Compensatory glomerular growth after unilateral nephrectomy is VEGF dependent

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.     

Kidney growth in normal and diabetic mice is not affected by human insulin-like growth factor binding protein-1 administration

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.     

Short-term insulin treatment and aortic expressions of IGF-1 receptor and VEGF mRNA in diabetic rats

We investigated the relationship between the changes in vascular responsiveness and growth factor mRNA expressions induced by 1-wk treatment with high-dose insulin in control and established streptozotocin (STZ)-induced diabetes. Aortas from diabetic rats, but not those from insulin-treated diabetic rats, showed impaired endothelium-dependent relaxation in response to ACh (vs. untreated controls). The ACh-induced nitrite plus nitrate (NOx) level showed no significant difference between controls and diabetics. Insulin treatment increased NOx only in diabetics. In diabetics, insulin treatment significantly increased the aortic expressions of endothelial nitric oxide synthase (eNOS) mRNA and VEGF mRNA. The expression of IGF-1 mRNA was unaffected by diabetes or by insulin treatment. In contrast, the mRNA for the aortic IGF-1 receptor was increased in diabetics and further increased in insulin-treated diabetics. In aortic strips from age-matched control rats, IGF-1 caused a concentration-dependent relaxation. This relaxation was significantly stronger in strips from STZ-induced diabetic rats. These results suggest that in STZ-diabetic rats, short-term insulin treatment can ameliorate endothelial dysfunction by inducing overexpression of eNOS and/or VEGF mRNAs possibly via IGF-1 receptors. These receptors were increased in diabetes, perhaps as result of insulin deficiency.     

Resveratrol Attenuates Diabetic Nephropathy via Modulating Angiogenesis

Angiogenesis plays an important role in the pathogenesis of diabetic nephropathy (DN). In the present study, we investigated the therapeutic potential of resveratrol, a polyphenol with antiangiogenic activity in DN. In a type 1 diabetic rat model, resveratrol treatment blunted the increases of urine albumin excretion, kidney weight and creatinine clearance rate. The increases of glomerular diameter, mesangium accumulation, glomerular basement membrane thickness and renal fibrosis in diabetic rats were also reduced by resveratrol treatment. In the diabetic kidney, increased expression of vascular endothelial growth factor (VEGF), Flk-1 and angiopoietin 2, and reduced expression of Tie-2 were observed. These changes in angiogenic hormones and associated receptors were attenuated by resveratrol treatment. No changes in angiopoietin 1 expression were detected among each group of rats. Resveratrol also significantly downregulated high glucose-induced VEGF and Flk-1 expressions in cultured mouse glomerular podocytes and endothelial cells, respectively. These effects were attenuated by knocking-down silent information regulator 1 (Sirt1) expression. In contrast, upregulation of Sirt1 in cultured endothelial cells reduced Flk-1 expression. Increased permeability and cellular junction disruption of cultured endothelial cells caused by VEGF were also inhibited by resveratrol pretreatment. Taken together, the present study demonstrated that resveratrol may attenuate DN via modulating angiogenesis.     

Appropriateness of the Zucker Diabetic Fatty rat as a model for diabetic microvascular late complications

Male obese Zucker Diabetic Fatty (ZDF) rats develop type 2 diabetes around eight weeks of age, and are widely used as a model for human diabetes and its complications. The objective of the study was to test whether the complications manifested in the kidney and nerves of ZDF rats really correspond to human diabetic complications in their being related to the hyperglycaemic state. Four groups of ZDF rats were used. One lean (Fa/?) and one obese (fa/fa) untreated group served as non-diabetic and diabetic controls. In two further groups of obese (fa/fa) rats, diabetes was prevented by pioglitazone or delayed by food restriction. All rats were monitored up to 35 weeks of age with respect to their blood glucose, HbA1c and insulin levels, their kidney function (urinary glucose excretion, renal glucose filtration, glomerular filtration rate, albumin/creatinine ratio), and their nerve function (tactile and thermal sensory threshold and nerve conduction velocity). Pioglitazone prevented the development of diabetes, while food restriction delayed its onset for 8-10 weeks. Accordingly, kidney function parameters were similar to lean non-diabetic rats in pioglitazone-treated rats and significantly improved in food-restricted rats compared with obese controls. Kidney histology paralleled the functional results. By contrast, nerve functional evaluations did not mirror the differing blood glucose levels. We conclude that the ZDF rat is a good model for diabetic nephropathy, while alterations in nerve functions were not diabetes-related.     

Impaired nitric oxide synthase-dependent dilatation of cerebral arterioles in type II diabetic rats

The goals of this study were to determine the effects of type II diabetes mellitus on nitric oxide synthase-dependent responses of cerebral arterioles and on endothelial nitric oxide synthase (eNOS) protein in cerebral arterioles. We examined dilatation of cerebral (pial) arterioles in 13-15 week old male lean and diabetic obese Zucker rats in response to nitric oxide synthase-dependent agonists (acetylcholine and adenosine diphosphate (ADP)) and a nitric oxide synthase-independent agonist (nitroglycerin). We found that acetylcholine (10 microM) increased cerebral arteriolar diameter by 10 +/- 3% (mean +/- SE) in lean Zucker rats, but by only 2 +/- 2% in diabetic obese Zucker rats (p<0.05). In addition, ADP (100 microM) increased cerebral arteriolar diameter by 20 +/- 2% in lean Zucker rats, but by only 8 +/- 2% in diabetic obese Zucker rats (p<0.05). In contrast, nitroglycerin produced similar vasodilatation in lean and diabetic obese Zucker rats. Thus, impaired dilatation of cerebral arterioles in diabetic obese Zucker rats is not related to non-specific impairment of vasodilatation. Following these functional studies, we harvested cerebral microvessels for Western blot analysis of eNOS protein. We found that eNOS protein was significantly higher in diabetic obese Zucker rats than in lean Zucker rats (p<0.05). Thus, type II diabetes mellitus impairs nitric oxide synthase-dependent responses of cerebral arterioles. In addition, eNOS protein from cerebral blood vessels is increased in diabetic obese Zucker rats.     

Resveratrol ameliorates early diabetic nephropathy associated with suppression of augmented TGF-β/smad and ERK1/2 signaling in streptozotocin-induced diabetic rats

Diabetic nephropathy (DN) is the major cause of end-stage renal disease. The early changes in DN are characterized by an increased in kidney size, glomerular volume, and kidney function, followed by the accumulation of glomerular extracellular matrix, increased urinary albumin excretion (UAE), glomerular sclerosis, and tubular fibrosis. Resveratrol (RSV) has been shown to ameliorate hyperglycemia and hyperlipidemia in streptozotocin-induced diabetic rats. In the present study, we examined the beneficial effects of RSV on DN and explored the possible mechanism of RSV action.Male Sprague–Dawley rats were injected with streptozotocin at 65 mg/kg body weight. The induction of diabetes mellitus (DM) was confirmed by a fasting plasma glucose level ≥300 mg/dL and symptoms of polyphagia and polydipsia. The DM rats were treated with or without RSV at 0.75 mg/kg body weight 3 times a day for 8 weeks. Animals were sacrificed and kidney histology was examined by microscopy. Urinary albumin excretion, glomerular hypertrophy and expressions of fibronectin, collagen IV, and TGF-β in the glomeruli were alleviated in RSV-treated DM rats, but not in untreated DM rats. In addition, RSV treatment reduced the thickness of the glomerular basement membrane (GBM) to the original thickness and increased nephrin expressions to normal levels in DM rats. Moreover, RSV inhibited phosphorylation of smad2, smad3 and ERK1/2 in diabetic rat kidneys. This is the first report showing that RSV alleviates early glomerulosclerosis in DN through TGF-β/smad and ERK1/2 inhibition. In addition, podocyte injuries of diabetic kidneys are lessened by RSV.     

Microvascular disease precedes the decline in renal function in the streptozotocin-induced diabetic rat

Diabetic nephropathy is a progressive and generalized vasculopathic condition associated with abnormal angiogenesis. We aim to determine whether changes in renal microvascular (MV) density correlate with and play a role in the progressive deterioration of renal function in diabetes. We hypothesize that MV changes represent the early steps of renal injury that worsen as diabetes progresses, initiating a vicious circle that leads to irreversible renal injury. Male nondiabetic (ND) or streptozotocin-induced diabetic (D) Sprague-Dawley rats were followed for 4 or 12 wk. Renal blood flow and glomerular filtration rate (GFR) were measured by PAH and (125)I-[iothalamate], respectively. Renal MV density was quantified ex vivo using three-dimensional micro computed tomography and JG-12 immunoreactivity. Vascular endothelial growth factor (VEGF) levels (ELISA) and expression of VEGF receptors and factors involved in MV remodeling were quantified in renal tissue by Western blotting. Finally, renal morphology was investigated by histology. Four weeks of diabetes was associated with increased GFR, accompanied by a 34% reduction in renal MV density and augmented renal VEGF levels. However, at 12 wk, while GFR remained similarly elevated, reduction of MV density was more pronounced (75%) and associated with increased MV remodeling, renal fibrosis, but unchanged renal VEGF compared with ND at 12 wk. The damage, loss, and subsequent remodeling of the renal MV architecture in the diabetic kidney may represent the initiating events of progressive renal injury. This study suggests a novel concept of MV disease as an early instigator of diabetic kidney disease that may precede and likely promote the decline in renal function.     

High circulating vascular endothelial growth factor (VEGF) is related to a better systolic function in diabetic hypertensive patients

BACKGROUND: VEGF seems to have a protective role on cardiac microcirculation, but no data are available on its action on cardiac function and morphology in diabetic patients. We sought to test the hypothesis that circulating VEGF levels could influence the cardiac performance in type 2 diabetic hypertensive patients. METHODS: We studied 30 patients with type 2 diabetes and hypertension, without severe cardiac, retinal, renal and peripheral vascular damage. Ten non-diabetic hypertensive patients represented the control group. VEGF plasma levels (ELISA) and echocardiographic parameters were evaluated. RESULTS: Diabetic patients had VEGF plasma levels higher than hypertensive non-diabetic subjects [median 82 (IQR 12-190) vs 50.5 (IQR 28-77) pg/mL, p=0.05]. Simple linear regression analysis showed that VEGF levels are related to relative wall thickness (RWT) and both endocardial and midwall systolic parameters in the diabetic patients. Multiple linear regression analysis showed that RWT and ejection fraction (EF) were the only independent correlates of VEGF (r2=0.274, p=0.03, p=0.05; respectively). CONCLUSIONS: Our data showed that high VEGF plasma levels are associated to a better systolic function in diabetic hypertensive patients with cardiac remodeling. VEGF may play a role in the improvement of cardiac performance in diabetes.     

Association between endothelin-1 and collagen deposition in db/db diabetic mouse kidneys

Endothelin-1 has been implicated in diabetic kidney injury, but there are few firm data establishing the temporal and spatial expression of kidney endothelin-1 in diabetes. We performed an immunohistochemical and histopathological analysis to determine endothelin-1 peptide expression in the kidneys of diabetic db/db mice and non-diabetic db/m controls. Diabetic mice were studied at 8 weeks, before histological damage is evident, and again at 16 weeks, when significant glomerular injury has occurred. Urinary endothelin-1 was 6.2- and 3.6-fold higher in 8- and 16-week diabetic mice compared to age-matched controls (P<0.01 db/db vs. db/m). Compared to non-diabetic kidneys, immunoreactive endothelin-1 was first elevated 2.5-fold (P=0.02) in the tubulointerstitial compartment at 8-week and remained high (3.8-fold, P<0.01) at 16 weeks. In contrast, glomerular endothelin-1 was elevated 3.2-fold (P=0.03) only in 16-week diabetic mice. Glomerular and tubulointerstitial endothelin-1 were unchanged in 8- and 16-week non-diabetic mice. Elevated endothelin-1 in diabetic mice associated temporally and spatially with collagen deposition, especially in the tubulointerstitial compartment. The localization of kidney endothelin-1 is consistent with a role for this peptide in renal fibrogenesis. These results also highlight the potential role of ET-1 in the pathogenesis of early tubulointerstitial changes in diabetes.     

Nox4 NAD(P)H oxidase mediates hypertrophy and fibronectin expression in the diabetic kidney

Renal hypertrophy and extracellular matrix accumulation are early features of diabetic nephropathy. We investigated the role of the NAD(P)H oxidase Nox4 in generation of reactive oxygen species (ROS), hypertrophy, and fibronectin expression in a rat model of type 1 diabetes induced by streptozotocin. Phosphorothioated antisense (AS) or sense oligonucleotides for Nox4 were administered for 2 weeks with an osmotic minipump 72 h after streptozotocin treatment. Nox4 protein expression was increased in diabetic kidney cortex compared with non-diabetic controls and was down-regulated in AS-treated animals. AS oligonucleotides inhibited NADPH-dependent ROS generation in renal cortical and glomerular homogenates. ROS generation by intact isolated glomeruli from diabetic animals was increased compared with glomeruli isolated from AS-treated animals. AS treatment reduced whole kidney and glomerular hypertrophy. Moreover, the increased expression of fibronectin protein was markedly reduced in renal cortex including glomeruli of AS-treated diabetic rats. Akt/protein kinase B and ERK1/2, two protein kinases critical for cell growth and hypertrophy, were activated in diabetes, and AS treatment almost abolished their activation. In cultured mesangial cells, high glucose increased NADPH oxidase activity and fibronectin expression, effects that were prevented in cells transfected with AS oligonucleotides. These data establish a role for Nox4 as the major source of ROS in the kidneys during early stages of diabetes and establish that Nox4-derived ROS mediate renal hypertrophy and increased fibronectin expression.     

Stimulatory effect of IGF-I and VEGF on eNOS message, protein expression, eNOS phosphorylation and nitric oxide production in rat glomeruli, and the involvement of PI3-K signaling pathway.

Nitric oxide (NO) is reported to be involved in the pathogenesis of renal hyperfiltration in the early stage of diabetic nephropathy. We set out to determine whether IGF-I and/or VEGF165 directly stimulate NO production in rat glomeruli and whether the expression of NO synthase (NOS) isoforms as well as eNOS phosphorylation contribute to NO generation by IGF-I and VEGF. Long-term exposure to IGF-I and/or VEGF165 augments NO production through increased eNOS mRNA, protein expression and phosphatidylinositol 3-kinase (PI3-K) signaling pathway plays a major role in this process; short-term exposure to IGF-I and/or VEGF(165) activates eNOS activity via phosphorylation by a PI3-K/Akt dependent pathway. Our data suggest the great possibility that increased endogenous IGF-I and VEGF may be responsible for the up-regulation of eNOS expression and NO production which contributes to glomerular hyperfiltration in early diabetic kidneys. IGF-I is a newly described growth factor that up-regulates eNOS expression and PI3-K plays a major role in this process.     

Endothelin antagonism normalizes VEGF signaling and cardiac function in STZ-induced diabetic rat hearts

Abnormal alterations in cardiac expression of vascular endothelial growth factor (VEGF) as well as its receptors and impairment in the development of coronary collaterals have recently been reported in diabetic subjects. However, the presence of pharmacological intervention on these defects in diabetes remains unsettled. Here, we studied the effect of endothelin (ET) receptor blockade on cardiac VEGF signaling pathways and cardiac function in Sprague-Dawley rats 5 wk after induction of type I diabetes with streptozotocin (65 mg/kg ip) in comparison with age-matched control rats. After streptozotocin (1 wk), some diabetic rats were treated with the ET receptor antagonist SB-209670 (1 mg/day) for 4 wk. VEGF, its receptors, and its angiogenic signaling molecules [phosphorylated Akt and endothelial nitric-oxide synthase (eNOS)] were analyzed by Western blot, ELISA, real-time PCR, and immunohistochemistry, and cardiac function was evaluated by echocardiography. Coronary capillary morphology was assessed by lectin and enzymatic double staining. We found significant decreases in cardiac expression of VEGF, its receptors, phosphorylation of Akt and eNOS, and coronary capillary density in diabetic rats compared with controls. Treatment of diabetic rats with SB-209670 reversed these alterations to the control levels and ameliorated impairment of cardiac function. From a molecular point of view, the present study is the first to indicate the potential usefulness of an ET receptor antagonist in the treatment of cardiac dysfunction in type I diabetes.     

Progression of early phase diabetic nephropathy in streptozotocin-induced diabetic rats: evaluation of various kidney-related parameters

Diabetic nephropathy (DN) is one of the serious secondary complications of diabetes, which results in end-stage renal failure. Reports on the progressive nature of early phase DN especially with respect to kidney parameters such as kidney weight, type IV collagen excretion, total kidney and urinary glycosaminoglycans (GAGs) are few. This work was undertaken to determine systematically the progression of early phase DN in relation to various kidney-related parameters for a period of four months. Experimentally-induced diabetic rats were grouped based on fasting blood glucose levels. Various basic and kidney-related parameters such as kidney weight, microalbuminuria, urinary excretion of GAGs and type IV collagen, total kidney GAGs, histopathology, glomerular area and glomerular volume were examined in control and diabetic rats. There was a progressive increase in fasting blood sugar, urine sugar, kidney weight, microalbuminuria, urine glycosaminoglycans, urine type IV collagen, glomerular area and glomerular volume but there was a progressive decrease in kidney glycosaminoglycans. Glomerular sclerotic condition was aggravated with the increase in duration of diabetes from 1 to 4 months. Onset of DN in rats begins subtly after one month of diabetes but gets vitiated and more pronounced at the end of four months.     

Increased levels of vascular endothelial growth factor and advanced glycation end products in aqueous humor of patients with diabetic retinopathy.

Clinical studies have shown a relationship between diabetic retinopathy and vascular endothelial growth factor (VEGF) levels in ocular fluid. Advanced glycation end products (AGEs) have been implicated in diabetes complications, including diabetic retinopathy. Nepsilon-(carboxymethyl) lysine (CML) is a glycoxidation product that may be a marker of oxidative stress. In this study, we used enzyme-linked immunosorbent assays to determine the levels of VEGF, non-CML AGE and CML in the aqueous humor and serum of 82 Japanese patients with type 2 diabetes and 60 non-diabetic subjects. VEGF, non-CML AGE, and CML concentrations in aqueous humor and serum were then compared with the severity of diabetic retinopathy. Immunohistochemical detection analysis of non-CML AGE and CML was also performed using retinal tissues from patients with progressive diabetic retinopathy. Aqueous levels of VEGF, non-CML AGE and CML increased along with the progression of diabetic retinopathy compared to age-matched controls. After coagulation therapy, the VEGF, non-CML AGE, and CML levels were significantly reduced. Immunostaining showed diffuse co-localization of non-CML AGE and CML around microvessels and in the glial cells of proliferative membranes from patients with progressive diabetic retinopathy. These findings suggest that glycation and glycoxidation reactions (or oxidation, as revealed by CML) may contribute to both the onset and progression of diabetic retinopathy.     

Glomerular filtration and renal volume in type II diabetes (non-insulin-dependent): study in normal and microalbuminuria patients]

In type 2 diabetes elevated glomerular filtration rate (GFR) and increased renal volume (RV), often accompanied to normo or microalbuminuria, were demonstrated. This condition is considered a pathogenetic factor for clinical nephropathy. As this topic is little studied in type 2 diabetes, we have investigated 73 type 2 diabetic patients (34 normo and 39 microalbuminuric), looking for a correlation between GFR, RV, hypertension, duration of diabetes and indexes of metabolic control. GFR was measured by a scintigraphy, after infusion of 99Tc-DTPA. Renal volume was determined by ultrasound scanning. Between the groups GFR and RV weren't different; elevated GFR was demonstrated in 3 patients; increased RV in 1 patient. In the hypertensive group GFR was lower than in normotensive group and in controls. Multivariate analysis in stepwise demonstrated that GFR presents a negative correlation to systolic blood pressure as in normo as in microalbuminuric patients. In the normotensive group GFR didn't correlate to the other variables. The present data suggest that in type 2 diabetes there is a little prevalence of glomerular hyperfiltration and increased renal volume and that hypertension plays a role on GFR of hypertensive diabetic patients.     

Effect of Insulin on ACE2 Activity and Kidney Function in the Non-Obese Diabetic Mouse

We studied the non-obese diabetic (NOD) mice model because it develops autoimmune diabetes that resembles human type 1 diabetes. In diabetic mice, urinary albumin excretion (UAE) was ten-fold increased at an “early stage” of diabetes, and twenty-fold increased at a “later stage” (21 and 40 days, respectively after diabetes diagnosis) as compared to non-obese resistant controls. In NOD Diabetic mice, glomerular enlargement, increased glomerular filtration rate (GFR) and increased blood pressure were observed in the early stage. In the late stage, NOD Diabetic mice developed mesangial expansion and reduced podocyte number. Circulating and urine ACE2 activity were markedly increased both, early and late in Diabetic mice. Insulin administration prevented albuminuria, markedly reduced GFR, blood pressure, and glomerular enlargement in the early stage; and prevented mesangial expansion and the reduced podocyte number in the late stage of diabetes. The increase in serum and urine ACE2 activity was normalized by insulin administration at the early and late stages of diabetes in Diabetic mice. We conclude that the Diabetic mice develops features of early kidney disease, including albuminuria and a marked increase in GFR. ACE2 activity is increased starting at an early stage in both serum and urine. Moreover, these alterations can be completely prevented by the chronic administration of insulin.     

Anthocyanin-Rich Purple Corn Extract Inhibit Diabetes-Associated Glomerular Angiogenesis

Diabetic nephropathy (DN) is one of the major diabetic complications and the leading cause of end-stage renal disease. Abnormal angiogenesis results in new vessels that are often immature and play a pathological role in DN, contributing to renal fibrosis and disrupting glomerular failure. Purple corn has been utilized as a daily food and exerts disease-preventive activities. This study was designed to investigate whether anthocyanin-rich purple corn extract (PCE) prevented glomerular angiogenesis under hyperglycemic conditions. Human endothelial cells were cultured in conditioned media of mesangial cells exposed to 33 mM high glucose (HG-HRMC-CM). PCE decreased endothelial expression of vascular endothelial growth factor (VEGF) and hypoxia inducible factor (HIF)-1α induced by HG-HRMC-CM. Additionally, PCE attenuated the induction of the endothelial marker of platelet endothelial cell adhesion molecule (PECAM)-1 and integrin β3 enhanced in HG-HRMC-CM. Endothelial tube formation promoted by HG-HRMC-CM was disrupted in the presence of PCE. In the in vivo study employing db/db mice treated with 10 mg/kg PCE for 8 weeks, PCE alleviated glomerular angiogenesis of diabetic kidneys by attenuating the induction of VEGF and HIF-1α. Oral administration of PCE retarded the endothelial proliferation in db/db mouse kidneys, evidenced by its inhibition of the induction of vascular endothelium-cadherin, PECAM-1 and Ki-67. PCE diminished the mesangial and endothelial induction of angiopoietin (Angpt) proteins under hypeglycemic conditions. The induction and activation of VEGF receptor 2 (VEGFR2) were dampened by treating PCE to db/db mice. These results demonstrate that PCE antagonized glomerular angiogenesis due to chronic hyperglycemia and diabetes through disturbing the Angpt-Tie-2 ligand-receptor system linked to renal VEGFR2 signaling pathway. Therefore, PCE may be a potent therapeutic agent targeting abnormal angiogenesis in DN leading to kidney failure.     

Urinary excretion of glucagon-like peptide 1 (GLP-1) 7-36 amide in human type 2 (non-insulin-dependent) diabetes mellitus.

The urinary excretion of insulinotropic glucagon-like peptide 1 (GLP-1) was investigated as an indicator of renal tubular integrity in 10 healthy subjects and in 3 groups of type 2 diabetic patients with different degrees of urinary albumin excretion rate. No significant difference emerged between the groups with respect to age of the patients, known duration of diabetes, metabolic control, BMI, or residual beta-cell pancreatic function. Endogenous creatinine clearance was significantly reduced under conditions of overt diabetic nephropathy, compared with normo and microalbuminuric patients (p < 0.01). Urinary excretion of GLP-1 was significantly higher in normoalbuminuric patients compared to controls (490.4 +/- 211.5 vs. 275.5 +/- 132.1 pg/min; p < 0.05), with further increase under incipient diabetic nephropathy conditions (648.6 +/- 305 pg/min; p < 0.01). No significant difference resulted, in contrast, between macroproteinuric patients and non-diabetic subjects. Taking all patients examined into account, a significant positive relationship emerged between urinary GLP-1 and creatinine clearance (p = 0.004). In conclusion, an early tubular impairment in type 2 diabetes would occur before the onset of glomerular permeability alterations. The tubular dysfunction seems to evolve with the development of persistent microalbuminuria. Finally, the advanced tubular involvement, in terms of urinary GLP1 excretion, under overt diabetic nephropathy conditions would be masked by severe concomitant glomerular damage with the coexistence of both alterations resulting in a peptide excretion similar to control subjects.