Air Pollution: Challenges to Human Health in Pakistan.

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Association of the BB genotype of the ABO gene with the risk of acute myocardial infarction in hospital-based study.

Objectives: The ABO gene locus has been identified to be associated with myocardial infarction in patients with coronary heart disease. The primary focus of this hospital-based study was to explore the relationship of ABO blood groups and ABO genotypes with acute myocardial infarction (AMI) in Karachi, Pakistan. Methods: In a comparative cross-sectional study, an equal number of adult AMI patients and healthy controls (n=275 in each group; age range 30-70 years, both males and females) were recruited from the Aga Khan University and NICVD, Karachi, with informed consent. The blood samples were analyzed for ABO blood groups and other biomarkers. PCR followed by RFLP techniques were employed for determining the ABO genotypes. Multinomial regression was used to evaluate the association of genotypes with the risk of AMI. Results: Thirteen different combinations of ABO genotypes were observed while the O2O2 and A2A2 genotypes were not detected. No significant association based on the distribution of blood groups A, B, O and AB among AMI patients and healthy individuals was observed. The odds of AMI were 3.32 times in subjects with BB genotype as compared to subjects with OO genotypes after adjustment of age, gender, body mass index, heart rate, total cholesterol, and waist circumference [AOR (95% CI) =3.32 (1.36-8.08), p-value =0.008]. Conclusion: Our hospital-based study indicates that ABO genotype BB was significantly associated with the risk of AMI. This harmful effect of the BB genotype could have a possible relationship with AMI's development in the Pakistani population.

Lack of association of HFE gene polymorphism with high body iron status in Pakistani patients with type 2 diabetes mellitus.

OBJECTIVE: The Aim of this study was to investigate the relationship of 3 common polymorphisms in the HFE gene (C282Y, H63D and S65C) with high body iron status in a population of Pakistani subjects with type 2 diabetes mellitus (DM) and to explore if there is any novel mutation in HFE gene in a sample of Pakistani subjects with type 2 DM. METHODS: In a case-control design, 200 healthy controls and 200 consecutive adult subjects with type 2 DM (both gender; age range of 30-70 years) were enrolled with informed consent. Their serum samples were analyzed for body iron status (ratio of concentration of soluble transferrin receptor to ferritin concentration). DNA from blood was screened for HFE gene polymorphisms via polymerase chain reaction, followed by restriction fragment length polymorphism or via Sanger sequencing to identify any novel mutation(s) in HFE gene. RESULTS: We found that there was lack of any association between HFE polymorphism and body iron status in Pakistani subjects with type 2 DM and healthy controls. H63D was the most common polymorphism found in this population. Single base substitution of G nucleotide instead of C at the codon position 187 in the HFE gene exon 2 was discovered in one subject with DM. There was also a lack of association between D allele (variant allele of H63D) and type 2 DM. A significant relationship was found between CG genotype and abnormal albuminuria in subjects with type 2 DM (p = 0.036). CONCLUSION: In conclusion, HFE gene polymorphism is not associated either with high body iron status or type 2 DM in a hospital based Pakistani population and variant allele of H63D polymorphism appears to be associated with diabetic nephropathy.

Higher DNA methylation of ABO gene promoter is associated with acute myocardial infarction in a hospital-based population in Karachi.

OBJECTIVE: To find out if there is any relationship of methylation status of ABO gene promoter with the risk of acute myocardial infarction (AMI) in a hospital-based Pakistani population in Karachi, Pakistan. METHODS: A case control study comprising of 39 adult AMI patients (both males and females; age range 30-70 years) and 39 normal healthy controls (both males and females and similar age range) nested in a large study (to see the relationship of ABO genotypes with AMI) was designed to investigate the methylation status of ABO gene promoter and its association with AMI. The study was carried out at the Aga Khan University, Karachi during July 2018 to June 2019. DNA isolated from samples of AMI patients and normal healthy controls were converted into bisulphite DNA using a kit method. Methylation specific polymerase chain reaction was carried out to determine the methylation status of ABO gene promoter in both cases and controls. Logistic regression was used to find out any association between increased methylation status of ABO gene promoter and risk of AMI. RESULTS: A significantly higher percentage of DNA methylation of the ABO gene promoter was observed in AMI patients as compared to normal healthy controls (82.1% vs. 35.9%; p value <0.001). This higher methylation status of ABO gene promoter was associated with AMI and the odds of AMI in this population were more than 6-fold in subjects with methylated gene promoter compared to those with unmethylated gene promoter after adjusting with age and waist circumference [AOR (95% CI) = 6.27 (1.76-22.3); p value = 0.005]. CONCLUSION: The ABO gene promoter's hypermethylation appears to be increasing the risk of AMI in a hospital-based Pakistani population in Karachi, Pakistan.

Relationship of sociodemographic factors with serum levels of vitamin D in a healthy population of Pakistan.

High prevalence of vitamin D deficiency has been reported from Pakistan. Association of sociodemographic factors with vitamin D status has received little attention in this region. Therefore, we embarked on investigating the relationship of sociodemographic factors with vitamin D levels in a healthy Pakistani population. Venous blood from 226 healthy participants (age range 19-69 years) was collected and analyzed for serum concentrations of 25(OH) vitamin D [25(OH)D] and other related biomarkers. Demographic characteristics of the study participants were collected. Vitamin D deficiency (25(OH)D levels less than 20 ng/ml) was found to be 75% in this cohort. Gender, sunlight exposure and monthly household income emerged as predictors of hypovitaminosis D. Mean serum 25(OH)D levels in the groups with monthly household income less than Pakistani Rupees (PKR) 20,000, between PKR 20,000-50,000 and above PKR 50,000 were found to be 11.0±7.5, 13.9±9.6 and16.9±11.7 ng/ml, respectively. Using logistic regression the odds of having vitamin D deficiency was 3.22 (95% CI, 1.65-6.28) in the group with household income less than PKR 50,000 per month compared to the group with household income more than PKR 50,000 per month when the model was adjusted for gender and exposure to sunlight. There is an association between household income and hypovitaminosis D in a healthy Pakistani population.

Vitamin E deficiency in South Asian population and the therapeutic use of alpha-tocopherol (Vitamin E) for correction of anemia.

Mild to moderate vitamin E deficiency because of inadequate consumption of vitamin E-rich foods and intestinal fat malabsorption is common in growing children, women of reproductive age and elderly South Asian population. Severe vitamin E deficiency may lead to peripheral and motor neurodegenerative diseases (e.g ataxia and motor skeletal myopathy), impaired immune response and free radical-induced hemolytic anemias. Vitamin E insufficiency and/or deficiency status in the general Pakistani population has not been sufficiently investigated. Moreover, there are challenges in determining vitamin E status in apparently healthy humans due to variations in their age, sources of consumed vitamin E and plasma lipid levels. Oxidative stress-induced reactive oxygen species have been shown to cause ineffective erythropoiesis and enhanced lysis of erythrocytes in some of the experimental animals and humans. Several studies on patients with various types of inherited hemolytic anemias, chronic renal disease, premature low birth infants and apparently healthy humans have shown that vitamin E might be therapeutically effective in the prevention and/ or treatment of anemia in these subjects.

Faculty Development Initiatives: A prerequisite for capacity building and enhanced productivity in a medical institution.

OBJECTIVE: To determine the contribution of teaching, learning and assessment forum's initiatives on professional development of faculty and staff. METHODS: This retrospective study was conducted at the Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, from July to December 2016, and comprised teaching, learning and assessment activities carried out from 2012 to 2015. The responses acquired from feedback evaluation were recorded at the end of activity on a Likert-type scale ranging from 1-5. Positive responses were presented for each variable with respective activity type across the study years. The association of the effectiveness of teaching, learning and assessment between type of event and yearly outcome was also assessed. RESULTS: A total of 66activities were held during the study period. Of them, 49(74.24%) were workshops/human resource trainings, 5(7.57%) were courses and 12(18.18%) were seminars. Together, they involved over 500 participants. Objectives, disclosure statement, contents, level of interaction, acquired knowledge, time management, queries responded, organisational activity, course material and overall assessment showed consistent positive response across the years, but the acquisition of new knowledge differed significantly (p<0.05) through the study years. CONCLUSIONS: Teaching, learning and assessment initiatives, play a positive role in professional development of faculty and staff.

Lack of association of statin use with vitamin D levels in a hospital based population of type 2 diabetes mellitus patients.

OBJECTIVE: To investigate the relationship of statins (drug given to reduce serum levels of LDL-cholesterol) on vitamin D levels of Pakistani type 2 diabetes mellitus (DM) patients in a hospital in Karachi. METHODS: In a cross-sectional survey, 312 consecutive patients with type 2 DM (219 males and 93 females, age 22-70 years) were recruited with informed consent. A questionnaire was administered to find out whether they were statin users or non-users. Serum was analyzed for concentrations of 25(OH) vitamin D [25(OH)D] and other related biomarkers such as serum cholesterol, triglycerides, HDL-cholesterol, LDL-cholesterol, phosphate and calcium using kit methods. Multiple Linear Regression was used to evaluate association of statin use with serum levels of vitamin D while adjusting for related covariates including duration of statin use, duration of type 2 DM and smoking. RESULTS: Mean concentrations of serum cholesterol, and LDL-cholesterol were lower among statin users compared to statin non-users (P < 0.01), while HDL-cholesterol levels were higher (P<0.01). No relationship was observed between statin use and serum levels of vitamin D (P=0.768), when adjusted for age, gender, BMI, duration of type 2 DM, smoking, serum cholesterol and LDL-cholesterol. The adjusted regression coefficient (ß) and standard error [SE(ß)] for statin use duration were 0.012 (0.042), when serum levels of vitamin D was taken as an outcome. CONCLUSION: Lack of association was found between statin use and vitamin D levels in a hospital-based population of Pakistani patients with type 2 DM.

CBS mutations and MTFHR SNPs causative of hyperhomocysteinemia in Pakistani children.

Three index patients with hyperhomocysteinemia and ocular anomalies were screened for cystathionine beta synthase (CBS) and methylenetetrahydrofolate reductase (MTHFR) polymorphisms. Genotyping of hyperhomocysteinemia associated MTHFR polymorphisms C677T (rs1801133) and A1298C (rs1801131) was done by PCR-restriction fragment length polymorphism. Sanger sequencing was performed for CBS exonic sequences along with consensus splice sites. In the case of MTHFR polymorphisms, all the patients were heterozygous CT for the single nucleotide polymorphism (SNP) C677T and were therefore carriers of the risk allele (T), while the patients were homozygous CC for the risk genotype of the SNP A1298C. CBS sequencing resulted in the identification of two novel mutations, a missense change (c.467T>C; p.Leu156Pro) in exon 7 and an in-frame deletion (c.808_810del; p.Glu270del) in exon 10. In addition, a recurrent missense mutation (c.770C>T; p.Thr257Met) in exon 10 of the gene was also identified. The mutations were present homozygously in the patients and were inherited from the carrier parents. This is the first report from Pakistan where novel as well as recurrent CBS mutations causing hyperhomocysteinemia and lens dislocation in three patients from different families are being reported with the predicted effect of the risk allele of the MTHFR SNP in causing hyperhomocysteinemia.

Association of Vitamin D binding protein polymorphism with risk of type 2 diabetes mellitus in a Pakistani urban population: A case control study.

OBJECTIVE: To assess if genotypes/diplotypes of vitamin D binding protein have any association with type 2 diabetes mellitus. METHODS: This case-control study was conducted from January 2013 to July 2015 at the endocrinology clinics of the Aga Khan University Hospital, Karachi, and comprised adult patients with type 2 diabetes and their age- and gender-matched healthy controls. Venous blood was obtained and assessed for serum/plasma 25 hydroxyvitamin D, parathyroid hormone, calcium, alkaline phosphatase and creatinine. Deoxyribonucleic acid was isolated and genotyping was done by polymerase chain reaction-restriction fragment length polymorphism procedures. RESULTS: Of the 330 participants, there were 165(50%) cases and as many controls. There were 116(70.3%) males and 49(29.7%) females in each group. The mean age of the patients was 48.82±9.23 years and that of the controls was 46.27±8.77 years (range: 22-70 years) (p=0.010) Mean serum concentration of 25 hydroxy vitamin D was significantly higher among the patients compared to the controls (p<0.001), but not significantly different by genotypes or diplotypes (p>0.05). Multiple conditional logistic regression revealed an association of group-specific 1-2 genotype with patients when adjusted for age, body mass index, and serum levels of 25 hydroxy vitamin D with matched adjusted odds ratio (95% confidence interval) being 3.1(1.22-7.88). CONCLUSIONS: Group-specific 1-2 genotype of vitamin D binding protein gene was associated with the risk of type 2 diabetes.

Association of vitamin D deficiency and VDBP gene polymorphism with the risk of AMI in a Pakistani population.

OBJECTIVE: To investigate the relationship of vitamin D deficiency and risk of AMI in a Pakistani population, and to find out any association between vitamin D binding protein (VDBP) genotypes and risk of AMI in this population. METHODS: In a comparative cross-sectional study, 246 patients (age: 20-70 years; 171 males and 75 females) with first AMI were enrolled with informed consent. Similarly, 345 healthy adults (230 males and 115 females) were enrolled as controls. Their fasting serum samples were analyzed for 25 (OH) vitamin D, lipids and other biomarkers using kit methods, while DNA was analyzed for VDBP genotypes using PCR-RFLP based methods. Chi-squared test and logistic regression were used for association of vitamin D deficiency and VDBP genotypes with AMI. RESULTS: Mean serum concentration of 25(OH) vitamin D was significantly lower in AMI patients compared to healthy subjects (p=0.015) and percent vitamin D deficiency was higher in AMI patients compared to healthy subjects (p=0.003). VDBP IF-IF genotype was positively associated with the risk of AMI in subject above 45 years after adjusting for potential confounders [OR = 9.86; 95% CI=1.16 to 83.43]. CONCLUSION: Vitamin D deficiency and VDBP IF-IF genotype are associated with AMI in Pakistani adults.

Association of vitamin D deficiency with poor glycaemic control in diabetic patients.

OBJECTIVE: An association between serum levels of vitamin D and glycaemic control in type-2 diabetes mellitus (DM) patients has been reported in some of the studies carried out in the West. However, there are no reports on this relationship in Pakistani diabetic patients. The aim of this study was to ascertain whether vitamin D levels have any influence on glycaemic control in Pakistani patients with type-2 DM. METHODS: In a cross-sectional survey, relationship between serum levels of 25-hydroxy vitamin D (25(OH)D) and glycated haemoglobin (HbA1C) was examined in 141 type-2 diabetic patients including 102 males and 39 females; age range 22 to 70 years, visiting the Aga Khan University Hospital during July 2013-April 2014. Venous blood was collected and analyzed for serum/plasma levels of 25(OH)D and related biomarkers using kit methods. HbA1C levels <7.0% and >7.0% were taken as indicators of good and poor glycaemic control, respectively. An association between 25(OH)D and HbA1C was investigated using regression analysis. RESULTS: Percent vitamin D deficiency (serum level of 25(OH)D < 20 ng/ml) was significantly higher in patients with poor glycaemic control compared to patients with good glycaemic control (58.7% vs. 30.6%; p-value=0.006). Binary logistic regression analysis revealed positive association between vitamin D deficiency and poor glycaemic control while adjusting for BMI, serum levels of albumin, alanine aminotransferase and alkaline phosphatase (OR, 4.86 (95% CI, 1.9-11.9; p-value<0.001). CONCLUSIONS: The association between vitamin D deficiency and abnormal HbA1C in Pakistani diabetic patients is suggestive that patients with hypovitaminosis D could benefit from vitamin D supplementation.

Polymorphisms in MTHFR, MS and CBS genes and premature acute myocardial infarction in a Pakistani population.

High prevalence of premature coronary heart disease in Pakistanis compared to other populations points towards the genetic predisposition of this population to develop this disease. Since no investigations have been carried out in Pakistan to study the relationship of polymorphisms in genes involved in homocysteine cycle, the objective of the present study was to find out if there is any association of methylenetetrahydrofolate reductase (MTHFR) C677T, A1298C; methionine synthase (MS) A2756G; cystathionine-ß-synthase (CBS) 844ins68, G919A polymorphisms with premature acute myocardial infarction (AMI) in a population of Pakistani patients with this disease. In a cross-sectional study, DNA samples of 143 AMI patients (age <45 years) and 153 healthy controls were genotyped for the above mentioned polymorphisms using PCR-RFLP methods. Plasma/serum samples of both patients and healthy controls were screened for homocysteine, folate and vitamin B12. One way ANOVA and chi-squared test were used for analysis of data. Mean plasma homocysteine levels in premature AMI patients and healthy controls were found to be 23±17.2 and 23±13.4 µmol/l, respectively which are higher than the upper normal limit of this biomarker (15µmol/l). MTHFR 677 CT genotype in healthy controls and MTHFR 677 TT genotype in AMI patients were found to have significantly increased levels of plasma homocysteine (p value <0.05), while all other polymorphisms did not show any significant difference in mean levels of homocysteine between AMI patients and healthy controls. Moreover, no association was observed between MTHFR C677T, A1298C; MS A2756C; CBS844ins68 polymorphisms and premature AMI in this population. This indicates that common polymorphisms in MTHFR, MS and CBS genes have no role in premature AMI in Pakistani population.

Major dietary patterns and risk of acute myocardial infarction in young, urban Pakistani population.

OBJECTIVE: To investigate the role of dietary intake in the development of premature acute myocardial infarction (AMI) in a hospital-based Pakistani population in Karachi. METHODS: In a case control study, 203 consecutive patients (146 males and 57 females) with their first AMI and age below 45 years were enrolled with informed consent. Similarly, 205 gender and age matched (within 3 years) healthy adults were also included as controls. Dietary intake of both cases and controls was assessed by using a simple 14-item food frequency questionnaire. Using factor analysis, 3 major dietary patterns- prudent dietary pattern, combination dietary pattern and western dietary pattern were identified. Fasting plasma/serum of both cases and controls were analyzed for homocysteine, folate, vitamin B12, blood Pb, ferritin, cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides. ANOVA and conditional logistic regression were used to predict the association of dietary patterns with AMI. RESULTS: Consumption of prudent diet, characterized by high consumption of legumes, vegetables, wheat, chicken and fruits, is protective against the risk of premature AMI. Moderate to high consumption of combination diet, characterized by high intake of eggs, fish, fruits, juices and coffee was associated with decreased risk of AMI. No association was observed between western diet, characterized by high intake of meat, fish and tea with milk and risk of AMI. CONCLUSIONS: Consumption of a prudent dietary pattern and a combination dietary pattern is protective against the risk of AMI in a Pakistani population.

Short Communication: Lack of association between MTHFR gene polymorphisms and response to methotrexate treatment in Pakistani patients with rheumatoid arthritis.

Methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms have been reported to be associated with response to methotrexate (MTX) in certain populations of patients with rheumatoid arthritis (RA). This study aims at investigating any relationship of two single nucleotide polymorphisms (SNPs) in MTHFR gene, C677T and A1298C with response to therapy with MTX in Pakistani RA patients. Allelic frequencies of the two polymorphisms (C677T and A1298C) were determined in 67 RA patients (9 males and 58 females; mean age 42.87 ± 13.5 years) who had previously participated in a prospective clinical trial. Fifty-one patients had received MTX and were followed up for response up to 6 months. Genotyping of the two MTHFR polymorphisms was carried out using PCR-RFLP, while fasting concentration of plasma homocysteine was determined using a kit method. Twenty-eight patients were found to be "good responders", while twenty-three were "poor responders". MTHFR 1298C and MTHFR 677T alleles' frequencies in "good responders" were not different from frequencies in "poor responders" (0.574 vs. 0.521; p=0.6 and 0.197 vs. 0.196; p=0.75, respectively). Plasma homocysteine levels in female RA patients were significantly higher compared to general population in Karachi (13.1 ± 6.7 µmol/l vs. 11.4 ± 5.3 µmol/l; p<0.001). MTHFR C677T and A1298C polymorphisms are not associated with response to MTX in a population of Pakistani RA patients.

Review: Apolipoprotein E (Apo E) gene polymorphism and coronary heart disease in Asian populations.

Apolipoprotein E (Apo E) is a basic component of very low-density lipoprotein (VLDL) and high-density lipoprotein (HDL). It plays an important role in the clearance of cholesterol from circulation, and thereby slows down the process of atherosclerosis. Its 3 isoforms, E2, E3 and E4 are encoded by 3 alleles, e2, e3 and e4, respectively. E3 is the most common isoform in most populations in the world, while E2 is the least frequent isoform. A meta-analysis of several studies conducted on Asian populations revealed that carriers of e4 allele had 42% higher risk of coronary heart disease (CHD), while e2 allele had no significant association with this disease. Epidemiological studies performed in this region showed that E3 was the most prevalent isoform and most likely to be involved in CHD in Asia. Studies conducted in India indicated that individuals with e3/4 and e4/4 genotypes had considerably higher prevalence of dyslipidemia as compared to other genotypes, and hypertensive patients had high frequency of e4 allele. However, several other studies failed to show a relationship between ApoE gene polymorphism and CHD. Inadequate statistical power, low allele frequency, CHD phenotypes could be some of the possible reasons for conflicting results of some of these studies. This area of research is wide open and epidemiological studies with large sample size would be required to ascertain the relationships between ApoE gene polymorphism and CHD.

Low doses of colony-stimulating factors lead to resolution of neutropenia in cancer patients through increased levels of dihydrofolate reductase.

Low doses of granulocyte- colony stimulating factor (G-CSF) and granulocyte macrophage- colony stimulating factor (GM-CSF) have been shown to be beneficial in reducing duration of systemic antibiotic therapy and in-patient hospitalization by decreasing the period of neutropenia in cancer patients undergoing chemotherapy. Since the underlying mechanism is unclear, the aim of this study was to investigate whether the administration of G-CSF and GM-CSF in two different doses (low dose and standard dose) would result into resolution of neutropenia with concomitant increase in multiple forms of dihydrofolate reductase (DHFR, a pivotal enzyme in the pathway of de novo DNA synthesis). Thirty seven cancer patients (26 males and 11 females; age 14-73 years) having chemotherapy-induced neutropenia (absolute neutrophil counts <500/µl) were treated with colony stimulating factor (CSF) in the following manner: 11 received GM-CSF (7 received a dose 250 µg/m2 and 4 received a dose of 100 µg/m(2)); 26 received G-CSF (14 received a dose of 5 µg/kg and 12 received a dose of 2.5 µg/kg). CSFs was given every day till the absolute neutrophil count was more than 1,000/µl. Ten ml blood was collected from each patient and analyzed for total leukocyte count (TLC) and active DHFR and immunoreactive nonfunctional form of DHFR (IRE) in the cytoplasm of blood leukocytes by using methotrexate binding assay and enzyme-linked immunosorbent assay (ELISA). A significant increase (p<0.05) in concentrations of both active DHFR and IRE following stimulation with low as well as standard doses of CSFs was observed along with increase in the TLC. There was no significant difference in number of days to resolution of neutropenia at these two doses, indicating that even low doses of CSFs are clinically effective. Along with an increase in TLC, the levels of DHFR increased even at low doses of CSF suggesting that this might be one of the mechanisms for CSF-induced proliferation of leukocytes in neutropenic cancer patients.

Trans fatty acids - A risk factor for cardiovascular disease.

Trans fatty acids (TFA) are produced either by hydrogenation of unsaturated oils or by biohydrogenation in the stomach of ruminant animals. Vanaspati ghee and margarine have high contents of TFA. A number of studies have shown an association of TFA consumption and increased risk of cardiovascular disease (CVD). This increased risk is because TFA increase the ratio of LDL cholesterol to HDL cholesterol. Food and Agriculture Organization of the United Nations and World Health Organization have come up with the recommendation that the contents of TFA in human dietary fat should be reduced to less than 4%. There is high prevalence of CVD in Pakistan. High consumption of vanaspati ghee which contains 14.2-34.3% of TFA could be one of the factors for this increased burden of CVD in Pakistan. Consumption of dietary fat low in TFA would be helpful in reducing the risk of CVD in South Asia. Denmark by banning the sale of food items with TFA has brought down the number of deaths due to coronary heart disease by nearly 50% over a period of 20 years. Public awareness about the adverse effects of TFA on human health would be extremely important. Media can play a very effective role in educating the masses and advocating the policy for the sale of only low TFA food items. Literature sources: Google and US National Library of Medicine, National Institute of Health were the sources of papers cited in this review article.

Smokeless tobacco use: a risk factor for hyperhomocysteinemia in a Pakistani population.

BACKGROUND: Smokeless tobacco (ST) use is highly prevalent in the South Asian populations. While there have been a number of reports on association of ST consumption with cancer, very few studies have been conducted to investigate its relationship with cardiovascular disease. Hyperhomocysteinemia is a well-recognized risk factor for cardiovascular disease; however, its association with ST use has never been investigated. The objective of this study was to evaluate the relationship of ST use with hyperhomocysteinemia in an urban Pakistani population. METHODOLOGY/PRINCIPAL FINDINGS: In a cross-sectional study for assessment of risks of hyperhomocysteinemia, 872 healthy adults (355 males and 517 females of age range 18-60 years) were recruited from a low-income population in Karachi, Pakistan. A detailed questionnaire was administered which included information about smoking, non-smoking, use of ST alone (chewing as well as sniffing) and use of ST with betel nuts. Fasting serum/plasma levels of homocysteine, folate, vitamin B12 and pyridoxal phosphate (PLP; a coenzymic form of vitamin B6) were analyzed. In this population, 43.4% males and 15.5% females were found to be regular users of ST products. Laborers and vendors were the major ST consumers. Smoking was not found to be associated with plasma/serum concentrations of homocysteine, folate, vitamin B12 and PLP. However, homocysteine concentrations in the group which consumed ST alone and the group which consumed ST along with betel nut were significantly higher compared to the non-user group (17.7±7.5 µmol/L, 25.48 µmol/L vs. 11.95 µmol/L, respectively; p<0.01). Odds ratio for the association of hyperhomocysteinemia (>15 µmol/L) was 11-fold higher in the ST-consumer group compared to the non-user group, [OR (95%CI)  = 11.34 (7.58-16.96); p<0.001], when the model was adjusted for age, gender, folate and vitamin B12 status. CONCLUSION: This study shows a positive association between ST consumption and hyperhomocysteinemia in a low-income urban Pakistani population.