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

Serum 25-Hydroxyvitamin D Is Associated With Prediabetes, Type 2 Diabetes Mellitus, and Insulin Resistance in Children: A Systematic Review and Dose-Response Meta-analysis of Epidemiologic Studies

CONTEXT

Although several investigations have been conducted on the association between serum vitamin D levels and prediabetes and type 2 diabetes mellitus (T2DM) in children and adolescents, their findings are inconsistent.

OBJECTIVE

We conducted a systematic review and dose-response meta-analysis to summarize this subject.

DATA SOURCES

The electronic databases of ISI Web of Science, Scopus, PubMed, and motor engineering of Google Scholar were comprehensively searched up to May 2023.

DATA EXTRACTION

Epidemiologic studies that investigated the risk of hyperglycemia and insulin resistance in relation to serum 25-hydroxy vitamin D levels in children and adolescents were included.

DATA ANALYSIS

Twenty-two investigations, with a total of 38 622 participants, were systematically reviewed. Meta-analysis of 15 studies (n = 32 720 participants) showed that participants with the highest serum vitamin D levels had 42% lower risk of hyperglycemia, compared with those in the lowest category of serum vitamin D levels (relative risk [RR] = 0.58; 95%CI, 0.48, 0.71). Moreover, pooling 8 studies (n = 10 465 participants) illustrated that highest serum vitamin D level was associated with a 44% lower risk of insulin resistance compared with the lowest serum vitamin D level (RR = 0.56; 95%CI, 0.37, 0.83). Based on linear dose-response analysis, each 10 nmol/L increment in serum 25-hydroxy vitamin D was associated with a 6% decreased risk of hyperglycemia and insulin resistance in children. Furthermore, nonlinear dose-response analysis revealed that increasing serum vitamin D concentration from 40 nmol/L to sufficient values (>50 nmol/L) was associated with a decreasing trend in risk of hyperglycemia and insulin resistance.

CONCLUSION

This meta-analysis revealed inverse associations between serum vitamin D levels and hyperglycemia and insulin resistance in children and adolescents, in a dose-response manner. Increasing serum vitamin D concentration from 40 nmol/L to sufficient values (>50 nmol/L) was associated with a decreasing trend in hyperglycemia and insulin resistance risk. Systematic Review Registration: PROSPERO registration no. CRD42023458155.

The Associations of Vitamin D Level with Metabolic Syndrome and Its Components Among Adult Population: Evidence from National Health and Nutrition Examination Survey 2017-2018

Background and Purpose: Vitamin D can both stimulate and inhibit adipogenesis, indicating that associations of the vitamin D level with some metabolic disorders may be nonlinear. This cross-sectional study aims to explore potential nonlinear associations of the 25-hydroxy vitamin D [25(OH)D] level with metabolic syndrome (MetS) and its components. Methods: Adults without previously diagnosed specific noncommunicable disease were selected from the National Health and Nutrition Examination Survey 2017-2018 (n = 870). Their demographic, physical, and laboratory data were obtained. The associations of serum 25(OH)D with MetS and its components were analyzed using logistic regression. Restricted cubic spline was applied to flexibly model the nonlinear association if the nonlinearity test was statistically significant. Results: The 25(OH)D level was inversely associated with risk of MetS [adjusted odds ratio (OR) = 0.986; 95% confidence interval (CI) = 0.978-0.993] and most MetS components, but not with the risk of raised triglycerides (adjusted OR = 0.996; 95% CI = 0.988-1.005). The association of serum 25(OH)D with central obesity risk was significantly nonlinear (P for the nonlinearity test: 0.037). The OR for risk of central obesity decreased rapidly with increase in serum 25(OH)D concentration until the concentration reached 50 nmol/L, and then, the intensity of decrease in OR slowed down. Conclusions: Vitamin D is inversely associated with MetS, but not all MetS components. A nonlinear association between the vitamin D level and risk of central obesity has been found for the first time among the adult population, which reflects the complex roles of vitamin D in lipid metabolism. Although vitamin D deficiency (<50 nmol/L) was defined to avoid abnormal calcium and phosphorus metabolism, preventing its deficiency may also be beneficial for reduction of central obesity risk.

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.

Serum Vitamin D Status in Older Adults: A Cohort Study

Background

Vitamin D is best known as a key regulator of bone metabolism and calcium and phosphate homeostasis. This study aimed to assess the effect of different factors on the five-year changes in serum vitamin D concentration among older adults.

Methods

This cohort study was conducted on adults aged ≥60 years living in Amirkola, in the North of Iran, from 2012 to 2017. Serum 25-hydroxyvitamin D (25-OH vitamin D) concentrations of <20, 20-29.99, and ≥30 ng/mL, respectively, were used to designate vitamin D deficiency, insufficiency, and sufficiency. Any variation between the second and baseline values of the 25-OH vitamin D concentration was reported as a five-year difference. Data were analyzed using SPSS version 17.0, and Chi square, t test, one-way ANOVA, and Tukey HSD post hoc tests were employed. P values less than 0.05 were considered statistically significant.

Results

The mean serum concentration of 25-OH vitamin D at baseline and follow-up examination in 1011 individuals was 34.68±33.18 and 23.88±14.91, respectively (P<0.001). Following a five-year follow-up, vitamin D deficiency, insufficiency, and sufficiency were found in 452 (44.7%), 334 (33.0%), and 225 (22.3%) cases, respectively. The reduction in serum 25-OH vitamin D concentration after five years was significantly influenced by the administration of vitamin D (P=0.013) and calcium (P=0.007) supplements, serum profile of parathyroid hormone (PTH) (P=0.010), calcium (P=0.021), and phosphorous (P=0.021). However, age, sex, body mass index, metabolic syndrome, and physical activity had no significant impact (P>0.05).

Conclusion

Regardless of age, sex, body mass index, metabolic syndrome, or physical activity, the mean serum concentration of vitamin D decreased over a five-year follow-up.

The gut microbiota-bile acid axis mediates the beneficial associations between plasma vitamin D and metabolic syndrome in Chinese adults: A prospective study

BACKGROUND & AIMS

Previous studies have suggested that circulating 25-hydroxyvitamin D (25 [OH]D, VD) and the gut microbiota-bile acid axis play crucial roles in metabolic health. Exploring the mediating role of the gut microbiota-bile acid axis would improve our understanding of the mechanisms underlying the effects of VD on human metabolic health. This study examined the association between plasma 25(OH)D and the prevalence/incidence of metabolic syndrome (MetS) and the mediating role of the gut microbiota-bile acid axis.

METHODS

This prospective study included 3180 participants with plasma 25(OH)D data at baseline and 2966 participants with a 9-year follow-up. MetS was determined every three years. The gut microbiota was analyzed by 16S rRNA sequencing in 1752 participants, and targeted bile acid metabolites in feces were further determined in 974 participants using UPLC‒MS/MS at the middle of the study. Mediating roles of microbiota and bile acids in the VD-MetS associations were analyzed using mediation/path analyses adjusted for potential confounders.

RESULTS

Among the 2966 participants who were followed-up, 1520, 193, 647, and 606 were MetS-free (normal), recovered, had incident MetS, and had persistent MetS, respectively. The multivariable-adjusted ORs (95% CIs) of MetS prevalence were 0.65 (0.50, 0.84) for baseline MetS and 0.46 (0.33, 0.65) for 9-year persistent MetS in quartile 4 (compared to quartile 1) of plasma 25(OH)D (median: 37.7 vs. 19.6, ng/ml). The corresponding HR (95% CI) of 9-year MetS incidence was 0.71 (0.56, 0.90) (all P-trend < 0.05). Higher VD concentrations were associated with greater α-diversity of the gut microbiota, which was inversely correlated with MetS risk. The groups classified by VD and MetS status had significantly different β-diversity. Ruminiclostridium-6 and Christensenellaceae R-7 group were enriched in the high-VD group and were inversely associated with MetS. However, opposite associations were observed for Lachnoclostridium and Acidaminococcus. The overlapping differential microbial score (ODMS) developed from the four differential genera explained 12.2% of the VD-MetS associations (P_mediation = 0.015). Furthermore, the fecal bile acid score created from 11 differential bile acids related to ODMS and MetS mediated 34.2% of the association between ODMS and MetS (P_mediation = 0.029). Path analyses showed that the inverse association between plasma 25(OH)D and MetS could be mediated by the gut microbiota-bile acid axis.

CONCLUSIONS

The findings suggest that the gut microbiota-bile acid axis partially mediates the beneficial association between plasma 25(OH)D and the risk of persistent MetS and incident MetS in the Chinese population.

Nutritional Assessment of the Symptomatic Patient on a Plant-Based Diet: Seven Key Questions

Plant-based diets, both vegan and vegetarian, which emphasize grains, vegetables, fruits, legumes, nuts, and seeds are increasingly popular for health as well as financial, ethical, and religious reasons. The medical literature clearly demonstrates that whole food plant-based diets can be both nutritionally sufficient and medically beneficial. However, any person on an intentionally restrictive, but poorly-designed diet may predispose themselves to clinically-relevant nutritional deficiencies. For persons on a poorly-designed plant-based diet, deficiencies are possible in both macronutrients (protein, essential fatty acids) and micronutrients (vitamin B12, iron, calcium, zinc, and vitamin D). Practitioner evaluation of symptomatic patients on a plant-based diet requires special consideration of seven key nutrient concerns for plant-based diets. This article translates these concerns into seven practical questions that all practitioners can introduce into their patient assessments and clinical reasoning. Ideally, persons on plant-based diets should be able to answer these seven questions. Each serves as a heuristic prompt for both clinician and patient attentiveness to a complete diet. As such, these seven questions support increased patient nutrition knowledge and practitioner capacity to counsel, refer, and appropriately focus clinical resources.

Association between insulin resistance and abnormal menstrual cycle in Chinese patients with polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder, which is characterized by insulin resistance (IR) and menstrual cycle disorders. IR is thought of as a pivotal cause of PCOS and related comorbidities. However, the link between IR and abnormal menstrual cycles in PCOS should be further studied. In this study, we clarified the dose-response relationship between IR and abnormal menstrual cycles in patients with PCOS.

RESULTS

In this retrospective study including 140 patients with PCOS, we found that there was a dose-response relationship between the increased HOMA-IR index and the level of menstrual cycle disorders (1.61 [95%CI: 1.37-1.85] for normal menstruation, 2.02 [95%CI: 1.61-2.44] for oligomenorrhea, 2.35 [95%CI:1.96-2.75] for amenorrhea, P for trend = 0.003). Further stratification analyses showed that this dose-response relationship was more evident in the patients who were younger, had higher BMI, higher AFC numbers, elevated levels of testosterone, anti-Müllerian hormone, inhibin B, and prolactin levels, and had a lower progestogen level.

CONCLUSIONS

Our study has established an association between IR and abnormal menstrual cycles in patients with PCOS, which can be affected by age, BMI, and hormone levels. Our results might be helpful for further prevention and treatment of amenorrhea in PCOS.

The management of erectile dysfunction in men with diabetes mellitus unresponsive to phosphodiesterase type 5 inhibitors

INTRODUCTION

Erectile dysfunction is associated with diabetes mellitus with an estimated prevalence of 52.5% in the diabetic population. The first-line therapy for erectile dysfunction is phosphodiesterase type 5 inhibitors, but data suggest that diabetic men may be less responsive than non-diabetic men. Thus, other treatments, including intracavernosal injections, intraurethral prostaglandin, vacuum erection devices and penile prosthetic surgery, should be considered in management of diabetic men with erectile dysfunction refractory to phosphodiesterase type 5 inhibitors. Furthermore, combination therapy of phosphodiesterase type 5 inhibitors and other oral treatments such as arginine or l-carnitine may have synergistic effects resulting in better outcomes. In addition, there are novel therapies such as low-intensity shockwave therapy and stem-cell therapy, which may also be effective in targeted treatment modalities. Furthermore, studies suggest that erectile dysfunction can be improved by targeting concurrent comorbidities or metabolic diseases such as depression, hypertension, hypogonadism, and dyslipidaemia. We present an evidence-based narrative review focusing on the management of erectile dysfunction in diabetic men who have not responded to phosphodiesterase type 5 inhibitors.

CONCLUSIONS

Both clinicians and patients should be aware of the different management options in diabetic patients who have not responded to phosphodiesterase type 5 inhibitors.

The crucial role and mechanism of insulin resistance in metabolic disease

Insulin resistance (IR) plays a crucial role in the development and progression of metabolism-related diseases such as diabetes, hypertension, tumors, and nonalcoholic fatty liver disease, and provides the basis for a common understanding of these chronic diseases. In this study, we provide a systematic review of the causes, mechanisms, and treatments of IR. The pathogenesis of IR depends on genetics, obesity, age, disease, and drug effects. Mechanistically, any factor leading to abnormalities in the insulin signaling pathway leads to the development of IR in the host, including insulin receptor abnormalities, disturbances in the internal environment (regarding inflammation, hypoxia, lipotoxicity, and immunity), metabolic function of the liver and organelles, and other abnormalities. The available therapeutic strategies for IR are mainly exercise and dietary habit improvement, and chemotherapy based on biguanides and glucagon-like peptide-1, and traditional Chinese medicine treatments (e.g., herbs and acupuncture) can also be helpful. Based on the current understanding of IR mechanisms, there are still some vacancies to follow up and consider, and there is also a need to define more precise biomarkers for different chronic diseases and lifestyle interventions, and to explore natural or synthetic drugs targeting IR treatment. This could enable the treatment of patients with multiple combined metabolic diseases, with the aim of treating the disease holistically to reduce healthcare expenditures and to improve the quality of life of patients to some extent.

The Association between Atherosclerotic Disease Risk Factors and Serum 25-Hydroxyvitamin D Concentration in Japanese Subjects

Recent studies have described that vitamin D deficiency/insufficiency is associated with hypertension, insulin resistance, and dyslipidemia, which are major components of metabolic syndrome causing atherosclerosis. Therefore, we investigated the relationship between serum 25-hydroxyvitamin D [25(OH)D] concentration and atherosclerotic disease risk factors in healthy Japanese adults. In the present cross-sectional study, 1,177 subjects (348 males and 829 females) aged 20-72 y living in Japan (34.7-35.0ºN) were evaluated for vitamin D status by measuring serum 25(OH)D concentration. Atherosclerotic disease risk factors were defined as the presence of two or more of the following three risk factors: high blood pressure, dyslipidemia, and hyperglycemia. The percentages of vitamin D deficient and insufficient subjects were 33% and 46% in males and 59% and 32% in females, respectively. Subjects with atherosclerotic disease risk factors were significantly older and had higher BMI than those without it in both sexes. Male subjects with atherosclerotic disease risk factors had significantly lower physical activity and serum 25(OH)D concentration than those without it. In a logistic regression analysis adjusted for confounding factors, serum 25(OH)D concentration showed a significant inverse association with risk factors of atherosclerotic disease in males (OR=0.951, 95%CI: 0.906-0.998), but not in females. A covariance structure analysis also suggested that serum 25(OH)D level has a direct association with risk factors of atherosclerotic disease. In conclusion, we have demonstrated that low serum 25(OH)D level is a significant factor for increased atherosclerotic disease risk factors in males.

Bone mineral density and lipid profiles in older adults: a nationwide cross-sectional study

It has been hypothesized that lipid profiles are associated with bone mineral density (BMD), but previous results have been controversial. In this study, serum triglycerides showed a significant inverse association with BMD, and the relationship is thought to correlate with vitamin D status among older adults.

INTRODUCTION

The purpose of this study was to investigate the relationship between lipid profiles and bone mineral density (BMD) in older adults using data from the Korean National Health and Nutrition Examination Survey (KNHANES).

METHODS

We enrolled men older than 50 years and postmenopausal women who participated in the KNHANES 2008-2011. Subjects with liver cirrhosis, thyroid disease, or renal dysfunction and those receiving treatment for hyperlipidemia or osteoporosis were excluded.

RESULTS

A total of 4323 subjects (2286 men and 2037 women) was analyzed. The prevalence of osteoporosis was 8.7% in men older than 50 years and 38.4% in postmenopausal women. Osteopenia and osteoporosis groups were generally older and tended to have a lower body mass index compared to the normal group (p for trend < 0.001). The correlation between each lipid profile and BMD was analyzed in the linear model adjusted for age and body mass index. Total cholesterol and high-density lipoprotein cholesterol showed a negative correlation with BMD in the total population, but there was no significant correlation when analyzed separately for men and women. Triglycerides had a negative association with whole-body BMD in both men and women (p < 0.05). The adjusted odds ratio of logarithmic triglyceride level for osteoporosis was 2.50 (95% confidence interval 1.13-5.51) in women older than 65 years.

CONCLUSION

Serum triglycerides showed a significant inverse association with BMD, and the relationship is thought to correlate with vitamin D status among older adults.

Sedentary time and the risk of metabolic syndrome: A systematic review and dose-response meta-analysis

The dose-response association between sedentary time and the risk of metabolic syndrome is unclear, which indicates an important knowledge gap in public health. The objective of this study was to determine the categorical and continuous dose-response associations between sedentary time and the risk of metabolic syndrome. A systematic literature search of English articles published in PubMed, CINHAL, Embase, and Web of Science Core Collection prior to June 2022 was conducted. All cohort and cross-sectional studies that examined the association between sedentary time and the risk of metabolic syndrome were considered, and duplicate and non-related studies were excluded. Data extraction using a standardized chart and quality assessment using two appraisal tools were also performed. Two independent reviewers were involved in these processes. In categorical meta-analyses, the pooled effect sizes for metabolic syndrome associated with different categories of sedentary time were calculated by comparing the highest and intermediate with the lowest categories. In continuous meta-analyses, the linear and nonlinear dose-response associations were estimated using generalized least squares and restricted cubic spline models, respectively. Data were collected and analyzed from March to June 2022. Four prospective cohort studies and 22 cross-sectional studies with 105,239 participants and 16,185 MetS cases were included in this study. In categorical analyses, both intermediate (median duration: 4.11 h/day; pooled OR: 1.17, 95% CI: 1.08-1.26, P &lt; 0.001) and high levels (median duration: 7.26 h/day; pooled OR: 1.71, 95% CI: 1.43-2.04, P &lt; 0.001) of total sedentary time were significantly associated with an increased risk of metabolic syndrome. Similarly, a significant association between screen time and the risk of metabolic syndrome was also found in intermediate (median duration: 2.22 h/day; pooled OR: 1.20, 95% CI: 1.10-1.32, P &lt; 0.001) and high levels (median duration: 3.40 h/day; pooled OR: 1.63, 95% CI: 1.44-1.86, P &lt; 0.001) of exposure. Of note, these associations were significantly stronger in women. Different patterns of the behavior-disease association were not observed in children, adolescents, and adults. The findings of continuous meta-analyses could not provide solid evidence for the linearity and nonlinearity of the behavior-disease association. This study demonstrated that long-time sedentary behavior was associated with a higher risk of MetS independent of physical activity and the patterns of association varied by gender instead of age. These findings have implications for future guideline recommendations on physical activity, sedentary behavior, and prevention of metabolic syndrome.

Vitamin D Levels in Newly Diagnosed Breast Cancer Patients according to Tumor Sub-Types

Vitamin D is an important regulator of bone health. In addition, as a ligand for a nuclear receptor expressed in breast cancer cells, vitamin D exerts neoplasia modulating effects in breast cancer. However, despite extensive investigations, associations of vitamin D levels with breast cancer patient characteristics and disease sub-types are conflicting. A retrospective review of medical records of consecutive breast cancer patients treated and followed in a single cancer center was undertaken. All patients with 25-hydroxyvitamin D (25-OHD, the circulating form of vitamin D) measurements available within 3 months of their diagnosis and before the start of any systemic treatment were included. Characteristics of patients and tumors with sufficient levels of 25-OHD were compared with those of patients with 25-OHD insufficiency. Two hundred ninety-two patients were included in the study. Almost two-thirds of the patients were 25-OHD insufficient, defined as having 25-OHD levels below 75 nmol/L. Compared with the group of patients who were 25-OHD sufficient, patients with 25-OHD insufficiency were younger and more often obese. Tumors of patients with 25-OHD insufficiency were more often ductal, of higher grade, and ER negative. 25-OHD insufficiency is prevalent in breast cancer patients and even more prevalent in younger and obese patients. 25-OHD insufficiency is associated with cancers that have aggressive characteristics, including higher grade and ER negativity.

Unravelling the Contribution of the rs7041 and rs4588 Polymorphisms of the GC Gene and Serum VDBP Levels for Developing Metabolic Syndrome in the Mexican Population

Metabolic syndrome (MetS) is a multifactorial disorder integrated by a constellation of cardiovascular risk factors. The genetic and environmental determinants of MetS are not fully elucidated. This study investigated the association of two common single nucleotide polymorphisms (SNPs) on GC, rs7041 and rs4588, derived haplotypes, and serum vitamin D binding protein (VDBP) levels with the susceptibility to suffer MetS in Mexican adults. We included 1924 individuals; clinical and biochemical data were obtained through standard methods. Genotyping was performed through predesigned TaqMan assays. Logistic regression models were used to assess the associations of interest. Prevalence of MetS was 52.9% in the whole population, being more frequent in women. We observed that some association results differed between sexes. The GG genotype of the rs7041 was associated with increased odds of MetS in women. For the rs4588, the CA genotype had a protective effect against MetS in women. The haplotype GC2 was associated with reduced odds for MetS and some of its components in women. Our data suggest that VDBP serum levels were influenced by genotypes/haplotypes and this interplay seems to influence the risk of MetS. Our data provide reliable evidence regarding the association of GC polymorphisms with MetS risk in Mexican women.

Association between circulating 25-hydroxyvitamin D and cardiometabolic risk factors in adults in rural and urban settings

Background

An inverse association between vitamin D status and cardiometabolic risk has been reported but this relationship may have been affected by residual confounding from adiposity and physical activity due to imprecise measures of these variables. We aimed to investigate the relationship between serum 25-hydroxyvitamin D (25(OH)D) and cardiometabolic risk factors, with adjustment for objectively-measured physical activity and adiposity.

Methods

This was a population-based cross-sectional study in 586 adults in Cameroon (63.5% women). We assessed markers of glucose homoeostasis (fasting blood glucose (BG), 2 h post glucose load BG, HOMA-IR)) and computed a metabolic syndrome score by summing the sex‐specific z‐scores of five risk components measuring central adiposity, blood pressure, glucose, HDL cholesterol and triglycerides.

Results

Mean±SD age was 38.3 ± 8.6 years, and serum 25(OH)D was 51.7 ± 12.5 nmol/L. Mean 25(OH)D was higher in rural (53.4 ± 12.8 nmol/L) than urban residents (50.2 ± 12.1 nmol/L), p = 0.002. The prevalence of vitamin D insufficiency (<50 nmol/L) was 45.7%. There was an inverse association between 25(OH)D and the metabolic syndrome score in unadjusted analyses (β = −0.30, 95% CI −0.55 to −0.05), which became non-significant after adjusting for age, sex, smoking status, alcohol intake and education level. Serum 25(OH)D was inversely associated with fasting BG (−0.21, −0.34 to −0.08)), which remained significant after adjustment for age, sex, education, smoking, alcohol intake, the season of data collection, BMI and physical activity (−0.17, −0.29 to −0.06). There was an inverse association of 25(OH)D with 2-h BG (−0.20, −0.34 to −0.05) and HOMA-IR (−0.12, −0.19 to −0.04) in unadjusted analysis, but these associations became non-significant after adjustment for potential confounders.

Conclusion

Vitamin D insufficiency was common in this population. This study showed an inverse association between vitamin D status and fasting glucose that was independent of potential confounders, including objectively measured physical activity and adiposity, suggesting a possible mechanism through insulin secretion.

Acanthosis Nigricans Is a Strong Predictor of Low Blood Calcidiol Levels in Children and Adolescents

Background: Clinical consensus differs as to when blood vitamin D (VD) levels should be measured in children. Obesity and metabolic syndrome are risk factors for low VD levels and are also associated with acanthosis nigricans (AN). Objectives: To test whether the clinical diagnosis of AN is a strong predictor for vitamin D deficiency (VDD) in children. Methods: Within the study period (2015-2020), we identified 677 consecutive individuals (age <18 years) with available calcidiol measurements and compared those with (n = 273) and without (n = 404) AN. Bivariate associations and the occurrence of AN were tested using the chi-squared test. Multivariate logistic regression was performed to control for confounding variables, and adjusted odds ratios with 95% confidence intervals (CI) were reported. Multiple regression analysis was performed, and unstandardized beta coefficients, standard errors, and standardized beta coefficients were reported. Results: Individuals with AN had 3.6 times higher odds of VDD than those without (95% CI: 1.38-9.51, P = 0.009). Males had 0.41 times lower odds of having AN than females (95% CI: 0.21-0.79, P = 0.008). Individuals with vitamin D sufficiency (VDS) were much less likely to be diagnosed with metabolic syndrome compared with those who were vitamin D deficient (P = 0.011), even after adjusting for body mass index z-scores. Conclusion: Children and adolescents with AN are at a higher risk of VDD and should likely be tested for low calcidiol levels.

Clinical Practice in the Prevention, Diagnosis and Treatment of Vitamin D Deficiency: A Central and Eastern European Expert Consensus Statement

Vitamin D deficiency has a high worldwide prevalence, but actions to improve this public health problem are challenged by the heterogeneity of nutritional and clinical vitamin D guidelines, with respect to the diagnosis and treatment of vitamin D deficiency. We aimed to address this issue by providing respective recommendations for adults, developed by a European expert panel, using the Delphi method to reach consensus. Increasing the awareness of vitamin D deficiency and efforts to harmonize vitamin D guidelines should be pursued. We argue against a general screening for vitamin D deficiency but suggest 25-hydroxyvitamin D (25(OH)D) testing in certain risk groups. We recommend a vitamin D supplementation dose of 800 to 2000 international units (IU) per day for adults who want to ensure a sufficient vitamin D status. These doses are also recommended for the treatment of vitamin D deficiency, but higher vitamin D doses (e.g., 6000 IU per day) may be used for the first 4 to 12 weeks of treatment if a rapid correction of vitamin D deficiency is clinically indicated before continuing, with a maintenance dose of 800 to 2000 IU per day. Treatment success may be evaluated after at least 6 to 12 weeks in certain risk groups (e.g., patients with malabsorption syndromes) by measurement of serum 25(OH)D, with the aim to target concentrations of 30 to 50 ng/mL (75 to 125 nmol/L).

Gut microbiota and vitamin status in persons with obesity: A key interplay

There are numerous factors involved in obesity progression and maintenance including systemic low-grade inflammation, adipose tissue dysfunction, or gut microbiota dysbiosis. Recently, a growing interest has arisen for vitamins' role in obesity and related disorders, both at the host and gut bacterial level. Indeed, vitamins are provided mostly by food, but some, from the B and K groups in particular, can be synthesized by the gut bacterial ecosystem and absorbed in the colon. Knowing that vitamin deficiency can alter many important cellular functions and lead to serious health issues, it is important to carefully monitor the vitamin status of patients with obesity and potentially already existing comorbidities as well as to examine the dysbiotic gut microbiota and thus potentially altered bacterial metabolism of vitamins. In this review, we examined both murine and human studies, to assess the prevalence of sub-optimal levels of several vitamins in obesity and metabolic alterations. This review also examines the relationship between vitamins and the gut microbiota in terms of vitamin production and the modulation of the gut bacterial ecosystem in conditions of vitamin shortage or supplementation. Furthermore, some strategies to improve vitamin status of patients with severe obesity are proposed within this review.

Metabolic Syndrome and Sarcopenia

Skeletal muscle is a major organ of insulin-induced glucose metabolism. In addition, loss of muscle mass is closely linked to insulin resistance (IR) and metabolic syndrome (Met-S). Skeletal muscle loss and accumulation of intramuscular fat are associated with a variety of pathologies through a combination of factors, including oxidative stress, inflammatory cytokines, mitochondrial dysfunction, IR, and inactivity. Sarcopenia, defined by a loss of muscle mass and a decline in muscle quality and muscle function, is common in the elderly and is also often seen in patients with acute or chronic muscle-wasting diseases. The relationship between Met-S and sarcopenia has been attracting a great deal of attention these days. Persistent inflammation, fat deposition, and IR are thought to play a complex role in the association between Met-S and sarcopenia. Met-S and sarcopenia adversely affect QOL and contribute to increased frailty, weakness, dependence, and morbidity and mortality. Patients with Met-S and sarcopenia at the same time have a higher risk of several adverse health events than those with either Met-S or sarcopenia. Met-S can also be associated with sarcopenic obesity. In this review, the relationship between Met-S and sarcopenia will be outlined from the viewpoints of molecular mechanism and clinical impact.

Relationship and Effects of Vitamin D on Metabolic Syndrome: A Systematic Review

Metabolic syndrome (MetS) is a persistent public health problem in the United States (U.S.) due to its increasing prevalence and its positive correlation with type-2 diabetes (T2DM) and cardiovascular disease (CVD). According to National Cholesterol Education Program's Adult Treatment Panel III (NCEP-ATP III) criteria, MetS has six main components, which are obesity, dyslipidemia, raised blood pressure (BP), insulin resistance (IR) or glucose intolerance, pro-inflammatory state, and prothrombotic state. Vitamin D (Vit D) regulates the absorption of calcium and phosphorus and thus, is universally accepted as an essential vitamin for bone strength as well as a facilitator of immune system function. Vit D was also shown to reduce the risks of CVD, multiple sclerosis, and developing seasonal flu. We conducted a systematic review to identify the general association between Vit D level and MetS, to highlight specific associations between Vit D level and individual components of MetS, and finally, to explore the effects of Vit D supplementation on each component of MetS. In this paper, we reviewed 14 recent studies investigating the relationships between Vit D, MetS, and components of MetS. From the review of seven studies, we confirmed a significant association between Vit D and MetS as a whole. Four out of the five observational studies we reviewed support that Vit D level is significantly associated with the following components of MetS: obesity and BMI, dyslipidemia, BP, and insulin and glucose metabolism. We did not discover any significant relationship between Vit D level and other MetS components. The review of seven additional randomized clinical trials (RCT)-based studies suggest that Vit D supplementation has significant effects on BP, abdominal obesity, and insulin and glucose metabolism.