Quercetin Increases Hepatic Homocysteine Remethylation and Transsulfuration in Rats Fed a Methionine-Enriched Diet

Quercetin modulates the liver metabolic profile in a chronic unpredictable mild stress rat model based on metabolomics technology

Depression is the most prevalent psychiatric disease, and its pathogenesis is still unclear. Currently, studies on the pathogenesis of depression are mainly focused on the brain. The liver can modulate brain function via the liver-brain axis, indicating that the liver plays an important role in the development of depression. This study aims to explore the protective effect of quercetin against chronic unpredictable mild stress (CUMS)-induced metabolic changes and the corresponding mechanisms in the rat liver based on untargeted metabolomics technology. In this study, 96 male rats were divided into six groups: control, different doses of quercetin (10 mg per kg bw or 50 mg per kg bw), CUMS, and CUMS + different doses of quercetin. After 8 weeks of CUMS modeling, the liver samples were collected for metabolomics analysis. A total of 17 altered metabolites were identified, including D-glutamic acid, S-adenosylmethionine, lithocholylglycine, L-homocystine, prostaglandin PGE2, leukotriene E4, cholic acid, 5-methyltetrahydrofolic acid, taurochenodeoxycholic acid, S-adenosylhomocysteine, deoxycholic acid, folic acid, L-methionine, leukotriene C5, estriol-17-glucuronide, PE, and PC, indicating that methionine metabolism, bile acid metabolism, and phosphatidylcholine biosynthesis are the major pathways involved in CUMS-induced hepatic metabolic disorders. Hepatic methylation damage may play a role in the pathophysiology of depression, as evidenced by the first discovery of the abnormality of hepatic methionine metabolism. Abnormal changes in hepatic bile acids may provide stronger evidence for depression pathogenesis involving the microbiota-gut-brain axis, suggesting that the liver is involved in depression development and may be a treatment target. The quercetin treatment alleviated the CUMS-induced liver metabolism disorder, suggesting that quercetin may protect against depression by regulating liver metabolism.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

Homocysteine promotes hepatic steatosis by activating the adipocyte lipolysis in a HIF1α-ERO1α-dependent oxidative stress manner

Hyperhomocysteinemia (HHcy) is related to liver diseases, such as nonalcoholic fatty liver (NAFL). Although the precise pathogenesis of NAFL is still largely unknown, the links between organs seem to play a vital role. The current study aimed to explore the role of white adipose tissue in homocysteine (Hcy)-induced NAFL. Blood samples from nonhyperhomocysteinemia or hyperhomocysteinemia individuals were collected to assess correlation between Hcy and triglyceride (TG) or free fatty acids (FFAs) levels. C57BL/6 mice were maintained on a high-methionine diet or administered with Hcy (1.8 g/L) in the drinking water to establish an HHcy mouse model. We demonstrated that Hcy activated adipocyte lipolysis and that this change was accompanied by an increased release of FFAs and glycerol. Excessive FFAs were taken up by hepatocyte, which resulted in lipid accumulation in the liver. Treatment with acipimox (0.08 g kg ⁻¹ day ⁻¹), a potent chemical inhibitor of lipolysis, markedly decreased Hcy-induced NAFL. Mechanistically, hypoxia-inducible factor 1α (HIF1α)-endoplasmic reticulum oxidoreductin 1α (ERO1α) mediated pathway promoted H₂O₂ accumulation and induced endoplasmic reticulum (ER) overoxidation, ER stress and more closed ER-lipid droplet interactions, which were responsible for activating the lipolytic response. In conclusion, this study reveals that Hcy activates adipocyte lipolysis and suggests the potential utility of targeted ER redox homeostasis for treating Hcy-induced NAFL.

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Hcy elevates adipocyte lipolysis process.

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Inhibition of adipocyte lipolysis via acipimox improves the Hcy-induced nonalcoholic fatty liver.

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Adipocyte lipolytic response relies on ERO1α-mediated oxidative stress.

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Activation of adipocyte HIF1α mediates ERO1α upregulation.

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Deficiency of adipocyte HIF1α alleviates the Hcy-induced lipolytic response and nonalcoholic fatty liver.

Homocysteine and psoriasis

Psoriasis is caused by a complex interplay among the immune system, genetic background, autoantigens, and environmental factors. Recent studies have demonstrated that patients with psoriasis have a significantly higher serum homocysteine (Hcy) level and a higher prevalence of hyperhomocysteinaemia (HHcy). Insufficiency of folic acid and vitamin B₁₂ can be a cause of HHcy in psoriasis. Hcy may promote the immuno-inflammatory process in the pathogenesis of psoriasis by activating Th1 and Th17 cells and neutrophils, while suppressing regulatory T cells. Moreover, Hcy can drive the immuno-inflammatory process by enhancing the production of the pro-inflammatory cytokines in related to psoriasis. Hcy can induce nuclear factor kappa B activation, which is critical in the immunopathogenesis of psoriasis. There may be a link between the oxidative stress state in psoriasis and the effect of HHcy. Hydrogen sulfide (H₂S) may play a protective role in the pathogenesis of psoriasis and the deficiency of H₂S in psoriasis may be caused by HHcy. As the role of Hcy in the pathogenesis of psoriasis is most likely established, Hcy can be a potential therapeutic target for the treatment of psoriasis. Systemic folinate calcium, a folic acid derivative, and topical vitamin B12 have found to be effective in treating psoriasis.

Effects of Multivitamin, Multimineral and Phytonutrient Supplementation on Nutrient Status and Biomarkers of Heart Health Risk in a Russian Population: A Randomized, Double Blind, Placebo Controlled Study

The primary objective of this clinical study was to evaluate the effect of a dietary multivitamin, multimineral and phytonutrient (VMP) supplement on blood nutrient status and biomarkers of heart health risk in a Russian population. One hundred twenty healthy adults (40-70 years) were recruited for a 56-day (eight-week) randomized, double blind, placebo controlled study with parallel design. Subjects were divided into two groups and received either a VMP or a placebo (PLA) supplement. Blood nutrient levels of β-carotene, α-tocopherol, vitamin C, B6, B12, red blood cell (RBC) folate, Zinc and Selenium were measured at baseline and on Days 28 and 56, and quercetin was measured at baseline and on Day 56. Blood biomarkers of heart health, i.e. homocysteine (Hcy), high-sensitivity C-reactive protein (hs-CRP), oxidized LDL (ox-LDL), gamma-glutamyl transferase (GGT), uric acid and blood lipid profile, were measured at baseline and Day 56. Dietary VMP supplementation for 56 days significantly increased circulating levels of quercetin, vitamin C, RBC folate and partially prevented the decline in vitamin B6 and B12 status. Both serum Hcy and GGT were significantly reduced (-3.97 ± 10.09 µmol/L; -1.68 ± 14.53 U/L, respectively) after VMP supplementation compared to baseline. Dietary VMP supplementation improved the nutrient status and reduced biomarkers of heart health risk in a Russian population.

Glutathione homeostasis is significantly altered by quercetin via the Keap1/Nrf2 and MAPK signaling pathways in rats

Previously, we showed that 0.5% quercetin simultaneously decreased serum homocysteine and glutathione (GSH) levels in rats. The aim of the present study was to investigate the effects of 0.5% quercetin on GSH metabolism, related enzymes and signal pathways in rats. Rats were fed the control diet and 0.5% quercetin-supplemented diet for 6 weeks. The results showed that quercetin reduced serum and hepatic content of GSH and the ratio of GSH and oxidized glutathione (GSSG), enhanced hepatic activity and mRNA expression of glutathione S-transferase (GST), inhibited hepatic activity and mRNA expression of glutamate cysteine ligase (GCL), and decreased hepatic glutathione reductase (GR) mRNA expression. Levels of phosphorylated p38 and extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinases (MAPKs) increased, while that of nuclear factor E2-like 2 (Nrf2) protein decreased after quercetin treatment. However, no significant hepatotoxicity was noted. We concluded that quercetin treatment altered hepatic GSH metabolism by modulating GSH metabolic enzyme activities and mRNA expression in rats, and p38, ERK1/2 MAPKs, and Nrf2 were involved in modulating GSH metabolism-related enzymes.

The Effects of Subchronic Methionine Overload Administered Alone or Simultaneously with L-cysteine or N-acetyl-L-cysteine on Body Weight, Homocysteine Levels and Biochemical Parameters in the Blood of Male Wistar Rats

Hyperhomocysteinemia (HHC), both basal and after methionine load, may occur due to genetic disorders or deficiencies of nutrients that affect the remethylation or trans-sulphuration pathways during methionine metabolism. HHC is involved in the pathogenesis of many illnesses as a result of its prooxidative effect and its impairment of antioxidative protection. The aim was to examine the effects of subchronic methionine overload on the body weight and standard biochemical parameters in rat serum and to examine whether simultaneous subchronic intraperotoneal administration of methionine alone or together with L-cysteine or N-acetyl-cysteine resulted in a change in the body weight and biochemical parameters in the rat serum. The research was conducted during a three-week period (male Wistar albino rats, n=36, body weight of approximately 160 g, age of 15-20 days), and the animals were divided into a control group and three experimental groups of 8-10 animals each: a) control group (0.9% sodium chloride 0.1-0.2 ml/day); b) methionine (0.8 mmol/kg/bw/day) (MET group); c) methionine (0.8 mmol/kg/bw/day) + L-cysteine (7 mg/kg/bw/day) (L-cys+MET group); and d) methionine (0.8 mmol/kg/bw/day) + N-acetyl-L-cysteine (50 mg/kg/bw/day) (NAC+MET group). In addition to the body weight monitoring, the levels of total homocysteine and the standard biochemical parameters in blood samples (plasma or serum) were determined. The results indicated that monitoring the homocysteine levels and standard biochemical parameters in blood could be used for analysis and could provide an excellent guideline for distinguishing between toxic and non-toxic doses of methionine intake, which may be meaningful for clinical applications.