A Pathophysiologic Primary Prevention Review of Aspirin Administration to Prevent Cardiovascular Thrombosis.

OBJECTIVE: Cardiovascular disease is the leading metabolic cause of mortality in the United States. Among current therapies, low-dose aspirin has been shown to reduce cardiovascular thrombosis. However, aspirin also causes major complications (hemorrhagic stroke and gastrointestinal bleeding). The American Heart Association recommends that aspirin only be prescribed for "high-risk" individuals. No guidelines are available as to the duration of aspirin therapy. METHODS: A reasonable approach to aspirin administration is to determine the appropriateness of aspirin therapy based on the pathophysiology of coronary artery thrombosis. It suggests that the coronary artery calcium (CAC) score be used as the basis for determining "high risk." This score was shown to accurately predict future cardiovascular events. The greater the CAC score, the greater the extent of coronary artery atherosclerotic plaque and future cardiovascular risk. RESULTS: A CAC score >400 places an individual at very-high 10-year risk for an atherosclerotic event. Since aggressive medical therapy initiates stabilization of unstable atherosclerotic plaques within 1 month and reversal within 2 years, this treatment significantly reduces the risk of the individual for a cardiovascular event. Thus, most individuals aged <75 years with a CAC score of >400 should receive aspirin therapy for a maximum of 2 years. CONCLUSION: Utilization of a CAC score greatly simplifies the decision of whom to treat with aspirin and for what duration. Importantly, focusing on two factors (hemorrhage and plaque stabilization) is easily understood by both the physician and the patient. ABBREVIATIONS: CAC = coronary artery calcium; CVD = cardiovascular disease; LDL = low-density lipoprotein; OCT = optical coherence tomography.

Cholesterol Review: A Metabolically Important Molecule.

OBJECTIVE: Cholesterol is an important molecule in humans and both its excess and its deficiency cause disease. Most clinicians appreciate its role in stabilizing cellular plasma membranes but are unaware of its myriad other functions. METHODS: This review highlights cholesterol's newly recognized important roles in human physiology and pathophysiology. RESULTS: The basis for cholesterol's ubiquitous presence in eukaryote organisms is its three part structure involving hydrophilic, hydrophobic, and rigid domains. This structure permits cholesterol to regulate multiple cellular processes ranging from membrane fluidity and permeability to gene transcription. Cholesterol not only serves as a molecule of regulation itself, but also forms the backbone of all steroid hormones and vitamin D analogs. Cholesterol is responsible for growth and development throughout life and may be useful as an anticancer facilitator. Because humans have a limited ability to catabolize cholesterol, it readily accumulates in the body when an excess from the diet or a genetic abnormality occurs. This accumulation results in the foremost cause of death and disease (atherosclerosis) in the Western world. Identification of cholesterol's disease-producing capabilities dates back 5,000 years to the Tyrolean iceman and more recently to ancient mummies from many cultures throughout the world. In contrast, a deficiency of cholesterol in the circulation may result in an inability to distribute vitamins K and E to vital organs with serious consequences. CONCLUSION: Understanding the benefits and hazards of cholesterol in the clinical setting will improve the endocrinologist's ability to control diseases associated with this unique molecule. ABBREVIATIONS: CVD = cardiovascular disease; HDL = high-density lipoprotein; LDL = low-density lipoprotein; NPC1L1 = Niemann-Pick C-1-like-1 protein; U.S. = United States; USDA = U.S. Department of Agriculture.

Positive predispositions, quality of life and chronic illness.

This study assessed the extent to which being predisposed towards engaging in acts of gratitude and forgiveness is associated with enhanced quality of life (QoL), and whether these associations are mediated by positive and negative affective states. The study sample comprised 327 people with one of three chronic illnesses (arthritis, chronic obstructive pulmonary disease and diabetes). Participants completed self-report measures of two positive predispositions (the tendencies towards gratitude and forgiveness), two affective states (positive and negative) and three indices of QoL (physical, psychological and satisfaction with life). As hypothesised, gratitude, and to a lesser extent forgiveness, predicted enhanced QoL, with most effects mediated via increased positive affect. Findings support the view that predispositions towards interpersonal gratitude, and possibly interpersonal forgiveness, may bolster the QoL of people living with chronic physical illness. Consistent with contemporary theories of positive emotion, gratitude appears to have its effects via enhancing positive affect. The study adds to the emerging evidence that a predisposition towards gratitude benefits QoL and extends past findings by identifying a mechanism that is important in people with chronic illnesses.

Interpreting the Coronary Artery Calcium Score - Critical Information for the Practicing Physician.

Coronary artery calcium scanning is a routine test for assessing the severity of atherosclerosis in asymptomatic individuals. This inexpensive, noninvasive test quantifies the calcium deposition in the 4 principal coronary arteries. Correct interpretation is important to the physician (for recommending therapy) and to the patient (for determining his or her lifetime risk of a cardiovascular event). A score of 0 indicates that a cardiovascular event is extremely unlikely in the next 5 years. In contrast, a score greater than 0 portends a coronary event. The higher the score, the greater the risk. Both the arterial location of the calcium and the number of coronary arteries involved alter the interpretation of the calcium score. At any given age, females have significantly lower scores than males. One-third of individuals with scores greater than 1000 will have a cardiovascular event within 3 years. For all elevated calcium scores, aggressive treatment is warranted, including significant lifestyle changes and medications to reduce low-density lipoprotein cholesterol. Understanding the importance of the coronary artery calcium score will result in improved therapy and patient compliance.

Risk of radiation exposure during endovascular aortic repair.

OBJECTIVE: Exposure to radiation doses above 2 Gray (Gy) can cause skin burns. There is also a lifetime cancer risk of ≈5.5% for every Sievert (Sv) of radiation. We assessed the radiation burden associated with endovascular treatment of the aorta. METHOD: Thoracic (TEVAR), Infra-renal (IEVAR) and branched/fenestrated (BEVAR/FEVAR) endovascular aortic repairs were studied. The prospectively recorded dosimetric parameters included: fluoroscopy time and dose area product (DAP). Exposure films, placed underneath 10 patients intra-operatively, recorded skin dose and were used to calculate skin (Gy) and tissue (Sv) doses. RESULTS: The TEVAR cohort (n = 232) were younger (p < 0.0001) than BEVAR/FEVAR (n = 53) and IEVAR (n = 630). The median DAP was higher (p = 0.004) in the BEVAR/FEVAR group compared with IEVAR and TEVAR: 32,060 cGy cm(2) (17,207-213,322) vs 17,300 cGy cm(2) (10,940-33,4340) vs 19,440 cGy cm2 (11,284-35,101), respectively. The equivalent skin doses were BEVAR/FEVAR: 1.3 Gy (0.71-8.75); IEVR: 0.71 Gy (0.44-13.7); TEVAR: 0.8 Gy (0.46-1.44). The whole body effective doses were BEVAR/FEVAR: 0.096 Sv (0.052-0.64); IEVR: 0.053 Sv (0.033-1.00); TEVAR: 0.058 Sv (0.034-0.11). CONCLUSIONS: The radiation exposure during endovascular aortic surgery is relatively low for the majority but some patients are exposed to very high doses. Efforts to minimise intra-operative exposure and graft surveillance methods that do not use radiation may reduce the cumulative lifetime malignancy risk.

A Simplified Approach to Reducing Cardiovascular Risk.

CONTEXT: Cardiovascular disease remains the number one cause of morbidity and mortality in the United States, despite major advances in our understanding of its pathogenesis and prevention. One reason for this continued epidemic is the poor adherence to treatment guidelines by caregivers and the lack of understanding by patients relative to its reversibility with treatment. Current guidelines are complex and often contradictory; there are at least 21 organizations publishing guidelines. OBJECTIVE: This article proposes a simplified approach that is based on the low-density lipoprotein (LDL) hypothesis stating that the lower the LDL cholesterol (LDL-C), the less the cardiovascular disease. This goal focuses on obtaining a plasma LDL-C <50 mg/dL. DESIGN: A positive coronary artery calcium scan in conjunction with an intermediate online cardiovascular risk score will identify individuals with substantial cardiovascular disease risk. With lifestyle improvements (including a low cholesterol diet) and low-dose hypolipemic generic oral medications, this LDL-C concentration is readily achievable in the majority of asymptomatic patients at risk for atherosclerosis. CONCLUSION: Controlling the cardiovascular epidemic will require participation of both the patient and the physician caregiver. By simplifying the therapeutic regimen, patient compliance will increase, and an important reduction in cardiovascular morbidity and mortality will follow.

Glucagon regulation of plasma ketone body concentration in human diabetes.

The present study was designed to test the hypothesis that physiological concentrations of glucagon may increase plasma ketone body concentration when sufficient free fatty acid substrate is available to support hepatic ketogenesis. Physiological elevations of plasma glucagon concentration were produced by a constant infusion of hormone, and increased plasma-free fatty acid availability was produced by simultaneous heparin injection to induce intravascular lipolysis. In the five insulin-dependent subjects studied, when plasma glucagon concentration remained at the normal basal level of 72+/-14 pg/ml during control saline infusion, the heparin-induced increase in free fatty acid availability resulted in approximately a 20% increase in plasma ketone body concentration. In contrast, when plasma glucagon concentration was elevated by hormone infusion to the physiological level of 215+/-35 pg/ml, the heparin-induced increases in free fatty acid availability resulted in approximately an 80% increase in plasma ketone body concentration. These results suggest that physiological elevations in plasma glucagon concentration may augment ketonemia in diabetic man when simultaneous elevations in plasma-free fatty acid arepresent.

Radioimmunoassay of beta lipoprotein-protein of rat serum.

A double antibody radioimmunoassay for rat serum beta lipoprotein-protein (beta Lp-protein) is described. The protein was purified by ultracentrifugation, selective heparin-manganous precipitation, and gel filtration on Sephadex G-200. Antiserum was prepared in rabbits by biweekly immunization and absorbed with nonbeta lipoprotein containing rat serum. Iodination with (125)I and purification by gel filtration provided a radiolabeled protein which was > 98% displaced by purified beta lipoprotein in the immunoassay. The radioimmunoassay was sensitive to beta Lp-protein concentrations from 0.1 to 1.5 mug. Specificity of the immunoassay for beta Lp-protein was established by comparison of the displacement curves obtained with serum very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL), and density (d) > 1.21 fractions and with the beta and alpha migrating lipoproteins eluted from paper electrophoretograms. Suitability of the assay for measuring beta Lp-protein in serum was established by demonstrating 100% recovery of beta lipoprotein added to whole serum and by the absence of immunoreactive beta Lp-protein in serum of orotic acid-treated rats. Examination of sera from six other vertebrates species revealed partial cross-reactivity. Normal rat serum was found to contain 0.25+/-0.01 mg/ml of beta Lp-protein and hepatic production by an isolated perfused rat liver system was determined as 0.145 mg/hr.

Kinetic studies of plasma free fatty acid and triglyceride metabolism in man.

Plasma transport of free fatty acids (FFA) and triglyceride fatty acids (TGFA) was studied in seven subjects with normal lipid metabolism, one case of total lipodystrophy, and one case of familial hyperlipemia (Type V). Studies were carried out after intravenous injection of radioactive FFA, of lipoproteins previously labeled in vitro in the triglyceride moiety, or both. Computer techniques were used to evaluate a series of multicompartmental models, and a general model is proposed that yields optimum fitting of experimental data for both FFA and TGFA. The results show that as much as 20-30% of FFA leaving the plasma compartment in normal subjects is transported to an exchanging extravascular pool and quickly reenters the plasma pool as FFA. The rate of irreversible delivery of FFA from plasma to tissues averaged 358 muEq/min in normals. The lipodystrophy patient, despite the virtual absence of adipose tissue (confirmed at autopsy), had a plasma FFA concentration and a total FFA transport, both more than twice normal. Total TGFA transport ranged from 25 to 81 muEq/min in four normal controls. The rate constant for TGFA turnover in the patient with Type V hyperlipemia was so small that total transport could not be quantified from the data available; the TGFA half-life was over 500 min. In two normal subjects given injections of autologous lipoproteins labeled in vitro with triolein-(14)C and simultaneously given oleic acid-(3)H, it was shown that the time course for the disappearance of the TGFA in the in vitro labeled samples conformed almost exactly to that of the physiologically labeled lipoprotein TGFA synthesized from injected FFA (as evidenced by the simultaneous fitting of both sets of data using the same multicompartmental model and the same rate constants). Radioactivity appeared in the plasma FFA fraction at a significant rate after injection of plasma labeled in vitro with TGFA. It was estimated that as much as 50% of the total TGFA transported underwent rapid and rather direct conversion to FFA in the two normal subjects studied this way. The kinetic data suggest that such conversion of TGFA to FFA was not preceded by any extensive dilution, such as would result from complete mixing with tissue triglyceride stores.

Kinetic analysis of 25-hydroxyvitamin D3 metabolism in strontium-induced rickets in the chick.

Kinetic data analysis was used to derive a six-compartment computer model which describes the in vivo [3H]25-hydroxyvitamin D3 ([3H]25-OHD3) metabolism in control and strontium rachitic chicks. Plasma concentrations of 25-OHD3 (13 pmol/ml) and 25, 25-dihydroxyvitamin D3 (0.9 pmol/ml) were 18 and 125% greater than controls, respectively, whereas the corresponding level for 1alpha,25-dihydroxyvitamin D3 (0.3 pmol/ml) was only 30% of control. Plasma disappearance of 25-HOD3 was fitted using a two-compartment model in which the metabolite extrapolated half-life was nearly twice as large for strontium rachitic chicks (71 compared to 41 h). Intestinal sequestration of 1alpha,25-dihydroxyvitamin D3 was assumed to be irreversible and was fitted by a single exponential term in which metabolite uptake rate and tissue concentration in strontium rickets was suppressed to 20 and 10% of control, respectively. In contrast, uptake of 25-OHD3 by the intestine was observed to occur by a reversible process in which metabolite concentration was 45% greater in the strontium rachitic compared to control group. The developed compartment model accepts time-dependent control or perturbed metabolite data for the plasma and (or) intestinal pools and provides quantitative values for metabolite pool size, flux rate, and turnover time.

Antibodies to T- and L-isoforms of the cytoskeletal protein, fimbrin, in patients with systemic lupus erythematosus.

The cytoskeleton is a complex network of proteins that maintain cell shape, mobility, and organelle function. Its components can be divided into three distinct classes: microfilaments, microtubules, and intermediate filaments. Fimbrins are microfilament proteins, a family of cytoplasmic phosphoproteins. Expression of the L-fimbrin isoform is restricted to replicating blood cells and expression of the T-fimbrin isoform to replicating cells of solid tissues. Sera from normals and from patients with systemic lupus erythematosus (SLE), juvenile arthritis, rheumatoid arthritis, Sjögren's syndrome, osteoarthritis, vasculitis, scleroderma, and mixed connective tissue disease were tested for the presence of antibodies to T- and L-fimbrin by ELISA, using purified recombinant fimbrin. The mean OD of sera from SLE patients was significantly higher than in normals (T-fimbrin, P less than 0.0001; L-fimbrin, P less than 0.001). 48 of 98 SLE sera had antibodies to T-fimbrin; 32 had antibodies to L-fimbrin; 20 had antibodies to both; 28 had only anti-T, and 12 had only anti-L-fimbrin. The mean OD for sera of the other rheumatic diseases was not significantly different from normals. The presence of either L- or T-fimbrin antibody was associated with pleuropericarditis (P = 0.015), photosensitivity (P = 0.011), and anti-Sm antibody (P = 0.010). Central nervous system SLE was associated with the presence of the L-fimbrin antibody alone (P = 0.016). There was a strong association between DR7 (but not other MHC alleles) and anti-L-fimbrin antibodies in SLE patients (chi square = 18; P less than 0.00002). No MHC association was observed with anti-T-fimbrin antibodies.

Ligand binding by recombinant domains from insect ecdysone receptors.

The ligand binding domains (LBDs) from the EcR and USP proteins of four insect pests (Lucilia cuprina, Myzus persicae, Bemisia tabaci, Helicoverpa armigera) were purified as recombinant heterodimers. The K(d) values for [(3)H]-ponasterone A binding by LBD heterodimers that included the hinge regions (i.e., DE/F heterodimers) ranged 0.7-2.5 nM, with K(i) values for ecdysteroid and dibenzoylhydrazine ligands ranging from 0.1 nM to >448 microM. The K(d) and K(i) values for a recombinant H. armigera LBD heterodimer that lacked D-regions (i.e., an E/F heterodimer) were approximately 4 times higher than those for its DE/F counterpart. Rate constants were estimated for the L. cuprina LBD heterodimer. A fluorescein-inokosterone conjugate (K(i)~40 nM) was used to develop a novel binding assay based on fluorescence polarization. This assay, which ranked the affinity of competitor ecdysteroids in the same order as the [(3)H]-ponasterone A binding assay, is well suited to high-throughput screening. Ponasterone A had a higher affinity than muristerone A for the recombinant hemipteran LBD heterodimers, whereas the reverse was true for the recombinant dipteran one. The same preference was observed when these ligands were tested as inducers of ecdysone receptor-controlled gene expression in transfected mammalian cells. The binding data obtained in vitro using recombinant LBD heterodimers reflects the ability of agonists to induce transgene expression in recombinant mammalian cells, and can also reflect their efficacy as larvicides.

Management of Asymptomatic Patients With Positive Coronary Artery Calcium Scans.

BACKGROUND: The widespread availability of the coronary artery calcium scan to diagnose coronary artery atheroma semiquantitatively and its prognostic significance has frequently resulted in a difficult therapeutic decision for physicians caring for asymptomatic patients. PATIENTS AND RISK FACTORS: Of particular concern are patients over 40 years of age and young adults characterized by multiple cardiovascular risk factors. The correct prognostic interpretation of coronary artery calcium scores and the potential benefits and risks of various therapeutic modalities need to be understood. CONCLUSION: This review describes the therapeutic choices available to endocrinologists and provides recommendations for various treatment options.