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Evidence for leptin expression in fishes
R M Johnson1, T M Johnson, R L Londraville
1University of Akron, Department of Biology, Akron, Ohio 44325-3908, USA.
The Journal of Experimental Zoology
|May 8, 2000
Summary
Researchers found the fat-regulating hormone leptin in bony fish, similar to mammals. Fish leptin levels changed with feeding status and body fat, indicating its conserved role in ectotherms.
Area of Science:
- Comparative Physiology
- Endocrinology
- Fish Biology
Background:
- Leptin is a key hormone regulating fat metabolism and energy balance in mammals.
- Its presence and function in ectothermic vertebrates, like bony fish, remain largely unexplored.
Purpose of the Study:
- To investigate the presence and characteristics of leptin in various bony fish species.
- To determine if fish leptin exhibits similar regulatory functions as observed in mammals, particularly concerning feeding status and body adiposity.
Main Methods:
- Screening of fish tissues (blood, brain, heart, liver) using anti-mouse leptin antibodies.
- Detection of immunoreactive bands via electrophoresis.
- Measuring blood leptin concentrations in fed versus fasted green sunfish.
- Correlating brain leptin levels with body fat percentage in white crappie and bluegill.
Main Results:
- Low molecular-weight (16 kDa) leptin-like immunoreactive bands were detected across multiple fish species, including green sunfish, bluegill, largemouth bass, white crappie, channel catfish, and rainbow trout.
- Fed green sunfish exhibited significantly higher blood leptin concentrations (approximately threefold) compared to fasted sunfish.
- Brain leptin concentration showed a positive correlation with body fat percentage in white crappie and bluegill.
Conclusions:
- This study provides the first evidence for leptin expression and its conserved physiological role in an ectotherm.
- The findings suggest that leptin plays a role in energy homeostasis and fat regulation in bony fish, mirroring its function in mammals.