Possible Interaction: Tretinoin and Beta Carotene

“Dietary supplementation with beta-carotene at 30 mg/day results in an increased serum trans-retinoic acid concentration in patients with a prior colonic polyp.”

“The benign polyp subjects (n = 17) receiving beta-carotene showed a significant rise in serum trans-retinoic acid at three months compared with Time 0.”

“The trans-retinoic acid values from the colon cancer group receiving beta-carotene (n = 11) or placebo (n = 10) were significantly lower than the values from the beta-carotene-supplemented colon polyp group.”

“Simultaneous treatment with a retinoid and beta-carotene or astaxanthin resulted in supra-additive Cx43 expression, again indicating separate mechanisms of gene regulation.”

“In summary, apocarotenals or beta-carotene upregulated RA target genes suggesting promotion, not inhibition, of RA signaling in BEAS-2B cells.”

“In trials with lung cancer end-points, administration of retinoids either was ineffective or, in the case of beta-carotene , led to greater lung cancer incidence and mortality.”

“In contrast, low-dose beta-carotene can prevent the decreased lung retinoic acid and the smoke-induced lung lesions.”

“We demonstrated previously that smoke exposure and/or high-dose beta-carotene supplementation decreases levels of retinoic acid and retinoic acid receptor beta (RARbeta) protein, but increase levels of c-Jun and proliferating cellular nuclear antigen protein in the lungs of ferrets.”

“Incubation of various concentrations of RA with the lung microsomal fraction from ferrets exposed to cigarette smoke, a pharmacological dose of beta-carotene or their combination dose-dependently increased the levels of 4-oxo-RA and 18-hydroxy-RA compared with that of the control ferrets.”

“With or without …), the perfusion of beta-carotene (10 microM) … rise of retinoic acid in portal blood (+2.6 +/- 0.6 nmol/L and + 4.1 +/- 0.6 nmol/L, respectively) and … retinoic acid were detected in the intestinal mucosa (19 +/- 3 pmol/g and 36 +/- pmol/g, respectively.”

“Likewise, beta-carotene probably also acts subsequent to breakdown to retinoic acid.”

“… RA concentration in the portal …-fold with perfusion of beta-C (P < 0.05), and remained at 18 nmol/L during the perfusion of beta-C. The single peak of … was shown to consist of four separate peaks by GC-MS, which may be cis-trans isomers of RA.”