Renner Sarah W, Walker Lauren M, Forsberg Lawrence J, Sexton Jonathan Z, Brenman Jay E
Genetics and Molecular Biology Curriculum, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
PLoS One. 2017 Apr 24;12(4):e0176502. doi: 10.1371/journal.pone.0176502. eCollection 2017.
Carbonic anhydrases are a family of enzymes that catalyze the reversible condensation of water and carbon dioxide to carbonic acid, which spontaneously dissociates to bicarbonate. Carbonic anhydrase III (Car3) is nutritionally regulated at both the mRNA and protein level. It is highly enriched in tissues that synthesize and/or store fat: liver, white adipose tissue, brown adipose tissue, and skeletal muscle. Previous characterization of Car3 knockout mice focused on mice fed standard diets, not high-fat diets that significantly alter the tissues that highly express Car3. We observed lower protein levels of Car3 in high-fat diet fed mice treated with niclosamide, a drug published to improve fatty liver symptoms in mice. However, it is unknown if Car3 is simply a biomarker reflecting lipid accumulation or whether it has a functional role in regulating lipid metabolism. We focused our in vitro studies toward metabolic pathways that require bicarbonate. To further determine the role of Car3 in metabolism, we measured de novo fatty acid synthesis with in vitro radiolabeled experiments and examined metabolic biomarkers in Car3 knockout and wild type mice fed high-fat diet. Specifically, we analyzed body weight, body composition, metabolic rate, insulin resistance, serum and tissue triglycerides. Our results indicate that Car3 is not required for de novo lipogenesis, and Car3 knockout mice fed high-fat diet do not have significant differences in responses to various diets to wild type mice.
碳酸酐酶是一类催化水和二氧化碳可逆缩合形成碳酸的酶，碳酸会自发解离为碳酸氢盐。碳酸酐酶III（Car3）在mRNA和蛋白质水平上都受到营养调控。它在合成和/或储存脂肪的组织中高度富集，如肝脏、白色脂肪组织、棕色脂肪组织和骨骼肌。先前对Car3基因敲除小鼠的研究主要集中在喂食标准饮食的小鼠上，而非显著改变高表达Car3组织的高脂饮食小鼠。我们观察到，在用氯硝柳胺治疗的高脂饮食小鼠中，Car3的蛋白质水平较低，氯硝柳胺是一种已发表的可改善小鼠脂肪肝症状的药物。然而，尚不清楚Car3仅仅是反映脂质积累的生物标志物，还是在调节脂质代谢中具有功能性作用。我们将体外研究重点放在了需要碳酸氢盐的代谢途径上。为了进一步确定Car3在代谢中的作用，我们通过体外放射性标记实验测量了从头脂肪酸合成，并检测了高脂饮食喂养的Car3基因敲除小鼠和野生型小鼠的代谢生物标志物。具体而言，我们分析了体重、身体组成、代谢率、胰岛素抵抗、血清和组织甘油三酯。我们的结果表明，从头脂肪生成不需要Car3，高脂饮食喂养的Car3基因敲除小鼠对各种饮食的反应与野生型小鼠没有显著差异。
