Victoria Alvarez

Genetic variation in the renin-angiotensin system and athletic performance

Abstract The D allele at the angiotensin-I-converting enzyme (ACE)-insertion/deletion polymorphism has been associated with an increased risk of developing several pathological processes, such as coronary heart disease and ventricular hypertrophy. Individuals with the DD genotype show a significantly increased left-ventricular mass in response to physical training, compared to the II genotype (which would be associated with the lowest plasma ACE levels) and the ID genotype. The II genotype has been linked to a greater anabolic response. In accordance with a role for ACE in the response to rigorous physical training, a higher frequency of the I allele has been reported to exist among elite rowers and high-altitude mountaineers. Sixty elite (professional) athletes (25 cyclists, 20 long-distance runners, and 15 handball players), and 400 healthy controls were genotyped for the DNA polymorphisms of the ACE, angiotensinogen (Ang) and angiotensin receptor type 1 (AT1) genes. Plasma ACE levels showed a strong correlation with the I/D genotype in our population. The I-allele occurred at a significantly higher frequency in athletes compared to controls (P=0.0009). Gene and genotype frequencies for the Ang and AT1 polymorphisms did not differ between athletes and controls. Since the frequency of the ACE I allele was significantly increased among our elite athletes, we conclude that the ACE polymorphism represents a genetic factor that contributes to the development of an elite athlete.

Angiotensin-converting enzyme and angiotensin II receptor 1 polymorphisms: association with early coronary disease

OBJECTIVE To examine the association between coronary artery disease and polymorphisms at the angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT1R) genes. METHODS A total of 181 patients younger than 50 years and 240 controls from the same homogeneous Caucasian population (Asturias, Northern Spain) were genotyped (using polymerase chain reaction) for the ACE insertion/deletion (ACE-I/D) and the AT1R A/C transversion (AT1R-A/C) (3-untranslated region) polymorphisms. RESULTS The DD-genotype was at a non-significant higher frequency among patients (50%) than in controls (41%). No difference between the two groups was found for the AT1R-genotypes. Distribution of ACE-genotypes according to AT1R-genotypes showed a significant association between ACE-DD and AT1R-CC and early coronary disease. Among the CC patients 58% were DD, compared to 21% among the controls (p = 0.02; OR = 5.32, 95% CI = 1.45, 19.51). We determined the distribution of these genotypes among the hypertensive and non-hypertensive patients. Frequencies of ACE- or AT1R-genotypes did not differ between the two groups. However, we found an interaction between the DD- and CC-genotypes in the group of normotensives. Among the CC patients, 13% of the hypertensives and 75% of the normotensives were DD (p = 0.014). CONCLUSIONS Our results indicate a synergistic contribution of ACE and AT1R polymorphisms to the risk of coronary artery disease. This gene-gene interaction could have clinical implications. Approximately 2% of individuals in our population are CC + DD, and the genotyping of both polymorphisms could identify those with a high relative risk for coronary artery disease.

Mutation analysis of the p53, APC, and p16 genes in the Barrett's oesophagus, dysplasia, and adenocarcinoma.

AIMS: To study the loss of heterozygosity and the presence of mutations at the p53, p16/CDKN2, and APC genes in Barretts oesophagus, low grade dysplastic oesophageal epithelium, and adenocarcinoma of the oesophagus; to relate the presence of alterations at these genes with the progression from Barretts oesophagus to adenocarcinoma. METHODS: DNA was extracted from paraffin blocks containing tissue from Barretts oesophagus (12 samples), low grade dysplasia (15 cases), and adenocarcinoma (14 cases). Loss of heterozygosity (LOH) at the p53, p16, and APC genes was determined by comparing the autoradiographic patterns of several microsatellite markers between the normal tissue and the malignant tissue counterpart. SSCP was used to determine the presence of mutations at p53 (exons 5 to 8), p16 (exon 2), and APC. Homozygous deletion of the p16 gene was defined through polymerase chain reaction followed by Southern blot. RESULTS: LOH at the p53, p16, and APC genes was not observed in Barretts oesophagus without dysplasia, and increased to 90% (p53), 89% (p16), and 60% (APC) in the adenocarcinomas. The p53 gene was mutated in only two adenocarcinomas (codons 175 and 245). In one case a mutation at the APC gene (codon 1297) was found. No patient had mutation at the second exon of p16. However, this gene was homozygously deleted in three of the 12 adenocarcinomas. CONCLUSIONS: The tumour suppressor genes p53, p16, and APC are often deleted in adenocarcinomas derived from Barretts oesophagus. Mutations at these genes are also found in the adenocarcinomas, including the homozygous deletion of the p16 gene. However, the absence of genetic alterations in the Barretts oesophagus and the low grade dysplastic epithelia suggest that mutations at these genes develop later in the progression from Barretts oesophagus to adenocarcinoma.

Genetic polymorphism of N-acetyltransferase-2, glutathione S-transferase-M1, and cytochromes P450IIE1 and P450IID6 in the susceptibility to head and neck cancer.

AIMS: To analyse the allele frequencies of DNA polymorphisms at the genes for cytochromes P450IIE1 and P450IID6, N-acetyltransferase-2, and glutathione S-transferase-M1 in patients with head and neck squamous cell carcinoma, in an attempt to define genetic factors involved in the susceptibility to this cancer, which is strongly associated with tobacco consumption. METHODS: Determination of restriction fragment length polymorphism (RFLP) at cytochromes P450IIE1/P450IID6 and NAT2 genes, and the presence of homozygous deletion of the GSTM1 gene, in 200 controls and 75 head and neck cancer patients. Allelic frequencies between the two groups were compared using a chi 2 test, and odds ratio with 95% confidence intervals were calculated. RESULTS: There was no evidence of an association between alleles of CYP2D6 and CYP2E1 and head and neck cancer in our population. Similarly, frequencies of individuals lacking the GSTM1 gene did not differ between controls and patients. However, individuals with the NAT2-SA phenotype were at higher risk of developing head and neck cancer. The frequencies of the most common SA genotype (homozygous for the NAT2*5 allele) were higher in patients than in controls (27% v 15%, respectively). Slow acetylators homozygous for the NAT2*6 allele, the second most common SA allele, were also more common in patients than in controls (11% v 5%, respectively). CONCLUSIONS: Slow NAT2 activity is a risk factor possibly leading to the development of head and neck cancer in response to tobacco carcinogens.

Angiotensin converting enzyme and endothelial nitric oxide synthase DNA polymorphisms and late onset Alzheimer's disease

OBJECTIVES Several lines of evidence suggest that the endothelial constitutive nitric oxide synthase (ecNOS) and angiotensin converting enzyme (ACE) may have a role in Alzheimers disease. ACE is widely expressed in the brain, and a DNA polymorphism at the ACE gene has been linked to the risk for late onset Alzheimers disease. Nitric oxide (NO) production by microglial cells, astrocytes, and brain microvessels is enhanced in patients with Alzheimers disease. There is a growing evidence that NO is involved in neuronal death in Alzheimers disease, and the oxidative stress caused by NO in the brain could be a pathogenic mechanism in Alzheimers disease. The objective was to determine if two DNA polymorphisms at the ecNOS and ACE genes that have been linked with different levels of enzyme expression, have some effect on the risk of developing late onset Alzheimer disease. METHODS A total of 400 healthy controls younger than 65 years and 350 patients with Alzheimers disease (average age 72 years) were genotyped for the ACE and ecNOS polymorphisms. To define a possible role for these polymorphisms in longevity 117 healthy controls older than 85 years were also analysed. Genomic DNA was obtained and amplified by polymerase chain reaction, and genotypes were defined following a previously described procedure. Gene and genotype frequencies between patients and controls were compared statistically. RESULTS Gene and genotype frequencies for the ecNOS and ACE polymorphisms did not differ between both groups of healthy controls (<65 years and >85 years). EcNOS gene and genotype frequencies were similar between patients and controls. There was a slight but significantly increased frequency of the ACE-I allele among patients with Alzheimers disease compared with controls (p=0.03; OR=1.28, 95%CI= 1.04;1.58). CONCLUSIONS The ACE-I allele was associated with a slightly increased risk of developing late onset Alzheimers disease.

The Toll‐like receptor 4 (Asp299Gly) polymorphism is a risk factor for Gram‐negative and haematogenous osteomyelitis

Osteomyelitis is a bone infection caused mostly by Staphylococcus aureus but also by Gram‐negative bacteria. Toll‐like receptors (TLRs), after recognizing microbial products, induce a signal in neutrophils, leading to NF‐κB activation and transcription of pro‐inflammatory genes. Polymorphisms in TLR2 (Arg753Gln) and TLR4 (Asp299Gly, Thr399Ile) genes are associated with bacterial infections, we therefore studied these polymorphisms in osteomyelitis patients. Homozygotes for the TLR4 (Asp299Gly) polymorphism were significantly more frequent among the 80 osteomyelitis patients than in the 155 healthy controls (3/80, 3·8%versus 0/155, 0%; P = 0·038). Carriers of one or two G alleles of this tlr4 polymorphism were more likely to have Gram‐negative, haematogenous and/or chronic osteomyelitis than those without this mutation (P < 0·031). Patients with the TLR4 (Thr399Ile) mutant, which cosegregates with the TLR4 (Asp299Gly), were also carriers of this second polymorphism. No differences for the TLR2 (Arg753Gln) genotypes were found between patients and controls. Neutrophils of patients homozygous for the TLR4 (Asp299Gly) polymorphism showed lower LPS‐induced apoptosis reduction, phosphorylation of the inhibitor of NF‐κB, and lower IL‐6 and TNF‐α levels (P < 0·05). We report here for the first time an association between this TLR4 polymorphism and susceptibility to Gram‐negative bacteria and haematogenous osteomyelitis.

LRRK2 R1441G in Spanish patients with Parkinson's disease

Pathogenic mutations in leucine-rich repeat kinase 2 (LRRK2; PARK8) have been implicated in autosomal dominant, late-onset Parkinsons disease (PD). The LRRK2 4321C>G (R1441G) mutation was originally identified in Spanish families originating from the Basque region. Within this ethnicity, Lrrk2 R1441G substitutions have been suggested as a frequent cause of disease. Herein we have assessed another referral-based series of 225 patients with PD from the neighboring region of Asturias, Northern Spain. The LRRK2 4321C>G mutation was found in 5 (2.7%) of sporadic, late-onset patients and was not present in control subjects. Although patients with a Lrrk2 R1441G substitution are apparently unrelated, they share a chromosome 12q12 haplotype not found in controls and indicative of a common founder.

Mitochondrial DNA polymorphisms and risk of Parkinson's disease in Spanish population

Mutations in mitochondrial DNA (mtDNA) have been implicated in the development of Parkinsons disease (PD). Mitochondrial function is necessary to supply the energy required for cell metabolism, and mutations in mitochondrial genes should have a deleterious effect in neuronal function. An association between several common mtDNA-polymorphisms and the risk of PD has been described. To test this association among Spanish patients, we genotyped 271 PD-patients and 230 healthy controls for 13 single-nucleotide polymorphisms (SNPs) through polymerase chain reaction (PCR) followed by digestion with a restriction enzyme. Alleles at eight of these SNPs define nine common European haplotypes, the mitochondrial haplogroups. In our population, no haplogroup showed significantly different frequencies between patients and controls. A significant association was found for the 4336T/C SNP (a polymorphism in the tRNA gln gene), with allele 4336C having a significantly increased frequency in PD-women compared to controls (OR=4.45; 95%CI=1.23-15.96; p=0.011). We also sequenced five of the complex I genes (ND1 to ND5) in the patients who were 4336C, and no mutation in these genes was found. We also found a significantly reduced frequency of 10398G in patients (p=0.009; OR=0.53), confirming a previously described protective effect for this allele in PD. In conclusion, we provided further evidence of the involvement of mitochondrial DNA variation in PD. In agreement with previous reports, we described a higher risk for PD among women with the mitochondrial 4336C allele in our population, and a protective effect for 10398G.

Profile of microRNAs in the plasma of Parkinson's disease patients and healthy controls

The pathological hallmark of Parkinson’s disease (PD) is the loss of dopaminergic neurons and the presence of Lewy bodies and Lewy neurites in the substantia nigra pars compacta, corpus striatum and brain cortex [1]. PD is a complex disease caused by the interaction of genetic/ inherited and environmental/acquired risk factors [2]. MicroRNAs (miRNAs) are small RNAs that control gene expression by binding to the 30 UTRs of mRNAs [3]. Postmortem analysis of brain tissues and in vitro studies have identified several miRNAs implicated in PD. MiR-133b was shown to be downregulated in PD brains and to promote the survival of dopaminergic neurons [4]. MiR-433 was related with PD through targeting the FGF20, which in turn regulates the expression of a-synuclein [5]. MiR-7 targets a-synuclein and could regulate oxidative stress and cell death, while miR-184 and let-7 regulate dopaminergic neurons survival and activity [6, 7]. Recently, a miRNA profiling of PD brains identified early downregulation of miR-34b/c, modulating mitochondrial function in areas with pathological affectation [8]. Plasma (circulating) miRNAs have been proposed as biomarkers for several diseases and aging [9, 10]. Our aim was to characterize the plasma miRNA profile in PD patients and healthy controls, to determine its usefulness as a biomarker for PD. The study was approved by the Ethical Committee of Hospital Universitario Central de Asturias (HUCA) in accordance with the ethical standards of the Declaration of Helsinki and all the participants signed an informed consent. The study cohort consisted of sexand age-matched healthy controls (n = 25; mean age 67.6; 52 % males) and patients (n = 31; mean age 63.9; 55 % males) who fulfilled the PD-clinical diagnosis criteria [11]. None of the patients were receiving drugs for PD-treatment or had a diagnosis of cardiovascular or tumor disease. Full details of the experimental procedure are available as supplementary material. Briefly, blood was collected in tubes with EDTA, centrifuged and plasma was aliquoted (350 ll). A total of 2 pg of a synthetic Arabidopsis thaliana miRNA (Ath-miR-159a; 5 ll of a 0.4 pg/ll dilution) was immediately added and each aliquot stored at -80 C until use. Ath-miR-159a was used as control of the extraction process (supplementary material). Total plasma RNA was extracted (TRIzol LS Reagent, Ambion) and resuspended in 25 ll of RNAse-free water. Five ll of each sample were retrotranscribed (RT) with the Megaplex RT primers Human pool A and TaqMan microRNA Reverse transcription kit (Applied Biosystems). Three ll of the RT product were pre-amplified with the Megaplex Preamp primers Human pool A and TaqMan Universal Master Mix no AmpErase UNG (Applied Biosystems). All the preamplifications were assayed with a custom Ath-miR-159a Taqman assay in an ABI 7500 Real-Time PCR (Applied Electronic supplementary material The online version of this article (doi:10.1007/s00415-013-6900-8) contains supplementary material, which is available to authorized users.

Evidence of the association of BIN1 and PICALM with the AD risk in contrasting European populations.

Recent genome-wide association studies have identified 5 loci (BIN1, CLU, CR1, EXOC3L2, and PICALM) as genetic determinants of Alzheimers disease (AD). We attempted to confirm the association between these genes and the AD risk in 3 contrasting European populations (from Finland, Italy, and Spain). Because CLU and CR1 had already been analyzed in these populations, we restricted our investigation to BIN1, EXO2CL3, and PICALM. In a total of 2816 AD cases and 2706 controls, we unambiguously replicated the association of rs744373 (for BIN1) and rs541458 (for PICALM) polymorphisms with the AD risk (odds ratio [OR] = 1.26, 95% confidence interval [CI] [1.15-1.38], p = 2.9 × 10(-7), and OR = 0.80, 95% CI [0.74-0.88], p = 4.6 × 10(-7), respectively). In a meta-analysis, rs597668 (EXOC3L2) was also associated with the AD risk, albeit to a lesser extent (OR = 1.19, 95% CI [1.06-1.32], p = 2.0 × 10(-3)). However, this signal did not appear to be independent of APOE. In conclusion, we confirmed that BIN1 and PICALM are genetic determinants of AD, whereas the potential involvement of EXOC3L2 requires further investigation.