Vu Thu Thuy Nguyen

Administration of systemic retinoids such as acitretin has not been approved yet for pediatric patients. An adverse event of retinoid-therapy that occurs with lower prevalence in children than in adults is hyperlipidemia. This might be based on the lack of comorbidities in young patients, but must not be neglected. Especially for the development of the human brain up to young adulthood, dysbalance of lipids might be deleterious. Here, we provide for the first time an in-depth analysis of the influence of subchronic acitretin-administration on lipid composition of brain parenchyma of young wild type mice. For comparison and to evaluate the systemic effect of the treatment, liver lipids were analogously investigated. As expected, triglycerides increased in liver as well as in brain and a non-significant increase in cholesterol was observed. However, specifically brain showed an increase in lyso-phosphatidylcholine and carnitine as well as in sphingomyelin. Group analysis of lipid classes revealed no statistical effects, while single species were tissue-dependently changed: effects in brain were in general more subtly as compared to those in liver regarding the mere number of changed lipid species. Thus, while the overall impact of acitretin seems comparably small regarding brain, the change in individual species and their role in brain development and maturation has to be considered.

The primary cilium is an organelle with a central role in cellular signal perception. Mutations in genes that encode cilia-associated proteins result in a collection of human syndromes collectively termed ciliopathies. Of these, the Bardet-Biedl syndrome (BBS) is considered one of the archetypical ciliopathies, as patients exhibit virtually all respective clinical phenotypes, such as pathological changes of the retina or the kidney. However, the behavioral phenotype associated with ciliary dysfunction has received little attention thus far. Here, we extensively characterized the behavior of two rodent models of BBS, Bbs6/Mkks, and Bbs8/Ttc8 knockout mice concerning social behavior, anxiety, and cognitive abilities. While learning tasks remained unaffected due to the genotype, we observed diminished social behavior and altered communication. Additionally, Bbs knockout mice displayed reduced anxiety. This was not due to altered adrenal gland function or corticosterone serum levels. However, hypothalamic expression of Lsamp, the limbic system associated protein, and Adam10, a protease acting on Lsamp, were reduced. This was accompanied by changes in characteristics of adult hypothalamic neurosphere cultures. In conclusion, we provide evidence that behavioral changes in Bbs knockout mice are mainly found in social and anxiety traits and might be based on an altered architecture of the hypothalamus.

Neurodegenerative diseases such as Alzheimer’s disease (AD) have long been acknowledged as mere disorders of the central nervous system (CNS). However, in recent years the gut with its autonomous nervous system and the multitude of microbial commensals has come into focus. Changes in gut properties have been described in patients and animal disease models such as altered enzyme secretion or architecture of the enteric nervous system. The underlying cellular mechanisms have so far only been poorly investigated. An important organelle for integrating potentially toxic signals such as the AD characteristic A-beta peptide is the primary cilium. This microtubule-based signaling organelle regulates numerous cellular processes. Even though the role of primary cilia in a variety of developmental and disease processes has recently been recognized, the contribution of defective ciliary signaling to neurodegenerative diseases such as AD, however, has not been investigated in detail so far. The AD mouse model 5xFAD was used to analyze possible changes in gut functionality by organ bath measurement of peristalsis movement. Subsequently, we cultured primary enteric neurons from mutant mice and wild type littermate controls and assessed for cellular pathomechanisms. Neurite mass was quantified within transwell culturing experiments. Using a combination of different markers for the primary cilium, cilia number and length were determined using fluorescence microscopy. 5xFAD mice showed altered gut anatomy, motility, and neurite mass of enteric neurons. Moreover, primary cilia could be demonstrated on the surface of enteric neurons and exhibited an elongated phenotype in 5xFAD mice. In parallel, we observed reduced β-Catenin expression, a key signaling molecule that regulates Wnt signaling, which is regulated in part via ciliary associated mechanisms. Both results could be recapitulated via in vitro treatments of enteric neurons from wild type mice with A-beta. So far, only a few reports on the probable role of primary cilia in AD can be found. Here, we reveal for the first time an architectural altered phenotype of primary cilia in the enteric nervous system of AD model mice, elicited potentially by neurotoxic A-beta. Potential changes on the sub-organelle level—also in CNS-derived neurons—require further investigations.

The gut brain axis seems to modulate various psychiatric and neurological disorders such as Alzheimer’s disease (AD). Growing evidence has led to the assumption that the gut microbiome might contribute to or even present the nucleus of origin for these diseases. In this regard, modifiers of the microbial composition might provide attractive new therapeutics. Aim of our study was to elucidate the effect of a rigorously changed gut microbiome on pathological hallmarks of AD. 5xFAD model mice were treated by antibiotics or probiotics (L. acidophilus and L. rhamnosus) for 14 weeks. Pathogenesis was measured by nest building capability and plaque deposition. The gut microbiome was affected as expected: antibiotics significantly reduced viable commensals, while probiotics transiently increased Lactobacillaceae. Nesting score, however, was only improved in antibiotics-treated mice. These animals additionally displayed reduced plaque load in the hippocampus. While various physiological parameters were not affected, blood sugar was reduced and serum glucagon level significantly elevated in the antibiotics-treated animals together with a reduction in the receptor for advanced glycation end products RAGE—the inward transporter of Aβ peptides of the brain. Assumedly, the beneficial effect of the antibiotics was based on their anti-diabetic potential.

Physical activity is considered a promising preventive intervention to reduce the risk of developing Alzheimer’s disease (AD). However, the positive effect of therapeutic administration of physical activity has not been proven conclusively yet, likely due to confounding factors such as varying activity regimens and life or disease stages. To examine the impact of different routines of physical activity in the early disease stages, we subjected young 5xFAD and wild-type mice to 1-day (acute) and 30-day (chronic) voluntary wheel running and compared them with age-matched sedentary controls. We observed a significant increase in brain lactate levels in acutely trained 5xFAD mice relative to all other experimental groups. Subsequent brain RNA-seq analysis did not reveal major differences in transcriptomic regulation between training durations in 5xFAD mice. In contrast, acute training yielded substantial gene expression changes in wild-type animals relative to their chronically trained and sedentary counterparts. The comparison of 5xFAD and wild-type mice showed the highest transcriptional differences in the chronic and sedentary groups, whereas acute training was associated with much fewer differentially expressed genes. In conclusion, our results suggest that different training durations did not affect the global transcriptome of 3-month-old 5xFAD mice, whereas acute running seemed to induce a similar transcriptional stress state in wild-type animals as already known for 5xFAD mice.

Physical activity is considered a promising preventive intervention to reduce the risk of developing Alzheimer’s disease (AD). However, the positive effect of exercise therapy has not been proven conclusively yet, likely due to confounding factors such as varying activity regimens and life or disease stages. To examine the impact of different routines of physical exercise in the early disease stages, we subjected young 5xFAD and wild-type mice to 1-day (acute) and 30-day (chronic) voluntary wheel running and compared them with age-matched sedentary controls. We observed a significant increase in brain lactate levels in acutely trained 5xFAD mice relative to all other experimental groups. Subsequent brain RNA-seq analysis did not reveal major differences in transcriptomic regulation between training durations in 5xFAD mice. In contrast, acute training yielded substantial gene expression changes in wild-type animals relative to their chronically trained and sedentary counterparts. The comparison of 5xFAD and wild-type mice showed the highest transcriptional differences in the chronic and sedentary groups, whereas acute training was associated with much fewer differentially expressed genes. In conclusion, our results suggest that different training durations did not affect the global transcriptome of 3-month-old 5xFAD mice, whereas acute running seemed to induce a similar transcriptional stress state in wild-type animals as already known for 5xFAD mice.

Four drugs are currently approved for the treatment of Alzheimer’s disease (AD) by the FDA. Three of these drugs—donepezil, rivastigmine, and galantamine—belong to the class of acetylcholine esterase inhibitors. Memantine, a NMDA receptor antagonist, represents the fourth and a combination of donepezil and memantine the fifth treatment option. Recently, the gut and its habitants, its microbiome, came into focus of AD research and added another important factor to therapeutic considerations. While the first data provide evidence that AD patients might carry an altered microbiome, the influence of administered drugs on gut properties and commensals have been largely ignored so far. However, the occurrence of digestive side effects with these drugs and the knowledge that cholinergic transmission is crucial for several gut functions enforces the question if, and how, this medication influences the gastrointestinal system and its microbial stocking. Here, we investigated aspects such as microbial viability, colonic propulsion, and properties of enteric neurons, affected by assumed intestinal concentration of the four drugs using the mouse as a model organism. All ex vivo administered drugs revealed no direct effect on fecal bacteria viability and only a high dosage of memantine resulted in reduced biofilm formation of E. coli. Memantine was additionally the only compound that elevated calcium influx in enteric neurons, while all acetylcholine esterase inhibitors significantly reduced esterase activity in colonic tissue specimen and prolonged propulsion time. Both, acetylcholine esterase inhibitors and memantine, had no effect on general viability and neurite outgrowth of enteric neurons. In sum, our findings indicate that all AD symptomatic drugs have the potential to affect distinct intestinal functions and with this—directly or indirectly—microbial commensals.

Wheat amylase trypsin inhibitors (ATIs) represent a common dietary protein component of gluten-containing cereals (wheat, rye, and barley). They act as toll-like receptor 4 ligands, and are largely resistant to intestinal proteases, eliciting a mild inflammatory response within the intestine after oral ingestion. Importantly, nutritional ATIs exacerbated inflammatory bowel disease and features of fatty liver disease and the metabolic syndrome in mice. For Alzheimer’s disease (AD), both inflammation and altered insulin resistance are major contributing factors, impacting onset as well as progression of this devastating brain disorder in patients. In this study, we evaluated the impact of dietary ATIs on a well-known rodent model of AD (5xFAD). We assessed metabolic, behavioral, inflammatory, and microbial changes in mice consuming different dietary regimes with and without ATIs, consumed ad libitum for eight weeks. We demonstrate that ATIs, with or without a gluten matrix, had an impact on the metabolism and gut microbiota of 5xFAD mice, aggravating pathological hallmarks of AD. If these findings can be translated to patients, an ATI-depleted diet might offer an alternative therapeutic option for AD and warrants clinical intervention studies.