Figure 2. ATRA but not vitamin A declines in idiopathic dilated cardiomyopathy.

(A) Chemical structures of the retinoid species quantified from myocardial biopsies by reversed-phase chromatography and mass spectrometry. Retinyl esters represent the in situ retinoid reserve, or storage form, of retinol. Retinol, or vitamin A, is the metabolic precursor of retinaldehyde and all-trans retinoic acid (ATRA). Other geometric isomers of retinoic acid include 13-cis-RA and 9,13-cis-RA. The potent RXR ligand, 9-cis-RA, was not detected in the heart. (B–F) Quantitation of endogenous cardiac retinoids. Differences between group means were assessed by a 2-tailed t test (* denotes P < 0.05). N values are given in parentheses. (B) Retinol levels were significantly elevated in patients with idiopathic dilated cardiomyopathy (IDCM) relative to donor heart tissue. (C) A similar trend was noted for retinyl esters, though the difference was not significant. (D) ATRA was significantly lower in IDCM than among donors, as were levels of 13-cis-RA (E). (F) 9,13-cis-RA did not differ significantly.