Uncovering predictors of low hippocampal volume: Evidence from a large-scale machine-learning-based study in the UK Biobank.

INTRODUCTION: Hippocampal atrophy is an established biomarker for conversion from the normal ageing process to developing cognitive impairment and dementia. This study used a novel hypothesis-free machine-learning approach, to uncover potential risk factors of lower hippocampal volume using information from the world's largest brain imaging study. METHODS: A combination of machine learning and conventional statistical methods were used to identify predictors of low hippocampal volume. We run gradient boosting decision tree modelling including 2891 input features measured before magnetic resonance imaging assessments (median 9.2 years, range 4.2-13.8 years) using data from 42,152 dementia-free UK Biobank participants. Logistic regression analyses were run on 87 factors identified as important for prediction based on Shapley values. False discovery rate adjusted P-value <0.05 was used to declare statistical significance. RESULTS: Older age, male sex, greater height, and whole-body fat free mass were the main predictors of low hippocampal volume with the model also identifying associations with lung function and lifestyle factors including smoking, physical activity, and coffee intake (corrected P<0.05 for all). Red blood cell count and several red blood cell indices such as haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular volume, mean reticulocyte volume, mean sphered cell volume, and red blood cell distribution width were among many biomarkers associated with low hippocampal volume. CONCLUSION: Lifestyles, physical measures, and biomarkers may affect hippocampal volume, with many of the characteristics potentially reflecting oxygen supply to the brain. Further studies are required to establish causality and clinical relevance of these findings.

Phenome-wide association study of ovarian cancer identifies common comorbidities and reveals shared genetics with complex diseases and biomarkers.

BACKGROUND: Ovarian cancer (OC) is commonly diagnosed among older women who have comorbidities. This hypothesis-free phenome-wide association study (PheWAS) aimed to identify comorbidities associated with OC, as well as traits that share a genetic architecture with OC. METHODS: We used data from 181,203 white British female UK Biobank participants and analysed OC and OC subtype-specific genetic risk scores (OC-GRS) for an association with 889 diseases and 43 other traits. We conducted PheWAS and colocalization analyses for individual variants to identify evidence for shared genetic architecture. RESULTS: The OC-GRS was associated with 10 diseases, and the clear cell OC-GRS was associated with five diseases at the FDR threshold (p = 5.6 × 10-4 ). Mendelian randomizaiton analysis (MR) provided robust evidence for the association of OC with higher risk of "secondary malignant neoplasm of digestive systems" (OR 1.64, 95% CI 1.33, 2.02), "ascites" (1.48, 95% CI 1.17, 1.86), "chronic airway obstruction" (1.17, 95% CI 1.07, 1.29), and "abnormal findings on examination of the lung" (1.51, 95% CI 1.22, 1.87). Analyses of lung spirometry measures provided further support for compromised respiratory function. PheWAS on individual OC variants identified five genetic variants associated with other diseases, and seven variants associated with biomarkers (all, p ≤ 4.5 × 10-8 ). Colocalization analysis identified rs4449583 (from TERT locus) as the shared causal variant for OC and seborrheic keratosis. CONCLUSIONS: OC is associated with digestive and respiratory comorbidities. Several variants affecting OC risk were associated with other diseases and biomarkers, with this study identifying a novel genetic locus shared between OC and skin conditions.

Alterations in GLP-1 and PYY release with aging and body mass in the human gut.

The lining of our intestinal surface contains an array of hormone-producing cells that are collectively our bodies' largest endocrine cell reservoir. These "enteroendocrine" (EE) cells reside amongst the billions of absorptive epithelial and other cell types that line our gastrointestinal tract and can sense and respond to the ever-changing internal environment in our gut. EE cells release an array of important signalling molecules that can act as hormones, including glucagon-like peptide (GLP-1) and peptide YY (PYY) which are co-secreted from L cells. While much is known about the effects of these hormones on metabolism, insulin secretion and food intake, less is understood about their secretion from human intestinal tissue. In this study we assess whether GLP-1 and PYY release differs across human small and large intestinal tissue locations within the gastrointestinal tract, and/or by sex, body weight and the age of an individual. We identify that the release of both hormones is greater in more distal regions of the human colon, but is not different between sexes. We observe a negative correlation of GLP-1 and BMI in the small, but not large, intestine. Increased aging correlates with declining secretion of both GLP-1 and PYY in human large, but not small, intestine. When the data for large intestine is isolated by region, this relationship with age remains significant for GLP-1 in the ascending and descending colon and in the descending colon for PYY. This is the first demonstration that site-specific differences in GLP-1 and PYY release occur in human gut, as do site-specific relationships of L cell secretion with aging and body mass.

Hypothesis-free discovery of novel cancer predictors using machine learning.

BACKGROUND: Cancer is a leading cause of morbidity and mortality worldwide, and better understanding of the risk factors could enhance prevention. METHODS: We conducted a hypothesis-free analysis combining machine learning and statistical approaches to identify cancer risk factors from 2828 potential predictors captured at baseline. There were 459,169 UK Biobank participants free from cancer at baseline and 48,671 new cancer cases during the 10-year follow-up. Logistic regression models adjusted for age, sex, ethnicity, education, material deprivation, smoking, alcohol intake, body mass index and skin colour (as a proxy for sun sensitivity) were used for obtaining adjusted odds ratios, with continuous predictors presented using quintiles (Q). RESULTS: In addition to smoking, older age and male sex, positively associating features included several anthropometric characteristics, whole body water mass, pulse, hypertension and biomarkers such as urinary microalbumin (Q5 vs. Q1 OR 1.16, 95% CI = 1.13-1.19), C-reactive protein (Q5 vs. Q1 OR 1.20, 95% CI = 1.16-1.24) and red blood cell distribution width (Q5 vs. Q1 OR 1.18, 95% CI = 1.14-1.21), among others. High-density lipoprotein cholesterol (Q5 vs. Q1 OR 0.84, 95% CI = 0.81-0.87) and albumin (Q5 vs. Q1 OR 0.84, 95% CI = 0.81-0.87) were inversely associated with cancer. In sex-stratified analyses, higher testosterone increased the risk in females but not in males (Q5 vs. Q1 ORfemales 1.23, 95% CI = 1.17-1.30). Phosphate was associated with a lower risk in females but a higher risk in males (Q5 vs. Q1 ORfemales 0.94, 95% CI = 0.90-0.99 vs. ORmales 1.09, 95% CI 1.04-1.15). CONCLUSIONS: This hypothesis-free analysis suggests personal characteristics, metabolic biomarkers, physical measures and smoking as important predictors of cancer risk, with further studies needed to confirm causality and clinical relevance.

Genetically instrumented LDL-cholesterol lowering and multiple disease outcomes: A Mendelian randomization phenome-wide association study in the UK Biobank.

AIMS: Lipid-lowering medications are widely used to control blood cholesterol levels and manage a range of cardiovascular and lipid disorders. We aimed to explore the possible associations between LDL lowering and multiple disease outcomes or biomarkers. METHODS: We performed a Mendelian randomization phenome-wide association study (MR-PheWAS) in 337 475 UK Biobank participants to test for associations between four proposed LDL-C-lowering genetic risk scores (PCSK9, HMGCR, NPC1L1 and LDLR) and 1135 disease outcomes, with follow-up MR analyses in 52 serum, urine, imaging and clinical biomarkers. We used inverse-variance weighted MR in the main analyses and complementary MR methods (weighted median, weighted mode, MR-Egger and MR-PRESSO) as sensitivity analyses. We accounted for multiple testing with false discovery rate correction (P < 2.0 × 10-4 for phecodes, P < 1.3 × 10-2 for biomarkers). RESULTS: We found evidence for an association between genetically instrumented LDL lowering and 10 distinct disease outcomes, suggesting potential causality. All genetic instruments were associated with hyperlipidaemias and cardiovascular diseases in the expected directions. Biomarker analyses supported an effect of LDL-C lowering through PCSK9 on lung function (FEV [beta per 1 mg/dL lower LDL-C -1.49, 95% CI -2.21, -0.78]; FVC [-1.42, 95% CI -2.29, -0.54]) and through HMGCR on hippocampal volume (beta per 1 mg/dL lower LDL-C 6.09, 95% CI 1.74, 10.44). CONCLUSIONS: We found genetic evidence to support both positive and negative effects of LDL-C lowering through all four LDL-C-lowering pathways. Future studies should further explore the effects of LDL-C lowering on lung function and changes in brain volume.

Association Between Metabolically Different Adiposity Subtypes and Osteoarthritis: A Mendelian Randomization Study.

OBJECTIVE: In this Mendelian randomization (MR) study, the objective was to investigate the causal effect of metabolically different adiposity subtypes on osteoarthritis. METHODS: We performed 2-sample MR using summary-level data for osteoarthritis (10,083 cases and 40,425 controls) from a genome-wide association using the UK Biobank, and for site-specific osteoarthritis from the Arthritis Research UK Osteoarthritis Genetics consortium. We used 3 classes of genetic instruments, which all increase body mass index but are associated with different metabolic profiles (unfavorable, neutral, and favorable). Primary analysis was performed using inverse variance weight (IVW), with additional sensitivity analysis from different MR methods. We further applied a nonlinear MR using UK Biobank data to understand the nature of the adiposity-osteoarthritis relationship. RESULTS: Greater metabolically unfavorable and metabolically neutral adiposity were associated with higher odds of osteoarthritis (IVW odds ratio [OR] 1.56 [95% confidence interval (95% CI) 1.31, 1.85] and OR 1.60 [95% CI 1.15, 2.23], respectively). The estimate for the association between metabolically favorable adiposity and osteoarthritis was similar, although with notable imprecision (OR 1.55 [95% CI 0.70, 3.41]). Using site-specific osteoarthritis, metabolically unfavorable, neutral, and favorable adiposity were all associated with higher odds of knee osteoarthritis (OR 1.44 [95% CI 1.04, 1.98], OR 2.28 [95% CI 1.04, 4.99], and OR 6.80 [95% CI 2.08, 22.19], respectively). We found generally consistent estimates with a wider confidence interval crossing the null from other MR methods. The nonlinear MR analyses suggested a nonlinear relationship between metabolically unfavorable adiposity and osteoarthritis (Pnonlinear  = 0.003). CONCLUSION: Metabolic abnormalities did not explain the association between greater adiposity and the risk of osteoarthritis, which might suggest that the association is largely due to a mechanical effect on the joints.

Milk consumption and risk of twelve cancers: A large-scale observational and Mendelian randomisation study.

BACKGROUND & AIMS: Milk consumption is a modifiable lifestyle factor that has been associated with several cancer types in observational studies. Limited evidence exists regarding the causality of these relationships. Using a genetic variant (rs4988235) near the lactase gene (LCT) locus that proxies milk consumption, we conducted a comprehensive survey to assess potential causal relationships between milk consumption and 12 types of cancer. METHODS: Our analyses were conducted using white British participants of the UK Biobank (n = up to 255,196), the FinnGen cohort (up to 260,405), and available cancer consortia. We included cancers with previous evidence of an association with milk consumption in observational studies, as well as cancers common in both UK Biobank and FinnGen populations (>1000 cases). We evaluated phenotypic associations of milk intake and cancer incidence in the UK Biobank, and then used a Mendelian randomisation (MR) approach to assess causality in the UK Biobank, FinnGen consortium, and combined analyses incorporating additional consortia data for five cancers. In MR meta-analyses, case numbers for cancers of breast, ovary, uterus, cervix, prostate, bladder and urinary tract, colorectum, and lung ranged between 6000 and 148,000 cases, and between 780 and 1342 cases for cancers of the liver, mouth, stomach and diffuse large B-cell lymphoma. RESULTS: In observational analyses, milk consumption was associated with higher risk of bladder and urinary tract cancer (OR 1.23, 95% CI 1.03-1.47), but not with any other cancer. This association was not confirmed in the MR analysis, and genetically predicted milk consumption showed a significant association only with lower risk of colorectal cancer (0.89, 0.81-0.98 per additional 50 g/day). In the MR analyses conducted among individual cohorts, genetically predicted milk consumption provided evidence for an association with lower colorectal cancer in the FinnGen cohort (0.85, 0.74-0.97), and in the UK Biobank greater risk of female breast cancer (1.12, 1.03-1.23), and uterine cancer in pre-menopausal females (3.98, 1.48-10.7). CONCLUSION: In a comprehensive survey of milk-cancer associations, we confirm of a protective role of milk consumption for colorectal cancer. Our analyses also provide some suggestion for higher risks of breast cancer and premenopausal uterine cancer, warranting further investigation.

Metabolic profile predicts incident cancer: A large-scale population study in the UK Biobank.

BACKGROUND AND AIMS: Analyses to predict the risk of cancer typically focus on single biomarkers, which do not capture their complex interrelations. We hypothesized that the use of metabolic profiles may provide new insights into cancer prediction. METHODS: We used information from 290,888 UK Biobank participants aged 37 to 73 years at baseline. Metabolic subgroups were defined based on clustering of biochemical data using an artificial neural network approach and examined for their association with incident cancers identified through linkage to cancer registry. In addition, we evaluated associations between 38 individual biomarkers and cancer risk. RESULTS: In total, 21,973 individuals developed cancer during the follow-up (median 3.87 years, interquartile range [IQR] = 2.03-5.58). Compared to the metabolically favorable subgroup (IV), subgroup III (defined as "high BMI, C-reactive protein & cystatin C") was associated with a higher risk of obesity-related cancers (hazard ratio [HR] = 1.26, 95 % CI = 1.21 to 1.32) and hematologic-malignancies (e.g., lymphoid leukemia: HR = 1.83, 95%CI = 1.44 to 2.33). Subgroup II ("high triglycerides & liver enzymes") was strongly associated with liver cancer risk (HR = 5.70, 95%CI = 3.57 to 9.11). Analysis of individual biomarkers showed a positive association between testosterone and greater risks of hormone-sensitive cancers (HR per SD higher = 1.32, 95%CI = 1.23 to 1.44), and liver cancer (HR = 2.49, 95%CI =1.47 to 4.24). Many liver tests were individually associated with a greater risk of liver cancer with the strongest association observed for gamma-glutamyl transferase (HR = 2.40, 95%CI = 2.19 to 2.65). CONCLUSIONS: Metabolic profile in middle-to-older age can predict cancer incidence, in particular risk of obesity-related cancer, hematologic malignancies, and liver cancer. Elevated values from liver tests are strong predictors for later risk of liver cancer.

Metabolic profile-based subgroups can identify differences in brain volumes and brain iron deposition.

AIMS: To evaluate associations of metabolic profiles and biomarkers with brain atrophy, lesions, and iron deposition to understand the early risk factors associated with dementia. MATERIALS AND METHODS: Using data from 26 239 UK Biobank participants free from dementia and stroke, we assessed the associations of metabolic subgroups, derived using an artificial neural network approach (self-organizing map), and 39 individual biomarkers with brain MRI measures: total brain volume (TBV), grey matter volume (GMV), white matter volume (WMV), hippocampal volume (HV), white matter hyperintensity (WMH) volume, and caudate iron deposition. RESULTS: In metabolic subgroup analyses, participants characterized by high triglycerides and liver enzymes showed the most adverse brain outcomes compared to the healthy reference subgroup with high-density lipoprotein cholesterol and low body mass index (BMI) including associations with GMV (ßstandardized -0.20, 95% confidence interval [CI] -0.24 to -0.16), HV (ßstandardized -0.09, 95% CI -0.13 to -0.04), WMH volume (ßstandardized 0.22, 95% CI 0.18 to 0.26), and caudate iron deposition (ßstandardized 0.30, 95% CI 0.25 to 0.34), with similar adverse associations for the subgroup with high BMI, C-reactive protein and cystatin C, and the subgroup with high blood pressure (BP) and apolipoprotein B. Among the biomarkers, striking associations were seen between basal metabolic rate (BMR) and caudate iron deposition (ßstandardized 0.23, 95% CI 0.22 to 0.24 per 1 SD increase), GMV (ßstandardized -0.15, 95% CI -0.16 to -0.14) and HV (ßstandardized -0.11, 95% CI -0.12 to -0.10), and between BP and WMH volume (ßstandardized 0.13, 95% CI 0.12 to 0.14 for diastolic BP). CONCLUSIONS: Metabolic profiles were associated differentially with brain neuroimaging characteristics. Associations of BMR, BP and other individual biomarkers may provide insights into actionable mechanisms driving these brain associations.

Healthy Lifestyle, Genetic Risk and Brain Health: A Gene-Environment Interaction Study in the UK Biobank.

Genetic susceptibility and lifestyle affect the risk of dementia but there is little direct evidence for their associations with preclinical changes in brain structure. We investigated the association of genetic dementia risk and healthy lifestyle with brain morphometry, and whether effects from elevated genetic risk are modified by lifestyle changes. We used prospective data from up to 25,894 UK Biobank participants (median follow-up of 8.8 years), and defined healthy lifestyle according to American Heart Association criteria as BMI < 30, no smoking, healthy diet and regular physical activity). Higher genetic risk was associated with lower hippocampal volume (beta −0.16 cm3, 95% CI −0.22, −0.11) and total brain volume (−4.34 cm3, 95% CI −7.68, −1.01) in participants aged ≥60 years but not <60 years. Healthy lifestyle was associated with higher total brain, grey matter and hippocampal volumes, and lower volume of white matter hyperintensities, with no effect modification by age or genetic risk. In conclusion, adverse effects of high genetic risk on brain health were only found in older participants, while adhering to healthy lifestyle recommendations is beneficial regardless of age or genetic risk.

Infection of Human Retinal Pigment Epithelial Cells with Dengue Virus Strains Isolated during Outbreaks in Singapore.

Prevalence of dengue retinopathy varies across epidemics, with the disease linked to circulation of dengue virus serotype 1 (DENV-1). The retinal pigment epithelium has been implicated in the pathology. We investigated infectivity, molecular response, and barrier function of epithelial cells inoculated with DENV strains from different outbreaks in Singapore. Monolayers of human retinal pigment epithelial cells (multiple primary cell isolates and the ARPE-19 cell line) were inoculated with six DENV strains, at multiplicity of infection of 10; uninfected and recombinant strain-infected controls were included where relevant. Infectivity and cell response were assessed primarily by RT-qPCR on total cellular RNA, and barrier function was evaluated as electrical resistance across monolayers. Higher viral RNA loads were measured in human retinal pigment epithelial cells infected with DENV-1 strains from the 2005 Singapore epidemic, when retinopathy was prevalent, versus DENV-1 strains from the 2007 Singapore epidemic, when retinopathy was not observed. Type I interferon (IFN) transcripts (IFN-ß and multiple IFN-stimulated genes) were up-regulated, and impact on barrier function was more pronounced, for cells infected with DENV-1 strains from the 2005 versus the 2007 Singapore epidemics. Aside from serotype, strain of DENV may determine the potential to induce retinal pathology. Identification of molecular markers of disease-associated DENV strains may provide insights into the pathogenesis of dengue retinopathy.

Olorinab (APD371), a peripherally acting, highly selective, full agonist of the cannabinoid receptor 2, reduces colitis-induced acute and chronic visceral hypersensitivity in rodents.

ABSTRACT: Abdominal pain is a key symptom of inflammatory bowel disease and irritable bowel syndrome, for which there are inadequate therapeutic options. We tested whether olorinab-a highly selective, full agonist of the cannabinoid receptor 2 (CB2)-reduced visceral hypersensitivity in models of colitis and chronic visceral hypersensitivity (CVH). In rodents, colitis was induced by intrarectal administration of nitrobenzene sulfonic acid derivatives. Control or colitis animals were administered vehicle or olorinab (3 or 30 mg/kg) twice daily by oral gavage for 5 days, starting 1 day before colitis induction. Chronic visceral hypersensitivity mice were administered olorinab (1, 3, 10, or 30 mg/kg) twice daily by oral gavage for 5 days, starting 24 days after colitis induction. Visceral mechanosensitivity was assessed in vivo by quantifying visceromotor responses (VMRs) to colorectal distension. Ex vivo afferent recordings determined colonic nociceptor firing evoked by mechanical stimuli. Colitis and CVH animals displayed significantly elevated VMRs to colorectal distension and colonic nociceptor hypersensitivity. Olorinab treatment significantly reduced VMRs to control levels in colitis and CVH animals. In addition, olorinab reduced nociceptor hypersensitivity in colitis and CVH states in a concentration- and CB2-dependent manner. By contrast, olorinab did not alter VMRs nor nociceptor responsiveness in control animals. Cannabinoid receptor 2 mRNA was detected in colonic tissue, particularly within epithelial cells, and dorsal root ganglia, with no significant differences between healthy, colitis, and CVH states. These results demonstrate that olorinab reduces visceral hypersensitivity through CB2 agonism in animal models, suggesting that olorinab may provide a novel therapy for inflammatory bowel disease- and irritable bowel syndrome-associated abdominal pain.

A Gut-Intrinsic Melanocortin Signaling Complex Augments L-Cell Secretion in Humans.

OBJECTIVE: Hypothalamic melanocortin 4 receptors (MC4R) are a key regulator of energy homeostasis. Brain-penetrant MC4R agonists have failed, as concentrations required to suppress food intake also increase blood pressure. However, peripherally located MC4R may also mediate metabolic benefits of MC4R activation. Mc4r transcript is enriched in mouse enteroendocrine L cells and peripheral administration of the endogenous MC4R agonist, α-melanocyte stimulating hormone (α-MSH), triggers the release of the anorectic hormones Glucagon-like peptide-1 (GLP-1) and peptide tyrosine tyrosine (PYY) in mice. This study aimed to determine whether pathways linking MC4R and L-cell secretion exist in humans. DESIGN: GLP-1 and PYY levels were assessed in body mass index-matched individuals with or without loss-of-function MC4R mutations following an oral glucose tolerance test. Immunohistochemistry was performed on human intestinal sections to characterize the mucosal MC4R system. Static incubations with MC4R agonists were carried out on human intestinal epithelia, GLP-1 and PYY contents of secretion supernatants were assayed. RESULTS: Fasting PYY levels and oral glucose-induced GLP-1 secretion were reduced in humans carrying a total loss-of-function MC4R mutation. MC4R was localized to L cells and regulates GLP-1 and PYY secretion from ex vivo human intestine. α-MSH immunoreactivity in the human intestinal epithelia was predominantly localized to L cells. Glucose-sensitive mucosal pro-opiomelanocortin cells provide a local source of α-MSH that is essential for glucose-induced GLP-1 secretion in small intestine. CONCLUSION: Our findings describe a previously unidentified signaling nexus in the human gastrointestinal tract involving α-MSH release and MC4R activation on L cells in an autocrine and paracrine fashion. Outcomes from this study have direct implications for targeting mucosal MC4R to treat human metabolic disorders.

Unlocking the causal link of metabolically different adiposity subtypes with brain volumes and the risks of dementia and stroke: A Mendelian randomization study.

To establish causal evidence for the association of adiposity-related metabolic abnormalities with brain volumes, and the risks of dementia and stroke, we applied 1- and 2-sample Mendelian randomization (MR) analyses using up to 336,309 UK Biobank participants. We used 3 classes of genetic instruments, which all increase body mass index but are associated with different metabolic profiles (unfavorable, neutral and favorable). We validated the instruments using anthropometric and cardio-metabolic traits. Both metabolically unfavorable and metabolically neutral adiposity associated with lower gray matter volume (GMV, -9.28 cm3, -12.90 to -5.66 and -12.02 cm3, -20.07 to -3.97, respectively). Metabolically favorable adiposity was tentatively associated with a higher GMV (16.21 cm3, -0.21 to 32.68). No causal evidence was seen for white matter and hippocampal volume, and volume of white matter hyperintensities, or with the risks of dementia and stroke (all p > 0.60). These findings suggest that obesity-related metabolic abnormalities may contribute to GMV atrophy, warranting further studies.

Experimentally Induced Bladder Permeability Evokes Bladder Afferent Hypersensitivity in the Absence of Inflammation.

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic urological condition characterised by urinary urgency, frequency and pelvic pain, that significantly impacts the quality of life for ∼5% of women. Bladder sensation is coordinated by primary afferent sensory neurons that innervate the bladder wall, translating bladder stretch into signals that travel to the brain via the spinal cord. Whilst the pathophysiology of IC/BPS remains unknown, an increase in the permeability of the bladder urothelium has been proposed as an initiating cause. Here we experimentally increased bladder permeability and tracked bladder afferent sensitivity for up to 28 days. We found that one day after increasing bladder epithelial permeability with in vivo bladder infusion of protamine sulfate, mechanosensitive bladder afferents exhibited significant hypersensitivity to bladder filling. This mechanical hypersensitivity was characterised by significantly increased peak afferent firing rates and a decrease in the activation threshold of individual afferents. Bladder afferent hypersensitivity occurred in the absence of inflammation and changes in bladder muscle compliance, indicating a direct sensitisation of peripheral afferent endings. Bladder afferent mechanosensitive responses to distension returned to control levels by day 7 post-protamine sulfate treatment and remained at control levels at 28-days post-treatment. Here we demonstrate, contrary to the prevailing hypothesis, that increased bladder permeability alone does not induce chronic bladder afferent sensitisation. Whilst experimentally induced changes in bladder permeability are able to induce transient bladder afferent hypersensitivity in the absence of inflammation, highly regulated homeostatic mechanisms exist to rapidly repair the urothelial barrier and normalise bladder afferent mechanosensitivity. Together, these data suggest that additional pathophysiology is required to induce chronic bladder dysfunction.

Apolipoprotein E (APOE) genotype-associated disease risks: a phenome-wide, registry-based, case-control study utilising the UK Biobank.

BACKGROUND: The three main alleles of the APOE gene (ε4, ε3 and ε2) carry differential risks for conditions including Alzheimer's disease (AD) and cardiovascular disease. Due to their clinical significance, we explored disease associations of the APOE genotypes using a hypothesis-free, data-driven, phenome-wide association study (PheWAS) approach. METHODS: We used data from the UK Biobank to screen for associations between APOE genotypes and over 950 disease outcomes using genotype ε3ε3 as a reference. Data was restricted to 337,484 white British participants (aged 37-73 years). FINDINGS: After correction for multiple testing, PheWAS analyses identified associations with 37 outcomes, representing 18 distinct diseases. As expected, ε3ε4 and ε4ε4 genotypes associated with increased odds of AD (p ≤ 7.6 × 10-46), hypercholesterolaemia (p ≤ 7.1 × 10-17) and ischaemic heart disease (p ≤ 2.3 × 10-4), while ε2ε3 provided protection for the latter two conditions (p ≤ 3.7 × 10-10) compared to ε3ε3. In contrast, ε4-associated disease protection was seen against obesity, chronic airway obstruction, type 2 diabetes, gallbladder disease, and liver disease (all p ≤ 5.2 × 10-4) while ε2ε2 homozygosity increased risks of peripheral vascular disease, thromboembolism, arterial aneurysm, peptic ulcer, cervical disorders, and hallux valgus (all p ≤ 6.1 × 10-4). Sensitivity analyses using brain neuroimaging, blood biochemistry, anthropometric, and spirometric biomarkers supported the PheWAS findings on APOE associations with respective disease outcomes. INTERPRETATION: PheWAS confirms strong associations between APOE and AD, hypercholesterolaemia, and ischaemic heart disease, and suggests potential ε4-associated disease protection and harmful effects of the ε2ε2 genotype, for several conditions. FUNDING: National Health and Medical Research Council of Australia.

Accelerated brain aging towards transcriptional inversion in a zebrafish model of the K115fs mutation of human PSEN2.

BACKGROUND: The molecular changes involved in Alzheimer's disease (AD) progression remain unclear since we cannot easily access antemortem human brains. Some non-mammalian vertebrates such as the zebrafish preserve AD-relevant transcript isoforms of the PRESENILIN genes lost from mice and rats. One example is PS2V, the alternative transcript isoform of the PSEN2 gene. PS2V is induced by hypoxia/oxidative stress and shows increased expression in late onset, sporadic AD brains. A unique, early onset familial AD mutation of PSEN2, K115fs, mimics the PS2V coding sequence suggesting that forced, early expression of PS2V-like isoforms may contribute to AD pathogenesis. Here we use zebrafish to model the K115fs mutation to investigate the effects of forced PS2V-like expression on the transcriptomes of young adult and aged adult brains. METHODS: We edited the zebrafish genome to model the K115fs mutation. To explore its effects at the molecular level, we analysed the brain transcriptome and proteome of young (6-month-old) and aged (24-month-old) wild type and heterozygous mutant female sibling zebrafish. Finally, we used gene co-expression network analysis (WGCNA) to compare molecular changes in the brains of these fish to human AD. RESULTS: Young heterozygous mutant fish show transcriptional changes suggesting accelerated brain aging and increased glucocorticoid signalling. These early changes precede a transcriptional 'inversion' that leads to glucocorticoid resistance and other likely pathological changes in aged heterozygous mutant fish. Notably, microglia-associated immune responses regulated by the ETS transcription factor family are altered in both our zebrafish mutant model and in human AD. The molecular changes we observe in aged heterozygous mutant fish occur without obvious histopathology and possibly in the absence of Aß. CONCLUSIONS: Our results suggest that forced expression of a PS2V-like isoform contributes to immune and stress responses favouring AD pathogenesis. This highlights the value of our zebrafish genetic model for exploring molecular mechanisms involved in AD pathogenesis.

Relationship between Serum 25(OH)D and Depression: Causal Evidence from a Bi-Directional Mendelian Randomization Study.

The relationship between depression and vitamin D deficiency is complex, with evidence mostly from studies affected by confounding and reverse causality. We examined the causality and direction of the relationship between 25-hydroxyvitamin D (25(OH)D) and depression in bi-directional Mendelian randomization (MR) analyses using information from up to 307,618 white British participants from the UK Biobank and summary results from the SUNLIGHT (n = 79,366) and Psychiatric Genomics consortia (PGC 113,154 cases and 218,523 controls). In observational analysis, the odds of depression decreased with higher 25(OH)D concentrations (adjusted odds ratio (OR) per 50% increase 0.95, 95%CI 0.94-0.96). In MR inverse variance weighted (IVW) using the UK Biobank, there was no association between genetically determined serum 25(OH)D and depression (OR per 50% higher 0.97, 95%CI 0.90-1.05) with consistent null association across all MR approaches and in data from PGC consortium. In contrast, genetic liability to depression was associated with lower 25(OH)D concentrations (MR IVW -3.26%, -4.94%--1.55%), with the estimates remaining generally consistent after meta-analysing with the consortia. In conclusion, we found genetic evidence for a causal effect of depression on lower 25(OH)D concentrations, however we could not confirm a beneficial effect of nutritional vitamin D status on depression risk.

Activation of pruritogenic TGR5, MrgprA3, and MrgprC11 on colon-innervating afferents induces visceral hypersensitivity.

Itch induces scratching that removes irritants from the skin, whereas pain initiates withdrawal or avoidance of tissue damage. While pain arises from both the skin and viscera, we investigated whether pruritogenic irritant mechanisms also function within visceral pathways. We show that subsets of colon-innervating sensory neurons in mice express, either individually or in combination, the pruritogenic receptors Tgr5 and the Mas-gene-related GPCRs Mrgpra3 and Mrgprc11. Agonists of these receptors activated subsets of colonic sensory neurons and evoked colonic afferent mechanical hypersensitivity via a TRPA1-dependent mechanism. In vivo intracolonic administration of individual TGR5, MrgprA3, or MrgprC11 agonists induced pronounced visceral hypersensitivity to colorectal distension. Coadministration of these agonists as an "itch cocktail" augmented hypersensitivity to colorectal distension and changed mouse behavior. These irritant mechanisms were maintained and enhanced in a model of chronic visceral hypersensitivity relevant to irritable bowel syndrome. Neurons from human dorsal root ganglia also expressed TGR5, as well as the human ortholog MrgprX1, and showed increased responsiveness to pruritogenic agonists in pathological states. These data support the existence of an irritant-sensing system in the colon that is a visceral representation of the itch pathways found in skin, thereby contributing to sensory disturbances accompanying common intestinal disorders.

Sugar Responses of Human Enterochromaffin Cells Depend on Gut Region, Sex, and Body Mass.

Gut-derived serotonin (5-HT) is released from enterochromaffin (EC) cells in response to nutrient cues, and acts to slow gastric emptying and modulate gastric motility. Rodent studies also evidence a role for gut-derived 5-HT in the control of hepatic glucose production, lipolysis and thermogenesis, and in mediating diet-induced obesity. EC cell number and 5-HT content is increased in the small intestine of obese rodents and human, however, it is unknown whether EC cells respond directly to glucose in humans, and whether their capacity to release 5-HT is perturbed in obesity. We therefore investigated 5-HT release from human duodenal and colonic EC cells in response to glucose, sucrose, fructose and α-glucoside (αMG) in relation to body mass index (BMI). EC cells released 5-HT only in response to 100 and 300 mM glucose (duodenum) and 300 mM glucose (colon), independently of osmolarity. Duodenal, but not colonic, EC cells also released 5-HT in response to sucrose and αMG, but did not respond to fructose. 5-HT content was similar in all EC cells in males, and colonic EC cells in females, but 3 to 4-fold higher in duodenal EC cells from overweight females (p < 0.05 compared to lean, obese). Glucose-evoked 5-HT release was 3-fold higher in the duodenum of overweight females (p < 0.05, compared to obese), but absent here in overweight males. Our data demonstrate that primary human EC cells respond directly to dietary glucose cues, with regional differences in selectivity for other sugars. Augmented glucose-evoked 5-HT release from duodenal EC is a feature of overweight females, and may be an early determinant of obesity.