👤 Megan L Wolfe

Functional decline may be an early indicator of dementia. This study examined the trajectories of frailty, grip strength, and gait speed over the 11 years prior to dementia, compared to matched individuals without dementia. A total of 1092 dementia cases were matched on age, sex and education to 4368 controls from a cohort of community-dwelling older adults recruited in Australia and the USA, aged 65 years or above at recruitment. Frailty was characterised by a deficit-accumulation index involving 67 items. Hand grip strength and gait speed were measured regularly by physical examination. Linear mixed-effects models estimated the backward trajectories of frailty, grip strength and gait speed before dementia, compared to controls. Secondary analyses were stratified by sex and ApoE ε4 carrier status. Higher frailty burden, with a steeper increase over time, was found in the years before dementia, compared to controls (P-interaction < .001). Hand grip strength and gait speed declined more rapidly in dementia cases than in controls (P-interaction < .001 for both). Differences between cases and controls became consistently significant four to six years prior to dementia (P-contrast < .001). An earlier divergence across all three measures was observed for females, and to a lesser extent in ApoE ε4 non-carriers. Functional decline occurs within the decade before dementia onset, with gait speed being the earliest indicator. These findings support the utility of functional measures as early markers of dementia risk, with potential implications for targeted monitoring and preventative strategies. Show less

Air pollution is linked to dementia, but evidence from low-exposure settings is limited. We examined sex-specific associations between long-term exposure to fine particulate matter ≤2.5 µm in diameter (PM2.5) and dementia risk in older adults living in Australia. In 16,145 dementia-free Aspirin in Reducing Events in the Elderly (ASPREE) participants (≥70 years; median follow-up 10.3 years), Cox models assessed associations between 1-year mean PM2.5 (continuous and guideline-based categories) and incident dementia, adjusting for demographic, lifestyle, environmental, and genetic factors. Subgroup analyses by sex, apolipoprotein E genotype (APOE), and age were conducted. Overall associations were null, but with a trend for increased risk at exposures >10 versus ≤5 µg/m Findings suggest a threshold of >10 µg/m Show less

Promising evidence indicates that treating hearing loss with hearing aids (HAs) could reduce dementia risk. We extend this evidence by investigating the effect of HAs on plasma biomarkers of Alzheimer's disease and related dementias (ADRD). We emulated two target trials using observational data from Australian participants of the ASPREE study. Eligible participants had self-reported hearing problems, no past HA use, and were dementia-free. HA prescriptions and frequency of HA use were measured by questionnaire. Phosphorylated-tau181 (pTau181), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), and amyloid-β (Aβ) 42/40 were measured after approximately 6-8 years. We estimated the effect of new HA prescription (first target trial) and the frequency of HA use (second target trial) using targeted maximum likelihood estimation, with multiple imputation for missing data. Across imputed datasets, a median of 2842 eligible individuals were included (mean age 75 years, 48% female), with a median of 735 receiving a new HA prescription. Among survivors, the estimated mean differences comparing HA prescription and no HA prescription were 1.8 pg/mL (95% CI: -0.6, 4.1), 0.1 pg/mL (-7.8, 8.0), -2.2 pg/mL (-14.5, 10.1), and -0.7 (-2.6, 1.2) for the concentrations of pTau181, NfL, GFAP, and (Aβ42 × 1000)/Aβ40, respectively. Mean differences did not differ substantially across levels of potential baseline effect modifiers, including APOE-ε4 genotype and cognition. In community-dwelling older people with hearing loss and no dementia, we found minimal effects of HA prescription and frequency of HA use on plasma ADRD biomarkers after a 7-year follow-up. Show less

Sickle cell disease (SCD) is a common inherited blood disorder among African Americans (AA), with premature mortality which has been associated with prolongation of the heart rate-corrected QT interval (QTc), a known risk factor for sudden cardiac death. Although numerous genetic variants have been identified as contributors to QT interval prolongation in the general population, their impact on SCD patients remains unclear. This study used an unweighted polygenic risk score (PRS) to validate the previously identified associations between SNPs and QTc interval in SCD patients, and to explore possible interactions with other factors that prolong QTc interval in AA individuals with SCD. In SCD patients, candidate genetic variants associated with the QTc interval were genotyped. To identify any risk SNPs that may be correlated with QTc interval prolongation, linear regression was employed, and an unweighted PRS was subsequently constructed. The effect of PRS on the QTc interval was evaluated using linear regression, while stratification analysis was used to assess the influence of serum alanine transaminase (ALT), a biomarker for liver disease, on the PRS effect. We also evaluated the PRS with the two subcomponents of QTc, the QRS and JTc intervals. Out of 26 candidate SNPs, five risk SNPs were identified for QTc duration under the recessive model. For every unit increase in PRS, the QTc interval prolonged by 4.0 ms (95% CI: [2.0, 6.1]; p-value: <0.001) in the additive model and 9.4 ms in the recessive model (95% CI: [4.6, 14.1]; p-value: <0.001). Serum ALT showed a modification effect on PRS-QTc prolongation under the recessive model. In the normal ALT group, each PRS unit increased QTc interval by 11.7 ms (95% CI: [6.3, 17.1]; p-value: 2.60E-5), whereas this effect was not observed in the elevated ALT group (0.9 ms; 95% CI: [-7.0, 8.8]; p-value: 0.823). Several candidate genetic variants are associated with QTc interval prolongation in SCD patients, and serum ALT acts as a modifying factor. The association of a CPS1 gene variant in both QTc and JTc duration adds to NOS1AP as evidence of involvement of the urea cycle and nitric oxide metabolism in cardiac repolarization in SCD. Larger replication studies are needed to confirm these findings and elucidate the underlying mechanisms. Show less

Background The risk of atherosclerotic cardiovascular disease (ASCVD) increases sharply with age. Some older individuals, however, remain unaffected despite high predicted risk. These individuals may carry cardioprotective genetic variants that contribute to resilience. Our aim was to assess whether asymptomatic older individuals without prevalent ASCVD carry cardioprotective genetic variants that contribute to ASCVD resilience. Methods and Results We performed a genome-wide association study using a 10-year predicted ASCVD risk score as a quantitative trait, calculated only in asymptomatic older individuals aged ≥70 years without prevalent ASCVD. Our discovery genome-wide association study of N=12 031 ASCVD event-free individuals from the ASPREE (Aspirin in Reducing Events in the Elderly) trial identified 2 independent variants, rs9939224 ( Show less

The skin serves as the interface between the body and the environment and plays a fundamental role in innate antimicrobial host immunity. Antiviral proteins (AVPs) are part of the innate host defense system and provide protection against viral pathogens. How breach of the skin barrier influences innate AVP production remains largely unknown. In this study, we characterized the induction and regulation of AVPs after skin injury and identified a key role of TRPV1 in this process. Transcriptional and phenotypic profiling of cutaneous wounds revealed that skin injury induces high levels of AVPs in both mice and humans. Remarkably, pharmacologic and genetic ablation of TRPV1-mediated nociception abrogated the induction of AVPs, including Oas2, Oasl2, and Isg15 after skin injury in mice. Conversely, stimulation of TRPV1 nociceptors was sufficient to induce AVP production involving the CD301b Show less

Gastric inhibitory polypeptide (GIP) is a regulatory peptide expressed in the mammalian upper small intestine, and both GIP and its receptor (GIPR) are expressed in the cortex and hippocampus regions of the brain as well. While learning and memory deficits have been observed in GIPR Show less

Btn1p the yeast homolog of human CLN3, which is associated with juvenile Batten disease has been implicated in several cellular pathways. Yeast cells lacking BTN1 are unable to couple ATP hydrolysis and proton pumping activities by the vacuolar ATPase (V-ATPase). In this work, we demonstrate that changes in extracellular pH result in altered transcription of BTN1, as well as a change in the glycosylation state and localization of Btn1p. At high pH, Btn1p expression was increased and the protein was mainly located in vacuolar membranes. However, low pH decreased Btn1p expression and changed its location to undefined punctate membranes. Moreover, our results suggest that differential Btn1p localization may be regulated by its glycosylation state. Underlying pathogenic implications for Batten disease of altered cellular distribution of CLN3 are discussed. Show less

Plasma levels of high-density lipoprotein cholesterol (HDL-C) are known to be heritable, but only a fraction of the heritability is explained. We used a high-density genotyping array containing single-nucleotide polymorphisms (SNPs) from HDL-C candidate genes selected on known biology of HDL-C metabolism, mouse genetic studies, and human genetic association studies. SNP selection was based on tagging SNPs and included low-frequency nonsynonymous SNPs. Association analysis in a cohort containing extremes of HDL-C (case-control, n=1733) provided a discovery phase, with replication in 3 additional populations for a total meta-analysis in 7857 individuals. We replicated the majority of loci identified through genome-wide association studies and present on the array (including ABCA1, APOA1/C3/A4/A5, APOB, APOE/C1/C2, CETP, CTCF-PRMT8, FADS1/2/3, GALNT2, LCAT, LILRA3, LIPC, LIPG, LPL, LRP4, SCARB1, TRIB1, ZNF664) and provide evidence that suggests an association in several previously unreported candidate gene loci (including ABCG1, GPR109A/B/81, NFKB1, PON1/2/3/4). There was evidence for multiple, independent association signals in 5 loci, including association with low-frequency nonsynonymous variants. Genetic loci associated with HDL-C are likely to harbor multiple, independent causative variants, frequently with opposite effects on the HDL-C phenotype. Cohorts comprising subjects at the extremes of the HDL-C distribution may be efficiently used in a case-control discovery of quantitative traits. Show less

Defects in cholesterol synthesis result in a wide variety of symptoms, from neonatal lethality to the relatively mild dysmorphic features and developmental delay found in individuals with Smith-Lemli-Opitz syndrome. We report here the identification of mutations in sterol-C4-methyl oxidase–like gene (SC4MOL) as the cause of an autosomal recessive syndrome in a human patient with psoriasiform dermatitis, arthralgias, congenital cataracts, microcephaly, and developmental delay. This gene encodes a sterol-C4-methyl oxidase (SMO), which catalyzes demethylation of C4-methylsterols in the cholesterol synthesis pathway. C4-Methylsterols are meiosis-activating sterols (MASs). They exist at high concentrations in the testis and ovary and play roles in meiosis activation. In this study, we found that an accumulation of MASs in the patient led to cell overproliferation in both skin and blood. SMO deficiency also substantially altered immunocyte phenotype and in vitro function. MASs serve as ligands for liver X receptors α and β(LXRα and LXRβ), which are important in regulating not only lipid transport in the epidermis, but also innate and adaptive immunity. Deficiency of SMO represents a biochemical defect in the cholesterol synthesis pathway, the clinical spectrum of which remains to be defined. Show less

Although numerous epidemiological studies have provided convincing evidence for an increase in the prevalence of colorectal cancer (CRC) in obese individuals, the precise mechanisms involved have not been elucidated. Glucose-dependent insulinotropic polypeptide (GIP) is a gastrointestinal regulatory peptide whose primary physiologic role is to stimulate postprandial pancreatic insulin secretion. Like insulin, GIP has been linked to enhanced nutrient efficiency, which occurred during the course of evolution. Its expression is increased in obesity, and we thus initiated studies to examine whether GIP might contribute to the pathogenesis of obesity-related CRC. RT-PCR and Western analysis demonstrated the presence of the GIP receptor (GIPR) in several human CRC cell lines. GIP stimulated the proliferation of MC-26 cells, a mouse CRC cell line, in a concentration-dependent manner. Western analysis showed that GIP induced the activity of several downstream signaling molecules known to be involved in cellular proliferation in a concentration- and time-dependent manner. These studies indicate that the presence of GIP receptors in CRC may enable ligand binding and, in so doing, stimulate CRC cell proliferation. The overexpression of GIP, which occurs in obesity, might thereby be contributing to the enhanced rate of carcinogenesis observed in obesity. Show less

In addition to its role as the primary mediator of the enteroinsular axis, glucose-dependent insulinotropic polypeptide (GIP) may play a critical role in the development of obesity. The purpose of these studies was to characterize the effects of GIP and its receptor (GIPR) in adipocyte development and signaling. Effects of GIP and GIPR on differentiated 3T3-L1 cells were analyzed using Western blot analysis, Oil-Red-O staining, cyclic adenosine monophosphate radioimmunoassay, immunofluorescence microscopy, and glucose uptake measurements. To determine whether GIP and GIPR are important components in adipocyte development, the expression profile of GIPR during differentiation was examined. GIPR protein expression was enhanced during the differentiation process, and coincubation with its ligand GIP augmented the expression of aP2, a fat cell marker. Conversely, the suppression of GIPR expression by a specific short hairpin RNA attenuated Oil-Red-O staining and aP2 expression, suggesting that the GIPR may play a critical role in adipocyte development. To investigate specific signaling components that may mediate the effects of GIP, we analyzed Akt, glucose transporter-4, and glucose uptake, all of which are modulated by insulin in fat cells. Like insulin, GIP induced the activation of Akt in a concentration-dependent manner, promoted membrane glucose transporter-4 accumulation, and enhanced [(3)H]-2-deoxyglucose uptake. These studies provide further evidence for an important physiologic role for GIP in lipid homeostasis and possibly in the pathogenesis of obesity. Furthermore, our data indicate that the GIPR might represent a suitable target for the treatment of obesity. Show less

Lymphoblast cell lines established from individuals with juvenile Batten disease (JNCL) bearing mutations in CLN3 and yeast strains lacking Btn1p (btn1-Delta), the homolog to CLN3, have decreased intracellular levels of arginine and defective lysosomal/vacuolar transport of arginine. It is important to establish the basis for this decrease in arginine levels and whether restoration of arginine levels would be of therapeutic value for Batten disease. Previous studies have suggested that synthesis and degradation of arginine are unaltered in btn1-Delta. Using the yeast model for the Batten disease, we have determined that although btn1-Delta results in decreased intracellular arginine levels, it does not result from altered arginine uptake, arginine efflux or differences in arginine incorporation into peptides. However, expression of BTN1 is dependent on arginine and Gcn4p, the master regulator of amino acid biosynthesis. Moreover, deletion of GCN4 (gcn4-Delta), in combination with btn1-Delta, results in a very specific growth requirement for arginine. In addition, increasing the intracellular levels of arginine through overexpression of Can1p, the plasma membrane basic amino acid permease, results in increased cell volume and a severe growth defect specific to basic amino acid availability for btn1-Delta, but not wild-type cells. Therefore, elevation of intracellular levels of arginine in btn1-Delta cells is detrimental and is suggestive that btn1-Delta and perhaps mutation of CLN3 predispose cells to keep arginine levels lower than normal. Show less

The physiological effects of glucose-dependent insulinotropic polypeptide (GIP) are mediated through specific receptors expressed on target cells. Because aberrant GIP receptor (GIPR) expression has been implicated in abnormal GIP responses associated with type 2 diabetes mellitus and food-induced Cushing's syndrome, we sought to identify factors that regulate the GIPR. We previously demonstrated that sequences between -1 and -100 of the GIPR gene were sufficient to direct transcription in a rat insulinoma cell line (RIN38). In the present study, we compared the 5'-flanking regions of the rat and human GIPR gene and demonstrated 88% identity within the first 92 bp. Subsequent serial deletion analyses showed that the region between -85 and -40 is essential for maximal promoter activity. Within this region, we identified three putative Sp1 binding motifs, located at positions -77, -60, and -50, that can specifically bind both Sp1 and Sp3. Whereas mutation of the Sp1 sites at -50 and -60 led to 36 and 40% reduction in promoter activity, respectively, mutation of the Sp1 motif at -70 did not affect promoter activity. Cotransfection of S2 Schneider cells with GIPR-luciferase chimeric constructs and either Sp1 or Sp3 expression vectors indicated that both Sp1 and the long form of Sp3 activate transcription through binding to the Sp1 sites located between -100 and -40. Lastly, chromatin immunoprecipitation analyses revealed that both Sp1 and Sp3 bind to the GIPR promoter region in RIN38 cells. These results indicate that cell-specific expression of GIPR is associated with the binding of the transcription factors Sp1 and Sp3 to the GIPR promoter. Show less

The Glucose-dependent insulinotropic polypeptide receptor (GIPR) is a member of the secretin-vasoactive intestinal polypeptide family of G-protein coupled receptors possessing seven transmembrane domains. We report here the cloning and the exon-intron structure of the rat GIPR gene, along with the identification and characterization of its 5'-flanking region. The coding region of the GIPR gene spans approximately 10.2 kilobases and contains 13 exons. Three additional exons, two encoding either 5' or 3' untranslated sequences and one contained in a novel alternatively spliced mRNA, were identified. The 5'-flanking sequences contained a number of transcription factor binding motifs, including a cAMP response element, an octamer binding site, three SP1 sites and an initiator element. However, neither a CAAT motif nor TATA box were found. Transient transfection assays demonstrated that the 5'-flanking region of the GIPR gene can efficiently promote transcription in RIN38 cells and that deletion of 50 base pairs containing a potential SPI binding sites leads to a 2.4-fold loss of transcriptional activity. In addition, transient transfection experiments comparing the relative promoter activities of 5'-flanking sequences of the GIPR gene in RIN38 and rat-2 cells suggests that distal negative regulatory sequences may control cell-specific expression. Show less