Cell Biology International ISSN 1065-6995
doi: 10.1002/cbin.10920
RESEARCH ARTICLE
Pathological lesions and global DNA methylation in rat prostate
under streptozotocin-induced diabetes and melatonin
supplementation
Marina Guimar
~
aes Gobbo
1,2
, Guilherme Henrique Tamarindo
1,2
, Daniele Lisboa Ribeiro
3
,
Silvana Gisele Pegorin de Campos
2
, Sebasti
~
ao Roberto Taboga
2
and Rejane Maira G
oes
2
*
1 Department of Functional and Structural Biology, Institute of Biology, P.O.Box: 6109, University of Campinas—UNICAMP, 13083–970, Campinas, SP,
Brazil
2 Department of Biology, Institute of Biosciences, Humanities and Exact Sciences, Univ Estadual Paulista—UNESP, 15054–970, S
~
ao Jos
e do Rio Preto, SP,
Brazil
3 Department of Histology-ICBIM, Federal University of Uberlandia, Uberl
^
andia, Minas Gerais, Brazil
Abstract
Chronic hyperglycemia increases production of reactive oxygen species, which favors carcinogenesis. The association between
diabetes and prostate cancer is controversial. Melatonin has antioxidant, anti-inflammatory, and antiproliferative properties.
We investigated whether low doses of melatonin prevent the tissue alterations caused by diabetes and alter prostate histology
of healthy rats. We also investigated whether experimental diabetes promoted the development of pathological lesions in
the ventral prostate of rats. Melatonin was provided in drinking water (10 mg/kg/day) from age 5 weeks until the end of
experiment. Diabetes was induced at 13 weeks by administration of streptozotocin (40 mg/kg, ip). Rats were euthanized at 14
or 21 weeks. Histological and stereological analyses were carried out and the incidence and density of malignant and pre-
malignant lesions were assessed. Immunohistochemical assays of a-actin, cell proliferation (PCNA), Bcl-2, glutathione
S-transferase (GSTPI), and DNA methylation (5-methylcytidine) were performed. Melatonin did not elicit conspicuous
changes in the prostate of healthy animals; in diabetic animals there was a higher incidence of atrophy (93%), microinvasive
carcinoma (10%), proliferative inflammatory atrophy, PIA (13%), prostatitis (26%), and prostate intraepithelial neoplasia, PIN
(20%) associated with an increase of 40% in global DNA methylation. Melatonin attenuated epithelial and smooth muscle cell
(smc) atrophy, especially at short-term diabetes—and normalized incidence of PIN (11%), inflammatory cells infiltrates,
prostatitis (0%) and PIA (0%) at long-term diabetes. MLT was effective in preventing inflammatory disorders and PIN under
diabetic condition. Although MLT has antioxidant action, it did not influence DNA methylation and not avoid carcinogenesis
at low doses.
Keywords: diabetes; melatonin; prostate; prostate cancer; rat
Introduction
The association between diabetes mellitus (DM) and prostate
cancer is controversial. Some clinical studies have associated
DM, especially type-1, with a lower risk of prostate cancer,
attributed to the protective effects of insulin lack and lower
testosterone levels (Moreira et al., 2011; Fall et al., 2013; Xu
et al., 2013; Yu et al., 2013). This is due because insulin
Ã
Corresponding author: e-mail: marinagobbo@gmail.com
Abbreviations: 5MeC, 5-methylcytidine; AGE, Advanced glycation end products; RAGE, Advanced glycation end products receptor; AMPK, AMP-
activated protein kinase; Bcl-2, Anti-apoptotic protein; C1, Control animals of short-term experiment; C2, Control animals of long-term experiment; M1,
Control animals treated with MLT of short-term experiment; M2, Control animals treated with MLT of short-term experiment; DM, Diabetes mellitus;
DAB, Diaminobenzidine; GLUT2, Glucose transporter type 2; GSTPI, Glutathione S-transferase pi; PIN, Intraepithelial neoplasia; LH, Luteinizing hormone;
MLT, Melatonin; MTR1, Melatonin receptor type 1; D1, One-week-diabetic rats; MD1, One-week-diabetic rats treated with MLT; PCNA, Proliferating cell
nuclear antigen; PIA, Proliferative inflammatory atrophy; PIN, Prostate intraepithelial neoplasia; PKA, Protein kinases A; PKB, Protein kinases B; PKC,
Protein kinases C; ROS, Reactive oxygen species; smc, Smooth muscle cells; STZ, Streptozotocin; D2, Two-month-diabetic rats; MD2, Two-month-
diabetic rats treated with MLT.
470
Cell Biol Int 42 (2018) 470–487 © 2018 International Federation for Cell Biology
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