RESUMO
Excessive intake of fructose results in metabolic syndrome (MS) and kidney damage, partly mediated by its metabolism by fructokinase-C or ketohexokinase-C (KHK-C). Osthol has antioxidant properties, is capable of regulating adipogenesis, and inhibits KHK-C activity. Here, we examined the potential protective role of osthol in the development of kidney disease induced by a Western (high-fat/high-sugar) diet. Control rats fed with a high-fat/high-sugar diet were compared with two groups that also received two different doses of osthol (30 mg/kg/d or 40 mg/kg/d body weight BW). A fourth group served as a normal control and received regular chow. At the end of the follow-up, kidney function, metabolic markers, oxidative stress, and lipogenic enzymes were evaluated. The Western diet induced MS (hypertension, hyperglycemia, hypertriglyceridemia, obesity, hyperuricemia), a fall in the glomerular filtration rate, renal tubular damage, and increased oxidative stress in the kidney cortex, with increased expression of lipogenic enzymes and increased kidney KHK expression. Osthol treatment prevented the development of MS and ameliorated kidney damage by inhibiting KHK activity, preventing oxidative stress via nuclear factor erythroid 2-related factor (Nrf2) activation, and reducing renal lipotoxicity. These data suggest that the nutraceutical osthol might be an ancillary therapy to slow the progression of MS and kidney damage induced by a Western diet.
Assuntos
Cumarínicos/farmacologia , Dieta Ocidental/efeitos adversos , Frutoquinases/antagonistas & inibidores , Nefropatias/prevenção & controle , Síndrome Metabólica/prevenção & controle , Animais , Cumarínicos/uso terapêutico , Dieta da Carga de Carboidratos/efeitos adversos , Dieta Hiperlipídica/efeitos adversos , Frutoquinases/metabolismo , Frutose/metabolismo , Nefropatias/etiologia , Nefropatias/metabolismo , Masculino , Síndrome Metabólica/etiologia , Síndrome Metabólica/metabolismo , Fator 2 Relacionado a NF-E2 , Estresse Oxidativo , Substâncias Protetoras/farmacologia , Substâncias Protetoras/uso terapêutico , Ratos , Ratos WistarRESUMO
Currently, there is the paradox of low water intake but increased intake of sugar-sweetened beverages (SB) in several populations; those habits are associated with an increased prevalence of metabolic derangements and greater chronic disease mortality. Persistent heat dehydration and increased SB intake stimulate the continued release of vasopressin and overactivation of the polyol-fructokinase pathway, synergizing each other, an effect partially mediated by oxidative stress. The objective of the present study was to evaluate whether water restriction concurrent with SB hydration can cause renal damage by stimulating similar pathways as heat dehydration. Three groups of male Wistar rats (n = 6) were fluid restricted; from 10 am to 12 pm animals could rehydrate with tap water (W), or sweetened beverages, one prepared with 11% of a fructose-glucose combination (SB), or with the noncaloric edulcorant stevia (ST). A normal control group of healthy rats was also studied. The animals were followed for 4 weeks. Markers of dehydration and renal damage were evaluated at the end of the study. Fluid restriction and water hydration mildly increased urine osmolality and induced a 15% fall in CrCl while increased the markers of tubular damage by NAG and KIM-1. Such changes were in association with a mild overexpression of V1a and V2 renal receptors, polyol fructokinase pathway overactivation, and increased renal oxidative stress with reduced expression of antioxidant enzymes. Hydration with SB significantly amplified those alterations, while in stevia hydrated rats, the changes were similar to the ones observed in water hydrated rats. These data suggest that current habits of hydration could be a risk factor in developing kidney damage.
Assuntos
Nefropatias , Rim/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Bebidas Adoçadas com Açúcar/efeitos adversos , Animais , Desidratação/metabolismo , Desidratação/patologia , Frutoquinases/metabolismo , Frutose/efeitos adversos , Frutose/farmacologia , Glucose/efeitos adversos , Glucose/farmacologia , Rim/patologia , Nefropatias/induzido quimicamente , Nefropatias/metabolismo , Nefropatias/patologia , Masculino , Ratos , Ratos Wistar , Receptores de Vasopressinas/metabolismoRESUMO
Chronic vasopressin secretion induced by recurrent mild heat stress exposure is significantly enhanced by limited rehydration with a fructose-containing beverage both in rodents and in humans. Moreover, this effect has been associated with upregulation of the polyol-fructokinase pathway and increased renal oxidative stress. Previously, we have shown that pharmacological inhibition of both V1a and V2 vasopressin receptors with conivaptan improved such renal alterations. The aim of this study was to evaluate the independent contributions of V1a and V2 receptors to the renal damage caused by mild heat stress and limited rehydration with a fructose-containing beverage. Osmotic minipumps were used to deliver either relcovaptan (0.64 mg/day) or tolvaptan (0.25 mg/day) in male Wistar rats for two weeks. Corresponding dilution vehicles were used as controls. To induce dehydration, rats were exposed to mild heat stress (37 °C for 1 h, Monday to Friday). All groups received a 10% fructose solution as a rehydration fluid for 2 h after mild heat stress. For the remainder of the day and on weekends, rats received tap water. The independent blockade of either the V1a or the V2 receptor prevented renal damage, reduced oxidative stress, and decreased plasma cortisol and systemic inflammation. However, the beneficial effects were regulated by different mechanisms. Tolvaptan inhibited polyol-fructokinase pathway overactivation, while relcovaptan prevented upregulation of the renin-angiotensin system and SGK1 expression. These data suggest that both V1a and V2 receptors participate in renal damage caused by heat stress-induced dehydration when fructose-containing beverages are used as rehydration fluids.
Assuntos
Bebidas/análise , Frutose/metabolismo , Resposta ao Choque Térmico , Receptores de Vasopressinas/metabolismo , Animais , Hidratação , Resposta ao Choque Térmico/efeitos dos fármacos , Hidrocortisona/sangue , Proteínas Imediatamente Precoces/genética , Proteínas Imediatamente Precoces/metabolismo , Indóis/farmacologia , Córtex Renal/metabolismo , Masculino , Estresse Oxidativo/efeitos dos fármacos , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Pirrolidinas/farmacologia , Ratos , Ratos Wistar , Insuficiência Renal Crônica/metabolismo , Insuficiência Renal Crônica/patologia , Sistema Renina-Angiotensina/efeitos dos fármacos , Temperatura , Tolvaptan/farmacologia , Regulação para Cima/efeitos dos fármacosRESUMO
Recently repeated heat stress and dehydration have been reported to cause oxidative stress and kidney damage that is enhanced by rehydrating with fructose solutions. We hypothesized that antioxidants might provide a novel way to prevent kidney damage. To test this hypothesis, mild heat stress was induced by exposing rats to 37 °C during 1 h in a closed chamber. The supplementation with water-soluble antioxidants (Antiox), ascorbic acid 1% plus N-acetyl cysteine 600 mg/L was done either in the 10% fructose 2 h rehydration fluid immediately after heat stress (Fructose 10% + Antiox), and/or in the tap water (Water + Antiox) for the remainder of the day, or in both fluids. After 4 weeks, control rats exposed to heat with fructose rehydration developed impaired renal function, tubular injury, intrarenal oxidative stress, a reduction in Nrf2-Keap1 antioxidant pathway, stimulation of vasopressin and the intrarenal polyol-fructokinase pathway. In contrast, dosing the antioxidants in the tap water (i.e., before the heat exposure and rehydration with fructose) preserved renal function, prevented renal tubule dysfunction and avoided the increase in systemic blood pressure. These effects were likely due to the amplification of the antioxidant defenses through increased Nrf2 nuclear translocation stimulated by the antioxidants and by the prevention of polyol fructokinase pathway overactivation. More studies to understand the mechanisms implicated in this pathology are warranted as there is recent evidence that they may be operating in humans as well.
Assuntos
Antioxidantes/farmacologia , Bebidas , Frutose/efeitos adversos , Resposta ao Choque Térmico , Nefropatias/metabolismo , Transporte Ativo do Núcleo Celular , Aldeído Redutase/metabolismo , Animais , Antioxidantes/administração & dosagem , Pressão Sanguínea , Núcleo Celular/metabolismo , Desidratação , Hidratação , Frutoquinases/metabolismo , Glutationa/metabolismo , Masculino , Óxido Nítrico Sintase Tipo III/metabolismo , Polímeros/metabolismo , Transporte Proteico , Ratos , Ratos WistarRESUMO
BACKGROUND: An epidemic of chronic kidney disease (CKD) of unknown cause has emerged along the Pacific Coast of Central America. The disease primarily affects men working manually outdoors, and the major group affected is sugarcane workers. The disease presents with an asymptomatic rise in serum creatinine that progresses to end-stage renal disease over several years. Renal biopsies show chronic tubulointerstitial disease. While the cause remains unknown, recent studies suggest that it is driven by recurrent dehydration in the hot climate. Potential mechanisms include the development of hyperosmolarity with the activation of the aldose reductase-fructokinase pathway in the proximal tubule leading to local injury and inflammation, and the possibility that renal injury may be the consequence of repeated uricosuria and urate crystal formation as a consequence of both increased generation and urinary concentration, similar to a chronic tumor lysis syndrome. The epidemic is postulated to be increasing due to the effects of global warming. SUMMARY: An epidemic of CKD has led to the death of more than 20,000 lives in Central America. The cause is unknown, but appears to be due to recurrent dehydration. Potential mechanisms for injury are renal damage as a consequence of recurrent hyperosmolarity and/or injury to the tubules from repeated episodes of uricosuria. KEY MESSAGES: The epidemic of CKD in Mesoamerica may be due to chronic recurrent dehydration as a consequence of global warming and working conditions. This entity may be one of the first major diseases attributed to climate change and the greenhouse effect.
Assuntos
Doenças dos Trabalhadores Agrícolas/diagnóstico , Desidratação/diagnóstico , Aquecimento Global , Falência Renal Crônica/diagnóstico , Insuficiência Renal Crônica/diagnóstico , Adulto , Doenças dos Trabalhadores Agrícolas/sangue , Doenças dos Trabalhadores Agrícolas/epidemiologia , Doenças dos Trabalhadores Agrícolas/patologia , Aldeído Redutase/metabolismo , América Central/epidemiologia , Creatinina/sangue , Desidratação/sangue , Desidratação/epidemiologia , Desidratação/patologia , Progressão da Doença , Ativação Enzimática , Frutoquinases/metabolismo , Temperatura Alta , Humanos , Falência Renal Crônica/sangue , Falência Renal Crônica/epidemiologia , Falência Renal Crônica/patologia , Túbulos Renais Proximais/metabolismo , Túbulos Renais Proximais/patologia , Masculino , Insuficiência Renal Crônica/sangue , Insuficiência Renal Crônica/epidemiologia , Insuficiência Renal Crônica/patologia , Ácido Úrico/sangueRESUMO
UNLABELLED: Fructose intake from added sugars has been implicated as a cause of nonalcoholic fatty liver disease. Here we tested the hypothesis that fructose may interact with a high-fat diet to induce fatty liver, and to determine if this was dependent on a key enzyme in fructose metabolism, fructokinase. Wild-type or fructokinase knockout mice were fed a low-fat (11%), high-fat (36%), or high-fat (36%) and high-sucrose (30%) diet for 15 weeks. Both wild-type and fructokinase knockout mice developed obesity with mild hepatic steatosis and no evidence of hepatic inflammation on a high-fat diet compared to a low-fat diet. In contrast, wild-type mice fed a high-fat and high-sucrose diet developed more severe hepatic steatosis with low-grade inflammation and fibrosis, as noted by increased CD68, tumor necrosis factor alpha, monocyte chemoattractant protein-1, alpha-smooth muscle actin, and collagen I and TIMP1 expression. These changes were prevented in the fructokinase knockout mice. CONCLUSION: An additive effect of high-fat and high-sucrose diet on the development of hepatic steatosis exists. Further, the combination of sucrose with high-fat diet may induce steatohepatitis. The protection in fructokinase knockout mice suggests a key role for fructose (from sucrose) in this development of steatohepatitis. These studies emphasize the important role of fructose in the development of fatty liver and nonalcoholic steatohepatitis.
Assuntos
Dieta Hiperlipídica , Fígado Gorduroso/etiologia , Frutoquinases/fisiologia , Sacarose/administração & dosagem , Animais , Ingestão de Energia , Frutose/metabolismo , Fígado/metabolismo , Fígado/patologia , Camundongos , Camundongos Endogâmicos C57BL , Aumento de PesoRESUMO
Fructose in sweetened beverages (SB) increases the risk for metabolic and cardiorenal disorders, and these effects are in part mediated by a secondary increment in uric acid (UA). Rodents have an active uricase, thus requiring large doses of fructose to increase plasma UA and to induce metabolic syndrome and renal hemodynamic changes. We therefore hypothesized that the effects of fructose in rats might be enhanced in the setting of uricase inhibition. Four groups of male Sprague-Dawley rats (n = 7/group) were studied during 8 wk: water + vehicle (V), water + oxonic acid (OA; 750 mg/k BW), sweetened beverage (SB; 11% fructose-glucose combination) + V, and SB + OA. Systemic blood pressure, plasma UA, triglycerides (TG), glucose and insulin, glomerular hemodynamics, renal structural damage, renal cortex and liver UA, TG, markers of oxidative stress, mitDNA, fructokinase, and fatty liver synthase protein expressions were evaluated at the end of the experiment. Chronic hyperuricemia and SB induced features of the metabolic syndrome, including hypertension, hyperuricemia, hyperglycemia, and systemic and hepatic TG accumulation. OA alone also induced glomerular hypertension, and SB alone induced insulin resistance. SB + OA induced a combined phenotype including metabolic and renal alterations induced by SB or OA alone and in addition also acted synergistically on systemic and glomerular pressure, plasma glucose, hepatic TG, and oxidative stress. These findings explain why high concentrations of fructose are required to induce greater metabolic changes and renal disease in rats whereas humans, who lack uricase, appear to be much more sensitive to the effects of fructose.