In ATTR-CM, transthyretin proteins become unstable and fold the wrong way. You can picture TTR protein folding like making a paper airplane. If you fold one wing in the opposite direction, your airplane won’t fly.
When TTR proteins don’t fold right, they can’t move like they should. Then, they build up in your organs, including your heart, says Tadeo Diaz Balderrama, MD, a cardiologist for SSM Health in Fond du Lac, Wisconsin. This can lead to symptoms of heart failure, like shortness of breath and swelling in your legs.
Vitamin A fits into this equation when you treat ATTR-CM with medications that decrease the amount of the TTR proteins that transport it.
“Vitamin A (retinol) does not circulate freely in the blood,” says Julia Zumpano, RD, who specializes in metabolic nutrition and clinical nutrition at Cleveland Clinic in Ohio. “Instead, retinol binds to a carrier protein called retinol-binding protein (RBP).” Then, this combination connects to TTR, which helps your body use vitamin A, says Zumpano.
ATTR-CM treatments work in two ways:
- Stabilizers hold TTR proteins in place so they can’t fold incorrectly.
- Silencers lower the amount of TTR proteins made by your liver.
“Silencers can cause a functional vitamin A deficiency since they reduce the overall production of TTR, the primary vitamin A protein transporter,” says Dr. Hicks.
ATTR-CM silencers include:
- patisiran (Onpattro)
- inotersen (Tegsedi)
- vutrisiran (Amvuttra)
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