The Activities of Antioxidant Enzymes and Monoamine Oxidase and Uncoupling Protein 1 Content in Brown Fat of Hypo- and Hyperthyroid Rats

Brown Adipose Tissue-A Translational Perspective

Brown adipose tissue (BAT) displays the unique capacity to generate heat through uncoupled oxidative phosphorylation that makes it a very attractive therapeutic target for cardiometabolic diseases. Here, we review BAT cellular metabolism, its regulation by the central nervous and endocrine systems and circulating metabolites, the plausible roles of this tissue in human thermoregulation, energy balance, and cardiometabolic disorders, and the current knowledge on its pharmacological stimulation in humans. The current definition and measurement of BAT in human studies relies almost exclusively on BAT glucose uptake from positron emission tomography with 18F-fluorodeoxiglucose, which can be dissociated from BAT thermogenic activity, as for example in insulin-resistant states. The most important energy substrate for BAT thermogenesis is its intracellular fatty acid content mobilized from sympathetic stimulation of intracellular triglyceride lipolysis. This lipolytic BAT response is intertwined with that of white adipose (WAT) and other metabolic tissues, and cannot be independently stimulated with the drugs tested thus far. BAT is an interesting and biologically plausible target that has yet to be fully and selectively activated to increase the body's thermogenic response and shift energy balance. The field of human BAT research is in need of methods able to directly, specifically, and reliably measure BAT thermogenic capacity while also tracking the related thermogenic responses in WAT and other tissues. Until this is achieved, uncertainty will remain about the role played by this fascinating tissue in human cardiometabolic diseases.

Histamine mediates behavioural and metabolic effects of 3-iodothyroacetic acid, an endogenous end product of thyroid hormone metabolism

BACKGROUND AND PURPOSE

3-Iodothyroacetic acid (TA1) is an end product of thyroid hormone metabolism. So far, it is not known if TA1 is present in mouse brain and if it has any pharmacological effects.

EXPERIMENTAL APPROACH

TA1 levels in mouse brain were measured by HPLC coupled to mass spectrometry. After i.c.v. administration of exogenous TA1 (0.4, 1.32 and 4 μg·kg(-1) ) to mice, memory acquisition-retention (passive avoidance paradigm with a light-dark box), pain threshold to thermal stimulus (51.5°C; hot plate test) and plasma glucose (glucorefractometer) were evaluated. Similar assays were performed in mice pretreated with s.c. injections of the histamine H1 receptor antagonist pyrilamine (10 mg·kg(-1) ) or the H2 receptor antagonist zolantidine (5 mg·kg(-1) ). TA1 (1.32 and 4 μg·kg(-1) ) was also given i.c.v. to mice lacking histidine decarboxylase (HDC(-/-) ) and the corresponding WT strain.

KEY RESULTS

TA1 was found in the brain of CD1 but not of HDC mice. Exogenous TA1 induced amnesia (at 0.4 μg·kg(-1) ), stimulation of learning (1.32 and 4 μg·kg(-1) ), hyperalgesia (0.4, 1.32 and 4 μg·kg(-1) ) and hyperglycaemia (1.32 and 4 μg·kg(-1) ). All these effects were modulated by pyrilamine and zolantidine. In HDC(-/-) mice, TA1 (1.32 and 4 μg·kg(-1) ) did not increase plasma glucose or induce hyperalgesia.

CONCLUSIONS AND IMPLICATIONS

Behavioural and metabolic effects of TA1 disclosed interactions between the thyroid and histaminergic systems.

Antioxidant status in the serum of persons with intellectual disability and hypothyroidism: a pilot study

Hypothyroidism (HPO) in humans is widely believed to impair health. The biochemical factors mediating decline in health, however, are poorly elucidated. Pathological consequences of HPO point to a high potential for antioxidant imbalance. The objectives of this study were to investigate the major antioxidants in persons with intellectual disability (ID) and HPO in order to find the effect of chronic disease on the level of antioxidative parameters. This is a prospective, nonrandomized study. A total of 11 people with HPO and 11 age-matched healthy participants were examined. The following antioxidative defense were examined: superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px), and glutathione reductase (GR) as well as two biochemical parameters creatinine and albumin. Compared to healthy control subjects without complications, persons with ID and HOP had significantly lower SOD (p<0.05), catalase (p<0.05), GSH-Px (p<0.05), except the GR level (p=NS). A significant correlation was found between age and gender and AO values in experimental group SOD (r=-0.882), catalase (r=-0.724) and GSH-Px (r=-0.782). Our preliminary results confirm the hypothesis that there is a reduction of the antioxidative defense in persons with HPO and in particularly among males.