High-fat diet leads to elevated lipid accumulation and endoplasmic reticulum stress in oocytes, causing poor embryo development.

The present study was designed to investigate the effect of diet-induced obesity on endoplasmic reticulum (ER) stress in oocytes. Swiss albino mice (3 weeks old) were fed with a high-fat diet (HFD) for 8 weeks. Oocytes were assessed for lipid droplet accumulation, oxidative stress, ER stress and their developmental potential in vitro. High lipid accumulation (P < 0.01) and elevated intracellular levels of reactive oxygen species were observed in both germinal vesicle and MII oocytes of HFD-fed mice (P < 0.05 and P < 0.01 respectively compared with control). Further, expression of the ER stress markers X-box binding protein 1 (XBP1), glucose-regulated protein 78 (GRP78), activating transcription factor 4 (ATF4) and activating transcription factor 6 (ATF6) was significantly (P < 0.001) higher in oocytes of the HFD than control group. Oocytes from HFD-fed mice exhibited poor fertilisation and blastocyst rates, a decrease in total cell number and high levels of DNA damage (P < 0.01) compared with controls. In conclusion, diet-induced obesity resulted in elevated lipid levels and higher oxidative and ER stress in oocytes, which contributed to the compromised developmental potential of embryos.