Lara M. Gomes

Evaluation of Krebs cycle enzymes in the brain of rats after chronic administration of antidepressants

Several works report brain impairment of metabolism as a mechanism underlying depression. Citrate synthase and succinate dehydrogenase are enzymes localized within cells in the mitochondrial matrix and are important steps of Krebs cycle. In addition, citrate synthase has been used as a quantitative enzyme marker for the presence of intact mitochondria. Thus, we investigated citrate synthase and succinate dehydrogenase activities from rat brain after chronic administration of paroxetine, nortriptiline and venlafaxine. Adult male Wistar rats received daily injections of paroxetine (10mg/kg), nortriptiline (15mg/kg), venlafaxine (10mg/kg) or saline in 1.0mL/kg volume for 15 days. Twelve hours after the last administration, the rats were killed by decapitation, the hippocampus, striatum and prefrontal cortex were immediately removed, and activities of citrate synthase and succinate dehydrogenase were measured. We verified that chronic administration of paroxetine increased citrate synthase activity in the prefrontal cortex, hippocampus, striatum and cerebral cortex of adult rats; cerebellum was not affected. Chronic administration of nortriptiline and venlafaxine did not affect the enzyme activity in these brain areas. Succinate dehydrogenase activity was increased by chronic administration of paroxetine and nortriptiline in the prefrontal cortex, hippocampus, striatum and cerebral cortex of adult rats; cerebellum was not affected either. Chronic administration of venlafaxine increased succinate dehydrogenase activity in prefrontal cortex, but did not affect the enzyme activity in cerebellum, hippocampus, striatum and cerebral cortex. Considering that metabolism impairment is probably involved in the pathophysiology of depressive disorders, an increase in these enzymes by antidepressants may be an important mechanism of action of these drugs.

Decaffeinated green tea extract rich in epigallocatechin-3-gallate prevents fatty liver disease by increased activities of mitochondrial respiratory chain complexes in diet-induced obesity mice

Nonalcoholic fatty liver disease has been considered the hepatic manifestation of obesity. It is unclear whether supplementation with green tea extract rich in epigallocatechin-3-gallate (EGCG) influences the activity of mitochondrial respiratory chain complexes and insulin resistance in the liver. EGCG regulated hepatic mitochondrial respiratory chain complexes and was capable of improving lipid metabolism, attenuating insulin resistance in obese mice. Mice were divided into four groups: control diet+water (CW) or EGCG (CE) and hyperlipidic diet+water (HFW) or EGCG (HFE). All animals received water and diets ad libitum for 16 weeks. Placebo groups received water (0.1 ml/day) and EGCG groups (0.1 ml EGCG and 50 mg/kg/day) by gavage. Cytokines concentrations were obtained by ELISA, protein expression through Western blotting and mitochondrial complex enzymatic activity by colorimetric assay of substrate degradation. HFW increased body weight gain, adiposity index, retroperitoneal and mesenteric adipose tissue relative weight, serum glucose, insulin and Homeostasis Model Assessment of Basal Insulin Resistance (HOMA-IR); glucose intolerance was observed in oral glucose tolerance test (OGTT) as well as ectopic fat liver deposition. HFE group decreased body weight gain, retroperitoneal and mesenteric adipose tissue relative weight, HOMA-IR, insulin levels and liver fat accumulation; increased complexes II-III and IV and malate dehydrogenase activities and improvement in glucose uptake in OGTT and insulin sensitivity by increased protein expression of total AKT, IRα and IRS1. We did not find alterations in inflammatory parameters analyzed. EGCG was able to prevent obesity stimulating the mitochondrial complex chain, increasing energy expenditure, particularly from the oxidation of lipid substrates, thereby contributing to the prevention of hepatic steatosis and improved insulin sensitivity.

Effects of acute and chronic treatment elicited by lamotrigine on behavior, energy metabolism, neurotrophins and signaling cascades in rats.

The present study was aimed to investigate the behavioral and molecular effects of lamotrigine. To this aim, Wistar rats were treated with lamotrigine (10 and 20 mg/kg) or imipramine (30 mg/kg) acutely and chronically. The behavior was assessed using forced swimming test. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), Proteina Kinase B (PKB, AKT), glycogen synthase kinase 3 (GSK-3) and B-cell lymphoma 2 (Bcl-2) levels, citrate synthase, creatine kinase and mitochondrial chain (I, II, II-III and IV) activities were assessed in the brain. The results showed that both treatments reduced the immobility time. The BDNF were increased in the prefrontal after acute treatment with lamotrigine (20 mg/kg), and the BDNF and NGF were increased in the prefrontal after chronic treatment with lamotrigine in all doses. The AKT increased and Bcl-2 and GSK-3 decreased after both treatments in all brain areas. The citrate synthase and creatine kinase increased in the amygdala after acute treatment with imipramine. Chronic treatment with imipramine and lamotrigine (10 mg/kg) increased the creatine kinase in the hippocampus. The complex I was reduced and the complex II, II-III and IV were increased, but related with treatment and brain area. In conclusion, lamotrigine exerted antidepressant-like, which can be attributed to its effects on pathways related to depression, such as neurotrophins, metabolism energy and signaling cascade.

Palmitoleic Acid (N-7) Attenuates the Immunometabolic Disturbances Caused by a High-Fat Diet Independently of PPARα

Palmitoleic acid (PMA) has anti-inflammatory and antidiabetic activities. Here we tested whether these effects of PMA on glucose homeostasis and liver inflammation, in mice fed with high-fat diet (HFD), are PPAR-α dependent. C57BL6 wild-type (WT) and PPAR-α-knockout (KO) mice fed with a standard diet (SD) or HFD for 12 weeks were treated after the 10th week with oleic acid (OLA, 300 mg/kg of b.w.) or PMA 300 mg/kg of b.w. Steatosis induced by HFD was associated with liver inflammation only in the KO mice, as shown by the increased hepatic levels of IL1-beta, IL-12, and TNF-α; however, the HFD increased the expression of TLR4 and decreased the expression of IL1-Ra in both genotypes. Treatment with palmitoleate markedly attenuated the insulin resistance induced by the HFD, increased glucose uptake and incorporation into muscle in vitro, reduced the serum levels of AST in WT mice, decreased the hepatic levels of IL1-beta and IL-12 in KO mice, reduced the expression of TLR-4 and increased the expression of IL-1Ra in WT mice, and reduced the phosphorylation of NF 𝜅B (p65) in the livers of KO mice. We conclude that palmitoleate attenuates diet-induced insulin resistance, liver inflammation, and damage through mechanisms that do not depend on PPAR-α.

Gold nanoparticles alter parameters of oxidative stress and energy metabolism in organs of adult rats.

This study evaluated the parameters of oxidative stress and energy metabolism after the acute and long-term administration of gold nanoparticles (GNPs, 10 and 30 nm in diameter) in different organs of rats. Adult male Wistar rats received a single intraperitoneal injection or repeated injections (once daily for 28 days) of saline solution, GNPs-10 or GNPs-30. Twenty-four hours after the last administration, the animals were killed, and the liver, kidney, and heart were isolated for biochemical analysis. We demonstrated that acute administration of GNPs-30 increased the TBARS levels, and that GNPs-10 increased the carbonyl protein levels. The long-term administration of GNPs-10 increased the TBARS levels, and the carbonyl protein levels were increased by GNPs-30. Acute administration of GNPs-10 and GNPs-30 increased SOD activity. Long-term administration of GNPs-30 increased SOD activity. Acute administration of GNPs-10 decreased the activity of CAT, whereas long-term administration of GNP-10 and GNP-30 altered CAT activity randomly. Our results also demonstrated that acute GNPs-30 administration decreased energy metabolism, especially in the liver and heart. Long-term GNPs-10 administration increased energy metabolism in the liver and decreased energy metabolism in the kidney and heart, whereas long-term GNPs-30 administration increased energy metabolism in the heart. The results of our study are consistent with other studies conducted in our research group and reinforce the fact that GNPs can lead to oxidative damage, which is responsible for DNA damage and alterations in energy metabolism.

Brain energy metabolism is activated after acute and chronic administration of fenproporex in young rats.

Obesity is a chronic disease of multiple etiologies, including genetic, metabolic, environmental, social, and other factors. Pharmaceutical strategies in the treatment of obesity include drugs that regulate food intake, thermo genesis, fat absorption, and fat metabolism. Fenproporex is the second most commonly consumed amphetamine‐based anorectic worldwide; this drug is rapidly converted in vivo into amphetamine. Studies suggest that amphetamine induces neurotoxicity through generation of free radicals and mitochondrial apoptotic pathway by cytochrome c release, accompanied by a decrease of mitochondrial membrane potential. Mitochondria are intracellular organelles that play a crucial role in ATP production. Thus, in the present study we evaluated the activities of some enzymes of Krebs cycle, mitochondrial respiratory chain complexes and creatine kinase in the brain of young rats submitted to acute and chronic administration of fenproporex. In the acute administration, the animals received a single injection of fenproporex (6.25, 12.5 or 25 mg/kg i.p.) or tween. In the chronic administration, the animals received a single injection daily for 14 days of fenproporex (6.25, 12.5 or 25 mg/Kg i.p.). Two hours after the last injection, the rats were sacrificed by decapitation and the brain was removed for evaluation of biochemical parameters. Our results showed that the activities of citrate synthase, malate dehydrogenase and succinate dehydrogenase were increased by acute and chronic administration of fenproporex. Complexes I, II, II–III and IV and creatine kinase activities were also increased after acute and chronic administration of the drug. Our results are consistent with others reports that showed that some psychostimulant drugs increased brain energy metabolism in young rats.

Evaluation of the protective effect of Ilex paraguariensis and Camellia sinensis extracts on the prevention of oxidative damage caused by ultraviolet radiation

We evaluated the effects green and mate teas on oxidative and DNA damages in rats exposed to ultraviolet radiation. Were utilized 70 adult male Wistar rats that received daily oral or topic green or mate tea treatment during exposed to radiation by seven days. After, animals were killed by decapitation. Thiobarbituric acid-reactive species levels, protein oxidative damage were evaluated in skin and DNA damage in blood. Our results show that the rats exposed to ultraviolet radiation presented DNA damage in blood and increased protein carbonylation and lipid peroxidation in skin. Oral and topic treatment with green tea and mate tea prevented lipid peroxidation, both treatments with mate tea also prevented DNA damage. However, only topic treatment with green tea and mate tea prevented increases in protein carbonylation. Our findings contribute to elucidate the beneficial effects of green tea and mate tea, here in demonstrated by the antioxidant and antigenotoxic properties presented by these teas.

Omega-3 fatty acids alter behavioral and oxidative stress parameters in animals subjected to fenproporex administration

Studies have consistently reported the participation of oxidative stress in bipolar disorder (BD). Evidences indicate that omega-3 (ω3) fatty acids play several important roles in brain development and functioning. Moreover, preclinical and clinical evidence suggests roles for ω3 fatty acids in BD. Considering these evidences, the present study aimed to investigate the effects of ω3 fatty acids on locomotor behavior and oxidative stress parameters (TBARS and protein carbonyl content) in brain of rats subjected to an animal model of mania induced by fenproporex. The fenproporex treatment increased locomotor behavior in saline-treated rats under reversion and prevention model, and ω3 fatty acids prevented fenproporex-related hyperactivity. Moreover, fenproporex increased protein carbonyls in the prefrontal cortex and cerebral cortex, and the administration of ω3 fatty acids reversed this effect. Lipid peroxidation products also are increased in prefrontal cortex, striatum, hippocampus and cerebral after fenproporex administration, but ω3 fatty acids reversed this damage only in the hippocampus. On the other hand, in the prevention model, fenproporex increased carbonyl content only in the cerebral cortex, and administration of ω3 fatty acids prevented this damage. Additionally, the administration of fenproporex resulted in a marked increased of TBARS in the prefrontal cortex, hippocampus, striatum and cerebral cortex, and prevent this damage in the prefrontal cortex, hippocampus and striatum. In conclusion, we are able to demonstrate that fenproporex-induced hyperlocomotion and damage through oxidative stress were prevented by ω3 fatty acids. Thus, the ω3 fatty acids may be important adjuvant therapy of bipolar disorder.

Intracerebroventricular administration of α-ketoisocaproic acid decreases brain-derived neurotrophic factor and nerve growth factor levels in brain of young rats.

Maple syrup urine disease (MSUD) is an inherited aminoacidopathy resulting from dysfunction of the branched-chain keto acid dehydrogenase complex, leading to accumulation of the branched-chain amino acids (BCAA) leucine, isoleucine and valine as well as their corresponding transaminated branched-chain α-ketoacids. This disorder is clinically characterized by ketoacidosis, seizures, coma, psychomotor delay and mental retardation whose pathophysiology is not completely understood. Recent studies have shown that oxidative stress may be involved in neuropathology of MSUD. However, the effect of accumulating α-ketoacids in MSUD on neurotrophic factors has not been investigated. Thus, the objective of the present study was to evaluate the effects of acute intracerebroventricular administration of α-ketoisocaproic acid (KIC) on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) levels in the brains of young male rats. Ours results showed that intracerebroventricular administration of KIC decreased BDNF levels in hippocampus, striatum and cerebral cortex, without induce a detectable change in pro-BDNF levels. Moreover, NGF levels in the hippocampus were reduced after intracerebroventricular administration of KIC. In conclusion, these data suggest that the effects of KIC on demyelination and memory processes may be mediated by reduced trophic support of BDNF and NGF. Moreover, lower levels of BDNF and NGF are consistent with the hypothesis that a deficit in this neurotrophic factor may contribute to the structural and functional alterations of brain underlying the psychopathology of MSUD, supporting the hypothesis of a neurodegenerative process in MSUD.

Omega-3 fatty acid supplementation decreases DNA damage in brain of rats subjected to a chemically induced chronic model of Tyrosinemia type II

Tyrosinemia type II is an inborn error of metabolism caused by a mutation in a gene encoding the enzyme tyrosine aminotransferase leading to an accumulation of tyrosine in the body, and is associated with neurologic and development difficulties in numerous patients. Because the accumulation of tyrosine promotes oxidative stress and DNA damage, the main aim of this study was to investigate the possible antioxidant and neuroprotective effects of omega-3 treatment in a chemically-induced model of Tyrosinemia type II in hippocampus, striatum and cerebral cortex of rats. Our results showed chronic administration of L-tyrosine increased the frequency and the index of DNA damage, as well as the 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels in the hippocampus, striatum and cerebral cortex. Moreover, omega-3 fatty acid treatment totally prevented increased DNA damage in the striatum and hippocampus, and partially prevented in the cerebral cortex, whereas the increase in 8-OHdG levels was totally prevented by omega-3 fatty acid treatment in hippocampus, striatum and cerebral cortex. In conclusion, the present study demonstrated that the main accumulating metabolite in Tyrosinemia type II induce DNA damage in hippocampus, striatum and cerebral cortex, possibly mediated by free radical production, and the supplementation with omega-3 fatty acids was able to prevent this damage, suggesting that could be involved in the prevention of oxidative damage to DNA in this disease. Thus, omega-3 fatty acids supplementation to Tyrosinemia type II patients may represent a new therapeutic approach and a possible adjuvant to the curren t treatment of this disease.