Clock gene per 2 daily rhythm: Correlation with the serum level of uncoupling protein 1 (UCP1) in goat and horse

Recent studies evidenced that the circadian rhythm of Per2 is involved in adaptive thermogenesis by the modulating transcription of uncoupling protein 1 (UCP1). For this purpose, we investigated the linkage between the daily rhythm of Per2 and UCP1 in ruminant and non-ruminant mammalian species. Five clinically healthy, not pregnant, and not lactating Maltese female goats and five clinically healthy, not pregnant, and not lactating Italian Saddle horses were enrolled in the study. All animals were housed under natural photoperiod (sunrise 05:05, sunset 20:55) and environmental temperature and humidity. Goats were kept individually in 3.0 × 2.0 m box, horses were housed individually in 3.5 × 3.5 m box; all boxes were equipped with an opening window. On each subject, blood samples were collected every 4 h for a 48-h period. The Per2 gene expression was determined on blood samples collected in PAX gene Blood RNA Tube, whereas UCP1 concentration was assessed on serum. Per2 and UCP1 levels were statistically influenced by the species (p < 0.0001) and the time of data collection (p < 0.0001), but not by the day of monitoring. Per2 showed daily rhythmicity, statistically different in mesor and amplitude between the two species, diurnal in goats, nocturnal in horses; with the same robustness. UCP1 did not show daily rhythmicity. During the experimental period the two parameters showed a negative correlation in horses. According to the findings herein obtained, we can claim that the role of Per2 in the thermogenesis induced by the beige adipocytes throughout UCP1 activation did not reflect what found in other mammal species, but further studies are required to establish their correlation in equids.