Kiss1 mRNA and kisspeptin immunoreactivity are differentially regulated in hypothalamus and visceral fat in a rat model of polycystic ovary syndrome (PCOS)
Russell Brown1,2, Diane Wilkinson3, Syed Imran1,3, Alain Caraty4 & Michael Wilkinson1,2
Introduction: The hypothalamic kiss1/kisspeptin system is pivotal in controlling fertility. However, kiss1 transcripts were also quantified in rat fat, where expression was regulated by oestradiol (Brown et al. 2008) and by dihydrotestosterone (DHT; Brown et al. 2009). In human fat, microarray analysis revealed abnormal, multiple gene expression in obese PCOS patients (Corton et al. 2007). In the present experiments we used a rat model (Manneras et al. 2007) to determine the possible influence of PCOS on adipose and brain kiss1 expression.
Methods: Weanling female rats (PD 21) were anaesthetized and given subcutaneous pellets that continuously released DHT (Innov. Res. of America; 83 μg/day; 60 days). Controls received sham surgery. Rats were killed at PD47 and PD81 by: a) decapitation, for RNA samples, or b) intracardiac perfusion with paraformaldehyde. RNA was isolated from basal hypothalamus (HYP), pituitary (PIT) ovary and visceral fat (FAT), and kiss1 mRNA was quantified by realtime RT-PCR. Kisspeptin immunoreactivity (KP-ir) was localized by immunohistochemistry.
Results: At PD47, HYP kiss1 mRNA was largely undetectable in DHT rats compared to controls, whereas significant increases were seen in FAT (+ ninefold; P<0.01) and ovary (+ threefold; P<0.05). PIT kiss1 expression was unaffected. At PD81 kiss1 mRNA remained elevated in FAT (fourfold; P<0.05) but levels had reverted to normal in HYP and ovary. Hypothalamic KP-ir partially reflected kiss1 mRNA levels, i.e. fibre and cell body staining was severely reduced by DHT at PD47. However at PD81 KP-ir in nerve fibres, but not cell bodies, was essentially restored to control levels.
Conclusions: These data suggest that extended DHT treatment differentially affects kiss1 expression in female rat tissues, but is reversible to some degree by PD81, when the DHT pellets are likely to be depleted. We conclude that atypical kiss1 expression may contribute to the multiple tissue abnormalities observed in PCOS. Funded by IWK, Atlee Endowment and UIMRF/Capital Health.