The Relationship between Vitamin D and Type 2 Diabetes Is Intriguing: Glimpses from the Spect-China Study

Serum 25-hydroxyvitamin D, genetic susceptibility, and the risk of incident type 2 diabetes: A prospective cohort in East China

BACKGROUND

The serum vitamin D level varies widely by population, and studies have linked vitamin D levels with the risk of type 2 diabetes mellitus (T2DM). However, the relationship is inconsistent and the impact of vitamin D on T2DM among East Chinese adults is unclear. The study aimed to investigate the association between serum 25-hydroxyvitamin D (25[OH]D) levels and the risk of T2DM and evaluated whether the association is modified by genetic predisposition.

METHODS

In the Survey on Prevalence in East China for Metabolic Diseases and Risk Factors (SPECT-China) cohort, 1862 participants free of T2DM at baseline were included. A weighted genetic risk score was calculated with 28 variants associated with T2DM. Hierarchical logistic models were used to examine the association of serum 25(OH)D and genetic risk with T2DM.

RESULTS

After a 5-year follow-up, 132 cases of T2DM were documented. We observed no significant association between quartiles of serum 25(OH)D and T2DM risk after multivariable adjustment (χ 2 = 0.571, Pfor trend = 0.426). Compared to those in the lowest quartile of 25(OH)D, the odds ratios (ORs) (95% confidence interval [CI]) for participants with increased quartiles were 1.29 (0.74-2.25), 1.35 (0.77-2.36), and 1.27 (0.72-2.24), respectively. We observed a positive association of glycated hemoglobin (HbA1c) with 25(OH)D at baseline (β = 1.752, P = 0.001) and after follow-up (β = 1.385, P = 0.003), and a negative association of ln conversion homeostasis model assessment (HOMA)-β with 25(OH)D at baseline (β = -0.982, P = 0.021). There was no significant interaction between 25(OH)D and diabetes genetic predisposition on the risk of T2DM (χ 2 = 2.710, Pfor interaction = 0.100). The lowest OR (95% CI) of T2DM was among participants with low genetic risk and the highest quartile of 25(OH)D (0.17 [0.05-0.62]).

CONCLUSION

Serum 25(OH)D may be irrelevant to the risk of incident T2DM among East Chinese adults regardless of genetic predisposition.

The role of systemic inflammation in the association between serum 25-hydroxyvitamin D and type 2 diabetes mellitus

BACKGROUND & AIMS

The association between serum 25-hydroxyvitamin D [25(OH)D] and type 2 diabetes mellitus (T2DM) remains inconclusive. Moreover, whether inflammatory biomarkers are involved in this association has not been explored. This study aims to investigate serum 25(OH)D in relation to T2DM in a Chinese population and provide clues for the inflammatory mechanism whereby serum 25(OH)D deficiency increases T2DM risk.

METHODS

A cross-sectional study of 47,803 participants aged 18-96 years was performed in a health management center in 2017. Multivariate linear or logistic regression models and mediation analysis were used to examine the relationships between serum 25(OH)D, inflammatory biomarkers (white blood cell counts and mean platelet volume), and T2DM.

RESULTS

Of the 47,803 participants included, 5.2% were diabetic and 51.4% were serum 25(OH)D deficient. The study revealed a significant inverse association between serum 25(OH)D and T2DM risk after adjustment for potential confounders (P for trend = 0.002); the multivariate-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) across serum 25(OH)D levels (sufficiency, insufficiency, and deficiency) were 1.00 (reference), 1.17 (1.03-1.33), and 1.25 (1.09-1.43), respectively. This study also showed a significant indirect effect of serum 25(OH)D on T2DM risk through total white blood cell count, neutrophil count, lymphocyte count, and monocyte count (P values < 0.05); the proportions mediated were 9.89%, 7.51%, 2.94%, and 2.82%, respectively.

CONCLUSIONS

Serum 25(OH)D deficiency was independently associated with an elevated risk of T2DM in a Chinese adult population and low-grade systemic inflammation might be one of its biological mechanisms.

Sex-Specific Association between Serum 25-Hydroxyvitamin D and Metabolic Risk Factors in T2DM Patients

OBJECTIVE

To evaluate the relationship between serum 25-hydroxyvitamin (25(OH)D) levels and metabolic risk factor levels in patients with type 2 diabetes mellitus (T2DM) on a sex-specific basis.

METHODS

Our study comprised 507 patients with T2DM (321 men, 186 women; median age, 59 years). The metabolic risk factors examined included lipoprotein(a), glycated albumin (GA-L), and random blood glucose (RBG); the levels of these parameters were determined enzymatically. Serum 25(OH)D levels were measured by commercial ELISA kits. Participants were divided into low and high 25(OH)D groups according to the median 25(OH)D concentration (13.2 ng/mL). Two-way analysis of covariance and multiple linear regression analysis were performed.

RESULTS

The median 25(OH)D concentration was 13.9 ng/mL in men and 12.2 ng/mL in women. 25(OH)D levels inversely correlated with levels of three metabolic risk factors in a sex-dependent manner after adjusting for several confounding factors. These were lipoprotein(a) in men (141.3 ± 137.9 and 195.3 ± 204.8 mg/L in high and low 25(OH)D groups, respectively; P < 0.05); GA-L in women (22.2 ± 8.8 vs. 23.3 ± 7.3% in high and low 25(OH)D groups, respectively; P < 0.05). In a subgroup analysis, serum 25(OH)D levels inversely correlated with lipoprotein(a) levels in men (β = -0.185, P = 0.002) and RBG levels in women (β = -0.176, P = 0.028).

CONCLUSION

Higher serum 25(OH)D levels indicate a more favorable lipid profile in men and a more favorable glucose profile in women.

A Comparison Study of Vitamin D Deficiency among Older Adults in China and the United States

Vitamin D deficiency is a common health concern worldwide. We aim to compare the prevalence of vitamin D deficiency among older adults (65+) in China and the United States (US). We used data from the 2011 wave of Chinese Longitudinal Healthy Longevity Survey (CLHLS) in China (n = 2180), and 2011–2014 National Health and Nutrition Examination Survey (NHANES) in the US (n = 2283). Serum 25-hydroxyvitamin D [25(OH)D] was measured and a level of under 30/50 nmol/L was defined as vitamin D severe deficiency/deficiency. Risk factors of vitamin D deficiency were examined by multivariate regression models. We found that the mean 25(OH)D concentration was lower in China than in the US (45.1 vs. 83.5 nmol/L), with Chinese elderly lower than American elderly for every age group. 70.3% in China and 17.4% in the US were considered as vitamin D deficiency (30.6% and 3.4% were considered as severe deficiency). Older age, females, ethnic minorities, higher household income, self-rated “very bad” health, and never drinkers, were statistically significant in predicting lower serum 25(OH)D levels in China. In the US, males, ethnic minorities, lower income, self-rated “very bad” health, physically inactive, overweight, and obese were related to lower serum 25(OH)D levels. Our findings suggest that different interventional strategies are needed to improve vitamin D deficiency and its associated negative health outcomes in China and the US.

Evaluation and comparison of serum vitamin D and calcium levels in periodontally healthy, chronic gingivitis and chronic periodontitis in patients with and without diabetes mellitus - a cross-sectional study

Objective: Limited data are available with respect to the relation of vitamin D and calcium with periodontal infections and type-2 diabetes mellitus (T2DM). The aim of this cross-sectional study was to evaluate the levels of vitamin D and calcium in serum of periodontally healthy, chronic gingivitis and chronic periodontitis patients with and without T2DM. Material and methods: The study evaluated 100 patients equally divided into five groups (Group I to Group V) according to the inclusion criteria. Clinical parameters and serum 25-hydroxyvitamin D level were assessed. Other laboratory investigations comprised of random blood sugar, glycated haemoglobin and serum calcium. Results: The probing pocket depth and clinical attachment loss were found to be greater in chronic periodontitis and chronic periodontitis with diabetes mellitus, while the vitamin D and calcium levels were found to be least in these groups. When vitamin D and calcium levels were compared between periodontal disease with diabetes to that of non-diabetics, statistically significant difference were found between the two with p-value of .001 indicating decrease in levels of vitamin D and calcium with increase in RBS and HbA1c values. Conclusion: Vitamin D and calcium levels are inversely correlated with random blood sugar and glycated haemoglobin and also probing pocket depth and clinical attachment loss, thus contributing towards increase in periodontal disease severity.