Investigating the Influence of Triglycerides on Oocyte Competence, Via a Systematic Review and a Randomised Controlled Trial

Background: A growing body of evidence suggests that dyslipidaemia, frequently caused by increased dietary fat intake, results in a poorer prognosis for patients seeking assisted reproduction. Such elevated serum triglycerides may be reflected in the follicular fluid. Compositional changes to this milieu have been implicated in oocyte competence, however, the influence of triglycerides specifically is unclear. A Mediterranean style diet has been reported to improve reproductive outcomes, but the underlying mechanisms for this remain undetermined. One plausible explanation is that increased omega-3 fatty acid intake, as part of a Mediterranean style diet, may lower systemic triglyceride levels, reducing any negative implications. Aims: To perform a systematic review of the existing publications relating to follicular triglyceride concentration and its influence on oocyte competence. Also, to investigate the impact of a 6-week dietary intervention, involving omega-3 supplementation, on serum and follicular triglyceride concentrations, and subsequent invitro fertilisation (IVF) outcome parameters. Methods: A search strategy was designed and applied to four databases as part of a systematic review of the literature. Two reviewers independently assessed the resulting publications for relevance. After the dietary intervention, triglyceride concentration and fatty acid composition, in serum and follicular fluid, was determined using solid phase extraction and gas chromatography with flame-ionisation detection. Results from the trial cohort were compared with that of the placebo and correlated with relevant IVF outcome parameters. Results: The published studies included were observational in nature and subject to a moderate or high risk of bias. Significantly lower triglyceride concentrations were observed in samples from the trial group. Fertilisation rate was reduced in the trial group. Omega-3 fatty acids were significantly increased in the triglyceride fraction of both serum and follicular fluid from the trial group. Conclusion: The dietary intervention reduced the increase in serum and follicular triglycerides during ovarian stimulation, but fertilisation rates were also reduced. The intervention was of sufficient length and dose to alter both triglyceride concentration and fatty acid composition. Further, focused research is required to elucidate the impact of triglycerides in follicular fluid