Determining the role for uric acid in non-alcoholic steatohepatitis development and the utility of urate metabolites in diagnosis: An opinion review

Prevalence and association of hyperuricemia with liver function in Saudi Arabia: a large cross-sectional study

BACKGROUND

Hyperuricemia is linked to an increased risk of various chronic diseases, but data on the prevalence and association of hyperuricemia with liver function in Saudi Arabia are scarce.

OBJECTIVES

Evaluate the prevalence, association, and risk measures of hyperuricemia and liver function in the Saudi population.

DESIGN

Retrospective, cross-sectional analysis.

SETTING

Database on large portion of Saudi population.

PATIENTS AND METHODS

Laboratory data, age, and gender of the studied subjects were collected from Al Borg Diagnostics. Subjects were stratified, based on their uric acid (UA) levels, into three groups: hypouricemic, normouricemic, and hyperuricemic. The association of UA with liver enzymes was examined in all three groups.

MAIN OUTCOME MEASURES

Association of serum UA levels with alanine transaminase (ALT), aspartate transferase (AST), alkaline phosphatase (ALP), and total bilirubin (TB).

SAMPLE SIZE

13 314 subjects.

RESULTS

Our study showed that the prevalence of hyperuricemia in the Saudi population is 17.3% (20.3% in males and 15.1% in females). We also found a positive correlation between ALT, AST, and TB with UA levels. The risk of being hyperuricemic was significantly increased in individuals with elevated ALT, AST, and TB. Individuals with elevated ALT, AST, and total TB had a higher chance of having hyperuricemia than those with normal activity. Notably, ALT, AST, and TB had good discriminating capacity for hyperuricemia.

CONCLUSIONS

Hyperuricemia is highly prevalent in the Saudi population and is associated with compromised liver function. However, further studies are needed to elucidate the mechanisms underlying these findings in large prospective cohort studies in different populations.

LIMITATIONS

Lack of data on other potential confounding variables.

Liver Fat Scores for Noninvasive Diagnosis and Monitoring of Nonalcoholic Fatty Liver Disease in Epidemiological and Clinical Studies

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with the metabolic syndrome and type 2 diabetes and independently contributes to long-term complications. Being often asymptomatic but reversible, it would require population-wide screening, but direct diagnostics are either too invasive (liver biopsy), costly (MRI) or depending on the examiner's expertise (ultrasonography). Hepatosteatosis is usually accommodated by features of the metabolic syndrome (e.g. obesity, disturbances in triglyceride and glucose metabolism), and signs of hepatocellular damage, all of which are reflected by biomarkers, which poorly predict NAFLD as single item, but provide a cheap diagnostic alternative when integrated into composite liver fat indices. Fatty liver index, NAFLD LFS, and hepatic steatosis index are common and accurate indices for NAFLD prediction, but show limited accuracy for liver fat quantification. Other indices are rarely used. Hepatic fibrosis scores are commonly used in clinical practice, but their mandatory reflection of fibrotic reorganization, hepatic injury or systemic sequelae reduces sensitivity for the diagnosis of simple steatosis. Diet-induced liver fat changes are poorly reflected by liver fat indices, depending on the intervention and its specific impact of weight loss on NAFLD. This limited validity in longitudinal settings stimulates research for new equations. Adipokines, hepatokines, markers of cellular integrity, genetic variants but also simple and inexpensive routine parameters might be potential components. Currently, liver fat indices lack precision for NAFLD prediction or monitoring in individual patients, but in large cohorts they may substitute nonexistent imaging data and serve as a compound biomarker of metabolic syndrome and its cardiometabolic sequelae.

Dietary Long-Chain Fatty Acids Accelerate Metabolic Dysfunction in Guinea Pigs with Non-Alcoholic Steatohepatitis

The composition of dietary fatty acids may be important for the development and progression of metabolic syndrome and non-alcoholic steatohepatitis (NASH). This study investigated the effect of two high-fat diets based on coconut oil, containing predominantly medium-chain fatty acids (MCFA), or cocoa butter, containing mainly long-chain fatty acids (LCFA), on glucose homeostasis and NASH in guinea pigs following 16 and 32 weeks of diet. At week 16, glucose intolerance was increased in the LCFA animals compared to the MCFA animals (p < 0.001), with both groups differing from the controls by week 32 (p < 0.0001), supported by increased hemoglobin A1c (p < 0.05). NASH was present in both high-fat groups from week 16, with advancing fibrosis appearing more progressive in the LCFA animals at week 16. In agreement, gene expression showed overall increased expression of NASH target genes in the LCFA animals compared to the MCFA animals at weeks 16 and 32 (p < 0.05 and p < 0.0001, respectively). The LCFA animals also displayed increased plasma uric acid at both time points (p < 0.05), a phenomenon linked to NASH in humans. In conclusion, this study reports that a diet high in LCFA promotes metabolic imbalance and may accelerate NASH-associated hepatic fibrosis. This highlights the importance of a critical evaluation of fatty acid composition when investigating NASH-associated endpoints.

Association of serum uric acid-to-high-density lipoprotein cholesterol ratio with non-alcoholic fatty liver disease in American adults: a population-based analysis

Objective

Non-invasive disease indicators are currently limited and need further research due to the increased non-alcoholic fatty liver disease (NAFLD) prevalence worldwide. The serum uric acid-to-high-density lipoprotein cholesterol ratio (UHR) has been recognized as a novel inflammatory and metabolic marker. Herein, we explored the correlation between UHR and the risk of NAFLD in-depth.

Methods

A total of 3,766 participants were included in our survey, and the National Health and Nutrition Examination Survey (NHANES) 2017-2018 cycle provided the cross-sectional study population. Weighted multivariable logistic regression and multivariate linear regression analyses were performed to assess the association between the UHR and the odds of NAFLD and liver steatosis and fibrosis severity, respectively. Moreover, we explored the non-linear relationship between the UHR and NAFLD by the generalized additive model.

Results

NAFLD probabilities were statistically demonstrated to be positively correlated with the UHR (OR = 1.331 per SD increase, 95% CI: 1.100, 1.611). The positive connection of the UHR with NAFLD risk persisted significantly in female subjects but not in male subjects in subgroup analyses stratified by gender. The non-linear relationship analysis demonstrated that a UHR between ~20 and 30% suggested a saturation effect of NAFLD risk. Furthermore, a dramatically positive correlation was found between the UHR and hepatic steatosis severity but not fibrosis. Finally, the receiver operating characteristic analysis suggested that UHR had a better predictive value for NAFLD than either serum uric acid (sUA) or high-density lipoprotein cholesterol (HDL) alone [UHR (area under curve): 0.6910; 95% CI: 0.6737-0.7083; P < 0.0001].

Conclusion

Our investigation revealed that the elevated UHR level was independently related to an increased NAFLD risk and the severity of liver steatosis in American individuals. The correlation differed according to sex. This non-invasive indicator may enhance the capacity to predict the onset of NAFLD and may uncover alternative therapeutic interventional targets.

Mitochondria, oxidative stress and nonalcoholic fatty liver disease: A complex relationship

According to the 'multiple-hit' hypothesis, several factors can act simultaneously in nonalcoholic fatty liver disease (NAFLD) progression. Increased nitro-oxidative (nitroso-oxidative) stress may be considered one of the main contributors involved in the development and risk of NAFLD progression to nonalcoholic steatohepatitis (NASH) characterized by inflammation and fibrosis. Moreover, it has been repeatedly postulated that mitochondrial abnormalities are closely related to the development and progression of liver steatosis and NAFLD pathogenesis. However, it is difficult to determine with certainty whether mitochondrial dysfunction or oxidative stress are primary events or a simple consequence of NAFLD development. On the one hand, increasing lipid accumulation in hepatocytes could cause a wide range of effects from mild to severe mitochondrial damage with a negative impact on cell fate. This can start the cascade of events, including an increase of cellular reactive nitrogen species (RNS) and reactive oxygen species (ROS) production that promotes disease progression from simple steatosis to more severe NAFLD stages. On the other hand, progressing mitochondrial bioenergetic catastrophe and oxidative stress manifestation could be considered accompanying events in the vast spectrum of abnormalities observed during the transition from NAFL to NASH and cirrhosis. This review updates our current understanding of NAFLD pathogenesis and clarifies whether mitochondrial dysfunction and ROS/RNS are culprits or bystanders of NAFLD progression.

Non-Alcoholic Steatohepatitis (NASH) and Organokines: What Is Now and What Will Be in the Future

Non-alcoholic steatohepatitis (NASH) is characterized by steatosis, lobular inflammation, and enlargement of the diameter of hepatocytes (ballooning hepatocytes), with or without fibrosis. It affects 20% of patients with non-alcoholic fatty liver disease (NAFLD). Due to liver dysfunction and the numerous metabolic changes that commonly accompany the condition (obesity, insulin resistance, type 2 diabetes, and metabolic syndrome), the secretion of organokines is modified, which may contribute to the pathogenesis or progression of the disease. In this sense, this study aimed to perform a review of the role of organokines in NASH. Thus, by combining descriptors such as NASH, organokines, oxidative stress, inflammation, insulin resistance, and dyslipidemia, a search was carried out in the EMBASE, MEDLINE-PubMed, and Cochrane databases of articles published in the last ten years. Insulin resistance, inflammation and mitochondrial dysfunction, fructose, and intestinal microbiota were factors identified as participating in the genesis and progression of NASH. Changes in the pattern of organokines secretion (adipokines, myokines, hepatokines, and osteokines) directly or indirectly contribute to aggravating the condition or compromise homeostasis. Thus, further studies involving skeletal muscle, adipose, bone, and liver tissue as endocrine organs are essential to better understand the modulation of organokines involved in the pathogenesis of NASH to advance in the treatment of this disease.

A Population Based Study of Liver Function amongst Adults with Hyperuricemia and Gout in the United States

To examine the association between uric acid levels and liver enzyme functions amongst adults with hyperuricemia and gout in the United States. The National Health and Nutrition Examination Survey (NHANES) data from 2007 to 2016 was used to study the research objective. Data were analyzed for descriptive statistics and for differences using the t test, Chi-square test and ANOVA. A regression analysis was performed to determine association between demographics and liver enzymes. A p value of <0.05 or <0.001 was considered statistically significant. A total of 14,946 adults (≥20 yrs.) were included in this study. Sample mean age was 49 ± 0.15 yrs., and 54% were female. Overall, 15% adults had elevated uric acid levels (≥6.8 mg/dL), men had significantly higher uric acid levels than women (6 mg/dL vs. 4.8 mg/dL). High uric acid levels were associated with more than two times higher odds of elevated ALT, AST and GGT (p < 0.001). Similarly, gender-based target uric acid values were associated with two-fold increased odds of GGT, over one-and-a-half fold higher odds of ALT and AST (p < 0.001). Regression analysis showed significant association between age, gender, race/ethnicity, body mass index, and hypertension and ALT, AST, ALP, total bilirubin and GGT (p < 0.001). Adults with hyperuricemia and gout are most likely to develop liver dysfunctions and suffer associated morbidities. Such patients need to be appropriately monitored and managed for their liver functions and to prevent associated morbidities.

Purine metabolites and complex diseases: role of genes and nutrients

PURPOSE OF REVIEW

Purines have several important physiological functions as part of nucleic acids and as intracellular and extracellular signaling molecules. Purine metabolites, particularly uric acid, have been implicated in congenital and complex diseases. However, their role in complex diseases is not clear and they have both beneficial and detrimental effects on disease pathogenesis. In addition, the relationship between purines and complex diseases is affected by genetic and nutritional factors. This review presents latest findings about the relationship between purines and complex diseases and the effect of genes and nutrients on this relationship.

RECENT FINDINGS

Evidence from recent studies show strong role of purines in complex diseases. Although they are causal in only few diseases, our knowledge about their role in other diseases is still evolving. Of all the purines, uric acid is the most studied. Uric acid acts as an antioxidant as well as a prooxidant under different conditions, thus, its role in disease also varies. Other purines, adenosine and inosine have been less studied, but they have neuroprotective properties which are valuable in neurodegenerative diseases.

SUMMARY

Purines are molecules with great potential in disease pathogenesis as either metabolic markers or therapeutic targets. More studies need to be conducted to understand their relevance for complex diseases.

Fructose and the Liver

Chronic diseases represent a major challenge in world health. Metabolic syndrome is a constellation of disturbances affecting several organs, and it has been proposed to be a liver-centered condition. Fructose overconsumption may result in insulin resistance, oxidative stress, inflammation, elevated uric acid levels, increased blood pressure, and increased triglyceride concentrations in both the blood and liver. Non-alcoholic fatty liver disease (NAFLD) is a term widely used to describe excessive fatty infiltration in the liver in the absence of alcohol, autoimmune disorders, or viral hepatitis; it is attributed to obesity, high sugar and fat consumption, and sedentarism. If untreated, NAFLD can progress to nonalcoholic steatohepatitis (NASH), characterized by inflammation and mild fibrosis in addition to fat infiltration and, eventually, advanced scar tissue deposition, cirrhosis, and finally liver cancer, which constitutes the culmination of the disease. Notably, fructose is recognized as a major mediator of NAFLD, as a significant correlation between fructose intake and the degree of inflammation and fibrosis has been found in preclinical and clinical studies. Moreover, fructose is a risk factor for liver cancer development. Interestingly, fructose induces a number of proinflammatory, fibrogenic, and oncogenic signaling pathways that explain its deleterious effects in the body, especially in the liver.

Associations between serum trace elements and inflammation in two animal models of nonalcoholic fatty liver disease

Background

The comparison of hepatic steatosis animal models has allowed the understanding of mechanisms involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and the progression to nonalcoholic steatohepatitis (NASH). We investigated the changes in serum levels of trace elements and inflammation markers in fatty livers using two rat models of NAFLD, the methionine and choline deficient (MCD) diet model and Obese-Zucker rats.

Material and methods

NAFLD was induced in male Wistar rats by 3-week MCD diet administration, after which, blood samples were collected. 12-week old Obese (fa/fa) and Lean (fa/-) male Zucker rats were also used. Serum levels of hepatic enzymes, Urea, Uric acid, Ca^2+, Cl, Fe, K, Na, Mg and Zn were quantified, as well as the inflammation markers TNF-alpha, IL-1beta and IL-6.

Results

In MCD rats, a serum increase in Cl, Mg and Na and a decrease in Ca^2+, Zn were detected in comparison with control rats. An increase in only serum Ca²⁺ was found in Obese-Zucker rats. In MCD rat serum, Zn was inversely correlated with IL-1beta, IL-6, TNF-alpha, Urea and Uric Acid; Ca²⁺ was inversely correlated with IL-1beta, IL-6 and Urea; Cl and Mg were directly correlated with Uric Acid and Urea, respectively. In Obese-Zucker rats, Cl and IL-1beta were inversely correlated, whereas Ca²⁺ and Urea where directly correlated, as well Fe and TNF-alpha.

Conclusions

The serum concentrations of trace elements change significantly only in MCD rats, which spontaneously progress to NASH. The causes of these changes may be a result of defense strategies of the organism, which is regulated by immunoregulatory cytokines. These results might suggest that the impairment of trace element status should be taken into account when the effectiveness of a pharmacological treatment is under evaluation.

Repeated double cross-validation applied to the PCA-LDA classification of SERS spectra: a case study with serum samples from hepatocellular carcinoma patients

Intense label-free surface-enhanced Raman scattering (SERS) spectra of serum samples were rapidly obtained on Ag plasmonic paper substrates upon 785 nm excitation. Spectra from the hepatocellular carcinoma (HCC) patients showed consistent differences with respect to those of the control group. In particular, uric acid was found to be relatively more abundant in patients, while hypoxanthine, ergothioneine, and glutathione were found as relatively more abundant in the control group. A repeated double cross-validation (RDCV) strategy was applied to optimize and validate principal component analysis-linear discriminant analysis (PCA-LDA) models. An analysis of the RDCV results indicated that a PCA-LDA model using up to the first four principal components has a good classification performance (average accuracy was 81%). The analysis also allowed confidence intervals to be calculated for the figures of merit, and the principal components used by the LDA to be interpreted in terms of metabolites, confirming that bands of uric acid, hypoxanthine, ergothioneine, and glutathione were indeed used by the PCA-LDA algorithm to classify the spectra.