Evaluation of serum arginase I as an oxidative stress biomarker in a healthy Japanese population using a newly established ELISA

Possible contribution of hepatocyte secretion to the elevation of plasma exosomal arginase-1 in high-fat diet-fed mice

AIMS

The elevation of arginase in vascular tissues decreases nitric oxide production, which is considered as an early step of atherosclerosis in obesity. Previously, we found that arginase-1, one of arginase isozymes, was elevated in the blood plasma of obese adults. The purpose of this study is to elucidate the mechanism by which obesity increases arginase-1 levels in the blood.

MAIN METHODS

C57/BL6J male mice fed a high-fat diet (HFD) for 12 weeks were analyzed for factors related to nitric oxide/arginine metabolism and plasma exosomes. To explore the arginase secretory organs, the protein expression levels were analyzed in several organs. To further investigate the relationship between exosomal arginase-1 in plasma, blood glucose levels and arginase-1 in the liver, HepG2 (the human hepatoma cell line) was analyzed after treatment with high glucose.

KEY FINDINGS

The increase in arginase activity in the plasma of HFD-fed mice was positively corelated with blood glucose levels and was accompanied by an increase in exosomal arginase-1 levels. Among the organs that highly express arginase, the liver of HFD-fed mice showed a significant increase in arginase-1. The expression of arginase-1 in exosomes and total lysates of HepG2 cells were increased by high glucose exposure.

SIGNIFICANCE

Increased exosomal arginase-1 in plasma contributes to increased plasma arginase activity in obesity. The liver is a candidate organ for the secretion of exosomal arginase-1 into plasma, and the p38 pathway induced by high glucose levels may be involved.

Plasma Arginase-1 Level Is Associated with the Mental Status of Outpatients with Chronic Liver Disease

While plasma arginase-1 has been suggested as a biomarker of mental status in healthy individuals, it has not been evaluated in patients with chronic liver disease. This cross-sectional study investigated the utility of plasma arginase-1 for screening mental status in patients with chronic liver disease. This study included outpatients with chronic liver disease who underwent regular check-ups at Okayama University Hospital between September 2018 and January 2019. In addition to the standard blood tests, the plasma arginase-1 level was analyzed. The patients’ mental status was assessed using the Japanese version of the General Health Questionnaire-28 (GHQ-28). The associations between mental status and various parameters, including plasma arginase-1, were investigated using logistic regression analysis. Among 114 participating patients, 8 were excluded, comprising 6 with insufficient blood samples for plasma arginase-1 measurement and 2 with incomplete questionnaires. Multivariate binomial logistic regression analysis revealed that plasma arginase-1 was significantly and negatively associated with the GHQ-total score, especially somatic symptoms. Therefore, plasma arginase-1 may be a useful biomarker for assessing the mental status of outpatients with chronic liver disease.

Blood metabolic signatures of hikikomori, pathological social withdrawal

Background

A severe form of pathological social withdrawal, ‘hikikomori,’ has been acknowledged in Japan, spreading worldwide, and becoming a global health issue. The pathophysiology of hikikomori has not been clarified, and its biological traits remain unexplored.

Methods

Drug-free patients with hikikomori (n = 42) and healthy controls (n = 41) were recruited. Psychological assessments for the severity of hikikomori and depression were conducted. Blood biochemical tests and plasma metabolome analysis were performed. Based on the integrated information, machine-learning models were created to discriminate cases of hikikomori from healthy controls, predict hikikomori severity, stratify the cases, and identify metabolic signatures that contribute to each model.

Results

Long-chain acylcarnitine levels were remarkably higher in patients with hikikomori; bilirubin, arginine, ornithine, and serum arginase were significantly different in male patients with hikikomori. The discriminative random forest model was highly performant, exhibiting an area under the ROC curve of 0.854 (confidential interval = 0.648–1.000). To predict hikikomori severity, a partial least squares PLS-regression model was successfully created with high linearity and practical accuracy. In addition, blood serum uric acid and plasma cholesterol esters contributed to the stratification of cases.

Conclusions

These findings reveal the blood metabolic signatures of hikikomori, which are key to elucidating the pathophysiology of hikikomori and also useful as an index for monitoring the treatment course for rehabilitation.

Urinary 8-OHdG as a Biomarker for Oxidative Stress: A Systematic Literature Review and Meta-Analysis

Oxidative stress reflects a disturbance in the balance between the production and accumulation of reactive oxygen species (ROS). ROS are scavenged by the antioxidant system, but when in excess concentration, they can oxidize proteins, lipids, and DNA. DNA damage is usually repaired, and the oxidized products are excreted in urine. 8-hydroxy-2-deoxyguanosine is considered a biomarker for oxidative damage of DNA. It is needed to define background ranges for 8-OHdG, to use it as a measure of oxidative stress overproduction. We established a standardized protocol for a systematic review and meta-analysis to assess background ranges for urinary 8-OHdG concentrations in healthy populations. We computed geometric mean (GM) and geometric standard deviations (GSD) as the basis for the meta-analysis. We retrieved an initial 1246 articles, included 84 articles, and identified 128 study subgroups. We stratified the subgroups by body mass index, gender, and smoking status reported. The pooled GM value for urinary 8-OHdG concentrations in healthy adults with a mean body mass index (BMI) ≤ 25 measured using chemical methods was 3.9 ng/mg creatinine (interquartile range (IQR): 3 to 5.5 ng/mg creatinine). A significant positive association was observed between smoking and urinary 8-OHdG concentrations when measured by chemical analysis. No gender effect was observed.

Association of arginase I or nitric oxide-related factors with job strain in healthy workers

This study evaluated the associations between job strain and arginase I in 378 healthy Japanese factory workers by a cross-sectional study measuring nitric oxide (NO)-related parameters (arginase I, L-arginine, exhaled nitric oxide (FeNO), and NOx), clinical parameters, and job strain using a Japanese version of the Job Content Questionnaire by Karasek. Arginase I and FEV1% were negatively correlated with job strain and positively correlated with job control and social support. FeNO and hs-CRP were negatively correlated with job strain. Multiple regression analysis showed negative association of arginase I with job strain and positive association with job control and social support in females. It is concluded that serum levels of arginase I may be useful biomarkers for the diagnosis of job stress in healthy female workers, although many factors can be influencing the data.

Effects of exercise training on nitric oxide, blood pressure and antioxidant enzymes

The relationship between exercise training and nitric oxide-related parameters was examined in a cross-sectional study and an intervention study. A cross-sectional study using 184 employees was conducted to observe the association of exercise habits with serum arginase (ELISA and activity), l-arginine, l-citrulline, l-ornithine, NOx, exhaled nitric oxide, blood pressure, FEV1%, hs-CRP, HDL-cholesterol, IgE, and life style factors. An intervention study was also conducted to evaluate the changes of serum arginase I, nitric oxide-related parameters, and mRNA levels of anti-oxidant enzymes in blood monocytes before and after 1 h of aerobic exercise training per day for a month. Exercise habits were associated with increased arginase activity and a moderate alcohol drinking habit, after adjustment with several covariates. Aerobic exercise training induced a decrease in l-arginine and diastolic blood pressure and induced an increase in NO2⁻ and urea. Moreover, mRNA expression of anti-oxidant enzymes, such as catalase and GPX1, and a life elongation enzyme, SIRT3, were significantly increased after aerobic exercise. The results that aerobic exercise training increased NO generation, reduced blood pressure, and induced anti-oxidant enzymes via SIRT3 suggest that exercise training may be an important factor for the prevention of disease by inducing intrinsic NO and anti-oxidant enzymes.

Aging with higher fractional exhaled nitric oxide levels are associated with increased urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine concentrations in elder females

Indoor air pollutants from environmental tobacco smoke and cooking fume can induce oxidative stress and inflammatory response, which generate oxidatively damaged DNA in human body. Among 2224 adults, levels of FENO and urinary 8-oxodG were measured using a nano coulomb nitric oxide analyzer and a high performance liquid chromatography system with electrochemical detector, respectively. Association between aging with higher FENO levels and urinary 8-oxodG levels were analyzed using multiple linear regression analysis. Nonsmoking women aged 64 years and over, with higher FENO (≥ 25 part per billion) and self-catering but without passive smoking had a higher risk of increased urinary 8-oxodG (△% of urinary 8-oxodG: 81.3 %, 95 % CI: 27.4-158.0 %) levels, particularly these elderly women with using liquefied petroleum gas for cooking, had a higher risk for increased urinary 8-oxodG levels (△% of urinary 8-oxodG: 100.2 %, 95 % CI: 95 % CI: 35.3-196.3 %), compared with those aged less than 64 years, with lower FENO (< 25 part per billion). Cooking activity aggravated aging-related the aging-induced in urinary 8-oxodG excretion among nonsmoking women aged 64 years and over but without passive smoking.

l-Arginine administration attenuates airway inflammation by altering l-arginine metabolism in an NC/Nga mouse model of asthma

Changes in l-arginine metabolism, including increased arginase levels and decreased nitric oxide production, are involved in the pathophysiology of asthma. In this study, using an intranasal mite-induced NC/Nga mouse model of asthma, we examined whether administration of l-arginine ameliorated airway hyperresponsiveness and inflammation by altering l-arginine metabolism. Experimental asthma was induced in NC/Nga mice via intranasal administration of mite crude extract (50 µg/day) on 5 consecutive days (days 0-4, sensitization) and on day 11 (challenge). Oral administration of l-arginine (250 mg/kg) was performed twice daily on days 5-10 for prevention or on days 11-13 for therapy. On day 14, we evaluated the inflammatory airway response (airway hyperresponsiveness, the number of cells in the bronchoalveolar lavage fluid, and the changes in pathological inflammation of the lung), arginase expression and activity, l-arginine bioavailability, and the concentration of NOx, the end products of nitric oxide. Treatment with l-arginine ameliorated the mite-induced inflammatory airway response. Furthermore, l-arginine administration attenuated the increases in arginase expression and activity and elevated the NOx levels by enhancing l-arginine bioavailability. These findings indicate that l-arginine administration may contribute to the improvement of asthmatic symptoms by altering l-arginine metabolism.