Folic acid supplementation prevents high fructose-induced non-alcoholic fatty liver disease by activating the AMPK and LKB1 signaling pathways

Dietary folate intake and all-cause mortality and cardiovascular mortality in American adults with non-alcoholic fatty liver disease: Data from NHANES 2003 to 2018

BACKGROUND

The relationship between dietary folate intake and prior mortality in adult patients with Non-alcoholic Fatty Liver Disease (NAFLD) has not been clearly studied. We aimed to examine the relationship between dietary folate intake and all-cause and cardiovascular (CVD) mortality in adult NAFLD patients in the US.

METHODS

Using data from National Health and Nutrition Examination Survey (NHANES) 2003-2018 and associated mortality data we conducted a cohort study of US adult NAFLD subjects. Multivariable Cox proportional hazards regression models were used to evaluate the relationship between dietary folate intake and both all-cause mortality and CVD mortality, accounting for potential confounders. The study employed restricted cubic spline analysis to investigate the non-linear association between dietary folate levels and mortality from all causes and cardiovascular disease.

RESULTS

Our final cohort consisted of 3,266 NAFLD patients, with a median follow-up of 10.3 years, 691 deaths were observed, including 221 cardiovascular deaths. Compared to participants with a folate intake in Quartile 1 (≤250 μg/d), those in Quartile 4 (≥467.5 μg/d) had multivariable-adjusted hazard ratios of 0.69 (95% CI, 0.51-0.94) for all-cause mortality (p for trend = 0.028) and 0.55 (95% CI, 0.29-1.04) for CVD mortality (p for trend = 0.107). A non-linear relationship between dietary intake and risk of death was not observed.

CONCLUSION

Greater dietary folate intake is associated with a reduced risk of all-cause in American adults with NAFLD. Higher dietary folate intake not found to be associated with lower CVD mortality. These findings suggest that dietary folate may improve the prognosis of adult NAFLD patients. The measured-response relationship between dietary folate intake and mortality in patients with NAFLD requires further investigation.

Serum folate levels and risk of metabolic dysfunction-associated steatotic liver disease: results from a cross-sectional study and Mendelian randomization analysis

Background

Evidence from observational studies on the association between folate and metabolic dysfunction-associated steatotic liver disease (MASLD) is conflicting.

Aims

This study aimed to investigate the association between serum folate concentration and MASLD and further assess the causal relationship using Mendelian randomization (MR) analysis.

Methods

To investigate the causal relationship between serum folate and MASLD, we conducted a cross-sectional study that selected 1,117 participants from the 2017-2020 National Health and Nutrition Examination Survey (NHANES). The association between serum folate level and the risk of MASLD was evaluated under a multivariate logistic regression model. In addition, we conducted a two-sample MR study using genetic data from a large genome-wide association study (GWAS) to compare serum folate level (37,465 individuals) and MASLD (primary analysis: 8,434 cases/770,180 controls; Secondary analysis:1,483 cases/17,781 controls) were performed to infer causal relationships between them. Inverse variance weighted (IVW) was used as the primary method of MR Analysis.

Results

The results from the NHANES database showed that Tertile 3 group (Tertile 3: ≥ 48.6 nmol/L) had a significantly lower risk (OR = 0.58, 95% CI: 0.38-0.88, p = 0.010) of MASLD than Tertile 1 group (Tertile 1: < 22.3 nmol/L) after complete adjustments. However, in the IVW of MR analysis, there was no causal relationship between serum folate level and MASLD risk in the primary analysis (OR = 0.75, 95% CI: 0.55-1.02, p = 0.065) and secondary analysis (OR = 0.83, 95% CI: 0.39-1.74, p = 0.618).

Conclusion

In observational analyses, we observed an inverse association between higher serum folate concentrations and a reduced risk of MASLD. Our MR study generated similar results, but the association failed to reach the significance threshold of p < 0.05, suggesting that our MR study does not support a causal relationship between serum folate levels and MASLD risk. Additional research involving a larger number of cases would contribute to enhancing the confirmation of our preliminary findings.

Role of Folate in Liver Diseases

Folate is a water-soluble B vitamin involved in the synthesis of purines and pyrimidines and is one of the essential vitamins for human growth and reproduction. Folate deficiency due to low dietary intake, poor absorption of folate, and alterations in folate metabolism due to genetic defects or drug interactions significantly increases the risk of diseases such as neural tube defects, cardiovascular disease, cancer, and cognitive dysfunction. Recent studies have shown that folate deficiency can cause hyperhomocysteinemia, which increases the risk of hypertension and cardiovascular disease, and that high homocysteine levels are an independent risk factor for liver fibrosis and cirrhosis. In addition, folate deficiency results in increased secretion of pro-inflammatory factors and impaired lipid metabolism in the liver, leading to lipid accumulation in hepatocytes and fibrosis. There is substantial evidence that folate deficiency contributes to the development and progression of a variety of liver diseases, including non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), alcoholic liver disease (ALD), viral hepatitis, hepatic fibrosis, and liver cancer. Here we review key studies on the role of folate in the pathophysiology of liver diseases, summarize the current status of studies on folate in the treatment of liver diseases, and speculate that folate may be a potential therapeutic target for liver diseases.

Folic acid supplementation prevents high body fat-induced bone loss through TGR5 signaling pathways

Osteoporosis caused by bone loss is one of the serious global public health problems. Folic acid is a B vitamin with multiple physiological functions such as lipid regulation and antioxidant capacity, and its potential to improve bone loss has attracted our attention. Through NHANES database analysis, we found that folic acid intake was significantly correlated with whole-body bone mineral density (BMD) in people aged 20-60 years, and the association may be mediated by the body fat rate. Male C57Bl/6 mice were fed either a normal diet or a high-fat diet, and folic acid was added to drinking water for supplementation. Our results indicated that mice with high body fat showed bone microstructure damage and bone loss, while folic acid supplementation improved bone quality. At the same time, we found that mice with high body fat exhibited abnormal blood lipids, dysregulation of intestinal flora, and metabolic disorders. Folic acid supplementation improved these phenomena. Through the network analysis of intestinal flora and metabolites, we found that LCA and TGR5 may play important roles. The results showed that folic acid promoted the expression of LCA and TGR5 in mice, increased the phosphorylation of AMPK, and decreased the phosphorylation of NF-κB and ERK, thereby reducing bone loss. In summary, folic acid intake is closely related to BMD, and folic acid supplementation can prevent high body fat-induced bone loss. Our study provides new ideas and an experimental basis for preventing bone loss and osteoporosis.

Association of serum folate with prevalence of non-alcoholic fatty liver disease among adults (NHANES 2011-2018)

Background

Folate was involved in oxidative stress, hepatic lipid metabolism and chronic hepatic inflammation. However, evidence about the association between serum folate level and non-alcoholic fatty liver disease (NAFLD) in general population is scarce. This study aimed to explore the relationship between serum folate level and NAFLD among adults.

Methods

7,146 adult participants aged 20 years and over who have complete data of serum folate level and liver function biomarkers in NHANES 2011-2018 were included. Serum folate level was measured by isotope-dilution high-performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). And suspected NAFLD was defined according to the United States fatty liver index (USFLI). Logistic regression and the restricted cubic spline models were performed.

Results

Serum folate level was inversely associated with the presence of NAFLD. When comparing the second, third and fourth quartiles of serum folate level to the lowest quartile, the adjusted ORs of the presence of NAFLD were 0.62 (0.49-0.78), 0.65 (0.51-0.84), and 0.43 (0.32-0.56) respectively (p for trend<0.001). The non-linear and L-shaped relationship was found between serum folate level and the presence of NAFLD in the restricted cubic spline regression (p for non-linearity <0.01). Consistent with serum total folate, serum 5-Methyltetrahydrofolate level was also inversely associated with the presence of NAFLD.

Conclusion

Higher serum folate level may be negatively associated with NAFLD.

Mild methylenetetrahydrofolate reductase deficiency accelerates liver triacylglycerol and uric acid accumulation in fructose-fed mice

A genetic predisposition to hepatic steatosis may be associated with dietary patterns. We hypothesized that a common variant in human methylenetetrahydrofolate reductase (MTHFR 677C→T) was previously associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). In this study, we investigated the relationship between the human MTHFR polymorphism and NAFLD using fructose-fed male C57BL/6 Mthfr^+/+ and Mthfr^+/- mice, a model for the human gene variant. Mice were fed an 8% fructose solution for 12 weeks. Mthfr^+/- mice had significantly increased abdominal fat mass and hepatic triglyceride (TG) but displayed a similar liver mass when compared with Mthfr^+/+ mice. Liver morphology showed that mild MTHFR deficiency induced liver lipid droplet deposition and inflammatory cell infiltration, suggesting accelerated lipid accumulation in the liver. Moreover, mild MTHFR deficiency increased hepatic xanthine oxidase activity and uric acid accumulation. Using untargeted lipidomics, we identified 116 differentially expressed lipids species in the liver of Mthfr^+/- mice when compared with Mthfr^+/+ animals. The most significant lipid increase was observed in 47 TGs, followed by 33 phosphatidylcholines in Mthfr^+/- mice liver. When compared with Mthfr^+/+ liver, 9 TGs were dramatically decreased in Mthfr^+/- liver. These changes were associated with upregulated gene expressions related to triglyceride synthesis and storage. Thus, Mthfr^+/- mice developed NAFLD disease. These findings suggested the Mthfr variant may be at an increased risk of liver steatosis on a fructose solution diet.

Associations of serum folate and vitamin C levels with metabolic dysfunction-associated fatty liver disease in US adults: A nationwide cross-sectional study

Background

Clinical research results on the relationship between folate and non-alcoholic fatty liver disease are contradictory. Metabolic dysfunction-associated fatty liver disease (MAFLD) is a recently proposed concept. Evidence about the relationship between serum folate and MAFLD, especially considering the status of serum vitamin C, is scarce. This study was aimed to investigate the association of serum folate levels with the prevalence of MAFLD, and further to analyze the potential impact of serum vitamin C status on their association.

Methods

Totally 2,797 participants from National Health and Nutrition Examination Survey (NHANES) 2017-2018 were included. Vibration-controlled transient elastography was used to detect liver steatosis and fibrosis. Participants were divided in groups based on the tertiles of serum folate or vitamin C, and the serum folate or vitamin C level in T1 was low. Logistic regression analysis in the complex sample module was performed to illustrate the association of serum folate levels with the prevalence of MAFLD. Stratification analysis by serum vitamin C status was performed as well.

Results

Compared with the serum folate levels of T1 group, participants in the T3 group had 47.9% lower risk of MAFLD [OR = 0.521 (95% CI: 0.401-0.677)]. However, when participants were stratified by serum vitamin C levels, there was no association between the serum folate levels and MAFLD in the T1 or T2 group. Among participants in the T3 group of vitamin C status, participants in the T3 group of serum folate had a 63.6% lower risk of MAFLD compared with the T1 group [OR = 0.364 (95% CI: 0.147-0.903)].

Conclusions

High serum folate level is associated with lower prevalence of MAFLD, especially in participants with sufficient vitamin C.

Folic acid ameliorates alcohol-induced liver injury via gut–liver axis homeostasis

The gut–liver axis (GLA) plays an important role in the development of alcohol-induced liver injury. Alcohol consumption is typically associated with folic acid deficiency. However, no clear evidence has confirmed the effect of folic acid supplementation on alcohol-induced liver injury via GLA homeostasis. In this study, male C57BL/6J mice were given 56% (v/v) ethanol and 5.0 mg/kg folic acid daily by gavage for 10 weeks to investigate potential protective mechanisms of folic acid in alcohol-induced liver injury via GLA homeostasis. Histopathological and biochemical analyses showed that folic acid improved lipid deposition and inflammation in the liver caused by alcohol consumption and decreased the level of ALT, AST, TG, and LPS in serum. Folic acid inhibited the expression of the TLR4 signaling pathway and its downstream inflammatory mediators in the liver and upregulated the expression of ZO-1, claudin 1, and occludin in the intestine. But compared with the CON group, folic acid did not completely eliminate alcohol-induced intestine and liver injury. Furthermore, folic acid regulated alcohol-induced alterations in gut microbiota. In alcohol-exposed mice, the relative abundance of Bacteroidota was significantly increased, and the relative abundance of unclassified_Lachnospiraceae was significantly decreased. Folic acid supplementation significantly increased the relative abundance of Verrucomicrobia, Lachnospiraceae_NK4A136_group and Akkermansia, and decreased the relative abundance of Proteobacteria. The results of Spearman’s correlation analysis showed that serum parameters and hepatic inflammatory cytokines were significantly correlated with several bacteria, mainly including Bacteroidota, Firmicutes, and unclassified_Lachnospiraceae. In conclusion, folic acid could ameliorate alcohol-induced liver injury in mice via GLA homeostasis to some extent, providing a new idea and method for prevention of alcohol-induced liver injury.

Baicalein Prevents Fructose-Induced Hepatic Steatosis in Rats: In the Regulation of Fatty Acid De Novo Synthesis, Fatty Acid Elongation and Fatty Acid Oxidation

Non-alcoholic fatty liver disease (NAFLD), ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), hepatic fibrosis and even hepatocellular carcinoma, is a liver disease worldwide without approved therapeutic drugs. Baicalein (BAL), a flavonoid compound extracted from the Traditional Chinese Medicine (TCM) Scutellariae Radix (Scutellaria baicalensis Georgi.), has been used in TCM clinical practice for thousands of years to treat liver diseases due to its "hepatoprotective effect". However, the underlying liver-protecting mechanisms remain largely unknown. Here, we found that oral administration of BAL significantly decreased excess serum levels of triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), aspartate aminotransferase (AST) as well as hepatic TG in fructose-fed rats. Attenuation of the increased vacuolization and Oil Red O staining area was evident on hepatic histological examination in BAL-treated rats. Mechanistically, results of RNA-sequencing, western-blot, real-time quantitative PCR (RT-qPCR) and hepatic metabolomics analyses indicated that BAL decreased fructose-induced excessive nuclear expressions of mature sterol regulatory element-binding protein 1c (mSREBP1c) and carbohydrate response element-binding protein (ChREBP), which led to the decline of lipogenic molecules [including fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), elongation of very long chain fatty acids 6 (ELOVL6), acetyl-CoA carboxylase (ACC)], accompanying with the alternation of hepatic fatty acids composition. Meanwhile, BAL enhanced fatty acid oxidation by activating AMPK/PGC1α signaling axis and PPARα signal pathway, which elicited high expression of carnitine palmitoyl transferase 1α (CPT1α) and Acyl-CoA oxidase 1 (ACO1) in livers of fructose-fed rats, respectively. BAL ameliorated fructose-induced hepatic steatosis, which is associated with regulating fatty acid synthesis, elongation and oxidation.

The importance of AMPK in obesity and chronic diseases and the relationship of AMPK with nutrition: a literature review

This review will examine the role of 5'-adenosine monophosphate-activated protein kinase (AMPK) in the treatment of obesity, medical nutrition and chronic diseases, and its relationship with nutrition. In the literature, the number of studies examining the direct relationship of AMPK with nutrition is negligible. For this reason, information on the subject has been compiled from all the studies that can be accessed by searching the terms AMPK and disease, AMPK and health, AMPK and exercise, AMPK and nutrition. It can be stated that AMPK is inhibited in many pathological conditions such as inflammation, diabetes, aging and cancer, and AMPK activation has positive effects in many diseases such as insulin resistance, diabetes, obesity, cancer and Alzheimer's. When the relationship between nutrition and AMPK is examined, it is seen that food intake inhibits AMPK, but especially high-carbohydrate and fatty diets are more effective at this point. In addition, high fructose corn sirup and long chain saturated fatty acids increased by consumption of industrial foods and frequent meals appear to be an inactivator for AMPK. For AMPK activation in medical nutrition therapy, it is recommended to use methods such as evening fasting and intermittent fasting, taking into account the human circadian rhythm.

The Association between Non-Alcoholic Fatty Liver Disease (NAFLD) and Advanced Fibrosis with Serological Vitamin B12 Markers: Results from the NHANES 1999-2004

Background: There is evidence that vitamin B12 and associated metabolite levels are changed in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH); however, their association has been in dispute. Methods: We included 8397 individuals without previous liver condition or excess alcohol intake from the National Health and Nutrition Examination Survey (NHANES) 1999–2004. NAFLD was diagnosed with Fatty Liver Index (FLI) ≥ 60 or USFLI ≥ 30, and participants with advanced fibrosis risks were identified with elevated non-alcoholic fatty liver disease fibrosis score (NFS), fibrosis 4 index (FIB-4), or aspartate aminotransferase (AST)/platelet ratio index (APRI). Step-wide logistic regression adjusting for confounders was used to detect the association between NAFLD or advanced fibrosis with serum vitamin B12, folate, red blood cell folate (RBC folate), homocysteine (HCY), and methylmalonic acid (MMA). Results: The weighted prevalence of NAFLD was 44.2%. Compared with non-NAFLD participants, patients with NAFLD showed significantly increased RBC folate level and RBC counts, decreased serum vitamin B12 and folate, and similar HCY and MMA levels. NAFLD with advanced fibrosis risk had higher MMA and HCY, reduced serum vitamin B12, and similar serum folate and RBC folate levels than NAFLD with low fibrosis risk. Only RBC folate was independently associated with an increased risk of NAFLD (OR (95% CI): 2.24 (1.58, 3.18)). In all participants, MMA (OR: 1.41 (1.10, 1.80)) and HCY (OR: 2.76 (1.49, 5.11)) were independently associated with increased risk for advanced fibrosis. In participants with NAFLD, this independent association still existed (OR: 1.39 (1.04, 1.85) for MMA and 1.95 (1.09, 3.46) for HCY). In all participants, the area under the receiver operating characteristic curve (ROC AUC) on fibrosis was 0.6829 (0.6828, 0.6831) for MMA and 0.7319 (0.7318, 0.7320) for HCY; in participants with NAFLD, the corresponding ROC AUC was 0.6819 (0.6817, 0.6821) for MMA and 0.6926 (0.6925, 0.6928) for HCY. Conclusion: Among vitamin B12-associated biomarkers, RBC folate was independently associated with elevated NAFLD risk, whereas MMA and HCY were associated with increased risk for advanced fibrosis in the total population and NAFLD participants. Our study highlighted the clinical diagnostic value of vitamin B12 metabolites and the possibility that vitamin B12 metabolism could be a therapeutic target for NASH. Further studies using recent perspective data with biopsy proven NASH could be conducted to validate our results.