Hypertrophy In Diabetic Rats Research Articles

Effects ofRheum officinale on the renal hypertrophy and hyperfiltration in the streptozotocin-induced diabetic rats

To study the effects ofRheum officinale (RO) on epidermal growth factor (EGF) in renal hypertrophy in the diabetic rats were induced by streptozotocin. The results showed that renal hypertrophy occurred in the diabetic rats, but not in the RO-treated rats. Urine EGF was 38.2±16.6 ng/24 h at day 28 in the control, and it was significantly increased from day 7 in the diabetic rats (477.8±187.2 ng/24 h at day 7, 328.2±153.9 ng/24 h at day 28), while in the RO-treated rats it was significantly less than that in the diabetic rats (282.2±112.5 ng/24 h at day 7, 258.3±72.3 ng/24 h at day 28). Moreover, glomerular filtration rate and renal blood flow reduced in RO-treated diabetic rats as compared with streptozotocin diabetic rats. Because kidney is the main source of urine EGF and EGF has been shown to induce renal growth both in vitro and in vivo. It is indicated that EGF may be able to initiate renal hypertrophy in diabetic rats, and the effect of RO on the renal hypertrophy is probably relative to the inhibition of renal EGF production resulted from RO treatment.

Expression of transforming growth factor-β1 during diabetic renal hypertrophy

Experimental type I diabetes mellitus is characterized by an early increase in kidney weight and glomerular volume, but changes in gene expression accompanying diabetic renal growth have not been fully elucidated. In the current study, total RNA was extracted from renal cortex and isolated glomeruli of streptozotocin-induced diabetic rats 24 hours, 48 hours, 96 hours, one and two weeks after the onset of hyperglycemia (blood glucose > 15 mmol/liter), insulin-treated diabetic rats (blood glucose < 6.0 mmol/liter), and normal rats. RNA samples were reverse transcribed (RT) and subjected to polymerase chain reaction (PCR) amplication with specific 5' and 3' primers for rat transforming growth factor (TGF-beta 1) and beta-actin. RT-PCR analysis revealed that glomerular TGF-beta 1 mRNA levels increased relative to beta-actin as early as 24 hours after the onset of hyperglycemia, reaching a plateau after 96 hours that was sustained at one and two weeks. In cortical samples, TGF-beta 1 mRNA levels increased less abruptly, reaching a peak one week after the onset of hyperglycemia. Intensive insulin treatment to normalize blood glucose levels attenuated the rise in glomerular and renal cortical TGF-beta 1 mRNA. Cryostat sections of rat kidneys were immunostained for TGF-beta 1 utilizing a polyclonal anti-porcine TGF-beta 1 antibody and semiquantitative scoring of TGF-beta 1 immunostaining revealed a twofold increase in diabetic glomeruli after two weeks compared to normal glomeruli. Increased segmental immunostaining for TGF-beta 1 was also evident in cortical tubules of diabetic rats. These studies establish that TGF-beta 1 expression in the kidney increases during the phase of rapid renal hypertrophy in diabetic rats. Normalization of blood glucose levels with insulin treatment attenuates the increase in TGF-beta 1 expression.

Octreotide suppresses the kidney weight and glomerular hypertrophy in diabetic rats

It was previously demonstrated that initial kidney hypertrophy has been seen in diabetic animals and somatostatin infusion suppresses GFR and serum insulin like growth factor (IGF-1) in diabetic patients. I studied the effects of somatostatin analogue (octreotide) on glomerular hypertrophy in diabetic rats. The animals were randomized into six groups: two groups of streptozocin (STZ) induced diabetic, insulin-treated diabetic and non-diabetic rat groups. One of these three groups were treated with two daily subcutaneous injections of octreotide (10 micrograms x 2) for a period of five weeks. In diabetic rats, body weight, blood sugar, glucose excretion, serum insulin, urinary volume, urinary protein, serum creatinine or creatinine clearance did not differ in diabetic rats with vs. without octreotide injection, but kidney weight (2.97 +/- 0.12 vs. 3.28 +/- 0.08 mg, P < 0.05; mean +/- SEM) and estimated glomerular volume (9.13 +/- 0.22 vs. 12.77 +/- 0.34 x 10(5) microns 3, P < 0.001) were all reduced in diabetic rats with octreotide when compared with untreated diabetic rats. In non-diabetic rats, octreotide reduced body weight (340.3 +/- 6.5 vs. 367.1 +/- 3.8g, P < 0.01) and kidney weight (2.29 +/- 0.08 vs. 2.51 +/- 0.04 g, P < 0.05) when compared with non-diabetic rats without octreotide. Urinary protein excretion (8.57 +/- 1.39 vs. 14.29 +/- 1.53 mg/day, P < 0.05), serum 1GF-1 concentration (956.3 +/- 180.7 vs. 1546.1 +/- 88.1 mg/day, P < 0.05) and estimated glomerular volume (7.69 +/- 0.16 vs. 9.72 +/- 0.15 x 10(5) microns 3, P < 0.001) significantly differed in insulin treated diabetic rats with vs. without octreotide.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidermal Growth Factor in Renal Hypertrophy in Streptozotocin-Diabetic Rats

Epidermal growth factor (EGF) concentrations in the plasma, kidneys and urine of 31 streptozotocin-diabetic rats and 21 insulin-treated diabetic rats were measured to study the role of EGF in initiating renal hypertrophy in the diabetic rats. Renal hypertrophy occurred from day 7 in the diabetic rats, but not in the insulin-treated rats. Renal EGF was not different between the diabetic and control rats, while that in the insulin-treated rats was significantly less than in the diabetic rats. There were no significant changes in plasma EGF in any of the rats. Urine EGF was 119 +/- 7.9 ng/day at day 7 in the control rats but it was significantly increased from day 2 in the diabetic rats (320 +/- 52.9 ng/day at day 2 and 298 +/- 18.4 ng/day at day 7), while in the insulin-treated rats it was significantly less than that in the diabetic rats (134 +/- 8.34 ng/day at day 2 and 220 +/- 15.2 ng/day at day 7). Since the kidney is the main source of urine EGF and EGF has been shown to induce renal growth both in vitro and in vivo, we conclude that EGF may have initiated renal hypertrophy in diabetic rats.

Dietary fish oil enhances renal hypertrophy in experimental diabetes

Renal hypertrophy occurs early in the natural history of human and experimental diabetes and may be a manifestation of the same pathophysiological process which ultimately results in diabetic nephropathy. The precise biological events which stimulate and regulate this growth process remain incompletely understood. We postulated that renal eicosanoids contribute to the development of renal hypertrophy in diabetes. We elected to test the effects of suppression of dienoic eicosanoid metabolism (arachidonic acid metabolism) on renal hypertrophy in diabetic rats by feeding fish oil. Diabetic rats fed fish oil had markedly reduced insulin requirements compared to control rats pair-fed a beef tallow-rich diet. The concentrations of prostaglandin E 2, 6-keto-prostaglandin F 1α, and thromboxane B 2 were depressed in the renal cortex of diabetic rats fed fish oil. This alteration in eicosanoid metabolism was associated with a substantial enhancement of diabetic renal hypertrophy. These results indicate that dietary fish oil has profound effects on renal eicosanoid metabolism in experimental diabetes and that these autocoids may participate in the biological events which regulate diabetic renal hypertrophy.

Vascular filtration function in galactose-fed versus diabetic rats: The role of polyol pathway activity

These studies were undertaken to assess the effects of increased galactose ( v increased glucose) metabolism via the polyol pathway on vascular filtration function in the kidneys, eyes, nerves, and aorta. Quantitative radiolabeled tracer techniques were used to assess glomerular filtration rate (GFR) and regional tissue vascular clearance of plasma 131I-bovine serum albumin (BSA) in five groups of male Sprague-Dawley rats: nondiabetic controls, streptozotocin-diabetic rats, nondiabetic tats fed a 50% galactose diet, diabetic rats treated with sorbinil (an aldose reductase inhibitor), and galactose-fed rats treated with sorbinil. Sorbinil was added to the diet to provide a daily dose of ≈.2 mmol/kg body weight. After 2 months of diabetes or galactose ingestion, albumin clearance was increased twofold to fourfold in the eye (anterior uvea, choroid, and retina), sciatic nerve, aorta, and kidney; GFR was increased approximately twofold and urinary excretion of endogenous albumin and IgG were increased approximately 10-fold. Sorbinil treatment markedly reduced or completely prevented all of these changes in galactose-fed, as well as in diabetic rats. These observations support the hypothesis that increased metabolism of glucose via the sorbitol pathway is of central importance in mediating virtually all of the early changes in vascular filtration function associated with diabetes in the kidney, as well as in the eyes, nerves, and aorta. On the other hand, renal hypertrophy in diabetic rats and polyuria, hyperphagia, and impaired weight gain in galactose-fed and in diabetic rats were unaffected by sorbinil and therefore are unlikely to be mediated by increased polyol metabolism.