Plasma and white adipose tissue lipid composition in marmots

Abstract

White adipose tissue biopsies and plasma samples were obtained from hibernating yellow-bellied marmots (Marmota flaviventris) maintained in the laboratory. In addition, biopsies and plasma samples were obtained from normothermic animals in the field and laboratory. Measurement of plasma free fatty acid (FA) levels indicated that winter laboratory animals exhibited increased lipolysis. Additionally, analysis of white adipose tissue triacylglycerol revealed that the FA composition of the storage fat in animals maintained on the standard laboratory diet is remarkably simple and uniform between different adipose depots in the same animal. Three FAs (palmitic, oleic, and linoleic acids) made up greater than 95% of the total. Triene (alpha-linolenate) was found in newly captured animals, but the percentage of this FA decreased rapidly when the animals were maintained on the standard laboratory diet. Throughout the hibernation season (October to April), white adipose tissue-saturated FA percentage decreased, monoene percentage remained constant, and diene percentage increased. Analysis of plasma FA composition suggested that these animals tended to metabolize saturated FAs from stored lipid during hibernation and that dienes were mobilized briefly after the last arousal from hibernation in spring. From these observations, we hypothesize that marmots preferentially metabolize saturated fats during the hibernation period and that essential FAs of the omega 6 series tend to be metabolized more slowly than other FAs. These characteristics suggest that marmots are a valuable animal model in which to study lipid metabolism.

Selective mobilization of fatty acids from adipose tissue in migratory birds

“…Several investigators have studied changes in adipose tissue fatty acid composition under conditions of fasting, nutritional stress and/or hibernation (Falkenstein et al, 2001;Florant et al, 1990;Groscolas, 1990;Nieminen et al, 2006;Soppela and Nieminen, 2002). When selective mobilization of fatty acids has been observed, it has often been interpreted as adaptive (for example to maintain metabolism and functions of essential PUFA or to maintain fluidity of fat reserves) (Falkenstein et al, 2001;Nieminen et al, 2006;Soppela and Nieminen, 2002).…”

“…In recent studies, it has become clear that the proportions of the specific fatty acid species mobilized differ somewhat from their proportions in the TRIG from which they were released (Herzberg and Skinner, 1997;Hollenberg and Angel, 1963;Raclot and Groscolas, 1993;Soppela and Nieminen, 2002). This fatty acid selectivity has been demonstrated in both in vivo (Herzberg and Skinner, 1997;Nieminen et al, 2006;Soppela and Nieminen, 2002) and in vitro (Raclot and Groscolas, 1993;Raclot et al, 1995) studies and has led to adaptive explanations regarding the functions of the specific fatty acids that are selectively retained or mobilized (Falkenstein et al, 2001;Florant et al, 1990;Nieminen et al, 2006;Soppela and Nieminen, 2002). However, in a recent review, Raclot concluded that differential mobilization of fatty acids occurs primarily due to the molecular structure of each fatty acid species; fatty acids that are shorter, more unsaturated and have their double bonds closer to the methyl end are more polar and are preferentially mobilized (Raclot, 2003).…”

“…The goals of this study, therefore, were to characterize the selective mobilization of fatty acids in vitro for two migratory bird species and to investigate any changes in selective fatty acid mobilization associated with the migratory period in one of the species. Specifically, we were interested in whether migratory state would result in an increase in mobilization of 18:2n6 (Soppela and Nieminen, 2002) or a selective retention of 18:2n6, perhaps to conserve this fatty acid for use during breeding (Florant et al, 1990;Mostafa et al, 1994).…”

Performance-enhancing role of dietary fatty acids in a long-distance migrant shorebird: the semipalmated sandpiper

“…One possible reason for this conversion is to decrease the overall vulnerability of lipid reserves to degradation, PUFA being particularly sensitive to peroxidation (Gutierrez et al, 2006). Like semipalmated sandpipers, other migrant birds (Blem, 1990), some mammals (Florant et al, 1990) and fish (Lund and Sidell, 1992) also store most of their lipids as oleate, and to a lesser extent as palmitate. This remarkably ubiquitous preference for storing monounsaturates has never been explained (Weber et al, 2003).…”

Are long chain acyl CoAs responsible for suppression of mitochondrial metabolism in hibernating 13-lined ground squirrels?

“…It is therefore not surprising that the level of free fatty acids in the plasma of hibernators is elevated for the duration of the hibernation season (Florant et al, 1990). From the plasma, free fatty acids diffuse into tissues and are converted into fatty acyl CoAs in the cytosol before being metabolized by beta-oxidation.…”