|Year : 2020 | Volume
| Issue : 1 | Page : 9-13
The effect of vitamin C on toxic metals, antioxidant minerals, oxidative stress, and lipid profile of automobile workers
Chikaodili Nwando Obi-Ezeani1, Chudi Emmanuel Dioka2, Samuel Chukwuemeka Meludu3, Ifeoma Joy Onuora4
1 Department of Chemical Pathology, Chukwuemeka Odumegwu Ojukwu University, Awka, Nigeria
2 Department of Chemical Pathology, Nnamdi Azikiwe University, Nnewi, Nigeria
3 Department of Human Biochemistry, Nnamdi Azikiwe University, Nnewi, Nigeria
4 Department of Chemical Pathology, School of Medical Laboratory Technicians, Iyienu Mission Hospital, Ogidi, Anambra, Nigeria
|Date of Submission||15-May-2020|
|Date of Decision||24-May-2020|
|Date of Acceptance||31-May-2020|
|Date of Web Publication||30-Jun-2020|
Dr. Chikaodili Nwando Obi-Ezeani
Department of Chemical Pathology, Chukwuemeka Odumegwu Ojukwu University, Awka, Anambra
Source of Support: None, Conflict of Interest: None
Context: Automobile workers (AMWs) are exposed to lots of toxic chemicals with associated adverse health consequences. The adverse health effects are mainly attributed to oxidative stress, however, antioxidant vitamins may aid in ameliorating these adverse effects. Aim: The aim of this study was to examine the effect of Vitamin C supplementation on toxic metals, antioxidant minerals, oxidative stress, and lipid profile of AMWs. Settings and Design: Twenty-nine AMWs and 30 controls aged 19–55 years were recruited for this study. Subsequently, 27 AMWs received 500 mg Vitamin C tablets daily for 2 months. Subjects and Methods: Five milliliters of fasting blood samples was collected before intervention and at 1- and 2-month intervals for biochemical analyses. Blood lead (Pb), cadmium (Cd), selenium (Se), and zinc (Zn) were analyzed using atomic absorption spectrophotometer, malondialdehyde (MDA) and total antioxidant capacity (TAC) were measured spectrophotometrically, total cholesterol (TC), high-density lipoprotein (HDL), and triglyceride (TG) were measured enzymatically, whereas MDA/TAC, low-density lipoprotein (LDL), very LDL (VLDL), and non-HDL (nHDL) were calculated. Statistical Analysis: Data were analyzed, and statistical significance was set at P < 0.05. Results: The mean levels of Pb, Cd, MDA, MDA/TAC ratio, TC, LDL, VLDL, TG, and nHDL were significantly higher, whereas Se and Zn were significantly lower in AMWs compared to controls (P < 0.05). After 2 months of supplementation, Pb and TG levels decreased significantly, whereas Se, Zn, and HDL levels increased significantly compared to their values at 1 month and baseline (P < 0.05). MDA, MDA/TAC, TC, LDL, VLDL, and nHDL decreased progressively, whereas TAC level increased progressively from baseline to 2 months of Vitamin C intake (P < 0.05). Conclusion: Vitamin C reduced blood lead and oxidative stress, improved antioxidant defense, and may modulate dyslipidemia and adverse cardiovascular outcomes in AMWs.
Keywords: Antioxidant, lipid profile, oxidative stress, toxic metals, Vitamin C
|How to cite this article:|
Obi-Ezeani CN, Dioka CE, Meludu SC, Onuora IJ. The effect of vitamin C on toxic metals, antioxidant minerals, oxidative stress, and lipid profile of automobile workers. J Integr Health Sci 2020;8:9-13
|How to cite this URL:|
Obi-Ezeani CN, Dioka CE, Meludu SC, Onuora IJ. The effect of vitamin C on toxic metals, antioxidant minerals, oxidative stress, and lipid profile of automobile workers. J Integr Health Sci [serial online] 2020 [cited 2020 Oct 21];8:9-13. Available from: https://www.jihs.in/text.asp?2020/8/1/9/288681
| Introduction|| |
Automobile workers (AMWs) are occupationally exposed to an array of hazardous substances including toxic metals, heavy metal contaminated dust, fumes, and polycyclic aromatic hydrocarbons  which adversely affect their health by altering various biological and biochemical processes; these adverse health effects are mainly attributed to oxidative stress. Oxidative stress is an imbalance between oxidants and antioxidants which could result to various pathological conditions including cancers, cardiovascular diseases, and others. These toxic chemicals or substances are known to increase the generation of reactive oxygen species (ROS) and consequently oxidation of biomolecules including proteins, lipids, and nucleic acids. Lipid peroxidation which enhances oxidative stress as well as altered lipid parameters is known to increase the risk of cardiovascular diseases (CVDs), however, dietary supplements including antioxidant vitamins may play a vital role in the prevention or reduction of CVD risk in this group of workers.
VC, also known as ascorbic acid, is naturally present in many fruits and vegetables such as oranges, watermelon, pineapple, and grapefruit and also available as a dietary supplement in the form of tablets, capsules, or suspensions. It is a vital nutrient and antioxidant that scavenges free radicals, protecting against oxidative damage. VC is one of the essential vitamins in humans since they lack the enzyme L-gulonolactone oxidase required in the last step of its synthetic pathway. Vitamin C may help prevent or delay the development of some diseases in which oxidative stress plays a causal role by limiting the damaging effects of the free radicals through its antioxidant activity.
Since oxidative stress and dyslipidemia are contributing factors to the development of cardiovascular disorders (CVDs), maintenance of appropriate antioxidant status, lipids and lipoprotein levels as well as reduction of oxidative stress, especially in high-risk individuals, is paramount. Studies have evaluated VC effect on some biochemical parameters in apparently healthy individuals and certain disease conditions, however, none has been carried out on AMWs. This study, therefore, examined the levels of toxic metals, antioxidant minerals, oxidative stress markers, and lipid profile of AMWs and the subsequent effect of VC supplementation.
| Subjects and Methods|| |
Study participants and design
Fifty-nine male individuals aged between 19 and 55 years made up of 29 AMWs and 30 age-matched occupationally unexposed controls in Emene, Enugu, were recruited for this study. The AMWs were recruited on voluntary basis after written informed consent was obtained. Subsequently, 27 out of the 29 workers received 500 mg Vitamin C tablets (Mason Natural, USA) daily for a period of 2 months.
Blood sample collection
Five milliliters of fasting blood samples was collected from all participants before the intervention and at 1- and 2-month intervals for biochemical analyses. 3 mL of the blood sample was transferred into K2EDTA tubes for blood lead (Pb), cadmium (Cd), selenium (Se) and zinc (Zn) analysis while 2 mL was transferred into plain tubes and centrifuged. The sera obtained were then used for malondialdehyde (MDA), total antioxidant capacity (TAC), total cholesterol (TC), high-density lipoprotein (HDL) and triglyceride (TG) analysis. Low-density lipoprotein (LDL), very LDL (VLDL) were estimated.
Apparently healthy consenting male participants aged 19–55 years who have worked in the automobile workshop for 1 year or more were included in the study, whereas participants with any history of chronic diseases such as diabetes and heart disease or on any vitamin, mineral, herbal supplement, or lipid-lowering drugs were excluded from the study.
This study was approved by Nnamdi Azikiwe University Teaching Hospital Research Ethics Committee with approval number NAUTH/CS/66/Vol.10/20/2017/021 and conformed to all the ethical requirements of the Helsinki Declaration.
Blood metals (Pb and Cd) and trace elements (Se and Zn) analyses were conducted using Varian AA240 atomic absorption spectrophotometer (USA) according to the method of the American Public Health Association.
MDA was determined using colorimetric method described by Gutteridge and Wilkins. TAC was determined using ferric-reducing ability of plasma method as described by Benzie and Strain, and MDA/TAC ratio was calculated. TC, HDL, and TG were determined by enzymatic colorimetric method as described by Roeschlaw et al., Grove, and Fossati and Prencipe, respectively. LDL and VLDL were estimated by calculation according to the formula given by Friedewald et al. Non-HDL (nHDL) was estimated by calculating the difference between TC and HDL.
The Statistical Package for the Social Sciences (SPSS) version 23.0 (SPSS Inc, Chicago, IL, USA) was used for statistical analysis. The variables were expressed as mean ± standard deviation; the independent Student's t-test and paired t-test were used to assess the mean difference between two unrelated and related variables, respectively. The level of significance was considered at P < 0.05.
| Results|| |
In [Table 1], the mean blood Pb, Cd, and serum MDA and MDA/TAC ratio were significantly higher, whereas the mean blood Se and Zn were significantly lower in the AMWs when compared to the control group (P < 0.05). The mean serum TAC level in the AMWs did not differ significantly from the controls (P = 0.072).
|Table 1: Toxic metals, antioxidant minerals, and oxidative stress markers of automobile workers and controls|
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In [Table 2], the mean levels of TC, LDL, VLDL, TG, and nHDL were significantly higher in the AMWs when compared to the controls (P < 0.05), however, the mean HDL level in the AMWs was not significantly different from the controls (P = 0.321).
In [Table 3], the blood Pb, Cd, Se, and Zn levels after 1 month of Vitamin C supplementation did not differ significantly from their baseline values (P > 0.05). However, after 2 months of supplementation, the mean blood Pb level decreased significantly, whereas the mean Se and Zn levels increased significantly (P < 0.05) compared to their values at 1 month and baseline. The mean levels of blood Cd did not differ significantly from baseline to 2 months of Vitamin C intake (P > 0.05). The mean levels of MDA and MDA/TAC ratio decreased progressively, whereas the mean TAC level increased progressively from baseline to 2 months of Vitamin C intake.
|Table 3: Toxic metals, antioxidant minerals, and oxidative stress markers of automobile workers at different stages of Vitamin C supplementation|
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In [Table 4], the mean levels of TC, LDL, VLDL, and nHDL decreased progressively from baseline to 2 months of Vitamin C intake. The mean levels of HDL and TG after 1 month of Vitamin C supplementation did not differ significantly from their baseline values (P = 0.266 and P = 0.052, respectively), however, HDL level increased significantly, whereas TG decreased significantly after 2 months of supplementation when compared to their values at 1 month and baseline (P < 0.05).
|Table 4: Lipid profile parameters of automobile workers at different stages of Vitamin C supplementation|
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| Discussion|| |
The present study examined the levels of toxic metals, antioxidant minerals, oxidative stress markers, and lipid profile of AMWs and the subsequent effect of Vitamin C supplementation. Higher blood lead and cadmium levels were observed in the AMWs, which suggest higher exposure of this group of workers to these toxic metals. These findings correspond with those of Bal et al. and Obi-Ezeani et al. who also reported a similar increase in blood lead and cadmium levels, respectively, in humans occupationally exposed to these toxic metals.
Lead and cadmium have been reported to alter biochemical indices  and consequently disrupting various biochemical processes including antioxidant defense system through inhibition of various enzymes as well as displacement of antioxidant minerals resulting in oxidative stress which triggers the adverse health outcomes. Accordingly, the present study showed significant alterations in the measured biochemical indices of AMWs which may have possibly resulted from exposure to these metals.
The lower levels of blood selenium and zinc in the AMWs observed in this study may be attributed to the ability of the toxic metals to displace or interfere with the metabolism of these antioxidant minerals otherwise known as trace elements  at various levels including intestinal absorption, distribution in tissues, and biological functions. This corresponds with the reports of Dioka et al. and Basu et al. who, respectively, observed significant reductions in blood zinc and selenium levels in workers exposed to lead. Adejumo et al. in their study on occupationally exposed automotive workers in Benin City, however, reported a higher blood zinc level which they attributed to inhalation of welding fumes containing zinc oxide during welding of galvanized materials or oral intake of contaminated foods in the auto repair workshops.
These antioxidant minerals form vital components of the antioxidant enzymes, and as such, reductions in these essential elements invariably result in the inhibition of antioxidant enzymes and consequently excessive production of ROS, oxidative stress, and tissue damage.
This study also observed higher MDA and MDA/TAC ratio in the AMWs which is suggestive of oxidative stress in these workers. MDA is a product of lipid peroxidation, whereas TAC measures the cumulative antioxidant activity in a biological sample, and both were used to evaluate the oxidative stress level in these workers. MDA/TAC ratio was used as an index of oxidative stress status. Although the TAC level did not differ from the controls, the elevated MDA level may indicate lipid peroxidation from enhanced generation of ROS which impairs the antioxidant system  as evidenced by the higher MDA/TAC ratio observed in these workers. Adekola et al. had earlier reported a similar increase in MDA levels in male automechanics in Ibadan, Nigeria.
Significant elevations in the levels of TC, LDL, VLDL, TG, and nHDL were also observed in the AMWs, and this may be attributed to the adverse effects of lead and cadmium on lipid metabolism  as they have been shown to alter normal lipid and lipoprotein fractions through lipid peroxidation, thereby increasing the risk of CVD in these workers. It may equally be attributed to the ability of these metals to enhance the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme in cholesterol biosynthesis, thereby enhancing cholesterol synthesis. Studies on exposure to these toxic metals have equally demonstrated similar alterations in lipid profile parameters.,
This study recorded a significant reduction in blood lead level in the AMWs after 2 months of Vitamin C intake, and this reduction may be attributed to increased urinary elimination of lead which subsequently reduces blood and tissue levels of this metal. Blood cadmium levels were, however, not altered by Vitamin C supplementation, and this may probably be due to the inability of the given dose (500 mg) to effectively reduce the metal ions in blood, or that Vitamin C may not be an appropriate agent for the reduction of blood cadmium in the exposed persons.
Vitamin C supplementation was also found to increase the blood selenium and zinc levels in these workers after 2 months of intake, and this may be related to the action of this antioxidant vitamin in reducing the blood lead level in the AMWs and subsequently increasing the levels of these trace elements. Other researchers likewise reported that Vitamin C enhances the expression of antioxidant enzyme activity,, which possibly increased zinc and selenium levels.
Vitamin C supplementation equally improved oxidative stress markers in the AMWs as depicted in the progressive reduction in serum levels of MDA and MDA/TAC ratio with a corresponding increase in serum TAC level from baseline to 2 months as observed in this study. This may be due to the antioxidant nature of this vitamin which acts by forming less reactive compounds with ROS or reducing free radical reactions, oxidative stress, and lipid peroxidation and consequently improving antioxidant status. The findings from this study are in agreement with the reports of El-Tohamy and El-Nattat  who reported a protective effect of Vitamin C against heavy metal-induced oxidative stress.
The present study also recorded significant reductions in the elevated serum levels of TC, LDL, VLDL, and nHDL after 1 and 2 months of Vitamin C supplementation. Serum TG and HDL levels, however, reduced and increased, respectively, after 2 months in the AMWs. These results indicate that Vitamin C may be involved in the maintenance of normal lipid and lipoprotein levels which could be attributed to its ability to activate 7α-hydroxylase, the enzyme that enhances the conversion of plasma cholesterol to bile acid, and subsequently improving cholesterol levels. The reduced serum TG level may be from enhanced uptake and removal of VLDL from plasma which is facilitated by this vitamin.
| Conclusion|| |
This study, therefore, suggests that Vitamin C may represent a potential dietary supplement for reducing blood lead and oxidative stress, improving antioxidant defense, and modulating dyslipidemia and adverse cardiovascular outcomes in AMWs.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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