👤 Carol Ann Huff

We report the discovery of a chemical series that enhances ApoE secretion from human astrocytes through mechanisms independent of LXR agonism. Target deconvolution of hits from a phenotypic screen in astrocytoma cells employed chemoproteomics, photoaffinity probes, in vitro KINOMEscan analysis, and targeted siRNA knockdown experiments. Photoaffinity labeling coupled with quantitative chemical proteomics identified aryl hydrocarbon receptor (AhR), a transcription factor not previously associated with ApoE secretion, as the primary target. A diverse panel of AhR agonists and antagonists together with genetic knockdown confirmed that ApoE secretion increases when AhR activity is reduced. Using a luciferase reporter assay, we demonstrated that active series analogs exhibit AhR antagonism while inactive compounds do not. Since deletion of AhR has severe peripheral effects, chronic inhibition of AhR is not an attractive therapeutic approach for Alzheimer's disease; nevertheless, these results position AhR as a modulator of ApoE secretion and a biological pathway worth exploring. Show less

The treatment of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) has evolved to include several new options. The NCCN Guidelines for WM/LPL provide a framework on which to base decisions regarding diagnosis, treatment, assessment of response to treatment, and follow-up of both newly diagnosed and previously treated WM/LPL. Show less

Genome-wide association studies (GWAS) have identified multiple loci associated with plasma lipid concentrations. Common variants at these loci together explain <10% of variation in each lipid trait. Rare variants with large individual effects may also contribute to the heritability of lipid traits; however, the extent to which rare variants affect lipid phenotypes remains to be determined. Here we show an accumulation of rare variants, or a mutation skew, in GWAS-identified genes in individuals with hypertriglyceridemia (HTG). Through GWAS, we identified common variants in APOA5, GCKR, LPL and APOB associated with HTG. Resequencing of these genes revealed a significant burden of 154 rare missense or nonsense variants in 438 individuals with HTG, compared to 53 variants in 327 controls (P = 6.2 x 10(-8)), corresponding to a carrier frequency of 28.1% of affected individuals and 15.3% of controls (P = 2.6 x 10(-5)). Considering rare variants in these genes incrementally increased the proportion of genetic variation contributing to HTG. Show less

Heart failure is a leading cause of death of people in South Asia, and cardiomyopathy is a major cause of heart failure. Myosin binding protein C (MYBPC3) is expressed in the heart muscle, where it regulates the cardiac response to adrenergic stimulation and is important for the structural integrity of the sarcomere. Mutations in the MYBPC3 gene are associated with hypertrophic or dilated cardiomyopathies. A 25-base-pair deletion in intron 32 causes skipping of the downstream exon and is associated with familial cardiomyopathy. To date, this deletion is found primarily in India and South Asia, although it is also found at low frequency in Southeast Asia. In order to better characterise the distribution of this variant, we determined its frequency in 447 individuals from 19 populations, including 10 populations from India and neighbouring populations from Pakistan and Nepal. The deletion frequency is over 8% in some of our Indian samples, and it is not present in any of the populations we sampled outside of India. The differences in the deletion frequencies among populations in India are consistent with patterns of variation previously reported and with patterns we observed among Indian populations based on high-density SNP chip data. Our results indicate that the MYBPC3 deletion is primarily found among Indian populations and that its distribution is consistent with genome-wide patterns of variation in India. Show less

Numerous single nucleotide polymorphisms (SNPs) have been found in recent genome wide association studies (GWAS) to be associated with subtle plasma triglyceride (TG) variation in normolipidemic subjects. However, since these GWAS did not specifically evaluate patients with rare disorders of lipoprotein metabolism--'hyperlipoproteinemia' (HLP)--it remains largely unresolved whether any of these SNP determinants of modest physiological changes in TG are necessarily also determinants of most HLP phenotypes. To address this question, we evaluated 28 TG-associated SNPs from GWAS in 386 unrelated adult patients with one of five Fredrickson phenotypes (HLP types 2A, 2B, 3, 4 and 5) and 242 matched normolipidemic controls. We found that several SNPs associated with TG in normolipidemic samples, including APOA5 p.S19W and -1131T>C, TRIB1 rs17321515, TBL2 rs17145738, GCKR rs780094, GALNT2 rs4846914 and ANGPTL3 rs12130333, were significantly associated with HLP types 2B, 3, 4 and 5. The findings indicate that: (i) the TG-associated Fredrickson HLP types 2B, 3, 4 and 5 are polygenic traits; (ii) these Fredrickson HLP types share numerous genetic determinants among themselves; and (iii) genetic determinants of modest TG variation in normolipidemic population samples also underlie--to an apparently even greater degree--susceptibility to these rare HLP phenotypes. Thus, the TG-associated Fredrickson HLP types 2B, 3, 4 and 5, although historically considered to be distinct are actually complex traits sharing among them several common genetic determinants seen in GWAS of normolipidemic population samples. Show less

Several known candidate gene variants are useful markers for diagnosing hyperlipoproteinemia. In an attempt to identify other useful variants, we evaluated the association of two common APOA5 single-nucleotide polymorphisms across the range of classic hyperlipoproteinemia phenotypes. We assessed plasma lipoprotein profiles and APOA5 S19W and -1131T>C genotypes in 678 adults from a single tertiary referral lipid clinic and in 373 normolipidemic controls matched for age and sex, all of European ancestry. We observed significant stepwise relationships between APOA5 minor allele carrier frequencies and plasma triglyceride quartiles. The odds ratios for hyperlipoproteinemia types 2B, 3, 4 and 5 in APOA5 S19W carriers were 3.11 (95% CI 1.63-5.95), 4.76 (2.25-10.1), 2.89 (1.17-7.18) and 6.16 (3.66-10.3), respectively. For APOA5 -1131T>C carriers, the odds ratios for these hyperlipoproteinemia subtypes were 2.23 (95% CI 1.21-4.08), 3.18 (1.55-6.52), 3.95 (1.85-8.45) and 4.24 (2.64-6.81), respectively. The overall odds ratio for the presence of either allele in lipid clinic patients was 2.58 (95% CI 1.89-3.52). A high proportion of patients with four classic hyperlipoproteinemia phenotypes are carriers of either the APOA5 S19W or -1131T>C variant or both. These two variants are robust genetic biomarkers of a range of clinical hyperlipoproteinemia phenotypes linked by hypertriglyceridemia. Show less

Recent genome-wide association (GWA) studies have identified new genetic determinants of complex quantitative traits, including plasma triglyceride (TG). We hypothesized that common variants associated with mild TG variation identified in GWA studies would also be associated with severe hypertriglyceridemia (HTG). We studied 132 patients of European ancestry with severe HTG (fasting plasma TG > 10 mmol/l), who had no mutations found by resequencing of candidate genes, and 351 matched normolipidemic controls. We determined genotypes for: GALNT2 rs4846914, TBL2/MLXIPL rs17145738, TRIB1 rs17321515, ANGPTL3 rs12130333, GCKR rs780094, APOA5 rs3135506 (S19W), APOA5 rs662799 (-1131T > C), APOE (isoforms) and LPL rs328 (S447X). We found that: (i) genotypes, including those of APOA5 S19W, APOA5 -1131T > C, APOE, GCKR, TRIB1 and TBL2/MLXIPL, were significantly associated with severe HTG; (ii) odds ratios for these genetic variables were significant in both univariate and multivariate regression analyses, irrespective of the presence or absence of diabetes or obesity; (iii) a significant fraction-about one-quarter-of the explained variation in disease status was associated with these genotypes. Therefore, common SNPs (single nucleotide polymorphisms) that are associated with mild TG variation in GWA studies of normolipidemic subjects are also associated with severe HTG. Our findings are consistent with the emerging model of a complex genetic trait. At the extremes of a quantitative trait, such as severe HTG, are found the cumulative contributions of both multiple rare alleles with large genetic effects and common alleles with small effects. Show less

We undertook studies of the association between common genomic variations in APOC3, APOA5, APOE and PON1 genes and variation in biochemical phenotypes in a sample of Greenlanders. Genetic association study of quantitative lipoprotein traits. In a sample of 1,310 adult Greenlanders, fasting plasma lipid, lipoprotein and apolipoprotein (apo) concentrations were assessed for association with known functional genomic variants of APOC3, APOA5, APOE and PON1. For significantly associated polymorphisms, between-genotype differences were examined in closer detail. We found that (1) the APOE restriction isotype was associated with variation in plasma total and LDL cholesterol and apo B (all p < .0001); (2) the APOC3 promoter genotype was associated with variation in plasma triglycerides, HDL cholesterol and apo A-I (all p < .002); (3) the APOA5 codon 19 genotype was associated with variation in plasma triglycerides (p = .027); and (4) the PON1 codon 192 genotype was associated with variation in total and LDL cholesterol and apo B (all p < .05). Taken together, our results suggest that common genetic variations in APOC3, APOA5, APOE and PON1 are associated with significant variation in intermediate traits in plasma lipoprotein metabolism in Greenlanders; the associations are similar to those observed for these variants in other populations. Show less

Common polymorphisms in the promoter of the APOC3 gene have been associated with hypertriglyceridemia and may impact on phenotypic expression of the metabolic syndrome (MetS). The rs7566605 marker, located near the INSIG2 gene, has been found to be associated with obesity, making it also a potential genetic determinant for MetS. The objective of this study is to examine the APOC3 -455T>C and the INSIG2 rs7566605 polymorphisms as potential genetic determinants for MetS in a multi-ethnic sample. Subjects were genotyped for both the APOC3 -455T>C and INSIG2 rs7566605 polymorphisms, and classified for the presence or absence of MetS (NCEP ATP III and IDF definitions). The total study population included 2675 subjects (> or =18 years of age) from six different geographical ancestries. For the overall study population, the prevalence of MetS was 22.6% (NCEP ATP III definition). Carriers of > or =1 copy of APOC3 -455C were more likely to have MetS (NCEP ATP III definition) than noncarriers (carrier odds ratio 1.73, 95% CI 1.40 to 2.14, adjusting for age and study group). The basis of the association was related not only to a higher proportion of -455C carriers meeting the triglyceride and high-density lipoprotein cholesterol criteria, but also the blood pressure criteria compared with wild-type homozygotes. Plasma apo C-III concentrations were not associated with APOC3 -455T>C genotype. The INSIG2 rs7566605 polymorphism was not associated with MetS or measures of obesity. Meta-analysis of the sample of multiple geographic ancestries indicated that the functional -455T>C promoter polymorphism in APOC3 was associated with an approximately 2-fold increased risk of MetS, whereas the INSIG2 rs7566605 polymorphism was not associated with MetS. Show less

Mitochondrial damage and dysfunction are thought to play an important role in the pathogenesis of sepsis-induced organ failures. Unfortunately, specific markers of mitochondrial damage in vital organs do not currently exist. Recently, carbomyl phosphate synthase (CPS)-1, a protein primarily localized to liver mitochondria, was found to be present in high concentrations in the plasma of septic humans. Thus, we hypothesized that the circulatory release of CPS-1 would correlate with mitochondrial damage or impaired mitochondrial function in the liver in a clinically relevant model of sepsis. Prospective, randomized, controlled animal study. University medical center research laboratory. Male, Balb/C mice, aged 10-12 wks. Animals were assigned to receive cecal ligation and puncture (CLP sepsis) or sham operation and compared with untreated controls. Plasma CPS-1 levels and liver mitochondrial variables, including morphology, respiratory activity, mass (i.e., cardiolipin content), and protein carbonylation, were assessed at various time points (8, 24, and 48 hrs and 6 days) after surgery. Oxidant stress (i.e., carbonylation) was detected within 8 hrs of CLP and persisted through 48 hrs. Plasma CPS-1 levels increased dramatically at 24 hrs, remained significantly elevated at 48 hrs, and normalized by 6 days in the sepsis group. Abnormalities of liver mitochondrial morphology and function coincided with increased plasma CPS-1 levels. Mitochondrial depletion in the liver was not due to cell death but was associated with increased lysosomal clearance. Increased expression of mitochondrial biogenesis factors preceded restoration of mitochondrial variables and normalization of CPS-1 levels by day 6. Circulating CPS-1 is a marker of mitochondrial damage and depletion in the liver during the subacute phase of CLP sepsis. From a mechanistic standpoint, mitochondrial depletion is not due to cell death but is apparently related to the removal of damaged mitochondria by lysosomes (i.e., autophagy), followed by repletion of mitochondrial populations. Further studies are needed to determine the clinical utility of CPS-1 as a marker of sepsis severity. Show less