Nitric Oxide Synthesis Is Reduced in Subjects With Type 2 Diabetes and Nephropathy (original) (raw)
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Diabetes, Obesity and Metabolism, 1999
Objective: Nitric oxide (NO) has been proposed to play a signi®cant role in renal function. In addition, NO production has been found to increase in diabetes mellitus. The present study aimed to clarify the mechanism responsible for NO action in renal function in rats with short (10 days) or prolonged periods (8 weeks) of diabetic induction. Methods: Male Wistar rats were induced to develop diabetes mellitus by intraperitoneal injection of streptozotocin (STZ) (65 mg/kg b.w.), whereas the age-matched control rats were given normal saline. After diabetic induction for 10 days or 8 weeks, the experiment was begun. Three consecutive periods of 30 min each, were designed consisting of one control period, the ®rst and the second period of L-arginine or L-NAME or insulin infusion. Mean arterial pressure (MAP) was determined every 15 min. Arterial blood and urine samples were collected to determine the plasma glucose level (PG), glomerular ®ltration rate (GFR), effective renal plasma¯ow (ERPF), urine¯ow rate (V), urinary protein excretion (Upro), fractional excretion of glucose (FEG) and fractional excretion of sodium (FENa) in each period. Results: No signi®cant differences of MAP were apparent between control rats and rats with diabetic induction. L-arginine infusion had no effect whereas L-NAME markedly increased MAP in normal rats and rats after the short period of diabetes induction. Pressor response to L-NAME in rats exposed to the prolonged period of diabetes induction was lower than that of age-matched control rats. During L-NAME infusion, the PG level signi®cantly declined from 394.9 6 13.1± 338.0 6 14.1 mg/dl and from 399.9 6 7.9±354.3 6 18.8 mg/dl in rats after short and prolonged periods of diabetic induction, respectively. GFR signi®cantly increased whereas ERPF slightly increased in diabetic rats. The elevation of GFR could be reversed by L-NAME or insulin infusion but it increased again after simultaneous infusion of insulin and glucose. Increases in V, the Upro and FEG without changes of FENa, were apparent in diabetic rats. Either L-arginine or L-NAME infusion could not reverse elevations of V, Upro and FEG. The rise of both V and Upro was reversed along with the attenuation of high FEG during insulin infusion, and it rose again close to the diabetic level during simultaneous infusion of insulin and glucose. Elevation of GFR, V and Upro appeared along with a rise of the PG level by » 300±350 mg/ dl in diabetic rats. Conclusions: Both NO and hyperglycaemia are involved in modulating renal hyper®ltration in diabetic rats. The elevations of urine¯ow rate and urinary excretion of both protein and glucose would be expected to represent the reduction of renal tubular reabsorption rather than renal hyper®ltration in diabetic rats. NO does not participate in the change of renal tubular function in diabetic rats. There was a parallel change of urine¯ow rate and urinary excretion of protein in diabetic rats. The rise of the PG level itself would account for the increases of GFR, V, Upro and FEG in diabetic rats. Glomerular hyper®ltration, diuresis and proteinuria in diabetic rats are not exhibited until the PG level rises to » 300±350 mg/ dl.
Serum Nitric Oxide as a Biochemical Marker for Diabetic Nephropathy
The realization that diabetic nephropathy is associated with nitric oxide production, create a great incentive to study the level of nitric oxide in diabetic patients and to ascertain its relation with renal impairment. This study aimed to find out whether serum nitric oxide can be considered as a biochemical marker in diabetic nephropathy. A total of 240 subjects (age and sex matched) were enrolled in this study and divided into two groups; diabetic group included 120 diabetic patients (type 1 and type 2) and control group included 120 apparently healthy subjects. Blood samples were collected from all the individuals and laboratory measurements for HbA1c, serum glucose, urea, creatinine and nitric oxide were done. Urine samples were also collected for measurement of microalbuminuria. The patients were classified into three main groups on the basis of blood pressure and nephropathy. Group 1: Diabetic, normotensive patients; Group 2: Diabetic, hypertensive patients; Group 3: Diabetic, hypertensive patients with nephropathy then group 3 was divided into 3 subgroups according to the stage of diabetic nephropathy: Diabetic incipient nephropathy, diabetic overt nephropathy and diabetic with end stage renal disease. The mean value of serum nitric oxide level was significantly lower in diabetic patients when compared to controls (26.1±1.37 µmol/l) for diabetic normotensive patients, (15.2±0.97 µmol/l) for diabetic hypertensive patients, and (17.4±17.5 µmol/l for diabetic hypertensive patients with nephropathy versus 30.6±2.18 µmol/l for healthy controls). The mean serum nitric oxide (50.9±1.89 µmol/l) and glomerular filtration rate (132±13.9 ml/min), were significantly higher in diabetic patients with early nephropathy (Diabetic incipient nephropathy) than diabetic overt nephropathy (10.1±1.32µmol/l and 44.5±6.36 ml/min), and diabetic with end stage renal disease ((4.9±0.63 µmol/l and 10.5±3.16 ml/min). It is evident from the present study that serum nitric oxide is the major biochemical marker for microvascular complications of diabetes mellitus such as nephropathy. The data support the use of raised serum nitric oxide as a marker for early incipient diabetic nephropathy and a low serum nitric oxide for overt and end stage diabetic nephropathy. The decreases being proportionate to the degree of renal impairment.
Diabetes, 2003
Defective endothelium is a key event in the development of atherosclerosis in diabetes: alteration of the L-arginine-nitric oxide (NO) pathway has been suggested. We propose a modeling approach of the L-arginine-NO pathway in vivo in both control and type 2 diabetic subjects based on the intravenous bolus injection of L-[ 15 N]arginine and subsequent noncompartmental and compartmental model analysis of L-[ 15 N] arginine in plasma and [ 15 N]nitrate in the urine. No differences in arginine kinetics were observed between normal subjects and diabetic patients. [ 15 N]nitrates were detectable up to 48 h from the L-15 [N]arginine administration; no differences were found in the tracerto-tracee ratio in each urine collection. However, the NO synthesis in plasma from arginine was lower (P ؍ 0.05 for the noncompartmental and 0.1208 for the compartmental analysis, by Mann-Whitney test) in diabetic patients than in control subjects when expressed both in absolute terms (50% decrease) and as percentage of NO turnover (30% decrease). This new modeling approach of L-arginine-NO pathway provides a detailed picture of arginine kinetics and nitrate metabolism. From our data, it appears that noncomplicated type 2 diabetic patients have a decreased conversion of arginine to NO. Diabetes 52:795-802, 2003 E RESEARCH DESIGN AND METHODS Patients. Six men with type 2 diabetes with no clinical or laboratory evidence of atherosclerotic cardiovascular disease were studied . Current treatments included diet (n ϭ 4) and diet plus sulfonylureas (n ϭ 2). Antidiabetic treatment was stopped 7 days before the study. Informed consent was obtained after the study was approved by the Research Ethics Committee of the University of Padova. Healthy volunteers were recruited from local staff in the hospital and university. All subjects underwent a full health screen. There was no evidence of autonomic neuropathy according to bedside cardiovascular reflexes. Subjects with a urinary albumin excretion rate Ͼ20 g/min were excluded. None had diabetic retinopathy. To rule out preexisting known risk factors, only subjects with no history of hypertension, dyslipidemia, cerebrovascular disease, ischemic heart disease, or peripheral artery disease were recruited. In each diabetic patient, regional atherosclerotic manifestations were excluded by Doppler ultrasound of the carotid arteries and of the femoropoliteal axis arteries. Coronary artery disease was also excluded on the basis of stress dipiridamole echocardiography and by the World Health Organization questionnaire.
Nitric oxide in ischaemic acute renal failure of streptozotocin diabetic rats
Diabetologia, 1996
Changes in nitric oxide (NO) levels were determined in ischaemic acute renal failure in streptozotocin-induced diabetes mellitus rats. Two weeks after streptozotocin administration and immediately after right nephrectomy, the left renal artery was occluded for 60 rain. Similar procedures were carried out in non-diabetic rats. The nitrite (NOz) + nitrate (NO3) levels were measured in plasma and urine. The effects of chronic oral supplementation with Larginine and an NO synthase inhibitor (N-omega-nitro-L-arginine) were also studied in both diabetic and non-diabetic rats before and after renal artery clamping. The rats with diabetic acute renal failure had a much lower creatinine clearance (90 _+ 22 ~tl 9 min-~ 9 100 g body weight-1, p < 0.005), and higher fractional excretion of sodium (FENa)% (10.90+ 4.2, p < 0.001) and protein excretion (2078 + 69 ~tg/ ml creatinine clearance, p < 0.001) compared with the respective values in the non-diabetic groups (163 +_ 30; 1.46 + 86; 453.3 + 31). The plasma and urine NO 2 + NO 3 levels were significantly higher in the untreated diabetic rats compared with the untreated normal rats before ischaemia (p < 0.001). The ischaemic acute renal failure in non-diabetic rats increased the plasma and urinary NO 2 + NO 3 excretion after ischaemia. The urinary excretion of these metabolites decreased significantly and their plasma levels remained unchanged in the ischaemic diabetic rats. The rc-arginine administration resulted in a small but significantly higher creatinine clearance after clamping in the non-diabetic rats. The NO synthase inhibitor caused deterioration in renal function in all ischaemic and non-ischaemic groups. In summary, the greater vulnerability to ischaemia of the diabetic kidney seems to be associated with both impaired response to and impaired production of NO. [Dia
Nitric oxide modulation of renal and cardiac hemodynamics in type 2 diabetes
European Journal of Endocrinology, 2002
Objective: To evaluate endothelial function in type 2 diabetic patients with and without diabetic nephropathy. Methods: We studied the effects of systemic infusion of the nitric oxide (NO) synthase inhibitor N Gmonomethyl-L-arginine (L-NMMA) on cardiovascular and renal hemodynamics in six type 2 diabetic patients with microalbuminuria (D2-MA), six type 2 diabetic patients with normoalbuminuria (D2-NA) and five control subjects. Both type 2 diabetic patients and control subjects had mild arterial hypertension. Results: L-NMMA infusion decreased the cardiac index in all groups. A reduction in glomerular filtration rate (GFR) and an increase in filtration fraction were observed only in controls. Renal plasma flow decreased in controls and D2-NA patients and renal vascular resistance increased in all groups. Conclusions: The effect of L-NMMA on cardiac output was similar in controls and type 2 diabetic patients with and without diabetic nephropathy. In contrast, the effect on GFR was impaired in both diabetic groups, suggesting that glomerular NO homeostasis is altered in type 2 diabetes. Moreover the discrepancy, in diabetic patients, between cardiac and renal effects during L-NMMA infusion suggests that the modulation of glomerular hemodynamics is independent from NO-regulated cardiac output.
The aim of this study was to evaluate whether L-Arginine (L-Arg) supplementation modifies nitric oxide (NO) system and consequently aquaporin-2 (AQP2) expression in the renal outer medulla of streptozotocin-diabetic rats at an early time point after induction of diabetes. Male Wistar rats were divided in four groups: Control, Diabetic, Diabetic treated with LArginine and Control treated with L-Arginine. Nitric oxide synthase (NOS) activity was estimated by [ 14 C] L-citrulline production in homogenates of the renal outer medulla and by NADPH-diaphorase staining in renal outer medullary tubules. Western blot was used to detect the expression of AQP2 and NOS types I and III; real time PCR was used to quantify AQP2 mRNA. The expression of both NOS isoforms, NOS I and NOS III, was decreased in the renal outer medulla of diabetic rats and L-Arg failed to prevent these decreases. However, L-Arg improved NO production, NADPH-diaphorase activity in collecting ducts and other tubular structures, and NOS activity in renal homogenates from diabetic rats. AQP2 protein and mRNA were decreased in the renal outer medulla of diabetic rats and L-Arg administration prevented these decreases. These results suggest that the decreased NOS activity in collecting ducts of the renal outer medulla may cause, at least in part, the decreased expression of AQP2 in this model of diabetes and constitute additional evidence supporting a role for NO in contributing to renal water reabsorption through the modulation of AQP2 expression in this pathological condition. However, we cannot discard that another pathway different from NOS also exists that links L-Arg to AQP2 expression.
Diabetes, 2000
The role of nitric oxide (NO) and free radicals in the development of microvascular disease in type 1 diabetes remains unclear. We have measured NO and isoprostane (a stable marker of in vivo lipid peroxidation) production in 13 type 1 diabetic subjects with normal urinary albumin excretion and 13 healthy volunteers. Whole-body NO synthesis was quantified by measuring the urinary excretion of 15 N-nitrate after the intravenous administration of L-[ 15 N] 2 -arginine. The urinary excretion of the major urinary metabolite of 15-F 2t -isoprostane (8-iso-prostaglandin-F 2␣ ), 2,3-dinor-5,6-dihydro-F 2t -IsoP, was quantified as a marker of in vivo lipid peroxidation. Whole-body NO synthesis was significantly higher in diabetic subjects compared with control subjects (342 vs. 216 nmol 15 N-nitrate/mmol creatinine [95% CI of the difference 45-207], P = 0.005). This increase was not explained by a difference in renal function between the 2 groups. There was no difference in 2,3-dinor-5,6-dihydro-F 2t -IsoP excretion between diabetic subjects and control subjects (44.8 ± 7.8 vs. 41.4 ± 10.0 ng/mmol creatinine, mean ± 95% CI). However, there was an inverse correlation between NO synthesis and free radical activity in subjects with diabetes (r = -0.62, P = 0.012) that was not observed in control subjects (r = 0.37, P = 0.107). We conclude that whole-body NO synthesis is higher in type 1 diabetic subjects with normal urinary albumin excretion than in control subjects. The inverse correlation between isoprostane production and NO synthesis in diabetic subjects is consistent with the hypothesis that NO is being inactivated by reactive oxygen species. NMMA, N G -monomethyl-L-arginine; MANOVA, multivariate analysis of variance; NO, nitric oxide; O 2 -, superoxide; ONOO -, peroxynitrite; UAER, urinary albumin excretion rate.
Role of Renal Nitric Oxide Synthase in Diabetic Kidney Disease during the Chronic Phase of Diabetes
Nephron Physiology, 2006
Background: Several studies have suggested that an early increase in renal nitric oxide (NO) production or activity mediates pathophysiologic and morphologic changes in diabetic nephropathy. To evaluate the role of NO in developing diabetic kidney disease, we studied the NO system in streptozotocin (STZ)-induced diabetic rats for a period of 8 weeks. Methods: Control rats, STZ-induced diabetic rats, and STZ-induced diabetic rats treated with insulin were monitored and sacrificed at 1, 2, and 8 weeks. Urinary cGMP was measured, and the levels and activity of NO synthase (NOS) isoforms in the kidney cortex were determined at specific times by immunoblotting and diaphorase staining. Results: Diabetic rats had increased kidney weight, urinary volume, glucose, sodium and potassium excretion, which was precluded by insulin treatment. Creatinine clearance was increased in the diabetic group and reversed by insulin treatment. Urinary cGMP decreased by 71, 93, and 92% at 1, 2, and 8 weeks of...