Effects of empagliflozin on progression of chronic kidney disease: a prespecified secondary analysis from the empa-kidney trial

BACKGROUND

Sodium-glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and included individuals aged 18 years or older with an estimated glomerular filtration rate (eGFR) of 20 to less than 45 mL/min per 1·73 m2, or with an eGFR of 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher. We explored the effects of 10 mg oral empagliflozin once daily versus placebo on the annualised rate of change in estimated glomerular filtration rate (eGFR slope), a tertiary outcome. We studied the acute slope (from randomisation to 2 months) and chronic slope (from 2 months onwards) separately, using shared parameter models to estimate the latter. Analyses were done in all randomly assigned participants by intention to treat. EMPA-KIDNEY is registered at ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and then followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroups of eGFR included 2282 (34·5%) participants with an eGFR of less than 30 mL/min per 1·73 m2, 2928 (44·3%) with an eGFR of 30 to less than 45 mL/min per 1·73 m2, and 1399 (21·2%) with an eGFR 45 mL/min per 1·73 m2 or higher. Prespecified subgroups of uACR included 1328 (20·1%) with a uACR of less than 30 mg/g, 1864 (28·2%) with a uACR of 30 to 300 mg/g, and 3417 (51·7%) with a uACR of more than 300 mg/g. Overall, allocation to empagliflozin caused an acute 2·12 mL/min per 1·73 m2 (95% CI 1·83-2·41) reduction in eGFR, equivalent to a 6% (5-6) dip in the first 2 months. After this, it halved the chronic slope from -2·75 to -1·37 mL/min per 1·73 m2 per year (relative difference 50%, 95% CI 42-58). The absolute and relative benefits of empagliflozin on the magnitude of the chronic slope varied significantly depending on diabetes status and baseline levels of eGFR and uACR. In particular, the absolute difference in chronic slopes was lower in patients with lower baseline uACR, but because this group progressed more slowly than those with higher uACR, this translated to a larger relative difference in chronic slopes in this group (86% [36-136] reduction in the chronic slope among those with baseline uACR <30 mg/g compared with a 29% [19-38] reduction for those with baseline uACR ≥2000 mg/g; ptrend<0·0001).

INTERPRETATION

Empagliflozin slowed the rate of progression of chronic kidney disease among all types of participant in the EMPA-KIDNEY trial, including those with little albuminuria. Albuminuria alone should not be used to determine whether to treat with an SGLT2 inhibitor.

FUNDING

Boehringer Ingelheim and Eli Lilly.

Impact of primary kidney disease on the effects of empagliflozin in patients with chronic kidney disease: secondary analyses of the EMPA-KIDNEY trial

BACKGROUND

The EMPA-KIDNEY trial showed that empagliflozin reduced the risk of the primary composite outcome of kidney disease progression or cardiovascular death in patients with chronic kidney disease mainly through slowing progression. We aimed to assess how effects of empagliflozin might differ by primary kidney disease across its broad population.

METHODS

EMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA). Patients were eligible if their estimated glomerular filtration rate (eGFR) was 20 to less than 45 mL/min per 1·73 m2, or 45 to less than 90 mL/min per 1·73 m2 with a urinary albumin-to-creatinine ratio (uACR) of 200 mg/g or higher at screening. They were randomly assigned (1:1) to 10 mg oral empagliflozin once daily or matching placebo. Effects on kidney disease progression (defined as a sustained ≥40% eGFR decline from randomisation, end-stage kidney disease, a sustained eGFR below 10 mL/min per 1·73 m2, or death from kidney failure) were assessed using prespecified Cox models, and eGFR slope analyses used shared parameter models. Subgroup comparisons were performed by including relevant interaction terms in models. EMPA-KIDNEY is registered with ClinicalTrials.gov, NCT03594110.

FINDINGS

Between May 15, 2019, and April 16, 2021, 6609 participants were randomly assigned and followed up for a median of 2·0 years (IQR 1·5-2·4). Prespecified subgroupings by primary kidney disease included 2057 (31·1%) participants with diabetic kidney disease, 1669 (25·3%) with glomerular disease, 1445 (21·9%) with hypertensive or renovascular disease, and 1438 (21·8%) with other or unknown causes. Kidney disease progression occurred in 384 (11·6%) of 3304 patients in the empagliflozin group and 504 (15·2%) of 3305 patients in the placebo group (hazard ratio 0·71 [95% CI 0·62-0·81]), with no evidence that the relative effect size varied significantly by primary kidney disease (pheterogeneity=0·62). The between-group difference in chronic eGFR slopes (ie, from 2 months to final follow-up) was 1·37 mL/min per 1·73 m2 per year (95% CI 1·16-1·59), representing a 50% (42-58) reduction in the rate of chronic eGFR decline. This relative effect of empagliflozin on chronic eGFR slope was similar in analyses by different primary kidney diseases, including in explorations by type of glomerular disease and diabetes (p values for heterogeneity all >0·1).

INTERPRETATION

In a broad range of patients with chronic kidney disease at risk of progression, including a wide range of non-diabetic causes of chronic kidney disease, empagliflozin reduced risk of kidney disease progression. Relative effect sizes were broadly similar irrespective of the cause of primary kidney disease, suggesting that SGLT2 inhibitors should be part of a standard of care to minimise risk of kidney failure in chronic kidney disease.

FUNDING

Boehringer Ingelheim, Eli Lilly, and UK Medical Research Council.

DVO Leitlinie 2017 zur Prophylaxe, Diagnostik und Therapie der Osteoporose bei postmenopausalen Frauen und Männern

Diese DVO Leitlinien, die in erster Linie für Allgemeinmediziner und Spezialisten für Knochenerkrankungen bestimmt sind, sollten von allen im klinischen und ambulanten Bereich tätigen medizinischen Fachkräften angewendet werden. Ziel der Leitlinie ist die Verbesserung der Diagnose, Prävention und Behandlung von Osteoporose und der Folgen der Erkrankung auf der Grundlage evidenzbasierter Medizin.

Klare Empfehlungen, welche Patienten zu diagnostizieren und behandeln sind (basierend auf Risikofaktoren [einschließlich sekundärer Osteoporose]) sowie Primär-, Sekundär- oder Tertiärprävention werden dargestellt, mit dem Schwerpunkt auf der postmenopausalen Osteoporose und der Osteoporose bei Männern.

Die Identifizierung von Patienten mit einem hohen Risiko für Frakturen wird hervorgehoben, und spezifische Schwellenwerte für die Intervention sind definiert (20 % Hüftfrakturrisiko innerhalb von 10 Jahren diagnostischer Schwellenwert, 30 % Hüftfrakturrisiko innerhalb von 10 Jahren therapeutische Schwelle). Die Diagnose von Osteoporose basiert auf der Anamnese des Patienten, der körperlichen Untersuchung, dem Funktionstest (z. B. Timed Up and Go Test), konventionellen Röntgenaufnahmen der Brust- und Lendenwirbelsäule und der Bestimmung der Knochenmineraldichte (BMD) durch das DXA Verfahren.

Die Anamnese ist entscheidend für die Abschätzung des Frakturrisikos auf der Grundlage von 40 wissenschaftlich überprüften Risikofaktoren, die das Frakturrisiko mindestens verdoppeln (z. B. Begleiterkrankungen, Hüftfrakturen in der Familie, prävalente Frakturen an jedem Ort, Lebensstil, Anwendung von Medikamenten, körperliche Aktivität und Stürze). Röntgenaufnahmen der Brust- und Lendenwirbelsäule sind wichtig, um prävalente Wirbelkörperfrakturen zu erkennen. Beim Fehlen eines großen Traumas kann jede Fraktur bei Erwachsenen über dem Alter von 50 Jahren eine Diagnose von Osteoporose nahelegen, mit dem höchsten Risiko für eine nachfolgende Fraktur innerhalb einer kurzen Zeit nach der ersten Fraktur. BMD-Messungen mit DXA sind wichtig, um das individuelle Frakturrisiko besser abschätzen zu können. Eine grundlegende Laboruntersuchung ist obligatorisch, um verschiedene Formen der sekundären Osteoporose ausschließen zu können.

Der DVO-Patientenfindungs-Algorithmus basiert auf dem Geschlecht, Alter, Knochenmineraldichte und vorbestehenden Frakturen als wichtigste Informationen. Die Indikation für eine aktive anti-osteoporotische Therapie kann durch multiple Risikofaktoren modifiziert und verfeinert werden. Dieser Algorithmus wurde seit dem Richtlinien-Update 2006 verwendet und wurde entsprechend der internationalen Literatur zu Risikofaktoren für Osteoporose und osteoporotische Frakturen aktualisiert und angepasst.

Die Behandlung der Osteoporose enthält viele Therapiepfeiler. Zusammen mit Empfehlungen für Bewegung, Physiotherapie und Sturzprävention sowie Ernährung (z. B. Calcium, Vit. D), werden pharmakologische Behandlungen basierend auf evidenzbasierter Medizin empfohlen. Die aktiven Anti-Osteoporose-Medikamente müssen für die Indikation postmenopausale Osteoporose und männliche Osteoporose in Deutschland, Österreich und der Schweiz zugelassen sein. Das Management und die Vorbeugung von häufigen oder seltenen Nebenwirkungen aufgrund von Anti-Osteoporose-Behandlungen, die in der klinischen Praxis angewendet werden, werden ebenfalls detailliert behandelt.

Cinacalcet treatment of primary hyperparathyroidism

Although parathyroidectomy remains the only curative approach to most primary hyperparathyroidism cases, medical treatment with cinacalcet HCl has been proven to be a reasonable alternative for several patient subgroups. Cinacalcet almost always controls hypercalcemia and hypophosphatemia sufficiently. PTH levels are lowered, and cognitive parameters improve. While an increase in bone mineral density DEXA scan scores was not demonstrated in cinacalcet trials, the same applies to more than half of patients after parathyroidectomy. Medical therapy should be first choice in patients with hyperplasia in all glands rather than an isolated adenoma (10-15%), patients with persisting HPT following unsuccessful surgery or inoperable cases due to comorbidities, and patients detected in lab screens for hypercalcemia before developing symptoms who should be treated early but are usually reluctant to undergo surgery. Nephrolithiasis was not found to occur more frequently in cinacalcet trial groups, but urine calcium excretion as one major risk factor of this complication of primary HPT may increase on cinacalcet. Patients carrying the rs1042636 polymorphism of the calcium-sensing receptor gene respond more sensitively to cinacalcet and have a higher risk of calcium stone formation. Cinacalcet is usually administered twice daily but three or four doses per day should be discussed to mimic the beneficial pulsatile PTH-pattern.

[Is there a correlation between C-reactive protein and calcification inhibitors with cardiovascular parameters and risk factors in hemodialysis patients?]

BACKGROUND AND OBJECTIVE

Patients on hemodialysis exhibit a drastically increased cardiovascular mortality. Inflammation, hyperphosphatemia and lack of calcification inhibitors are uremia-associated risk factors for vascular calcification. Functional and morphological vascular parameters are used to assess cardiovascular risk. The aim of our study was to analyse the relation between pulse wave velocity (PWV) and intima-media-thickness (IMT) with calcification inhibitors.

METHODS

A cohort of 97 hemodialysis patients was consecutively selected and investigated (age 56 +/- 9 years). Carotid-femoral PWV, carotid IMT, left ventricular ejection fraction and septum thickness were determined. These parameters were correlated with serum levels of CRP and calcification inhibitors (fetuin-A and osteoprotegerin [OPG]).

RESULTS

Both PWV and IMT showed a positive correlation with age and systolic blood pressure and a negative correlation with Kt/V (dialysis efficiency). Additionally, fetuin-A was negatively associated with CRP and positively with cholesterol and triglycerides. Serum levels of the calcification inhibitors fetuin-A and OPG were not correlated to PWV or IMT.

CONCLUSION

The lack of correlation of calcification inhibitors with PWV and IMT means that functional and morphological measurements of vascular properties can not necessarily be replaced by analysing "biomarkers".

Sticky platelet syndrome: an underrecognized cause of graft dysfunction and thromboembolic complications in renal transplant recipients

Sticky platelet syndrome (SPS) leads to hyperaggregabilty of platelets in response to physiologic stimuli. In this report we describe three patients with clinical symptoms of SPS after renal transplantation. The first patient developed an infarction of her transplant kidney with additional, subsequent renal microinfarctions. The second patient suffered multiple strokes and deep vein thrombosis with episodes of pulmonary embolism and ischemic bowel disease due to colonic microinfarctions. The third patient experienced a long episode of unexplained respiratory and graft dysfunction immediately after transplantation until therapy for SPS was initiated, at which point symptoms resolved quickly. Kidney transplant recipients with SPS may be at increased risk of developing thrombosis, given that most immunosuppressive drugs are known to induce either endothelial cell damage or augment platelet aggregation. All patients awaiting renal transplantation should be screened for a history of thrombosis and, if appropriate, tested for SPS. Affected patients should receive dose-adjusted acetylsalicylic acid.

Novel insights into vascular calcification

Vascular calcification is not just a hallmark of uremic arterio- and atherosclerosis, but also a significant cardiovascular risk factor in patients with chronic kidney disease. In contrast to the previous assumption that vascular calcification predominantly occurs by passive precipitation of calcium and phosphate ions, recent research led to the insight that extraosseous calcification is a highly regulated process. High serum phosphate and calcium levels may induce a process of osteogenic 'bone-like' differentiation of vascular smooth muscle cells, while deficiencies of calcification inhibitors or a disturbed balance towards calcification inducers may have a relevant pathophysiological influence on the initiation and progression of calcified lesions. This overview summarizes some of the best explored novel risk factors for disturbances of calcium and phosphate homeostasis and points to the integral role of hyperphosphatemia as a modifiable key trigger in calcification processes.

Association of serum fetuin-A levels with mortality in dialysis patients

Calcifying atherosclerosis is an active process, which is controlled by calcification inhibitors and inducers. Fetuin-A, an acute phase glycoprotein, is one of the more powerful circulating inhibitors of hydroxyapatite formation. A prospective multicenter cohort study was initiated to include both hemodialysis (HD) and peritoneal dialysis (PD) patients in an evaluation of the association of serum fetuin-A levels with both cardiovascular (CV) and non-CV mortality. An increase in the serum fetuin-A concentration of 0.1 g/l was associated with a significant reduction in all-cause mortality of 13%. There was a significant 17% reduction in non-CV mortality and a near significant reduction in CV mortality. This association of fetuin-A and mortality rates was comparable in both HD and PD patients even when corrected for factors, including but not limited to age, gender, primary kidney disease, C-reactive protein levels, and nutritional status. We conclude that serum fetuin-A concentrations may be a general predictor of mortality in dialysis patients.

Bisphosphonates prevent experimental vascular calcification: Treat the bone to cure the vessels?

Bisphosphonates are inhibitors of bone resorption that are widely used to treat osteoporosis. Price and colleagues demonstrate that ibandronate suppressed the development of uremia-related vascular calcification in rats. These findings extend the link between bone remodeling and vascular calcification to the context of chronic renal failure, opening perspectives toward novel therapeutic strategies.

Kidney failure and the gut: p-cresol and the dangers from within

Previously, uremic toxins were sometimes regarded as a large, mysterious, but also anonymous group of factors potentially contributing to morbidity and mortality in end-stage renal disease. By identifying the protein-bound solute p-cresol as a risk factor for mortality in dialysis patients, Bammens and colleagues for the first time present evidence of a clinically relevant uremic toxin in relation to clinical outcome.

Implantation of a new access device for hemodialysis (Dialock): initial experience in 5 patients

PURPOSE

A new hemodialysis access port system was implanted.

METHODS

The Dialock consists of a port-like double-valve, implanted subcutaneously below the clavicle, which is attached to two catheters, placed in the right atrium via the jugular vein. The device has been implanted in 5 patients (4 female, 1 male).

RESULTS

In all 5 patients the implantation of the catheters and the port was technically successful. Total average duration of dialysis was 3.6 months. Two patients developed a port pocket hematoma 10-14 days post implantation, one of them required surgical revision. One port was explanted due to septicemia, whereas a port infection was not confirmed. One patient showed a thrombotic occlusion of both catheter tips 8 days after implantation, fixed by catheter exchange. Another patient presented with slight migration of the port catheters, which was managed by refixation of the port within the pocket. Beside these complications, the devices were working well.

CONCLUSION

The Dialock system offers an interesting alternative to external catheters for hemodialysis. With respect to the complications it deserves further studies to determine its future role in the field of vascular access.

Imaging techniques in the diagnosis of dialysis-related amyloidosis

beta(2)-microglobulin amyloidosis (A beta(2)M) is a major determinant of morbidity in patients on dialysis treatment. Symptoms of A beta(2)M amyloid are mainly related to (peri-)articular amyloid deposition. Imaging techniques [i.e., joint ultrasonography, X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) findings], as well as conventional bone scans, are helpful in the screening of local lesions but are relatively nonspecific and/or not sensitive enough. Scintigraphic techniques using radiolabeled serum amyloid P component (SAP) or the radiolabeled A beta(2)M precursor protein, beta(2)M, generate more specific results. A beta(2)M deposits have been visualized in several long-term hemodialysis patients by using (123)I-labeled SAP. However, this scan did not show tracer accumulation in some frequently involved sites such as hips or shoulders, and frequently labeled the spleen, which is usually spared from A beta(2)M deposits. Improvements in technical sensitivity and specificity could be achieved by scanning with (131)I-labeled beta(2)M: this technique detected tracer accumulations corresponding to the typical distribution pattern of A beta(2)M. Further, both the radiation exposure and the optical resolution of this latter scan have been refined by substituting (111)In for (131)I. In a final step we generated recombinant human beta(2)M (rh beta(2)M). While (111)In rh beta(2)M again failed to show significant tracer accumulation over joint regions in patients on short-term hemodialysis without evidence of A beta(2)M, local tracer accumulations similar to those observed with natural, (111)In-labeled beta(2)M could be demonstrated in long-term hemodialysis patients with evidence of A beta(2)M. In conclusion, scintigraphy for A beta(2)M with (111)In-labeled rh beta(2)M provides a homogeneous and safe recombinant protein source and represents a suitable detection method of beta(2)M amyloid deposits in dialysis patients.

beta2-microglobulin-derived amyloidosis: an update

The present review attempts to summarize recent developments in the field of beta2-microglobulin-derived amyloidosis (A(beta2)m amyloidosis) in patients on chronic dialysis therapy. A key factor in the pathogenesis is the uremic retention of the precursor molecule, beta2-microglobulin (beta2m). However, secondary modifications of the molecule such as limited proteolysis, conformational changes, and the formation of advanced glycation end products have also been described. Finally, in order to explain the striking predilection of the disease for synovial and periarticular structures, a role of local predisposing factors within the synovial membrane (for example, of the particular constituents of the extracellular matrix) must also be postulated. With respect to clinical symptomatology, recent data have confirmed that clinically manifest signs of the amyloidosis represent only the tip of the iceberg, since histologically amyloid deposition is much more widespread. Noninvasive diagnosing of the disease has been advanced by technical changes of the beta2m scintigraphy. Finally, there is accumulating evidence that prevention of the disease not only includes the usage of high-flux synthetic membranes for hemodialysis or hemodiafiltration, but that other factors contribute to the clinical manifestations of amyloidosis such as the dialysate composition and its microbacteriological quality. Such factors, which have changed over the last years as part of general improvements in dialysis care, may explain why the prevalence of the amyloidosis appears to decrease.

Fatal cytomegalovirus pneumonia after preemptive antiviral therapy in a renal transplant recipient

Cytomegalovirus (CMV) infections occur with an incidence of up to 70% in renal transplant patients and mortality is low due to effective antiviral drugs. We report here the case of a patient who suffered from an uncommonly severe and therapy-resistant pulmonary CMV infection. During the disease course, CMV-PCR from alveolar cells and lung biopsy material was repeatedly negative despite high CMV pp65 antigenemia. CMV pneumonia was finally diagnosed from a biopsy obtained by open thoracotomy revealing positive CMV immunostaining of lung tissue. The patient died of respiratory failure though double-treatment using both ganciclovir and foscavir was administered. Post mortem, the clinically suspected resistance to both antiviral drugs, but not to cidofovir, could be proven by bioassay testing of in vitro growth responses using viral cultures. CMV pneumonia may thus not be diagnosed by standard PCR techniques in rare cases and may be resistant to the available antiviral therapy. Severe CMV pneumonia may benefit from novel antiviral drugs such as cidofovir, which is currently used in the treatment of CMV retinitis in HIV patients.

Effect of high NaCl diet on spontaneous hypertension in a genetic rat model with reduced nephron number

OBJECTIVE

An inherited reduction in nephron number has been implicated in the development of salt-sensitive hypertension and end stage renal disease. The Munich Wistar Frömter (MWF) rat represents a genetic model with a 30-50% reduction of nephrons compared with normal rats. MWF rats develop spontaneous hypertension and increased urinary albumin excretion (UAE). We addressed the question whether the inherited defect in this model leads to salt-sensitive hypertension.

METHODS

At the age of 6 weeks, we started male and female MWF/Fub rats and salt-resistant Lewis (Lew) reference rats on either a normal NaCl (0.2%) or a high NaCl (8%) diet (n = 8, each group). Systolic blood pressure (SBP) and UAE were measured at 14 weeks.

RESULTS

Under a normal diet, MWF/Fub rats demonstrated significantly elevated SBP compared to Lew rats both in male (165 +/- 2 versus 133 +/- 3 mmHg, P < 0.0001) and female (156 +/- 3 versus 134 +/- 3 mmHg, P < 0.0001) rats. After high NaCl treatment, SBP was significantly higher in both male and female MWF/Fub rats (+55 mmHg and +36 mmHg, P < 0.0001, respectively) compared with MWF/ Fub under a normal diet UAE was also significantly higher in male and female MWF/Fub rats after high NaCl excess (P < 0.0005, respectively). In contrast, both SBP and UAE remained unchanged in response to high NaCl in Lew rats.

CONCLUSIONS

Our findings demonstrate that both the hypertension and UAE are sensitive to high NaCl loading in female and male MWF/Fub rats. Thus, an inborn nephron deficit may lead to salt-sensitive hypertension and renal dysfunction.

The morphology of mesangial cells cultured at high density and in collagen gels

Primary mesangial cells (rat) from monolayer cultures of the 6th to 12th passage and permanent SV40 Mes13 cells were grown at high density in organoid culture at the medium/air interphase. After adaptation to the in vitro conditions, both mesangial cell types developed after 7 days a synthesis apparatus (endoplasmic reticulum, Golgi apparatus) and produced matrix which consisted of Lamina densa-like material, collagenous fibrils and filaments. Unspecific contacts, gap junctions and adhesion belts could be demonstrated in the contact areas. Additionally, some cells exhibited thick bundles of actin filaments. A close resemblance of the mesangial cells in high density culture to those in vivo can, therefore, be stated. Hence, they differentiated with regard to their matrix formation, contraction and contact behaviour and can therefore be used for experimental studies within a short culture period of 7 days. Cell aggregates in monolayer culture and in cultures in collagen gels had not differentiated at this stage.

Acute glomerular upregulation of ornithine decarboxylase is not essential for mesangial cell proliferation and matrix expansion in anti-Thy-1-nephritis

BACKGROUND

Pathways of L-arginine metabolism including nitric oxide, agmatine and polyamine synthesis are upregulated during glomerular inflammation in experimental glomerulonephritis. In anti-Thy-1-glomerulonephritis L-arginine-deficient diets ameliorate the disease course in this model. However, it is unclear which metabolic pathway is affected by this substrate depletion. Since polyamines are important proproliferative molecules, we studied the effect of specific polyamine synthesis blockade in vivo on mesangial cell proliferation and glomerular fibrosis in this model.

METHODS

Anti-Thy-1-glomerulonephritis was induced in male Sprague-Dawley rats by single-bolus injection of monoclonal ER4-antibodies. Rats were treated with difluoromethylornithine (0.5-2% in the drinking water), a selective inhibitor of the rate-limiting enzyme of polyamine synthesis, ornithine decarboxylase (ODC). Mesangial cell proliferation and matrix expansion were evaluated in PAS-stained kidney tissues. Glomerular TGF-beta and biglycan-mRNA-expression were determined by Northern blot analysis and albuminuria was measured using a competitive ELISA. Data were compared to untreated controls.

RESULTS

Though complete inhibition of ODC activity was achieved at any time point, difluoromethlornithine treatment had no significant effect on albuminuria, glomerular matrix protein expression and mesangial cell count in this model.

CONCLUSIONS

The acute upregulation of glomerular ODC activity above baseline in anti-Thy1-glomerulonephritis is not pathophysiologically important for disease development however, biological effects of available polyamine pools cannot be excluded by our study.

Normalizing the expression of nitric oxide synthase by low-dose AT1 receptor antagonism parallels improved vascular morphology in hypertensive rats

In essential hypertension, stroke and kidney damage may result from an impaired interaction of vasoregulatory systems. Stroke-prone spontaneously hypertensive rats (SHRSP) were studied to analyze the effects of a low-dose treatment of the angiotensin II type 1 receptor (AT1) blocker candesartan cilexetil on the expression of nitric oxide synthases (NOS) and on vascular structure. Both treated and untreated SHRSP were kept on a stroke-promoting dietary regimen, and compared with Wistar Kyoto rats (WKY). Early mortality of untreated SHRSP was prevented by the treatment. In untreated SHRSP, cerebral intraparenchymal vessels of the parietal lobe showed lesions of the vascular wall and its periphery, such as proteinaceous deposits, perivascular dilated spaces, increase in phagocytic cells, and decreased actin immunostaining. Renal lesions were more pronounced comprising arteriolar occlusion, extensive loss of actin, increased alpha1(IV) collagen expression, and glomerular sclerotic as well as tubulointerstitial lesions. Beneficial effects of the AT1 blockade were more pronounced in brain than in kidney. Activity profile of NOS showed increased NADPH diaphorase staining in media and endothelium of SHRSP; endothelial NOS3 immunoreactivity was decreased, but instead, inducible NOS2 increased in untreated SHRSP. These changes were largely prevented in the treated group. NOS activity in macula densa cells was unchanged, whereas afferent arteriolar renin levels were increased in untreated SHRSP. Results demonstrate an effective reduction of hypertensive vascular changes with a nonpressor dose of candesartan. A "role switch" of vascular NOS in hypertension from physiologic NOS3 toward deleterious NOS2 is suggested, and its prevention by the AT1 blocker points to an angiotensin II-dependent, nitric oxide-mediated pathway that may impair endothelial function and aggravate defects of the blood-brain barrier and kidney structures.

Nitric oxide in sepsis-syndrome: potential treatment of septic shock by nitric oxide synthase antagonists

Nitric oxide (NO) is an effector molecule with multiple effects on various organ systems. The most prominent physiological actions of NO as a biological mediator include cGMP-dependent vasodilation and cytotoxicity against pathogens in the unspecific immune defense. Sepsis syndrome is a complex disease entity mostly caused by overwhelming bacterial infections. It has a high mortality rate of 40 to 60%. Catecholamine-resistant hypotension and myocardial depression are regarded as major factors contributing to death in septic patients. In septic shock, a pathophysiologically increased NO production occurs due to an excessive induction of the inducible NO synthase (iNOS). Inducible nitric oxide synthase up-regulation is probably caused by bacterial endo- and exotoxins as well as by an increase of circulating pro-inflammatory cytokines. It may be a key factor leading to pronounced vasodilation and myocardial toxicity. Experimental studies have confirmed that NO overproduction causes severe hypotension in septic animals. Treatment with competitive NOS-inhibitors abolishes this hypotension in animals as well as in septic patients. However, their use is complicated by concomitant decreases in cardiac index and oxygen delivery. Conclusive data on mortality in animals and patients with sepsis-syndrome treated by NOS antagonists are not available. This article discusses current concepts concerning the L-arginine/NO system in the pathophysiology of and as a potential therapeutic target in septic shock.

[Nitric oxide, L-arginine and the kidney. Experimental studies of new therapy approaches]

BACKGROUND

Nitric oxide (NO) is a small gaseous molecule with multiple biological effects. NO is produced from the semi-essential amino acid L-arginine by NO synthases (NOS). In the kidney, neuronal NOS (bNOS), which is localized in the macula densa, and endothelial NOS (ecNOS) are involved in the regulation of glomerular hemodynamics. Dysfunction of these enzymes may cause glomerular hypertension and increased intraglomerular platelet aggregation. NO production in high tissue concentrations can be achieved by activation of an inducible NOS isoform (iNOS) and may act as a potent mediator of inflammation in immune-mediated renal diseases. Selective inhibition of iNOS may, therefore, become a novel anti-inflammatory approach in the treatment of glomerulonephritis. Based on experimental data, the potential importance of NO and other metabolites of L-arginine in the pathophysiology and therapy of renal diseases is summarized in this article.

CONCLUSION

Modulation of the renal L-arginine/NO-system represents a promising therapeutic target in the treatment of acute an chronic kidney diseases.