Abstract
BackgroundHypothyroidism (HO) can significantly impair lipid metabolism and increase cardiovascular disease risk. Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease. Our previous study demonstrated that HHcy significantly induced insulin resistance and impaired coronary artery endothelial function in patients with either hypertension or HO. In the present study, we studied whether plasma levels of high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-I (Apo A-I) were altered in patients with HO, and if so, whether this change was mediated by HHcy.MethodsA total of 258 subjects were enrolled and divided into the following three groups: control group (n = 94), HO group (n = 73), and subclinical hypothyroidism (SHO) group (n = 91). Additionally, all groups were subdivided based on the subjects’ Hcy levels into HHcy (plasma Hcy level over 15 μmol/l) and normal Hcy subgroups. The plasma levels of lipid indexes were measured. Statistical analyses were performed to evaluate the correlations between groups.ResultsThe plasma Hcy levels were significantly higher in the HO group than in the SHO or control groups (all p < 0.05). Moreover, levels of Apo A-I and HDL-C were markedly reduced in the HHcy subgroup compared with the normal Hcy subgroup for patients with either HO (Apo A-I: p < 0.05; HDL-C: p < 0.01) or SHO (Apo A-I: p < 0.05; HDL-C: p < 0.01). In addition, the plasma Hcy levels were negatively correlated with levels of Apo A-I in all three groups (HO group: r = − 0.320, SHO group: r = − 0.337 and control group: r = − 0.317; all p < 0.01).ConclusionsHcy levels were significantly increased in patients with HO or SHO. These increased Hcy levels may impair cardiovascular function via the inhibition of Apo A-1 expression and impairment of its antioxidant capacity. Our findings provide new insights into the pathogenesis of hypothyroidism-induced metabolic disorders.
Highlights
Hypothyroidism (HO) can significantly impair lipid metabolism and increase cardiovascular disease risk
The CHOL, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), Apo apolipoprotein A-I (A-I) and Apolipoprotein B (Apo B) values in the HO group were significantly higher than those in the subclinical hypothyroidism (SHO) and control groups; no differences were detected between the SHO and control groups [CHOL: 5.98 ± 1.67 vs. 5.09 ± 1.21 and 5.00 ± 1.00 mmol/l; HDL-C: 1.62 ± 0.40 vs. 1.47 ± 0.33 and 1.47 ± 0.30 mmol/l; LDL-C: 3.47± 1.21 vs. 3.03 ± 0.95 and 2.89 ± 0.81 mmol/l; apolipoprotein A-I (Apo A-I): 1.49 ± 0.38 vs. 1.34 ± 0.28 and 1.35 ± 0.27 g/l (Fig. 1); Apo B: 1.01 ± 0.34 vs. 0.92 ± 0.26 and 0.89 ± 0.24 g/l; respectively; all p < 0.05]
Levels of CHOL were higher in the H-HO group than in the H-SHO and H-control groups; no difference was detected between the H-SHO and H-control groups (6.24 ± 2.06 vs. 5.26 ± 1.69 and 5.03 ± 0.90 mmol/l, respectively, p < 0.05)
Summary
Hypothyroidism (HO) can significantly impair lipid metabolism and increase cardiovascular disease risk. Our previous study demonstrated that HHcy significantly induced insulin resistance and impaired coronary artery endothelial function in patients with either hypertension or HO. We studied whether plasma levels of high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A-I (Apo A-I) were altered in patients with HO, and if so, whether this change was mediated by HHcy. Hypothyroidism (HO) and subclinical hypothyroidism (SHO), the two most common endocrine disorders, can induce metabolic dysfunction [1] and increase the risk of cardiovascular disease [2, 3]. Our previous study demonstrated that HHcy induced insulin resistance in patients with HO or SHO [15] and impaired coronary artery endothelial function in patients with hypertension or hypertriglyceridemia [16, 17].
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