Unpredictable chronic mild stress differentially impacts resting brain glucose metabolism in fatty acid-binding protein 7 deficient mice

Potential safety implications of fatty acid-binding protein inhibition

Fatty acid-binding proteins (FABPs) are small intracellular proteins that regulate fatty acid metabolism, transport, and signalling. There are ten known human isoforms, many of which are upregulated and involved in clinical pathologies. As such, FABP inhibition may be beneficial in disease states such as cancer, and those involving the cardiovascular system, metabolism, immunity, and cognition. Recently, a potent, selective FABP5 inhibitor (ART26.12), with 90-fold selectivity to FABP3 and 20-fold selectivity to FABP7, was found to be remarkably benign, with a no-observed-adverse-effect level of 1000 mg/kg in rats and dogs, showing no genotoxicity, cardiovascular, central, or respiratory toxicity. To understand the potential implication of FABP inhibition more fully, this review systematically assessed literature investigating genetic knockout, knockdown, and pharmacological inhibition of FABP3, FABP4, FABP5, or FABP7. Analysis of the literature revealed that animals bred not to express FABPs showed the most biological effects, suggesting key roles of these proteins during development. FABP ablation sometimes exacerbated symptoms of disease models, particularly those linked to metabolism, inflammatory and immune responses, cardiac contractility, neurogenesis, and cognition. However, FABP inhibition (genetic silencing or pharmacological) had a positive effect in many more disease conditions. Several polymorphisms of each FABP gene have also been linked to pathological conditions, but it was unclear how several polymorphisms affected protein function. Overall, analysis of the literature to date suggests that pharmacological inhibition of FABPs in adults is of low risk.

The role of fatty acid-binding protein 5 and 7 on locomotor, anxiety and social behavior: Interaction with NMDA signaling

The endocannabinoid system has been shown to be a powerful mediator of anxiety, learning and memory, as well as nociception behaviors. Exogenous cannabinoids like delta-9-tetrahydrocannabinol mimic the naturally occurring endogenous cannabinoids found in the mammalian central and peripheral nervous system. The hydrophobic properties of endocannabinoids mean that these psychoactive compounds require help with cellular transport. A family of lipid intracellular carriers called fatty acid-binding proteins (FABPs) can bind to endocannabinoids. Pharmacological inhibition or genetic deletion of FABP subtypes 5 and 7 elevates whole-brain anandamide (AEA) levels, a type of endocannabinoid. This study examined locomotor behavior, anxiety-like behavior, and social behavior in FABP5-/- and FABP7-/- mice. Furthermore, we measured N-methyl-D-aspartate (NMDA) receptor levels in the brain to help identify potential underlying mechanisms related to the behavioral findings. Results showed that both male and female FABP5-/- mice exhibited significantly lower activity when compared with both FABP5/7+/+ (control) and FABP7-/-. For social behavior, male, but not female, FABP5-/- mice spent more time interacting with novel mice compared with controls (FABP5/7+/+) and FABP7-/- mice. No significant difference was found for anxiety-like behavior. Results from the NMDA autoradiography revealed [3H] MK-801 binding to be significantly increased within sub-regions of the striatum in FABP7-/- compared with control. In summary, these results show that FABP5 deficiency plays a significant role in locomotion activity, exploratory behavior, as well as social interaction. Furthermore, FABP7 deficiency is shown to play an important role in NMDA receptor expression, while FABP5 does not.

Maternal supplementation with n-3 fatty acids affects placental lipid metabolism, inflammation, oxidative stress, the endocannabinoid system, and the neonate cytokine concentrations in dairy cows

BACKGROUND

The placenta plays a crucial role in supporting and influencing fetal development. We compared the effects of prepartum supplementation with omega-3 (n-3) fatty acid (FA) sources, flaxseed oil (FLX) and fish oil (FO), on the expression of genes and proteins related to lipid metabolism, inflammation, oxidative stress, and the endocannabinoid system (ECS) in the expelled placenta, as well as on FA profile and inflammatory response of neonates. Late-pregnant Holstein dairy cows were supplemented with saturated fat (CTL), FLX, or FO. Placental cotyledons (n = 5) were collected immediately after expulsion, and extracted RNA and proteins were analyzed by RT-PCR and proteomic analysis. Neonatal blood was assessed for FA composition and concentrations of inflammatory markers.

RESULTS

FO increased the gene expression of fatty acid binding protein 4 (FABP4), interleukin 10 (IL-10), catalase (CAT), cannabinoid receptor 1 (CNR1), and cannabinoid receptor 2 (CNR2) compared with CTL placenta. Gene expression of ECS-enzyme FA-amide hydrolase (FAAH) was lower in FLX and FO than in CTL. Proteomic analysis identified 3,974 proteins; of these, 51-59 were differentially abundant between treatments (P ≤ 0.05, |fold change| ≥ 1.5). Top canonical pathways enriched in FLX vs. CTL and in FO vs. CTL were triglyceride metabolism and inflammatory processes. Both n-3 FA increased the placental abundance of FA binding proteins (FABPs) 3 and 7. The abundance of CNR1 cannabinoid-receptor-interacting-protein-1 (CNRIP1) was reduced in FO vs. FLX. In silico modeling affirmed that bovine FABPs bind to endocannabinoids. The FLX increased the abundance of inflammatory CD44-antigen and secreted-phosphoprotein-1, whereas prostaglandin-endoperoxide synthase 2 was decreased in FO vs. CTL placenta. Maternal FO enriched neonatal plasma with n-3 FAs, and both FLX and FO reduced interleukin-6 concentrations compared with CTL.

CONCLUSION

Maternal n-3 FA from FLX and FO differentially affected the bovine placenta; both enhanced lipid metabolism and modulated oxidative stress, however, FO increased some transcriptional ECS components, possibly related to the increased FABPs. Maternal FO induced a unique balance of pro- and anti-inflammatory components in the placenta. Taken together, different sources of n-3 FA during late pregnancy enhanced placental immune and metabolic processes, which may affect the neonatal immune system.

Preventive impacts of vitamin C on memory damage caused by unpredictable chronic mild stress in relation to biochemical parameters in the hippocampus of male rats

The present study focused on examining the impact of vitamin C (Vit C) administration on the function of memory and the status of oxidative stress (OS) in the hippocampal area of the brain using an unpredictable chronic mild stress (UCMS) model in rats. To this end, 50 male Wistar rats (11-12 weeks of age at the start of the study) were assigned to five groups of six animals, including control, UCMS, UCMS + Vit C 50 mg/Kg, UCMS + Vit C 100 mg/Kg, and UCMS + Vit C 400 mg/Kg. The animals received daily intraperitoneal injections of Vit C at a certain time (9 am) before the initiation of a stressor. UCMS, including a progression of typical stressors, was applied for four weeks. Subsequently, using the passive avoidance (PA) and Morris water maze (MWM) tests were performed to investigate learning and memory. Eventually, hippocampal tissues were evaluated in terms of OS criteria. The results revealed that the latency to enter the dark chamber (P < 0. 01 and P < 0.05, PA test) and the time spent in the target quadrant (P < 0.0001, MWM test) were shorter in the UCMS group, while latency to discover the platform was longer (P < 0.05 and P < 0.001, MWM test) compared to the control group. However, UCMS decreased the content of thiol (P < 0.0001), as well as the activities of catalase (P < 0.0001) and superoxide dismutase (P < 0.0001), whereas the concentration of malondialdehyde (P < 0.01) increased in the hippocampal region of the brain in comparison to the control group. Interestingly, Vit C treatment reversed the mentioned effects of UCMS. Therefore, the latency to enter the dark chamber (P < 0. 05 and P < 0.01,1 and 24 h after the shock, PA test, UCMS + Vit C 400) and the time spent in the target quadrant (P < 0. 01 and P < 0.05, MWM test, UCMS + Vit C 400 and UCMS + Vit C 100, respectively) were longer in the UCMS + Vit C groups. Moreover, Vit C increased the content of thiol (P < 0.05, UCMS + Vit C 400), as well as the activity of catalase (P < 0.001, UCMS + Vit C 400) and superoxide dismutase (P < 0.0001, UCMS + Vit C 400, UCMS + Vit C 100), whereas the concentration of malondialdehyde (P < 0. 05 and P < 0.01, UCMS + Vit C 100, UCMS + Vit C 400) decreased in the hippocampal region of the brain in comparison to the UCMS group. Overall, these results suggest that Vit C could reverse UCMS-induced learning and memory impairment possibly through the modulation of brain OS.Key points Memory and learning impairments were induced by unpredictable chronic mild stress (UCMS)Vitamin C could prevent cognitive impairments caused by UCMS in rats by attenuation of oxidative stress in the brain.

FABP5 is important for cognitive function and is an important regulator of the physiological effects and pharmacokinetics of acute Δ9 tetrahydrocannabinol inhalation in mice

Fatty acid binding protein 5 (FABP5) interacts with the endocannabinoid system in the brain via intracellular transport of anandamide, as well as Δ9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis. Previous work has established the behavioral effects of genetic deletion of FABP5, but not in the presence of THC. The present study sought to further elucidate the role of FABP5 on the pharmacokinetic and behavioral response to THC through global deletion. Adult FABP5+/+ and FABP5-/- mice were tested for behavioral response to THC using Open Field (OF), Novel Object Recognition (NOR), T-Maze, Morris Water Maze (MWM), and Elevated Plus Maze (EPM). An additional cohort of mice was used to harvest blood, brains, and liver samples to measure THC and metabolites after acute administration of THC. Behavioral tests showed that some cognitive deficits from FABP5 deletion, particularly in MWM, were blocked by THC administration, while this was not observed in other measures of memory and anxiety (such as T-Maze and EPM). Measurement of THC and metabolites in blood serum and brain tissue through UPLC-MS/MS analysis showed that the pharmacokinetics of THC was altered by FABP5. The present study shows further evidence of the importance of FABP5 in cognitive function. Additionally, results showed that FABP5 is an important regulator of the physiological effects and pharmacokinetics of THC.

FABP7: a glial integrator of sleep, circadian rhythms, plasticity, and metabolic function

Sleep and circadian rhythms are observed broadly throughout animal phyla and influence neural plasticity and cognitive function. However, the few phylogenetically conserved cellular and molecular pathways that are implicated in these processes are largely focused on neuronal cells. Research on these topics has traditionally segregated sleep homeostatic behavior from circadian rest-activity rhythms. Here we posit an alternative perspective, whereby mechanisms underlying the integration of sleep and circadian rhythms that affect behavioral state, plasticity, and cognition reside within glial cells. The brain-type fatty acid binding protein, FABP7, is part of a larger family of lipid chaperone proteins that regulate the subcellular trafficking of fatty acids for a wide range of cellular functions, including gene expression, growth, survival, inflammation, and metabolism. FABP7 is enriched in glial cells of the central nervous system and has been shown to be a clock-controlled gene implicated in sleep/wake regulation and cognitive processing. FABP7 is known to affect gene transcription, cellular outgrowth, and its subcellular localization in the fine perisynaptic astrocytic processes (PAPs) varies based on time-of-day. Future studies determining the effects of FABP7 on behavioral state- and circadian-dependent plasticity and cognitive processes, in addition to functional consequences on cellular and molecular mechanisms related to neural-glial interactions, lipid storage, and blood brain barrier integrity will be important for our knowledge of basic sleep function. Given the comorbidity of sleep disturbance with neurological disorders, these studies will also be important for our understanding of the etiology and pathophysiology of how these diseases affect or are affected by sleep.