Sylvia Berman

The effect of sitagliptin versus glibenclamide on arterial stiffness, blood pressure, lipids, and inflammation in type 2 diabetes mellitus patients.

AIM This study evaluated the effect of sitagliptin versus glibenclamide on arterial stiffness, blood pressure, lipid profile, oxidative stress, and high-sensitivity C-reactive protein (hsCRP) in type 2 diabetes mellitus patients. SUBJECTS AND METHODS Forty diabetes patients, inadequately controlled on metformin, were randomly assigned to either sitagliptin (100 mg/day) or glibenclamide (5 mg/day) for 3 months. Following a 1-month washout period, a crossover switch from glibenclamide to sitagliptin and vice versa was performed for an additional 3 months. Arterial stiffness, 24-h ambulatory blood pressure monitoring, lipids, hsCRP, glycated hemoglobin, fasting glucose, STAT-8-isoprostane (a measure of oxidative stress), body mass index (BMI), and waist circumference were measured at baseline and at 3 months with each of the study drugs. RESULTS Thirty-four patients completed the study. Glibenclamide had a better glucose-lowering effect than sitagliptin, but this was associated with more hypoglycemic events. BMI increased following glibenclamide treatment, whereas sitagliptin proved weight-neutral. Mean BMI gain was +0.5±1.0 kg/m(2) for glibenclamide versus -0.01±0.9 kg/m(2) for sitagliptin (P<0.001). Triglyceride levels significantly dropped following sitagliptin, although they remained unaltered after glibenclamide treatment. Mean triglyceride decrease was -18.4±45 mg/mL after sitagliptin but -0.2±57 mg/dL following glibenclamide treatment (P=0.018). There was no change in low-density lipoprotein, high-density lipoprotein, arterial stiffness, blood pressure monitoring, hsCRP, or STAT-8-isoprostane with each of the study drugs. CONCLUSIONS Sitagliptin, but not glibenclamide, demonstrated a significant beneficial effect on BMI and triglyceride levels. However, arterial stiffness, blood pressure, oxidative stress, and inflammatory status were not significantly affected by adding sitagliptin or glibenclamide to metformin-treated type 2 diabetes patients.

Effect of captopril treatment on recuperation from ischemia/reperfusion-induced acute renal injury

BACKGROUND Ischemia/reperfusion triggers acute kidney injury (AKI), mainly via aggravating hypoxia, oxidative stress, inflammation and renin-angiotensin system (RAS) activation. We investigated the role of angiotensin-converting enzyme (ACE) inhibition on the progression of AKI in a rat model of ischemia/reperfusion. METHODS Ninety-nine Sprague-Dawley rats were subjected to 1 h ischemia/reperfusion and/or left unilateral nephrectomy, with concurrent intraperitoneal implantation of Alzet pump. Via this pump, they were continuously infused with captopril 0.5 mg/kg/day, captopril 2 mg/kg/day or saline. The rats were sacrificed following 24, 48 or 168 h. Blood samples, 24-h urine collections and kidneys were allocated, to evaluate renal function, angiotensin-II, nitric oxide (NO), apoptosis, hypoxia, oxidative stress and inflammation. RESULTS Serum creatinine and cystatin-C significantly increased in ischemic rats, coinciding with histopathologic intrarenal damage, decreased NO, augmented angiotensin-II, interleukin (IL)-6, IL-10, transforming growth factor-beta. At the acute reperfusion stage, captopril prevented excessive angiotensin-II synthesis, ameliorated renal dysfunction, inhibited intrarenal inflammation and improved histopathologic findings. Most of the renoprotective effects of captopril were limited predominantly to acute reperfusion stage. Concurrently, captopril significantly decreased NO availability, exacerbated intrarenal hypoxia and augmented oxidative stress. CONCLUSIONS At the acute stage of renal ischemia/reperfusion-induced AKI, ACE inhibition substantially contributed to the amelioration of acute injury by improving renal function, inhibiting systemic and intrarenal angiotensin-II, attenuating intrarenal inflammation and preserving renal tissue structure. Later on, at the post-reperfusion stage, most of the beneficial effects of captopril administration on the recuperating post-ischemic kidney were no longer evident. Concurrently, ACE inhibition exacerbated intrarenal hypoxia and accelerated oxidative stress, indicating that renal adaptation to some consequences of ischemia does require bioavailability of RAS components.

Contrast media augmented apoptosis of cultured renal mesangial, tubular, epithelial, endothelial, and hepatic cells.

Peer A, Averbukh Z, Berman S, et al. Contrast Media Augmented Apoptosis of Cultured Renal Mesangial, Tubular, Epithelial, Endothelial, and Hepatic Cells. Invest Radiol 2003;38:177–182. Rationale and Objective. Nephrotoxicity of contrast media, resulting in apoptosis and acute necrosis of tubular cells, is well documented. No studies concerning mesangial cells apoptosis have been published yet. Aim Apoptosis of cultured mesangial, tubular, and hepatic cell lines was investigated following exposure to different contrast media. Methods. Apoptosis was assessed by TUNEL assay and verified by Mayer Hematoxylin staining. Results. Iopromide, Ioxaglate, and Ioxatalamate induced apoptosis in all cell cultures at final concentrations ranged from 0.1% to 10.0%. However, only 1% to 10% Iomeprol elicited a significant apoptosis. Moreover, at 10% concentration, Iomeprol induced significantly less apoptosis than Iopromide, Ioxaglate, or Ioxatalamate. Conclusions. First, Iomeprol, which has a different physico-chemical properties, proved to be less proapoptotic compared with other contrast compounds. Second, all types of cells similarly respond by apoptosis to contrast media induced injury. However, apoptosis of mesangial cells might generate additional deleterious effects in vivo.

PPAR-γ Activation Inhibits Angiotensin II Synthesis, Apoptosis, and Proliferation of Mesangial Cells from Spontaneously Hypertensive Rats

Background/Aim: The angiotensin II level is elevated in subjects genetically prone to develop hypertension, triggering renal hypercellularity, cytokine production, and matrix deposition. Angiotensin-converting enzyme inhibition and/or angiotensin II type 1 receptor blockade attenuate renal damage. Rosiglitazone, a peroxisome proliferator-activated receptor gamma agonist possessing antihypertensive and anti-inflammatory properties, was demonstrated to provide better renal protection than angiotensin-converting enzyme inhibitors. We studied the effects of in vivo peroxisome proliferator-activated receptor gamma activation by rosiglitazone on angiotensin II synthesis, proliferation, and apoptosis of mesangial cells of spontaneously hypertensive rats versus normotensive Sprague-Dawley rats. Methods: The animals consumed either a high-sodium diet (8% Na) or a normal-sodium diet (0.5% Na). Half of each group received rosiglitazone at 5 mg/kg/day. After 3 weeks, all rats were sacrificed and the mesangial cells isolated and cultured. Angiotensin II was assessed by radioimmunoassay, apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, and cell proliferation by [3H]thymidine incorporation. Results: Only the spontaneously hypertensive rats which consumed the high-sodium diet developed hypertension (185 ± 6 mm Hg vs. basal 128 ± 5 mm Hg; p = 0.0007) which was attenuated by rosiglitazone (to 126 ± 4 mm Hg; p = 0.34). Angiotensin II synthesis, proliferation, and apoptosis were exaggerated in mesangial cell cultures from Sprague-Dawley rats and, more so, spontaneously hypertensive rats fed the high-sodium diet, but were inhibited in cultures from rosiglitazone-treated animals. Conclusions: Peroxisome proliferator-activated receptor gamma activation, in addition to lowering blood pressure, suppresses angiotensin II synthesis and downregulates angiotensin-II-mediated proliferation and apoptosis of mesangial cells. In the context of hypertension-induced renal damage, this would mean that the renoprotective role of rosiglitazone extends beyond glycemic and lipidemic control.

Application of normobaric hyperoxia therapy for amelioration of haemorrhagic shock-induced acute renal failure*

BACKGROUND Hypoxia resultant from haemorrhagic shock is the primary cause of kidney damage. Application of normobaric hyperoxia therapy (NHT) is an acceptable treatment for acute haemorrhagic shock. We investigated the effect of NHT on amelioration of haemorrhagic shock-induced rat renal failure. METHODS Twenty-four Sprague-Dawley rats were subjected to gradual blood withdrawal/reperfusion, followed by 12-h, 24-h or 48-h NHT. Verification/monitoring of intrarenal hypoxia was performed using Hypoxyprobe-TM-1. Subsequently, cystatin C, urea and creatinine were assessed in serum by a Hitachi autoanalyser, and NO, 3-nitro-tyrosine, STAT-8-isoprostane and NF-kB in renal medullae and cortices by specific ELISAs. RESULTS In rats subjected to haemorrhagic shock, 12- to 48-h NHT significantly reduced intrarenal Hypoxyprobe-TM-1 stained areas and attenuated augmentation of urea, creatinine and cystatin C. Haemorrhagic shock resulted in a 10-fold drop of intrarenal NO availability. 12-h and 24-h, but not 48-h, NHT significantly increased cortical/medullar NO synthesis, the latter, however, not approaching the pre-shock values. Significant shock-induced accumulation of STAT-8-isoprostane and 3-nitro-tyrosine was further exacerbated by NHT. Haemorrhagic shock activated NF-kB in ischaemic tissues, which was not attenuated by NHT. CONCLUSIONS (1) 12- to 48-h NHT decreased intrarenal hypoxia signs and ameliorated deterioration of renal functions in a rat model of haemorrhagic shock-induced renal failure. (2) 12- to 24 h NHT improved bioavailability of NO in cortices/medullae of kidneys recuperating from haemorrhagic shock. (3) If any anti-inflammatory activities were stimulated by NHT, they would not be mediated via the NF-kB pathway. (4) Despite NHT-associated elevation of reactive oxygen species (ROS), early oxygen supply proved mandatory for effective recuperation of ischaemic kidney from detrimental consequences of haemorrhagic shock.

Differential Effects of N-Acetylcysteine, Theophylline or Bicarbonate on Contrast-Induced Rat Renal Vasoconstriction

Background: Vasoconstriction and reactive oxygen species (ROS) accumulation following contrast media (CM) injection are the key factors triggering CM-induced nephropathy. We compared the effects of N-acetylcysteine (NAC), theophylline or sodium bicarbonate on intrarenal vasoconstriction and ROS generation in a rat model of CM-induced nephropathy. Methods: Following a 3-day dehydration, Sprague-Dawley rats received CM (Telebrix) or sham ‘CM’ injection of 0.9% saline. Part of them received NAC, theophylline or bicarbonate prior to CM. Medullar renal blood flow was estimated by laser Doppler. The animals were sacrificed 1, 15 or 30 min after the respective treatments, their kidneys allocated and intrarenal STAT-8 isoprostane, PGE2 and NO assessed. Results: Vasoconstriction was significantly attenuated by NAC. Theophylline only mildly attenuated the perfusion drop at 15 min, and was ineffective following 30 min. Unlike theophylline or bicarbonate, NAC significantly augmented intrarenal PGE2. NAC, theophylline but not bicarbonate, gradually increased intrarenal NO. In all experimental variables, CM-induced ROS accumulation, represented by STAT-8 isoprostane estimation, progressed undisturbed. Conclusions: (1) CM-induced intrarenal vasoconstriction was efficiently prohibited by NAC but not bicarbonate or theophylline; (2) the vasodilatory effect of NAC was mediated via increased PGE2 synthesis, and (3) ROS accumulation was a primary renal response to CM-induced injury, not affected by any pharmacologic manipulations.

Enhanced angiotensin II production by renal mesangium is responsible for apoptosis/proliferation of endothelial and epithelial cells in a model of malignant hypertension.

Objective The systemic renin–angiotensin system (RAS) plays a crucial role in the pathogenesis of malignant hypertension. However, the intrarenal RAS might be at least equally important. We investigated the relationship between intrarenal RAS and mesangial, epithelial and endothelial cell proliferation/apoptosis in a model of malignant hypertension. Methods Cultured murine mesangial cells were subjected to 160 mmHg hydrostatic pressure for 1 h. Angiotensin II was assessed by radio-immunoassay (RIA); pro-metalloproteinase-1 (pro-MMP-1) by enzyme-linked immunosorbent assay (ELISA); hydrogen peroxide (H2O2) by photocolorimetric assay, apoptosis by terminal dUTP (2-deoxyuridine 5′-triphosphate) nick-end labelling (TUNEL), p53 by western blot and proliferation by [3H]thymidine incorporation, with or without angiotensin II and/or angiotensin II type 1/angiotensin II type 2 (AT-1/AT-2) receptor blockers. Endothelial and epithelial cells were similarly treated, and the same parameters evaluated. Further, untreated cells of both lines were cultured in conditioned medium of mesangial cells exposed to pressure. Their proliferation, apoptosis and angiotensin II production were also assessed. Results High hydrostatic pressure increased angiotensin II production by mesangial cells, coinciding with augmented apoptosis and proliferation. Co-stimulation with exogenous angiotensin II amplified both effects. Pressure per se evoked no response in endothelial/epithelial cells, while exogenous angiotensin II stimulated proliferation and apoptosis. No augmentation of p53 expression was evident. These effects were abolished by anti-angiotensin-II peptide, saralasine and losartan, but not by PD123319. Incubation of untreated cells in medium of mesangium subjected to pressure, augmented proliferation and apoptosis. No significant changes were noticed in pro-MMP or H2O2. Conclusions Mesangium plays a deleterious role in the pathogenesis of malignant hypertension. High hydrostatic pressure stimulates angiotensin II synthesis by mesangial cells. The latter is responsible for hypercellularity and apoptotic death of mesangial, endothelial and epithelial cells. In this model, exaggerated apoptosis and proliferation are mediated via the angiotensin II pathway independently of p53 gene activation.

N-Acetylcysteine Ameliorates Amphotericin-Induced Nephropathy in Rats

Background: Amphotericin B may cause acute reduction in renal function. N-acetylcysteine (NAC) has a renoprotective activity in several nephrotoxic renal insults, but its effect on amphotericin-induced renal failure has not been investigated yet. Methods: Acute renal failure was induced in 30 Sprague-Dawley rats by a single intraperitoneal injection of amphotericin B (50 mg/kg). NAC (10 mg/kg) in isotonic saline or isotonic saline alone were administered daily for 4 days, starting 1 day before the amphotericin B injection. Glomerular filtration rate (GFR) was assessed using 99m-technetium diethylene triaminepentaacetic acid. Before and following amphotericin B administration, a 24-hour urine collection was performed for sodium, potassium and magnesium determination. The kidneys were preserved for pathologic examination. Results: Amphotericin B induced a significant decrease of GFR in both groups. Four days after amphotericin injection the GFR in the NAC-treated group was significantly higher than in the control group (0.62 ± 0.20 vs. 0.46 ± 0.14 ml/min, p = 0.042). Histologic signs of acute tubular necrosis were attenuated in the NAC-treated group. There were no significant differences between the groups in sodium, potassium and magnesium urine excretion after amphotericin injection. Conclusions: NAC treatment exerted a renoprotective effect on deterioration of GFR in a rat model of amphotericin-induced renal failure. No functional protection on tubular function, as obviated by similar polyuria and urine losses of potassium and magnesium in both groups, was observed.

Hyperglycaemia, inflammation, RAS activation: three culprits to blame for acute kidney injury emerging in healthy rats during general anaesthesia.

Aim:  Major surgery under general anaesthesia might evoke acute kidney injury (AKI), sometimes culminating in end stage renal disease. We investigated the roles of hyperglycaemia, inflammation and renin‐angiotensin system (RAS) activation in induction of AKI following anaesthesia by different anaesthetic drugs and/or regimens.

Magnesium administration may improve heart rate variability in patients with heart failure

BACKGROUND AND AIM Intracellular magnesium (icMg) depletion may coexist with normomagnesemia. Mg deficiency (serum and/or intracellular) and decreased heart rate variability (HRV) are common in heart failure (HF). Since both are predictors of poor prognosis, it was of interest to evaluate the effect of Mg supplementation on HRV in patients with HF. METHODS AND RESULTS We investigated the effect of Mg administration on HRV in normomagnesemic patients with systolic HF. HRV, serum Mg and icMg were determined before and after 5-week 300 mg/day Mg citrate treatment in 16 patients (group 1). The control group included 16 Mg-non-treated HF patients (group 2). HRV was determined by a non-linear dynamics analysis, derived from the chaos theory, which calculates HRV-correlation dimension (HRV-CD). After 5 weeks, serum Mg (mmol/l) increased more significantly in group 1 (from 0.78+/-0.04 to 0.89+/-0.06, p<0.001), than in group 2 (from 0.79+/-0.07 to 0.84+/-0.06, p=0.042). IcMg and HRV-CD increased significantly only in group 1 (from 59+/-7 to 66+/-9 mmol/g cell protein, p=0.025, and from 3.47+/-0.42 to 3.94+/-0.36, p<0.001, respectively). In group 2, the differences in the respective parameters were 63+/-12 to 66+/-9 mmol/g cell protein (p=0.7) and 3.59+/-0.42 to 3.55+/-0.4 (p=0.8). CONCLUSION Mg administration to normomagnesemic patients with systolic HF increases serum Mg, icMg and HRV-CD. Increasing of HRV by Mg supplementation may prove beneficial to HF patients.