Metabolic problems as insulin resistance and incapacity of maintaining normoglycaemia are frequent reported problems associated to women estrous cycle. In humans, luteal phase of estrous cycle lasts 14 days, in which plasma 17²-estradiol (E2) and progesterone (P4) levels fluctuate concomitantly. Estrous cycle in the bitch differs from other domestic species and from humans as well. Nevertheless, metabolic alterations as insulin resistance further causing Diabetes mellitus have also been described associated to the luteal phase, which, in the dog may last from 60 to 75 days. This period, named diestrus in the canine species, is characterized by increasing of plasma P4 in the first third and fluctuations of plasma E2 along the whole period, not necessarily in a concomitant way. Glucose is a molecule that requires transportation by carrier proteins (GLUTs) to the intracellular environment in the majority of cells. Insulin resistance development may be accompanied by alteration of tissue expression of some glucose transporters, as GLUT 4, present mainly in muscles and adipose tissue, which are considered insulin-sensitive tissues. Until present data there is no report on the cycle-dependent hormonal alterations that may influence GLUT 4 expression in insulin-sensitive tissues. Moreover, GLUT 4 protein and mRNA have been detected by our group in canine luteal tissue with varying expression over diestrus. We hypothesize that canine corpus luteum (CL), striated muscle and adipose tissue express GLUT 4 in a hormonal (P4, E2 and insulin)-dependent manner over diestrus. The canine estrous cycle constitutes an ideal study model because luteal phase lasts 60 days and hormonal-dependent alterations may be better pursued. To test this hypothesis, 32 female dogs will be submitted to election ovariosalpingo-hysterectomy (OSH) on days 10, 20, 30, 40, 50, 60, 70 and 80 (n = 4 per group) after ovulation (considered the day in which plasma P4 concentrations reached 5 ng/mL). Five hundred mg of subcutaneous adipose tissue, 0.5 g of rectus abdominis muscle as well as the corpora lutea will be collected and frozen in liquid nitrogen. Some CLs will be fixed in buffered formalin for tissue localization of the studied proteins, regulators of GLU 4 expression (insulin receptor, HIF-1±, NF-º²), that have not been described yet for the dog CL. Frozen tissues will be submitted to protein and RNA extraction for determination of protein and gene expression of the same above mentioned proteins. Five mL blood will also be collected, prior to anesthesia induction, for measurement of P4, E2, insulin and glucose in peripherical plasma. Some CLs from days 20, 40, 60 and 80 will be submitted to cell culture under different hormonal stimuli and GLUT 4 mRNA expression will be determined by real time PCR. Besides of detailed characterization of hormonal influence on metabolic processes occurring along diestrus, we intend to better comprehend the mechanisms involved in the diestrus associated development of insulin resistance and also suggest intervention therapies, based on the results, for the bitch and even for the women. (AU)
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(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MEDEIROS DE CARVALHO SOUSA, LIZA MARGARETH;
SILVA, RENATA DOS SANTOS;
DA FONSECA, VANESSA UEMURA;
LEANDRO, RAFAEL MAGDANELO;
DI VINCENZO, THIAGO SENNA;
ALVES-WAGNER, ANA BARBARA;
MACHADO, UBIRATAN FABRES;
PAPA, PAULA DE CARVALHO.
Is the canine corpus luteum an insulin-sensitive tissue?.
Journal of Endocrinology,
Web of Science Citations: 0.