Low-dose treatment with trimethylamine N-oxide — a compound linked with the consumption of fish, seafood and a primarily vegetarian diet — reduced heart thickening (cardiac fibrosis) and markers of heart failure in an animal model of hypertension, according to a new study published in the American Journal of Physiology – Heart and Circulatory Physiology.
Trimethylamine N-oxide is found at high concentrations in the tissues of some fish and shellfish.
“Trimethylamine N-oxide (TMAO) levels in the blood significantly increase after eating TMAO-rich food such as fish and vegetables,” explained study senior author Dr. Marcin Ufnal from the Medical University of Warsaw in Poland and colleagues.
“In addition, the liver produces TMAO from trimethylamine, a substance made by gut bacteria.”
“The cause of high TMAO levels in the blood and the compound’s effects on the heart and circulatory system are unclear.”
It was previously thought that TMAO blood plasma levels — and heart disease risk — rise after the consumption of red meat and eggs.
“However, it seems that a fish-rich and vegetarian diet, which is beneficial or at least neutral for cardiovascular risk, is associated with a significantly higher plasma TMAO than red meat- and egg-rich diets, which are considered to increase the cardiovascular risk,” the scientists said.
The team examined the effect of TMAO in a rat model of hypertension.
One group of hypertensive rats was given low-dose TMAO supplements in their drinking water, and another group received plain water.
They were compared to a control group of rats that does not have the same genetic predisposition and received plain water.
The dosage of TMAO was designed to increase blood TMAO levels approximately four times higher than what the body normally produces.
The rats were given TMAO therapy for either 12 weeks or 56 weeks and were assessed for heart and kidney damage and high blood pressure.
TMAO treatment did not affect the development of high blood pressure in any of the hypertensive rats. However, condition of the animals given the compound was better than expected, even after more than a year of low-dose TMAO treatment.
“The new finding is that 4-5-fold increase in plasma TMAO does not exert negative effects on the circulatory system,” the study authors said.
“In contrast, a low-dose TMAO treatment is associated with reduced cardiac fibrosis and markers of failing heart in spontaneously hypertensive rats.”
“Our study provides new evidence for a potential beneficial effect of a moderate increase in plasma TMAO on pressure-overloaded heart,” they said.
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Tomasz Huc et al. Chronic, Low-Dose Tmao Treatment Reduces Diastolic Dysfunction and Heart Fibrosis in Hypertensive Rats. American Journal of Physiology – Heart and Circulatory Physiology, published online September 28, 2018; doi: 10.1152/ajpheart.00536.2018
