Treatments of Hemodynamic Maladjustment and Oxidative Stress Prevent Renal Disease Progression in Chronically Severe Glomerulonephritides

Decreased microcirculatory function measured by perfusion index is a novel indicator of diabetic kidney disease in patients with type 2 diabetes

AIMS/INTRODUCTION

Diabetic kidney disease has been considered as an important risk factor of cardiovascular disease. Chronic hypoxia is considered to be the main cause of renal injury. Diminished microcirculatory blood flow could be associated with hypoxia in the kidney. Whether diminished microcirculation is associated with diabetic kidney disease has not yet been reported. Here, we investigated the correlation between microcirculatory function and diabetic kidney disease in patients with type 2 diabetes.

MATERIALS AND METHODS

Our cross-sectional study included 574 patients who were admitted to Matsushita Memorial Hospital in Moriguchi, Japan, for type 2 diabetes. Microcirculatory function was assessed using the perfusion index (PI), which represents the level of circulation through peripheral tissues. We measured the PI for all patients.

RESULTS

The median age and PI values were 70 years (range 60-77 years) and 2.8% (range 1.6-4.8%). Multiple regression analyses showed that the PI independently correlated with the logarithm of urinary albumin excretion (P = 0.009) and estimated glomerular filtration rate (P = 0.005), respectively. Multiple logistic regression analyses showed that patients with systolic blood pressure (SBP) greater than the median and PI less than or equal to the median (high-low group) had a significantly increased odds of albuminuria compared with those with SBP less than or equal to the median and PI greater than the median (low-high group), and patients with SBP greater than the median and PI less than or equal to the median (high-low group) had a significantly increased odds of estimated glomerular filtration rate <60 mL/min per 1.73 m2 compared with those with SBP less than or equal to the median and PI greater than the median (low-high group) or SBP greater than the median and PI greater than the median (high-high group).

CONCLUSIONS

PI could be a novel indicator of diabetic kidney disease in patients with type 2 diabetes.

A mildly altered vascular homeostasis in early stage of CKD

BACKGROUND

A continuous increase in number of CKD patients entering ESRD is a growing public health threat, which reflects the present therapeutic failure usually initiating at the late stage of CKD.

OBJECTIVE

To study the mechanism of vascular repair in CKD patients associated with mildly impaired renal function, which included angiogenic factors such as VEFG, angiopoietin-1, and flt-1 (VEGFR1); and antiangiogenic factors such as angiopoietin-2 and KDR (VEGFR2).

RESULTS

A mild defect in angiogenic factor-namely, angiopoietin-1-was observed, whereas VEGF and flt-1 (VEGFR1) were within normal limit. Also, antiangiogenic factor-namely, angiopoietin-2-was mildly elevated, whereas KDR (VEGFR2) remained within normal limit.

CONCLUSION

The mechanism of vascular repair appears to be adequately functional in the early stage of CKD. Therapeutic intervention at this stage can improve renal perfusion and restore renal function as indicated in normoalbuminuric, type 2 diabetic nephropathy. The authors encourage changing the conceptual view of treatment under common treatment at late stage of CKD to treatment at early stage of CKD under an environment favorable for renal regeneration.

Altered Renal Function in Normoalbuminuric Type 2 Diabetes

Altered renal function namely enhanced FE Mg and impaired hemodynamics is observed in normoalbuminuric type 2 diabetes. Since FE Mg correlates directly with tubulointerstitial fibrosis, enhanced FE Mg reflects tubulointerstitial disease even in normoalbuminuric type 2 diabetes. This implies that microalbuminuria is not sensitive to early detect diabetic nephropathy.

Microalbuminuria--a biomarker of renal microvascular disease

Microalbuminuria (amount greater than 30-300 mg/day) reflects an abnormal glomerular capillary permeability to protein. It is usually dependent upon three mechanisms. First, loss of negatively charged surface of the glomerular capillary wall secondary to circulating toxic substances injury-namely, oxidative stress and proinflammatory cytokines-allows the albumin with negatively charged surface to freely escape into the urine. Second, intraglomerular hypertension and hemodynamic maladjustment secondary to glomerular endothelial dysfunction increases filtration pressure and enhances sized selective proteinuria leakage. Third, podocyte injury leads to a vicious cycle of hemodynamic maladjustment and endothelial and podocyte injuries. All three of these mechanisms induce glomerular endothelial injury and microalbuminuria, which reflects renal microvascular disease.

Uric acid excretion and dopamine-induced glomerular filtration response in patients with IgA glomerulonephritis

BACKGROUND/AIM

It is unknown to what extent uric acid (UA) may affect vessel function and participate in tubulointerstitial damage. We examined the relationship between intrarenal vessel function and serum UA and its excretion in association with urinary N-acetyl-beta-D-glucosaminidase (NAG).

METHODS

In 50 IgA patients (mean age 34.7 +/- 9.3 years) and 15 controls (mean age 33.5 +/- 6.9 years) with a creatinine clearance of 99.4 +/- 21.6 and 118.1 +/- 17.2 ml/min, respectively, the renal vascular function was estimated based on the dopamine-induced glomerular filtration response (DIR; see text). The DIR was measured using two 120-min creatinine clearance values (before and after intravenous administration of 2 g/kg/min dopamine). Serum UA, triglycerides and cholesterol and urinary NAG (24 h) and protein and UA excretion were measured.

RESULTS

Patients with IgA nephropathy versus controls: DIR 8.80 +/- 6.6 vs. 12.83% (p < 0.01), NAG 7.25 +/- 3.30 vs. 4.69 +/- 1.12 U/g creatinine (p < 0.01), and fractional UA excretion 7.80 +/- 2.20 versus 6.29 +/- 1.80% (p < 0.01). A negative correlation between DIR and NAG was found; regression analysis showed a more prominent relationship in the patients (NAG = 9.99 - 0.29x DIR) than in the controls (NAG = 5.50 - 0.06x DIR). UA and urate excretion and NAG in the patients correlated with DIR (r = -0.39, p < 0.02; r = -0.29, p < 0.04, and r = 0.59, p < 0.001, respectively). Multivariate analysis showed an association of DIR (R(2) = 0.39) with NAG but not with proteinuria and UA and UA excretion; the NAG excretion (R(2) = 0.56) correlated significantly with UA and DIR.

CONCLUSION

It is suggested that UA plays a role, associated with tubular dysfunction, in the regulation of intrarenal vessel function.

Chronic hypoxia and tubulointerstitial injury: a final common pathway to end-stage renal failure

Recent studies emphasize the role of chronic hypoxia in the tubulointerstitium as a final common pathway to end-stage renal failure. When advanced, tubulointerstitial damage is associated with the loss of peritubular capillaries. Associated interstitial fibrosis impairs oxygen diffusion and supply to tubular and interstitial cells. Hypoxia of tubular cells leads to apoptosis or epithelial-mesenchymal transdifferentiation. This in turn exacerbates fibrosis of the kidney and subsequent chronic hypoxia, setting in train a vicious cycle whose end point is ESRD. A number of mechanisms that induce tubulointerstitial hypoxia at an early stage have been identified. Glomerular injury and vasoconstriction of efferent arterioles as a result of imbalances in vasoactive substances decrease postglomerular peritubular capillary blood flow. Angiotensin II not only constricts efferent arterioles but, via its induction of oxidative stress, also hampers the efficient utilization of oxygen in tubular cells. Relative hypoxia in the kidney also results from increased metabolic demand in tubular cells. Furthermore, renal anemia hinders oxygen delivery. These factors can affect the kidney before the appearance of significant pathologic changes in the vasculature and predispose the kidney to tubulointerstitial injury. Therapeutic approaches that target the chronic hypoxia should prove effective against a broad range of renal diseases. Current modalities include the improvement of anemia with erythropoietin, the preservation of peritubular capillary blood flow by blockade of the renin-angiotensin system, and the use of antioxidants. Recent studies have elucidated the mechanism of hypoxia-induced transcription, namely that prolyl hydroxylase regulates hypoxia-inducible factor. This has given hope for the development of novel therapeutic approaches against this final common pathway.