O-217 Evaluating the impact of obesity on oocyte quality, using 2 main factors in cumulus cells (CC) and follicular fluid (FF) which reflect oocyte quality
Authors: Sigal E , Shalom-Paz E , Shavit M , Michaeli M , Polotov D , Rotfarb N 
Published: July 2024

Abstract

Study question
How obesity impacts oocyte quality through analysis of mtDNA expression in CC and levels of proteins BMP-15 and HSPG2 in FF?

Summary answer
There is correlation between increased BMI and lower levels of BMP15 and a decreased expression of mtDNA that reflect decreased oocyte quality in overweight women.

What is known already
Obesity impacts female health and impairs fertility. There is limited evidence suggesting that obesity impairs oocyte quality. BMP-15 (Bone morphogenetic protein 15) is a protein synthesized by oocyte, is a factor predicting quality of the oocyte and female fertility. Heparan sulfate proteoglycan 2 (HSPG2) is a protein secreted from granulosa cells and there are limited studies regarding the function of HSPG2 in reproduction including oocyte quality. BMP-15 and HSPG2 secreted to FF. Oocyte quality was demonstrated to be influenced by mtDNA (mitochondrial DNA) content in CC.

Study design, size, duration
Prospective observational cohort study performed between February 2022 until June 2022 in a single university-affiliated hospital. Total of 50 patients were enrolled.

Participants/materials, setting, methods
Women who underwent IVF or ICSI cycles were included. Exclusion criteria were patients older than 40 years, fertility preservation, unbalanced endocrine disorders and less than 4 follicles at the time of OPU (oocyte pick-up). Follicular fluid and cumulus cells were collected following OPU. mtDNA was assessed by quantitative real-time PCR. BMP-15 and HSPG2 were measured with ELISA method quantitatively. Lipid profile, hormonal profile and C-reactive protein were evaluated in blood and follicular fluid samples.

Main results and the role of chance
Patients were divided based on BMI, 28 patients with BMI &lt; 25 (Group 1) and 22 with BMI &gt; 25 (Group 2). A significant increase in BMP-15 in FF (38.8 ± 32.5 vs. 14.3 ± 10.8 ng/ml; p = 0.001) and mitochondrial DNA in CC (1.10 ± 0.3 vs. 0.87 ± 0.18 Fold change expression; p = 0.016) were found in group 1. Significantly higher CRP in blood (7.1 ± 5.4 vs. 3.4 ± 4.3; p = 0.015) and FF (5.2 ± 3.8 vs. 1.5 ± 1.6; p = 0.002) and LDL level in blood (91 ± 27 vs. 71 ± 22; p = 0.008) in group 2. HDL levels were significantly higher in group 1 in the blood (50 ± 12 vs. 62 ± 18; p = 0.015) and FF (20.9 ± 7.2 vs. 34 ± 26; p = 0.05). The fresh clinical pregnancy rate demonstrated a trend toward better results in group 1 (47.8% vs. 28.6%: p = 0.31), as well as in FET (69.2% vs. 53.8; P = 0.69).

Limitations, reasons for caution
Research included relatively small number of participants. We can’t report our cumulative pregnancy rate since not all frozen embryos were transferred yet.

Wider implications of the findings
Obesity is an increasing worldwide problem and impairs fertility outcome. Our study demonstrates decreased oocyte quality in the group of overweight women through 2 important markers BMP-15 and mtDNA. We recommend our patients to lose weight and improve their lifestyle in order to overcome those impaired quality markers.

Trial registration number
Not applicable