Hypothyroidism Affects Vascularization and Promotes Immune Cells Infiltration into Pancreatic Islets of Female Rabbits

Abstract

Thyroidectomy induces pancreatic edema and immune cells infiltration similarly to that observed in pancreatitis. In spite of the controverted effects of hypothyroidism on serum glucose and insulin concentrations, the number and proliferation of Langerhans islet cells as well as the presence of extracellular matrix are affected depending on the islet size. In this study, we evaluated the effect of methimazole-induced hypothyroidism on the vascularization and immune cells infiltration into islets. A general observation of pancreas was also done. Twelve Chinchilla-breed female adult rabbits were divided into control (n = 6) and hypothyroid groups (n = 6, methimazole, 0.02% in drinking water for 30 days). After the treatment, rabbits were sacrificed and their pancreas was excised, histologically processed, and stained with Periodic Acid-Schiff (PAS) or Masson's Trichrome techniques. Islets were arbitrarily classified into large, medium, and small ones. The external and internal portions of each islet were also identified. Student-t-test and Mann-Whitney-U test or two-way ANOVAs were used to compare variables between groups. In comparison with control rabbits, hypothyroidism induced a strong infiltration of immune cells and a major presence of collagen and proteoglycans in the interlobular septa. Large islets showed a high vascularization and immune cells infiltration. The present results show that hypothyroidism induces pancreatitis and insulitis.

Hypothyroidism Induces a Moderate Steatohepatitis Accompanied by Liver Regeneration, Mast Cells Infiltration, and Changes in the Expression of the Farnesoid X Receptor

“…Although we did not find any difference in the averaged cross-sectional area of hepatocytes among groups, the moderate steatosis and the perisinusoidal fibrosis observed in hypothyroid rabbits could be enough to affect the hepatic vascularization [34]. Indeed, hypothyroidism modifies the blood vessels into pancreatic islets [19]. Contrary to a severe steatosis [35,36], the moderate steatosis induced by a short-time hypothyroidism in female rabbits allows the regeneration of the liver.…”

“…For the experiment, control (n = 6) and hypothyroid (Hypo; n = 6) rabbits were daily provided with pellet food and tap water ad libitum during one month. The hypothyroidism was induced by a treatment with 0.02 % methimazole (MMI; approximate diary dosage of 10 mg/kg, Sigma) in the drinking water [19,20]. The Guidelines of Mexican Law of Production, Care and Use Laboratory Animals (NOM-062-ZOO-1999) were followed throughout the study.…”

“…Liver sections cut in microtome were stained with the Periodic-Acid Shift (PAS) technique to observe the presence of glycogen into the hepatocytes [21]. Other liver sections cut in microtome were staining with the Masson's trichrome technique for evaluating the extent of fibrosis [19].…”

The Roles of Thyroid and Thyroid Hormone in Pancreas: Physiology and Pathology

“…Regarding the study of mechanisms, an in vivo study demonstrated that methimazole-induced hypothyroidism promotes immune cell infiltration into pancreatic islets of female rabbits, which could be inducing pancreatitis and insulitis [ 79 ]. Other mechanisms involved in islet dysfunction may be related to different signals.…”

Electron microscopic study of changes in pancreatic exocrine secretory cells in both early and late stages of hypothyroidism

“…In patients with hypothyroidism, violations of exocrine and endocrine functions of the pancreas are often revealed. The relationship of the pancreas with the thyroid gland is not completely disclosed; although the structural and functional features of the insular apparatus of the pancreas under hypothyroidism are described in the literature in details [12][13][14], the peculiarities of pancreatic lesions in hypothyroidism remain insufficiently studied.…”