Short term treatment by fenofibrate enhances oxidative activities towards long-chain fatty acids in the liver of lean Zucker rats

The synergistic ameliorative activity of peroxisome proliferator-activated receptor-alpha and gamma agonists, fenofibrate and pioglitazone, on hippocampal neurodegeneration in a rat model of insulin resistance

Insulin resistance (IR) is a risk factor for metabolic disorders and neurodegeneration. Peroxisome proliferator-activated receptor (PPAR) agonists have been proven to mitigate the neuronal pathology associated with IR. However, the synergetic efficacy of these agonists is yet to be fully described. Hence, we aimed to investigate the efficacy of PPARα/γ agonists (fenofibrate and pioglitazone) on a high-fat diet (HFD) and streptozotocin (STZ)-induced hippocampal neurodegeneration. Male Wistar rats (200 ± 25 mg/body weight [BW]) were divided into five groups. The experimental groups were fed on an HFD for 12 weeks coupled with 5 days of an STZ injection (30 mg/kg/BW, i.p) to induce IR. Fenofibrate (FEN; 100 mg/kg/BW, orally), pioglitazone (PIO; 20 mg/kg/BW, orally), and their combination were administered for 2 weeks postinduction. Behavioral tests were conducted, and blood was collected to determine insulin sensitivity after treatment. Animals were killed for assessment of oxidative stress, cellular morphology characterization, and astrocytic evaluation. HFD/STZ-induced IR increased malondialdehyde (MDA) levels and decreased glutathione (GSH) levels. Evidence of cellular alterations and overexpression of astrocytic protein was observed in the hippocampus. By contrast, monotherapy of FEN and PIO increased the GSH level (p < 0.05), decreased the MDA level (p < 0.05), and improved cellular morphology and astrocytic expression. Furthermore, the combined treatment led to improved therapeutic activities compared to monotherapies. In conclusion, FEN and PIO exerted a therapeutic synergistic effect on HFD/STZ-induced IR in the hippocampus.

Fenofibrate Administration Reduces Alcohol and Saccharin Intake in Rats: Possible Effects at Peripheral and Central Levels

We have previously shown that the administration of fenofibrate to high-drinker UChB rats markedly reduces voluntary ethanol intake. Fenofibrate is a peroxisome proliferator-activated receptor alpha (PPARα) agonist, which induces the proliferation of peroxisomes in the liver, leading to increases in catalase levels that result in acetaldehyde accumulation at aversive levels in the blood when animals consume ethanol. In these new studies, we aimed to investigate if the effect of fenofibrate on ethanol intake is produced exclusively in the liver (increasing catalase and systemic levels of acetaldehyde) or there might be additional effects at central level. High drinker rats (UChB) were allowed to voluntary drink 10% ethanol for 2 months. Afterward, a daily dose of fenofibrate (25, 50 or 100 mg/kg/day) or vehicle (as control) was administered orally for 14 days. Voluntary ethanol intake was recorded daily. After that time, animals were deprived of ethanol access for 24 h and administered with an oral dose of ethanol (1 g/kg) for acetaldehyde determination in blood. Fenofibrate reduced ethanol voluntary intake by 60%, in chronically drinking rats, at the three doses tested. Acetaldehyde in the blood rose up to between 80 μM and 100 μM. Considering the reduction of ethanol consumption, blood acetaldehyde levels and body weight evolution, the better results were obtained at a dose of 50 mg fenofibrate/kg/day. This dose of fenofibrate also reduced the voluntary intake of 0.2% saccharin by 35% and increased catalase levels 2.5-fold in the liver but showed no effects on catalase levels in the brain. To further study if fenofibrate administration changes the motivational properties of ethanol, a conditioned-place preference experiment was carried out. Animals treated with fenofibrate (50 mg/kg/day) did not develop ethanol-conditioned place preference (CPP).In an additional experiment, chronically ethanol-drinking rats underwent two cycles of ethanol deprivation/re-access, and fenofibrate (50 mg/kg/day) was given only in deprivation periods; under this paradigm, fenofibrate was also able to generate a prolonged (30 days) decreasing of ethanol consumption, suggesting some effect beyond the acetaldehyde-generated aversion. In summary, reduction of ethanol intake by fenofibrate appears to be a consequence of a combination of catalase induction in the liver and central pharmacological effects.

Fenofibrate--a lipid-lowering drug--reduces voluntary alcohol drinking in rats

The administration of disulfiram raises blood acetaldehyde levels when ethanol is ingested, leading to an aversion to alcohol. This study was aimed at assessing the effect of fenofibrate on voluntary ethanol ingestion in rats. Fenofibrate reduces blood triglyceride levels by increasing fatty acid oxidation by liver peroxisomes, along with an increase in the activity of catalase, which can oxidize ethanol to acetaldehyde. UChB drinker rats were allowed to consume alcohol 10% v/v freely for 60 days, until consumption stabilized at around 7 g ethanol/kg/24 h. About 1-1.2 g ethanol/kg of this intake is consumed in the first 2 h of darkness of the circadian cycle. Fenofibrate subsequently administered (50 mg/kg/day by mouth [p.o.]) for 14 days led to a 60-70% (p < 0.001) reduction of 24-h ethanol consumption. When ethanol intake was determined within the first 2 h of darkness, the reduction was 85-90% (p < 0.001). We determined whether animals chronically allowed access to ethanol and subsequently treated with fenofibrate, would a) increase liver catalase activity, and b) increase blood acetaldehyde levels after a 24-h ethanol deprivation and the subsequent administration of 1 g ethanol/kg. The oral administration of 1 g ethanol/kg produced a rapid increase in blood (arterial) acetaldehyde in fenofibrate-treated animals versus controls also administered 1 g/kg ethanol (70 μM vs. 7 μM; p < 0.001). Liver catalase activity following fenofibrate treatment was increased 3-fold (p < 0.01). Other hepatic enzymes responsible for the metabolism of ethanol (alcohol dehydrogenase and aldehyde dehydrogenase) remained unchanged. No liver damage was induced, as measured by serum glutamic-pyruvic transaminase (GPT) activity. The effect of fenofibrate in reducing alcohol intake was fully reversible. Overall, in rats allowed chronic ethanol intake, by mouth (p.o.), fenofibrate administration increased liver catalase activity and reduced voluntary ethanol intake. The administration of 1 g ethanol/kg (p.o.) to these animals increased blood acetaldehyde levels in fenofibrate-treated animals, suggesting the possible basis for the reduction in ethanol intake.

High content screening for non-classical peroxisome proliferators

Peroxisomes are ubiquitous cellular organelles that perform vital functions including fatty acid beta-oxidation, plasmalogen synthesis, and detoxification of harmful oxidative species. In rodents numerous compounds that increase peroxisome biogenesis also alleviate metabolic syndrome (MetS)/type 2 diabetes (T2D) symptoms. However, compounds that increase peroxisome biogenesis in rodents largely do not increase peroxisome biogenesis in humans. We designed a novel genetically encoded high throughput screening (HTS) high content assay to identify small molecule compounds that function as peroxisome proliferators in human cells. From this assay we have confirmed that 4-phenylbutyrate (PBA), a PPAR independent peroxisome proliferator and chemical chaperone, increases peroxisome proliferation in human cells and serves as a positive control for our screen. We performed a small pilot and larger 15,000 compound production screen with an overall Z' factor of 0.74 for 384-well plate format, providing a valuable screening tool for identifying peroxisome modulator compounds. From this screen we have identified 4 existing drugs and 10 novel compounds, some with common scaffolds 1000X more potent than PBA. It is hoped that these novel compounds may serve as scaffolds for testing for efficacy in alleviating MetS/T2D symptoms both in mouse models and ultimately human disease.

Involvement of microsomal vesicles in part of the sensitivity of carnitine palmitoyltransferase I to malonyl-CoA inhibition in mitochondrial fractions of rat liver

Liver mitochondrial fractions as normally isolated contain only 10-20% of total mitochondria and may not be representative of the whole mitochondrial population. This study was designed to evaluate the dependence of the sensitivity of carnitine palmitoyl-transferase I (CPT I) to malonyl-CoA inhibition in mitochondrial fractions that are not normally studied. Four fractions prepared from rat liver were found to be contaminated to different extents by microsome vesicles, on the basis of marker-enzyme activities and micrographic data. Purification of mitochondrial fractions on a Percoll gradient decreased to some extent the microsomal contamination, which was due in part to the existence of close bonds between microsomes and the outer membranes of mitochondria. A greater degree of contamination of mitochondrial fractions by microsomes was correlated with a greater sensitivity of CPT I to malonyl-CoA inhibition. Attempts were made to enhance the sensitivity of CPT I to malonyl-CoA with the use of microsomes. Measurements performed by adding mitochondria and microsomes in the same CPT I assay failed to demonstrate any significant enhancement of malonyl-CoA inhibition. However, addition of ATP to a mixture of mitochondria and microsomes was shown to trigger the binding of both particles, as assessed by enzymic and micrographic data, and to increase the sensitivity of CPT I to malonyl-CoA inhibition. These results demonstrated that the binding of microsomes to mitochondria, unlike the simple mixing of both particles, was capable of altering the sensitivity of CPT I to malonyl-CoA. The data also suggest that this process could be of physiological importance, owing to the frequency of contiguous zones between mitochondria and endoplasmic reticulum observed in sections of intact liver cells.