Regional variation of white adipocyte lipolysis during the annual cycle ofthe alpine marmot

During winter, hibernating animals rely on their lipid stores for survival. In vitro lipolytic activity of isolated adipocytes from gonadal and subcut aneous white adipose tissue (WAT) was studied in captive alpine marmots (Ma rmota marmota) at two different times of their yearly cycle. During the sum mer, when marmots were eating, adipocyte responsiveness and sensitivity to isoprenaline and noradrenaline were higher in gonadal than in subcutaneous WAT. During hibernation, when marmots were spontaneously fasting, both the response and sensitivity to catecholamines decreased in gonadal WAT to the level of subcutaneous WAT. A similar pattern of response was also observed when lipolysis was stimulated with glucagon but the lipolytic rate was thre e times lower than with catecholamines. Adenosine deaminase (ADA) had a mar ked stimulatory effect on lipolysis, especially during the 'feeding' period , suggesting that adenosine may be a potent lipolytic modulator in marmot a dipocytes. It is concluded that in marmots, lipolysis could be differential ly regulated between fat depots during the annual cycle possibly to optimiz e either the building-up or the use of fat reserves. (C) 1999 Elsevier Scie nce Inc. All rights reserved.