Welcome to February. If you are reading this, and live in the Northern Hemisphere, you’ve made it through most of the winter.
So far you probably shoveled anywhere between 6 and 250 inches of snow off of your driveway, and possibly scraped off at least three inches of ice off your windshield. You have probably slipped and fallen on the ice in front of shocked strangers no fewer than five times, and if you are really lucky, you’ve had a vehicle towed in the middle of the night for being parked in a snow removal zone.
It may be a little too late to make this decision for this year, but next year, you swear you’re going to just skip winter, and hibernate.
Hibernation is a state of dormancy that is common in mammals during cold seasons. Possibly the most prolific hibernators are Alaskan black bears, which hibernate about seven months out of each year. That sounds nice, doesn’t it? During this time, the bears’ heart rate drops to about 14 beats per minute, their metabolism reduces by about 75%, and their body temperature fluctuates between 30°C-36°C. It’s not just bears that hibernate; smaller mammals such as ground squirrels, bats, and deer mice also hibernate through the winter. There are slight physiological variations due to the differences in surface area to volume (bears are big), however the overall theme is the same. To survive this reduced state of function, there is a shift from the use of carbohydrates as a primary source of fuel, to using fats instead. This is noted by altered regulation of metabolic pathways and inhibition of energy-costly protein synthesis processes.1 Calcium, phosphorus and urea are recycled to prevent bone and muscle loss.2
To prepare for hibernation, animals need to accumulate as much fat as possible in the months leading up to this point. You can do this too, and your best bet is to consume foods that have been stuffed with other foods. This may include cream cheese-stuffed pancakes with Nutella spread on top, pizza with a cheese-and-bacon stuffed crust, double stuffed Oreos, macaroni and cheese nuggets stuffed with mayo and deep-fried, cheesecake-stuffed chocolate chip cookies, fried chicken-stuffed donuts, pork-rind-stuffed croissants….
You get the idea. The greatest part is after you pack in all of these foods, you’ll spend the next few months burning the fat off while you sleep. In fact, you may even notice that you’ve lost a bit of weight as you wake up to sunshine and springtime flowers.
If you like the idea of skipping one winter, why not skip all of the winters? After all, you’ve never done anything half-assed in your entire life. Critters such as water bears (tardigrades), rotifers, some types of insects, and nematodes can do this by allowing themselves to freeze in a preserved state (cryobiosis), where they can remain dormant for years, decades, and possibly even centuries. Interestingly, the active lifespan of water bears is typically less than a year; adding in a period or two of dormancy could hypothetically extend the total lifespan many times over.3
Just think. In time, climate change will result in an increase in global temperatures just enough so that chances are, the winters where you live won’t be so dammed cold. This is a fantastic idea.
I suppose you could also move to a warmer location. But, moving is the worst and the job market isn’t great, so cryobiosis it is.
The main strategy to cryobiosis is to avoid inter- and intracellular ice formation. As it turns out, ice crystals are very damaging to cellular integrity, and the added weight of ice increases the risk of physical damage through crushing force. This is why jack-o’-lanterns never really do well after the first good November freeze, and why we can’t simply preserve ourselves by taking a ride in a tank full of liquid nitrogen. Pro-tip: If you want your decorative gourds to last longer, keep them indoors and out of the cold. Then it can be decorative gourd season until January at the very least.
There are a number of different cellular and biochemical mechanisms designed to protect cells from freezing and desiccation at the onset of cryobiosis; these include the use of protective proteins (heat shock and chaperones) as well as assorted antioxidants that may differ slightly from frozen critter to frozen critter.4 One mechanism that most of our freezable critters seem to have in common is the replacement of water inside the cell with trehalose. 4 5 Trehalose is a disaccharide (like sucrose), synthesized from glycogen in response to a drop in temperature. What makes it so special is that it takes on a gel-like structure, which acts as a protectant of cells and their contents, stabilizes proteins in their native state, and avoids the formation of damaging ice crystals. During a state of cryobiosis, trehalose may account for up to 20% of the critter’s dry weight.4 The fine details of all that occurs before, during, and after cryobiosis are currently being sorted out, but as it stands, after the temperature rises again trehalose is catabolized into glucose, and the critter resumes its normal metabolic processes.
Ideally, if you entered a state of cryobiosis you could just settle in for the next few decades, then resume your normal activities without skipping a metabolic beat. This would allow us to extend our normal lifespan to see beyond the year 2100, and possibly even further.
OK, enough daydreaming. The big question now is, could humans do this?
Humans have most of the proper enzymatic machinery for hibernation, but we don’t do it for relatively unknown reasons. The reigning theory is that humans evolved out of tropical and subtropical ecosystems, and never really adapted to cold climates like bears and other mammals. Even after we started colonizing cold climates, we were always a little too busy, and would run the risk of someone stealing our stuff if we were to sleep for half the year. Despite these issues, there are a few stories of determined individuals that claim to have hibernated.6 So, perhaps it is possible.
Cryobiosis is a little more far-fetched. It very well could be that trehalose is toxic to us, as vertebrates lack the enzymes needed to synthesize trehalose, but we still have enzymes to break the stuff down into glucose.5 Despite this, being able to achieve a state of cryobiosis is absolutely desirable, as it opens up the door to completely new and awesome technologies. Examples of this include, bodily preservation and revival for medical purposes, and being able to survive a long ride through space on our way to our new Earth, as we are in the process of irredeemably trashing the current one. A little bit of genetic engineering will be necessary to allow us to synthesize and tolerate our own trehalose, but we can work on that. Necessity is the mother of invention after all.
I know it’s obvious, but I feel like I should remind everyone that one we enter a state of cryobiosis, we are good to go, and can be jettisoned into space. Just make sure that you pin a DO NOT DISCARD note on yourself in some manner so that you are not mistaken for a shrunken corpse.
1 Klug, BJ. and Brigham, RM. 2015. Changes to metabolism and cell physiology that enable mammalian hibernation. Spring Science Reviews. DOI 10.1007/540362-015-0030-x
2 Nelson, RA. 1980. Protein and fat metabolism in hibernating bears. Fed. Proc. 39:2955-2958
3 Herkewitz, W. Secrets of the water bear, the only animal that can survive in space. Popular Mechanics, August 7th, 2014.
4 Gusev et al., 2014. Comparative genome sequencing reveals genomic signature of extreme desiccation tolerance in the anhydrobiotic midge. Nature Communications. DOI: 10.1038/ncomms5784
5 Jain, NK. And Roy, I. 2009. Effect of trehalose on protein structure. Protein Science 18:24-36