@Copyright 1985 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0163-4984/85/0811-0167502.00
Serum Zinc and Copper in Hyperlipoproteinemia G. UZA,1'2'* SILVIA GABOR, 1 AGOTHA KOVATS,2 R, VLAICU, 2 AND M. CCICCIIANU 2 1Institute of Hygiene and Public Health, and 21Hedical Clinic I, Cluj-Napoca, Romania Received July 7, 1984; Accepted April 18, 1985
ABSTRACT Starting from experimental observations demonstrating that a high ratio of zinc to copper led to hypercholesterolemia in rats, serum Zn and Cu levels were measuied by atomic absorption spectrophotometry in 65 normolipemic controls and in 100 subjects with various types of hyperlipoproteinemia (HLP). Serum Zn levels did not significantly differ from control values in any type of HLP. However, hyperlipoproteinemic patients with obvious clinical atherosclerosis displayed significantly lower serum-Zn concentration than hyperlipoproteinemic subjects without clinical symptoms. On the other hand, w h e n compared to control subjects, serum Cu levels were not found to be decreased, but rather increased, in hyperlipoproteinemic patients with or without atherosclerosis. As a result, the Zn:Cu ratio appeared to be lower than normal in hyperlipoproteinemic patients with cardiovascular disease. It is conceivable that changes of these trace elements should be rather connected to vessel injury and associated disease than to HLP which, at least in humans, is not accompanied by a high Z n : C u ratio. Index Entries: Serum Zn, Cu, and Z n : C u ratio in hyperlipoproteinemia; zinc, in hypercholesterolemic serum; hyperlipoproteinemia, and Zn, Cu, and Z n : C u ratio in serum. *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research
] 67
VoL 8, 1985
168
Uza et al.
INTRODUCTION It has been s h o w n that a relative or absolute deficiency of Cu, characterized by a high ratio of Zn to Cu, caused an increase of serum cholesterol in rats, which then also developed cardiovascular lesions (1,2). It was found as well that Zn therapy lowered the plasma level of the "antiatherogenic" high density lipoprotein (3). These data suggesting a possible relationship between the ratio of Zn to Cu and the d e v e l o p m e n t of hypercholesterolemia (HLP) p r o m p t e d us to investigate the behavior of serum Zn and Cu in hyperlipidemic h u m a n s with or without obvious clinical atherosclerosis.
METHODS AND MATERIALS Clinical Material The 169 subjects u n d e r investigation were divided into the following groups:
A. Control Subjects This group included 65 subjects aged 23-69 yr (mean age, 35.29 _+ 1.62 yr) with serum cholesterol less than 240 mmol/L and serum triglycerides less than 150 mmol/L. B. Hyperlipidemic Subjects This group, including 100 subjects aged 20-73 yr (mean age, 53.63 _+ 1.36 yr) was subdivided according to the type of HLP; 20 subjects (11 m e n and 9 women) were considered to be heterozygous for HLP type IIa, 42 subjects (21 m e n and 21 women) were presenting a lipoprotein pattern compatible with a mixed HLP (HLP type IIb); type IV was attributable to 32 subjects (25 men and 11 women); and six subjects with fasting chylomicronemia were classified as having HLP type V; 41 subjects with HLP exhibited obvious clinical symptoms of atherosclerosis (coronary, cerebral, peripheral, or multiple tocalizations). Occurrence of atherosclerosis in a subclinical form could not, however, be excluded in the remaining 59 HLP subjects w h o were without cardiovascular complaints. These last-mentioned HLP subjects were also younger (mean age, 49.88 + 1.77 yr) than those with obvious clinical atherosclerosis (mean age, 57.42 _+ 1.63 yr). No patients were acutely ill w h e n investigated. Patients with liver or kidney disease, as well as those u n d e r g o i n g a therapy that might have influenced the plasma level of the minerals investigated, were not included in the study.
Biological Trace Element Research
VoL 8, 1985
Serum Zinc and Copper in Hyperlipoproteinemia
169
Serum Lipids and ll~'nerals Analysis Indication of the m e t h o d s u s e d for analysis of s e r u m lipids a n d lipoproteins as well as criteria for the classification of the patients into the various t y p e s of H L P w e r e given in p r e v i o u s p a p e r s .(4-6). S a m p l e s of v e n o u s blood w e r e collected u n d e r fasting c o n d i t i o n s a v o i d i n g m e t a l c o n t a m i n a t i o n . S e r u m Z n a n d Cu c o n c e n t r a t i o n w e r e e s t i m a t e d by m e a n s of a Perkin Elmer M o d e l 300, Flame A t o m i c S p e c t r o p h o t e m e t e r o p e r a t i n g at 213.8 n m for Z n a n d 324.7 for Cuo
Statistical Analysis Statistical significance was a s s e s s e d by the two-tailed S t u d e n t t-test.
RESULTS As s h o w n in Table 1 a n d Fig. 1, c h a n g e s affecting s e r u m Z n in the various t y p e s of H L P w e r e not significant, while s e r u m Cu level t e n d e d to be h i g h e r t h a n m e a n n o r m a l value in all the investigated types of HLP. W h e n the h y p e r l i p i d e m i c subjects w e r e c o n s i d e r e d according to the p r e s e n c e or absence of clinical atherosclerosis it was h o w e v e r n o t e d t h a t the s e r u m level of Z n is significantly lower in patients with o b v i o u s s y m p t o m s of vascular disease. This decrease of s e r u m Zn associated to a h i g h e r t h a n n o r m a l c o n c e n t r a t i o n of s e r u m Cu led to an i m p o r t a n t d i m i n u t i o n of the Z n / C u ratio (see Table 2). It s h o u l d be m e n t i o n e d t h a t TABLE 1 Behavior of Serum Lipids as Well as of Zn and Cu Levels in Control Subjects and in Various Types of HLP~ Cholesterol, p-g/L Controls ( 6 5 )
Triglyceride, ~xg/L
Zn, ~xg/dL
Cu, ~x/dL
117.67 _+ 4.43
106.77 _+ 4.05
Zn/Cu
197.35 __+ 3.67
t16.00 • 4.43
1.19 +_ 0.06
IIa (20)
37t.70"** _+ 21.88
153.55" • 12.03
114.75 t28.35" _+ 8.26 _+ 10.93
0.95 ** _ 0.07
[Ib (42)
347.98*** ___ 6.75
278.57*** • 11.60
122.04 -+ 5.60
150.02"** • 8.95
0.91 *** -+ 0.065
IV (32)
316.36"** • 10.88
562.13"** § 60.45
122.63 -+ 4.85
121.6 * _+ 6.82
1.07 _+ 0.07
V (6)
378.50*** • 47.00
1959.50"** • 557.88
139.33 132.83 • 12.41 _ 26.71
1.23 + 0.20
~Mean v a l u e _+ s t a n d a r d error of the m e a n , N u m b e r of s u b j e c t s in p a r e n t h e s e s . Statistical s i g n i f i c a n c e v e r s u s control subjects: * p < 0.05; ** p < 0.01; *** p < 0,001,
Biological Trace Element Research
VoL 8, 1985
170
Uza et al. i
260" 240
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2(301 160" 140" :n.
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V
Fig. 1. Serum Zn (a) and Cu (b) concentrations in controls (A) and subjects with HLP type IIa, IIb, IV, and V:., Hyperlipidemic subjects displaying clinical atheroscterosis; o, hyperlipidemic subjects without symptoms of atherosclerosis. Biological Trace Element Research
Vol. 8, 1985
Serum Zinc and Copper in Hyperlipoproteinemia
171
TABLE 2 Serum Zn and Cu Concentrations and the Zn/Cu Ratio in Controls (A), Subjects with HLP but Without Clinical Symptoms of Atherosclerosis (B), and in HLP Patients with Clinical Symptoms of Vascular Disease (C) Serum Zn, Fg/dL A. Controls (N = 65) B. HLP without clinical atherosclerosis (N = 59) C. HLP with clinical symptoms of atherosclerosis (N 41) STATISTICAL SIGNIFICANCE A vs B B vs C B vs C
Serum Cu, Zn/Cu ~xg/dL ratio
117.67 • 4.43 133.45 • 3.16
106.77 _+ 4.05 135.66 • 6.29
1.19 _+ 0.06 1.14 +_ 0.06
107.55 • 4.16
138.15 +__ 7.02
0.84 + 0.05
(p)
Serum Zinc and Copper in Hyperlipoproteinemia G. UZA,1'2'* SILVIA GABOR, 1 AGOTHA KOVATS,2 R, VLAICU, 2 AND M. CCICCIIANU 2 1Institute of Hygiene and Public Health, and 21Hedical Clinic I, Cluj-Napoca, Romania Received July 7, 1984; Accepted April 18, 1985
ABSTRACT Starting from experimental observations demonstrating that a high ratio of zinc to copper led to hypercholesterolemia in rats, serum Zn and Cu levels were measuied by atomic absorption spectrophotometry in 65 normolipemic controls and in 100 subjects with various types of hyperlipoproteinemia (HLP). Serum Zn levels did not significantly differ from control values in any type of HLP. However, hyperlipoproteinemic patients with obvious clinical atherosclerosis displayed significantly lower serum-Zn concentration than hyperlipoproteinemic subjects without clinical symptoms. On the other hand, w h e n compared to control subjects, serum Cu levels were not found to be decreased, but rather increased, in hyperlipoproteinemic patients with or without atherosclerosis. As a result, the Zn:Cu ratio appeared to be lower than normal in hyperlipoproteinemic patients with cardiovascular disease. It is conceivable that changes of these trace elements should be rather connected to vessel injury and associated disease than to HLP which, at least in humans, is not accompanied by a high Z n : C u ratio. Index Entries: Serum Zn, Cu, and Z n : C u ratio in hyperlipoproteinemia; zinc, in hypercholesterolemic serum; hyperlipoproteinemia, and Zn, Cu, and Z n : C u ratio in serum. *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research
] 67
VoL 8, 1985
168
Uza et al.
INTRODUCTION It has been s h o w n that a relative or absolute deficiency of Cu, characterized by a high ratio of Zn to Cu, caused an increase of serum cholesterol in rats, which then also developed cardiovascular lesions (1,2). It was found as well that Zn therapy lowered the plasma level of the "antiatherogenic" high density lipoprotein (3). These data suggesting a possible relationship between the ratio of Zn to Cu and the d e v e l o p m e n t of hypercholesterolemia (HLP) p r o m p t e d us to investigate the behavior of serum Zn and Cu in hyperlipidemic h u m a n s with or without obvious clinical atherosclerosis.
METHODS AND MATERIALS Clinical Material The 169 subjects u n d e r investigation were divided into the following groups:
A. Control Subjects This group included 65 subjects aged 23-69 yr (mean age, 35.29 _+ 1.62 yr) with serum cholesterol less than 240 mmol/L and serum triglycerides less than 150 mmol/L. B. Hyperlipidemic Subjects This group, including 100 subjects aged 20-73 yr (mean age, 53.63 _+ 1.36 yr) was subdivided according to the type of HLP; 20 subjects (11 m e n and 9 women) were considered to be heterozygous for HLP type IIa, 42 subjects (21 m e n and 21 women) were presenting a lipoprotein pattern compatible with a mixed HLP (HLP type IIb); type IV was attributable to 32 subjects (25 men and 11 women); and six subjects with fasting chylomicronemia were classified as having HLP type V; 41 subjects with HLP exhibited obvious clinical symptoms of atherosclerosis (coronary, cerebral, peripheral, or multiple tocalizations). Occurrence of atherosclerosis in a subclinical form could not, however, be excluded in the remaining 59 HLP subjects w h o were without cardiovascular complaints. These last-mentioned HLP subjects were also younger (mean age, 49.88 + 1.77 yr) than those with obvious clinical atherosclerosis (mean age, 57.42 _+ 1.63 yr). No patients were acutely ill w h e n investigated. Patients with liver or kidney disease, as well as those u n d e r g o i n g a therapy that might have influenced the plasma level of the minerals investigated, were not included in the study.
Biological Trace Element Research
VoL 8, 1985
Serum Zinc and Copper in Hyperlipoproteinemia
169
Serum Lipids and ll~'nerals Analysis Indication of the m e t h o d s u s e d for analysis of s e r u m lipids a n d lipoproteins as well as criteria for the classification of the patients into the various t y p e s of H L P w e r e given in p r e v i o u s p a p e r s .(4-6). S a m p l e s of v e n o u s blood w e r e collected u n d e r fasting c o n d i t i o n s a v o i d i n g m e t a l c o n t a m i n a t i o n . S e r u m Z n a n d Cu c o n c e n t r a t i o n w e r e e s t i m a t e d by m e a n s of a Perkin Elmer M o d e l 300, Flame A t o m i c S p e c t r o p h o t e m e t e r o p e r a t i n g at 213.8 n m for Z n a n d 324.7 for Cuo
Statistical Analysis Statistical significance was a s s e s s e d by the two-tailed S t u d e n t t-test.
RESULTS As s h o w n in Table 1 a n d Fig. 1, c h a n g e s affecting s e r u m Z n in the various t y p e s of H L P w e r e not significant, while s e r u m Cu level t e n d e d to be h i g h e r t h a n m e a n n o r m a l value in all the investigated types of HLP. W h e n the h y p e r l i p i d e m i c subjects w e r e c o n s i d e r e d according to the p r e s e n c e or absence of clinical atherosclerosis it was h o w e v e r n o t e d t h a t the s e r u m level of Z n is significantly lower in patients with o b v i o u s s y m p t o m s of vascular disease. This decrease of s e r u m Zn associated to a h i g h e r t h a n n o r m a l c o n c e n t r a t i o n of s e r u m Cu led to an i m p o r t a n t d i m i n u t i o n of the Z n / C u ratio (see Table 2). It s h o u l d be m e n t i o n e d t h a t TABLE 1 Behavior of Serum Lipids as Well as of Zn and Cu Levels in Control Subjects and in Various Types of HLP~ Cholesterol, p-g/L Controls ( 6 5 )
Triglyceride, ~xg/L
Zn, ~xg/dL
Cu, ~x/dL
117.67 _+ 4.43
106.77 _+ 4.05
Zn/Cu
197.35 __+ 3.67
t16.00 • 4.43
1.19 +_ 0.06
IIa (20)
37t.70"** _+ 21.88
153.55" • 12.03
114.75 t28.35" _+ 8.26 _+ 10.93
0.95 ** _ 0.07
[Ib (42)
347.98*** ___ 6.75
278.57*** • 11.60
122.04 -+ 5.60
150.02"** • 8.95
0.91 *** -+ 0.065
IV (32)
316.36"** • 10.88
562.13"** § 60.45
122.63 -+ 4.85
121.6 * _+ 6.82
1.07 _+ 0.07
V (6)
378.50*** • 47.00
1959.50"** • 557.88
139.33 132.83 • 12.41 _ 26.71
1.23 + 0.20
~Mean v a l u e _+ s t a n d a r d error of the m e a n , N u m b e r of s u b j e c t s in p a r e n t h e s e s . Statistical s i g n i f i c a n c e v e r s u s control subjects: * p < 0.05; ** p < 0.01; *** p < 0,001,
Biological Trace Element Research
VoL 8, 1985
170
Uza et al. i
260" 240
220" A
2(301 160" 140" :n.
c
N
120"
E 10080'
o
A
180" "x
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IIb
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V
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2601
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240 o
220 200
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180
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160 LD
140
~ 120
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9
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0 0
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II b
IV
V
Fig. 1. Serum Zn (a) and Cu (b) concentrations in controls (A) and subjects with HLP type IIa, IIb, IV, and V:., Hyperlipidemic subjects displaying clinical atheroscterosis; o, hyperlipidemic subjects without symptoms of atherosclerosis. Biological Trace Element Research
Vol. 8, 1985
Serum Zinc and Copper in Hyperlipoproteinemia
171
TABLE 2 Serum Zn and Cu Concentrations and the Zn/Cu Ratio in Controls (A), Subjects with HLP but Without Clinical Symptoms of Atherosclerosis (B), and in HLP Patients with Clinical Symptoms of Vascular Disease (C) Serum Zn, Fg/dL A. Controls (N = 65) B. HLP without clinical atherosclerosis (N = 59) C. HLP with clinical symptoms of atherosclerosis (N 41) STATISTICAL SIGNIFICANCE A vs B B vs C B vs C
Serum Cu, Zn/Cu ~xg/dL ratio
117.67 • 4.43 133.45 • 3.16
106.77 _+ 4.05 135.66 • 6.29
1.19 _+ 0.06 1.14 +_ 0.06
107.55 • 4.16
138.15 +__ 7.02
0.84 + 0.05
(p)
