Relationship of Lung Function with Homocysteine, Vitamin B 12 and Folic Acid Level in Metabolic Syndrome

Background: Metabolic syndrome (MetS) is a complex metabolic disorder and with debilitating effects on many organs including lung function impairment. Hyperhomocysteinaemia is caused by nutritional deficiency of vitamin B 12 and folic acid can increase this risk further. Both the metabolic syndrome and hyperhomocysteinaemia adversely affect the lung function. But no study was found in Bangladeshi MetS in this regard. Objective: To assess the relationship of lung function with serum homocysteine, vitamin B 12 and folic acid level in metabolic syndrome . Methods: This cross-sectional study was conducted in the department of physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka from November, 2019 to April, 2020. A total of 60 female subjects were selected with the age ranging from 25-45 year by purposive sampling. Among them 30 metabolic syndrome patients were included in the study group (group A) and 30 age and sex matched apparently healthy subjects constituted comparison group (group B). Serum homocysteine, vitamin B 12 , folic acid and other biochemical parameters and the lung function of all subjects were assessed. Data were expressed as mean±SD. Spirometric measures were expressed as percent of predicted value. Statistical analysis was done by Independent sample ‘t’ test and Pearson’s correlation coefficient test. Results: In this study, the mean percentage of predicted value of FVC, FEV 1 and, PEFR were significantly lower ( p <0.001) in group A than those of group B. The mean serum homocysteine level was higher and vitamin B 12 and folic acid level were lower in metabolic syndrome patients compared to comparison group and the difference was statistically significant only for homocysteine ( p <0.05). In addition, the FVC and FEV 1 were significantly negatively correlated ( p <0.05) with serum homocysteine and FVC was significantly positively correlated ( p <0.05) with serum folic acid level in group A. Conclusion: The present study reveals that impairment of lung function is related to higher level of homocysteine and lower level of folic acid in metabolic syndrome.

to evaluate ventilatory function of lung. It is widely used and well recognized procedure for assessing lung function 7 .
Several studies found higher level of homocysteine and/or lower level of vitamin B 12 and folic acid in MetS [8][9][10] . On the contrary, some studies found no significant changes in homocysteine, vitamin B 12 and folic acid level in this group of patients. 11,12 Homocysteine is toxic, nonproteogenic sulfer containing amino acid which is produced from demethylation of dietary methionine in the liver. Homocysteine is metabolised either via transsulfuration or remethylation pathway. About half of the intracellular homocysteine remethylated to methionine by methionine synthase. Vitamin B 12 and folic acid are required for this reaction. Other half of homocystein transsulfurated to cystein with the help of cystathione E-synthase which require vitamin B 6 as a cofactor. The cystein ultimately converted to sulfate and cleared from the body via urine. [13][14][15] Aberrant homocysteine metabolism leads to cytotoxicity by redox imbalance and oxidative stress by elevated protein, nucleic acid and carbohydrate oxidation and lipoperoxidation. 16 Lower level of vitamin B 12 strongly correlates with lipid peroxidation and folic acid minimize oxidative stress. 17,18 Hyperhomocysteinaemia causes oxidative stress in rat lung by lipid peroxidation, oxidative damage to protein and disrupted enzymatic and non-enzymatic antioxidant defense. 19 Several studies observed the relationship of lung function with homocysteine, vitamin B 12 and folic acid in general population and in COPD patients. [20][21][22] Despite reports regarding relationship between lung function and homocysteine, vitamin B 12 and folic acid level in general population and in COPD patients, there is no evidence of investigating relationship between them in MetS. Exploring this relationship may be helpful in prevention, early diagnosis and effective management of impaired lung function related morbidity in this group of patients.

Materials and Methods
This was a cross sectional study, conducted in the depertment of physiology, BSMMU from November 2019 to April 2020. The protocol of this study was approved by Institutional Review Board, BSMMU, Dhaka. Thirty diagnosed MetS patients with age range 25-45 years were included in the study group. Another 30 age and sex matched apparently healthy subject were taken as comparison group who were in good physical health. All the subjects were free from respiratory, cardiac, renal and chronic liver disease. Individual having thyroid disorders, malignancy, menopause and on nutritional supplement like multivitamins (within 120 days) were excluded from the study. The study group were selected from the Department of Endocrinology, OPD, BSMMU, Dhaka who were diagnosed as metabolic syndrome. The comparison group were collected among the relatives and attendants of patients, hospital staff and subjects available in the BSSMU campus and also through personal contacts from different areas of Bangladesh.
After selection of the subjects, thorough information was given to them about the objectives and study procedure. Informed written consent was obtained from all the participants who were voluntarily participated. The patients were also allowed freedom to withdraw herself from the study even after participation whenever they feel. Detail dietary, family, menstrual and medical history were taken and thorough physical examination, anthropometric measurement including waist circumference were recorded on a data schedule. Then 10 ml venous blood was collected in fasting condition from ante-cubital vein of each subject of both groups for estimation of FPG, fasting lipid profile, serum creatinine, serum alanine aminotransferase. If these were normal, the other biochemical variables were estimated.
After final selection serum homocysteine, vitamin B 12 , folic acid were assessed from the preserved blood by chemiluminescent immunoassay. The selected subjects were again requested to attend the department of physiology with all preparation of lung function test on next day. To assess lung function, spirometry was done using a portable spirometer (PONY FX, cosmed, Italy] in the lung function laboratory in the department of physiology.
Data were expressed as mean ± SD. Spirometric measures were expressed as percent of predicted value. Independent sample 't' test was done to compare mean value of all parameters between study group and comparison group. Pearson's correlation test was done to see the relationship of lung function parameters with serum homocysteine, vitamin B 12 and folic acid level in metabolic syndrome patients by using SPSS.

Results
In this study, total 60 subjects were enrolled. Among them 30 were study subjects and 30 were age, sex matched apparently healthy comparison subjects. Data were collected from all the subjects. The mean percentage of predicted value of FVC and FEV 1       The present study revealed that, FEV 1 /FVC ratio is higher but non significant in metabolic syndrome patients when compared to healthy subjects. Almost similar findings were reported by Soares et al. 6 Whereas, Negm et al reported significantly higher FEV 1 /FVC ratio in metabolic syndrome patient than healthy subjects. 3  The current study revealed that serum vitamin B 12 and folic acid were lower in MetS patients than those of comparison group but those were statistically nonsignificant. But Guven and Inanc, Maiti and Das and Narang, Singh and Dange found significantly lower these parameters in MetS patients in comparison to healthy individuals. [8][9][10] In this study, Pearson's correlation coefficient (r) test was performed to observe the relationship of lung function measures with serum homocysteine, vitamin B 12 and folic acid level in metabolic syndrome.
In metabolic syndrome group mean FVC, FEV1, FEV1/FVC, PEFR and FEF 25-75% were negatively correlated with serum homocysteine level but only FVC and FEV1 were statistically significant (p<0.05). Almost similar findings were observed by Nunomiya et al. in general population. 22 In metabolic syndrome group, mean FVC, FEV1, FEV1/FVC, PEFR and FEF 25-75% were negatively correlated with serum vitamin B 12 level but these were statistically non-significant. No previous study was available to compare these findings.
In metabolic syndrome group, mean FVC, FEV1, FEV1/FVC, PEFR and FEF 25-75% were positively correlated with serum folic acid level but it was statistically significant only for FVC (p<0.05). No previous study was available to compare these findings.

Conclusion
Based on the results of the present study, it can be concluded that, impairment of lung function is related to higher level of homocysteine and lower level of folic acid in metabolic syndrome.