Folate inhibits lipid deposition via the autophagy pathway in chicken hepatocytes

Excessive fat deposition affects the efficiency and quality of broiler meat production. To understand the molecular mechanism underlying abdominal fat content of broiler lines under divergent selection, we have attempted multiple genetics and genomics methods previously. However, the molecular mechanism of hepatic fat deposition remains largely unknown. On broiler lines divergently selected for abdominal fat content, we performed integrated mRNA and lncRNA sequencing on liver tissues. Key genes and signaling pathways related to the biosynthesis, elongation and metabolism of fatty acids, metabolic pathways, and folate biosynthesis were revealed. Then, primary hepatocytes (sex determined) were isolated and cultured, and treatment concentrations of folate and palmitic acid were optimized. Expression profiling on primary hepatocytes treated by folate and/or palmitic acid revealed that folic acid inhibited lipid deposition in a sex-dependent way, through regulating transcriptional and protein levels of genes related to DNA methylation, lipid metabolism (mTOR/SREBP-1c/PI3K), and autophagy (LAMP2/ATG5) pathways. Taken together, folate could interfere with hepatic lipid deposition possibly through the involvement of the autophagy pathway in broilers.

Transcriptome Analysis of Effects of Folic Acid Supplement on Gene Expression in Liver of Broiler Chickens

Folic acid is a water-soluble B vitamin, and plays an important role in regulating gene expression and methylation. The liver is the major site of lipid biosynthesis in the chicken. Nevertheless, how gene expression and regulatory networks are affected by folic acid in liver of broilers are poorly understood. This paper conducted the RNA-seq technology on the liver of broilers under folic acid challenge investigation. First, 405 differentially expressed genes (DEGs), including 157 significantly upregulated and 248 downregulated, were detected between the control group (C) and the 5 mg folic acid group (M). Second, 68 upregulated DEGs and 142 downregulated DEGs were determined between C group and 10 mg folic acid group (H). Third, there were 165 upregulated genes and 179 downregulated genes between M and H groups. Of these DEGs, 903 DEGs were successfully annotated in the public databases. The functional classification based on GO and KEEGG showed that “general function prediction only” represented the largest functional classes, “cell cycle” (C vs. M; M vs. H), and “neuroactive ligand-receptor interaction” (C vs. H) were the highest unique sequences among three groups. SNP analysis indicated that numbers of C, M and H groups were 145,450, 146,131, and 123,004, respectively. Total new predicted alternative splicing events in C, M, and H groups were 9,521, 9,328, and 8,929, respectively. A protein-protein interaction (PPI) network was constructed, and the top 10 hub genes were evaluated among three groups. The results of real time PCR indicated that mRNA abundance of PPARγ and FAS in abdominal fat of M and H groups were reduced compared with the C group (P < 0.05). Ultramicroscopy results showed that folic acid could reduce lipid droplets in livers from chickens. Finally, contents of LPL, PPARγ, and FAS in abdominal fat were decreased with the folic acid supplmented diets (P < 0.01). These findings reveal the effects of folic acid supplemention on gene expression in liver of broilers, which can provide information for understanding the molecular mechanisms of folic acid regulating liver lipid metabolism.

Ability of dietary factors to affect homocysteine levels in mice: a review

Homocysteine is associated with several diseases, and a series of dietary factors are known to modulate homocysteine levels. As mice are often used as model organisms to study the effects of dietary hyperhomocysteinemia, we collected data about concentrations of vitamin B₁₂, vitamin B₆, folate, methionine, cystine, and choline in mouse diets and the associated plasma/serum homocysteine levels. In addition, we more closely examined the composition of the control diet, the impact of the mouse strain, sex and age, and the duration of the dietary intervention on homocysteine levels. In total, 113 out of 1103 reviewed articles met the inclusion criteria. In the experimental and control diets, homocysteine levels varied from 0.1 to 280 µmol/l. We found negative correlations between dietary vitamin B₁₂ (rho = − 0.125; p < 0.05), vitamin B₆ (rho = − 0.191; p < 0.01) and folate (rho = − 0.395; p < 0.001) and circulating levels of homocysteine. In contrast, a positive correlation was observed between dietary methionine and homocysteine (methionine: rho = 0.146; p < 0.05). No significant correlations were found for cystine or choline and homocysteine levels. In addition, there was no correlation between the duration of the experimental diets and homocysteine levels. More importantly, the data showed that homocysteine levels varied widely in mice fed control diets as well. When comparing control diets with similar nutrient concentrations (AIN-based), there were significant differences in homocysteine levels caused by the strain (ANOVA, p < 0.05) and age of the mice at baseline (r = 0.47; p < 0.05). When comparing homocysteine levels and sex, female mice tended to have higher homocysteine levels than male mice (9.3 ± 5.9 µmol/l vs. 5.8 ± 4.5 µmol/l; p = 0.069). To conclude, diets low in vitamin B₁₂, vitamin B₆, or folate and rich in methionine are similarly effective in increasing homocysteine levels. AIN recommendations for control diets are adequate with respect to the amounts of homocysteine-modulating dietary parameters. In addition, the mouse strain and the age of mice can affect the homocysteine level.

Folic acid and vitamin B12 supplementation in subjects with type 2 diabetes mellitus: A multi-arm randomized controlled clinical trial

OBJECTIVE

This study was conducted to investigate and compare the effects of add-on folic acid and vitamin B12 supplementation on glycaemic control, insulin resistance and serum lipid profile in subjects with type 2 diabetes mellitus.

STUDY DESIGN & INTERVENTION

This study was a randomized, multi-arm, open-label clinical trial. 80 patients with type 2 diabetes and on stable oral antidiabetics were enrolled and 20 patients each were randomly allocated to one of the four groups - Group A: add-on Folic acid (5 mg/day); Group B: add-on Methylcobalamin (500 mcg/day); Group C: add-on Folic acid (5 mg/day) + Methylcobalamin (500 mcg/day) and Group D: Standard oral anti-diabetic drugs. The patients were followed up after 8 weeks.

RESULTS

HbA1c improved significantly in Groups B and C [median changes from baseline - 1.2 % (- 13 mmol/mol) and - 1.5 % (- 16 mmol/mol) respectively, p values 0.04 and 0.02 respectively] compared to Group D. Groups B and C also showed significant improvements in plasma insulin, insulin resistance and serum adiponectin compared to Group D. Serum homocysteine declined significantly in all three groups with add-on supplementation compared to standard treatment. No improvement in the lipid profile was noted in any of the groups.

CONCLUSIONS

Add-on supplementation with vitamin B12 improved glycaemic control and insulin resistance in patients with type 2 diabetes mellitus.

Folate and Vitamin B12 in Morbid Obesity: The Influence of Folate on Anti-Atherogenic Lipid Profile

Previous studies showed a high prevalence of micronutrient deficiencies in obese subjects, with low folate and vitamin B12 serum levels and intakes. Correlations between vitamins and lipids have been investigated both in animal and human studies. The aim of our study is to evaluate the influence of dietetic and serum levels of folate and vitamin B12 on lipid pattern in morbidly obese subjects. We also analysed the relationship between serum concentrations and dietary intake of these micronutrients, and compared the intakes to the Recommended Levels of Nutrients and Energy Intakes (LARN). In 122 morbidly obese patients, mean BMI 45 ± 7 kg/m², we evaluated anthropometric parameters, hepatic, glyco/lipid profile, total folate and vitamin B12, blood pressure, and finally nutritional intakes in a subgroup of 68 patients using a food frequency questionnaire about the frequency of food consumption and daily water intake. These values were determined in obese patients before and one year after sleeve gastrectomy. Both before and after surgery, levels of vitamins and minerals remained in normal range compared to LARN. According to univariate analysis, at baseline folate showed a significantly positive correlation with high-density lipoprotein cholesterol (p = 0.028, ρ = 0.204), apolipoprotein A-I (p = 0.006, ρ = 0.268) and vitamin B12 (p = 0.040, ρ = 0.192), and a significantly negative correlation with triglycerides (p = 0.049, ρ = -0.184). Folate and vitamin B12 levels do not correlate with their nutritional intakes, which remain within recommended range after surgery. In conclusion the correlation between folate and anti-atherogenic lipid profile is confirmed also in a large group of morbid obese patients.

Identification of differentially expressed genes in broiler offspring under maternal folate deficiency

Folate plays an important role in DNA and RNA synthesis by donating methyl groups. To investigate the effects of maternal folate deficiency (FD) on the abdominal adipose transcriptome and on the accumulation of lipid droplets in the liver tissue of chicken offspring, differentially expressed genes (DEGs) of FD were identified with digital gene expression tag profiling. Ultramicroscopy suggested that the size of lipid droplets in hepatocytes increased with FD, while the lipid droplets population number was largely not affected. The serum parameters assay showed that the concentrations of MTHFR (476.57 vs. 395.27), DHFR (45.056 vs. 38.952), LPL (50.408 vs. 48.677), HCY (4.354 vs. 3.836), LEP (9.951 vs. 8.673), and IGF2 (1209.4 vs. 1027.7) in offspring serum of the FD group were significantly higher than those of the normal folate (NF) group ( P < 0.01). The 442 DEGs between NF and FD groups were identified by digital gene expression profiling. Considering the DEGs in the FD groups vs. NF groups, 179 genes were upregulated while 263 downregulated, and in particular, 145 upregulated and 214 downregulated DEGs were successfully annotated with the nonredundant database. Gene Ontology analysis showed that FD mainly affected cellular processes, cell part and binding, cell killing, virions, and receptor regulator activity. With pathway analysis, it indicated that 123 unigenes were assigned to 115 KEGG pathways, but only five of 115 these pathways were significantly enriched with P values ≤ 0.05. Taken together, these results provide a foundation for further studying the responses of offspring to maternal FD in breeding chickens.

Role of folate in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a spectrum of chronic liver conditions that are characterized by steatosis, inflammation, fibrosis, and liver injury. The global prevalence of NAFLD is rapidly increasing in proportion to the rising incidence of obesity and type 2 diabetes. Because NAFLD is a multifaceted disorder with many underlying metabolic abnormalities, currently, there is no pharmacological agent that is therapeutically approved for the treatment of this disease. Folate is a water-soluble B vitamin that plays an essential role in one-carbon transfer reactions involved in nucleic acid biosynthesis, methylation reactions, and sulfur-containing amino acid metabolism. The liver is the primary organ responsible for storage and metabolism of folates. Low serum folate levels have been observed in patients with obesity and diabetes. It has been reported that a low level of endogenous folates in rodents perturbs folate-dependent one-carbon metabolism, and may be associated with development of metabolic diseases such as NAFLD. This review highlights the biological role of folate in the progression of NAFLD and its associated metabolic complications including obesity and type 2 diabetes. Understanding the role of folate in metabolic disease may position this vitamin as a potential therapeutic for NAFLD.

Low serum vitamin B-12 and folate concentrations and low thiamin and riboflavin intakes are inversely associated with greater adiposity in Mexican American children

BACKGROUND

Micronutrient status may be a contributing factor to the development of childhood obesity in many industrializing countries passing the nutritional transition. The few studies investigating associations between serum concentrations of vitamin B and intake of B vitamins with adiposity, however, have reported inconsistent findings.

OBJECTIVE

The aim of the study was to examine associations between serum vitamin B-12 and folate concentrations and intakes of B vitamins with body fat by using data on 1131 Mexican American children 8-15 y of age included in NHANES 2001-2004.

METHODS

Children's body mass index (BMI), trunk fat mass (TrFM), and total body fat mass (TBFM) were used as body adiposity (BA) measures. Serum concentrations of folate and vitamin B-12 were measured in blood samples collected from children. Intake of B vitamins was collected according to 24-h dietary recall. Associations of BA with serum concentrations of vitamin B-12 and folate and intake of B vitamins were determined by using linear and multinomial regression models.

RESULTS

Serum concentrations of vitamin B-12 and folate were inversely associated with BMI (β: -2.68, P < 0.01; β = -1.33, P < 0.01), TrFM (β:-3.32, P < 0.01; β: -0.14, P < 0.05), and TBFM (β:-1.93, P < 0.01; β: -3.19; P < 0.01). Higher serum concentrations of vitamin B-12 were associated with a reduced risk of obesity (OR: 0.48; 95% CI: 0.31, 0.77; P < 0.001). Thiamin and riboflavin intakes were inversely associated with BMI (β:-1.35, P < 0.05; β: -1.11, P < 0.05) and TrFM (β:-1.26, P < 0.05; β: -1.37, P < 0.05).

CONCLUSION

Similar inverse associations between BA and status of both vitamin B-12 and folate and intake of thiamin and riboflavin suggest that these micronutrients may play a role in adipogenesis and risk of childhood obesity.

Folic acid supplementation attenuates high fat diet induced hepatic oxidative stress via regulation of NADPH oxidase

Diets high in saturated fat and cholesterol facilitate weight gain, a predisposing factor that contributes to the onset of obesity and metabolic disorders. Hepatic oxidative stress is commonly reported in various animal models of obesity and has been associated with enhanced expression of NADPH oxidase. We have previously reported several antioxidant mechanisms through which folic acid confers protection during hyperhomocysteinemia-induced oxidative stress. The objective of the present study was to investigate whether folic acid supplementation ameliorates high-fat diet induced oxidative stress in the liver, and to identify the underlying mechanisms. Male C57BL/6J mice were fed a control diet, a high-fat diet, or a high-fat diet supplemented with folic acid for 12 weeks. A high-fat diet led to increased body mass, hepatic lipid peroxidation, and liver injury. There was a significant increase in hepatic NADPH oxidase activity, which was associated with enhanced expression of several NADPH-oxidase subunits. Folic acid supplementation had a protective effect against high-fat diet induced hepatic oxidative stress and liver injury. Further analysis revealed that the antioxidant effect of folic acid was attributed, in part, to transcriptional regulation of NADPH oxidase. These results suggested that folic acid supplementation may be hepatoprotective from liver injury associated with a high-fat diet.