A new study, investigating links between gut bacteria and type 2 diabetes risks, has found that altering the microbiome can lower insulin resistance and change fat tissue metabolism.
The findings suggest that blocking gut bacteria from producing high levels of trimethylamine N-oxide (TMAO) may be what resets these parameters to reduce risks.
Previous studies have associated higher TMAO levels with higher incidence of type 2 diabetes. TMAO is also closely linked to insulin resistance.
Habitually, when we talk about resistance to insulin, it’s in reference to glucose and fat metabolism, but there’s a question as to whether such a resistance also affects protein metabolism.
TMAO happens to be a chemical by-product produced by specialised gut bacteria during the digestion of certain amino acids from protein, including choline, methionine, lecithin and carnitine – found in red meat, processed meats and egg yolks.
There is a large body of evidence, notably from Dr. Stanley Haze, to show that dietary choline is metabolized by bacteria in our gut and then converted by the liver into TMAO.
Unsurprisingly, previous research also found TMAO to be linked to higher risks of heart disease. In some people with type 2 diabetes, there can be subtle abnormalities during the digestion of these TMAO-spiking amino acids.
When it comes to methionine and arginine, this may mean higher risks for vascular complications and insulin resistance. Those with high TMAO, in a study that followed 4,000 adults for three years, had a 2.5-fold increased risk of heart attack too.
Sadly, the solution may not be as easy as avoiding methionine or choline-rich protein foods. Many studies did not prove that eating choline-rich foods (or any other foods) increases TMAO levels over time.
In other words, even if eating that food does increase total TMAO levels, most people are able to quickly and efficiently clear that TMAO from their blood by excreting it in the urine. This makes it doubtful that diet is the only factor elevating it.
if eating choline-rich foods did increase the risk of heart disease (via TMAO or any other mechanism), we’d expect to see higher rates of coronary heart disease (CHD) in those that eat more egg, for example. Yet numerous studies have failed to find any such association.
Other factors that are likely to explain an increase in TMAO include differences in the gut microbiome that predispose toward increased TMAO production. Research suggests that large intakes of whole grains increase gut bacteria associated with the highest TMAO.
The second factor researchers looked at is flavin-containing monooxygenase 3 (FMO3). Increased TMAO in the liver raises levels of an enzyme called FMO3 that carries out this conversion. Fmo3 activity is upregulated with insulin resistance.
All of these findings taken together tend to suggest that high levels of TMAO from excess methionine-rich protein foods (lean protein and muscle meat) are associated with higher type 2 diabetes risks.
The study is published in the Cell Reports journal.

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