📌 The essence in one sentence
A bacterium widespread in our gut converts a nutrient found in fruit and grains into a molecule that protects the liver — and people with "fatty liver" disease have much less of it.
Your gut is home to trillions of invisible allies
About 38 trillion bacteria live in your gut. Far from being enemies, most are valuable allies: they digest food you couldn't process on your own, produce vitamins, and make molecules that influence your health far beyond your belly.
Among the most valuable molecules they produce is butyrate — a small fatty acid with big ambitions. It feeds the cells lining your gut, reduces inflammation, and helps regulate blood sugar. When it's in short supply, problems pile up.
A bacterium with a unique gift
Researchers from UCLouvain and several other universities took interest in a bacterium named Dysosmobacter welbionis. It's present in nearly everyone's gut — 8 out of 10 people carry it.
The discovery is unprecedented: this bacterium uses myo-inositol — a natural compound found in oranges, whole grains, beans, and nuts — to make butyrate. It's the first gut bacterium ever confirmed to do this.
~80 %
of humans
carry this bacterium in their gut
1st
confirmed bacterium
converting inositol into butyrate
The liver connection
The study also looked at what happens in people with hepatic steatosis — commonly called "non-alcoholic fatty liver": a buildup of fat in the liver that affects about 1 in 4 adults worldwide.
Result: these people have much less D. welbionis in their gut than healthy individuals. And the more advanced the disease, the scarcer the bacterium becomes. Mouse experiments confirmed that administering this bacterium improved blood sugar and reduced fat buildup in the liver.
Why it matters for tomorrow
This discovery opens the door to a next-generation probiotic: not a classic yogurt lactobacillus, but a bacterium selected for precise metabolic capabilities. The researchers even identified two strains without antibiotic resistance — a key safety criterion for future therapeutic use.
⚠️ What this doesn't mean
Eating more fruit or buying myo-inositol supplements is not a validated solution against fatty liver. Human clinical trials haven't yet been conducted. These results are promising, but don't yet constitute a medical recommendation.
📌 The essence in one sentence
Lee et al. describe the first experimentally confirmed myo-inositol → butyrate fermentation pathway in a human gut bacterium, and show that D. welbionis abundance is inversely associated with MASLD across three independent cohorts.
Background: gut butyrate and metabolic health
Short-chain fatty acids (SCFAs) — acetate, propionate, butyrate — are the flagship metabolites of the gut microbiota. Butyrate is the primary energy source of colonocytes, regulates gene expression through epigenetic mechanisms, modulates inflammatory responses, and its deficiency has been associated with metabolic-associated steatotic liver disease (MASLD).
Dysosmobacter welbionis, identified in 2020, belongs to the Oscillospiraceae family. Its particularity: it produces butyrate from inositol, not from classic polysaccharides. Until this study, the exact biochemical mechanism remained unknown.
What the study achieved
1. Metagenomic epidemiology — Three human cohorts:
- USA (Caussy et al.): significant reduction of D. welbionis in MASLD vs. controls (p<0.05)
- Finland (Jian et al.): reduction confirmed
- Spain/Italy, n=686: inverse correlation with the hepatic fibrosis score (rSpearman = −0.13, p<0.001)
2. Mouse model — Supplementation with D. welbionis J115T (>10⁹ CFU/day) in mice on a high-fat diet improved glucose tolerance, reduced liver weight, and decreased lipid droplets — across four independent studies.
3. Biochemistry — Cultures on ¹³C-labeled myo-inositol, tracked by NMR and mass spectrometry, reconstructed the metabolic pathway step by step.
The myo-inositol → butyrate pathway
Myo-inositol
↓ Scyllo-inosose
↓ 3,5/4-trihydroxycyclohexan-1,2-dione
↓ 5-deoxy-D-glucuronate
↓ 2-deoxy-5-keto-D-gluconate-6-phosphate
↓ 3-oxopropionate (C3-C4 cleavage)
↓ Acetyl-CoA → condensation ×2
↓ Butyrate + Acetate
19 new strains — two probiotic candidates
| Parameter |
Value |
| Total pangenome | 8,141 genes |
| Core genome | 2,136 genes |
| Inositol → butyrate pathway | Conserved in 23/23 strains |
| Strains without AMR resistance | 2 strains (W28, CLA-AA-H189) |
⚠️ Limitations to know
Human associations are observational — causality is not established. The HFD mouse model reproduces early-stage steatosis but not established steatohepatitis or fibrosis.
Verifiable sources
Lee C-H, Bui TPN, Petitfils C, Van Hul M, Cani PD et al. Novel myo-inositol to butyrate fermentation pathway in the prevalent human gut species Dysosmobacter welbionis. Gut. 2026. doi:10.1136/gutjnl-2025-336617.
📌 The essence in one sentence
Through integrated proteogenomics and ¹³C isotopic tracing, Lee et al. characterize a non-canonical myo-inositol → butyrate pathway conserved in the D. welbionis pangenome, with a class II aldolase substituting for an IolJ absent from the genome, and establish an inverse association with MASLD/fibrosis in three independent metagenomic cohorts.
Metagenomic epidemiology: three cohorts
| Cohort |
Population |
Main result |
| Caussy et al. (USA) | non-MASLD (n=51), MASLD without fibrosis (n=17), cirrhosis (n=25) | Significant reduction (p<0.05) |
| Jian et al. (Finland) | non-MASLD (n=26), MASLD (n=12) | Reduction confirmed |
| FLORINASH (Spain/Italy) | n=686 | rSpearman=−0.13, 95%CI [−0.20;−0.05], p=9.02×10⁻⁴ |
¹³C isotopic tracing and high-resolution NMR
J115T culture in modified YCFA medium + [¹³C₆]myo-inositol. Supernatant analysis at 48h by high-resolution ¹³C NMR + LC-MS/MS. Four intermediates confirmed: 3,5/4-trihydroxycyclohexan-1,2-dione, scyllo-inosose, 5-dehydro-2-deoxy-D-gluconate, 5-dehydro-2-deoxy-D-gluconate-6-phosphate.
Non-canonical pathway: the IolJ aldolase is absent
The normally expected enzyme — IolJ (5-dehydro-2-deoxyphosphogluconate aldolase, EC 4.1.2.29) — is absent from the J115T genome (3,576,546 bp, GC = 58.9%, 3,510 CDS). Two class II FBP aldolases (EIO64_00052/00053), carrying the TIGR01859 domain, are induced ×2–3 on inositol. An oxoacid dehydrogenase complex (EIO64_03047–03050) would catalyze the 3-oxopropionate → acetyl-CoA + CO₂ conversion.
Pangenomic analysis (25 genomes)
| Parameter |
Value |
| Total pangenome | 8,141 genes |
| Core genome | 2,136 genes |
| Average genome size | 3,594,757 ± 12,628 bp |
| Intra-species ANI | >98% |
| Pangenome structure | Open |
⚠️ Conflicts of interest & funding
PDC is an editor of Gut. WMdV and PDC are inventors on patent applications. PDC was co-founder of Enterosys. Funding: FRFS-WELBIO, FNRS, EOS (n°40007505), ERC Advanced Grant.
Full primary sources
Lee C-H, Bui TPN, Petitfils C, Van Hul M, Cani PD et al. Novel myo-inositol to butyrate fermentation pathway in the prevalent human gut species Dysosmobacter welbionis, a bacterium associated with improved metabolic and liver health. Gut. 2026;0:1–15. doi:10.1136/gutjnl-2025-336617.