Graduate School of Nutritional and Environmental Sciences, Global COE Program, The University of Shizuoka, Shizuoka, Japan.
Nutrition. 2010 Nov-Dec;26(11-12):1151-6. doi: 10.1016/j.nut.2009.09.006. Epub 2010 Jan 25.
β-Carotene is an abundant carotenoid with potent antioxidative activities and accumulates in adipose tissue. However, its physiologic functions are poorly understood. In this study, we examined whether accumulation of β-carotene for 4 d in insulin-resistant 3T3-L1 adipocytes alters the expression of genes related to insulin sensitivity.
The 3T3-L1 adipocytes were treated with/without 10 or 20 μM β-carotene during differentiation for 4 d. The cells treated with 10 μM β-carotene for 4 d were subsequently incubated with/without 5 ng/mL of tumor necrosis factor-α for 48 h in the medium without β-carotene. The mRNA levels of genes in the cells and adiponectin protein levels in the medium were determined by real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Reactive oxygen species levels in the cells were assessed by oxidation of 2',7'-dichlorodihydrofluorescein diacetate.
β-Carotene treatment at a concentration of 20 μM, but not 10 μM, in 3T3-L1 adipocytes during differentiation for 4 d enhanced the expression of genes related to insulin sensitivity, including adiponectin, adipocyte lipid-binding protein, glucose transporter-4, peroxisome proliferator-activated receptor-γ2, and adiponectin protein in the medium. Tumor necrosis factor-α treatment repressed the expression of these genes and adiponectin protein in the medium and induced reactive oxygen species levels. In contrast, cells that accumulated β-carotene at a concentration of 10 μM did not show these alterations.
The accumulation of the β-carotene in 3T3-L1 adipocytes restores the expression of genes related to insulin sensitivity and reactive oxygen species levels in insulin-resistant adipocytes.
β-胡萝卜素是一种丰富的类胡萝卜素，具有强大的抗氧化活性，并在脂肪组织中积累。然而，其生理功能知之甚少。在这项研究中，我们研究了胰岛素抵抗的 3T3-L1 脂肪细胞中 β-胡萝卜素积累 4 天是否会改变与胰岛素敏感性相关的基因表达。
在分化的 4 天中，用/不用 10 或 20 μM β-胡萝卜素处理 3T3-L1 脂肪细胞。用 10 μM β-胡萝卜素处理 4 天的细胞，随后在不含 β-胡萝卜素的培养基中用/不用 5 ng/mL 的肿瘤坏死因子-α孵育 48 小时。通过实时逆转录-聚合酶链反应和酶联免疫吸附试验分别测定细胞中的基因的 mRNA 水平和培养基中的脂联素蛋白水平。通过 2'，7'-二氯二氢荧光素二乙酸酯的氧化来评估细胞中的活性氧水平。
在分化的 4 天中，用 20 μM 而非 10 μM 的浓度处理 3T3-L1 脂肪细胞会增强与胰岛素敏感性相关的基因的表达，包括脂联素、脂肪细胞脂质结合蛋白、葡萄糖转运蛋白-4、过氧化物酶体增殖物激活受体-γ2 和培养基中的脂联素蛋白。肿瘤坏死因子-α处理抑制了这些基因和培养基中的脂联素蛋白的表达，并诱导了活性氧水平。相比之下，积累了 10 μM β-胡萝卜素的细胞没有表现出这些变化。
3T3-L1 脂肪细胞中 β-胡萝卜素的积累恢复了胰岛素抵抗脂肪细胞中与胰岛素敏感性相关的基因表达和活性氧水平。
