Effects of vitamin D and/or calcium intervention on sleep quality in individuals with prediabetes: a post hoc analysis of a randomized controlled trial.

PURPOSE: The aim of this study was to evaluate the effects of vitamin D and/or calcium supplementation on sleep quality in individuals with prediabetes. METHODS: A 24-week randomized controlled trial (RCT) was conducted in a 212 Chinese population with prediabetes. Participants were randomly assigned to four groups: vitamin D + calcium group (1600 IU/day + 500 mg/day, n = 53), vitamin D group (1600 IU/day, n = 54), calcium group (500 mg/day, n = 51), and control group (placebo, n = 54). The Pittsburgh Sleep Quality Index (PSQI) was used as the primary outcome to assess sleep quality. Questionnaires and fasting blood samples were collected at baseline and post-intervention for demographic assessment and correlation index analysis. RESULTS: After a 24-week intervention, a significant difference was observed in serum 25(OH)D concentration among the four groups (P < 0.05), and the total PSQI score in vitamin D + calcium group was lower compared to the preintervention levels. Subgroup analyses revealed improved sleep quality with calcium supplementation (P < 0.05) for specific groups, including women, individuals with a low baseline 25(OH)D level (< 30 ng/mL), and individuals in menopause. Moreover, correlation analysis revealed a negative correlation between the extent of change in sleep efficiency scores before and after the calcium intervention and the degree of change in insulin efficiency scores (r = - 0.264, P = 0.007), as well as the magnitude of change in islet beta cell function (r = - 0.304, P = 0.002). CONCLUSIONS: The combined intervention of vitamin D and calcium, as well as calcium interventions alone, exhibits substantial potential for improving sleep quality in individuals with prediabetes. CLINICAL TRIAL REGISTRATION: The trial was registered in August 2019 as ChiCTR190002487.

Effect of Vitamin D and/or Calcium Supplementation on Pancreatic ß-Cell Function in Subjects with Prediabetes: A Randomized, Controlled Trial.

So far, the potential role of vitamin D in ß-cell function remains a matter of debate. Therefore, a randomized, placebo-controlled trial (RCT) was conducted to evaluate the effect of a vitamin D supplement with or without calcium on ß-cell function in a Chinese population with prediabetes. Two hundred and forty-three subjects were randomly assigned in a 2-by-2 factorial-design RCT to receive either 1600 IU/day vitamin D3 with/or 500 mg/day calcium for 24 weeks. The results showed that oral administration of vitamin D and calcium could increase the secretion of insulin. Vitamin D-insufficient individuals displayed an increment in the disposition index (adjusted change = 0.31, 95%CI: 0.07, 0.56) after treatment by vitamin D + calcium. It illustrated that supplementation with vitamin D and calcium might improve the function of pancreatic ß-cell in prediabetes with low serum 25(OH)D levels. However, further studies are needed to confirm the findings. Given the low vitamin D content in natural foods, it is necessary to fortify processed foods with vitamin D.

GC gene polymorphisms found with type 2 diabetes and low vitamin D status among rural Chinese in Henan province.

BACKGROUND AND OBJECTIVES: Accumulating evidence suggests that vitamin D may be involved in the pathogenesis of type 2 diabetes (T2D). Group-specific component (GC) gene is the most important transporter of vitamin D and plays a regulatory role in vitamin D metabolism. We aimed to evaluate the association of GC gene polymorphisms with T2D susceptibility and vitamin D status in the Chinese rural population. METHODS AND STUDY DESIGN: A total of 1372 subjects were eligible in this cross-sectional study. Three SNPs of the GC gene (rs7041, rs4588, and rs2282679) were genotyped by TaqMan probe assays. Logistic regression and Kruskal-Wallis one-way analysis were performed to determine the possible risk genotype for T2D and vitamin D metabolite concentrations, respectively. RESULTS: The serum 25-hydroxyvitamin D3 [25(OH)D3] and vitamin D binding protein (DBP) concentrations were significantly lower in the T2D group than the non-T2D group. GG genotype carriers of rs7041 (T>G) were more likely to have T2D compared with AA carriers (OR=2.00, 95% CI: 1.19-3.37). Variants of rs4588 (C>A) and rs2282679 (A>C) were associated with a lower risk of T2D under the dominant inheritance model (OR=0.65, 95% CI: 0.48-0.88; OR=0.66, 95% CI: 0.49-0.90, respectively). We further found that non-T2D subjects with the AA genotype of rs4588 had significantly higher 25(OH)D3 concentrations than the CC genotype (p=0.022). In contrast, the T2D cases with the CC genotype of rs2282679 had lower DBP concentrations compared to the AA genotype (p=0.020). CONCLUSIONS: Our study indicates a potential role for GC gene polymorphisms in T2D susceptibility and vitamin D metabolite concentrations in the Chinese rural population.

The Association Between GC Gene Polymorphisms and Metabolic Syndrome in Chinese Rural Population: A Case-Control Study.

BACKGROUND: GC (group-specific component globulin) encoding VDBP (Vitamin D binding protein) polymorphisms have been associated with susceptibility to some diseases such as diabetes, obesity, osteoporosis, and polycystic ovary syndrome, but the evidence for metabolic syndrome (MetS) in the Chinese rural population is inconclusive. Therefore, we investigated the relationship between GC variants (rs7041, rs4588, rs2282679, and rs705117) and MetS risk as well as VDBP levels in the Chinese rural population. PATIENTS AND METHODS: The participants (range of age: 20-90 years) of this case-control study were recruited from the northern Chinese Han rural population. We matched 445 MetS cases with non-MetS controls in a 1:1 ratio by sex, age (within 5 years). Real-time PCR technology was carried out by TaqMan assays to examine the four variants of rs7041, rs4588, rs2282679, and rs705117 within the GC gene. To identify the association of GC gene polymorphisms with MetS, we calculated ORs using a conditional logistic regression model adjusted for potential confounding factors. RESULTS: We observed inverse associations of CA and AA genotypes of rs4588 with risk of MetS (OR = 0.678, 95% CI 0.505-0.910, P = 0.010; 0.603, 95% CI 0.373-0.973, P = 0.039, respectively) compared with carriers of CC genotype. A similar relationship was also found between rs2282679 and MetS, showing that carrying AC genotype of rs2282679 can decrease the risk of MetS (OR = 0.683, 95% CI 0.509-0.917, P = 0.011) compared with carriers of AA genotype. The results of correlation analysis between MetS components and GC polymorphisms showed that the ORs of AA genotype of rs4588 with high level of TG (triglycerides) and low level of HDL-C (high-density lipoprotein cholesterol) were 0.473 (95% CI 0.245-0.911, P = 0.025) and 0.268 (95% CI 0.117-0.615, P = 0.002), respectively; the ORs of CC genotype of rs2282679 with high level of TG and low level of HDL-C were 0.428 (95% CI 0.217-0.842, P = 0.014) and 0.263 (95% CI 0.110-0.628, P = 0.003), respectively. However, there was no significant association between the concentration of VDBP and MetS risk. CONCLUSION: Among the Chinese rural population, GC polymorphism was associated with lower metabolic syndrome susceptibility, which might be through affecting blood lipid levels (TG and HDL-C).