Immunohistochemical Analysis of Intestinal and Central Nervous System Morphology in an Obese Animal Model (Danio rerio) Treated with 3,5-T2: A Possible Farm Management Practice?

Abstract

<jats:p>The 3,5-diiodo-L-thyronine (3,5-T2) is an endogenous metabolite of thyroid hormones, whose administration to rodents fed high-fat diet (HFD) prevents body weight increase and reverts the expression pattern of pro-inflammatory factors associated to HFD. The diet-induced obese (D.I.O.) zebrafish (Danio rerio) has been recently used as an experimental model to investigate fundamental processes underlying central and peripheral obesity-driven inflammation. Herein, we aim to understand the role of 3,5-T2 in regulating central and peripheral inflammation in D.I.O. model of zebrafish. 3,5-T2 (10 nM and 100 nM) was administered with the obesity-inducing diet (D.I.O. with 3,5-T2) or after 4 weeks of obesity-inducing diet (D.I.O. flw 3,5-T2). 3,5-T2 significantly increased the body weight and serum triglyceride levels in D.I.O. zebrafish in both conditions. Moreover, 3,5-T2 sustained or increased inflammation in the anterior (AI) and mid (MI) intestine when administered with the obesity-inducing diet, as indicated by the immunoexpression of the inflammatory markers tumor-necrosis factor-α (TNFα), cyclooxygenase 2 (COX2), calnexin, caspase 3, and proliferating cell nuclear antigen (PCNA). On the contrary, when 3,5-T2 was administered after the obesity-inducing diet, partly reverted the intestinal alteration induced by D.I.O. In addition, brain inflammation, as indicated by the increase in the activation of microglia, was detected in D.I.O. zebrafish and D.I.O. treated with 3,5-T2. These findings reveal that the effects of 3,5-T2 on fish intestine and brain can deviate from those shown in obese mammals, opening new avenues to the investigation of the potential impact of this thyroid metabolite in different diseases including obesity.</jats:p>

Dietary Supplementation with a Blend of Hydrolyzable and Condensed Tannins Ameliorates Diet-Induced Intestinal Inflammation in Zebrafish (Danio rerio)

“…In the end, the sections were incubated with the avidin-biotin complex (ABC Kit; Vectastain, Vector Laboratories, CA, USA) for 1h, followed by revelation with 0.05% 3 -diaminobenzidine (DAB) (DAB Sigma Fast, Sigma-Aldrich, St. Louis, MO, USA). The antibody specificity was proven, as reported by Imperatore et al [41,42]. Specifically, negative controls were performed by omitting the primary antibodies, and they did not show any positivity (Figure S1).…”

“…The immunohistochemical technique was performed as described by Imperatore et al [41]. Briefly, after dewaxing, sections of the mid-intestine were stained with the following primary antibodies: a monoclonal anti-tumor necrosis factor-α (TNFα) antibody raised in mouse (code ab1793, Abcam, Cambridge, UK) or a polyclonal anti-cyclooxygenase 2 (COX2) antibody raised in rabbit (code 69720, NovaTeinBio, Woburn, MA, USA).…”

Immunohistochemical and Physiological Research on Farm Animals

“…Imperatore and colleagues [20] analyze the effect of 3,5-diiodo-L-thyronine (3,5-T2), an endogenous metabolite of thyroid hormones whose administration to rodents fed a high-fat diet (HFD) prevents body weight increase and reverts the expression pattern of pro-inflammatory factors associated with HFD, in a diet-induced obese (D.I.O.) zebrafish (Danio rerio) model.…”