Prevention of Hypertension with or without Renin-Angiotensin System Inhibition Precludes Nephrin Loss in the Early Stage of Experimental Diabetes Mellitus

Specific Mechanisms Underlying Right Heart Failure: The Missing Upregulation of Superoxide Dismutase-2 and Its Decisive Role in Antioxidative Defense

AIMS

Research into right ventricular (RV) physiology and identification of pathomechanisms underlying RV failure have been neglected for many years, because function of the RV is often considered less important for overall hemodynamics and maintenance of blood circulation. In view of this, this study focuses on identifying specific adaptive mechanisms of the RV and left ventricle (LV) during a state of chronic nitric oxide (NO) deficiency, one of the main causes of cardiac failure. NO deficiency was induced in rats by L-NAME feeding over a 4 week period. The cardiac remodeling was then characterized separately for the RV/LV using quantitative real-time polymerase chain reaction, histology, and functional measurements.

RESULTS

Only the RV underwent remodeling that corresponded morphologically and functionally with the pattern of dilated cardiomyopathy. Symptoms in the LV were subtle and consisted primarily of moderate hypertrophy. A massive increase in reactive oxygen species (ROS) (+4.5±0.8-fold, vs. control) and a higher degree of oxidized tropomyosin (+46%±4% vs. control) and peroxynitrite (+32%±2% vs. control) could be identified as the cause of both RV fibrosis and contractile dysfunction. The expression of superoxide dismutase-2 was specifically increased in the LV by 51%±3% and prevented the ROS increase and the corresponding structural and functional remodeling.

INNOVATION

This study identified the inability of the RV to increase its antioxidant capacity as an important risk factor for developing RV failure.

CONCLUSION

Unlike the LV, the RV did not display the necessary adaptive mechanisms to cope with increased oxidative stress during a state of chronic NO deficiency.

[Urinary excretion of markers for podocyte injury in patients with diabetes mellitus]

AIM

To estimate the urinary excretion of markers for podocyte injury, to specify their value for the early diagnosis of diabetic nephropathy (DN), and to access the risk of its progression in patients with diabetes mellitus (DM) with varying degrees of albuminuria/proteinuria.

SUBJECT AND METHODS

Seventy-four diabetic patients (30 with type 1 DM and 44 with type 2 DM) were examined and divided into 3 groups according to the urinary concentration in one urinary portion: 1) 41 patients with normal albuminuria (NAU) (<20 mg/l); 2) 13 patients with microalbuminuria (MAU) (20-200 mg/l); 3) 20 patients with proteinuria (PU) (>200 mg/l). A control group included 10 healthy individuals. The urinary levels of the podocyte structural proteins nephrin and podocin were determined by enzyme immunoassay.

RESULTS

Nephrinuria (NU) was detected in 63, 77, and 80% of the patients with NAU, MAU, and PU, respectively. Podocinuria (PDU) was found in 78, 54, and 83% of those with NAU, MAU, and PU, respectively. NU in DN with PU was significantly higher than that in DM with NAU. In the NAU, MAU, and PU subgroups, podocin excretion was equally higher and did not differ between the types of DM. There was a direct correlation of NU with albuminuria, which was stronger in the MAU subgroup. In the patients with DM with varying degrees of albuminuria, the values of NU and PDU correlated directly to serum creatinine levels and inversely with glomerular filtration rate. NU directly correlated with glycated hemoglobin levels in the patients with types 1 and 2 DM of less than 5 years' duration and a direct significant correlation of systolic blood pressure with NU was found in those with type 2 DM.

CONCLUSION

Determination of urinary nephrin and podocin levels may be used for the early preclinical diagnosis of DN and the monitoring of the glomerular apparatus in DM.

The contribution of hypertension to diabetic nephropathy and retinopathy: the role of inflammation and oxidative stress

Diabetes and hypertension frequently coexist and constitute the most notorious combination for the pathogenesis of diabetic nephropathy and retinopathy. Large clinical trials have clearly demonstrated that tight control of glycemia and/or blood pressure significantly reduces the incidence and progression of diabetic retinopathy (DR) and nephropathy. However, the mechanism by which hypertension interacts with diabetes to induce and/or exacerbate nephropathy and retinopathy is very unclear. Substantial evidence implicates the involvement of chronic inflammation and oxidative stress in the pathogenesis of DR and nephropathy. In addition, hypertension causes oxidative stress and inflammation in the kidney and retina. In the present review, we summarized data obtained from our research along with those from other groups to better understand the role of hypertension in the pathogenesis of diabetic nephropathy and retinopathy. It is suggested that oxidative stress and inflammation may be common denominators of kidney and retinal damage in the concomitant presence of diabetes and hypertension.

Angiotensin-(1–7) reduces proteinuria and diminishes structural damage in renal tissue of stroke-prone spontaneously hypertensive rats

Angiotensin (ANG)-(1–7) constitutes an important functional end-product of the renin-angiotensin-aldosterone system that acts to balance the physiological actions of ANG II. In the kidney, ANG-(1–7) exerts beneficial effects by inhibiting growth-promoting pathways and reducing proteinuria. We examined whether a 2-wk treatment with a daily dose of ANG-(1–7) (0.6 mg·kg−1·day−1) exerts renoprotective effects in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP). Body weight, glycemia, triglyceridemia, cholesterolemia, as well as plasma levels of Na+ and K+ were determined both at the beginning and at the end of the treatment. Also, the weekly evolution of arterial blood pressure, proteinuria, and creatinine clearance was evaluated. Renal fibrosis was determined by Masson's trichrome staining. Interleukin (IL)-6, tumor necrosis factor (TNF)-α, and nuclear factor-κB (NF-κB) levels were determined by immunohistochemistry and confirmed by Western blotting analysis. The levels of glomerular nephrin were assessed by immunofluorescence. Chronic administration of ANG-(1–7) normalized arterial pressure, reduced glycemia and triglyceridemia, improved proteinuria, and ameliorated structural alterations in the kidney of SHRSP as shown by a restoration of glomerular nephrin levels as detected by immunofluorescence. These results were accompanied with a decrease in both the immunostaining and abundance of IL-6, TNF-α, and NF-κB. In this context, the current study provides strong evidence for a protective role of ANG-(1–7) in the kidney.