Sanja Hajnšek

The influence of C3435T polymorphism of ABCB1 gene on penetration of phenobarbital across the blood-brain barrier in patients with generalized epilepsy.

BACKGROUND Epilepsy is refractory to medical treatment in about one-third of the patients. The exact pathological mechanism of epilepsy pharmacoresistance is still unclear, but a decreased antiepileptic drug (AED) uptake into the brain is suspected to play a role. P-glycoprotein (Pgp), a transmembrane transporter encoded by ABCB1 gene and located at the endothelial cells of the blood-brain barrier (BBB), has been associated with epilepsy pharmacoresistance. OBJECTIVE To analyze the effect of two ABCB1 gene polymorphisms, C3435T and G2677T/A, on phenobarbital (PB) concentrations in the cerebrospinal fluid (CSF) and serum (S) and to assess the relationship of ABCB1 polymorphisms to phenobarbital penetration across BBB in vivo and seizure frequency. METHODS CSF PB and S PB concentrations were measured in 60 patients with idiopathic primary generalized epilepsy receiving phenobarbital monotherapy. CSF/S PB concentration ratio was calculated as an index of phenobarbital penetration across BBB. The patients were genotyped for the ABCB1 gene C3435T and G2677T/A polymorphisms. Seizure frequency was recorded during the 6-month phenobarbital monotherapy. RESULTS Patients with different C3435T polymorphism had significantly different CSF PB concentrations and CSF/S PB concentration ratio. In comparison with CT heterozygotes and TT homozygotes, CC homozygotes had a significantly lower CSF PB concentration (p=0.006) and CSF/PB concentration ratio (p<0.001). G2677T/A polymorphism showed no such effect (p=0.466). CC genotype and low CSF/S PB concentration ratio correlated with increased seizure frequency. CONCLUSIONS C3435T polymorphism of ABCB1 gene was demonstrated in vivo to significantly influence the CSF/S PB concentration ratio and seizure frequency.

Association study of a functional catechol-o-methyltransferase polymorphism and smoking in healthy Caucasian subjects

Tobacco smoking is a global health problem. The association of a functional common polymorphism in the catechol-o-methyltransferase gene (COMT Val158Met) with smoking behavior has been extensively studied, but with divergent findings. In the present study the frequency of COMT genotypes and alleles was evaluated in 578 male and a smaller group of 79 female unrelated, medication-free Caucasian healthy subjects of Croatian origin. Smokers were classified as subjects smoking <or=10 cigarettes per day, while subjects who never smoked in their life were regarded as nonsmokers. A chi(2)-test with standardized residuals and Bonferroni correction revealed significant (P=0.017) differences in Met/Met, Met/Val or Val/Val genotype frequency between male smokers and nonsmokers. This significant association between COMT Val158Met polymorphism and smoking was not detected in female subjects, due to the small number of women, which represents a limitation of the study. Our results confirmed the significant association between COMT variants and smoking, which was due to the higher frequency of Val/Val homozygotes in male smokers compared to male nonsmokers. These results suggest that carriers of the high activity COMT variant are more prone to develop a higher level of nicotine dependence, or that they release more dopamine than carriers of Met/Met or Met/Val genotypes.

Brain derived neurotrophic factor Val66Met polymorphism and psychotic symptoms in Alzheimer's disease

OBJECTIVE Alzheimers disease (AD) is an irreversible, progressive neurodegenerative disorder with a high prevalence. Since behavioral disturbances, such as psychotic symptoms, represent a key feature of AD, genes related to dopamine, serotonin and brain derived neurotrophic factor (BDNF), are considered as candidate genes for AD. BDNF is a neurotrophin that regulates neurodevelopment, neuroplasticity, and neuronal functions. BDNF is involved in the etiopathogenesis of psychiatric and neurodegenerative disorders. A single base pair polymorphism (BDNF Val66Met) was reported to be associated with AD and/or schizophrenia, as well as other psychoses, although some studies failed to replicate these findings. The aim of the study was to evaluate the association between BDNF Val66Met variants and AD, as well as onset of AD or presence of psychotic symptoms in AD. METHOD BDNF Val66Met was analyzed in 211 patients with AD and in 402 aged healthy control subjects. All subjects were ethnically homogenous Caucasians from Croatia, and were subdivided according to the gender, onset of AD, and presence of psychotic symptoms. A χ(2) test, with Bonferroni correction and standardized residuals were used to evaluate the data. RESULTS Distribution of the BDNF Val66Met genotypes differed significantly between male and female AD patients with or without psychotic symptoms. This difference was due to the significant contribution of the Met/Val genotype and the combined Met/Met and Met/Val genotypes between psychotic and non-psychotic symptoms in male, but not in female patients with AD. The frequency of the gene variants of the BDNF Val66Met did not differ significantly among male and female patients with AD and control subjects, or between male and female patients with early or late onset AD. There were significant sex related differences in age, duration of illness and scores of dementia between patients with AD. CONCLUSION Our male patients were younger, had shorter duration of illness, and had less severe dementia and higher cognitive performance than female AD patients. The gene variants of the BDNF Val66Met polymorphism were significantly associated with the presence of psychotic symptoms in male, but not in female patients with AD. The results had adequate statistical power to suggest that BDNF Val66Met was not related to susceptibility to AD or the onset of AD, but that presence of one or two Met alleles of BDNF Val66Met polymorphism might present a risk factor for psychosis in AD.

Determination of cortical language dominance using functional transcranial Doppler sonography in left-handers.

OBJECTIVE Verbal analytical functions are primarily related to the left hemisphere in right-handers, but there is yet no agreement about cortical language dominance in left-handers. Also, there are some contradictory reports about sex differences in cortical language lateralization. The aim of this study is to investigate cortical language dominance in left-handers and to explore gender influence on cortical language representation. METHODS We performed functional transcranial Doppler sonography (previous validated for determination of cerebral language lateralization) during a word generation task, measuring changes in mean cerebral blood flow velocity (BFVmean) in both middle cerebral arteries (MCA) in 150 healthy subjects (75 left-handers and 75 right-handers). In left-handers we observed significant increase BFVmean in right MCA in 58 (77.3%) subjects. Bilateral increase was observed in 11 (14.7%) subjects and increase in left MCA in 6 (8%) subjects. In right-handed group 93.3% subjects showed left cortical dominance, while 6.7% showed bilateral language representation. RESULTS Current results showed significant (P<0.0001) right hemispheric language dominance in healthy left-handed subjects. CONCLUSIONS Our results showed significant difference in hemispheric dominance for verbal function between righthanders and lefthanders. Also there is statistically insignificant female gender tendency for bilateral hemispheric language representation in both handedness.

Association between lamotrigine concentrations and ABCB1 polymorphisms in patients with epilepsy.

Background: Epilepsy is treated with a variety of anticonvulsants that are often used concomitantly. Therefore, therapeutic drug monitoring is often necessary. Along with clinical and environmental factors, genetic predisposition has been recognized to be relevant for interindividual variability in drug response. Polymorphic transporter proteins such as P-glycoprotein significantly influence pharmacokinetics and bioavailability of many structurally unrelated drugs. The aim of the study was to evaluate the impact of polymorphisms in the P-glycoprotein–encoding gene ABCB1 (C1236T, G2677T/A, C3435T) on antiepileptic drug disposition. Methods: We recruited 222 patients with epilepsy who were prescribed lamotrigine in monotherapy or polytherapy. Lamotrigine plasma concentrations were analyzed and compared with ABCB1 gene variants. The ABCB1 genotyping was performed by real-time polymerase chain reaction methods. The therapeutic drug monitoring was performed by high-performance liquid chromatography–diode array detector (DAD) and immunoassay. Results: A significant correlation was confirmed between lamotrigine concentration and additional drugs (P < 0.001). In the whole group, statistical analysis showed correlations between lamotrigine concentrations and ABCB1 C1236T variants: 10.1 and 6.5 &mgr;mol/L for CC versus CT + TT, respectively (P = 0.021), and for dose corrected lamotrigine 0.068 and 0.053 &mgr;mol·L−1·mg−1, for CC versus CT + TT, respectively (P = 0.017). Analysis of a specific haplotype showed that 1236C–2677G–3435C carriers had higher lamotrigine concentrations than 1236T–2677G–3435T carriers (P < 0.001), followed by 1236T–2677T–3435C carriers (P < 0.001). Conclusions: ABCB1 C1236T, G2677T/A, C3435T polymorphisms have an influence on lamotrigine serum concentrations.

Growth hormone and insulin growth factor-I levels in plasma and cerebrospinal fluid of patients with multiple sclerosis

Multiple sclerosis (MS) has several clinically different forms. Whereas the illness progresses slowly in most of the patients, 10% have an aggressively progressive course with fatal outcome without signs of remyelination capability. The process of remyelination depends on numerous interactive factors, including the presence of various growth factors, the most important of which in the adult is insulin growth factor-I (IGF-I). On the other hand, the most powerful postnatal regulator of IGF-I is growth hormone (GH), which also acts as a neuroprotective and an antiapoptotic agent, and has direct influence on myelination. Levels of these growth factors have never been examined in the cerebrospinal fluid (CSF) of patients with MS. The levels of IGF-I and GH were measured in serum and CSF of 46 MS patients and compared with those of 49 patients with no evidence of demyelinating disease. The only positive finding was a deficiency of GH in the CSF of MS patients. The possible implications of those findings in the etiopathogenesis of MS will be discussed.

Unraveling the biological mechanisms in Alzheimer's disease — Lessons from genomics

Alzheimers disease (AD) is the most common form of dementia and the most common neurodegenerative disease, with a complex genetic background. Genome-wide association studies (GWAS) have yielded important new insights into genetic mechanisms of AD pathology. Current results unequivocally confirm apolipoprotein E (APOE) as a major genetic risk factor for development of late onset AD. Additional associations of more than twenty genes have also been identified and replicated in subsequent genetic studies. Despite the exciting new GWAS data which have emerged in the last few years, it has become clear that common variants within the genome cannot fully explain the underlying genetic risk for AD. Novel approaches such as genome-wide analysis of copy number variations (CNV) or low-frequency rare functional gene variants may provide additional insight into genetic basis of AD. In this review we summarize the findings of eighteen GWAS studies in AD performed to date, with an emphasis on potential future developments in the quest for genetic risk factors of AD.

Personalized medicine in neurodegenerative diseases: how far away?

Neurodegenerative diseases are characterized by progressive dysfunction of the nervous system as a result of neuronal loss in the brain and spinal cord. Despite extensive research efforts aimed at development of new disease-modifying therapeutics, there is still no effective treatment to halt neurodegenerative processes. Thus, modification of current therapeutic and diagnostic research strategies is a goal of increasing urgency. The biggest limitation in neurodegenerative disease research is the lack of appropriate biomarkers. Discovery of universal biomarkers capable of diagnosing patients with neurodegenerative diseases, monitoring their response to therapy, and predicting disease progression seems to be a tall order. Instead, a combination of different methodologies in the discovery of biomarkers specific for each described aspect of the disease seems to be a more viable approach. Although application of personalized medicine in diagnosis and treatment of neurodegenerative diseases may seem far off, some recent developments, such as utilizing specific biological therapies in multiple sclerosis, microRNA profiling as a source of novel biomarkers in Parkinson’s disease, or combination of neuroimaging and proteomic analyses in diagnosis of Alzheimer’s disease patients, already point to the way clinical neurology may integrate new achievements in everyday practice. Combination of genomic, proteomic, glycomic, and metabolomic approaches may yield novel insights into molecular mechanisms of disease pathophysiology, which could then be integrated and translated into clinical neurology. Based on the developments during the past decade, it is feasible to predict that a personalized approach to treating neurological disorders will become more widely applicable in the coming years.

The association of multiple sclerosis and Hodgkin's disease: the role of Epstein—Barr virus infection:

The aetiology of multiple sclerosis (MS) is still an unresolved question. Several recently reported studies are implicating Epstein—Barr virus (EBV) as one of the key players in MS pathogenesis. We present a 21-year-old male patient with a history of EBV-related infectious mononucleosis in puberty and Hodgkins disease two years previously treated with irradiation and chemotherapy. The patient presented with spastic paraparesis that resolved promptly on corticosteroid treatment. There were no signs of Hodgkins disease relapse. In the next three years he had three more bouts of the disease and he was diagnosed with relapse—remitting MS. There is evidence of EBV involvement in MS pathogenesis; the association of MS with EBV-related infectious mononucleosis and Hodgkins disease being just one of them. Although there are many unanswered questions, it is clear that without EBV seropositivity MS in adults is extremely rare. Multiple Sclerosis 2008; 14: 284—287. http://msj.sagepub.com

Level of sFas/APO 1 in serum and cerebrospinal fluid in multiple sclerosis

The aim of the study was to measure sFas/APO 1 serum and cerebrospinal fluid (CSF) levels in patients with relapsing-remitting multiple sclerosis (MS) during relapses, as an index of inhibition of apoptosis of activated lymphocytes in eight patients with clinically definite multiple sclerosis, and 12 healthy controls. The level of serum and CSF sFas/APO 1 was determined by commercially available enzyme-linked immunosorbent assay (ELISA) kits. No significant differences were detected in the sFas/APO 1 serum level between patients and controls, but the levels in CSF was lower in the former. Our results suggest the possibility of Fas mediated apoptosis as a contributing factor in the pathogenesis of multiple sclerosis.