Association of serum vitamin D status with gestational diabetes mellitus and other laboratory parameters in early pregnant women

Causal association between serum 25-hydroxyvitamin D levels and gestational diabetes mellitus: a bidirectional two-sample Mendelian randomization study

PURPOSE

Previous investigations have assessed the connection between vitamin D deficiency and an increased risk of gestational diabetes mellitus (GDM); however, the findings remain inconsistent. The purpose of this study was to investigate the causal relationship between 25-hydroxyvitamin D (25OHD) levels and GDM.

METHODS

Summary statistics data from genome-wide association studies (GWASs) were used to perform a bidirectional two-sample Mendelian randomization (MR) study. A total of 417,580 Europeans from the UK Biobank provided summary statistics data for 25OHD. The tenth data release of the FinnGen study provided the data for GDM, comprising 14,718 cases and 215,592 controls. For the univariate MR (uvMR) investigations, we employed the inverse variance weighted (IVW) method as our major analytical approach. Multiple sensitivity analyses were performed to evaluate the robustness of the results. Moreover, multivariate MR (mvMR) studies were conducted to account for potential confounding variables, including obesity, insulin resistance, and lipid traits.

RESULTS

In the forward MR study, uvMR analysis did not provide evidence supporting a causal effect of 25OHD levels on the risk of GDM [IVW odds ratio (OR): 1.07, 95% confidence interval (CI): 0.95 to 1.19, p = 0.273]. After adjusting for obesity, fasting insulin levels, and lipid traits, the findings from the mvMR analysis aligned with those of the uvMR analysis. In the reverse MR study, uvMR analysis indicated that GDM had no causal effect on serum 25OHD levels (IVW β = -0.003, p = 0.804), and the robustness of this finding was confirmed in the mvMR study.

CONCLUSION

Our MR research revealed no causal effect of serum 25OHD levels on GDM, suggesting that 25OHD deficiency does not correlate with an increased risk of GDM. Furthermore, our reverse analysis revealed no causal effect of GDM on 25OHD levels.

Novel insights into the genetic architecture of pregnancy glycemic traits from 14,744 Chinese maternities

Glycemic traits are critical indicators of maternal and fetal health during pregnancy. We performed genetic analysis for five glycemic traits in 14,744 Chinese pregnant women. Our genome-wide association study identified 25 locus-trait associations, including established links between gestational diabetes mellitus (GDM) and the genes CDKAL1 and MTNR1B. Notably, we discovered a novel association between fasting glucose during pregnancy and the ESR1 gene (estrogen receptor), which was validated by an independent study in pregnant women. The ESR1-GDM link was recently reported by the FinnGen project. Our work enhances the findings in East Asian populations and highlights the need for independent studies. Further analyses, including genetic correlation, Mendelian randomization, and transcriptome-wide association studies, provided genetic insights into the relationship between pregnancy glycemic traits and hypertension. Overall, our findings advance the understanding of genetic architecture of pregnancy glycemic traits, especially in East Asian populations.

Maternal vitamin D status and risk of gestational diabetes mellitus in twin pregnancies: a longitudinal twin pregnancies birth cohort study

BACKGROUND

Gestational diabetes mellitus (GDM) is a common complication of pregnancy, with significant short-term and long-term implications for both mothers and their offspring. Previous studies have indicated the potential benefits of vitamin D in reducing the risk of GDM, yet little is known about this association in twin pregnancies. This study aimed to investigate maternal vitamin D status in the second trimester and examine its association with the risk of GDM in twin pregnancies.

METHODS

We conducted a prospective cohort study based on data from the Chongqing Longitudinal Twin Study (LoTiS). Peripheral blood serum was collected from the mothers in the second trimester to measure 25(OH)D concentrations. GDM was diagnosed at 23-26 weeks of gestation using a 75-g 2-h oral glucose tolerance test. We used multivariable logistic regression analyses to examine the correlations between vitamin D status and the risk of GDM.

RESULTS

Of the total participants, 93 (29.9%) women were diagnosed with GDM. The mean serum 25(OH)D concentration in the second trimester was 31.1 ± 11.2 ng/mL, and the rate of vitamin D insufficiency and deficiency were 23.5% and 18.7%, respectively. Compared to women with a 25(OH)D concentration < 30 ng/mL, those with a 25(OH)D concentration ≥ 30 ng/mL had a significantly lower risk of GDM (RR 0.61; 95% CI: 0.43, 0.86), especially those who were overweight before pregnancy (RR 0.32; 95% CI: 0.16, 0.64). The restricted cubic splines model showed an inverted J-shaped relationship between vitamin D concentrations and GDM risk.

CONCLUSIONS

The risk of GDM was significantly reduced in twin pregnant women with vitamin D concentrations ≥ 30 ng/mL in the second trimester.

TRIAL REGISTRATION

ChiCTR-OOC-16,008,203. Retrospectively registered on 1 April 2016.

Vitamin D Supplementation for the Outcomes of Patients with Gestational Diabetes Mellitus and Neonates: A Meta-Analysis and Systematic Review

BACKGROUND

Prevention and timely treatment of gestational diabetes mellitus (GDM) are important to the prognosis of pregnant women and neonates. We aimed to conduct a meta-analysis to evaluate the effects and safety of vitamin D supplementation on GDM patients and neonates, to provide insights into clinical GDM treatment.

METHODS

Two authors searched the Medline, PubMed, Cochrane Library, Web of Science, Embase, CNKI, and Wanfang databases for randomized controlled trials (RCTs) on the effects and safety of vitamin D supplementation in GDM patients. The quality of the included RCTs was evaluated according to Cochrane handbook. RevMan 5.3 software was used for statistical analysis.

RESULTS

A total of 20 RCTs involving 1682 GDM patients were finally included, of whom 837 received vitamin D supplementation. Vitamin D supplementation in GDM patients increased the serum 25(OH)D level (SMD = 4.07, 95% CI: (2.73, 5.41)) and HDL level (SMD = 0.41, 95% CI: (0.23, 0.58)) and reduced serum LDL (SMD = -0.49, 95% CI: (-0.68, -0.29)), TG (SMD = -0.59, 95% CI: (-1.01, -0.17)), and TC (SMD = -0.67, 95% CI: (-1.19, -0.14)) levels in GDM patients (all P < 0.05). Besides, vitamin D supplementation reduced the risk of premature birth (OR = 0.37, 95% CI: (0.22, 0.62)), hyperbilirubinemia (OR = 0.38, 95% CI: (0.25, 0.58)), and neonatal hospitalization (OR = 0.38, 95% CI: (0.25, 0.58)) of neonates (all P < 0.05). No significant publication bias in synthesized results was found (all P > 0.05).

CONCLUSIONS

Vitamin D supplementation improves the blood lipid level in GDM patients and reduces adverse neonatal outcomes. The dose and duration of vitamin D supplementation for safety need to be further investigated in future high-quality studies.