The α7 nicotinic acetylcholine receptor is a pentameric ligand-gated ion channel that mediates cholinergic signaling. It has attracted attention because of its roles in neurological disorders and inflammation, which have encouraged the development of synthetic effectors. Those compounds include orthosteric agonists that act on the receptor’s extracellular domain and positive allosteric modulators, known as PAMs, that act in its transmembrane domain. The new research examined endogenous polyunsaturated free fatty acids, or PUFAs, whose ability to modulate α7 receptor function was known but whose site of action had remained unresolved.

Using two-electrode voltage-clamp electrophysiology, Awad and colleagues characterized a series of PUFAs and established structure–activity relationships governing their negative allosteric modulation. The potency of inhibition depended on the length of the hydrophobic tail, the number of double bonds in that tail and the polarity of the head group. These results identified the tested lipids as negative allosteric modulators, or NAMs, and showed that relatively small changes in molecular structure can alter how strongly they suppress receptor activity.

The researchers then combined coarse-grained molecular-dynamics simulations with mutational analysis to search for the molecular basis of that activity. Two candidate locations emerged within the receptor’s transmembrane domain. A major “structural” site lies within the M1 and M4 helices of a single subunit, but mutations and simulations indicated that this location does not contribute to the NAM effect. By contrast, the smaller M3-positive/M1-negative site lies at an interface between adjacent subunits. Mutations in this region strongly impaired NAM activity, making it the principal functional site identified by the study rather than the larger intrachain pocket.

The functionally important intersubunit site overlaps the location associated with synthetic PAMs. This overlap establishes a common structural hotspot at which chemically different modulators can produce opposing effects on the α7 receptor: the tested PUFAs inhibit it, whereas PAMs enhance it. The study did not demonstrate effects in people or establish clinical consequences, and the findings concern the receptor systems and compounds tested. Its principal implication is for the molecular design of α7 receptor modulators and for understanding how endogenous lipid regulation may influence receptor function.

Subject of Research: Molecular mechanisms of polyunsaturated fatty-acid negative allosteric modulation of the α7 nicotinic receptor

Article Title: Pharmacological analysis of negative allosteric modulation of the α7 nicotinic receptor by polyunsaturated free fatty acids

Article References: Awad, N., Sandberg, J., Barilone, N., Lustig, M., Corringer, P.-J., Brannigan, G., & Prevost, M. S. (2026). Pharmacological analysis of negative allosteric modulation of the α7 nicotinic receptor by polyunsaturated free fatty acids. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06498-2

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06498-2

Keywords: α7 nicotinic receptor, polyunsaturated fatty acids, negative allosteric modulators, electrophysiology, molecular dynamics, mutational analysis, transmembrane binding site, ligand-gated ion channel, cholinergic signaling, Pharmacological, analysis, negative

The research team, led by investigators at Brigham and Women’s Hospital and Harvard Medical School including M. Elizabeth Moss and Bruce Levy, applied a technique known as lipid mediator metabololipidomics, using liquid chromatography coupled with tandem mass spectrometry, to profile hundreds of fat-derived signaling molecules in blood plasma. Their subjects came from two cohorts totaling 106 participants with recent SARS-CoV-2 infection. Sixty-four went on to meet clinical criteria for Long COVID, defined by the National Academies as an infection-associated chronic condition persisting at least three months, while 42 fully recovered. By comparing lipid profiles between these groups at different time points, the researchers could ask whether the chemistry of inflammation resolution differs in people who develop the syndrome.

The logic behind the approach rests on a well-established but underappreciated branch of immunology. Essential polyunsaturated fatty acids such as arachidonic acid, docosahexaenoic acid, and eicosapentaenoic acid are not merely fuel; they are raw materials for an entire pharmacopeia of signaling molecules. Lipoxygenase enzymes convert these fats into specialized pro-resolving mediators, including lipoxins, resolvins, protectins, and maresins, which actively coordinate the return of tissues to homeostasis after injury or infection. In a self-limited inflammatory response, the body performs a metabolic class switch, pivoting from pro-inflammatory prostaglandins and leukotrienes to these pro-resolving mediators. If that switch fails, inflammation can smolder indefinitely.

The first major finding came from the acute phase. In samples drawn within 30 days of a positive test, participants who would later develop Long COVID showed significantly elevated levels of three products of the 12-lipoxygenase enzyme: 12-hydroxyeicosatetraenoic acid from arachidonic acid, 14-hydroxydocosahexaenoic acid from DHA, and 12-hydroxyeicosapentaenoic acid from EPA. This association held even after the researchers statistically controlled for the severity of the initial infection, gender, and self-reported race. A composite score aggregating all 12-lipoxygenase products was likewise a significant predictor of later Long COVID, as were aggregate measures of arachidonic acid and EPA metabolism. Notably, the pattern was not simply a byproduct of generalized platelet activation, since thromboxane products of platelet cyclooxygenase were not elevated.

The 12-lipoxygenase signal is intriguing because the enzyme is highly expressed in platelets and sits at the crossroads of clotting and inflammation. Acute SARS-CoV-2 infection is known to trigger endothelial inflammation, angiogenesis, platelet activation, and microthrombi, and the new data suggest that selective 12-lipoxygenase activation, which can occur through thrombin receptors, collagen signaling, or immune complexes independently of the cyclooxygenase pathway, may link these processes to the later development of persistent symptoms. The researchers also observed that reduced levels of interleukin-22 and of resolvin D1, a DHA-derived pro-resolving mediator, in the acute phase predicted Long COVID risk, hinting that a deficit in resolution chemistry may accompany the excess lipoxygenase activity.

After the first month, the picture shifted. In cross-sectional samples collected more than a month post-infection, the correlation structure of the lipidome itself had changed. In recovered participants, intermediates derived from the same parent fatty acid tended to rise and fall together, indicating that metabolism was organized around the available fats. In Long COVID participants, this within-family correlation was lost for the DHA and EPA families, while a strong signature of 5-lipoxygenase activation emerged across fatty acid families. The authors interpret this as an uncoupling of PUFA metabolism in Long COVID, in which enzyme activity, rather than substrate availability, drives the lipid profile, consistent with disrupted lipid mediator class switching.

Longitudinal sampling over the first year after infection sharpened the temporal picture. Levels of 15-HETE, an arachidonic acid product, remained significantly higher in Long COVID participants, while resolvin D1 was consistently lower; indeed, resolvin D1 was undetectable in 14.3 percent of Long COVID samples but in none of the recovered samples. Several metabolites, including 17-HDoHE, 14-HDoHE, and lipoxin A4, showed significant interactions with time, diverging between the groups in the three-to-nine-month window after infection. These trajectories suggest that lipoxygenase activity remains elevated for months in Long COVID even as production of key pro-resolving mediators stays depressed, a combination that could sustain defective resolution of inflammation.

The study also intersected with another leading hypothesis about Long COVID: persistence of viral proteins. Using ultra-sensitive single molecule array assays, the researchers detected SARS-CoV-2 spike protein in a subset of both Long COVID and recovered participants long after acute infection, and unsupervised clustering of the multidimensional data separated samples largely by the presence or absence of spike. Within Long COVID samples, plasma levels of 17-HDoHE correlated significantly with spike protein abundance, a relationship absent in recovered participants. When the team clustered Long COVID samples using lipid mediators alone, four distinct biochemical subtypes emerged, one enriched in 17-HDoHE and another almost entirely lacking resolvin D1, hinting that Long COVID may encompass several metabolically distinct endotypes rather than a single disease process.

The authors are careful to note limitations. The cohorts were modest in size, particularly the recovered group in the longitudinal arm, and clinical status was determined by chart review rather than validated survey instruments. Medication use, especially aspirin, which can suppress 12-lipoxygenase activity, and dietary intake of omega-3 fatty acids were not captured, and parent fatty acid levels were not quantified. Many bioactive mediators fell below detection limits in plasma, prompting the authors to call for serum-based analyses that could better distinguish deficient substrate from dysregulated enzymatic machinery.

Even so, the findings open concrete paths forward. Elevated 12-lipoxygenase products in the first month of infection could serve as an early biomarker identifying patients at risk of Long COVID before symptoms become chronic, and the results dovetail with an ongoing randomized controlled trial, ARACOV-02, testing whether supplementation with pro-resolving mediator precursors such as 17-HDoHE, 14-HDoHE, and 18-HEPE, combined with telerehabilitation, can improve outcomes in established disease. More broadly, the work reframes Long COVID as a disorder of failed inflammatory resolution, a concept that may ultimately connect viral persistence, platelet biology, and fat metabolism into a single mechanistic story, and offers researchers a biochemical handle on one of the pandemic’s most stubborn legacies.

Subject of Research: Lipoxygenase-catalyzed metabolism of essential polyunsaturated fatty acids in Long COVID

Article Title: Long COVID is associated with lipoxygenase-catalyzed metabolism of essential polyunsaturated fatty acids

Article References: Moss, M. E., Pons, S., Tavares, L. P., Tang, Y., Alter, G., Karlson, E., Baden, L., Walt, D. R., & Levy, B. D. (2026). Long COVID is associated with lipoxygenase-catalyzed metabolism of essential polyunsaturated fatty acids. iScience, 29(11), Article 117581. https://doi.org/10.1016/j.isci.2026.117581

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117581

Keywords: Long COVID, SARS-CoV-2, lipoxygenase, polyunsaturated fatty acids, specialized pro-resolving mediators, lipidomics, inflammation resolution, resolvin D1, platelets, spike protein, 12-HETE, iScience

The appeal of microalgae in wastewater treatment lies in their basic biology. These photosynthetic microorganisms feed on exactly the compounds that make sewage an environmental hazard: nitrogen and phosphorus compounds that otherwise drive eutrophication, the oxygen-depleting overgrowth of aquatic ecosystems. Conventional treatment plants remove these nutrients through energy-intensive physicochemical and biological processes that also generate secondary sludge. Microalgae, by contrast, assimilate ammonium and phosphate directly into their cells, converting pollutants into biomass that can then be harvested for feed, fertilizers, nutraceuticals, or biofuels. The catch has always been economics: large-scale algal cultivation demands enormous quantities of freshwater and synthetic nutrients, precisely the inputs that wastewater could replace.

The Brazilian team, led by researchers at the Federal University of Pelotas, tackled this challenge by working with a strain isolated directly from local wastewater, on the logic that microorganisms adapted to local conditions and effluent variability should outperform laboratory strains in real-world systems. Molecular identification confirmed the isolate as Tetradesmus obliquus: sequencing of the 18S ribosomal RNA gene revealed 99.69 percent identity with reference sequences, and phylogenetic analysis placed the strain, designated CICLO_00125, within a well-supported Tetradesmus obliquus clade. Microscopy showed the characteristic four-cell coenobia and ellipsoidal cells typical of the species, a genus already recognized for rapid growth, high nutrient uptake, and metabolic plasticity in eutrophic environments.

The experimental design paired two wastewater matrices with three inoculation densities. Raw domestic wastewater, collected before any treatment, was compared with primary-treated wastewater that had undergone mesh filtration, chemical flocculation with aluminum sulfate, and sedimentation. Each effluent was inoculated with the alga at 10, 20, or 30 percent of the culture volume, and the six combinations were cultivated for 14 days in aerated flasks under continuous LED illumination, alongside uninoculated controls. This setup allowed the researchers to disentangle two variables that are rarely evaluated together: how much the effluent has been pretreated, and how many algal cells are added at the start.

The two effluents turned out to be strikingly different cultivation environments. Raw wastewater carried higher concentrations of ammonium, phosphate, iron, and manganese, along with high turbidity that limits light penetration. Primary treatment removed nearly all the suspended particles and trace metals, dropping optical density from 0.34 to 0.07 and pushing iron and manganese below detection, but it also stripped away some nutrients, reducing phosphate from 7.22 to 4.03 milligrams per liter. The clarified effluent offered better light for photosynthesis but a leaner nutritional menu, a trade-off that shaped everything that followed.

The standout bioremediation result came from the lowest inoculum density in treated wastewater. There, the alga removed 62.46 percent of ammonium and an impressive 98.56 percent of phosphate over 14 days, while simultaneously achieving the highest specific growth rate of the entire study, 0.16 per day, and the highest biomass productivity, 42.54 milligrams per liter per day. Counterintuitively, adding more cells did not improve removal. At the two higher inoculum densities in treated wastewater, phosphate removal collapsed to 42.80 percent and a mere 7.59 percent, even though final biomass concentrations were comparable. The researchers attribute this to self-shading: denser cultures reduce the light reaching each individual cell, and light drives the energy-hungry active transport of phosphate and its storage as polyphosphate, the so-called luxury uptake mechanism. High pH values above 10 in those dense cultures confirmed that bulk photosynthesis continued, pointing the finger at per-cell irradiance rather than culture-wide metabolic failure.

Nutrient removal in the raw wastewater followed a different logic. Turbidity constrained algal photosynthesis, but the effluent’s rich organic load fueled resident bacteria, which likely contributed substantially to ammonium transformation through nitrification and other microbial processes. The highest volumetric ammonium removal rate of the study, 3.40 milligrams per liter per day, occurred in raw wastewater at the highest inoculum density, under conditions least favorable to algal photosynthesis, a hint that the microalgae-bacteria consortium, not the alga alone, was doing much of the work. The authors are careful to note that bacterial contributions were not directly quantified, since nitrogen fluxes and community composition were not measured, but the pattern is consistent with a growing literature on metabolically coupled algal-bacterial systems, in which algae supply oxygen for bacterial nitrification while bacteria release carbon dioxide that feeds algal growth.

Metal removal added another dimension to the bioremediation story. Iron concentrations fell by up to 99 percent in inoculated treatments, and in the treated wastewater both iron and manganese dropped below detection limits, with manganese removal efficiencies of 80 to 100 percent. Because removal did not scale with inoculum density, the researchers conclude that a rapid, saturable passive biosorption onto cell-surface and exopolysaccharide functional groups dominates the process, followed by slower intracellular uptake, with abiotic co-precipitation of metal hydroxides at elevated pH contributing as well. The consistently lower residual metal concentrations in inoculated cultures compared with controls mark the alga’s contribution clearly.

Perhaps the most commercially intriguing finding is that the two wastewaters yielded biochemically distinct biomass. Biomass grown in raw wastewater accumulated significantly more carbohydrates, up to 32.68 percent, and more chlorophyll, reaching 14.46 milligrams per gram, likely a photoacclimation response to the dim, turbid environment. Biomass from treated wastewater, especially at the lowest inoculum, contained up to 45.83 percent protein, a level comparable to conventional protein crops, and a lipid fraction in which polyunsaturated fatty acids made up 72.70 to 78.90 percent of the total, dominated by alpha-linolenic and linoleic acids, the omega-3 and omega-6 essential fatty acids prized in nutrition. The researchers link this PUFA enrichment to the thylakoid membrane lipids that proliferate in fast-growing, light-replete cells. Putative long-chain PUFAs, including signals matching docosahexaenoic acid, appeared at levels higher than typically reported for this genus, though the authors caution that these identifications are preliminary and based on relative peak areas rather than absolute yields.

The study stops short of declaring the technology ready for prime time. Harvesting dilute algal cultures remains an energy bottleneck, effluent composition varies seasonally, and non-sterile cultivation carries contamination risks, while the fate of trace contaminants in wastewater-grown biomass would need application-specific assessment before any use in feed or food. Still, the demonstration that a single, locally adapted algal strain can clean real sewage, remove trace metals, and produce biomass whose composition can be steered between carbohydrate-rich and protein-and-PUFA-rich profiles simply by choosing the effluent and the inoculum density, is a meaningful step toward wastewater treatment plants that do not just dispose of waste but harvest it. Pilot-scale trials with techno-economic and life-cycle analysis are the logical next test for this circular bioeconomy vision.

Subject of Research: Bioremediation of domestic wastewater by a native Tetradesmus obliquus strain for production of protein- and PUFA-rich microalgal biomass

Article Title: Integration of domestic wastewater and native Tetradesmus obliquus for bioremediation and production of biomass rich in protein and polyunsaturated fatty acids

Article References: do Amaral, D. S., Werner, L., Pagano, A. D., Leitzke, A. F., Hakbart Boneman, D., La Rosa Novo, D., Nunes, L. S., Bueno, D. T., Laporta, L. V., Crizel, R. L., Filho, A. V., Campos, V. F., & de Pereira, C. M. P. (2026). Integration of domestic wastewater and native Tetradesmus obliquus for bioremediation and production of biomass rich in protein and polyunsaturated fatty acids. Environmental Science and Pollution Research, 33(30), 15417-15442. https://doi.org/10.1007/s11356-026-38213-w

Image Credits: AI Generated

DOI: 10.1007/s11356-026-38213-w

Keywords: Tetradesmus obliquus, microalgae, wastewater treatment, bioremediation, polyunsaturated fatty acids, protein, biomass productivity, inoculum density, circular bioeconomy, nutrient removal, eutrophication, biosorption

The research team began with the human disease itself. Examining liver tissue from patients with Wilson disease, they documented a constellation of metabolic injuries: impaired antioxidant capacity, abundant markers of lipid peroxidation, and, crucially, a coordinated downregulation of two linked molecules, the nuclear receptor PPARα and its downstream target FABP1, the liver fatty acid-binding protein. The same pattern appeared in the Atp7b-deficient mouse model, the standard animal proxy for the disease, and it was visible at both the transcriptomic and proteomic levels. That consistency across species and measurement platforms suggested the pair was not an incidental casualty of liver damage but an active participant in it.

To test causality, the investigators turned to hepatocytes grown in culture and exposed them to copper. The metal accumulated in the nuclear-enriched fraction of the cells, consistent with earlier reports that excess copper impairs hepatic nuclear receptor function, and it repressed PPARα and FABP1 expression in a time-dependent manner. With the protective axis weakened, the cells became strikingly vulnerable to RSL3, a chemical tool that inhibits the lipid-repair enzyme GPX4 and thereby triggers ferroptosis. Copper exposure lowered the threshold at which RSL3 killed the cells and amplified lipid peroxidation, the biochemical signature of the ferroptotic process.

The team then ran the experiment in reverse. Silencing PPARα or FABP1 in hepatocytes reproduced the copper effect almost exactly, lowering the resistance of the cells to ferroptotic stress and boosting peroxidation. Conversely, pharmacological inhibition of ferroptosis partially rescued the copper-treated cells, confirming that the cell death pathway in play was ferroptosis rather than apoptosis or necrosis. Together, the gain-of-function and loss-of-function data make a strong argument that the PPARα–FABP1 axis is not merely correlated with copper toxicity but functionally required for hepatocyte survival under copper overload.

Why would losing FABP1 matter so much? The protein is among the most abundant in the hepatocyte cytosol, where it shuttles fatty acids and, importantly, buffers polyunsaturated fatty acids, the very lipid species most prone to peroxidation. Prior work has shown that L-FABP directly interacts with PPARα in primary hepatocytes and that the protein carries intrinsic antioxidant activity. When FABP1 levels fall, polyunsaturated fatty acids are left exposed to oxidative attack, and the resulting peroxidized phospholipids, particularly those derived from arachidonic acid, are known to be the navigational signals that steer cells toward ferroptosis.

The lipidomics evidence reinforced this mechanistic picture. By integrating previously published lipidomic datasets, the researchers found that peroxidized polyunsaturated fatty acids accumulate in Wilson disease, matching the oxylipin profiles reported in patient plasma and in mouse models of the disorder. In their own experiments, overexpressing FABP1 mitigated arachidonic acid–driven lipid peroxidation and protected cells from ferroptosis. In other words, restoring the fat-binding protein partially rebuilt the cellular firewall that copper had torn down, providing a proof of concept that the axis can be targeted therapeutically.

The clinical implications extend beyond mechanism into prognosis. The team measured hepatic FABP1 expression and circulating FABP1 levels in their patient cohort and found that both declined as disease severity increased. Lower FABP1 was associated with greater inflammatory activity and more advanced fibrosis stage, and the circulating levels showed moderate predictive value for adverse outcomes. If these findings hold up in larger and more diverse cohorts, a simple blood measurement of FABP1 could eventually complement existing tools for staging Wilson disease and flagging patients at risk of rapid progression, an appealing prospect in a condition where early diagnosis dramatically alters the trajectory.

The study also reframes a long-running debate about how copper kills liver cells. Recent literature has highlighted cuproptosis, a copper-triggered cell death mechanism involving mitochondrial protein aggregation, as a candidate explanation for copper toxicity. The new data do not settle that debate, but they add a parallel and arguably better-substantiated route: copper suppresses a nuclear receptor program, the loss of that program strips away lipid protection, and the cell slides into ferroptosis. Notably, the PPARα–FABP1–ferroptosis connection has precedent elsewhere; downregulation of the axis has been implicated in ferroptosis in IgA nephropathy and in the lipid-rich microenvironment of gastric cancer metastasis, suggesting a broadly conserved vulnerability that Wilson disease happens to exploit.

Therapeutically, the findings point in two directions. The established standard of care for Wilson disease, copper chelation and zinc therapy to block metal absorption, remains the foundation, and the new work does not challenge it. But the study suggests that patients may benefit from approaches that shore up the ferroptosis defense system directly, whether by activating PPARα, restoring FABP1, or deploying ferroptosis inhibitors, particularly during acute presentations when copper levels cannot be lowered overnight. Ferroptosis has already been implicated as an inflammatory trigger in other liver diseases, including nonalcoholic steatohepatitis, so agents that dampen lipid peroxidation could have value across a spectrum of hepatic injury, with Wilson disease as a genetically defined setting in which to test them.

Caveats remain. The rescue effects of ferroptosis inhibition were partial, indicating that copper inflicts damage through additional pathways that the PPARα–FABP1 axis does not capture. The predictive value of circulating FABP1 was moderate rather than decisive, and the clinical cohort, while ethically approved and conducted under the Declaration of Helsinki, will need expansion before biomarker claims become practice. Still, the study delivers something Wilson disease research has lacked: a coherent, experimentally validated mechanism that connects the metal, a master metabolic regulator, a fat-binding protein, and a defined mode of cell death, all anchored to measurable correlates of human disease severity. It turns a decades-old question, how copper destroys the liver, into a set of answerable, and potentially druggable, molecular problems.

Subject of Research: Copper-induced suppression of the PPARα–FABP1 axis and ferroptosis in Wilson disease

Article Title: Copper-induced suppression of the PPARα–FABP1 axis sensitizes hepatocytes to ferroptosis in Wilson disease

Article References: Li, Y., Wu, Y., Zhou, Y., Zhao, L., Xu, Z., Zhang, Y., & Zhou, N. (2026). Copper-induced suppression of the PPARα–FABP1 axis sensitizes hepatocytes to ferroptosis in Wilson disease. Journal of Molecular Medicine, 104(1), Article 119. https://doi.org/10.1007/s00109-026-02725-2

Image Credits: AI Generated

DOI: 10.1007/s00109-026-02725-2

Keywords: Wilson disease, copper overload, ferroptosis, PPARα, FABP1, lipid peroxidation, hepatocytes, liver fibrosis, ATP7B, polyunsaturated fatty acids, nuclear receptor, biomarker

The central character in this story is NHR-68, a nuclear hormone receptor in the worm that belongs to a family of transcription factors with close evolutionary cousins throughout the animal kingdom, including humans. Nuclear hormone receptors are molecular sensors that bind small lipid-like molecules and then switch entire suites of genes on or off. Because they sit at the junction of metabolism and gene regulation, they are ideally positioned to answer one of the most fundamental questions in immunology: when an animal’s energy reserves are limited, how does the body decide how much to invest in defense? The new study shows that NHR-68 is one of the answers, acting in parallel with a related receptor called NHR-10 to control genes involved in polyunsaturated fatty acid metabolism inside the intestine.

What makes the finding striking is the dual output of this single regulatory node. When the researchers removed NHR-68 from the worms, the animals lost their ability to maintain proper levels of linoleic acid, and that metabolic disruption had a surprising consequence: the worms became impaired in their pathogen avoidance behavior. In laboratory assays, healthy C. elegans can sense dangerous bacteria and move away from them, a learned and innate behavioral defense that complements the molecular weapons deployed by their cells. Worms lacking NHR-68 were worse at this evasion, suggesting that the fat chemistry of the gut is somehow whispering instructions to the nervous system about which microbes to avoid.

The team then tested this idea from several directions, and the results converged on the same conclusion. When they supplemented the worms’ diet with linoleic acid, the avoidance behavior was restored, indicating that the fatty acid itself is a sufficient driver of the behavior. Even more telling were the genetic experiments targeting the worm’s fat synthesis machinery. Inhibiting fat-3, a gene required for desaturating fatty acids in a way that elevates linoleic acid levels, enhanced the worms’ pathogen avoidance. Conversely, blocking fat-2, which sits upstream in the pathway and is required to synthesize linoleic acid in the first place, diminished the behavior. In other words, the more linoleic acid available, the better the worm avoided danger; the less available, the worse it performed. This dose-like relationship between a dietary lipid and a survival behavior is exactly the kind of clean causal chain that experimental biologists dream of finding.

Localization experiments added another crucial layer. NHR-68, the researchers showed, acts specifically in the intestine, the organ that in C. elegans serves as both the primary metabolic hub and a major immune tissue. From this intestinal vantage point, changes in lipid metabolism influence a neural circuit that depends on AWC, a pair of olfactory sensory neurons well known to worm neurobiologists for their role in detecting volatile cues. The implication is that the gut and the brain are in constant metabolic conversation, and that the content of that conversation, carried at least in part by fatty acid signals, shapes how the animal perceives and responds to threats in its environment. This is a form of intestine-to-neuron communication that transforms a metabolic state into a behavioral decision.

But the story does not end with behavior. NHR-68 also turned out to be a brake on the worm’s classical molecular immune responses. The receptor suppresses the activation of two major defense pathways: PMK-1, a p38 MAPK signaling cascade that orchestrates transcriptional responses to infection, and DAF-16, the worm’s FOXO transcription factor that governs stress resistance and longevity. These pathways are the heavy artillery of invertebrate immunity, driving the expression of antimicrobial genes and other protective programs. By holding them in check, NHR-68 appears to enforce a balance, preventing the energetically expensive molecular defense machinery from running at full throttle when behavioral avoidance, a cheaper strategy, might suffice.

This trade-off logic is at the heart of what immunologists call defense allocation. Mounting a molecular immune response costs energy: it requires transcription, translation, and cellular remodeling, all of which draw on the same finite pools of nutrients and metabolic capacity that the animal needs for growth, reproduction, and maintenance. Fleeing a pathogen, by contrast, is comparatively cheap. The new findings suggest that the worm’s physiology has evolved a mechanism to weigh these options, using intestinal lipid status as the currency of the decision. When linoleic acid homeostasis is intact and NHR-68 is active, the animal invests in avoidance behavior while keeping molecular defenses moderated. When the system is perturbed, the balance shifts, and the consequences ripple through both the immune system and the nervous system simultaneously.

The evolutionary implications are considerable. Nuclear hormone receptors, p38 MAPK pathways, and FOXO transcription factors are all conserved across the animal tree, and linoleic acid is an essential fatty acid for humans as well as worms. While no one should assume that the exact circuit operates unchanged in mammals, the study provides a proof of principle that gut lipid metabolism can be wired directly into neural threat-detection circuits and immune regulation through a defined transcriptional mechanism. It adds momentum to a growing body of research on the gut-brain axis, a field that has largely focused on neural signals, hormones, and microbial metabolites but is now revealing that the lipid composition of the intestine itself may carry instructive information to the nervous system.

There are also practical horizons. If lipid metabolism influences pathogen avoidance and immune tuning in a genetically tractable animal, then similar metabolic levers might exist in other species, raising questions about how diet, fatty acid supplementation, and metabolic disease shape infection risk and behavioral responses to contaminated environments. The finding that elevating linoleic acid enhances avoidance, while blocking its synthesis diminishes it, points to specific enzymatic nodes, such as the fat-2 and fat-3 desaturases, whose activity levels could in principle tune an animal’s defensive posture. Whether pharmacological or dietary manipulation of these nodes could influence immunity in more complex organisms remains an open question, but the worm data provide a concrete molecular starting point for such investigations.

For now, the study stands as an elegant demonstration that immunity is not a single system but a coordinated portfolio of strategies, and that the coordination is written into the metabolism of the gut. A tiny worm, sensing a patch of dangerous bacteria, makes its escape decision with the help of a fatty acid whose levels are set by a nuclear receptor in its intestine, and that same receptor quietly arbitrates how aggressively the animal’s cells will fight if avoidance fails. It is a vivid reminder, delivered by one of biology’s most reliable model organisms, that the line between metabolism, behavior, and immunity is far thinner than textbooks once suggested, and that understanding host defense requires following the fat.

Subject of Research: Intestinal lipid metabolism and gut-brain signaling in the control of behavioral and molecular immunity in C. elegans

Article Title: Intestinal lipid metabolism controls molecular and behavioral immunity through NHR-68 and gut–brain signaling in Caenorhabditis elegans

Article References: Ren, J., Sang, Y., Kim, Y.-M., Nakayasu, E. S., & Aballay, A. (2026). Intestinal lipid metabolism controls molecular and behavioral immunity through NHR-68 and gut–brain signaling in Caenorhabditis elegans. PLOS Biology, 24(9), e3004026. https://doi.org/10.1371/journal.pbio.3004026

Image Credits: AI Generated

DOI: 10.1371/journal.pbio.3004026

Keywords: Caenorhabditis elegans, NHR-68, linoleic acid, gut-brain axis, pathogen avoidance, innate immunity, nuclear hormone receptor, PMK-1 p38 MAPK, DAF-16 FOXO, polyunsaturated fatty acids, intestinal metabolism, PLOS Biology

Aldolase catalyzes the fourth step of glycolysis, cleaving fructose-1,6-bisphosphate into two three-carbon sugars, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Because these triose phosphates feed both the lower half of glycolysis and the glycerol backbone used to build lipids, the enzyme sits at a critical junction of central carbon metabolism. Most of what is known about aldolase comes from medical research, particularly cancer biology, where studies have shown that blocking aldolase can push glucose-6-phosphate into the pentose phosphate pathway, increasing the production of NADPH, the reducing power that cells use for biosynthesis. The Xiamen University team, led by Yiting Zhang and Xueping Ling, asked whether the same logic could be applied to a microbe whose entire commercial value depends on how much reducing power and carbon skeleton it can pour into fatty acid synthesis.

To find out, the researchers constructed a knockout strain by replacing the aldolase gene, designated ALDOA, with a bleomycin resistance cassette through homologous recombination. They amplified roughly 420-base-pair sequences flanking the gene, ligated them into the pBlue-zeo plasmid around the resistance marker, and introduced the construct into wild-type cells by electroporation. Transformants were selected on plates containing 50 milligrams per liter of bleomycin, and PCR sequencing of the homologous arms confirmed that the native gene had been successfully replaced. The resulting strain, called ΔALDOA, was then compared with the wild type over a 168-hour shake-flask fermentation using glucose-based medium.

The immediate consequences of the deletion were negative for bulk productivity. Final biomass in the knockout strain was 9.6 percent lower than the wild-type maximum, and total lipid production fell by 23.2 percent. During active growth the deficits were even larger: at 96 hours the mutant’s cell dry weight was up to 40.61 percent below the wild type, and at 72 hours its lipid yield lagged by as much as 49.34 percent. Glucose consumption told a similar story. The wild-type strain essentially exhausted the sugar supply by 120 hours, whereas the knockout had used only about half of it at that point and needed until 168 hours to finish. Intriguingly, the mutant actually consumed glucose faster than the wild type in the earliest phase of cultivation, apparently ramping up overall metabolism to compensate for the metabolic bottleneck, before its impaired glycolysis caught up with it in the middle and later stages.

The fatty acid composition, however, moved in a very different direction. At 120 hours the proportion of saturated fatty acids in the knockout strain was about 17.4 percent lower than in the wild type, driven mainly by reductions in the C16:0 and C14:0 species. Polyunsaturated fatty acids, including DHA, docosapentaenoic acid, and eicosapentaenoic acid, rose by 28.0 percent overall, with DHA itself up 22.9 percent and EPA up a remarkable 75.0 percent. When the team broke the lipid pool down into triglycerides and phospholipids, they found that polyunsaturated fatty acids are mostly stored in triglycerides, at 35 to 48 percent of that fraction, while phospholipids carry 10 to 15 percent and contain no detectable EPA at all. The knockout boosted the polyunsaturated content of triglycerides specifically, with DHA rising 27.4 percent at 72 hours and 20.8 percent at 120 hours, while the main saturated species, C16:0, dropped by 46.5 percent and 36.0 percent at the same time points.

Phospholipidomics provided a mechanistic explanation rooted in how DHA travels through the cell. Phosphatidylcholine, the most abundant phospholipid in Schizochytrium at roughly half of the total, is known to be the first docking site for newly synthesized DHA before the fatty acid is transferred to triglycerides for storage. In the knockout strain, the proportion of phosphatidylcholine was 11.5 percent higher than the wild type at 72 hours and 7.5 percent higher at 120 hours, and lysophosphatidylcholine, its precursor in the glycerophosphorylcholine acylation pathway, reached 4.8 times the control level at 72 hours. Meanwhile, phosphatidylglycerol, a phospholipid tied to cell growth, collapsed by 92.2 percent at 72 hours, and phosphatidylinositol, phosphatidylserine, and phosphatidic acid all declined as well. Because these species are built through the Kennedy pathway from dihydroxyacetone phosphate-derived precursors, their depletion directly reflects the loss of aldolase activity upstream.

Gene expression analysis reinforced the picture. Transcripts of the fatty acid synthase gene, which produces saturated fatty acids, fell in the mutant, while the chain length factor gene of the anaerobic polyketide synthase cluster, responsible for elongating polyunsaturated chains, rose sharply in the middle and later stages of fermentation. The gene for glucose-6-phosphate dehydrogenase, the gateway enzyme of the pentose phosphate pathway, followed a similar pattern, indicating enhanced flux through that route and a greater supply of NADPH for fatty acid desaturation and elongation. Transcripts of phosphatidic acid phosphatase and diacylglycerol acyltransferase, the enzymes that convert phosphatidic acid into triglycerides via the Kennedy pathway, decreased, whereas the genes for phospholipid diacylglycerol choline phosphate transferase, or PDAT, and lysophosphatidylcholine acyltransferase, or LPCAT, were strongly upregulated. Together these shifts suggest the mutant builds its triglycerides increasingly through the phosphatidylcholine route, shuttling DHA from phospholipid storage into neutral lipid reserves.

Metabolomics by gas chromatography-mass spectrometry identified 35 differential metabolites that mapped the rewiring across glycolysis, the tricarboxylic acid cycle, the pentose phosphate pathway, and amino acid and sterol synthesis. Sugar alcohols associated with the oxidative pentose phosphate route surged, with arabitol up 4.06-fold and ribitol up 7.84-fold at 120 hours. The knockout strain also accumulated protective metabolites: inositol, a signaling molecule against oxidative stress, rose threefold, and mannitol, a hydroxyl radical scavenger, increased 1.23-fold, while glycine rose to supply precursors for glutathione synthesis. Flow cytometry using a fluorescent probe confirmed that reactive oxygen species were lower in the mutant at both measured time points. Since polyunsaturated fatty acids are vulnerable to free-radical oxidation, the reduced oxidative environment plausibly helps preserve the DHA the cells do make, complementing the increased reducing power available for synthesizing it in the first place.

The authors propose a coherent metabolic model: deleting ALDOA weakens glycolysis and the TCA cycle, slowing growth, and starves the Kennedy pathway of dihydroxyacetone phosphate, cutting total lipid and phospholipid output. In compensation, carbon is pushed into the pentose phosphate pathway, raising NADPH for polyunsaturated fatty acid synthesis, while the cell reinforces the glycerophosphorylcholine acylation route and PDAT-mediated transfer so that more DHA is bound to phosphatidylcholine and then moved into triglycerides. The trade-off is clear, with less biomass but a richer omega-3 profile per cell. The team notes that future work using CRISPR or RNA interference to tune, rather than abolish, aldolase expression could improve DHA accumulation without the growth penalty, offering a new metabolic engineering strategy for one of the world’s most important microbial oil producers.

Subject of Research: Aldolase gene disruption and carbon flux redistribution for DHA synthesis in Schizochytrium

Article Title: Functions of aldolase in lipid synthesis of Schizochytrium sp. by gene disruption to switch carbon metabolism

Article References: Zhang, Y., Wu, X., Guo, X., Li, K., Lu, Y., Lin, X., & Ling, X. (2024). Functions of aldolase in lipid synthesis of Schizochytrium sp. by gene disruption to switch carbon metabolism. Blue Biotechnology, 1(1), Article 17. https://doi.org/10.1186/s44315-024-00014-6

Image Credits: AI Generated

DOI: 10.1186/s44315-024-00014-6

Keywords: Schizochytrium, aldolase, DHA, polyunsaturated fatty acids, glycolysis, pentose phosphate pathway, carbon flux, metabolic engineering, phospholipids, triglycerides, NADPH, marine biotechnology