Francesca Sampietro

Telomere Length in Peripheral Blood Mononuclear Cells Is Associated with Folate Status in Men

Human chromosomes are capped by telomeres, which consist of tandem repeats of DNA and associated proteins. The length of the telomeres is reduced with increasing cell divisions except when the enzyme telomerase is active, as in stem cells and germ cells. Telomere dysfunction has been associated with development of age-related pathologies, including cancer, cardiovascular disease, Alzheimers disease, and Parkinsons disease. DNA damage in the telomeric region causes attrition of telomeres. Because folate provides precursors for nucleotide synthesis and thus affects the integrity of DNA, including that of the telomeric region, folate status has the potential to influence telomere length. Telomere length is epigenetically regulated by DNA methylation, which in turn could be modulated by folate status. In this study, we determined whether folate status and the 677C > T polymorphism of the methylene tetrahydrofolate reductase (MTHFR) gene are associated with the telomere length of peripheral blood mononuclear cells in healthy men. The results of our study showed that plasma concentration of folate was associated with telomere length of peripheral blood mononuclear cells in a nonlinear manner. When plasma folate concentration was above the median, there was a positive relationship between folate and telomere length. In contrast, there was an inverse relationship between folate and telomere length when plasma folate concentration was below the median. The MTHFR 677C > T polymorphism was weakly associated (P = 0.065) with increased telomere length at below-median folate status. We propose that folate status influences telomere length by affecting DNA integrity and the epigenetic regulation of telomere length through DNA methylation.

Hyperhomocysteinaemia and poor vitamin B status in chronic obstructive pulmonary disease

BACKGROUND AND AIMS Patients with chronic obstructive pulmonary disease (COPD) are at increased atherothrombotic risk. Preliminary findings have suggested that COPD patients may have increased plasma total homocysteine (tHcy), a cardiovascular risk factor often caused by a poor B vitamin status, but plasma levels of such vitamins were not measured. The aim of this study was to investigate hyperhomocysteinaemia in COPD and to determine whether it may be secondary to poor plasma concentrations of B vitamins. METHODS AND RESULTS We performed a case-control, cross-sectional study of 42 patients with COPD and 29 control subjects. Folate, vitamin B12, vitamin B6, tHcy, renal function, C-reactive protein, blood gases and lipids were measured in patients and controls. COPD patients had higher plasma tHcy (median: 13.9mumol/l, interquantile range [IQR]: 12.1-18.5 versus 11.5, IQR: 10.1-14, p=0.002) and lower circulating folate (median: 2.5ng/ml, IQR: 1.2-3.3 versus 2.8, IQR: 2.1-4 of controls, p=0.03) than controls had. Compared to the control group, COPD was associated with higher tHcy concentrations also after adjusting for smoking, heart failure, renal function and C-reactive protein with logistic regression analysis (OR 1.36, 95% CI 1.06-1.72, p=0.01). In the COPD group, low levels of folate (beta=-0.27, p=0.02) and vitamin B12 (beta=-0.24, p=0.04), and hypertriglyceridaemia (beta=0.580, p<0.0001) were independent predictors of the presence of high tHcy concentrations in a multiple linear regression model (adjusted R(2)=0.522). CONCLUSION COPD patients have a poor B vitamin status and, as a consequence, increased tHcy. These abnormalities may contribute to the COPD-related atherothrombotic risk.

Evaluation of the prevalence of severe hyperhomocysteinemia in adult patients with thrombosis who underwent screening for thrombophilia

INTRODUCTION Treatment with B-vitamins and betaine reduces the high risk of thrombosis in patients with homocystinuria, a metabolic syndrome that is characterized by severe hyperhomocysteinemia (HHcy). In contrast, there is no clear demonstration that B-vitamins reduce the risk of thrombosis in patients with mild HHcy: for this reason, many question the clinical utility of measuring total Hcy (tHcy) in patients with thrombosis. However, thrombosis may be the first clinical manifestation of homocystinuria in patients reaching adulthood without signs and symptoms of the syndrome. AIM 1) to measure the prevalence of severe, previously undiagnosed, HHcy among patients with thrombosis 2) to profile these patients on the basis of their characteristics. METHODS Six Italian Thrombosis Centers completed a first questionnaire, reporting tHcy levels in patients with thrombosis who underwent thrombophilia screening, and a second questionnaire, reporting the characteristics of patients with severe HHcy (tHcy>100μmol/L). RESULTS Of 19,678 cross-sectionally collected patients with thrombosis who underwent thrombophilia screening in the last 12.5years (median value, range 6-17), 38 had severe HHcy (0.2%). Their median age at diagnosis was 47years (range 19-83) and the median level of tHcy was 130μmol/L (range 101-262). Venous thromboembolism (71%) was more frequent than arterial thromboembolism (26%); recurrent thrombosis occurred in 42% of cases. CONCLUSIONS Measurement of tHcy in adult patients with thrombosis may reveal the presence of severe HHcy. Since treatment of patients with severe HHcy decreases the risk of thrombosis, measurement of tHcy in patients with thrombosis may prove clinically useful.

Genotype-independent in vivo oxidative stress following a methionine loading test: Maximal platelet activation in subjects with early-onset thrombosis

BACKGROUND Methionine ingestion (100mg/kg) identifies subjects in whom fasting total homocysteine (tHcy) may be normal but the post-methionine load (PML) tHcy is abnormally high. METHODS In 96 subjects [54 M/42 F, 40.4 ± 12.3 yrs old; 28 with the 68 bp844 ins of the cystathionine-β-synthase gene (CBSins+); 20 homozygotes for the C677T mutation of the methylene-tetrahydrofolate reductase gene (MTHFR++); 13 with the combination of the two, and 35 without any of them], we have evaluated in vivo oxidative stress and platelet activation, as reflected by urinary excretions of 8-iso-PGF(2α) and of 11-dehydro-TXB(2) respectively, before and after a methionine load test (PML). A history of early-onset thrombosis (18 arterial, 32 venous, 2 both) was present in 52/96 of them. RESULTS Baseline; tHcy was highest in MTHFR++ carriers (p < 0,05); 8-iso-PGF(2α) and 11-dehydro-TXB(2) levels were independent of sex, MTHFR++ and/or CBSins + (p > 0.05). PML; The ~3-fold increase (p < 0.01 vs baseline) in tHcy reached a plateau within 6-8 hrs. Mean PML tHcy was maximal in MTHFR++ carriers (p = 0.000). 8-iso-PGF(2α) and 11-dehydro-TXB(2) increase reached a maximum within 4 hrs. 11-dehydro-TXB(2) increase was highest (p = 0.023 vs baseline) in subjects with a history of thrombosis. Baseline 11-dehydro-TXB(2) and a history of thrombosis independently predicted PML 11-dehydro-TXB(2) (β = 0.287, p = 0.000 and β = 0.308, p = 0.026, respectively).The PML increase in 8-iso-PGF(2α) or in 11-dehydro-TXB(2) were comparable in the different genotypes (p > 0.05). CONCLUSION Regardless genotypes associated with moderate hyperhomocysteinemia, following a methionine loading test, in vivo oxidative stress and platelet activation occur, being the latter maximal in subjects with a history of early-onset thrombosis.

Poor vitamin B6 status: A novel potential thrombotic factor in chronic obstructive pulmonary disease

Vitamin B6 participates as a coenzyme to >100 reactions and is required for the degradation of homocysteine, a strong predictor of atherothrombotic events. Low circulating vitamin B6, however, predisposes to arterial and venous thrombosis, independently of hyperhomocysteinaemia [1]. Populations studies suggest an intriguing link between low vitamin B6 and systemic chronic inflammation, presumably because vitamin B6 is consumed during inflammation [2]. Chronic Obstructive Pulmonary Disease (COPD) is a long-lasting systemic inflammatory illness and confers an independent higher risk of atherothrombotic events [3]. While investigating hyperhomocysteinaemia in COPD, we have described for the first time lower vitamin B6 plasma concentrations in COPD patients than in matched controls [4]. We have now re-analyzed our study sample to determine the mechanisms accounting for this COPD-related poor vitamin B6 status. Vitamin B6 was measured in 38 COPD outpatients (mean age standard deviation 71.4 7.9, 32 males) and in 30 non-COPD controls (70.6 5.74, 22 males) [4]. All participants were asked not to change their usual dietary habits. Pyridoxal-50-phosphate, the phosphorylated compound of vitamin B6, was measured by a home-made radioimmunoassay [5]. Plasma vitamin B6 was significantly lower in COPD patients than in controls (41.2 34.7 versus 56.7 33.1 nmol/l, pZ 0.03), and 30 out of the 38 patients with COPD (78.9%) had vitamin B6 below the median value of the control group (Fig. 1). In the total sample of COPD patients and controls (n Z 68), vitamin B6 significantly correlated with forced expiratory volume in 1 s, % predicted, (FEV1%) (r Z 0.24, p Z 0.04), FEV1/forced vital capacity (FEV1/FVC) (r Z 0.30, p Z 0.01), C-reactive protein (CRP) (r Z 0.25, p Z 0.04) and with folic acid (r Z 0.47, p < 0.0001). Among COPD patients (n Z 38), vitamin B6 significantly correlated with FEV1/FVC (r Z 0.32, p Z 0.04). In the total group, low FEV1/FVC (p Z 0.03) and low folate (p Z 0.009), were independent