|Year : 2021 | Volume
| Issue : 1 | Page : 30-34
Does copper has a role in vitiligo? Analysis of tissue and serum copper in vitiligo
S.A. Archana, Vinutha Rangappa, T.G. Savitha, B. Jayadev, P.A. Kushalappa, P.K. Ashwini
Department of Dermatology, JSS Medical College, Shivarathreeshwara Nagar, JSS Academy of Higher Education & Research Centre, Mysuru, Karnataka, India
|Date of Submission||07-Feb-2020|
|Date of Decision||23-May-2020|
|Date of Acceptance||11-Jul-2020|
|Date of Web Publication||07-Apr-2021|
MD Vinutha Rangappa
Department of Dermatology, JSS Medical College, Shivarathreeshwara Nagar, JSS Academy of Higher Education & Research, Mysuru 570015, Karnataka
Source of Support: None, Conflict of Interest: None
Background: Vitiligo is an acquired, primary, idiopathic disorder characterized by depigmented macules and patches. Melanin, a natural pigment of skin, requires amino acid tyrosine for its synthesis. Tyrosinase, a key regulatory enzyme, is a copper (Cu) dependent enzyme. Thus, Cu plays a role in melanogenesis however, we need to look at the role of Cu in the pathogenesis of vitiligo. Aim: To estimate serum and tissue copper levels in vitiligo patients, and to compare with first degree relatives of patients and control group. Materials and Methods: All cases of vitiligo attending tertiary care hospital were included in the study. Venous blood samples were collected from subjects, first degree relatives and controls, punch biopsy specimens were collected from lesional and non-lesional skin of cases, controls and were analysed using inductively coupled plasma emission spectrometry. Results: Of 60 patients, serum Cu levels in cases were found to be low in 35, normal in 22 and high in 3. Mean serum Cu of first degree relatives was also low. Mean lesional Cu was 1.3 μg/g and non-lesional Cu was 1.4μg/g in vitiligo patients, which was lower than tissue Cu levels of controls(1.9 μg/g) (p value > 0.05). Conclusions: In our study the lesional and non-lesional Cu levels were lower in vitiligo patients. This low Cu levels may lead to reduced activity of enzyme tyrosinase, which is essential in the process of melanogenesis. Though role of Cu in melanogenesis is proven, its role in pathogenesis of vitiligo needs to be studied further.
Keywords: Copper (Cu), tyrosinase, vitiligo
|How to cite this article:|
Archana S, Rangappa V, Savitha T, Jayadev B, Kushalappa P, Ashwini P. Does copper has a role in vitiligo? Analysis of tissue and serum copper in vitiligo. Pigment Int 2021;8:30-4
| Introduction|| |
Vitiligo is an acquired pigmentary disorder of the skin and mucous membranes. It is characterized by circumscribed depigmented macules and patches. The prevalence of vitiligo is 0.1% to 3% in different ethnic and racial groups. Because of its pigmentary disfigurement, vitiligo is more significant in the dark-skinned population, with a major impact on the quality of life of patients.
It is a multifactorial polygenic disorder with a complex pathogenesis, related to both genetic and nongenetic factors. Several theories have been proposed about the pathogenesis of vitiligo, but the precise cause behind melanocyte destruction remains unknown. Theories regarding the destruction of melanocytes include autoimmune mechanisms, cytotoxic mechanisms, an intrinsic defect of melanocytes, oxidant-antioxidant mechanisms and neural mechanism.
Of the many natural pigments displayed by human skin, melanin, if not most prominent, is perhaps the most significant. Its formation in the skin has been well documented over the past years.
Melanin which imparts pigment to skin requires the amino acid tyrosine for its synthesis. Melanin synthesis starts with the conversion of tyrosine to dihydroxyphenylalanine (DOPA) by the action of tyrosinase, a key regulatory enzyme. Action of this enzyme is Cu dependent. Thus, Cu plays an important role in melanogenesis. The best-known example is that of Cu and its role in wool pigmentation. The loss of pigment found in its deficiency states in sheep has been attributed to a breakdown in the earlier stages of melanin synthesis, which are catalysed by the Cu dependent enzyme tyrosinase.
This study was undertaken to estimate serum and tissue copper levels in vitiligo patients and to compare with first degree relatives of patients and control group.
To know whether tissue Cu along with serum levels play a role in the pathogenesis of vitiligo.
| Methodology|| |
A hospital-based, cross-sectional prospective study was conducted for a period of one and a half year. Sixty clinically diagnosed cases of vitiligo, their first-degree relatives and 60 age and sex matched healthy controls were included in the study. Subjects on Cu supplements, age < 18 years, pregnancy and lactating women were excluded from the study. Study was approved by Institutional Ethics Committee.
Sample size was calculated according to the formula
P − expected proportion in population based on previous studies
Since the previous similar studies were very old, we took the statistics of vitiligo patients attending our department for 6 months and calculated p as 4%
Venous blood (5 ml) was collected from all the subjects, centrifuged and serum was separated. Punch biopsy specimens were collected from lesional and non-lesional skin of cases and normal skin of control group. Concentrated nitric acid was used to dissolve the specimen and then analysed for Cu levels using inductively coupled plasma emission spectrometry (ICP).
Inductively Coupled Plasma Emission Spectrometer (ICP) is the most advanced equipment being used across the globe for analysing environmental and biological samples for the presence of elements and their quantity. The equipment is highly sensitive and can measure up to parts per billion (ppb) level or in percentage level. Apart from analysing various samples like environmental waste, industrial effluent, chemicals and polymers, it has been used to analyse biological samples such as blood, saliva and tissue for identifying trace elements and metals.
Statistical data were analysed using SPSS 22 version software. Symptom profile of all cases were represented as percentages. Continuous data was represented as mean and standard deviation. Independent t test was used as test of significance to identify the mean difference between two groups. Pearson correlation was used to see the correlation between two quantitative variables. P value < 0.05 was considered as statistically significant.
| Results|| |
Sixty cases of vitiligo attending the outpatient department of Dermatology, Venereology and Leprosy who fulfilled the inclusion and exclusion criteria along with patients’ first-degree relatives and controls were studied for a period of one and a half year.
Mean age of subjects in cases was 42 ± 16.5 years and in controls was 40.2 ± 13.8 years. Majority of cases i.e. 44 (73.3%) had vitiligo vulgaris, 9 (15%) focal lesions, 4 (6.7%) acrofacial lesion, 2 (3.3%) acral lesion and 1 (1.7%) had segmental lesions. Among cases majority (55%) had lesions < 1 year, 30% 1–3 years, 8.5% 3–5 years and 6.7% for >5 years.
In the study, mean serum Cu among cases was 59.8μg/dL and in control 55.4 μg/dL. There was no significant difference in mean serum Cu between cases and controls. (Normal serum Cu levels-63.7-140.12 μg/dL). Serum Cu levels of first-degree relatives were 48. 8μg/dL. Details of Cu levels in each group have been given in [Table 1].
Mean Cu levels among cases in lesional tissue was 1.26 μg/g, in non-lesional 1.4 μg/g and in control 1.9 μg/g. Significant positive correlation was observed between lesional Cu and non-lesional Cu in cases and also between lesional Cu levels of cases from that of controls [Table 2]. No significant correlation was observed between serum and tissue Cu levels among cases.
|Table 2 Correlation between serum copper, lesional copper, non lesional copper in cases|
Click here to view
| Discussion|| |
Melanocytes produce the melanin pigments in melanosomes. Tyrosinase is the key cuproenzyme which initiates the pigment synthesis using its substrate amino acid tyrosine. The activity of tyrosinase directly correlates to the cellular pigmentation. Defects in tyrosinase transport to melanosomes or mutations in the enzyme or reduced intracellular Cu levels results in loss of tyrosinase activity in melanosomes.
The mean age of cases was 42.0 years in present study. The majority of patients were in age group of 31–40 years (31.7%). However various other studies showed age of onset of vitiligo in first or second decade of life., There seems to be no gender difference in vitiligo with males and females being equally affected.,, But there are few studies where either male or female preponderance were noted.,
Vitiligo is a condition of long duration. The duration of the disease in our study group ranged from 3 months to 15 years. Duration of vitiligo was less than 5 years for 93.3% of cases and more than 5 years for 6.7% patients. Majority had vitiligo of duration of <1yr (55%).
The commonest morphological pattern was vitiligo vulgaris (73.3%), followed by focal type, acrofacial, acral and segmental type. The frequency of distribution of clinical types of vitiligo varies in different studies. However, according to the reports generalized vitiligo was found to be more common., Few studies showed focal type to be the commonest morphological pattern. In contrast to our study, Shankar K et al study showed segmental type to be second common type after generalised vitiligo.
Estimation of serum Cu levels in vitiligo was done long back. In recent past, not many studies are done on this. In a meta-analysis, the levels of serum Cu and zinc (Zn) were compared between cases and controls. Both were significantly lower in vitiligo patients than controls. The studies of Shameer et al., Bruske and Salfeld, and Tsiskarishvili indicated that decreased levels of serum Cu and Zn causes vitiligo. The role of Cu and Zn is mainly to promote melanogenesis and provide a physiological defence against oxidative stress. It is well known that tyrosinase has a key role in pigmentation process and Cu and Zn are both cofactors for this. Imbalance in this system plays an important pathogenic role in vitiligo. In contrast, few authors showed serum Zn and Cu levels were significantly higher in vitiligo patients compared to controls. The authors thought that the increased serum Zn and Cu levels was due to increased apoptosis of peripheral blood mononuclear cells in vitiligo patients. Furthermore, melanin is a colloidal pigment and has high affinity for metal ions; therefore Cu, Zn and other metal ions are found in high levels in pigmented tissues involved in melanin synthesis. As melanocytes degenerate in vitiligo patients, less Cu and Zn are utilized for melanin synthesis, which consequently raise levels of Cu and Zn in serum.,, In view of this discrepancy, we reinvestigated this aspect to try and find an answer. There are controversial reports where serum and hair Cu and serum magnesium levels in patients with alopecia areata. Iron, ferritin, vitamin B12 and folate are also evaluated in vitiligo patients, but no statistical difference noted. In our study, 58.3% patients had decreased and 5% had increased serum Cu levels. Out of those with decreased serum Cu, 71.4% had disease duration of 1–5 years and 65.7% belonged to vulgaris type. Mean serum Cu levels in vitiligo patients were found to be higher than controls, though lower than the reference value. The low levels of serum Cu in first degree relatives could not be explained. Thus, low serum copper levels may result in decreased binding of Cu ions to the enzyme tyrosinase, which is essential for enzyme activity and melanogenesis and play a role in vitiligo. Low serum Cu levels in controls can be due to nutritional deficiency.
Tu Caixia et al. study showed that, Cu value of skin suction blistering fluid in vitiliginous lesions was significantly lower than that in the unaffected sites. The histochemical observations done by Arya M et al and Behl PN showed a comparative reduction in the Cu content of vitiliginous skin., These suggested that Cu might be related to the pathogenesis of vitiligo. However, the above two studies did not take uninvolved skin and controls into consideration. We found that tissue Cu levels of lesional skin was lower than that of non-lesional skin of vitiligo patients though statistically insignificant (P = 0.752). We also found that tissue Cu levels of vitiligo patients were lower than that of controls.
Vitiligo patients have reduced Cu levels in both serum and lesional tissue. However, in our study, out of 35 with decreased serum Cu, only 51.4% had low lesional Cu levels, and this was not statistically significant. Also, significant positive correlation was observed between lesional and non-lesional Cu in cases i.e, with increase in lesional Cu, there was increase in non-lesional Cu as well.
In 1935, Gorter conclusively demonstrated the fact that Cu-free diets resulted in depigmentation of the hair of rats, rabbits and cats and that this depigmentation disappeared following administration of Cu. Naraska reported on the relationship of Cu to pigmentation in Mongolian spot. He found that Cu was more highly concentrated in Mongolian spot than in the surrounding regions. Serum Cu was significantly lower in 66 patients with premature canities, as compared to normal controls in one study. In Menkes disease, an X- linked recessive condition, defective Cu absorption with low Cu levels is seen in blood, liver and hair. In this condition also hairs appear light in colour and diffuse cutaneous pigmentary dilution occurs due to decreased activity of tyrosinase, a Cu-dependent enzyme.Increased serum Cu content resulting from decreased incorporation of Cu by active sites of the tyrosinase molecules, is a factor determining the low enzyme activity in depigmented areas. This suggestion is supported by the data of a study on total Cu content in skin, which was many times higher than the total Cu content of serum. After decreased incorporation of Cu into the tyrosinase molecules in the melanocytes, an elevation of the serum Cu level can be observed. In the present study we found that majority of vitiligo patients had low serum Cu levels. Mean lesional and non-lesional Cu levels of cases were lower than the controls, though not statistically significant. Thus, low serum and tissue Cu levels may result in decreased binding of Cu ions to the enzyme tyrosinase, which is essential for enzyme activity and thus the process of melanogenesis, may possibly be affected in patients with vitiligo. However, this cannot be proved conclusively.
This study was limited by lack of standard reference range for tissue copper levels and small sample size.
There are conflicting reports about the role of Cu in vitiligo. In our study the lesional and non-lesional Cu levels were lower in vitiligo patients when compared to controls, though it was not statistically significant. The role of Cu in melanogenesis is proven but its role in pathogenesis of vitiligo needs to be studied further.
I would like to thank Dr. Mahesh V, Department of Preventive and social medicine, Sri Devaraj Urs Medical College for statistical analysis of data and IADVL for giving Scholorship in Dermacon 2016. I thank Dr Veeranna S, Dr Kanthraj G R, Dr Ranugha PSS for all the support.
Financial support and sponsorship
The authors received Rs. 1,85,000 from IADVL Research Grants 2015.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]