Renal development in high-glucose ambience and diabetic embryopathy

Maternal diabetes modulates kidney formation in murine progeny: the role of hedgehog interacting protein (HHIP)

AIMS/HYPOTHESIS

We hypothesised that maternal diabetes impairs kidney formation in offspring via augmented expression of hedgehog interacting protein (HHIP). Our gene-array results were performed in neonatal kidneys from our murine model of maternal diabetes and indicated that Hhip expression was significantly modulated by maternal diabetes.

METHODS

We systematically examined the functional role of HHIP in kidney formation in our murine maternal diabetes model and elucidated the potential mechanisms related to dysnephrogenesis in vitro.

RESULTS

The kidneys of the offspring of diabetic dams, compared with those of the offspring of control non-diabetic dams, showed retardation of development--small kidneys and less ureteric bud (UB) branching morphogenesis. Augmented HHIP expression was observed in the offspring of diabetic dams, initially localised to differentiated metanephric mesenchyme and UB epithelium and subsequently in maturing glomerular endothelial and tubulointerstitial cells. The heightened HHIP targeting TGF-β1 signalling was associated with dysmorphogenesis. In vitro, HHIP overexpression decreased sonic hedgehog and paired box gene 2 proteins (SHH and PAX2, respectively) and increased transcriptional nuclear factor-kappa B (NFκB, p50/p65), phosphorylation of p53, and TGF-β1 expression. In contrast, overexpression of PAX2 inhibited HHIP and NFκB and activated SHH, N-myc and p27(Kip1) expression. Moreover, high glucose stimulated HHIP expression, and then targeted TGF-β1 signalling. Thus, PAX2, via a negative autocrine feedback mechanism, attenuated the stimulatory effect of high glucose on HHIP expression.

CONCLUSIONS/INTERPRETATION

Maternal diabetes modulates kidney formation in young progeny mediated, at least in part, via augmented HHIP expression.

Risk factors for renal function impairment in a series of 502 patients born with spinal dysraphisms

OBJECTIVE

To evaluate the risk of renal damage in a large series of patients affected by spinal dysraphism.

METHODS

Renal function was studied in 502 spinal dysraphisms treated over the last 25 years in a single center: 283 meningomyelocele (MMC), 90 caudal regression syndrome (CRS) and 129 spinal lipoma (SL) cases. In patients with normal and impaired renal function, we compared congenital renal anomalies, vesicoureteric reflux, bladder voiding pattern and upper tract dilatation, analyzing the results with the Fisher test.

RESULTS

Neuropathic bladder was observed in 97% of MMC, 60% of CRS, and 39% of SL cases. There was some degree of renal function impairment in 19 MMC (6.7%), 11 CRS (12%, increased to 20% if considering only neuropathic bladder patients), and two SL (1.5%) cases. Renal agenesis was more frequent in CRS (13%), but was not associated with decreased renal function. Overall, vesicoureteric reflux and upper tract dilatation were more frequent in patients with renal damage. Insufficient bladder voiding was statistically associated with renal damage only in the CRS population. Intermittent catheterization did not represent a protective factor against renal damage in patients able to void without significant residual urine.

CONCLUSION

This study has increased our understanding of the prognostic risk factors for renal deterioration. More prospective studies are necessary to confirm these results and correlate treatment with renal outcome.

High glucose promotes nascent nephron apoptosis via NF-kappaB and p53 pathways

A hyperglycemic environment in utero reduces kidney size and nephron number due to nascent nephron apoptosis. However, the underlying mechanisms are incompletely understood. The present study investigated whether the nascent nephron apoptosis promoted by high glucose is mediated via the transcription factor NF-κB and p53 signaling pathways. Neonatal mouse kidneys from the offspring of nondiabetic, diabetic, and insulin-treated diabetic dams were used for in vivo studies, and MK4 cells, an embryonic metanephric mesenchymal (MM) cell line, were used for in vitro studies. Neonatal kidneys of the offspring of diabetic mothers exhibited an increased number of apoptotic cells and reactive oxygen species (ROS) generation, enhanced NF-κB activation, and nuclear translocation of its subunits (p50 and p65 subunits) as well as phosphorylation (Ser 15) of p53 compared with kidneys of offspring of nondiabetic mothers. Insulin treatment of diabetic dams normalized these parameters in the offspring. In vitro, high-glucose (25 mM) induced ROS generation and significantly increased MK4 cell apoptosis and caspase-3 activity via activation of NF-κB pathway, with p53 phosphorylation and nuclear translocation compared with normal glucose (5 mM). These changes in a high-glucose milieu were prevented by transient transfection of small interfering RNAs for dominant negative IκBα or IKK or p53. Our data demonstrate that high glucose-induced nascent nephron apoptosis is mediated, at least in part, via ROS generation and the activation of NF-κB and p53 pathways.

Caudal dysplasia syndrome and sirenomelia: are they part of a spectrum?

Caudal dysplasia syndrome (CDS) is associated with hypoplastic lower extremities, caudal vertebrae, sacrum, neural tube, and urogenital organs. Sirenomelia is characterized by a single lower extremity, absent sacrum, urogenital anomalies, and imperforate anus. There is controversy in the medical literature about whether sirenomelia and CDS are part of the spectrum of the same malformation. Patients with CDS and sirenomelia were identified from our pathology files from 1991 to 2006. Maternal history, pathologic examination, and radiographs were collected and tabulated. We found 9 cases with CDS and 6 with sirenomelia. Fully 7 of 9 patients with CDS (77.7%) versus none of sirenomelic babies were infants of diabetic mothers. Congenital heart disease was present in 5 patients with CDS (55.5%) and none of the infants with sirenomelia. Of 9 children with CDS 2 (22.2%) had bilateral renal agenesis versus 66% of sirenomelics. Single umbilical artery was found in 33% of cases with CDS and 100% of children with sirenomelia. External genitalia were ambiguous in 2 of 9 patients (22.2%) with CDS and in all patients with sirenomelia. Imperforate anus was found in 10 cases (66.6%) divided as 4 of 9 babies with CDS (44.4%) and all patients with sirenomelia. Three patients with CDS had concomitant maternal diabetes mellitus and chronic hypertension. These babies also had cleft lip and palate. Congenital heart disease was found in 55.5% of cases with CDS and none of the children with sirenomelia. We conclude that although CDS and sirenomelia share many similar features, they are two different entities.

Cancers of the urinary tract among American Indians and Alaska Natives in the United States, 1999-2004

BACKGROUND

Assessment of the kidney parenchyma ("kidney") and urinary bladder ("bladder") cancer burden among American Indians and Alaska Natives (AI/AN) has been limited. Using a database with improved classification for AI/AN, the authors described patterns of these 2 cancers among AI/AN and non-Hispanic whites (NHW) in the United States.

METHODS

Cases diagnosed during 1999 to 2004 were identified through National Program of Cancer Registries and the Surveillance, Epidemiology and End Results program and linked to the Indian Health Service (IHS) registration records. Age-adjusted incidence rates, rate ratios (RR), annual percent change, and stage at diagnosis were stratified by IHS Contract Health Service Delivery Area (CHSDA) counties to adjust for misclassification.

RESULTS

Kidney cancer incidence among AI/AN in CHSDA counties exceeded that among NHW (RR, 1.51; 95% confidence interval [CI], 1.42-1.61), and was highest among AI/AN in the Northern Plains, Southern Plains, Alaska, and Southwest. Average annual increases were highest among AI/AN (5.9%) and NHW (5.9%) males aged 20 to 49 years, although statistically significant only among NHW. Conversely, bladder cancer incidence was significantly lower among AI/AN than NHW (RR, 0.40; 95% CI, 0.37-0.44). For both sites, AI/AN were significantly less likely to be diagnosed at an earlier stage than NHW.

CONCLUSIONS

AI/AN have about 50% greater risk of kidney cancer and half the risk of bladder cancer than NHW. Although reasons for these enigmatic patterns are not known, sustained primary prevention efforts through tobacco cessation and obesity prevention are warranted.

Long-term urologic outcome in patients with caudal regression syndrome, compared with meningomyelocele and spinal cord lipoma

BACKGROUND/PURPOSE

The long-term urologic outcome in a large series of patients with neural tube defects was evaluated.

METHODS

The following clinical parameters in 398 patients ranging from 1 to 37 years of age--69 with caudal regression syndrome (CRS), 244 with meningomyelocele (MMC), and 85 with spinal lipoma (SL)--were studied: congenital renal anomalies, renal function, vesico-ureteric reflux, upper tract dilatation, urodynamic pattern, and urinary continence.

RESULTS

Single kidney was much more frequent in CRS (20.3%), compared with MMC (1.2%) and SL (0%). Vesico-ureteric reflux was found in 37.7% of patients with CRS, 43.0% of MMC, and 21.2% of SL. Patients with CRS had a higher risk of impaired renal function (8.7%), compared with MMC (5.3%) and SL (1.2%). Neuropathic bladder was found in 61% of patients with CRS, 98% of MMC, and 42% of SL. Among them, clean intermittent catheterization and drugs allowed 30% of patients with CRS, 45% of MMC, and 71% of SL to be dry for more than 4 hours.

CONCLUSIONS

Diagnosis influences the urologic outcome in neural tube defect. In CRS, the incidence of renal agenesis and vesico-ureteric reflux was unexpectedly high. The risk of renal damage and, in those with neuropathic bladder, of urinary incontinence, was similar to patients with MMC.

The influence of L-arginine on blood pressure, vascular nitric oxide and renal morphometry in the offspring from diabetic mothers

The present study was designed to evaluate the effects of L-arginine (L-arg) supplementation on blood pressure, vascular nitric oxide content, and renal morphometry in the adult offspring from diabetic mothers. Diabetes mellitus was induced in female rats with a single dose of streptozotocin (50 mg/kg), before mating. The offspring was divided into four groups: group C (controls); group DO (diabetic offspring); group CA (controls receiving 2% L-arg solution dissolved in 2% sucrose in the drinking water) and group DA (DO receiving the L-arg solution). Oral supplementation began after weaning and continued until the end of the experiments. In DO, hypertension was observed, from 3 mo on. In DA, pressure levels were not different from C and CA. In 6-mo-old animals, basal NO production (assessed by DAF-2) was significantly depressed in DO in comparison to controls. The NO production was significantly increased after stimulation with Ach or BK in all groups, the increase being greater in control than in DO rats. L-arg was able to improve the NO production and to prevent the glomerular hypertrophy in the DO. Our data suggest that the bioavailability of NO is reduced in the DO, because L-arg corrected both the hypertension and glomerular hypertrophy.

Reactive oxygen species in the presence of high glucose alter ureteric bud morphogenesis

Renal malformations are a major cause of childhood renal failure. During the development of the kidney, ureteric bud (UB) branching morphogenesis is critical for normal nephrogenesis. These studies investigated whether renal UB branching morphogenesis is altered by a high ambient glucose environment and studied underlying mechanism(s). Kidney explants that were isolated from different periods of gestation (embryonic days 12 to 18) from Hoxb7-green fluorescence protein mice were cultured for 24 h in either normal d-glucose (5 mM) or high d-glucose (25 mM) medium with or without various inhibitors. Alterations in renal morphogenesis were assessed by fluorescence microscopy. Paired-homeobox 2 (Pax-2) gene expression was determined by real-time quantitative PCR, Western blotting, and immunohistology. The results revealed that high d-glucose (25 mM) specifically stimulates UB branching morphogenesis via Pax-2 gene expression, whereas other glucose analogs, such as d-mannitol, l-glucose, and 2-deoxy-d-glucose, had no effect. The stimulatory effect of high glucose on UB branching was blocked in the presence of catalase and inhibitors of NADPH oxidase, mitochondrial electron transport chain complex I, and Akt signaling. Moreover, in in vivo studies, it seems that high glucose induces, via Pax-2 (mainly localized in UB), acceleration of UB branching but not nephron formation. Taken together, these data demonstrate that high glucose alters UB branching morphogenesis. This occurs, at least in part, via reactive oxygen species generation, activation of Akt signaling, and upregulation of Pax-2 gene expression.

Reactive oxygen species and nuclear factor-kappa B pathway mediate high glucose-induced Pax-2 gene expression in mouse embryonic mesenchymal epithelial cells and kidney explants

Diabetic mellitus confers a major risk of congenital malformations, and is associated with diabetic embryopathy, affecting multiple organs including the kidney. The DNA paired box-2 (Pax-2) gene is essential in nephrogenesis. We investigated whether high glucose alters Pax-2 gene expression and aimed to delineate its underlying mechanism(s) of action using both in vitro (mouse embryonic mesenchymal epithelial cells (MK4) and ex vivo (kidney explant from Hoxb7-green florescent protein (GFP) mice) approaches. Pax-2 gene expression was determined by reverse transcriptase-polymerase chain reaction, Western blotting, and immunofluorescent staining. A fusion gene containing the full-length 5'-flanking region of the human Pax-2 promoter linked to a luciferase reporter gene, pGL-2/hPax-2, was transfected into MK4 cells with or without dominant negative IkappaBalpha (DN IkappaBalpha) cotransfection. Fusion gene expression level was quantified by cellular luciferase activity. Reactive oxygen species (ROS) generation was measured by lucigenin assay. Embryonic kidneys from Hoxb7-GFP mice were cultured ex vivo. High D(+) glucose (25 mM), compared to normal glucose (5 mM), specifically induced Pax-2 gene expression in MK4 cells and kidney explants. High glucose-induced Pax-2 gene expression is mediated, at least in part, via ROS generation and activation of the nuclear factor kappa B signaling pathway, but not via protein kinase C, p38 mitogen-activated protein kinase (MAPK), and p44/42 MAPK signaling.

Experimental mechanisms of diabetic embryopathy and strategies for developing therapeutic interventions

A high frequency of birth defects is seen in infants born to diabetic mothers. The mechanisms by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remain to be addressed. It has been shown that increases in programmed cell death are one of the factors causing embryonic malformations. Hyperglycemia-induced apoptosis is associated with oxidative stress, lipid peroxidation, and decreased antioxidant defense capacity in the embryos. Recent studies have revealed that mitogen-activated protein kinases as intracellular signaling factors are involved in hyperglycemia-induced embryopathy. Based on the findings, interventions to prevent embryonic malformations have been explored. Strategies include supplementation of molecules that are deficient in the embryos under hyperglycemic conditions and antioxidants to alleviate the adverse effects of oxidative stress. The ultimate goal is to develop multi-nutrient dietary supplements to eliminate embryonic abnormalities induced by maternal diabetes.

Renal-specific oxidoreductase biphasic expression under high glucose ambience during fetal versus neonatal development

BACKGROUND

Renal-specific oxidoreductase (RSOR) has been recently identified in mice kidneys of diabetic animals, and it is developmentally regulated. Its expression during fetal, neonatal, and postnatal periods was assessed under high glucose ambience.

METHODS

Whole-mount immunofluorescence and confocal microscopy were performed to assess the effect of high glucose on the morphogenesis of mice fetal kidneys. RSOR mRNA and protein expression was assessed by competitive polymerase chain reaction (PCR) and immunoprecipitation methods in embryonic kidneys (day E13 to E17) subjected to high glucose ambience and by Northern and Western blot analyses of kidneys of newborn and 1-week-old mice with hyperglycemia. The spatiotemporal changes in the RSOR expression were assessed by in situ hybridization analyses and immunofluorescence microscopy. In addition, the extent of apoptosis in the kidneys was determined by terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) assay.

RESULTS

Whole-mount microscopy of the embryonic metanephroi revealed a dose-dependent disruption in the ureteric bud iterations with reduced population of the nascent nephrons. Both gene and protein expressions were reduced in day E13 to E17 metanephroi, while increased in kidneys of newborn and 1-week-old mice. In day E13 and day E15 kidneys, the RSOR was expressed in the ureteric bud branches and some of the immature tubules, and its expression was reduced with high glucose treatment. In day E17 kidneys the RSOR was expressed in the tubules of the deeper cortex, and its expression was marginally decreased. In newborn kidneys, this enzyme was expressed in the subcortical tubules and it spread to the entire width of the renal cortex in hyperglycemic state. In 1-week-old mice kidneys, the RSOR was localized to the entire cortex, and in animals with blood glucose above 300 mg/dL, its intensity increased with extension of expression into the outer medullary tubules. A dose-dependent fulminant apoptosis was observed in day E13 to E17 kidneys subjected to high glucose ambience. In newborn and 1-week-old mice control kidneys, the apoptosis was minimal although slightly increased during hyperglycemia.

CONCLUSION

High glucose has a differential effect on the RSOR expression in kidneys during the embryonic versus neonatal/postnatal period. This may partly be related to the differential degree of apoptosis, a process reflective of oxidant stress that is seen in diabetic milieu, which as previously has been shown to adversely effect the modulators of fetal development and thereby the morphogenesis of the kidney and RSOR expression.

Long-term effects of maternal diabetes on vascular reactivity and renal function in rat male offspring

Fetal growth impairment can occur in pregnancy complicated by diabetes. Although several studies have focused the effects of nutritional status on intrauterine development, the long-term impact of maternal diabetes on vascular and renal function in the offspring is poorly investigated. In the present study, blood pressure profiles and renal function parameters were investigated in the offspring of diabetic rats (DO). Female rats were made diabetic throughout gestation with a single dose of streptozotocyn (STZ) 10 d before mating. After weaning, the offspring had free access to food and water. Arterial pressure was evaluated every 15 d. Functional and morphometric kidney studies were performed in newborn, 3, 6 and 12-mo-old male rats in DO and in controls, C. Although maternal diabetes did not affect nephron number in the young adult rat, glomerular hypertrophy developed from 3 mo on. Glomerular Filtration Rate and Renal Plasma Flow were observed to be significantly decreased in DO when compared with C, from 3 mo on. In DO, hypertension was observed from 8 wk on and persisted elevated throughout the experimental period (12 mo). Vascular reactivity, evaluated in mesenteric arterial bed showed a decreased endothelium-dependent vasodilatation in 12-mo-old DO animals, while preserved response to sodium nitroprusside was demonstrated. Our data show that exposure to intrauterine diabetes induced by STZ does not affect nephron number in the young offspring but can cause permanent changes in Nitric Oxide (NO)-related vascular response, which, in turn may accelerate the natural age-related nephron loss.

Cell Biology of Diabetic Kidney Disease

In large part cellular dysfunctions induced by chronic hyperglycemia are similar in type-1 and -2 diabetes. In both instances chronic hyperglycemia induces injury to a multitude of organs by affecting various target cells. The cells affected may include those derived from of epithelial or mesenchymal progenitors; and at times hyperglycemia may induce phenotypic changes with epithelial-mesenchymal transformation. In the majority of target cells the high-glucose ambience activates various intracellular pathways that are similar except for minor exceptions that are related to the selective expression of various molecules in a given cell type. Keeping in perspective a common paradigm applicable to most of the cells, a brief discussion of different hyperglycemia-induced cellular events pertaining to various pathways is described in this review. They include fluxes of glucose intermediaries in various cellular metabolic pathways, generation of advanced glycation end products (AGEs) and their extra- and intracellular effects, the role of protein kinase C, transforming growth factor-beta, guanosine triphosphate-binding proteins and reactive oxygen species (ROS) in various cellular signaling events. The latter, i.e., ROS, may be central to several intracellular pathways and modulate various events in a reciprocal manner. The information compiled under various subtitles of this synopsis is derived from an enormous amount of literature data summarized in several recent excellent reviews, and thus further reading of them is suggested to gather detailed comprehensive information on each of the subjects.

Developmental renal pathology: its past, present, and future

Congenital anomalies of the kidney and urinary tract are responsible for approximately 40% of cases of childhood end-stage renal failure in the United States. This article describes the spectrum of developmental renal lesions in children (including renal agenesis, dysplasias, hereditary hydronephrosis, autosomal recessive and dominant polycystic kidneys, vesicoureteral reflux, diabetic embryopathy, some teratogenic drugs affecting renal development, and syndromes associated with renal dysplasias). The article quotes some historic references that established the foundation for further studies; reviews the embryology, pathology, postnatal renal development, and its possible consequences of renal function; as well as recent advances in fetal ultrasonography and molecular biology with some novel treatment and diagnostic modalities. Finally, an attempt is made to predict several future avenues in pharmacogenetics that are being built currently and that will allow a better prognosis for many children with congenital renal conditions.