In the fat around the heart and blood vessels of heart failure patients, a specific enzyme called MAO-A is much more common and makes more harmful chemicals than its cousin MAO-B.

Scientific Claim

Monoamine oxidase A (MAO-A) is the predominant isoform expressed in human epicardial and perivascular adipose tissue from patients with heart failure, contributing more to local oxidative stress than MAO-B.

Original Statement

“The human cardiovascular adipose tissues contain both MAO isoforms, predominantly MAO-A. ... The protein expression of MAO-A isoform was significantly higher ... as compared to the one of MAO-B.”

From study:Methylene blue reduces monoamine oxidase expression and oxidative stress in human cardiovascular adipose tissue

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The study directly quantified and compared MAO-A and MAO-B expression in human tissue samples using validated methods. The claim accurately reflects the observed dominance of MAO-A without overextending to causality.

Evidence from Studies

Supporting (1)

Methylene blue reduces monoamine oxidase expression and oxidative stress in human cardiovascular adipose tissue

Cross-Sectional Study

Human

2025 Apr

This study found that in fat around the hearts of heart failure patients, a protein called MAO-A is the main type producing harmful stress molecules, and blocking it with methylene blue reduces that stress.

Contradicting (0)

No contradicting evidence found

Source Study

Methylene blue reduces monoamine oxidase expression and oxidative stress in human cardiovascular adipose tissue

Score: 33

DOI: 10.1007/s11010-024-05092-z

Similar Assertions

In the fat around the heart and blood vessels of heart failure patients, the MAO-A enzyme is much more common than the MAO-B enzyme.

98%

When fat tissue around the heart and blood vessels from heart failure patients was soaked in a small amount of methylene blue for a day, the levels of a specific enzyme (MAO-A) that makes harmful molecules went down.

83%

When fat tissue around the heart and blood vessels was soaked in a blue dye called methylene blue for a day in the lab, it made less of a harmful enzyme and produced fewer damaging chemicals, which might help explain how the dye could protect cells.

78%

The fat directly on the heart makes more harmful chemicals than the fat around blood vessels, and this matches with it having more of the enzyme MAO-A.

71%

When the fat tissue was given serotonin (a chemical that MAO-A breaks down), it made more harmful molecules—but adding methylene blue stopped some of that increase.

71%