Pregestational fructose-induced metabolic syndrome in Wistar rats causes sexually dimorphic behavioral changes in their offspring.

Metabolic syndrome (MetS), marked by enduring metabolic inflammation, has detrimental effects on cognitive performance and brain structure, influencing behavior. This study aimed to investigate whether maternal MetS could negatively impact the neurodevelopment and metabolism of offspring. To test this hypothesis, 2 months old female Wistar rats were subjected to a 10-week regimen of tap water alone or supplemented with 20% fructose to induce MetS. Dams were mated with healthy males to generate litters: OC (offspring from control dams) and OMetS (offspring from dams with MetS). To isolate prenatal effects, all pups were breastfed by control nurse dams, maintaining a standard diet and water ad libitum until weaning. Behavioral assessments were conducted between postnatal days (PN) 22 and 95, and metabolic parameters were analyzed post-sacrifice on PN100. Results from the elevated plus maze, the open field, and the marble burying tests revealed a heightened anxiety-like phenotype in OMetS females. The novel object recognition test showed that exclusively OMetS males had long-term memory impairment. In the reciprocal social interaction test, OMetS displayed a lower number of social interactions, with a notable increase in "socially inactive" behavior observed exclusively in females. Additionally, in the three-chamber test, social preference and social novelty indexes were found to be lower solely among OMetS females. An increase in visceral fat concomitantly with hypertriglyceridemia was the relevant postmortem metabolic finding in OMetS females. In summary, maternal MetS leads to enduring damage and adverse effects on offspring neurobehavior and metabolism, with notable sexual dimorphism.

Lipid peroxidation and neuroinflammation: A possible link between maternal fructose intake and delay of acquisition of neonatal reflexes in Wistar female rats.

Fructose is a common sweetener found in the daily diet supplemented to many processed and ultra-processed foods and beverages. Consumption of fructose-sweetened beverages has drastically increased in the last decades and is widely associated with metabolic disease, systemic pro-inflammatory status, and adverse transgenerational effects. To date, the impact of maternal fructose intake in brain function of the offspring is less explored. Therefore, the aim of this study was first, to investigate adverse effects in developmental milestones of the progeny of mothers with metabolic syndrome (MetS), induced by ad libitum consumption of a 20% fructose solution, and second to identify possible molecular changes in the nervous system of the newborns associated with maternal fructose intake. Wistar rats were randomly separated into two groups with access to water or fructose (20% w/v in water) for 10 weeks. After MetS was confirmed, dams were mated with control males and continued drinking water or fructose solution during gestation. At postnatal day (PN) 1, a subgroup of offspring of each sex was sacrificed and brains were dissected for oxidative stress and inflammatory status analysis. Changes in the developmental milestones due to maternal fructose consumption were studied (PN3-PN21) in another subgroup of offspring. Sexually dimorphic effects were found on the progeny's acquisition of neurodevelopmental milestones, in brain lipid peroxidation, neuroinflammation, and antioxidative defensive response. Our results suggest that dams' MetS, induced by fructose intake, disrupts brain redox homeostasis in female offspring and affects sensorimotor brain circuitry which may have a translational value for studying neurodevelopmental diseases.

Diacylglycerol levels modulate the cellular distribution of the nicotinic acetylcholine receptor.

Diacylglycerol (DAG), a second messenger involved in different cell signaling cascades, activates protein kinase C (PKC) and D (PKD), among other kinases. The present work analyzes the effects resulting from the alteration of DAG levels on neuronal and muscle nicotinic acetylcholine receptor (AChR) distribution. We employ CHO-K1/A5 cells, expressing adult muscle-type AChR in a stable manner, and hippocampal neurons, which endogenously express various subtypes of neuronal AChR. CHO-K1/A5 cells treated with dioctanoylglycerol (DOG) for different periods showed augmented AChR cell surface levels at short incubation times (30min-4h) whereas at longer times (18h) the AChR was shifted to intracellular compartments. Similarly, in cultured hippocampal neurons surface AChR levels increased as a result of DOG incubation for 4h. Inhibition of endogenous DAG catabolism produced changes in AChR distribution similar to those induced by DOG treatment. Specific enzyme inhibitors and Western blot assays revealed that DAGs exert their effect on AChR distribution through the modulation of the activity of classical PKC (cPKC), novel PKC (nPKC) and PKD activity.

Altered lipid homeostasis in Sertoli cells stressed by mild hyperthermia.

Spermatogenesis is known to be vulnerable to temperature. Exposures of rat testis to moderate hyperthermia result in loss of germ cells with survival of Sertoli cells (SC). Because SC provide structural and metabolic support to germ cells, our aim was to test the hypothesis that these exposures affect SC functions, thus contributing to germ cell damage. In vivo, regularly repeated exposures (one of 15 min per day, once a day during 5 days) of rat testes to 43 °C led to accumulation of neutral lipids. This SC-specific lipid function took 1-2 weeks after the last of these exposures to be maximal. In cultured SC, similar daily exposures for 15 min to 43 °C resulted in significant increase in triacylglycerol levels and accumulation of lipid droplets. After incubations with [3H]arachidonate, the labeling of cardiolipin decreased more than that of other lipid classes. Another specifically mitochondrial lipid metabolic function, fatty acid oxidation, also declined. These lipid changes suggested that temperature affects SC mitochondrial physiology, which was confirmed by significantly increased degrees of membrane depolarization and ROS production. This concurred with reduced expression of two SC-specific proteins, transferrin, and Wilms' Tumor 1 protein, markers of SC secretion and differentiation functions, respectively, and with an intense SC cytoskeletal perturbation, evident by loss of microtubule network (α-tubulin) and microfilament (f-actin) organization. Albeit temporary and potentially reversible, hyperthermia-induced SC structural and metabolic alterations may be long-lasting and/or extensive enough to respond for the decreased survival of the germ cells they normally foster.

The position of the double bond in monounsaturated free fatty acids is essential for the inhibition of the nicotinic acetylcholine receptor.

Free fatty acids (FFAs) are non-competitive antagonists of the nicotinic acetylcholine receptor (AChR). Their site of action is supposedly located at the lipid-AChR interface. To elucidate the mechanism involved in this antagonism, we studied the effect that FFAs with a single double-bond at different positions (ω6, ω9, ω11 and ω13 cis-18:1) have on different AChR properties. Electrophysiological studies showed that only two FFAs (ω6 and ω9) reduced the duration of the channel open-state. The briefest component of the closed-time distribution remained unaltered, suggesting that ω6 and ω9 behave as allosteric blockers. Fluorescence resonance energy transfer studies indicated that all FFAs locate at the lipid-AChR interface, ω6 being restricted to annular sites and all others occupying non-annular sites. The perturbation of the native membrane order by FFAs was evaluated by DPH (1,6-diphenyl-1,3,5-hexatriene) and Laurdan fluorescence polarization studies, with the greatest decrease observed for ω9 and ω11. AChR conformational changes produced by FFAs present at the lipid bilayer were evaluated by fluorescence quenching studies of pyrene-labeled AChR and also using the AChR conformational-sensitive probe crystal violet. All cis-FFAs produced AChR conformational changes at the transmembrane level, but only ω9, ω11 and ω13 perturbed the resting state. Thus, the position and isomerism of the torsion angle of unsaturated FFAs are probably a key factor in terms of AChR blockage, suggesting that FFAs with a unique cis double bond at a superficial position inside the membrane directly inhibit AChR function by perturbing a potential conserved core structure for AChR gating at that level.

Chaperoning α7 neuronal nicotinic acetylcholine receptors.

The α7 subtype of nicotinic acetylcholine receptors (AChRs) is one of the most abundant members of the Cys-loop family of receptors present in the central nervous system. It participates in various physiological processes and has received much attention as a potential therapeutic target for a variety of pathologies. The importance of understanding the mechanisms controlling AChR assembly and cell-surface delivery lies in the fact that these two processes are key to determining the functional pool of receptors actively engaged in synaptic transmission. Here we review recent studies showing that RIC-3, a protein originally identified in the worm Caenorhabditis elegans, modulates the expression of α7 AChRs in a subtype-specific manner. Potentiation of AChR expression by post-transcriptional events is also critically assessed.

Wnt-7a induces presynaptic colocalization of alpha 7-nicotinic acetylcholine receptors and adenomatous polyposis coli in hippocampal neurons.

Nicotinic acetylcholine receptors (nAChRs) contribute significantly to hippocampal function. Alpha7-nAChRs are present in presynaptic sites in hippocampal neurons and may influence transmitter release, but the factors that determine their presynaptic localization are unknown. We report here that Wnt-7a, a ligand active in the canonical Wnt signaling pathway, induces dissociation of the adenomatous polyposis coli (APC) protein from the beta-catenin cytoplasmic complex and the interaction of APC with alpha7-nAChRs in hippocampal neurons. Interestingly, Wnt-7a induces the relocalization of APC to membranes, clustering of APC in neurites, and coclustering of APC with different, presynaptic protein markers. Wnt-7a also increases the number and size of coclusters of alpha7-nAChRs and APC in presynaptic terminals. These short-term changes in alpha7-nAChRs occur in the few minutes after ligand exposure and involve translocation to the plasma membrane without affecting total receptor levels. Longer-term exposure to Wnt-7a increases nAChR alpha7 subunit levels in an APC-independent manner and increases clusters of alpha7-nAChRs in neurites via an APC-dependent process. Together, these results demonstrate that stimulation through the canonical Wnt pathway regulates the presynaptic localization of APC and alpha7-nAChRs with APC serving as an intermediary in the alpha7-nAChR relocalization process. Modulation by Wnt signaling may be essential for alpha7-nAChR expression and function in synapses.

Lamotrigine is an open-channel blocker of the nicotinic acetylcholine receptor.

Lamotrigine is an antiepileptic drug employed in the treatment of partial epilepsies. We studied its possible interaction with channels other than its known therapeutic target, the voltage-gated sodium channel, using the adult muscle nicotinic acetylcholine receptor as a model system. At the single-channel level, lamotrigine caused a dose-dependent (a) diminution in mean open time, (b) increase in mean burst duration and (c) increase in the area of a new closed-time component. A simple linear channel blocking mechanism accounts for these results. Thus, lamotrigine exerts a blocking action on the muscle nicotinic acetylcholine receptor.