Food restriction promotes damage reduction in rat models of type 2 diabetes mellitus.

There are several animal models of type 2 diabetes mellitus induction but the comparison between models is scarce. Food restriction generates benefits, such as reducing oxidative stress, but there are few studies on its effects on diabetes. The objective of this study is to evaluate the differences in physiological and biochemical parameters between diabetes models and their responses to food restriction. For this, 30 male Wistar rats were distributed in 3 groups (n = 10/group): control (C); diabetes with streptozotocin and cafeteria-style diet (DE); and diabetes with streptozotocin and nicotinamide (DN), all treated for two months (pre-food restriction period). Then, the 3 groups were subdivided into 6, generating the groups CC (control), CCR (control+food restriction), DEC (diabetic+standard diet), DER (diabetic+food restriction), DNC (diabetic+standard diet) and DNR (diabetic+food restriction), treated for an additional two months (food restriction period). The food restriction (FR) used was 50% of the average daily dietary intake of group C. Throughout the treatment, physiological and biochemical parameters were evaluated. At the end of the treatment, serum biochemical parameters, oxidative stress and insulin were evaluated. Both diabetic models produced hyperglycemia, polyphagia, polydipsia, insulin resistance, high fructosamine, hepatic damage and reduced insulin, although only DE presented human diabetes-like alterations, such as dyslipidemia and neuropathy symptoms. Both DEC and DNC diabetic groups presented higher levels of protein carbonyl groups associated to lower antioxidant capacity in the plasma. FR promoted improvement of glycemia in DNR, lipid profile in DER, and insulin resistance and hepatic damage in both diabetes models. FR also reduced the protein carbonyl groups of both DER and DNR diabetic groups, but the antioxidant capacity was improved only in the plasma of DER group. It is concluded that FR is beneficial for diabetes but should be used in conjunction with other therapies.

Acute exercise and caffeine improve insulin-induced hypoglycemia in normal and malnourished rats / Exercício agudo e cafeína melhoram a hipoglicemia induzida por insulina em ratos normais e desnutridos

In food restriction, hypoglycemic episodes can be more severe and persistent. This study assessed the influence of acute exercise and caffeine on the insulin-induced hypoglycemia in freely-fed or malnourished (50% food restriction) young rats. At the age of 60 days, rats under overnight fasting received an insulin injection to cause an episode of hypoglycemia. In some animals, hypoglycemia was preceded by an acute session of exercise, in others, caffeine was orally given 15 minutes after insulin injection; or exercise and caffeine were combined. Blood samples were collected at regular intervals for five hours after insulin injection. A beneficial effect of both exercise or caffeine on the hypoglycemic episode in the malnourished rats was found. In the control rats, the association of exercise+caffeine was more beneficial than either intervention alone. It is discussed that exercise and caffeine, alone or combined, can be used as exogenous anti-hypoglycemic resources, but considering the nutritional status of the subject.

Na restrição alimentar, os episódios de hipoglicemia podem ser mais severos e persistentes. Este trabalho avaliou a influência do exercício agudo e da cafeína sobre a hipoglicemia induzida por insulina em ratos jovens alimentados livremente ou desnutridos (50% de restrição alimentar) desde o nascimento. Aos 60 dias de idade, os ratos em jejum noturno receberam injeção de insulina para causar um episódio de hipoglicemia. Em alguns animais, a hipoglicemia foi precedida por sessão aguda de exercício; em outros foi administrada a cafeína via oral, 15 min. após a injeção de insulina; ou foi associada a exercício e cafeína. Amostras de sangue foram coletadas em intervalos regulares por 5h desde a aplicação da insulina. Registrou-se efeito benéfico do exercício e da cafeína isolados sobre o episódio hipoglicêmico nos ratos desnutridos. Nos ratos controle, a associação de exercício+cafeína teve efeito benéfico mais acentuado do que as intervenções separadas. É discutido que exercício físico e cafeína, isolados ou combinados, podem ser explorados como recursos anti-hipoglicêmicos exógenos, levando-se em consideração porém o estado nutricional do indivíduo.