Diabetes is a well-known disease, i.e., generally caused by the disorder of insulin hormone metabolism, the disorder of hormone production, or the disruption of the production of membrane cell surface receptors on its target cells [4]. Diabetes has such complications as, retinopathy, nephropathy, and the involvement of the main peripheral arteries; it presents gastrointestinal motility disorders [5]. Thiamine is the first known B vitamin in energy supply, fat metabolism, and nucleotides. Besides, it plays an essential role as a coenzyme, especially in the formation and development of brain cells [8]. The accumulation of lead in the body can have destructive effects on the blood, bone marrow, kidney, and gastrointestinal blood cells [12]. In a report (Leff 2018), the injection of lead acetate in male mice with diabetes mellitus increased fasting blood glucose levels [15]. This study was designed to investigate the effects of thiamine and lead acetate on the colon of diabetic rats.

In all stages of this research, the ethical principles of working with laboratory animals in the laboratory of Shahrekord University were considered. This study was approved by the Research Ethics Committee of Shahrekord Veterinary School. In total, 63 rats with an average weight of 220-200 g were prepared from the animal house of Shahrekord University.
The examined rats were classified into 9 groups, as follows:
1) Diabetes+acetate group 200 ppm;
2) Thiamine+acetate group 200 ppm;
3) Thiamine group+lead acetate 1000 ppm;
4) Diabetes+thiamine+lead acetate 1000 ppm group;
5) Diabetes group;
6) Diabetes+thiamine group;
7) Diabetes+thiamine+acetate group 200 ppm;
8) Diabetes+acetate group 1000 ppm;
9) Control group.
After 20 days of treatment, the explored rats were anesthetized with ether anesthetic and facilitated by human methods. The abdominal cavity was opened and the large intestine came out of the cavity. Different layers of colon tissue, including mucosa, submucosa, muscle, and adventitia were examined under a microscope for histology and histometric. For stereological evaluation, using point grade, the area of different wall layers of the colonic tissue structure was examined.

The morphometric findings revealed that the mean thickness of the mucosal-submucosal layer was the highest in treatment group 6 (diabetes+thiamine) and the lowest in group 7 (diabetes+thiamine+acetate 200 ppm) (Figures 1 A, B & C). 



These results also indicated that these differences were significant in groups 6 and 7, compared to other treatment groups and the controls, except for group 5 (diabetic group) concerning analysis at P<0.05. Morphometric results revealed a significant difference in the mean thickness of the smooth muscle layer of the colon wall in treatment groups 1 to 8, except for group 2 (thiamine+200 ppm lead acetate), compared to the control group (P<0.05). The obtained results presented no significant difference between the mean thickness of the muscle layer of group 2 and the control group (P<0.05). The average area of the mucosal-submucosal layer data suggested that in groups 1 and 8, there was a significant difference, compared to the control group (P<0.05); in both of them, a decrease was observed in this area. The results of the area parameter study in the muscle layer of the colon indicated that only in group 1, there was a significant difference, compared to the control group (P<0.05). Besides, this difference was in the direction of increasing the area.
Examining serous layer surface presented no significant difference, compared to the control group (P<0.05). There was only a significant difference between the groups of diabetes+lead 200 acetate and thiamine+lead 200 acetates in this respect.

The present study investigated the histomorphometric changes of different layers of the colon in diabetic rats. As the present study revealed, the effects of thiamine and lead acetate in two different doses were well evident on the colon wall layers. The obtained data highlighted a significant decrease in the thickness of the mucosal-submucosal layer of groups 1, 7, and 8 (diabetes + acetate 1000 & 200 groups & diabetes + thiamine + lead acetate 200 groups), compared to the control group; this decreasing trend well reflects the damaging effects of lead acetate on the thickness of the mucosal-submucosal layer. The results of some studies suggested that free radicals are the main cause of many disorders in diabetes [21]. The collected results indicated that the thickness of the muscle layer, including decreasing changes in group 5 (diabetes) compared to the controls. However, Nowak et al. (1995) found that, in contrast to the data of the present study, induced experimental diabetes increased the thickness of the muscle layer [27]. Surface findings from the study of colonic tissue stereology presented that in group 1, the average area of different tissue layers was significantly different from the control group. These changes signified the effects of diabetes and lead acetate on colon tissue in the direction of increasing (mucosal layer area-submucosal) and decreasing (muscle layer area and adventitia). The results of another study revealed that diabetes caused a peripheral and longitudinal enlargement of the colon wall [29]. Considering the induction of experimental diabetes and subsequent administration of thiamine in the rats of the treatment group, thiamine, in some of the studied groups, has improved effects on muscle layer thickness and adventitia layer thickness. However, the mean area of the mucosal layer was not affected by the improving effects of thiamine.

This study was approved by the ethics code GRN1M1903 in the Faculty of Veterinary Medicine of Shahrekord University. Furthermore, all the methods used, including facilitation, were performed per the ethical principles of animal restraint.

The project was supported by Faculty of Veterinary Medicine, Vice Chancellor for Research, Shahrekord University.

Conceptualization: Rahmat Allah Fatahian, Soren Nouraei; Research: Rahm Atollah Fatahian, Alborz Yadalahi; Editors: Soren Nouraei, Alborz Yadalahi, Rahmat Allah Fatahian.

The authors declared no conflicts of interest.

The authors want to thank all staff of the Physico-Pharmacology and Histo-Pathology Laboratories, as well as the esteemed Vice Chancellor for Research of Shahrekord University and Faculty.

 

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