Increased Lung Uric Acid Deteriorates Pulmonary Arterial Hypertension

Serum uric acid and pulmonary arterial hypertension: A two-sample Mendelian randomization study

BACKGROUND

Observational studies have suggested a correlation between hyperuricemia and pulmonary arterial hypertension (PAH), yet the causal relationship remains uncertain. We aimed to establish this link using Mendelian Randomization (MR) methods.

OBJECTIVES

Based on publicly accessible data, our study employs MR to determine the causal relationship between uric acid (UA) and PAH.

METHOD

MR analysis was conducted among individuals of European descent. Genetic instruments linked to UA (p-value < 5 × 10-8) were extracted from the Chronic Kidney Disease Genetic Consortium and genome-wide association study databases. PAH risk genetic associations were sourced separately. We employed four MR methods (MR-Egger, weighted median, inverse variance weighted, and weighted mode) with selected instrumental variables to assess the causal association between UA and PAH. MR-PRESSO was used to evaluate pleiotropy and outlier Single Nucleotide Polymorphisms (SNPs), while Cochran's Q test and funnel plot assessed SNP heterogeneity. Leave-one-out analysis examined SNP impacts on causal assessment.

RESULT

Two-sample MR analysis revealed a positive, causal relationship between UA levels and PAH.

CONCLUSION

Our MR analysis provides robust evidence of a causal link between serum UA and PAH, suggesting UA's potential as a biomarker and therapeutic target for PAH.

The Pulmonary Artery Pulsatility Index Provides No Additional Prognostic Information in Pediatric Pulmonary Arterial Hypertension

BACKGROUND/OBJECTIVES

The pulmonary artery pulsatility index (PAPi, calculated as (SPAP - DPAP)/mRAP) has been suggested as a measure of right ventricular-vascular coupling (RVVC) and as a prognostic parameter in cardiovascular conditions, particularly right ventricular failure. This retrospective study investigated the relationship between the PAPi and its components with disease severity parameters, the RVVC, and clinical outcomes in children with pulmonary arterial hypertension (PAH).

METHODS

We analyzed data from 111 children from the Dutch National Registry with PAH. The PAPi (median 6.0 [3.9-8.3]) was calculated from heart catheterization data and the RVVC was determined as the TAPSE/sPAP ratio via echocardiography (0.25 ± 0.12 mm/mmHg). Disease severity was characterized by clinical, hemodynamic, and laboratory data. Cox proportional hazard modeling assessed the PAPi's predictive value for transplant-free survival.

RESULTS

There was no correlation between the RVVC and PAPi (R = -0.208, p = 0.111, n = 60). The PAPi correlated negatively with uric acid (R = -0.387, p < 0.001) but not with other disease severity parameters. Mean right atrial pressure correlated with multiple disease severity indicators. Transplant-free survival rates at 1, 3, and 5 years were 87%, 79%, and 73%, respectively. Neither the PAPi nor its components correlated with transplant-free survival.

CONCLUSIONS

In conclusion, the PAPi does not correlate with the RVVC and this study could not demonstrate any prognostic value of the PAPi regarding disease severity or outcomes in children with PAH, challenging its utility in this population.

Utility of serum uric acid levels in excluding pulmonary hypertension in severe chronic lung disease: insights from a tertiary care center

Hyperuricemia is a known predictor of World Health Organization (WHO) Group 1 pulmonary hypertension (PH) (pulmonary arterial hypertension), but its role in excluding PH secondary to chronic lung diseases (WHO Group 3) remains unclear. We retrospectively analyzed data from 323 patients with severe chronic pulmonary diseases who underwent evaluation for lung transplantation at a tertiary medical center between June 2017 and February 2023. We examined the association between hyperuricemia (serum uric acid > 6 mg/dL or > 0.357 mmol/L) and PH [mean pulmonary arterial pressure (MPAP) > 20 mmHg]. Compared to the normouricemia group (n = 211), hyperuricemic patients (n = 112) were more likely to be younger (P = 0.02), male (P < 0.001), and present with PH (P = 0.001) and severe PH (MPAP > 35 mmHg; P < 0.001). These patients also had a higher body mass index (P = 0.004), plasma N-terminal pro-B-type natriuretic peptide (P < 0.001), serum creatinine (P < 0.001), and C-reactive protein levels (P = 0.03). Significant associations with PH included higher body mass index (P = 0.005), uric acid levels (P < 0.001), total lung capacity (P = 0.02), and residual volume (P = 0.01); shorter 6-min walk test distance (P = 0.005); and lower forced expiratory volume in one second (P = 0.006) and diffusing capacity for carbon monoxide (P < 0.001). Multivariate analysis showed elevated uric acid levels remained significantly associated with PH (OR 1.29, 95% CI 1.05-1.58, P = 0.01). In conclusion, normal serum uric acid levels serve as a significant predictor for excluding pulmonary hypertension in patients with severe chronic lung diseases.

Microbiota-gut-liver-brain axis and hepatic encephalopathy

Hepatic encephalopathy (HE) is a clinical manifestation of neurological and psychiatric abnormalities that are caused by complications of liver dysfunction including hyperammonemia, hyperuricemia, and portal hypertension. Accumulating evidence suggests that HE could be reversed through therapeutic modifications of gut microbiota. Multiple preclinical and clinical studies have indicated that gut microbiome affects the physiological function of the liver, such as the regulation of metabolism, secretion, and immunity, through the gut-liver crosstalk. In addition, gut microbiota also influences the brain through the gut-brain crosstalk, altering its physiological functions including the regulation of the immune, neuroendocrine, and vagal pathways. Thus, key molecules that are involved in the microbiota-gut-liver-brain axis might be able to serve as clinical biomarkers for early diagnosis of HE, and could be effective therapeutic targets for clinical interventions. In this review, we summarize the pathophysiology of HE and further propose approaches modulating the microbiota-gut-liver-brain axis in order to provide a comprehensive understanding of the prevention and potential clinical treatment for HE with a microbiota-targeted therapy.

The potential relationship of coronary artery disease and hyperuricemia: A cardiometabolic risk factor

Coronary arterial disease (CAD) is the leading cause of mortality in the world. Hyperuricemia has recently emerged as a novel independent risk factor of CAD, in addition to the traditional risk factors such as hyperlipidemia, smoking, and obesity. Several clinical studies have shown that hyperuricemia is strongly associated with the risk, progression and poor prognosis of CAD, as well as verifying an association with traditional CAD risk factors. Uric acid or enzymes in the uric acid production pathway are associated with inflammation, oxidative stress, regulation of multiple signaling pathways and the renin-angiotensin-aldosterone system (RAAS), and these pathophysiological alterations are currently the main mechanisms of coronary atherosclerosis formation. The risk of death from CAD can be effectively reduced by the uric acid-lowering therapy, but the interventional treatment of uric acid levels in patients with CAD remains controversial due to the diversity of co-morbidities and the complexity of causative factors. In this review, we analyze the association between hyperuricemia and CAD, elucidate the possible mechanisms by which uric acid induces or exacerbates CAD, and discuss the benefits and drawbacks of uric acid-lowering therapy. This review could provide theoretical references for the prevention and management of hyperuricemia-associated CAD.

Negative Effects of Chronic High Intake of Fructose on Lung Diseases

In the modern diet, excessive fructose intake (>50 g/day) had been driven by the increase, in recent decades, of the consumption of sugar-sweetened beverages. This phenomenon has dramatically increased within the Caribbean and Latin American regions. Epidemiological studies show that chronic high intake of fructose related to sugar-sweetened beverages increases the risk of developing several non-communicable diseases, such as chronic obstructive pulmonary disease and asthma, and may also contribute to the exacerbation of lung diseases, such as COVID-19. Evidence supports several mechanisms—such as dysregulation of the renin−angiotensin system, increased uric acid production, induction of aldose reductase activity, production of advanced glycation end-products, and activation of the mTORC1 pathway—that can be implicated in lung damage. This review addresses how these pathophysiologic and molecular mechanisms may explain the lung damage resulting from high intake of fructose.

Association between serum uric acid and α-klotho protein levels in the middle-aged population

This study investigated the association between hyperuricemia and serum klotho protein levels in a representative sample of adults in the United States. We included 11,734 adults aged 40–80 years with available data of serum klotho, uric acid, covariates related to demographics, health behavior-related variables, and medical histories. Hyperuricemia was defined as a serum uric acid level of ≥7.0 mg/dL in men and ≥6.0 mg/dL in women. The geometric mean of serum klotho was 806.5 pg/mL (95% confidence interval: 801.7–811.4). The log-klotho level was negatively correlated with the uric acid level (r = −0.154; p < 0.0001). After adjustment for potential covariates, each one-unit increase in uric acid was significantly associated with a decrease in the log-klotho level (adjusted beta = −0.028; p < 0.0001). Compared with subjects without hyperuricemia, those with hyperuricemia had significantly lower serum klotho levels (adjusted beta = −0.062; p < 0.0001). We found a significant inverse association between serum uric acid and serum klotho levels in the general population, that is, an increase in serum uric acid levels was associated with a decrease in klotho levels. This finding suggests that loss of klotho may be due to the progression of hyperuricemia or, subsequently, gout.