Therapeutic Modalities in Diabetic Nephropathy: Future Approaches

DMP-1 attenuates oxidative stress and inhibits TGF-β activation in rats with diabetic kidney disease

Introduction: DMP-1 supplement has a satisfactory effect on diabetic kidney disease in patients with whether T1DM or T2DM. Oxidative stress and TGF-β signal pathway activation are essential in the pathogenesis of DKD. We aim to investigate the effect of DMP-1 on oxidative stress and TGF-β activation in rats with DKD.

Materials and methods: Male Wistar rats were enrolled and randomly allocated into five groups: Control group, STZ group (60 mg/kg, ip), DMP-1 low dose group (0.5 g/kg/day, ig), DMP-1 medium dose group (1.0 g/kg/day, ig) and DMP-1 high dose group (2.0 g/kg/day, ig). The levels of UREA, BUN, UCr, β₂-MG, mALB, NOS, CAT, MDA and T-AOC were measured after 8 weeks treatment. And rats’ left kidneys were harvested to detect the expression of TGF-β, Smad2/3 and Smad7 by immunohistochemical analysis.

Results: DMP-1 treatment has protective effects on kidney injury induced by STZ, which is demonstrated as following criteria: (1) a significant reduction in levels of UREA (p < 0.05), BUN (p < 0.05), UCr (p < 0.05), β2-MG (p < 0.05) and mALB (p < 0.05) in rats treated by DMP-1 compared with the ones injected with STZ only; (2) an apparent increment levels of NOS (p < 0.05), CAT (p < 0.05) and T-AOC (p < 0.05), while reduction in level of MDA (p < 0.05) in DMP-1 groups compared with STZ group; (3) a significant inhibition of TGF-β and Smad2/3 overexpression induced by STZ in kidney tissue. What’s more, DMP-1 can increase Smad7 expression.

Conclusion: DMP-1 could slow pathological process and protect kidney from DKD injury by decreasing oxidative stress and inhibiting TGF-β signal pathway activation in rats.

Effects of Low-Protein Diets Supplemented with Ketoacid on Expression of TGF-β and Its Receptors in Diabetic Rats

TGF-β₁ has been recognized as a key mediator in DN. This study aimed to observe the effects of low-protein diets supplemented with ketoacid on mRNA and protein expression of TGF-β and TβRI and t TβRII receptors in the renal tissue of diabetic rats. A diabetes model was established in 72 male SD rats. They were then equally randomized to three groups: NPD group, LPD group, and LPD + KA group. Additional 24 male SD rats receiving normal protein diets were used as the control. Eight rats from each group were sacrificed at weeks 4, 8, and 12 after treatment, from which SCr, BUN, serum albumin, and 24 h urinary protein excretion were collected. The expressions of TGF-β₁, TβRI, and TβRII in LPD and LPD + KA groups were significantly lower than those in NPD group and lower in LPD + KA group than those in LPD group. Low-protein diets supplemented with ketoacid have been demonstrated to provide a protective effect on the renal function as represented by reduced SCr, BUN, and urinary protein excretion, probably through downregulating the gene expression of TGF-β₁ and its receptors in LPD + KA group.

Sulodexide therapy for the treatment of diabetic nephropathy, a meta-analysis and literature review

Sulodexide is a heterogeneous group of sulfated glycosaminoglycans (GAGs) that is mainly composed of low-molecular-weight heparin. Clinical studies have demonstrated that sulodexide is capable of reducing urinary albumin excretion rates in patients with type 1 and type 2 diabetes, suggesting that sulodexide has renal protection. However, this efficacy remains inconclusive. In this article, we used meta-analysis to summarize the clinical results of all prospective clinical studies in order to determine the clinical efficacy and safety of sulodexide in diabetic patients with nephropathy. Overall, sulodexide therapy was associated with a significant reduction in urinary protein excretion. In the sulodexide group, 220 (17.7%) achieved at least a 50% decrease in albumin excretion rate compared with only 141 (11.5%) in the placebo. The odds ratio comparing proportions of patients with therapeutic success between the sulodexide and placebo groups was 3.28 (95% confidence interval, 1.34-8.06; P=0.01). These data suggest a renoprotective benefit of sulodexide in patients with diabetes and micro- and macroalbuminuria, which will provide important information for clinical use of this drug as a potential modality for diabetic nephropathy, specifically, the prevention of end-stage renal disease that is often caused by diabetes.

Risks of rapid decline renal function in patients with type 2 diabetes

Progressive rising population of diabetes and related nephropathy, namely, diabetic kidney disease and associated end stage renal disease has become a major global public health issue. Results of observational studies indicate that most diabetic kidney disease progresses over decades; however, certain diabetes patients display a rapid decline in renal function, which may lead to renal failure within months. Although the definition of rapid renal function decline remained speculative, in general, it is defined by the decrease of estimated glomerular filtration rate (eGFR) in absolute rate of loss or percent change. Based on the Kidney Disease: Improving Global Outcomes 2012 clinical practice guidelines, a rapid decline in renal function is defined as a sustained decline in eGFR of > 5 mL/min per 1.73 m(2) per year. It has been reported that potential factors contributing to a rapid decline in renal function include ethnic/genetic and demographic causes, smoking habits, increased glycated hemoglobin levels, obesity, albuminuria, anemia, low serum magnesium levels, high serum phosphate levels, vitamin D deficiency, elevated systolic blood pressure, pulse pressure, brachial-ankle pulse wave velocity values, retinopathy, and cardiac autonomic neuropathy. This article reviews current literatures in this area and provides insight on the early detection of diabetic subjects who are at risk of a rapid decline in renal function in order to develop a more aggressive approach to renal and cardiovascular protection.

Systolic blood pressure as a predictor of incident albuminuria and rapid renal function decline in type 2 diabetic patients

AIMS

Albuminuria and a reduced estimated glomerular filtration rate (eGFR) are known risk factors of poor cardiovascular outcomes in diabetic patients. We here aimed to investigate the determinants of incident albuminuria and rapid progression of renal dysfunction in patients with type 2 diabetes.

METHODS

Type 2 diabetic outpatients (n=215) with a mean baseline eGFR of 87±20 mLmin(-1)1.73 m(-2) were followed for 12 months. Urinary albuminuria was defined according to the urine albumin-to-creatinine ratio (UACR).

RESULTS

Among 132 patients with normoalbuminuria at baseline, 20 (15.2%) progressed to a more advanced stage of albuminuria within 1 year, and 20.5% of the 215 patients experienced a rapid decline in eGFR (eGFR reduction >5 mLmin(-1)1.73 m(-2)year(-1)). After adjusting for potential confounders, both baseline UACR and systolic blood pressure (SBP) were found to be significant independent factors for incident albuminuria and a rapid decline of eGFR in separate models. Using receiver operating characteristic curves, systolic blood pressures of 132 and 138 mmHg were found to predict incident albuminuria and a rapid decline of eGFR, respectively.

CONCLUSIONS

In addition to baseline UACR, SBP is one of the most powerful modifiable independent risk factors for incident albuminuria and a rapid renal function decline in type 2 diabetic patients without symptomatic cardiovascular disease.

Novel therapies for diabetic kidney disease

The number of people diagnosed with diabetes is rising throughout the world, which in turn drives upward the global frequency of diabetic kidney disease (DKD). Individuals with DKD are at an increased risk for premature death, cardiovascular disease, and other severe illnesses that result in frequent hospitalizations and increased health-care utilization. Current treatments concentrate on controlling hyperglycemia and hypertension with the specific use of renin-angiotensin system inhibitors. Although such measures reduce the risk of progressive kidney disease, DKD remains the leading cause of ESRD and the major risk amplifier for death in this population. Therefore, novel therapeutic approaches are urgently needed. Ideas for novel targets for therapy are founded on recent advances in understanding DKD mechanisms that are based on experimental models and human observations. The purpose of this review is to describe the epidemiology and present knowledge of DKD pathophysiology as the basis for novel therapies including inhibitors of Janus kinases (JAK), protein kinase C, fibrosis, advanced glycation end products treatments, and endothelin.

Low protein diet inhibits uric acid synthesis and attenuates renal damage in streptozotocin-induced diabetic rats

AIM

Several studies indicated that hyperuricemia may link to the worsening of diabetic nephropathy (DN). Meanwhile, low protein diet (LPD) retards exacerbation of renal damage in chronic kidney disease. We then assessed whether LPD influences uric acid metabolism and benefits the progression of DN in streptozotocin- (STZ-) induced diabetic rats.

METHODS

STZ-induced and control rats were both fed with LPD (5%) and normal protein diet (18%), respectively, for 12 weeks. Vital signs, blood and urinary samples for UA metabolism were taken and analyzed every 3 weeks. Kidneys were removed at the end of the experiment.

RESULTS

Diabetic rats developed into constantly high levels of serum UA (SUA), creatinine (SCr) and 24 h amounts of urinary albumin excretion (UAE), creatinine (UCr), urea nitrogen (UUN), and uric acid (UUA). LPD significantly decreased SUA, UAE, and blood glucose, yet left SCr, UCr, and UUN unchanged. A stepwise regression showed that high UUA is an independent risk factor for DN. LPD remarkably ameliorated degrees of enlarged glomeruli, proliferated mesangial cells, and hyaline-degenerated tubular epithelial cells in diabetic rats. Expression of TNF-α in tubulointerstitium significantly decreased in LPD-fed diabetic rats.

CONCLUSION

LPD inhibits endogenous uric acid synthesis and might accordingly attenuate renal damage in STZ-induced diabetic rats.

Diabetic kidney disease and the cardiorenal syndrome: old disease, new perspectives

In this article, the literature is reviewed regarding the role of blood pressure variability and nocturnal nondipping of blood pressure as well as the presence of diabetic kidney disease (DKD), in the absence of albuminuria, as risk predictors for progressive DKD. The importance of glycemic and blood pressure control in patients with diabetes and chronic kidney disease, and the use of oral hypoglycemic agents and antihypertensive agents in this patient cohort, are also discussed.

Metabolic syndrome and associated chronic kidney diseases: nutritional interventions

Lifestyle changes such as dietary habits, sedentary life and consumption of energy-dense foods that have occurred over the years has led to an epidemic of abdominal obesity, which in turn resulted in dramatic increase in the prevalence of metabolic syndrome (MetS). Different expert panels have provided various definitions for MetS to enable a clinical diagnosis and treatment of patients at risk of associated complications. Obesity and obesity mediated MetS has been paralleled by escalation in the incidence of chronic kidney disease (CKD). A better understanding of the pathophysiology of MetS and identification of individuals with MetS early in the life course could be important for initiating interventions such as lifestyle modification and dietary restrictions that form the basis for prevention and treatment of MetS and related co-morbidities including CKD. This review is intended to provide a comprehensive summary of the evolution of definition of MetS and association of MetS with CKD. In particular, mechanism of obesity and diabetes mediated CKD and emerging dietary therapies for MetS associated CKD will be discussed.