Rat Plasma Clearance Rate and Organ Distribution of β-Hexosaminidase Isoenzymes from Human Serum

beta-Hexosaminidase (EC 3.2.1.30) is markedly increased in human serum in liver disease, chronic alcoholism, and pregnancy. Knowledge of the clearance rate of plasma/serum beta-hexosaminidase is necessary to evaluate this increase. We studied the plasma clearance of beta-hexosaminidase isoenzymes (purified from human serum and placenta) after their infusion into rat circulation. A recently developed enzyme immunoassay method was used to measure the human beta-hexosaminidase isoenzymes; this method relies on both immunoreactivity and enzyme activity, so intact human isoenzymes were measured. In comparison with the placental isoenzymes (t1/2 less than 2 min), the serum forms showed a considerably slower clearance (t1/2 = 2-4 h). However, desialylation of the serum forms resulted in their rapid clearance (t1/2 less than 2 min). The organ localization of the enzyme eliminated from the circulation was investigated 24 h after infusion. Placental and native serum isoenzymes accumulated mainly in the liver and the spleen. Desialylated serum forms were almost exclusively localized to the liver.

Elevated plasma homocysteine level in vascular dementia reflects the vascular disease process

Background

Patients with vascular dementia (VaD) exhibit particularly elevated levels of plasma total homocysteine (tHcy) compared to patients with other psychogeriatric diseases.

Methods

We investigated the main determinants (age, renal impairment, cobalamin/folate status and presence of extracerebral vascular disease) of plasma tHcy in 525 patients with VaD. Furthermore, 270 patients with depression were used as a reference group to reveal the potential specificity of elevated plasma tHcy in patients with VaD.

Results

Elevated plasma tHcy levels in patients with VaD could only partly be attributed to cobalamin/folate deficiency or renal impairment. Plasma tHcy might also be related to the vascular disease process since patients with depression and vascular disease exhibited similar plasma tHcy levels to patients with VaD.

Conclusion

Our findings suggest that elevated plasma tHcy might be a sensitive marker for the vascular disease process in patients with VaD and that the level also is a reflection of changes in the other main determinants of plasma tHcy.

Elevated plasma homocysteine level is not primarily related to Alzheimer's disease

BACKGROUND

A moderate elevation of plasma total homocysteine (tHcy) is considered a potential risk factor for Alzheimer's disease (AD).

METHODS

We have investigated the main determinants (age, renal impairment, cobalamin/folate status and the presence of vascular disease) of plasma tHcy in 326 patients with AD, and also in 281 patients with mild cognitive impairment (MCI), since about half of these patients develop AD during the first 5 years.

RESULTS

Elevated plasma tHcy in patients with AD could mainly be attributed to cobalamin/folate deficiency or renal impairment. Younger patients (below 75 years) with AD and patients with MCI without cobalamin/folate deficiency or renal impairment showed normal levels of plasma tHcy.

CONCLUSION

Our findings suggest that plasma tHcy is not primarily involved in the pathogenesis of AD but rather a reflection of changes of the main determinants of plasma tHcy in AD patients.

Survival in a large elderly population of patients with dementia and other forms of psychogeriatric diseases

BACKGROUND

Dementia and other psychogeriatric diseases in elderly patients bring an increased risk of death. Better knowledge of prognosis in elderly patients affected by dementia or mental illness should be of great importance in order to improve care plans and assist in medical decisions.

METHODS

We have investigated the survival time in 2,112 patients with dementia and other forms of psychogeriatric diseases, enrolled during 1990 to 2005 and followed up until 2009, and the influence of diagnoses, plasma homocysteine level, presence of vascular disease and renal impairment.

RESULTS

The survival time after diagnosis in most diagnostic groups is about a third compared to an average population of similar age and sex. Age was the main predictor of survival time in all patients.

CONCLUSIONS

All diagnoses, except in patients with subjective cognitive impairments, showed an increased mortality. These estimates can be used for prognosis and planning for patients, carers, service providers and policy makers.

Plasma homocysteine, brain imaging and cognition in older patients with mental illness

BACKGROUND

Total plasma homocysteine (tHcy) concentration is elevated in older patients with mental illness, and patients with vascular disease have higher plasma tHcy concentration than patients without vascular disease. Plasma tHcy has been reported to be associated with cognitive functions. The mechanism by which plasma tHcy may influence cognitive functions is not clear.

METHOD

We have investigated the relation between plasma tHcy, brain imaging findings (computer tomography scan [CT]) and cognition, measured as Mini mental state examination (MMSE), in 395 consecutively enrolled older patients with mental illness.

RESULTS

Age and plasma tHcy were significant predictors of MMSE score, whereas pathological CT findings, indicating cerebrovascular disease, showed no prediction of MMSE score.

CONCLUSION

The relation between plasma tHcy and cognition is not mediated by cerebrovascular disease as evaluated by pathological CT findings.

The use of N-terminal pro-brain natriuretic Peptide to evaluate vascular disease in elderly patients with mental illness

Background

Serum N-terminal pro-brain natriuretic peptide (NT-proBNP) is regarded as a sensitive marker of cardiovascular disease. Vascular disease plays an important role in cognitive impairment.

Method

In 447 elderly patients with mental illness, serum NT-proBNP level and the presence or absence of vascular disease according to the medical record were used to categorize patients in different subgroups of vascular disease.

Results and Conclusion

Patients with vascular disease and elevated serum NT-proBNP level had a lower cognition level, shorter survival time, lower renal function and a higher percentage of pathological brain imaging than patients with vascular disease and normal NT-proBNP level. Thus, elevated serum NT-proBNP level might be helpful to detect patients who have a more severe cardiovascular disease.

Plasma homocysteine and cognition in elderly patients with dementia or other psychogeriatric diseases

BACKGROUND

Total plasma homocysteine (tHcy) concentration is elevated in elderly patients with mental illness, and patients with vascular disease have higher plasma tHcy concentrations than patients without vascular disease. Increasing evidence indicates that vascular risk factors play a role in the development of cognitive impairment.

METHOD

We have investigated the relation between plasma tHcy, its determinants and cognition, measured as MMSE, in 448 consecutively enrolled patients with dementia or other psychogeriatric diseases.

RESULTS

Multiple regression analyses showed that plasma tHcy was related to cognitive function in all patients as well as in demented and non-demented patients. The apparent close relationship between plasma tHcy and cognition was mainly dependent on its determinant age, whereas the other determinants of plasma tHcy exhibited a limited influence on the relation between plasma tHcy and cognition. Plasma tHcy has its own, albeit modest, relationship to cognitive function (predictive value about 5%).

CONCLUSION

Plasma tHcy itself seems to play a minor role in cognitive impairment in patients with dementia or other psychogeriatric diseases. When investigating the relation between plasma tHcy and cognition, it is important to consider the distribution of the main determinants of plasma tHcy and to correct plasma tHcy for these variables.

The clinical use of N-terminal-pro brain natriuretic peptide in elderly patients with mental illness

BACKGROUND

Serum N-terminal-pro brain natriuretic peptide (NT-proBNP) is regarded as a marker of vascular disease and has previously been shown to exhibit an increased frequency of pathological values in elderly patients with mental illness with vascular disease compared to patients without vascular disease. Vascular disease plays an important role in cognitive impairment in elderly patients with mental illness.

METHOD

We have investigated the relation between NT-proBNP, vascular disease and cognition in consecutively enrolled elderly patients with mental illness.

RESULTS

NT-proBNP level is increased in patients with vascular disease compared to patients without vascular disease, and a logistic regression analysis showed that NT-proBNP was a significant predictor of vascular disease. However, NT-proBNP level did not predict cognition as assessed by MMSE score. NT-proBNP level also showed a highly significant relation to mortality in all patients.

CONCLUSION

Determinations of NT-proBNP could be used in elderly patients with mental illness to detect patients in need of control and treatment of vascular risk factors. The levels of NT-proBNP may also provide prognostic information.

Plasma homocysteine, apolipoprotein E status and vascular disease in elderly patients with mental illness

BACKGROUND

Total plasma homocysteine (tHcy) concentration is increased in elderly patients with mental illness. Also, patients with vascular disease have significantly higher plasma tHcy concentration compared with patients without vascular disease. Apolipoprotein E (apoE) status is associated with cardiovascular disease and a major genetic risk factor is inheritance of the e4 allele. In the present study, we investigated the association between plasma tHcy and apoE status.

METHODS

The relation between apoE status, plasma tHcy and vascular disease was investigated in a cohort of consecutively enrolled elderly patients with mental illness (n=328).

RESULTS

Plasma tHcy concentrations were increased (p<0.01) in carriers of APOE4 (13.6 micromol/L; 9.2-21.7 micromol/L) compared to non-carriers (12.4 micromol/L; 8.3-19.9 micromol/L). The proportion of patients with vascular disease was significantly (p<0.001) increased among carriers (61%) compared to non-carriers (42%). An increased percentage (p<0.001) of APOE4 carriers was observed in patients with Alzheimer's disease (AD) with (71%) or without vascular disease (42%), and in patients with vascular dementia (VaD) (54%) compared to a reference group (34%).

CONCLUSIONS

Since carriers of APOE4 showed an increased likelihood of vascular disease, these patients need more intensive control of other modifiable vascular risk factors. Furthermore, the association between plasma tHcy and the presence of APOE4 might be attributed to an increased proportion of vascular disease in APOE4 carriers.

Association between plasma homocysteine levels and mortality in elderly patients with mental illness

BACKGROUND/METHOD

Total plasma homocysteine (tHcy) concentration is elevated in elderly patients with mental illness. Plasma tHcy is known to be associated with cardiovascular disease, renal impairment and negative lifestyle factors, and has been shown to predict mortality in human subjects. Epidemiological data on this topic in elderly patients with mental illness are missing. We therefore investigated the association between plasma tHcy levels and mortality in these patients.

RESULTS

The group of deceased patients showed higher age, higher plasma tHcy, lower renal function and lower serum folate than patients who were still alive. Only age, plasma tHcy and the presence of vascular disease significantly influenced mortality.

CONCLUSION

The association between plasma tHcy level and mortality risk was probably explained in part by the two plasma tHcy determinants age and presence of vascular disease. The determination of plasma tHcy in elderly patients with mental illness may help to identify patients in need of more intensive treatment.

Asymmetric dimethylarginine and total homocysteine in plasma after oral methionine loading

BACKGROUND

Elevation of homocysteine (Hcy) and asymmetric dimethylarginine (ADMA) in plasma are believed to be involved in the pathogenesis of cardiovascular disease (CVD). In humans, oral methionine loading results in acute elevation of plasma Hcy. This is associated with impaired NO-dependent vasodilatation, a mechanism that may explain the relationship between elevated Hcy and risk of CVD. ADMA, an endogenous competitive inhibitor of NO-synthase, may be elevated in plasma of patients with CVD. It was proposed that ADMA is synthesized in a methionine-dependent reaction which also forms Hcy. In this study plasma total homocysteine (tHcy) and ADMA concentrations were measured before and after oral methionine loading of human subjects.

METHODS

Plasma tHcy and ADMA levels were measured in 12 healthy males (age 32-58 years) before and after oral loading with L-methionine (100 mg/kg body weight in orange juice).

RESULTS

At noon, 4 h after methionine loading, tHcy and ADMA levels (35.4 +/- 10.9 and 0.80 +/- 0.13 micromol/L, mean +/- SD) were significantly higher than the corresponding values obtained at noon the day before (15.6 +/- 7.4 and 0.63 +/- 0.10 micromol/L, both p<0.001). Noon values 4 h after methionine loading were also significantly higher than values obtained immediately before the methionine load (13.7 +/- 5.9 and 0.66 +/- 0.10 micromol/L, both p<0.001). Reinvestigation of 8 of 12 subjects showed that at 4 and 8 h after compared with levels immediately before methionine loading there was a significant increase in tHcy (28.4 +/- 10.2 and 33.45 +/- 11.1 vs. 10.8 +/- 3.3 micromol/L, both p<0.001). However, the corresponding ADMA levels did not increase (0.73 +/- 0.17 and 0.76 +/- 0.22 vs. 0.70 +/- 0.10 micromol/L, both not significant).

CONCLUSIONS

No clear evidence was found to support the supposition that methionine-induced hyperhomocysteinaemia may be accompanied by elevated levels of ADMA, an endogenous competitive NO-synthase inhibitor that may represent an alternative pathogenic mechanism for homocysteine-associated impairment of endothelial NO-dependent functions.

Plasma homocysteine levels and different forms of vascular disease in patients with dementia and other psychogeriatric diseases

BACKGROUND

Total plasma homocysteine (tHcy) concentration is elevated in patients with psychogeriatric disease. There are many different determinants of plasma tHcy concentration, including the presence of vascular disease.

METHOD

We investigated plasma tHcy levels in several different subgroups of vascular disease and also the relation between plasma tHcy and renal function in patients with psychogeriatric disease.

RESULTS

All different groups of patients with vascular disease exhibited an elevated level of plasma tHcy compared to patients without vascular disease even after exclusion of patients with folate/cobalamin deficiency. Patients with elevated serum creatinine with or without vascular disease exhibited significantly increased plasma tHcy compared to the respective groups of patients without elevated serum creatinine. Patients with vascular dementia and Alzheimer's disease with concomitant vascular disease exhibited significantly increased plasma tHcy levels compared to patients without vascular disease.

CONCLUSION

The presence of vascular disease increases the level of plasma tHcy and renal impairment further increases the elevated plasma tHcy level. Furthermore, the findings suggest similar influence on plasma tHcy turnover irrespective of whether the vascular disease is of cerebral or extracerebral origin or only manifests itself as arrhythmia or hypertension.

Urinary beta-hexosaminidase excretion in polycystic kidney disease

The urinary excretion of beta-hexosaminidase in relation to creatinine was studied during one year in 30 consecutive patients with polycystic kidney disease (S-creatinine 75-1 000 micro mol/l) and 30 healthy controls. The excretion of beta-hexosaminidase was significantly increased in the patients and was positively correlated to S-creatinine and to the relative increase in S-creatinine during the year of the study. No correlation was found between the enzyme excretion and age, mean blood pressure, number of antihypertensive drugs, proteinuria or pyuria. A significant rise in beta-hexosaminidase excretion was observed in two patients with acute cyst bleeding and/or kidney infarction.

Urinary excretion of beta-hexosaminidase in patients with vesico-ureteric reflux

Urinary excretion of beta-hexosaminidase was studied in 50 patients with vesico-ureteric reflux (VUR) in order to obtain information on the renal injury in this disease. There was no correlation between urinary enzyme excretion and the degree of VUR. Patients without pyelonephritis changes and with normal serum creatinine values showed normal excretion of beta-hexosaminidase. Patients with pyelonephritic changes but normal serum creatinine had enzyme activity towards the upper limit of the normal range whilst patients with pyelonephritic changes and decreased renal function (high serum creatinine) showed increased excretion of urinary beta-hexosaminidase. Some of the patients with VUR and asymptomatic bacteriuria exhibited increased excretion of urinary beta-hexosaminidase and six with acute pyelonephritis had very high levels. These findings indicate that the infective process plays an essential role, besides VUR, in the development of kidney damage.

Diagnostic significance of lysosomal enzymes in different types of leukemias

The activities of seven different leukocyte hydrolases were studied in 19 patients and ten controls. There was a strong positive correlation between the monocyte count and the activities of the lysosomal enzymes (N-acetyl-beta-glucosaminidase, alpha-fucosidase, beta-galactosidase, and alpha-mannosidase). High alpha-fucosidase and alpha-mannosidase activities were also found in the eosinophilic granulocytes. Using simple commercially available synthetic substrates, it is possible to study the activities of the lysosomal enzymes in different types of leukemias and to recognize the monocytic leukemias even when they present with very immature precursor cells in the peripheral blood.

Clinical and diagnostic considerations in Fabry's disease

Three patients with Fabry's disease with a similar clinical picture, including recurrent burning sensations in the extremities, hypohidrosis and slowly progressive renal insufficiency, have been investigated metabolically at different stages of renal impairment. One patient died after three unsuccessful renal transplantations in a 4-year period of intermittent haemodialysis with disabling pains. One successfully transplanted patient is still alive and well, 12 years after the start of therapy. Thermolabile alpha-galactosidase has been demonstrated in his urine. The third patient has slowly progressive renal impairment. No therapeutic enzyme replacement available today is ideal. Early diagnosis is therefore necessary to increase the possibilities of prenatal diagnosis and genetic counseling.

Serum beta-hexosaminidase in diabetes mellitus with reference to the type of treatment

A significantly increased serum level of beta-hexosaminidase was found in an unselected group of 85 diabetics. When the patients were divided into three groups according to type of treatment, increased enzyme levels were found only in patients treated with oral hypoglycemic agents or diet while insulin-treated patients had normal serum levels of beta-hexosaminidase. There was a positive correlation between beta-hexosaminidase and blood glucose concentration for the entire patient series. When grouped according to treatment, a positive correlation was found only in the insulin-treated group despite its normal serum activity of beta-hexosaminidase. Serum beta-hexosaminidase of patients with retinopathy did not differ from the mean value of their group. It is concluded that the activity of beta-hexosaminidase in diabetics can produce different results depending on the type of patients under study.

Diagnostic potential of urinary enzymes and beta 2-microglobulin in acute urinary tract infection

Urinary excretions of beta 2-microglobulin (beta 2M), N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase, beta-glucuronidase, acid and neutral alpha-glucosidase as indicators of proximal tubular dysfunction were measured in patients with acute upper and lower urinary tract infection (UTI) and fever of non-renal origin. The sensitivity of beta 2M was 67% and of NAG 49% as assessed in more than 100 episodes of acute pyelonephritis. Combined use of beta 2M and NAG increased the sensitivity to 75%. The degree of beta 2-microglobulinuria and enzymuria was comparable in patients with acute pyelonephritis and fever due to non-renal infections. The excretion of beta 2M and the various enzymes was too variable and unpredictable in individual cases to be useful as diagnostic indicator. In localizing an acute UTI, tests for proximal tubular dysfunction seem to be of no more clinical value than properly measured body temperature.

Clinical trial: B vitamins improve health in patients with coeliac disease living on a gluten-free diet

BACKGROUND

Patients with coeliac disease living on a gluten-free diet show vitamin deficiency and reduced subjective health status.

AIM

To study the biochemical and clinical effects of B vitamin supplementation in adults with longstanding coeliac disease.

METHODS

In a double blind placebo controlled multicentre trial, 65 coeliac patients (61% women) aged 45-64 years on a strict gluten-free diet for several years were randomized to a daily dose of 0.8 mg folic acid,0.5 mg cyanocobalamin and 3 mg pyridoxine or placebo for 6 months. The outcome measures were psychological general well-being (PGWB) and the plasma total homocysteine (tHcy) level, marker of B vitamin status.

RESULTS

Fifty-seven patients (88%) completed the trial. The tHcy level was baseline median 11.7 micromol/L (7.4-23.0), significantly higher than in matched population controls [10.2 micromol/L (6.7-22.6) (P < 0.01)]. Following vitamin supplementation, tHcy dropped a median of 34% (P < 0.001), accompanied by significant improvement in well-being (P < 0.01), notably Anxiety (P < 0.05) and Depressed Mood (P < 0.05) for patients with poor well-being.

CONCLUSIONS

Adults with longstanding coeliac disease taking extra B vitamins for 6 months showed normalized tHcy and significant improvement in general well-being, suggesting that B vitamins should be considered in people advised to follow a gluten-free diet.

C-reactive protein: vascular risk marker in elderly patients with mental illness

BACKGROUND

There is increasing evidence that vascular disease contributes to cognitive impairment and dementia. Clarification of the role of vascular risk factors in dementia is important because most are modifiable, in contrast to other risk factors such as age and genetics.

METHODS

In 428 patients with mental illness we have investigated the relation of vascular disease to diagnoses, and a biochemical parameter, C-reactive protein (CRP), which is associated with inflammation and vascular disease.

RESULTS

Patients with vascular disease showed higher CRP levels than patients without vascular disease. Furthermore, patients with Alzheimer's disease showed lower CRP levels than patients with vascular dementia, mild cognitive impairment or depression. There is no obvious reason for this finding, since it could not be attributed to drug treatment.

CONCLUSION

The findings indicate that the control of conventional vascular risk factors and therapy could be guided by the level of CRP.

Homocysteine, cystatin C and N-terminal-pro brain natriuretic Peptide. Vascular risk markers in elderly patients with mental illness

BACKGROUND

There is increasing evidence that vascular disease contributes to cognitive impairment and dementia. Clarification of the role of vascular risk factors in dementia is important because most are modifiable, in contrast to other risk factors such as age and genetics.

METHODS

In 451 patients with mental illness we have investigated three biochemical markers related to vascular disease, total plasma homocysteine (tHcy), cystatin C, and N-terminal-pro brain natriuretic peptide (NT-proBNP), and their association with vascular disease, diagnoses, and brain imaging findings (CT).

RESULTS

Plasma tHcy, serum cystatin C, and serum NT-proBNP showed significantly increased frequencies of elevated levels in patients with vascular disease, in patients with a pathological CT finding indicating cerebrovascular disease, and in patients above 75 years of age.

CONCLUSION

It is possible that the control of conventional vascular risk factors and therapy could be guided by the level of plasma tHcy, serum cystatin C, and serum NT-proBNP. Patients with an elevation of any of these three parameters could be selected for a lower target level of risk factors such as blood pressure, hyperlipidemia etc. than conventional target levels.

Elevated plasma homocysteine concentration in elderly patients with mental illness is mainly related to the presence of vascular disease and not the diagnosis

BACKGROUND

Plasma total homocysteine (tHcy) is often elevated in patients with mental illness. Since patients with mental illness and vascular disease exhibit a higher plasma tHcy concentration than patients without vascular disease, it is possible that elevated plasma tHcy in mental illness is mainly due to concomitant vascular disease.

METHODS

We have investigated plasma tHcy, cobalamin/folate status, renal function and the presence of vascular disease in patients with vascular dementia (VaD, n = 501), Alzheimer's disease (AD, n = 300), depression (n = 259) and in healthy subjects (n = 144) stratified according to age (below and above 75 years).

RESULTS

Plasma tHcy concentration showed the highest increase in patients with VaD compared to patients with AD or depression. After the exclusion of patients with cobalamin/folate deficiencies and increased serum creatinine, patients with AD or depression above 75 years with vascular disease showed a similar elevation of plasma tHcy concentration as patients with VaD. Furthermore, patients with AD and depression without vascular disease showed a similar plasma tHcy concentration to healthy subjects.

CONCLUSION

The findings imply that elevated plasma tHcy concentration in elderly patients with mental illness is mainly associated with the presence of vascular disease and is not related to the specific psychogeriatric diagnosis.

Plasma homocysteine is elevated in elderly patients with memory complaints and vascular disease

BACKGROUND

There is an association between elevated plasma total homocysteine (tHcy) and vascular disease in elderly patients suffering from organic and non-organic mental disease. The main objective of the present study was to investigate the relationship between plasma tHcy concentration and vascular disease in elderly patients with memory complaints.

METHODS

In 108 patients with memory complaints the concentration of plasma tHcy was related to the presence of vascular disease. Furthermore, different determinants of plasma tHcy concentration were measured.

RESULTS

Patients with confirmed memory complaints (CMC, n = 86) which fulfilled the criteria of mild cognitive impairment were divided into two categories, with and without vascular disease. The CMC group without vascular disease showed similar biochemical and brain imaging findings to patients with subjective memory complaints (SMC, n = 22). The group of CMC patients with vascular disease had higher age, higher plasma tHcy, lower serum folate and lower renal function than patients without vascular disease.

CONCLUSION

The finding of two subgroups of patients with CMC supports the notion that mild cognitive impairment is a heterogenous clinical entity with multiple aetiological factors. The elevated plasma tHcy in the group of CMC patients with vascular disease is likely to be associated with vascular disease.

Traces of copper ions deplete glutathione in human hepatoma cell cultures with low cysteine content

BACKGROUND

Cell death induced by intracellular glutathione depletion has been reported to be dependent on the presence of trace amounts of extracellular copper ions. Since little is known about the relationship between glutathione depletion and copper homeostasis, we have in the present study further investigated the role of low amounts of copper ions in glutathione depletion.

METHODS

Glutathione turnover was investigated in HeLa and hepatoma cell cultures with normal and low cysteine content in the presence of copper ions (1 and 10micromol/L) and two other glutathione-stimulating agents (lipoic acid and mercury ions).

RESULTS

Copper ions (10micromol/L) caused relatively small increases in total amount of glutathione (the sum of the intracellular and the extracellular amount of glutathione) in HeLa and hepatoma cell cultures with normal cysteine levels (420nmol/mL) compared to control cell cultures, whereas lipoic acid and mercury ions strongly increased total glutathione in both types of cell cultures. Lower amount of total glutathione was observed in cell cultures with a lower cysteine levels (84nmol/mL), which is similar to that in human plasma. A strongly decreased total amount of glutathione in the presence of copper ions was observed in hepatoma cell cultures with lower cysteine levels, whereas the other agents showed effects similar to those described for cell cultures with normal cysteine levels.

CONCLUSION

Glutathione synthesis in hepatoma cell cultures is probably more sensitive to a low cysteine level than HeLa cell cultures, and the presence of copper ions further decreases the availability of cysteine probably by increasing the disulfide binding to cysteine residues in extracellular proteins, which causes a further decrease of total glutathione.

Plasma homocysteine, cobalamin/folate status, and vascular disease in a large population of psychogeriatric patients

BACKGROUND

Cobalamin/folate deficiency and vascular disease are prevalent in elderly subjects and may lead to mental symptoms, but may even more often influence the severity of other organic and non-organic mental diseases. In the present study, we have evaluated cobalamin-folate status and the presence of vascular disease in 1,982 psychogeriatric patients investigated and diagnosed in a psychogeriatric clinic. The objective of the present study is to obtain information on the role of cobalamin/folate status and vascular disease in different diagnoses of psychogeriatric patients and their association with plasma homocysteine (tHcy).

METHODS

We have measured serum cobalamin, blood/serum folate, serum creatinine, plasma tHcy and evaluated the presence of vascular disease in 1,982 well-defined psychogeriatric patients.

RESULTS AND CONCLUSIONS

The present study indicates that cobalamin/folate deficiencies do not play an important role in cognitive dysfunction in psychogeriatric patients, since only about 7% of the study population had metabolic cobalamin/folate deficiencies. Furthermore, cobalamin/folate deficiencies were rare in younger patients (below 70 years of age). We were also able to confirm our previous finding that there was no association between dementia of Alzheimer type (AD) and plasma tHcy level or metabolic cobalamin/folate deficiencies. Furthermore, we observed a low proportion of vascular disease in patients with AD, which does not give support for an association between well-defined AD and the presence of vascular disease. The presence of vascular disease was higher and of similar degree in patients with mild cognitive impairment and depression, which indicates an association between these diagnoses and the presence of vascular disease. The present study also shows that at plasma tHcy levels below 14 micromol/l, the likelihood of cobalamin/folate deficiency is small and further investigation of cobalamin/folate status could be omitted.

Oxidative stress decreases extracellular homocysteine concentration in human hepatoma (HepG2) cell cultures

BACKGROUND

Mild hyperhomocysteinemia is associated with premature vascular disease. The mechanism behind the vascular injuries is, however, still unknown. Homocysteine may be catabolized in the trans-sulfuration pathway to cysteine. Cystathionine beta-synthase, which catalyses the first step in the trans-sulfuration pathway is redox-sensitive. We have therefore investigated total extracellular homocysteine turnover in the presence of oxidative stress in human cell lines.

METHODS

The turnover of total extracellular homocysteine in HeLa and hepatoma cell cultures has been investigated in the presence of hydrogen peroxide. Furthermore, the effect of hydrogen peroxide on the removal of high amounts of exogenously added homocysteine was also studied.

RESULTS

Total extracellular homocysteine concentration in hepatoma cell cultures decreased in the presence of hydrogen peroxide, whereas the extracellular homocysteine concentration in HeLa cell cultures was not influenced. There was no significant change of intracellular homocysteine in any type of cell cultures. Furthermore, the presence of hydrogen peroxide did not increase the removal of exogenously added homocysteine.

CONCLUSION

The presence of hydrogen peroxide probably increases the activity of the trans-sulfuration pathway in hepatoma cell cultures, which increases the intracellular use of homocysteine and lowers its extracellular release. Consequently this mechanism might tend to lower total plasma homocysteine concentration in oxidative stress.

The effect of different antioxidants on glutathione turnover in human cell lines and their interaction with hydrogen peroxide

BACKGROUND

Glutathione plays crucial roles in antioxidant defence and glutathione deficiency contributes to oxidative stress and may therefore play a key role in the pathogenesis of many diseases. The objectives of the present study were to evaluate the effects on glutathione turnover of thiol and non-thiol antioxidants in human cell cultures and if any of the antioxidant had a short-term cellular effect against different levels of hydrogen peroxide.

METHODS

We have investigated the effect on the total glutathione amount in HeLa and hepatoma cell cultures of thiol antioxidants in comparison with non-thiol antioxidants, such as a copper chelator, Vitamin C, and a flavonoid. Furthermore, we have investigated the short-term (within 24h) interaction of the different antioxidants with hydrogen peroxide.

RESULTS AND CONCLUSION

Lipoic acid and quercetin (Quer) were the two antioxidants that showed the highest stimulation of glutathione synthesis in cell cultures as judged by the total glutathione amount. However, no antioxidant protected against hydrogen peroxide present in concentrations that lowered cell protein. This finding may be attributed to the fact that it is necessary to incubate cell cultures with antioxidants or small doses of oxidants for a period before the cultures are exposed to hydrogen peroxide in order to enhance the antioxidant defence. The presence of Quer and Vitamin C lowered cell protein and total glutathione even in cell cultures containing hydrogen peroxide in concentrations that did not lower cell protein. This finding might be attributed to pro-oxidant properties and formation of excess reactive oxygen species in the presence of Quer and Vitamin C.

Plasma homocysteine and vascular disease in psychogeriatric patients

BACKGROUND

There is a high frequency (40-50%) of elevated plasma total homocysteine (tHcy) concentrations in elderly patients with mental disorders, and patients with a history of vascular disease exhibit significantly higher plasma tHcy concentration than patients without vascular disease.

METHOD

The main objective of the present study was to further investigate the association between plasma tHcy concentration and vascular disease in psychogeriatric patients. We have therefore investigated 304 psychogeriatric patients and determined plasma tHcy and its most important determinants (folate and cobalamin status and renal function), and the natriuretic peptide N-terminal-pro brain natriuretic peptide (NT-proBNP). The patients were classified into several groups of vascular disease according to the findings of brain imaging and presence of a history/symptoms indicating manifest occlusive arteriosclerotic vascular disease.

RESULTS

Plasma tHcy concentration is associated with the presence of vascular disease in psychogeriatric patients. The presence of vascular disease is also associated with higher age, higher serum NT-proBNP, renal impairment and lower serum folate concentration than in patients without vascular disease. The significant association between plasma tHcy concentration and vascular disease remained after correction for age and for cystatin C differences between the groups of patients without and with vascular disease. In the present population with only 16% of the patients showing elevated plasma tHcy, renal function was a more important determinant for plasma tHcy concentration than folate status.

CONCLUSION

Plasma tHcy concentration is associated with vascular disease. In the present population of psychogeriatric patients renal function is associated with vascular disease and elevated plasma tHcy concentration. Thus, the association between plasma tHcy concentration and vascular disease might partially be explained by impairment of renal function.

Plasma homocysteine and markers of bone metabolism in psychogeriatric patients

OBJECTIVE

In recent studies high plasma total homocysteine (tHcy) levels were reported to be associated with increased risk of osteoporotic fractures. In elderly psychogeriatric patients there is a high frequency of elevated plasma tHcy concentration. The present study therefore investigates the association between plasma tHcy concentration and markers of bone metabolism in psychogeriatric patients.

MATERIAL AND METHODS

A total of 152 psychogeriatric patients were investigated and plasma tHcy and its major determinants (serum folate, serum cobalamin and renal function) were measured. Osteocalcin and crosslaps were chosen as markers of bone metabolism.

RESULTS

Bone markers (crosslaps and osteocalcin) were increased in elderly patients with dementia compared to patients without dementia. Stepwise multiple regression analysis showed that plasma tHcy concentration made only a small contribution to the prediction of crosslaps in serum, whereas plasma tHcy concentration was not an independent predictor of serum osteocalcin.

CONCLUSIONS

The present study does not provide support for the hypothesis that a moderately increased plasma tHcy concentration is a risk factor for impaired bone metabolism.

The polyphenol quercetin strongly increases homocysteine production in a human hepatoma (Hep G2) cell line

OBJECTIVE

The metabolism of homocysteine is influenced by several dietary factors, including folate, cobalamin and possibly also the intake of polyhydroxylated phenolic compounds (polyphenols), which were shown to increase plasma homocysteine (tHcy) concentration. In order to reveal the cause of the increased plasma tHcy, we have therefore investigated the effects of a polyphenol in cell cultures from human cell lines.

DESIGN AND METHODS

We have studied the influence of the polyphenol quercetin (Quer) on intra- and extracellular homocysteine concentrations in HeLa and hepatoma cell cultures.

RESULTS

The main finding is an increased concentration of extracellular homocysteine in the presence of Quer in hepatoma cell cultures, whereas there were no significant changes of homocysteine concentration in HeLa cell cultures. There was no effect on cellular growth, as judged by cell protein. The presence of adenosyl-dialdehyde, an inhibitor of adenosyl-homocysteine hydrolase, abolished the increased extracellular concentration of homocysteine observed in hepatoma cell cultures in the presence of Quer.

CONCLUSION

The antioxidative agent Quer strongly increased the extracellular concentration of homocysteine in hepatoma cell cultures probably due to increased cellular methylation. In the human body, the same phenomenon might lead to increased plasma tHcy. Since elevated plasma tHcy is associated with premature vascular disease, high long-lasting dietary intake of polyphenols might be harmful. The interaction between Quer and homocysteine turnover may therefore warrant a re-evaluation of polyphenols as relatively harmless antioxidative food supplements or therapeutic antioxidative agents.

Bovine retinal pericytes are resistant to glucose-induced oxidative stress in vitro

Diabetic retinopathy is a sight-threatening complication of diabetes, and loss of pericytes represents early signs of its development. We tested the hypothesis that high glucose levels may induce signs of oxidative stress in cultured bovine retinal pericytes. Pericytes were exposed to either normal (5.5 mM) or high (22 mM) glucose levels for 1, 3, and 5 days. Signs of oxidative stress were measured by expression of copper/zinc superoxide dismutase, manganese superoxide dismutase, catalase, and glutathione peroxidase using real-time RTPCR. To elucidate the role of oxidative stress, we also measured glutathione (GSH) concentration in the cells and investigated the impact of thiol-reactive metal ions and hydrogen peroxide (H(2)O(2)) on intracellular GSH. Despite the stimulation with high glucose, thiol-reactive metal ions, or H(2)O(2), there was no clear increased expression of antioxidant enzymes or influence of GSH levels. Lipid peroxidation (malondialdehyde level) was increased in bovine aortic smooth muscle cells, but not in bovine retinal pericytes. The data indicate that pericytes do not develop oxidative stress in response to hyperglycemia. However, it is not definitively excluded that oxidative stress may occur after longer time periods of glucose stimulation.

Plasma homocysteine concentration and its relation to symptoms of vascular disease in psychogeriatric patients

BACKGROUND

There is a high frequency of elevated plasma total homocysteine (tHcy) concentrations in elderly patients with mental disorders. Psychogeriatric patients with a history of vascular disease exhibit a significantly higher plasma tHcy concentration than patients without vascular disease.

METHOD

The main reason for the present study is to further investigate the association between plasma tHcy concentration and vascular disease in psychogeriatric patients. We therefore investigated 152 psychogeriatric patients and determined plasma tHcy and its most important determinants (serum folate and serum cobalamin, serum cystatin C and serum creatinine). The patients were divided into two groups according to the presence of vascular disease. Eighty-seven patients had concomitant vascular disease. We also analysed the natriuretic peptide N-terminal pro brain natriuretic peptide (NT-proBNP) and protein S-100B in serum. NT-proBNP is a marker for congestive heart failure, whereas protein S-100B is a marker for brain damage.

RESULTS

The plasma tHcy concentration is elevated in the presence of dementia or vascular disease in psychogeriatric patients. The presence of dementia or vascular disease is also associated with higher age, renal impairment and lower serum folate concentration than in patients without dementia or vascular disease. Furthermore, we observed elevated serum concentrations of NT-proBNP in patients with dementia or vascular disease as a sign of poorer cardiovascular status. Likewise, protein S-100B concentrations were elevated in patients with dementia or vascular disease, possibly indicating brain damage in these groups of patients.

CONCLUSION

The high frequency of comorbidity of vascular disease and mental illness indicates a possibility to prevent and treat psychogeriatric disease by actively counteracting vascular disease in patients with psychogeriatric symptoms. Routine determination of NT-proBNP is valuable for obtaining information about cardiovascular status.

Plasma homocysteine and markers for oxidative stress and inflammation in patients with coronary artery disease--a prospective randomized study of vitamin supplementation

BACKGROUND

Elevated plasma levels of total homocysteine (tHcy) are associated with an increased risk of developing occlusive vascular diseases. To better illustrate the relationship between plasma tHcy concentration, oxidative stress, and inflammation in patients with coronary artery disease (CAD), we measured plasma 8-isoprostane-prostaglandin F 2 (Iso-P), plasma malondialdehyde (MDA), and several markers of inflammation. We also aimed to demonstrate the effects of vitamin supplementation on these markers.

METHODS

A total of 93 patients with ischemic heart disease were investigated. Of these, 34 had plasma tHcy < or =8 micromol/L, while 59 had plasma tHcy > or = 15.0 micromol/L. The 59 patients were randomized to open therapy with folic acid, 5 mg, pyridoxine, 40 mg, and cyancobalamin, 1 mg once daily for 3 months (n = 29) or to no vitamin treatment (n = 30). Blood samples were obtained from both groups before randomization and 3 months later. A sample was also obtained from the remaining 34 patients.

RESULTS

Plasma Iso-P, serum amyloid A (S-AA), and plasma intercellular adhesion molecule-1 (ICAM-1) concentrations were higher in patients with high plasma tHcy levels than in patients with low to normal tHcy levels. Plasma levels of P-, L-, E-selectins, MDA, C-reactive protein (CRP), and orosomucoid did not differ between the groups. Vitamin therapy reduced plasma tHcy from 17.4 (15.3/20.1) to 9.2 (8.3/10.3) micromol/L (25th and 75th percentiles in parentheses) (p<0.0001). Plasma levels of Iso-P remained unchanged and, of all inflammatory markers, only the S-AA concentrations were slightly reduced by the vitamin treatment, from 5.3 (2.2/7.0) ng/L at baseline to 4.6 (2.1/6.9) ng/L (p<0.05) after 3 months of vitamin supplementation.

CONCLUSION

Patients with CAD and high plasma tHcy levels had elevated plasma levels of Iso-P. The increase remained unaffected by plasma tHcy-lowering therapy, suggesting that homocysteine per se does not cause increased lipid peroxidation. Levels of plasma ICAM-1 and S-AA were increased in patients with high plasma tHcy, suggesting an association between homocysteinemia and low-grade inflammation.

Glutathione turnover in human cell lines in the presence of agents with glutathione influencing potential with and without acivicin inhibition of γ-glutamyltranspeptidase

BACKGROUND

We have previously shown that there were great discrepancies between different agents regarding their glutathione stimulating potential and that agents with mainly oxidative effects did not increase concentrations of glutathione in human cell cultures, in contrast to other thiol reactive agents. In order to evaluate whether increased glutathione degradation might be one reason for these discrepancies, we have investigated the effect of different agents with potential influence on glutathione metabolism in human cell cultures with or without acivicin inhibition of gamma-glutamyltranspeptidase (GT), since GT is responsible for the initial degradation of glutathione.

METHODS

Intra- and extracellular concentrations of glutathione were investigated in HeLa and hepatoma cell cultures, with and without acivicin inhibition of GT, in the presence of oxidative and electrophilic agents (copper ions, hydrogen peroxide and N-ethylmaleimide), hydroquinone, reducing agents (lipoic acid and N-acetylcysteine), and a thiol reactive metal (mercury ions).

RESULTS

There were great discrepancies between the different agents regarding their maximal glutathione response (the sum of the intracellular and the extracellular amount of glutathione) in cell cultures. There was only a small increase in total glutathione in the presence of hydrogen peroxide or N-ethylmaleimide before the cell protein decreased compared to findings with mercury ions, lipoic acid or hydroquinone. In both HeLa and hepatoma cell cultures, there were correlations between the original glutathione amount and the total glutathione amount observed after acivicin inhibition.

CONCLUSION

The relatively small increase of glutathione amount in the presence of oxidative and electrophilic agents compared to other thiol reactive agents is not due to increased GT degradation of glutathione.

Elimination of high amounts of extracellular homocysteine in human cell lines

BACKGROUND

Many clinical and epidemiological studies show that mild hyperhomocysteinemia is associated with premature vascular disease. Information about the metabolism of homocysteine is therefore essential for an understanding of its role in atherogenesis, thereby enabling a modulation of that risk.

METHODS

In the present study factors influencing the elimination of exogenously added homocysteine in HeLa and hepatoma cell cultures have been investigated with and without inhibition of the transmethylation pathway by adenosine-dialdehyde.

RESULTS

Agents with antioxidative effect (copper chelator and thiols) increased the metabolic removal of extracellular homocysteine in HeLa cell cultures, whereas in hepatoma cell cultures only the thiol N-acetylcysteine increased the elimination. The oxidative agent (copper ions) and cyst(e)ine transport inhibitors decreased the removal in both HeLa and hepatoma cell cultures. The inhibition of the transmethylation pathway by adenosine-dialdehyde increased the removal of exogenously added homocysteine and the addition of the different redox agents and cyst(e)ine transport inhibitors did not specifically influence this increase.

CONCLUSION

The elevated removal of exogenously added homocysteine in the presence of adenosine-dialdehyde might be attributed to limited availability of intracellular homocysteine, which leads to a larger amount of extracellular homocysteine being internalized.

High glutathione turnover in human cell lines revealed by acivicin inhibition of gamma-glutamyltranspeptidase and the effects of thiol-reactive metals during acivicin inhibition

BACKGROUND

Glutathione is the most abundant nonprotein sulfhydryl-containing compound and constitutes the largest component of the endogenous thiol buffer. Glutathione is known to have multifaceted physiological functions and is a critical factor in protecting organisms against toxicity and disease. Intracellular cysteine concentration is a limiting factor for glutathione synthesis.

METHODS

In the present study, the metabolism of intra- and extracellular glutathione in HeLa and hepatoma cell cultures is investigated by using different transport inhibitors for cellular uptake of cystine/cysteine.

RESULTS

There exist several ways of cystine/cysteine transport into HeLa and hepatoma cells, and inhibition of them decreased intracellular concentration of cystine/cysteine and in some cases also of glutathione. It was also shown that a large pool of total cell culture glutathione was located extracellularly in both HeLa and hepatoma cell cultures when gamma-glutamyltranspeptidase (GT) activity was inhibited by acivicin (ACI). Furthermore, the addition of thiol-reactive metal ions significantly increased the total amount of glutathione in hepatoma cell cultures during acivicin inhibition. Thus, occasional determinations of extracellular concentrations of glutathione without GT inhibition strongly underestimate the total turnover of glutathione in a cell culture.

CONCLUSION

This finding has important implications for future research in glutathione metabolism and the understanding of its role in human health and disease.

Clinical utility of serum holotranscobalamin as a marker of cobalamin status in elderly patients with neuropsychiatric symptoms

Early diagnosis of cobalamin deficiency is crucial, owing to the latent nature of this disorder and the resulting possible irreversible neurological damage. A normal serum cobalamin concentration does not reliably rule out a functional cobalamin deficiency and there does not at present seem to be any single diagnostic approach to achieve this diagnosis. A new marker for cobalamin status is the serum concentration of cobalamin bound to transcobalamin II (holoTC). Because methods suitable for routine use have been unavailable until recently, the clinical value of low holoTC is still uncertain. Furthermore, there is at the moment no gold standard or true reference method to diagnose subtle cobalamin deficiency, which makes evaluation of the clinical usefulness of holoTC and the estimation of sensitivity and specificity problematic. In this study, we aimed to assess whether low holoTC concentrations are congruent with other biochemical signs of cobalamin deficiency in a group of psychogeriatric patients. The findings in the present study show that holoTC is strongly related to serum cobalamin (0.68; p<0.001 in both patients and controls). Distribution of the different markers for cobalamin/folate status in the 33 patients with low levels of serum holoTC (below 40 pmol/l) showed that 17 patients had normal levels of the other markers for cobalamin status. This may indicate poor specificity of low holoTC for cobalamin deficiency. In 23 out of 176 patients with normal levels of holoTC we observed pathological levels of other markers for cobalamin deficiency. The use of holoTC in the present study group did not give significant additional information other than that given by serum cobalamin and therefore cannot be recommended in this clinical setting.

Extracellular concentration of homocysteine in human cell lines is influenced by specific inhibitors of cyst(e)ine transport

Despite the growing evidence that plasma homocysteine is a cardiovascular risk factor, the mechanism behind the vascular injuries is still unknown. Studies of the cellular uptake systems for homocysteine are scarce, but membrane transporters of cyst(e)ine seem to be involved. In the present study the cellular uptake of extracellular homocysteine in HeLa and hepatoma cell lines is investigated by using several different transport inhibitors for cellular uptake of cyst(e)ine. It is shown that systems A and Xc- are the main transport systems for homocysteine uptake in HeLa cells. It is also confirmed that the magnitude of homocysteine uptake in hepatoma cells is lower than in HeLa cells. However, in the presence of high amounts of extracellular homocysteine both cell types exhibited a high elimination of homocysteine, which was inhibited by the presence of inhibitors of systems A or Xc-. It is possible that there is normally a high turnover of homocysteine in cell cultures, which is not detected by occasional determinations of homocysteine concentrations. The complex pattern of homocysteine production, release, uptake and distribution between different cells in the body is important to examine further in order to possibly be able to modulate the elimination of homocysteine from circulation and thereby lower the risk of cardiovascular disease.

Plasma homocysteine concentration relates to the severity but not to the duration of Alzheimer's disease

BACKGROUND

It has been reported that plasma tHcy concentration is elevated in patients with Alzheimer's disease (AD) and relates to the progress or the development of AD. In the present study we have compared plasma tHcy concentrations at different times during the course of AD and with measures corresponding to the severity and the progress rate of AD.

METHODS

The study population consisted of 159 patients with AD. Three measures corresponding to the progress rate of AD were created by dividing the actual scores of the severity of the dementia, the Berger scale and the Katz index by the estimated duration.

RESULTS

AD patients without a history of cardiovascular disease did not show a significant increase of plasma tHcy concentration compared to the control subjects, whereas AD patients with cardiovascular disease exhibited a significant increase of plasma tHcy concentration compared to both control subjects and patients without cardiovascular disease. However, after creatinine adjustment of plasma tHcy in control subjects and AD patients a significant increase of plasma tHcy was observed also in AD patients without cardiovascular disease compared to controls. The concentration of plasma tHcy in AD patients with and without cardiovascular history did not increase with time after disease onset. Plasma tHcy concentration correlated with the severity of the disease. The correlations between plasma tHcy and measures of rate progression of AD did not improve compared with the correlations between plasma tHcy and the severity of dementia.

CONCLUSION

An interpretation of these findings may be that plasma tHcy is additionally increased in AD patients when a complication occurs, such as folate/cobalamin deficiency or a cardiovascular disease.

[Optimal use of markers for cobalamin/folate status. Results from a survey in a group of psychogeriatric patients]

Cobalamin/folate deficiency may lead to neuropsychiatric symptoms. This review summarizes present findings concerning the different markers for cobalamin/folate deficiency in psychogeriatric patients. These findings suggest the use of plasma homocysteine, serum cobalamin and serum folate to evaluate cobalamin/folate status in psychogeriatric patients, whereas the use of serum methylmalonic acid and whole blood folate could be omitted.

The postdialytic rise in the plasma total homocysteine concentration is delayed

BACKGROUND/AIMS

The mechanism behind the uremic hyperhomocysteinemia has not been elucidated. Possibly, dialyzable uremic toxins play a role, e.g. as enzyme inhibitors. If so, the conditions for enzymatic removal would be expected to improve after dialysis. Therefore, we studied the postdialytic pattern of the plasma total homocysteine (tHcy) concentration.

METHODS

We collected blood samples from 19 stable, vitamin-supplemented hemodialysis patients before and at 5, 60, as well as at 480 min after a dialysis session. The patients were studied after dialysis with a low-flux dialyzer (Polyflux 6L) and a high-flux dialyzer (Polyflux 14S).

RESULTS

The mean predialytic plasma tHcy concentration was 13.3 micromol/l which is considerably lower than the concentrations observed in our previous studies. In all patients, the plasma tHcy concentration fell during treatment with both types of dialyzers (average decrease 28 +/- 7%, p < 0.0001, and 31 +/- 8%, p < 0.0001, respectively). No postdialytic change in the plasma tHcy concentration was observed at 60 min after low-flux dialysis, however, after high-flux dialysis, the plasma tHcy concentration was significantly lower at 60 min postdialysis than at 5 min (3 +/- 8%, p < 0.05). At 480 min after dialysis, a significant postdialytic increase in the plasma tHcy concentration was found (6 +/- 9%, p < 0.01, and 11 +/- 5%, p < 0.0001, respectively) both in the case of low-flux and high-flux treatment.

CONCLUSION

In the postdialytic phase, we observed a short-lived stability in the plasma tHcy concentration, and in the case of high-flux dialysis, even a slight decrease in the plasma tHcy concentration. The results support the hypothesis that dialyzable substances interfere with homocysteine removal.

Risk of myocardial infarction in relation to plasma levels of homocysteine and inflammation-sensitive proteins: a long-term nested case-control study

Several studies have found that the homocysteine plasma level is associated with cardiovascular disease. The authors previously described a relationship between concentrations of fibrinogen and other inflammation-sensitive plasma proteins, namely, alpha1-antitrypsin, ceruloplasmin, haptoglobin, and orosomucoid (alpha1-acid glucoprotein) and the incidence of myocardial infarction (MI). Whether levels of these proteins are related to homocysteine has not been clarified. The aim of this study was to investigate whether a supposed relationship between homocysteine in plasma and the occurrence of MI is modified by these inflammation-sensitive proteins. A nested case-control study was designed, comprising 241 cases of MI, with a mean age of 48 years at baseline, and 241 controls matched for age, month of examination, and duration of follow-up. The mean homocysteine concentration did not differ between cases and controls and there was no association between the baseline homocysteine level and the time lapse before the occurrence of the MI. For the cases, there was no correlation between homocysteine and any of the measured proteins, but for the controls, homocysteine was weakly but significantly negatively correlated to haptoglobin and ceruloplasmin and slightly positively correlated to albumin. For the separated groups of cases and controls there was no association between the number of inflammation-sensitive proteins in the top quartiles and homocysteine concentration. In this population-based, prospective cohort study the occurrence of MI had no relationship to homocysteine baseline plasma level. Furthermore, there was no strong association between homocysteine and the concentrations of any of these inflammation-sensitive proteins.