Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disease. Dietary supplementation has become a promising strategy for managing NAFLD. Hesperetin, a citrus flavonoid, is mainly found in citrus fruits (oranges, grapefruit, and lemons) and possesses multiple pharmacological properties, including anti-cancer, anti-Alzheimer and anti-diabetic effects. However, the anti-NAFLD effect and mechanisms of hesperetin remain unclear. In this study, we investigated the therapeutic effect of hesperetin against NAFLD and the underlying mechanism in vitro and in vivo. In oleic acid (OA)-induced HepG2 cells, hesperetin upregulated antioxidant levels (SOD/GPx/GR/GCLC/HO-1) by triggering the PI3 K/AKT-Nrf2 pathway, alleviating OA-induced reactive oxygen species (ROS) overproduction and hepatotoxicity. Furthermore, hesperetin suppressed NF-κB activation and reduced inflammatory cytokine secretion (TNF-α and IL-6). More importantly, we revealed that this anti-inflammatory effect is attributed to reduced ROS overproduction by the Nrf2 pathway, as pre-treatment with Nrf2 siRNA or an inhibitor of superoxide dismutase (SOD) or/and glutathione peroxidase (GPx) abolished hesperetin-induced NF-κB inactivation and reductions in inflammatory cytokine secretion. In a rat model of high-fat diet (HFD)-induced NAFLD, we confirmed that hesperetin relieved hepatic steatosis, oxidative stress, inflammatory cell infiltration and fibrosis. Moreover, hesperetin activated the PI3 K/AKT-Nrf2 pathway in the liver, increasing antioxidant expression and inhibiting NF-κB activation and inflammatory cytokine secretion. In summary, our results demonstrate that hesperetin ameliorates hepatic oxidative stress through the PI3 K/AKT-Nrf2 pathway and that this antioxidative effect further suppresses NF-κB-mediated inflammation during NAFLD progression. Thus, our study suggests that hesperetin may be an effective dietary supplement for improving NAFLD by suppressing hepatic oxidative stress and inflammation.

According to traditional Chinese medicine (TCM) constitutional theory, individuals with phlegm-dampness constitution (PDC) are at increased risk for metabolic disorders. Previous studies have indicated that PDC individuals exhibit gene expression changes associated with metabolic disorders, even individuals with normal metabolic indices. However, the biological mechanisms underlying these changes remain unclear. The gut microbiota has recently emerged as a promising avenue for elucidating TCM principles. Here, we revealed that individuals with PDC have distinct gut microbiota and serum metabolite profiles. A decrease in phytosphingosine was associated with increased PDC scores and metabolic disorder severity. Subsequent experiments demonstrated that Flavonifractor plautii can biosynthesize phytosphingosine, which was also negatively correlated with the PDC score. Interestingly, both F. plautii and phytosphingosine levels decreased in PDC subjects with normal metabolic indices. Fecal transplantation from these individuals accelerated the development of metabolic disorders in mice. However, supplementation with F. plautii and phytosphingosine ameliorated metabolic disorders by increasing phytosphingosine levels in the gut‒hepatic axis. Mechanistic investigations confirmed that phytosphingosine can directly bind to hepatic peroxisome proliferator-activated receptor α (PPARα) and activate its nuclear transcription activity, thereby regulating downstream gene expression related to glucose‒lipid metabolism. Our research indicates that the decrease in F. plautii and its product, phytosphingosine, contributes to gene expression changes related to metabolic disorders in PDC individuals and increases their susceptibility to metabolic disorders. These findings suggest that diagnosing PDC may be beneficial for identifying at-risk populations among apparently healthy individuals, thereby advancing the broader field of metabolic disorder prevention and TCM integration.

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease worldwide; thus, a dietary supplement that can restrict hepatic fat accumulation is needed. Baicalein, a major component of Scutellaria baicalensis, is used as a dietary supplement in Eastern and Western cultures and can reduce hepatic fat accumulation. However, the detailed mechanism by which baicalein exerts this effect has yet to be elucidated in vivo and in vitro. In this study, we characterized the hepatic fat-lowering activity of baicalein and found that baicalein reduced hepatic fat accumulation by activating AMPK and suppressing SREBP1 cleavage, thus consequently inhibiting the transcriptional activity of SREBP1 and the synthesis of hepatic fat in oleic acid-induced HepG2 cells and high-fat diet-induced non-insulin-resistant mice. Moreover, baicalein improved NAFLD by decreasing TC, increasing HDLC, decreasing LDLC, affecting antioxidant activity, and exerting other effects. Therefore, the mechanism of baicalein with regard to NAFLD prevention and treatment might involve effects on multiple targets and pathways. Our study supports the use of baicalein as a dietary supplement due to its ability to reduce hepatic fat accumulation and to ameliorate NAFLD-related biochemical abnormalities.

Hyperuricemia is the result of increased production and/or underexcretion of uric acid. Hyperuricemia has been epidemiologically associated with multiple comorbidities, including metabolic syndrome, gout with long-term systemic inflammation, chronic kidney disease, urolithiasis, cardiovascular disease, hypertension, rheumatoid arthritis, dyslipidemia, diabetes/insulin resistance and increased oxidative stress. Dysregulation of xanthine oxidoreductase (XOD), the enzyme that catalyzes uric acid biosynthesis primarily in the liver, and urate transporters that reabsorb urate in the renal proximal tubules (URAT1, GLUT9, OAT4 and OAT10) and secrete urate (ABCG2, OAT1, OAT3, NPT1, and NPT4) in the renal tubules and intestine, is a major cause of hyperuricemia, along with variations in the genes encoding these proteins. The first-line therapeutic drugs used to lower serum uric acid levels include XOD inhibitors that limit uric acid biosynthesis and uricosurics that decrease urate reabsorption in the renal proximal tubules and increase urate excretion into the urine and intestine via urate transporters. However, long-term use of high doses of these drugs induces acute kidney disease, chronic kidney disease and liver toxicity. Therefore, there is an urgent need for new nephroprotective drugs with improved safety profiles and tolerance. The current systematic review summarizes the characteristics of major urate transporters, the mechanisms underlying the pathogenesis of hyperuricemia, and the regulation of uric acid biosynthesis and transport. Most importantly, this review highlights the potential mechanisms of action of some naturally occurring bioactive compounds with antihyperuricemic and nephroprotective potential isolated from various medicinal plants.

Silymarin has been used for improving hepatic damage and lipid disorders, but its action mechanism remains to be clarified. Here, we investigate the contributions of the gut microbiota to the improvement of liver lipid metabolism by silymarin. We find i) strong and significant microbial shifts upon silymarin but not silibinin treatment; ii) over 60% variations of liver fat are explained by silymarin-induced bacterial B12 production in male rats but not in male germ-free mice; iii) fecal microbiota transplantation confirms their protective roles against liver fat accumulation; iv) upregulation of one-carbon metabolism and fatty acid degradation pathways are observed based on the liver transcriptome analyses; and v) in humans the delta changes of serum B12 associate negatively with the fluctuations of serum triglycerides. Overall, we reveal a mechanism of action underpinning the lipid-lowering effect of silymarin via the gut microbiota and its vitamin B12 producing capabilities.