Effect of taurine on endotoxin-induced alterations in plasma asymmetric dimethylarginine, l-arginine and nitric oxide in guinea pigs

Impact of transesophageal echocardiography dynamic monitoring of left ventricular preload on postoperative gastrointestinal function in colorectal cancer patients undergoing radical surgery

Background

Patients undergoing intestinal tumour surgery are fasted preoperatively for a series of bowel preparations, which makes it difficult to assess the patients' volume, posing a challenge to intraoperative fluid replacement. Besides, inappropriate fluid therapy can cause organ damage and affect the prognosis of patients, and it increases the burden of patients and has a certain impact on patients and families.

Material and methods

The authors designed a single-centre, prospective, single-blinded, randomized, parallel-controlled trial. Fifty-four patients undergoing elective radical resection of colorectal cancer were selected and divided into two groups according to whether transesophageal echocardiography (TEE) was used or not during the operation, that is the goal-directed fluid therapy (GDFT) group (group T) guided by TEE and the restrictive fluid therapy group (group C). Fluid replacement was guided according to left ventricular end-diastolic volume index (LVEDVI) in group T and according to restrictive fluid replacement regimen in group C.

Results

The first postoperative exhaust time and defecation time in group T [(45±21), (53±24) h] were significantly shorter (P<0.05) than those in group C [(63±26), (77±30) h]. There were no significant differences (P>0.05) in liquid intake time and postoperative nausea and vomiting incidences between the two groups. The total intraoperative fluid volume in group T was significantly higher (P<0.05) than that in group C. There was no significant difference (P>0.05) in urine volume between the two groups. There were no significant differences (P>0.05) in lactate content, mean arterial pressure, and heart rate at various time points between the two groups. The length of hospital stay in group C [(18±4) days] was significantly longer (P<0.05) than that in group T [(15±4) days].

Conclusions

For patients undergoing colorectal cancer surgery, fluid therapy by monitoring LVEDVI resulted in faster recovery of gastrointestinal function and shorter hospital stay.

Modulation of endothelium-derived nitric oxide production and activity by taurine and taurine-conjugated bile acids

Taurine is a semiessential amino acid found at high concentrations in mammalian plasma and cells, where it regulates cellular functions such as ion flux, controls cell volume and serves as a substrate for conjugated bile acids (BAs). Exogenous administration of both taurine and taurine-conjugated BAs have also been implicated in the modulation of cardiovascular functions. This brief review summarizes the role of taurine and taurine-conjugated BAs in vascular relaxation through the modulation of endothelium-derived nitric oxide (NO). The effects of taurine on vascular health are controversial. However, in the presence of cardiometabolic risk factors, it has been proposed that taurine can increase vascular NO levels by increasing eNOS expression, eNOS phosphorylation on Ser1177, NO bioavailability, the level of antioxidative defense, and the l-arginine/NOS inhibitor asymmetric dimethylarginine (ADMA) ratio. The taurine-conjugated BA-mediated activation of Farnesoid X receptor (FXR), G protein-coupled BA receptor (TGR5) and/or muscarinic 3 receptor (M3) was also reported to increase vascular NO production. FXR activation increases eNOS expression and may reduce ADMA formation, while TGR5 increases mobilization of Ca²⁺ and phosphorylation of eNOS and Akt in endothelial cells. Furthermore, taurine and taurine-conjugated BAs might regulate NO synthesis and activity by enhancing H₂S generation. Several studies have demonstrated the beneficial effects of both taurine and taurine-conjugated BAs in reversing the endothelial dysfunction associated with diabetes, atherosclerosis, hypertension, obesity, malnutrition, and smoking. In addition, taurine-conjugated BAs have emerged as a potential treatment for portal hypertension. Despite these favorable findings, there is a need to further explore the mechanisms and signaling pathways underlying the endothelial effects of taurine and taurine-conjugated BAs. Here, we summarize the main findings regarding the effects of taurine and taurine-conjugated BAs on the endothelial dysfunction associated with altered NO metabolism in cardiovascular diseases.

Regulation of glucose and lipid metabolism by the pancreatic and extra-pancreatic actions of taurine

The beneficial actions of L-taurine (Tau) against glucose intolerance, obesity, type 2 diabetes (T2D), and non-alcoholic fat liver disease (NAFLD) have been linked to its antioxidant and anti-inflammatory effects, which ameliorate tissue insulin sensitivity. Importantly, there are several lines of evidence that indicate a direct action of Tau on the endocrine pancreas to regulate the secretion and paracrine actions of insulin, glucagon, and somatostatin. Furthermore, Tau can also ameliorate glucose metabolism through the enhancement of insulin signaling. However, some of the benefits of Tau upon intermediary metabolism may manifest via considerable antagonism of the action of insulin. Therefore, this review discusses the mechanisms of action by which Tau may regulate endocrine pancreatic morphofunction, and glucose and lipid homeostasis.

Time-Dependent Production of Endothelium-Related Biomarkers is Affected Differently in Hemorrhagic and Septic Shocks

Shock is associated with inflammation-induced endothelial dysfunction. The aim of this study was to determine time-dependent alteration of blood biomarkers related to endothelial function in hemorrhagic and septic shocks. Hemorrhagic shock was induced by bleeding the animals. A cecal ligation and incision model was used to induce septicemia. Resuscitation was carried out by infusion of lactated Ringer's solution. Resuscitation extended survival time in both shock groups. Blood pressure increased by resuscitation in the hemorrhagic shock but not in the septic shock. While hemorrhage caused a decrease in plasma levels of nitric oxide (NO) and hydrogen sulfide (H₂S), asymmetric dimethylarginine (ADMA) and total antioxidant capacity (TAC) levels were increased. Only NO and TAC levels at the late phase were reversed by resuscitation. On the other hand, plasma levels of NO, ADMA, and TAC were increased by septicemia and resuscitation did not alter the septicemia-induced increase. These results indicate that blood biomarkers related to endothelial function were differentially affected by hemorrhage and septicemia. The time scale of biomarker production should be taken into consideration for the diagnostic and therapeutic approaches to these life-threatening diseases.

The prominent role of the liver in the elimination of asymmetric dimethylarginine (ADMA) and the consequences of impaired hepatic function

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS), the enzyme which converts the amino acid arginine into nitric oxide (NO). ADMA has been identified as an important risk factor for cardiovascular diseases. Besides the role of ADMA in cardiovascular diseases, it also seems to be an important determinant in the development of critical illness, (multiple) organ failure, and the hepatorenal syndrome. ADMA is eliminated from the body by urinary excretion, but it is mainly metabolized by the dimethylarginine dimethylaminohydrolase (DDAH) enzymes that convert ADMA into citrulline and dimethylamine. DDAH is highly expressed in the liver, which makes the liver a key organ in the regulation of the plasma ADMA concentration. The prominent role of the liver in the elimination of ADMA and the consequences of impaired hepatic function on ADMA levels will be discussed in this article.