Débora Rieger

High fat and highly thermolyzed fat diets promote insulin resistance and increase DNA damage in rats.

Many studies have demonstrated that DNA damage may be associated with type 2 diabetes mellitus (T2DM) and its complications. The goal of this study was to evaluate the effects of the potential relationship between fat (thermolyzed) intake, glucose dyshomeostasis and DNA injury in rats. Biochemical parameters related to glucose metabolism (i.e., blood glucose levels, insulin tolerance tests, glucose tolerance tests and fat cell glucose oxidation) and general health parameters (i.e., body weight, retroperitoneal and epididymal adipose tissue) were evaluated in rats after a 12-month treatment with either a high fat or a high thermolyzed fat diet. The high fat diet (HFD) and high fat thermolyzed diet (HFTD) showed increased body weight and impaired insulin sensitivity at the studied time-points in insulin tolerance test (ITT) and glucose tolerance test (GTT). Interestingly, only animals subjected to the HFTD diet showed decreased epididymal fat cell glucose oxidation. We show which high fat diets have the capacity to reduce glycogen synthesis by direct and indirect pathways. HFTD promoted an increase in lipid peroxidation in the liver, demonstrating significant damage in lipids in relation to other groups. Blood and hippocampus DNA damage was significantly higher in animals subjected to HFDs, and the highest damage was observed in animals from the HFTD group. Striatum DNA damage was significantly higher in animals subjected to HFDs, compared with the control group. These results show a positive correlation between high fat diet, glucose dyshomeostasis, oxidative stress and DNA damage.

Alterations of PI3K and Akt signaling pathways in the hippocampus and hypothalamus of Wistar rats treated with highly palatable food

Abstract Background/objectives Highly palatable food (HPF), which is enriched in simple sugars and saturated fat, contributes to obesity and insulin resistance in humans. These metabolic changes are associated with serious complications of the central nervous system, including an elevated risk of cognitive dysfunction. We, herein, treated rats with HPF and then examined the insulin-signaling pathway, in particular, the levels of phosphatidylinositol-3 kinase (PI3K), Akt, and insulin receptor substrate-1 (IRS-1) in the hippocampus and hypothalamus. Methods Adult Wistar rats fed with HPF (heated or not during preparation) for 4 months and then measured the levels of PI3K, Akt, and IRS-1 in the hippocampus and hypothalamus, by western blotting and quantitative real-time polymerase chain reaction. Results We observed changes in body weight, glucose intolerance, and lipidemia, confirming that peripheral metabolic alterations were induced using this model. Hippocampal PI3K and hypothalamic Akt were affected in rats that are submitted to chronic exposure to an HPF diet. Moreover, heated HPF caused differentiated alterations in the regulatory subunit of PI3K in the hippocampus. Discussion Our data suggest that this diet alters insulin signaling differentially in each brain region, and that hippocampal changes induced by this diet could contribute to the understanding of cognitive impairments that are dependent on the hippocampus.

Experimental Hypothyroidism Inhibits δ-Aminolevulinate Dehydratase Activity in Neonatal Rat Blood and Liver:

The aim of this study was to investigate the potential relationship between hypothyroidism and δ-aminolevulinate dehydratase (δ-ALA-D) activity in rat blood and liver. Experimental hypothyroidism was induced in weanling rats by exposing their mothers to propylthiouracil (PTU) diluted in tap water (0.05% w/ v), ad libitum, during the lactational period (PTU group). Control (euthyroid) group included weanling rats whose mothers received just tap water, ad libitum, during the lactational period. Reverted-hypothyroid group (PTU + 3,3′,5-triiodo-L-thyronine [T3]) included weanling rats whose mothers were exposed to PTU similarly to those in the hypothyroid group, but pups received daily subcutaneous injections of T3 (20 μg/kg, from Postnatal Days 2–20). After the treatment, serum T3 levels were drastically decreased (around 70%) in the PTU group, and this phenomenon was almost reverted by exogenous T3. PTU decreased blood δ-ALA-D activity by 75%, and T3 treatment prevented such phenomena. Erythrocytes and hemoglobin levels were increased by 10% in PTU-treated animals and higher increments (around 25%) were observed in these parameters when exogenous T3 was coadministered. Dithiothreitol did not change blood δ-ALA-D activity of PTU-exposed animals when present in the reaction medium, suggesting no involvement of the enzyme’s essential thiol groups in PTU-induced δ-ALA-D inhibition. PTU did not affect blood δ-ALA-D activity in vitro. These results are the first to show a correlation between hypothyroidism and decreased δ-ALA-D activity and point to this enzyme as a potential molecule involved with hypothyroidism-related hematological changes.

Effects of glyoxal or methylglyoxal on the metabolism of amino acids, lactate, glucose and acetate in the cerebral cortex of young and adult rats

The in vitro effects of glyoxal and methylglyoxal on the metabolism of glycine, alanine, leucine, glutamate, glutamine, glucose, lactate and acetate were evaluated in cortico-cerebral slices from young (10-day-old) or adult (3-month-old) rats. In a first set of experiments with cortico-cerebral slices from young animals, the compounds glyoxal or methylglyoxal at 400 microM, increased the oxidation of alanine, leucine and glycine to CO(2) and decreased the protein synthesis from these amino acids. Lipid synthesis from alanine, leucine and glycine was not changed in the cortico-cerebral slices from young rats after glyoxals exposure. Moreover, glutamine oxidation to CO(2) decreased by glyoxals exposure, but glutamate oxidation was not affected. In a second set of experiments with brain slices from adult animals, glycine metabolism (oxidation to CO(2), conversion to lipids or incorporation into proteins) was not changed by glyoxals exposure. In addition, the oxidation rates of glucose, lactate, acetate, glutamine and glutamate to CO(2) were also not modified. Taken together, these results indicate that glyoxal disrupts the energetic metabolism of the rat cerebral cortex in vitro. However, only young animals were susceptible to such events, suggesting that the immature cerebral cortex is less capable of dealing with glyoxal than the mature one.

Dietary n-3 long-chain polyunsaturated fatty acids modify phosphoenolpyruvate carboxykinase activity and lipid synthesis from glucose in adipose tissue of rats fed a high-sucrose diet

Long‐chain polyunsaturated n‐3 fatty acids (n‐3 LCPUFAs) have hypolipidemic effects and modulate intermediary metabolism to prevent or reverse insulin resistance in a way that is not completely elucidated. Here, effects of these fatty acids on the lipid profile, phosphoenolpyruvate carboxykinase (PEPCK) activity, lipid synthesis from glucose in epididymal adipose tissue (Ep‐AT) and liver were investigated. Male rats were fed a high‐sucrose diet (SU diet), containing either sunflower oil or a mixture of sunflower and fish oil (SU–FO diet), and the control group was fed a standard diet. After 13 weeks, liver, adipose tissue and blood were harvested and analysed. The dietary n‐3 LCPUFAs prevented sucrose‐induced increase in adiposity and serum free fat acids, serum and hepatic triacylglycerol and insulin levels. Furthermore, these n‐3 LCPUFAs decreased lipid synthesis from glucose and increased PEPCK activity in the Ep‐AT of rats fed the SU–FO diet compared to those fed the SU diet, besides reducing lipid synthesis from glucose in hepatic tissue. Thus, the inclusion of n‐3 LCPUFAs in the diet may be beneficial for the prevention or attenuation of dyslipidemia and insulin resistance, and for reducing the risk of related chronic diseases. Copyright