The research team, led by Shuning Liu and Chang Liu of Beijing Sport University together with collaborators from Lanzhou University, Wuhan Sports University and other institutions, set out to determine whether syringaresinol could activate a well-known signaling circuit that connects muscle and fat tissue. This circuit runs through SIRT1, a NAD-dependent deacetylase enzyme long associated with calorie restriction and mitochondrial health, which in turn activates PGC-1α, the master regulator of mitochondrial biogenesis. PGC-1α then promotes expression of FNDC5, the membrane protein whose cleaved extracellular fragment is the hormone irisin. Irisin released into the bloodstream acts on adipose tissue, encouraging white fat cells to adopt brown-fat-like characteristics—producing heat, burning calories, and reshaping systemic energy balance.

In the laboratory phase of the study, the team used differentiated C2C12 myotubes, the standard cell model for mature skeletal muscle, and treated them with syringaresinol alongside two chemical reference compounds: SRT1720, a potent SIRT1 activator, and EX-527, a selective SIRT1 inhibitor. The results were striking. Myotubes exposed to syringaresinol showed increased irisin-related readouts, elevated ATP content, and higher citrate synthase activity, a classic indicator of enhanced mitochondrial oxidative capacity. At the molecular level, the compound produced transcriptional changes consistent with SIRT1/PGC-1α/FNDC5 activation and increased the abundance of both SIRT1 and PGC-1α proteins, placing syringaresinol squarely in the same mechanistic territory as established metabolic interventions.

The critical question was whether these effects genuinely depended on SIRT1. The inhibitor experiments provided the answer: when EX-527 blocked SIRT1 activity, the syringaresinol-driven responses in the myotubes were substantially attenuated. This pharmacological loss-of-function evidence supports the conclusion that SIRT1 signaling sits upstream of the observed changes and is required for syringaresinol to exert its influence on irisin production and mitochondrial markers in muscle cells. It is a level of mechanistic rigor that many plant-compound studies lack, and it gives the findings considerably more weight than simple correlation would allow.

But cell culture only goes so far, and the team therefore moved to a living system. Mice fed a high-fat diet—the standard model of diet-induced obesity—received syringaresinol by oral gavage at either a low or a high dose for 18 weeks, a substantial intervention period that allowed metabolic adaptations to fully develop. Over those weeks, the treated animals gained significantly less body weight than their untreated high-fat-diet counterparts. Crucially, food intake did not differ significantly between groups, which means the anti-obesity effect could not be explained by reduced appetite or caloric restriction. Something else was happening to the animals’ energy economy.

That something else appears to be a combination of circulating irisin and fat-tissue remodeling. Plasma measurements revealed that syringaresinol-treated mice had elevated levels of circulating irisin, consistent with the muscle-cell findings. The compound also improved lipid profiles, lowering the LDL-C/HDL-C ratio—a marker of cardiometabolic risk. In inguinal white adipose tissue, the subcutaneous fat depot most amenable to browning, expression of PGC-1α, uncoupling protein 1 (Ucp1), and Pparγ all increased. Ucp1 is the molecular signature of thermogenically active brown and beige fat: it short-circuits the mitochondrial proton gradient to generate heat instead of ATP, effectively burning calories as warmth. Its upregulation in white fat depots is the hallmark of the browning process that irisin was originally discovered to induce.

The original discovery of irisin in 2012 by Bruce Spiegelman’s group demonstrated that a PGC-1α-dependent myokine released from exercising muscle could drive brown-fat-like development in white fat and stimulate thermogenesis, and the field has since been searching for safe, practical ways to amplify this axis in people who cannot simply exercise their way out of metabolic disease. Recombinant irisin has been shown to induce weight loss in obese mice by increasing energy consumption and thermogenesis, and irisin has been linked to improved fatty acid oxidation and glucose utilization through AMPK signaling. Syringaresinol now emerges as a candidate nutritional tool for tapping into that same axis, working through the upstream SIRT1 node that is also targeted by compounds such as resveratrol and, more recently, by other dietary polyphenols like sesamol.

Syringaresinol itself is no newcomer to scientific attention. Prior studies have reported that it modulates gut microbiota and delays immunosenescence in middle-aged mice, protects against type 1 diabetic cardiomyopathy by reducing inflammation and oxidative stress, attenuates osteoarthritis through the NF-κB pathway, and even shows promise in models of cognitive decline and Alzheimer’s-related pathology. Toxicological testing of syringaresinol and its enterolignan metabolites has been carried out, and a comprehensive 2025 review has catalogued its plant sources, pharmacological activities, and pharmacokinetic characteristics. The new study adds weight management and the muscle–adipose endocrine axis to this expanding portfolio, positioning the compound as a multi-target nutritional agent rather than a single-action drug.

The researchers are appropriately careful about the limits of their evidence. In the published paper, they note that while the findings support syringaresinol as a candidate nutritional modulator of muscle–adipose metabolic communication, causal mediation of the in vivo effects by SIRT1, FNDC5, or irisin requires further pathway-specific validation. In other words, the mouse study shows correlations—less weight gain, more irisin, more Ucp1—but does not yet prove, through knockout models or receptor blockade, that irisin is the indispensable messenger carrying the benefit from muscle to fat. Human trials, which would represent the ultimate test, remain on the horizon. Still, the convergence of in vitro pharmacology, live-animal outcomes, and a mechanistic framework anchored in one of the most extensively studied metabolic pathways gives the work unusual coherence.

For a field wrestling with rising obesity rates and the modest long-term success of lifestyle interventions alone, the appeal of a plant-derived molecule that amplifies an exercise-like hormonal signal is obvious. Syringaresinol is found in common plant foods, has a documented safety profile, and now demonstrates the ability to switch on the SIRT1–PGC-1α–FNDC5/irisin axis in both cells and living animals under obesogenic conditions. If future work confirms causality and translates to humans, the compound—or optimized derivatives of it—could become part of a nutritional strategy that works with the body’s own thermogenic machinery rather than against appetite. For now, the message is more measured but still compelling: a molecule hidden in plants may teach muscle to talk to fat in a language that favors staying lean.

Subject of Research: Activation of the skeletal muscle SIRT1–FNDC5/irisin axis by the plant lignan syringaresinol and its effects on diet-induced obesity

Article Title: Syringaresinol activates the skeletal muscle SIRT1–FNDC5/irisin axis to enhance weight management

Article References: Syringaresinol activates the skeletal muscle SIRT1–FNDC5/irisin axis to enhance weight management. (n.d.). https://doi.org/10.1007/s13205-026-05027-z

Image Credits: AI Generated

DOI: 10.1007/s13205-026-05027-z

Keywords: syringaresinol, irisin, SIRT1, PGC-1α, FNDC5, skeletal muscle, adipose tissue browning, obesity, mitochondrial biogenesis, high-fat diet, lignan, weight management