Decreased expression of adipose CD36 and FATP1 are associated with increased plasma non-esterified fatty acids during prolonged fasting in northern elephant seal pups (Mirounga angustirostris).
The northern elephant seal pup (Mirounga angustirostris) undergoes a 2-3 month post-weaning fast, during which it depends primarily on the oxidation of fatty acids to meet its energetic demands. The concentration of non-esterified fatty acids (NEFAs) increases and is associated with the development of insulin resistance in late-fasted pups. Furthermore, plasma NEFA concentrations respond differentially to an intravenous glucose tolerance test (ivGTT) depending on fasting duration, suggesting that the effects of glucose on lipid metabolism are altered. However, elucidation of the lipolytic mechanisms including lipase activity during prolonged fasting in mammals is scarce. To assess the impact of fasting and glucose on the regulation of lipid metabolism, adipose tissue and plasma samples were collected before and after ivGTTs performed on early (2 weeks, N=5) and late (6-8 weeks; N=8) fasted pups. Glucose administration increased plasma triglycerides and NEFA concentrations in late-fasted seals, but not plasma glycerol. Fasting decreased basal adipose lipase activity by 50%. Fasting also increased plasma lipase activity twofold and decreased the expressions of CD36, FAS, FATP1 and PEPCK-C by 22-43% in adipose tissue. Plasma acylcarnitine profiling indicated that late-fasted seals display higher incomplete LCFA β-oxidation. Results suggest that long-term fasting induces shifts in the regulation of lipolysis and lipid metabolism associated with the onset of insulin resistance in northern elephant seal pups. Delineation of the mechanisms responsible for this shift in regulation during fasting can contribute to a more thorough understanding of the changes in lipid metabolism associated with dyslipidemia and insulin resistance in mammals.
School of Natural Sciences, University of California Merced, Merced, CA 95343, USA. jviscarra@ucmerced.edu
Jose Abraham
JA
Viscarra
José Pablo
JP
Vázquez-Medina
Ruben
R
Rodriguez
Cory D
CD
Champagne
Sean H
SH
Adams
Daniel E
DE
Crocker
Rudy M
RM
Ortiz
D000273:Adipose Tissue / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects; D018955:CD36 Antigens / Q000378:metabolism*; D002331:Carnitine / Q000031:analogs & derivatives / Q000097:blood; D002334:Carnitine O-Palmitoyltransferase / Q000378:metabolism; D005215:Fasting / Q000097:blood*; D050612:Fatty Acid Transport Proteins / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D005990:Glycerol / Q000097:blood; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood; D008049:Lipase / Q000097:blood; D050356:Lipid Metabolism / Q000187:drug effects; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism; D046048:Seals, Earless / Q000097:blood* / Q000378:metabolism*; D013997:Time Factors; D014280:Triglycerides / Q000097:blood
D018955:CD36 Antigens; D050612:Fatty Acid Transport Proteins; D005230:Fatty Acids, Nonesterified; D036341:Intercellular Signaling Peptides and Proteins; D014280:Triglycerides; C116917:acylcarnitine; D002334:Carnitine O-Palmitoyltransferase; D008049:Lipase; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D005947:Glucose; D005990:Glycerol; D002331:Carnitine