Authors: Shimozuru, Michito; Akari, Kamine; Tsubota, Toshio

Source: Canadian Journal of Zoology, Volume 90, Number 8, August 2012 , pp. 945-954(10)

Publisher: NRC Research Press

Abstract:

Body fat accumulation in the prehibernation period is crucial for survival and reproduction during hibernation for bears. Bear body mass increases rapidly during their autumnal hyperphagia phase, which is attributed not only to an increase in food availability, but also to physiological changes in lipid metabolism. To test this hypothesis, we investigated changes in blood biochemical values and mRNA expression levels of hepatic genes involved in lipid metabolism during the active period (June, August, October, and November) in Japanese black bears (<named-content content-type="subspecies" xlink:type="simple">Ursus thibetanus japonicus</named-content> Schlegel, 1857), which were fed a constant ration throughout this period. Blood biochemical analysis revealed that plasma triglyceride concentrations decreased in October and November, implying that peripheral triglyceride uptake was accelerated in autumn. The liver was sampled by needle biopsy. Real-time polymerase chain reaction (PCR) analysis revealed that mRNA expressions of enzymes involved in glycolysis (glucokinase), as well as fatty acid and triglyceride synthesis (ATP-citrate lyase, acetyl-CoA carboxykinase 1, fatty acid synthase, and diacylglycerol O-acyltransferase 2), increased in November, which suggests that hepatic lipogenesis becomes accelerated during the hyperphagia phase. These results suggest that lipid metabolism is seasonally controlled even without changes in food intake. These physiological changes seen in the prehibernation period would contribute to the rapid mass gain necessary for hibernation.

Keywords: Ursus thibetanus japonicus; bears; lipid metabolism; liver; hibernation; Ursus thibetanus japonicus; ours; métabolisme des lipides; foie; hibernation

Document Type: Research article

DOI: http://dx.doi.org/10.1139/z2012-062

Publication date: 2012-08-23

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