Xanthine oxidase in non-alcoholic fatty liver disease and hyperuricemia: One stone hits two birds

A cross-sectional study of the association between blood metal mixtures exposure and hyperuricemia

OBJECTIVES

To determine the association between blood metal mixture and HUA risk.

METHODS

A cross-sectional study was performed based on the populations from Kailuan cohort trial in China. Inductively coupled plasma mass spectrometry was utilized to detect the blood concentrations of iron (Fe), lead (Pb), calcium (Ca), copper (Cu), magnesium (Mg), zinc (Zn), selenium (Se), and manganese (Mn). Multivariate logistic regression (MLR) models and weighted quantile sum (WQS) regression models were employed to assess the relationships.

RESULTS

There were 3706 participants included in this study, and 464 (12.52%) were with HUA. The mean level of uric acid was 485.60 μmol/L in the subjects with HUA, which was remarkably increased compared to those without HUA (293.10 μmol/L). The multivariate-adjusted odds ratios (95% confidence intervals) of HUA were 2.15 (1.40, 3.29) for Pb, 3.42 (2.24, 5.23) for Fe, 1.61 (1.15, 2.25) for Ca, 3.06 (2.04, 4.59) for Mg, and 1.69 (1.26, 2.28) for Zn by comparing the highest and lowest metal quartiles using the single-metal logistic regression model. Meanwhile, the WQS regression models demonstrated a positive association between metal mixtures and HUA risk, to which, Fe, Mg, Pb, and Zn were the major contributors. Pb, Fe, and Zn were still robust in multiple-metal models. Age, gender, weight, smoking, and drinking status could modify these relationships with significant interactions.

CONCLUSIONS

Co-exposure to Fe, Pb, Ca, Cu, Zn, Mg, Se, and Mn were related to increased HUA risk in Chinese adults, of with, Pb, Fe, and Zn appeared to have greater impacts. These relationships were more obvious in adults aged < 60 years, or women, or overweight, or non-smoking, or drinking with significant interactions. Key Points • Increased Fe, Pb, Mg, Ca, and Zn were related to increased HUA risk in dose-response fashion among Chinese adults. • The metal mixture dominated by Fe, Mg, Pb, and Zn was positively associated with HUA risk. Fe, Pb, and Zn were still robust in MM model. • Such association was stronger showed in adults aged < 60 years, or women, or overweight, or non-smoking, or drinking with significant interactions.

Pathophysiological role and potential drug target of NLRP3 inflammasome in the metabolic disorders

NLRP3 plays a role in the development of autoinflammatory diseases. NLRP3, ASC, and Caspases 1 or 8 make up the NLRP3 inflammasome, which is an important part of innate immune system. The NLRP3 inflammasome-mediated inflammatory cytokines may also participate in metabolic disorders, such as diabetes, hyperlipidemia, atherosclerosis, non-alcoholic fatty liver disease, and gout. Hence, an overview of the NLRP3 regulation in these metabolic diseases and the potential drugs targeting NLRP3 is the focus of this review.

Polysaccharides from Alpinia oxyphylla fruit prevent hyperuricemia by inhibiting uric acid synthesis, modulating intestinal flora and reducing renal inflammation

Hyperuricemia (HUA) is one of the most common chronic diseases today, with a prevalence exceeding 14 % in both the United States and China. Current clinical treatments for HUA focus on promoting uric acid (UA) excretion and inhibiting UA production, but often neglect the strain on the liver and kidneys. The fruit of Alpinia oxyphylla (A. oxyphylla) is known to improve renal function, regulate metabolism, and exhibit anti-inflammatory effects; however, its effectiveness and mechanisms in treating HUA are not well understood. In this study, HUA mice induced by potassium oxonate and adenine were treated with A. oxyphylla polysaccharide (AFP) for 21 days. The levels associated with HUA were quantified using assay kits to evaluate the impact of AFP on HUA. Serum metabolomics and 16S rRNA sequencing were used to investigate the mechanisms by which AFP ameliorates HUA. The results showed that AFP treatment reduced abnormal biochemical levels, including UA, blood urea nitrogen, and creatinine, in HUA mice. AFP inhibited UA synthesis by regulating pyrimidine metabolism and the metabolism of alanine, aspartate and glutamate, reduced kidney inflammation, and promoted UA excretion by regulating intestinal flora. Thus, AFP appears to be an effective agent for alleviating HUA symptoms.

Association Between Serum Uric Acid Levels and Metabolic-Associated Fatty Liver Disease in Southeast China: A Cross-Sectional Study

Objective

This study aimed to explore the association between serum uric acid (sUA) levels and metabolic-associated fatty liver disease (MAFLD) in Southeast China.

Methods

We performed a cross-sectional study of 2605 subjects who underwent physical examination between 2015 and 2017 in Southeast China. To explore the association between sUA levels and the risk of MAFLD, we employed logistic regression, restricted cubic spline (RCS), subgroups and multiplicative interaction analysis.

Results

Logistic regression analysis showed a positive association between sUA and MAFLD [aOR total population (95% CI)= 1.90 (1.49 ~ 2.42)], [aOR male (95% CI)= 2.01 (1.54 ~ 2.62)], [aOR female (95% CI)= 1.15 (0.62 ~ 2.11)], respectively. The RCS plot presented a significant nonlinear dose-response relationship between sUA levels and MAFLD risk, and the risk of MAFLD increased significantly when sUA> 5.56 mg/dL (P nonlinear< 0.001). Subgroups analysis revealed that the positive association between sUA and MAFLD was consistent across strata of gender, age, BMI, drinking status, smoking status and tea drinking status. Significant associations between sUA and MAFLD were not only found in males but also existed in subjects whose age ≤60, BMI ≥24 kg/m2, drinkers, smokers and tea-drinkers. Adjusted ORs were estimated to be 2.01, 1.95, 2.11, 2.29, 2.64 and 2.20, respectively. Multiplicative interactions were not observed between gender, age, drinking status, smoking status, tea drinking status and sUA (all P interaction> 0.05).

Conclusion

According to our study, sUA was positively associated with the risk of MAFLD. Additionally, the risk of MAFLD increased significantly when sUA levels exceeded 5.56 mg/dL. Our study may help clarify whether sUA plays a diagnostic role in MAFLD.

Sex- and age-associated factors drive the pathophysiology of MASLD

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is strongly associated with obesity. Sex and age affect MASLD prevalence and pathophysiology. The use of animal models fed Western-style diets is vital for investigating the molecular mechanisms contributing to metabolic dysregulation and for facilitating novel drug target identification. However, the sex-associated and age-associated mechanisms underlying the pathophysiology remain poorly understood. This knowledge gap limits the development of personalized sex-specific and age-specific drug treatments.

METHODS

Young (7 wk) and aged (52 wk) male and female mice were fed a high-fat diet (HFD) or low-fat diet. Liver metabolome (>600 molecules) and transcriptome profiles were analyzed.

RESULTS

Male and female mice fed an HFD developed obesity, glucose intolerance, and hepatic steatosis. However, fasting blood glucose, insulin, and serum alanine aminotransferase levels were higher in males fed an HFD, indicating a more severe metabolic disease. In addition, males showed significant increases in liver diacylglycerides and glycosylceramides (known mediators of insulin resistance and fibrosis), and more changes in the transcriptome: extracellular matrix organization and proinflammatory genes were elevated only in males. In contrast, no major increase in damaging lipid classes was observed in females fed an HFD. However, aging affected the liver to a greater extent in females. Acylcarnitine levels were significantly reduced, suggestive of changes in fatty acid oxidation, and broad changes in the transcriptome were observed, including reduced oxidative stress response gene expression and alterations in lipid partitioning genes.

CONCLUSIONS

Here, we show distinct responses to an HFD between males and females. Our study underscores the need for using both sexes in drug target identification studies, and characterizing the molecular mechanisms contributing to the MASLD pathophysiology in aging animals.

Xanthine oxidase promotes hepatic lipid accumulation through high fat absorption by the small intestine

Background & Aims

There are no studies investigating the direct effects of elevated xanthine oxidase (XO) on lipid metabolism disorders. Here, we aimed to clarify the role of XO in lipid metabolism in a prospective cohort study and elucidate the underlying mechanisms.

Methods

The association between serum XO activity and metabolic associated steatotic liver disease (MASLD) was examined in Cox proportional hazard models in a population-based cohort of 3,358 participants (20-75 years) at baseline. In addition, mouse models were used to investigate the underlying mechanism for the association between overexpression of XO and the lipid metabolism disorders.

Results

After an average 5.8 years of follow up, we found elevated serum XO activity was associated with an increased risk of developing MASLD (hazard ratio [HR]: 2.08; 95% CI: 1.44-3.01; p-trend <0.001). Moreover, serum XO activity was significantly associated with serum triglyceride levels (r = 0.68, p <0.001). We demonstrated that hepatic XO expression increased in liver samples from patients with MASLD. Using tissue-specific Xdh knockin mice, we observed rapid lipid metabolism disorders under a high-fat diet rather than a normal chow diet. We found that XO overexpression promotes the absorption of excess dietary fat in the small intestine. Inhibition of XO also significantly reduced the absorption of fat in mice fed a high-fat diet.

Conclusions

Our study clarified the association between serum XO activity levels and the development of MASLD in a large population-based prospective cohort study. Furthermore, our mouse models demonstrated that XO overexpression promotes lipid accumulation through mechanisms involving excessive fat absorption by the small intestine.

Impact and implications

Using a prospective population-based cohort and various animal models, we have identified novel mechanisms by which xanthine oxidase regulates lipid metabolism. Our findings indicate that xanthine oxidase overexpression promotes lipid accumulation by increasing the absorption of excess dietary fat and possibly facilitating lipid transport in vivo. These results could be important for the development of therapies to treat diseases associated with lipid metabolism disorders.

Associations of Serum Per- and Polyfluoroalkyl Substances with Hyperuricemia in Adults: A Nationwide Cross-Sectional Study

There has been widespread concern about the health hazards of per- and polyfluoroalkyl substances (PFAS), which may be the risk factor for hyperuricemia with evidence still insufficient in the general population in China. Here, we conducted a nationwide study involving 9,580 adults aged 18 years or older from 2017 to 2018, measured serum concentrations of uric acid and PFAS (PFOA, PFOS, 6:2 Cl-PFESA, PFNA, PFHxS) in participants, to assess the associations of individual PFAS with hyperuricemia, and estimated a joint effect of PFAS mixtures. We found positive associations of higher serum PFAS with elevated odds of hyperuricemia in Chinese adults, with the greatest contribution from PFOA (69.37%). The nonmonotonic dose-response (NMDR) relationships were observed for 6:2 Cl-PFESA and PFHxS with hyperuricemia. Participants with less marine fish consumption, overweight, and obesity may be the sensitive groups to the effects of PFAS on hyperuricemia. We highlight the potential health hazards of legacy long-chain PFAS (PFOA) once again because of the higher weights of joint effects. This study also provides more evidence about the NMDR relationships in PFAS with hyperuricemia and emphasizes a theoretical basis for public health planning to reduce the health hazards of PFAS in sensitive groups.

Molybdenum's Role as an Essential Element in Enzymes Catabolizing Redox Reactions: A Review

Molybdenum (Mo) is an essential element for human life, acting as a cofactor in various enzymes crucial for metabolic homeostasis. This review provides a comprehensive insight into the latest advances in research on molybdenum-containing enzymes and their clinical significance. One of these enzymes is xanthine oxidase (XO), which plays a pivotal role in purine catabolism, generating reactive oxygen species (ROS) capable of inducing oxidative stress and subsequent organ dysfunction. Elevated XO activity is associated with liver pathologies such as non-alcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC). Aldehyde oxidases (AOs) are also molybdenum-containing enzymes that, similar to XO, participate in drug metabolism, with notable roles in the oxidation of various substrates. However, beneath its apparent efficacy, AOs' inhibition may impact drug effectiveness and contribute to liver damage induced by hepatotoxins. Another notable molybdenum-enzyme is sulfite oxidase (SOX), which catalyzes the conversion of sulfite to sulfate, crucial for the degradation of sulfur-containing amino acids. Recent research highlights SOX's potential as a diagnostic marker for HCC, offering promising sensitivity and specificity in distinguishing cancerous lesions. The newest member of molybdenum-containing enzymes is mitochondrial amidoxime-reducing component (mARC), involved in drug metabolism and detoxification reactions. Emerging evidence suggests its involvement in liver pathologies such as HCC and NAFLD, indicating its potential as a therapeutic target. Overall, understanding the roles of molybdenum-containing enzymes in human physiology and disease pathology is essential for advancing diagnostic and therapeutic strategies for various health conditions, particularly those related to liver dysfunction. Further research into the molecular mechanisms underlying these enzymes' functions could lead to novel treatments and improved patient outcomes.

The role and mechanism of pyroptosis and potential therapeutic targets in non-alcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is a clinical pathological syndrome characterized by the excessive accumulation of fat within liver cells, which can progress to end-stage liver disease in severe cases, posing a threat to life. Pyroptosis is a distinct, pro-inflammatory form of cell death, differing from traditional apoptosis. In recent years, there has been growing research interest in the association between pyroptosis and NAFLD, encompassing the mechanisms and functions of pyroptosis in the progression of NAFLD, as well as potential therapeutic targets. Controlled pyroptosis can activate immune cells, eliciting host immune responses to shield the body from harm. However, undue activation of pyroptosis may worsen inflammatory responses, induce cellular or tissue damage, disrupt immune responses, and potentially impact liver function. This review elucidates the involvement of pyroptosis and key molecular players, including NOD-like receptor thermal protein domain associated protein 3(NLRP3) inflammasome, gasdermin D (GSDMD), and the caspase family, in the pathogenesis and progression of NAFLD. It emphasizes the promising prospects of targeting pyroptosis as a therapeutic approach for NAFLD and offers valuable insights into future directions in the field of NAFLD treatment.

CRISPR/Cas9 Mediated Deletion of the Uox Gene Generates a Mouse Model of Hyperuricemia with Multiple Complications

Hyperuricemia is a common metabolic disorder with severe complications. We aimed to develop a mouse model for spontaneous hyperuricemia. Uox-/- mouse model was generated on C57BL/6J background by deleting exon 2-4 of Uox using the CRISPR/Cas9 system. The prototypic Uox -/-mice had 5.5-fold increased serum uric acid (1351.04±276.58μmol/L) as compared to the wild type mice (P<0.0001), but died by 4 weeks. After allopurinol (3ug/g) intervention, they all survived > 8 weeks. The serum uric acid was 612.55±146.98μmol/L in the 8-week-old allopurinol-rescued Uox -/-mice, which manifested multiple complications including severe renal insufficiency, hypertension, left ventricular remodeling and systolic dysfunction, aortic endothelial dysfunction, hepatic steatosis and elevated liver enzymes, as well as hyperglycemia and hypercholesteremia. The present Uox-/- mice developed spontaneous hyperuricemia complicated with urate nephropathy, cardiovascular disease and cardiometabolic disorders, and may provide a novel tool to study hyperuricemia associated early-onset cardiovascular disorders in human.

Anti-gouty arthritis and anti-inflammatory effects of curcumin nanoparticles in monosodium urate crystals induced Balb/C mice

Gout is a metabolic condition characterized by the accumulation of urate crystals in the synovial joints. These crystal depositions result in joint swelling and increased concentration of serum uric acid in blood. The commercially available drugs lower serum uric acid levels and reduce inflammation, but these standard therapies have many side effects. This study aimed to investigate anti-gout and anti-inflammatory properties of curcumin nanoparticles (CNPs). For this purpose, CNPs were prepared by dissolving curcumin into dichloromethane. Then, gout was induced by injecting monosodium urate crystals (MSU) in the ankle joint and in the intra-peritoneal cavity which caused ankle swelling and increased blood uric acid levels. CNPs in different concentrations (5, 10, and 20 ppm) and allopurinol were orally administered. The MSU crystals increased the xanthine oxidase levels both in serum and the liver. Moreover, MSU crystals increased the serum levels of interleukin 1β, interleukin-6, tumor necrosis factor-alpha, liver function tests markers, renal function tests markers, and lipid profiles. However, the administration of CNPs decreased the levels of all these variables. CNPs increased the serum high-density lipoprotein and interleukin-10 levels. Moreover, CNPs also reduced ankle swelling significantly. Hence, the levels of xanthine oxidase, uric acid and ankle swelling were reduced significantly by oral administration of CNPs. Our findings indicate that CNPs through their anti-inflammatory properties significantly alleviate gouty arthritis. Thus, the study concluded that CNPs can be developed as an efficient anti-gout agent with minimal side effects.

Metabolic signatures of metabolic dysfunction-associated steatotic liver disease in severely obese patients

BACKROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) can lead to liver fibrosis, cirrhosis, and hepatocellular carcinoma. Still, most patients with MASLD die from cardiovascular diseases indicating metabolic alterations related to both liver and cardiovascular pathology.

AIMS AND METHODS

The aim of this study was to assess biologic pathways behind MASLD progression from steatosis to metabolic dysfunction-associated steatohepatitis (MASH) using non-targeted liquid chromatography-mass spectrometry analysis in 106 severely obese individuals (78 women, mean age 47.7 7 ± 9.2 years, body mass index 41.8 ± 4.3 kg/m²) undergoing laparoscopic Roux-en-Y gastric bypass.

RESULTS

We identified several metabolites that are associated with MASLD progression. Most importantly, we observed a decrease of lysophosphatidylcholines LPC(18:2), LPC(18:3), and LPC(20:3) and increase of xanthine when comparing those with steatosis to those with MASH. We found that indole propionic acid and threonine were negatively correlated to fibrosis, but not with the metabolic disturbances associated with cardiovascular risk. Xanthine, ketoleucine, and tryptophan were positively correlated to lobular inflammation and ballooning but also with insulin resistance, and dyslipidemia, respectively. The results did not change when taking into account the most important genetic risk factors of MASLD.

CONCLUSIONS

Our findings suggest that there are several separate biological pathways, some of them independent of insulin resistance and dyslipidemia, associating with MASLD.

Uric acid formation is driven by crosstalk between skeletal muscle and other cell types

Hyperuricemia is implicated in numerous pathologies, but the mechanisms underlying uric acid production are poorly understood. Using a combination of mouse studies, cell culture studies, and human serum samples, we sought to determine the cellular source of uric acid. In mice, fasting and glucocorticoid treatment increased serum uric acid and uric acid release from ex vivo-incubated skeletal muscle. In vitro, glucocorticoids and the transcription factor FoxO3 increased purine nucleotide degradation and purine release from differentiated muscle cells, which coincided with the transcriptional upregulation of AMP deaminase 3, a rate-limiting enzyme in adenine nucleotide degradation. Heavy isotope tracing during coculture experiments revealed that oxidation of muscle purines to uric acid required their transfer from muscle cells to a cell type that expresses xanthine oxidoreductase, such as endothelial cells. Last, in healthy women, matched for age and body composition, serum uric acid was greater in individuals scoring below average on standard physical function assessments. Together, these studies reveal skeletal muscle purine degradation is an underlying driver of uric acid production, with the final step of uric acid production occurring primarily in a nonmuscle cell type. This suggests that skeletal muscle fiber purine degradation may represent a therapeutic target to reduce serum uric acid and treat numerous pathologies.

The Management of Diabetes with Hyperuricemia: Can We Hit Two Birds with One Stone?

Serum urate (SU) is an independent predictor for the incidence of diabetes. In current diabetes treatment regimens, there is insufficient appreciation of the importance of hyperuricemia (HU) in disease control and prevention. To summarize the updated knowledge on the effects of SU on β-cell function, insulin resistance and chronic diabetic complications, as well as to evaluate the management of patients with both HU and diabetes, we searched the MEDLINE PubMed database, and included 285 journal articles. An inverted U-shaped relationship between fasting plasma glucose and SU levels was established in this review. Elevated SU levels may enhance the development of chronic diabetic complications, including macrovascular and microvascular dysfunction. Diet and exercise are essential parts of the lifestyle changes necessary for HU and diabetes management. Glucose- and urate-lowering drug selection and combination should be made with the principle of ameliorating, and at least not deteriorating, diabetes and HU. Medical artificial intelligence technology and monitoring systems can help to improve the effectiveness of long-term management of HU and diabetes through digital healthcare. This study comprehensively reviews and provides a scientific and reliable basis for and viewpoints on the clinical management of diabetes and HU.

Allopurinol versus Febuxostat: A New Approach for the Management of Hepatic Steatosis in Metabolic Dysfunction-Associated Steatotic Liver Disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) includes patients with hepatic steatosis and at least one of five cardiometabolic risk factors. Xanthine oxidase (XO) represents a treatment target for MASLD. We aimed to evaluate the effect of two xanthine oxidase inhibitors, allopurinol and febuxostat, plus lifestyle modifications compared to lifestyle modifications alone on improving steatosis. Ninety MASLD patients were assigned to one of three groups for three months. Patients with hyperuricemia were given either allopurinol 100 mg or febuxostat 40 mg daily, along with lifestyle modifications. The third control group was only given lifestyle modifications, excluding all patients with hyperuricemia due to ethical concerns. The primary outcome was to measure the change in the controlled attenuation parameter (CAP) score as an indicator of steatosis from baseline after three months. The secondary outcome was to measure the change in serum uric acid (SUA) three months from baseline. The study found that the CAP score decreased significantly in the allopurinol group (p = 0.009), but the decline in the febuxostat or lifestyle groups was non-significant (p = 0.189 and 0.054, respectively). The SUA levels were significantly reduced in both the allopurinol and febuxostat groups (p < 0.001), with no statistical difference between the two groups (p = 0.496).

Natural mutations of human XDH promote the nitrite (NO2-)-reductase capacity of xanthine oxidoreductase: A novel mechanism to promote redox health?

Several rare genetic variations of human XDH have been shown to alter xanthine oxidoreductase (XOR) activity leading to impaired purine catabolism. However, XOR is a multi-functional enzyme that depending upon the environmental conditions also expresses oxidase activity leading to both O2·- and H2O2 and nitrite (NO2-) reductase activity leading to nitric oxide (·NO). Since these products express important, and often diametrically opposite, biological activity, consideration of the impact of XOR mutations in the context of each aspect of the biochemical activity of the enzyme is needed to determine the potential full impact of these variants. Herein, we show that known naturally occurring hXDH mutations do not have a uniform impact upon the biochemical activity of the enzyme in terms of uric acid (UA), reactive oxygen species (ROS) and nitric oxide ·NO formation. We show that the His1221Arg mutant, in the presence of xanthine, increases UA, O2·- and NO generation compared to the WT, whilst the Ile703Val increases UA and ·NO formation, but not O2·-. We speculate that this change in the balance of activity of the enzyme is likely to endow those carrying these mutations with a harmful or protective influence over health that may explain the current equipoise underlying the perceived importance of XDH mutations. We also show that, in presence of inorganic NO2-, XOR-driven O2·- production is substantially reduced. We suggest that targeting enzyme activity to enhance the NO2--reductase profile in those carrying such mutations may provide novel therapeutic options, particularly in cardiovascular disease.

Inhibiting Hepatocyte Uric Acid Synthesis and Reabsorption Ameliorates Acetaminophen-Induced Acute Liver Injury in Mice

BACKGROUND & AIMS

Acetaminophen (APAP) overdose is the most common cause of drug-induced liver injury worldwide. Uric acid (UA) is involved in sterile inflammation in many organs, but its role in APAP-induced liver injury remains elusive.

METHODS

We quantified the concentration of UA in the serum and liver tissues of APAP-overdosed mice and explored the changes in proteins involved in UA synthesis, absorption, and degeneration on APAP stimulation. We also examined the effects of inhibiting hepatocyte UA synthesis or reabsorption on APAP-induced liver injury in mice. Furthermore, we explored the process of UA clearance by peripheral macrophages.

RESULTS

APAP overdose significantly increased intrahepatic UA contents, which occurred earlier than apparent hepatocyte injury in APAP-overdosed mice. APAP overdose induced significant DNA leakage and may thereby increase the substrate of UA synthesis. APAP overdose also significantly increased the enzymatic activity of xanthine oxidase and urate oxidase and decreased the expression of the UA reabsorption transporter GLUT9 in hepatocytes. Inhibiting hepatocyte UA synthesis by febuxostat or reabsorption by hepatic-specific knockout of GLUT9 alleviated APAP-induced liver injury. Further experiments showed that monosodium urate but not soluble UA may be a major form of UA mediating hepatocyte injury. Additionally, monosodium urate further recruited circulating macrophages into the liver and then aggravated inflammation by increasing the levels of inflammatory factors and reactive oxygen species. Deletion of macrophages significantly ameliorated APAP-induced liver injury in mice.

CONCLUSIONS

APAP overdose induces excessive UA production and leads to local high concentrations in the liver, which further injures cells and induces liver inflammation. Inhibiting the production of UA may be a potential therapeutic option for treating APAP-induced liver injury.

Quercetin-enriched Lactobacillus aviarius alleviates hyperuricemia by hydrolase-mediated degradation of purine nucleosides

The development of hyperuricemia (HUA) and gout is associated with dysbiosis of the gut microbiota. Quercetin can reduce serum uric acid levels and thus alleviate HUA by modulating the gut microbiota. However, the detailed mechanisms involved in this process are not fully understood. Here, we showed that quercetin significantly reduced the serum uric acid level in a chicken HUA model by altering the chicken cecal microbiota structure and function and increasing the abundance of Lactobacillus aviarius. An L. aviarius strain, CML180, was isolated from the quercetin-treated chicken gut microbiota. Strain characterization indicated that quercetin promoted the growth of L. aviarius CML180 and increased its adhesion, hydrophobicity, and co-aggregation abilities. Gavage of live L. aviarius CML180 to a mouse model of HUA-established by adenosine and potassium oxonate-reduced the serum uric acid level and alleviated HUA. The ability of L. aviarius CML180 to decrease the level of uric acid was due to its degradation of purine nucleosides, which are the precursors for uric acid production. A nucleoside hydrolase gene, nhy69, was identified from the genome of L. aviarius CML180, and the resulting protein, Nhy69, exhibited strong purine nucleoside-hydrolyzing activity at mesophilic temperature and neutral pH conditions. These findings provide mechanistic insights into the potential of quercetin to treat HUA or gout diseases via a specific gut microbe.

Associations of circulating multiple metals with the risk of incident hyperuricemia and the average annual change in uric acid levels

BACKGROUND

Hyperuricemia has been linked to exposure to certain metals in cross-sectional studies. However, prospective studies evaluating the associations of multiple metal exposures with incident hyperuricemia are scarce.

OBJECTIVES

To prospectively investigate the associations of multiple metal/metalloid concentrations with incident hyperuricemia as well as average annual change in uric acid levels in a longitudinal cohort.

METHODS

A longitudinal cohort study included 3957 subjects who were free of cardiovascular disease with certain risk factors for cardiovascular disease at baseline. Incident hyperuricemia was ascertained if serum uric acid level was ≥ 420 μmol/L for men and ≥ 360 μmol/L for women during the follow-up visit in 2013. The relationships between 17 single plasma metals/metalloids and incident hyperuricemia were assessed using unconditional logistic regression models. For metals/metalloids significantly related to incident hyperuricemia, we further utilized generalized linear regression models to evaluate their associations with the average annual change in uric acid levels. Finally, we applied the weighted quantile sum (WQS) regression to investigate the joint effects of metals/metalloids on hyperuricemia risk and uric acid changes, and to identify the most significant metals.

RESULTS

After adjusting for potential confounders, plasma aluminum, arsenic, barium, lead, strontium, vanadium, and zinc concentrations were positively associated with incident hyperuricemia in both main analyses and sensitivity analyzes. Compared to the lowest quartiles, participants in the highest quartiles had 63 %-125 % higher risks of incident hyperuricemia (all FDR < 0.05). Furthermore, the positive associations of these seven metals with an average annual uric acid increase reinforced the findings. Finally, the WQS analyses showed that plasma metals mixtures were positively associated with the risk of incident hyperuricemia (OR: 1.47; 95 % CI: 1.23, 1.76) and the average annual change in uric acid levels (β: 3.17; 95 % CI: 2.42, 3.93), and strontium and vanadium were the most heavily weighted metals, respectively.

CONCLUSION

Our findings identify aluminum, arsenic, barium, lead, strontium, vanadium, and zinc exposures as independent risk factors for hyperuricemia and provide new insights into the prevention of hyperuricemia.

Protective effects of peanut skin extract on high-fat and high-fructose diet-induced kidney injury in rats

Chronic kidney disease (CKD) is becoming a major public health problem worldwide. This study aimed to explore whether peanut skin extract (PSE) has protective effects against high-fat and high-fructose (HF) diet-induced kidney injury. Rats were fed HF diet in the whole experiment, while rats in PSE-treated groups were supplemented with PSE. Finally, PSE reduced kidney tissue weight, perinephric fat weight, and levels of serum ammonia, creatinine, and urea nitrogen, along with decreases of renal IL-1β and TNF-α level. Histological examination indicated that PSE alleviated renal tubular dilatation, and degeneration and partial exfoliation of renal tubular epithelial cells. In addition, PSE decreased serum and urinary uric acid level, together with reductions of XOD production and XOD activity both in serum and liver, and down-regulated expressions of renal NLRP3 and ERS proteins. Thus, PSE may be a potential functional food for protecting against renal injury in high energy intake.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Non-alcoholic fatty liver disease (NAFLD) or metabolic (dysfunction)-associated fatty liver disease is the leading cause of chronic liver diseases defined as a disease spectrum comprising hepatic steatosis, non-alcoholic steatohepatitis (NASH), liver fibrosis, cirrhosis, and hepatic carcinoma. NASH, characterized by hepatocyte injury, steatosis, inflammation, and fibrosis, is associated with NAFLD prognosis. Ductular reaction (DR) is a common compensatory reaction associated with liver injury, which involves the hepatic progenitor cells (HPCs), hepatic stellate cells, myofibroblasts, inflammatory cells (such as macrophages), and their secreted substances. Recently, several studies have shown that the extent of DR parallels the stage of NASH and fibrosis. This review summarizes previous research on the correlation between DR and NASH, the potential interplay mechanism driving HPC differentiation, and NASH progression.

Association of serum uric acid with hepatic steatosis detected by controlled attenuation parameter in the United States population

BACKGROUND

The relationship between serum uric acid (SUA) and nonalcoholic fatty liver disease (NAFLD) has been previously reported. Controlled attenuation parameter (CAP) has better diagnostic performance than ultrasonography for assessing hepatic steatosis. The association of SUA with hepatic steatosis detected by CAP is worth further study.

METHODS

The US population aged 20 years or older from the National Health and Nutrition Examination Survey (NHANES) was assessed. Hepatic steatosis was evaluated by the controlled attenuation parameter (CAP). NAFLD status was defined as CAP values of 268 dB/m without hepatitis B or C virus infection or considerable alcohol consumption. Multiple imputations were performed to fill in the missing covariate values. Linear regression, logistic regression, and smooth curve fitting were used to examine the association.

RESULTS

In total, 3919 individuals participated in this study. There was a positive association between SUA (µmol/L) and CAP (β = 0.14, 95% CI: 0.12-0.17, P < 0.01). After stratification by sex, a significant relationship between SUA and CAP existed in both males (β = 0.12, 95% CI: 0.09-0.16, P < 0.01) and females (β = 0.17, 95% CI: 0.14-0.20, P < 0.01) after multiple imputation. The inflection points of the threshold effect of SUA on CAP were 487.7 µmol/L in males and 386.6 µmol/L in females. There was a positive association between SUA (mg/dL) and NAFLD (OR = 1.30, 95% CI: 1.23-1.37, P < 0.01). After stratification by race, positive relationships were also observed. Meanwhile, a positive relationship existed between hyperuricemia and NAFLD (OR = 1.94, 95% CI: 1.64-2.30, P < 0.01). The positive relationship was more significant in females than in males (P for interaction < 0.01).

CONCLUSIONS

There was a positive association between SUA and CAP, as well as between SUA and NAFLD. Subgroup studies stratified by sex and ethnicity demonstrated that the effects were consistent.

Association Between Serum Uric Acid and Non-Alcoholic Fatty Liver Disease: An Updated Systematic Review and Meta-Analysis

Objective

Recent epidemiological evidence shows that there is an association between serum uric acid (SUA) levels and nonalcoholic fatty liver disease (NAFLD). The purpose of this meta-analysis is to summarize all available evidence and assess the associations between SUA levels and NAFLD.

Methods

Using two databases, Web of Science and PubMed, observational studies were applied from the establishment of the databases to June 2022. We used a random effect model to construct the pooled odds ratio (OR) and 95% confidence interval (CI) to appraise the association between SUA levels and NAFLD. The Begg's test was conducted to appraise publication bias.

Results

A total of 50 studies were included, involving 2,079,710 participants (719,013 NAFLD patients). The prevalence and incidence rates (95% CIs) of NAFLD in the patients with hyperuricemia were 65% (57-73%) and 31% (20-41%), respectively. Compared to participants with lower levels of SUA, the pooled OR (95% CI) of NAFLD in those with higher levels of SUA was 1.88 (95% CI: 1.76-2.00). In the subgroup analyses, we found that SUA levels were positively associated with NAFLD in all subgroups, according to study design, study quality, sample size, sex, comparison, age, or country.

Conclusion

This meta-analysis shows that increased SUA levels are positively associated with NAFLD. The results suggested that reducing SUA levels can be a potential strategy for the prevention of NAFLD.

Registration Number

PROSPERO-CRD42022358431.

Positive correlation between fatty liver index and hyperuricemia in hypertensive Chinese adults: a H-type hypertension registry study

Background

Few studies have examined the relationship between fatty liver index (FLI) and hyperuricemia (HUA). This study explores the relationship between FLI and HUA in hypertensive patients.

Methods

A total of 13,716 hypertensive subjects were included in the current study. FLI, a simple index calculated from triglycerides (TG), waist circumference (WC), body mass index (BMI), and γ -glutamyltransferase (GGT), was used as a useful predictor of nonalcoholic fatty liver disease (NAFLD) distribution. HUA was defined as serum uric acid ≥ 360 μmol/L for females and ≥ 420 μmol/L for males.

Results

The mean value of total FLI was 31.8 ± 25.1. Multiple logistic analyses revealed a significant positive correlation between FLI and HUA (OR, 1.78; 95% CI: 1.69-1.87). A subgroup analysis demonstrated that the correlation between FLI (< 30 vs. ≥ 30) and HUA was significant in both sexes (P for interaction = 0.006). Further analyses stratified by sex indicated a positive correlation between FLI and HUA prevalence among male and female subjects. However, the correlation between FLI and HUA was stronger in female subjects than in males (male: OR, 1.70; 95% CI: 1.58-1.83; female: 1.85; 95% CI: 1.73-1.98).

Conclusion

This study demonstrates a positive correlation between FLI and HUA in hypertensive adults, but stronger in females than males.

Association of the android to gynoid fat ratio with nonalcoholic fatty liver disease: a cross-sectional study

Background

Nonalcoholic fatty liver disease (NAFLD) is becoming a severe global public health problem, and can developed into fibrotic nonalcoholic steatohepatitis (NASH), but its risk factors have not been fully identified. The objective of this study was to investigate the association between the android-to-gynoid fat ratio (A/G ratio) and the prevalence of NAFLD.

Methods

This cross-sectional study is based on the 2003-2006 and 2011-2018 cycles of the National Health and Nutrition Examination Survey and included 10,989 participants. Participants aged 20 and older without viral hepatitis or significant alcohol consumption were included. Dual-energy X-ray absorptiometry was used to assess body composition. NAFLD was diagnosed using the United States fatty liver index (US FLI). Multivariable logistic regression models were used to evaluate the association between the A/G ratio and NAFLD.

Results

The prevalence of NAFLD was 32.15% among the study population. Android percent fat and the A/G ratio were significantly higher in patients with NAFLD than in those without NAFLD [41.68% (0.25) vs. 32.80% (0.27), p < 0.001; 1.14 ± 0.01 vs. 0.94 ± 0.00, p < 0.001, respectively]. Logistic regression analysis showed that android percent fat was positively correlated to NAFLD (OR: 1.15, 95% CI: 1.11-1.18), while gynoid percent fat was negatively correlated to NAFLD (OR: 0.92, 95% CI: 0.90-0.94), and the A/G ratio was significantly associated with the prevalence of NAFLD (OR: 1.59, 95% CI: 1.38-1.82) and fibrotic NASH (OR: 2.01, 95% CI: 1.71-2.38). We also found that females had a notably diminished A/G ratio compared with males (0.91 vs. 1.12, p < 0.001). In addition, the female population proportion was negatively correlated with the A/G ratio, which may partly explain the lower prevalence of NAFLD in females. What is more, the OR value of the A/G ratio in the female subgroup was much higher than that in the male subgroup in all adjusted models.

Conclusion

A/G ratio is significantly associated with NAFLD and fibrotic NASH. Women have a lower A/G ratio than men, which may explain the sex difference in NAFLD prevalence. Furthermore, with a higher A/G ratio, the association between females and NAFLD are greatly elevated.

Innate Immune System in the Pathogenesis of Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a prevalent condition characterized by lipid accumulation in hepatocytes with low alcohol consumption. The development of sterile inflammation, which occurs in response to a range of cellular stressors or injuries, has been identified as a major contributor to the pathogenesis of NAFLD. Recent studies of the pathogenesis of NAFLD reported the newly developed roles of damage-associated molecular patterns (DAMPs). These molecules activate pattern recognition receptors (PRRs), which are placed in the infiltrated neutrophils, dendritic cells, monocytes, or Kupffer cells. DAMPs cause the activation of PRRs, which triggers a number of immunological responses, including the generation of cytokines that promote inflammation and the localization of immune cells to the site of the damage. This review provides a comprehensive overview of the impact of DAMPs and PRRs on the development of NAFLD.

Serum growth differentiation factor-15 and non-esterified fatty acid levels in patients with coronary artery disease and hyperuricemia

BACKGROUND

High serum NEFA and GDF-15 are risk factors for CAD and have been linked to detrimental cardiovascular events. It has been hypothesized that hyperuricemia causes CAD via the oxidative metabolism and inflammation. The current study sought to clarify the relationship between serum GDF-15/NEFA and CAD in individuals with hyperuricemia.

METHODS

Blood samples collected from 350 male patients with hyperuricemia(191 patients without CAD and 159 patients with CAD, serum UA > 420 μmol/L) to measure serum GDF-15 and NEFA concentrations with baseline parameters.

RESULTS

Serum circulating GDF-15 concentrations(pg/dL) [8.48(6.67,12.73)] and NEFA levels(mmol/L) [0.45(0.32,0.60)] were higher in hyperuricemia patients with CAD. Logistic regression analysis revealed that the OR (95% CI) for CAD were 10.476 (4.158, 26.391) and 11.244 (4.740, 26.669) in quartile 4 (highest) respectively. The AUC of the combined serum GDF-15 and NEFA was 0.813 (0.767,0.858) as a predictor of whether CAD occurred in male with hyperuricemia.

CONCLUSIONS

Circulating GDF-15 and NEFA levels correlated positively with CAD in male patients with hyperuricemia and measurements may be a useful clinical adjunct.

Outcomes of gout in patients with cirrhosis: A national inpatient sample-based study

BACKGROUND

Hyperuricemia is a prerequisite for the development of gout. Elevated serum uric acid (UA) levels result from either overproduction or decreased excretion. A positive correlation between serum UA levels, cirrhosis-related complications and the incidence of nonalcoholic fatty liver disease has been established, but it is unknown whether hyperuricemia results in worsening cirrhosis outcomes. We hypothesize that patients with cirrhosis will have poorer gout outcomes.

AIM

To explore the link between cirrhosis and the incidence of gout-related complications.

METHODS

This was a cross-sectional study. The national inpatient sample was used to identify patients hospitalized with gout, stratified based on a history of cirrhosis, from 2001 to 2013 via the International Classification of Diseases, Ninth Revision, Clinical Modification codes. Primary outcomes were mortality, gout complications and joint interventions. The χ² test and independent t-test were performed to assess categorical and continuous data, respectively. Multiple logistic regression was used to control for confounding variables.

RESULTS

Patients without cirrhosis were older (70.37 ± 13.53 years vs 66.21 ± 12.325 years; P < 0.05). Most patients were male (74.63% in the cirrhosis group vs 66.83%; adjusted P < 0.05). Patients with cirrhosis had greater rates of mortality (5.49% vs 2.03%; adjusted P < 0.05), gout flare (2.89% vs 2.77%; adjusted P < 0.05) and tophi (0.97% vs 0.75%; adjusted P = 0.677). Patients without cirrhosis had higher rates of arthrocentesis (2.45% vs 2.21%; adjusted P < 0.05) and joint injections (0.72% vs 0.52%; adjusted P < 0.05).

CONCLUSION

Gout complications were more common in cirrhosis. Those without cirrhosis had higher rates of interventions, possibly due to hesitancy with performing these interventions given the higher complication risk in cirrhosis.

Hyperuricemia as an effect modifier of the association between metabolic phenotypes and nonalcoholic fatty liver disease in Chinese population

BACKGROUND

Different metabolic phenotypes may be related to nonalcoholic fatty liver disease (NAFLD), but such association whether modified by serum uric acid levels is unknown. We examined the association between different metabolic phenotypes and NAFLD and further explore whether hyperuricemia could modify this association.

METHODS

A total of 2959 participants (mean age: 55.02 years) with medical checkups were recruited from Tianjin Medical University General Hospital. Participants were categorized into four groups according to their BMI levels and metabolically healthy status: metabolically healthy normal weight (MHNW), metabolically healthy overweight or obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy overweight or obese (MUO). Blood samples (including serum uric acid) were collected from participants after an overnight fast. NAFLD was diagnosed based on abdominal ultrasonography scanning. Data were analyzed using logistic regression models and the interaction effect model.

RESULTS

The prevalence of NAFLD in MHNW, MHO, MUNW, and MUO groups was 9.9% (7.9-12.0%), 42.8% (39.5-46.1%), 36.5% (31.2-41.9%), and 69.7% (66.8-72.6%), respectively. In multi-adjusted logistic models, the ORs (95% CIs) of NAFLD were 5.32 (4.01-7.04) for participants with MHO, 4.51 (3.17-6.40) for those with MUNW, and 13.68 (10.23-18.30) for those with MUO compared to those with MHNW. In the stratified analysis by uric acid levels, the prevalence of NAFLD was significantly higher in participants with MHO, MUNW, and MUO in the hyperuricemia group than those in the normal uric acid group, and the interaction effect of metabolic phenotypes and uric acid on NAFLD was statistical significant (P < 0.05).

CONCLUSIONS

MHO, MUNW, and MUO were associated with higher prevalence of NAFLD. Serum uric acid levels may modify the association between metabolically phenotypes and NAFLD.

Joint Effect of Multiple Metals on Hyperuricemia and Their Interaction with Obesity: A Community-Based Cross-Sectional Study in China

Metal exposures have been inconsistently related to the risk of hyperuricemia, and limited research has investigated the interaction between obesity and metals in hyperuricemia. To explore their associations and interaction effects, 3300 participants were enrolled from 11 districts within 1 province in China, and the blood concentrations of 13 metals were measured to assess internal exposure. Multivariable logistic regression, restricted cubic spline (RCS), Bayesian kernel machine regression (BKMR), and interaction analysis were applied in the single- and multi-metal models. In single-metal models, five metals (V, Cr, Mn, Co, and Zn) were positively associated with hyperuricemia in males, but V was negatively associated with hyperuricemia in females. Following the multi-metal logistic regression, the multivariate-adjusted odds ratios (95% confidence intervals) of hyperuricemia were 1.7 (1.18, 2.45) for Cr and 1.76 (1.26, 2.46) for Co in males, and 0.68 (0.47, 0.99) for V in females. For V and Co, RCS models revealed wavy and inverted V-shaped negative associations with female hyperuricemia risk. The BKMR models showed a significant joint effect of multiple metals on hyperuricemia when the concentrations of five metals were at or above their 55th percentile compared to their median values, and V, Cr, Mn, and Co were major contributors to the combined effect. A potential interaction between Cr and obesity and Zn and obesity in increasing the risk of hyperuricemia was observed. Our results suggest that higher levels of Cr and Co may increase male hyperuricemia risk, while higher levels of V may decrease female hyperuricemia risk. Therefore, the management of metal exposure in the environment and diet should be improved to prevent hyperuricemia.

Triglyceride-Glucose Index is Significantly Associated with the Risk of Hyperuricemia in Patients with Nonalcoholic Fatty Liver Disease

Purpose

The triglyceride-glucose (TyG) index is a new index of insulin resistance (IR), and its association with hyperuricemia (HUA) is unclear. The aim of this study was to investigate whether TyG is an independent risk factor for hyperuricemia (HUA) in patients with nonalcoholic fatty liver disease (NAFLD).

Patients and Methods

We retrospectively analyzed 461 patients with ultrasound-confirmed NAFLD and calculated the TyG index. Multivariate logistic regression was used to analyze the relationship between the TyG index and HUA in NAFLD patients. The correlation between the TyG index and HUA was further confirmed by a restricted cubic spline. Furthermore, the stability of the association between TyG index and HUA was examined using subgroup analysis. Receiver operating characteristic (ROC) curves were constructed to evaluate the predictive value of the TyG index on HUA. Multivariate linear regression was used to analyze the linear relationship between the TyG index and serum uric acid.

Results

A total of 166 HUA patients and 295 non-HUA patients were included in the study. The results of multivariate logistic regression analysis showed that after controlling the confounding risk factors, TyG was still an independent risk factor for HUA (OR = 2.00, 95% CI: 1.38 -2.91, p < 0.001). Restricted cubic splines showed that HUA risk increased linearly with TyG across the entire TyG range. The ROC curve showed that TyG index was better than triglyceride in predicting HUA in NAFLD patients, with AUC values of 0.62 and 0.59, respectively. Multiple linear regression analysis showed that TyG index was significantly positively correlated with blood uric acid (B = 1.37, 95% CI: 0.67-2.08, p < 0.001).

Conclusion

TyG index is an independent risk factor for HUA in patients with NAFLD. The increase of the TyG index level is closely related to the occurrence and development of HUA in patients with NAFLD.

Serum Uric Acid but Not Ferritin Level Is Associated with Hepatic Fibrosis in Lean Subjects with Metabolic Dysfunction-Associated Fatty Liver Disease: A Community-Based Study

Elevated serum ferritin and uric acid levels are common in patients with fatty liver disease. This study assessed the association between serum ferritin and uric acid levels and liver fibrosis in subjects with lean metabolic dysfunction-associated fatty liver disease (MAFLD). This cross-sectional study used data from a community screening examination for metabolic syndrome from December 2018 to September 2019 at Keelung Chang Gung Memorial Hospital. Subjects with lean MAFLD were defined as those with a body mass index (BMI) < 23 kg/m2 and hepatic steatosis according to the MAFLD criteria. A total of 182 lean subjects were included and were divided into lean MAFLD and lean healthy groups. Serum ferritin and uric acid concentrations were positively correlated with liver fibrosis, regardless of whether FIB-4, APRI, or NFS were used as references. Univariate logistic regression analysis showed that age and uric acid were associated with advanced liver fibrosis. After adjusting for potential confounders, only uric acid level was statistically significant in predicting the advanced liver fibrosis (OR = 6.907 (1.111−42.94), p = 0.038) in the lean MAFLD group. We found that an elevated serum uric acid level is an independent factor associated with advanced liver fibrosis in lean MAFLD subjects by noninvasive fibrosis scores.

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.

Obese female mice do not exhibit overt hyperuricemia despite hepatic steatosis and impaired glucose tolerance

Recent reports have clearly demonstrated a tight correlation between obesity and elevated circulating uric acid levels (hyperuricemia). However, nearly all preclinical work in this area has been completed with male mice, leaving the field with a considerable gap in knowledge regarding female responses to obesity and hyperuricemia. This deficiency in sex as a biological variable extends beyond unknowns regarding uric acid (UA) to several important comorbidities associated with obesity including nonalcoholic fatty liver disease (NAFLD). To attempt to address this issue, herein we describe both phenotypic and metabolic responses to diet-induced obesity (DIO) in female mice. Six-week-old female C57BL/6J mice were fed a high-fat diet (60% calories derived from fat) for 32 weeks. The DIO female mice had significant weight gain over the course of the study, higher fasting blood glucose, impaired glucose tolerance, and elevated plasma insulin levels compared to age-matched on normal chow. While these classic indices of DIO and NAFLD were observed such as increased circulating levels of ALT and AST, there was no difference in circulating UA levels. Obese female mice also demonstrated increased hepatic triglyceride (TG), cholesterol, and cholesteryl ester. In addition, several markers of hepatic inflammation were significantly increased. Also, alterations in the expression of redox-related enzymes were observed in obese mice compared to lean controls including increases in extracellular superoxide dismutase (Sod3), heme oxygenase (Ho)-1, and xanthine dehydrogenase (Xdh). Interestingly, hepatic UA levels were significantly elevated (~2-fold) in obese mice compared to their lean counterparts. These data demonstrate female mice assume a similar metabolic profile to that reported in several male models of obesity in the context of alterations in glucose tolerance, hepatic steatosis, and elevated transaminases (ALT and AST) in the absence of hyperuricemia affirming the need for further study.

Gypenosides counteract hepatic steatosis and intestinal barrier injury in rats with metabolic associated fatty liver disease by modulating the adenosine monophosphate activated protein kinase and Toll-like receptor 4/nuclear factor kappa B pathways

CONTEXT

Non-alcoholic fatty liver disease (NAFLD), the most common chronic liver disease, can develop into metabolic associated fatty liver disease (MAFLD). Gypenosides (GP), the main phytochemical component of Gynostemma pentaphylla (Thunb.) Makino (Cucurbitaceae), have been applied for treatment of metabolic diseases.

OBJECTIVE

We investigate how GP modulate MAFLD-related hepatic steatosis and intestinal barrier injury.

MATERIALS AND METHODS

In cell experiments, Caco-2 cells were treated with GP (150 or 200 μmol/L, 24 h), following lipopolysaccharide (LPS) exposure (10 μg/mL, 24 h) to mimic MAFLD in vitro. In in vivo experiments, control, model and model + GP groups were set. High fructose diet/high fat (HFD/HF)-fed (12 weeks) MAFLD rats received GP treatment (300 mg/kg, 6 weeks), followed by intra-peritoneal glucose tolerance test and histopathological examination of rat liver and intestinal mucosa using haematoxylin-eosin staining.

RESULTS

GP at 200 μM significantly reversed LPS-induced decreases in transepithelial electrical resistance (TER) value (25%), protein expression of occludin (two fold) and ZO-1 (four fold), and the ratio of p-AMPK to AMPK (five fold), while partially repressing LPS-induced leakage of FD4 (50%) and LPS-induced increases in the Toll-like receptor 4 (TLR4) level (50%) and the ratio of p-p65 to p65 (55%). Compared with the model rats, rats with GP treatment presented a reduction in gain of weight and glucose tolerance. In addition, GP alleviated HFD/HF-induced histopathological abnormalities in rat liver and intestinal mucosa.

CONCLUSIONS

GP attenuates hepatic steatosis and intestinal barrier injury in MAFLD rats via the AMPK and TLR4/nuclear factor kappa B (NF-κB) pathways, providing a potential treatment for MAFLD patients.

The visceral and liver fat are significantly associated with the prevalence of hyperuricemia among middle age and elderly people: A cross-sectional study in Chongqing, China

Background

The prevalence of hyperuricemia (HUA) has been increasing in recent years. HUA is a crucial risk factor for gout and an independent risk factor for cardiovascular diseases (CVDs). Identifying potentially modifiable factors of HUA is vital for preventing gout and even CVDs. This study aimed to explore the associations of fat distribution with HUA among middle-aged and elderly people in Chongqing, China.

Materials and methods

A cross-sectional study was conducted between July 2020 and September 2021. People who underwent quantitative computed tomography (QCT) scans were invited to participate in the study. A total of 3,683 individuals whose clinical characteristics and QCT-based fat distribution measurements included visceral fat area (VFA), subcutaneous fat area (SFA), and liver fat content (LFC) were well-recorded were included. HUA was defined as having a serum uric acid level greater than 420.0 μmol/L. Multivariate logistic regression models were used to evaluate the association between these adipose variables and HUA prevalence.

Results

The HUA prevalence was 25.6% (943/3,683), which was 39.6% (817/2,063) in men and 7.8% (126/1,620) in women. In the fully adjusted model (model 4), the comparison of the highest one with the lowest quartiles of adipose variables showed that the multivariable OR (95% confidence intervals) of HUA were 2.08 (1.36-3.16; P for trend = 0.001) for VFA, 0.89 (0.63-1.25; P for trend = 0.651) for SFA, and 1.83 (1.42-2.34; P for trend < 0.0001) for LFC. For VFA, the association was more evident in men than in women.

Conclusion

Higher VFA and LFC were significantly associated with the increased prevalence of HUA in middle-aged and elderly Chinese individuals. VFA and LFC may have a predictive effect on HUA. Controlling visceral and liver fat accumulation may be beneficial for middle-aged and older people. HUA can be prevented with specific effective healthy physical activity and balanced diet guidelines.

Potential role of tea drinking in preventing hyperuricaemia in rats: biochemical and molecular evidence

BACKGROUND

Lifestyle and diet play a significant role in hyperuricaemia. Accumulating evidence indicates that tea consumption is associated with hyperuricaemia and gout. However, diverse compounds in different types of tea make it quite difficult to determine the relevant molecular mechanism. Here, we compared the effects of six types of tea on hyperuricaemia induced by potassium oxonate (PO) and hypoxanthine in rats and investigated the possible underlying mechanisms.

METHODS

Rats were randomly assigned to ten groups: the control, hyperuricaemia model, benzbromarone positive control, traditional Chinese medicine Simiao San positive control, green tea, yellow tea, black tea, white tea, red tea, and cyan tea treatment groups. After 21 days, uric acid (UA), xanthine oxidase (XOD), alanine aminotransferase (ALT),blood urea nitrogen (BUN), and creatinine (CRE) were assessed. Serum levels of interleukin-1β (IL-1β) were measured with an enzyme-linked immunosorbent assay. Haematoxylin-eosin staining and immunohistochemistry were used to assess liver and kidney injury.

RESULTS

The levels of UA, CRE, and BUN in the treatment group were decreased to varying degrees. There was a significant reduction in UA, CRE, and BUN levels for yellow tea compared to the positive control drugs. Yellow tea suppressed XOD activity and alleviated hepatic and kidney injury. Network pharmacology and untargeted metabolomics indicated that ten yellow tea bioactive ingredients and 35 targets were responsible for preventing hyperuricaemia, which was mediated by 94 signalling pathways, including IL-1β and TNF.

CONCLUSION

These findings indicate that green tea cannot reduce the serum uric acid level of hyperuricaemic rats. Yellow tea can significantly improve hyperuricaemia by regulating the inflammatory response, autophagy, and apoptosis. This study provides a potential candidate for the treatment of hyperuricaemia and a basis for selecting therapeutic tea for patients with hyperuricaemia.

The regulation effect of GLUT9/SLC2A9 on intrahepatic uric acid level and metabolic associated fatty liver disease

BACKGROUND

Metabolic associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide. The important role of urid acid (UA) in MAFLD has been widely investigated. Our previous studies unveiled the elevation of serum UA levels independently predicts an increased risk of incident MAFLD. However, the role of intrahepatic UA in MAFLD has not been investigated yet. Glucose transporter 9 (GLUT9) is a key transporter that mediates the uptake of UA in hepatocytes.

METHODS

In this study, we first explored the clinical association between GLUT9 polymorphism and MAFLD. Blood samples of 247 male Chinese (127 were MAFLD patients) were collected and tested for the blood UA levels and genotype of the single nucleotide polymorphism (SNP) of GLUT9 (rs1014290). Next, Glut9 hepatic-specific knockout mice (Glut9^Hep-ko) were generated to investigate the role of hepatic GLUT9 in MAFLD in male mice.

RESULTS

We found that the GA/AA genotypes (rs1014290) were associated with elevated serum UA levels in MAFLD patients. Meanwhile, we found that Glut9^Hep-ko mice displayed lower intrahepatic UA levels, down-regulated lipogenesis genes expressions, and attenuated MAFLD symptoms after 12 weeks of high-fat diet feeding, compared with Glut9^Fl/Fl littermates. However, Glut9^Hep-ko mice and wild-type littermates showed no significant difference on hepatic fatty acid oxidation or inflammation.

CONCLUSIONS

Our results suggested that GLUT9 polymorphism was significantly associated with MAFLD, and hepatic-specific knockout of Glut9 significantly decreased intrahepatic contents and ameliorated diet-induced MAFLD in mice.

Xanthine oxidoreductase activity is correlated with hepatic steatosis

The enzyme xanthine oxidoreductase (XOR) catalyzes the synthesis of uric acid (UA) from hypoxanthine and xanthine, which are products of purine metabolism starting from ribose-5-phosphate. Several studies suggested a relationship between hyperuricemia and hepatic steatosis; however, few previous studies have directly examined the relationship between XOR activity and hepatic steatosis. A total of 223 subjects with one or more cardiovascular risk factors were enrolled. The liver-to-spleen (L/S) ratio on computed tomography and the hepatic steatosis index (HSI) were used to assess hepatic steatosis. We used a newly developed highly sensitive assay based on [¹³C₂, ¹⁵N₂] xanthine and liquid chromatography/triple quadrupole mass spectrometry to measure plasma XOR activity. Subjects with the L/S ratio of < 1.1 and the HSI of < 36 had increased XOR activity and serum UA levels. Independent of insulin resistance and serum UA levels, multivariate logistic regression analysis revealed that plasma XOR activity was associated with the risk of hepatic steatosis as assessed by the L/S ratio and HSI. According to the findings of this study, plasma XOR activity is associated with hepatic steatosis independent of insulin resistance and serum UA levels.

Ellagic acid ameliorates high fructose-induced hyperuricemia and non-alcoholic fatty liver in Wistar rats: Focusing on the role of C1q/tumor necrosis factor-related protein-3 and ATP citrate lyase

AIMS

High-fructose intake (HF) represents an inducible risk factor for non-alcoholic fatty liver disease (NAFLD). Present study aimed to illustrate the effect of HF diet (HFD) on the induction of NAFLD, hyperuricemia and role of ellagic acid as modulator.

MAIN METHODS

Twenty-four adult male albino rats were randomly divided into four groups (6/each). The first group received normal chow diet only while the others received 60 % HFD for 4 weeks and subdivided later into 3 groups. The first and second groups received allopurinol and ellagic acid, respectively while the third group received HFD only for extra 4 weeks.

KEY FINDINGS

Rats fed on HFD for 8 weeks displayed body weight gain, insulin resistance (IR), hyperglycemia, dyslipidemia, hyperuricemia with increased oxidative stress and hepatic lipogenic enzymes such as ATP citrate lyase (ACL), aldolase B, and fatty acid synthase (FAS), sterol regulatory element-binding protein 1 (SERBP-1c). C1q /tumor necrosis factor-related protein -3 (CTRP3), and phosphorylated AMP-activated protein kinase (p-AMPK) however showed significant decreases. Ellagic acid or allopurinol administration significantly decreased serum lipids, uric acid, glucose, insulin levels and hepatic contents of enzymes. Malondialdehyde (MDA), FAS, aldolase B, SERBP-1c, and xanthine oxidase (XO) hepatic contents showed significant decreases along with glutathione (GSH) increase as compared to fructose group where ellagic acid was more remarkable compared to allopurinol.

SIGNIFICANCE

Our findings indicated that ellagic acid had alleviated HFD-induced hyperuricemia, its associated NAFLD pattern as mediated through activation of CTRP3 and inhibition of ACL activities in a pattern more remarkable than allopurinol.

Prevalence and risk factors of hyperuricaemia in non-obese Chinese: a single-centre cross-sectional study

OBJECTIVES

Hyperuricaemia is closely related to metabolic diseases and is receiving increasing attention from all over the world. This study aimed to investigate the prevalence and factors associated with hyperuricaemia in non-obese Chinese population.

DESIGN

Retrospective cross-sectional study.

SETTING

A large general hospital that can provide health check-ups in Hangzhou, China.

PARTICIPANTS

A total of 5731 apparently healthy Chinese adults (2349 men and 3382 women) who took their health check-ups during the year of 2019.

EXCLUSION CRITERIA

(1) those with body mass index ≥24 kg/m2; (2) those with incomplete anthropometric and biochemical data; (3) those with a history of malignancy and (4) those under urate-lowering treatment.

PRIMARY AND SECONDARY OUTCOME MEASURES

The prevalence and factors associated with hyperuricaemia in non-obese Chinese adults.

RESULTS

Of the 5731 non-obese subjects enrolled, 538 (9.4%) were identified as having hyperuricaemia, specifically 16.3% in men and 4.6% in women. The prevalence of hyperuricaemia markedly increased in women aged above 50 years. The prevalence of hyperuricaemia was significantly higher in metabolically unhealthy participants with normal weight than in metabolically healthy participants with normal weight. Participants with hyperuricaemia showed a higher prevalence of metabolic syndrome and fatty liver disease than participants with normouraemia. Age, waist circumference, estimated glomerular filtration rate, blood urea nitrogen, excessive drinking and fatty liver were associated with hyperuricaemia in both genders.

CONCLUSION

The prevalence of hyperuricaemia was 9.4% in non-obese Chinese adults. Non-obese participants with hyperuricaemia also showed multiple metabolic disorders. We suggest that clinicians pay attention to serum uric acid level in non-obese patients.

Association of Metabolomic Change and Treatment Response in Patients with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is the major cause of chronic liver disease, yet cost-effective and non-invasive diagnostic tools to monitor the severity of the disease are lacking. We aimed to investigate the metabolomic changes in NAFLD associated with therapeutic responses. It was conducted in 63 patients with NAFLD who received either ezetimibe plus rosuvastatin or rosuvastatin monotherapy. The treatment response was determined by MRI performed at baseline and week 24. The metabolites were measured at baseline and week 12. In the combination group, a relative decrease in xanthine was associated with a good response to liver fat decrease, while a relative increase in choline was associated with a good response to liver stiffness. In the monotherapy group, the relative decreases in triglyceride (TG) 20:5_36:2, TG 18:1_38:6, acetylcarnitine (C2), fatty acid (FA) 18:2, FA 18:1, and docosahexaenoic acid were associated with a decrease in liver fat, while hexosylceramide (d18:2/16:0) and hippuric acid were associated with a decrease in liver stiffness. Models using the metabolite changes showed an AUC of >0.75 in receiver operating curve analysis for predicting an improvement in liver fat and stiffness. This approach revealed the physiological impact of drugs, suggesting the mechanism underlying the development of this disease.

The contribution of sterile inflammation to the fatty liver disease and the potential therapies

Hepatic inflammation is prevalent in several metabolic liver diseases. Recent scientific advances about the pathogenesis of metabolic liver diseases showed an emerging role of several damage-associated molecular patterns (DAMPs), including DNA, high-mobility group box 1 (HMGB1), ATP and uric acid. For these DAMPs to induce inflammation, they should stimulate pattern recognition receptors (PRRs), which are located in the hepatic immune cells like resident Kupffer cells, infiltrated neutrophils, monocytes or dendritic cells. As a consequence, proinflammatory cytokines like interleukins (ILs)-1β and 18 alongside tumor necrosis factor (TNF)-α are overproduced and released, leading to pronounced hepatic inflammation and cellular death. This review highlights the contribution of these DAMPs and PRRs in the settings of alcoholic and nonalcoholic steatohepatitis. The review also summarizes the therapeutic usefulness of targeting NLR family pyrin domain containing 3 (NLRP3)-inflammasome, Toll-like receptors (TLRs) 4 and 9, IL-1 receptor (IL-1R), caspase 1, uric acid and GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) in these hepatic inflammatory disorders.

The NLRP3 Inflammasome in Non-Alcoholic Fatty Liver Disease and Steatohepatitis: Therapeutic Targets and Treatment

Non-alcoholic fatty liver disease (NAFLD) is among the most prevalent primary liver diseases worldwide and can develop into various conditions, ranging from simple steatosis, through non-alcoholic steatohepatitis (NASH), to fibrosis, and eventually cirrhosis and hepatocellular carcinoma. Nevertheless, there is no effective treatment for NAFLD due to the complicated etiology. Recently, activation of the NLPR3 inflammasome has been demonstrated to be a contributing factor in the development of NAFLD, particularly as a modulator of progression from initial hepatic steatosis to NASH. NLRP3 inflammasome, as a caspase-1 activation platform, is critical for processing key pro-inflammatory cytokines and pyroptosis. Various stimuli involved in NAFLD can activate the NLRP3 inflammasome, depending on the diverse cellular stresses that they cause. NLRP3 inflammasome-related inhibitors and agents for NAFLD treatment have been tested and demonstrated positive effects in experimental models. Meanwhile, some drugs have been applied in clinical studies, supporting this therapeutic approach. In this review, we discuss the activation, biological functions, and treatment targeting the NLRP3 inflammasome in the context of NAFLD progression. Specifically, we focus on the different types of therapeutic agents that can inhibit the NLRP3 inflammasome and summarize their pharmacological effectiveness for NAFLD treatment.

Association between circulating cystatin C and hyperuricemia: a cross-sectional study

INTRODUCTION/OBJECTIVES

Circulating cystatin C has reportedly been related to cardiovascular disease, diabetes, and metabolic syndrome, apart from its traditional role in estimating the glomerular filtration rate. However, whether circulating cystatin C is related to hyperuricemia remains unclear.

METHOD

We included 2406 men and 1273 women who attended their annual health checkups in this study. Anthropometric and biochemical parameters were measured. Hyperuricemia was diagnosed as fasting serum uric acid > 420 µmol/L in men and women.

RESULTS

A total of 695 (18.9%) participants were diagnosed with hyperuricemia. Hyperuricemic patients had significantly higher serum cystatin C levels than healthy controls (0.91 (0.83-1.02) versus 0.82 (0.72-0.92) mg/L, P < 0.001). Serum cystatin C levels were positively related to the prevalence of hyperuricemia, which was 5.18%, 14.76%, 22.66%, and 31.24% in participants with serum cystatin C levels in the first, second, third, and fourth quartiles, respectively (P < 0.001 for trend). In stepwise multivariate logistic regression analysis, participants with serum cystatin C in the fourth quartile had a more than twofold increased risk of hyperuricemia (OR 2.262, 95% CI 1.495-3.422; P < 0.001) compared with those with serum cystatin C in the first quartile. In subgroup analyses, the fourth quartile of cystatin C was related to increased risks of hyperuricemia in both non-obese and obese participants (OR 4.405, 95% CI 1.472-13.184, P = 0.008; OR 1.891, 95% CI 1.228-2.911, P = 0.004, respectively), in non-metabolic syndrome participants (OR 3.043, 95% CI 1.692-5.473; P < 0.001) but not in metabolic syndrome participants (OR 1.689, 95% CI 0.937-3.045; P = 0.081), and in non-non-alcoholic fatty liver disease (non-NAFLD) (OR 2.128, 95% CI 1.424-3.180; P < 0.001, respectively) and young and middle-aged participants (OR 2.235, 95% CI 1.492-3.348, P < 0.001) but not in NAFLD and elderly participants.

CONCLUSIONS

This study revealed a positive association of circulating cystatin C with hyperuricemia. Key Points • Serum cystatin C is associated with an increased risk of hyperuricemia. • Serum cystatin C is a useful biomarker in distinguishing patients at high risk of having hyperuricemia.

No Evidence for a Causal Link between Serum Uric Acid and Nonalcoholic Fatty Liver Disease from the Dongfeng-Tongji Cohort Study

Background and Aims

Elevated serum uric acid (SUA) is associated with an increased risk of nonalcoholic fatty liver disease (NAFLD); however, whether this association is causal is undetermined.

Methods

Each participant from the Dongfeng-Tongji cohort study based on 27,009 retirees was interviewed face-to-face following a clinical examination. Covariance, logistic regression analysis, and instrumental variables were used to assess associations between SUA and (severity of) NAFLD and the causal link.

Results

Among 8,429 subjects free of NAFLD at baseline, 2,007 participants developed NAFLD after 5 years of follow-up. The multivariable-adjusted odds ratio (OR) for NAFLD for individuals in the fourth quartile of SUA level versus those in the first was 1.71 (95% CI: 1.45-2.01, P for trend <0.001) and was more dramatic in women or normal-weight persons. Furthermore, SUA was materially associated with greater mean markers of hepatic necroinflammation and greater probabilities of fibrosis. In genetic analyses, both single nucleotide polymorphisms (rs11722228 to SLC2A9 and rs2231142 to ABCG2) were pronouncedly associated with increased SUA concentrations, ranging from 0.19 to 0.22 mg/dl. No significant associations were observed between SNPs and potential confounders. No association was observed between the SUA-increasing allele and NAFLD, with an OR of 0.98 (95% CI: 0.90-1.08) per genetic score. This was not significantly different (P = 0.25) from what was expected (1.03, 95% CI: 1.03-1.03).

Conclusions

SUA was positively associated with NAFLD incidence especially in female and normal-weight individuals and the suspected progression risk of newly developed NAFLD. However, the Mendelian randomization analyses lend no causal evidence, suggesting high SUA as a marker and not a cause of NAFLD.

Association between liver-type fatty acid-binding protein and hyperuricemia before and after laparoscopic sleeve gastrectomy

BACKGROUND

Liver-type fatty acid-binding protein (FABP1) contributes to metabolic disorders. However, the relationship between FABP1 and hyperuricemia remains unknown. We aimed to evaluate the correlation between serum FABP1 and hyperuricemia in patients with obesity before and after laparoscopic sleeve gastrectomy (LSG).

METHODS

We enrolled 105 patients (47 men and 58 women) with obesity who underwent LSG. They were divided into two groups: normal levels of uric acid (UA) (NUA, n = 44) and high levels of UA (HUA, n = 61) with matching sexes. FABP1 levels and other biochemical parameters were measured at baseline and 3, 6, and 12 months after LSG.

RESULTS

Serum FABP1 levels were significantly higher in the HUA group than in the NUA group (34.76 ± 22.69 ng/mL vs. 25.21 ± 21.68 ng/mL, P=0.024). FABP1 was positively correlated with UA (r=0.390, P=0.002) in the HUA group. The correlation still existed after adjusting for confounding factors. Preoperative FABP1 levels were risk factors for hyperuricemia at baseline. UA and FABP1 levels decreased at 3, 6, and 12 months postoperatively. FABP1 showed a more significant decrease in the HUA group than in the NUA group at 12 months (27.06 ± 10.98 ng/mL vs. 9.54 ± 6.52 ng/mL, P=0.003). Additionally, the change in FABP1 levels positively correlated with changes in UA levels in the HUA group 12 months postoperatively (r=0.512, P=0.011).

CONCLUSIONS

FABP1 was positively associated with UA and may be a risk factor for hyperuricemia in obesity. FABP1 levels were higher but decreased more after LSG in obese patients with hyperuricemia than in those without hyperuricemia.