Seasonal changes in lipogenesis and lipolysis in isolated adipocytes from Svalbard and Norwegian reindeer

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Abstract
Arctic reindeer exhibit marked seasonal changes in fat deposition and mobilization. At intervals throughout the year, feed intake of both Svalbard (SR) and Norwegian reindeer (NR) together with the seasonal changes in size, lipogenic and lipolytic capacity of isolated adipocytes from both sub-species were measured. Feed intake of both NR and SR was maximal in Aug., but declined thereafter, reaching minimum values in Jan. (NR) and March (SR), 55 and 69% below the Aug. value, respectively. NR and SR adipocyte volume changed in parallel and were reduced to the same extent (69%) from their maximum in Aug. to their minimum in May. Adipocyte lipogenic capacity, measured as acetate incorporation into cellular lipid at saturated acetate concentrations, was lowest in Jan. (NR adipocytes) and March (SR adipocytes), 92 and 90%, respectively, below the maximum values, which were obtained in Aug. Lipolytic capacity measured as maximum adrenaline[epinephrine]-stimulated glycerol release, was high in SR adipocytes from March through to Oct. and in NR adipocytes from July through to Jan. Minimum lipolytic capacity was found in Jan. (SR adipocytes) and March (NR adipocytes). The present findings may be explained by alterations in lipogenic enzyme activtiy and in the lipolytic activation system.