Renal and microvascular effects of an aldose reductase inhibitor in experimental diabetes. Biochemical, functional and ultrastructural studies

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.

Therapeutic Modalities in Diabetic Nephropathy: Future Approaches

Diabetes mellitus is the leading cause of end stage renal disease and is responsible for more than 40% of all cases in the United States. Several therapeutic interventions for the treatment of diabetic nephropathy have been developed and implemented over the past few decades with some degree of success. However, the renal protection provided by these therapeutic modalities is incomplete. More effective approaches are therefore urgently needed. Recently, several novel therapeutic strategies have been explored in treating DN patients including Islet cell transplant, Aldose reductase inhibitors, Sulodexide (GAC), Protein Kinase C (PKC) inhibitors, Connective tissue growth factor (CTGF) inhibitors, Transforming growth factor-beta (TGF-β) inhibitors and bardoxolone. The benefits and risks of these agents are still under investigation. This review aims to summarize the utility of these novel therapeutic approaches.

A Random-Pattern Skin-Flap Model in Streptozotocin Diabetic Rats

BACKGROUND

Flap operations are frequently performed in diabetic patients. Nevertheless, we could find no experimental study examining diabetes mellitus's effect on the flaps' survival. For this reason, we designed this study as a random-pattern skin-flap model of diabetic rats in 1999.

METHODS

We used 72 rats weighing about 200 g each. The animals were divided into 2 groups, 1 experimental (diabetic) and 1 control (nondiabetic). Following their diabetic periods, we elevated the rats' modified McFarlane flaps and measured their viable flap areas.

RESULTS

The mean percentage of the flap area surviving was 51.40% in the 2-week experimental group. It was 48.20% in the 4-week experimental group and 36.70% in the 8-week experimental group. The mean percentage of flap area surviving was 65.87% in the united control group (the total of all control groups). The mean surviving skin-flap area in the united control group was significantly higher than in the 4- and 8-week experimental groups. Moreover, the mean surviving flap area in the 8-week experimental group was significantly lower than in the 2-week and 4-week experimental groups.

CONCLUSIONS

Our study demonstrated that a 4-week diabetic duration for rats is sufficient to observe diabetes' deleterious effects on the flaps' viability. These effects were significantly established, however, after 8 weeks of diabetes. To obtain definitive results, at least 8 weeks of diabetic duration are preferred for similar studies.

Effect of an aldose reductase inhibitor on type IV collagen production by human endothelial cells cultured in high glucose

Diabetic microangiopathy is characterized by a thickening of capillary basement membranes associated with type IV collagen accumulation. An increase in type IV collagen content of the aortic wall is also observed in macroangiopathy. In order to analyse the importance of the polyol pathway in the development of the collagen metabolism alterations seen in diabetic angiopathy and their prevention by aldose reductase inhibitors, we have studied the effects of sorbinil on the high glucose-induced stimulation of type IV collagen biosynthesis in human umbilical vein endothelial cells. Primary cultures were exposed to high glucose (16.7 mmol/l), with and without 0.11 mmol/l sorbinil, for 3 or 6 days after beginning of confluence. We measured the soluble type IV collagen secreted into the culture medium and the insoluble type IV collagen accumulated in the extracellular matrix and cells, by ELISA. We also studied [14C]proline incorporation into the newly synthesized collagenous and total proteins in the culture supernatant and in the extracellular matrix and cell fraction. High glucose decreased the number of cells and increased the amount of type IV collagen in the culture supernatant and in the extracellular matrix and cell fraction. It also increased proline incorporation into the newly synthesized collagenous and total proteins in the culture supernatant and in the extracellular matrix and cell fraction. Sorbinil corrected all these high glucose-induced alterations. The corrective effects of sorbinil on the proliferation and on type IV collagen metabolism of endothelial cells cultured in high glucose may be attributed to prevention of polyol pathway dysregulation.

Production of type IV collagen and 72-kDa gelatinase by human endothelial cells cultured in high glucose. Effects of a protein kinase C inhibitor, GF 109203X

Since diabetic microangiopathy and macroangiopathy are characterized by type IV collagen accumulation in vascular basement membranes, it was of interest to study type IV collagen production and type IV collagenase secretion by endothelial cells (EC) cultured in high glucose and to evaluate the role of protein kinase C (PKC) activation in the alterations induced by high glucose. Primary cultures of human umbilical vein EC were exposed to high glucose concentration for 3 days at the beginning of confluence. The number of EC decreased with glucose concentration from 5 to 50 mM. At 16.7 mM glucose concentration, the amount of type IV collagen, determined by a two-step ELISA, increased in the culture supernatant and in the insoluble fraction associated with the extracellular matrix and cells; proline incorporation was more markedly elevated in the collagenous than in the total proteins of the culture supernatant and of the extracellular matrix and cell extracts. Gelatin zymography of the culture supernatant showed that EC mainly produce a 72-kDa gelatinase known to degrade type IV collagen. At 16.7 mM glucose concentration, total gelatinase activity per millilitre of culture supernatant was reduced and the 72-kDa gelatinase activity measured on the zymogram scan was lowered. When EC were exposed to 16.7 mM glucose, the specific PKC inhibitor GF 109203X corrected the increases in type IV collagen concentration and in proline incorporation into the collagenous or total proteins present in he culture supernatant or in the extract of the insoluble fraction, including the extracellular matrix and cells. Our results show that soluble and insoluble type IV collagen accumulation by EC cultured at high glucose concentration is not only associated with increased synthesis of the collagenous and total proteins but also with decreased total 72-kDa gelatinase activity in the extracellular fluid. The observed effects of GF 109203X are in favor of the involvement of PKC activation in the type IV collagen accumulation.