higher SAF in DM patients indicated more accumulation of AGE compared with the nondiabetic population. Furthermore, HbA1c was considerably higher in DM patients. The MD of age, male gender, and BMI were significantly different between the DM individuals, compared with nondiabetic subjects, which can lead to altered SAF level and AGE production. There was a remarkable heterogeneity between diabetes and nondiabetes when measuring age, gender, and BMI, as well as HbA1c and SAF level.

Conclusion

This study could not confirm the validity of SAF as a surrogate marker in diabetes patients. Interestingly, metabolic load and high BMI can increase SAF, considerably. Altogether, SAF could be helpful in the future as a marker for metabolic syndrome or diabetes.

The effect of vitamin D supplementation on oxidative stress and inflammatory biomarkers in pregnant women: a systematic review and meta-analysis of clinical trials

Background

Vitamin D deficiency, a common problem among pregnant women, is linked with maternal inflammation, oxidative stress and consequent adverse pregnancy outcomes. The aim of this systematic review was to evaluate the effect of vitamin D supplementation on oxidative stress and inflammatory biomarkers in pregnant women according to the PRISMA guidance.

Methods

Four databases including PubMed/MEDLINE, Scopus, Web of Science and Cochrane were used for searching papers published until 25^th July 2022. Clinical trials that assessed 25-Hydroxyvitamin D (25(OH)D), inflammatory markers (including high sensitivity C-reactive protein (hs-CRP) and certain cytokines) and oxidative stress markers (including malondialdehyde (MDA), total antioxidant capacity (TAC) and glutathione (GSH)) in pregnant women, were included in this review. The primary search of three databases displayed 21571 records. After removing duplicates and irrelevant articles, 17 eligible RCTs included for more evaluation. Random effect model and Der Simonian-Laird method were used to pool the data of studies. Risk of bias assessed according to version 2 of the Cochrane risk-of-bias tool for randomized trials.

Results

According to the meta-analysis result, vitamin D supplementation caused a significant increase in the maternal circulating concentrations of 25(OH)D (SMD 2.07; 95%, CI 1.51, 2.63; p < 0.001), TAC (SMD 2.13, 95% CI 1.04 to 3.23, p < 0.001) and GSH (SMD 4.37, 95% CI 2.9 to 5.74, p < 0.001) as well as a significant decrease in the levels of MDA (SMD -0.46, 95% CI -0.87 to -0.05, p = 0.02). However, it had no significant impact on hs-CRP concentrations (SMD 0.24; 95% CI, -0.55, 1.03; p = 0.50).

Conclusion

In the present study, vitamin D supplementation led to increased levels of 25(OH)D, TAC and GSH and also decreased concentration of MDA. Nevertheless, because of low certainty of evidence, these findings have to be declared conservatively.

Trial registration

Registration code in PROSPERO website: CRD42020202600

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05132-w.

Protective role of vitamin D against oxidative stress in diabetic retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus. There is much evidence showing that a high level of mitochondrial overproduction of reactive oxygen species in the diabetic retina contributes in modifying cellular signalling and leads to retinal cell damage and finally to the development of DR pathogenesis. In the last few decades, it has been reported that vitamin D is involved in DR pathogenesis. Vitamin D, traditionally known as an essential nutrient crucial in bone metabolism, has also been proven to be a very effective antioxidant. It has been demonstrated that it modulates the production of advanced glycosylated end products, as well as several pathways including protein kinase C, the polyol pathway leading to the reduction of free radical formation. It prevents the translocation of nuclear factor kappa B, preventing the inflammatory response, acting as an immunomodulator, and modulates autophagy and apoptosis. In this review, we explore the molecular mechanisms by which vitamin D protects the eye from oxidative stress, in order to evaluate whether vitamin D supplementation may be useful to mitigate the deleterious effects of free radicals in DR.

Implications of advanced oxidation protein products and vitamin E in atherosclerosis progression

Introduction

Advanced oxidation protein products (AOPP) are considered as markers of oxidative stress and inflammation, and highly predictive of atherosclerosis. Vitamin E (Vit-E) is a powerful antioxidant, but no consensus on its effectiveness at the level of AOPP or the process of atherosclerosis has been made. Hence this was the aim of the present study.

Material and methods

A longitudinal study was conducted on 205 patients with chronic kidney disease (CKD) and 40 controls. The correlations between AOPP and glomerular filtration rate (GFR) and different biological markers were analyzed. Supra-aortic trunk echo-Doppler was conducted to assess the correlation of AOPP with intima-media thickness. The effects of Vit-E treatment on AOPP levels and atherosclerosis progression were also investigated.

Results

AOPP levels increased in parallel to the alteration of renal functions in CKD patients, compared to the control group (p < 0.05). The mean value of AOPP increased concomitantly with the intima-media thickness (p < 0.05). Furthermore, AOPP mean value was higher in patients with atherosclerotic plaques (p < 0.05) compared to those without plaques. Vit-E treatment stabilized the levels of AOPP but had no effect on the atherosclerotic progression.

Conclusions

AOPP were proved to be effective markers of oxidative stress and their high levels help to predict the progression of atherosclerosis. As a powerful antioxidant, Vit-E stabilized the AOPP levels.

Association of Vitamin D Level and Nerve Conduction Study Parameters with Cognitive Function in Diabetic Neuropathy Patients

BACKGROUND: Type 2 diabetes mellitus (T2DM) and its major long-term complication, diabetic polyneuropathy (DPN), continue to be a major global health problem and are important contributors of significant disability worldwide. Vitamin D plays a significant role in their pathogenesis as well as in the development of dementia in non-diabetic patients. Nevertheless, the role of Vitamin D in the development of cognitive impairment in DPN patients has not yet been extensively studied. AIM: We aimed to investigate the association between Vitamin D level and cognitive function in DPN patients and to evaluate several potential contributor factors to cognition, including demographic factors, glycemic control, and nerve conduction study (NCS) parameters. METHODS: Thirty-one DPN patients were included in this cross-sectional study. Patients were recruited from the outpatient endocrinology and neurology clinic of Haji Adam Malik General Hospital Medan Indonesia. We used the diabetic neuropathy examination (DNE) scale, diabetic neuropathy symptom (DNS) scale, and NCS to determine the presence and severity of the neuropathy. We measured the levels of Vitamin D, random blood sugar, and glycated hemoglobin (HbA1c). Cognitive function was assessed using the Indonesian version of Montreal Cognitive Assessment (MoCA-INA), trail making test A and B (TMT A and TMT B), and verbal fluency test. RESULTS: Most of the patients were female (80.6%), with a mean age of 55.71 ± 8.34 years. The proportion of patients with abnormal cognitive function was higher than cognitively unimpaired patients. The mean of MoCA-INA score and level of Vitamin D was lower than normal, 23.32 ± 3.00 and 24.91 ± 13.59 ng/ml, respectively. Using the Pearson correlation test, we did not find any significant association of Vitamin D level, NCS parameters, and other clinical characteristics with global cognitive function. Age and level of education were significantly associated with MoCA-INA score. Blood sugar level was significantly higher in patients with normal TMT-A and TMT-B tests compared to patients with abnormal results. CONCLUSION: Vitamin D and NCS parameters are not associated with cognitive function. Of the demographic and clinical characteristics, a significant association exists between age, level of education, and blood sugar level and cognition. This might suggest the complexity underlying cognitive impairment in T2DM patients.

Effect of vitamin D supplementation versus placebo on essential hypertension in patients with vitamin D deficiency: a double-blind randomized clinical trial

Findings from randomized trials addressing the effect of vitamin D supplementation and blood pressure are inconsistent and have been the subject of recent debate. This study aimed to assess the effect of vitamin D supplementation on primary hypertension. This double-blind randomized clinical trial was conducted on patients aged 26-84 years with essential hypertension from March 2017 to April 2019. Patients with vitamin D insufficiency (serum vitamin D levels 20-30 ng/ml) or vitamin D deficiency (serum vitamin D levels <20 ng/ml) were enrolled in the study. Patients were randomly assigned to receive vitamin D supplementation or placebo. Systolic and diastolic blood pressure was measured before the intervention and one and two months thereafter. Of 208 patients enrolled, 171 patients remained for analysis. The effect of vitamin D supplementation on systolic blood pressure was statistically significant in the first and second months after the intervention (P=0.004 and P=0.024, respectively). The effect of vitamin D supplementation on diastolic blood pressure was statistically significant in the first month after the intervention (P=0.046), but not in the second month (P=0.885). No evidence of drug side effects was reported in the two groups. The results of this trial are suggestive of the potential benefits of vitamin D supplementation on blood pressure end points. Therefore, the use of vitamin D may be recommended as an adjuvant drug in the treatment of essential hypertension in patients with vitamin D deficiency because it is safe and well-tolerated by the patients and can significantly reduce the systolic and diastolic blood pressure. Trial registration: Iranian Registry of Clinical Trials registration number: IRCT201703129014N151.

Vitamin D and advanced glycation end products and their receptors

Advanced glycation end products (AGEs) are destructive molecules in the body that, at high levels, contribute to the progression of various chronic diseases. Numerous studies have suggested a modifying effect of vitamin D on AGEs and their receptors. This study sought to summarize the effects of vitamin D on AGEs and their receptors, including receptor for AGEs (RAGE) and soluble receptor for AGEs (sRAGE). The search method initially identified 484 articles; 331 remained after duplicate removal. Thirty-five articles were screened and identified as relevant to the study topic. After critical analysis, 27 articles were included in the final analysis. Vitamin D treatment may possibly be beneficial to reduce AGE levels and to augment sRAGE levels, particularly in vitamin D-deficient situations. Treatment with this vitamin may be effective in reducing RAGE expression in some disease conditions, but might be even harmful under normal conditions. The inhibitory or stimulatory effects of vitamin D on AGE receptors are mediated by various signaling pathways, MAPK/NF-κB, ADAM10/MMP9 and AT1R. In populations with chronic diseases and concomitant hypovitaminosis D, vitamin D supplementation can be used as a strategy to ameliorate AGE-mediated complications by modifying the AGE-RAGE and sRAGE systems.

Therapeutic potential of vitamin D in AGE/RAGE-related cardiovascular diseases

Cardiovascular diseases (CVDs) are among the leading threats to human health. The advanced glycation end product (AGE) and receptor for AGE (RAGE) signaling pathway regulates the pathogenesis of CVDs, through its effects on arterial stiffness, atherosclerosis, mitochondrial dysfunction, oxidative stress, calcium homeostasis, and cytoskeletal function. Targeting the AGE/RAGE pathway is a potential therapeutic strategy for ameliorating CVDs. Vitamin D has several beneficial effects on the cardiovascular system. Experimental findings have shown that vitamin D regulates AGE/RAGE signaling and its downstream effects. This article provides a comprehensive review of the mechanistic insights into AGE/RAGE involvement in CVDs and the modulation of the AGE/RAGE signaling pathways by vitamin D.

Serum 25-hydroxyvitamin D3 is associated with advanced glycation end products (AGEs) measured as skin autofluorescence: The Rotterdam Study

Advanced glycation end products (AGEs) accumulate in tissues with aging and may influence age-related diseases. They can be estimated non-invasively by skin autofluorescence (SAF) using the AGE Reader™. Serum 25-hydroxyvitamin D₃ (25(OH)D₃) may inhibit AGEs accumulation through anti-oxidative and anti-inflammatory properties but evidence in humans is scarce. The objective was to investigate the association between serum 25(OH)D₃ and SAF in the population-based cohort study. Serum 25(OH)D₃ and other covariates were measured at baseline. SAF was measured on average 11.5 years later. Known risk factors for AGE accumulation such as higher age, BMI, and coffee intake, male sex, smoking, diabetes, and decreased renal function were measured at baseline. Linear regression models were adopted to explore the association between 25(OH)D₃ and SAF with adjustment for confounders. Interaction terms were tested to identify effect modification. The study was conducted in the general community. 2746 community-dwelling participants (age ≥ 45 years) from the Rotterdam Study were included. Serum 25(OH)D₃ inversely associated with SAF and explained 1.5% of the variance (unstandardized B = - 0.002 (95% CI[- 0.003, - 0.002]), standardized β = - 0.125), independently of known risk factors and medication intake. The association was present in both diabetics (B = - 0.004 (95% CI[- 0.008, - 0.001]), β = - 0.192) and non-diabetics (B = - 0.002 (95% CI[- 0.003, - 0.002]), β = - 0.122), both sexes, both smokers and non-smokers and in each RS subcohort. Serum 25(OH)D₃ concentration was significantly and inversely associated with SAF measured prospectively, also after adjustment for known risk factors for high SAF and the number of medication used, but the causal chain is yet to be explored in future studies.Clinical Trial Registry (1) Netherlands National Trial Register: Trial ID: NTR6831 ( http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=6831 ). (2) WHO International Clinical Trials Registry Platform: under shared catalogue number NTR6831 ( www.who.int/ictrp/network/primary/en/ ).

Luteolin Ameliorates Cognitive Impairments by Suppressing the Expression of Inflammatory Cytokines and Enhancing Synapse-Associated Proteins GAP-43 and SYN Levels in Streptozotocin-Induced Diabetic Rats

Luteolin, a flavonoid isolated from Cirsium japonicum, has antioxidant, anti-inflammatory and neuroprotective activities. Our previous studies brought a prospect that luteolin benefited diabetic rats with cognitive impairments. In this study, we examined whether luteolin could suppress the inflammatory cytokines, thus increasing synapse-associated proteins in streptozotocin (STZ)-induced diabetes in rat models. The model rats underwent luteolin treatment for 8 consecutive weeks, followed by assessment of cognitive performances with MWM test. Nissl staining was employed to assess the neuropathological changes in the hippocampus and the effects of luteolin on diabetic rats. With animals sacrificed, expressions of inflammatory cytokines including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) and synapse-associated proteins including growth-associated protein-43 (GAP-43) and synaptophysin (SYN) were determined. The results affirmed improvement of behavioral performances in the MWM test, downexpression of glycation end products (AGEs) in the plasma and the receptor for advanced glycation end products in the hippocampus, inhibition of IL-1β and TNF-α in both the hippocampus and plasma in diabetic rats. Furthermore, luteolin treatment upregulated the expressions of GAP-43 and SYN in the hippocampus. Thus, luteolin could ameliorate the cognitive dysfunctions in STZ-induced diabetic rat model.

Correlation between follicular fluid levels of sRAGE and vitamin D in women with PCOS

PURPOSE

The pro-inflammatory advanced glycation end products (AGEs) and their anti-inflammatory soluble receptors, sRAGE, play a role in the pathogenesis of PCOS. There is a correlation between vitamin D (vit D) and sRAGE in the serum, whereby vit D replacement increases serum sRAGE levels in women with PCOS, thus incurring a protective anti-inflammatory role.

OBJECTIVE

This study aims to compare levels of sRAGE, N-carboxymethyl-lysine (CML; one of the AGEs), and 25-hydroxy-vit D in the follicular fluid (FF) of women with or without PCOS, and to evaluate the correlation between sRAGE and 25-hydroxy-vit D in the FF.

MATERIAL AND METHODS

Women with (n = 12) or without (n = 13) PCOS who underwent IVF were prospectively enrolled.

RESULTS

Women with PCOS had significantly higher anti-Mullerian hormone levels, higher number of total retrieved and mature oocytes, and higher number of day 3 and day 5 embryos formed. Compared to women without PCOS, women with PCOS had significantly lower FF sRAGE levels. In women with PCOS, in women without PCOS, and in all participants together, there was a significant positive correlation between sRAGE and 25-hydroxy-vit D. sRAGE positively correlated with CML in women without PCOS but not in women with PCOS.

CONCLUSIONS

In women with PCOS, the low ovarian levels of the anti-inflammatory sRAGE suggest that sRAGE could represent a biomarker and a potential therapeutic target for ovarian dysfunction in PCOS. Whether there is a direct causal relationship between sRAGE and vit D in the ovaries remains to be determined.

Advanced Glycation End Products: Link between Diet and Ovulatory Dysfunction in PCOS?

PCOS is the most common cause of anovulation in reproductive-aged women with 70% experiencing ovulatory problems. Advanced glycation end products are highly reactive molecules that are formed by non-enzymatic reactions of sugars with proteins, nucleic acids and lipids. AGEs are also present in a variety of diet where substantial increase in AGEs can result due to thermal processing and modifications of food. Elevation in bodily AGEs, produced endogenously or absorbed exogenously from high-AGE diets, is further exaggerated in women with PCOS and is associated with ovulatory dysfunction. Additionally, increased expression of AGEs as pro-inflammatory receptors in the ovarian tissue has been observed in women with PCOS. In this review, we summarize the role of dietary AGEs as mediators of metabolic and reproductive alterations in PCOS. Once a mechanistic understanding of the relationship between AGEs and anovulation is established, there is a promise that such knowledge will contribute to the subsequent development of targeted pharmacological therapies that will treat anovulation and improve ovarian health in women with PCOS.