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Diabetes is currently one of the leading causes of end-stage renal failure requiring renal replacement therapy in the Western World. About 15% to 20% of type 1 diabetic patients and 30% to 40% of type 2 diabetic patients will eventually develop end-stage renal failure. To prevent the development or progression of diabetic kidney disease, good glycaemic control remains the cornerstone in the management of diabetic patients. Beyond glycaemic control, other metabolic factors have been shown to be involved in the development of diabetic kidney disease, i.e. advanced glycation endproducts (AGEs) and the aldose reductase pathway. Furthermore, an adequate control of high blood pressure and treatment of microalbuminuria are major therapeutic targes. To achieve adequate blood pressure control, a combination therapy with different classes of antihypertensive agents is often necessary, especially including angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Other vasoactive factors involved in diabetic nephropathy such as endothelin and nitric oxide will be covered briefly. Besides hyperglycaemia and high blood pressure, other risk factors have been identified in the development or progression of diabetic kidney disease: smoking, hyperlipidaemia, obesity and high protein intake. Their impact on renal function will be highlighted. Finally, recent research has also identified intracellular pathways such as the diacylglycerol-protein kinase C pathway and several growth factors, such as growth hormone, insulin-like growth factor, transforming growth factor-beta, vascular endothelial growth factor, and platelet derived growth factor as players in diabetic kidney disease.

Background: Subtotal renal ablation is characterized by initial glomerular hypertrophy, followed by progressive development of glomerulosclerosis and interstitial fibrosis. Vascular endothelial growth factor (VEGF) is involved in glomerular hypertrophy and dysfunction in several pathophysiological conditions. On the other hand, progressive glomerulosclerosis and tubulo-interstitial fibrosis in the remnant kidney have been associated with loss of VEGF expression. Methods: To explore the pathophysiological role of VEGF in the development of glomerular hypertrophy and renal damage in the remnant kidney model, we examined the effect of a neutralizing VEGF antibody on glomerular volume and kidney function in rats after subtotal nephrectomy or sham operation. Erythropoietin was administered to exclude a confounding effect of anaemia. Results: Six weeks after subtotal nephrectomy, plasma urea and creatinine concentrations, urinary albumin excretion, and mean glomerular volume were elevated in the placebo-treated uraemic rats as compared with the sham-operated rats. Inhibition of VEGF partially prevented the glomerular hypertrophy and largely prevented the rise in urinary albumin excretion, but did not affect creatinine clearance in uraemic rats. Conclusions: VEGF is a mediator of glomerular hypertrophy after subtotal renal ablation. In view of glomerular hypertrophy as the initial deleterious event ultimately leading to progressive glomerulosclerosis, agents that block this glomerular growth could be useful in preventing scarring in progressive renal disease.

Insulin-like growth factor I (IGF-I) accumulates in the kidney following the onset of diabetes, initiating diabetic renal hypertrophy. Increased renal IGF-I protein content, which is not reflected in messenger RNA (mRNA) levels, suggests that renal IGF-I accumulation is due to sequestration of circulating IGF-I rather than to local synthesis. It has been suggested that IGF-I is trapped in the kidney by IGF binding protein 1 (IGFBP-1). We administered purified human IGFBP-1 (hIGFBP-1) to nondiabetic and diabetic mice as three daily sc injections for 14 days, starting 6 days after induction of streptozotocin diabetes when the animals were overtly diabetic. Markers of early diabetic renal changes (i.e., increased kidney weight, glomerular volume, and albuminuria) coincided with accumulation of renal cortical IGF-I despite decreased mRNA levels in 20-day diabetic mice. Human IGFBP-1 administration had no effect on increased kidney weight or albuminuria in early diabetes, although it abolished renal cortical IGF-I accumulation and glomerular hypertrophy in diabetic mice. Increased IGF-I levels in kidneys of normal mice receiving hIGFBP-1 were not reflected on kidney parameters. IGFBP-1 administration in diabetic mice had only minor effects on diabetic renal changes. Accordingly, these results did not support the hypothesis that IGFBP-1 plays a major role in early renal changes in diabetes.

Type 2 diabetes is the most frequent cause of end-stage renal failure in many Western countries. Approximately 10-15 % of all type 2 diabetics are lean. Various growth factors and cytokines have been implicated in the pathophysiology of diabetic kidney disease, including vascular endothelial growth factor (VEGF). To elucidate a role for VEGF in the renal changes associated with type 2 diabetes, we examined the effect of a VEGF-antibody (ab) on early renal changes in the Goto-Kakizaki (GK) rat, a lean type 2 diabetes model. GK-rats were treated for 6 weeks with the VEGF-ab or with an isotype-matched irrelevant IgG. Wistar rats were used as non-diabetic controls. Placebo-treated GK-rats showed a pronounced increase in glomerular volume and urinary albumin excretion (UAE) and no change in the renal expression of endothelial nitric oxide synthase (eNOS) compared to placebo-treated non-diabetic controls. Kidney weight and creatinine clearance were no different between the groups. VEGF-ab treatment had no effect on glomerular volume, UAE, eNOS expression, body weight, blood glucose levels or food intake, but lowered serum insulin levels in non-diabetic and diabetic animals. We conclude that VEGF inhibition has minimal effects on early renal changes in GK-rats.

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.

Diabetic nephropathy in type 2 diabetic patients is a frequent complication associated with increased morbidity and mortality. Various growth factors and cytokines have been implicated in the pathogenesis of diabetic kidney disease, including vascular endothelial growth factor (VEGF). To explore a role for VEGF in renal changes in type 2 diabetes, we examined the renal effects of a neutralizing murine VEGF antibody in the diabetic db/db mouse, a model of obese type 2 diabetes. One group of db/db mice was treated for 2 months with a VEGF antibody, while another db/db group was treated for the same period with an isotype-matched irrelevant IgG. A third group consisting of nondiabetic db/+ mice was treated with the same isotype-matched IgG for 2 months. Placebo-treated db/db mice showed a pronounced increase in kidney weight, glomerular volume, basement membrane thickness (BMT), total mesangial volume, urinary albumin excretion (UAE), and creatinine clearance (CrCl) when compared with nondiabetic controls. In VEGF antibody-treated db/db mice, increases in kidney weight, glomerular volume, BMT, and UAE were attenuated, whereas the increase in CrCl was abolished. VEGF antibody administration tended to reduce expansion in total mesangial volume. These effects in diabetic animals were seen without impact on body weight, blood glucose, insulin levels, or food consumption. In conclusion, chronic inhibition of VEGF in db/db mice ameliorates the diabetic renal changes seen in type 2 diabetes.

High protein-induced glomerular hypertrophy is vascular endothelial growth factor-dependent.BackgroundVarious growth factors and cytokines have been implicated in different forms of kidney enlargement such as renal growth following induction of diabetes, unilateral nephrectomy, and exposure to high protein diet. Vascular endothelial growth factor (VEGF) is essential for normal renal development and plays a role in diabetes-associated renal and glomerular enlargement.MethodsTo elucidate a possible role for VEGF in high protein-induced renal/glomerular enlargement, we examined the effect of a neutralizing VEGF-antibody (VEGF-ab) on kidney weight and glomerular volume in mice fed a high protein diet for up to seven days.ResultsAt day 2 and day 7 of the experimental period, high protein diet induced a significant increase in the mean glomerular volume. This high protein-induced glomerular hypertrophy was completely prevented by treatment with VEGF-ab. Kidney weight was increased significantly only at day 7, and was not influenced by VEGF-ab treatment. High protein diet and/or VEGF-ab treatment had no effect on body weight, food intake, and liver or heart weight.ConclusionsThe administration of a neutralizing VEGF-ab in mice fed a high protein diet for one week completely abolished the glomerular hypertrophy seen in placebo-treated animals on the same diet, without affecting kidney and body weight. These results demonstrate, to our knowledge for the first time, that high protein-induced glomerular hypertrophy is VEGF-dependent.

Is folate a promising agent in the prevention and treatment of cardiovascular disease in patients with renal failure? Management of the conventional cardiovascular risk factors is insufficient to prevent the dramatic increase in atherosclerotic cardiovascular morbidity and mortality in patients with renal failure. Folate recently received attention as a potential alternative treatment option to decrease the excess cardiovascular risk in the uremic population. Folate administration is the principal treatment modality for hyperhomocysteinemia. Hyperhomocysteinemia is prevalent in more than 85% of patients with end-stage renal disease (ESRD) and is independently associated with increased odds for atherosclerotic cardiovascular disease. Several attempts have been made to normalize homocysteine levels in uremic patients with folate-based vitamin regimens. Although supraphysiologic doses of folic acid afford greater reductions in homocysteine levels than standard doses, the response to treatment is generally only partial and the large majority of ESRD patients have residual hyperhomocysteinemia. Several defects in folate metabolism have been described in uremia, which may explain the relative folate resistance in patients with renal failure, but their clinical relevance remains uncertain. It appears unlikely that the hyperhomocysteinemia in ESRD can be cured solely with folic acid supplements, since folate does not affect the prolonged plasma elimination of homocysteine, which is the primary defect in homocysteine metabolism in uremia. Folate restores endothelial dysfunction, associated with hyperlipidemia, diabetes and hyperhomocysteinemia. The beneficial effect appears to be independent of its homocysteine-lowering capacity and is possibly related to an improved bioavailability of nitric oxide. However, folate has failed to improve endothelial dysfunction in uremic patients. In the ESRD population, multiple metabolic and hemodynamic abnormalities adversely affect endothelial function. In addition, irreversible structural vascular disease already may be present. Folate should, therefore, probably be an integral part of an “endothelial protective regimen,” consisting of lipid-lowering agents, antihypertensives and antioxidant vitamins and started very early in patients with renal failure. Before large-scale folate administration can be recommended, effects on hard endpoints of cardiovascular disease need to be demonstrated in randomized trials. Such trials are currently underway in patients with normal renal function at high risk for cardiovascular disease, and one trial has recently been initiated in stable renal transplant recipients.

We present this case to emphasize the importance of early diagnosis and treatment of an acute severe hypercalcemic syndrome due to primary hyperparathyroidism as a consequence of an undiagnosed adenoma of the parathyroid gland.A 50-year-old man presented at another hospital with non-specific symptoms such as anorexia, nausea, vomiting, polyuria, dehydration, abdominal pain, weight loss, fatigue, muscular weakness, irritability and lethargy. Serum levels of calcium and parathyroid hormone (PTH) were markedly increased to 23.6 mg/dL (reference values 8.6-10.2 mg/dL) and1900 ng/L (reference values 14-72 ng/L) respectively. After initial treatment, the patient was transferred to the intensive care unit (ICU) of a tertiary care university hospital for further stabilization and treatment because the typical signs of hypercalcemia were not resolving. A parathyroid adenoma was diagnosed and a few days later a parathyroidectomy was performed. The postoperative course was uneventful and the patient could be discharged from the hospital in a good general condition.Acute primary hyperparathyroidism, also known as parathyroid storm or parathyroid crisis, is a rare but potentially fatal endocrine emergency if unrecognized and untreated. Appropriate diagnosis and immediate adequate management of hypercalcemia are important in reducing mortality. Nevertheless, mortality remains high, even with surgical treatment which is the cornerstone of the definitive therapy.

Advanced glycation endproducts (AGEs) have been implicated in the pathogenesis of diabetic kidney disease. The actions of AGEs are mediated both through a non-receptor mediated pathway and through specific receptors for AGEs (e.g. RAGE). To explore a potentially specific role for RAGE in renal changes in type 1 diabetes, we examined the renal effects of a neutralising murine RAGE-antibody (ab) in streptozotocin (STZ)-diabetic mice, a model of type 1 diabetes. One group of STZ-diabetic mice was treated for two months with the RAGE-ab, while another STZ-diabetic group was treated for the same period with an irrelevant immunoglobulin G (IgG). Two groups of non-diabetic NMRI mice were treated with either RAGE-ab or isotype-matched IgG for two months. Placebo-treated STZ-diabetic mice showed an increase in kidney weight, glomerular volume, basement membrane thickness (BMT), urinary albumin excretion (UAE) and creatinine clearance (CrCl), when compared with non-diabetic controls. In RAGE-ab-treated STZ-diabetic mice, the increase in kidney weight and UAE was reduced, while the increase in CrCl was abolished. RAGE-ab administration in NMRI mice caused a reduction in liver weight and an increase in BMT. Renal messenger RNA (mRNA) for connective tissue growth factor and collagen IVα1 was increased in placebo-treated diabetic animals. RAGE-ab treatment had no impact on the expression of these factors. The renal effects of RAGE-ab administration in STZ-diabetic mice were seen without impact on body weight, blood glucose or food consumption. In conclusion, the present data support the hypothesis that RAGE is an important pathogenic factor in the renal changes in an animal model of type 1 diabetes.

Background. Antagonism of vascular endothelial growth factor (VEGF) has improved the outcome in experimental nephropathies of various origins, including diabetic nephropathy in a type 1 diabetic rat model and a type 2 diabetic mouse model. Neutralizing VEGF antibodies prevented glomerular hypertrophy in these models. We examined the renal effects of VEGF blockade in an obese rat model of type 2 diabetic nephropathy and investigated the mechanism underlying the inhibition of glomerular hypertrophy. Methods. Twenty female Zucker diabetic fatty (ZDF) rats, fed a high-fat diet and aged 10 weeks, were treated with VEGF antibodies or an irrelevant isotype-matched IgG. Ten heterozygous ( fa/þ) littermates served as additional non-diabetic, lean controls. Urinary albumin excretion (UAE) and creatinine clearance (CrCl) were assessed at baseline, and at 3 and 5 weeks. Kidney weight and glomerular volume were determined at the end of the study. Glomerular apoptosis was examined with anti-active caspase-3 immunohistochemistry. Results. All obese animals had established diabetes, hyperlipidaemia and normal blood pressure, which were not influenced by VEGF antibody treatment. ZDF control rats had increased UAE, CrCl, kidney weights and glomerular volumes compared with nondiabetic, lean control rats. VEGF antibody treatment prevented the glomerular hypertrophy, but did not affect UAE, CrCl and kidney weight. Glomerular anti-active caspase-3 immunostaining was not different between the groups. Conclusions. Inhibition of VEGF prevented early glomerular hypertrophy in ZDF rats with established diabetes. Increased apoptosis of glomerular endothelial cells does not appear to underly the inhibition of glomerular growth.

Background. Type 2 diabetes has become the single most frequent cause of end-stage renal disease. The Goto-Kakizaki rat is currently used as a model for lean type 2 diabetes, but its renal changes have not been fully characterized. We investigated long-term functional and structural renal changes in the Goto-Kakizaki rat to evaluate if this animal model resembles the changes observed in human diabetic kidney disease. Methods. Urinary albumin excretion, creatinine clearance and blood pressure were measured at the age of 2, 8 and 14 months in 12 female Goto-Kakizaki rats and 10 female, non-diabetic Wistar rats. To study kidney morphology, kidney weight, glomerular volume, basement membrane thickness, mesangial fraction and total mesangial volume were determined at 14 months. Results. Urinary albumin excretion rose progressively over time in both groups, but was significantly higher in Goto-Kakizaki rats than in Wistar rats. Creatinine clearance decreased over time in Goto-Kakizaki rats but not in Wistar rats. Blood pressure was in the normotensive range in all animals throughout the study. Kidney weight, glomerular volume, basement membrane thickness, mesangial fraction and total mesangial volume were significantly higher in Goto-Kakizaki rats than in Wistar rats. Body weight and blood glucose levels were higher, whereas serum insulin levels were not different or lower in Goto-Kakizaki rats compared with Wistar rats. Conclusion. The Goto-Kakizaki rat is a lean, hyperglycaemic, euinsulinaemic, normotensive experimental model of type 2 diabetes with robust functional and structural renal changes.

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology. Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.

Advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetic kidney disease. The actions of AGEs are mediated both through a non–receptor-mediated pathway and through specific receptors for AGE (RAGEs). To explore a specific role for RAGE in renal changes in type 2 diabetes, we examined the renal effects of a neutralizing murine RAGE antibody in db/db mice, a model of obese type 2 diabetes. One group of db/db mice was treated for 2 months with the RAGE antibody, and another db/db group was treated for the same period with an irrelevant IgG. Two groups of nondiabetic db/+ mice were treated with either RAGE antibody or isotype-matched IgG for 2 months. Placebo-treated db/db mice showed a pronounced increase in kidney weight, glomerular volume, basement membrane thickness (BMT), total mesangial volume, urinary albumin excretion (UAE), and creatinine clearance compared with nondiabetic controls. In RAGE antibody–treated db/db mice, the increase in kidney weight, glomerular volume, mesangial volume, and UAE was reduced, whereas the increase in creatinine clearance and BMT was fully normalized. Notably, these effects in db/db mice were seen without impact on body weight, blood glucose, insulin levels, or food consumption. In conclusion, RAGE is an important pathogenetic factor in the renal changes in an animal model of type 2 diabetes.

Background Nephropathy is the most severe complication of diabetes mellitus. We investigated the effect of exogenous growth hormone (GH) administration on renal function and matrix deposition in the streptozotocin (STZ) model of type I-diabetic rat. Methods Adult female STZ-diabetic rats (D), non-diabetic control rats injected with saline (C) and control and diabetic rats injected with bovine GH for 3 months (CGH and DGH, respectively) were used. Results The usual renal hypertrophy seen in D animals was more pronounced in the DGH group. Creatinine clearance increased only in the D rats, but not in the other groups, including DGH. Albuminuria was observed in the D animals but was significantly elevated in the DGH group. Glomeruli from DGH animals showed more extensive matrix accumulation (manifested as an increase in mesangial/glomerular area ratio). Renal extractable insulin-like growth factor (IGF-I) mRNA was decreased in the D and DGH groups, but renal IGF-I protein was not significantly increased. Renal IGF binding protein-1 was increased in the D groups and further increased in the DGH group, at both the mRNA and protein levels. Conclusions GH-treated diabetic rats had less hyperfiltration and more albuminuria, concomitant with more glomerular matrix deposition, when compared with regular diabetic animals. This was associated with a significant increase in renal IGFBP-1, and dissociated from IGF-I changes. Thus, in this model, GH exacerbates the course of diabetic kidney disease.

Various growth factors and cytokines have been implicated in different forms of kidney enlargement. Vascular endothelial growth factor (VEGF) is essential for normal renal development and plays a role in diabetic glomerular enlargement. To explore a possible role for VEGF in compensatory renal changes after uninephrectomy, we examined the effect of a neutralizing VEGF-antibody (VEGF-Ab) on glomerular volume and kidney weight in mice treated for 7 days. Serum and kidney insulin-like growth factor I (IGF-I) levels were measured, since IGF-I has been implicated in the pathogenesis of compensatory renal growth, and VEGF has been suggested to be a downstream mediator of IGF-I. Placebo-treated uninephrectomized mice displayed an early transient increase in kidney IGF-I concentration and an increase in glomerular volume and kidney weight. In VEGF-Ab-treated uninephrectomized animals, increased glomerular volume was abolished, whereas renal hypertrophy was partially blocked. Furthermore, the renal effects of VEGF-Ab administration were seen without affecting the renal IGF-I levels. In conclusion, these results demonstrate that compensatory glomerular growth after uninephrectomy is VEGF dependent.

Udgivelsesdato: 2002-Mar It was recently discovered that the streptozotocin (STZ)-diabetic mouse model is characterised by GH hypersecretion in contrast to the STZ-diabetic rat, the former thus mimicking the changes in GH in human type 1 diabetes. Inhibition of circulating and renal IGF-I by long-acting somatostatin analogues reduces renal and glomerular growth and urinary albumin excretion in diabetic rats. The aim of the present study was to examine renal and glomerular growth in early experimental diabetes in mice along with changes in the GH/IGF-I axis following treatment with the somatostatin analogue octreotide. Balb/C(a) mice were randomised into non-diabetic controls, placebo-treated and octreotide-treated diabetic (50 microg/day) mice and examined 7 and 14 days after induction of diabetes. There was no effect of octreotide treatment on body weight, glycaemic control or food intake. However, octreotide treatment significantly inhibited renal and glomerular growth by the end of the study period when compared with placebo treatment. In addition, octreotide prevented an increase in kidney IGF-I by day 7. GH hypersecretion was observed in the diabetic groups but octreotide treatment reduced GH levels compared with placebo treatment by day 14. No significant differences in serum or kidney IGF-binding protein-3 levels were observed between placebo- and octreotide-treated diabetic mice. In conclusion, this new diabetic mouse model mimicking human type 1 diabetes is characterised by GH hypersecretion and the somatostatin analogue octreotide is able to prevent renal and glomerular growth, probably mediated through changes in circulating GH and local kidney IGF-I levels.