Letrozole-Induced Polycystic Ovary Syndrome Attenuates Cystathionine-β Synthase mRNA and Protein Abundance in the Ovaries of Female Sprague Dawley Rats.

Background: Polycystic ovary syndrome (PCOS) is an endocrine disorder that affects 10% of reproductive-aged women and leads to hyperandrogenism, anovulation, and infertility. PCOS has been associated with elevated serum homocysteine as well as altered methylation status; however, characterization of one-carbon metabolism (OCM) in PCOS remains incomplete.

Objectives: The aim of our research was to assess OCM in a letrozole-induced Sprague Dawley rat model of PCOS.

Methods: Five-week-old female rats (n = 36) were randomly assigned to letrozole [0.9 mg/kg body weight (BW)] treatment or vehicle (carboxymethylcellulose) control that was administered via subcutaneously implanted slow-release pellets every 30 d. For both treatment groups, 12 rats were randomly assigned to be euthanized during proestrus at one of the following time points: 8, 16, or 24 wk of age. Daily BW was measured and estrous cyclicity was monitored during the last 30 d of the experimental period. Ovaries were collected to assess mRNA and protein abundance of OCM enzymes.

Results: Letrozole-induced rats exhibited 1.9-fold higher cumulative BW gain compared with control rats across all age groups (P < 0.0001). Letrozole reduced the time spent at proestrus (P = 0.0001) and increased time in metestrus (P < 0.0001) of the estrous cycle. Cystathionine β-synthase (Cbs) mRNA abundance was reduced in the letrozole-induced rats at 16 (59%; P < 0.05) and 24 (77%; P < 0.01) wk of age. In addition, CBS protein abundance was 32% lower in 8-wk-old letrozole-induced rats (P = 0.02). Interestingly, betaine-homocysteine S-methyltransferase mRNA abundance increased as a function of age in letrozole-induced rats (P = 0.03).

Conclusion: These data demonstrate that letrozole-induced PCOS Sprague Dawley rats temporally decrease the ovarian abundance of Cbs mRNA and protein in the early stages of PCOS.