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Bixin, a carotenoid found in the seed of the Annatto plant, Bixa orellana, is a potent antioxidant. Carotenoids are readily absorbed from the diet; therefore, the purpose of this study was to examine uptake of bixin by plasma, lipoproteins, and leukocytes after dietary supplementation in domestic cats and to assess effects on immune response. Female domestic short hair cats (3 yr old; 4.79 ± 0.13 kg BW) were fed a single dose of 0, 1, 5, or 10 mg bixin, and blood was taken at 0, 1, 2, 4 and 8 h after administration (n = 6/ treatment) to determine acute absorption rate. Then, bixin was fed daily for 14 d to examine steady-state plasma concentrations and subcellular distribution. Following these preliminary experiments, cats (n = 8/treatment) were fed diets containing 0, 1, 5, or 10 mg bixin/d for 16 wk and blood was collected on wk 0, 6, 12, and 16 for analysis of leukocyte subpopulations, cell-mediated responsiveness, and inflammatory and oxidative biomarkers. Maximal uptake in plasma occurred 1 h after a single oral dose of bixin, with a maximal concentration of 0.119 μM and elimination half-life of 1.8 to 2.2 h. Daily feeding of bixin showed a steady-state plasma concentration of 0.110 μM at the greatest doses. Bixin was primarily associated with the high-density lipoprotein fraction of blood lipoproteins and was primarily distributed in mitochondrial fractions (58-59%) of but also in microsomal and nuclear fractions (37-44%). Leukocyte subpopulations in blood were variably affected by dietary bixin, with an increase (P < 0.05) in total T cells but a concurrent decrease (P < 0.05) in CD18+ and B cell subpopulations. However, plasma IgG increased (P < 0.05) in the 10-mg treatment group by wk 6. Lymphoproliferation was stimulated (P < 0.05) in the 5-mg bixin treatment group by wk 16, and delayed-type hypersensitivity response increased after nonspecific antigenic challenge. Conversely, when a specific challenge of vaccine was assessed on wk 12 and 16, responsiveness decreased (P < 0.05) in the 10-mg bixin treatment group. Bixin supplementation surprisingly caused an increase (P < 0.05) in α-acid glycoprotein but had no effect on natural killer cell activity, other subpopulations of leukocytes, or 8-oxo-2>-deoxyguanosine, a DNA damage biomarker. This experiment demonstrated dose-dependent uptake of bixin in plasma and blood lipoproteins and distribution in leukocyte subcellular components and an impacted immune response through cell-mediated and humoral actions. [ABSTRACT FROM AUTHOR]

Carotenoids are readily absorbed from the diet and distributed in blood leukocyte subcellular organelles. Bixin, a potent bioactive found in the seed of the Annatto plant, Bixa orellana, possesses antioxidant and anti-inflammatory properties. The purpose of this study was to determine the uptake of bixin by plasma, lipoproteins, and leukocytes in domestic dogs and to examine immunoprotective properties. To determine uptake kinetics, female Beagle dogs (2 yr; 9.1 ± 0.1 kg BW) were first fed a single dose by oral gavage of 0, 5, 10, 20, or 40 mg bixin, with blood collected at 0 to 16 h after administration (n = 6/treatment), and then fed daily with 0, 5, 10, 20, or 40 mg bixin/d, with blood collected at 0, 1, 2, 4, 6, 10, and 14 d. In a consecutive experiment, cell-mediated and humoral responses as well as oxidative biomarkers were measured following 16 wk of dietary supplementation with 0, 5, 10, or 20 mg bixin/d. Maximal absorption in plasma occurred by 0.5 h with an elimination half-life of 2.6 to 3.3 h after a single dose of bixin. Steady-state plasma concentrations were 0.053 μM after 14 d of 40 mg bixin/d. The majority of subcellular bixin was found in the leukocyte mitochondria and was associated with the high-density lipoprotein and low-density lipoprotein fractions of lipoproteins. Specific (vaccine) response increased (P < 0.05) but nonspecific mitogen response was unchanged after 12 wk of dietary bixin, as assessed by a delayed-type hypersensitivity assay. Both B cell plasma leukocyte subpopulations at 6 and 16 wk and IgG plasma concentration at 12 wk in the 10-mg treatment group increased (P < 0.05), although IgM production and other cell populations were unaffected. In addition, 8-oxo-2'-deoxyguanosine (8-OHdG), a DNA damage biomarker, was substantially reduced (P < 0.05) in all treatment groups by wk 16, and C-reactive protein (CRP) was suppressed at wk 12 (P < 0.05). Dietary supplementation with bixin showed no changes in lymphoproliferation in response to in vitro mitogenic challenge and had no effect in enhancing natural killer cell activity. In conclusion, bixin was readily absorbed in a dose-dependent manner in blood following oral administration and was then taken up by leukocytes, where it was primarily distributed to mitochondria but in other subcellular organelles as well. Bixin also appeared to stimulate immune response, as seen with cell-mediated responses, and exerted anti-inflammatory (reduced CRP) as well as antioxidative (reduced 8-OHdG) effects in dogs. [ABSTRACT FROM AUTHOR]