Julie Dumont

Background: Genome-wide association studies have identified the PTK2B gene, which encodes Proline-rich tyrosine kinase 2 (PYK2), as a genetic risk factor for Alzheimer’s disease (AD). However, its role in AD aetiology remains to be understood, as a complex contribution to amyloid β (Aβ) toxicity, tauopathy and neuronal dysfunction is suggested by contradictory evidence. Determining how the causal variant among AD-associated PTK2B variants impairs PYK2 function to trigger AD hallmarks could bring clarification. Methods: We combined in silico prediction tools with luciferase reporter assays in neuroblastoma cells to prioritize potential AD-associated PTK2B functional variants. We generated isogenic KOLF2.1J induced pluripotent stem cells (iPSCs) carrying the most relevant functional variant using CRISPR-Cas9 and differentiated them into human neuronal cultures (hNCs). We assessed PYK2 expression via immunoblotting, performed transcriptomic profiling using RNA-sequencing, analyzed neuronal network activity via multielectrode array (MEA) recordings, quantified synaptic density through immunocytochemistry in microfluidic devices, and assessed Tau phosphorylation and amyloid-precursor protein (APP) metabolism. Results: The rs28834970 regulatory variant was identified as the most functionally relevant in our model, with the C risk allele promoting transcription factor C/EBPβ binding within a cis-regulatory element. In hNCs, the homozygous rs28834970 CC genotype reduced total PYK2 levels by more than 80%, while increasing the proportion of phosphorylated (activated) PYK2. Transcriptomic analysis revealed 724 downregulated and 113 upregulated gene sets, with altered expression of genes involved in extracellular matrix organization, cytoplasmic translation and neurotransmitter secretion. MEA recordings showed reduced network recruitment and altered burst organization. Immunocytochemistry in microfluidic devices consistently revealed that rs28834970 impacts dendritic development and postsynaptic maturation. The risk genotype significantly elevated Tau phosphorylation at pathological sites (Thr181, Thr217, Thr231, Ser202-Thr205, Ser396-Ser404), and enhanced APP processing, resulting in decreased levels of APP and CTF but increased levels of sAPPα, sAPPβ and Aβ. Conclusion: The rs28834970 C risk allele mechanistically links AD susceptibility to downregulation of PTK2B /PYK2 expression and to the increase in Tau pathology and Aβ levels while compromising synaptic structure and function.

We developed a high content screening to investigate how Alzheimer disease (AD) genetic risk factors may affect synaptic mechanisms in rat primary neuronal cultures. Out of the target genes identified, we found that Plcg2 downregulation in mouse dentate gyrus neurons consistently disrupted dendritic morphology and synaptic function. In human neuronal cultures (hNCs), PLCG2 downregulation also impaired synaptic function and increased Aβ levels and Tau phosphorylation. Very rare PLCG2 loss-of-function (LoF) variants were associated with a 10-fold increased AD risk. PLCG2 LoF carriers exhibit low mRNA/protein PLCG2/ PLCγ2 levels and the R953* LoF mutation compromised synaptic function and increased AD hallmarks in hNCs. Single nuclei RNAseq analyses confirmed that the downregulation of PLCG2 impacted pathways related to synaptic and neuronal functions, potentially through neurexin in neurons. In conclusion, PLCγ2 downregulation could increase AD risk by impairing synaptic functions and increasing the Aβ levels and Tau phosphorylation in neurons.

Drug repurposing has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to favorable safety profile and pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC ₅₀ measured against SARS-CoV-2 in human pulmonary cells. This compound inhibits SARS-CoV-2 at a post-entry step. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and lowered pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients. Summary: Antivirals targeting SARS-CoV-2 are sorely needed. In this study, we screened a library of drug compounds and identified clofoctol as an antiviral against SARS-CoV-2. We further demonstrated that, in vivo, this compound reduces inflammatory gene expression and lowers pulmonary pathology.

Several randomized controlled trials (RCTs) and meta-analyses support the benefits of flavanols on cardiometabolic health, but the factors affecting variability in the responses to these compounds have not been properly assessed. The objectives of this meta-analysis were to systematically collect the RCTs-based-evidence of the effects of flavanol-containing tea, cocoa and apple products on selected biomarkers of cardiometabolic risk and to explore the influence of various factors on the variability in the responses to the consumption of these products. A total of 120 RCTs were selected. Despite a high heterogeneity, the intake of the flavanol-containing products was associated using a random model with changes (reported as standardized difference in means (SDM)) in body mass index (−0.15, p < 0.001), waist circumference (−0.29, p < 0.001), total-cholesterol (−0.21, p < 0.001), LDL-cholesterol (−0.23, p < 0.001), and triacylglycerides (−0.11, p = 0.027), and with an increase of HDL-cholesterol (0.15, p = 0.005). Through subgroup analyses, we showed the influence of baseline-BMI, sex, source/form of administration, medication and country of investigation on some of the outcome measures and suggest that flavanols may be more effective in specific subgroups such as those with a BMI ≥ 25.0 kg/m², non-medicated individuals or by specifically using tea products. This meta-analysis provides the first robust evidence of the effects induced by the consumption of flavanol-containing tea, cocoa and apple products on weight and lipid biomarkers and shows the influence of various factors that can affect their bioefficacy in humans. Of note, some of these effects are quantitatively comparable to those produced by drugs, life-style changes or other natural products. Further, RCTs in well-characterized populations are required to fully comprehend the factors affecting inter-individual responses to flavanol and thereby improve flavanols efficacy in the prevention of cardiometabolic disorders.

The molecular pathways underlying tau pathology–induced synaptic/cognitive deficits and neurodegeneration are poorly understood. One prevalent hypothesis is that hyperphosphorylation, misfolding, and fibrillization of tau impair synaptic plasticity and cause degeneration. However, tau pathology may also result in the loss of specific physiological tau functions, which are largely unknown but could contribute to neuronal dysfunction. In the present study, we uncovered a novel function of tau in its ability to regulate brain insulin signaling. We found that tau deletion leads to an impaired hippocampal response to insulin, caused by altered IRS-1 and PTEN (phosphatase and tensin homologue on chromosome 10) activities. Our data also demonstrate that tau knockout mice exhibit an impaired hypothalamic anorexigenic effect of insulin that is associated with energy metabolism alterations. Consistently, we found that tau haplotypes are associated with glycemic traits in humans. The present data have far-reaching clinical implications and raise the hypothesis that pathophysiological tau loss-of-function favors brain insulin resistance, which is instrumental for cognitive and metabolic impairments in Alzheimer’s disease patients.

Several epidemiological studies have linked flavonols with decreased risk of cardiovascular disease (CVD). However, some heterogeneity in the individual physiological responses to the consumption of these compounds has been identified. This meta‐analysis aimed to study the effect of flavonol supplementation on biomarkers of CVD risk such as, blood lipids, blood pressure and plasma glucose, as well as factors affecting their inter‐individual variability. Data from 18 human randomized controlled trials were pooled and the effect was estimated using fixed or random effects meta‐analysis model and reported as difference in means (DM). Variability in the response of blood lipids to supplementation with flavonols was assessed by stratifying various population subgroups: age, sex, country, and health status. Results showed significant reductions in total cholesterol (DM = −0.10 mmol/L; 95% CI: −0.20, −0.01), LDL cholesterol (DM = −0.14 mmol/L; Nutrients 2017, 9, 117 2 of 21 95% CI: −0.21, 0.07), and triacylglycerol (DM = −0.10 mmol/L; 95% CI: −0.18, 0.03), and a significant increase in HDL cholesterol (DM = 0.05 mmol/L; 95% CI: 0.02, 0.07). A significant reduction was also observed in fasting plasma glucose (DM = −0.18 mmol/L; 95%CI: −0.29, −0.08), and in blood pressure (SBP: DM = −4.84 mmHg; 95% CI: −5.64, −4.04; DBP: DM = −3.32 mmHg; 95% CI: -4.09, -2.55). Subgroup analysis showed a more pronounced effect of flavonol intake in participants from Asian countries and in participants with diagnosed disease or dyslipidemia, compared to healthy and normal baseline values. In conclusion, flavonol consumption improved biomarkers of CVD risk, however, country of origin and health status may influence the effect of flavonol intake on blood lipid levels

Socio-economic status (SES) is a strong determinant of eating behavior and the obesity risk. To determine which eating and lifestyle behaviors mediate the association between SES and obesity. We performed a case–control study of 318 obese people and 371 non-obese people in northern France. Ten eating behavior traits were assessed using the Three-Factor Eating Questionnaire Revised 21-Item and an eating attitude questionnaire (on plate size, the number of servings, reasons for stopping eating and the frequency of eating standing up, eating in front of the television set (TV) and eating at night). The SES score (in three categories) was based on occupation, education and income categories. Mediation analysis was performed using the test of joint significance and the difference of coefficients test. The age- and gender-adjusted obesity risk was higher for individuals in the low-SES groups (odds ratio (OR) (95% confidence interval (CI)=1.82 (1.48–2.24), P<0.0001). Additional servings were associated with a higher obesity risk (OR=3.43, P<0.0001). Cognitive restraint (P<0.0001) and emotional eating (P<0.0001) scores were higher in obese participants than in non-obese participants but did not depend on SES. Of the 10 potential factors tested, eating off a large plate (P=0.01), eating at night (P=0.04) and uncontrolled eating (P=0.03) significantly mediated the relationship between SES and obesity. Our results highlighted a number of obesogenic behaviors among socially disadvantaged participants: large plate size, uncontrolled eating and eating at night were significant mediators of the relationship between SES and the obesity risk.