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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polyamines are small biogenic molecules that are essential for cell cycle entry and progression and proliferation. They can also contribute to hypertrophy. The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, increases in the early diabetic kidney to enable renal hypertrophy. Inhibition of ODC in early diabetes attenuates diabetic renal hypertrophy and glomerular hyperfiltration. The current studies examine the temporal profile of renal ODC protein expression and localization, intrarenal polyamine levels, and sites of proliferation in kidneys of rats during the first 7 days of streptozotocin diabetes. ODC mRNA and protein content were increased in diabetic kidneys. High-performance liquid chromatography analysis showed increased intrarenal polyamine concentrations peaking after 24 h of diabetes. A subsequent increase in the number of proliferating proximal tubular cells was detected by in vivo 5-bromodeoxyuridine (BrdU) incorporation on day 3. Surprisingly, immunohistochemical studies revealed that increased ODC protein was apparent only in distal nephrons, whereas the main site of diabetic kidney hypertrophy is the proximal tubule. These findings raise the possibility that polyamines produced in the distal nephron may mediate the early diabetic kidney growth of the proximal tubules via a paracrine mechanism.
Diabetes 2003 May
PMID:Increased expression of ornithine decarboxylase in distal tubules of early diabetic rat kidneys: are polyamines paracrine hypertrophic factors? 1271 58

This study was designed to investigate the effect of hyperglycemia and angiotensin II (AngII) on renal hypertrophy and proteinuria in the pregnant diabetic rat. Secondary objectives were to evaluate changes in components of the renin-angiotensin axis and the effects of administration of losartan on pregnancy outcome. Fifty-three pregnant rats were allocated to 6 groups (1) nondiabetic controls (n = 12), (2) nondiabetic controls administered losartan (70-80 mg/kg/day; n = 10), (3) rats in which intravenous streptozotocin (STZ) was used to induce diabetes (55 mg/kg on day 10 of pregnancy; n = 10), (4) diabetic rats treated with losartan (n = 7), (5) diabetic rats treated with insulin (4 U/day; n = 7), and (6) diabetic rats treated with insulin and losartan (n = 7). Urinary protein excretion measured 4 days after STZ was 4 times greater in the rats with STZ-induced diabetes and significantly less in diabetic rats given losartan, insulin, or both. Postpartum kidney weight was greater in the rats with STZ-induced diabetes (2.04 +/- 0.21 g) than in the controls (1.37 +/- 0.14 g; P <.05) and reduced in the diabetic rats given losartan, insulin, or both (1.57 +/- 0.22, 1.73 +/- 0.13, and 1.51 +/- 0.14 g, respectively; P <.05). Plasma levels of angiotensin II in rats given losartan were more than 3.5 times greater than those in controls (749 +/- 436, 596 +/- 323, 567 +/- 349, and 159 +/- 28 pg/mL; P <.001). Postpartum activity of angiotensin-converting enzyme was increased in the untreated diabetic rats compared with that in control rats (162 +/- 12 vs 117 +/- 16 nmol/mL/min; P <.05). This increase was abolished by treatment with losartan or insulin. The number of newborns and mean weight of each newborn was similar in all groups. In summary, administration of losartan or insulin prevented, in part, kidney hypertrophy and protein excretion in the diabetic pregnant rat. Losartan did not affect the number or weight of newborns. Because angiotensin II receptor-blockers are contraindicated in pregnancy, good control of diabetes through the use of insulin should be advantageous.
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PMID:Insulin and losartan reduce proteinuria and renal hypertrophy in the pregnant diabetic rat. 1453 4

Oxidative damage has been suggested to be a contributing factor in the development to diabetic nephropathy (DN). Recently, there has been evidence that pentoxifylline (PTX) has free radical-scavenging properties; thus, its anti-inflammatory and renoprotective effects may be related to a reduction in reactive oxygen species production. It is likely that the pharmacological effects of PTX include an antioxidant mechanism as shown in in vitro assays. The aim of this study was to evaluate whether the reported renoprotective effects of PTX could be the result of its antioxidant actions in streptozotocin (STZ)-induced DN in rats. The administration of PTX over a period of 8 weeks, in addition to displaying renoprotective effects, caused a significant reduction in lipoperoxide levels (LPOS) in the diabetic kidney (P < 0.05), compared to untreated rats. These levels were comparable to those in the healthy kidney of experimental animals (P > 0.05). All untreated STZ rats exhibited an increase in LPOS as opposed to healthy controls (H) (P < 0.001). The total antioxidant activity (TAA) in plasma was increased significantly already after 2 days of STZ (P < 0.05). When we examined the progression of TAA in STZ rats, there was a significant decrease over 8 weeks (P < 0.05). PTX treatment caused an increase in TAA when compared to untreated STZ rats (P < 0.05). Renal hypertrophy was less evident in PTX-treated STZ than in untreated STZ rats, evaluated by kidney weight/body weight ratio. These results indicate that PTX decreases the oxidative damage induced by these experimental procedures and may increase antioxidant defense mechanisms in STZ-induced diabetes in rats.
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PMID:Pentoxifylline diminishes the oxidative damage to renal tissue induced by streptozotocin in the rat. 1576 38

Patients with diabetic nephropathy, characterised pathologically by glomerulosclerosis, may account for up to 40% of end-stage renal cases. The short-term (within 3 months) streptozotocin- or alloxan-induced rat model is often used but glomerulosclerosis is seldom reported and it is unclear what the primary renal lesions are. Diabetic rats were studied at 1, 3 and 6 months after a single injection of alloxan. Both methacrylate and paraffin-embedded renal sections were obtained and stained with PAS and haematoxylin. A morphometric study was performed with stereological methods to obtain the volumes and lengths or diameters of renal tubules and glomeruli. A key morphological change associated with sustained hyperglycaemia was the accumulation of glycogen granules in about half of the distal tubules and thin segments starting from 1 month after the experiment, which was then extended to about half of the proximal tubules at 6 months. Renal hypertrophy was seen with a 9% increase in the tubule diameter but not in the total length; glomerular morphology was basically unaffected. Further studies are needed to establish whether glomerulosclerosis would occur in longer term and whether this animal model would be appropriate to study the human condition of diabetes mellitus in terms of renal damage.
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PMID:Glycogen accumulation in renal tubules, a key morphological change in the diabetic rat kidney. 1594 46

Translation elongation factor-1 (EF-1) forms a primary site of regulation of protein synthesis and has been implicated amongst others in tumorigenesis, diabetes and cell death. To investigate whether diabetes-induced oxidative stress affects EF-1 gene expression, we used a free radical scavenger, vitamin E. The following groups of rats (5/group) were studied: control, vitamin E control, diabetic and diabetic treated with vitamin E. Markers of hyperglycemia, kidney function, oxidative stress, and kidney hypertrophy were elevated in diabetic rats. Increased urinary protein excretion indicated early signs of glomerular and tubular dysfunction. The mRNA and protein levels of the three EF-1 subunits (A, Balpha, and Bgamma) were determined in renal cortex extracts using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), northern blot analysis and western blotting. EF-1A mRNA expression in renal cortex extracts was significantly increased by at least 2-fold (p < 0.002) in diabetic rats; however, there was no change in the mRNA levels of EF-1Balpha and EF-1Bgamma subunits. Similar results were observed at the protein level. Treatment of diabetic rats with vitamin E for 10 days suppressed both glycemic and oxidative stresses in renal cortex and kidney hypertrophy. EF-1A mRNA and protein levels were also reduced to control levels. In conclusion, EF-1A but not EF-1Balpha and EF-1Bgamma gene expression is significantly enhanced in the renal cortex of diabetic rats. Normalization of enhanced EF-1A expression by vitamin E treatment suggests a role for EF-1A during diabetes-induced oxidative stress.
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PMID:Regulation of elongation factor-1 expression by vitamin E in diabetic rat kidneys. 1601 53

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.
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PMID:Nox4 NAD(P)H oxidase mediates hypertrophy and fibronectin expression in the diabetic kidney. 1613 19

Bitter gourd (Momordica charantia), a commonly consumed vegetable is used as an adjunct in the management of diabetes mellitus. A study was carried out to examine the effect of edible portion of bitter gourd at 10% level in the diet in streptozotocin induced diabetic rats. To evaluate the glycaemic control of bitter gourd during diabetes, diet intake, gain in body weight, water intake, urine sugar, urine volume, glomerular filtration rate and fasting blood glucose profiles were monitored. Water consumption, urine volume and urine sugar were significantly higher in diabetic controls compared to normal rats and bitter gourd feeding alleviated this rise during diabetes by about 30%. Renal hypertrophy was higher in diabetic controls and bitter gourd supplementation, partially, but effectively prevented it (38%) during diabetes. Increased glomerular filtration rate in diabetes was significantly reduced (27%) by bitter gourd. An amelioration of about 30% in fasting blood glucose was observed with bitter gourd feeding in diabetic rats. These results clearly provided experimental evidence that dried bitter gourd powder in the diet at 10% level improved diabetic status signifying its beneficial effect during diabetes.
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PMID:Effect of bitter gourd (Momordica charantia) on glycaemic status in streptozotocin induced diabetic rats. 1618 12

Early diabetic nephropathy is characterized by renal hypertrophy that is mainly due to proximal tubular hypertrophy. Mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase, and its signaling has been reported to regulate protein synthesis and cellular growth, specifically, hypertrophy. Therefore, we examined the effect of mTOR signaling on diabetic renal hypertrophy by using the specific inhibitor for mTOR, rapamycin. Ten days after streptozotocin-induced diabetes, mice showed kidney hypertrophy with increases in the phosphorylation of p70S6kinase and the expression of cyclin kinase inhibitors, p21(Cip1) and p27(Kip1), in the kidneys. The intraperitoneal injection of rapamycin (2 mg/kg/day) markedly attenuated the enhanced phosphorylation of p70S6kinase, the increment of cyclin-dependent kinase inhibitors, and renal enlargement without any changes of clinical parameters, including blood glucose, blood pressure, and food intake. Overexpression of a constitutive active form of p70S6kinase resulted in increased cell size of cultured mouse proximal tubule cells; thus, activation of p70S6kinase causes hypertrophy of proximal tubular cells. Our findings suggest that activation of mTOR signaling causes renal hypertrophy at the early stage of diabetes.
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PMID:Inhibition of mTOR signaling with rapamycin attenuates renal hypertrophy in the early diabetic mice. 1636 54

We tested the hypothesis that AMP-activated protein kinase (AMPK), an energy sensor, regulates diabetes-induced renal hypertrophy. In kidney glomerular epithelial cells, high glucose (30 mM), but not equimolar mannitol, stimulated de novo protein synthesis and induced hypertrophy in association with increased phosphorylation of eukaryotic initiation factor 4E binding protein 1 and decreased phosphorylation of eukaryotic elongation factor 2, regulatory events in mRNA translation. These high-glucose-induced changes in protein synthesis were phosphatidylinositol 3-kinase, Akt, and mammalian target of rapamycin (mTOR) dependent and transforming growth factor-beta independent. High glucose reduced AMPK alpha-subunit theronine (Thr) 172 phosphorylation, which required Akt activation. Changes in AMP and ATP content could not fully account for high-glucose-induced reductions in AMPK phosphorylation. Metformin and 5-aminoimidazole-4-carboxamide-1beta-riboside (AICAR) increased AMPK phosphorylation, inhibited high-glucose stimulation of protein synthesis, and prevented high-glucose-induced changes in phosphorylation of 4E binding protein 1 and eukaryotic elongation factor 2. Expression of kinase-inactive AMPK further increased high-glucose-induced protein synthesis. Renal hypertrophy in rats with Type 1 diabetes was associated with reduction in AMPK phosphorylation and increased mTOR activity. In diabetic rats, metformin and AICAR increased renal AMPK phosphorylation, reversed mTOR activation, and inhibited renal hypertrophy, without affecting hyperglycemia. AMPK is a newly identified regulator of renal hypertrophy in diabetes.
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PMID:A role for AMP-activated protein kinase in diabetes-induced renal hypertrophy. 1701 41

Transforming growth factor (TGF)-beta plays a critical role in diabetic nephropathy. To isolate the contribution of one of the signaling pathways of TGF-beta, the Smad3 gene in the mouse was knocked out at exons 2 and 3, and the effect was studied in streptozotocin (STZ)-induced diabetes over a period of 6 wk. TGF-beta activity was increased in the diabetic mice but was not able to signal via Smad3 in the knockout (KO) mice. As expected in the wild type, the kidneys of the STZ-diabetic mice showed both structural and functional defects that are characteristic of diabetic renal involvement. In the Smad3-KO mice, however, the defects that were improved were renal hypertrophy, mesangial matrix expansion, fibronectin overproduction, glomerular basement membrane thickening, plasma creatinine, and the blood urea nitrogen. The parameters not significantly altered by the Smad3-KO were albuminuria, reduction in podocyte slit pore density, and the increase in vascular endothelial growth factor abundance and activity. It seems that the absence of Smad3 modifies the natural course of murine diabetic nephropathy, providing renal functional protection and preventing structural lesions relating to kidney hypertrophy and matrix accumulation, even though albuminuria and changes in podocyte morphology persist. In conclusion, the effects of the Smad3-KO mirror the effects of anti-TGF-beta therapy in diabetes, suggesting that the chief component of TGF-beta signaling that is relevant to kidney disease is the Smad3 pathway.
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PMID:Interference with TGF-beta signaling by Smad3-knockout in mice limits diabetic glomerulosclerosis without affecting albuminuria. 1780 83


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