Investigational and Comparative Study in the Management of Diabetic Nephropathy

The objective of this study is to investigate and compare the safety and efficacy of selective (PDE5) enzyme inhibitor; tadalafil and non selective (PDE) inhibitor; pentoxifylline in diabetic nephropathy to improve glucose metabolism, lipid profile and decrease albuminuria.

Diabetic nephropathy(DN) is one of the major micro- vascular complications of diabetes mellitus and the leading cause of end-stage renal disease (ESRD) that require renal replacement therapies. The average incidence of diabetic nephropathy is 3% per year during the first 10 to 20 years after diabetes onset. Diabetic nephropathy occurs in 20-40% of all diabetic patients. Pathogenesis of diabetic nephropathy is complex and multi-factorial in which diabetes mellitus has more than pathway for initiation and progression of the disease. * Metabolic pathway: result in formation of advanced glycation end products (AGEs). * Inflammatory pathway: result in increase serum level of tumor necrosis factor-α(TNF . * Hemodynamic pathway: result in increase serum level of endothelin-1 which result in glomerular hypertension and hyper filtration. Tadalafil is a phosphodiesterase type 5 enzyme (PDE5) inhibitor used mainly in erectile dysfunction and pulmonary hypertension by a mechanism involving increase(NO-cGMP-PKG) signaling pathway. Tadalafil is a powerful pleiotropic drug that it can be used in DN as it can target more than pathway involved in pathogenesis of DN include hyperglycemia and endothelial dysfunction through increase (NO-cGMP) signaling pathway as well as hyperlipidemia. Animal studies reported that tadalafil increase significantly total antioxidant capacity(TAC),decrease significantly serum level of inflammatory marker (TNF- α), blood glucose level, serum creatinine ,serum urea and urinary albumin excretion all result in decrease renal inflammation, injury, necrosis and apoptosis. Pentoxifylline is a methyl xanthine derivative, non selective phosphodiesterase enzyme inhibitor used mainly to treat peripheral vascular diseases by improve blood flow, increase red blood cell flexibility and inhibit platelet aggregation. Pentoxifylline have been recently widely used in many animal studies and clinical trials to evaluate its efficacy in management of DN and the results were so promising.(14) Pentoxifylline can slow the decrease in eGFR, and significantly reduce albuminuria in which it can be effective alternative to ACEI in reducing albuminuria as proved by clinical trial.(15) The powerful effect of pentoxifylline in DN as it can affect several pathways implicated in pathogenesis of DN; it has hypoglycemic effect by decrease Significantly blood glucose, HbA1c and serum triglyceride, it also decrease pro inflammatory cytokines (TNF-α, IL-1, IL-6), reduce plasma level of malondialdehyde and increase glutathione level.(16) Neutrophil Gelatinase-Associated Lipocalin (NGAL): is a 25-kDa protein belong to lipocalin superfamily. The urinary concentration of NGAL increase in renal tubular damage as a result of both diminished reabsorption and increased release from renal tubules into urine indicating both proximal and distal tubular damage respectively.(17) NGAL is not considered a marker of renal function but a marker of structural damage of renal tubules, its level can quantify the degree of tubular damage.(18) NGAL can be used as a precocious marker of therapeutic response by application of NGAL measurement in monitoring the effectiveness of a particular treatment and predicting different clinical outcomes in the course of renal diseases