Vitamin B12 and Folate Markers Are Associated with Insulin Resistance During the Third Trimester of Pregnancy in South Asian Women, Living in the United Kingdom, with Gestational Diabetes and Normal Glucose Tolerance

Folic acid supplementation in a mouse model of diabetes in pregnancy alters insulin sensitivity in female mice and beta cell mass in offspring

Epidemiological studies have reported discrepant findings on the relationship between folic acid intake during pregnancy and risk for gestational diabetes mellitus (GDM). To begin to understand how folic acid impacts metabolic health during pregnancy, we determined the effects of excess folic acid supplementation (5× recommendation) on maternal and fetal offspring metabolic health. Using a mouse (female C57BL/6J) model of diet-induced diabetes in pregnancy (western diet) and control mice, we show that folic acid supplementation improved insulin sensitivity in the female mice fed the western diet and worsened insulin sensitivity in control mice. We found no unmetabolized folic acid in liver from supplemented mice suggesting the metabolic effects of folic acid supplementation are not due to unmetabolized folic acid. Male fetal (gestational day 18.5) offspring from folic acid supplemented dams (western and control) had greater beta cell mass and density than those from unsupplemented dams; this was not observed in female offspring. Differential sex-specific hepatic gene expression profiles were observed in the fetal offspring from supplemented dams but this differed between western and controls. Our findings suggest that folic acid supplementation affects insulin sensitivity in female mice, but is dependent on their metabolic phenotype and has sex-specific effects on offspring pancreas and liver.

The Influence of Maternal Folate Status on Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Maternal folate has been shown to relate to the risk of gestational diabetes mellitus (GDM). However, the existing studies have yielded inconsistent conclusions. The purpose of this study was to systematically review the association between maternal folate status and the risk of GDM. Observational studies up to 31 October 2022 were included. Study characteristics, the means and standard deviations (SDs) of folate levels (serum/red blood cell (RBC)), the odds ratios (ORs) with 95% confidence intervals (CIs) and the time for folate measurement were extracted. Compared with the non-GDM group, serum and RBC folate levels in women with GDM were significantly higher. Our subgroup analysis demonstrated that serum folate levels in the GDM group were significantly higher than in the non-GDM group only in the second trimester. RBC folate levels in the GDM group were significantly higher than in the non-GDM group in the first and second trimesters. Taking serum/RBC folate levels as continuous variables, the adjusted odds ratios of GDM risk showed that increased serum folate concentration rather than RBC folate elevated the risk of GDM. In the descriptive analysis, five studies reported high serum folate levels increased GDM risk, whereas the other five showed no association between serum folate levels and GDM risk. Moreover, the rest three studies pointed out high RBC folate levels increased GDM risk. Altogether we found that the risk of GDM is associated with high serum/plasma and RBC folate levels. Future studies should determine the recommended folic acid cutoff balancing the risk for GDM and fetal malformations.

Association of maternal folate and B12 vitamin status with gestational diabetes mellitus: still an open issue

OBJECTIVES

There is conflicting evidence about the role of folate and B₁₂in gestational diabetes mellitus (GDM) onset. The association of vitamin status with GDM was therefore revalued, also measuring the B₁₂active form holotranscobalamin.

METHODS

677 women were evaluated at 24-28 weeks of gestation when OGTT was carried out. The 'one-step' strategy was employed for GDM diagnosis. Odds ratio (OR) of having GDM was estimated to quantify the association with vitamin levels.

RESULTS

180 women (26.6%) had GDM. They were older (median, 34.6 vs. 33.3 years, p=0.019) and had higher body mass index (BMI) (25.8 vs. 24.1 kg/m², p<0.001). Multiparous women had lower levels of all evaluated micronutrients, while overweight lowered both folate and total B₁₂, but not holotranscobalamin. Lower total B₁₂(270 vs. 290 ng/L, p=0.005), but not holotranscobalamin, was observed in GDM, being weakly negatively correlated with fasting glycemia (r=-0.11, p=0.005) and 1-h OGTT serum insulin (r=-0.09, p=0.014). At multivariate analysis, age, BMI and multiparity remained the strongest GDM predictors, while total B₁₂(but not holotranscobalamin and folate) showed a slight protective effect (OR=0.996, p=0.038).

CONCLUSIONS

A weak association between total B₁₂ levels and GDM risk was shown, but it was not confirmed when holotranscobalamin was measured.

Pregnancy homocysteine and cobalamin status predict childhood metabolic health in the offspring

BACKGROUND

Inadequate pregnancy cobalamin status has been associated with adverse offspring metabolic health in Indian and Nepalese studies. Studies of pregnancy cobalamin status and mid-childhood health outside of Asia are scarce.

METHODS

Associations between pregnancy fasting plasma total homocysteine (tHcy), cobalamin status (plasma cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA)) and mid-childhood metabolic score (MetSco) ((including fat mass index (zFMI), homeostatic model assessment of insulin resistance (zHOMA-IR) and dyslipidemia (zTG - zHDLc)/2) z-scores)) were investigated in a prospective study of 293 mother-child dyads.

RESULTS

Highest versus low-mid pregnancy tHcy tertile was associated with higher mid-childhood MetSco, specifically with higher child zFMI. Stratifying by sex, the maternal tHcy-child MetSco association was limited to boys and confirmed for zFMI and zHOMA-IR. The maternal tHcy-child zFMI association was not mediated by birth weight z-score. First trimester plasma cobalamin was not associated with child outcomes, but other indicators of cobalamin status were. Lowest versus mid-high plasma holoTC tertile was associated with MetSco (specifically zFMI and zHOMA-IR) and highest versus low-mid plasma MMA tertile with higher MetSco and dyslipidemia in boys.

CONCLUSIONS

Moderately elevated pregnancy tHcy and low cobalamin status were associated with mid-childhood metabolic score in boys. The pregnancy tHcy-child zFMI association was not mediated by birth weight.

IMPACT

Fasting plasma total homocysteine (tHcy) during pregnancy and low cobalamin status during early pregnancy are associated with mid-childhood metabolic score and its components in the offspring. These findings were only significant in male offspring. The study provides new evidence that impaired one carbon metabolism during pregnancy is associated with negative health outcomes in the offspring, in a population with low prevalence of cobalamin deficiency. The maternal-offspring associations were observed in the functional markers of cobalamin status (holotranscobalamin and methylmalonic acid) and tHcy, not with plasma cobalamin concentration. Screening for low pregnancy cobalamin status should be considered.

Age- and ethnicity-related reference intervals for serum vitamin B12

BACKGROUND

Age and ethnicity are known to influence serum vitamin B₁₂ (B₁₂) concentration, yet universal reference intervals (RIs) are typically applied by laboratories. Both lower and upper RI limits for B₁₂ are clinically relevant. Low values suggest deficiency leading to anemia and/or neurological impairment, while high values are not always an innocuous consequence of high B₁₂ intake but are associated with some cancers, autoimmune, liver, and renal diseases. This work aimed to establish age- and ethnicity-related RIs for B₁₂ using a modified indirect method based on Hoffmann's approach.

METHODS

A total of 72,091 anonymized B₁₂ results (Jan 2018-Nov 2019) were analyzed from an ethnically-diverse South-East London general practice patient population. Patients belonged to five ethnic groups: Asian, Black, White, Mixed, or Other. Multiple records for the same patient and results with missing ethnicity were excluded from the analysis of adult RIs. B₁₂ analyses were performed using ARCHITECT® (Abbott Diagnostics).

RESULTS

B₁₂ was significantly higher in Black compared with Asian and White adults. There were no differences in B₁₂ between Asian and White adults. Children (all ethnicities) between 2 and 5 years old had the highest B₁₂. Because of the small number of children (up to the age of 13) in each ethnic-related age category, all ethnic groups were combined to obtain age-related RIs. The children's RIs ranged from 159 to 1025 pmol/L for 0-1-year-olds to 276-1102 pmol/L for 2-5-year-olds. The RIs for Black and White/Asian people >13 years of age were 166-805 pmol/L and 134-511 pmol/L respectively.

CONCLUSIONS

The application of age- and ethnicity-appropriate RIs into diagnostic practice will provide a more accurate evaluation of B₁₂ status when using the B₁₂ test alone or in combination with other markers.

Vitamin B12 and gestational diabetes mellitus: a systematic review and meta-analysis

The relationship between vitamin B12 and gestational diabetes mellitus (GDM) remains controversial. To comprehensively evaluate the relationship between vitamin B12 and GDM, and to provide more information on GDM prevention, this study provides a systematic review and meta-analysis of vitamin B12 and GDM. As of September 22, 2021, 304 articles were searched in PubMed, Web of Science, EMBASE, and Cochrane databases, of which 15 studies met the inclusion criteria. Results presented there was no association between maternal vitamin B12 concentration during the first trimester with GDM, however, low vitamin B12 concentration in the second or third trimester of pregnancy was related to an increased risk of GDM. Compared with the non-GDM group, the vitamin B12 concentration in the GDM group was remarkably decreased (MD: -10·79; 95%CI: -21·37, -0·21), and vitamin B12 deficiency increased the risk for GDM (OR: 1·59; 95%CI: 1·10, 2·29). These effects were more significant among Asians. In addition, an increased ratio of high folate to low vitamin B12 in serum also increased the risk of GDM (OR: 1·87; 95% CI: 1·46, 2·41). These results suggest that more vitamin B12 may need to be provided during pregnancy.