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Effect of omega 3 poliinsaturated fatty acids on quality of oocytes and fertility in mice with type 2 Diabetes

Abstract

Introduction: Evidence suggests that women with poorly controlled diabetes have an increased risk of infertility, miscarriage, obstetric complications, neonatal morbidity and mortality, and birth defects in their offspring, indicating that diabetes may have irreversible effects on female reproduction. Omega-3 polyunsaturated fatty acids (w-3 PUFA) appear to have a beneficial effect on the development of diabetes by protecting the pancreatic beta cells from damage caused by increased free radicals. Some studies report that these PUFA modulate the inflammatory response, modifying the evolution of type 2 diabetes (T2D). Our group's studies have shown that w-3 PUFA -enriched diets reduce the inflammatory response in animal models of acute and chronic inflammation through mechanisms associated with balance between pro and anti-inflammatory mediators. Food supplementation with w-3 PUFA seems to influence the synthesis of substances such as prostaglandins and steroid hormones involved in the regulation of reproductive function, which may affect ovulation and oocyte development. In addition, the PUFA composition of sperm and oocyte membranes appears to be important during fertilization. Although the ingestion of w-3 PUFA appears to interfere with the development of oocytes and in parallel may be beneficial for T2D, little is known about how these FA could modulate follicular development, oocyte maturation and subsequent embryonic development in T2D mothers. Objectives: The objectives of this project are: a) to study the effect of T2D on the induction of endoplasmic reticulum (ER)-stress in oocytes and also in pro and antiinflammatory tissue cytokines. b) to verify if dietary supplementation with fish oil, rich in w-3 PUFA, can prevent this stress, preserving the quality of the oocytes and diminishing the inflammatory response in mice submitted to the T2D model. Material and Methods: Female C57bl/6 mice, 2 months old, divided into 4 groups will be used: Control (C), Control treated with fish oil (CF), Diabetic (D) and Diabetic treated with fish oil (DF). C and CF will be fed standard diet and D and DF will receive hyperlipidic diet for 7 weeks. At the end of the fourth week, groups D and DF will receive, for 5 days, STZ diluted in citrate buffer (40 mg/kg/day) ip, while groups C and CF will receive the same volume of citrate buffer, ip. CF and DF will receive fish oil (2.0 g/kg), 3 times per week, orally, and groups C and D will receive water in the same volume throughout the experimental period. During 7 weeks of treatment, body weight, food and water intake will be measured weekly. In the last week, the animals will undergo the glucose tolerance test and the insulin tolerance test and 60 hours before euthanasia all animals will undergo ovarian super stimulation and ovulation induction with equine and human chorionic gonadotrophin. The animals will be anesthetized with sodium pentobarbital (60mg/kg) and lidocaine (5mg/kg) i.p. for blood samples collection and then euthanized. Pro- and anti-inflammatory tissue cytokines will be quantified by ELISA. The cumulus-oocyte complexes will be collected from oviducts and treated with hyaluranidase to remove cumulus cells and oocytes stored at -80 °C or fixed in paraformaldehyde. In the lysates of the oocytes will be analyzed by Western blotting the proteins caspase-3, XBP1 and ubiquitina and the proteasomal activity. The meiotic spindle will be evaluated by fluorescence microscopy, autophagy by immunofluorescence, using anti-LC3A and protein synthesis by the Click-iT® AHA Kit. (AU)