Hypothyroidism Exacerbates Thrombophilia in Female Rats Fed with a High Fat Diet

Clotting abnormalities are discussed both in the context with thyroid dysfunctions and obesity caused by a high fat diet. This study aimed to investigate the impact of hypo-, or hyperthyroidism on the endogenous thrombin potential (ETP), a master indicator of clotting activation, on Sprague Dawley rats fed a normal or high fat diet. Female Sprague Dawley rats (n = 66) were grouped into normal diet (ND; n = 30) and high-fat diet (HFD; n = 36) groups and subdivided into controls, hypothyroid and hyperthyroid groups, induced through propylthiouracil or triiodothyronine (T3) treatment, respectively. After 12 weeks of treatment ETP, body weight and food intake were analyzed. Successfully induced thyroid dysfunction was shown by T3 levels, both under normal and high fat diet. Thyroid dysfunction was accompanied by changes in calorie intake and body weight. In detail, compared to euthyroid controls, hypothyroid rats showed significantly increased—and hyperthyroid animals significantly decreased—ETP levels. High fat diet potentiated these effects in both directions. In summary, we are the first to show that hypothyroidism and high fat diet potentiate the thrombotic capacity of the clotting system in Sprague Dawley rats. This effect may be relevant for cardiovascular disease where thyroid function is poorly understood as a pathological contributor in the context of clotting activity and obesogenic nutrition.

Oxidized LDL Is Strictly Limited to Hyperthyroidism Irrespective of Fat Feeding in Female Sprague Dawley Rats

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.

Effect of fat feeding on pro-oxidant and anti-oxidant enzyme systems in rat intestine: possible role in the turnover of enterocytes

Immature epithelial cells generated in the crypt base undergo differentiation while progressing to the villus tip, where the cells upon apoptosis are detached from the underlying muscular tissue. We previously reported that lipid peroxidation might be involved in the turnover of enterocytes across the crypt-villus axis in rat intestine (Dig Dis Sci 52:1840-1844, 2007). To examine whether long-term feeding of fat with different fatty-acid composition influences this process, in the present study we investigated the effect of feeding fish oil (n - 3) and corn oil (n - 6) polyunsaturated fatty acids on lipid per-oxidation and anti-oxidant systems in different epithelial cell fractions isolated in rat intestine. Feeding fish oil or corn oil markedly enhanced lipid per-oxidation levels of enterocytes throughout villus height compared with control, but there was no difference in the distribution profile of pro- and anti-oxidant enzyme systems and lipid per-oxidation across the crypt-villus axis under these conditions. Analysis of lipid peroxidation levels in different cell fractions revealed that the thiobarbituric acid reactive substance were 9- to 11-fold higher at the villus tip compared with at the crypt base. The activities of glutathione reductase and glutathione-S-transferase were 2- to 5-fold higher in villus tip compared to the crypt region. However, the activities of superoxide dismutase and catalase were 6- to 8-fold high at the crypt base compared with at villus tip cells. Immunocytolocalization of superoxide dismutase showed high staining in crypt base compared with that in villus, tip cells. These findings further suggest that generation of reactive oxygen species in enterocytes across the crypt-villus axis may be involved in turnover of enterocytes across the crypt-villus unit in rat intestine.