Update on genetic risk factors for thrombosis and atherosclerotic vascular disease

Systemic chemotherapy interferes in homocysteine metabolism in breast cancer patients

BACKGROUND

Hyperhomocysteinemia in breast cancer (BC) patients can be a risk factor for thromboembolic events. This study aimed to evaluate homocysteine and its cofators (folic acid and vitamin B12) concentrations and platelet count at diagnosis of BC, 3 and 6 months after the beginning of chemotherapy treatment and to correlate them with clinical data.

METHODS

Thirty-five BC patients were included; blood samples were obtained by venipuncture. Plasmatic Hcy and cofactors concentrations were measured by competitive chemiluminescent enzyme immunoassay method. Platelet count was done using an automated analyzer. Statistical analysis was performed using the software SPSS.

RESULTS

During chemotherapy, homocysteine (P = 0.032) and vitamin B12 (P < 0.001) concentrations increased, while folate and platelets decreased (P < 0.001). Among the clinical data, the menopausal status showed significant positive correlation (P = 0.022) with homocysteine concentration increase.

CONCLUSIONS

Evaluation of homocysteine concentrations during chemotherapy is extremely important because their levels increase during chemotherapy treatment, thus increasing the risk of thromboembolism development.

Elevated levels of plasma homocysteine in postmenopausal women in Burkina Faso

BACKGROUND

Low levels of plasma homocysteine have been found in children and adult populations living in Burkina Faso in association with a low prevalence of coronary heart disease.

METHODS

Based on this finding, the levels of plasma homocysteine and other thiols (cysteine, cysteinylglycine, glutathione) in postmenopausal women living in Burkina Faso were evaluated with the aim of investigating whether age and life conditions influence plasma homocysteine and other thiol levels.

RESULTS

It was found that in older postmenopausal women the mean level of homocysteine was higher (16.4+/-6.6 micromol/L) than in fertile women (6.8+/-1.2 micromol/L) and that this increase was correlated with cysteine levels (166.6+/-44.6 micromol/L). While the glutathione level in postmenopausal women was lower (3.6+/-2.3 micromol/L) compared with fertile women (7.0+/-1.7 micromol/L), cysteinylglycine levels were within the normal range (29.9+/-9.3 micromol/L). No correlation was found between homocysteine levels and serum folate, vitamin B(12), vitamin B(6), cystatin C and serum creatinine levels. The older the women were, the higher were their plasma homocysteine levels: levels up to 20.2+/-9.1 micromol/L were found in those >70 years old.

CONCLUSIONS

The elevated levels of homocysteine in the postmenopausal women of Burkina Faso must be viewed as a characteristic of older age and its metabolic consequences.

Elevated plasma total homocysteine in centenarians

Homocysteine (Hcy) is a sulfur-containing metabolite of methionine and is an emerging independent risk factor for atherosclerosis. Previous studies have shown that age, gender, renal function and folic acid intake are the main factors influencing total plasma Hcy levels in humans. A unique approach to the science of human longevity is the natural model of centenarians. The objective of this study was to verify whether the previously determined risk factors for atherosclerosis and atherosclerosis-related diseases change with age and, finally, to establish the vitamin nutritional status role. We studied 54 centenarians (14 males and 40 females) aged between 100-107 years (mean age 102.6+/-1.8 years) living in Sicily (Italy), recruited via the Registry Office, and compared them with three control groups composed of subjects with different age ranges. Total plasma Hcy, folate, vitamin B12 and pyridoxal phosphate (PLP) levels were compared between the groups by the Student's t test. The comparison between centenarians and <65-year old, randomly selected individuals showed that in centenarians the mean value of serum creatinine levels was 18 micromol/l (p=0.000) higher, the mean total Hcy value was 22 micromol/l higher (p=0.000), the mean PLP value was 17.9 nmol/l lower (p=0.000), the mean folate level was 2.1 nmol/l lower (p<0.001) and vitamin B12 was 70.5 pmol/l lower (p=0.000). The comparison between centenarians and >65-year old, randomly selected individuals showed that in centenarians the mean value of serum creatinine levels was 8 micromol/l higher (p=0.037), the mean total Hcy value was 11.6 micromol/l higher (p=0.000) and the mean PLP value was 4.2 nmol/l higher (p=0.000). It seems that centenarians are protected by some mechanism (maybe genetic) that allows them a long survival despite the high value of homocysteinemia. On the other hand, it can by hypothesized that good vitamin intake is essential to live over 100 years.

Modification of brain aging and neurodegenerative disorders by genes, diet, and behavior

Multiple molecular, cellular, structural, and functional changes occur in the brain during aging. Neural cells may respond to these changes adaptively, or they may succumb to neurodegenerative cascades that result in disorders such as Alzheimer's and Parkinson's diseases. Multiple mechanisms are employed to maintain the integrity of nerve cell circuits and to facilitate responses to environmental demands and promote recovery of function after injury. The mechanisms include production of neurotrophic factors and cytokines, expression of various cell survival-promoting proteins (e.g., protein chaperones, antioxidant enzymes, Bcl-2 and inhibitor of apoptosis proteins), preservation of genomic integrity by telomerase and DNA repair proteins, and mobilization of neural stem cells to replace damaged neurons and glia. The aging process challenges such neuroprotective and neurorestorative mechanisms. Genetic and environmental factors superimposed upon the aging process can determine whether brain aging is successful or unsuccessful. Mutations in genes that cause inherited forms of Alzheimer's disease (amyloid precursor protein and presenilins), Parkinson's disease (alpha-synuclein and Parkin), and trinucleotide repeat disorders (huntingtin, androgen receptor, ataxin, and others) overwhelm endogenous neuroprotective mechanisms; other genes, such as those encoding apolipoprotein E(4), have more subtle effects on brain aging. On the other hand, neuroprotective mechanisms can be bolstered by dietary (caloric restriction and folate and antioxidant supplementation) and behavioral (intellectual and physical activities) modifications. At the cellular and molecular levels, successful brain aging can be facilitated by activating a hormesis response in which neurons increase production of neurotrophic factors and stress proteins. Neural stem cells that reside in the adult brain are also responsive to environmental demands and appear capable of replacing lost or dysfunctional neurons and glial cells, perhaps even in the aging brain. The recent application of modern methods of molecular and cellular biology to the problem of brain aging is revealing a remarkable capacity within brain cells for adaptation to aging and resistance to disease.

Epidemiology of venous thromboembolic disease

From the information presented in this article, it can be concluded that clinical suspicion of VTE should be increased in patients with a history of VTE, recent surgery, spinal cord injury, trauma, or malignancy. A variety of medical illnesses also increase the risk of venous thrombosis, including congestive heart failure, myocardial infarction, stroke with paresis, nephrotic syndrome, cigarette smoking, and obesity. Hypercoagulable states, such as antithrombin III deficiency, protein C deficiency, protein S deficiency, or factor V Leiden mutation should be considered in those patients who develop VTE in the absence of known risk factors. Additionally, the presence of vena caval filters does not exclude the possibility of PE or recurrent DVT. With a careful assessment of risk, physicians can hope to increase the diagnostic yield of VTE and decrease the significant morbidity and mortality of caused by this disease.

Inherited thrombophilia: a possible cause of in utero vascular thrombosis in children with intestinal atresia

BACKGROUND

Congenital atresia of the small and large intestine is thought to evolve from in utero mesenteric vascular occlusion of the corresponding intestinal segment. Because spontaneous thrombosis recently has been described in association with inherited thrombophilia, the authors wondered if inherited thrombophilia also might be found in babies with intestinal atresia.

METHODS

Genetic analysis was done on 28 children treated for congenital intestinal atresia. DNA was analyzed for point mutations to detect the 2 most common types of inherited thrombophilia, the G1691A mutation in the factor V gene (factor V Leiden) and the G20210A mutation in the prothrombin gene. In addition, other genetic risk factors for thrombosis were analyzed including the C677T mutation in the methylenetetrahydrofolate reductase gene (MTHFR) and 2 polymorphisms of the factor VII gene (the R353Q and the hypervariable region 4 polymorphisms).

RESULTS

The factor V Leiden mutation was present in 5 of 28 (18%) children treated for congenital intestinal atresia. This is increased significantly when compared with the reported carrier frequency of 3% to 7% in the general population and a reported carrier rate of 4.2% in the local population (P <.005). The R353Q polymorphism of the factor VII gene, specifically the RR genotype, was noted in 85% of patients with atresia with an expected frequency of 64% (P <.008). There were no significant associations noted between mutations in the prothrombin gene, the MTHFR gene, or the hypervariable region of the factor VII gene.

CONCLUSIONS

The factor V Leiden mutation and the RR subtype of the R353Q polymorphism of the factor VII gene are seen at an increased frequency in children with congenital intestinal atresia. This suggests that inherited thrombophilia may play a role in the etiology of these in utero mesenteric thrombotic events.

Review and management of patients with the prothrombin G20210A polymorphism

A single mutation in the 3'-untranslated region of the prothrombin gene, resulting in a G to A substitution, was recently reported. This finding added to the growing list of genetic disorders thought to be responsible for familial thrombophilia. Although most studies are in general agreement about the elevated risk of venous thrombosis in individuals carrying this mutation, its role in the first event of venous thromboembolism and recurrent events is unclear. Even less clear is the role that this mutation plays in the formation of arterial thrombosis (including coronary artery disease and cerebral ischemia), as studies show contradicting results. Because of this, it is not recommended as part of the routine screening of patients with venous thromboembolism. However, there are certain subgroups of patients who should undergo testing. The discovery of this prothrombin mutation has important clinical implications because it is the second most common cause of genetic thrombophilia, second only to the factor V Leiden. Moreover, its discovery likely will augment the clinician's ability to systematically risk-stratify an individual's likelihood of developing spontaneous thrombosis.

Color multiplexing hybridization probes using the apolipoprotein E locus as a model system for genotyping

Fluorescent hybridization probes were multiplexed for color genotyping of the apolipoprotein E locus using model oligonucleotide targets. Fluorescence resonance energy transfer was observed during adjacent hybridization of 3'-fluorescein-labeled "donor" probes paired with 5'-labeled "acceptor" probes with different emission spectra reporting at codons 112 and 158. The acceptor dyes emitted at either 640 nm (LightCycler Red 640) or 705 nm (LightCycler Red 705) and were monitored with a LightCycler, a thermal cycler with an integrated fluorimeter. The color of the acceptor dye identified each site and the characteristic melting temperatures of the fluorescein-labeled probes identified single base changes within each codon. Color compensation of temperature-dependent spectral overlap was applied to completely separate each channel. Competition between the probes and the complementary strand for the target sequence decreased resonance energy transfer, indicating an advantage of single-stranded target. Hybridization probes of the same length, but different GC content are T(m) shifted by the same amount during A:C mismatch duplex melting. Genotyping was optimal at both sites if melting curve analysis was preceded by a slow (1 degrees C/s) annealing phase. Although each site preferred different concentrations of Mg(2+) and target strand for optimal genotyping, conditions for multiplexing were found. This method, along with an appropriate amplification technique, should allow real-time multiplex genotyping from genomic DNA.