Gut Microbiome Health Linked to Social Circles

A new study of lemurs has determined social circles to be the most influential determinant of gut microbiome. What does this mean for humans? 


We influence one another more than we’ll ever know. Ideas, mores, customs, and religions spread through communities like contagions. So does bacteria, as we know from a history of infections as well as new research on the social circles of lemurs. This study might offer another insight into the complex and fascinating nature of what health entails. 

One major advance in recent years has been recognizing how relevant gut microbiome is to physical and cognitive health. Some researchers speculate that the microbiome might be the most relevant marker of fitness. We also know that the composition of the thousands of species of bacteria inside of your gut is multifactorial, relying on the food you consume, the environment you live in, behavioral patterns, and genetics. 

But how relevant are other people in your environment? That’s what a team, led by Amanda Perofsky, an NSF Graduate Research Fellow at the University of Texas at Austin, wanted to find out. Having spent time studying lemurs at the Kirindy Mitea National Park in western Madagascar, Perofsky’s academic career has been focused on the link between social behavior and disease risk in this wild sifaka population. 

The paper, published in Proceedings of the Royal Society B, focuses on gene sequencing and social network analysis and determines that denser grooming networks “have more homogeneous gut microbial compositions.” It should be noted that this particular species is more tightly knit than others: 

Higher-order social network structure—beyond just pairwise interactions—drives gut bacterial composition in wild lemurs, which live in smaller and more cohesive groups than previously studied anthropoid species.

Studying forty-seven lemurs from seven different social groups, the team discovered that 67.6 percent of variation in microbiome can be attributed to group membership. Even more surprisingly, 

Even after controlling for diet, kinship and habitat overlap, group membership was the single most informative predictor of gut microbiome diversity and similarity between individuals, revealing the importance of social network structures beyond the dyadic associations reported by prior studies.

This potentially overturns a common notion that infection spreads more quickly through tight-knit groups because of proximity to the affected. As Perfosky notes, social groups might make these lemurs more resistant to infection because their stable microbiomes ensure that members spread beneficial bacteria. 

It would be fascinating to understand if similar patterns affect the human microbiome. While we’re not known for daily grooming (outside of our immediate family, perhaps), we do know our actions influence others in ways that elude conscious detection. We also know how vulnerable we are to the bad habits of others, dietary and behavioral choices included. (To be fair, our good habits are also communicable.) 

While studies like this cannot be easily transferred to our species, they remind us of the inherent interconnectedness of social groups and our relationship to our environment. We know relationships are a critical component of individual health. Just how much that’s the case is continually becoming apparent. 

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Derek is the author of Whole Motion: Training Your Brain and Body For Optimal Health. Based in Los Angeles, he is working on a new book about spiritual consumerism. Stay in touch on Facebook and Twitter.

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Researchers hope the technology will further our understanding of the brain, but lawmakers may not be ready for the ethical challenges.

Still from John Stephenson's 1999 rendition of Animal Farm.
Surprising Science
  • Researchers at the Yale School of Medicine successfully restored some functions to pig brains that had been dead for hours.
  • They hope the technology will advance our understanding of the brain, potentially developing new treatments for debilitating diseases and disorders.
  • The research raises many ethical questions and puts to the test our current understanding of death.

The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?

But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.

What's dead may never die, it seems

The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.

BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.

The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.

As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.

The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.

"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.

An ethical gray matter

Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.

The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.

Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.

Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?

"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."

One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.

The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.

"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.

It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.

Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?

The dilemma is unprecedented.

Setting new boundaries

Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."

She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.

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