Abstract
Metabolic dysfunctions might play a crucial role in the pathophysiology of thyroid dysfunctions. This study aimed to investigate the impact of a controlled diet (normal versus high fat feeding) on hypothyroid and hyperthyroid Sprague Dawley rats. Female Sprague Dawley rats (n = 66) were grouped into normal diet (n = 30) and high-fat diet (n = 36) groups and subdivided into controls, hypothyroid and hyperthyroid groups, induced through propylthiouracil or triiodothyronine (T3) treatment, respectively. After 12 weeks of treatment metabolic parameters, such as oxidized LDL (oxLDL), malondialdehyde (MDA), 4-hydroxynonenal (HNE), the lipid profile, body weight and food intake parameters were analyzed. Successfully induced thyroid dysfunctions were shown by T3 levels, both under normal and high fat diet. Thyroid dysfunctions were accompanied by changes in calorie intake and body weight as well as in the lipid profile. In detail, hypothyroid rats showed significantly decreased oxLDL levels, whereas hyperthyroid rats showed significantly increased oxLDL levels. These effects were seen under high fat diet and were less pronounced with normal feeding. Taken together, we showed for the first time in female SD rats that only hyper-, but not hypothyroidism, is associated with high atherogenic oxidized LDL irrespective of normal or high-fat diet in Sprague Dawley rats.
Highlights
Thyroid dysfunctions comprise a complex network of diseases including malignant, inflammatory and autoimmune diseases of the thyroid gland [1,2,3]
We subsequently investigated the association of thyroid dysfunctions with lipid profile changes by linear regression analyses
We found an association of T3 with oxidized LDL (oxLDL) in both untreated control groups, with r = 0.702 and p = 0.024 under high-fat diet (HFD) and a not statistically significant association in the normal diet group with r = 0.630 and p = 0.051
Summary
Thyroid dysfunctions comprise a complex network of diseases including malignant, inflammatory and autoimmune diseases of the thyroid gland [1,2,3]. Thyroid diseases can by divided into hypo- and hyperthyroidism, according to thyroid hormone production, e.g., triiodothyronine (T3) [4]. There is established evidence that thyroid dysfunctions such as hypo- and hyperthyroidism as well as subclinical hypothyroidism are associated with metabolic dysfunctions, especially regarding dyslipidemia [5,6]. Associations with other lipid parameters, such as triglycerides, HDL cholesterol, and various lipoproteins with thyroid dysfunctions, are a matter of debate. Higher rates in both hypo- and hyperthyroidism have been reported [7]. The production of ROS contributes to atherogenic oxidized LDL, which further advances metabolic and cardiovascular risk. Findings especially regarding hypothyroidism and ROS are controversial to date
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