Yoram Yagil

Pyridorin in type 2 diabetic nephropathy.

Pyridoxamine dihydrochloride (Pyridorin, NephroGenex) inhibits formation of advanced glycation end products and scavenges reactive oxygen species and toxic carbonyls, but whether these actions translate into renoprotective effects is unknown. In this double-blind, randomized, placebo-controlled trial, we randomly assigned 317 patients with proteinuric type 2 diabetic nephropathy to twice-daily placebo; Pyridorin, 150 mg twice daily; or Pyridorin, 300 mg twice daily, for 52 weeks. At baseline, the mean age ± SD was 63.9±9.5 years, and the mean duration of diabetes was 17.6±8.5 years; the mean serum creatinine level was 2.2±0.6 mg/dl, and the mean protein-to-creatinine ratio was 2973±1932 mg/g. Regarding the primary end point, a statistically significant change in serum creatinine from baseline to 52 weeks was not evident in either Pyridorin group compared with placebo. However, analysis of covariance suggested that the magnitude of the treatment effect differed by baseline renal function. Among patients in the lowest tertile of baseline serum creatinine concentration, treatment with Pyridorin associated with a lower average change in serum creatinine concentration at 52 weeks (0.28, 0.07, and 0.14 mg/dl for placebo, Pyridorin 150 mg, and Pyridorin 300 mg, respectively; P=0.05 for either Pyridorin dose versus placebo); there was no evidence of a significant treatment effect in the middle or upper tertiles. In conclusion, this trial failed to detect an effect of Pyridorin on the progression of serum creatinine at 1 year, although it suggests that patients with less renal impairment might benefit.

Polymorphisms in the carboxy-terminus of the epithelial sodium channel in rat models for hypertension

Objective To investigate whether mutations in the C-terminus of the three subunits of the rat epithelial sodium channel (αβγ-rENaC) contribute to the hypertensive phenotype in five rat models for essential hypertension. Design We sequenced the C-terminal regions of α-, β- and γ-rENaC genes in five different hypertensive rat strains [spontaneously hypertensive rats (SHR), Dahl salt-sensitive (SS/Jr) rats, Milan hypertensive (MHS) rats, Sabra hypertensive (SBH) rats and Lyon hypertensive rats (LHR)] and their normotensive controls [Wistar–Kyoto (WKY) rats, Dahl salt-resistant (SR/Jr) rats, Milan normotensive (MNS) rats, Sabra normotensive (SBN) rats and Lyon normotensive rats (LNR)]. Identified polymorphisms were tested for cosegregation with blood pressure as well as for increased epithelial sodium channel (ENaC) activity. Methods Genomic DNA extracted from hypertensive and normotensive rat strains was amplified by the polymerase chain reaction and polymerase chain reaction fragments were sequenced. Cosegregation analysis was performed to test for correlations between blood pressure and different genotypes. The effects of a polymorphism on ENaC activity were assessed by functional expression in Xenopus laevis oocytes. The chromosomal location of the gene for γ-ENaC was determined by linkage analysis in an F2 (MHS × MNS) population. Results We found no polymorphisms at the C-terminus of α- and β-rENaC in the five rat models tested. We identified two polymorphisms at the C-terminus of the γ-subunit, one leading to an amino acid change. Milan strains (MNS and MHS) were polymorphic for this mutation. By cosegregation analysis we could exclude the possibility that there was a correlation between blood pressure and this polymorphism. Functional expression of the polymorphism caused no increase in ENaC activity assessed by measurement of the amiloride-sensitive sodium current in Xenopus oocytes. The gene for the γ-ENAC was located on rat chromosome 1. Conclusions No polymorphisms at the C-terminus of the three subunits of the epithelial sodium channel cosegregating with blood pressure were detected in five different genetic rat models for hypertension. If an altered ENaC activity contributes to the pathogenesis of hypertension in these rats, it must thus arise from mutations in other parts of the protein, from mutations outside the coding region impairing the proper regulation of one of the subunits or from mutations in an ENaC-associated protein.

Anti–TGF-β1 Antibody Therapy in Patients with Diabetic Nephropathy

TGF-β has been implicated as a major pathogenic factor in diabetic nephropathy. This randomized, double-blind, phase 2 study assessed whether modulating TGF-β1 activity with a TGF-β1-specific, humanized, neutralizing monoclonal antibody (TGF-β1 mAb) is safe and more effective than placebo in slowing renal function loss in patients with diabetic nephropathy on chronic stable renin-angiotensin system inhibitor treatment. We randomized 416 patients aged ≥25 years with type 1 or type 2 diabetes, a serum creatinine (SCr) level of 1.3-3.3 mg/dl for women and 1.5-3.5 mg/dl for men (or eGFR of 20-60 ml/min per 1.73 m2), and a 24-hour urine protein-to-creatinine ratio ≥800 mg/g to TGF-β1 mAb (2-, 10-, or 50-mg monthly subcutaneous dosing for 12 months) or placebo. We assessed a change in SCr from baseline to 12 months as the primary efficacy variable. Although the Data Monitoring Committee did not identify safety issues, we terminated the trial 4 months early for futility on the basis of their recommendation. The placebo group had a mean±SD change in SCr from baseline to end of treatment of 0.33±0.67 mg/dl. Least squares mean percentage change in SCr from baseline to end of treatment did not differ between placebo (14%; 95% confidence interval [95% CI], 9.7% to 18.2%) and TGF-β1 mAb treatments (20% [95% CI, 15.3% to 24.3%], 19% [95% CI, 14.2% to 23.0%], and 19% [95% CI, 14.0% to 23.3%] for 2-, 10-, and 50-mg doses, respectively). Thus, TGF-β1 mAb added to renin-angiotensin system inhibitors did not slow progression of diabetic nephropathy.

The use of standard imaging techniques and their diagnostic value in the workup of renal colic in the setting of intractable flank pain

OBJECTIVESnThis study reviews the rate at which diagnostic imaging techniques are used in patients with intractable flank pain attributed to renal colic who are admitted to the hospital through the emergency room and determines the diagnostic values of plain film of the abdomen {kidney, ureter, bladder [KUB]} and of ultrasonography (US) of the urinary tract, using intravenous urography (IVU) as the gold standard for establishing the presence of a calculus.nnnMETHODSnWe reviewed the medical records of 288 patients who were admitted to our medical center over a period of 5 consecutive years for intractable flank pain, the admission and working diagnosis in all cases being that of renal colic, and we retrieved all data pertaining to their diagnostic evaluation.nnnRESULTSnA total of 265 patients (92%) were subjected to KUB, 158 (55%) to IVU, and 135 (45%) to US of the renal-urinary tract. Two diagnostic imaging techniques were used in the same patient in the following combinations: KUB and IVU in 146 patients (51%), KUB and US in 110 (38%), and IVU and US in 60 (21%). Three imaging techniques (IVU, KUB, and US) were utilized in 54 patients (19%). The sensitivity and specificity of KUB alone were 95% and 65%, respectively, and the positive and negative predictive values were 82% and 88%. The sensitivity of US alone was 93%, its specificity 83%, the positive predictive value 93%, and the negative predictive value 83%. The sensitivity of combined KUB and US (requiring both tests to be positive for diagnosing the presence of a calculus) was 89%, the specificity 100%, the positive predictive value 100%, and the negative predictive value 81%.nnnCONCLUSIONSnOur data indicate that combining US with KUB provides the best diagnostic algorithm that approaches the yield of IVU in excluding the presence of a calculus in the renal-urinary tract in patients who present with intractable flank pain.

Farnesol Blocks the L-Type Ca2+ Channel by Targeting the α1C Subunit

Abstract —We recently demonstrated that farnesol, a 15-carbon isoprenoid, blocks L-type Ca2+ channels in vascular smooth muscle cells. To elucidate farnesol′s mechanism of action, we performed whole-cell and perforated-patch clamp experiments in rat aortic A7r5 cells and in Chinese hamster ovary (CHO) C9 cells expressing smooth muscle Ca2+ channel α1C subunits. Farnesol dose-dependently and voltage-independently inhibited Ba2+ currents in both A7r5 and CHOC9 cells, with similar half-maximal inhibitions at 2.6 and 4.3 mmol/L, respectively ( P =NS). In both cell lines, current inhibition by farnesol was prominent over the whole voltage range without changes in the current-voltage relationship peaks. Neither intracellular infusion of the stable GDP analogue guanosine-5′- O -(2-thiodiphosphate) (100 mmol/L) via the patch pipette nor strong conditioning membrane depolarization prevented the inhibitory effect of farnesol, which indicates G protein–independent inhibition of Ca2+ channels. In an analysis of the steady-state inactivation curve for voltage dependence, farnesol induced a significant, negative shift (≈10 mV) of the potential causing 50% channel inactivation in both cell lines ( P <0.001). In contrast, the steepness factor characterizing the voltage sensitivity of the channels was unaffected. Unlike pharmacological Ca2+ channel blockers, farnesol blocked Ca2+ currents in the resting state: initial block was 63±8% in A7r5 cells and 50±9% in CHOC9 cells at a holding potential of −80 mV. We then gave 500 mg/kg body weight farnesol by gavage to Sabra hypertensive and normotensive rats and found that farnesol reduced blood pressure significantly in the hypertensive strain for at least 48 hours. We conclude that farnesol may represent an endogenous smooth muscle L-type Ca2+ channel antagonist. Because farnesol is active in cells expressing only the pore-forming α1 subunit, the data further suggest that this subunit represents the molecular target for farnesol binding and principal action. Finally, farnesol has a blood pressure–lowering action that may be relevant in vivo.

Early blood pressure-independent cardiac changes in diabetic rats

Cardiac remodeling is a key event in both diabetic and hypertensive heart diseases. In the present study, we investigated early myocardial changes in an animal model, the male Sabra rat model (SBH/y) of salt-induced hypertension-rendered diabetic with streptozotocin. Control non-diabetic (C), diabetic (D), and D or C rats made hypertensive by salt loading (DS or CS) were studied after 6 weeks. M-mode echocardiography revealed that left ventricular internal dimension during diastole and systole were significantly increased in D and DS, but not in C or CS. Concurrently, we found in D and DS an increase in cardiac beta-myosin heavy chain, atrial natriuretic peptide, skeletal alpha-actin mRNA, type III collagen, and transforming growth factor-beta. Myocardial angiotensin-converting enzyme (ACE) mRNA levels were increased while ACE2 mRNA levels were decreased in both D and DS groups. Cardiac angiotensin-1 (AT1) receptor protein levels were unchanged but the levels of phosphorylated (p) ERK and Jun-NH(2)-protein kinase (JNK) were increased in D and DS. In conclusion, we detected early cardiac changes in diabetic rats that were unrelated to hypertension. The increase in ACE, the decrease in ACE2, and the increase in cardiac pERK and pJNK suggest an increase in free angiotensin II and AT1R signaling in the diabetic myocardium as a possible mechanism contributing to cardiac remodeling in diabetes.

Managing hyperphosphatemia in patients with chronic kidney disease on dialysis with ferric citrate: latest evidence and clinical usefulness

Ferric citrate is a novel phosphate binder that allows the simultaneous treatment of hyperphosphatemia and iron deficiency in patients being treated for end-stage renal disease with hemodialysis (HD). Multiple clinical trials in HD patients have uniformly and consistently demonstrated the efficacy of the drug in controlling hyperphosphatemia with a good safety profile, leading the US Food and Drug Administration in 2014 to approve its use for that indication. A concurrent beneficial effect, while using ferric citrate as a phosphate binder, is its salutary effect in HD patients with iron deficiency being treated with an erythropoietin-stimulating agent (ESA) in restoring iron that becomes available for reversing chronic kidney disease (CKD)-related anemia. Ferric citrate has also been shown in several studies to diminish the need for intravenous iron treatment and to reduce the requirement for ESA. Ferric citrate is thus a preferred phosphate binder that helps resolve CKD-related mineral bone disease and iron-deficiency anemia.

Peroxisome Proliferator-Activated Receptor–α: Friend or Foe?

The quest for better understanding for the pathophysiological basis of hypertension and atherosclerosis is ongoing. The complexity of hypertension and atherosclerosis and of the underlying mechanisms is becoming increasingly apparent. The number of candidate genes and molecular pathways that are involved is increasing in parallel. In the present issue of Hypertension, Tordjman et al1 explore the role of the candidate gene, peroxisome proliferator-activated receptor (PPAR)– (reviewed extensively and comprehensively in the Web site dedicated to PPAR: http://ppar.cas.psu.edu/), in the regulation of blood pressure and atherogenesis. The investigators follow up their previous observation that PPARdeficient mice were protected from hypertension and atherosclerosis. 2 They currently report that, in a mouse experimental model of high renin and elevated angiotensin II levels in which the PPAR gene has been knocked out, hypertension and diet-induced atherosclerosis are averted. PPAR is widely distributed in the vasculature, as well as in other tissues and organs. PPAR is a nuclear receptor, one in a family of at least 3 transcription factors that have been connected to cell metabolism and differentiation. The peroxisome, an intracellular organelle that is capable of selfreplicating, is present in all eukaryotic cells that contain enzymes, some of which are oxidative enzymes. The effects of PPAR that we are currently dealing with, affecting blood pressure and atherogenesis, however, are thought not to be related to peroxisome proliferation or activation but rather to other intracellular pathways, some of which have been elucidated, whereas others remain to be clarified.3 PPAR has pleiotropic effects and controls multiple gene targets that involve, among others, fatty acid oxidation, lipid metabolism, and inflammatory/vascular pathways. 3 As such, PPAR activity has been considered until now of benefit to the human organism. In the current study, Tordjman et al1 provide data that suggest that the absence of PPAR, not its presence or activation, is paradoxically associated with beneficial effects, such as prevention of the development of hypertension and attenuation of diet-induced atherosclerosis. Tordjman et al1 used in their study a transgenic mouse strain in which the human renin had been introduced along with the angiotensinogen gene, resulting in high renin–high angiotensin–high aldosterone hypertension. The investigators knocked out in this particular model of hypertension the gene encoding PPAR, resulting in genomic disruption, which led to a significant reduction in active renin and aldosterone and a parallel reduction in the level of blood pressure and cardiac hypertrophy. Additional findings in that study were diminished atherosclerosis at the aortic sinus and a reduction of foam cells in peritoneal macrophages. Fenofibrate, a PPAR activator, effectively increased blood pressure in the parental transgenic strain but did not affect blood pressure in the transgenic knockout strain. The investigators correctly concluded that, based on their findings in their specific mouse model, PPAR appears to fulfill a role in regulating blood pressure and atherogenesis. They further speculated that the mechanism whereby PPAR affects blood pressure involves the renin-angiotensin-aldosterone system. The simplicity and straightforward nature of the study

Adherence rates to ferric citrate as compared to active control in patients with end stage kidney disease on dialysis.

Introduction: Oral phosphate binders are the main stay of treatment of hyperphosphatemia. Adherence rates to ferric citrate, a recently approved phosphate binder, are unknown.

Genomic Research in Rat Models of Kidney Disease

Current understanding of the mechanisms underlying renal disease in humans is incomplete. Consequently, our ability to prevent the occurrence of renal disease or treat kidney disease once it develops is limited. There are objective difficulties in investigating kidney disease directly in humans, leading investigators to resort to experimental animal models that simulate renal disease in humans. Animal models have thus been a tool of major importance in the study of normal renal physiology and have been crucial in shedding light on the complex mechanisms involved in normal kidney function and in our current understanding of and ability to treat renal disease. Among the animal models, rat has been the preferred and most commonly used species for the investigation of renal disease. This chapter reviews what has been achieved over the years, using rat as a tool for the investigation of renal disease in humans, focusing on the contribution of rat genetics and genomics to the elucidation of the mechanisms underlying the pathophysiology of the major types of renal disease, including primary and secondary renal diseases.