Different Fatty Acid Composition Observed in Oocytes of Women With Overweight or Obesity

Human egg cell, computer artwork.
Oocyte fatty acid composition differs between women with normal weight vs overweight or obesity and may be related to poor IVF outcomes.

The fatty acid (FA) composition of oocytes from obese or overweight women is different than that of oocytes from women with normal weight, which may have an effect on the outcomes of in vitro fertilization (IVF), according to study results published in Fertility and Sterility.

Lipids and polyunsaturated fatty acids (PUFAs) have important roles in embryo-fetal development. The ratio of the longer-chain n-6 and n-3 PUFAs is closely related to dietary pattern and is often impaired in individuals with overweight or obesity. The goal of the current study was to explore the FA composition of the oocytes of obese or overweight women undergoing fertility treatments.

The prospective case-control study included participants undergoing IVF and intracytoplasmic sperm injection (ICSI) in 2 IVF centers. Analysis of oocyte FA composition was completed by gas chromatography. The women included in the study were classified according to body mass index (BMI) as normal, overweight, or obese. All oocytes were classified by their maturation stage.

The study cohort included 205 women (mean age, 36.24 years) with a total of 922 oocytes available for analysis. Male factor infertility (56.2%) was the main indication for IVF and ICSI, followed by idiopathic infertility (15.2%), tubal factor infertility (11.7%), and endometriosis (8.8%). Of the 922 studied oocytes, 381 were at the germinal vesicle

stage, 208 at the first meiotic metaphase, and 333 at the second meiotic metaphase. The researchers recorded 270 ICSI fertilization failures and 63 IVF failures.

Other than poorer results in the group of women with BMI >35 kg/m2, the results of the intervention were similar across the other BMI groups with regard to the total number of oocytes, metaphase II oocytes, and embryos obtained, as well as fertilization and pregnancy rates.

The researchers identified differences in FA pattern across the oocyte maturation stages, with significantly lower levels of γ-linolenic acid and α-linolenic acid in metaphase I and metaphase II oocytes, whereas levels of arachidonic acid were lower only in metaphase II oocytes. The n-6 to n-3 ratio and level of saturated FAs were highest in metaphase I oocytes.

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Oocytes from women with obesity had lower levels of saturated FAs and higher levels of monosaturated FAs. In addition, they had lower levels of n-3 PUFAs, but their n-6 to n-3 ratio was the lowest.

With regard to specific FAs, docosahexaenoic acid (DHA) levels were lower in women with normal weight compared with overweight women, as well as in overweight women compared with obese women. The opposite was noted for eicosapentaenoic acid, with the highest levels in normal-weight women followed by overweight women and lower levels in women with obesity. Women who were obese had the lowest arachidonic acid to DHA ratio and the highest DHA to α-linolenic ratio, with intermediate values in women who were overweight.

“Our study data could spark future investigations probing the FA content and ratios in oocytes through multiple potential interventions in women who are obese or overweight. These women could benefit from factors such as diet modifications, medications, weight changes, and exercise,” concluded the researchers.

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Matorras R, Exposito A, Ferrando M, et al. Oocytes of women who are obese or overweight have lower levels of n-3 polyunsaturated fatty acids compared with oocytes of women with normal weight. Fertil Steril. 2020;113(1):53‐61.