Endothelin-1, big endothelin-1, and nitric oxide in patients with chronic renal disease and hypertension

Pathological Hyperinsulinemia and Hyperglycemia in the Impaired Glucose Tolerance Stage Mediate Endothelial Dysfunction Through miR-21, PTEN/AKT/eNOS, and MARK/ET-1 Pathways

BACKGROUND

Impaired glucose tolerance (IGT) is an important prediabetic stage characterized by elevated concentrations of glucose and insulin in the blood. The pathological hyperglycemia and hyperinsulinemia in IGT may regulate the expression of microRNA-21 (miR-21) and affect the downstream insulin signaling pathways, leading to endothelial cell dysfunction and early renal damage.

METHODS

The individual and combined effects of insulin and glucose were investigated using human glomerular endothelial cells (HGECs). The expression levels of miR-21, and PTEN/AKT/eNOS and MAPK/ET-1 pathway proteins in the treated cells were measured. The levels of nitric oxide (NO) and endothelin-1 (ET-1) secreted by the cells were also measured. The role of miR-21 in mediating the regulatory effects of insulin and glucose was assessed by overexpression/inhibition of this miRNA using mimics/inhibitor.

RESULTS

High (>16.7 mmol/L) concentration of glucose upregulated the expression of miR-21, leading to the activation and inhibition of the PTEN/AKT/eNOS and MAPK/ET-1 pathways, and upregulation of NO and downregulation of ET-1 secretion, respectively. High (>25 ng/mL) concentration of insulin downregulated the expression of miR-21, and lead to the activation of the MAPK/ET-1 and inhibition of the PTEN/AKT/eNOS pathway, thereby upregulating the expression of ET-1 and downregulating the secretion of NO. MiR-21 was observed to play a key role by directly controlling the activation of the insulin signaling pathways when the cells were cotreated with different concentrations of insulin and glucose. The expression of miR-21 was found to be dependent on the relative concentration of insulin and glucose. Under simulated conditions of the IGT stage (8.3 mmol/L glucose + 50 ng/mL insulin), the inhibitory effect of high insulin concentration on miR-21 expression in the cells attenuated the activation by high glucose concentration, resulting in the downregulation of miR-21, upregulation of ET-1 and downregulation of NO secretion.

CONCLUSION

Taken together, these results indicate that high insulin and glucose concentrations regulate the secretory function of glomerular endothelial cells in opposite ways by regulating the expression of miRNA-21. Pathological concentrations of insulin and glucose in the IGT stage may lead to a decrease in miR-21 expression, thereby disordering the secretion of vasoactive factors, resulting in renal tubule ischemia.

Significance of Nitric Oxyde Saliva Concentration of the Patients with Renal Failure on Hemodialysis

Introduction:

An increase in nitric oxide (NO) synthesis concentration could help alleviate some pathological changes directly related to uremia.

Aim:

To investigate the concentration of nitric oxide in saliva of patients with terminal stage of chronic renal failure on hemodialysis and to investigate the effect of hemodialysis on concentration of nitric oxide in saliva of the patients with terminal stage of chronic renal failure on hemodialysis.

Material and Methods:

The study had a prospective character and included 60 respondents of both sexes, at age between 20 and 60 years. The control group included 30 healthy volunteers of both sexes (15 men and 15 women) of the same age, who were based on subjective and objective health status without any manifestations of pathophysiological changes. The group of patients with terminal stage of chronic renal failure on hemodialysis involved 30 patients of both sexes (15 men and 15 women). Inclusion criteria: hemodialysis duration more than 6 months and age between 20 and 60 years.

Results:

The amount of non-stimulated saliva collected during 15 minutes in patients with chronic renal failure was lower by 31.3% compared to the control group of healthy subjects (p<0.0001). Concentration of NO in saliva in patients with chronic renal failure was higher by 121% than in the control group (p<0.001). Concentration of NO in saliva in patients with chronic renal failure after hemodialysis was 121% lower than in the same subjects prior to hemodialysis (p<0.001). A statistically significant negative correlation (r=-0.381, p<0.05) was found between the hemodialysis duration in months and the level of NO in saliva of the patients with chronic renal failure prior to hemodialysis. There was no statistically significant correlation (r=-0.167, NS) between the hemodialysis duration in months and NO levels in saliva of the patients with chronic renal failure after hemodialysis treatment.

Conclusion:

Concentration of NO in saliva of the patients on hemodialysis was statistically significantly higher in relation to NO concentration in the saliva of healthy subjects and after hemodialysis was statistically significantly lower in relation to NO values prior to hemodialysis. Monitoring of changes in NO concentration dynamics in saliva of hemodialysis patients will probably be helpful in monitoring hemodialysis efficacy.

Dietary L-arginine intake and the incidence of coronary heart disease: Tehran lipid and glucose study

Background

We investigated the association of regular dietary intake of L-arginine and both the incidence of coronary heart disease (CHD) and changes of blood pressure.

Methods

Eligible adults (n = 2284) who participated in the Tehran Lipid and Glucose Study were followed for a mean of 4.7 years. Dietary intake of L-arginine was assessed at baseline (2006–2008); biochemical variables were evaluated at baseline and the follow-up examination. Multivariate Cox proportional hazard regression models adjusted for potential confounders were used to estimate the risk of CHD across tertiles of L-arginine intake. Linear regression models were also used to indicate the association of L-arginine intake with changes of serum lipids and blood pressure during the follow-up.

Results

Mean age of participants (42.8 % men) was 38.2 ± 13.4, at baseline. During a mean 4.7 ± 1.4 y of follow-up, 57 participants experienced CHD events. A significant negative association was observed between plant-derived L-arginine intake and changes of both systolic and diastolic blood pressure, whereas animal-derived L-arginine intake was related to increased levels of diastolic blood pressure (P < 0.01). Participants in the 2^nd tertile (1.45–1.78 g/d) had a significantly increased risk of CHD events compared to the participants in the 1^st tertile (<1.45 g/d) (HR = 1.90, 95 % CI = 1.03–3.58). The risk of CHD had a decreasing trend across increasing plant-derived L-arginine intake (HR = 1.0, HR = 0.91, 95 % CI = 0.51–1.62, HR = 0.72, 95 % CI = 0.39–1.32, P for trend = 0.03).

Conclusion

Higher intake of plant derived L-arginine may have a protective effect whereas animal-derived L-arginine may be a risk factor for development of hypertension and CHD events.

Nitric oxide and the cardiovascular system

Nitric oxide (NO) generated by endothelial cells to relax vascular smooth muscle is one of the most intensely studied molecules in the past 25 years. Much of what is known about NO regulation of NO is based on blockade of its generation and analysis of changes in vascular regulation. This approach has been useful to demonstrate the importance of NO in large scale forms of regulation but provides less information on the nuances of NO regulation. However, there is a growing body of studies on multiple types of in vivo measurement of NO in normal and pathological conditions. This discussion will focus on in vivo studies and how they are reshaping the understanding of NO's role in vascular resistance regulation and the pathologies of hypertension and diabetes mellitus. The role of microelectrode measurements in the measurement of [NO] will be considered because much of the controversy about what NO does and at what concentration depends upon the measurement methodology. For those studies where the technology has been tested and found to be well founded, the concept evolving is that the stresses imposed on the vasculature in the form of flow-mediated stimulation, chemicals within the tissue, and oxygen tension can cause rapid and large changes in the NO concentration to affect vascular regulation. All these functions are compromised in both animal and human forms of hypertension and diabetes mellitus due to altered regulation of endothelial cells and formation of oxidants that both damage endothelial cells and change the regulation of endothelial nitric oxide synthase.

Serum nitrate and nitrite levels in patients with hypertension and ischemic stroke depend on diet: a multicenter study

OBJECTIVES

Nitric oxide, NO, is the key vasorelaxing agent produced by vascular endothelium. Stable end products of NO oxidation, nitrate and nitrite (NOx), are considered as markers of endothelial dysfunction associated with hypertension. Our goal was to compare NOx levels in patients with hypertension on controlled low nitrate diet with NOx levels in general population without dietary restrictions.

PATIENTS AND METHODS

The study included 1005 participants split into 8 groups: healthy subjects (n=28) and patients with moderate (n=37) and malignant hypertension (n=24) on low nitrate diet; healthy subjects (n=9) and patients with stroke (n=44) on low nitrate diet; normotensive subjects (n=354) and patients with elevated blood pressure (n=430) and severe hypertension (n=79) without dietary restrictions.

RESULTS

In groups with controlled low NOx diet, patients with moderate and malignant hypertension had significantly (p<0.01) higher serum NOx versus healthy subject (66.9±18.8μM and 75.3±22.7μM versus 52.8±28.8μM, respectively). Patients with stroke had significantly (p=0.02) higher serum NOx levels versus corresponding group of healthy subjects (106.3±58.4μM versus 71.2±18.1μM, respectively). In the absence of dietary control, differences in serum NOx levels between normotensive subjects and patients with elevated blood pressure and severe hypertension were not significant (p>0.1).

CONCLUSION

Differences in serum NOx concentrations are associated with severity of hypertension only in patients on low nitrate diet. The highest concentrations of NOx were observed in patients with stroke. In the absence of dietary control, NOx levels were not associated with presence or severity of hypertension.