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Fucoxanthin is a marine carotenoid found in edible brown seaweeds. We previously reported that dietary fucoxanthin attenuates the weight gain of white adipose tissue (WAT) of diabetic/obese KK- A(y) mice. In this study, to evaluate the antiobesity and antidiabetic effects of fucoxanthin and fish oil, we investigated the effect on the WAT weight, blood glucose, and insulin levels of KK- A(y) mice. Furthermore, the expression level of uncoupling protein 1 (UCP1) and adipokine mRNA in WAT were measured. After 4 weeks of feeding, 0.2% fucoxanthin in the diet markedly attenuated the gain of WAT weight in KK- A(y) mice with increasing UCP1 expression compared with the control mice. The WAT weight of the mice fed 0.1% fucoxanthin and 6.9% fish oil was also significantly lower than that of the mice fed fucoxanthin alone. In addition, 0.2% fucoxanthin markedly decreased the blood glucose and plasma insulin concentrations in KK- A(y) mice. The mice fed with the combination diet of 0.1% fucoxanthin and fish oil also showed improvements similar to that of 0.2% fucoxanthin. Leptin and tumor necrosis factor (TNFalpha) mRNA expression in WAT were significantly down-regulated by 0.2% fucoxanthin. These results suggest that dietary fucoxanthin decreases the blood glucose and plasma insulin concentration of KK- A(y) along with down-regulating TNFalpha mRNA. In addition, the combination of fucoxanthin and fish oil is more effective for attenuating the weight gain of WAT than feeding with fucoxanthin alone.

Abstract. Fucoxanthin is a major carotenoid found in edible seaweed such as Undaria pinnatifida and Hijikia fusiformis. We investigated the suppressive effects of fucoxanthin and its metabolite, fucoxanthinol, on the differentiation of 3T3-L1 preadipocytes to adipocytes. Fucoxanthin inhibited intercellular lipid accumulation during adipocyte differentiation of 3T3-L1 cells. Furthermore, fucoxanthin was converted to fucoxanthinol in 3T3-L1 cells. Fucoxanthinol also exhibited suppressive effects on lipid accumulation and decreased glycerol-3-phosphate dehydrogenase activity, an indicator of adipocyte differentiation. The suppressive effect of fucoxanthinol was stronger than that of fucoxanthin. In addition, in 3T3-L1 cells treated with fucoxanthin and fucoxanthinol, peroxisome proliferator-activated receptor Á (PPARÁ), which regulates adipogenic gene expression, was down-regulated in a dosedependent manner. These results suggest that fucoxanthin and fucoxanthinol inhibit the adipocyte differentiation of 3T3-L1 cells through down-regulation of PPARÁ. Fucoxanthinol had stronger suppressive effects than fucoxanthin on adipocyte differentiation in 3T3-L1 cells.

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The major role of vibronic coupling through the in-phase, CC stretching (ν 1) mode in the 2Ag - to 1Ag - internal conversion of all-trans-β-carotene has been shown by the use of isotopic effects on the rate of internal conversion and on the strength of vibronic coupling as follows:  (1) The rates of internal conversion for all-trans-β-carotene having natural abundance isotope composition [NA], along with 2H-labeled [2H], 13C-labeled [13C], and 2H,13C-doubly labeled [2H,13C] all-trans-β-carotenes, were determined, by subpicosecond time-resolved absorption spectroscopy, to be in the ratio [NA]/[2H]/[13C]/[2H,13C] = 1:0.92:0.70:0.64. (2) The strength of vibronic coupling was estimated for each isotope species by using the frequency difference between the 2Ag - and 1Ag - states, which was determined, by picosecond Raman spectroscopy, to be in the ratio, [NA]/[2H]/[13C]/[2H,13C] = 1:1.21:0.89:1.07. On the other hand, a theory was presented to show that the nonadiabatic vibronic-coupling constant that determines the rate of internal conversion is proportional to the adiabatic vibronic-coupling constant that determines the frequency difference. The application of the observed relative strength of vibronic coupling to the Englman−Jortner equation, for a single mode ν 1, predicted the relative rates of internal conversion to be 1:0.80:0.72:0.60, which are in good agreement with those observed above. (3) A theory showing that the adiabatic vibronic-coupling constant is proportional to the product of the transition bond-order matrix and the L matrix was also presented. In a polyene model, the relative rates of internal conversion were predicted to be 1:0.94:0.68:0.64, which are in excellent agreement with the above observed values.

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Inhibitory effects of geometrical isomers of fucoxanthin -characteristic carotenoid of brown seaweeds -on the growth of various cancer cells and on human leukemia (HL-60), colon cancer (Caco-2) and prostate cancer cells (PC-3 and LNCap) was comparatively evaluated. All trans fucoxanthin was the major geometrical isomer (~88%) found in the fresh brown seaweed (Undaria pinnatifida) apart from a small amount of 13-cis and 13'-cis isomers (~9%). Incubation of the fucoxanthin isomeric mixtures, all trans fucoxanthin with a small amount of 13-cis and 13'-cis isomers, produced 9'-cis isomer (5%) and increased the contents of 13-cis, and 13'-cis isomers (27%). The antiproliferative effect of the mixture of 13-cis and 13'-cis isomers was stronger than all other geometrical isomers evaluated in the study. The inhibition of growth of HL-60 cells was higher in case of 13'-cis isomer followed by 13-cis and all-trans isomers. The potent inhibitory effect of 13-cis and 13'-cis fucoxanthin on HL-60 cells and Caco-2 cells could possibly be due to their higher apoptotis inducing activity.

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