👤 Amandine Caillaud

Amyloid-β (Aβ) plays a critical role in Alzheimer's disease (AD) and its accumulation in the brain is pivotal to disease progression and precedes memory and neuronal loss. Besides the severely handicapping brain symptoms, AD patients display early gastro-intestinal (GI) manifestations such as upper and lower GI dysmotility, in particular constipation. Although there is increasing evidence of Aβ accumulation in the gut, its pathogenic effects on enteric nervous system (ENS) connectivity and gut function as well as underlying pathophysiological mechanisms are poorly understood. Furthermore, studies have reported a gut to brain transmission of Aβ that causes memory deficits in mice. Therefore, identifying therapeutics which can reduce Aβ accumulation in the gut at an early stage of the disease could have the advantage of slowing or even reversing disease progression before severe alterations or irreversible damages at both intestinal and brain levels. Hence, in this study, we investigated the capacity of the short-fatty acid butyrate to restore Aβ-driven alteration of ENS connectivity and gut-brain functions in the SAMP8 mouse model of AD. Here we show that SAMP8 mice display a gut amyloid pathology, an alteration of ENS connectivity and gut defects prior to memory decline. BACE1, an Aβ-producing enzyme, expression and activity are increased whereas neprilysin, an Aβ-degrading enzyme, is decreased in the gut of SAMP8 mice, indicating a rise in the Amyloid Precursor Protein (APP) holoprotein processing and a reduction of Aβ clearance which promote an amyloidosis. In primary ENS cultures, Aβ causes a degradation of synaptic-associated proteins EphB2 and synaptophysin, leading to an alteration of ENS connectivity. In wild-type mice, intra-colon delivery of Aβ alters ENS connectivity and causes subsequent GI symptoms, recapitulating the phenotype of the SAMP8 mouse model of aging and AD. Moreover, Aβ impairs ENS connectivity in human induced pluripotent stem cell (iPSC)-derived intestinal organoids and explant cultures of human colon, indicating that Aβ causes ENS lesions in models of the human gut. Butyrate, a short-chain fatty acid derived from bacterial metabolism, reduces Aβ secretion and preserves enteric neuronal connectivity in vitro and in vivo, and blocks Aβ accumulation in the gut, brain and plasma in SAMP8 mice. In addition, butyrate ameliorates neuroinflammation and prevents gut dysfunction and memory deficit. Collectively, these findings suggest that Aβ promotes gut symptoms through alteration of ENS connectivity and butyrate counteracts these impairments with an amelioration of neuroinflammation and memory function in AD model. Show less

Atherosclerotic cardiovascular disease is the main cause of mortality worldwide and is strongly influenced by circulating low-density lipoprotein (LDL) cholesterol levels. Only a few genes causally related to plasma LDL cholesterol levels have been identified so far, and only 1 gene, Using next-generation sequencing, we identified a novel dominant rare variant in the Family members carrying the We identified and characterized a novel rare variant in the Show less

Mice expressing human apolipoprotein A-IV (apoA-IV) mainly in the intestine were obtained in an apolipoprotein E-deficient (apoE(0)) background (apoA-IV/E(0) mice). Quantification of aortic lesions and plasma lipid determination showed that compared with their control apoE(0) counterparts, the apoA-IV/E(0) mice are protected against atherosclerosis without an increase in HDL cholesterol. Because oxidized lipoproteins play an important role in atherogenesis, we tested whether the protection observed in these animals is accompanied by an in vivo reduction of the oxidation parameters. The lag time in the formation of conjugated dienes during copper-mediated oxidation, the aggregation state of LDL, and the presence of anti-oxidized LDL antibodies were measured. The presence of oxidized proteins in tissues and the presence of oxidation-specific epitopes in heart sections of atherosclerotic lesions were also analyzed. Except for lag time, the results showed that the oxidation parameters were reduced in the apoA-IV/E(0) mice compared with the apoE(0) mice. This suggests that human apoA-IV acts in vivo as an antioxidant. In addition, human apoA-IV accumulation was detected in the atherosclerotic lesions of apoA-IV/E(0) mice, suggesting that apoA-IV may inhibit oxidative damage to local tissues, thus decreasing the progression of atherosclerosis. Show less