Renal sodium handling and nighttime blood pressure.

Blood pressure follows a circadian rhythm with a physiologic 10% to 20% decrease during the night. There is now increasing evidence that a blunted decrease or an increase in nighttime blood pressure is associated with a greater prevalence of target organ damage and a faster disease progression in patients with chronic kidney diseases. Several factors contribute to the changes in nighttime blood pressure including changes in hormonal profiles such as variations in the activity of the renin-angiotensin and the sympathetic nervous systems. Recently, it was hypothesized that the absence of a blood pressure decrease during the nighttime (nondipping) is in fact a pressure-natriuresis mechanism enabling subjects with an impaired capacity to excrete sodium to remain in sodium balance. In this article, we review the clinical and epidemiologic data that tend to support this hypothesis. Moreover, we show that most, if not all, clinical conditions associated with an impaired dipping profile are diseases associated either with a low glomerular filtration rate and/or an impaired ability to excrete sodium. These observations would suggest that renal function, and most importantly the ability to eliminate sodium during the day, is indeed a key determinant of the circadian rhythm of blood pressure.

Heritability, determinants and reference values of renal length: a family-based population study.

OBJECTIVES: In this population-based study, reference values were generated for renal length, and the heritability and factors associated with kidney length were assessed. METHODS: Anthropometric parameters and renal ultrasound measurements were assessed in randomly selected nuclear families of European ancestry (Switzerland). The adjusted narrow sense heritability of kidney size parameters was estimated by maximum likelihood assuming multivariate normality after power transformation. Gender-specific reference centiles were generated for renal length according to body height in the subset of non-diabetic non-obese participants with normal renal function. RESULTS: We included 374 men and 419 women (mean ± SD, age 47 ± 18 and 48 ± 17 years, BMI 26.2 ± 4 and 24.5 ± 5 kg/m(2), respectively) from 205 families. Renal length was 11.4 ± 0.8 cm in men and 10.7 ± 0.8 cm in women; there was no difference between right and left renal length. Body height, weight and estimated glomerular filtration rate (eGFR) were positively associated with renal length, kidney function negatively, age quadratically, whereas gender and hypertension were not. The adjusted heritability estimates of renal length and volume were 47.3 ± 8.5 % and 45.5 ± 8.8 %, respectively (P < 0.001). CONCLUSION: The significant heritability of renal length and volume highlights the familial aggregation of this trait, independently of age and body size. Population-based references for renal length provide a useful guide for clinicians. KEY POINTS: • Renal length and volume are heritable traits, independent of age and size. • Based on a European population, gender-specific reference values/percentiles are provided for renal length. • Renal length correlates positively with body length and weight. • There was no difference between right and left renal lengths in this study. • This negates general teaching that the left kidney is larger and longer.

Expression of SCG10 and stathmin proteins in the rat olfactory system during development and axonal regeneration.

The membrane-associated protein SCG10 is expressed specifically by neuronal cells. Recent experiments have suggested that it promotes neurite outgrowth by increasing microtubule dynamics in growth cones. SCG10 is related to the ubiquitous but neuron-enriched cytosolic protein stathmin. To better understand the role played by SCG10 and stathmin in vivo, we have analyzed the expression and localization of these proteins in both the olfactory epithelium and the olfactory bulb in developing and adult rats, as well as in adult bulbectomized rats. The olfactory epithelium is exceptional in that olfactory receptor neurons constantly regenerate and reinnervate the olfactory bulb throughout animal life-span. SCG10 and stathmin expression in the olfactory receptor neurons was found to be regulated during embryonic and postnatal development and to correlate with neuronal maturation. Whereas SCG10 expression was restricted to immature olfactory receptor neurons (GAP-43-positive, olfactory marker protein-negative), stathmin was also expressed by the basal cells. In the olfactory bulb of postnatal and adult rats, a moderate to strong SCG10 immunoreactivity was present in the olfactory nerve layer, whereas no labeling was detected in the glomerular layer. Olfactory glomeruli also showed no apparent immunoreactivity for several cytoskeletal proteins such as tubulin and microtubule-associated proteins. In unilaterally bulbectomized rats, SCG10 and stathmin were seen to be up-regulated in the regenerating olfactory epithelium at postsurgery stages corresponding to olfactory axon regeneration. Our data strongly suggest that, in vivo, both SCG10 and stathmin may play a role in axonal outgrowth during ontogenesis as well as during axonal regeneration.

Atrial natriuretic peptides: reproducibility of renal effects and response of liver blood flow.

To assess the variability of the response to exogenous atrial natriuretic peptide (ANP), it was infused at the rate of 1 microgram/min for 2 h in 6 salt-loaded normal volunteers under controlled conditions on 2 occasions at an interval of 1 week. The effect on solute excretion and the haemodynamic and endocrine actions were highly reproducible. The constant ANP infusion caused a delayed and prolonged excretion of sodium, chloride and calcium, no change in potassium or phosphate excretion or in glomerular filtration rate but a marked decrease in renal plasma flow. Blood pressure, heart rate and the plasma levels of angiotensin II, aldosterone, arginine vasopressin and plasma renin activity were unaltered. The effect of a 2-h infusion of ANP 0.5 microgram/min or its vehicle on apparent hepatic blood flow (HBF) was also studied in 14 normal volunteers by measuring the indocyanine green clearance. A 21% decrease in HBF was observed in subjects who received the ANP infusion (p less than 0.01 vs vehicle). Thus, ANP infused at a dose that did not lower blood pressure decreased both renal and liver blood flow in normotensive volunteers. The renal and endocrine responses to ANP were reproducible over a 1-week interval.

Renal response to the angiotensin II receptor subtype 1 antagonist irbesartan versus enalapril in hypertensive patients.

OBJECTIVE: To compare the acute and sustained renal hemodynamic effects on hypertensive patients of 100 mg irbesartan and 20 mg enalapril each once daily. PATIENTS: Twenty patients (aged 35-70 years) with uncomplicated, mild-to-moderate essential hypertension and normal serum creatinine levels completed this study. STUDY DESIGN: After random allocation to treatment (n=10 per group), administration schedule (morning or evening) was determined by further random allocation, with crossover of schedules after 6 weeks' therapy. Treatment and administration assignments were double-blind. Twenty-four-hour ambulatory blood pressure was monitored before and after 6 and 12 weeks of therapy. Renal hemodynamics were determined on the first day of drug administration and 12 and 24 h after the last dose during chronic treatment. RESULTS: Administration of each antihypertensive agent induced a renal vasodilatation with no significant change in glomerular filtration rate. However, the time course appeared to differ: irbesartan had no significant acute effect 4 h after the first dose, but during chronic administration a renal vasodilatory response was found 12 and 24 h after the dose; enalapril was effective acutely and 12 h after administration, but no residual effect was found 24 h after the dose. Both antihypertensive agents lowered mean ambulatory blood pressure effectively, with no significant difference between treatments or between administration schedules (morning versus evening). CONCLUSIONS: Irbesartan and enalapril have comparable effects on blood pressure and renal hemodynamics in hypertensive patients with normal renal functioning. However, the time profiles of the renal effects appear to differ, which might be important for long-term renoprotective effects.

Switch to Sirolimus-based immunosuppresion in stable renal transplant recipients

Purpose: Sirolimus (SRL) has been used to replace calcineurin inhibitors (CNI) for various indications including CNI-induced toxicity. The aim of this study was to evaluate the efficacy and safety of switching from CNI to SRL in stable renal transplant recipients (RTR) with low grade proteinuria (<1 g/24 h). Methods and materials: Between 2001 and 2007, 41 patients (20 females, 21 males; mean age 47 ± 13) were switched after a median time post-transplantation of 73.5 months (range 0.2-273.2 months). Indications for switch were CNI nephrotoxicity (39%), thrombotic micro-angiopathy (14.6%), post-transplantation cancer (24.4%), CNI neurotoxicity (7.4%), or others (14.6%). Mean follow-up after SRL switch was 23.8±16.3 months. Mean SRL dosage and through levels were 2.4 ± 1.1 mg/day and 8 ± 2.2 ug/l respectively. Immunosuppressive regiments were SRL + mycophenolate mofetil (MMF) (31.7%), SRL + MMF + prednisone (36.58%), SRL + prednisone (19.51%), SRL + Azathioprine (9.75%), or SRL alone (2.43%). Results: Mean creatinine decreased from 164 to 143 μmol/l (p <0.03), mean estimated glomerular filtration rate (eGFR) increased significantly from 50.13 to 55.01 ml/minute (p <0.00001), mean systolic and diastolic blood pressure decreased from 138 to 132 mm Hg (p <0.03) and from 83 to78 mm Hg (p <0.01), but mean proteinuria increased from 0.21 to 0.63 g/24 h (p <0.001). While mean total cholesterolemia didn't increased significantly from 5.09 to 5.56 mmol/l (p = 0.06). The main complications after SRL switch were dermatitis (19.5%), urinary tract infections (24.4%), ankle edema (13.3%), and transient oral ulcers (20%). Acute rejection after the switch occurred in 7.3% of patients (n = 3), and 2 acute rejections were successfully treated with corticosteroids and 1 did not respond to treatment (not related to switch). SRL had to be discontinued in 17% of patients (2 nephrotic syndromes, 2 severe edema, 1 acute rejection, 1 thrombotic micro-angiopathy, and 1 fever). Conclusion: In conclusion, we found that switching from CNI to SRL in stable RTR was safe and associated with a significant improvement of renal function and blood pressure. Known side-effects of SRL led to drug discontinuation in less than 20% of patients and the acute rejection rate was 7.3%. This experience underlines the importance of patient selection before switching to SRL, in particular regarding preswitch proteinuria.

IV thrombolysis and renal function.

OBJECTIVE: To investigate the association of renal impairment on functional outcome and complications in stroke patients treated with IV thrombolysis (IVT). METHODS: In this observational study, we compared the estimated glomerular filtration rate (GFR) with poor 3-month outcome (modified Rankin Scale scores 3-6), death, and symptomatic intracranial hemorrhage (sICH) based on the criteria of the European Cooperative Acute Stroke Study II trial. Unadjusted and adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Patients without IVT treatment served as a comparison group. RESULTS: Among 4,780 IVT-treated patients, 1,217 (25.5%) had a low GFR (<60 mL/min/1.73 m(2)). A GFR decrease by 10 mL/min/1.73 m(2) increased the risk of poor outcome (OR [95% CI]): (ORunadjusted 1.20 [1.17-1.24]; ORadjusted 1.05 [1.01-1.09]), death (ORunadjusted 1.33 [1.28-1.38]; ORadjusted 1.18 [1.11-1.249]), and sICH (ORunadjusted 1.15 [1.01-1.22]; ORadjusted 1.11 [1.04-1.20]). Low GFR was independently associated with poor 3-month outcome (ORadjusted 1.32 [1.10-1.58]), death (ORadjusted 1.73 [1.39-2.14]), and sICH (ORadjusted 1.64 [1.21-2.23]) compared with normal GFR (60-120 mL/min/1.73 m(2)). Low GFR (ORadjusted 1.64 [1.21-2.23]) and stroke severity (ORadjusted 1.05 [1.03-1.07]) independently determined sICH. Compared with patients who did not receive IVT, treatment with IVT in patients with low GFR was associated with poor outcome (ORadjusted 1.79 [1.41-2.25]), and with favorable outcome in those with normal GFR (ORadjusted 0.77 [0.63-0.94]). CONCLUSION: Renal function significantly modified outcome and complication rates in IVT-treated stroke patients. Lower GFR might be a better risk indicator for sICH than age. A decrease of GFR by 10 mL/min/1.73 m(2) seems to have a similar impact on the risk of death or sICH as a 1-point-higher NIH Stroke Scale score measuring stroke severity.

Antidiabetic drugs and kidney disease - Recommendations of the Swiss Society for Endocrinology and Diabetology.

Patients with diabetes are at risk of early renal function decline. Therefore, kidney function needs monitoring at least once per year. Once the glomerular filtration rate (GFR) is less than 60 ml/min, the pharmacokinetics of antidiabetic drugs may be altered. Sulfonylurea and glinide therapies are associated with a risk of hypoglycaemia which is increased in the presence of renal impairment. Most sulfonylureas must be discontinued once GFR is <60 ml/min. Some glinides may be continued beyond this threshold, in particular repaglinide, which may be used in dialysis patients. In the absence of comorbidities, metformin can be continued at lower doses until a GFR of 45 ml/min, but must be withdrawn in case of dehydration or during the administration of a nephrotoxic drug including dye for radiological investigations. Glitazones may worsen water and sodium retention in patients with renal impairment. The pharmacokinetics of all DPP-IV inhibitors except linagliptin are altered with impaired renal function. Only sitagliptin, saxagliptin and linagliptin may be used in advanced kidney disease, but experience is as yet very limited. GLP-1 agonists are contraindicated in moderate to advanced kidney disease.

Renal responses to three types of renin-angiotensin system blockers in patients with diabetes mellitus on a high-salt diet: a need for higher doses in diabetic patients?

Objective Activation of the renal renin-angiotensin system in patients with diabetes mellitus appears to contribute to the risk of nephropathy. Recently, it has been recognized than an elevation of prorenin in plasma also provides a strong indication of risk of nephropathy. This study was designed to examine renin-angiotensin system control mechanisms in the patient with diabetes mellitus.Methods We enrolled 43 individuals with type 2 diabetes mellitus. All individuals were on a high-salt diet to minimize the contribution of the systemic renin-angiotensin system. After an acute exposure to captopril (25 mg), they were randomized to treatment with either irbesartan (300 mg) or aliskiren (300 mg) for 2 weeks.Results All agents acutely lowered blood pressure and plasma aldosterone, and increased renal plasma flow and glomerular filtration rate. Yet, only captopril and aliskiren acutely increased plasma renin and decreased plasma angiotensin II, whereas irbesartan acutely affected neither renin nor angiotensin II. Plasma renin and angiotensin II subsequently did increase upon chronic irbesartan treatment. When given on day 14, irbesartan and aliskiren again induced the above hemodynamic, renal and adrenal effects, yet without significantly changing plasma renin. Irbesartan at that time did not affect plasma angiotensin II, whereas aliskiren lowered it to almost zero.Conclusion The relative resistance of the renal renin response to acute (irbesartan) and chronic (irbesartan and aliskiren) renin-angiotensin system blockade supports the concept of an activated renal renin-angiotensin system in diabetes, particularly at the level of the juxtaglomerular cell, and implies that diabetic patients might require higher doses of renin-angiotensin system blockers to fully suppress the renal renin-angiotensin system. J Hypertens 29: 2454-2461 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.

Hyperhomocysteinemia is independently associated with albuminuria in the population-based CoLaus study.

Increased serum levels of homocysteine and uric acid have each been associated with cardiovascular risk. We analyzed whether homocysteine and uric acid were associated with glomerular filtration rate (GFR) and albuminuria independently of each other. We also investigated the association of MTHFR polymorphisms related to homocysteine with albuminuria to get further insight into causality. This was a cross-sectional population-based study in Caucasians (n = 5913). Hyperhomocysteinemia was defined as total serum homocysteine ≥ 15 μmol/L. Albuminuria was defined as urinary albumin-to-creatinine ratio > 30 mg/g. Uric acid was associated positively with homocysteine (r = 0.246 in men and r = 0.287 in women, P < 0.001). The prevalence of albuminuria increased across increasing homocysteine categories (from 6.4% to 17.3% in subjects with normal GFR and from 3.5% to 14.5% in those with reduced GFR, P for trend < 0.005). Hyperhomocysteinemia (OR = 2.22, 95% confidence interval: 1.60-3.08, P < 0.001) and elevated serum uric acid (OR = 1.27, 1.08-1.50, per 100 μmol/L, P = 0.004) were significantly associated with albuminuria, independently of hypertension and type 2 diabetes. The 2-fold higher risk of albuminuria associated with hyperhomocysteinemia was similar to the risk associated with hypertension or diabetes. MTHFR alleles related to higher homocysteine were associated with increased risk of albuminuria. In the general adult population, elevated serum homocysteine and uric acid were associated with albuminuria independently of each other and of renal function.

Meta-analysis identifies multiple loci associated with kidney function-related traits in east Asian populations.

Chronic kidney disease (CKD), impairment of kidney function, is a serious public health problem, and the assessment of genetic factors influencing kidney function has substantial clinical relevance. Here, we report a meta-analysis of genome-wide association studies for kidney function-related traits, including 71,149 east Asian individuals from 18 studies in 11 population-, hospital- or family-based cohorts, conducted as part of the Asian Genetic Epidemiology Network (AGEN). Our meta-analysis identified 17 loci newly associated with kidney function-related traits, including the concentrations of blood urea nitrogen, uric acid and serum creatinine and estimated glomerular filtration rate based on serum creatinine levels (eGFRcrea) (P < 5.0 × 10(-8)). We further examined these loci with in silico replication in individuals of European ancestry from the KidneyGen, CKDGen and GUGC consortia, including a combined total of ∼110,347 individuals. We identify pleiotropic associations among these loci with kidney function-related traits and risk of CKD. These findings provide new insights into the genetics of kidney function.

Serum 25-hydroxyvitamin D level and kidney function decline in a Swiss general adult population.

Molecular evidence suggests that levels of vitamin D are associated with kidney function loss. Still, population-based studies are limited and few have considered the potential confounding effect of baseline kidney function. This study evaluated the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline, and incidence of CKD and albuminuria. Baseline (2003-2006) and 5.5-year follow-up data from a Swiss adult general population were used to evaluate the association of serum 25-hydroxyvitamin D with change in eGFR, rapid eGFR decline (annual loss >3 ml/min per 1.73 m(2)), and incidence of CKD and albuminuria. Serum 25-hydroxyvitamin D was measured at baseline using liquid chromatography-tandem mass spectrometry. eGFR and albuminuria were collected at baseline and follow-up. Multivariate linear and logistic regression models were used considering potential confounding factors. Among the 4280 people included in the analysis, the mean±SD annual eGFR change was -0.57±1.78 ml/min per 1.73 m(2), and 287 (6.7%) participants presented rapid eGFR decline. Before adjustment for baseline eGFR, baseline 25-hydroxyvitamin D level was associated with both mean annual eGFR change and risk of rapid eGFR decline, independently of baseline albuminuria. Once adjusted for baseline eGFR, associations were no longer significant. For every 10 ng/ml higher baseline 25-hydroxyvitamin D, the adjusted mean annual eGFR change was -0.005 ml/min per 1.73 m(2) (95% confidence interval, -0.063 to 0.053; P=0.87) and the risk of rapid eGFR decline was null (odds ratio, 0.93; 95% confidence interval, 0.79 to 1.08; P=0.33). Baseline 25-hydroxyvitamin D level was not associated with incidence of CKD or albuminuria. The association of 25-hydroxyvitamin D with eGFR decline is confounded by baseline eGFR. Sufficient 25-hydroxyvitamin D levels do not seem to protect from eGFR decline independently from baseline eGFR.

Chronic kidney disease in type 2 diabetic patients followed-up by primary care physicians in Switzerland: prevalence and prescription of antidiabetic drugs.

QUESTION UNDER STUDY: The aim of this study was to assess the prevalence of chronic kidney disease (CKD) among type 2 diabetic patients in primary care settings in Switzerland, and to analyse the prescription of antidiabetic drugs in CKD according to the prevailing recommendations. METHODS: In this cross-sectional study, each participating physician was asked to introduce anonymously in a web database the data from up to 15 consecutive diabetic patients attending her/his office between December 2013 and June 2014. Demographic, clinical and biochemical data were analysed. CKD was classified with the KDIGO nomenclature based on estimated glomerular filtration rate (eGFR) and urinary albumin/creatinine ratio. RESULTS: A total of 1 359 patients (mean age 66.5 ± 12.4 years) were included by 109 primary care physicians. CKD stages 3a, 3b and 4 were present in 13.9%, 6.1%, and 2.4% of patients, respectively. Only 30.6% of patients had an entry for urinary albumin/creatinine ratio. Among them, 35.6% were in CKD stage A2, and 4.1% in stage A3. Despite prevailing limitations, metformin and sulfonylureas were prescribed in 53.9% and 16.5%, respectively, of patients with advanced CKD (eGFR <30 ml/min). More than a third of patients were on a dipeptidyl-peptidase-4 inhibitor across all CKD stages. Insulin use increased progressively from 26.8% in CKD stage 1-2 to 50% in stage 4. CONCLUSIONS: CKD is frequent in patients with type 2 diabetes attending Swiss primary care practices, with CKD stage 3 and 4 affecting 22.4% of cases. This emphasizes the importance of routine screening of diabetic nephropathy based on both eGFR and urinary albumin/creatinine ratio, the latter being largely underused by primary care physicians. A careful individual drug risk/benefit balance assessment is mandatory to avoid the frequently observed inappropriate prescription of antidiabetic drugs in CKD patients.

Modulation du cytochrome P450 dans un modèle murin d'insuffisance rénale chronique

Introduction : Les modèles murins sont grandement utilisés dans l’étude des maladies rénales et des pathologies associées. La concentration de la créatinine sérique est un bon indicateur de la filtration glomérulaire et en présence d’insuffisance rénale chronique (IRC), les concentrations de créatinine sérique (et la clairance) reflètent la sévérité de l’IRC. De plus, il a été démontré que l’IRC modifie le métabolisme des médicaments en diminuant l’activité et l’expression des enzymes hépatiques du cytochrome P450 (CYP450). Afin d’étudier la modulation du P450 par l’IRC avec un modèle murin et de confirmer nos résultats chez le rat, nous devons 1) développer un modèle d’IRC chez la souris, 2) mettre au point une technique de dosage des marqueurs de l’IRC et, 3) évaluer l’expression protéique du CYP450 en présence IRC. Matériel et Méthode : Trois modèles chirurgicaux d’IRC chez la souris ont été développés. Une méthode du dosage de la créatinine par chromatographie liquide à haute performance (CLHP) a été mise au point chez la souris et l’expression protéique du P450 a été mesurée par immunobuvardage de type Western. Résultats : Plusieurs paramètres de CLHP comme le pH, la concentration et le débit de la phase mobile modifient le pic d’élution et le temps de rétention de la créatinine. Concernant le modèle expérimental, on observe une perte de poids et une augmentation de la concentration plasmatique de la créatinine chez les souris avec une IRC. De plus, l’expression protéique de plusieurs isoformes du cytochrome P450 est modulée par l’IRC. Nous observons une diminution du CYP 2D de 42% (p < 0,01), du CYP 3A11 de 60% et du CYP 1A de 37% (p <0,01) par rapport aux souris témoins. On ne dénote aucun changement significatif au niveau de l’isoforme 2E1. Conclusion : Il est possible d’induire une insuffisance rénale chronique chez la souris suite à une néphrectomie. La technique de dosage de la créatinine par CLHP est précise et exacte et permet de caractériser la sévérité de l’IRC chez la souris. L’expression protéique du CYP450 est régulée à la baisse dans le foie des souris atteintes d’IRC.

Le diabète maternel influence la morphogenèse rénale et la programmation périnatale

Le diabète maternel est un facteur de risque majeur pour le développement de malformations congénitales. Dans le syndrome de l’embryopathie diabétique, l’exposition prolongée du fœtus à de hautes concentrations ambientes de glucose induit des dommages qui peuvent affecter plusieurs organes, dont les reins. Les malformations rénales sont la cause de près de 40 pourcent des cas d’insuffisance rénale infantile. L’hyperglycémie constitue un environnement utérin adverse qui nuit à la néphrogenèse et peut causer l’agenèse, la dysplasie (aplasie) ou l’hypoplasie rénale. Les mécanismes moléculaires par lesquels les hautes concentrations ambientes de glucose mènent à la dysmorphogenèse et aux malformations demeurent toutefois mal définis. Le diabète maternel prédispose aussi la progéniture au développement d’autres problèmes à l’âge adulte, tels l’hypertension, l’obésité et le diabète de type 2. Ce phénomène appelé ‘programmation périnatale’ a suscité l’intérêt au cours des dernières décennies, mais les mécanismes responsables demeurent mal compris. Mes études doctorales visaient à élucider les mécanismes moléculaires par lesquels le diabète maternel ou un environnement in utero hyperglycémique affecte la néphrogenèse et programme par la suite la progéniture a développer de l’hypertension par des observations in vitro, ex vivo et in vivo. Nous avons utilisé les cellules MK4, des cellules embryonnaires du mésenchyme métanéphrique de souris, pour nos études in vitro et deux lignées de souris transgéniques (Tg) pour nos études ex vivo et in vivo, soient les souris HoxB7-GFP-Tg et Nephrin-CFP-Tg. Les souris HoxB7-GFP-Tg expriment la protéine fluorescente verte (GFP) dans le bourgeon urétérique (UB), sous le contrôle du promoteur HoxB7. Les souris Nephrin-CFP expriment la protéine fluorescente cyan (CFP) dans les glomérules, sous le contrôle du promoteur nephrin spécifique aux podocytes. Nos études in vitro visaient à déterminer si les hautes concentrations de glucose modulent l’expression du gène Pax2 dans les cellules MK4. Les cellules MK4 ont été traitées pendant 24h avec du milieu contenant soit 5mM D-glucose et 20mM D-mannitol ou 25mM D-glucose et avec ou sans antioxydants ou inhibiteurs de p38 MAPK, p44/42 MAPK, PKC et NF-kB. Nos résultats ont démontré que le D-glucose élevé (25mM) augmente la génération des espèces réactives de l’oxygène (ROS) dans les cellules MK4 et induit spécifiquement l’expression du gène Pax2. Des analogues du glucose tels le D-mannitol, L-glucose ou le 2-Deoxy-D-glucose n’induisent pas cette augmentation dans les cellules MK4. La stimulation de l’expression du gène Pax2 par le D-glucose dans les cellules MK4 peut être bloquée par des inhibiteurs des ROS et de NF-kB, mais pas par des inhibiteurs de p38 MAPK, p44/42 MAPK ou PKC. Ces résultats indiquent que la stimulation de l’expression du gène Pax2 par les concentrations élevées de glucose est due, au moins en partie, à la génération des ROS et l’activation de la voie de signalisation NF-kB, et non pas via les voies PKC, p38 MAPK et p44/42 MAPK. Nos études ex vivo s’intéressaient aux effets d’un milieu hyperglycémique sur la morphogenèse de la ramification du bourgeon urétérique (UB). Des explants de reins embryonnaires (E12 à E18) ont été prélevés par micro-dissection de femelles HoxB7-GFP gestantes. Les explants ont ensuite été cultivés dans un milieu contenant soit 5mM D-glucose et 20mM D-mannitol ou 25mM D-glucose et avec ou sans antioxydants, catalase ou inhibiteur de PI3K/AKT pour diverses durées. Nos résultats ont démontré que le D-glucose stimule la ramification du UB de manière spécifique, et ce via l’expression du gène Pax2. Cette augmentation de la ramification et de l’expression du gène Pax2 peut être bloquée par des inhibiteurs des ROS et de PI3K/AKT. Ces études ont démontré que les hautes concentrations de glucose altèrent la morphogenèse de la ramification du UB via l’expression de Pax2. L’effet stimulant du glucose semble s’effectuer via la génération des ROS et l’activation de la voie de signalisation Akt. Nos études in vivo visaient à déterminer le rôle fondamental du diabète maternel sur les défauts de morphogenèse rénale chez la progéniture. Dans notre modèle animal, le diabète maternel est induit par le streptozotocin (STZ) chez des femelles HoxB7-GFP gestantes (E13). Les souriceaux ont été étudiés à différents âges (naissants et âgés de une, deux ou trois semaines). Nous avons examiné leurs morphologie rénale, nombre de néphrons, expression génique et les événements apoptotiques lors de cette étude à court terme. La progéniture des mères diabétiques avait un plus faible poids, taille et poids des reins, et possédait des glomérules plus petits et moins de néphrons par rapport à la progéniture des mères contrôles. La dysmorphogenèse rénale observée est peut-être causée par l’augmentation de l’apoptose des cellules dans la région du glomérule. Nos résultats ont montré que les souriceaux nés de mères diabétiques possèdent plus de podocytes apoptotiques et plus de marquage contre la caspase-3 active dans leurs tubules rénaux que la progéniture des mères contrôles. Les souriceaux des mères diabétiques montrent une augmentation de l’expression des composants du système rénine angiotensine (RAS) intrarénal comme l’angiotensinogène et la rénine, ainsi qu’une augmentation des isoformes p50 et p65 de NF-kB. Ces résultats indiquent que le diabète maternel active le RAS intrarénal et induit l’apoptose des glomérules, menant à une altération de la morphogenèse rénale de la progéniture. En conclusion, nos études ont permis de démontrer que le glucose élevé ou l’environnement in utero diabétique altère la morphogenèse du UB, qui résulte en un retard dans la néphrogenèse et produit des reins plus petits. Cet effet est dû, au moins en partie, à la génération des ROS, à l’activation du RAS intrarénal et à la voie NF-kB. Nos études futures se concentreront sur les mécanismes par lesquels le diabète maternel induit la programmation périnatale de l’hypertension chez la progéniture adulte. Cette étude à long terme porte sur trois types de progénitures : adultes nés de mères contrôles, diabétiques ou diabétiques traitées avec insuline pendant la gestation. Nous observerons la pression systolique, la morphologie rénale et l’expression de divers gènes et protéines. Nous voulons de plus déterminer si la présence d’un système antioxydant (catalase) peut protéger la progéniture des effets néfastes des ROS causés par l’environnement in utero hyperglycémique. Les souris Catalase-Tg expriment la catalase spécifiquement dans les tubules proximaux et nous permettrons d’explorer notre hypothèse sur le rôle des ROS dans notre modèle expérimental de diabète maternel.