Methylenetetrahydrofolate reductase deficiency and high-dose FA supplementation disrupt embryonic development of energy balance and metabolic homeostasis in zebrafish

Folic Acid and Methyltetrahydrofolate Supplementation in the Mthfr677C>T Mouse Model with Hepatic Steatosis

BACKGROUND/OBJECTIVES

The MTHFR677C>T gene variant results in a thermolabile MTHFR enzyme associated with elevated plasma homocysteine in TT individuals. Health risks associated with the TT genotype may be modified by dietary and supplemental folate intake. Supplementation with methyltetrahydrofolate (methylTHF) may be preferable to folic acid because it is the MTHFR product, and does not require reduction by DHFR to enter one-carbon folate metabolism. In the Mthfr677C>T mouse model for this variant, female 677TT (TT) mice have an increased incidence of hepatic steatosis. The objective of this study was to compare the effects of methylTHF and folic acid supplementation on hepatic steatosis and one-carbon metabolism in this model.

METHODS

Male and female C57BL/6J 677CC (CC) and TT mice were fed control (CD), 5xmethylTHF-supplemented (MFSD), or 5xfolic-acid-supplemented (FASD) diets for 4 months. Liver sections were assessed for steatosis by Oil Red O staining. One-carbon metabolites were measured in the liver and plasma. MTHFR protein expression was evaluated in the liver.

RESULTS

MFSD had no significant effect on plasma homocysteine, liver SAM/SAH ratios, or hepatic steatosis in males or females as compared to CD. MTHFR protein increased in MFSD TT female liver, but remained <50% of the CC. FASD had no effect on plasma homocysteine but it decreased the liver MTHFR protein and SAM/SAH ratios, and increased hepatic steatosis in CC females.

CONCLUSIONS

MethylTHF and folic acid supplementation had limited benefits for TT mice, while folic acid supplementation had negative effects on CC females. Further investigation is required to determine if these effects are relevant in humans.

Can Global DNA Methylation Be Influenced by Polymorphisms in Genes Involved in Epigenetic Mechanisms? A Review

BACKGROUND

Global methylation refers to the total methylation in the DNA and can also be inferred from the Line 1 and Alu regions, as these repeats are very abundant in the genome. The main function of DNA methylation is to control gene expression and is associated with both normal and pathological mechanisms. DNA methylation depends on enzymes that generate the methyl radical (e.g., methylenetetrahydrofolate reductase-MTHFR) and attach this radical to the DNA (DNA methyltransferases-DNMT). Genetic variants such as single nucleotide polymorphisms (SNP) in these genes can lead to changes in the activity or expression of MTHFR and DNMT proteins and consequently influence the DNA methylation profile. This review focuses on studies investigating inter-individual variations in the global DNA methylation profile associated with genetic polymorphisms in the MTHFR and DNMT genes.

METHODS

A narrative review was conducted, taking into account articles published in the last 15 years.

RESULTS

It was found that the SNPs rs1801131, rs1801133 and rs1537514 in the MTHFR gene, rs2241531, rs2228611, rs2228612, rs21124724 and the haplotype rs2288349, rs2228611, rs2228612, rs16999593 in the DNMT1 gene, rs2424909, rs998382, rs6058891, rs6058897, rs4911256, rs2889703 and rs1883729 in the DNMT3B were associated with the level of global DNA methylation, including LINE and Alu regions in different contexts. No association was found with polymorphisms in the DNMT3A gene.

CONCLUSIONS

It is concluded that polymorphisms in the MTHFR and DNMT genes may influence the global DNA methylation profile in health, inflammation, tumours and mental illness.

Zebrafish Feed Intake: A Systematic Review for Standardizing Feeding Management in Laboratory Conditions

Zebrafish are one of the most used animal models in biological research and a cost-effective alternative to rodents. Despite this, nutritional requirements and standardized feeding protocols have not yet been established for this species. This is important to avoid nutritional effects on experimental outcomes, and especially when zebrafish models are used in preclinical studies, as many diseases have nutritional confounding factors. A key aspect of zebrafish nutrition is related to feed intake, the amount of feed ingested by each fish daily. With the goal of standardizing feeding protocols among the zebrafish community, this paper systematically reviews the available data from 73 studies on zebrafish feed intake, feeding regimes (levels), and diet composition. Great variability was observed regarding diet composition, especially regarding crude protein (mean 44.98 ± 9.87%) and lipid content (9.91 ± 5.40%). Interestingly, the gross energy levels of the zebrafish diets were similar across the reviewed studies (20.39 ± 2.10 kilojoules/g of feed). In most of the reviewed papers, fish received a predetermined quantity of feed (feed supplied). The authors fed the fish according to the voluntary intake and then calculated feed intake (FI) in only 17 papers. From a quantitative point of view, FI was higher than when a fixed quantity (pre-defined) of feed was supplied. Also, the literature showed that many biotic and abiotic factors may affect zebrafish FI. Finally, based on the FI data gathered from the literature, a new feeding protocol is proposed. In summary, a daily feeding rate of 9-10% of body weight is proposed for larvae, whereas these values are equal to 6-8% for juveniles and 5% for adults when a dry feed with a proper protein and energy content is used.

Targeting one-carbon metabolism for cancer immunotherapy

BACKGROUND

One-carbon (1C) metabolism is a metabolic network that plays essential roles in biological reactions. In 1C metabolism, a series of nutrients are used to fuel metabolic pathways, including nucleotide metabolism, amino acid metabolism, cellular redox defence and epigenetic maintenance. At present, 1C metabolism is considered the hallmark of cancer. The 1C units obtained from the metabolic pathways increase the proliferation rate of cancer cells. In addition, anticancer drugs, such as methotrexate, which target 1C metabolism, have long been used in the clinic. In terms of immunotherapy, 1C metabolism has been used to explore biomarkers connected with immunotherapy response and immune-related adverse events in patients.

METHODS

We collected numerous literatures to explain the roles of one-carbon metabolism in cancer immunotherapy.

RESULTS

In this review, we focus on the important pathways in 1C metabolism and the function of 1C metabolism enzymes in cancer immunotherapy. Then, we summarise the inhibitors acting on 1C metabolism and their potential application on cancer immunotherapy. Finally, we provide a viewpoint and conclusion regarding the opportunities and challenges of targeting 1C metabolism for cancer immunotherapy in clinical practicability in the future.

CONCLUSION

Targeting one-carbon metabolism is useful for cancer immunotherapy.