👤 Christian Beyer

Food allergy (FA) arises from a complex interplay between an individual's genetic predisposition and environmental factors, and its prevalence is increasing. Genome-wide association studies to date have been hindered by small sample sizes and varying FA definitions. We sought to identify novel FA risk loci by conducting a genome-wide association study meta-analysis in children and adults by using a multiphenotype approach to ensure a good trade-off between sufficient sample size and valid FA definitions. Analyses were conducted separately in children and adults on the basis of the following FA phenotypes: self-report, doctor diagnosis, food-specific sensitization, and doctor diagnosis plus food-specific sensitization. A meta-analysis was performed of genome-wide association studies from up to 16 cohorts of people of European ancestry including 229,426 adults and 14,234 children. Models were adjusted for sex, age, principal components, and, if applicable, further study-specific confounders. Sensitivity models were additionally adjusted for hay fever. Replication was conducted in additional external cohorts and a validation in oral food challenge-defined FA cases. Thirty-seven single nucleotide polymorphisms met suggestive significance (P < 1 × 10 This study identified 37 single nucleotide polymorphisms suggestively associated with FA and demonstrated genetic differences across phenotypes. It highlights the need for a unified FA definition and sheds light on FA's shared genetic architecture with allergies. Show less

Thoracic aortic aneurysms frequently go undetected until serious complications like acute dissections or ruptures arise. Therefore, this study aims to identify potential blood circulating biomarkers enabling an easy and early diagnosis of thoracic aortic disease. Potential biomarker candidates were identified through two different techniques, untargeted and targeted proteomic as well as extracellular vesicle (EV) analyses. The biomarker levels were compared between two patient groups with thoracic aortic aneurysms and two control groups without thoracic aortic disease. In total, 80 patients (TAA group (n = 40) vs. control group (n = 40)) were matched for untargeted and targeted proteome analysis, and 85 for EV analysis (TAA group (n = 42) vs. control group (n = 43)), based on the availability of blood samples and excised aortic tissue. Levels of biomarker candidates were correlated with aortic diameter, patient age, and histological alterations in aortic tissue using linear and logistic regression models. The untargeted proteomic and EV analysis identified 1,037 and 1,077 proteins, respectively, of which 11 and 28 proteins showed significant differences in concentration between the study groups. Of these, 9 proteins correlated with the aortic diameter: ACTN1 (Regression coefficient B = 1.633, p < 0.001), CRP (B = 0.001, p = 0.004), TGM3 (B=-0.293, p = 0.010), KRT84 (B=-0.477, p = 0.010), IGHG3 (-0.267, p = 0.018), DPYSL2 (B = 0.644, p = 0.020), TSPAN8 (B-0.838, p = 0.042), IGKV3D-11 (B=-0.242, p = 0.046), and VDAC1 (B=-0.491, p = 0.047). Moreover, IGKV3D-11 (B=-3.257, p = 0.029), IGHG3 (B=-0.003, p = 0.034), and APOC3 (B=-2.104, p = 0.037) showed significant correlations with the grade of aortic medial layer degeneration. None of the proteins correlated with patient age. The study identified 9 biomarker candidates correlating with the aortic diameter. To enable the clinical use for diagnosis and prognostic assessment, these biomarkers need to be validated in larger external cohorts. Show less

Cholesteryl ester transfer protein (CETP) mediates the exchange of triglycerides (TG) from apolipoprotein B (ApoB)-containing lipoproteins to high-density lipoproteins (HDL) and the reciprocal exchange of cholesterol (C) from HDL to ApoB-containing lipoproteins. CETP inhibition increases HDL-C and decreases low-density lipoprotein cholesterol (LDL-C) while modestly decreasing TG. Considering that CETP inhibitors block removal of TG from TG-rich lipoproteins (TRL), it is interesting that CETP inhibition decreases TG concentrations. TG levels are largely regulated by lipoprotein lipase (LPL), the enzyme primarily responsible for hydrolyzing TG. The angiopoietin-like 3/8 complex (ANGPTL3/8) is the most potent circulating LPL inhibitor, while the TG-lowering apolipoprotein A5 (ApoA5) acts by suppressing ANGPTL3/8-mediated LPL inhibition. To better understand CETP biology, we studied the effects of CETP overexpression and CETP inhibition on the levels of ANGPTL3/8 and ApoA5 in circulation using dedicated immunoassays. CETP-overexpressing transgenic mice had increased TG and normal ANGPTL3/8 levels but manifested dramatically reduced ApoA5 concentrations. Administration of the CETP inhibitor evacetrapib had no effect on ANGPTL3/8 levels in CETP-overexpressing mice or in humans. However, evacetrapib administration increased ApoA5 concentrations in both species. In human subjects, evacetrapib treatment increased circulating ApoA5 levels in the late-stage ACCELERATE and ACCENTUATE studies by 160.1% and 204.7%, respectively. Our results uncover a previously unrecognized link between CETP and ApoA5 by showing that CETP overexpression reduces ApoA5 levels while CETP inhibition increases ApoA5 concentrations. Show less

The angiopoietin-like protein 3/8 complex (ANGPTL3/8) inhibits lipoprotein lipase (LPL) activity, primarily in oxidative tissues, and does so more potently than ANGPTL3, making ANPTL3/8 an attractive target for treating dyslipidemia. This study enrolled 48 adults (36 men, 12 women) with mixed hyperlipidemia to assess the primary outcome of safety and the secondary outcomes of pharmacokinetics and pharmacodynamics of ascending doses of LY3475766, a human monoclonal antibody that specifically blocks ANGPTL3/8-mediated inhibition of LPL activity. Participants received a single dose of LY3475766 or placebo. LY3475766 was well tolerated with no severe adverse events or adverse event-related discontinuations. Compared with placebo, LY3475766 dose-dependently reduced the concentration of triglycerides (-70%), remnant cholesterol (-86%), low-density lipoprotein cholesterol (-32%), non-high-density lipoprotein cholesterol (non-HDL-C) (-35%) and apolipoprotein B (-29%) while increasing HDL-C (+27%). LY3475766 thus significantly reduced atherogenic lipoprotein levels while increasing HDL-C levels; however, the effects on cardiovascular risk remain to be established. ClinicalTrials.gov registration: NCT04052594 . Show less

Tirzepatide, a glucose-dependent insulinotropic polypeptide/glucagon-like peptide 1 receptor (GIPR/GLP-1R) agonist, has, in clinical trials, demonstrated greater reductions in glucose, body weight, and triglyceride levels compared with selective GLP-1R agonists in people with type 2 diabetes (T2D). However, cellular mechanisms by which GIPR agonism may contribute to these improved efficacy outcomes have not been fully defined. Using human adipocyte and mouse models, we investigated how long-acting GIPR agonists regulate fasted and fed adipocyte functions. In functional assays, GIPR agonism enhanced insulin signaling, augmented glucose uptake, and increased the conversion of glucose to glycerol in a cooperative manner with insulin; however, in the absence of insulin, GIPR agonists increased lipolysis. In diet-induced obese mice treated with a long-acting GIPR agonist, circulating triglyceride levels were reduced during oral lipid challenge, and lipoprotein-derived fatty acid uptake into adipose tissue was increased. Our findings support a model for long-acting GIPR agonists to modulate both fasted and fed adipose tissue function differentially by cooperating with insulin to augment glucose and lipid clearance in the fed state while enhancing lipid release when insulin levels are reduced in the fasted state. Show less

Apolipoprotein AV (APOA5) lowers plasma triglyceride (TG) levels by binding to the angiopoietin-like protein 3/8 complex (ANGPTL3/8) and suppressing its capacity to inhibit lipoprotein lipase (LPL) catalytic activity and its ability to detach LPL from binding sites within capillaries. However, the sequences in APOA5 that are required for suppressing ANGPTL3/8 activity have never been defined. A clue to the identity of those sequences was the presence of severe hypertriglyceridemia in two patients harboring an Show less

Triglycerides (TG) are required for fatty acid transport and storage and are essential for human health. Angiopoietin-like-protein 8 (ANGPTL8) has previously been shown to form a complex with ANGPTL3 that increases circulating TG by potently inhibiting LPL. We also recently showed that the TG-lowering apolipoprotein A5 (ApoA5) decreases TG levels by suppressing ANGPTL3/8-mediated LPL inhibition. To understand how LPL binds ANGPTL3/8 and ApoA5 blocks this interaction, we used hydrogen-deuterium exchange mass-spectrometry and molecular modeling to map binding sites of LPL and ApoA5 on ANGPTL3/8. Remarkably, we found that LPL and ApoA5 both bound a unique ANGPTL3/8 epitope consisting of N-terminal regions of ANGPTL3 and ANGPTL8 that are unmasked upon formation of the ANGPTL3/8 complex. We further used ANGPTL3/8 as an immunogen to develop an antibody targeting this same epitope. After refocusing on antibodies that bound ANGPTL3/8, as opposed to ANGPTL3 or ANGPTL8 alone, we utilized bio-layer interferometry to select an antibody exhibiting high-affinity binding to the desired epitope. We revealed an ANGPTL3/8 leucine zipper-like motif within the anti-ANGPTL3/8 epitope, the LPL-inhibitory region, and the ApoA5-interacting region, suggesting the mechanism by which ApoA5 lowers TG is via competition with LPL for the same ANGPTL3/8-binding site. Supporting this hypothesis, we demonstrate that the anti-ANGPTL3/8 antibody potently blocked ANGPTL3/8-mediated LPL inhibition in vitro and dramatically lowered TG levels in vivo. Together, these data show that an anti-ANGPTL3/8 antibody targeting the same leucine zipper-containing epitope recognized by LPL and ApoA5 markedly decreases TG by suppressing ANGPTL3/8-mediated LPL inhibition. Show less

Microtubule actin crosslinking factor 1 (MACF1) plays a role in the coordination of microtubules and actin in multiple cellular processes. Here, we show that MACF1 is also critical for ciliogenesis in multiple cell types. Ablation of Macf1 in the developing retina abolishes ciliogenesis, and basal bodies fail to dock to ciliary vesicles or migrate apically. Photoreceptor polarity is randomized, while inner retinal cells laminate correctly, suggesting that photoreceptor maturation is guided by polarity cues provided by cilia. Deletion of MACF1 in adult photoreceptors causes reversal of basal body docking and loss of outer segments, reflecting a continuous requirement for MACF1 function. MACF1 also interacts with the ciliary proteins MKKS and TALPID3. We propose that a disruption of trafficking across microtubles to actin filaments underlies the ciliogenesis defect in cells lacking MACF1 and that MKKS and TALPID3 are involved in the coordination of microtubule and actin interactions. Show less

To investigate the role of liver X receptors (LXRs) in experimental skin fibrosis and evaluate their potential as novel antifibrotic targets. We studied the role of LXRs in bleomycin-induced skin fibrosis, in the model of sclerodermatous graft-versus-host disease (sclGvHD) and in tight skin-1 (Tsk-1) mice, reflecting different subtypes of fibrotic disease. We examined both LXR isoforms using LXRα-, LXRβ- and LXR-α/β-double-knockout mice. Finally, we investigated the effects of LXRs on fibroblasts and macrophages to establish the antifibrotic mode of action of LXRs. LXR activation by the agonist T0901317 had antifibrotic effects in bleomycin-induced skin fibrosis, in the sclGvHD model and in Tsk-1 mice. The antifibrotic activity of LXRs was particularly prominent in the inflammation-driven bleomycin and sclGvHD models. LXRα-, LXRβ- and LXRα/β-double-knockout mice showed a similar response to bleomycin as wildtype animals. Low levels of the LXR target gene ABCA-1 in the skin of bleomycin-challenged and control mice suggested a low baseline activation of the antifibrotic LXR signalling, which, however, could be specifically activated by T0901317. Fibroblasts were not the direct target cells of LXRs agonists, but LXR activation inhibited fibrosis by interfering with infiltration of macrophages and their release of the pro-fibrotic interleukin-6. We identified LXRs as novel targets for antifibrotic therapies, a yet unknown aspect of these nuclear receptors. Our data suggest that LXR activation might be particularly effective in patients with inflammatory disease subtypes. Activation of LXRs interfered with the release of interleukin-6 from macrophages and, thus, inhibited fibroblast activation and collagen release. Show less

Bardet-Biedl syndrome (BBS) is a rare hereditary autosomal recessive disease associated with several features including obesity, hypertension, and renal abnormalities. The underlying mechanisms of renal defects associated with BBS remain poorly defined. We examined the histological, molecular, and functional renal changes in BBS mouse models that have features of the human disorder. Interestingly, obese hypertensive Bbs4(-/-) mice exhibited inflammatory infiltration and renal cysts, whereas the obese normotensive Bbs2(-/-) mice had only minor inflammatory infiltration. Accordingly, the expression level of inducible nitric oxide synthase was elevated in the kidney of both BBS mice with a more marked increase in Bbs4(-/-) mice. In contrast, endothelial nitric oxide synthase expression was decreased in Bbs4(-/-), but not Bbs2(-/-), mice. Similarly, the expression levels of transient receptor potential vanilloid 1 and 4 channels as well as β- and γ-subunits of epithelial Na channel were significantly reduced only in the kidney of Bbs4(-/-) mice. Metabolic studies revealed changes in urine output and urinary concentrations of creatinine, blood urea nitrogen, sodium, and potassium with a more pronounced effect in Bbs4(-/-) mice. Finally, we found that calorie restriction which prevented obesity in BBS mice reversed the morphological and molecular changes found in Bbs2(-/-) and Bbs4(-/-) mice, indicating the kidney abnormalities associated with BBS are obesity related. These findings extend our understanding of the function of BBS proteins and emphasize the importance of these proteins in renal physiology. Show less

We have previously found that overexpression of CHF1/Hey2 in the myocardium prevents the development of phenylephrine-induced hypertrophy. To identify transcriptional pathways regulated by CHF1/Hey2, we cultured primary neonatal mouse cardiac myocytes from wild type and transgenic mice overexpressing CHF1/Hey2 and treated them with serum, a potent hypertrophic stimulus. We verified that overexpression of CHF1/Hey2 suppressed cardiac myocyte hypertrophy induced by serum and then determined transcriptional profiles by microarray hybridization. We identified and verified important downstream target genes by single gene analysis and qRT-PCR and then identified important biological processes by Gene Set Analysis using Biological Process Gene Sets from the Gene Ontology Consortium. We found that CHF1/Hey2 suppresses pathways involved in water transport, adenylate cyclase activity, embryonic eye morphogenesis, gut development and fluid transport after serum stimulation. Genes involved in protein dephosphorylation, demonstrate increased expression in myocytes overexpressing CHF1/Hey2, independent of serum treatment. Genes overexpressed prior to serum treatment are involved in regulation of transcription factor activity, nuclear protein export and steroid hormone receptor signaling. Genes overexpressed after serum treatment are involved in autophagy, apoptosis and mitochondrial biogenesis. Show less

We have previously found that CHF1/Hey2 prevents the development of phenylephrine-induced cardiac hypertrophy. To determine the role of CHF1/Hey2 in pressure overload hypertrophy, we performed ascending aortic banding on wild-type and transgenic mice overexpressing CHF1/Hey2 in the myocardium. We found that both wild-type and transgenic mice developed increased ventricular weight to body weight ratios 1 week after aortic banding. Wild-type mice also developed decreased fractional shortening after 1 week when compared to preoperative echocardiograms and sham-operated controls. Transgenic mice, in comparison, demonstrated preserved fractional shortening. Histological examination of explanted heart tissue demonstrated extensive fibrosis in wild-type hearts, but minimal fibrosis in transgenic hearts. TUNEL staining demonstrated increased apoptosis in the wild-type hearts but not in the transgenic hearts. Exposure of cultured neonatal myocytes from wild-type and transgenic animals to hydrogen peroxide, a potent inducer of apoptosis, demonstrated increased apoptosis in the wild-type cells. Gene Set Analysis of microarray data from wild-type and transgenic hearts 1 week after banding revealed suppression and activation of multiple pathways involving apoptosis, cell signaling, and biosynthesis. These findings demonstrate that CHF1/Hey2 promotes physiological over pathological hypertrophy through suppression of apoptosis and regulation of multiple transcriptional pathways. These findings also suggest that CHF1/Hey2 and its downstream pathways provide a variety of targets for novel heart failure drug discovery, and that genetic polymorphisms in CHF1/Hey2 may affect susceptibility to hypertrophy and heart failure. Show less

Liver X receptors (LXRs) regulate target genes that are critical in lipoprotein metabolism and atherosclerosis. Apolipoprotein AIV (ApoAIV) is an apolipoprotein that is associated with chylomicrons and high-density lipoproteins. Plasma ApoAIV level in humans is inversely correlated with coronary artery events and overexpression of ApoAIV in mice results in significant reduction in atherosclerosis. We report here that LXRs directly regulate apoAIV at the transcriptional level. Treatment of C57B6 mice with a synthetic LXR agonist, T0901317, resulted in significant increases in plasma apoAIV that was associated with high-density lipoprotein. Examination of both intestinal and liver apoAIV mRNA revealed specific increases in liver mRNA only. In a human heptoma HepG2 cell model, apoAIV mRNA was up-regulated upon the treatment with either native or synthetic LXR agonists. Nuclear run-on study revealed a significant increase in the ApoAIV transcriptional rate upon LXR activation. Examination of the human apoAIV proximal promoter revealed a potential LXR response element that demonstrated binding with HepG2 nuclear extracts. Cotransfection studies in HepG2 cells indicated that this responsive element was functional in mediating the human ApoAIV gene response to LXR agonists. In addition, we identified a functional LXR-responsive element at 3' end enhancer region of mouse ApoAIV gene. We conclude that ApoAIV is a direct target gene of LXRs that may contribute to the antiatherogenic effect of LXR activation. Show less