Proteomic analysis of liver in rats chronically exposed to fluoride.

Fluoride (F) is a potent anti-cariogenic element, but when ingestion is excessive, systemic toxicity may be observed. This can occur as acute or chronic responses, depending on both the amount of F and the time of exposure. The present study identified the profile of protein expression possibly associated with F-induced chronic hepatotoxicity. Weanling male Wistar rats (three-weeks old) were divided into three groups and treated with drinking water containing 0, 5 or 50 mg/L F for 60 days (n=6/group). At this time point, serum and livers were collected for F analysis, which was done using the ion-sensitive electrode, after hexamethyldisiloxane-facilitated diffusion. Livers were also submitted to histological and proteomic analyses (2D-PAGE followed by LC-MS/MS). Western blotting was done for confirmation of the proteomic data A dose-response was observed in serum F levels. In the livers, F levels were significantly increased in the 50 mg/L F group compared to groups treated with 0 and 5 mg/L F. Liver morphometric analysis did not reveal alterations in the cellular structures and lipid droplets were present in all groups. Proteomic quantitative intensity analysis detected 33, 44, and 29 spots differentially expressed in the comparisons between control vs. 5 mg/L F, control vs. 50 mg/L F, and 5 mg/L vs. 50 mg/L F, respectively. From these, 92 proteins were successfully identified. In addition, 18, 1, and 5 protein spots were shown to be exclusive in control, 5, and 50 mg/L F, respectively. Most of proteins were related to metabolic process and pronounced alterations were seen for the high-F level group. In F-treated rats, changes in the apolipoprotein E (ApoE) and GRP-78 expression may account for the F-induced toxicity in the liver. This can contribute to understanding the molecular mechanisms underlying hepatoxicity induced by F, by indicating key-proteins that should be better addressed in future studies.

Efeito da administração crônica de diferentes doses de fluoreto na glicemia, insulinemia e sinal insulínico em tecido muscular e hepático de ratos Wistar diabéticos e não diabéticos / Effect of chronic administration of different doses of fluoride on glucose, insulin and insulin signal in muscle and liver of diabetic and nondiabetic Wistar rats

O fluoreto (F) é amplamente empregado na Odontologia para o controle da cárie dentária. Entretanto apesar de suas propriedades terapêuticas, também pode oferecer riscos ao organismo se aplicado ou consumido de maneira indiscriminada ou inadequada. São encontrados estudos em humanos associando o consumo excessivo de F com intolerância à glicose. Estudos com animais submetidos a doses agudas ou crônicas altas de F revelam alterações na cascata de sinalização insulínica. Entretanto, seu efeito quando administrado em doses crônicas associadas àquelas equivalentes em humanos que recebam níveis ótimos de F através da água artificialmente fluoretada ou níveis aumentados através da água naturalmente fluoretada, ou ainda quando administrado a animais com diabetes já instalada, nunca foi testado. O presente trabalho teve por objetivo avaliar, em ratos normais ou com diabetes já instalada, expostos cronicamente a doses de F na água de beber que simulam a ingestão de F pela água natural e artificialmente fluoretada, parâmetros relacionados à interferência do F na resistência à insulina. Para tanto, foram utilizados inicialmente 214 ratos Wistar, com 60 dias de idade. Dentre estes, foi induzido diabetes em 133 animais por injeção intraperitoneal de estreptozotocina (50 mg/Kg peso corporal), sendo que 111 animais tiveram diabetes confirmado e foram aleatoriamente alocados a 3 grupos, diferindo em relação à concentração de F na água de beber (0, 10 ou 50 ppm), com a qual foram tratados por 22 dias. Oitenta e um animais não diabéticos foram também aleatoriamente alocados a estes 3 grupos. Decorrido o período experimental, os animais foram eutanasiados e foram avaliados: fluoremia, glicemia, insulinemia, concentração de F no fígado, a velocidade de desaparecimento da glicose sanguínea após estímulo insulínico (KITT), a resistência à insulina (HOMA2-IR), sensibilidade à insulina (%S) e função das células β pancreáticas (%B) e grau de fosforilação em tirosina do substrato...

Fluoride (F) is broadly used in Dentistry for caries control. However, despite its therapeutic properties, when used in excess, toxic signs and symptoms may occur. Studies conducted with humans have reported association between excessive F intake and glucose intolerance. Studies conducted with animals submitted to acute or high chronic doses of F have revealed alterations in the insulin signaling pathway. However, its effect when administered in chronic doses that simulate those present in the artificially or naturally fluoridated water ingested by humans, or when ingested by diabtetic animals, was not evaluated before. The present study aimed to evaluate in normoglycemic or diabetic rats chronically exposed to water containing F levels that simulate those present in the artificially or naturally fluoridated water, parameters related to the interference of F in the insulin resistance. For this purpose, 214 60-dayold Wistar rats were initially employed. Among these, diabetes was induced in 133 animals through intraperitoneal injection of streptozotocin (50 mg/Kg body weight).From these, 111 diabetic animals were randomly allocated to 3 groups that differed according to the F concentration on the water (0, 10 or 50 ppm) that was drank for 22 days. Eight-one non-diabetc animals were allocated to the same groups. After the experimental period, animals were euthanized and the following parameters were evaluated: fluoremia, glucemia, insulinemia, F concentration in the liver, velocity of disappearance of blood glucose (KITT), insulin resistance (HOMA2-IR), insulin sensitivity (%S), function of β pancreatic cells (%B), degree of insulin receptor substrate tyrosine phosphorylation state (pp 185, IRS-1/IRS-2) - after insulin stimulus in liver and muscle (Western blotting). Laboratory analyses revealed: 1) doseresponse for plasma and liver F concentrations that were higher in the diabetic animals compared to those non-diabetic; 2) glucemia was not...