Zinc level and obesity

Abstract

Background
Obesity is a chronic condition that is associated with disturbances in the metabolism of zinc. Therefore, the aim of this study was to investigate the relationship between serum zinc level and different clinical and biochemical parameters in obese individuals.
Patients and methods
Twenty-four individuals with BMI more than 30 kg/m 2 and 14 healthy controls (BMI < 24 kg/m 2 ) were assessed for BMI and waist circumference using anthropometric measurements. Colorimetric tests were carried out for the determination of zinc in serum.
Results
In this study, BMI and waist circumference were higher in the obese group than in the control group (P < 0.05). The mean serum zinc levels were 92 ± 31.1 and 101 ± 70 μg/dl in the obese group and control group (P > 0.05), respectively. There was a significant negative correlation between the serum zinc level and BMI, waist circumference and low-density lipoprotein (P < 0.05).
Conclusion
Plasma zinc concentration in obese individuals showed an inverse relationship with the waist circumference and BMI as well as serum low-density lipoprotein-cholesterol and correlated positively with high-density lipoprotein.

Full text

Original article 209
1110-7782 © 2013 The Egyptian Journal of Internal Medicine DOI: 10.4103/1110-7782.124985
Introduction
e essential trace element zinc (Zn) is important
for several bodily functions such as vision, taste
perception, cognition, cell reproduction, growth
and immunity. It plays a vital role in metabolisms,
particularly as a cofactor of many enzymes, required
for natural metabolic processes [1]. Zinc has three
major biological roles: Catalytic, structural and
regulatory. It is a structural constituent in numerous
proteins, including growth factors, cytokines, receptors,
enzymes, and transcription factors belonging to cellular
signalling pathways, and is essential for their biological
activity [2]. Moreover, it is implicated as a cofactor
in numerous cellular processes for an estimated 3000
human proteins including DNA and protein synthesis,
enzyme activity and intracellular signalling [3].
e human genome bioinformatics study revealed
that ∼10% of all proteins may bind with zinc. e
biological functions of these zinc-binding proteins are
maintained through cellular zinc levels [3]. erefore,
homoeostatic mechanisms that modulate zinc
absorption, distribution, cellular uptake and excretion
are vital for maintaining cellular functions. Moreover,
zinc’s fundamental and diverse roles in many cellular
processes require its delivery to the tissues and cells,
and also its intracellular availability and intracellular
distribution to be tightly controlled. ese processes
are governed by zinc transporters and channels and
by zinc-sensing molecules, such as metallothioneins
and metal-responsive element-binding transcription
factor-1 [4]. Disturbances in zinc homoeostasis have
been observed in many diseases, including diabetes
mellitus [5], cancer [6], autoimmune disease [7] and
cardiovascular disease [8]. Some studies have also
shown that obese individuals have low concentrations
of zinc in plasma, erythrocytes and serum, and that it
is associated with alterations in the metabolism of the
adipose tissue of these patients [9]. Zinc deciency
may also be associated with insulin resistance,
hyperglycaemia and impaired glucose tolerance.
e aim of this study was to dene the relationship
between the plasma zinc level and dierent clinical and
laboratory parameters in obese Egyptian individuals.
Patients and methods
Study population
is study was conducted in the National Nutrition
Institute (Cairo, Egypt). e study population
consisted of 24 individuals with BMI more than
30 kg/m2 selected from the outpatient clinic as well as
14 healthy individuals (BMI < 24 kg/m2) as the control
group. Both study groups were age-matched and sex-
matched. e participants were eligible for the study if
they were 20 years of age or older and not taking any
vitamin or mineral supplementation. Exclusion criteria
included factors that aect serum zinc levels, such as
kidney disorders, diabetes, cancer, acute infections,
Zinc level and obesity
Doaa S.E. Zakya, Eman A. Sultanc, Mahmoud F. Salimb, Rana S. Dawodd
Background
Obesity is a chronic condition that is associated with disturbances in the metabolism of zinc.
Therefore, the aim of this study was to investigate the relationship between serum zinc level
and different clinical and biochemical parameters in obese individuals.
Patients and methods
Twenty-four individuals with BMI more than 30 kg/m2 and 14 healthy controls (BMI < 24 kg/m2)
were assessed for BMI and waist circumference using anthropometric measurements.
Colorimetric tests were carried out for the determination of zinc in serum.
Results
In this study, BMI and waist circumference were higher in the obese group than in the control
group (P < 0.05). The mean serum zinc levels were 92 ± 31.1 and 101 ± 70 μg/dl in the obese
group and control group (P > 0.05), respectively. There was a signicant negative correlation
between the serum zinc level and BMI, waist circumference and low-density lipoprotein (P < 0.05).
Conclusion
Plasma zinc concentration in obese individuals showed an inverse relationship with the waist
circumference and BMI as well as serum low-density lipoprotein-cholesterol and correlated
positively with high-density lipoprotein.
Keywords:
low-density lipoprotein, obesity, serum zinc
Egypt J Intern Med 25:209–212
© 2013 The Egyptian Journal of Internal Medicine
1110-7782
Departments of aInternal Medicine, bClinical
Pathology, Al Azhar University, cDepartment
of Clinical Nutrition and dDiploma of Clinical
Nutrition, National Nutrition Institute, Cairo,
Egypt
Correspondence to Doaa S.E. Zaky, MD,
No. 3, Hay’et Tadrees Ein Shams University
Towers, El Zaafran Gardens (Ard Elmatbaah),
Abbasia, Cairo 11331 Egypt
Tel: +20 100 102 0282; Fax: 02-24857464;
e-mail: dsalah241@gmail.com
Received 2 September 2013
Accepted 2 October 2013
The Egyptian Journal of Internal Medicine
2013, 25:209–212
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210 The Egyptian Journal of Internal Medicine
and smoking. Patients and controls included in the
study underwent a standard procedure of detailed
history taking and a complete physical examination.
Blood pressure was recorded as a mean value of three
dierent measurements in the sitting position using
a sphygmomanometer. BMI was calculated using the
following equation: BMI = weight (kg) divided by
the square of the height (m). ose who voluntarily
decided to participate in the study were asked to sign
an informed consent.
Laboratory investigations
Sample collection
Peripheral blood samples were obtained after 12 h of
fasting. Five millilitres of blood were collected in a plain
vacuum tube, allowed to clot at room temperature, and
the serum was separated by centrifugation. Fasting
blood sugar, lipid prole [total cholesterol (TC),
triglyceride (TG), low-density lipoprotein (LDL)] and
high-density lipoprotein (HDL) were investigated.
Zinc uid monoreagent was used in the colorimetric
test for the determination of zinc in serum. Zinc
forms a red chelate complex with 2-(5-bromo-2-
pyridylazo)-5-(N-propyl-N-sulfopropyl-amino)-
phenol. e increase of absorbance was measured and
was proportional to the concentration of total zinc in
the sample. e values for lipid prole and zinc level
were as follows:
(1) Cholesterol: Normal value, less than 200 mg/dl;
borderline, 200–239 mg/dl; and high, 240 mg/dl
or above.
(2) TG: Value less than 150 mg/dl was considered
normal and 200–499 mg/dl was considered high;
was considered borderline when the level falls
within the above values.
(3) LDL: Value less than 100 mg/dl was considered
optimal and up to 129 mg/dl was near-optimal.
Borderline high LDL ranged from 130 to
159 mg/dl, whereas 160–189 mg/dl was considered
high. Above that level was categorized as very high.
(4) HDL: For men levels above 40 mg/dl and for
women levels above 50 mg/dl were considered
normal [10].
(5) Zinc: For men 165–118 μg/dl and for women
59–98 μg/dl were considered normal [11].
Statistical analysis
IBM SPSS Statistics (version 21.0, 2012; IBM Corp.,
USA) was used for data analysis. Data were expressed as
mean ± SD for quantitative parametric measurements
in addition to median percentiles for quantitative
nonparametric measurements, and both number
and percentage for categorized data. e following
tests were carried out: (i) comparison between two
independent mean groups for parametric data using
Student’s t-test; (ii) Pearson’s correlation test to study
the possible association between both the variables
among each group for parametric data. e P of error
of 0.05 was considered signicant, whereas that of 0.01
and 0.001were considered highly signicant.
Results
e anthropometric data revealed a highly signicant
increase in weight, BMI and waist circumference in the
obese group (99 ± 19, 38 ± 6.4 and 111 ± 16, respectively)
compared with the control group (61 ± 7, 22.7 ± 1.4 and
80 ± 3, respectively) as expected; however, no signicant
dierence was observed with respect to height. e
mean systolic and diastolic blood pressure was normal
in both groups; however, they were signicantly higher
in the obese group (127 ± 16 and 87 ± 11, respectively)
compared with the control group (112 ± 9 and 72 ± 7,
respectively) (Table 1).
e lipid prole showed no signicant dierence between
both groups in TC; however, LDL was signicantly
high in the obese group (120.6 ± 26.4) compared with
the control group (98 ± 18) and HDL was signicantly
low in the obese group (36.3 ± 7.1) compared with the
control group (53 ± 9.0). e mean TG level was also
signicantly high in the obese group compared with the
control group (108.2 ± 48.9 vs. 80 ± 31) and was within
the normal range in both groups. Also serum zinc level
was normal in both groups, although lower in the obese
than in the control group, yet there was no statistical
signicant dierence between them (Fig. 1).
Table 1 Comparison between control and obese group with
respect to demographic, clinical and laboratory data
Parameters Control group
(N = 14)
Obese group
(N = 24)
P
Age (years) 35.6 ± 4 38 ± 13
Female sex (%) 50 50
Anthropometric data
Wight (kg) 61 ± 7 99 ± 19 0.000
Height (cm) 164 ± 8 161 ± 10 0.349
BMI (kg/m2)22.7 ± 1.4 38 ± 6.4 0.000
Waist circumference (cm) 80 ± 3 111 ± 16 0.000
Blood pressure
Systolic blood pressure
(mmHg)
112 ± 9 127 ± 16 0.001
Diastolic blood pressure
(mmHg)
72 ± 7 87 ± 11 0.000
Laboratory data
Total cholesterol (mg/dl) 167 ± 18 178.5 ± 25 0.120
LDL (mg/dl) 98 ± 18 120.6 ± 26.4 0.004
HDL (mg/dl) 53 ± 9 36.3 ± 7.1 0.000
TG (mg/dl) 80 ± 31 108.2 ± 48.9 0.038
Zn (μg/dl) 101 ± 70 92 ± 31.1 0.655
HDL, high-density lipoprotein; LDL, low-density lipoprotein;
TG, triglyceride; Zn, zinc.
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Zinc level and obesity Doaa et al. 211
Signicant negative correlations were found between
serum zinc level and BMI, waist circumference and
LDL (P < 0.05); however, no signicant correlations
were found between zinc level and other clinical
parameters such as age, weight, height, blood pressure
and other biochemical parameters such as TC, TG and
HDL (Table 2).
Discussion
Our study was performed in 24 obese individuals as
well as 14 healthy controls to verify the serum zinc
status in obese patients and its relationship with
dierent clinical and laboratory parameters in those
patients. e mean concentrations of zinc in the serum
showed no statistically signicant dierence between
the control and the obese groups (P > 0.05). Ennes
Dourado Ferro et al. [12] also did not nd any signicant
dierence in plasma zinc concentration between the
obese and the control groups. However, they found
signicant dierence between both groups with
respect to erythrocyte zinc level. Erythrocytes contain
about 80% of zinc; however, it is only 16% in plasma.
Also, plasma zinc has fast dynamics and is inuenced
by several pathophysiological factors in response to
various conditions such as stress, infection, catabolism,
hormones and food intake. is well explains our
results of normal mean serum zinc level in both groups.
us, zinc level in erythrocytes can be considered as a
more sensitive parameter of zinc status than plasma or
serum level. Zinc concentration in the erythrocytes of
obese children and adolescents [13] and obese adult
men [14] revealed signicantly lower concentration
than in the control group. Feitosa et al. [15] explain
the lower concentrations of erythrocyte zinc in obese
patients as the inuence of inammatory process on the
metabolism of zinc as they found signicant negative
correlation between zinc and TNF-a. With respect
to clinical parameters, the mean value of serum zinc
showed signicant negative correlations with BMI and
waist circumference and no correlation with age or blood
pressure. e results consistent with the multivariate
regression analysis [12] demonstrated that the waist
circumference and BMI had negative correlation with
the concentration of zinc in erythrocytes. ese data are
associated with the fact that there is an accumulation
of adipose tissue with an increase in the production
of cortisol and adipocytokines, which in turn, results
in chronic inammation. e inammation promotes
the zinc accumulation in the liver and in adipocytes,
which may have contributed to the negative correlation
of serum zinc level with BMI and waist circumference
in obese individuals. Signicant negative correlations
also were found between serum zinc and TG (LDL-
cholesterol); whereas a signicant positive correlation
was found between serum zinc and HDL. Also, Al-
Sabaawy [16] revealed a signicant lower level of
serum zinc in hyperlipidemic nonobese patients
compared with the control group, as well as a signicant
negative correlation between serum zinc and TC, LDL
and TG. Multiple studies have revealed that zinc
supplementation had benecial eects on lipid proles
in patients with diabetes or metabolic syndrome [17,18].
Zinc supplementation increase HDL-cholesterol and
reduces TG in patients with type 2 diabetes [17].
However, the eect of zinc supplementation on lipid
prole and other metabolic factors in obesity are more
controversial among nondiabetic obese and nonobese
individuals. Zinc supplementation at 30 mg daily for
8 weeks increased serum zinc by 15% and urinary
zinc by 56%, but no signicant dierence was found
with respect to TG and HDL-cholesterol after zinc
supplementation [19]. Similarly, Beletate et al. [20]
reported that zinc supplementation for 4 weeks did
not have a benecial eect on lipid levels in normal
Figure 1
Zinc and lipid prole of control (nonobese) and obese groups. HDL,
high-density lipoprotein; LDL, low-density lipoprotein; TC, total
cholesterol; TG, triglyceride.
Table 2 Correlation between serum zinc level and clinical
and laboratory data in obese individuals
Variables R P
Age (years) −0.143 0.515
Weight (kg) −0.336 0.117
Height (cm) 0.105 0.635
BMI (kg/m2)−0.453 0.030
Waist circumference (cm) −0.418 0.047
Systolic blood pressure (mmHg) −0.196 0.371
Diastolic blood pressure (mmHg) −0.052 0.813
Total cholesterol (mg/dl) −0.362 0.090
LDL (mg/dl) −0.465 0.025
HDL (mg/dl) 0.07 0.750
TG (mg/dl) 0.282 0.193
HDL, high-density lipoprotein; LDL, low-density lipoprotein;
TG, triglyceride.
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212 The Egyptian Journal of Internal Medicine
glucose-tolerant obese women aged 25–45 years.
However, in another study, after receiving 20 mg
elemental zinc on a regular daily basis for 8 weeks, the
mean fasting plasma glucose, insulin and HOMA-
IR were decreased signicantly with no change in
BMI, waist circumference, LDL-cholesterol and TG.
Further research on the eect of zinc supplementation
on the lipid prole and the metabolic risks in obesity
should be performed in a larger cohort with a longer
follow-up period to determine the potential merits of
zinc-based intervention in obese patients. Sarmento
et al. [21] also revealed inverse association between
zinc and coronary artery disease, and Afridi et al. [22]
postulated that zinc deciency may predispose to
coronary artery disease in diabetes mellitus patients.
Further study are also required to prove LDL as a link
between increased cardiovascular risks with decreased
zinc concentration in obese nondiabetic individuals.
Conclusion
Plasma zinc concentration in obese individuals
presented an inverse relationship with the waist
circumference and BMI as well as serum LDL-
cholesterol and correlated positively with HDL.
Acknowledgements
Conicts of interest
There are no conicts of interest.
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