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

Abstract

Arctic reindeer exhibit marked seasonal changes in fat deposition and mobilization. At intervals throughout the year, therefore, we have measured 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. Feed intake of both NR and SR was maximal in August, but declined thereafter, reaching minimum values in January (NR) and March (SR), 55 and 69% below the August value, respectively. NR and SR adipocyte volume changed in parallel and were reduced to the same extent (69%) from their maximum in August to their minimum in May. Adipocyte lipogenic capacity, measured as acetate incorporation into cellular lipid at saturated acetate concentrations, was lowest in January (NR adipocytes) and March (SR adipocytes), 92 and 90%, respectively, below the maximum values, which were obtained in August. Lipolytic capacity, measured as maximum adrenaline-stimulated glycerol release, was high in SR adipocytes from March through to October and in NR adipocytes from July through to January. Minimum lipolytic capacity, on the other hand, was found in January (SR adipocytes) and March (NR adipocytes). The present findings may be explained by alterations in lipogenic enzyme activity and in the lipolytic activation system.

Adaptations to polar life in mammals and birds

“…It follows that the ptarmigans [and Arctic foxes (Fuglesteg et al, 2006)] seem to reduce their fat reserves according to a seasonally changing set-point for body mass, as the chance of death by starvation steadily diminishes with the return of light . This is also observed in Svalbard reindeer (Larsen et al, 1985;Tyler, 1987). The fat reserves (Fig.…”

Where clocks are redundant: weak circadian mechanisms in reindeer living under polar photic conditions

“…Data are plotted as weekly medians (quartiles) and fitted to a cosine model (Eq. 1; thick black line; amplitude of the annual cycle of daily activity increased with latitude, reflecting the greater amplitude of the appetite cycle in SR compared with NR (Larsen et al 1985). The quality of the forage on Arctic ranges, moreover, is very high in summer (White and Staaland 1983;Klein 1990;Sørmo et al 1997;Larter and Nagy 2001) and the rates of fermentation of fibre and of passage of digesta increase as a result (Orpin et al 1985;Mathiesen et al 1987; Fig.…”

“…Reindeer, like all northern species of cervids investigated so far, show a clear annual cycle in growth and fattening (Leader-Williams and Ricketts 1982;Reimers et al 1983;Tyler 1987). Their metabolic demands and, hence, also their appetite are correspondingly high in summer but much reduced in winter (Nilssen et al 1984;Larsen et al 1985;Mesteig et al 2000), fluctuating in accordance with an endogenous rhythm that represents a major adaptation to seasonal variation in the quality, abundance and availability of forage (see Barry et al 1991 for a review). Consequently, the reindeer were active for around 17 h·day −1 in summer (Fig.…”

Forage chemistry and the digestive system in reindeer (Rangifer tarandus tarandus) in northern Norway and on South Georgia

“…Mean (standard deviation) length (m) of the intestines in reindeer on South Georgia in summer (SG) (n = 10), and in northern Norway in late summer (NS) (n = 6) and winter (NW) (n = 11) compared with ruminants of the grazer and concentrate selector types. low-lignified food in summer, when appetite is high (Larsen et al, 1985;Mathiesen & Utsi, 1999). In Svalbard reindeer, which eat lignified forage in winter, RR contribute as much as 20% of BM (S0rmo et al, 1999), but in SG, NS and NW reindeer relative RR volumes were much smaller (Table 6).…”

“…Captive Norwegian reindeer calves {Rangifer t. tarandus) are severely limitated in their ability to utilise fibrous grasses (Aagnes et al, 1996). Reindeer have a cyclic pattern in appetite, with high voluntary food intake in summer and low intake in winter (Larsen et al, 1985). Appetite and availability of plants in the winter season seem therefore to influence the fill of digesta in these highly seasonal ruminants (Staaland et al, 1979;Tyler, 1999).…”