Bears are among the many most huge and highly effective animals on earth. They’re additionally very clever. They will use instruments, they’ve a remarkably acute sense of odor, good eyesight and listening to, and so they hibernate throughout inhospitable winters when the pickings are slim for meals.
Hibernating brown bears will keep of their dens for as much as seven months with out consuming or consuming. By some means their our bodies recycle waste with out having to urinate or defecate. Their metabolism and heartbeat decelerate significantly as they enter a not-quite-deep-sleep state often known as “torpor” that allows a bear to sense environmental stimuli with out turning into aroused. How is that this doable?
A latest report in Frontiers in Zoology sheds new gentle on the metabolic flexibility of animals that hibernate. A workforce of scientists from Norway, Sweden, and France have recognized seasonal shifts within the endocannabinoid system (ECS) of brown bears, which drive physiological adaptation throughout hibernation. The ECS regulates key organic processes – together with meals consumption, power storage and expenditure, sleep patterns, respiration, and coronary heart fee – that contribute to the metabolic, behavioral, and circadian changes that happen whereas animals hibernate.
Modifications in endocannabinoid tone had beforehand been documented in smaller animals that hibernate, however not in large-bodied hibernators. In accordance with Boyer et al (2020), the worldwide downregulation of the ECS in hibernating brown bears includes alterations in circulating endocannabinoids and different lipid neurotransmitters, in addition to in cannabinoid receptor exercise and ECS-related gene expression.
The European researchers documented particular differences due to the season within the fatty acid composition of winter-hibernating bears in comparison with summer-active bears. Throughout hibernation, brown bears expertise:
- Diminished CB1 and CB2 receptor signaling in muscle and adipose tissue, respectively.
- Decrease ranges of anandamide and 2AG (the 2 main endocannabinoids) in muscle and adipose tissue.
- Elevated serum ranges of DHA [docosahexaenoic acid], an omega-3 fatty acid important for wholesome mind perform.
- A threefold enhance within the plasma focus of OEA [oleoylethanolamide], an endocannabinoid-like compound, which suppresses starvation.
OEA & PPAR-alpha
When it comes to its molecular construction, OEA is a lipid compound carefully associated to anandamide (N-arachidonoylethanolamine), however in contrast to anandamide it acts independently of ECS pathways. OEA is an endogenous, high-affinity agonist (activator) of PPAR-alpha, a receptor on the floor of the cell’s nucleus, which regulates feeding and physique weight.
Whereas anandamide boosts urge for food by binding to CB1 (the “munchies” receptor), OEA decreases meals consumption by binding to PPAR-alpha. OEA additionally stimulates lipolysis, a metabolic course of that mobilizes saved power by changing fats to gas by way of fasting-induced ketogenesis.
The mixture of diminished CB1 exercise and heightened OEA plasma focus allows hibernating brown bears to maintain themselves with out consuming throughout months of torpor – whereas additionally sustaining the capability to sense stimuli from the setting.
The European scientists surmised that “past an total suppression of the ECS, seasonal shift in endocannabinoid compounds may very well be linked to bear’s peculiar options that embody hibernation with out arousal episodes and capability to react to exterior disturbance.”
“Don’t poke the bear”
There’s an outdated saying – “Don’t poke the bear” – which really applies extra to people than large, furry beasts that hibernate. It’s a blunt warning to not intentionally provoke or antagonize somebody who may turn into indignant or violent, particularly somebody with a fast mood who’s ready of energy or authority.
Maybe folks would reply much less to pokes if we have been extra like bears who don’t react to exterior disturbance once they’re hibernating. However we aren’t hibernators, and we will’t sleep via what’s shaping as much as be a horrible winter with COVID raging, deaths mounting, and starvation spreading world wide.
Apparently, we aren’t as adaptable as our hominid ancestors who endured ferocious winters and meals shortage “by slowing down their metabolisms and sleeping for months,” in response to a latest paper revealed in L’Anthropologie (Arsuaga and Bartsiokas, December 2020).
On this article, two archeologists analyzed the fossilized stays of early people present in Spain, which confirmed differences due to the season in bone development indicative of animals that hibernate. The researchers acknowledge that it “might sound like science fiction,” however they be aware that many mammals, together with lemurs and some different primates, are identified to hibernate: “This means that the genetic foundation and physiology for such a hypometabolism may very well be preserved in lots of mammalian species together with people.”
Based mostly on this newly unearthed archeological proof, scientists postulate that early people in Europe have been capable of entry “metabolic states that helped them to outlive for lengthy intervals of time in frigid circumstances with restricted provides of meals and sufficient shops of physique fats.” In different phrases, they hibernated.
Martin A. Lee is the director of Mission CBD and the creator of Smoke Signals: A Social History of Marijuana – Medical, Recreational and Scientific.
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