The vitamin D receptor (VDR) gene rs11568820 variant is associated with type 2 diabetes and impaired insulin secretion in Italian adult subjects, and associates with increased cardio-metabolic risk in children

The rs11568820 Variant in the Promoter Region of Vitamin D Receptor Gene Is Associated with Clinical Remission in Rheumatoid Arthritis Patients Receiving Tumor Necrosis Factor Inhibitors

The vitamin D receptor (VDR), binding to the active form of the vitamin, promotes the transcription of numerous genes involved in the proliferation of immune cells, cytokine production and lymphocyte activation. It is known that vitamin D deficiency can influence the risk of developing rheumatoid arthritis (RA) or modulate its disease activity. The aim of this study was to investigate a possible association between the rs11568820 (C > T) polymorphism in the promoter region of VDR gene and the response to therapy with anti-TNF drugs in patients with RA. A total of 178 consecutive Italian patients with RA treated with anti-TNF, naïve for biological therapy, were recruited. Disease activity data were evaluated using specific indices such as DAS28, CDAI and SDAI, measured at the start of therapy and subsequently at 22, 52, 104 and 240 weeks. A statistically significant association emerged between the rs11568820 variant allele of VDR gene and failure to remission assessed by CDAI and SDAI at 52 weeks, and by DAS28, CDAI and SDAI at 104 weeks of follow-up. Furthermore, the variant allele of this polymorphism was observed more frequently in patients who did not undergo sustained remission calculated by CDAI and SDAI. The variant T allele of rs11568820 in VDR gene is associated with a reduced remission rate with anti-TNFα drugs. These data suggest the role of VDR genetic variability in the response to therapy and in the achievement of remission.

Association between serum 25-hydroxyvitamin D and fasting blood glucose in osteoporosis patients

Osteoporosis (OP) is often associated with other complications, such as impaired glucose homeostasis. Vitamin D deficiency is common and has been linked to bone metabolism and the regulation of blood sugar levels. The aim of this study was to evaluate the independent relationship between serum 25-hydroxyvitamin D (25[OH]D) and fasting blood glucose levels (FBG) in a group of patients diagnosed with OP. This is a retrospective cross-sectional study from a prospectively collected database at our tertiary referral center. Consecutive 2084 OP patients who were hospitalization were finally analyzed in this study. FBG is the dependent variable, serum 25(OH)D level of OP patients is exposure variable of this study. There was a linear significantly negative association between serum 25(OH)D and FBG (β, - 0.02; 95% CI - 0.03 to - 0.01; P = 0.0011) in the fully adjusted models. Specifically, when serum 25(OH)D level was less than 23.39 ng/mL, FBG decreased by 0.04 mmol/L for every 1 ng/mL increase of serum 25(OH)D level. When serum 25(OH)D was greater than 23.39 ng/ mL, the negative association was insignificant (P = 0.9616). If the association is confirmed, the clinical management of blood glucose in OP patients with serum 25(OH)D deficiency has instructive implications.

Relevance of Serum Levels and Functional Genetic Variants in Vitamin D Receptor Gene among Saudi Women with Gestational Diabetes Mellitus

Background: This study explored the association between ApaI-TaqI Single Nucleotide Polymorphisms (SNPs) in a Vitamin D receptor (VDR) and the risk of Gestational Diabetes Mellitus (GDM) in Saudi women, along with the serum levels of vitamin D. Methods: Ninety women with GDM and 90 non-GDM women were enrolled, based on the inclusion and exclusion criteria for pregnant women enrolled in a single-center study. Blood samples were retrieved from 180 pregnant women using ethylenediaminetetraacetic acid (EDTA) tubes. Serum samples were used to measure the vitamin D, 25-hydroxyvitamin D (25(OH)D or calcidiol), and lipid profiles. Blood was used to measure the hemoglobin A1c levels and to isolate the DNA. The polymerase chain reaction (PCR) was performed for the ApaI (rs79785232), BsmI (rs1544410), FokI (rs2228570), and TaqI (rs731236) SNPs in the VDR gene using restriction fragment length polymorphism analysis. Validation was performed using Sanger sequencing. Statistical analyses were performed between the patients with and without GDM using various statistical software packages. Results: The Hardy-Weinberg equilibrium analysis was statistically significant (p > 0.05). The ApaI, BsmI, and TaqI SNPs were associated with alleles, genotypes, and different genetic models (p < 0.05). Vitamin D levels were associated with deficient levels (p = 0.0002), as well as with a normal and overweight body mass index (p = 0.0004). When vitamin D levels were measured with GDM covariates, the fasting plasma glucose (FPG) (p = 0.0001), postprandial blood glucose (PPBG) (p < 0.0001), oral glucose tolerance test (OGTT)-1 h (p = 0.005), high-density lipoprotein (p = 0.022), and low-density lipoprotein cholesterol (LDLc) (p = 0.001) levels were significantly different. When similar vitamin D levels were measured for each genotype, we confirmed that the ApaI SNP was associated with sufficient levels (p < 0.0001), whereas the BsmI, FokI, and TaqI (p < 0.05) were associated with insufficient levels. The logistic regression model confirmed that the first hour of the OGTT (p = 0.005) was strongly associated with GDM, whereas the analysis of variance confirmed that FPG and PPBG (p < 0.05) were strongly associated with all the SNPs evaluated in the VDR gene. Additionally, the second hour of the OGTT (p = 0.048) and LDLc (p = 0.049) were associated with the ApaI and FokI SNP. Moreover, the first hour OGTT (p = 0.045) and lipid profile parameters (p < 0.05) were associated. Haplotype analysis revealed positive associations among the examined SNPs, which seemed compatible with the hypothesis that variants and combinations of multiple SNP genotypes enhance the risk of GDM in women. Haplotype analysis revealed that different combinations of alleles, such as AGCC, CATT, CGTC, AGTC, and CATT (p < 0.05), were strongly associated. The linkage disequilibrium (LD) analysis showed a strong association with all combinations (p < 0.05). Among the gene-gene interactions, all possible combinations showed a positive association (p < 0.05). Conclusions: Low vitamin D levels were observed in women with GDM. The ApaI, BsmI, and TaqI SNPs were associated with genotype and allele frequencies (p < 0.05). Vitamin D and the SNPs in the VDR gene were associated, according to the ANOVA, logistic regression, haplotype analysis, LD analysis, and the generalized multifactor dimensionality reduction model (p < 0.05).

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

Association Between Expression of Vitamin D Receptor and Insulin-Like Growth Factor 1 Receptor Among Breast Cancer Patients

Background

Vitamin D receptor (VDR) and insulin-like growth factor 1 receptor (IGF1R) are known to be involved in breast cancer (BC) progression. Our previous work reported a correlation of differential localization of IGF1R with hormone receptor status in BC. A recent report described VDR and IGF1R as potential indicators of BC prognosis, but their interplay was not discussed. The present study focused on understanding the association of VDR expression with IGF1R activation, different molecular markers, and subtypes of BC.

Methods

A retrospective study was designed to evaluate the VDR expression among 48 BC patients pathologically diagnosed as invasive BC and were surgically treated at Sharjah Breast Care Center, University Hospital Sharjah (UHS), United Arab Emirates (UAE). Formalin-fixed paraffin-embedded (FFPE) tumor blocks with appropriate clinicopathological data were subjected to immunohistochemistry (IHC), and VDR protein expression was interpreted based on the staining intensity (SI) and the percentage of the positively stained cells (PP).

Results

Nearly 44% of cases in the study were vitamin D deficient. A positive VDR expression with strong intensity (score > 4) was seen in 27 cases (56.3%). The expression pattern for VDR was equally distributed in cytoplasm and nucleus. For the IGF1R intensity, 24 cases (50%) of total cohort showed strong expression. A significant association was detected between IGF1R and VDR expression (P = 0.031).

Conclusions

The present study identified positive association between IGF1R and VDR expression where most of the cases with strong VDR expression displayed strong IGF1R expression. These findings may contribute to current understanding on the role of VDR in BC and its interaction with IGF1R.

The Association of Gene Variants in the Vitamin D Metabolic Pathway and Its Interaction with Vitamin D on Gestational Diabetes Mellitus: A Prospective Cohort Study

The present prospective study included 2156 women and investigated the effect of gene variants in the vitamin D (VitD) metabolic and glucose pathways and their interaction with VitD levels during pregnancy on gestational diabetes mellitus (GDM). Plasma 25(OH)D concentrations were measured at the first and second trimesters. GDM subtype 1 was defined as those with isolated elevated fasting plasma glucose; GDM subtype 2 were those with isolated elevated postprandial glucose at 1 h and/or 2 h; and GDM subtype 3 were those with both elevated fasting plasma glucose and postprandial glucose. Six Gc isoforms were categorized based on two GC gene variants rs4588 and rs7041, including 1s/1s, 1s/2, 1s/1f, 2/2, 1f/2 and 1f/1f. VDR-rs10783219 and MTNR1B-rs10830962 were associated with increased risks of GDM and GDM subtype 2; interactions between each other as well as with CDKAL1-rs7754840 were observed (P_interaction < 0.05). Compared with the 1f/1f isoform, the risk of GDM subtype 2 among women with 1f/2, 2/2, 1s/1f, 1s/2 and 1s/1s isoforms and with prepregnancy body mass index ≥24 kg/m² increased by 5.11, 10.01, 10, 14.23, 19.45 times, respectively. Gene variants in VitD pathway interacts with VitD deficiency at the first trimester on the risk of GDM and GDM subtype 2.

The combination of omega-3 fatty acids with high doses of vitamin D3 elevate A1c levels: A randomized Clinical Trial in people with vitamin D deficiency

PURPOSE

This randomised clinical trial (RCT) was created to assess the influence of 1,25-dihydroxyvitamin D (VD₃ ), omega-3 fatty acids (n-3FA) and their combination (D+) on glycated haemoglobin (A1c) levels in Jordanian peoples with vitamin D deficiency (VDD).

PARTICIPANTS AND METHODS

This RCT was designed to examine the follow-up (2 months) effect of either 50 000 IU VD₃ , 300 mg n-3FA, or the combination of the two supplements on glycated Haemoglobin (A1c) levels in 146 Jordanian women and men with VDD, aged from 25 to 55 years. The eligible participants were randomised into four groups: Control (C); VD₃ supplementation (50 000 IU of VD₃ was taken weekly) (D₃ ); n-3FA supplementation (300 mg of omega-3FA was taken daily) (n-3FA); VD₃ and omega-3 supplementation group (D+) with the same protocol as the previous two groups.

RESULTS

The combination therapy (n-3FA plus VD3) for 8 weeks significantly increased A1c levels (5.79 ± 0.34 vs 5.41 ± 0.33, P < .001). Tukey test for post hoc comparisons of A1c at follow-up showed that the A1c mean levels were remarkably higher in the D+ study group comparing to the control group (5.78 vs 5.38).

CONCLUSION

The intervention of n-3FA alone or in combination with high doses of VD₃ may lead to negative effects on glycaemic control or accelerate the insulin resistance's development in susceptible people for diabetes mellitus (type 2).

TaaI/Cdx-2 AA Variant of VDR Defines the Response to Phototherapy amongst Patients with Psoriasis

1,25-dihydroxyvitamin-D₃ plays a central role in the immune system via binding to the vitamin D receptor. VDR polymorphisms have been associated with multiple autoimmune disorders, including psoriasis. Until now, five VDR polymorphisms, FokI, ApaI, BsmI, TaqI and TaaI/Cdx2, have been studied in psoriasis, with contradicting results. Therefore, this study aimed to evaluate the association of VDR polymorphisms with susceptibility to psoriasis, effectiveness of NB-UVB phototherapy and concentration of proinflammatory cytokines and vitamin D amongst the Polish population. VDR polymorphisms were analyzed by PCR-RFLP or real-time PCR. We found that the frequency of the TaaI/Cdx-2 GG genotype was significantly higher in psoriasis patients and was associated with regulation of IL-17 and IL-23 concentration. Moreover, TaaI/Cdx-2 AA might have a significant effect on the response to phototherapy amongst patients with psoriasis. Our results suggest that VDR is a susceptibility factor for psoriasis development. Moreover, TaaI/Cdx-2 variants have a significant effect on the response to phototherapy amongst patients with psoriasis and regulation of inflammatory response via decrease of IL-17 and IL-23 level after UVB phototherapy in the Polish population. Results of our study provide some evidence in support of the hypothesis that the vitamin D signaling pathway may be of relevance for pathogenesis and treatment of psoriasis.

Vitamin D pathway-related gene polymorphisms and their association with metabolic diseases: A literature review

PURPOSE

Given that the relationship between vitamin D status and metabolic diseases such as obesity and type 2 diabetes (T2D) remains unclear, this review will focus on the genetic associations, which are less prone to confounding, between vitamin D-related single nucleotide polymorphisms (SNPs) and metabolic diseases.

METHODS

A literature search of relevant articles was performed on PubMed up to December 2019. Those articles that had examined the association of vitamin D-related SNPs with obesity and/or T2D were included. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data. In total, 73 articles were included in this review.

RESULTS

There is a lack of research focusing on the association of vitamin D synthesis-related genes with obesity and T2D; however, the limited available research, although inconsistent, is suggestive of a protective effect on T2D risk. While there are several studies that investigated the vitamin D metabolism-related SNPs, the research focusing on vitamin D activation, catabolism and transport genes is limited. Studies on CYP27B1, CYP24A1 and GC genes demonstrated a lack of association with obesity and T2D in Europeans; however, significant associations with T2D were found in South Asians. VDR gene SNPs have been extensively researched; in particular, the focus has been mainly on BsmI (rs1544410), TaqI (rs731236), ApaI (rs7975232) and FokI (rs2228570) SNPs. Even though the association between VDR SNPs and metabolic diseases remain inconsistent, some positive associations showing potential effects on obesity and T2D in specific ethnic groups were identified.

CONCLUSIONS

Overall, this literature review suggests that ethnic-specific genetic associations are involved. Further research utilizing large studies is necessary to better understand these ethnic-specific genetic associations between vitamin D deficiency and metabolic diseases.

Association Between Cardiovascular Risk Factors and 25(OH)D Levels in Obese Patients

Background: Obesity is associated with lower levels of 25-hydroxyvitamin D [25(OH)D] and higher cardiovascular risk related to metabolic syndrome (MetS). Our purpose was to investigate if there is an association between levels of 25(OH)D and the components of MetS in an obese sample. Methods: This cross-sectional study enrolled obese patients referred for bariatric surgery in a specialized clinic. Secondary data were gathered as follows: glycemic and lipid profiles, 25(OH)D, anthropometric parameters, and clinical and sociodemographic information. The results were presented as means (standard deviations) or medians and interquartile intervals or absolute and relative frequencies. The patients were divided into three groups based on 25(OH)D terciles for analysis and were compared using ANOVA, Kruskal-Wallis or chi-squared tests. The correlations were calculated by Spearman's or Pearson's correlation tests. Results: We studied 299 patients, with the majority being women (74.9%). The patients' average (SD) age and 25(OH)D level were 36 (9) years and 25.8 (7.5) ng/mL, respectively. There was no association between vitamin D and MetS or its components. A progressive decrease in total cholesterol, low-density lipoprotein cholesterol (LDL-c), and nonhigh-density lipoprotein cholesterol (HDL-c) was observed as the serum vitamin D level increased, although only the latter reached statistical significance (P = 0.033). The correlation analysis showed a negative linear association between 25(OH)D and total cholesterol (r = -0.157; P = 0.047), 25(OH)D and LDL-c (r = -0.164; P = 0.038), and 25(OH)D and non-HDL-c (r = -0.176; P = 0.026). Conclusions: There was a negative correlation between 25(OH)D levels and the atherogenic profile but none with the MetS.

Vitamin D-related genes and cardiometabolic markers in healthy children: a Mendelian randomisation study

Observational studies show associations between low serum 25-hydroxyvitamin D (25(OH)D) and cardiometabolic risk markers. This Mendelian randomisation study examined associations between cardiometabolic markers in children and SNP in genes related to vitamin D metabolism (DHCR7; group-specific complement (GC); cytochrome P450 subfamily IIR1 (CYP2R1); and CYP24A1) and action (CYP27B1 and VDR). In 699 healthy 8–11-year-old children, we genotyped eleven SNP. We generated a genetic risk score based on SNP associated with low 25(OH)D and investigated associations between this and blood pressure, plasma lipids and insulin. Furthermore, we examined whether SNP related to vitamin D actions modified associations between 25(OH)D and the cardiometabolic markers. All GC and CYP2R1 SNP influenced serum 25(OH)D. A risk score based on four of the six SNP was associated with 3·4 (95 % CI 2·6, 4·2) mmol/l lower 25(OH)D per risk allele (P < 0·001), but was not associated with the cardiometabolic markers. However, interactions were indicated for the three VDR SNP (Pinteraction < 0·081) on associations between 25(OH)D and TAG, systolic blood pressure and insulin, which all decreased with increasing 25(OH)D only in major allele homozygotes (β –0·02 (95 % CI –0·04, –0·01) mmol/l; β –0·5 (95 % CI –0·9, –0·1) mmHg; and β –0·5 (95 % CI –1·4, 0·3) pmol/l, respectively). In conclusion, genetic variation affected 25(OH)D substantially, but the genetic score was not associated with cardiometabolic markers in children. However, VDR polymorphisms modified associations with vitamin D, which warrants further investigation of VDR's role in the relationship between vitamin D and cardiometabolic risk.

Association between serum 25-hydroxyvitamin D, hemoglobin A1c and fasting blood glucose levels in adults with diabetes mellitus

In the present study, the aim was to investigate the association between serum 25-hydroxyvitamin D concentration and measures of glycemic control including hemoglobin A1c (HbA1c) and fasting blood glucose (FBG) in adult patients with diabetes mellitus (DM) from the north of Jordan. Another aim was to compare serum levels of 25-hydroxyvitamin D between patients with good glycemic control and patients with uncontrolled DM. This was a cross-sectional study that included 261 participants with DM. The concentration of 25-hydroxyvitamin D was measured using electrochemiluminescence immunoassay, HbA1c was measured using turbidimetric inhibition immunoassay and FBG was measured using the hexokinase method. Data regarding other clinical variables were obtained from medical records or by self-reporting. Participants with good glycemic control exhibited significantly higher levels of 25-hydroxyvitamin D compared with participants with uncontrolled DM (P=0.03). Participants with sufficient vitamin D status (>30 ng/ml in serum) exhibited significantly lower HbA1c level compared with participants with deficient vitamin D (<20 ng/ml) status (P=0.02). Correlation analysis determined significant inverse correlations between 25-hydroxyvitamin D levels and HbA1c and FBG levels (r=-0.23 and -0.17, respectively, both P<0.01). There were also significant correlations between duration of DM and HbA1c and FBG levels (both r=0.21, P<0.01). HbA1c level was also inversely correlated with participants' age (r=-0.19, P<0.01). Further multiple linear regression analysis revealed an inverse significant association between HbA1c and 25-hydroxyvitamin D levels (F=12.95, R²=0.48, P<0.01) but did not identify a similar association between FBG and 25-hydroxyvitamin D levels. These findings may encourage further research to identify if vitamin D supplementation may improve measures of glycemic control, and how vitamin D may affect glucose homeostasis in patients with DM.

The vitamin D receptor functional variant rs2228570 (C>T) does not associate with type 2 diabetes mellitus

AIM

Vitamin D acts through the binding to the vitamin D receptor (VDR). Several polymorphisms in VDR gene have been studied. Among these, the rs2228570 C>T (FokI) variant has been demonstrated to be functional, leading to a protein with a different size and activity. So far, genetic studies on the association between VDR gene rs2228570 single nucleotide polymorphism (SNP) and type 2 diabetes mellitus (T2DM) showed contradictory results. Thus, we performed an association study in a large cohort of adult Italian subjects with T2DM and in nondiabetic controls.

MATERIALS AND METHODS

For this study, 1713 subjects, 883 T2DM patients and 830 controls, were genotyped for the polymorphism. All participants without a diagnosis of diabetes underwent oral glucose tolerance test (OGTT), with measurement of glucose and insulin levels. Indices of insulin resistance (Homeostatic model assessment of insulin resistance, insulin sensitivity index), secretion (homeostatic model assessment for beta-cell, corrected insulin response at 30 minutes) and disposition index were calculated.

RESULTS

Genotype distributions and allele frequencies did not show difference between T2DM subjects and controls. We did not find significant differences among the three genotypes regarding gender, age, BMI, waist, hip, waist-to-hip ratio, and blood pressure. There were also no significant differences in lipid parameters, aspartate aminotransferase, and alanine aminotransferase levels. We tested for association with OGTT-derived data and surrogate indices of insulin resistance and secretion. We did not find significant differences among the genotypes in any of above-mentioned parameters. Furthermore, vitamin D levels were measured in a subgroup of subjects. We did not find significant differences among the genotypes.

CONCLUSIONS

Our study does not provide evidence for the association of the rs2228570 polymorphism with T2DM in a Caucasian population.

Weight gain since age of 20 as risk of metabolic syndrome even in non-overweight individuals

PURPOSE

Metabolic syndrome (MetS), regardless of the presence of obesity, is known as a risk of diabetes and cardiovascular disease. Weight gain after age 20 reported to be associated with these diseases. Impact of the difference between the body mass index (BMI) at examination and BMI at age 20 (ΔBMI_exa-20y) on MetS, especially in non-overweight individuals, remains to be elucidated.

METHODS

We analyzed the data of 24,363 individuals (14,301 men and 10,062 women) in this cross-sectional study. The diagnosis of MetS was diagnosed when three or more of the following criteria were present: hypertension, hyperglycemia, hypertriglyceridemia, low HDL-cholesterol level, and abdominal obesity. Logistic regression was performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) adjusting for age, alcohol, smoking, exercise, and BMI at examination.

RESULTS

Compared to the lowest ΔBMI_exa-20y tertile (ΔBMI_exa-20y < 1.2 kg/m² in men and ≤0 kg/m² in women), the highest tertile (ΔBMI_exa-20y ≥ 3.2 kg/m² in men and ≥2.0 kg/m² in women) was associated with the risk of the presence of MetS (multivariate OR = 1.80, 95%CI 1.53-2.11, p < 0.001 in men and OR = 3.27, 95%CI 2.22-4.96, p < 0.001 in women). This result was also applicable in non-overweight individuals (multivariate OR = 2.06, 95%CI 1.46-2.92, p < 0.001 in men and OR = 2.49, 95%CI 1.40-4.64, p < 0.001 in women).

CONCLUSIONS

Our analyses showed that ΔBMI_exa-20y is associated with the risk of the presence of MetS, even in non-overweight individuals. It is thus important to check weight changes from early adulthood, even in non-overweight individuals.

The Arg282Ser missense mutation in APOA5 gene determines a reduction of triglyceride and LDL-cholesterol in children, together with low serum levels of apolipoprotein A-V

Background

Apolipoprotein A-V (ApoA-V) is a recognized regulator of plasma triglycerides (TGs), and previous studies have shown associations between variants in APOA5 (apolipoprotein-A5) gene and high TG levels. Recently, a new association between the Arg282Ser missense mutation (rs778114184 G > T) in APOA5 gene and decreased triglyceride levels has been shown in an adult population from Sardinia.

In this study we add further insight into the role of APOA5 by exploring whether this association begins early in life in children, or becomes manifest only in adulthood. We performed the genetic association analysis of APOA5 in a cohort of 925 overweight and obese children and adolescents from Sardinia, Italy, to see if the genetic burden is already at play before modifying risk factors are interacting.

Results

We identified 24 heterozygous subjects for the Arg282Ser variant and no homozygous subject. Here we show that the Arg282Ser mutation in APOA5 gene is associated with a significant reduction of TG (−15.5 mg/dl), total (−18.1 mg/dl) and LDL-cholesterol (−14.8 mg/dl) levels in overweight/obese children and adolescents, indicating that indeed this association appears early in life. Also, we observed a significant reduction in serum apoA-V levels in heterozygous children.

Conclusions

Our data clearly show that the Arg282Ser mutation in APOA5 gene determines a reduction of TG, total and LDL-cholesterol and apolipoprotein A-V levels in overweight/obese children and adolescents, demonstrating that this mutation has the power to affect lipid levels already since childhood.

Vitamin D deficiency and diabetes

Vitamin D deficiency has been linked to the onset of diabetes. This review summarizes the role of Vitamin D in maintaining the normal release of insulin by the pancreatic beta cells (β-cells). Diabetes is initiated by the onset of insulin resistance. The β-cells can overcome this resistance by releasing more insulin, thus preventing hyperglycaemia. However, as this hyperactivity increases, the β-cells experience excessive Ca2+ and reactive oxygen species (ROS) signalling that results in cell death and the onset of diabetes. Vitamin D deficiency contributes to both the initial insulin resistance and the subsequent onset of diabetes caused by β-cell death. Vitamin D acts to reduce inflammation, which is a major process in inducing insulin resistance. Vitamin D maintains the normal resting levels of both Ca2+ and ROS that are elevated in the β-cells during diabetes. Vitamin D also has a very significant role in maintaining the epigenome. Epigenetic alterations are a feature of diabetes by which many diabetes-related genes are inactivated by hypermethylation. Vitamin D acts to prevent such hypermethylation by increasing the expression of the DNA demethylases that prevent hypermethylation of multiple gene promoter regions of many diabetes-related genes. What is remarkable is just how many cellular processes are maintained by Vitamin D. When Vitamin D is deficient, many of these processes begin to decline and this sets the stage for the onset of diseases such as diabetes.

Nutritional rickets: vitamin D, calcium, and the genetic make-up

BACKGROUND

The prevalence of vitamin D (vitD) deficiency presenting as rickets is increasing worldwide. Insufficient sun exposure, vitD administration, and/or calcium intake are the main causes. However, vitD system-related genes may also have a role.

METHODS

Prospective study: 109 rachitic children completed a 6-mo study period or until rachitic manifestations disappeared. Thirty children were selected as controls. Clinical and biochemical data were evaluated at baseline in patients and controls and biochemistry re-evaluated at radiological healing. Therapy was stratified in three different protocols. Fifty-four single-nucleotide polymorphisms (SNPs) of five vitD system genes (VDR, CP2R1, CYP27B1, CYP24A1, and GC) were genotyped and their association with clinical and biochemcial data was analyzed.

RESULTS

Therapy response was similar in terms of radiological healing although it was not so in terms of biochemical normalization. Only VDR gene (promoter, start-codon, and intronic genotypes) was rickets-associated in terms of serum 25-OH-D, calcium, radiological severity and time needed to heal. Eight patients with sufficient calcium intake and 25-OH-D levels carried a VDR genotype lacking minor allele homozygous genotypes at SNPs spread along the gene.

CONCLUSION

Although patients presented epidemiologic factors strongly contributing to rickets, genetic modulation affecting predisposition, severity, and clinical course is exerted, at least in part, by VDR gene polymorphic variation.

The protective role of vitamin D on the heart and the kidney

For a long time, vitamin D was regarded as an essential component for the maintenance of appropriate calcium metabolism. Indeed, the calcium-related functions were broadly studied and validated in numerous clinical and epidemiologic studies. All of these vitamin D effects are mediated by a specific receptor. Remarkably, recent investigations show that the vitamin D receptor (VDR) also affects autoimmunity and by these means, the course of neoplasias and tissue inflammation. Moreover, the VDR regulates genes that affect cellular activity including cell differentiation and apoptosis and, by these means, angiogenesis. Actually, vitamin D deficiency has been associated with structural and functional cardiovascular changes that can be reversed by receptor stimulation. In this regard, some of the injurious effects of vitamin D deficiency such as myocardial hypertrophy and high blood pressure seem linked to increased renin-angiotensin activity. Interestingly, chronic renal disease, a condition often associated with greater cardiovascular risk, high blood pressure, myocardial hypertrophy and inappropriate stimulation of the renin angiotensin system, is also tied to inadequate vitamin D activity. In fact, studies in several animal models such as the rat ureteral obstruction model, the 5/6 nephrectomy model and others, clearly show that VDR stimulation prevents both structural and functional changes in the heart and the kidney. Clinical trials are needed to validate the vitamin D potential benefits in chronic kidney disease and its associated cardiovascular risk.