Serum lactic dehydrogenase as a marker of joint damage in rheumatoid arthritis

Lactate metabolism in rheumatoid arthritis: Pathogenic mechanisms and therapeutic intervention with natural compounds

BACKGROUND

Rheumatoid arthritis (RA) is a common chronic and systemic autoimmune disease characterized by persistent inflammation and hyperplasia of the synovial membrane, the degradation of cartilage, and the erosion of bones in diarthrodial joints. The inflamed joints of patients with RA have been recognized to be a site of hypoxic microenvironment which results in an imbalance of lactate metabolism and the accumulation of lactate. Lactate is no longer considered solely a metabolic waste product of glycolysis, but also a combustion aid in the progression of RA from the early stages of inflammation to the late stages of bone destruction.

PURPOSE

To review the pathogenic mechanisms of lactate metabolism in RA and investigate the potential of natural compounds for treating RA linked to the regulation of imbalance in lactate metabolism.

METHODS

Research advances in our understanding of lactate metabolism in the pathogenesis of RA and novel pharmacological approaches of natural compounds by targeting lactate metabolic signaling were comprehensively reviewed and deeply discussed.

RESULTS

Lactate produced by RA synovial fibroblasts (RASFs) acts on targeted cells such as T cells, macrophages, dendritic cells and osteoclasts, and affects their differentiation, activation and function to accelerate the development of RA. Many natural compounds show therapeutic potential for RA by regulating glycolytic rate-limiting enzymes to limit lactate production, and affecting monocarboxylate transporter and acetyl-CoA carboxylase to inhibit lactate transport and conversion.

CONCLUSION

Regulation of imbalance in lactate metabolism offers novel therapeutic approaches for RA, and natural compounds capable of targeting lactate metabolic signaling constitute potential candidates for development of drugs RA.

Elevated Serum Lactate Dehydrogenase Predicts Unfavorable Outcomes After rt-PA Thrombolysis in Ischemic Stroke Patients

Background and Purpose

Currently, acute ischemic stroke (AIS) is one of the most common and serious diseases in the world and is associated with very high mortality and morbidity even after thrombolysis therapy. This study aims to research the relationship between lactic dehydrogenase (LDH) and prognosis in AIS patients treated with intravenous rtPA.

Method

This study (a Multicenter Clinical Trial of Revascularization Treatment for Acute Ischemic Stroke, TRAIS) included 527 AIS patients in 5 cooperative medical institutions in China from January 2018 to February 2021. The primary outcome was major disability and death within 3 months (mRS score of 3–6), and the secondary outcomes were early neurological improvement (ENI), early neurological deterioration (END), moderate-severe cerebral edema (CE), and symptomatic intracranial hemorrhage (sICH).

Results

The mean age of the 527 patients was 65.6 ± 11.7 years, and the median baseline NIHSS score was 4 (interquartile range, 2–7). The median serum LDH level was 184 U/L (interquartile range, 163–212 U/L). In total, 287 (54.5%) patients acquired ENI, 68 (13.0%) patients suffered END, 53 (12.1%) patients were observed with moderate-severe CE, and 28 (6.2%) patients showed sICH. Within 3 months, 127 (25.15%) patients experienced the primary outcome and 42 (8.3%) patients died. Serum LDH levels before thrombolysis showed an independent association with the risk of primary outcome [adjusted odds ratio, 3.787; (95% CI, 1.525–9.404); P = 0.014]. When log-transformed LDH increased each standard deviation, the risk of primary outcome was raised by 80.1% (95% CI, 28.9–251.7%). A positive linear dependence between the risk of primary outcome and serum LDH levels (P of linearity = 0.0248, P of non-linearity = 0.8284) was shown in multivariable-adjusted spline regression models. Pre-thrombolysis LDH quartile also provided a conventional risk model and significant improvement of the prediction for clinical outcomes, with a net reclassification improvement index (NRI) = 41.86% (P < 0.001) and integrated discrimination improvement (IDI) = 4.68% (P < 0.001).

Conclusions

Elevated serum LDH levels predicted unfavorable clinical outcomes after intravenous thrombolysis in AIS patients.

Serum lactate dehydrogenase activities as systems biomarkers for 48 types of human diseases

Most human diseases are systems diseases, and systems biomarkers are better fitted for diagnostic, prognostic, and treatment monitoring purposes. To search for systems biomarker candidates, lactate dehydrogenase (LDH), a housekeeping protein expressed in all living cells, was investigated. To this end, we analyzed the serum LDH activities from 172,933 patients with 48 clinically defined diseases and 9528 healthy individuals. Based on the median values, we found that 46 out of 48 diseases, leading by acute myocardial infarction, had significantly increased (p < 0.001), whereas gout and cerebral ischemia had significantly decreased (p < 0.001) serum LDH activities compared to the healthy control. Remarkably, hepatic encephalopathy and lung fibrosis had the highest AUCs (0.89, 0.80), sensitivities (0.73, 0.56), and specificities (0.90, 0.91) among 48 human diseases. Statistical analysis revealed that over-downregulation of serum LDH activities was associated with blood-related cancers and diseases. LDH activities were potential systems biomarker candidates (AUCs > 0.8) for hepatic encephalopathy and lung fibrosis.

Abnormal lipid metabolism in a rat model of arthritis: one possible pathway

Collagen-induced arthritis (CIA) animal model is associated with systemic manifestations, including alteration of lipid metabolism. In the present study, one possible pathway of altered lipid metabolism is proposed. Specimens of joint tissue and plasma were collected from the CIA and control rats, and quantitative analysis of lipid components was performed by nuclear magnetic resonance (NMR) spectroscopy technique. Correlation analysis was performed between the level of lipid components and antioxidant enzymes, lactate dehydrogenase (LDH), lipid peroxidation (LP), and cytokines in joint tissue and plasma. Differentiation between the CIA and control rats was established on the basis of the quantity of lipid components in the joint tissue and plasma. Positive correlation was observed for all the enzymes vs. lipid components as well as LP vs. lipid components in plasma and joint tissue. Positive correlation was observed for enzymes in plasma and joint tissue. A negative correlation was observed in between the plasma and joint tissue with the level of lipid components. Cytokine levels were also correlated with the level of lipid components and ratios of saturated fatty acids/unsaturated fatty acids in plasma and joint tissue. Inflammatory disease activity in CIA rats with synovitis brought about a significant change in lipid metabolism. Taken together, the results of our study are delineating a possible pathway of altered lipid metabolism in the CIA rat model, thereby contributing further to an understanding of the pathophysiology of rheumatoid arthritis (RA).

Plasma and peripheral leukocyte beta-N-acetylhexosaminidase isoenzymes and disease activity in rheumatoid arthritis

OBJECTIVES

Recently it has been suggested that serum beta-N-acetylhexosaminidase (Hex) could be a joint destruction marker in rheumatoid arthritis (RA) patients. However, a large amount of serum Hex activity has its source from platelets, and the blood platelet-count is often increased in RA, which may have masked the significance of the results. The purpose of this study was to investigate the relationship between plasma activity of Hex and disease activity or severity.

DESIGN AND METHODS

In 51 patients with RA, with an evolution period for the illness of 10.9 +/- 1.2 yr (range 1-40 yr), we determined the total Hex activity together with its Hex A and B isoenzymes in plasma and in mononuclear (MN) and polymorphonuclear (PMN) leukocytes.

RESULTS

The plasma activity of total Hex and Hex B isoenzyme was slightly higher in the group of patients studied (p < 0.01), together with the specific activity of total Hex, Hex A and B in PMN leukocytes (p < 0.001) than in the control group. No significant correlation was found between plasma or leukocyte Hex and the radiologic evaluation of the disease (Sharp's modified method), or the patient's functional capacity (modified Health Assessment Questionnaire). Likewise, a significant correlation between Hex activity and laboratory inflammation markers (C reactive protein, sialic acid, erythrocyte sedimentation rate) or the evolution time of the disease was not found.

CONCLUSIONS

The plasma activity of total Hex, or even of its isoenzymes Hex A and Hex B, does not appear to be a reliable marker of erosion and cartilage degradation in RA patients. Liver function appears to be the major determinant for the plasma Hex activity in these patients.