Cerebrospinal and blood levels of amino acids as potential biomarkers for Parkinson's disease: review and meta-analysis

BACKGROUND AND PURPOSE

The present systematic review and meta-analysis aims to establish the possible value of cerebrospinal fluid (CSF) and serum/plasma levels of amino acids as markers of Parkinson's disease (PD).

METHODS

This is a review of four databases (PubMed, Embase, MEDLINE and Web of Science - Core Collection) from 1966 to 14 March 2020, with identification of references of interest for the topic. The meta-analysis of eligible studies was done using R software package meta, following the PRISMA and MOOSE guidelines.

RESULTS

Compared with age- and sex-matched controls, PD patients showed decreased CSF levels of glutamate and taurine and increased CSF levels of tyrosine; decreased serum/plasma levels of aspartate, serine, tryptophan and lysine, and increased serum/plasma proline and homocysteine levels.

CONCLUSION

Despite the limitations of this study due to the important variability of results between different series, our findings suggest the value of CSF or serum/plasma levels of several amino acids in the discrimination of PD patients from healthy subjects, related to the levels of some amino acids.

Update on genetics of essential tremor

Despite the research, few advances in the etiopathogenesis on essential tremor (ET) have been made to date. The high frequency of positive family history of ET and the observed high concordance rates in monozygotic compared with dizygotic twins support a major role of genetic factors in the development of ET. In addition, a possible role of environmental factors has been suggested in the etiology of ET (at least in non-familial forms). Although several gene variants in the LINGO1 gene may increase the risk of ET, to date no causative mutated genes have been identified. In this review, we summarize the studies performed on families with tremor, twin studies, linkage studies, case-control association studies, and exome sequencing in familial ET.

Genetic variants of the arachidonic acid pathway in non-steroidal anti-inflammatory drug-induced acute urticaria

BACKGROUND

To date, genetic studies of hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAIDs) have been carried out mainly in aspirin-induced asthma and to a lesser extent in chronic urticaria, with no studies in patients with acute urticaria (AU), the most common entity induced by these drugs.

OBJECTIVE

In this work, we analysed the association of common variants of 15 relevant genes encoding both enzymes and receptors from the arachidonic acid (AA) pathway with NSAID-induced AU.

METHODS

Patients were recruited in several Allergy Services that are integrated into the Spanish network RIRAAF, and diagnosed of AU induced by cross-intolerance (CRI) to NSAIDs. Genotyping was carried out by TaqMan allelic discrimination assays.

RESULTS

A total of 486 patients with AU induced by CRI to NSAIDs and 536 unrelated controls were included in this large Spanish case-control study. Seven variants from 31 tested in six genes were associated in a discovery study population from Malaga (0.0003 ≤ p-value ≤ 0.041). A follow-up analysis in an independent sample from Madrid replicated three of the SNPs from the ALOX15 (rs7220870), PTGDR (rs8004654) and CYSLTR1 (rs320095) genes (1.055x10(-6) ≤meta-analysis p-value ≤ 0.003).

CONCLUSIONS AND CLINICAL RELEVANCE

Genetic variants of the AA pathway may play an important role in NSAID-induced AU. These data may help understand the mechanism underlying this disease.

Variability of the L-Histidine decarboxylase gene in allergic rhinitis

BACKGROUND

Nonsynonymous polymorphisms in genes coding for histamine-metabolizing enzymes, diamine oxidase and histamine N-methyltransferase are related to the risk of developing allergic diseases. The role of polymorphisms in the histidine decarboxylase gene remains unexplored. The objective of this study is to identify novel polymorphisms in the human histidine decarboxylase gene and to analyse the clinical association of nonsynonymous polymorphisms with rhinitis.

METHODS

We performed a single-strand conformational polymorphism analysis of the histidine decarboxylase gene sequence. The presence of two nonsynonymous polymorphisms Thr31Met (rs17740607) and Glu644Asp (rs2073440) was analysed in 442 unrelated patients with allergic rhinitis, 233 of whom also had asthma, and in 486 healthy subjects.

RESULTS

We observed three novel polymorphisms designated as ss50402829, ss50402830 and ss50402831-(rs17740607) with allele frequencies = 0.005, 0.208 and 0.073, respectively. Statistically significant differences were observed for the histidine decarboxylase Glu644Asp (rs2073440) polymorphism, with OR (95% CI) values for homozygous carriers of the Glu644 allele equal to 3.12 (1.75-5.56, P < 0.00005) for all patients, 3.38 (1.54-7.44, P = 0.002) for patients with rhinitis alone, and 2.92 (1.43-5.95), P = 0.003 for patients with rhinitis + asthma, when compared with healthy controls. A significant Glu644 gene-dose effect was observed for overall patients (P = 0.0001), for patients with rhinitis alone (P = 0.005) and for patients with rhinitis + asthma (P = 0.010).

CONCLUSIONS

The HDC allele Glu644 in homozygosity increases the risk of developing rhinitis in the studied population. This adds to increasing evidence supporting a prominent role of genetic variations related to histamine homeostasis in the risk to develop allergic diseases.

Lack of association of LINGO1 rs9652490 and rs11856808 SNPs with familial essential tremor

BACKGROUND

  Essential tremor (ET) is a frequent movement disorder with a substantial family aggregation. A genome-wide association study has recently shown that LINGO1 gene variants are associated with increased risk of ET.

METHODS

  We intended to replicate these findings by genotyping rs9652490 and rs11856808 in a series of 226 familial ET subjects and 1117 healthy controls from referral movement disorder clinics in Spain.

RESULTS

  We were unable to replicate the association between LINGO1 variants and familial ET.

CONCLUSIONS

  Our results indicate that the LINGO1 variants analyzed are not a major risk factor for developing familial ET in our population, which suggests the existence of other unknown genetic risk factors responsible for familial ET in the Spanish population.

Paraoxonase 1 (PON1) polymorphisms and risk for essential tremor

BACKGROUND

The polymorphic enzyme human serum paraoxonase 1 (PON1), encoded by the gene PON1 (chromosome 7q21.3), plays a major role in the metabolism of organophosphorus compounds. We investigated the possible association between the PON1 genotype and allelic variants of the polymorphisms Leu55Met and Glu192Arg, and the risk for essential tremor (ET).

METHODS

We studied the frequency of the PON1 genotypes and allelic variants in 201 patients with ET and 220 healthy controls using a PCR-RLFP method.

RESULTS

The frequencies of the PON1 genotypes and allelic variants of the polymorphisms Leu55Met and Gln192Arg did not differ significantly between patients with ET and controls. These polymorphisms were unrelated with the age of onset of ET.

CONCLUSIONS

PON1 polymorphisms are not related with the risk for ET.

Impairment of rapid repetitive finger movements and visual reaction time in patients with essential tremor

BACKGROUND AND PURPOSE

The question whether patients with essential tremor (ET) have slowed movements as part of their clinical manifestations is still a matter of controversy. We analyzed basic motor function in patients with ET and in healthy matched controls.

METHODS

We studied 61 patients with ET and 122 age- and sex-matched controls. Evaluation included four timed tests (pronation-supination, finger tapping and movement between two points, all with both hands, and walking test); and three tests performed on a personal computer (speed for pressing repetitively a key - frequency, visual reaction time and movement time, all with both hands).

RESULTS

Essential tremor patients showed higher mean values for right and left finger tapping, left movement between two points; and with right and left frequency and reaction time. In the logistic regression study, ET patients showed significantly higher values than controls for right and left finger tapping; mean, SD, maximum and rank values of right and left frequency; and mean, SD, minimum, maximum and rank values of right and left visual reaction time. Tremor severity was not correlated with the altered values.

CONCLUSIONS

Patients with ET showed impaired motor performance, at least in some tasks, such as rapid repetitive finger movements (finger tapping and frequency) and visual reaction time (impairment was not related with tremor severity). This probably means that patients with ET have some degree of bradykinesia.

Histamine-N-methyl transferase polymorphism and risk for multiple sclerosis

BACKGROUND

Histamine N-methyltransferase (HNMT) is the main metabolizing enzyme of histamine (a mediator of inflammation implicated in the pathogenesis of multiple sclerosis-MS) in the CNS. We have investigated the possible association between a single nucleotide polymorphism of the HNMT (chromosome 2q22.1), that causes the amino acid substitution Thr105Ile (decreasing enzyme activity) and the risk for MS.

METHODS

We studied the frequency of the HNMT genotypes and allelic variants in 228 MS patients and 295 healthy controls using a PCR-RLFP method.

RESULTS

The frequencies of the HNMT genotypes and allelic variants did not differ significantly between MS patients and controls, and were unrelated with the age of onset of MS, gender, and course of MS.

CONCLUSION

The HNMT polymorphism is not related with the risk for MS.

Effect of common NAT2 variant alleles in the acetylation of the major clonazepam metabolite, 7-aminoclonazepam

We investigated the role of NAT2 on clonazepam acetylation, using transiently expressed human NAT2 alleles. The NAT25*B and the NAT2*6A variant alleles cause a 20 and 22-fold reduction in the Vmax, respectively. We conclude that NAT2 is responsible for 7-aminoclonazepam acetylation and that NAT2 gene polymorphisms impair such metabolic pathway.

[The H63D mutation in the HFE gene is related to the risk of hepatocellular carcinoma]

AIM

To disclose whether mutations in the HFE gene inducing liver iron overload are related to the risk of hepatocellular carcinoma (HCC) in otherwise predisposed patients.

PATIENTS AND METHODS

One hundred and ninety-six patients (161 males) diagnosed with HCC and 181 healthy controls were included in the study. All subjects were white Spaniards.C282Y and H63D mutations in the HFE gene were identified in leucocyte genomic DNA using a polymerase chain reaction (PCR) and specific restriction enzymes. RESULTS (CASES/CONTROLS): 1. Genotype distribution: a) C282Y mutation: homozygotes 1/0, heterozygotes 12/23, wild type 183/158 (p = 0.07, non significant); b) H63D mutation: homozygotes 9/5, heterozygotes 85/52, wild type 102/124 (0dds ratio 2.00, 95% C.I. 1.29-3.12, p = 0.002. Four cases and 6 controls were carriers of heterozygous mixed genotypes. 2. Allele frequencies: a) C282Y mutation: wild type allele 378/339, mutated allele 14/23 (p = 0.11, non significant); b) H63D mutation: wild type allele 289/300, mutated allele 103/62 (0dds ratio 1.72, 95% C.I. 1.19-2.50, p = 0.004). Age at diagnosis, gender and etiology of the underlying liver disease do not influence these findings.

CONCLUSION

The C282Y mutation in the HFE gene is not related to the risk of HCC in non-hemochromatosis patients. The H63D mutation is associated with a higher risk of HCC in cirrhotic patients irrespective of their underlying liver disease.

Glutathione-S-transferase P1 polymorphism and risk for essential tremor

Glutathione-S-transferases (GST) are polymorphic enzymes that participate in the metabolism of carcinogens (including those of tobacco smoke) and pesticides. We investigated the possible association between the GSTP1 genotype and allelic variants and the risk for essential tremor (ET). We studied the frequency of the GSTP1 genotypes and allelic variants in 200 patients with ET and 220 healthy controls using PCR-RFLP method. The association between GSTP1 polymorphism and the exposure to some environmental factors (agricultural work, pesticides, well-water and smoking-cigarettes habit) was also studied in a subgroup of patients. The frequencies of the GSTP1 genotypes and allelic variants did not differ significantly between patients with ET and controls or between patients with ET exposed to agricultural work, well water and cigarette smoking versus those non-exposed. Mutated allelic variants were significantly more frequent in patients with ET exposed to pesticides versus those non-exposed. GSTP1 polymorphism was unrelated with the age of onset of ET. GSTP1 genotypes and allelic variants were not related with the risk for ET with the possible exception of those patients exposed to pesticides.

Polymorphisms of histamine-metabolizing enzymes and clinical manifestations of asthma and allergic rhinitis

BACKGROUND

Polymorphisms of enzymes involved in histamine biodisposition may affect clinical symptoms in diseases related to histamine, such as asthma or allergic rhinitis (AR).

OBJECTIVE

This study aims to analyse two common polymorphisms in genes coding for histamine-metabolizing enzymes in patients with allergic diseases.

METHODS

Five-hundred and sixty-five individuals participated in the study, including 270 unrelated patients with asthma and/or AR recruited from a single centre and 295 healthy volunteers. Participants were analysed for the presence of Thr105Ile and His645Asp amino acid substitutions at histamine N-methyltransferase (HNMT) and diamine oxidase (amiloride binding protein 1) enzymes, respectively, by amplification-restriction procedures.

RESULTS

The variant HNMT allele frequencies were slightly higher among patients with asthma [16.0%, 95% confidence interval (CI) 12.0-20.0] and among patients with rhinitis (13.2, 95% CI 10.3-16.1) as compared with healthy subjects (11.5 95% CI 8.9-14.1). The variant ABP1 allele frequencies were similar among patients with asthma (30.8%, 95% CI 25.7-35.9), rhinitis (28.7, 95% CI 24.8-32.6) and healthy subjects (26.8 95% CI 23.2-30.3). Individuals carrying mutated ABP1 alleles presented allergy symptoms with significantly lower IgE levels as compared with individuals without mutated genes, with a significant gene-dose effect (P<0.001). In addition, the percentage of individuals presenting symptoms without eosinophilia was significantly higher among homozygous carriers of ABP1 variant alleles (P<0.020) as compared with the rest of the atopic patients.

CONCLUSION

There is a lack of association between the allelic variants studied and the risk of developing allergic asthma and rhinitis. However, patients carrying the His645Asp polymorphism of ABP1 are more prone to developing symptoms with lower IgE levels.

[Clinical pharmacogenomics for CYP2C8 and CYP2C9: general concepts and application to the use of NSAIDs]

OBJECTIVE

To study the major mutations in genes CYP2C8 and CYP2C9, their frequency in populations of diverse ethnical descent, their analysis methods, and the major drugs with affected metabolism, with a special emphasis on NSAIDs.

METHOD

Repeated searches of Pubmed (January 1966-January 2006) and Scholar Google were performed. All searches were restricted to studies in humans, and papers not written in Spanish or English were excluded.

RESULTS

Ten allelic variants of CYP2C8 and 24 of CYP2C have been reported. Not all of them exert a relevant effect on drug metabolism. In Caucasians 22% of CYP2C8 genes and 31% of CYP2C9 genes have mutations. In Asians fewer than 1% and nearly 3% are mutated, respectively. Major identification methods include endonuclease digestion, PCR, pyrosequencing, and microarrays. Not all NSAIDs are exclusive substrates for CYP2C8/9. The usefulness of allelic variant analysis varies with each individual drug. The risk for digestive hemorrhage associated with the CYP2C9 genotype is particularly relevant when using aceclofenac, celecoxib, diclofenac, ibuprofen, indomethacin, lornoxicam, piroxicam, or naproxen.

CONCLUSIONS

Although CYP2C8/9 activity plays an essential role in the metabolism of and clinical response to many NSAIDs, the use of pharmacogenomic techniques is not equally useful for all these drugs.

Increased frequency of rapid acetylator genotypes in patients with brain astrocytoma and meningioma

OBJECTIVES

The arylamine N-acetyltransferase (NAT2) is a polymorphic enzyme involved in deactivation and activation of carcinogens through N- and O-acetylation. We investigated the association between the genetic NAT2 polymorphism and brain tumors by analysis of genomic DNA from 71 brain tumor patients and 258 healthy controls.

MATERIALS AND METHODS

Seven single nucleotide polymorphisms of the NAT2 gene were studied by using allele-specific polymerase chain reaction amplification.

RESULTS

Ten different NAT2 allelic variants were identified in both patient and control groups. A higher number of individuals carrying functional NAT2 genes, and therefore with a rapid acetylation phenotype, was found in brain tumor patients vs healthy volunteers (OR 1.79, 95% CI 1.05-3.05; P < 0.05). This is observed either for patients suffering from meningioma or astrocytoma, and this is due to an increase of the wild-type NAT2*4 allelic variant frequency (OR 1.48, 95% CI 0.99-2.19), and a reduction of the commonest defective allelic variant NAT2*5B in the brain tumor patients, compared with healthy subjects (OR 0.54, 95% CI 0.37-0.80).

CONCLUSIONS

This observation indicates that NAT2 could be considered as a low-penetrance gene for brain tumors, and that individuals carrying rapid acetylation alleles are at increased risk of developing brain tumors.

Leflunomide-induced acute hepatitis

Leflunomide, a new immunomodulatory agent, was prescribed to a 67-year-old female patient with rheumatoid arthritis. Fifteen days later she developed diarrhoea and elevated liver enzymes. A liver biopsy showed a pattern of acute hepatitis. The patient was homozygous for the rare CYP2C9*3 allele, which determines the slowest metabolic rate for CYP2C9 enzymatic activity, that is probably involved in the metabolism of leflunomide. Liver damage subsided in few weeks. This case illustrates the risk of hepatotoxicity by leflunomide and suggests that it is possibly related to CYP2C9 polymorphism.

Expression of paclitaxel-inactivating CYP3A activity in human colorectal cancer: implications for drug therapy

Cytochrome P450 3A is a drug-metabolising enzyme activity due to CYP3A4 and CYP3A5 gene products, that is involved in the inactivation of anticancer drugs. This study analyses the potential of cytochrome P450 3A enzyme in human colorectal cancer to impact anticancer therapy with drugs that are cytochrome P450 3A substrates. Enzyme activity, variability and properties, and the ability to inactivate paclitaxel (taxol) were analysed in human colorectal cancer and healthy colorectal epithelium. Cytochrome P450 3A enzyme activity is present in healthy and tumoral samples, with a nearly 10-fold interindividual variability. Nifedipine oxidation activity+/-s.d. for colorectal cancer microsomes was 67.8+/-36.6 pmol min(-1) mg(-1). The K(m) of the tumoral enzyme (42+/-8 microM) is similar to that in healthy colorectal epithelium (36+/-8 microM) and the human liver enzyme. Colorectal cancer microsomes metabolised the anticancer drug paclitaxel with a mean activity was 3.1+/-1.2 pmol min(-1) mg(-1). The main metabolic pathway is carried out by cytochrome P450 3A, and it is inhibited by the cytochrome P450 3A-specific inhibitor ketoconazole with a K(I) value of 31 nM. This study demonstrates the occurrence of cytochrome P450 3A-dependent metabolism in colorectal cancer tissue. The metabolic activity confers to cancer cells the ability to inactivate cytochrome P450 3A substrates and may modulate tumour sensitivity to anticancer drugs.

N-acetyltransferase 2 polymorphism is not related to the risk of advanced alcoholic liver disease

BACKGROUND

Ethanol abuse is the most prevalent cause of liver cirrhosis in Spain. Genetic polymorphisms affect the activity of the enzymes involved in ethanol metabolism and in processing the toxic by-products generated in the liver. N-acetyltransferase 2 (NAT2) is a polymorphic phase 2 enzyme not involved in these processes, but recent data suggest that the most prevalent slow acetylator genotype protects against the risk of advanced alcoholic liver disease (ALD). We have identified six single nucleotide polymorphisms (SNP) at the NAT2 gene locus in order to disclose whether such an association exists.

METHODS

Genomic DNA from 95 ALD patients (15 with superimposed hepatocellular carcinoma (HCC)) and from 258 healthy individuals was analysed for SNPs at the coding region of the NAT2 gene by means of allele-specific polymerase chain reaction.

RESULTS

There are no differences in the relative frequencies of the eight identified NAT2 alleles (including the wild-type allele) nor in the distribution of predicted phenotypes (54% of slow acetylators in each group). Twelve patients with HCC (80%) were slow acetylators (P < 0.05).

CONCLUSIONS

There is no relationship between the NAT2 genotype and the risk of ALD. Slow acetylator genotype may predispose to the development of HCC in severe ALD patients not infected by the hepatitis C virus.