Hepatocyte nuclear factors 1α/4α and forkhead box A2 regulate the solute carrier 2A2 (Slc2a2) gene expression in the liver and kidney of diabetic rats

AIMS: Solute carrier 2a2 (Slc2a2) gene codifies the glucose transporter GLUT2, a key protein for glucose flux in hepatocytes and renal epithelial cells of proximal tubule. In diabetes mellitus, hepatic and tubular glucose output has been related to Slc2a2/GLUT2 overexpression; and controlling the expression of this gene may be an important adjuvant way to improve glycemic homeostasis. Thus, the present study investigated transcriptional mechanisms involved in the diabetes-induced overexpression of the Slc2a2 gene. MAIN METHODS: Hepatocyte nuclear factors 1α and 4α (HNF-1α and HNF-4α), forkhead box A2 (FOXA2), sterol regulatory element binding protein-1c (SREBP-1c) and the CCAAT-enhancer-binding protein (C/EBPβ) mRNA expression (RT-PCR) and binding activity into the Slc2a2 promoter (electrophoretic mobility assay) were analyzed in the liver and kidney of diabetic and 6-day insulin-treated diabetic rats. KEY FINDINGS: Slc2a2/GLUT2 expression increased by more than 50% (P<0.001) in the liver and kidney of diabetic rats, and 6-day insulin treatment restores these values to those observed in non-diabetic animals. Similarly, the mRNA expression and the binding activity of HNF-1α, HNF-4α and FOXA2 increased by 50 to 100% (P<0.05 to P<0.001), also returning to values of non-diabetic rats after insulin treatment. Neither the Srebf1 and Cebpb mRNA expression, nor the SREBP-1c and C/EBP-β binding activity was altered in diabetic rats. SIGNIFICANCE: HNF-1α, HNF-4α and FOXA2 transcriptional factors are involved in diabetes-induced overexpression of Slc2a2 gene in the liver and kidney. These data point out that these transcriptional factors are important targets to control GLUT2 expression in these tissues, which can contribute to glycemic homeostasis in diabetes.

Unilateral giant renal angiomyolipoma and pulmonary lymphangioleiomyomatosis

Angiomyolipomas (AMLs) are mesenchymal neoplasms, named so because of the complex tissue composition represented by variable proportions of mature adipose tissue, smooth muscle cells, and dysmorphic blood vessels. Although AMLs may rise in different sites of the body, they are mostly observed in the kidney and liver. In the case of renal AMLs, they are described in two types: isolated AMLs and AMLs associated with tuberous sclerosis (TS). While most cases of AMLs are found incidentally during imaging examinations and are asymptomatic, others may reach huge proportions causing symptoms. Pulmonary lymphangioleiomyomatosis (LAM) is a rare benign disease characterized by cystic changes in the pulmonary parenchyma and smooth muscle proliferation, leading to a mixed picture of interstitial and obstructive disease. AML and LAM constitute major features of tuberous sclerosis complex (TSC), a multisystem autosomal dominant tumor-suppressor gene complex diagnosis. The authors report the case of a young female patient who presented a huge abdominal tumor, which at computed tomography (CT) show a fat predominance. The tumor displaced the right kidney and remaining abdominal viscera to the left. Chest CT also disclosed pulmonary lesions compatible with lymphangioleiomyomatosis. Because of sudden abdominal pain accompanied by a fall in the hemoglobin level, the patient underwent an urgent laparotomy. The excised tumor was shown to be a giant renal AML with signs of bleeding in its interior. The authors call attention to the diagnosis of AML and the huge proportions that the tumor can reach, as well as for ruling out the TSC diagnosis, once it may impose genetic counseling implications.

NF-κB activation mediates crystal translocation and interstitial inflammation in adenine overload nephropathy

Adenine overload promotes intratubular crystal precipitation and interstitial nephritis. We showed recently that these abnormalities are strongly attenuated in mice knockout for Toll-like receptors-2, -4, MyD88, ASC, or caspase-1. We now investigated whether NF-κB activation also plays a pathogenic role in this model. Adult male Munich-Wistar rats were distributed among three groups: C (n = 17), receiving standard chow; ADE (n = 17), given adenine in the chow at 0.7% for 1 wk and 0.5% for 2 wk; and ADE + pyrrolidine dithiocarbamate (PDTC; n = 14), receiving adenine as above and the NF-κB inhibitor PDTC (120 mg•kg-1•day-1 in the drinking water). After 3 wk, widespread crystal deposition was seen in tubular lumina and in the renal interstitium, along with granuloma formation, collagen accumulation, intense tubulointerstitial proliferation, and increased interstitial expression of inflammatory mediators. Part of the crystals were segregated from tubular lumina by a newly formed cell layer and, at more advanced stages, appeared to be extruded to the interstitium. p65 nuclear translocation and IKK-α increased abundance indicated activation of the NF-κB system. PDTC treatment prevented p65 migration and normalized IKK-α, limited crystal shift to the interstitium, and strongly attenuated interstitial fibrosis/inflammation. These findings indicate that the complex inflammatory phenomena associated with this model depend, at least in part, on NF-κB activation, and suggest that the NF-κB system may become a therapeutic target in the treatment of chronic kidney disease.

In search of mechanisms associated with mesenchymal stem cell-based therapies for acute kidney injury

Acute kidney injury (AKI) is classically described as a rapid loss of kidney function. AKI affects more than 15% of all hospital admissions and is associated with elevated mortality rates. Although many advances have occurred, intermittent or continuous renal replacement therapies are still considered the best options for reversing mild and severe AKI syndrome. For this reason, it is essential that innovative and effective therapies, without side effects and complications, be developed to treat AKI and the end-stages of renal disease. Mesenchymal stem cell (MSC) based therapies have numerous advantages in helping to repair inflamed and damaged tissues and are being considered as a new alternative for treating kidney injuries. Numerous experimental models have shown that MSCs can act via differentiation-independent mechanisms to help renal recovery. Essentially, MSCs can secrete a pool of cytokines, growth factors and chemokines, express enzymes, interact via cell-to-cell contacts and release bioagents such as microvesicles to orchestrate renal protection. In this review, we propose seven distinct properties of MSCs which explain how renoprotection may be conferred: 1) anti-inflammatory; 2) pro-angiogenic; 3) stimulation of endogenous progenitor cells; 4) anti-apoptotic; 5) anti-fibrotic; 6) anti-oxidant; and 7) promotion of cellular reprogramming. In this context, these mechanisms, either individually or synergically, could induce renal protection and functional recovery. This review summarises the most important effects and benefits associated with MSC-based therapies in experimental renal disease models and attempts to clarify the mechanisms behind the MSC-related renoprotection. MSCs may prove to be an effective, innovative and affordable treatment for moderate and severe AKI. However, more studies need to be performed to provide a more comprehensive global understanding of MSC-related therapies and to ensure their safety for future clinical applications.

Changes in renal glucose transporters in an animal model of metabolic syndrome

Considering the similarity between structural, hemodynamic, and functional changes of obesity-related renal disease and diabetic nephropathy, we hypothesized that renal glucose transporter changes occur in obesity as in diabetes. The aim of the work was to evaluate GLUT1 and GLUT2 in kidneys of an animal model of metabolic syndrome. Neonate spontaneously hypertensive rats (SHR), n=15/group, were treated with monosodium glutamate (5 mg/g) (MetS) for 9 days and compared with saline-treated Wistar-Kyoto (C) and SHR (H) rats. Lee index, systolic arterial pressure (SAP), glycemia, insulin resistance, triglycerides, and HDL cholesterol were evaluated at 3 and 6 months. Medullar GLUT1 and cortical GLUT2 were analyzed by Western blot. MetS vs. C and H rats had the highest Lee index (p<0.001) and insulin resistance (3-months C: 4.3±0.7, H: 3.9±0.9, MetS: 2.7±0.6; 6-months C: 4.2±0.6, H: 3.8±0.5, MetS: 2.4±0.6% • min−1, p<0.001), similar glycemia, and the lowest HDL-cholesterol at 6-months (p<0.001). In the MetS and H rats, SAP was higher vs. C at 3-months (p<0.001) and 6-months (C: 151±15, H: 190±11, MetS: 185±13 mm Hg, p<0.001) of age. GLUT1 was ̴ 13× lower (p<0.001) at 3-months, reestablishing its content at 6-months in MetS group, while GLUT2 was 2× higher (p<0.001) in this group at 6-months of age. Renal GLUT1 and GLUT2 are modulated in kidney of rats with metabolic syndrome, where obesity, insulin resistance and hypertension coexist, despite normoglycemia. Like in diabetes, cortical GLUT2 overexpression may contribute to the development of kidney disease

Renal GLUT1 reduction depends on angiotensin-converting enzyme inhibition in diabetic hypertensive rats

Aims: Angiotensin-converting enzyme (ACE) inhibitors are used in diabetic kidney disease to reduce systemic/intra-glomerular pressure. The objective of this study was to investigate whether reducing blood pressure (BP) could modulate renal glucose transporter expression, and urinary markers of diabetic nephropathy in diabetic hypertensive rats treated with ramipril or amlodipine. Main methods: Diabetes was induced in spontaneously-hypertensive rats (~210 g) by streptozotocin (50 mg/kg). Thirty days later, animals received ramipril 15 μg/kg/day (R, n =10), or amlodipine 10 mg/kg/day (A, n= 8,) or water (C, n = 10) by gavage. After 30-day treatment, body weight, glycaemia, urinary albumin and TGF-β1 (enzyme-linked immunosorbent assay) and BP (tail-cuff pressure method) were evaluated. Kidneys were removed for evaluation of renal cortex glucose transporters (Western blotting) and renal tissue ACE activity (fluorometric assay). Key findings: After treatments, body weight (p = 0.77) and glycaemia (p = 0.22) were similar among the groups. Systolic BP was similarly reduced (p < 0.001) in A and R vs. C (172.4 ± 3.2; 186.7 ± 3.7 and 202.2 ± 4.3 mm Hg; respectively). ACE activity (C: 0.903 ± 0.086; A: 0.654 ± 0.025, and R: 0.389 ± 0.057 mU/mg), albuminuria (C: 264.8 ± 15.4; A: 140.8 ± 13.5 and R: 102.8 ± 6.7 mg/24 h), and renal cortex GLUT1 content (C: 46.81 ± 4.54; A: 40.30 ± 5.39 and R: 26.89 ± 0.79 AU) decreased only in R (p < 0.001, p < 0.05 and p < 0.001; respectively). Significance:We concluded that the blockade of the renin–angiotensin systemwith ramipril reduced earlymarkers of diabetic nephropathy, a phenomenon that cannot be specifically related to decreased BP levels.

Complicações microvasculares da diabetes

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Determinación precoz de nefropatía diabética en base a parametros de laboratorio

Es importante diagnosticar tempranamente la afección renal y prevenir las alteraciones a nivel microvascular, para lo cual hemos tomado en consideración la determinación de la nicroalbuminuria, los niveles sanguíneos de fibrinógeno cuya elevación es considerada como factor de riesgo de la nefropatía. Los parámetros de control glucémico generados por la hemoglobina glicosilada y la fructosamina constituyen hasta hoy el mejor método para el control del metabolismo de los carboidratos, forman parte de nuestros objetivos, determinar sus valores. En nuestro estudio el 52 por ciento de la población estudiada presenta microalbuminuria basal positiva. El 70 por ciento de los investigados presenta un control dentro de parámetros normales, sin embargo el 52 por ciento de los pacientes con DM, a pesar de este buen control, presentan nofropatía irreversible. Del total de nefrópatas [52 por ciento], el 29 por ciento de los pacientes son del sexo femenino el 23 por ciento son del sexo masculino. Se observó que los años de evolución de la biabetes, tienen especial importancia en cuanto a la producción de la nefropatía, del 100 por cien de pacientes nefrópatas el 58 por ciento tenía entre 5 y 14 años de haber sido diagnosticado de diabetes.