- Researchers mapped gut made molecules that enter the liver first and then spread through the bloodstream
- Diet, genetics and microbiome disruption changed which molecules showed up and in what amounts
- One molecule tested in liver cells improved insulin signalling, pointing to possible drug targets in future
A team working at Harvard has identified a set of small molecules made in the gut that travel into the liver and may influence how the body handles energy and blood sugar.
The work focuses on metabolites that are enriched in blood draining directly from the intestine into the liver, before they are processed and sent into wider circulation.
That route matters. The hepatic portal vein carries much of the blood from the gut straight to the liver, meaning it is the first place the liver sees microbiome derived chemicals.
In the liver, these compounds can be altered, cleared or passed on, and some then reach the heart and the rest of the body.
By comparing blood from the portal vein with blood from the general circulation, the researchers aimed to pinpoint which gut derived metabolites are most likely to affect liver metabolism and insulin sensitivity.
The study used mice with different underlying risks for obesity and type 2 diabetes.
In healthy animals, the researchers detected large numbers of metabolites that were enriched in portal vein blood compared with peripheral blood.
When mice genetically prone to obesity and type 2 diabetes were fed a high fat diet, the number of portal vein enriched metabolites dropped sharply.
The message is straightforward: what you eat can change which microbial products reach the liver, and it can do so in a way that may worsen metabolic health in susceptible hosts.
Genetics also appeared to matter.
Metabolite patterns in mice prone to metabolic disease looked different from those in a strain that is naturally more resistant to metabolic syndrome.
That suggests the host’s biology helps shape the microbiome output, not just the other way round.
To probe cause and effect, the team disrupted the gut microbiome in susceptible mice using an antibiotic approach aimed at particular intestinal microbes.
As expected, the microbiome changed and so did the metabolite mix in both portal vein and peripheral blood.
One notable change was an increase in mesaconate, a compound linked to core energy metabolism.
The researchers then tested mesaconate and related isomers directly on hepatocytes, the main functional cells of the liver. In these lab experiments, exposure improved insulin signalling and shifted the activity of genes involved in fat production and fat burning in the liver.
That does not mean mesaconate is a ready made treatment, but it does support the broader point of the paper: specific microbiome linked metabolites can alter liver biology in ways that are relevant to insulin resistance.
The next step is the hard part. The team plans to characterise these metabolites in more detail and work out how they are produced, which microbes are responsible and how diet and genetics steer the whole system.
If those links can be nailed down, some of these molecules could become biomarkers, prevention targets or even the basis for new therapies. For now, this is a promising map of a route between gut chemistry and metabolic disease, not a finished treatment.
Reference: Muñoz VR et al. Portal vein enriched metabolites as intermediate regulators of the gut microbiome in insulin resistance. Cell Metabolism. 2025;37(10):2048. doi: 10.1016/j.cmet.2025.08.005
