Influence of tumor necrosis factor-α on estradiol, progesterone, insulin-like growth factor-II, and insulin-like growth factor binding protein-1, 2, and 3 in cultured human luteinized granulosa cells

One-carbon metabolism, insulin resistance, and fecundability in a Singapore prospective preconception cohort study

BACKGROUND

One-carbon metabolism, which consists of the folate cycle, methionine cycle, and trans-sulphuration pathway, is associated with nucleotide synthesis. However, the association between one-carbon metabolites, metabolic status, and reproductive health remains poorly understood.

OBJECTIVES

We examined the association between the one-carbon cycle plasma metabolites and fecundability and determined whether it is modified by metabolic health status, as assessed by insulin resistance (IR).

METHODS

This prospective cohort study utilized data from the Singapore PREconception Study of long-Term maternal and child Outcomes. Fasting blood samples were collected, and one-carbon cycle metabolites were measured. Fecundability was measured by time to pregnancy in menstrual cycles within a year of enrollment. We identified patterns in plasma one-carbon cycle metabolites using principal component (PC) analysis. We estimated fecundability ratios (FRs) and confidence intervals (CIs), with confounder adjustment using discrete-time proportional hazards models. IR was determined using the Homeostatic Model Assessment 2 Insulin Resistance score, classified into lower IR (<0.65) and higher IR (≥0.65). The role of IR was examined through interaction tests and stratification.

RESULTS

We identified 3 one-carbon cycle PCs. PC1, characterized by higher folate and lower homocysteine concentrations; PC2, characterized by higher concentrations of dimethylglycine, choline, methionine, and betaine; and PC3, characterized by higher concentrations of vitamins B2, B12, and B6. Each z-score increase in PC1 was associated with a 17% increase in fecundability (FR: 1.17; 95% CI: 1.03, 1.33). The association between PC1 and fecundability was more evident in women with lower IR (FR: 1.30; 95% CI: 1.08, 1.57) but was attenuated in those with higher IR (FR: 1.09; 95% CI: 0.92, 1.30), with a P-for-interaction of 0.127. PC2 and PC3 were not associated with fecundability.

CONCLUSIONS

Our findings suggest that higher folate and lower homocysteine concentrations, which reflected the interlinked folate and methionine cycles, were associated with higher fecundability in preconception women with lower IR but less so in those with higher IR.

CLINICAL TRIAL REGISTRATION

This trial was registered at ClinicalTrials.gov as NCT03531658 (https://www.

CLINICALTRIALS

gov/study/NCT03531658).

Folate, homocysteine and the ovarian cycle among healthy regularly menstruating women

STUDY QUESTION

How are concentrations of plasma homocysteine and serum folate associated with reproductive hormones and anovulation in regularly menstruating women?

SUMMARY ANSWER

Higher homocysteine was associated with sporadic anovulation and hormonal changes that may be indicative of impaired ovulatory function, but higher serum folate was associated only with higher luteal phase progesterone.

WHAT IS KNOWN ALREADY

Higher folate levels as well as some variants in genes relevant to one-carbon metabolism, are associated with improved reproductive outcomes and responses to fertility treatment, but only a few small studies have explored the relationship between markers of one-carbon metabolism and menstrual cycle characteristics.

STUDY DESIGN, SIZE, DURATION

The BioCycle Study (2005-2007) is a prospective, longitudinal cohort of 259 regularly menstruating women not using hormonal contraceptives or dietary supplements who were followed for up to two menstrual cycles.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum folate and reproductive hormones were measured up to eight times per cycle and plasma homocysteine up to three times. Linear mixed models were used to estimate associations between serum folate or plasma homocysteine and log-transformed reproductive hormone levels while accounting for multiple observations and cycles per woman. Generalized estimating equations were used to examine risk of sporadic anovulation. All models were adjusted for age, race, body mass index, cigarette and alcohol use, and energy and fiber intake.

MAIN RESULTS AND THE ROLE OF CHANCE

Higher plasma homocysteine concentrations were associated with lower total estradiol across the cycle (adjusted percent change per unit increase in homocysteine [aPC] -2.3%, 95% CI: -4.2, -0.03), higher follicle stimulating hormone around the time of expected ovulation (aPC 2.4%, 95% CI: 0.2, 4.7) and lower luteal phase progesterone (aPC -6.5%, 95% CI: -11.1, -1.8). Higher serum folate concentrations were associated with higher luteal phase progesterone (aPC per unit increase in folate 1.0%, 95% CI: 0.4, 1.6). Higher homocysteine concentrations at expected ovulation were associated with a 33% increased risk of sporadic anovulation. We observed no risk associated with decreased folate concentrations, but a higher ratio of folate to homocysteine at ovulation was associated with a 10% decreased risk of anovulation.

LIMITATIONS, REASONS FOR CAUTION

Our results are generalizable to healthy women with adequate serum folate levels. The independent influence of homocysteine should be confirmed in larger cohorts and among women with folate deficiency or increased risks of anovulation.

WIDER IMPLICATIONS OF THE FINDINGS

If these findings are confirmed, it is possible that lowering homocysteine with B-vitamins through diet or supplementation could improve ovulatory function in some women.

Study FUNDING/COMPETING INTEREST(S)

This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (Contract numbers: HHSN275200403394C, HHSN275201100002I and Task one HHSN27500001). None of the authors has any conflicts of interest to disclose.

Influence of vascular endothelial growth factor on the expression of insulin-like growth factor-II, insulin-like growth factor binding protein-2 and 5 in human luteinized granulosa cells

The aim of the present study was to investigate the influence of vascular endothelial growth factor (VEGF) on the expression of insulin-like growth factor (IGF)-II, insulin-like growth factor binding protein (IGFBP)-2 and in cultured human luteinized granulosa cells (LGCs). Human LGCs were obtained from the follicular fluid by transvaginal oocyte aspiration from 30 infertile patients undergoing controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF). The cells were cultured for 72 h with VEGF at concentrations of 0.1, 1.0, and 10.0 ng/ml. The cells not treated with VEGF served as controls. Reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the expression of IGF-II, IGFBP-2, and 5 mRNA. The expression of IGF-II mRNA in the 10.0 ng/ml of VEGF group was significantly higher than that in the control group. Treatment with 10.0 ng/ml of VEGF significantly increased the expression of IGFBP-5 mRNA than all other groups. There were no statistically significant differences in the expression of IGFBP-2 mRNA among all the groups. VEGF may play a regulator role in human ovarian physiology by modulating the expression of IGF-II and IGFBP-5 in LGCs.