Pathway analysis shows association between FGFBP1 and hypertension.

Variants in the gene encoding fibroblast growth factor 1 (FGF1) co-segregate with familial susceptibility to hypertension, and glomerular upregulation of FGF1 associates with hypertension. To investigate whether variants in other members of the FGF signaling pathway may also associate with hypertension, we genotyped 629 subjects from 207 Polish families with hypertension for 79 single nucleotide polymorphisms in eight genes of this network. Family-based analysis showed that parents transmitted the major allele of the rs16892645 polymorphism in the gene encoding FGF binding protein 1 (FGFBP1) to hypertensive offspring more frequently than expected by chance (P=0.005). An independent cohort of 807 unrelated Polish subjects validated this association. Furthermore, compared with normotensive subjects, hypertensive subjects had approximately 1.5- and 1.4-fold higher expression of renal FGFBP1 mRNA and protein (P=0.04 and P=0.001), respectively. By immunohistochemistry, hypertension-related upregulation of FGFBP1 was most apparent in the glomerulus and juxtaglomerular space. Taken together, these data suggest that FGFBP1 associates with hypertension and that systematic analysis of signaling pathways can identify previously undescribed genetic associations.

Chronic nicotine exposure exacerbates acute renal ischemic injury.

Recent epidemiological reports showed that smoking has a negative impact on renal function and elevates the renal risk not only in the renal patient but perhaps also in the healthy population. Studies suggested that nicotine, a major tobacco alkaloid, links smoking to renal dysfunction. While several studies showed that smoking/chronic nicotine exposure exacerbates the progression of chronic renal diseases, its impact on acute kidney injury is virtually unknown. Here, we studied the effects of chronic nicotine exposure on acute renal ischemic injury. We found that chronic nicotine exposure increased the extent of renal injury induced by warm ischemia-reperfusion as evidenced by morphological changes, increase in plasma creatinine level, and kidney injury molecule-1 expression. We also found that chronic nicotine exposure elevated markers of oxidative stress such as nitrotyrosine as well as malondialdehyde. Interestingly, chronic nicotine exposure alone increased oxidative stress and injury in the kidney without morphological alterations. Chronic nicotine treatment not only increased reactive oxygen species (ROS) production and injury but also exacerbated oxidative stress-induced ROS generation through NADPH oxidase and mitochondria in cultured renal proximal tubule cells. The resultant oxidative stress provoked injury through JNK-mediated activation of the activator protein (AP)-1 transcription factor in vitro. This mechanism might exist in vivo as phosphorylation of JNK and its downstream target c-jun, a component of the AP-1 transcription factor, is elevated in the ischemic kidneys exposed to chronic nicotine. Our results imply that smoking may sensitize the kidney to ischemic insults and perhaps facilitates progression of acute kidney injury to chronic kidney injury.

Inhibition of estradiol synthesis attenuates renal injury in male streptozotocin-induced diabetic rats.

We previously showed that the male streptozotocin (STZ)-induced diabetic rat exhibits decreased circulating testosterone and increased estradiol levels. While supplementation with dihydrotestosterone is partially renoprotective, the aim of the present study was to examine whether inhibition of estradiol synthesis, by blocking the aromatization of testosterone to estradiol using an aromatase inhibitor, can also prevent diabetes-associated renal injury. The study was performed on male Sprague-Dawley nondiabetic, STZ-induced diabetic, and STZ-induced diabetic rats treated with 0.15 mg/kg of anastrozole, an aromatase inhibitor (Da) for 12 wk. Treatment with anastrozole reduced diabetes-associated increases in plasma estradiol by 39% and increased plasma testosterone levels by 187%. Anastrozole treatment also attenuated urine albumin excretion by 42%, glomerulosclerosis by 30%, tubulointerstitial fibrosis by 32%, along with a decrease in the density of renal cortical CD68-positive cells by 50%, and protein expression of transforming growth factor-ß by 20%, collagen type IV by 29%, tumor necrosis factor-α by 28%, and interleukin-6 by 25%. Anastrozole also increased podocin protein expression by 18%. We conclude that blocking estradiol synthesis in male STZ-induced diabetic rats is renoprotective.

Cutting edge: developmental up-regulation of IFN-gamma-inducible lysosomal thiol reductase expression leads to reduced T cell sensitivity and less severe autoimmunity.

Reactivity to self-peptide/MHC complexes is required for selection of the TCR repertoire in the thymus but can also promote autoimmunity. Reduced TCR sensitivity of mature T cells is thought to help control the autoreactivity in peripheral T cells. The molecular basis for reduced sensitivity of peripheral T cells is not known. We found that peripheral T cells, but not immature thymocytes, lacking IFN-gamma-inducible lysosomal thiol reductase (GILT) display increased sensitivity to TCR ligation. GILT-/- peripheral T cells express reduced levels of mitochondrial superoxide dismutase 2 and consequently display higher levels of reactive oxygen radicals and ERK1/2 phosphorylation following activation. The increased sensitivity of GILT-deficient T cells results in a more severe hyperglycemia associated with streptozotocin-induced diabetes. GILT expression levels progressively increase in T cells with maturation. These data suggest that regulation of GILT expression may be a mechanism of T cell differentiation-associated changes in sensitivity to TCR engagement.

Role of renal microcirculation in experimental renovascular disease.

BACKGROUND: Renal artery stenosis (RAS) causes renal injury partly via microvascular (MV) endothelial dysfunction and damage. Vascular endothelial growth factor (VEGF) is crucial for preservation of microvasculature and promotes vascular proliferation and endothelial repair. We have previously shown that MV rarefaction is associated with decreased VEGF in the kidney exposed to chronic RAS, accompanied by deteriorated renal function and fibrosis. We hypothesized that preserving the renal microcirculation in the stenotic kidney will halt the progression of renal damage. METHODS: Unilateral RAS was induced in 16 pigs. In eight, VEGF (0.05 micrograms/kg) was infused intra-renally at the onset of RAS. After 6 weeks, single-kidney haemodynamics and function were assessed using in vivo multi-detector computed tomography (CT). Renal microvessels, angiogenic pathways and morphology were investigated ex vivo using micro-CT, real-time PCR and histology. RESULTS: Blood pressure and degree of RAS was similar in RAS and RAS + VEGF pigs. Single-kidney renal blood flow (RBF) and glomerular filtration rate (GFR) were reduced in RAS compared to Normal (221.1 +/- 46.5 and 29.9 +/- 3.8 vs. 522.5 +/- 60.9 and 49.3 +/- 3.4 mL/min, respectively, P < 0.05), accompanied by decreased cortical MV density and increased renal fibrosis. Pre-emptive administration of VEGF preserved MV architecture, attenuated fibrosis and normalized RBF and GFR (510.8 +/- 50.9 and 39.9.1 +/- 4.1 mL/min, P = not significant vs. Normal). CONCLUSIONS: This study underscores the importance of the renal microcirculation in renovascular disease. Intra-renal administration of VEGF preserved renal MV architecture and function of the stenotic kidney, which in turn preserved renal haemodynamics and function and decreased renal fibrosis. These observations suggest that preventing renal MV loss may be a potential target for therapeutic approaches for patients with chronic renovascular disease.

Dose-dependent effects of dihydrotestosterone in the streptozotocin-induced diabetic rat kidney.

We recently reported that castration exacerbates albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis associated with diabetic renal disease. The aim of the present study was to examine whether these effects of castration can be attenuated with dihydrotestosterone (DHT) supplementation. The study was performed in castrated male Sprague-Dawley, streptozotocin-induced diabetic rats treated with 0 mg/day DHT (DHT(0)), 0.75 mg/day DHT (DHT(0.75)), or 2.0 mg/day DHT (DHT(2.0)) for 14 wk. Treatment with 0.75 mg/day DHT attenuated castration-associated increases in urine albumin excretion (DHT(0), 81.2 +/- 18.1; DHT(0.75), 26.57 +/- 5.8 mg/day; P < 0.05), glomerulosclerosis (DHT(0), 1.1 +/- 0.79; DHT(0.75), 0.43 +/- 0.043 arbitrary units; P < 0.001), tubulointerstitial fibrosis (DHT(0), 1.3 +/- 0.12; DHT(0.75), 1.1 +/- 0.096 AU; P < 0.05), collagen type IV [DHT(0), 3.2 +/- 0.11; DHT(0.75), 2.1 +/- 0.070 relative optical density (ROD); P < 0.01], transforming growth factor-beta (DHT(0), 3.2 +/- 0.16; DHT(0.75), 2.1 +/- 0.060 ROD; P < 0.01), IL-6 (DHT(0), 0.37 +/- 0.011; DHT(0.75), 0.27 +/- 0.014 ROD; P < 0.05), and protein expression and reduced CD68-positive cell abundance (DHT(0), 17 +/- 0.86; DHT(0.75), 4.4 +/- 0.55 cells/mm(2); P < 0.001). In contrast, treatment with 2.0 mg/day DHT exacerbated all these parameters. These data suggest that the detrimental effects of castration in the diabetic kidney can be attenuated with low doses of DHT, whereas high doses augment the adverse effects of castration, and these effects appear to be influenced by estradiol. We conclude that the effects of DHT are dose dependent but caution should be taken when DHT supplementation is considered in the treatment of diabetic renal disease.

Fibroblast growth factor 1 gene and hypertension: from the quantitative trait locus to positional analysis.

BACKGROUND: The distal portion of the long arm of chromosome 5 is linked to hypertension and contains functional candidate blood pressure-regulating genes. METHODS AND RESULTS: Tightening the grid of microsatellite markers under this quantitative trait locus in the Silesian Hypertension Study (629 individuals from 207 Polish hypertensive families) provided enhanced support for linkage of this region to blood pressure (maximal Z=3.51, P=0.0002). The fine mapping, comparative genomics, and functional prioritization identified fibroblast growth factor 1 gene (FGF1) as the positional candidate. Linkage disequilibrium mapping based on 51 single nucleotide polymorphisms spanning the locus showed no overlap between 3 independent haploblocks of FGF1 and the adjacent extragenic chromosomal regions. Single and multilocus family-based analysis revealed that genetic variation within FGF1 haploblock 1 was associated with hypertension and identified a common intronic single nucleotide polymorphism, rs152524, as the major driver of this association (P=0.0026). Real-time quantitative polymerase chain reaction and Western blotting analysis of renal tissue obtained from subjects undergoing unilateral nephrectomy showed an increase in both mRNA and protein FGF1 expression in hypertensive patients compared with normotensive controls. Renal immunohistochemistry revealed that FGF1 was expressed exclusively within the glomerular endothelial and mesangial cells. CONCLUSIONS: Our data demonstrate that genetic variation within FGF1 cosegregates with elevated blood pressure in hypertensive families and that this association is likely to be mediated by upregulation of renal FGF1 expression. The results of our study will need to be replicated in other cohorts.

Estrogens and the diabetic kidney.

BACKGROUND: Across all ages, the incidence and rate of progression of most nondiabetic renal diseases are markedly higher in men compared with age-matched women. These observations suggest that female sex may be renoprotective. In the setting of diabetes, however, this female protection against the development and progression of renal disease is diminished. OBJECTIVE: This review aimed to summarize our current understanding of sex differences in the development and progression of diabetic renal disease, and of the contribution of sex hormones, particularly estrogens, to the pathophysiology of this disease. We also attempted to answer why female sex does not protect the diabetic kidney. METHODS: Using terms such as gender, sex, diabetes, diabetic nephropathy, estrogens, and sex hormones, the PubMed database was searched for English-language articles; targeted searches were conducted using terms such as gender/sex differences in diabetic renal disease. No restrictions were imposed on publication dates. RESULTS: Although the existing data regarding the sex differences in the incidence and progression of diabetic renal disease are inconclusive, the undisputed fact is that women with either type 1 or type 2 diabetes mellitus exhibit a much higher incidence of renal disease compared with nondiabetic women. It is conceivable that the loss of female sex as a renoprotective factor in diabetes may be related to the abnormal regulation of sex hormone concentrations. Both clinical and experimental data suggest that diabetes may be associated with an imbalance in estradiol concentrations. Supplementation with 17beta-estradiol or administration of selective estrogen receptor modulators reduces the incidence of diabetes and attenuates the progression of diabetic renal disease. CONCLUSIONS: Serum concentrations of ovarian hormones may provide a new means for predicting future risk of renal complications in diabetes. Exogenous steroid hormones may be an effective treatment for attenuating the progression of diabetic nephropathy.

Age-related renal disease in female Dahl salt-sensitive rats is attenuated with 17 beta-estradiol supplementation by modulating nitric oxide synthase expression.

BACKGROUND: The incidence of chronic renal disease in women increases with aging, especially after menopause, suggesting that loss of sex hormones may contribute to the development and progression of renal disease. However, the mechanisms by which sex hormones, particularly estrogens, contribute to the disease process are unclear. OBJECTIVE: The present study examined the effects of ovariectomy (OVX) with or without 17 beta-estradiol (E2) supplementation (OVX+E2) on the expression of inducible (iNOS) and endothelial (eNOS) nitric oxide synthase in the kidney. METHODS: The study was performed in young (4 months [4M]) and aged (12 months [12M]) female Dahl salt-sensitive rats fed a low-sodium (0.1% NaCl) diet. At 3 months of age, the animals were either subjected to sham surgery, OVX, or OVX with implantation of an E2 silastic pellet. The treatments were administered for either 1 or 9 months, rendering the animals 4 months of age or 12 months of age at the time of sacrifice, respectively. Renal expression of NOS isoforms was measured by Western blotting and immunohistochemistry. RESULTS: OVX in the aged rats was associated with 35% and 25% decreases in medullary iNOS (mean [SEM] relative optical density [ROD]: 4M OVX, 1.81 [0.14] vs 12M OVX, 1.17 [0.16]; P < 0.05) and eNOS (mean ROD: 4M OVX, 1.91 [0.09] vs 12M OVX, 1.43 [0.15]; P < 0.05) protein expression, respectively, and a 25-fold increase in the abundance of CD68-positive cells, indicating macrophage infiltration (mean cells/mm2: 4M OVX, 1.18 [0.09] vs 12M OVX, 30.0 [0.74]; P < 0.001). E2 supplementation either partially or completely attenuated these changes in iNOS (mean ROD: 4M OVX+E2, 2.26 [0.08] vs 12M OVX+E2, 1.70 [0.09]; P < 0.05), eNOS (mean ROD: 4M OVX+E2, 2.03 [0.07] vs 12M OVX+E2, 1.77 [0.11]; P = NS) and CD68 (mean cells/mm2: 4M OVX+E2, 1.46 [0.07] vs 12M OVX+E2, 6.87 [1.6]; P < 0.01) associated with OVX in the aging kidney. CONCLUSIONS: These data suggest that ovarian E2 loss with aging may contribute to the development of age-related renal disease through downregulation of iNOS and eNOS protein abundance and increased renal inflammation in this animal model. Furthermore, E2 supplementation may be protective in the aging kidney by attenuating these changes.

Vasoactive hormones and the diabetic kidney.

Diabetic nephropathy is the single most common cause of end-stage renal disease (ESRD) and accounts for significant morbidity and mortality. While the incidence of ESRD increased dramatically in the 1980s and 1990s, the U.S. Renal Data System (USRDS) 2005 Annual Data Report shows that 338 out of every million Americans had kidney failure in 2003, down slightly from 340 per million in 2002. This report shows that the numbers of people developing ESRD have stabilized despite the persistent increase in the number of people diagnosed with type 2 diabetes mellitus (T2DM). These data attest to both the efficacy of the currently available therapeutic regimens for the treatment of ESRD as well as better overall patient care. Unfortunately, these encouraging statistics do not apply to all patients. According to the USRDS report, the most marked ESRD decrease was seen in young Caucasian men (<40 years of age), while in other patient groups, particularly African Americans, ESRD has not changed much at all. These observations suggest that more in-depth studies, addressing specific issues, such as race, are needed to understand the disease process fully in order to create novel therapeutic strategies to eradicate the disease completely in all patient populations. The most commonly used therapeutic treatments for diabetic nephropathy are angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (Ang II) receptor blockers (ARBs), implicating the importance of the renin-angiotensin-aldosterone system (RAAS) in the pathophysiology of diabetic nephropathy. The RAAS is not the only vasoactive hormonal system that is involved in the disease process. Over the past decade, studies have suggested that other vasoactive hormones, including endothelin, urotensin II, and the kallikrein-kinin system (KKS), are instrumental in mediating structural and functional alterations in the renal vasculature and parenchyma, leading to the development and progression of diabetic nephropathy. This review will summarize our current understanding of the contribution of vasoactive hormones in the pathophysiology of diabetic nephropathy with specific emphasis on the RAAS, especially the more recently identified components of this hormonal pathway.

Renoprotective effects of a selective estrogen receptor modulator, raloxifene, in an animal model of diabetic nephropathy.

BACKGROUND/AIMS: Our previous studies have shown that supplementation with 17beta-estradiol (E2) from the onset of diabetes attenuates diabetic nephropathy. However, E2 is accompanied by feminizing effects as well as adverse side effects on other organs. The current study examined the renoprotective effects of a selective estrogen receptor modulator, raloxifene (RAL), in an experimental model of diabetic nephropathy. RAL activates estrogen receptors and estrogen-receptor-mediated cellular events without the side effects of E2. METHODS: The study was performed in Sprague-Dawley nondiabetic (ND), streptozotocin-induced diabetic (D) and streptozotocin-induced D + RAL rats (n = 6/group). RESULTS: After 12 weeks of treatment, D was associated with increased urine albumin excretion (ND: 4.2 +/- 0.4; D: 41.3 +/- 9.0 mg/day), glomerulosclerosis [glomerulosclerotic index; ND: 0.26 +/- 0.04; D: 1.86 +/- 0.80 arbitrary units (AU)], tubulointerstitial fibrosis (tubulointerstitial fibrosis index; ND: 0.37 +/- 0.05; D: 2.12 +/- 0.50 AU), increased collagen type I [ND: 1.31 +/- 0.07; D: 4.65 +/- 0.09 relative optical density (ROD)], collagen type IV (ND: 0.64 +/- 0.03; D: 1.37 +/- 0.11 ROD) and transforming growth factor beta (TGF-beta) protein expression (ND: 0.65 +/- 0.08; D: 1.25 +/- 0.10 ROD), increased density of CD68-positive cells (ND: 1.37 +/- 3.02; D: 29.2 +/- 1.74 cells/mm2) and increased plasma levels of interleukin-6 (ND: 14.8 +/- 5.0; D: 51.3 +/- 14.0 pg/ml). Treatment with RAL partially or fully attenuated these processes (urine albumin excretion: 21.0 +/- 5.0 mg/day; glomerulosclerotic index: 0.40 +/- 0.06 AU; tubulointerstitial fibrosis index: 0.20 +/- 0.04 AU; collagen type I: 2.55 +/- 0.49 ROD; collagen type IV: 0.70 +/- 0.09 ROD; TGF-beta: 0.91 +/- 0.08 ROD; CD68: 6.03 +/- 2.38 cells/mm2; interleukin-6: 31.2 +/- 5.0 pg/ml). CONCLUSIONS: Our data indicate that treatment with RAL attenuates albuminuria and renal structural changes associated with diabetes.

Interactions between angiotensin ll and atrial natriuretic peptide in renomedullary interstitial cells: the role of neutral endopeptidase.

BACKGROUND/AIMS: Neutral endopeptidase (NEP) inhibition attenuates renal damage in the diabetic kidney, but little is known about the mechanisms of this renoprotective effect. METHODS: We examined the interaction between angiotensin II (Ang II) and atrial natriuretic peptide (ANP) under low (5 mM) and high (30 mM) glucose conditions, on cell proliferation and extracellular matrix (ECM) synthesis in renomedullary interstitial cells (RMICs) derived from wild-type (WT) and NEP-deficient (NEP-) mice. RESULTS: Under high glucose conditions, Ang II (10(-6)M) increased cell proliferation (control, 174.3 +/- 16.9; Ang II, 846.3 +/- 91.0 cpm/well) and ECM synthesis (control, 22.3 +/- 3.1; Ang II, 79.0 +/- 9.6 cpm/cell) in RMICs derived from WT and NEP- mice to a similar extent. ANP (10(-7)M) reduced Ang II-induced cell proliferation and ECM synthesis in RMICs derived from both strains, but more efficiently in RMICs derived from NEP- mice. The Ang II-induced cell proliferation and ECM synthesis was attenuated with AT1 receptor blockade, but more efficiently in RMICs-derived NEP- mice. CONCLUSIONS: This data shows that ANP and AT1 receptor blockade attenuate Ang II-induced RMIC proliferation and ECM synthesis more efficiently in the absence of NEP. These results support the concept that NEP inhibition is beneficial in attenuating abnormal cell growth and ECM metabolism associated with diabetic nephropathy.

Diabetic nephropathy is associated with decreased circulating estradiol levels and imbalance in the expression of renal estrogen receptors.

BACKGROUND: The incidence of cardiovascular and renal disease is lower in premenopausal women than in aged-matched men. However, in the setting of diabetes mellitus (DM), this "female advantage" no longer exists: the incidence and progression of DM and its associated end-organ complications are equal in men and women, regardless of age. We have recently reported that estrogen supplementation attenuates the progression of diabetic nephropathy, suggesting that lack of estrogen may nullify female sex as a protective factor against DM. OBJECTIVE: This study examined circulating levels of estradiol in DM and expression of estrogen receptor subtypes (ERa and ERP) in the nondiabetic (ND) and diabetic (D) kidney. METHODS: : The study was performed in ND and streptozotocin-induced D Sprague-Dawley rats after 2 weeks (male and female) and 12 weeks (female) of DM. The animals (N = 8/group) were kept either intact, ovariectomized (OVX), or OVX with 17beta-estradiol (E(2)) supplementation (OVX + E(2), 5 mug/kg/d). Plasma estradiol levels were measured by enzyme-linked immunosorbent assay, and expression of renal ERalpha and ERbeta was measured by immunohistochemistry and Western blot analysis. RESULTS: DM was associated with reduced circulating estradiol levels (ND: mean [SEM] 37.1 [7.2]; D: 24.5 [9.3] pg/mL; P < 0.05). The diabetic kidney exhibited increased expression of ERalpha protein (ND: 0.82 [0.06]; D: 1.15 [0.09] arbitrary units; P < 0.05), but no differences in ERP were observed. This resulted in an overall increase in the ratio of ERalpha/ERbeta protein expression in the diabetic kidney. No differences in the expression of ERa were observed in either females or males with similar glycemic levels after 2 weeks of DM. CONCLUSIONS: Reduced circulating levels of estradiol and imbalance in the expression of estrogen receptor subtypes in the diabetic kidney may explain why female sex is no longer a protective factor in the setting of DM. Thus, estradiol supplementation may be an effective regimen in attenuating the onset and progression of diabetic renal complications.

Estrogen regulates adrenal angiotensin AT1 receptors by modulating AT1 receptor translation.

Hypertension and associated cardiovascular disease increase after menopause. Angiotensin AT(1) receptor (AT(1)R) antagonists are effective treatments, in part, by inhibiting angiotensin II (Ang II)-induced aldosterone release from the adrenal zona glomerulosa (ZG). Estrogen decreases the number of AT(1)Rs in the adrenal gland and attenuates acute Ang II-induced aldosterone release. Here, we examined the effects of 17beta-estradiol (E(2)) on AT(1)R gene regulation in the rat adrenal cortex (AC). Female rats were ovariectomized and injected with vehicle or E(2). Immunohistochemistry revealed the presence of both estrogen receptor (ER)alpha and ERbeta in the ZG, and E(2) treatment increased the intensity of their nuclear staining. Under conditions in which AT(1)R maximal binding capacity was decreased by 46%, chronic miniosmotic pump Ang II-induced aldosterone secretion was reduced by 43%. E(2) treatment had no effect on AT(1a)R and AT(1b)R mRNA levels in the AC, whereas the AT(1)R mRNA polysome distribution in sucrose gradients was shifted to lighter fractions, indicating that E(2) treatment reduces AT(1)R translation. RNA binding proteins (RBPs) in AC extracts formed complexes with the 5' leader sequence (5'LS), coding region, and the 3'-untranslated region (3'UTR); however, only the activity of 5'LS RBPs was regulated by E(2) treatment. These data suggest that E(2), acting through its receptors in the ZG, reduces AT(1)R density and Ang II-induced aldosterone release, primarily by inhibiting AT(1)R translation, possibly by blocking ribosomal scanning caused by increased steric hindrance from 5'LS RBPs. Dysregulation of this posttranscriptional mechanism may contribute to the increased incidence of cardiovascular disease associated with menopause.

Obesity, metabolic syndrome and diabetic nephropathy.

Diabetic nephropathy is becoming an increasingly important cause of morbidity and mortality worldwide owing to the increasing prevalence of type 2 diabetes, largely driven by increasing obesity. There is considerable evidence that obesity, hypertension and other elements of the metabolic syndrome also contribute to the progression of renal disease independent of diabetes. How they interact and contribute to diabetic nephropathy, however, is not completely understood. Clinical diabetic nephropathy is preceded by an increase in glomerular filtration rate, microalbuminuria and glomerular hypertrophy. Poor glycemic control and elevated systolic blood pressure exacerbate proteinuria and renal injury that may culminate in end-stage renal disease. A similar sequence of events may lead to obesity-related renal disease even in the absence of diabetes. This chapter compares and contrasts factors involved in the development of glomerular hemodynamic and kidney pathological processes associated with diabetes and obesity.

Geminin overexpression induces mammary tumors via suppressing cytokinesis.

Aneuploidy plays an important role in the development of cancer. Here, we uncovered an oncogenic role for geminin in mitotic cells. In addition to chromatin, tyrosine phosphorylated geminin also localizes to centrosome, spindle, cleavage furrow and midbody during mitosis. Geminin binding to Aurora B prevents its binding to INCENP, and thus activation leading to lack of histone H3-(serine 10) phosphorylation, chromosome condensation failure, aborted cytokinesis and the formation of aneuploid, drug resistance cells. Geminin overexpressing human mammary epithelial cells form aneuploid, aggressive tumors in SCID mice. Geminin is overexpressed in more than half of all breast cancers analyzed. The current study reveals that geminin is a genuine oncogene that promotes cytokinesis failure and production of aneuploid, aggressive breast tumors when overexpressed and thus a worthy therapeutic target (oncotarget) for aggressive breast cancer.

Association between testosterone, estradiol and sex hormone binding globulin levels in men with type 1 diabetes with nephropathy.

Male sex is a risk factor for development and progression of diabetic nephropathy; however, the relationship between sex hormone levels and diabetic nephropathy in type 1 diabetic men is unknown. This was a prospective follow-up study as part of the nationwide Finnish Diabetic Nephropathy (FinnDiane) Study; 297 patients were followed for 5.9+/-1.5 years. Serum total testosterone (Tt) and estradiol (Te), calculated free testosterone (cFt) and estradiol (cFe) and sex hormone binding globulin were measured at baseline and correlated with urinary albumin excretion rate, estimated glomerular filtration rate and markers of metabolic syndrome. Diabetes without renal disease was associated with decreased Tt (p<0.001), Te (p<0.001) and cFt (p=0.001) levels compared with healthy non-diabetic men. With progression of renal disease from micro- to macroalbuminuria, this decrease in serum Tt was even more pronounced. Cox regression showed that cFt and cFe were independent predictors of the progression from macroalbuminuria to end-stage renal disease. Our study shows that men with type 1 diabetes exhibit dysregulated sex hormone levels, which is most pronounced in men with progressive renal disease, suggesting that sex hormones may play a role in the pathogenesis of diabetic nephropathy associated with type 1 diabetes.

Expression of aromatase, androgen and estrogen receptors in peripheral target tissues in diabetes.

Our previous studies have shown that diabetes in the male streptozotocin (STZ)-induced diabetic rat is characterized by a decrease in circulating testosterone and concomitant increase in estradiol levels. Interestingly, this increase in estradiol levels persists even after castration, suggesting extra-testicular origins of estradiol in diabetes. The aim of the present study was to examine whether other target organs of diabetes may be sources of estradiol. The study was performed in male Sprague-Dawley non-diabetic (ND), STZ-induced diabetic (D) and STZ-induced diabetic castrated (Dcas) rats (n=8-9/group). 14 weeks of diabetes was associated with decreased testicular (ND, 26.3+/-4.19; D, 18.4+/-1.54; P<0.05), but increased renal (ND, 1.83+/-0.92; D, 7.85+/-1.38; P<0.05) and ocular (D, 23.4+/-3.66; D, 87.1+/-28.1; P<0.05) aromatase activity. This increase in renal (Dcas, 6.30+/-1.25) and ocular (Dcas, 62.7+/-11.9) aromatase activity persisted after castration. The diabetic kidney also had increased levels of tissue estrogen (ND, 0.31+/-0.01; D, 0.51+/-0.11; Dcas, 0.45+/-0.08) as well as estrogen receptor alpha protein expression (ND, 0.63+/-0.09; D, 1.62+/-0.28; Dcas, 1.38+/-0.20). These data suggest that in male STZ-induced diabetic rats, tissues other than the testis may become sources of estradiol. In particular, the diabetic kidney appears to produce estradiol following castration, a state that is associated with a high degree or renal injury. Overall, our data provides evidence for the extra-testicular source of estradiol that in males, through an intracrine mechanism, may contribute to the development and/or progression of end-organ damage associated with diabetes.

Tumor necrosis factor-alpha antagonist etanercept decreases blood pressure and protects the kidney in a mouse model of systemic lupus erythematosus.

Chronic inflammation has been implicated in the pathology of hypertension; however, the role for specific cytokines remains unclear. We tested whether tumor necrosis factor-α blockade with etanercept (Etan) reduces mean arterial pressure in a female mouse model of systemic lupus erythematosus (SLE). SLE is a chronic inflammatory disorder with prevalent hypertension. Thirty-week-old SLE (NZBWF1) and control mice (NZW/LacJ) received Etan (0.8 mg/kg SC weekly) for 4 weeks or vehicle. Mean arterial pressure (in millimeters of mercury) was increased in SLE mice (150±5 versus 113±5 in controls; P<0.05) and was lower in Etan-treated SLE mice (132±3) but not controls (117±5). Albuminuria (in micrograms per milligram of creatinine) was elevated in SLE mice (28 742±9032 versus 1075±883; P<0.05) and was lower in Etan-treated SLE mice (8154±3899) but not control animals (783±226). Glomerulosclerosis (in percentage of glomeruli) was evident in SLE mice (2.5±1.6 versus 0.0±0.0 in controls; P<0.05) and was ameliorated in Etan-treated SLE mice (0.1±0.1). Renal cortex CD68(+) cell staining (in percentage of area) was elevated in SLE mice (4.75±0.80 versus 0.79±0.12 in controls; P<0.05) and was lower in Etan-treated SLE mice (2.28±0.32) but not controls (1.43±0.25). Renal cortex NADPH oxidase activity (relative light units per milligram of protein) was higher in SLE mice compared with controls (10 718±1276 versus 7584±229; P<0.05) and lowered in Etan-treated SLE mice (6645±490). Renal cortex nuclear factor κB (phosphorylated and nonphosphorylated) was increased in SLE mice compared with controls and lower in Etan-treated SLE mice. These data suggest that TNF-α mechanistically contributes to the development of hypertension in a chronic inflammatory disease through increased renal nuclear factor κB, oxidative stress, and inflammation.

Sex, diabetes and the kidney.

The incidence and the rate of progression of nondiabetic renal disease is generally greater in men compared with age-matched women, suggesting that the female sex is protective and/or that the male sex is a risk factor for the development and progression of nondiabetic renal disease. In diabetes, even though the male sex still appears to be a risk factor, this relationship is not as strong as it is in nondiabetic renal disease. Experimental evidence suggests that both estrogens and androgens play an important role in the pathophysiology of renal disease. Thus one of the potential mechanisms for the absence of a clear sex difference in the setting of diabetes may be alterations in sex hormone levels. Indeed, studies suggest that diabetes is a state of an imbalance in sex hormone levels; however, whether these changes correlate with the decline in renal function associated with diabetes is unclear. Furthermore, diabetic renal disease rarely develops before puberty, and the onset of puberty accelerates microalbuminuria, supporting the idea of the involvement of sex hormones in the development and progression of the disease. However, other than a handful of experimental studies indicating that treatment with or removal of sex hormones alters the course of diabetic renal disease, very few studies have actually directly examined the correlation between sex hormones and the disease development and progression. Further studies are necessary to determine the precise contribution of sex hormones in the pathophysiology of diabetic renal disease to develop novel and potentially sex-specific therapeutic treatments.