| 1. |
- Pirinen, E., et al.
(författare)
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Enhanced polyamine catabolism alters homeostatic control of white adipose tissue mass, energy expenditure, and glucose metabolism
- 2007
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Ingår i: Mol Cell Biol. - 0270-7306. ; 27:13, s. 4953-67
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Tidskriftsartikel (refereegranskat)abstract
- Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha) is an attractive candidate gene for type 2 diabetes, as genes of the oxidative phosphorylation (OXPHOS) pathway are coordinatively downregulated by reduced expression of PGC-1 alpha in skeletal muscle and adipose tissue of patients with type 2 diabetes. Here we demonstrate that transgenic mice with activated polyamine catabolism due to overexpression of spermidine/spermine N(1)-acetyltransferase (SSAT) had reduced white adipose tissue (WAT) mass, high basal metabolic rate, improved glucose tolerance, high insulin sensitivity, and enhanced expression of the OXPHOS genes, coordinated by increased levels of PGC-1 alpha and 5'-AMP-activated protein kinase (AMPK) in WAT. As accelerated polyamine flux caused by SSAT overexpression depleted the ATP pool in adipocytes of SSAT mice and N(1),N(11)-diethylnorspermine-treated wild-type fetal fibroblasts, we propose that low ATP levels lead to the induction of AMPK, which in turn activates PGC-1 alpha in WAT of SSAT mice. Our hypothesis is supported by the finding that the phenotype of SSAT mice was reversed when the accelerated polyamine flux was reduced by the inhibition of polyamine biosynthesis in WAT. The involvement of polyamine catabolism in the regulation of energy and glucose metabolism may offer a novel target for drug development for obesity and type 2 diabetes.
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| 2. |
- Broggi, J, et al.
(författare)
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Local adaptation to winter conditions in a passerine spreading north: A common-garden approach
- 2005
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Ingår i: Evolution. - 1558-5646. ; 59:7, s. 1600-1603
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Tidskriftsartikel (refereegranskat)abstract
- Sedentary passerine birds living in temperate and boreal regions need a high metabolic capacity for thermogenesis to survive winter conditions. As a consequence of the increased thermogenic capacity, basal energetic demands rise at a time when resources and time to acquire them decrease. In a previous study, great tits (Parus major) from two localities in Fennoscandia with contrasting winter conditions differed in their metabolic response to ambient temperature. To investigate the physiological basis underlying interpopulation differences we performed a common-garden experiment to test whether these differences were genetically based. We found basal metabolic rate to be higher in birds originating from transferred eggs from the southern population compared to the ones from the northern population, contrary to the relationship among birds living in their region of origin. Despite previous evidence suggesting that gene flow prevents local adaptation at the northern range limits of a species expanding northward, we found that great tits differ in their reaction norm to winter conditions according to the population of origin.
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| 3. |
- Broggi, J, et al.
(författare)
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Metabolic response to temperature variation in the great tit: an interpopulation comparison
- 2004
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Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 73:5, s. 967-972
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Tidskriftsartikel (refereegranskat)abstract
- 1. We studied the resting metabolic rate (MR) from two great tit Parus major (Linnaeus) populations living in different winter regimes. Birds from the two different localities were exposed individually to +25 °C, 0 °C and −10 °C for the night in three consecutive sessions in random order. 2. Birds from Lund (Sweden) had a lower basal MR, as measured at thermoneutrality (+25 °C), than had birds from Oulu (Finland). Nevertheless, below thermoneutrality, birds from Oulu spent relatively more energy, especially at −10 °C. 3. Although the energy needed for thermoregulation decreased with increasing basal MR this relation is at a higher metabolic cost for birds in Oulu than for birds in Lund. 4. The higher basal MR in Oulu is probably a consequence of a higher maximal MR needed in the severe cold. Further, the observed MRs below thermoneutrality are lower than expected from published data. This suggests that all birds were probably hypothermic at −10 °C, particularly Lund birds, and that the use of controlled hypothermia in great tits may be more common than thought previously. Great tits seem to rely primarily on metabolic adjustment to cope with the harsh climatic conditions in the northernmost parts of its distribution.
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| 4. |
- Broggi, J., et al.
(författare)
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Sources of variation in winter basal metabolic rate in the great tit
- 2007
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 21:3, s. 528-533
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Tidskriftsartikel (refereegranskat)abstract
- 1. Basal metabolic rate (BMR) is the most widely used standard measurement of the cost of living. Despite the acknowledged phenotypic flexibility of BMR, little is known about the patterns of variation in wild animal populations. 2. We studied the sources of variation in BMR of great tit Parus major (L.) among individuals from two wild populations: Oulu (northern Finland) and Lund (southern Sweden) during six consecutive years. 3. By means of a multivariate approach, we found year, locality, date, previous week average minimum temperature, age, body mass, and the interaction between locality and year were the factors retained in the final model, together explaining 71.1% of the total variation in BMR. 4. Birds from Oulu (n = 168) had a higher BMR than Lund birds (n = 156), and their BMR varied more between years than that of Lund birds. The two populations reacted in the same way to the other sources of variation examined. 5. Great tits from both populations showed a positive relationship between BMR and body mass and a negative relationship between BMR and date, previous week average minimum temperature and age. 6. This study highlights the need to standardize BMR measurements when testing predictions about metabolic rates from individuals of wild populations.
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