Energy homeostasis regulatory peptides in hibernating grizzly bears

Titin isoform switching is a major cardiac adaptive response in hibernating grizzly bears.

The hibernation phenomenon captures biological as well as clinical interests to understand how organs adapt. Here we studied how hibernating grizzly bears (Ursus arctos horribilis) tolerate extremely low heart rates without developing cardiac chamber dilation. We evaluated cardiac filling function in unanesthetized grizzly bears by echocardiography during the active and hibernating period. Beca...

Mama Grizzly and the polar bears.

A recent paper on the matrilineal population history of two sister species, Ursus maritimus (polar bears) and Ursus arctos (brown bears), based on mtDNA sequence analysis, reveals a comparatively recent introgression. The authors propose that it represents a signature of environ mental stress in marginal habitats [1]. In a nutshell, it means that all modern polar bears probably belong to a mate...

Trophic cascades from wolves to grizzly bears in Yellowstone.

We explored multiple linkages among grey wolves (Canis lupus), elk (Cervus elaphus), berry-producing shrubs and grizzly bears (Ursus arctos) in Yellowstone National Park. We hypothesized competition between elk and grizzly bears whereby, in the absence of wolves, increases in elk numbers would increase browsing on berry-producing shrubs and decrease fruit availability to grizzly bears. After wo...

Natriuretic Peptides: New Players in Energy Homeostasis

In this issue of Diabetes, Miyashita et al. (1) provide compelling new evidence that natriuretic peptides (NPs) play a key role in the regulation of body weight and energy metabolism. In a series of complementary experiments, the investigators show that the NP–cyclic guanosine monophosphate (cGMP) signaling system increases the capacity for fat oxidation, activates mitochondrial biogenesis, and...

Den selection by grizzly bears on a managed landscape