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A Sulfur-Rich Cousin of a Common Supplement Rewires a Muscle Repair Signal Against Aging
A Japanese-led team reports that lipoic acid trisulfide (LASSS), a three-sulfur relative of the common antioxidant alpha-lipoic acid, does something unexpected to hepatocyte growth factor (HGF), the protein that wakes up dormant muscle stem cells. Beyond simply protecting HGF from the chemical damage (tyrosine nitration) that accumulates with age, LASSS appears to chemically remodel HGF so that it binds its receptor c-met more than twice as strongly, and this enhancement survives even after all free LASSS is washed away. A companion antioxidant trisulfide (GSSSG) and ordinary lipoic acid did neither, which rules out a simple antioxidant explanation. In mice, drinking LASSS beforehand blocked the muscle-disuse-driven nitration of HGF. This is early-stage biochemistry and cell work, not a longevity or lifespan trial, but it points at a candidate small molecule for age-related muscle wasting.
Muscle repair depends on a quiet reserve force. Tucked against each muscle fiber sit satellite cells, stem cells that normally sleep until injury or mechanical stress calls them into action. The wake-up signal is a protein called HGF, and it works only if it can dock onto its receptor, c-met. Previous work from this same group showed that as animals age, HGF gets chemically vandalized. A reactive molecule called peroxynitrite, produced when nitric oxide meets superoxide, tacks a nitro group onto two specific tyrosine amino acids (positions 198 and 250) sitting right at the receptor-binding sites. The damaged HGF can no longer bind well, the stem cells stay asleep, and muscle loses its ability to repair itself. This helps explain why aging muscle wastes and gets replaced by fibrous tissue and fat.
The new study asks whether sulfur-rich molecules can prevent that sabotage. The researchers tested two trisulfides, structures with three sulfur atoms in a row, known for potent redox chemistry. Both glutathione trisulfide (GSSSG) and lipoic acid trisulfide (LASSS) protected HGF from nitration and preserved its ability to activate stem cells in a dish. That was the expected antioxidant result.
The surprise came at higher doses. LASSS did not merely shield HGF. It seemed to transform it. After treating HGF with LASSS and then thoroughly washing away every trace of unreacted LASSS by ultrafiltration, the treated HGF still bound its receptor more than twice as strongly as untreated HGF. GSSSG and plain lipoic acid produced no such effect. Because the enhancement persisted after washout and happened without any peroxynitrite present, it cannot be explained by antioxidant scavenging. The authors propose that LASSS, being small and having an unusual ring-shaped trisulfide, reaches internal disulfide bonds near tyrosine 198 and chemically remodels them, locking HGF into a higher-affinity shape that also resists later nitration.
The team then took the idea into live mice. Using a tail-suspension model that mimics disuse-induced muscle loss, they showed that three days of LASSS in the drinking water beforehand prevented the disuse-driven nitration of HGF in calf muscles. GSSSG did not. The work is preliminary and mechanistically incomplete, but it introduces a genuinely new idea: a supplement-like molecule that upgrades a repair signal rather than just defending it.
Actionable Insights
Before anything else, a caution. This is a test-tube and cell-culture study with one small mouse experiment. It does not test a human supplement, does not measure muscle strength or mass gains, and does not measure lifespan. There is no take-home dose you can act on today. LASSS is not the same thing as the alpha-lipoic acid sold in stores. Ordinary lipoic acid did nothing in this study, so buying lipoic acid supplements will not reproduce these results.
What the study does suggest, in principle, is a target. The core idea is that age-related muscle decline is driven partly by a repairable chemical injury to a single signaling protein, not just by irreversible wear. That is an optimistic framing worth watching.
On the magnitude of the effect. The headline number is a more than two-fold (greater than 100 percent) increase in HGF receptor binding, which is a large relative effect for a biochemical readout. In the stem cell activation assay, nitrated HGF fell essentially to the no-signal baseline, while LASSS treatment restored activity to roughly 80 to 100 percent of healthy HGF. LASSS-treated HGF also reached maximum stem cell activation at a concentration as low as 1 nanogram per milliliter, below the 2.5 to 10 range normally needed, implying a leftward potency shift of several fold. These are strong signals in isolated systems. Whether any of it translates to measurable muscle benefit in a living human is completely untested.
Context and Source
- Open Access Paper: Enhanced HGF with increased receptor affinity and nitration-dysfunction resistance through interaction with lipoic acid trisulfide.
- Lead institution: Kyushu University, Graduate School of Agriculture, Fukuoka, Japan. Collaborating institutions include Kafrelsheikh University (Egypt), Azabu University (Japan), and the University of Manitoba (Canada).
- Journal: Scientific Reports (Nature Portfolio), 2026
- Impact evaluation: The most recent Journal Impact Factor for Scientific Reports is about 4.9 (2025 JCR, released 2026), with a CiteScore of 6.7. The impact score of this journal is 4.9, evaluated against a typical high-end range of 0 to 60+ for top general science, therefore this is a Low-to-Medium impact journal.
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Part 4: Actionable Intelligence
A framing warning before any numbers. LASSS is an investigational research chemical, not a supplement or drug. The dose translated below is a paper-exercise extrapolation from a 3-day nitration-imaging endpoint in young mice, not a validated human regimen. Treat every figure in this section as illustrative arithmetic, not clinical guidance.
The Translational Protocol (Rigorous Extrapolation)
Animal dose used in the paper: about 50 micrograms per gram body weight per day, oral, in drinking water. That equals 50 mg/kg/day in mice, given for 3 days before disuse. This is the only in vivo dose reported.
Human Equivalent Dose by body-surface-area normalization (FDA guidance, “Estimating the Maximum Safe Starting Dose,” 2005). The standard formula is:
HED (mg/kg) = Animal dose (mg/kg) times (Animal Km divided by Human Km)
Standard Km factors: mouse Km = 3, human (adult) Km = 37.
Show the math:
HED = 50 mg/kg times (3 divided by 37) HED = 50 times 0.081 HED = about 4.05 mg/kg
Converting to whole-body doses:
For a 60 kg adult: 4.05 times 60 = about 243 mg per day. For a 70 kg adult: 4.05 times 70 = about 284 mg per day.
So the theoretical human-equivalent oral dose is roughly 240 to 285 mg per day of LASSS. Two heavy caveats. First, BSA scaling assumes comparable absorption and metabolism, which is untested for LASSS. Second, a mouse Km of 3 and human Km of 37 are population approximations; the true HED band is wide. This number tells you an order of magnitude (hundreds of milligrams), nothing more precise. [Confidence: Medium for the arithmetic, Low for biological validity]
Pharmacokinetics (PK/PD)
Direct LASSS human PK: Safety Data Absent. No published bioavailability, Cmax, Tmax, half-life, volume of distribution, or clearance for LASSS in humans or animals was found.
What is known indirectly. LASSS is poorly water soluble and heat sensitive, which is why formulation groups have wrapped it in beta-cyclodextrin clathrates to improve solubility and thermal stability. That poor solubility predicts erratic and probably low oral bioavailability for the unformulated molecule. As a trisulfide it is a hydrogen sulfide (H2S) donor, so part of its in vivo action is likely mediated by slow sulfane-sulfur or H2S release rather than by intact-molecule distribution.
The closest PK proxy is the parent alpha-lipoic acid: short plasma half-life (roughly 30 minutes), oral bioavailability near 30 percent and reduced by food, cleared mainly by reduction to dihydrolipoic acid and beta-oxidation rather than by cytochrome P450. If LASSS behaves even loosely like its parent, expect a short-lived systemic exposure that argues for divided dosing or a controlled-release formulation. This is inference, not measurement. [Confidence: Low]
Safety and Toxicity
LASSS-specific NOAEL: Safety Data Absent. LASSS-specific LD50: Safety Data Absent. LASSS-specific Phase I data: Safety Data Absent. No human trials of LASSS exist. LASSS-specific CYP450, liver, or kidney signals: Safety Data Absent.
Proxy data from alpha-lipoic acid, offered only as a rough floor and explicitly not a substitute:
Oral LD50 in rats is generally reported at greater than 2000 mg/kg, with some studies citing lower figures around 1200 mg/kg, so ALA is of low acute oral toxicity. Sub-chronic and chronic NOAEL values cluster around 60 to 90 mg/kg/day (a 4-week study gave about 61.9 mg/kg/day, a 2-year rat study gave 60 mg/kg/day, a 90-day study gave 90 mg/kg/day). Higher doses near 121 mg/kg/day produced slight liver enzyme changes and histopathology in liver and mammary gland. ALA does not appear to be a major CYP450 substrate or inhibitor. Its principal clinically relevant signal is hypoglycemia, because ALA improves insulin sensitivity and glucose uptake; rare autoimmune insulin syndrome has been reported in predisposed individuals.
The critical point: adding a reactive third sulfur changes the chemistry. LASSS is an H2S donor and a cysteine-disulfide-remodeling agent, which is precisely what makes it interesting and also what makes ALA safety data an unreliable guarantee. Reactive supersulfides can hit off-target thiols on many proteins (the paper itself shows LASSS modifies BSA), so a clean ALA record does not transfer. Without a dedicated LASSS toxicology package, human use cannot be considered characterized for safety. [Confidence: High that the data are absent]