Pathogenesis and course of renal disease in IDDM/NIDDM: differences and similarities

Effect of methanolic fraction of Kalanchoe crenata on metabolic parameters in adriamycin-induced renal impairment in rats

Objectives:

To investigate the effect of Kalanchoe crenata methanolic fraction (MEKC) on proteinuria, glucosuria, and some other biochemical parameters in adriamycin-induced renal impairment in rats.

Materials and Methods:

Ether anesthetized rats received three intravenous injections (days 0, 14, and 28) of 2 mg/kg body weight of adriamycin. Repeated doses of the extract (0, 50, and 68 mg/kg b.w.) and losartan (10 mg/kg b.w.) were administered orally once daily, for 6 weeks, to these rats. Kidney functions were assessed through biochemical parameters.

Results:

MEKC decreased proteinuria and also the urinary excretion of creatinine, glucose, and urea significantly in diseased rats. A decrease in serum levels of creatinine, urea, potassium, alkaline phosphatase, conjugate bilirubin, and alanine transaminase level was also recorded in nephropathic rats, but plasma levels of uric acid and glucose remained unchanged. Moreover, the plant extract markedly (P < 0.05) increased plasma sodium and decreased (P < 0.01) the urinary sodium and potassium levels.

Conclusions:

The results indicated that the treatment with the methanolic fraction of K. crenata may improve proteinuria and all other symptoms due to adriamycin-induced nephropathy and, more than losartan, could ameliorate kidney and liver functions. K. crenata could be a potential source of new oral antinephropathic drug.

Renal histopathology of a baboon model with type 2 diabetes

Naturally occurring type 2 diabetes has been found in a colony of baboons. Ongoing characterization of the baboon colony maintained at the Southwest National Primate Research Center has revealed a significant range of glucose sensitivity with some animals clearly diabetic.   Seven baboons, four with diabetes and three without diabetes, underwent histopathological investigation. Three diabetic animals were diagnosed using fasting blood glucose, hemoglobin A1C, and intravenous glucose tolerance test, and a fourth one was known to have hyperglycemia. One control baboon and three baboons with diabetes had microalbuminuria. On kidney biopsy, diabetic baboons had thickening of the glomerular basement membrane and mesangial matrix expansion compared to controls. Immunohistochemistry showed the diabetic animals had increased mesangial expression of cellular fibronectin ED-A. Two diabetic animals with microalbuminuria had evidence of mesangiolysis with the formation of an early nodule. One diabetic animal had a Kimmestiel-Wilson nodule. We conclude that the baboon represents a useful primate model of diabetes and nephropathy that resembles the nephropathy associated with type 2 diabetes in humans.

Evaluation of the effect of oxidative stress and vitamin E supplementation on renal function in rats with streptozotocin-induced Type 1 diabetes

We investigated the possible role of reactive oxygen species (ROS) on renal function in experimental diabetes.

MATERIALS AND METHODS

Seven groups of male rats were studied. Group I consisted of control animals. Diabetes was induced (by streptozotocin) in the animals in the other groups and they received either insulin or vitamin E (300 or 600 mg/kg), both insulin and vitamin E, or no treatment for 4 weeks. At the end of the study, blood pressure was measured and parameters of kidney function and oxidative stress were evaluated in serum and kidney tissue samples.

RESULTS

Diabetic animals had higher blood pressures; increased serum glucose, urea, creatinine, cyclic guanosine monophosphate (cGMP); increased kidney tissue levels of malondialdehyde and inducible nitric oxide synthetase (iNOS); and reduced serum glutathione peroxidase when compared with control animals. Blood glucose levels in diabetic animals were controlled by insulin and not by any dose of vitamin E alone. However, all other measured parameters improved towards control levels with either insulin or vitamin E in either dose. An additive beneficial effect was observed on the levels of iNOS and cGMP when both forms of treatment were used in diabetic animals.

CONCLUSIONS

We conclude that ROS may play an important role in diabetes-induced nephropathy in this rat model. Vitamin E supplementation in addition to insulin can have additive protective effects against deterioration of renal function in this model.

Renal microvascular injury in diabetes: RAGE and redox signaling

Diabetic nephropathy remains a major cause of morbidity and mortality in the diabetic population and is the leading cause of end-stage renal failure in the Western World. Despite current therapeutics including intensified glycemic control and blood pressure lowering agents, renal disease continues to progress relentlessly in diabetic patients, albeit at a lower rate. It is well recognized that metabolic and hemodynamic factors play a central role in accelerating renal disease in diabetes. However, recent experimental studies have suggested that increased generation of reactive oxygen species (ROS) as a result of the diabetic milieu may play a central role in the progression of diabetic microvascular complications. These ROS appear to be generated primarily from mitochondrial sources and via the enzyme, NADPH oxidase. This review focuses on how ROS play a deleterious role in the diabetic kidney and how they are involved in crosstalk among various signaling pathways, ultimately leading to renal dysfunction and structural injury.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

The role of cell cycle proteins in Glomerular disease

Although initially identified and characterized as regulators of the cell cycle and hence proliferation, an extended role for cell cycle proteins has been appreciated more recently in a number of physiologic and pathologic processes, including development, differentiation, hypertrophy, and apoptosis. Their precise contribution to the cellular response to injury appears to be dependent on both the cell type and the nature of the initiating injury. The glomerulus offers a remarkable situation in which to study the cell cycle proteins, as each of the 3 major resident cell types (the mesangial cell, podocyte, and glomerular endothelial cell) has a specific pattern of cell cycle protein expression when quiescent and responds uniquely after injury. Defining their roles may lead to potential therapeutic strategies in glomerular disease.

Impaired saline-stimulated diuresis and natriuresis in the conscious hypertensive glucose-intolerant rat

BACKGROUND

A major complication of type 2 diabetes is renal dysfunction, a condition that worsens with coexistence of systemic hypertension. However, less is known regarding the renal impact of the prediabetic condition characterized by glucose intolerance. Therefore, we tested the hypothesis that chronic glucose intolerance leads to abnormal renal function, a condition also exacerbated by concurrent systemic hypertension.

METHODS

A rat model of concomitant NaCl-sensitive hypertension and glucose intolerance was used to study renal function. Glucose intolerance was produced by administering streptozotocin to neonatal Wistar-Kyoto rats, and systemic hypertension was induced by combining dietary NaCl excess with unilateral nephrectomy. Hemodynamic and renal excretory responses were determined in conscious animals before and after administration of a 30-min isotonic saline challenge (5% of body weight, intravenously).

RESULTS

Nine-month-old glucose-intolerant rats fed a normal NaCl diet did not manifest impairment in saline-stimulated diuresis and natriuresis. By contrast, 3-month-old glucose-intolerant rats fed a high NaCl diet displayed an exaggerated diuretic and natriuretic response to a saline challenge. Although saline-stimulated diuresis and natriuresis were enhanced in the hypertensive rats, they were reduced in the hypertensive glucose-intolerant animals. The reduction in renal excretory function of the latter group was caused by alterations in both glomerular function and tubular reabsorption of fluid and sodium.

CONCLUSIONS

The coexistence of systemic hypertension and glucose intolerance result in impaired renal excretory function. This defect could be important, as hypertension can develop before the onset of overt type 2 diabetes.

Blood pressure control early in diabetes: a balance between angiotensin II and nitric oxide

1. Hyperglycaemia can lead to hypertension in long- standing diabetes through cumulative effects to cause progressive glomerular injury. However, it is not known how hyperglycaemia directly affects blood pressure control. Moreover, it has been difficult to isolate the actions of hyperglycaemia from other factors that can influence blood pressure. Recent studies at the earliest stages of type I diabetes have started to address these issues. 2. In humans and in animal models of type I diabetes, there is evidence that onset of hyperglycaemia can increase blood pressure. The increase is mild and has been linked to angiotensin (Ang) II, possibly due to slight overstimulation of the system in response to hyperglycaemia. 3. We have reported recently that onset of hyperglycaemia causes severe hypertension in rats that are treated chronically with N(G)-nitro-L-arginine methyl ester and the hypertension is accompanied by a progressive increase in AngII and absence of hyperfiltration. This suggests that nitric oxide (NO), at the early stages of diabetes, is important in mediating the increase in glomerular filtration rate and in preventing hypertension. 4. We propose a hypothesis based on these results that hyperglycaemia at the earliest stages of diabetes induces hyperfiltration and natriuresis and also activates a compensatory hypertensive stimulus (likely AngII) in an attempt to maintain normal blood pressure. A critical balance exists between these forces and NO plays a pivotal role by attenuating AngII- mediated renal vasoconstriction and facilitating the increase in glomerular filtration rate.

The future of clinical trials in chronic renal disease: outcome of an NIH/FDA/Physician Specialist Conference. Evaluation of Clinical Trial Endpoints in Chronic Renal Disease Study Group

For people with chronic renal insufficiency, the therapeutic goal is to prevent progression to end-stage renal disease, a serious condition that can only be treated with dialysis and kidney transplantation. Although restriction of dietary protein slows the progression of renal disease somewhat, the principal treatment to slow chronic renal disease is appropriate reduction of blood pressure. Antihypertensive agents, particularly those that produce sustained, long-term reductions in proteinuria, such as angiotensin-converting enzyme inhibitors, not only decrease blood pressure but also preserve renal function. Clinical trials to evaluate these and other drug therapies in renal disease progression have used both "hard end points" (e.g., dialysis, transplantation, death) and intermediate end points of renal disease progression (e.g., doubling of serum creatinine concentration, reductions in proteinuria). Trials that have used hard end points typically recruited patients with advanced renal disease to demonstrate a difference in therapies within a period of 2 to 5 years. However, proteinuria reduction, along with a decrease in the time to doubling of serum creatinine in very early diabetic renal disease, could demonstrate an altered natural history of renal disease. Although hard end points are indicators of a drug's efficacy in reducing cardiovascular events or preserving renal function, they do not assess the impact of a treatment on altering the natural history of early renal disease. For clinical trials of people with all but the most advanced renal disease, use of intermediate end points of renal disease progression is the only practical option for assessment of treatment efficacy and effectiveness. Given the available data on proteinuria reduction and doubling of serum creatinine from clinical trials, these end points, taken together, appear to provide an acceptable means of assessing a treatment's impact on slowing renal disease progression.