Hypertaurinemia in bile duct-ligated rats after surgery: the effect of gut endotoxin restriction on organ fluxes and oxidative status

Changes in Protein Metabolism and Early Development of Sarcopenia in Mice With Cholestatic Liver Disease

BACKGROUND

Sarcopenia is a frequent complication of liver cirrhosis. Here, we chose a mouse model of cholestatic liver disease (CLD) to gain mechanistic insights into the development of sarcopenia from the earliest stages of chronic liver injury. Particular attention was paid to protein metabolism, metabolite profiles, and mediators of CLD-induced muscle wasting.

METHODS

Male C57BL/6 J mice underwent bile duct ligation (BDL), sham surgery, or served as untreated controls. The observation phase lasted from the preoperative stage to postoperative day 14. Metabolic cage experiments were performed to determine the nitrogen balance (N-BAL), nitrogen metabolite profiles, and total energy expenditure (TEE) using doubly labelled water. The fractional protein synthesis rate (FPSR) was assessed using 2H5-ring-phenylalanine. Plasma concentrations of inflammatory markers, metabolites, and enzymes associated with liver damage were investigated. Muscle strength and volume were assessed using a grip strength meter and MRI, respectively. Gene expression was analysed by real-time PCR.

RESULTS

BDL caused CLD with necroses and inflammation, increased bilirubin (p < 0.0001) and conjugated bile acids (p < 0.05), and reduced food intake (p < 0.0001) and body weight (p < 0.0001; each vs. sham). Compared to controls, BDL mice showed lower N-BAL (p < 0.05), reduced TEE (p < 0.01), and lower FPSR in the liver (p < 0.05) and quadriceps muscle (p < 0.001). Arginine was the only plasma amino acid that was diminished after BDL compared to controls and sham treatment (p < 0.0001). Reduced muscle strength was observed as early as d3/d4 after BDL (p < 0.001; vs. sham), while muscle volume decreased from d6 to d13 (p < 0.05). In quadriceps muscle, a lower nuclei-to-fibre ratio (p < 0.001) and elevated 1-methyl-histidine (1-MH) (p < 0.001) were detected, whereas 3-MH was increased in the urine of BDL mice (p < 0.001; each vs. sham). The quadriceps muscle of BDL mice contained higher mRNA levels of atrophy-associated genes (Trim63: p < 0.0001, Fbxo32: p < 0.01) and Mstn (p < 0.05), but lower levels of genes involved in mitochondrial function (Cpt-1b: p < 0.05, Pgc-1α: p < 0.01; each vs. sham). In the plasma of BDL mice, elevated protein levels of TNF receptor-1 (p < 0.0001) and HGF-1 (p < 0.05) were observed, while myostatin was diminished (p < 0.05; each vs. sham).

CONCLUSIONS

Sarcopenia occurs early in CLD and is a multicausal process. Relevant pathophysiologies include reduced protein synthesis, degradation of muscle proteins, arginine deficiency, a systemic pro-inflammatory and catabolic state, and muscle toxicity of bile acids. Consequently, the treatment of sarcopenia should focus both on eliminating the cause of the cholestasis and on symptomatic measures such as anti-inflammatory treatment, lowering the bile acid level, and targeted compensation of deficiencies.

The pathogenesis of renal injury in obstructive jaundice: A review of underlying mechanisms, inducible agents and therapeutic strategies

Kidney injury is one of the main complications of obstructive jaundice (OJ) and its pathogenesis has not been clarified. As an independent risk factor for OJ associated with significant morbidity and mortality, it can be mainly divided into two types of morphological injury and functional injury. We called these dysfunctions caused by OJ-induced kidney injury as OJKI. However, the etiology of OJKI is still not fully clear, and research studies on how OJKI becomes a facilitated factor of OJ are limited. This article reviews the underlying pathological mechanism from five aspects, including metabolisms of bile acids, hemodynamic disturbances, oxidative stress, inflammation and the organic transporter system. Some nephrotoxic drugs and measures that can enhance or reduce the renal function with potential intervention in perioperative periods to alleviate the incidence of OJKI were also described. Furthermore, a more in-depth study on the pathogenesis of OJKI from multiple aspects for exploring more targeted treatment measures were further put forward, which may provide new methods for the prevention and treatment of clinical OJKI and improve the prognosis.

Human taurine metabolism: fluxes and fractional extraction rates of the gut, liver, and kidneys

Taurine is involved in numerous biological processes. However, taurine plasma level decreases in response to pathological conditions, suggesting an increased need. Knowledge on human taurine metabolism is scarce and only described by arterial-venous differences across a single organ. Here we present taurine organ fluxes using arterial-venous concentration differences combined with blood flow measurements across the 3 major organ systems involved in human taurine metabolism in patients undergoing hepatic surgery. In these patients, we collected blood from an arterial line, portal vein, hepatic vein, and renal vein, and determined blood flow of the hepatic artery, portal vein, and renal vein using Doppler ultrasound. Plasma taurine was determined by high-performance liquid chromatography, and net organ fluxes and fractional extraction rates were calculated. Seventeen patients were studied. No differences were found between taurine concentrations in arterial, portal venous, hepatic venous, and renal venous plasma. The only significant finding was a release of taurine by the portally drained viscera (P = .04). Our data show a net release of taurine by the gut. This probably is explained by the enterohepatic cycle of taurine. Future studies on human taurine metabolism are required to determine whether taurine is an essential aminosulfonic acid during pathological conditions and whether it should therefore be supplemented.

Effects of taurine on nitric oxide and 3-nitrotyrosine levels in spleen during endotoxemia

Taurine (2-aminoethanesulfonic acid) is a free sulfur-containing β-amino acid which has antioxidant, antiinflammatory and detoxificant properties. In the present study, the role of endotoxemia on peroxynitrite formation via 3-nitrotyrosine (3-NT) detection, and the possible antioxidant effect of taurine in lipopolysaccharide (LPS)-treated guinea pigs were aimed. 40 adult male guinea pigs were divided into four groups; control, endotoxemia, taurine and taurine+endotoxemia. Animals were administered taurine (300 mg/kg), LPS (4 mg/kg) or taurine plus LPS intraperitoneally. After 6 h of incubation, when highest blood levels of taurine and endotoxin were attained, the animals were sacrificed and spleen samples were collected. The amounts of 3-nitrotyrosine and taurine were measured by HPLC, and reactive nitrogen oxide species (NOx) which are stable end products of nitric oxide was measured spectrophotometrically in spleen tissues. LPS administration significantly decreased the concentration of taurine whilst increased levels of 3-NT and NOx compared with control group. It was determined that taurine treatment decreased the levels of 3-nitrotyrosine and NOx in taurine+endotoxemia group. The group in which taurine was administered alone, contradiction to well-known antioxidant effect, taurine caused elevated concentration of 3-NT and NOx. This data suggest that taurine protects spleen against oxidative damage in endotoxemic conditions. However, the effect of taurine is different when it is administered alone. In conclusion, taurine may act as an antioxidant during endotoxemia, and as a prooxidant in healthy subjects at this dose.

Progress in diagnosis and treatment of cholestasis

Cholestasis can be considered a clinically frequent syndrome caused by complicated factors. Although investigation of cholestasis has been carried out at molecular biology level its pathogenesis can be more clearly recognized. However, the diagnosis and management of intrahepatic cholestasis has not improved. How to identify the pathophysiological and pharmacological targets of cholestatic liver disease is a challenging issue facing clinicians, pathophysiologists and pharmacologists.