Hyperhomocysteinemia is associated with impaired fracture healing in mice

Hyperhomocysteinemia (HHCY) has been shown to disturb bone metabolism and to increase the incidence of osteoporosis and osteoporotic fractures. However, there is a complete lack of information on whether these metabolic alterations affect bone repair. The aim of this study was to analyze the impact of HHCY on fracture healing. One group of mice was fed a homocystine-supplemented diet (n = 12), whereas another group received the accordant standard diet for control (n = 13). Four weeks after the stable fixation of a closed femoral fracture, animals were killed to prepare bones for histomorphometric and biomechanical analyses. In addition, blood samples were obtained to evaluate serum concentration of homocysteine (HCY). Quantitative analysis of blood samples revealed severe HHCY as indicated by significantly increased serum concentrations of HCY in animals fed the homocystine-supplemented diet (102.2 +/- 64.5 micromol/l) compared to controls (2.8 +/- 1.5 micromol/l). Biomechanical evaluation of bone repair revealed significantly decreased bending stiffness of the femora of homocystine-fed animals (45.5 +/- 18.2 N/mm) compared with controls (64.6 +/- 15.8 N/mm). Histomorphometric analysis demonstrated a slightly smaller callus diameter in HHCY animals but no significant differences in the tissue composition of the callus. In conclusion, the homocystine-supplemented diet leads to severe HHCY, which is associated with an impaired biomechanical quality of the healing bone.

Hyperhomocysteinemia induces a tissue specific accumulation of homocysteine in bone by collagen binding and adversely affects bone

BACKGROUND

Recently, hyperhomocysteinemia (HHCY) has been suggested to have adverse effects on bone. This study investigated if an experimental HHCY in rats induces an accumulation of homocysteine (HCY) in bone tissue that is accompanied by bone loss and reduced bone strength.

MATERIAL AND METHODS

HHCY was induced in healthy rats by either a methionine (Meth)- or a homocystine (Homo)-enriched diet and compared with controls. Homocystine is the product of two disulfide linked HCY molecules. Tissue and plasma concentrations of HCY, S-adenosylhomocysteine (SAH) and S-adenosylmethionine (SAM) were measured. Bones were assessed by biomechanical testing, histomorphometry, microCT and the measurement of biochemical bone turnover markers in plasma.

RESULTS

Meth and Homo animals developed a significant HHCY that was accompanied by a tissue specific accumulation of HCY (1300 to 2000% vs. controls). 65% of HCY in bone was bound to collagen of the extracellular matrix. The SAH / SAM-ratio in bone and plasma of Meth and Homo animals exhibited a tissue specific increase indicating a reduced methylation capacity. Accumulation of HCY in bone was characterized by a distinct reduction of cancellous bone (proximal femur: -25 to -35%; distal femur -56 to -58%, proximal tibia: -28 to -43%). Accordingly, bone strength was significantly reduced (-9 to -12%).

CONCLUSION

A tissue specific accumulation of HCY in bone may be a promising mechanism explaining adverse effects of HHCY on bone. A reduced methylation capacity of bone cells might be another relevant pathomechanism.

Low serum vitamin B12 is associated with recurrent pregnancy loss in Syrian women

BACKGROUND

Hyperhomocysteinemia and B-vitamin deficiency are associated with recurrent abortion. Recent studies have not investigated functional markers of vitamin B12 deficiency, such as methylmalonic acid.

METHODS

A total of 43 consecutive Syrian women with unexplained recurrent abortion and 32 pregnant controls were enrolled in the study. Serum folate, vitamin B12, methylmalonic acid and plasma homocysteine were determined.

RESULTS

Vitamin B12 was significantly decreased in patients with recurrent abortion compared to controls (mean concentrations 197 vs. 300 pg/mL, p=0.004). The lowest mean serum vitamin B12 (172 pg/mL) was observed in primary aborters. Homocysteine was elevated in aborters in comparison to controls (8.3 vs. 7.1 micromol/L, p=0.093). Folate and methylmalonic acid did not differ significantly between the study groups. A highly significant correlation between homocysteine and methylmalonic acid and vitamin B12 was observed only in patients but not in controls (p<0.001 and p=0.002, respectively). In the logistic regression model, only serum vitamin B12 emerged with a significant odds ratio.

CONCLUSIONS

The results confirm low serum vitamin B12 in recurrent abortion patients. However, methylmalonic acid did not support that functional vitamin B12 plays a role in this group. This unexpected result might be due to a decrease of the metabolically inert vitamin B12 fraction (holohaptocorrin) or confounding factors. Further studies are necessary to investigate the role of vitamin B12 deficiency in recurrent abortion.

Decreased p66Shc promoter methylation in patients with end-stage renal disease

BACKGROUND

p66Shc is a stress response protein and partially regulated by epigenetic modifications. Mice lacking p66Shc have reduced atherosclerosis, increased resistance to oxidative stress and a prolonged life time. The aim of the present study was to compare promoter methylation of the p66Shc gene between healthy controls and patients with end-stage renal disease (ESRD). There are two reasons for studying patients with ESRD. First, patients with ESRD have a disturbed homocysteine metabolism, and second an increased risk of morbidity and mortality from cardiovascular disease is a constant finding in these patients.

METHODS

In our study, we measured fasting levels of homocysteine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and 8-isoprostane in 22 patients and in 26 healthy, age- and sex-matched controls. The methylation of the p66Shc promoter and Line-1, as surrogate marker of whole genome methylation was quantified in peripheral blood mononuclear cells.

RESULTS

In comparison to the control group, homocysteine, SAM, SAH, 8-isoprostane and whole genome methylation were significantly elevated in ESRD patients, while the p66Shc promoter methylation was significantly reduced. A significant correlation was found between SAH and p66Shc promoter methylation in the patient group. This observation underlines the role of SAH as a potent inhibitor of methyltransferases. Using backward regression analysis, we demonstrated that 8-isoprostane has a significant influence on p66Shc promoter methylation. In the control group and in patients with ESRD, increasing 8-isoprostane levels were linked to an elevated promoter methylation.

CONCLUSIONS

Under physiological conditions, based on the results of the control group, the p66Shc expression is more silenced through epigenetic modifications. The atherosclerotic risk is dramatically increased in ESRD patients; therefore, our experimental results of methylation are in accordance with the clinical situation.

Disturbed homocysteine and methionine cycle intermediates S-adenosylhomocysteine and S-adenosylmethionine are related to degree of renal insufficiency in type 2 diabetes

BACKGROUND

Diabetic nephropathy is a common complication in patients with type 2 diabetes that may increase atherothrombotic risk. Hyperhomocysteinemia (HHcy) further increases the risk in those patients. We studied concentrations of total homocysteine (tHcy) and its related metabolites S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) in relation to B-vitamin status and renal function in patients with type 2 diabetes who developed diabetic nephropathy.

METHODS

The study included 93 patients with renal failure and type 2 diabetes. Chronic kidney disease was classified into four subgroups according to the National Kidney Foundation based on glomerular filtration rate plus pathologic abnormalities or markers of kidney damage.

RESULTS

Serum or plasma concentrations of the metabolites increased significantly with worsening of renal function, whereas serum concentrations of the B vitamins (folate, vitamins B12 and B6) did not differ appreciably between the groups. Moreover, plasma concentrations of AdoHcy and AdoMet were markedly increased in patients with kidney failure compared with those in stage 2 (median AdoHcy, 112.7 vs 10.5 nmol/L; median AdoMet, 162.0 vs 80.0 nmol/L). The AdoMet/AdoHcy ratio was more than 80% lower in patients with renal failure compared with stage 2. Vitamin B12 was a significant determinant of concentrations of AdoMet, tHcy, methylmalonic acid (MMA), and cystathionine.

CONCLUSIONS

Increased plasma concentrations of tHcy and methionine cycle intermediates (AdoMet, AdoHcy) are related to disturbed renal function in patients with type 2 diabetes. Vitamin B12 and/or folate are significant predictors of tHcy, cystathionine, MMA, and AdoMet. The effect of therapeutic doses of the B vitamins on AdoMet, AdoHcy, and their ratio should be tested in renal patients.

The usefulness of holotranscobalamin in predicting vitamin B12 status in different clinical settings

Serum concentrations of homocysteine (Hcy) and methylmalonic acid (MMA) become increased in B12-deficient subjects and are therefore, considered specific markers of B12 deficiency. Serum level of holotranscobalamin (holoTC) becomes decreased before the development of the metabolic dysfunction. We investigated the usefulness of holoTC in diagnosing B12 deficiency in some clinical settings. We measured serum concentrations of holoTC, MMA, Hcy and total B12 in omnivores, vegetarians, elderly people and haemodialysis patients. Our results indicated that the incidence of holoTC <35 pmol/L was highest in the vegans (76%). Low holoTC and elevated MMA were detected in 64% of the vegans and 43% of the lacto- and lacto-ovovegetarians. An elevated MMA and a low holoTC were found in subjects with total serum B12 as high as 300 pmol/L. The distribution of holoTC in elderly people was similar to that in younger adults (median holoTC 55 pmol/L in both groups). A low holoTC and an elevated MMA were found in 16% of the elderly group. An elevated MMA and a normal holoTC were found in 20% of the elderly group who had a relatively high median serum concentration of creatinine (106.1 micromol/L). Serum concentrations of holoTC in dialysis patients were considerably higher than all other groups (median 100 pmol/L). This was also associated with severely increased serum levels of MMA (median 987 nmol/L). From these results it can be concluded that serum concentration of holoTC is a much better predictor of B12 status than total B12. This was particularly evident in case of dietary B12 deficiency. Serum concentrations of holoTC as well as MMA can be affected by renal dysfunction. Elevated MMA and normal holoTC in patients with renal insufficiency may not exclude vitamin B12 deficiency. HoloTC seems not to be a promising marker in predicting B12 status in renal patients.

The vegetarian lifestyle and DNA methylation

Vegetarians have a lower intake of vitamin B

Homocysteine increases during endurance exercise

Hyperhomocysteinemia is a risk factor for cardiovascular and other diseases. Recently many endogenous and exogenous modulators of homocysteine (Hcy) have become known, e.g., B-vitamins. However, little is known about the effect of exercise on Hcy. The purpose of this study was to investigate the effect of three different types of acute endurance exercise on serum Hcy. We measured Hcy in 100 recreational athletes (87 males, 13 females) who participated in a marathon race (n = 46), a 100 km run (100 km; n = 12) or a 120 km mountain bike race (n = 42). Blood samples were taken before, 15 min and 3 h after the race. In athletes with pre-race Hcy > 12 micromol/l we also determined folate and vitamin B12. Marathon running induced a Hcy increase of 64%, while mountain biking and 100 km running had no significant effect on Hcy. Pre-race Hcy (25th-75th percentile) overall; marathon race; 100 km; mountain bike race was 9.7 (7.1-11.5) micromol/l; 9.8 (7.4-11.1) micromol/l; 10.2 (6.6-13.2) micromol/l; 9.1 (6.9-13.5) micromol/l, respectively. At 15 min and 3 h post-race, Hcy was 11.9 (8.4-16.4) micromol/l; 16.1 (12.7-20.4) micromol/l; 9.5 (7.8-15.9) micromol/l; 8.8 (7.1-11.2) micromol/l, respectively, and 11.5 (8.9-15.7) micromol/l; 14.9 (11.5-20.0) micromol/l; 10.0 (8.1-11.8) micromol/l; 9.4 (7.4-12.1) micromol/l, respectively. The change in Hcy correlated negatively with the running time. Twenty-three athletes had pre-race Hcy levels > 12 micromol/l, which were associated with relatively low folate (14.3 (11.6-18.9) nmol/l) and vitamin B12 levels (231 (183-261) pmol/l). Endurance exercise may induce a considerable Hcy increase, which varies between different disciplines and is most probably determined by the duration and intensity of exercise. Furthermore, about 25% of recreational endurance athletes exhibited hyperhomocysteinemia in association with low vitamin B12 and folate levels.

Comparison of the influence of volume-oriented training and high-intensity interval training on serum homocysteine and its cofactors in young, healthy swimmers

BACKGROUND

Since homocysteine (Hcy) is a risk factor for cardiovascular and other diseases, it is important to know how exercise can modify it. Previous studies have suggested that endurance training influences Hcy. However, little is known about the effect of training intensity on Hcy.

MATERIALS AND METHODS

We investigated Hcy, vitamin B12, vitamin B6, folate and methylmalonic acid (MMA) before and after 3 weeks of volume-oriented training (VOL) (30 km/week) and high-intensity interval training (HIT) (20 km/week) in 20 young swimmers (16 +/- 2 years). Afterward, the athletes completed 5 days of recovery training.

RESULTS

The training induced a Hcy increase in HIT and VOL (6.47 +/- 0.95 micromol/l vs. 7.44 +/- 1.17 micromol/l and 7.33 +/- 1.92 micromol/l vs. 8.28 +/- 1.42 micromol/l, respectively) that persisted during the recovery period (8.02 +/- 1.69 micromol/l and 8.00 +/- 1.81 micromol/l, respectively). Vitamin B12 was unchanged after the training (539 +/- 166 ng/l vs. 556 +/- 192 ng/l and 480 +/- 144 ng/l vs. 491 +/- 124 ng/l, respectively) but decreased during the recovery period (459 +/- 134 ng/l and 451 +/- 116 ng/l, respectively). Folate showed an increase during the training (9.07 +/- 2.01 microg/l vs. 11.71 +/- 4.08 microg/l and 10.34 +/- 2.32 microg/l vs. 11.13 +/- 4.64 microg/l, respectively), which was reversible by the end of the recovery training (8.57 +/- 1.98 microg/l and 9.60 +/- 2.38 microg/l, respectively). Vitamin B6 and MMA did not change. For none of the measured parameters were there significant differences between HIT and VOL.

CONCLUSION

Three weeks of strenuous swimming caused a prolonged Hcy increase, which was accompanied by changes in vitamin B12 and folate. The magnitude of these effects was not influenced by the training intensity.

Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians

BACKGROUND

Vegetarians have a lower intake of vitamin B-12 than do omnivores. Early and reliable diagnosis of vitamin B-12 deficiency is very important.

OBJECTIVE

The objective was to investigate vitamin B-12 status in vegetarians and nonvegetarians.

DESIGN

The study cohort included 66 lactovegetarians or lactoovovegetarians (LV-LOV group), 29 vegans, and 79 omnivores. Total vitamin B-12, methylmalonic acid, holotranscobalamin II, and total homocysteine concentrations were assayed in serum.

RESULTS

Of the 3 groups, the vegans had the lowest vitamin B-12 status. In subjects who did not consume vitamins, low holotranscobalamin II (< 35 pmol/L) was found in 11% of the omnivores, 77% of the LV-LOV group, and 92% of the vegans. Elevated methylmalonic acid (> 271 nmol/L) was found in 5% of the omnivores, 68% of the LV-LOV group, and 83% of the vegans. Hyperhomocysteinemia (> 12 micromol/L) was present in 16% of the omnivores, 38% of the LV-LOV group, and 67% of the vegans. The correlation between holotranscobalamin II and vitamin B-12 was weak in the low serum vitamin B-12 range (r = 0.403) and strong in the high serum vitamin B-12 range (r = 0.769). Holotranscobalamin II concentration was the main determinant of total homocysteine concentration in the vegetarians (beta = -0.237, P < 0.001). Vitamin B-12 deficiency led to hyperhomocysteinemia that was not probable in the upper folate range (> 42.0 nmol/L).

CONCLUSIONS

Vegan subjects and, to a lesser degree, subjects in the LV-LOV group had metabolic features indicating vitamin B-12 deficiency that led to a substantial increase in total homocysteine concentrations. Vitamin B-12 status should be monitored in vegetarians. Health aspects of vegetarianism should be considered in the light of possible damaging effects arising from vitamin B-12 deficiency and hyperhomocysteinemia.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism and the B-vitamins: a facet of nature-nurture interplay

BACKGROUND

Methylenetetrahydrofolate reductase 677 (MTHFR 677) polymorphism may provoke hyperhomocysteinemia when folate status is low. The influence of MTHFR 677 mutation on homocysteine (HCY) levels in relation to vitamin B12 and folate status was investigated in the current study.

SUBJECTS AND METHODS

113 vegetarians, 123 omnivorous Germans, and 117 omnivorous Syrians were recruited. MTHFR 677 genotype, HCY, methylmalonic acid (MMA), total serum vitamin B12, serum folate, and vitamin B6 were determined using conventional methods.

RESULTS

Omnivorous Germans displayed the lowest HCY levels compared with vegetarians and Syrians (median 8.0, 10.4, and 11.3 micromol/l, respectively). The highest serum folate and the highest MMA levels were found in vegetarians (median folate = 30.0; MMA = 355 nmol/l). Among vegetarians and Syrians, TT subjects had higher HCY levels than other genotypes which were, however, no longer significant in the highest folate tertiles. When the data were pooled, the odds ratio (OR, 95% CI) for HCY > 12 micromol/l was 3.81 (1.55-9.34) in TT compared with CC subjects. The OR increased to 28.85 (4.63-179.62) in TT subjects who had folate in the lowest tertile, and to 21.84 (4.81-99.1) in TT subjects who had MMA in the highest MMA tertile.

CONCLUSION

MTHFR 677 TT individuals are more liable to hyperhomocysteinemia under vitamin B12 deficiency than the other two genotypes. In such a case, relative folate shortage may progressively increase HCY levels. TT individuals may have increased folate and vitamin B12 requirements compared to the other CC and CT genotypes.

Functional Vitamin B12 Deficiency and Determination of Holotranscobalamin in Populations at Risk

BACKGROUND

The prevalence of a sub-clinical functional vitamin B12 deficiency in the general population is higher than previously expected. Total serum vitamin B12 may not reliably indicate vitamin B12 status. To get more specificity and sensitivity in diagnosing vitamin B12 deficiency, the concept of measuring holotranscobalamin II (holoTC), a sub-fraction of vitamin B12, has aroused great interest. HoloTC as a biologically active vitamin B12 fraction promotes a specific uptake of its vitamin B12 by all cells. In this study we investigated the diagnostic value of storage (holoTC) of vitamin B12 and functional markers (methylmalonic acid (MMA)) of vitamin B12 metabolism in populations who are at risk of vitamin B12 deficiency.

SUBJECTS AND METHODS

Our study included 93 omnivorous German controls, 111 German and Dutch vegetarian subjects, 122 Syrian apparently healthy subjects, 127 elderly Germans and finally 92 German pre-dialysis renal patients. Serum concentrations of homocysteine (Hcy) and MMA were measured by gas chromatography-mass spectrometry, folate and vitamin B12 by chemiluminescence immunoassay, and holoTC by utilizing a RIA test.

RESULTS

High Hcy (>12 micromol/l), high MMA (>271 nmol/l) resp. low holoTC (vitamin B12) in serum were detected in 15%, 8% resp. 13% (1%) of German controls, 36%, 60%, resp. 72% (30%) of vegetarians, 42%, 48% resp. 50% (6%) of Syrians, 75%, 42%, resp. 21% (7%) of elderly subjects and 75%, 67% resp. 4% (2%) of renal patients. The lowest median levels of holoTC were observed in vegetarians, followed by the Syrian subjects (23 and 35 pmol/l, respectively). Renal patients had significantly higher levels of holoTC compared to the German controls (74 vs. 54 pmol/l). In the vitamin B12 range between 156 pmol/l (conventional cut-off level) and 241 pmol/l, both mean concentrations of holoTC and MMA were in the pathological range. HoloTC was the earliest marker for vitamin B12 deficiency followed by MMA. Vitamin B12 deficiency causes folate trapping. A higher folate level is required to keep Hcy normal. The relationship between MMA and holoTC seemed dependent on renal function. In renal patients with a glomerular filtration rate below 36 ml/min, a significantly lower mean level of MMA was detected within the highest tertile of holoTC concentration, compared to the lowest tertile. Thus, in renal patients, a higher serum concentration of circulating holoTC is required to deliver sufficient amounts of holoTC into the cells.

CONCLUSION

Our data support the concept that the measurement of holoTC and MMA provides a better index of cobalamin status than the measurement of total vitamin B12. HoloTC is the most sensitive marker, followed by MMA. The use of holoTC and MMA enables us to differentiate between storage depletion and functional vitamin B12 deficiency. Renal patients have a higher requirement of circulating holoTC. In renal dysfunction, holoTC cannot be used as a marker of vitamin B12 status.

The Role of Genetic Factors in the Development of Hyperhomocysteinemia

Moderate hyperhomocysteinemia has been identified as a new independent risk factor for cardiovascular and neurodegenerative diseases. This fact has produced interest in the study of genetic variants involved in homocysteine metabolism and its relationship to pathogenesis. Recently, more than 15 different genes were studied for their relationship to plasma homocysteine levels. We determined the influence of genetic variants in five genes (5,10-methylenetetrahydrofolate reductase (MTHFR) 677C --> T, serine hydroxymethyltransferase (SHMT) 1420C --> T, thymidylate synthase (TS) 2R --> 3R, catechol-O-methyltransferase (COMT) 1947G --> A and transcobalamin (TC) 776C --> G) on plasma homocysteine, folic acid and parameters of vitamin B12 metabolism in 111 vegetarians (mean age: 46 +/- 15 years) and 118 healthy seniors (mean age: 82 +/- 6.5 years). Median homocysteine concentration in plasma was significantly influenced by the MTHFR genotypes in both populations. In the vegetarians the median homocysteine level was increased by 8 micromol/l in individuals homozygous for the mutation as compared to wild-type or heterozygous genotypes (20.4 micromol/l vs. 12.9 and 12.7 micromol/l, respectively). This unexpected increase was observed although the folate levels were in medium to elevated ranges. Our results suggest that vegetarians have a higher demand for folate to neutralize the genotype effect. Preclinical vitamin B12 deficiency in vegetarians may be the cause for disturbed remethylation and folate trap. Plasma homocysteine was not significantly influenced by the SHMT, TS, COMT and TC mutations. In addition, for the TC mutation a trend toward cellular vitamin B12 deficiency was observed. The methylmalonic acid (MMA) levels were slightly elevated and the holotranscobalamin-II (holoTC-II) levels decreased. In the vegetarian group a significant relationship between the COMT genotype and holoTC-II concentration in plasma was determined, whereas the high activity COMT genotype (G/G) resulted in increased levels (35 micromol/l vs. 21 micromol/l for heterozygous and low activity genotypes). The MMA levels were inversely correlated to holoTC-II concentrations. In conclusion, the study on vegetarians and seniors documents interesting lifestyle-genotype interactions. Although the TC and COMT mutations influence cellular vitamin B12 metabolism, this effect did not result in overt homocysteine elevation.

The impact of vegetarianism on some haematological parameters

OBJECTIVE

Subjects adopting a vegetarian diet are liable to vitamin B12 and iron deficiencies. Co-existing vitamin B12 and iron deficiencies may give an equivocal haematological picture, which may, in turn, delay making an early diagnosis. The current work was undertaken to investigate some haematological parameters in relation to vitamin B12 and iron status in vegetarians.

SUBJECTS AND METHODS

Twenty-nine vegans, 64 lacto- and lacto-ovo-vegetarians, in addition to 20 occasional meat eaters, were enrolled for this study. The total group included 49 males and 64 females aged [mean (SD) = 46(15) yr]. Complete blood count, methylmalonic acid (MMA), homocysteine (HCY), ferritin, and transferrin concentrations and percentage transferrin saturation were assayed, using conventional methods.

RESULTS

Vegans displayed the highest MMA and HCY levels (median MMA = 708 nmol L(-1); HCY = 12.8 micromol L(-1)). A lower lymphocyte count and a higher mean corpuscular volume (MCV) were found in vegans compared with lacto- or lacto-ovo-vegetarians (median = 1.51 x 10(9) vs. 1.83 x 10(9) L(-1); 92 vs. 89 fL, respectively). Vitamin B12-deficient subjects in the higher range of transferrin saturation percentage had higher MCV than vitamin B12-deficient subjects in the lower transferrin saturation range (mean MCV = 92 vs. 89 fL). A lower platelet count was found in the highest quartile of MMA (mean = 211 x 10(9) L(-1)) and in the highest quartile of HCY (mean = 215 x 10(9) L(-1)), compared with the other quartiles. Lower lymphocyte and platelet counts and higher MCV were found in subjects with elevated MMA and HCY, compared to those with normal metabolites. Factors that explained the variations in MCV were red blood cell count, ferritin, transferrin saturation, and methylmalonic acid levels.

CONCLUSION

vitamin B12 and iron status were compromised by a vegetarian diet. Variations in mean corpuscular volume were determined by iron and vitamin B12 status. Lower lymphocyte and platelet count were accompanied by metabolic evidence that indicated vitamin B12 deficiency.

Homocysteine levels in patients treated with lipid apheresis: effect of a vitamin therapy

BACKGROUND

Patients treated with lipid apheresis already suffer from familial hypercholesterolemia and severe coronary heart disease: any additional risk factor is dangerous for these patients. Hyperhomocysteinemia has been recognized as an independent risk factor for atherosclerotic disease. We checked the frequency of hyperhomocysteinemia in lipid apheresis patients and measured the effect of a vitamin therapy.

MATERIALS AND METHODS

Sixteen heterozygous patients (10 males, 6 females) were studied, who were being treated by three different apheresis procedures. Homocysteine was measured using an enzyme conversion immunoassay. Cystathionine and methylmalonic acid were assessed by gas chromatography/mass spectrometry. Serum levels of folic acid, vitamin B12, and vitamin B6 were also determined. The patients received a vitamin therapy (3 mg folate, 60 microg cyanocobalamine, 10 mg pyridoxine hydrochloride daily) for 12 weeks.

RESULTS

In 9 out of 16 patients, plasma homocysteine levels were found to be elevated (> 12 micromol L(-1)). Cystathionine concentrations were also increased, especially in those patients with elevated homocysteine. Methylmalonic acid levels were not elevated. Serum folic acid, vitamin B6, and vitamin B12 concentrations were initially in the normal range and not correlated to plasma homocysteine. The vitamin therapy reduced the plasma homocysteine concentrations in all patients significantly by 33%. Among those patients with elevated homocysteine levels, the optimal range < 12 micromol L(-1) for homocysteine was rarely reached.

CONCLUSIONS

In patients treated with lipid apheresis, a hyperhomocysteinemia can be frequently seen. The constellation of both elevated homocysteine and cystathionine levels points to the existence of tissue vitamin deficiencies, folate and vitamin B-6, which were improved by vitamin supplements. Because methylmalonic acid was mostly normal, a vitamin B-12 deficiency was not proven.

Genetic defects as important factors for moderate hyperhomocysteinemia

The genes for the enzymes methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MS), methionine synthase reductase (MSR) and cytathionine-beta-synthase (CBS) play an important role in homocysteine metabolism. Rare mutations in these genes cause severe hyperhomocysteinemia and clinical symptoms. Growing interest has focused on common mutations with moderate effects on homocysteine levels. We studied 280 subjects of different age groups for the following mutations: MTHFR677C-->T and 1298A-->C, MS2756A-->G, MSR66A-->G and the 68 bp insertion in the CBS gene. The median value for homocysteine increased significantly with age (median homocysteine levels: 7.5, 12.4 and 16.5 micromol/l in the age groups 20-43, 65-75 and 85-96 years, respectively). The genotypes of the MTHFR677C-->T mutation were associated with differences in plasma homocysteine levels, but without reaching significance. Individuals homozygous for the MTHFR677C-->T mutation had a 2.3 micromol/l higher median homocysteine level compared to individuals with the wild-type allele. This effect was pronounced in combination with low folate levels and abolished with higher folate in plasma. For the other three mutations no association with homocysteine values could be determined. The analysis of homocysteine metabolite cystathionine by backward regression analysis revealed a significant correlation of the MS2756A-->G mutation with cystathionine level. This increase could indicate a disturbed remethylation. In summary, larger and homogeneous study populations are necessary to quantify the small effects of common mutations on homocysteine levels. This may also be the reason that no effects of genetic interactions between two genotypes were observed.

Homocysteine, cystathionine, methylmalonic acid and B-vitamins in patients with renal disease

Moderate hyperhomocysteinemia is very frequent in renal patients. Aside from homocysteine (HCY) itself, the metabolites methylmalonic acid (MMA) and cystathionine (CYS) supply further information about disturbances in HCY metabolism. In two groups of renal patients, transplant and hemodialysis patients, we measured HCY, MMA and CYS and evaluated their diagnostic value for impaired HCY metabolism due to vitamin deficiency and renal insufficiency. We investigated serum samples from 63 transplant patients and 38 patients undergoing hemodialysis. HCY, MMA and CYS were assayed by gas chromatography-mass spectrometry, vitamin B6 by HPLC, B12 and folate by chemiluminescence immunoassay. The determination of HCY, MMA, and CYS in renal patients provides specific information about intracellular disturbances of HCY metabolism. The frequency of increased metabolite levels in renal patients was much higher than the frequency of lowered vitamin concentrations in serum. Furthermore, the metabolite levels in transplant patients were only moderately increased, whereas they were strongly increased in patients on hemodialysis (HCY 19.2 vs. 28.8 micromol/l, MMA 292 vs. 1025 nmol/l, CYS 733 vs. 2711 nmol/l). Our findings may support the use of MMA determination in the diagnosis of vitamin B12 deficiency in renal patients. Compared to vitamin B12 deficiency, renal dysfunction itself appears to cause only a modest elevation in serum MMA. Regression analysis revealed that the moderate elevation of HCY and CYS in transplant patients is mainly a consequence of impaired remethylation of HCY to methionine with activated transsulfuration, whereas the mildly elevated MMA level is attributable to renal dysfunction. In patients on hemodialysis, all three metabolites were markedly elevated, indicating a strongly disturbed HCY metabolism. Based on a backward regression, we discovered that the HCY metabolism was strongly disturbed by renal insufficiency and vitamin deficiency. The markedly elevated HCY level was mainly attributable to functional vitamin B12 deficiency indicated by high MMA, and the strong CYS elevation was due to renal dysfunction and inhibition of this pathway by low levels of vitamin B6. In conclusion, besides HCY, the determination of MMA and CYS levels supports an early diagnosis of B-vitamin deficiency in renal patients. MMA is a more sensitive indicator of intracellular vitamin B12 deficiency than vitamin B12 in serum.

Total homocysteine, vitamin B(12), and total antioxidant status in vegetarians

BACKGROUND

Decreasing or eliminating animal products from the diet decreases the intake of some essential nutrients, such as vitamin B(12), which may lead to hyperhomocysteinemia. We investigated vitamin B(12)-dependent metabolism and oxidative stress in groups with various or no intake of meat or animal products.

METHODS

We investigated 44 high meat eaters, 19 low meat eaters, 34 lacto-ovo/lacto vegetarians, and 7 vegan vegetarians. Homocysteine (HCY) was assayed by HPLC, methylmalonic acid (MMA) by capillary gas chromatography-mass spectrometry, serum folate and vitamin B(12) with a chemiluminescence immunoassay, and total antioxidant status (TAS) by a Randox method.

RESULTS

The mean serum HCY concentration of vegetarians was significantly increased, and in vegans the median concentration exceeded 15 micromol/L. Vegetarians had a higher serum concentration of MMA but a lower TAS. Vitamin B(12) and folate did not differ significantly between vegetarian and omnivorous subjects. Overall, HCY and MMA were significantly correlated. Vitamin B(12) correlated negatively with MMA, HCY, and folate, whereas the correlation with TAS was positive. Backward regression analysis revealed an independent influence of MMA on HCY, of HCY and vitamin B(12) on MMA, and of vitamin B(12) on TAS. The increased MMA concentration suggested a 25% frequency of functional vitamin B(12) deficiency in all vegetarians. Serum vitamin B(12) was below the lower reference limit in only five subjects.

CONCLUSIONS

Functional vitamin B(12) deficiency in vegetarians may contribute to hyperhomocysteinemia and decreased TAS, which may partly counteract the beneficial lifestyle of vegetarians. However, increased serum HCY is most likely not responsible for the lower TAS values in vegetarians. We recommend assaying of MMA and HCY to investigate functional vitamin B(12) status.

Total Homocysteine, Vitamin B12, and Total Antioxidant Status in Vegetarians

Background: Decreasing or eliminating animal products from the diet decreases the intake of some essential nutrients, such as vitamin B12, which may lead to hyperhomocysteinemia. We investigated vitamin B12-dependent metabolism and oxidative stress in groups with various or no intake of meat or animal products.

Methods: We investigated 44 high meat eaters, 19 low meat eaters, 34 lacto-ovo/lacto vegetarians, and 7 vegan vegetarians. Homocysteine (HCY) was assayed by HPLC, methylmalonic acid (MMA) by capillary gas chromatography–mass spectrometry, serum folate and vitamin B12 with a chemiluminescence immunoassay, and total antioxidant status (TAS) by a Randox method.

Results: The mean serum HCY concentration of vegetarians was significantly increased, and in vegans the median concentration exceeded 15 μmol/L. Vegetarians had a higher serum concentration of MMA but a lower TAS. Vitamin B12 and folate did not differ significantly between vegetarian and omnivorous subjects. Overall, HCY and MMA were significantly correlated. Vitamin B12 correlated negatively with MMA, HCY, and folate, whereas the correlation with TAS was positive. Backward regression analysis revealed an independent influence of MMA on HCY, of HCY and vitamin B12 on MMA, and of vitamin B12 on TAS. The increased MMA concentration suggested a 25% frequency of functional vitamin B12 deficiency in all vegetarians. Serum vitamin B12 was below the lower reference limit in only five subjects.

Conclusions: Functional vitamin B12 deficiency in vegetarians may contribute to hyperhomocysteinemia and decreased TAS, which may partly counteract the beneficial lifestyle of vegetarians. However, increased serum HCY is most likely not responsible for the lower TAS values in vegetarians. We recommend assaying of MMA and HCY to investigate functional vitamin B12 status.

Role of homocysteine, cystathionine and methylmalonic acid measurement for diagnosis of vitamin deficiency in high-aged subjects

BACKGROUND

Intracellular B-vitamin and folate deficiency indicated by hyperhomocysteinemia is very frequent in the elderly population. Hyperhomocysteinemia increases the risk of atherothrombotic diseases and neuropsychiatric complications. Our aim was to evaluate the prevalence of increased serum metabolite concentrations in subjects of a higher age, and whether the measurement of metabolite concentrations is more effective in diagnosing B-vitamin deficiency than mere homocysteine.

MATERIALS AND METHODS

Homocysteine (HCY), cystathionine (CYS) and methylmalonic acid (MMA) were investigated in serum together with vitamin B-12, B-6 and folate in 90 high-aged subjects (85-102 years), 92 seniors (65-75 years), and in 50 younger subjects (19-50 years).

RESULTS

Elderly subjects (high-aged and senior) had elevated serum concentrations of metabolites. High-aged subjects had a higher frequency of pathological increases than seniors: HCY 62% vs. 24%; MMA 62% vs. 23%; CYS 81% vs. 36%. Folate and vitamin B-6 concentrations were significantly decreased in both elderly groups; vitamin B-12 was only decreased in high-aged subjects. Utilising vitamin B-6, B-12 and folate for diagnosis of intracellular vitamin deficiency, the rate was 30% in seniors and 55% in high aged subjects. However, utilising the metabolites (HCY, MMA and CYS) for the diagnosis of intracellular vitamin deficiency, there was a distinctly increased rate of 55% in seniors respective to 90% in high-aged subjects. Backward multiple regression analysis revealed that only folate, MMA, creatinine and age were independent variables influencing the HCY concentration. Furthermore, the MMA concentration was significantly and independently influenced by folate, vitamin B-12, HCY and creatinine, and the serum concentration of CYS by vitamin B-12, creatinine and age.

CONCLUSION

The metabolites HCY, MMA and CYS are sensitive indicators diagnosing impaired remethylation of homocysteine to methionine with parallel activation of catabolic pathway. Compared to mere HCY or B-vitamins in serum, the efficiency of diagnosing a disturbed HCY metabolism increases very much in utilising the metabolites HCY, MMA and CYS. For differential diagnosis, parallel measurement of folate and creatinine is recommended. The early and correct diagnosis of B-vitamin deficiency in elderly subjects is of high clinical relevance.

Measurement of thiols in human plasma using liquid chromatography with precolumn derivatization and fluorescence detection

A liquid chromatography (LC) method for the simultaneous measurement of the main low molecular mass thiols (i.e., cysteine, cysteinylglycine, homocysteine, and glutathione) in human plasma is described. The sample treatment consists of the reduction of disulfide bounds with tri-n-butylphosphine and protein precipitation with trichloroacetic acid followed by precolumn derivatization with a thiol-selective fluorogenic reagent (7-fluoro-2,1,3-benzoxadiazole-4-sulfonamide). The structure of thiol derivatives is assessed using electrospray ionization-mass spectrometry (MS). The stability of resulting adducts in acidic medium (24 h at 10 degrees C) allows the automation of the technique and a high throughput of samples (approximately 50 per day). Separation is complete within 12 min using isocratic reversed-phase mode, and detection is operated by spectrofluorimetry (lambda ex = 385 nm and lambda em = 515 nm). Quantitation is performed by an internal standardization mode using thioglycolic acid. The LC method is fully validated, and homocysteine concentrations obtained in plasma samples are compared with values measured using either fluorescence polarization immunoassay or capillary gas chromatography-MS; a good correlation is observed between LC and both methods. The method has been applied in daily use to a large-scale study in a human healthy population, and some resulting data are discussed.

A new serial transfer explant cell culture system for human prostatic cancer tissues preventing selection toward diploid cells

An improved explant cell culture technique to avoid selection of prostatic adenocarcinoma cells toward diploid cells is described. This method is based on 1) histologically characterized tissue explants, 2) the use of polyethylenteraphthalate (PET) membranes as growth surface, which are part of special inserts in six-well-plates to allow 3) cocultivation with heterologous fibroblasts, and 4) coating of the membranes with elements of the extracellular matrix. The main characteristic of this particular approach is the serial transfer of the tissue explant from one membrane to the other. Up to ten serial transfer steps could be performed to produce cell monolayers growing out of the same tissue specimen. Using this approach, 21 prostatic carcinoma specimens that were obtained from 13 primary prostatic adenocarcinomas after radical prostatectomy were cultivated. Ploidy of the cells was monitored by fluorescence in situ DNA hybridization using the centromere specific DNA probes pUC1.77, p alpha 7t1, and pY3.4. Interestingly, a high aneuploidy rate of the cell cultures was found with maintainance of aneuploidy in 18 (86%) of the 21 paraffin-embedded cancer tissue specimens with proved aneuploidy. Although a slight decrease of the proportion of aneuploid cells during serial transfer was observed, significant aneuploid cell populations were retained up to a maximum of ten transfer steps. These findings indicate that selection toward diploid cells can be prevented by improved cell culture techniques that mimic the in vivo situation.