Body temperature is a more important modulator of lifespan than metabolic rate in two small mammals

[Mito]

Abstract​

The relationships between metabolic rate, body temperature (Tb), body composition and ageing are complex, and not fully resolved. In particular, Tb and metabolic rate often change in parallel, making disentangling their effects difficult. Here we show that in both sexes of mice and hamsters exposure to a temperature of 32.5 °C leads to a reduced lifespan, coincident with lowered metabolic rate and elevated Tb with no change in body composition. We exploit the unique situation that when small mammals are exposed to hot ambient temperatures their Tb goes up, at the same time that their metabolic rate goes down, allowing us to experimentally separate the impacts of Tb and metabolic rate on lifespan. The impact of ambient temperature on lifespan can be reversed by exposing the animals to elevated heat loss by forced convection, which reverses the effect on Tb but does not affect metabolic rate, demonstrating the causal effect of Tb on lifespan under laboratory conditions for these models. The impact of manipulations such as calorie restriction that increase lifespan may be mediated via effects on Tb, and measuring Tb may be a useful screening tool for putative therapeutics to extend the human lifespan

Body temperature is a more important modulator of lifespan than metabolic rate in two small mammals - Nature Metabolism

Zhao et al. uncouple the effects of body temperature and metabolic rate on lifespan in two rodent models, showing that in warm conditions, where body temperature is elevated and metabolic rate reduced, lifespan is reduced. Reversal of increased body temperature reverses the negative impact of...

www.nature.com

 

[yerrag]

The impact of ambient temperature on lifespan can be reversed by exposing the animals to elevated heat loss by forced convection, which reverses the effect on Tb but does not affect metabolic rate, demonstrating the causal effect of Tb on lifespan under laboratory conditions for these models.

I have difficulty understanding what is meant here. I don't understand why forced convection to cause heat loss reverses the effect on Tb and doesn't affect the metabolic rate. I also don't understand why they don't simply lower the ambient temperature as a control.

I usually don't like to read further when the authors don't make their language clear in the abstract. Or I'm just too dumb to figure out their meaning.

 

[Mito]

I have difficulty understanding what is meant here. I don't understand why forced convection to cause heat loss reverses the effect on Tb and doesn't affect the metabolic rate. I also don't understand why they don't simply lower the ambient temperature as a control.

I usually don't like to read further when the authors don't make their language clear in the abstract. Or I'm just too dumb to figure out their meaning.

Not sure but presumably they verified no change in metabolic rate using that method. Maybe lowering the ambient temperature does effect the metabolic rate?

“We separated the effect of body temperature on lifespan from metabolic rate in two species of small rodents exposed to high temperatures. We are excited about the findings, particularly that using small fans to blow air over the animals reversed the effect of high ambient temperature on lifespan by decreasing body temperature without changing metabolic rate,” said ZHAO Zhijun from Wenzhou University, who was the first and co-corresponding author of this study.

Live Fast, Die Young? Or Live Cold, Die Old? - Neuroscience News

Body temperature exerts a greater effect on longevity and lifespan than metabolic rate, researchers report.

neurosciencenews.com

 

[yerrag]

It seems like a study to point out the obvious. Having an electric fan to cool you in warm weather does wonderful things to your health.

The cooling effect must lower stress. And if I were continually subjected to hugh temperatures beyond my comfort levels, I would likely die sooner.

 

[Elie]

It seems like a study to point out the obvious. Having an electric fan to cool you in warm weather does wonderful things to your health.

The cooling effect must lower stress. And if I were continually subjected to hugh temperatures beyond my comfort levels, I would likely die sooner.

I understood it to be the opposite. by using the fan to cool them, their body temp decreased and so did their lifespan.

 

[ecstatichamster]

I will observe somewhat on subject, that I have not seen any studies showing higher body temperatures leading to greater longevity, in a given organism. That doesn’t mean that higher body temperatures don’t lead to longevity. It just means that the current paradigm set in stone is the “rate of living” hypothesis.

In this study, the supposition is that higher ambient temperatures allows lower metabolic rate, and greater longevity.

Dr. Peat is the only person I have known who has claimed greater longevity with higher metabolic rate.

 

[yerrag]

I understood it to be the opposite. by using the fan to cool them, their body temp decreased and so did their lifespan.

From the second link posted:

When mice and hamsters are exposed to high temperatures, at the top of their thermoneutral zone, their metabolism falls while their body temperature goes up. “We found that exposing the rodents to these conditions shortened their lifespans. Lower metabolism didn’t lengthen their lives, but higher temperatures shortened it,” said Prof. John R. Speakman from SIAT, a co-corresponding author of the study.

 

[Elie]

From the second link posted:

When mice and hamsters are exposed to high temperatures, at the top of their thermoneutral zone, their metabolism falls while their body temperature goes up. “We found that exposing the rodents to these conditions shortened their lifespans. Lower metabolism didn’t lengthen their lives, but higher temperatures shortened it,” said Prof. John R. Speakman from SIAT, a co-corresponding author of the study.

oh. Thank you for clarifying.
What is considered "normal" temperature for a mouse or a hamster?

 

[yerrag]

oh. Thank you for clarifying.
What is considered "normal" temperature for a mouse or a hamster?

Since we live on the same ecosystem, I would assume the same normal temperature we live in.

 

[Elie]

Since we live on the same ecosystem, I would assume the same normal temperature we live in.

"exposure to a temperature of 32.5 °C leads to a reduced lifespan..."
so it must be lower than that, no?

 

[yerrag]

"exposure to a temperature of 32.5 °C leads to a reduced lifespan..."
so it must be lower than that, no?

I think so.

Plus, I cannot imagine myself living in that weather, day in and day out, with no wind without a break and be able to not think of dying.

 

[Rafe]

I can’t access the full paper, it’s behind a paywall.

From what is summarized they are making an assumption that body temp when the skin is exposed to fanning in a hot enclosure is separated from metabolic rate. “We’re excited that we did this.”

I don’t see how that’s true.

Fanning hot air is just how a convection oven works, which just makes meat cook faster & more evenly. Even if the meat isn’t as stressed about it. How did they measure body temp and metabolic rate?

Sure, a breeze in a desert in the daytime may make you feel better. But would it really lower your metabolic rate?

Besides that, a high temp measured with a thermometer can be from stress or from a high metabolism.

That’s a central RP point: how things look can be deceptive. So you have to figure out what the physiology is responding to. One of the ways to do that is to look at the environment it’s in.

That project isn’t doing that.

 

[Beastmode]

I will observe somewhat on subject, that I have not seen any studies showing higher body temperatures leading to greater longevity, in a given organism. That doesn’t mean that higher body temperatures don’t lead to longevity. It just means that the current paradigm set in stone is the “rate of living” hypothesis.

In this study, the supposition is that higher ambient temperatures allows lower metabolic rate, and greater longevity.

Dr. Peat is the only person I have known who has claimed greater longevity with higher metabolic rate.

I wonder if there's a distinction b/n higher body temps being driven my a stress vs healthy oxidative metabolism even considered in these studies?

Peat is the only one I've ever heard as well.

Having a higher body temp only seems logical if it's driven by proper fuel and a not stressful life. When I tell my health driven people my body temp and pulse range, they can't see in anyway that it's healthy or ideal. When I was hypothyroid, exercising the most and eating less I couldn't get my resting body temp and pulse at this healthy range. Even when I share this, it still doesn't compute for others outside this forum.

 

[ww3not4me]

We are not rodents almost nothing research wise concerning anything to do with metabolism means anything to a human. Just look at all the rodent studies that seem like miracles that do not crossover to humans in any way at all!!!

Look at all the studies over the year that have demonstrated that air-conditioning shortens human life spans.

Then you have what is clearly a bad study attempting to separate body temp. from metabolism. Trying to separate the two is at best like merging 2 slinky spring toys together and then attempting to move one with out moving the other. Sure there is some slop between the two but it is not possible to move one with out moving the other. If it goes on long enough you will see the body seek hemostasis.

This sort of research has already been done on humans. We got all of this sort of medical information concerning humans from the Germans at the end of WWII. The research was graphic and often carried out to the persons death in extreme heat and cold. The Germans used Jews for this research. They were not looking to extend life but we know exactly how tightly coupled metabolism and ambient temp is tied in humans. It is hard to decouple it you need drugs to decouple it.

In terms of using a fan in an attempt at recreating this in a human would be a waste energy given the increasing cost it is a waste. Much better to include fasting in your diet as a tool. Under eating. Exercising less if you exercise excessively! Cultures in Okinawa with long lives eat a lot of dreaded vegetables, lots of sodium, some seafood and very little meat from land based animals. I doubt they are drinking OJ regularly or taking in very specific amounts of fructose. Those spots in China with the longest lives with the fewest disease eat a diet high in those pesky vegetables. I am no vegan that is for sure but reality does not match lab studies with rodents very often when talking about carry over to humans!

I think we as humans already have plenty of life span research and observations based on geography observing humans that for the most part are born and die close to the same spot over most of their lives. We already know that your latitude does impact your life expectancy. The most obvious observable factor being temp.

To be clear my problem with this study is that they are stupid enough to think you can decouple metabolism from ambient conditions. It is just as ignorant as if someone said we are going to decouple metabolism from calorie intake. Just does not work that way.

 

[Mito]

I can’t access the full paper, it’s behind a paywall.

View: https://twitter.com/johnspeakman4/status/1503718321178521600?s=21

 

[Rafe]

Mito, thank you!

I just wanted to put down why I wasn’t addressing the details.