Fasting Reduces Plasma Leptin- and Ghrelin-Immunoreactive Peptide Concentrations of the Burbot (Lota Iota) at 2°C But Not at 10°C

Abstract

The effects of fasting at two water temperatures (2 and 10°C) on plasma leptin- and ghrelin-immunoreactive peptide concentrations and energy metabolism were investigated in the burbot (Lota Iota), a freshwater gadoid, which lives in cold waters and tolerates long periods of fasting. Burbot were assigned to fed and fasted groups at 2 and 10°C. Leptin- and ghrelin-immunoreactive peptides were identified in burbot plasma. Fasting at 2°C reduced the plasma leptin- and ghrelin-immunoreactive peptide concentrations and reduced the relative liver weights and the liver and muscle glycogen concentrations. The concentrations of the leptin- and ghrelin-immunoreactivities correlated positively with each other. At 10°C there were decreased plasma thyroxine levels in both sexes, and slightly lower plasma testosterone concentrations in males. The results support previous studies in stating that immunoreactivities resembling mammalian leptin and ghrelin can be detected in burbot plasma and liver, but the specific functions of these peptides will have to be determined in future studies.