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Biomedical subjects

A T Remaley

Publications and source records attributed to A T Remaley.

At least 19 recordsLinked to original sources
PubMed2005

Brain lesions on MRI and endogenous sex hormones in elderly men.

We investigated the association between MRI detected brain lesions and levels of endogenous sex hormones in Japanese-American men aged 74-95 years. Logistic regression was used to estimate the association (OR (95% CI)) of MRI outcome with tertiles of bioavailable testosterone, 17beta estradiol and sex hormone binding globulin (SHBG). There was a significantly increased risk for cerebral atrophy in the highest tertile of testosterone (3.1 (1.2-7.8)) compared to the lowest. We also found that men with the highest estradiol had a higher risk of lacunes (1.92 (1.1-3.2)). These relationships did not change with adjustment for the other sex hormones, cardiovascular risk factors, or other brain lesions. In contrast, men with the highest SHBG had a lower risk both of cerebral atrophy and lacunes, after adjusting for sex hormones and cardiovascular risk factors. There were no associations between sex hormones and hippocampal atrophy, white matter lesions, and large infarcts. Because the levels of hormone were measured close in time to the acquisition of the MRI, these associations may reflect neurodegeneration in brain regions regulating hormone levels.

Aged↗
PubMed2005

Tangier disease: still more questions than answers.

High-density lipoproteins (HDLs) play a central role in transporting cholesterol from peripheral tissues to the liver for elimination from the body. Impairment of HDL-mediated cholesterol transport favors cholesterol deposition in the arterial wall and promotes development of arteriosclerosis. Tangier disease is a severe HDL deficiency syndrome characterized by the accumulation of cholesterol in tissue macrophages and prevalent atherosclerosis. A three-decade search for a culprit in Tangier disease led to the identification of mutations in a cell membrane protein called ABCA1, which mediates the secretion of excess cholesterol from cells into the HDL metabolic pathway. Because of its ability to deplete cells of cholesterol and to raise plasma HDL levels, ABCA1 has become a promising therapeutic target for preventing cardiovascular disease.

ATP Binding Cassette Transporter 1↗
PubMed2002

Serum thyroxine level and cognitive decline in euthyroid older women.

BACKGROUND: Clinical and subclinical hypothyroidism is associated with cognitive impairment. OBJECTIVE: This study investigated the association between thyroxine (T(4)) and thyroid-stimulating hormone (TSH) level and change over time in cognitive performance in a sample of older women with normal thyroid gland function. METHODS: T(4) and TSH were measured at baseline in 628 women (> or = 65 years) enrolled in the Women's Health and Aging Study, a community-based study of physically impaired women. Cognitive function was assessed at baseline and after 1, 2, and 3 years, using the Mini-Mental State Examination (MMSE). Incident cognitive decline was defined as a decrease of more than one point/year in MMSE score between baseline and the end of the follow-up. The analysis included 464 subjects with normal thyroid gland function with a baseline and at least one follow-up MMSE. RESULTS: At baseline there was no association between T(4) and TSH level and cognitive function. In longitudinal analysis, adjusting for age, race, level of education, and other covariates, compared with women in the highest T(4) tertile (8.1 to 12.5 microg/dL), those in the lowest tertile (4.5 to 6.5 microg/dL) had a greater decline in MMSE score (-0.25 point/year vs -0.12 point/year; p = 0.04). A total of 95 women (20.5%) had cognitive decline during the study period (mean MMSE decline, 5.5 points). Compared with women in the highest T(4) tertile, those in the lowest tertile had a twofold risk of cognitive decline (adjusted relative risk, 1.97; 95% CI, 1.10 to 3.50). The results were not modified by baseline cognitive and physical function. There was no association between baseline TSH level and change in cognitive function. CONCLUSIONS: In older women, low T(4) levels, within the normal range, were associated with a greater risk of cognitive decline over a 3-year period. Thyroid hormone levels may contribute to cognitive impairment in physically impaired women.

Aged↗
PubMed2001

Cellular localization and trafficking of the human ABCA1 transporter.

ABCA1, the ATP-binding cassette protein mutated in Tangier disease, mediates the efflux of excess cellular sterol to apoA-I and thereby the formation of high density lipoprotein. The intracellular localization and trafficking of ABCA1 was examined in stably and transiently transfected HeLa cells expressing a functional human ABCA1-green fluorescent protein (GFP) fusion protein. The fluorescent chimeric ABCA1 transporter was found to reside on the cell surface and on intracellular vesicles that include a novel subset of early endosomes, as well as late endosomes and lysosomes. Studies of the localization and trafficking of ABCA1-GFP in the presence of brefeldin A or monensin, agents known to block intracellular vesicular trafficking, as well as apoA-I-mediated cellular lipid efflux, showed that: (i) ABCA1 functions in lipid efflux at the cell surface, and (ii) delivery of ABCA1 to lysosomes for degradation may serve as a mechanism to modulate its surface expression. Time-lapse fluorescence microscopy revealed that ABCA1-GFP-containing early endosomes undergo fusion, fission, and tubulation and transiently interact with one another, late endocytic vesicles, and the cell surface. These studies establish a complex intracellular trafficking pathway for human ABCA1 that may play important roles in modulating ABCA1 transporter activity and cellular cholesterol homeostasis.

ATP Binding Cassette Transporter 1↗
PubMed2001

Analysis of glomerulosclerosis and atherosclerosis in lecithin cholesterol acyltransferase-deficient mice.

To evaluate the biochemical and molecular mechanisms leading to glomerulosclerosis and the variable development of atherosclerosis in patients with familial lecithin cholesterol acyl transferase (LCAT) deficiency, we generated LCAT knockout (KO) mice and cross-bred them with apolipoprotein (apo) E KO, low density lipoprotein receptor (LDLr) KO, and cholesteryl ester transfer protein transgenic mice. LCAT-KO mice had normochromic normocytic anemia with increased reticulocyte and target cell counts as well as decreased red blood cell osmotic fragility. A subset of LCAT-KO mice accumulated lipoprotein X and developed proteinuria and glomerulosclerosis characterized by mesangial cell proliferation, sclerosis, lipid accumulation, and deposition of electron dense material throughout the glomeruli. LCAT deficiency reduced the plasma high density lipoprotein (HDL) cholesterol (-70 to -94%) and non-HDL cholesterol (-48 to -85%) levels in control, apoE-KO, LDLr-KO, and cholesteryl ester transfer protein-Tg mice. Transcriptome and Western blot analysis demonstrated up-regulation of hepatic LDLr and apoE expression in LCAT-KO mice. Despite decreased HDL, aortic atherosclerosis was significantly reduced (-35% to -99%) in all mouse models with LCAT deficiency. Our studies indicate (i) that the plasma levels of apoB containing lipoproteins rather than HDL may determine the atherogenic risk of patients with hypoalphalipoproteinemia due to LCAT deficiency and (ii) a potential etiological role for lipoproteins X in the development of glomerulosclerosis in LCAT deficiency. The availability of LCAT-KO mice characterized by lipid, hematologic, and renal abnormalities similar to familial LCAT deficiency patients will permit future evaluation of LCAT gene transfer as a possible treatment for glomerulosclerosis in LCAT-deficient states.

Animals↗
PubMed2001

Apolipoprotein specificity for lipid efflux by the human ABCAI transporter.

ABCAI, a member of the ATP binding cassette family, mediates the efflux of excess cellular lipid to HDL and is defective in Tangier disease. The apolipoprotein acceptor specificity for lipid efflux by ABCAI was examined in stably transfected Hela cells, expressing a human ABCAI-GFP fusion protein. ApoA-I and all of the other exchangeable apolipoproteins tested (apoA-II, apoA-IV, apoC-I, apoC-II, apoC-III, apoE) showed greater than a threefold increase in cholesterol and phospholipid efflux from ABCAI-GFP transfected cells compared to control cells. Expression of ABCAI in Hela cells also resulted in a marked increase in specific binding of both apoA-I (Kd = 0.60 microg/mL) and apoA-II (Kd = 0.58 microg/mL) to a common binding site. In summary, ABCAI-mediated cellular binding of apolipoproteins and lipid efflux is not specific for only apoA-I but can also occur with other apolipoproteins that contain multiple amphipathic helical domains.

ATP Binding Cassette Transporter 1↗
PubMed2001

A case of spurious hypercalcitoninemia: a cautionary tale on the use of plasma calcitonin assays in the screening of patients with thyroid nodules for neoplasia.

The measurement of plasma CT has an important role as a screening test for medullary thyroid carcinoma (MTC) in patients with thyroid nodules. However, elevated plasma CT levels should be interpreted within the context of the overall clinical picture in each individual case and carefully validated before therapeutic decisions are made. We present the case of a 17-yr-old girl who was referred to us with a thyroid nodule and elevated plasma CT levels, as measured by a one-site RIA not involving prior plasma extraction. Plasma CT was re-measured using two different methods, a RIA with prior plasma extraction and a two-site immunochemiluminometric assay (ICMA), and was either very low or undetectable. Subsequently, samples were re-assayed using the initially applied CT RIA; plasma CT levels were again found to be elevated. These elevations were of a spurious nature, probably caused by the presence of an unidentified substance in the patient's plasma interfering with the measurement of CT in the initially used RIA. Our patient was eventually diagnosed with Hashimoto's thyroiditis, and had no evidence of MTC. As several conditions can cause either true or spurious hypercalcitoninemia, we suggest that elevated plasma CT levels should be confirmed at least once before other extensive diagnostic investigations are initiated or thyroidectomy is recommended. Finally, the assay selected should detect only the mature CT molecule.

Adolescent↗
PubMed2001

Measurement of cholesterol in plasma and other body fluids.

Measurement of cholesterol has become increasingly important with recognition of its predictive association with cardiovascular diseases. Government and professional groups in the United States and other countries have developed consensus guidelines for using cholesterol and the lipoproteins in identifying patients at risk and in managing therapies. Accuracy in the measurements is essential not only for reliable classification of patients, but also in public health/wellness programs and in research. Laboratory experts have developed requisite analytical performance targets and guidelines for measurements. Manufacturers of diagnostic reagents and laboratories can assure accuracy by accessing the Cholesterol Reference Method Laboratory Network, which offers reference methods for total, high-density lipoprotein, and low-density lipoprotein cholesterol. Recommendations for controlling pre-analytical sources of variation and uniform interpretation of patient results facilitate reliable classification of patients. Driven by increasing workloads and the need for increased efficiency in laboratory testing, dramatic improvements have been made in recent years in automating laboratory analyzers, as well as the methods used for lipoprotein analysis. Newer technology allows multiple sequential measurements in the same cuvette, as well as point-of-care measurements, using strip tests and compact analyzers. Efforts continue to develop reliable, minimally invasive tests in body fluids other than serum.

Analysis of Variance↗
PubMed2001

PPAR-alpha and PPAR-gamma activators induce cholesterol removal from human macrophage foam cells through stimulation of the ABCA1 pathway.

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that regulate lipid and glucose metabolism and cellular differentiation. PPAR-alpha and PPAR-gamma are both expressed in human macrophages where they exert anti-inflammatory effects. The activation of PPAR-alpha may promote foam-cell formation by inducing expression of the macrophage scavenger receptor CD36. This prompted us to investigate the influence of different PPAR-activators on cholesterol metabolism and foam-cell formation of human primary and THP-1 macrophages. Here we show that PPAR-alpha and PPAR-gamma activators do not influence acetylated low density lipoprotein-induced foam-cell formation of human macrophages. In contrast, PPAR-alpha and PPAR-gamma activators induce the expression of the gene encoding ABCA1, a transporter that controls apoAI-mediated cholesterol efflux from macrophages. These effects are likely due to enhanced expression of liver-x-receptor alpha, an oxysterol-activated nuclear receptor which induces ABCA1-promoter transcription. Moreover, PPAR-alpha and PPAR-gamma activators increase apoAI-induced cholesterol efflux from normal macrophages. In contrast, PPAR-alpha or PPAR-gamma activation does not influence cholesterol efflux from macrophages isolated from patients with Tangier disease, which is due to a genetic defect in ABCA1. Here we identify a regulatory role for PPAR-alpha and PPAR-gamma in the first steps of the reverse-cholesterol-transport pathway through the activation of ABCA1-mediated cholesterol efflux in human macrophages.

ATP Binding Cassette Transporter 1↗
PubMed2001

An ATP-binding cassette gene (ABCG5) from the ABCG (White) gene subfamily maps to human chromosome 2p21 in the region of the Sitosterolemia locus.

We characterized a new human ATP-binding cassette (ABC) transporter gene that is highly expressed in the liver. The gene, ABCG5, contains 13 exons and encodes a 651 amino acid protein. The predicted protein is closely related to the Drosophila white gene and a human gene, ABCG1, which is induced by cholesterol. This subfamily of genes all have a single ATP-binding domain at the N-terminus and a single C-terminal set of transmembrane segments. ABCG5 maps to human chromosome 2p21, between the markers D2S117 and D2S119. The abundant expression of this gene in the liver suggests that the protein product has an important role in transport of specific molecule(s) into or out of this tissue.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2001

ABCA1 overexpression leads to hyperalphalipoproteinemia and increased biliary cholesterol excretion in transgenic mice.

The discovery of the ABCA1 lipid transporter has generated interest in modulating human plasma HDL levels and atherogenic risk by enhancing ABCA1 gene expression. To determine if increased ABCA1 expression modulates HDL metabolism in vivo, we generated transgenic mice that overexpress human ABCA1 (hABCA1-Tg). Hepatic and macrophage expression of hABCA1 enhanced macrophage cholesterol efflux to apoA-I; increased plasma cholesterol, cholesteryl esters (CEs), free cholesterol, phospholipids, HDL cholesterol, and apoA-I and apoB levels; and led to the accumulation of apoE-rich HDL1. ABCA1 transgene expression delayed 125I-apoA-I catabolism in both liver and kidney, leading to increased plasma apoA-I levels, but had no effect on apoB secretion after infusion of Triton WR1339. Although the plasma clearance of HDL-CE was not significantly altered in hABCA1-Tg mice, the net hepatic delivery of exogenous 3H-CEt-HDL, which is dependent on the HDL pool size, was increased 1.5-fold. In addition, the cholesterol and phospholipid concentrations in hABCA1-Tg bile were increased 1.8-fold. These studies show that steady-state overexpression of ABCA1 in vivo (a) raises plasma apoB levels without altering apoB secretion and (b) raises plasma HDL-C and apoA-I levels, facilitating hepatic reverse cholesterol transport and biliary cholesterol excretion. Similar metabolic changes may modify atherogenic risk in humans.

ATP Binding Cassette Transporter 1↗
PubMed2001

Triple lipid screening test: a homogeneous sequential assay for HDL-cholesterol, total cholesterol, and triglycerides.

BACKGROUND: The analysis of lipids in serum lipoprotein fractions is useful in assessing the risk for coronary artery disease, but it typically involves performing multiple tests. An automated single-tube assay, referred to as the triple lipid screening (TLS) test, can be used for measuring HDL-cholesterol (HDL-C), total cholesterol, and triglycerides (TGs) with no specimen pretreatment. METHODS: The first part of the assay is based on a homogeneous assay for HDL-C that uses either an anti-apolipoprotein B antibody (TLS-A test) or a polyanion (TLS-B test) that blocks the enzymatic measurement of cholesterol on the non-HDL fraction. After the addition of deoxycholate, which solubilizes the unreacted cholesterol from the non-HDL fraction, the remaining cholesterol in the sample is subsequently measured enzymatically. Using the same enzyme detection system as the cholesterol assay, TGs are measured in the last step, after the addition of the enzymes for the TG assay. RESULTS: The TLS assay (y) had acceptable analytic performance and compared favorably with standard tests (x) for each analyte: for HDL-C, TLS-A = 0.99x + 0.19 (R = 0.980); TLS-B = 1.00x - 0.15 (R = 0.974); for total cholesterol, TLS-A = 1.03x + 0.12 (R = 0.997); TLS-B = 1.07x - 0.30 (R = 0.965); and for TGs, TLS-A = 1.02x + 0.02 (R = 0.988); TLS-B = 1.04x - 0.28 (R = 0.980). CONCLUSIONS: The TLS test is a single-tube homogeneous assay for the analysis of all of the major serum lipoprotein fractions and can be used as a simple screening test for the detection of hyperlipidemia.

Autoanalysis↗
PubMed2001

Regulation and intracellular trafficking of the ABCA1 transporter.

The discovery of the role of the ATP-binding cassette transporter A1 (ABCA1) in mediating apolipoprotein A-I-mediated efflux has led to a dramatic increase in our knowledge of the molecular mechanisms involved in cholesterol efflux and cellular metabolism. In this review, we discuss several aspects of ABCA1 regulation including i) transcriptional regulation, ii) substrate specificity and availability, iii) accessory proteins, iv) acceptor specificity and availability, and v) protein trafficking. The majority of studies of ABCA1 regulation to date have focused on the identification of promoter elements that determine ABCA1 gene transcription. Here we also review the potential functional role of ABCA1 in reverse cholesterol transport. Given the key role that ABCA1 plays in cholesterol homeostasis, it is likely that there are multiple mechanisms for controlling the overall transporter activity of ABCA1.

ATP Binding Cassette Transporter 1↗
PubMed2000

Heat shock protein 60 is a high-affinity high-density lipoprotein binding protein.

A new 55-kDa HDL/apolipoprotein binding protein was demonstrated in plasma membrane preparations of the human cell lines and primary cultured hepatocytes. Analysis of specific binding by ligand immunoblots of HDL, apoA-I, and apoA-II to a partially purified 55-kDa PA-I plasma membrane preparation demonstrated a K(d,HDL) = 50 nM (10 microg/ml), K(d,apoA-II) = 20 nM (0.4 microg/ml), and K(d, apoA-I) = 330 nM (10 microg/ml). Following preparative SDS-PAGE electrophoresis of a plasma membrane preparation isolated from human PA-I cells, fractions with apoA-II binding activity were collected, concentrated, and subjected to two-dimensional electrophoresis. Internal microprotein sequencing of the 55-kDa protein band revealed the binding protein as being heat shock protein 60 (hsp60). The hsp60 monoclonal antibody LK-1 blocked apoA-II binding to the 55-kDa HBP preparation. In summary, these results provide a potential mechanism to explain the known association between immunity developed against hsp60 and the development of atherosclerosis.

Amino Acid Sequence↗
PubMed2000

Increased levothyroxine requirements presenting as "inappropriate" TSH secretion syndrome in a patient with nephrotic syndrome.

Patients with primary thyroid failure on levothyroxine (LT4) replacement who develop nephrotic syndrome (NS) may rarely present with an increase in LT4 requirements. In this report, we describe a patient with thyroid failure following radioactive iodine ablation for Graves' disease who required an escalation of LT4 doses following the onset of NS. The case presented with disproportionately elevated TSH levels in the presence of normal (or slightly subnormal) thyroid hormone levels, thus, masquerading as a state of "inappropriate" TSH secretion. This pattern of extreme dysregulation in thyroid function indices due to urinary loss of thyroid hormones has not been previously described in NS, and, therefore, extends the spectrum of endocrine manifestations of NS.

Adult↗
PubMed2000

Sensitive immunoassay of tissue cell proteins procured by laser capture microdissection.

Coupling laser capture microdissection (LCM) with sensitive quantitative chemiluminescent immunoassays has broad applicability in the field of proteomics applied to normal, diseased, or genetically modified tissue. Quantitation of the number of prostate-specific antigen (PSA) molecules/cell was conducted on human prostate tissue cells procured by LCM from fixed and stained frozen sections. Under direct microscopic visualization, laser shots 30 microm in diameter captured specific cells from the heterogeneous tissue section onto a polymer transfer surface. The cellular macromolecules from the captured cells were solubilized in a microvolume of extraction buffer and directly assayed using an automated (1.5 hour) sandwich chemiluminescent immunoassay. Calibration of the chemiluminescent assay was conducted by developing a standard curve using known concentrations of PSA. After the sensitivity, precision, and linearity of the chemiluminescent assay was verified for known numbers of solubilized microdissected tissue cells, it was then possible to calculate the number of PSA molecules per microdissected tissue cell for case samples. In a study set of 20 cases, using 10 replicate samples of 100 laser shots per sample, the within-run (intraassay) SD was approximately 10% of the mean or less for all cases. In this series the number of PSA molecules per microdissected tissue cell ranged from 2 x 10(4) to 6. 3 x 10(6) in normal epithelium, prostate intraepithelial neoplasia (PIN), and invasive carcinoma. Immunohistochemical staining of human prostate for PSA was compared with the results of the soluble immunoassay for the same prostate tissue section. Independent qualitative scoring of anti-PSA immunohistochemical staining intensity paralleled the LCM quantitative immunoassay for each tissue subpopulation and verified the heterogeneity of PSA content between tissue subpopulations in the same case. Extraction buffers were successfully adapted for both secreted and membrane-bound proteins. This technology has broad applicability for the quantitation of protein molecules in pure populations of tissue cells.

Calibration↗
PubMed2000

Limitations on the quantitative determination of telomerase activity by the electrophoretic and ELISA based TRAP assays.

Telomerase is a promising new tumor marker and can be detected using the TRAP (Telomeric Repeat Amplification Protocol) method. To address factors affecting its quantitative determination, we evaluated two commercial TRAP assays, an electrophoretic and an ELISA assay formats, using cultured cells and human tumor samples. We found that both TRAP assays had a limited linearity from 250 to 5000 tumor cells, with a similar intra-assay variation. The quantification of TRAP products was affected by high cell number in sample, the presence of non-tumor cells, and interfering substances in patient specimens. Because both assays have different limitations, determination of telomerase by a combined use of the two may provide more accurate information on the telomerase activity in a specimen. Extracts of specimens should also be tested at several concentrations to insure that the result is not being falsely decreased by an inhibitor. The quantitative results for telomerase activity by the TRAP assays, however, should be interpreted cautiously.

Cell Count↗