Ine Levels Research Articles

Population variation and genetics of plasma homocyst(e)ine level

A high level of plasma homocyst(e)ine (H(e)) has been reported to be an independent risk factor for coronary heart disease (CHD), at least in some populations. We have determined the H(e) concentration in the plasma of two series of Norwegians in order to establish a baseline for future analysis of people with CHD. The mean sex- and age-adjusted homocyst(e)ine level was 10.6 (range 4.84-29.88) in one series and 10.5 (range 3.76-40.57) in the other. The H(e) level appeared to be independent of other proven or potential risk factors or protective factors with respect to CHD. The intraclass correlation coefficient in monozygotic (MZ) twins is a (possibly inflated) estimate of heritability. We have examined two series of MZ twins. The intraclass correlation coefficient was significant in both series. In one series, the Pearson correlation coefficient was 0.53 and the Kendall correlation coefficient 0.38. In the other, the values were 0.56 and 0.46, respectively. We conclude that in the population examined, H(e) levels exhibit significant heritability.

Hyperhomocyst(e)inemia, anti-estrogen antibodies and other risk factors for thrombosis in women on oral contraceptives

Hyperhomocyst(e)inemia was shown to be associated with vascular occlusion in atherosclertotic patients. We have conducted a study to determine if hyperhomocyst(e)inemia was also related to the vascular events observed in women on oral contraceptives, presumably having little or no atherosclerosis. Two hundred women receiving oral contraceptives were included in the study: 100 were healthy controls and 100 had documented vascular occlusion. Determination of serum homocyst(e)ine and anti-estrogen antibody levels wore performed under blind conditions. They were evaluated in logistic regression models in which age and smoking were also included. Women with vascular occlusion had higher levels of homocyst(e)ine ( P < 0.001) and of anti-estrogen antibodies ( P < 0.001) when compared to controls. They were also older ( P < 0.001) and more frequently smokers ( P < 0.05). The above mentioned variables were, in isolation, independent predictors of vascular occlusion. Moreover, a model assessing those variables and their interactions indicated that the levels of anti-estrogen antibodies and smoking increased the predictability in older women, as well as the levels of age-adjusted homocyst(e)ine. The study suggests that the above factors can identify women at risk and that determination of anti-estrogen antibodies and homocyst(e)ine levels may help to detect women predisposed to vascular occlusions when taking oral contraceptives.

Survival ofEscherichia coli andYersinia enterocolitica in stream water: Comparison of field and laboratory exposure

Experiments were done to compare the influence of three aquatic exposure methods on the behavior of pathogenic and nonpathogenic enteric bacteria (Yersinia enterocolitica andEscherichia coli). Bacterial suspensions were exposed to stream water in membrane diffusion chambers in situ as well as in the laboratory using a large vessel of stream water and in enclosed bottles. The persistence of culturability of the bacterial suspensions was dependent upon the method of aquatic exposure. This difference was most apparent during the initial six days of each experiment. A steady decline in colony forming units was seen after a short stationary period in chambers in situ, while there was an abrupt increase in bacteria within chambers exposed in the laboratory. A rapid initial decrease was observed in the experimental variation using bottles, accompanied by higher levels of injury inE. coli and reduced expression of plasmid-borne virulence phenotypes inY. enterocolitica. However, there were no changes in the plasmid profiles of either organism throughout the 21-day duration of the experiments. In addition, the survival and injury of pathogenic and nonpathogenic strains of both test bacteria was very similar with aquatic exposure. These results suggest that the response of enteric bacteria in aquatic environments is influenced by experimental design as well as other factors and that the comparison of survival data should only be attempted when similar methods are used.

Prevalence of familial hyperhomocyst(e)inemia in men with premature coronary artery disease.

Elevated plasma levels of homocyst(e)ine have been reported to be more prevalent in patients with coronary artery disease (CAD) than in controls. The purpose of this study was to determine whether this elevation was genetic. We determined homocyst(e)ine levels in 176 men with premature CAD (greater than 50% stenosis of a major epicardial coronary artery occurring before the age of 60 years) and in 255 controls free of cardiovascular disease. Homocyst(e)ine levels were higher in the CAD group compared with controls (13.9 +/- 6.7 versus 10.9 +/- 4.9 nmol/ml, p less than 0.001); in addition, 28% of CAD patients had homocyst(e)ine levels above the 90th percentile of controls. Statistical analysis revealed that homocyst(e)ine levels were not related to the presence of hypertension or diabetes, smoking, or plasma levels of lipoprotein cholesterol and apolipoproteins A-I and B. The families of 71 CAD patients were sampled (selected on the basis of availability of relatives) and included 60 spouses and 239 first-degree relatives; 370 subjects were thus sampled. Spearman correlations between probands and spouses (r = 0.264, p = 0.041) and between mean values for parent and offspring (r = 0.356, p = 0.002) for homocyst(e)ine levels indicated that homocyst(e)ine levels are in part genetically determined. In 20 families (28.2%), the proband had homocyst(e)ine levels greater than the 90th percentile; familial segregation was observed in 10 of these kindreds. Therefore, 14% of CAD patients had familial hyperhomocyst(e)inemia. In conclusion, our data suggest that plasma homocyst(e)ine is a risk factor for the development of CAD, independent of other cardiovascular risk factors, and that this elevation is in part genetically determined.

Estimates of heritability of plasma homocyst(e)ine levels in aging adult male twins

Plasma homocyst(e)ine level was determined for 96 identical (MZ) and 92 fraternal (DZ) adult male twins aged 59-69. There was no difference in mean between MZ (10.31 nmol/ml) and DZ (10.36 nmol/ml) twins. The intraclass correlation coefficient of the log-transformed homocyst(e)ine level in 43 complete MZ and 39 complete DZ pairs was 0.55 and 0.19, respectively. The MZ correlation was significantly (p less than 0.05) greater than the DZ correlation, suggesting that the level of plasma homocyst(e)ine is genetically influenced.

Colestipol plus niacin therapy elevates plasma homocyst(e)ine levels

The Cholesterol-Lowering Atherosclerosis Study (CLAS) was a randomized, placebo-controlled angiographic trial that tested the efficacy of colestipol plus niacin therapy for the reduction of blood low-density lipoprotein cholesterol level and the increase of blood high-density lipoprotein cholesterol level. One hundred sixty-two nonsmoking men from 40 to 59 years old who had udergone coronary bypass surgery were followed for 2 years and of these, 103 (57 drug treated, 46 placebo treated) were followed for 4 years. Average 4-year drug dose levels were niacin, 4.2 g/d, and colestipol, 30 g/d. Frozen plasma samples drawn during the fourth trial year and after cessation of therapy were assayed for homocyst(e)ine There was a statistically significant difference between the drug and placebo groups with respect to on-trial homocyst(e)ine, (P < 0.01), with the drug group demonstrating higher levels. After therapy was withdrawn, there was a significant group difference in homocyst(e)ine change, (P < 0.001), with a median decrease of 5.99 nmol/mL in the drug group and a median increase of 0.98 nmol/mL in the placebo group. These results indicate that homocyst(e)ine levels are elevated by treatment with colestipol plus niacin.

The association of elevated plasma homocyst(e)ine with progression of symptomatic peripheral arterial disease

Plasma homocyst(e)ine (the sum of free and bound homocysteine, homocystine, and the mixed disulfide homocysteine-cysteine, expressed as homocysteine) levels were determined by high performance liquid chromatography in 214 patients with symptomatic (claudication, rest pain, gangrene, amputation) lower extremity arterial occlusive disease and/or symptomatic (stroke, cerebral transient ischemic attacks) cerebral vascular disease and in 103 control persons. Mean plasma homocyst(e)ine was significantly higher in patients than in controls (14.37 ± 6.89 nmol/ml vs 10.10 ± 2.16, p < 0.05). Thirtynine percent of patients (83 of 214) had plasma homocyst(e)ine values greater than control mean + 2 standard deviations. Plasma homocyst(e)ine values were contrasted to age, male sex, diabetes, hypertension, smoking, renal failure, and plasma cholesterol. No difference was found in the incidence and/or level of any of these risk factors when patients with normal plasma homocyst(e)ine were compared to those with elevated plasma homocyst(e)ine, both by univariate and multivariate analysis. Patients with elevated plasma homocyst(e)ine were more likely to demonstrate clinical progression of lower extremity disease and of coronary artery disease, but not of cerebral vascular disease than were patients with normal plasma homocyst(e)ine, and the rate of progression was more rapid (p = 0.002). Progression of lower extremity disease as assessed in the vascular laboratory was also more common in patients with elevated plasma homocyst(e)ine (p = 0.01). We conclude that elevated plasma homocyst(e)ine is an independent risk factor for symptomatic lower extremity disease or cerebral vascular disease or both. Symptomatic patients with lower extremity disease and with elevated plasma homocyst(e)ine also appear to have more rapid progression of disease.

The association of elevated plasma homocyst(e)ine with progression of symptomatic peripheral arterial disease

Plasma homocyst(e)ine (the sum of free and bound homocysteine, homocystine, and the mixed disulfide homocysteine-cysteine, expressed as homocysteine) levels were determined by high performance liquid chromatography in 214 patients with symptomatic (claudication, rest pain, gangrene, amputation) lower extremity arterial occlusive disease and/or symptomatic (stroke, cerebral transient ischemic attacks) cerebral vascular disease and in 103 control persons. Mean plasma homocyst(e)ine was significantly higher in patients than in controls (14.37 +/- 6.89 nmol/ml vs 10.10 +/- 2.16, p less than 0.05). Thirty-nine percent of patients (83 of 214) had plasma homocyst(e)ine values greater than control mean + 2 standard deviations. Plasma homocyst(e)ine values were contrasted to age, male sex, diabetes, hypertension, smoking, renal failure, and plasma cholesterol. No difference was found in the incidence and/or level of any of these risk factors when patients with normal plasma homocyst(e)ine were compared to those with elevated plasma homocyst(e)ine, both by univariate and multivariate analysis. Patients with elevated plasma homocyst(e)ine were more likely to demonstrate clinical progression of lower extremity disease and of coronary artery disease, but not of cerebral vascular disease than were patients with normal plasma homocyst(e)ine, and the rate of progression was more rapid (p = 0.002). Progression of lower extremity disease as assessed in the vascular laboratory was also more common in patients with elevated plasma homocyst(e)ine (p = 0.01). We conclude that elevated plasma homocyst(e)ine is an independent risk factor for symptomatic lower extremity disease or cerebral vascular disease or both. Symptomatic patients with lower extremity disease and with elevated plasma homocyst(e)ine also appear to have more rapid progression of disease.

Plasma homocyst(e)ine levels in men with premature coronary artery disease

Plasma homocyst(e)ine (that is, the sum of free and bound homocysteine and its oxidized forms, homocystine and homocysteine-cysteine mixed disulfide) levels were determined in 170 men (mean age ± SD 50 ± 7 years) with premature coronary artery disease diagnosed at coronary angiography and in 255 control subjects clinically free of coronary artery disease (mean age 49 ± 6 years). Patients with coronary artery disease had a higher homocyst(e)ine level than control subjects (13.66 ± 6.44 versus 10.93 ± 4.92 nmol/ml, p < 0.001). High density lipoprotein (HDD cholesterol levels were lower (32 ± 10 versus 46 ± 13 mg/dl, p < 0.001) and triglycerides levels were higher (193 ± 103 versus 136 ± 106 mg/dl, p < 0.001) in the coronary disease group. Plasma total cholesterol and low density lipoprotein (LDL) cholesterol levels were not significantly different between patients with coronary disease and control subjects. The presence of hypertension, smoking or diabetes mellitus did not significantly alter homocyst(e)ine levels in the patient or the control group. Patients who were not taking a beta-adrenergic blocking drug (n = 70) had a nonsignificantly higher homocyst(e)ine level than did patients taking this class of drugs (n = 100) (14.67 ± 8.92 versus 12.95 ± 3.77 nmol/ml, p = 0.087). By design, none of the control subjects were taking a beta-blocker. No significant correlations were observed between homocyst(e)ine and age, serum cholesterol, LDL cholesterol, HDL cholesterol or triglyceride levels. It is concluded that an elevated plasma homocyst(e)ine level is an independent risk factor for the development of premature coronary atherosclerosis in men.

Hyperhomocyst(e)inemia in Utah siblings with early coronary disease

To test the hypothesis that plasma homocyst(e)ine (H|e|) level is a risk factor for early familial coronary heart disease (EFCHD), H(e) was measured in frozen samples from 33 men and 4 women with EFCHD and in 30 male and 18 female control participants matched for age and sex from the University of Utah Cardiovascular Genetics Research Clinic, Salt Lake City, Utah. To test for familial correlation, these participants were selected to include 13 males sibling pairs with EFCHD, 13 male sibling pairs as control subjects, and 13 spouse pairs as control subjects (all matched for age). Compared with control subjects, mean H(e) levels were significantly higher in persons with EFCHD for both men (14.31 vs. 11.09 nmol/mL; P=0.022) and women (9.51 vs 7.40; P=0.020). Most of the difference came from a few cases in 3 EFCHD sibling pairs. This observation was confirmed by a commingling analysis, which detected significant bimodality of plasma H(e) levels among the men with EFCHD (P=0.02). One sibling pair with early coronary heart disease despite normal plasma lipids, lipoproteins, and apolipoproteins, showed concordant elevations of H(e) levels greater than any levels seen among control subjects. Strong familial correlation of plasma H(e) was observed among all 26 male sibling pairs (r=0.52; P<0.01) and was present separately in male siblings with EFCHD (r=0.44) and control siblings (r=0.60). There was no significant familial correlation in spouse pairs (r=-0.15, NS). H(e) was an independent predictor of EFCHD (P=0.014) in a multivariate analysis of the men that included smoking, blood lipids, anthropometrics, and presence or absence of diabetes as other potential predictors of EFCHD. These data suggest that hyperhomocyst(e)inemia is an inherited abnormality that might explain some occurrence of early familial coronary heart disease.

Elevated plasma homocyst(e)ine concentration as a possible independent risk factor for stroke.

Homocyst(e)ine refers to the sulfur-containing amino acids homocysteine, homocystine, and homocysteine-cysteine mixed disulfide, which normally exist in plasma in both the free and protein-bound forms. Marked hyperhomocyst(e)inemia is associated with well-recognized complications of occlusive thrombotic events and a characteristic syndrome. It is less clear whether mild to moderate elevations in plasma homocyst(e)ine concentrations (i.e., 1.5-5-fold increases) also represent a risk factor for stroke and, if so, whether it is independent of other recognized risk factors. To examine these questions we compared the plasma homocyst(e)ine levels in 41 patients with acute strokes, 27 patients with transient ischemic attacks, 31 patients with recognized risk factors for but no recent symptoms of cerebrovascular disease, and 31 normal volunteers (controls). Plasma homocyst(e)ine concentration was moderately but significantly higher in the patients than in the controls (p less than 0.0001). Approximately 30% of the patients had homocyst(e)ine levels higher than the controls. No relation was found between homocyst(e)ine concentration and other recognized stroke risk factors or stroke type; however, a positive correlation was found between serum uric acid and plasma homocyst(e)ine levels. These data suggest that a moderately elevated plasma homocyst(e)ine concentration may be an independent risk factor for cerebrovascular disease.

Homocyst(E)ine levels in men with premature coronary artery disease

Homocyst(E)ine levels in men with premature coronary artery disease

Homocysteinemia due to folate deficiency

We examined the relationship between serum folate and total homocyst(e)ine levels by determining protein-bound homocyst(e)ine in stored serum from 19 subjects with subnormal serum folate (less than 2 ng/mL), 137 subjects with low normal serum folate (between 2.0 and 3.9 ng/mL), 44 subjects with normal serum folate (between 4.0 and 17.9 ng/mL), and 38 subjects with high serum folate (above 18 ng/mL). Eighty-four percent of the subjects with subnormal serum folate and 56% of the subjects with low normal serum folate had more than 7.05 nmol/mL serum total homocyst(e)ine (ie, more than two standard deviations above the normal mean). Thirty-two percent of these subjects had more than a three-fold increase in serum total homocyst(e)ine. These observations support the hypothesis that depletion of tissue folate causes homocysteinemia in nonhomocystinuric subjects. Subnormal as well as low normal concentrations of serum folate appear to produce an accumulation of homocyst(e)ine. In addition, relatively normal levels of serum total homocyst(e)ine were observed in four pregnant women with low serum folate, supporting previous suggestions of an influence of female sex hormone(s) in homocysteine metabolism.

Reactions of cyst(e)ine concentration in plasma of Merino sheep from two genetic groups to fasting and ACTH injection

Two experiments were conducted with two groups of Merino sheep which, as a result of selective breeding, differed in average wool production and average concentration of cyst(e)ine in plasma. In the first experiment, 10 ewes from each flock were fasted for 49 h. Seven blood samples were collected from each ewe and the plasma assayed for total cyst(e)ine (free plus disulfide bound). After an initial decrease in concentration of 2.65 8mol l-1 between 0 and 4 h, the concentration of cyst(e)ine increased linearly throughout the period of fasting (0.22 8mol l-1 h-1). These responses were similar in sheep from the two flocks so that sheep from the high wool producing flock maintained a lower concentration of cyst(e)ine throughout the period of fasting (50.4 v. 60.9 8mol l-1, P &lt; 0.05). In the second experiment, with sheep from the same two genotypes, both cortisol and cyst(e)ine levels in plasma were monitored for 8 h after an injection of synthetic ACTH: 0, 0.2 or 0.4 i.u. kg-I liveweight. Twelve sheep per flock were studied in each of two replicates. Cortisol levels increased following the ACTH injections with the higher dose level giving higher levels of cortisol and more sustained responses for 7 h. The raised cortisol levels were not associated with any changes in the concentration of cyst(e)ine in plasma, and a 17% lower concentration of cyst(e)ine in the sheep of the high producing flock was maintained throughout the experiment. As the raised cortisol levels did not influence the concentrations of cyst(e)ine in plasma of these laboratory sheep, a shed sampling procedure involving venepuncture should be satisfactory for comparisons of the concentration of cyst(e)ine between groups of animals. If the sampling involves extended periods of fasting, some corrections may be necessary to account for the changes in concentration associated with period of fasting.

Homocyst(e)ine Accumulation in Pigs Fed Diets Deficient in Vitamin B-6: Relationship to Atherosclerosis

The early onset of atherosclerotic lesions in homocystinuric individuals has implicated homocyst(e)ine in the development of atherosclerosis. Two trials were conducted in which diets totally or partially deficient in vitamin B-6 were fed to pigs to investigate the accumulation of homocyst(e)ine in the plasma and the development of vascular lesions. In one trial plasma free homocyst(e)ine levels were 179 and 43 µmol/liter in deficient and adequate pigs, respectively, on day 24, while cysteine levels were 39 and 155 µmol/liter. The concentration of plasma protein-bound homocysteine and cysteine reflected the plasma-free values. Because pigs deficient in pyridoxine could be used only over short time intervals, pigs in trial 2 received 0, 0.03, 0.3 or 3 mg (i.e., 0, 2, 20 or 200% of allowance) of supplemental pyridoxine · HCl per kilogram diet. After 12 weeks pigs deficient and adequate in vitamin B-6 were injected intravenously with Evan's blue dye and the vascular trunk perfused with 2% glutaraldehyde. The aorta and major organs were removed and examined for vascular lesions. Grossly no significant lesions were seen. Light microscopy revealed occasional foci of intimal degeneration and mural thickening in the renal arterioles of pigs deficient in vitamin B-6. An area of focal medial necrosis was observed in one of the pigs deficient in vitamin B-6. Pigs fed diets containing 0.03 mg pyridoxine · HCl per kilogram diet had homocyst(e)ine concentrations not different from pigs fed diets with no added pyridoxine. Animals fed diets containing 0.3 mg pyridoxine · HCl per kilogram had homocyst(e)ine concentrations slightly higher than controls fed 3.0 mg/kg. Feed intake and weight gain increased with increasing pyridoxine in the diet. Swine offer an excellent vascular model for humans. Diets partially deficient in vitamin B-6 which cause the homocyst(e)ine concentration to increase, but allow better growth and feed consumption than diets totally deficient in pyridoxine, could be fed to pigs to study homocyst(e)ine-induced vascular damage over extended period of time.

Cysteine activation in cultured cystinotic cells. The specific activity of cysteinyl-tRNA synthetase and tRNACys and the determination of the Michaelis-Menten constants for cysteinyl-tRNA synthetase.

This study explored the possibility whether an altered cysteinyl-tRNA synthetase might lead to the faulty regulation of cyst(e)ine levels in cystinotic cells. This hypotheses is attractive, since amino acid activation is important in the regulation of amino acid metabolism in microorganisms. By using cultured fibroblasts from patients with cystinosis, those cell components responsible for cysteine activation were examined: cyst(e)ine, the cysteinyl-tRNA levels, cysteinyl-tRNA synthetase activity, and the K(m) of cysteine, ATP, and tRNA(Cys) for cysteinyl-tRNA synthetase, Fibroblasts from two patients with the infantile form of cystinosis were labeled for three days with [(35)S]-cystine. In comparison with normal cells, these cells contained high levels of free cysteine and cystine. Labeled fibroblasts from a patient with the adolescent form of the disease contained elevated levels of cystine, although elevated cysteine levels were not detected. The ratio of acceptor activity of tRNA(Cys) to tRNA(Leu) in cystinotic cells was 0.46 in cystinotic cells and 0.54 in normal cells. The specific activity of cysteinyl-tRNA synthetase measured in fibroblasts of two infantile and one adolescent form was: 6.1, 2.2, and 2.1 pmol of [(14)C]aminoacyl-tRNA formed/mug protein/10 min, respectively. In addition, the cysteine K(m)'s for the same cells, respectively, were: 3.1 muM, 1.5 muM, and 1.2 muM. The corresponding data for specific activities of two normal cell lines were 2.0 and 5.1 pmol [(14)C]aminoacyl tRNA formed/mug protein/10 min, with K(m)'s of 3.0 muM and 1.7 muM. These data indicate that cystinotic cells contain levels of tRNA(Cys) and Cys-tRNA synthetase comparable to normal cells. In addition, within the cystinotic cells, the relative level of the Cys-tRNA synthetase and tRNA(Cys) to those of leucine and alanine are comparable to normal cells. Finally, the K(m) of Cys-tRNA synthetase for ATP and tRNA is similar in normal and cystinotic cells.

Structure of the boson missing-mass spectrum

In a previous paper (1) we described a possible threefold s t ructure of the boson missing-mass spec t rum of the process = + p + X + p using the C E R N data(2) (P=lab= ( 3 . 1 5 . 5 ) GeV/e and It I = (0 .10 .0 .46) (GeV/c)2). Recen t ly we have got new exper imenta l da ta (3) of the same process supplied f rom C E R N I H E P (P=l~b= 25, 45 GeV/c and 0.17 > n is assigned to each represen ta t ive peak. The peak number m a y be the angular m o m e n t u m of the leading t ra jec tory , or m a y be connected to in ternal orbi ta l angular m o m e n t u m L in the nonrela t iv is t ic quark model by n = L + 1. A t any ra te the peak number n should be regarded as a sort of quan tum number to be assigned to the above meson clusters. Theoret ical ly , m a n y daughter levels are considered to belong to each leading level. Using the Veneziano model, all the levels of the n . t h tower (including leading and daughte r levels) degenerate g iv ing one mass level. The degeneracy is, of course, an ideal one, but ac tua l ly the levels would spli t into m a n y mass levels. Call t hem hypothet ica l . The number spec t rum of the Veneziano hyperf ine levels rapidly increases vs. mass l ike an exponent ia l funct ion. Fol lowing the spectrum,