Effects of cold exposure, exogenous melatonin and short-day treatment on the weight-regulation and body temperature of the Siberian hamster (Phodopus sungorus).
Study Goal
The researchers aimed to determine how winter acclimatization, exogenous melatonin, and endogenous melatonin affect plasma leptin and ghrelin concentrations and their role in winter adaptations in Siberian hamsters.
Results Summary
Cold exposure (winter acclimatization) and melatonin treatments lowered plasma leptin, insulin, and testosterone while increasing ghrelin, reduced body fat, and induced torpor bouts. The study found that short photoperiod alone did not elevate ghrelin; low ambient temperature combined with short day length was required.
Population
Siberian hamsters
Effective Dosage
Not specified
Duration
Not specified
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
winter acclimatization | decrease | plasma leptin concentrations | Siberian hamster | - | were lower | #1 |
winter acclimatization | decrease | plasma insulin concentrations | Siberian hamster | - | were lower | #2 |
winter acclimatization | decrease | testicular testosterone concentrations | Siberian hamster | - | were lower | #3 |
winter acclimatization | increase | plasma ghrelin concentration | Siberian hamster | - | was higher | #4 |
exogenous melatonin | decrease | plasma leptin concentrations | Siberian hamster | - | were lower | #5 |
exogenous melatonin | decrease | plasma insulin concentrations | Siberian hamster | - | were lower | #6 |
exogenous melatonin | decrease | testicular testosterone concentrations | Siberian hamster | - | were lower | #7 |
endogenous melatonin | decrease | plasma leptin concentrations | Siberian hamster | - | were lower | #8 |
endogenous melatonin | decrease | plasma insulin concentrations | Siberian hamster | - | were lower | #9 |
endogenous melatonin | decrease | testicular testosterone concentrations | Siberian hamster | - | were lower | #10 |
winter acclimatization, exogenous melatonin, endogenous melatonin | decrease | body temperatures during photo- and scotophase | treated hamsters | - | were lower | #11 |
winter acclimatization, exogenous melatonin, endogenous melatonin | neutral | torpor bouts | treated hamsters | - | were observed | #12 |
winter acclimatization, exogenous melatonin, endogenous melatonin | decrease | absolute body fat masses | treated groups | - | were lower | #13 |
winter acclimatization, exogenous melatonin, endogenous melatonin | decrease | relative body fat masses | treated groups | - | were lower | #14 |
exposure to short photoperiod | no change | plasma ghrelin levels | - | - | did not induce elevated | #15 |
OBJECTIVE: To investigate how winter acclimatization (WA), exogenous melatonin (MEL) or endogenous melatonin (SD) affect plasma leptin and ghrelin concentrations and how leptin and ghrelin contribute to the regulation of different adaptations to wintering in the Siberian hamster. RESULTS: The plasma leptin and insulin and testicular testosterone concentrations were lower in the WA, MEL and SD groups, whereas the plasma ghrelin concentration was higher due to the WA treatment. In the treated hamsters, body temperatures during photo- and scotophase were lower throughout the study and torpor bouts were observed. The absolute and relative body fat masses were lower in all treated groups. CONCLUSIONS: Siberian hamsters reduce their feeding in winter, although just the opposite is suggested by the lower leptin concentrations in all treated groups and the higher ghrelin concentration in the WA group. The positive correlation between plasma leptin and testicular testosterone indicates a possible interaction between them. Torpor bouts were related to a lowered body mass and plasma leptin concentration. Exposure to short photoperiod did not induce elevated plasma ghrelin levels; the response required a low ambient temperature together with short day length.