Higher Blood Uric Acid in Female Humans and Mice as a Protective Factor against Pathophysiological Decline of Lung Function

Elevated uric acid is associated with a low bone mineral density in pre- but not post-menopausal women with rheumatoid arthritis: a pilot study

INTRODUCTION

The role of uric acid (UA) on bone metabolism is controversially discussed. Higher UA levels have been associated with higher T-scores and a reduced incidence of fractures in postmenopausal women. However, in the context of rheumatoid arthritis (RA), the role of UA remains unclear. This pilot study aimed to investigate the association of UA levels with bone mineral density in RA female and male patients.

METHODS

This pilot study analyzed patients with RA to explore preliminary associations. We utilized data from the Rh-GIOP cohort, a prospective monocentric observational study focusing on bone health in chronic rheumatic diseases. To assess the association between UA levels and the lowest T-scores measured at the lumbar spine, hip, or femur, we used linear regression with adjustment for various confounders. An interaction term was included to evaluate differential associations in pre- and postmenopausal women.

RESULTS

Data on dual X-ray absorptiometry (DXA) measurements and serum UA levels were analyzed in a total of 206 patients. Among the 167 women 16 were premenopausal (age 40 ± 8 years) and 149 postmenopausal (age 65 ± 10 years). As expected, postmenopausal had lower T-scores than premenopausal patients (-1.53 ± 1.01 versus - 0.41 ± 1.29, respectively). No association of UA levels with T-scores was found when analyzing the whole cohort (Slope β: -0.04; p = 0.45). However, a significant negative correlation of UA with T-scores in premenopausal (Slope β: -0.98; p = 0.014), but not postmenopausal (Slope β: -0.04; p > 0.05) women was found.

CONCLUSION

Uric acid appears to be negatively associated with bone mineral density in premenopausal but not in postmenopausal women with RA. Thus, the impact of UA on bone health seems to depend on the hormonal status of women. Further investigations are required to validate these results in a larger cohort of patients and to investigate the underlying mechanisms.

T3 Intratracheal Therapy Alleviates Pulmonary Pathology in an Elastase-Induced Emphysema-Dominant COPD Mouse Model

Chronic obstructive pulmonary disease (COPD) is a complex pulmonary condition characterized by bronchitis, emphysema, and mucus stasis. Due to the variability in symptoms among patients, traditional approaches to treating COPD as a singular disease are limited. This led us to focus on phenotype/endotype classifications. In this study, we explore the potential therapeutic role of thyroid hormone (T3) by using mouse models: emphysema-dominant elastase-induced COPD and airway-dominant C57BL/6-βENaC-Tg to represent different types of the disease. Here, we showed that intratracheal T3 treatment (40, 80 μg/kg, i.t., every other day) resulted in significant improvements regarding emphysema and the enhancement of respiratory function in the elastase-induced COPD model. T3-dependent improvement is likely linked to the up-regulation of Ppargc1a, a master regulator of mitochondrial biogenesis, and Gclm, a factor associated with oxidative stress. Conversely, neither short- nor long-term T3 treatments improved COPD pathology in the C57BL/6-βENaC-Tg mice. Because the up-regulation of extrathyroidal T3-producing enzyme Dio2, which is also considered a marker of T3 requirement, was specifically observed in elastase-induced COPD lungs, these results demonstrate that exogenous T3 supplementation may have therapeutic potential for acute but not chronic COPD exacerbation. Moreover, this study highlights the relevance of considering not only COPD phenotypes but also COPD endotypes (expression levels of Ppargc1a and/or Dio2) in the research and development of better treatment approaches for COPD.

Uric acid en route to gout

Gout and hyperuricemia (HU) have generated immense attention due to increased prevalence. Gout is a multifactorial metabolic and inflammatory disease that occurs when increased uric acid (UA) induce HU resulting in monosodium urate (MSU) crystal deposition in joints. However, gout pathogenesis does not always involve these events and HU does not always cause a gout flare. Treatment with UA-lowering therapeutics may not prevent or reduce the incidence of gout flare or gout-associated comorbidities. UA exhibits both pro- and anti-inflammation functions in gout pathogenesis. HU and gout share mechanistic and metabolic connections at a systematic level, as shown by studies on associated comorbidities. Recent studies on the interplay between UA, HU, MSU and gout as well as the development of HU and gout in association with metabolic syndromes, non-alcoholic fatty liver disease (NAFLD), and cardiovascular, renal and cerebrovascular diseases are discussed. This review examines current and potential therapeutic regimens and illuminates the journey from disrupted UA to gout.

Getting sweeter: new evidence for glucose transporters in specific cell types of the airway?

New technologies such as single-cell RNA sequencing (scRNAseq) has enabled identification of the mRNA transcripts expressed by individual cells. This review provides insight from recent scRNAseq studies on the expression of glucose transporters in the epithelial cells of the airway epithelium from trachea to alveolus. The number of studies analyzed was limited, not all reported the full range of glucose transporters and there were differences between cells freshly isolated from the airways and those grown in vitro. Furthermore, glucose transporter mRNA transcripts were expressed at lower levels than other epithelial marker genes. Nevertheless, these studies highlighted that there were differences in cellular expression of glucose transporters. GLUT1 was the most abundant of the broadly expressed transporters that included GLUT8, 10, and 13. GLUT9 transcripts were more common in basal cells and GLUT12 in ionocytes/ciliated cells. In addition to alveolar cells, SGLT1 transcripts were present in secretory cells. GLUT3 mRNA transcripts were expressed in a cell cluster that expressed monocarboxylate (MCT2) transporters. Such distributions likely underlie cell-specific metabolic requirements to support proliferation, ion transport, mucous secretion, environment sensing, and airway glucose homeostasis. These studies have also highlighted the role of glucose transporters in the movement of dehydroascorbic acid/vitamin C/myoinositol/urate, which are factors important to the innate immune properties of the airways. Discrepancies remain between detection of mRNAs, protein, and function of glucose transporters in the lungs. However, collation of the data from further scRNAseq studies may provide a better consensus and understanding, supported by qPCR, immunohistochemistry, and functional experiments.

Personal PM2.5 Elemental Components, Decline of Lung Function, and the Role of DNA Methylation on Inflammation-Related Genes in Older Adults: Results and Implications of the BAPE Study

Epidemiological evidence of the effects of PM_2.5 elements on lung function and DNA methylation is limited. We conducted a longitudinal panel study of 76 healthy older adults aged 60-69 years in Jinan, China, from September 2018 to January 2019. We periodically measured individual 72 h PM_2.5 and element concentrations, lung function, and DNA methylation levels of eight inflammation-related genes. We used linear mixed-effect models to investigate the effects of exposure to personal PM_2.5 elements on the lung function and DNA methylation. Mediation analysis was used to investigate the underlying effect mechanism. Negative changes in the ratio of forced expiratory volume in 1 s to forced vital capacity, ranging from -1.23% [95% confidence interval (CI): -2.11%, -0.35%] to -0.77% (95% CI: -1.49%, -0.04%), were significantly associated with interquartile range (IQR) increases in personal PM_2.5 at different lag periods (7-12, 13-24, 25-48, 0-24, 0-48, and 0-72 h). Arsenic (As), nickel, rubidium (Rb), selenium, and vanadium were significantly associated with at least three lung function parameters, and IQR increases in these elements led to 0.12-5.66% reductions in these parameters. PM_2.5 elements were significantly associated with DNA methylation levels. DNA methylation mediated 7.28-13.02% of the As- and Rb-related reduced lung function. The findings indicate that exposure to elements in personal PM_2.5 contributes to reduced lung function through DNA methylation.

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.

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.

Association Between Serum Uric Acid and Lung Function in People with and without Chronic Obstructive Pulmonary Disease

Background

The effect of serum uric acid (SUA) levels on lung function in chronic obstructive pulmonary disease (COPD) people remained unclear. We aimed to investigate the association between SUA and lung function.

Methods

A cross-sectional study was performed to measure the SUA levels and lung function in 2797 consecutive eligible individuals. Of these, individuals in our study were divided into two groups, the COPD group (n=1387) and the non-COPD group (n=1410). The diagnosis of COPD is defined as post-bronchodilator first second of forced expiratory volume (FEV₁)/forced vital capacity (FVC) ratio of less than 0.70. Multivariable adjustment linear models were applied to estimate the effect of SUA levels on FEV₁% predicted, FVC% predicted, and FEV₁/FVC stratified by COPD status.

Results

After multivariable adjustment, each 1 mg/dL increase of SUA was significantly associated with a decrease in FEV₁% predicted (−1.63%, 95% confidence interval [CI] −2.37 to −0.90), FVC % predicted (−0.89%, 95% CI −1.55 to −0.24), and FEV₁/FVC (−0.70%, 95% CI −1.10 to −0.30). In the COPD group, each 1 mg/dL increase of SUA was significantly associated with decreases in FEV₁% predicted (−1.87%, 95% CI −2.91 to −0.84), FVC% predicted (−1.35%, 95% CI −2.35 to −0.34), and FEV₁/FVC (−0.63%, 95% CI −1.18 to −0.08). However, no significant association between lung function and SUA was found among people without COPD.

Conclusion

High SUA levels were associated with lower lung function, especially in COPD patients. However, no statistically significant effect of SUA on lung function was found in people without COPD.

Research progress on related mechanisms of uric acid activating NLRP3 inflammasome in chronic kidney disease

Hyperuricemia is an independent risk factor for the progression of chronic kidney disease. High levels of uric acid can lead to a series of pathological conditions, such as gout, urinary stones, inflammation, and uric acid nephropathy. There is a close relationship between uric acid and the NLRP3 inflammasome. NLRP3 inflammasome activation can cause cell damage and even death through endoplasmic reticulum stress, lysosome destruction, mitochondrial dysfunction, and the interaction between the Golgi apparatus and extracellular vesicles. In addition, the NLRP3 inflammasome acts as a molecular platform, triggering the activation of caspase-1 and the lysis of IL-1β, IL-18 and Gasdermin D (GSDMD) through different molecular mechanisms. Cleaved NT-GSDMD forms pores in the cell membrane and triggers pyrophosphorylation, thereby inducing cell death and releasing many intracellular proinflammatory molecules. In recent years, studies have found that hyperuricemia or uric acid crystals can activate NLRP3 inflammasomes, and the activation of NLRP3 inflammasomes plays an important role in kidney disease. This article reviews the possible pathophysiological mechanisms by which uric acid activates inflammasomes and induces kidney damage at the cellular and molecular levels.

Serum urate and lung cancer: a cohort study and Mendelian randomization using UK Biobank

BACKGROUND

Serum urate is the most abundant small molecule with antioxidant properties found in blood and the epithelial lining fluid of the respiratory system. Moderately raised serum urate is associated with lower rates of lung cancer and COPD in smokers but whether these relationships reflect antioxidant properties or residual confounding is unknown.

METHODS

We investigated the observational and potentially causal associations of serum urate with lung cancer incidence and FEV1 using one-sample Mendelian randomization (MR) and the UK Biobank resource. Incident lung cancer events were identified from national cancer registries as FEV1 was measured at baseline. Observational and genetically instrumented incidence rate ratios (IRRs) and risk differences per 10,000 person-years (PYs) by smoking status were estimated.

RESULTS

The analysis included 359,192 participants and 1,924 lung cancer events. The associations between measured urate levels and lung cancer were broadly U-shaped but varied by sex at birth with the strongest associations in current smoking men. After adjustment for confounding variables, current smoking men with low serum urate (100 µmol/L) had the highest predicted lung cancer incidence at 125/10,000 PY (95%CI 56-170/10,000 PY) compared with 45/10,000 PY (95%CI 38-47/10,000 PY) for those with the median level (300 µmol/L). Raised measured urate was associated with a lower baseline FEV1. The MR results did not support a causal relationship between serum urate and lung cancer or FEV1.

CONCLUSIONS

We found no evidence that serum urate is a modifiable risk factor for respiratory health or lung cancer.

Why Does Hyperuricemia Not Necessarily Induce Gout?

Hyperuricemia is a risk factor for gout. It has been well observed that a large proportion of individuals with hyperuricemia have never had a gout flare(s), while some patients with gout can have a normuricemia. This raises a puzzle of the real role of serum uric acid (SUA) in the occurrence of gout flares. As the molecule of uric acid has its dual effects in vivo with antioxidant properties as well as being an inflammatory promoter, it has been placed in a delicate position in balancing metabolisms. Gout seems to be a multifactorial metabolic disease and its pathogenesis should not rely solely on hyperuricemia or monosodium urate (MSU) crystals. This critical review aims to unfold the mechanisms of the SUA role participating in gout development. It also discusses some key elements which are prerequisites for the formation of gout in association with the current therapeutic regime. The compilation should be helpful in precisely fighting for a cure of gout clinically and pharmaceutically.

High Serum Uric Acid Was a Risk Factor for Incident Asthma: An Open Cohort Study

Background

Several cross-sectional studies have suggested an association between SUA and asthma. However, few studies have investigated this relationship longitudinally. Although SUA is an independent risk factor for chronic kidney disease and cardiovascular diseases, its contribution to incident asthma remains uncertain.

Objective

To determine whether a high SUA was a risk factor for adult incident asthma.

Methods

By using health care data from the Shandong multicenter health check-up, 76,369 participants, aged 20 to 79 years, were identified who had an SUA determination with a mean follow-up period of 3.73±2.21 years. Multivariate modeling employed Cox proportional hazards models to verify the association between SUA and incident asthma by adjusting age, BMI, smoking habits, drinking habits, and asthma-like diseases.

Results

A total of 51,389 individuals were included in the analysis. Cut-off values of SUA able to discriminate asthma status were identified by means of maximally selected rank statistics in the whole participants (≥376.80umol/L), women (≥314.45umol/L), and men (≥376.80umol/L). Multivariate Cox regression analyses adjusted for covariates (age, body mass index (BMI), smoking habit, drinking habit, and asthma-like disease) identified an independent association between SUA and incident asthma in the whole participants (hazard ratio (HR) 2.92, 95% confidence intervals (CI), 1.76–4.48, P=0.00) and men (HR 3.02, 95% CI 1.70–5.39, P=0.00), but not in women.

Conclusion

The results of the current study confirmed that high SUA was an independent risk factor for incident asthma after adjustment of potential covariates and suggested that a cut-off value related to incident asthma could be identified only in men.