GiOPARK Project: The Genetic Study of Parkinson's Disease in the Croatian Population.

Parkinson's disease is a neurological disorder that affects motor function, autonomic functions, and cognitive abilities. It is likely that both genetic and environmental factors, along with age, contribute to the cause. However, there is no comprehensive guideline for genetic testing for Parkinson's disease, and more research is needed to understand genetic variations in different populations. There has been no research on the genetic background of Parkinson's disease in Croatia so far. Therefore, with the GiOPARK project, we aimed to investigate the genetic variants responsible for Parkinson's disease in 153 Croatian patients with early onset, familial onset, and sporadic late-onset using whole-exome sequencing, along with multiplex ligation-dependent probe amplification and Sanger sequencing in select patients. We found causative variants in 7.84% of the patients, with GBA being the most common gene (4.58%), followed by PRKN (1.96%), ITM2B (0.65%), and MAPT (0.65%). Moreover, variants of uncertain significance were identified in 26.14% of the patients. The causative variants were found in all three subgroups, indicating that genetic factors play a role in all the analyzed Parkinson's disease subtypes. This study emphasizes the need for more inclusive research and improved guidelines to better understand the genetic basis of Parkinson's disease and facilitate more effective clinical management.

The effects of microbiota abundance on symptom severity in Parkinson's disease: A systematic review.

Introduction: Parkinson's disease (PD) is neurodegenerative disease with a multifactorial etiopathogenesis with accumulating evidence identifying microbiota as a potential factor in the earliest, prodromal phases of the disease. Previous research has already shown a significant difference between gut microbiota composition in PD patients as opposed to healthy controls, with a growing number of studies correlating gut microbiota changes with the clinical presentation of the disease in later stages, through various motor and non-motor symptoms. Our aim in this systematic review is to compose and assess current knowledge in the field and determine if the findings could influence future clinical practice as well as therapy in PD. Methods: We have conducted a systematic review according to PRISMA guidelines through MEDLINE and Embase databases, with studies being selected for inclusion via a set inclusion and exclusion criteria. Results: 20 studies were included in this systematic review according to the selected inclusion and exclusion criteria. The search yielded 18 case control studies, 1 case study, and 1 prospective case study with no controls. The total number of PD patients encompassed in the studies cited in this review is 1,511. Conclusion: The link between gut microbiota and neurodegeneration is a complex one and it depends on various factors. The relative abundance of various microbiota taxa in the gut has been consistently shown to have a correlation with motor and non-motor symptom severity. The answer could lie in the products of gut microbiota metabolism which have also been linked to PD. Further research is thus warranted in the field, with a focus on the metabolic function of gut microbiota in relation to motor and non-motor symptoms.

Lack of association between C282Y and H63D polymorphisms in the hemochromatosis gene and risk of multiple sclerosis: A meta-analysis.

Increasing evidence supports the potential role of iron metabolism in multiple sclerosis (MS). Previous studies examining the association between polymorphisms of the hemochromatosis gene (HFE) and susceptibility to MS have yielded inconsistent results. In the present study, a meta-analysis of 7 studies was performed conducted in populations of Caucasian origin using the Comprehensive Meta-analysis 3.0 software. The strength of association between the C282Y and H63D polymorphisms in HFE and MS risk was estimated by odds ratios with 95% confidence intervals. Cochran's Q statistic and I2 tests were applied to quantify heterogeneity between studies. An Egger's test was used to estimate publication bias. The C282Y and H63D polymorphisms had no significant association with increased MS risk (all P≥0.05) in the following genetic comparison models: Dominant model (YY + CY vs. CC or DD + HD vs. HH) and allele contrast (Y vs. C or D vs. H). No apparent publication bias or significant heterogeneity was found between studies. These results suggest that the HFE polymorphisms C282Y and H63D are not associated with susceptibility to MS in populations of Caucasian origin. Further studies should be performed in a larger series of MS patients to evaluate the contribution of HFE and other genetic variants associated with iron regulation in the development and progression of MS.

A rare Y-autosome translocation found in a patient with nonobstructive azoospermia: Case report.

Y­autosome translocations are relatively uncommon in humans, with t(Y;1) stated to be even rarer. On the contrary, pericentric inversion 9 is the most commonly seen inversion  of chromosome . Although considered to have no significant effect on male fertility, the literature reporting on reproductive risks for both aberrations remains controversial. We report here, as far as we know, the first case of a unique combination of balanced reciprocal translocation t(Y;1) with pericentric inversion of chromosome 9 in a patient with nonobstructive azoospermia (NOA) and an otherwise normal phenotype. Our patient was a 37-year-old Caucasian male sent to our Department due to azoospermia reported by semen analysis. The cytogenetic analysis revealed a balanced reciprocal translocation including chromosomes Y and 1 in all observed metaphases: 46, X,t(Y;1)(q12;q21) and a pericentric inversion of chromosome 9: inv(9)(p12q13). By performing metaphase FISH, the t(Y;1) translocation was confirmed. By means of multiplex-PCR, no Y-chromosome microdeletions were detected in the AZF regions. This report demonstrates a unique karyotype showing balanced reciprocal translocation t(Y;1)(q12;q21) with pericentric inversion 9: inv(9)(p12q13), in a patient with NOA, and highlights the importance of appropriate genetic counseling for patients with regard to the medical management of balanced chromosomal aberrations.

Association of circadian rhythm genes ARNTL/BMAL1 and CLOCK with multiple sclerosis.

Prevalence of multiple sclerosis varies with geographic latitude. We hypothesized that this fact might be partially associated with the influence of latitude on circadian rhythm and consequently that genetic variability of key circadian rhythm regulators, ARNTL and CLOCK genes, might contribute to the risk for multiple sclerosis. Our aim was to analyse selected polymorphisms of ARNTL and CLOCK, and their association with multiple sclerosis. A total of 900 Caucasian patients and 1024 healthy controls were compared for genetic signature at 8 SNPs, 4 for each of both genes. We found a statistically significant difference in genotype (ARNTL rs3789327, P = 7.5·10-5; CLOCK rs6811520 P = 0.02) distributions in patients and controls. The ARNTL rs3789327 CC genotype was associated with higher risk for multiple sclerosis at an OR of 1.67 (95% CI 1.35-2.07, P = 0.0001) and the CLOCK rs6811520 genotype CC at an OR of 1.40 (95% CI 1.13-1.73, P = 0.002). The results of this study suggest that genetic variability in the ARNTL and CLOCK genes might be associated with risk for multiple sclerosis.

Identification of rare genetic variation of NLRP1 gene in familial multiple sclerosis.

The genetic etiology and the contribution of rare genetic variation in multiple sclerosis (MS) has not yet been elucidated. Although familial forms of MS have been described, no convincing rare and penetrant variants have been reported to date. We aimed to characterize the contribution of rare genetic variation in familial and sporadic MS and have identified a family with two sibs affected by concomitant MS and malignant melanoma (MM). We performed whole exome sequencing in this primary family and 38 multiplex MS families and 44 sporadic MS cases and performed transcriptional and immunologic assessment of the identified variants. We identified a potentially causative homozygous missense variant in NLRP1 gene (Gly587Ser) in the primary family. Further possibly pathogenic NLRP1 variants were identified in the expanded cohort of patients. Stimulation of peripheral blood mononuclear cells from MS patients with putatively pathogenic NLRP1 variants showed an increase in IL-1B gene expression and active cytokine IL-1ß production, as well as global activation of NLRP1-driven immunologic pathways. We report a novel familial association of MS and MM, and propose a possible underlying genetic basis in NLRP1 gene. Furthermore, we provide initial evidence of the broader implications of NLRP1-related pathway dysfunction in MS.

Angiotensin-converting enzyme insertion/deletion gene polymorphism and interferon-ß treatment response in multiple sclerosis patients: a preliminary report.

We investigated the effect of the functional insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene on the response to interferon-ß (IFN-ß) therapy in Croatian and Slovenian patients with multiple sclerosis (MS). A total of 275 IFN-ß treated MS patients [162 responders (Rs) and 113 nonresponders (NRs)] were genotyped by PCR. The ACE I/D genotype distribution and allele frequencies did not differ between female Rs and NRs. However, male NRs tended to have a greater prevalence of the DD genotype (P=0.073; odds ratio: 2.64; 95% confidence interval: 0.91-7.60) and a significantly higher frequency of the D allele (P=0.022; odds ratio: 2.43; 95% confidence interval: 1.13-5.20) than male Rs. Multiple forward stepwise regression analysis indicated that the negative response to IFN-ß therapy was associated with the ACE-DD genotype in men (ß=0.371; multiple R change: 0.132; P=0.009) and a higher pretreatment relapse rate in both men (ß=-0.438; multiple R change: 0.135; P=0.015) and women (ß=-0.208; multiple R change: 0.042; P=0.034). The ACE I/D polymorphism and pretreatment relapse rate accounted for ∼26.7% of the IFN-ß response variability among the men in the sample. Further studies of a larger number of MS patients from different populations are necessary to evaluate these preliminary findings.

The lack of association between angiotensin-converting enzyme gene insertion/deletion polymorphism and nicotine dependence in multiple sclerosis.

OBJECTIVE: Blood-borne angiotensin II is generated from angiotensinogen via cleavage by renin and angiotensin-converting enzyme (ACE), an enzymatic cascade known as the renin-angiotensin system (RAS). Several lines of evidence indicate that ACE, beyond its classical role of mediating blood pressure regulation, might contribute to the etiology of substance addictions by influencing dopaminergic signaling. A functional insertion/deletion (I/D) polymorphism of the ACE gene was associated with risk for being a smoker among individuals with depression and with smoking severity in studies comprising patients with depression and healthy controls. Several reports have described significantly increased ACE activity in cerebrospinal fluid and serum among MS patients. Furthermore, in our previous work with MS patients from Croatian and Slovenian populations, we demonstrated that the ACE-I/D polymorphism contributes to an elevated MS risk among male patients. Here we investigated whether the ACE-I/D polymorphism might influence smoking behavior among patients with MS. PATIENTS AND METHODS: Genotyping was performed in 521 patients (males/females: 139/382) using polymerase chain reaction. RESULTS: We revealed no significant differences in ACE genotype and allele frequencies between smokers and nonsmokers and no significant association between the ACE-I/D polymorphism and either pack-year smoking history or number of cigarettes smoked daily (p > .05, respectively). CONCLUSION: The ACE-I/D polymorphism does not contribute either to risk for nicotine dependence or to smoking severity among MS patients. In the context of reports on the ACE-I/D polymorphism and nicotine dependence among healthy controls and patients with depression, we may speculate that the mechanism by which this polymorphism influences nicotine dependence risk differs in MS compared to depression, although not compared to a healthy population. In addition to angiotensin II, other potential ACE substrates, such as substance P and neurotensin, which also influence dopaminergic neurotransmission (and are proposed to be associated with MS), may deserve study in future.

The Role of Iron and Iron Overload in Chronic Liver Disease.

The liver plays a major role in iron homeostasis; thus, in patients with chronic liver disease, iron regulation may be disturbed. Higher iron levels are present not only in patients with hereditary hemochromatosis, but also in those with alcoholic liver disease, nonalcoholic fatty liver disease, and hepatitis C viral infection. Chronic liver disease decreases the synthetic functions of the liver, including the production of hepcidin, a key protein in iron metabolism. Lower levels of hepcidin result in iron overload, which leads to iron deposits in the liver and higher levels of non-transferrin-bound iron in the bloodstream. Iron combined with reactive oxygen species leads to an increase in hydroxyl radicals, which are responsible for phospholipid peroxidation, oxidation of amino acid side chains, DNA strain breaks, and protein fragmentation. Iron-induced cellular damage may be prevented by regulating the production of hepcidin or by administering hepcidin agonists. Both of these methods have yielded successful results in mouse models.

The role of TPA I/D and PAI-1 4G/5G polymorphisms in multiple sclerosis.

BACKGROUND: Previous studies have shown impaired fibrinolysis in multiple sclerosis (MS) and implicated extracellular proteolytic enzymes as important factors in demyelinating neuroinflammatory disorders. Tissue-type plasminogen activator (t-PA) and its inhibitor (PAI-1) are key molecules in both fibrinolysis and extracellular proteolysis. In the present study, an association of the TPA Alu I/D and PAI-1 4G/5G polymorphisms with MS was analyzed within the Genomic Network for Multiple Sclerosis (GENoMS). METHODS: The GENoMS includes four populations (Croatian, Slovenian, Serbian, and Bosnian and Herzegovinian) sharing the same geographic location and a similar ethnic background. A total of 885 patients and 656 ethnically matched healthy blood donors with no history of MS in their families were genotyped using PCR-RFLP. RESULTS: TPA DD homozygosity was protective (OR = 0.79, 95% CI 0.63-0.99, P = 0.037) and PAI 5G5G was a risk factor for MS (OR = 1.30, 95% CI 1.01-1.66, P = 0.038). A significant effect of the genotype/carrier combination was detected in 5G5G/I carriers (OR = 1.39 95% CI 1.06-1.82, P = 0.017). CONCLUSIONS: We found a significantly harmful effect of the combination of the PAI-1 5G/5G genotype and TPA I allele on MS susceptibility, which indicates the importance of gene-gene interactions in complex diseases such as MS.

Low frequency of HFE gene mutations in Croatian patients suspected of having hereditary hemochromatosis.

BACKGROUND: Hereditary hemochromatosis (HH) is a common autosomal recessive disorder in populations of European descent. It is characterized by a variable prevalence of mutations in the hemochromatosis gene (HFE) in different countries and a complex relationship between the HFE genotype and the HH phenotype. Genetic analysis has not been conducted in Croatian patients with iron overload. The aim of this study was to determine whether HFE mutations, C282Y, H63D, and S65C were correlated with clinical and biochemical parameters in Croatian patients with suspected HH. MATERIAL/METHODS: Clinical examination, biochemical analysis, and genotyping were performed in 175 patients suspected of having HH. The control group consisted of 350 healthy blood donors. RESULTS: Among the patients, 20% had genotypes related to HH--7.4% were homozygous for C282Y, 6.3% were compound heterozygous for C282Y and H63D, 5.7% were homozygous for H63D, and 0.6% was compound heterozygous for C282Y and S65C. The allelic frequencies were 14.6% for C282Y mutation, 23.7% for H63D mutation, and 1.4% for S65C mutation. A comparison of the clinical and laboratory profiles of patients revealed that C282Y homozygotes had higher frequencies of all clinical symptoms and higher levels of biochemical parameters than others. The C282Y/H63D compound heterozygotes and H63D homozygotes were found to be clinically important, despite the fact that they were associated with less severe disease. CONCLUSIONS: Our results show that HFE mutations are responsible for only about 20% of Croatian patients with suspected HH. Screening with biochemical methods and HFE genotyping may be not sufficient for diagnoses in the Croatian population.

Functional inference of methylenetetrahydrofolate reductase gene polymorphisms on enzyme stability as a potential risk factor for Down syndrome in Croatia.

Understanding the biochemical structure and function of the methylenetetrahydrofolate reductase gene (MTHFR) provides new evidence in elucidating the risk of having a child with Down syndrome (DS) in association with two common MTHFR polymorphisms, C677T and A1298C. The aim of this study was to evaluate the risk for DS according to the presence of MTHFR C677T and A1298C polymorphisms as well as the stability of the enzyme configuration. This study included mothers from Croatia with a liveborn DS child (n=102) or DS pregnancy (n=9) and mothers with a healthy child (n=141). MTHFR C677T and A1298C polymorphisms were assessed by PCR-RFLP. Allele/genotype frequencies differences were determined using chi square test. Odds ratio and the 95% confidence intervals were calculated to evaluate the effects of different alleles/genotypes. No statistically significant differences were found between the frequencies of allele/genotype or genotype combinations of the MTHFR C677T and A1298C polymorphisms in the case and the control groups. Additionally, the observed frequencies of the stable (677CC/1298AA, 677CC/1298AC, 677CC/1298CC) and unstable (677CT/1298AA, 677CT/1298AC, 677TT/1298AA) enzyme configurations were not significantly different. We found no evidence to support the possibility that MTHFR polymorphisms and the stability of the enzyme configurations were associated with risk of having a child with DS in Croatian population.

Interleukin 7 receptor alpha polymorphism rs6897932 and susceptibility to multiple sclerosis in the Western Balkans.

The interleukin 7 receptor alpha single nucleotide polymorphism rs6897932 was identified as a multiple sclerosis susceptibility-modifying polymorphism in genome-wide and gene scan studies, mainly in populations in western countries. The aim of this study was to investigate the association of interleukin 7 receptor alpha rs6897932 with multiple sclerosis in populations from the Western Balkans: Serbia, Croatia, and Slovenia. A total of 678 unrelated white patients and 597 unrelated, ethnically matched healthy controls were included in the study. Genotyping was performed by real-time polymerase chain reaction. We found no significant difference in genotype or allele frequencies between controls and patients with multiple sclerosis either separately in Serbian, Croatian, and Slovenian populations or in the whole sample from the Western Balkans. The odds ratio for multiple sclerosis in this study was 1.04 (0.86-1.25) for the C allele. It is known that demographic as well as environmental factors have a substantial role in multiple sclerosis development, as well as population genetic background. The results of this study indicate that other types of genome variants should be required for the development and/or progression of multiple sclerosis, which may vary among populations.

The impact of hemochromatosis mutations and transferrin genotype on gonadotropin serum levels in infertile men.

OBJECTIVE: To address the possibility that HFE mutations and TF gene polymorphism cause dysfunction of spermatogenesis and/or the hypothalamic-pituitary-gonadal axis via contribution to long-term iron overload in the testes and brain. DESIGN: Case-control and association study. SETTING: Clinic of obstetrics and gynecology and university-based research laboratory. PATIENT(S): 127 infertile men (including 97 with idiopathic infertility) and 188 controls of proven fertility. INTERVENTION(S): Polymerase chain reaction/restriction fragment length polymorphism (PCR-RFLP). MAIN OUTCOME MEASURE(S): HFE mutations and transferrin allelic polymorphism, and testosterone, prolactin, and gonadotropin serum levels. RESULT(S): The frequencies of the analyzed alleles and genotypes showed no statistically significant difference between infertile men and controls. Sperm count and progressive sperm motility did not correlate with HFE or TF genotype, or their combination. After excluding patients with clinical hypogonadism or varicocele from further analysis, a statistically significant correlation between serum follicle-stimulating hormone and luteinizing hormone levels and the combined HFE H63D/TFC2 genotype was found in 97 men with idiopathic infertility. CONCLUSION(S): The combined HFE H63D/TF-C2 genotype contributed to 4.1% and 10.6% of follicle-stimulating hormone and luteinizing hormone variation, respectively, in infertile men, raising mean hormonal values above the normal physiologic range. Therefore, HFE and TF genes together may influence the hypothalamic-pituitary-gonadal axis, functioning at the pituitary or testes level.

PAI and TPA gene polymorphisms in multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated chronic inflammatory demyelinating disease of the central nervous system. It manifests as acute focal inflammatory demyelination and axonal loss with limited remyelination and results in the chronic multifocal sclerotic plaques. Previously published data showed impaired fibrinolysis in MS. Tissue plasminogen activator t-PA is a serine protease that catalyses the activation of plasmin, which mediates the effects of fibrinolytic system. Alu insertion/deletion (I/D) genetic polymorphism in TPA gene in MS patients has not been analysed previously. The major inhibitor of t-PA is plasminogen activator inhibitor-1 (PAI-1). Its gene expression is modulated by functional genetic polymorphism in the promoter (4G/5G). In the present study, an association of two genetic polymorphisms with MS, its progression and subtype were analysed. TPA DD/PAI-1 4G4G genotype combination has reached a borderline significance for reduced risk for MS (OR = 0.543, 95% CI 0.301-0.978, P = 0.04), suggesting a gene-gene interaction. The explanation for this interaction may be a complex interplay between these two pleiotropic proteins within the brain tissue and in plasma.

Tumor necrosis factor-alpha-308 gene polymorphism in Croatian and Slovenian multiple sclerosis patients.

Previous findings regarding the role of TNF-alpha-308 gene polymorphism in multiple sclerosis (MS) are contradictory. The aim of this study was to investigate the possible influence of TNF-alpha-308 polymorphism on MS susceptibility and the MS disease process in a Croatian and Slovenian population. Genotyping was performed in 338 patients and 460 healthy controls. The TNF2 allele was present in 123 (26.8%) healthy controls vs. 67 (19.9%) MS patients (p = 0.023, odds ratio = 0.68, 95% confidence interval = 0.48-0.95), suggesting that carriage of the TNF2 allele might decrease MS risk. The difference in TNF2 allele carrier frequency between patients and controls was identified in the relapsing-remitting MS group. There was no association between TNF2 allele carrier status and age at disease onset or disease progression. Our results suggest that, in the study populations, the TNF-alpha-308 polymorphism may play a role in MS susceptibility.

No association of CCR5delta32 gene mutation with multiple sclerosis in Croatian and Slovenian patients.

Several studies investigating the role of the CCR5delta32 mutation in multiple sclerosis (MS) have reported varied, often contradictory results. Therefore in the present study we have analysed whether the CCR5delta32 mutation is associated with the risk of/or disease process in Croatian and Slovene MS patients. Three hundred and twenty-five MS patients and 356 healthy controls were genotyped by the polymerase chain reaction method. Our results showed no significant differences in the distribution of CCR5delta32 mutations between MS and control subjects, indicating that this mutation does not influence susceptibility to MS. Furthermore, we did not observe that CCR5delta32 carrier-status could modulate age of disease onset or progression of the disease. It is therefore our conclusion that the present study indicates that the CCR5delta32 mutation is neither protective of, nor a risk factor, for MS development.

Frequency of CCR5 gene 32-basepair deletion in Croatian normal population.

A 32-basepair deletion polymorphism in the CCR5 chemokine receptor gene (CCR5 TROKUT 32) could increase the resistance to HIV-1 infection or delayed progression to AIDS. This mutant allele is common among Caucasians of Western European descent, but has not been observed in people of African or Asian ancestry. Genetic studies provided in European countries have shown a highest prevalence in Nordic countries and the lowest in the Southern European and Mediterranean populations. We genotyped 303 randomly selected healthy Croatians for the prevalence of CCR5 TROKUT 32 mutation. CCR5 TROKUT 32 allele frequency in Croatia of 7.1% fits in the observed European north/south gradient. This first report of CCR5 TROKUT 32 mutation in Croatian population provides additional information on its frequency and geographical distribution in Slavic populations in South-Eastern Europe. Moreover, our data may have important implications for the prediction and prevention of HIV/AIDS in a tourist country such as Croatia.