Vasopressin Mediates the Renal Damage Induced by Limited Fructose Rehydration in Recurrently Dehydrated Rats.

Recurrent dehydration and heat stress cause chronic kidney damage in experimental animals. The injury is exacerbated by rehydration with fructose-containing beverages. Fructose may amplify dehydration-induced injury by directly stimulating vasopressin release and also by acting as a substrate for the aldose reductase-fructokinase pathway, as both of these systems are active during dehydration. The role of vasopressin in heat stress associated injury has not to date been explored. Here we show that the amplification of renal damage mediated by fructose in thermal dehydration is mediated by vasopressin. Fructose rehydration markedly enhanced vasopressin (copeptin) levels and activation of the aldose reductase-fructokinase pathway in the kidney. Moreover, the amplification of the renal functional changes (decreased creatinine clearance and tubular injury with systemic inflammation, renal oxidative stress, and mitochondrial dysfunction) were prevented by the blockade of V1a and V2 vasopressin receptors with conivaptan. On the other hand, there are also other operative mechanisms when water is used as rehydration fluid that produce milder renal damage that is not fully corrected by vasopressin blockade. Therefore, we clearly showed evidence of the cross-talk between fructose, even at small doses, and vasopressin that interact to amplify the renal damage induced by dehydration. These data may be relevant for heat stress nephropathy as well as for other renal pathologies due to the current generalized consumption of fructose and deficient hydration habits.

Rehydration with soft drink-like beverages exacerbates dehydration and worsens dehydration-associated renal injury.

Recurrent dehydration, such as commonly occurs with manual labor in tropical environments, has been recently shown to result in chronic kidney injury, likely through the effects of hyperosmolarity to activate both vasopressin and aldose reductase-fructokinase pathways. The observation that the latter pathway can be directly engaged by simple sugars (glucose and fructose) leads to the hypothesis that soft drinks (which contain these sugars) might worsen rather than benefit dehydration associated kidney disease. Recurrent dehydration was induced in rats by exposure to heat (36°C) for 1 h/24 h followed by access for 2 h to plain water (W), a 11% fructose-glucose solution (FG, same composition as typical soft drinks), or water sweetened with noncaloric stevia (ST). After 4 wk plasma and urine samples were collected, and kidneys were examined for oxidative stress, inflammation, and injury. Recurrent heat-induced dehydration with ad libitum water repletion resulted in plasma and urinary hyperosmolarity with stimulation of the vasopressin (copeptin) levels and resulted in mild tubular injury and renal oxidative stress. Rehydration with 11% FG solution, despite larger total fluid intake, resulted in greater dehydration (higher osmolarity and copeptin levels) and worse renal injury, with activation of aldose reductase and fructokinase, whereas rehydration with stevia water had opposite effects. In animals that are dehydrated, rehydration acutely with soft drinks worsens dehydration and exacerbates dehydration associated renal damage. These studies emphasize the danger of drinking soft drink-like beverages as an attempt to rehydrate following dehydration.

Renal oxidative stress induced by long-term hyperuricemia alters mitochondrial function and maintains systemic hypertension.

We addressed if oxidative stress in the renal cortex plays a role in the induction of hypertension and mitochondrial alterations in hyperuricemia. A second objective was to evaluate whether the long-term treatment with the antioxidant Tempol prevents renal oxidative stress, mitochondrial alterations, and systemic hypertension in this model. Long-term (11-12 weeks) and short-term (3 weeks) effects of oxonic acid induced hyperuricemia were studied in rats (OA, 750 mg/kg BW), OA+Allopurinol (AP, 150 mg/L drinking water), OA+Tempol (T, 15 mg/kg BW), or vehicle. Systolic blood pressure, renal blood flow, and vascular resistance were measured. Tubular damage (urine N-acetyl-ß-D-glucosaminidase) and oxidative stress markers (lipid and protein oxidation) along with ATP levels were determined in kidney tissue. Oxygen consumption, aconitase activity, and uric acid were evaluated in isolated mitochondria from renal cortex. Short-term hyperuricemia resulted in hypertension without demonstrable renal oxidative stress or mitochondrial dysfunction. Long-term hyperuricemia induced hypertension, renal vasoconstriction, tubular damage, renal cortex oxidative stress, and mitochondrial dysfunction and decreased ATP levels. Treatments with Tempol and allopurinol prevented these alterations. Renal oxidative stress induced by hyperuricemia promoted mitochondrial functional disturbances and decreased ATP content, which represent an additional pathogenic mechanism induced by chronic hyperuricemia. Hyperuricemia-related hypertension occurs before these changes are evident.

Sodium-glucose cotransporter inhibition prevents oxidative stress in the kidney of diabetic rats.

UNLABELLED: The hyperglycemia triggers several chronic diabetic complications mediated by increased oxidative stress that eventually causes diabetic nephropathy. The aim of this study was to examine if the sodium-glucose cotransporter (SGLT2) inhibition prevents the oxidative stress in the kidney of diabetic rats. METHODS: The diabetic rat model was established by intraperitoneal injection of streptozotocin (50 mg/kg). The inhibition of SGLT2 was induced by daily subcutaneous administration of phlorizin (0.4 g/kg). Oxidative stress was assessed by catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities and by immunohistochemical analysis of 3-nitrotyrosine (3-NT). RESULTS: Streptozotocin-induced diabetes caused hyperglycemia and lower body weight. The CAT activity decreased in cortex and medulla from diabetic rats; in contrast, the GPx activity increased. Furthermore the 3-NT staining of kidney from diabetic rats increased compared to control rats. The inhibition of SGLT2 decreased hyperglycemia. However, significant diuresis and glucosuria remain in diabetic rats. The phlorizin treatment restores the CAT and GPX activities and decreases 3-NT staining. CONCLUSION: The inhibition of SGLT2 by phlorizin prevents the hyperglycemia and oxidative stress in kidney of diabetic rats, suggesting a prooxidative mechanism related to SGLT2 activity.

Ursodeoxycholic acid decreases sodium-glucose cotransporter (SGLT2) expression and oxidative stress in the kidney of diabetic rats.

UNLABELLED: Oxidative stress has been associated with diabetic complications like nephropathies. Recent studies indicate that ursodeoxycholic acid (UDCA) may be beneficial preventing diabetes-induced oxidative stress and secondary complications. Thus, we study if the UDCA-treatment decreases the expression of sodium-glucose cotransporter (SGLT2) and the oxidative stress in the kidney of diabetic rats. METHODS: The diabetes model was established by intraperitoneal injection of streptozotocin (50mg/kg). SGLT2 expression was evaluated by western blot and RT-PCR. Oxidative stress was assessed by catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase activities (SOD) and immunohistochemical analysis of 3-nitrotyrosine (3-NT). RESULTS: Streptozotocin-induced diabetes caused hyperglycemia and lower body weight. The SGLT2 expression and mRNA levels increased in cortex of kidney from diabetic rats. The CAT activity decreased in cortex and medulla from diabetic rats, otherwise the GPx activity increased. Furthermore the 3-NT staining of kidney from diabetic rats increased compared to control rats. The UDCA treatment was able to decrease hyperglycemia and prevents the SGLT2 over-expression, restores the CAT and GPX activities and decreases 3-NT staining. CONCLUSION: The UDCA treatment prevents the over-expression of SGLT2 and oxidative stress in kidney of diabetic rats.

Proximal femoral epiphysis anatomy in chilean population: orthopedic and forensic aspects / Anatomía del epífisis proximal del fémur en la población chilena. Aspectos traumatológicos y forenses

From a biomechanical standpoint, bone geometry and density are factors correlated to the bone resistance of the femur when supporting body weight, with geometric parameters like the diameter of the femoral head and neck, the length of the femoral neck, and the femoral neck angle as determinant factors in the incidence of hip fractures, which increase in frequency and seriousness in osteoporotic patients. In Chile, morphometric data that contributes to relating the anatomy of the proximal epiphysis of the femur as an associated factor in hip fractures does not exist; likewise, there are no anthropometric indexes that may contribute to the forensic sciences. The purpose of this study is to establish average measurements of the proximal epiphysis of the femur in the adult Chilean population. Descriptive Study. The proximal epiphyses of 81 dry adult femurs were analyzed (44 right and 37 left bones), measuring the following parameters: length of the femoral neck (LN), femoral neck angle (FNA), circumference of the femoral head (CH) and circumference of the femoral neck (CN). The statistical relationship between the measurements and the side of each sample was analyzed (t-test p=0.05). The average lengths were LN= 3.59cm (+/- 0.43 cm); FNA= 124.17 (+/- 6.37), CH= 14.34 cm (+/- 1.27 cm) and CN= 9.7 cm (+/- 0.87 cm). No significant differences between the left and right sides were found. Average numbers were obtained for the anatomy of the proximal femoral epiphysis from a sample in the Chilean population. With the data obtained, we propose to carry out anatomo-clinical, epidemiologic and forensic studies in this population.

Desde un punto de vista biomecánico, la geometría y la densidad ósea son factores correlacionados con la resistencia del hueso del fémur al apoyar el peso corporal, con los parámetros geométricos, como el diámetro de la cabeza femoral y el cuello, la longitud del cuello del fémur, y el ángulo del cuello femoral factores determinantes en la incidencia de fracturas de cadera, que aumentan en frecuencia y gravedad en los pacientes con osteoporosis. En Chile, no existen datos morfométricos que relacionen la anatomía de la epífisis proximal del fémur como un factor asociado a las fracturas de cadera ni índices antropométricos que pueden contribuir a las ciencias forenses. El propósito de este estudio es establecer las medidas promedio de la epífisis proximal de fémur en población adulta chilena. Estudio Descriptivo. Se analizaron la epífisis proximal de 81 fémures adultos secos (44 derechos y 37 izquierdos), midiendo los siguientes parámetros: longitud del cuello femoral (LC) , ángulo cérvico-diafisiario femoral (ACD), circunferencia de la cabeza femoral (CCa) y circunferencia del cuello femoral (CCu). Se analizó la relación estadística de las medidas con el lado de cada muestra (test Chi cuadrado p:0,05) Las longitudes promedios fueron LC: 3,59 cm (+/- 0,43 cm); ACD: 124,17 (+/- 6,37 cm); CCa: 14,34 cm (+/- 1,27 cm) y CCu: 9,7 cm (+/- 0,87 cm). No se encontraron diferencias significativas entre el lado derecho e izquierdo. Los resultados proponen la necesidad de realizar estudios anatomo-clínicos y epidemiológicos actualizados en población chilena donde la geometría de la epífisis proximal del fémur se incluya dentro del análisis.

Sphingosine-1-phosphate induced vasoconstriction is increased in the isolated perfused kidneys of diabetic rats.

We observed that in isolated perfused rat kidneys, sphingosine-1-phosphate produces S1P(2) receptor-mediated vasoconstriction, and this response increased in kidneys of diabetic rats. These results suggest that the antagonists of S1P(2) receptor may have potential as drugs to control diabetes-induced vascular complications.

Contribution of renal purinergic receptors to renal vasoconstriction in angiotensin II-induced hypertensive rats.

To investigate the participation of purinergic P2 receptors in the regulation of renal function in ANG II-dependent hypertension, renal and glomerular hemodynamics were evaluated in chronic ANG II-infused (14 days) and Sham rats during acute blockade of P2 receptors with PPADS. In addition, P2X1 and P2Y1 protein and mRNA expression were compared in ANG II-infused and Sham rats. Chronic ANG II-infused rats exhibited increased afferent and efferent arteriolar resistances and reductions in glomerular blood flow, glomerular filtration rate (GFR), single-nephron GFR (SNGFR), and glomerular ultrafiltration coefficient. PPADS restored afferent and efferent resistances as well as glomerular blood flow and SNGFR, but did not ameliorate the elevated arterial blood pressure. In Sham rats, PPADS increased afferent and efferent arteriolar resistances and reduced GFR and SNGFR. Since purinergic blockade may influence nitric oxide (NO) release, we evaluated the role of NO in the response to PPADS. Acute blockade with N(ω)-nitro-l-arginine methyl ester (l-NAME) reversed the vasodilatory effects of PPADS and reduced urinary nitrate excretion (NO(2)(-)/NO(3)(-)) in ANG II-infused rats, indicating a NO-mediated vasodilation during PPADS treatment. In Sham rats, PPADS induced renal vasoconstriction which was not modified by l-NAME, suggesting blockade of a P2X receptor subtype linked to the NO pathway; the response was similar to that obtained with l-NAME alone. P2X1 receptor expression in the renal cortex was increased by chronic ANG II infusion, but there were no changes in P2Y1 receptor abundance. These findings indicate that there is an enhanced P2 receptor-mediated vasoconstriction of afferent and efferent arterioles in chronic ANG II-infused rats, which contributes to the increased renal vascular resistance observed in ANG II-dependent hypertension.

Enalaprilat-mediated activation of kinin b(1) receptors and vasodilation in the rat isolated perfused kidney.

The present study evaluated whether enalaprilat (the active form of enalapril, an angiotensin-converting enzyme inhibitor) activates B(1) receptors. We observed that the levels of B(1) receptor mRNA and protein expression were upregulated in the kidneys of diabetic rats. Bradykinin (BK)-induced renal vasodilation decreased in isolated perfused kidneys of diabetic rats, but des-Arg(9)-BK-induced renal vasodilation increased. Enalaprilat also produced vasodilation in the isolated perfused kidneys of control and diabetic rats. The response to des-Arg(9)-BK or enalaprilat was blocked by Lys-(des-Arg(9), Leu(8))-BK (a B(1) receptor antagonist) and N-nitro-L-arginine methyl ester (an inhibitor of nitric oxide synthase). These results suggest that enalaprilat activates B(1) receptors and stimulates the production of nitric oxide in the kidneys of both control and diabetic rats.

Effect of phlorizin on SGLT2 expression in the kidney of diabetic rats.

BACKGROUND: The purpose of our study was to determine whether increased SGLT2 expression in the kidney of diabetic rats was associated with the development of hypertension and to investigate the effect of phlorizin (P) on blood pressure and SGLT2 expression in diabetic rats. METHODS: The animals were divided into two groups: Control (C) and streptozotocin-induced diabetic (D) rats were used to evaluate SGLT2 activity in brush border membrane vesicles (BBMV) using a rapid filtration technique. Others animals were divided into two groups: Normal (NSD) or high salt diet (4%)(HSD), and subdivided in four groups: C, C+P, D, D+P. Systolic blood pressure (SBP) was recorded for 30 days by the use of a telemetric system and at day 30 urine samples (24 h) were collected to evaluate renal function and SGLT2 expression in the renal cortex. RESULTS: At day 30, diabetic animals with NSD or HSD exhibited hyperglycemia, lower body weight, glycosuria, diuresis, decrease natriuresis, increased SBP values and SGLT2 expression. In diabetic rats, phlorizin treatment decreased hyperglycemia and prevented development of hypertension, decreased SGLT2 activity in BBMV but did not modify SGLT2 expression. CONCLUSIONS: In conclusion, SGLT2 inhibition prevented the development of hypertension in diabetic rats as well as hyperglycemia, suggesting a hypertensive mechanism associated with SGLT2 activity and the likelihood that increased SGLT2 expression may be associated with progression of diabetic renal complications.

Effect of treatment with losartan on salt sensitivity and SGLT2 expression in hypertensive diabetic rats.

Sodium-glucose cotransporters (SGLTs) in the kidney, may be involved in hypertension, diabetes and salt sensitivity. We evaluate the effect of losartan on blood pressure (BP) and SGLT2 expression in diabetic rats with high or normal salt diet. Losartan prevented an increase in BP and SGLT2 expression in diabetic rats.