TY - JOUR
T1 - Effects of insulin on lipid metabolism of larvae and metamorphosing landlocked sea lamprey, Petromyzon marinus
AU - Kao, Yung Hsi
AU - Youson, John H.
AU - Holmes, John A.
AU - Al-Mahrouki, Azza
AU - Sheridan, Mark A.
N1 - Funding Information:
We gratefully acknowledge R. G. Manzon and J. A. Heinig (University of Toronto) for their technical help. This work was supported by grants from the National Science Foundation, USA (OSR 9452892 and IBN 9723058) to M. A. S., from the Great Lakes Fishery Commission to J. H. Y. and J. A. H., and from the Natural Sciences and Engineering Research Council of Canada (A5945) to J. H. Y.
PY - 1999/6
Y1 - 1999/6
N2 - This study was designed to examine the role of insulin (INS) in regulating changes in lipid metabolism of larval and metamorphosing landlocked lamprey, Petromyzon marinus. Larvae and stage 6 metamorphosing individuals were injected intraperitoneally once per day for 2 days with either saline (0.6%), bovine INS (100 ng/g body weight), or alloxan (0.2 mg/g body weight). Insulin administration resulted in depressed plasma fatty acid (FA) levels, whereas alloxan injection elevated plasma FA levels at both life cycle intervals. In larvae, INS-induced hypolipidemia was attended by increased lipid concentration in kidney and muscle, reduced rates of lipolysis in kidney, liver, and muscle (as indicated by decreased triacylglycerol lipase activity), and, to a lesser extent, by higher rates of lipogenesis in kidney and muscle (as evidenced by higher acetyl-CoA carboxylase and/or diacylglycerol acyltransferase activities). In general, the effects of alloxan were opposite of those of INS. The alloxan-induced increase in plasma FA was supported by an enhanced rate of lipolysis in the kidney, a relatively lower rate of fatty acid synthesis in kidney, liver, and muscle, and a relatively lower renal rate of TG synthesis. In stage 6 metamorphosing lamprey, the INS-induced decline in plasma FA was attended by reduced renal and hepatic rates of lipolysis and by enhanced lipogenesis, as indicated by increased renal and hepatic rates of de novo fatty acid synthesis and hepatic and muscular rates of TG synthesis. In contrast, the increase in plasma FA induced by alloxan in stage 6 animals was supported by reduced TG synthesis in liver. Immunocytochemistry revealed that alloxan was not cytotoxic to pancreatic β cells, suggesting that the effects of alloxan were extrapancreatic in the time frame of our study. Because insulin-induced lipogenesis and antilipolysis is similar to the pattern of lipid metabolism (phase I) displayed by lamprey during their spontaneous metamorphosis, INS may play a role, possibly in concert with other factors, in coordinating metamorphosis-associated changes in lipid metabolism.
AB - This study was designed to examine the role of insulin (INS) in regulating changes in lipid metabolism of larval and metamorphosing landlocked lamprey, Petromyzon marinus. Larvae and stage 6 metamorphosing individuals were injected intraperitoneally once per day for 2 days with either saline (0.6%), bovine INS (100 ng/g body weight), or alloxan (0.2 mg/g body weight). Insulin administration resulted in depressed plasma fatty acid (FA) levels, whereas alloxan injection elevated plasma FA levels at both life cycle intervals. In larvae, INS-induced hypolipidemia was attended by increased lipid concentration in kidney and muscle, reduced rates of lipolysis in kidney, liver, and muscle (as indicated by decreased triacylglycerol lipase activity), and, to a lesser extent, by higher rates of lipogenesis in kidney and muscle (as evidenced by higher acetyl-CoA carboxylase and/or diacylglycerol acyltransferase activities). In general, the effects of alloxan were opposite of those of INS. The alloxan-induced increase in plasma FA was supported by an enhanced rate of lipolysis in the kidney, a relatively lower rate of fatty acid synthesis in kidney, liver, and muscle, and a relatively lower renal rate of TG synthesis. In stage 6 metamorphosing lamprey, the INS-induced decline in plasma FA was attended by reduced renal and hepatic rates of lipolysis and by enhanced lipogenesis, as indicated by increased renal and hepatic rates of de novo fatty acid synthesis and hepatic and muscular rates of TG synthesis. In contrast, the increase in plasma FA induced by alloxan in stage 6 animals was supported by reduced TG synthesis in liver. Immunocytochemistry revealed that alloxan was not cytotoxic to pancreatic β cells, suggesting that the effects of alloxan were extrapancreatic in the time frame of our study. Because insulin-induced lipogenesis and antilipolysis is similar to the pattern of lipid metabolism (phase I) displayed by lamprey during their spontaneous metamorphosis, INS may play a role, possibly in concert with other factors, in coordinating metamorphosis-associated changes in lipid metabolism.
KW - Insulin
KW - Lamprey
KW - Lipogenesis
KW - Lipolysis
KW - Metamorphosis
KW - Petromyzon marinus
UR - http://www.scopus.com/inward/record.url?scp=0033064602&partnerID=8YFLogxK
U2 - 10.1006/gcen.1999.7265
DO - 10.1006/gcen.1999.7265
M3 - Article
C2 - 10336828
AN - SCOPUS:0033064602
SN - 0016-6480
VL - 114
SP - 405
EP - 414
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
IS - 3
ER -