👤 Linu M John

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

Impaired cerebral glucose metabolism is a hallmark of Alzheimer's disease (AD). Lactate is an alternative brain fuel; however, whole-body lactate metabolism has not been measured in AD. The Lactate for Energy and Neurocognition Trial (NCT05207397) was a single-arm trial that enrolled 24 cognitively healthy (CH) older adults and 12 cognitively impaired (CI) participants. Subjects underwent a stable isotope lactate infusion to evaluate lactate metabolism, cognitive testing, and blood biomarker analyses. pTau217, brain-derived tau (BD-tau), pTau181, glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), total tau, and brain-derived neurotrophic factor (BDNF) were analyzed by Simoa HD-X (Quanterix). Lactate metabolic clearance rate did not differ between CH and CI subjects (p = 0.988). After infusion, global cognition was improved (p < 0.001) and plasma pTau217 (-33.8%, p < 0.001), BD-tau (-32.6%, p < 0.001), pTau181 (-21.4%, p < 0.001), GFAP (-39.7%, p < 0.001), and NfL (-19.5%, p < 0.001) were reduced. Lactate turnover was not different between diagnosis groups. Lactate infusion improved cognition and reduced AD fluid biomarkers. Individuals with Alzheimer's disease (AD) can metabolize lactate as well as healthy controls. Lactate infusion might improve global cognition and processing speed. Lactate infusion results in significant decrease of AD fluid biomarkers. Show less

Obesity and weight regulation disorders are determined by the combined effects of genetics and environment. Polygenic obesity results from the combination of common variants in several genes which predisposes the individual to obesity and its related complications. In contrast, monogenic obesity results from changes in single genes, especially those in leptin-melanocortin pathway, and presents with early onset severe obesity, with or without other syndromic features. Rare variants in melanocortin 4 receptor are the commonest form of monogenic obesity. In addition, structural variation in small or large segments of chromosomes may also present with syndromic forms of obesity. Prader-Willi Syndrome, caused by imprinting errors in chromosome 15q11-13, is the most prevalent genetic cause of severe hyperphagia and obesity. With the advances in technologies, the past decade has witnessed a revolution in the identification of novel genetic causes of obesity, primarily in genes related to the leptin melanocortin pathway. The availability of safe melanocortin analogs holds the potential for targeted therapies for some of these disorders. This review summarizes known and novel rare genetic forms of obesity, along with approaches for the clinical investigation of copy number and sequence variants. The goal is to provide a reference for practicing clinicians to encourage genetic testing in obesity. IMPACT: What does this article add to the existing literature? Genetic obesity is an expanding frontier with potential to change management. Here, we summarize current information on the genetic causes of obesity and provide guidance for genetic testing. Emerging treatments may provide targeted precise treatment and change management practices. Show less

Alzheimer's disease (AD) pathology is complex and involves mitochondrial dysfunction. There are emerging therapies targeting mitochondrial function in clinical trials for AD. This highlights the need for biomarkers that measure mitochondrial function. We determined the utility of a novel blood-based mitochondrial biomarker, the mitochondrial functional index (MFI), in the context of AD in a pilot study. In vitro and in vivo models of AD had a reduced MFI. MFI was lower in human AD subjects and APOE 𝜀4 carriers. Receiver operating characteristic analysis showed MFI had a higher area under the curve than other plasma biomarkers. The MFI biomarker correlated with the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating (CDR) scale. This study highlights the potential utility of MFI as a functional blood-based mitochondrial biomarker to interrogate energy metabolism. Ongoing studies are examining the relationship of MFI with brain energy metabolism outcomes. The MFI biomarker is reduced in cell and animal models of AD. The MFI biomarker is reduced in human AD subjects and APOE ε4 carriers. The MFI biomarker can discriminate between subjects with normal cognition and AD with better performance than other plasma biomarkers. The MFI biomarker correlates with cognitive scores. Show less

Overexpression of the low-density lipoprotein receptor (LDLR) is known to decrease apolipoprotein E (APOE) levels and alleviate amyloid beta (Aβ) pathology. We hypothesized that inhibiting the Inducible Degrader of LDLR (IDOL), an enzyme that ubiquitinates LDLR for degradation, would increase endogenous LDLR levels and attenuate amyloid pathology. To investigate the cell-type-specific role of IDOL, we generated Idol conditional knockout mice on an Aβ-amyloidosis mouse model and performed biochemical, histological, and multi-omics analyses. We demonstrated that neuronal, but not microglial, Idol deletion reduced amyloid accumulation and altered brain LDLR and APOE levels, indicating the critical role of neuronal IDOL-LDLR in amyloid pathology. In addition, neuronal Idol deletion increased the levels of Reelin receptors important for synaptic function, and single-nuclei RNA sequencing revealed significant changes associated with synaptic organization. Neuronal IDOL, but not microglial IDOL, plays a key role in Alzheimer's disease pathogenesis by regulating the levels of brain APOE receptors. Neuronal, but not microglial, Idol deletion reduces amyloid burden and modulates brain APOE and LDLR levels. Deletion of neuronal Idol increases the levels of APOER2 and VLDLR, the Reelin receptors, in the brain. Single-nuclei RNA sequencing highlights the neuronal IDOL's impact on inhibitory neurons and synaptic organization. Targeting neuronal IDOL may provide multiple therapeutic benefits in Alzheimer's disease by modulating APOE receptors. Show less

Inhibition of amyloid precursor protein (APP) beta-site cleaving enzyme 1 (BACE1) has been a target for Alzheimer's disease (AD) therapeutic development. Here, we report our identification of APP-selective BACE1 (ASBI) inhibitors that are selective for APP as the substrate and BACE1 as the target enzyme. A known fluoro aminohydantoin (FAH) inhibitor compound was identified by screening a compound library for inhibition of BACE1 cleavage of a maltose binding protein (MBP)-conjugated-APPC125 substrate followed by optimization and IC50 determination using the P5-P5' activity assay. Optimization of the screening hit led to candidate FAH65, which displays selectivity for inhibition of APP cleavage with little activity against other BACE1 substrates neuregulin 1 (NRG1) or p-selectin glycoprotein ligand-1 (PSGL1). FAH65 shows little inhibitory activity against other aspartyl proteases cathepsin D (Cat D) and BACE2. FAH65 reduces BACE1 cleavage products soluble APPβ (sAPPβ) and the β C-terminal fragment (βCTF), as well as amyloid-β (Aβ) 1-40 and 1-42, both in vitro in cells and in vivo in an animal model of AD. In a murine model of AD, FAH65 improved the discrimination score in the Novel Object Recognition (NOR) memory testing paradigm. The active enantiomer of racemate FAH65, FAH65E(-), displays good brain-penetrance and target engagement, meriting further pre-clinical development as an ASBI that may reduce Aβ levels and overcome the deleterious effects of the non-selective BACE1 inhibitors that have failed in the clinic. FAH65E(-) has the potential to be a first-in-class oral therapy that could be used in conjunction with an approved anti-Aβ antibody therapy for AD. Show less

To examine the adaptive behaviour profiles of children with monogenic neurodevelopmental disorders (NDDs) to determine whether syndrome-specific or transdiagnostic approaches provide a better understanding of the adaptive behavioural phenotypes of these NDDs. This cross-sectional study included parents and caregivers of 243 (48% female) individuals (age range = 1-25 years; mean = 8 years 10 months, SD = 5 years 8 months) with genetically confirmed monogenic NDDs (CDK13, DYRK1A, FOXP2, KAT6A, KANSL1, SETBP1, BRPF1, and DDX3X). Parents and caregivers completed the Vineland Adaptive Behavior Scales, Third Edition to assess communication, daily living, socialization, and motor skills. Linear regression models comparing mean adaptive behaviours between monogenic NDDs, adjusting for the presence of intellectual disability, revealed few group differences. Children with variants in BRPF1 or KANSL1 had better adaptive behaviour skills compared to children with variants in CDK13, DDX3X, DYRK1A, and KAT6A, although group differences varied across domains. A latent profile analysis showed compelling evidence for a five-profile model. These profiles were homogeneous, with similar delays across the subdomain scores in each profile. Additionally, each monogenic NDD was represented in each profile, with a few exceptions. Transdiagnostic approaches to understand adaptive behaviour in monogenic NDDs provide a better understanding of individual strengths and challenges, enabling more targeted support. Show less

Evaluation of weight loss drugs is usually performed in diet-induced obese mice housed at ∼22°C. This is a cold stress that increases energy expenditure by ∼35% compared to thermoneutrality (∼30°C), which may overestimate drug-induced weight loss. We investigated five anti-obesity mechanisms that have been in clinical development, comparing weight loss in mice housed at 22°C vs. 30°C. Glucagon-like peptide-1 (GLP-1), human fibroblast growth factor 21 (hFGF21), and melanocortin-4 receptor (MC4R) agonist induced similar weight losses. Peptide YY elicited greater vehicle-subtracted weight loss at 30°C (7.2% vs. 1.4%), whereas growth differentiation factor 15 (GDF15) was more effective at 22°C (13% vs. 6%). Independent of ambient temperature, GLP-1 and hFGF21 prevented the reduction in metabolic rate caused by weight loss. There was no simple rule for a better prediction of human drug efficacy based on ambient temperature, but since humans live at thermoneutrality, drug testing using mice should include experiments near thermoneutrality. Show less

The glucose-dependent insulinotropic polypeptide (GIPR) and glucagon-like peptide (GLP-1R) receptor agonists are insulin secretagogues that have long been shown to improve glycemic control and dual agonists have demonstrated successful weight loss in the clinic. GIPR and GLP-1R populations are located in the dorsal vagal complex where receptor activity-modifying proteins (RAMPs) are also present. According to recent literature, RAMPs not only regulate the signaling of the calcitonin receptor, but also that of other class B G-protein coupled receptors, including members of the glucagon receptor family such as GLP-1R and GIPR. The aim of this study was to investigate whether the absence of RAMP1 and RAMP3 interferes with the action of GIPR and GLP-1R agonists on body weight maintenance and glucose control. To this end, WT and RAMP 1/3 KO mice were fed a 45% high fat diet for 22 weeks and were injected daily with GLP-1R agonist (2 nmol/kg/d; NN0113-2220), GIPR agonist (30 nmol/kg/d; NN0441-0329) or both for 3 weeks. While the mono-agonists exerted little to no body weight lowering and anorectic effects in WT or RAMP1/3 KO mice, but at the given doses, when both compounds were administered together, they synergistically reduced body weight, with a greater effect observed in KO mice. Finally, GLP-1R and GIP/GLP-1R agonist treatment led to improved glucose tolerance, but the absence of RAMPs resulted in an improvement of the HOMA-IR score. These data suggest that RAMPs may play a crucial role in modulating the pharmacological actions of GLP-1 and GIP receptors. Show less

Discovery of pan-antagonist ligands for the melanocortin receptors will help identify the physiological activities controlled by these receptors. The previously reported MC3R/MC4R antagonist Ac-DPhe(pI)-Arg-Nal(2')-Arg-NH Show less

ROS1 fusions are well treatable aberrations in NSCLC. Besides solvent-front mutations (SFM) in resistance to targeted therapy, small-scale ROS1 mutations are largely unknown. We exploratively analyzed the clinical and molecular characteristics of small-scale ROS1 mutations in NSCLC patients without activating ROS1 fusions or SFMs. Next-generation sequencing was performed on tissue samples from NSCLC patients within the Network Genomic Medicine. Patients with ROS1 fusions and SFMs were excluded. We analyzed clinical characteristics of patients harboring small-scale ROS1-mutations, ROS1- and co-occurring mutations, and their response to systemic therapy. Of 10,396 patients analyzed, 101 (1.0%) patients harbored small-scale ROS1 mutations. Most patients were male (73.3%) and smokers (96.6%). Nearly half of the patients presented with squamous-cell carcinoma (SqCC, 40.4%). Most mutations were transversions (50.5%), and 66% were in the kinase domain. Besides TP53 mutations (65.3%), KRAS (22.8%), EGFR (5.9%), PIK3CA (9.9%) and FGFR1-4 mutations (8.9%) co-occurred. In 10 (9.9%) patients, ROS1 mutation was the only aberration detected. Median overall survival (mOS) differed significantly in patients with or without KRAS co-mutations (9.7 vs 21.5 months, p = 0.02) and in patients treated with or without immune-checkpoint blockade (ICB) during treatment (21.5 vs 4.4 months, p = 0.003). The cohort's clinical characteristics contrasted ROS1-fused cohorts. Co-occurrence of KRAS mutations led to shortened survival and patients benefited from ICB. Our data does not support the idea of ROS1 small-scale mutations as strong oncogenic drivers in NSCLC, but rather as relevant bystanders altering the efficacy of treatment approaches. Show less

While the Arabian population has a high prevalence of metabolic disorders, it has not been included in global studies that identify genetic risk loci for metabolic traits. Determining the transferability of such largely Euro-centric established risk loci is essential to transfer the research tools/resources, and drug targets generated by global studies to a broad range of ethnic populations. Further, consideration of populations such as Arabs, that are characterized by consanguinity and a high level of inbreeding, can lead to identification of novel risk loci. We imputed published GWAS data from two Kuwaiti Arab cohorts (n = 1434 and 1298) to the 1000 Genomes Project haplotypes and performed meta-analysis for associations with 13 metabolic traits. We compared the observed association signals with those established for metabolic traits. Our study highlighted 70 variants from 9 different genes, some of which have established links to metabolic disorders. By relaxing the genome-wide significance threshold, we identified 'novel' risk variants from 11 genes for metabolic traits. Many novel risk variant association signals were observed at or borderline to genome-wide significance. Furthermore, 349 previously established variants from 187 genes were validated in our study. Pleiotropic effect of risk variants on multiple metabolic traits were observed. Fine-mapping illuminated rs7838666/CSMD1 rs1864163/CETP and rs112861901/[INTS10,LPL] as candidate causal variants influencing fasting plasma glucose and high-density lipoprotein levels. Computational functional analysis identified a variety of gene regulatory signals around several variants. This study enlarges the population ancestry diversity of available GWAS and elucidates new variants in an ethnic group burdened with metabolic disorders. Show less

To investigate the origins and stages of vertebrate adaptive radiation, we reconstructed the spatial and temporal histories of adaptive alleles underlying major phenotypic axes of diversification from the genomes of 202 Caribbean pupfishes. On a single Bahamian island, ancient standing variation from disjunct geographic sources was reassembled into new combinations under strong directional selection for adaptation to the novel trophic niches of scale-eating and molluscivory. We found evidence for two longstanding hypotheses of adaptive radiation: hybrid swarm origins and temporal stages of adaptation. Using a combination of population genomics, transcriptomics, and genome-wide association mapping, we demonstrate that this microendemic adaptive radiation of novel trophic specialists on San Salvador Island, Bahamas experienced twice as much adaptive introgression as generalist populations on neighboring islands and that adaptive divergence occurred in stages. First, standing regulatory variation in genes associated with feeding behavior ( Show less

High-density lipoprotein (HDL) levels are inversely associated with cardiovascular risk. Cholesteryl ester transfer protein inhibition with evacetrapib results in a marked increase in HDL and reduction in low-density lipoprotein (LDL) levels. We evaluated the impact of treatment with evacetrapib versus placebo in the subset of 8236 patients with diabetes mellitus (DM) enrolled in the Assessment of Clinical Effects of Cholesteryl Ester Transfer Protein Inhibition with Evacetrapib in Patients at a High Risk for Vascular Outcomes trial. Time to first occurrence of any component of the primary composite endpoint of cardiovascular death, myocardial infarction, stroke, revascularization, and hospitalization for unstable angina was compared among patients with DM randomized to treatment with evacetrapib (n=4127) or placebo (n=4109) over a median of 26 months of follow-up. The mean baseline LDL at initiation was 80 mg/dL with a mean baseline HDL of 44 mg/dL. In patients with DM, evacetrapib resulted in a 131% mean increase in HDL levels and a 32% mean decrease in LDL at 3 months that was sustained during the course of the trial. At 6 months, hemoglobin A1c (HbA1c) levels were lower with evacetrapib than placebo (7.08% vs 7.15%, p=0.023). Composite event rates were higher in patients with DM than without DM (Kaplan-Meier estimates: 15.2% vs 10.6%, HR 1.46, 95% CI 1.30 to 1.64, p<0.001). In the DM group, event rates for the composite endpoint (14.5% evacetrapib vs 16% placebo, HR 0.95, 95% CI 0.85 to 1.07, p=0.38) and individual components of the composite were similar for both evacetrapib and placebo groups. No significant treatment interaction between treatment assignment and diabetes status was noted. Despite a favorable increase in HDL, and decreases in LDL and HbA1c levels in patients with DM, we observed no benefits of treatment with evacetrapib on prespecified clinical outcomes in this high-risk population. Show less

COVID-19 is caused by Severe Acute Respiratory Syndrome Coronavirus-2, which has infected over thirty eight million individuals worldwide. Emerging evidence indicates that COVID-19 patients are at a high risk of developing coagulopathy and thrombosis, conditions that elevate levels of D-dimer. It is believed that homocysteine, an amino acid that plays a crucial role in coagulation, may also contribute to these conditions. At present, multiple genes are implicated in the development of these disorders. For example, single-nucleotide polymorphisms (SNPs) in FGG, FGA, and F5 mediate increases in D-dimer and SNPs in ABO, CBS, CPS1 and MTHFR mediate differences in homocysteine levels, and SNPs in TDAG8 associate with Heparin-induced Thrombocytopenia. In this study, we aimed to uncover the genetic basis of the above conditions by examining genome-wide associations and tissue-specific gene expression to build a molecular network. Based on gene ontology, we annotated various SNPs with five ancestral terms: pulmonary embolism, venous thromboembolism, vascular diseases, cerebrovascular disorders, and stroke. The gene-gene interaction network revealed three clusters that each contained hallmark genes for D-dimer/fibrinogen levels, homocysteine levels, and arterial/venous thromboembolism with F2 and F5 acting as connecting nodes. We propose that genotyping COVID-19 patients for SNPs examined in this study will help identify those at greatest risk of complications linked to thrombosis. Show less

Family history, a well-established risk factor for breast cancer, can have both genetic and environmental contributions. Shared environment in families as well as epigenetic changes that also may be influenced by shared genetics and environment may also explain familial clustering of cancers. Epigenetic regulation, such as DNA methylation, can change the activity of a DNA segment without a change in the sequence; environmental exposures experienced across the life course can induce such changes. However, genetic-epigenetic interactions, detected as methylation quantitative trait loci (mQTLs; a.k.a. meQTLs) and haplotype-dependent allele-specific methylation (hap-ASM), can also contribute to inter-individual differences in DNA methylation patterns. To identify differentially methylated regions (DMRs) associated with breast cancer susceptibility, we examined differences in white blood cell DNA methylation in 29 candidate genes in 426 girls (ages 6-13 years) from the LEGACY Girls Study, 239 with and 187 without a breast cancer family history (BCFH). We measured methylation by targeted massively parallel bisulfite sequencing (bis-seq) and observed BCFH DMRs in two genes: ESR1 (Δ4.9%, P = 0.003) and SEC16B (Δ3.6%, P = 0.026), each of which has been previously implicated in breast cancer susceptibility and pubertal development. These DMRs showed high inter-individual variability in methylation, suggesting the presence of mQTLs/hap-ASM. Using single nucleotide polymorphisms data in the bis-seq amplicon, we found strong hap-ASM in SEC16B (with allele specific-differences ranging from 42% to 74%). These findings suggest that differential methylation in genes relevant to breast cancer susceptibility may be present early in life, and that inherited genetic factors underlie some of these epigenetic differences. Show less

Brown and beige adipocytes combust nutrients for thermogenesis and through their metabolic activity decrease pro-atherogenic remnant lipoproteins in hyperlipidemic mice. However, whether the activation of thermogenic adipocytes affects the metabolism and anti-atherogenic properties of high-density lipoproteins (HDL) is unknown. Here, we report a reduction in atherosclerosis in response to pharmacological stimulation of thermogenesis linked to increased HDL levels in APOE*3-Leiden.CETP mice. Both cold-induced and pharmacological thermogenic activation enhances HDL remodelling, which is associated with specific lipidomic changes in mouse and human HDL. Furthermore, thermogenic stimulation promotes HDL-cholesterol clearance and increases macrophage-to-faeces reverse cholesterol transport in mice. Mechanistically, we show that intravascular lipolysis by adipocyte lipoprotein lipase and hepatic uptake of HDL by scavenger receptor B-I are the driving forces of HDL-cholesterol disposal in liver. Our findings corroborate the notion that high metabolic activity of thermogenic adipocytes confers atheroprotective properties via increased systemic cholesterol flux through the HDL compartment. Show less

Despite a high prevalence of metabolic trait related diseases in Arabian Peninsula, there is a lack of convincingly identified genetic determinants for metabolic traits in this population. Arab populations are underrepresented in global genome-wide association studies. We genotyped 1965 unrelated Arab individuals from Kuwait using Cardio-MetaboChip, and tested SNP associations with 13 metabolic traits. Models based on recessive mode of inheritance identified Chr15:40531386-rs12440118/ZNF106/W->R as a risk variant associated with glycated-hemoglobin at close to 'genome-wide significant' p-value and five other risk variants 'nominally' associated (p-value ≤ 5.45E-07) with fasting plasma glucose (rs7144734/[OTX2-AS1,RPL3P3]) and triglyceride (rs17501809/PLGRKT; rs11143005/LOC105376072; rs900543/[THSD4,NR2E3]; and Chr12:101494770/IGF1). Furthermore, we identified 33 associations (30 SNPs with 12 traits) with 'suggestive' evidence of association (p-value < 1.0E-05); 20 of these operate under recessive mode of inheritance. Two of these 'suggestive' associations (rs1800775-CETP/HDL; and rs9326246-BUD13/TGL) showed evidence at genome-wide significance in previous studies on Euro-centric populations. Involvement of many of the identified loci in mediating metabolic traits was supported by literature evidences. The identified loci participate in critical metabolic pathways (such as Ceramide signaling, and Mitogen-Activated Protein Kinase/Extracellular Signal Regulated Kinase signaling). Data from Genotype-Tissue Expression database affirmed that 7 of the identified variants differentially regulate the up/downstream genes that mediate metabolic traits. Show less

The flaviviruses dengue virus (DENV) and Zika virus (ZIKV) are severe health threats with rapidly expanding ranges. To identify the host cell dependencies of DENV and ZIKV, we completed orthologous functional genomic screens using RNAi and CRISPR/Cas9 approaches. The screens recovered the ZIKV entry factor AXL as well as multiple host factors involved in endocytosis (RAB5C and RABGEF), heparin sulfation (NDST1 and EXT1), and transmembrane protein processing and maturation, including the endoplasmic reticulum membrane complex (EMC). We find that both flaviviruses require the EMC for their early stages of infection. Together, these studies generate a high-confidence, systems-wide view of human-flavivirus interactions and provide insights into the role of the EMC in flavivirus replication. Show less

Liver X receptors (LXRs) α and β are nuclear hormone receptors that are widely expressed in the kidney. They promote cholesterol efflux from cells and inhibit inflammatory responses by regulating gene transcription. Here, we hypothesised (1) that LXR deficiency would promote renal decline in a mouse model of diabetes by accelerating intraglomerular cholesterol accumulation and, conversely, (2) that LXR agonism would attenuate renal decline in diabetes. Diabetes was induced with streptozotocin (STZ) and maintained for 14 weeks in Lxrα/β (+/+) (Lxrα, also known as Nr1h3; Lxrβ, also known as Nr1h2) and Lxrα/β (-/-) mice. In addition, STZ-injected DBA/2J mice were treated with vehicle or the LXR agonist N,N-dimethyl-hydroxycholenamide (DMHCA) (80 mg/kg daily) for 10 weeks. To determine the role of cholesterol in diabetic nephropathy (DN), mice were placed on a Western diet after hyperglycaemia developed. Even in the absence of diabetes, Lxrα/β (-/-) mice exhibited a tenfold increase in the albumin:creatinine ratio and a 40-fold increase in glomerular lipid accumulation compared with Lxrα/β (+/+) mice. When challenged with diabetes, Lxrα/β (-/-) mice showed accelerated mesangial matrix expansion and glomerular lipid accumulation, with upregulation of inflammatory and oxidative stress markers. In the DN-sensitive STZ DBA/2J mouse model, DMHCA treatment significantly decreased albumin and nephrin excretion (by 50% each), glomerular lipids and plasma triacylglycerol (by 70%) and cholesterol (by 48%); it also decreased kidney inflammatory and oxidative stress markers compared with vehicle-treated mice. These data support the idea that LXR plays an important role in the normal and diabetic kidney, while showing that LXR, through its inhibitory effect on inflammation and cholesterol accumulation in glomeruli, could also be a novel therapeutic target for DN. Show less

Axon regeneration in the injured adult CNS is reportedly inhibited by myelin-derived inhibitory molecules, after binding to a receptor complex comprised of the Nogo-66 receptor (NgR1) and two transmembrane co-receptors p75/TROY and LINGO-1. However, the post-injury expression pattern for LINGO-1 is inconsistent with its proposed function. We demonstrated that AMIGO3 levels were significantly higher acutely than those of LINGO-1 in dorsal column lesions and reduced in models of dorsal root ganglion neuron (DRGN) axon regeneration. Similarly, AMIGO3 levels were raised in the retina immediately after optic nerve crush, whilst levels were suppressed in regenerating optic nerves, induced by intravitreal peripheral nerve implantation. AMIGO3 interacted functionally with NgR1-p75/TROY in non-neuronal cells and in brain lysates, mediating RhoA activation in response to CNS myelin. Knockdown of AMIGO3 in myelin-inhibited adult primary DRG and retinal cultures promoted disinhibited neurite growth when cells were stimulated with appropriate neurotrophic factors. These findings demonstrate that AMIGO3 substitutes for LINGO-1 in the NgR1-p75/TROY inhibitory signalling complex and suggests that the NgR1-p75/TROY-AMIGO3 receptor complex mediates myelin-induced inhibition of axon growth acutely in the CNS. Thus, antagonizing AMIGO3 rather than LINGO-1 immediately after CNS injury is likely to be a more effective therapeutic strategy for promoting CNS axon regeneration when combined with neurotrophic factor administration. Show less

Obesity is globally prevalent and highly heritable, but its underlying genetic factors remain largely elusive. To identify genetic loci for obesity susceptibility, we examined associations between body mass index and ∼ 2.8 million SNPs in up to 123,865 individuals with targeted follow up of 42 SNPs in up to 125,931 additional individuals. We confirmed 14 known obesity susceptibility loci and identified 18 new loci associated with body mass index (P < 5 × 10⁻⁸), one of which includes a copy number variant near GPRC5B. Some loci (at MC4R, POMC, SH2B1 and BDNF) map near key hypothalamic regulators of energy balance, and one of these loci is near GIPR, an incretin receptor. Furthermore, genes in other newly associated loci may provide new insights into human body weight regulation. Show less

The APOA1-C3-A5 gene cluster plays an important role in the regulation of lipids. Asian Indians have an increased tendency for abnormal lipid levels and high risk of Coronary Artery Disease (CAD). Therefore, the present study aimed to elucidate the relationship of four single nucleotide polymorphisms (SNPs) in the Apo11q cluster, namely the -75G>A, +83C>T SNPs in the APOA1 gene, the Sac1 SNP in the APOC3 gene and the S19W variant in the APOA5 gene to plasma lipids and CAD in 190 affected sibling pairs (ASPs) belonging to Asian Indian families with a strong CAD history. Genotyping and lipid assays were carried out using standard protocols. Plasma lipids showed a strong heritability (h2 48% - 70%; P < 0.0001). A subset of 77 ASPs with positive sign of Logarithm of Odds (LOD) score showed significant linkage to CAD trait by multi-point analysis (LOD score 7.42, P < 0.001) and to Sac1 (LOD score 4.49) and -75G>A (LOD score 2.77) SNPs by single-point analysis (P < 0.001). There was significant proportion of mean allele sharing (pi) for the Sac1 (pi 0.59), -75G>A (pi 0.56) and +83C>T (pi 0.52) (P < 0.001) SNPs, respectively. QTL analysis showed suggestive evidence of linkage of the Sac1 SNP to Total Cholesterol (TC), High Density Lipoprotein-cholesterol (HDL-C) and Apolipoprotein B (ApoB) with LOD scores of 1.42, 1.72 and 1.19, respectively (P < 0.01). The Sac1 and -75G>A SNPs along with hypertension showed maximized correlations with TC, TG and Apo B by association analysis. The APOC3-Sac1 SNP is an important genetic variant that is associated with CAD through its interaction with plasma lipids and other standard risk factors among Asian Indians. Show less

The polarization of a neuron generally results in the formation of one axon and multiple dendrites, allowing for the establishment of neuronal circuitry. The molecular mechanisms involved in priming one neurite to become the axon, particularly those regulating the microtubule network, remain elusive. Here we report the identification of DOCK7, a member of the DOCK180-related protein superfamily, as a Rac GTPase activator that is asymmetrically distributed in unpolarized hippocampal neurons and selectively expressed in the axon. Knockdown of DOCK7 expression prevents axon formation, whereas overexpression induces formation of multiple axons. We further demonstrate that DOCK7 and Rac activation lead to phosphorylation and inactivation of the microtubule destabilizing protein stathmin/Op18 in the nascent axon and that this event is important for axon development. Our findings unveil a pathway linking the Rac activator DOCK7 to a microtubule regulatory protein and highlight the contribution of microtubule network regulation to axon development. Show less

To describe the pathophysiologic features of retinal degeneration in Batten disease (juvenile neuronal ceroid lipofuscinosis [JNCL]) caused by mutations in the CLN3 gene. Comparative human tissue study. The retina and other ocular tissues of a 22-year-old man with JNCL were compared with the same tissues of a healthy 30-year-old man. DNA from whole blood and RNA from retina were used for genotype analysis. The retinas, corneas, conjunctiva, and ciliary body were processed for histopathologic and immunofluorescence analysis. Genomic DNA was subjected to polymerase chain reaction (PCR) and nucleotide sequence analyses. Reverse transcriptase/PCR and sequence analysis were performed on retinal RNA. The JNCL donor was heterozygous for a approximately 1 kb deletion in CLN3, as found in most JNCL patients. The other allele had a single base pair deletion in exon 6 that resulted in a frame shift. Gross pathology of the JNCL retina resembled that in retinitis pigmentosa, including deposits of bone spicule pigment. Histopathologic studies revealed loss of neurons from all retinal layers. Immunofluorescence labeling with antibodies to rhodopsin, recoverin, and cone opsin demonstrated degenerate rods and cones with short outer segments in the far periphery. Autofluorescent lipopigment granules were prominent in ganglion cells and some cells of the inner nuclear layer, but not in the photoreceptors. The retinal pigment epithelium (RPE) had fewer lipofuscin granules than the control specimen. Increased numbers of lipofuscin granules were found in the epithelia of the ciliary body and conjunctiva, but not in the cornea of the JNCL eye. Immunofluorescence studies revealed degenerate rods and cones in the far periphery. Lipofuscin granules were decreased in the RPE, consistent with loss of photoreceptor outer segments. The novel finding that degenerate photoreceptors did not contain autofluorescent inclusions suggests that granule accumulation may not precede photoreceptor degeneration in JNCL. The presence of normal photoreceptor proteins in the degenerate rods and cones suggests that these cells may be capable of functional regeneration if a therapy for Batten disease is developed. Show less