Distribution of xenobiotic metabolising enzyme genotypes in different Tunisian populations.

BACKGROUND: The N-acetyltransferase 2 (NAT2) and glutathione transferase enzymes play a crucial role in the metabolism of xenobiotics. Genetic polymorphisms affecting these enzymes can modify their activities with an effect on individual susceptibility for different pathologies. These metabolic phenotypes occur with varying prevalence in different populations. AIM: This study sought to analyse the prevalence of important allelic variants of NAT2, GSTM1 and GSTT1 in different Tunisian populations and compare them to other previously reported data. SUBJECTS AND METHODS: A total of 253 unrelated subjects from different Tunisian populations participated in this study. Subjects were examined with respect to the frequency of slow NAT2, GSTM1*0 and GSTT1*0 genotypes. RESULTS: The frequency of 'slow' NAT2, GSTM1*0 and GSTT1*0 genotypes in the Tunisian population were, respectively, estimated at 23.3%, 53.75% and 29.24%. The frequency of slow NAT2 and GSTM1*0 genotypes were significantly different between the North, Centre and South of Tunisia. However, this study doesn't report any significant differences in the genotype distribution between Cosmopolitan, Arab and Berber populations. CONCLUSIONS: In conclusion, these data indicate that the Tunisian population is highly heterogenic and, therefore, a strict definition of the populations involved in studies investigating the clinical effect of polymorphisms is required.

Relationship of thyroid function with obesity and type 2 diabetes in euthyroid Tunisian subjects.

OBJECTIVES: Although a relationship between obesity and metabolic consequences with thyroid function has been reported, the underlying pathogenesis is not completely known. In the current study, we evaluated the thyroid function in obese and/or diabetic patients compared to healthy normal weight peers, exploring the possible association between components of metabolic syndrome and thyroid function parameters. METHODS: We recruited 108 subjects (56 male and 52 female). In all subjects, thyroid stimulating hormone (TSH), free thyroxine (FT4), fasting plasma levels of insulin and glucose, homeostasis model assessment for insulin resistance, and obesity parameters were assessed. RESULTS: We found that circulating levels of TSH and FT4 were significantly increased in overweight and obese subjects. However, the data do not reveal any change of these hormones in diabetics. Multivariate linear regression analysis showed that TSH was directly associated with both obesity and insulin resistance parameters (p < 0.05). FT4 was negatively associated only with obesity parameters (p < 0.05). CONCLUSIONS: Our data strongly support that the changes of thyroid hormones may be influenced by adiposity and its metabolic consequences, such as insulin resistance. This relationship can be explained by a cross talk between adipose tissue release and thyroid function. Nevertheless, metformin treatment seems to affect thyroid function in diabetic patients by maintaining plasma thyrotropin levels to subnormal levels.

The effect of tobacco, XPC, ERCC2 and ERCC5 genetic variants in bladder cancer development.

BACKGROUND: In this work, we have conducted a case-control study in order to assess the effect of tobacco and three genetic polymorphisms in XPC, ERCC2 and ERCC5 genes (rs2228001, rs13181 and rs17655) in bladder cancer development in Tunisia. We have also tried to evaluate whether these variants affect the bladder tumor stage and grade. METHODS: The patients group was constituted of 193 newly diagnosed cases of bladder tumors. The controls group was constituted of non-related healthy subjects. The rs2228001, rs13181 and rs17655 polymorphisms were genotyped using a polymerase chain reaction-restriction fragment length polymorphism technique. RESULTS: Our data have reported that non smoker and light smoker patients (1-19PY) are protected against bladder cancer development. Moreover, light smokers have less risk for developing advanced tumors stage. When we investigated the effect of genetic polymorphisms in bladder cancer development we have found that ERCC2 and ERCC5 variants were not implicated in the bladder cancer occurrence. However, the mutated homozygous genotype for XPC gene was associated with 2.09-fold increased risk of developing bladder cancer compared to the control carrying the wild genotype (p = 0.03, OR = 2.09, CI 95% 1.09-3.99). Finally, we have found that the XPC, ERCC2 and ERCC5 variants don't affect the tumors stage and grade. CONCLUSION: These results suggest that the mutated homozygous genotype for XPC gene was associated with increased risk of developing bladder. However we have found no association between rs2228001, rs13181 and rs17655 polymorphisms and tumors stage and grade.

In vivo prevention of bladder urotoxicity: purified hydroxytyrosol ameliorates urotoxic effects of cyclophosphamide and buthionine sulfoximine in mice.

Urotoxicity is a troublesome complication associated with cyclophosphamide (CP) and L-buthionine-SR-sulfoximine (BSO) treatment in chemotherapy. With this concern in mind, the present study investigated the potential effects of a hydroxytyrosol extract from olive mill waste (OMW) on urotoxicity induced by acute CP and BSO doses using a Swiss albino mouse model. Toxicity modulation was evaluated by measuring lipid peroxidation (LPO) and antioxidants in urinary bladder. The findings revealed that the hydroxytyrosol extract exerted a protective effect not only on LPO but also on enzymatic antioxidants. When compared to the controls, the CP-treated animals underwent significant decreases in the glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GP), and catalase (CAT) activities. The level of glutathione (GSH) was also reduced with increased doses of LPO in the CP-treated animals. L-Buthionine-SR-sulfoximine treatment exerted an additive toxic effect on the CP-treated animals. Interestingly, pretreatment with the hydroxytyrosol extract restored the activities of all enzymes back to normal levels and exhibited an overall protective effect on the CP- and BSO-induced toxicities in urinary bladder. The restoration of GSH through the treatment with the hydroxytyrosol extract can play an important role in reversing CP-induced apoptosis and free radical-mediated LPO. 

Combined analysis of smoking, TP53, and FGFR3 mutations in Tunisian patients with invasive and superficial high-grade bladder tumors.

In our cohort, FGFR3 mutations were detected in 31.1% of bladder tumors and are associated with lower stage and grade. Concerning TP53, 62 mutations were found in tumors from 44 cases (48.88%) and are associated with advanced forms. The combined analysis of FGFR3 and TP53 mutations in our cohort showed an independent distribution. In addition, we have reported that FGFR3 mutations spectrum depends on the intensity of tobacco use (pack years: PY). Finally, we have found that the FGFR3wt/TP53mut genotype, which was associated with advanced bladder tumors; was overrepresented in light smokers (PY < 40) compared to nonsmoker patients (p =.01).

Human subcutaneous adipose tissue Glut 4 mRNA expression in obesity and type 2 diabetes.

Cellular resistance to insulin caused by reduced glucose transport and metabolism is a primary defect leading to the development of metabolic disease. While the etiology of insulin resistance is multifactorial, reduced insulin action is associated with impaired activity of the glucose transporter GLUT4 in insulin-sensitive tissues. Yet, the role of adipose tissue GLUT4 deregulation in the pathogenesis of insulin resistance, obesity, and diabetes is still unclear. In this study, we assessed the relative GLUT4 level in human subcutaneous adipose tissue from obese, diabetic, and diabetic obese versus control subjects, using a real-time PCR method. GLUT4 mRNA levels were considerably decreased among type 2 diabetic patients compared with those of the controls (P < 0.01), whereas no such difference was found between obese and normal-weight controls. Multiple linear regressions analysis in both diabetic non-obese and diabetic obese groups showed a negative correlation between GLUT4 mRNA expression and both markers of obesity or insulin resistance (P < 0.01). However, in obese group, GLUT4 was inversely associated only with HOMA-IR (P < 0.01). Our findings showed that adipose GLUT4 gene expression changes were more related to insulin resistance and type 2 diabetes rather than to obesity.

MTHFR gene polymorphisms and bladder cancer susceptibility: a meta-analysis including race, smoking status and tumour stage.

Epidemiological studies have investigated that functional polymorphisms in the methylene-tetrahydrofolate reductase (MTHFR) gene may play an essential role in bladder carcinogenesis, but the numerous published studies have reported inconclusive results. The objective of the current study was to conduct an updated analysis in order to investigate the association between polymorphisms in the MTHFR gene and risk of bladder cancer. We searched the Pubmed database for all articles published up to March 31, 2011 that addressed bladder cancer and polymorphisms and variants or mutations of MTHFR for analysis using statistical software. Results for two polymorphisms (C677T and A1298C) in 27 case-control were studies from 15 articles indicated individuals carrying the 677T allele (TC or TT+TC) to have a reduction to a 29% or 21% compared to the wild genotype (CC) in mixed populations (OR: 0.71, 95%CI: 0.55-0.93 or OR: 0.79, 95%CI: 0.64-0.97, respectively) and it is shown that there is significant positive associations between A1298C polymorphism and bladder cancer in Africans (OR: 1.24, 95%CI: 1.02-1.52 for C vs.A; OR: 1.35, 95%CI: 1.10-1.66 for CA vs. AA; OR: 1.29, 95%CI: 1.08-1.55 for CC+CA vs. AA). However, no significant relationship was found in two polymorphisms in the stratified analysis by smoking status. Interestingly, individuals carrying the 677T allele (TT+TC) demonstrated a higher percentage of invasive than superficial cases (OR: 1.38, 95%CI: 1.13-1.69). The results from the current update analysis suggest that C677T and A1298C polymorphisms in the MTHFR gene are associated with bladder cancer risk and prognosis. Further evaluation based on more studies with larger groups of patients are now required.

Smoking and polymorphisms in folate metabolizing genes and their effects on the histological stage and grade for bladder tumors.

Folates are the common sources of DNA synthesis and methylation. Cigarette smoking and genetic susceptibility of folate enzymes are two suspected factors most closely associated with bladder cancer development. This study sought to determine the effect of smoking and genetic polymorphisms in folate metabolizing enzymes on the histological stage and grade of bladder tumors in Tunisian patients. A total of 130 patients with urothelial cell carcinomas were examined with respect to smoking status, MTHFR (5,10-methylenetetrahydrofolate reductase), MTR (methionine synthase), MTRR (methionine synthase reductase) and TYMS (thymidylate synthase) genotypes distribution. Our data have reported that tobacco, MTHFR, MTR and MTRR genotypes were not associated with bladder tumor stage. Only TYMS 3R*G/3R*C genotype was associated with increased risk of developing invasive tumors compared to reference group (RR = 1.74; 95% CI: 0.97-3.12). When we studied the superficial bladder tumor group, we have shown a significant statistical differences for the TYMS 3R*G/2R genotype. This genotype presented a 1.68-fold increased risk of developing high grade tumors compared to reference group (RR = 1.68; 95% CI: 1.12-2.54). Moreover, we have shown that patients having at least one copy of 2R allele were at 4.23-fold increased risk for developing high grade tumors compared to reference group (P = 0.022).

Smoking and polymorphisms in xenobiotic metabolism and DNA repair genes are additive risk factors affecting bladder cancer in Northern Tunisia.

Cancer epidemiology has undergone marked development since the nineteen-fifties. One of the most spectacular and specific contributions was the demonstration of the massive effect of smoking and genetic polymorphisms on the occurrence of bladder cancer. The tobacco carcinogens are metabolized by various xenobiotic metabolizing enzymes, such as the super-families of N-acetyltransferases (NAT) and glutathione S-transferases (GST). DNA repair is essential to an individual's ability to respond to damage caused by tobacco carcinogens. Alterations in DNA repair genes may affect cancer risk by influencing individual susceptibility to this environmental exposure. Polymorphisms in NAT2, GST and DNA repair genes alter the ability of these enzymes to metabolize carcinogens or to repair alterations caused by this process. We have conducted a case-control study to assess the role of smoking, slow NAT2 variants, GSTM1 and GSTT1 null, and XPC, XPD, XPG nucleotide excision-repair (NER) genotypes in bladder cancer development in North Tunisia. Taken alone, each gene unless NAT2 did not appear to be a factor affecting bladder cancer susceptibility. For the NAT2 slow acetylator genotypes, the NAT2*5/*7 diplotype was found to have a 7-fold increased risk to develop bladder cancer (OR = 7.14; 95% CI: 1.30-51.41). However, in tobacco consumers, we have shown that Null GSTM1, Wild GSTT1, Slow NAT2, XPC (CC) and XPG (CC) are genetic risk factors for the disease. When combined together in susceptible individuals compared to protected individuals these risk factors give an elevated OR (OR = 61). So, we have shown a strong cumulative effect of tobacco and different combinations of studied genetic risk factors which lead to a great susceptibility to bladder cancer.

The impact of smoking and polymorphic enzymes of xenobiotic metabolism on the stage of bladder tumors: a generalized ordered logistic regression analysis.

Cigarette smoking is the predominant risk factor for bladder cancer in males and females. The tobacco carcinogens are metabolized by various xenobiotic metabolizing enzymes such as N-acetyltransferases (NAT) and glutathione S-transferases (GST). Polymorphisms in NAT and GST genes alter the ability of these enzymes to metabolize carcinogens. In this paper, we conduct a statistical analysis based on logistic regressions to assess the impact of smoking and metabolizing enzyme genotypes on the risk to develop bladder cancer using a case-control study from Tunisia. We also use the generalized ordered logistic model to investigate whether these factors do have an impact on the progression of bladder tumors.

Combined effect of NAT2, MTR and MTHFR genotypes and tobacco on bladder cancer susceptibility in Tunisian population.

BACKGROUND: Cigarette smoking is the predominant risk factor for bladder cancer. This risk may be modified by polymorphisms in carcinogens metabolism genes; including those involving the N-acetyl transferase 2 (NAT2) which have been correlated with decreased enzyme activities. Moreover, folate insufficiency can induces carcinogenesis by decreasing DNA methylation. Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) are enzymes that play central roles in the folate metabolic pathway. The MTHFR 677*T and MTR 2756*G variants are associated with decreased enzyme activity. METHODS: In this work, we have conducted a case-control study in order to assess the combined effect of tobacco, slow NAT2 variants, MTHFR 677*T and MTR 2756*G alleles on bladder cancer development in North Tunisia. RESULTS: For MTR A2756G, alleles and genotypic distributions differed significantly between cases and controls (p = 0.00009, OR = 3.27, CI 95% 1.76-6.12). While, in non-smokers patients the slow NAT2 did not appear to influence bladder cancer susceptibility; our results suggested that it might act with an additive contribution with tobacco as well as with that determined by MTR 2756 AG or 2756 GG genotypes (p = 0.0008). Identical cumulative effect was detected for slow NAT2 and MTHFR 677*T variant (p = 0.0003; OR = 36.6; CI 95% 3.4-935.3). CONCLUSION: The strongest result obtained by this study was for an additive effect between smoking status, slow NAT2 variants, MTR 2756*G and MTHFR 677*T alleles, in affecting bladder cancer risk.

Combined effect of smoking and inherited polymorphisms in arylamine N-acetyltransferase 2, glutathione S-transferases M1 and T1 on bladder cancer in a Tunisian population.

Cigarette smoking is the predominant risk factor for bladder cancer in males and females. The tobacco carcinogens are metabolized by various xenobiotic metabolizing enzymes, such as the super-families of N-acetyltransferases (NAT) and glutathione S-transferases (GST). Polymorphisms in NAT and GST genes alter the ability of these enzymes to metabolize carcinogens. We have conducted this case-control study to assess the role of smoking, slow NAT2 variants, and GSTM1 and GSTT1 null genotypes in bladder cancer development in North Tunisia. In all groups of patients, we have shown that GSTM1 and GSTT1 null genotypes did not appear to be a factor affecting bladder cancer susceptibility. For the NAT2 slow acetylator genotype, the NAT2*5/*7 diplotype was found to have a 7-fold increased risk of bladder (OR=7.14; 95% CI: 1.30-51.41). Furthermore, we found that NAT2 slow acetylator individuals temporarily carrying wild-type GSTT1 or GSTM1 null genotypes have a strong increased risk of bladder cancer (OR= 26 and 22.17, respectively). This cumulative effect was estimated at 12 for smokers harboring slow or an intermediate NAT2, GSTM1 null, and wild-type GSTT1 genotypes compared to non-smokers carrying rapid NAT2, wild-type GSTM,1 and GSTT1 null genotypes (p=0.02; OR=12; CI 95% 1-323.76).

Polymorphisms in one-carbon metabolism pathway genes and risk for bladder cancer in a Tunisian population.

Cigarette smoking is the most important risk factor for bladder cancer. Moreover, epidemiologic studies have implicated several genetic variations interfering with methyl group metabolisms in susceptibility for a variety of cancers. Examples of these variations can be found in genes of the folate metabolic pathway, which is crucial in the provision of methyl groups for DNA, RNA, and protein methylation, as well as in purine and pyrimidine synthesis. We conducted a case-control study to examine the relationship between the methylenetetrahydrofolate reductase (MTHFR C677 T and MTHFR A1298C), methionine synthase (5-methyltetrahydrofolate-homocysteine methyltransferase, MTR A2756 G), methionine synthase reductase (5-methyltetrahydrofolate-homocysteine methyltransferase reductase, MTRR A66 G and MTRR C524 T), and thymidylate synthase (TYMS 2R-->3R and G/C) genotypes and the risk for bladder cancer in a Tunisian population. The isolated MTHFR 677 *T, MTRR 66 *G and MTRR 524 *T variants did not appear to influence bladder cancer susceptibility. The 3R *C/3R *C genotype for the TYMS gene appears to be a protective factor against bladder cancer development (P=0.0001; OR=0.12; 95% CI=0.03-0.40). However, patients heterozygous for MTHFR A1298C or MTR A2756 G genotypes have 1.62- and 2.13-fold higher risk, respectively, of developing bladder cancer. Moreover, the combined study of MTHFR 1298 *C and MTR 2756 *G variants with either or both MTRR 66GG and TYMS 3R *G/3R *G genotypes suggests a cumulative effect. Finally, this study evidenced that interaction between gene variations involved in folate metabolism and risk of bladder cancer increased dramatically among smokers.