Renoprotective evaluations of different angiotensin inhibitors on Diabetic Nephropathy in Rats

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Kawa F. Dizaye (1)
Asmaa A. Ahmed (2)

(1) PhD. Head of Department of Pharmacology, College of Medicine. Hawler Medical University, Erbil, Iraq
(2) MSc. Rizgary Teaching Hospital, Ministry of Health, Erbil, Iraq


Correspondence:
Prof. Dr. Kawa Dizaye
Professor of Pharmacology
Hawler Medical University, Erbil, Iraq
Tel: 009647504452392
Web: hmu.edu.iq
Email: kawa.dizaye@hmu.edu.iq

Diabetic nephropathy is a major microvascular complication of diabetes, representing the leading cause of end stage renal disease in the world. Diabetic nephropathy is characterized by a progressive increase in urinary albumin excretion (microalbuminuria) and a decline in glomerular filtration rate (GFR), which occurs in association with an increase in blood pressure, ultimately leading to end stage renal disease (1, 2).

Basic and clinical research supports the use of renin angiotensin aldosterone system (RAAS) inhibitors in diabetic nephropathy (3, 4, 5).

Several basic and clinical studies, mainly in diabetic patients, have provided evidence that some antihypertensive agents that inhibit the renin angiotensin aldosterone system (RAAS), like angiotensin II type 1 receptor blockers (ARB) and angiotensin-converting enzyme inhibitors (ACEI), are renoprotective (6, 7). The reno-protection provided by these drugs seems at least partly independent of BP lowering and related perhaps to the inhibition of the RAS (8, 9, 10).

Several mechanisms participate in the renal protection afforded by angiotensin inhibitors. ACEIs increase the permeability selectivity of the filtering membrane, thereby diminishing exposure of the mesangium to proteinaceous factors that may stimulate mesangial cell proliferation and matrix production, two processes that contribute to expansion of the mesangium in diabetic nephropathy. Since angiotensin II is a growth factor, reductions in the intrarenal levels of angiotensin II may further attenuate mesangial cell growth and matrix production (11, 12, 13).

Thus, there do not appear to be significant differences between ACEI and ARBs in type 2 diabetic patients with nephropathy based on a small number of comparison studies.

Other studies in hypertensive type 2 diabetics with early nephropathy comparing ACEIs and ARBs have also failed to show significant differences in the effects of these two drug classes on BP and urinary albumin excretion (14, 15). Only a few studies have addressed the question of whether ACE inhibitors are better than ARBs or vice versa.

This study is designed to compare the effectiveness of different angiotensin inhibitors, direct renin (DR) inhibitor (Aliskiren), ACEI (Ramipril) ARBs (Irbesartan) in prevention and treatment of nephropathy in rat induced diabetes.

Animals
Healthy adult albino rats of both sexes were used in the present study. Their weight ranged from 250-300 grams. Rats were grouped and kept in separate animal cages at the animal house of the College of Medicine under prevailing atmospheric conditions (room temperature of about 25c).

The animals were maintained on a balanced diet (bread, barley, carrots, lettuce, milk) and fresh-water supply.

Induction of experimental diabetes
Diabetes was induced by a single intraperitoneal injection of 120mg/kg body weight of alloxan dissolved in distilled water immediately before injection 16. Alloxan treated animals were allowed to drink 5% of glucose overnight to prevent the potentially fatal hypoglycemia occurring as a result of massive insulin release following alloxan injection (17).

Rats showing blood glucose levels above 180 mg/dl were considered to be diabetic (18) and used for drug treatment.

Experimental design
Thirty rats were divided into five groups each consisting of 6 rats in order to study the effect of different angiotensin inhibitors (Ramipril, Irbesartan, Aliskiren) during the 21 days study period:

Group I: Normal control rats given D.W
Group II: Control diabetic rats given D.W
Group III: Diabetic rats given Ramipril 10mg/kg.
Group IV: Diabetic rats given Irbesartan 10mg/kg.
Group V: Diabetic rats given Aliskiren 10 mg/kg.

The solution of drugs was freshly prepared in normal saline before administration by an oral gavage every morning.

Collection of samples
1-Urine
After 3 days, and at the end of drug treatment, all of the animals were kept in metabolic cages. Animals were fasted but allowed free access to water. Urine sample were collected after 24 hours in urine collecting bottles from which the urine collected was tested for: Albumin, Creatinine, Na+ excretion rate and K+ excretion rate, glomerular filtration rate and others.

2-Blood
At the end of drug treatment, all of the animals were fasted overnight but allowed free access to water. The next morning, blood samples were taken by cardiac puncture into a plastic syringe under a combination of ketamine in a dose of 75 mg/kg with xylazine in a dose of 10 mg/kg. At 10th day and at the end of experiment (after 21 days), a 24 hours urine collection was carried out by using the metabolic cage. The urine was checked for the albumin and total protein by using Cybow diagnostic kits (DFI co. Ltd, Gimhae- City, Gyung- Nam, Korea).

Statistical Analysis
All data are expressed as the mean ± standard error means (M ± SEM). The results were evaluated by using the Statistical Package for the Social Sciences (SPSS Version 21) computer program and the differences in all parameters between diabetic and non-diabetic rats were analyzed by a one-way analysis of variables (ANOVA). The comparison between groups was done using Duncan test. A change was considered statistically significant when P<0.05.

The experiments were carried out with the approval of the ethic committee of Hawler Medical University/college of Medicine.

Effect of Ramipril, Irbesartan, and Aliskiren on the blood pressure and heart rate of diabetic rats
In alloxan-induced diabetic rats, a significant high elevation in blood pressure was seen when compared to the normal control group, Table 1. The heart rate of diabetic rats was moderately higher than that of the normal control. A significant reduction in blood pressure was observed following oral 10 mg/kg administration of all the angiotensin inhibitors (Ramipril, Irbesartan, and Aliskiren) when compared to the diabetic group. Table (1).

Ramipril and aliskiren treated group had a significant reduction in their heart rate, while irbesartan caused non-significant changes when compared to the diabetic group.

Table 1: The effects of 10 mg/kg of angiotensin inhibitors on the blood pressure & heart rate of the diabetic rats

* Similar letters indicate no significant differences.
* Different letters indicate significant differences at P < 0.05.

Effect of angiotensin inhibitors on the renal function of diabetic rats
The urine flow of the diabetic rats was significantly higher than the normal control group. Aliskiren caused a significant reduction in the urine flow when compared to the diabetic rats, while ramipril, and irbesartan produced a non-significant reduction in the urine flow when compared with both groups. While the glomerular filtration rate (GFR) of diabetic rats was found to be significantly lower than normal rats. Angiotensin inhibitors (Ramipril, Irbesartan, & Aliskiren) induced a significant improvement in the GFR when compared to the diabetic group Table (2).

In alloxan-induced diabetic rats there was a marked elevation in albuminuria when compared to the control animals. Daily oral administration of angiotensin inhibitors for 21 days caused a significant reduction in albumin excreted through urine when compared to the diabetic group.

Table 2: The effects of 10 mg/kg of angiotensin inhibitors on the urine flow, GFR, and albuminuria of the diabetic rats

* Similar letters indicate no significant differences.
* Different letters indicate significant differences at P < 0.05.

The effect of different angiotensin inhibitors on Na+ concentration in the urine, were non-significantly reduced in comparison to the diabetic animals, although the urinary Na+ concentration did not return to the normal value. Table (3). The Irbesartan treated rats did not show a significant improvement in Na+ excretion rate, while Ramipril and Aliskiren treated rats induced a significant reduction in Na+ excretion rate. As shown in Table (3) there was a significant reduction in Na+ serum concentration level of angiotensin inhibitors treated rats when compared to the diabetic rats. In comparison to the diabetic rats, the percentage of Na+ reabsorption in the angiotensin inhibitors treatment groups were non-significantly reduced. Table (3).

Table 3: Effects of angiotensin inhibitors on the renal excretion of Na+ of the diabetic rats

* Similar letters indicate no significant differences.
* Different letters indicate significant differences at P < 0.05.

Effect of angiotensin inhibitors on the renal excretion of K+ of the diabetic rats
Following the induction of diabetes by alloxan, there was a reduction in K+ urine concentration accompanied by an increase in the urinary potassium excretion rate. There was a significant elevation in K+ urine concentration in the groups which received different angiotensin inhibitors in comparison with diabetic group.

The angiotensin inhibitor treated rats showed a significant decrease in the K+ excretion rate in comparison to the diabetic rats, albeit not reaching the normal range. The serum concentration of K+ was increased significantly in diabetic and treated rats with angiotensin inhibitors when compared to the control group. Table (4).

Table 4: Effects of different angiotensin inhibitors on the renal excretion of K+ of the diabetic rats

* Similar letters indicate no significant differences.
* Different letters indicate significant differences at P < 0.05.

Effect of angiotensin inhibitors on the biochemical parameters (blood glucose, serum urea, & serum creatinine) of the diabetic rats
Following the treatment of diabetic animals with angiotensin inhibitors Ramipril, Irbesartan, and Aliskiren at a dose of 10 mg/kg for 21 days, a significant reduction in the blood glucose and serum urea were noticed when compared to the diabetic group. The ramipril, irbesartan, and aliskiren did not significantly change the serum creatinine in comparison to the diabetic rats. Table (5).

Table 5: Effect of angiotensin inhibitors on the biochemical parameters of the diabetic rats

* Different letters indicate significant differences at P < 0.05.

Several randomized trials have shown that improved glycemic control in both type 1 and 2 diabetic patients decreases the risk of diabetic nephropathy and other complications. Although significant improvement in the treatment of diabetic nephropathy has occurred over the past 25 years, as a result, pharmacological inhibition of the RAS has been proposed as a key strategy in reducing kidney damage beyond the predicted effects as a result of blood pressure reduction. (19, 20, 21).

In diabetic rats, a definite and elevated blood pressure was seen when compared to the normal control group, while the heart rate of diabetic rats was moderately higher than that of the normal group. The result obtained from experiments on rats through detecting the effect of (Ramipril, Irbesartan, and Aliskiren) on blood pressure and heart rate, showed that there was a statistically significant decrease in blood pressure with a non-significant decrease in heart rate. Ramipril and irbesartan were better than aliskiren in decreasing Blood pressure. The hypotensive effect of different angiotensin inhibitors may be explained by the vasodilating effects of ACEI on the glomerular efferent arterioles, where it prevents the Ang-II formation (22). Inhibition of angiotensin lowers systemic vascular resistance and blood pressure; this is not surprising when the renal vessels are exceptionally sensitive to the vasoconstrictor actions of angiotensin II (23). Angiotensin inhibitor increases renal blood flow without increasing GFR; thus reducing the filtration fraction. Both the afferent and efferent arterioles are dilated as well as causing systemic arteriolar dilatation. ACEI increases the compliance of large arteries, which contributes to systolic pressure reduction (24).

The urine flow of the diabetic rats was significantly higher than the normal control group, while the glomerular filtration rate (GFR) of diabetic rats was found to be significantly lower than in the normal rats. In the present study, the result obtained from the experiment on rats for detecting the effect of different angiotensin inhibitors (Ramipril, Irbesartan, and Aliskiren) on urine flow and glomerular filtration rate, showed a significant improvement in the urine flow and GFR. Both ramipril and irbesartan had a superior renoprotective effect than that of aliskiren. The renal protection effect of different angiotensin inhibitors may be explained by ACEI probably attenuating the progression of renal insufficiency in patients with a variety of nondiabetic nephropathies, and may arrest the decline in GFR even in patients with severe renal disease (25, 26, 27). Normally, GFR is slightly reduced by angiotensin II; however, during renal artery hypotension, the effects of angiotensin II on the efferent arteriole predominate, leading to increased renal blood flow, hence increasing GFR. Therefore, blockade of the renin-angiotensin system may cause acute renal failure in patients with bilateral renal artery stenosis and in patients with unilateral stenosis who have only a single kidney (7). Angiotensin II variably influences GFR via several mechanisms such as constricting the afferent arterioles, which reduces intra-glomerular pressure and GFR, or by contracting the mesangial cells, which decreases the capillary surface area within the available glomerulus which subsequently leads to decrease GFR, and it could be due to constricting effect on the efferent arterioles, which increases intra-glomerular pressure which increases GFR (28, 29).

The result of this experiment is in agreement with a study by Weidmann et al (1995) who concluded that GFR is better preserved in ACEI treated groups (30). Furthermore, Lebovitz et al (1996) (31) declared that enalapril prevented falling in GFR in hypertensive patients. However, the result of the present study does not agree with Kasiske et al (1993) who found that ACEI is more superior to B blockers in decreasing GFR among diabetic patients (32). Parving and Rossing (1994)) concluded that lisinopril has no significant effects in decreasing GFR in diabetic nephropathic patients 33 . Moreover, Barnett et al (2005) showed that the rate of GFR decrease was equivalent in both enalapril and telmisartan treated patients (34).

In the present study a marked elevation in albuminuria was seen in diabetic rats. Increased glomerular pressure associated with diabetes can be enhanced by aII-mediated constriction of the glomerular arterioles, causing further elevation in microcirculatory pressure within the glomerulus, and leading to excretion of albumin, and thus to the development of microalbuminuria and proteinuria (35). While after the oral administration of (ramipril, irbesartan and aliskiren) a significant reduction in urinary albumin was noticed. In addition, both ramipril and irbesartan better reduced the albumin in the urine. This result is in agreement with studies conducted by Chan et al (2000), and Jerums et al (2001) who reported that treatment with ACEI & aliskiren decrease albumin excretion rate (36, 37).

Studies in streptozotocin diabetic rats have demonstrated that both AIIB and ACEi blocked the development of hypertension and significantly decreased albuminuria 38. Whereas in the DETAIL (Diabetic exposed to telmisartam and enalapril) study there were no significant differences in albumin excretion rate in both enalapril and telmisartan treated patients (34).

Several mechanisms have been suggested for antiproteinuric effects of RAS inhibition. First, it may be related to a reduction in intraglomerular blood pressure independently of systemic blood pressure by vasodilatation preferentially of the postglomerular arterioles (39). Second, RAS inhibition may improve the charge and size selectivity of the glomerular membrane (40), which may be related, in part, to reduced loss of glomerular nephrin, which has been suggested to play a central role in the function of the glomerular filtration barrier (41).
The administration of both ramipril and aliskiren induced a significant change in Na+ excretion rate, while irbesartan did not show any significant improvement in diabetic rats. On the other hand the effect of ramipril, irbesartan, and aliskiren on the Na+ concentration in the urine was non-significant.

There was a non - significant reduction in the level of serum Na+ concentration in all treated rats. The percentage of Na+ reabsorption in the angiotensin inhibitor treatment group was non - significantly reduced but still lower than the control group.

However, it has been suggested that angiotensin II can act presynaptically to potentiate the release of norepinephrine from sympathetic nerve terminals and thus enhancing the renin release from the renal tubule (42, 43). The rise in sodium level in diabetic rats could be related to the fact that angiotensin II stimulates the zona glomerulosa of the adrenal cortex to increase the synthesis and secretion of aldosterone which acts on the distal and collecting tubules to cause retention of Na+ and excretion of K+ and H+. The stimulant effect of angiotensin II on aldosterone synthesis and release is enhanced under conditions of hyponatremia or hyperkalemia and reduced when concentrations of Na+ and K+ in plasma are altered in the opposite directions (44). Very low concentrations of angiotensin II stimulate Na+/H+ exchange in the proximal tubule; an effect that increases Na+, Cl-, and angiotensin II may reduce Na+ excretion in part by diminishing medullary blood flow.
In the present study, the significant decrease in the K+ excretion rate accompanied by a non-significant rise in the serum K+ level were detected following administration of ramipril, irbesartan, and aliskiren. These effects could be explained by suppression of endogenous aldosterone and worsening kidney function (45). Despite some reduction in the concentration of aldosterone, significant K+ retention is rarely encountered in patients with normal renal function who have not been taking other drugs that cause K+ retention (46).

In this study, the level of blood glucose in diabetic rats was significantly increased when compared to the control group. This result in accordance with studies of Bilal et al (1998), Azuma et al (2007) who suggested that elevated blood glucose levels in diabetes are caused by a defect in production and or secretion of the hormone insulin (47, 48). In this study the elevation of blood glucose level indicate that this effect is caused by the direct influence of alloxan on pancreatic beta cells.

Treatment with angiotensin inhibitors Ramipril, Irbesartan, and Aliskiren caused a significant reduction in the blood glucose level of diabetic rats. However, aliskiren was better in reducing blood glucose than the other two drugs.

In this study the hypoglycemic effect of angiotensin inhibitors may be due to increased rate of glucose uptake into the cell, and to improve glucose metabolism (49, 50). Clarification of the mechanism of this effect is in progress. In patients with essential hypertension, plasma insulin and blood glucose levels increase together, indicating reduced insulin sensitivity. Because of this, even without the onset of diabetes, a latent rise in blood glucose level may be seen. Angiotensin receptor blocker and ACEI can improve glucose metabolism via blocking the inhibitory effect of angiotensin II on insulin signal transmission (51, 52). On the other hand, the vasodilatory action of angiotensin inhibitor may increase the access of insulin and glucose to the skeletal muscle tissue, the main site of insulin- mediated removal of glucose 53. The result of hypoglycemic effects of ramipril, irbesartan, and aliskiren in the diabetic rats is in agreement with other studies done by Jacobsen et al (2003), Lau et al (2004), Dizaye and Rashid (2009) (54, 55, 56). Subsequent studies indicated that telmisartan also suppressed the new onset of diabetes (53).

In the present study ramiprl, irbesartan, and aliskiren did not significantly decrease serum creatinine, and this effect was compatible with the finding of Lewis et al (2001) who suggested that the level of serum creatinine was not significantly changed by irbesartan in nephropathic patients (21). Along the same lines, are the data from other studies which showed that serum creatinine levels did not significantly change in the ACEI group (57, 58). However, the result of this study was in disagreement with the study of Brenner et al (2001), who found that there was 25% reduction for doubling the serum creatinine level after using ACEi (20).

Administration of different angiotensin inhibitors (ramipril, irbesartan, and aliskiren) could slow the progression of nephropathy in alloxan induced diabetic rats. Both ramipril and irbesartan had the same renoprotective effects for most parameters.

1. Cooper WO, Hernandez-Diaz S, Arbogast PG, Dudley JA, Dyer S, Gideon PS, et al. Major congenital malformations after first-trimester exposure to ACE inhibitors. New England Journal of Medicine. 2006;354(23):2443-51.
2. Caramori ML, Mauer M. Diabetes and nephropathy. Current opinion in nephrology and hypertension. 2003;12(3):273-82.
3- Koike H. New pharmacologic aspects of CS-866, the newest angiotensin II receptor antagonist. The American journal of cardiology. 2001;87(8):33-6.
4- Koike H, Sada T, Mizuno M. In vitro and in vivo pharmacology of olmesartan medoxomil, an angiotensin II type AT1 receptor antagonist. Journal of hypertension Supplement: official journal of the International Society of Hypertension. 2001;19(1):S3-14.
5- Mizuno M, Sada T, Kato M, Koike H. Renoprotective effects of blockade of angiotensin II AT1 receptors in an animal model of type 2 diabetes. Hypertension Research. 2002;25(2):271-8.
6- Remuzzi G, Schieppati A, Ruggenenti P. Nephropathy in patients with type 2 diabetes. New England Journal of Medicine. 2002;346(15):1145-51.
7- Jafar TH, Schmid CH, Landa M, Giatras I, Toto R, Remuzzi G, et al. Angiotensin-converting enzyme inhibitors and progression of nondiabetic renal disease: a meta-analysis of patient-level data. Annals of internal medicine. 2001;135 (2):73-87.
8-Brenner G, Stevens C. Pharmacology. Fourth eddition. Saunders, Elsevier publisher: 2013. P. 96.
9- Parving H-H, Lehnert H, Bröchner-Mortensen J, Gomis R, Andersen S, Arner P. The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes. New England Journal of Medicine. 2001;345 (12):870-8.
10- Valderrabano F, Berthoux FC, Jones EH, Mehls O. Report on management of renal failure in Europe, XXV, 1994 end stage renal disease and dialysis report. Population. 1996;52 (65):62.
11- Salvetti A, Mattei P, Sudano I. Renal protection and antihypertensive drugs. Drugs. 1999;57(5):665-93.
12- Wingard DL, Barrett-Connor EL, Scheidt-Nave C, McPhillips JB. Prevalence of cardiovascular and renal complications in older adults with normal or impaired glucose tolerance or NIDDM: a population-based study. Diabetes Care. 1993;16(7):1022-5.
13- Mann JF, Gerstein HC, Pogue J, Bosch J, Yusuf S. Renal insufficiency as a predictor of cardiovascular outcomes and the impact of ramipril: the HOPE randomized trial. Annals of internal medicine. 2001;134(8):629-36.
14-Lacourcière Y, Bélanger A, Godin C, Hallé J-P, Ross S, Wright N, et al. Long-term comparison of losartan and enalapril on kidney function in hypertensive type 2 diabetics with early nephropathy. Kidney international. 2000;58(2):762-9.
15- Mogensen CE, Neldam S, Tikkanen I, Oren S, Viskoper R, Watts RW, et al. Randomised controlled trial of dual blockade of renin-angiotensin system in patients with hypertension, microalbuminuria, and non-insulin dependent diabetes: the candesartan and lisinopril microalbuminuria (CALM) study. Bmj. 2000;321(7274):1440-4.
16- Sultan AH, Dizaye KF, Banna HB. Histological, Immunocytochemical and Biochemical study of the effect of Adiantum capillus on alloxan induced diabetic rats.
17- Kumar GPS, Arulselvan P, Kumar DS, Subramanian SP. Anti-diabetic activity of fruits of Terminalia chebula on streptozotocin induced diabetic rats. Journal of health science. 2006;52(3):283-91.
18-Nair R, Shukla V, Chanda S. Assessment of Polyalthia longifolia var. pendula for hypoglycemic and antihyperglycemic activity. J Clin Diagn Res. 2007;1:1-3.
19-Rao RP, Jain A, Srinivasan B. Dual therapy versus monotherapy of trandolapril and telmisartan on diabetic nephropathy in experimentally induced type 2 diabetes mellitus rats. Journal of Renin-Angiotensin-Aldosterone System. 2011;12(3):169-75.
20- Brenner BM, Cooper ME, de Zeeuw D, Keane WF, Mitch WE, Parving H-H, et al. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. New England Journal of Medicine. 2001;345(12):861-9.
21- Lewis EJ, Hunsicker LG, Clarke WR, Berl T, Pohl MA, Lewis JB, et al. Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes. New England Journal of Medicine. 2001;345(12):851-60.
22- Lansang MC, Price DA, Laffel LM, Osei SY, Fisher ND, Erani D, et al. Renal vascular responses to captopril and to candesartan in patients with type 1 diabetes mellitus. Kidney international. 2001;59(4):1432-8
23- Brunton LL, Chabner B, Knollmann BC. Goodman & Gilman's the pharmacological basis of therapeutics: McGraw-Hill Medical New York; 2011. 806
24- Cherney DZ, Scholey JW, Jiang S, Har R, Lai V, Sochett EB, et al. The effect of direct renin inhibition alone and in combination with ACE inhibition on endothelial function, arterial stiffness, and renal function in type 1 diabetes. Diabetes care. 2012;35(11):2324-30.
25- Maschio G, Alberti D, Janin G, Locatelli F, Mann JF, Motolese M, et al. Effect of the angiotensin-converting-enzyme inhibitor benazepril on the progression of chronic renal insufficiency. New England Journal of Medicine. 1996;334(15):939-45.
26- Kshirsagar AV, Joy MS, Hogan SL, Falk RJ, Colindres RE. Effect of ACE inhibitors in diabetic and nondiabetic chronic renal disease: a systematic overview of randomized placebo-controlled trials. American journal of kidney diseases. 2000;35(4):695-707.
27- Praga M, Gutiérrez E, González E, Morales E, Hernández E. Treatment of IgA nephropathy with ACE inhibitors: a randomized and controlled trial. Journal of the American Society of Nephrology. 2003;14(6):1578-83.
28- Pelayo JC, Ziegler MG, Blantz RC. Angiotensin II in adrenergic-induced alterations in glomerular hemodynamics. American Journal of Physiology-Renal Physiology. 1984;247(5):F799-F807.
29- Rang HP, Ritter JM, Flower RJ, Henderson G. Rang & Dale's Pharmacology: With student consult online access: Elsevier Health Sciences; 2014. P=358
30- Weidmann P, Schneider M, Böhlen L. Therapeutic efficacy of different antihypertensive drugs in human diabetic nephropathy: an updated meta-analysis. Nephrology, dialysis, transplantation. 1995;10:39-45.
31- Lebovitz HE, Wiegmann TB, Cnaan A, Shahinfar S, Sica DA, Broadstone V, et al. Renal protective effects of enalapril in hypertensive NIDDM: role of baseline albuminuria. Kidney International Supplement. 1994(45).
32- Kasiske BL, Kalil RS, Ma JZ, Liao M, Keane WF. Effect of antihypertensive therapy on the kidney in patients with diabetes: a meta-regression analysis. Annals of internal medicine. 1993;118(2):129-38.
33- Parving H-H, Rossing P. The use of antihypertensive agents in prevention and treatment of diabetic nephropathy. Current opinion in nephrology and hypertension. 1994;3(3):292-300.
34- Barnett AH, Bain SC, Bouter P, Karlberg B, Madsbad S, Jervell J, et al. Angiotensin-receptor blockade versus converting-enzyme inhibition in type 2 diabetes and nephropathy. New England Journal of Medicine. 2004;351(19):1952-61.
35- Kunz R, Friedrich C, Wolbers M, Mann JF. Meta-analysis: effect of monotherapy and combination therapy with inhibitors of the renin-angiotensin system on proteinuria in renal disease. Annals of internal medicine. 2008;148(1):30-48.
36- Chan JC, Ko GT, Leung DH, Cheung RC, Cheung MY, So W-Y, et al. Long-term effects of angiotensin-converting enzyme inhibition and metabolic control in hypertensive type 2 diabetic patients. Kidney international. 2000;57(2):590-600.
37- Jerums G, Allen TJ, Campbell DJ, Cooper ME, Gilbert RE, Hammond JJ, et al. Long-term comparison between perindopril and nifedipine in normotensive patients with type 1 diabetes and microalbuminuria. American journal of kidney diseases. 2001;37(5):890-9.
38- Sano T, Kawamura T, Matsumae H, Sasaki H, Nakayama M, Hara T, et al. Effects of long-term enalapril treatment on persistent microalbuminuria in well-controlled hypertensive and normotensive NIDDM patients. Diabetes Care. 1994;17(5):420-4.
39- Imanishi M, Yoshioka K, Konishi Y, Okumura M, Okada N, Sato T, et al. Glomerular hypertension as one cause of albuminuria in type II diabetic patients. Diabetologia. 1999;42(8):999-1005.
40-Andersen S, Tarnow L, Rossing P, Hansen BV, Parving H-H. Renoprotective effects of angiotensin II receptor blockade in type 1 diabetic patients with diabetic nephropathy. Kidney international. 2000;57(2):601-6.
41- Bonnet F, Cooper ME, Kawachi H, Allen TJ, Boner G, Cao Z. Irbesartan normalises the deficiency in glomerular nephrin expression in a model of diabetes and hypertension. Diabetologia. 2001;44(7):874-7.
42- Suzuki Y, Matsumura Y, Egi Y, Morimoto S. Effects of Losartan, a nonpeptide angiotensin II receptor antagonist, on norepinephrine overflow and antidiuresis induced by stimulation of renal nerves in anesthetized dogs. Journal of Pharmacology and Experimental Therapeutics. 1992;263(3):956-63.
43- Takishita S, Muratani H, Sesoko S, Teruya H, Tozawa M, Fukiyama K, et al. Short-term effects of angiotensin II blockade on renal blood flow and sympathetic activity in awake rats. Hypertension. 1994;24(4):445-50.
44- Bautista R, Manning R, Martinez F, del Carmen Avila-Casado M, Soto V, Medina A, et al. Angiotensin II-dependent increased expression of Na+-glucose cotransporter in hypertension. American Journal of Physiology-Renal Physiology. 2004;286(1):F127-F33.
45- Weir R, McMurray JJ, Puu M, Solomon SD, Olofsson B, Granger CB, et al. Efficacy and tolerability of adding an angiotensin receptor blocker in patients with heart failure already receiving an angiotensin-converting inhibitor plus aldosterone antagonist, with or without a beta blocker. Findings from the Candesartan in Heart failure: Assessment of Reduction in Mortality and morbidity (CHARM)-Added trial. European journal of heart failure. 2008;10(2):157-63.
46- Yusuf S, Teo KK, Pogue J. Telmisartan, ramipril, or both in patients at high risk for vascular events. N Engl J Med. 2008;2008(358):1547-59.
47- ÜSTÜNDA B, Mehmet Ç, ÖZERCAN IH, NAZIROGLU M, ILHAN N. Angiotensin Converting Enzyme Activity in the Serum, Lung, Liver and Kidney in Streptozotocin-Induced Diabetic Rats and Diabetic Nephropathy. Turkish Journal of Medical Sciences. 1998;28(3):231-8.
48- Azuma K, Minami Y, Ippoushi K, Terao J. Lowering effects of onion intake on oxidative stress biomarkers in streptozotocin-induced diabetic rats. Journal of clinical biochemistry and nutrition. 2007;40(2):131-40.
49- Folli F, Kahn CR, Hansen H, Bouchie JL, Feener EP. Angiotensin II inhibits insulin signaling in aortic smooth muscle cells at multiple levels. A potential role for serine phosphorylation in insulin/angiotensin II crosstalk. Journal of Clinical Investigation. 1997;100(9):2158.
50-- Folli F, Saad M, Velloso L, Hansen H, Carandente O, Feener E, et al. Crosstalk between insulin and angiotensin II signalling systems. Experimental and clinical endocrinology & diabetes. 1999;107(02):133-9.
51- Furuhashi M, Ura N, Higashiura K, Murakami H, Tanaka M, Moniwa N, et al. Blockade of the renin-angiotensin system increases adiponectin concentrations in patients with essential hypertension. Hypertension. 2003;42(1):76-81.
52- Fujimoto M, Masuzaki H, Tanaka T, Yasue S, Tomita T, Okazawa K, et al. An angiotensin II AT 1 receptor antagonist, telmisartan augments glucose uptake and GLUT4 protein expression in 3T3-L1 adipocytes. FEBS letters. 2004;576(3):492-7.
53- Ridker PM, Gaboury CL, Conlin PR, Seely EW, Williams GH, Vaughan DE. Stimulation of plasminogen activator inhibitor in vivo by infusion of angiotensin II. Evidence of a potential interaction between the renin-angiotensin system and fibrinolytic function. Circulation. 1993;87(6):1969-73.
54- Jacobsen P, Andersen S, Jensen BR, Parving H-H. Additive effect of ACE inhibition and angiotensin II receptor blockade in type I diabetic patients with diabetic nephropathy. Journal of the American Society of Nephrology. 2003;14(4):992-9.
55- Lau T, Carlsson P-O, Leung P. Evidence for a local angiotensin-generating system and dose-dependent inhibition of glucose-stimulated insulin release by angiotensin II in isolated pancreatic islets. Diabetologia. 2004;47(2):240-8.
56- Dizaye K, Rashid BZ. Effects of Ramipril on glycosylated hemoglobin and liver function tests in hypertensive patients. MIDDLE EAST JOURNAL OF INTERNAL MEDICINE. 2009.
57- Ravid M, Savin H, Jutrin I, Bental T, Katz B, Lishner M. Long-term stabilizing effect of angiotensin-converting enzyme inhibition on plasma creatinine and on proteinuria in normotensive type II diabetic patients. Annals of Internal Medicine. 1993;118(8):577-81.
58- Mann JF, Gerstein HC, Yi Q-L, Franke J, Lonn EM, Hoogwerf BJ, et al. Progression of renal insufficiency in type 2 diabetes with and without microalbuminuria: results of the Heart Outcomes and Prevention Evaluation (HOPE) randomized study. American Journal of Kidney Diseases. 2003;42(5):936-42.