TY - JOUR
T1 - Nutrition-regulated lipolysis in rainbow trout (Oncorhynchus mykiss) is associated with alterations in the ERK, PI3K-Akt, JAK-STAT, and PKC signaling pathways
AU - Bergan, Heather E.
AU - Kittilson, Jeffrey D.
AU - Sheridan, Mark A.
N1 - Funding Information:
We would like to thank Elle Kvam, Chad Walock, Dillon Marquart, Lindsey Norbeck, Andrea Hanson, Lincoln Martin, Elizabeth Ellens, Jacob Froehlich, and Dr. Peggy Biga for their assistance. We also thank Prof. Akiyoshi Takahasi and Dr. Shunsuke Moriyama for generously providing salmonid GH. This work was supported by NSF Grant IOS 0920116 to M.AS.
PY - 2012/5/1
Y1 - 2012/5/1
N2 - Previous studies have shown that food deprivation, which occurs naturally in the life cycle of many species of fish, results in cessation of growth and catabolism of stored energy reserves, including lipids. In this study, we used rainbow trout (Oncorhynchus mykiss) to identify the cellular mechanisms involved with this metabolic shift. Fish were placed on one of five dietary regimes-fed continuously for 2 or 4. weeks, fasted continuously for 2 or 4. weeks, or fasted 2. weeks then refed 2. weeks-and the effects on organismal growth and lipid catabolism and on the activation state of signaling elements (e.g., Akt, ERK, JAK-STAT, PKC) in selected tissues were measured. Fasting for either 2 or 4. weeks significantly retarded growth in terms of body weight, body length, and body condition; refeeding restored growth such that body length and body condition were similar to measures seen in continuously fed fish. Fasting activated lipid catabolism by stimulating the mRNA expression and catalytic activity of hormone-sensitive lipase (HSL). Two HSL-encoding mRNAs have been characterized, and the expression of both forms of mRNA in 2- and 4-week fasted fish were significantly elevated over levels in fed fish in all tissues. In adipose tissue, liver, and white muscle, HSL activity was significantly elevated in 2- and 4-week fasted fish compared to fed animals; whereas in red muscle, HSL activity was significantly elevated compared to fed fish after 4. weeks of fasting. Refeeding reversed both fasting-associated HSL mRNA expression and HSL activity. Fasting resulted in the deactivation of Akt, JAK2, and STAT5 in adipose tissue, liver, and red and white muscle. By contrast, fasting activated ERK and PKC in all tissues measured. Refeeding reversed fasting-associated alterations in the activation state of all signal elements. These findings suggest that deactivation of Akt and JAK-STAT in conjunction with activation of ERK and PKC underlie fasting-associated growth retardation and lipolysis.
AB - Previous studies have shown that food deprivation, which occurs naturally in the life cycle of many species of fish, results in cessation of growth and catabolism of stored energy reserves, including lipids. In this study, we used rainbow trout (Oncorhynchus mykiss) to identify the cellular mechanisms involved with this metabolic shift. Fish were placed on one of five dietary regimes-fed continuously for 2 or 4. weeks, fasted continuously for 2 or 4. weeks, or fasted 2. weeks then refed 2. weeks-and the effects on organismal growth and lipid catabolism and on the activation state of signaling elements (e.g., Akt, ERK, JAK-STAT, PKC) in selected tissues were measured. Fasting for either 2 or 4. weeks significantly retarded growth in terms of body weight, body length, and body condition; refeeding restored growth such that body length and body condition were similar to measures seen in continuously fed fish. Fasting activated lipid catabolism by stimulating the mRNA expression and catalytic activity of hormone-sensitive lipase (HSL). Two HSL-encoding mRNAs have been characterized, and the expression of both forms of mRNA in 2- and 4-week fasted fish were significantly elevated over levels in fed fish in all tissues. In adipose tissue, liver, and white muscle, HSL activity was significantly elevated in 2- and 4-week fasted fish compared to fed animals; whereas in red muscle, HSL activity was significantly elevated compared to fed fish after 4. weeks of fasting. Refeeding reversed both fasting-associated HSL mRNA expression and HSL activity. Fasting resulted in the deactivation of Akt, JAK2, and STAT5 in adipose tissue, liver, and red and white muscle. By contrast, fasting activated ERK and PKC in all tissues measured. Refeeding reversed fasting-associated alterations in the activation state of all signal elements. These findings suggest that deactivation of Akt and JAK-STAT in conjunction with activation of ERK and PKC underlie fasting-associated growth retardation and lipolysis.
KW - Lipolysis
KW - Nutritional state
KW - Signal transduction
UR - http://www.scopus.com/inward/record.url?scp=84859926735&partnerID=8YFLogxK
U2 - 10.1016/j.ygcen.2011.12.013
DO - 10.1016/j.ygcen.2011.12.013
M3 - Article
C2 - 22202604
AN - SCOPUS:84859926735
VL - 176
SP - 367
EP - 376
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
SN - 0016-6480
IS - 3
ER -