Insights from worms could help scientists harness the power of dietary restriction for longevity

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The pursuit of a longer life may currently be trending for tech bros, but the notion of a fountain of youth, or even immortality, has intrigued people for millennia.

Yet, some of the more evidence-based methods to increase longevity, such as dieting, are decidedly unpleasant to maintain over time.

Research from the lab of Scott Leiser, Ph.D., of Molecular and Integrative Physiology Department at University of Michigan Medical School, uncovers interesting connections between a longevity gene, behavior and the environment.

The findings bring scientists closer to understanding the underlying biological mechanisms that might be exploited to extend life without the downsides.

The first study, appearing in PNAS, uses a worm (the popular research model species, C. elegans) to further explain the effect of environmental cues and food access on longevity.

“Believe it or not, most of the central ideas and types of metabolism we study are conserved from worms to people,” said Leiser.

When we perceive the environment, we release hormones like adrenaline or dopamine. Worms do the exact same thing; their neurons respond to the environment and change their physiology accordingly,” he explained.

Previous research has shown that stress like food scarcity can promote survival.

Intriguingly, foundational work in flies from Leiser’s U-M colleague Scott Pletcher, Ph.D., showed that the mere smell of food can reverse this effect.

Leiser, along with project leader Elizabeth Kitto, Ph.D., and with support from Safa Beydoun, Ph.D., wondered whether other sensory inputs, like touch, would also mitigate the life-extending effects of dietary restriction, and if so, how?

To test this, they placed worms on a bed of beads with a texture similar to the E. coli buffet they would normally encounter during feeding.

The touch of the beads was enough to blunt the expression of a gene in the intestine related to longevity (fmo-2) and in doing so, reduced the life extension effect of dietary restriction.

Leiser discovered that fmo-2 is a gene that is necessary and sufficient to extend lifespan downstream from dietary restriction in 2015.

“The fmo-2 enzyme remodels metabolism, and as a result increases lifespan,” he explained. “Without the enzyme, dietary restriction does not lead to a longer lifespan.”

Specifically, their experiment showed that touch activates a circuit that modulates signals from cells that release dopamine and tyramine, which decreases intestinal fmo-2 induction and thus the longevity effect of a restricted diet.

Most importantly for human health, the work demonstrates that these circuits can be manipulated, said Leiser.

“If we could induce fmo-2 without taking away food, we could activate the stress response and trick your brain into making you long-lived.”

Before this can happen, however, it’s important to understand how else fmo-2 affects organisms.

In another study, published in Science Advances, the team demonstrated that the enzyme affects behavior in noticeable ways.

Worms engineered to overexpress fmo-2 were apathetic to positive and negative changes in their environment: they did not flee from potentially harmful bacteria and when presented with food, didn’t slow to eat after a brief fast the way normal worms did.

Worms engineered to completely lack fmo-2 also explored their environments less often than normal worms did. Both behavioral states, they found, were caused by a change in tryptophan metabolism.

“There are going to be side effects to any intervention to extend life–and we think one of the side effects will be behavioral,” said Leiser.

“By understanding this pathway, we could potentially provide supplements to offset some of these negative behavioral effects.”

Leiser plans to continue to study the connection between the brain, metabolism, behavior and health with the hopes of contributing to the development of drugs to target these innate pathways.

“Investigating all of the individual signals that our brain is responding to from the gut is a hot but not well understood area.”

Additional authors: Ella Henry, Megan L. Schaller, Mira Bhandari, Sarah A. Easow, Angela M. Tuckowski, Marshall B. Howington, Ajay Bhat, Aditya Sridhar, Eugene Chung, Charles R. Evans

Papers cited:

“Metabolic regulation of behavior by the intestinal enzyme FMO-2,” Science Advances. DOI: 0.1126/sciadv.adx3018

“Rewarding touch limits lifespan through neural to intestinal signaling,” PNAS. DOI: 0.1073/pnas.2423780122

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Journal

Science Advances

DOI

10.1126/sciadv.adx3018 

 

Double disadvantage hurts more than twice as much

Complexity Science Hub

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image: 

This interactive visualization illustrates how social fairness can be influenced by structural factors through the story of two fictional planets – Monos and Duos, inhabited by cats and dogs. It demonstrates how differences such as species or color can affect rankings and lead to hidden inequalities.

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Credit: Please credit © Complexity Science Hub/Liuhuaying Yang if you wish to use this image or other material from the visualization.

Belonging to more than one marginalized group can make building and maintaining social connections significantly harder, often in ways that go far beyond a simple sum of disadvantages. A new study shows how inequalities in social ties don’t just add up – they can amplify one another.

Why do some people have more friendships, more support, and more opportunities – while others seem to have far fewer? Is it simply a matter of personal choices, or do structural patterns play a deeper role?

For individuals who belong to a disadvantaged social group, forming connections tends to be more difficult. And for those who belong to multiple such groups, the challenge is even greater. A new study from the Complexity Science Hub (CSH) together with TU Graz, published in Science Advances, reveals that differences in the number of social ties across groups cannot be explained merely by tallying up individual forms of discrimination. “Instead, disadvantages can amplify one another when they intersect,” says study author Samuel Martin-Gutierrez.

To understand how different aspects of identity, such as gender and ethnicity, affect social networks, the researchers developed a mathematical model and tested it using friendship data from around 40,000 U.S. high school students. “Our findings show that tie disadvantages often emerge in unexpected ways when multiple identity traits overlap,” states Fariba Karimi, head of the Algorithmic Fairness research group at the Complexity Science Hub and professor at TU Graz.

BIRDS OF A FEATHER

Social networks don’t form at random. Who we are – our gender, ethnicity, socioeconomic background – influences whom we connect with. We tend to form relationships with those who are similar to us, a phenomenon known as homophily.

On a larger scale, this tendency means that certain groups are more likely to be well-connected both within their communities and to the central, influential parts of the social network. These groups enjoy greater access to social information and mutual support, which can, in turn, condition broader access to opportunities.

Marginalized groups, on the other hand, are pushed to the periphery of the social network. They not only have fewer connections to its central parts but also tend to be connected to others who are themselves less well-connected, making it harder to access opportunities, such as jobs or educational pathways. “When majority groups mostly connect among themselves, it creates a kind of structural invisibility for minorities,” explains Martin-Gutierrez, who conducted the research while at the CSH.

COMPOUNDING DISADVANTAGES

But what does this mean for people who belong to more than one marginalized group – such as women with a migrant background from low-income families? “When someone falls into more than one marginalized category, the effects don’t simply add up – they can intensify in nonlinear and sometimes unexpected ways,” says Martin-Gutierrez.

Until now, these so-called intersectional inequalities have been understudied. Much of the existing research has focused on how individual identity traits, such as gender or ethnicity, affect social tie formation. “What sets our study apart is that we show how multiple identity factors can interact to shape social networks,” explains Martin-Gutierrez. “Depending on group size, connection preferences, and correlations between traits, entirely new and complex patterns of advantage and disadvantage can emerge.”

REAL-WORLD SCHOOL DATA

To capture these intersectional dynamics, the researchers developed a network model and tested it against real data from over 40,000 U.S. high school students from the years 1994/95. The patterns of tie inequality predicted by the model closely matched the observed friendship patterns, with about 92% accuracy.

The dataset included students’ self-nominated friendships – each student listed who they considered friends, as well as demographic details like gender, ethnicity, and grade level.

The findings clearly demonstrate how overlapping disadvantages can interact: While girls generally had more friends than boys, Black girls were the exception and, together with Asian boys, had among the fewest connections – fewer than Black boys, and far fewer than white girls. In their case, the structural disadvantages of being both Black and female outweighed the broader trend that girls tend to be nominated as friends more often than boys.

White girls, by contrast, had the most social ties. As members of both the ethnic majority and a gender group more likely to receive friendship nominations, they benefited from multiple structural advantages. White boys still gained from being part of the ethnic majority, resulting in higher overall popularity compared to Black boys. “One surprising pattern we observed was that in certain grade levels, Black boys were better connected than others, despite facing two layers of structural disadvantage,” says Martin-Gutierrez. “This is an example of emergent intersectionality: unexpected advantages that arise from complex interactions between group preferences, group sizes, and contextual factors,” adds Karimi.

“These kinds of effects have often remained hidden in earlier studies because they focused on one trait at a time,” Karimi notes. “Our findings underscore how important it is to consider people in their full complexity.” This new method, the researchers say, could help inform the design of schools, social platforms, and policy programs – making it easier to identify and address structural disadvantage early on.

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EXPLORING SOCIAL FAIRNESS YOURSELF

In this interactive visualization, you can discover what social fairness means – and how it can be influenced.

In a fictional parallel universe, there are two planets: Monos and Duos, inhabited by cats and dogs. Each year, the ten most popular residents are ranked based on their social connections.

Playfully explore whether this ranking system is fair. Do certain factors – such as species or color – lead to hidden inequalities that favor some groups over others? You can create your own planet and experiment with these factors to see how they affect the rankings.

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ABOUT THE STUDY

The study “Intersectional inequalities in social ties” by Samuel Martin-Gutierrez, Mauritz N. Cartier van Dissel, and Fariba Karimi is published in Science Advances (doi: 10.1126/sciadv.adu9025). 

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ABOUT THE COMPLEXITY SCIENCE HUB

The Complexity Science Hub (CSH) is Europe’s research center for the study of complex systems. We derive meaning from data from a range of disciplines – economics, medicine, ecology, and the social sciences – as a basis for actionable solutions for a better world. CSH members are Austrian Institute of Technology (AIT), BOKU University, Central European University (CEU), Graz University of Technology, Interdisciplinary Transformation University Austria (IT:U), Medical University of Vienna, TU Wien, University of Continuing Education Krems, Vetmeduni Vienna, Vienna University of Economics and Business, and Austrian Economic Chambers (WKO).

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Journal

Science Advances

DOI

10.1126/sciadv.adu9025 

Method of Research

Computational simulation/modeling

Subject of Research

People

Article Title

Intersectional inequalities in social ties

Article Publication Date

5-Nov-2025

 

Paradox of rotating turbulence finally tamed with world-class ‘hurricane-in-a-lab’

Scientists have solved a long-standing contradiction in fluid dynamics, setting a new baseline for theoretical and practical research on turbulence

Okinawa Institute of Science and Technology (OIST) Graduate University

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image: 

Left graph follows the conventional approach of plotting the energy spectrum, E(k), where energy is a is distributed across different eddy sizes represented by the wavenumber k. The wavenumber is inversely proportional to eddy size – large k corresponds to small eddies.

The inertial range refers to the scale of eddies that are smaller than the largest vortices – those spanning the full width of the container – but still larger than the smallest eddies where energy is lost as heat. Kolmogorov predicted that within the inertial range, the energy spectrum is proportional to eddy size, with energy decreasing at a constant of rate of -5/3: E(k)∝k−5/3. The celebrated “-5/3rd power law” has been found universal across virtually all turbulent flows – with the frustrating exception of TC flows. As is seen on the graph, most of the energy spectra do not follow Kolmogorov’s power law.

Right graph shows the same spectra rescaled by Kolmogorov’s general law, from which the -5/3rd law is derived, and which goes beyond the inertial range to include scales where energy dissipates into heat. Here, Kolmogorov predicted that energy spectra, rescaled using viscosity v and the smallest scale of motion η, become the universal function F(kη) at the small scales. The collapse of the rescaled data onto the universal curve F(kη), shown in gray, peeling off only at the extreme ends, demonstrates the small-scale universality of Kolmogorov’s framework across turbulent flows. 

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Credit: Barros et al., 2025

From stirring milk in your coffee to fearsome typhoon gales, rotating turbulent flows are everywhere. Yet, these spinning currents are as scientifically complex as they are banal. Describing, modelling, and predicting turbulent flows have important implications across many fields, from weather forecasting to studying the formation of planets in the accretion disk of nascent stars.

Two formulations are at the heart of the study of turbulence: Kolmogorov’s universal framework for small-scale turbulence, which describes how energy propagates and dissipates through increasingly small eddies; and Taylor-Couette (TC) flows, which are very simple to create yet exhibit extremely complex behaviors, thereby setting the benchmark for the study of the fundamental characteristics of complex flows.

For the past many decades, a central contradiction between these potent formulations has plagued the field. Despite extensive experimental research and despite being found universal to almost all turbulent flows, Kolmogorov’s framework has apparently failed to apply to turbulent TC flows.

But now, after nine years developing a world-class TC setup at the Okinawa Institute of Science and Technology (OIST), researchers have finally resolved this tension by conclusively demonstrating that, contrary to the prevailing understanding, Kolmogorov’s framework does apply universally to the small scales of turbulent TC flows – precisely as predicted. Their findings are now published in Science Advances. “The problem has long stood out like a sore thumb in the field,” says Professor Pinaki Chakraborty of the Fluid Mechanics Unit at OIST, who led the study. “With this discrepancy solved, and with the inauguration of the OIST-TC setup, we have set a new baseline for studying these complex flows.”

Universality lost in the search for a power law in Taylor-Couette flows

Taylor-Couette flows are very simple to create, appearing in closed flows between two independently rotating cylinders. They are also extremely complex, exhibiting a wide range of different turbulent behaviors. Notably, these flows lead to the formation of rotating, turbulent vortices called Taylor rolls – think of the vertical swirling currents of air in a typhoon that is itself rotating horizontally – the analysis of which have helped establish several core assumptions that are central to the field of fluid dynamics today.

In 1941, the influential mathematician Andrey Kolmogorov published a short paper with an elegant formulation on the complexity of turbulent fluids, wherein he described it as an idealized energy cascade. “If you stir a pool of water with a big spoon,” explains Prof. Chakraborty, “you are adding energy to the water as movement in the form of a large vortex. This vortex splits into smaller and smaller eddies, until finally dissipating as heat. While easy to observe, it was extremely difficult to describe this cascade mathematically – until Kolmogorov.”

However, while Kolmogorov’s celebrated -5/3rd law has been found universal across virtually all turbulent flows, the important TC flows have apparently evaded his framework. Despite many experiments over the past decades, the findings have repeatedly failed to fit the small-scale universality that the -5/3rd law predicts.

Universality regained through data collapse

The inconsistency has long bothered Prof. Chakraborty and other physicists alike. For as he puts it, “how can Kolmogorov’s power law be universal if it doesn’t apply to one of the most important flow regimes in fluid mechanics?” This ‘ugliness’ spurred the development of a new experimental setup at OIST that, while simple in principle, took nine years of engineering ingenuity to work, owing to the difficulty of housing precise sensors within a cylinder spinning at thousands of rpm, surrounded by liquid cooled to a constant temperature encased in another spinning cylinder, all capable of producing turbulent flows at Reynolds numbers – a measure of disorder in turbulent flows – up to 106, among the highest achieved in the world.

“When we analyzed the energy spectra measured through the new OIST-TC setup using the conventional approach, we indeed found that Kolmogorov’s power law does not fit. And that’s when we decided to look beyond the celebrated -5/3rd law, which only applies to the inertial range,” explains Dr. Julio Barros, first author of the paper. The team broadened the scope from the inertial range to the general domain of small-scale flows, including the smallest eddies that dissipate energy into heat. At these scales, Kolmogorov predicted that when accounting for dissipative effects, the rescaled energy spectra collapse onto a single, universal curve F(kη). And for the team, applying this comparatively less-studied aspect of Kolmogorov’s framework paid off: “Rescaling the measurements by the general theory yielded the universality that Kolmogorov predicted. The framework holds.”

This elegant solution to the inconsistency of universality in Kolmogorov’s theory unlocks the potential of turbulent TC flows as powerful tools for studying theoretical and applied fluid mechanics, especially in conjunction with the new OIST-TC setup. Prof. Chakraborty summarizes: “The beauty of TC flow setups is that they are closed systems. No pumps, no obstructions in the flow. We can study the flow of whatever liquid and additive that we desire – sediments, bubbles, polymers, and so forth. And by reconciling TC flows with Kolmogorov’s theory, we now have a solid reference point.”

 

By rehabilitating Taylor-Couette flows with Kolmogorov’s small-scale universality, researchers have created a powerful baseline for the study of various phenomena involving rotational turbulence, both in theory and practice, like weather systems, engines, or planets forming around distant stars.

Credit

Typhoon and propeller wake: NASA via Wikimedia Commons (Public Domain). Accretion disk visualization: P. Marenfeld and NOIRLab/NSF/AURA via Wikimedia Commons (CC BY 4.0)

Taylor-Couette flows at OIST-TC [VIDEO] 

Spinning liquid in the OIST-TC flow setup at different levels of turbulent disorder measured in Reynolds number (Rei). Taylor rolls – rows of vortices that are themselves rotating – are clearly visible in the post-processed footage, where the previous frame has been subtracted from the present.

Credit

Butcher et al., (2024) Flow 4 E30.

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Journal

Science Advances

DOI

10.1126/sciadv.ady4417 

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Universality in the small scales of turbulent Taylor–Couette flow

Article Publication Date

5-Nov-2025