Influência do estresse oxidativo associado ao envelhecimento na sinalização da insulina em modelo de ratas tratadas com frutose

• Ano de defesa: 2014
• Autor(a) principal: Thomaz, Fernanda Malanconi [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo
• Palavras-chave em Português: Oxidative stress; Aging; Insulin resistance; Insulin signaling; Fructose; Estresse oxidativo; Envelhecimento; Resistência à insulina; Sinalização de insulina; Frutose
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=1321819; http://repositorio.unifesp.br/handle/11600/47492

Aging is a complex biological phenomenon often followed by socioeconomic changes that have a big impact on the nutritional status and needs of the elderly. Among the theories of aging, the free radical theory presents the aging process as a consequence of oxidative damage to cells and tissues, associated with a progressive increase in the chance of morbidity and mortality. This imbalance between ligh levels of oxidants and low levels of antioxidants is named as oxidative stress (OS). In addition to its association with a number of pathological processes, OS has been proposed as one of the causes of insulin resistance, since the substrates of the insulin receptor (IRS) may be inactivated with OS. IRS-1 and IRS-2 also have potential phosphorylation sites that are substrates for various kinases, including NFkB, JNK / SAPK and p-38 / MAPK, which are known for inactivation of the insulin signaling pathway. Therefore, we evaluate the influence of oxidative stress associated with aging in the expression and activation of JNK / MAPK and in the expression of elements of the insulin signaling pathway, such as IR-β, Akt and p-Akt in soleus, liver and adipose tissues from young (6 m.o.) and elderly (21-24 m.o.) Wistar female rats. The animals were placed in 4 groups: young control (JC), young fructose (JF), elderly control (IC), elderly fructose (IF). The animals which were submitted by insulin resistance treatment ingested fructose (100 mg / L) in the drinking water for 12 weeks, food and water intake of all groups was controlled. At the end of the treatment, GTT (glucose tolerance test) and ITT (Insulin Tolerance Test) were performed to confirm the efficacy of the animal model. To assess oxidative stress, the animals were anesthetized with ketamine and xylazine, and after perfusion with saline, the tissues were collected for the experiments. All the measurements to evaluate oxidative stress were performed by colorimetric methods. In the liver, the activities of superoxide dismutase (SOD) and catalase (CAT), were measured. The levels of oxidized (GSSG) and total (GSH) glutathione, as well as lipid peroxidation indicators were assessed in both liver and soleus skeletal muscle, as well as . In order to study the signaling pathways, another batch of animals was injected with regular insulin (0.1U / kg) and 15 minutes after injection they were anesthetized with pentobarbital and euthanized. In these animals, white adipose tissue (mesenteric, gonadal, and retroperitoneal) samples were collected and weighed for the study of adiposity of the animal model. Quantification of IR- β, JNK / SAPK and Akt expression and phosphorylation levels of Akt and JNK/ MAPK in the liver, soleus muscle and retroperitoneal adipose tissue were performed by Western blotting. No change was observed in the activity of SOD and CAT enzymes in liver, but a tendency to increase peroxidative potential in this tissue was observed after fructose treatment. The levels of total glutathione (GSHT) increased significantly in the IC group (compared to IF) and fructose treatment elicited an upward trend in treated groups and JF and IF, compared to their controls. Hepatic oxidized glutathione (GSSG) proved to be increased only in the IF group compared to its control IC. Moreover, in the soleus muscle of the animals, both age and treatment provided significant increase in the concentrations of GSSG and GSHT. Regarding cell signaling results, JNK phosphorylation (p-JNK) in the soleus tended to increase in the IC group compared to JC, accompanied by decreased levels of phosphorylated Akt (p-Akt) in the same groups. The expression of JNK in this tissue remained unchanged, but there was a trend of decrease in the expression of Akt. In the liver, p-Akt levels remained unchanged in the groups studied, as the level of p-JNK and expression of JNK. Although it has been demonstrated an increase in adiposity in fructose-treated animals, it has not been possible to identify any change in insulin signaling pathways, nor an increase of lipid peroxidation in the retroperitoneal adipose tissue in groups treated with fructose. Therefore it can be concluded that aging is a relevant factor in insulin signaling pathways in soleus muscle as changes were observed in this tissue. These effects can be possibly attributed to the decrease in the expression and phosphorylation of Akt that was observed in these subjects, resulting in lower performance of this signal transduction pathway. Our results suggest a potential antioxidant activity of estrogen in female rats treated with fructose, since there was a possible compensation in oxidative stress parameters following fructose treatment .