Cellular mechanisms regulating fuel metabolism in mammals: role of adipose tissue and lipids during prolonged food deprivation.
Food deprivation in mammals results in profound changes in fuel metabolism and substrate regulation. Among these changes are decreased reliance on the counter-regulatory dynamics by insulin-glucagon due to reduced glucose utilization, and increased concentrations of lipid substrates in plasma to meet the energetic demands of peripheral tissues. As the primary storage site of lipid substrates, adipose tissue must then be a primary contributor to the regulation of metabolism in food deprived states. Through its regulation of lipolysis, adipose tissue influences the availability of carbohydrate, lipid, and protein substrates. Additionally, lipid substrates can act as ligands to various nuclear receptors (retinoid x receptor (RXR), liver x receptor (LXR), and peroxisome proliferator-activated receptor (PPAR)) and exhibit prominent regulatory capabilities over the expression of genes involved in substrate metabolism within various tissues. Therefore, through its control of lipolysis, adipose tissue also indirectly regulates the utilization of metabolic substrates within peripheral tissues. In this review, these processes are described in greater detail and the extent to which adipose tissue and lipid substrates regulate metabolism in food deprived mammals is explored with comments on future directions to better assess the contribution of adipose tissue to metabolism.
Department of Molecular and Cellular Biology, University of California, Merced, 5200 N Lake Rd., Merced, CA 95343, USA. jviscarra@ucmerced.edu
Jose Abraham
JA
Viscarra
Rudy Martin
RM
Ortiz
D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D004734:Energy Metabolism; D005508:Food Deprivation; D005786:Gene Expression Regulation; D006801:Humans; D050356:Lipid Metabolism; D008066:Lipolysis; D000071518:Liver X Receptors; D008322:Mammals; D057093:Orphan Nuclear Receptors / Q000235:genetics / Q000378:metabolism; D047492:Peroxisome Proliferator-Activated Receptors / Q000235:genetics / Q000378:metabolism; D047488:Retinoid X Receptors / Q000235:genetics / Q000378:metabolism; D013217:Starvation / Q000378:metabolism* / Q000662:veterinary
D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D047492:Peroxisome Proliferator-Activated Receptors; D047488:Retinoid X Receptors