Effect of genetic and metabolic alterations on mitochondrial function in oocytes: model based on obesity and diabetes

• Grant number: 25/22855-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2025
• End date: October 31, 2026
• Field of knowledge: Biological Sciences - Genetics - Human and Medical Genetics
• Principal Investigator: Marcos Roberto Chiaratti
• Grantee: Giovana Martins Campos Simioni
• Host Institution: Centro de Ciências Biológicas e da Saúde (CCBS). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 25/13891-8 - Effect of genetic and metabolic alterations on mitochondrial function in oocytes, AP.R

Abstract

Recent evidence shows that maternal obesity predisposes offspring to metabolic disturbs including obesity, diabetes and cardiac diseases. The presence of dysfunctional mitochondria in the oocyte of obese/diabetic females is pointed as a potential mechanism to explain these phenotypes once damaged/dysfunctional mitochondria may be passed down to offspring and contribute with the onset of metabolic disturbs. One possible hypothesis to explain this increase of mitochondrial abnormalities is the oocyte deficiency of obese/diabetic females to clear dysfunctional mitochondria by autophagy, which constitutes an important intracellular mechanism of organelle recycling. Given the relevance of this topic, the aim of the present proposal is to investigate the effect of obesity and diabetes on oocyte mitochondrial function and assess if this effect relies on autophagy. To that aim, females of the C57BL/6Unib strain will be fed a high-fat diet (HFD) to induce obesity; as control, the same mouse strain will be fed a normal-fat diet (NFD). After 16 weeks, females on HFD will be treated with streptozotocin (STZ) to destroy part of their beta-pancreatic cells and development of a phenotype similar to type 2 diabetes, making up two experimental groups: NFD and HFD+STZ. Additionally, the same protocol used to induce obesity/diabetes will be applied to C57BL/6Unib females that are conditional knockout for Atg7 through the use of a Zp3-Cre driver (exclusively expressed in oocytes); as control, a mouse line with a similar genetic background will be used, except that they will not carry the Zp3-Cre driver and will be kept in NFD. The mice will be subject to glucose tolerance test (GTT) immediately before and two weeks after the STZ treatment. After the third week of the STZ treatment, the mice will be superovulated for oocyte collection from antral follicles. Mitochondrial function (estimated based on mitochondrial membrane potential) will be assessed using confocal microscopy from the fluorescence ratio of TMRE (ThermoFisher Scientific) and MitoTrakcer Green FM (ThermoFisher Scientific) probes. Also, the number, volume and distribution of mitochondria in relation to total oocyte volume will be recorded based on MitoTracker Green FM staining. Furthermore, mitochondrial function heterogeneity will be evaluated across organelles of a single oocyte. It will be considered at least three mice per group and a processing of a minimum of 10 oocytes per animal for each variable. Statistical analysis will be carried out to test if main factors (e.g., diet and genotype) or their interaction affect variable of interest. We expect with this project to contribute with the understanding of the mechanisms that shape the transmission of dysfunctional mitochondria from mother to offspring.