Gilbert L I, Chino H
J Lipid Res. 1974 Sep;15(5):439-56.
Many insect species are almost completely dependent on lipids for their metabolic needs, although this is usually a function of developmental stage. The primary storage organ is the fat body, which can constitute 50% of the fresh weight of the insect and also acts as the major metabolic center (analogous to the vertebrate adipose tissue and liver). Bathing the fat body (and all other tissues and organs) is the hemolymph, the main functions of which are to transport nutrient substrates to utilization sites and to deliver metabolic wastes to the excretory system. Although neutral lipids are stored as triglycerides, in times of need they appear to be endergonically released into the hemolymph as diglycerides in the majority of insects thus far studied (particularly silkmoths and locusts). Indeed, diglycerides constitute the largest neutral lipid fraction in the hemolymph of silkmoths, locusts, cockroaches, bugs, etc. In the hemolymph the diglyceride is found as a constituent of specific lipoproteins, and one specific lipoprotein class (lipoprotein I; high density lipoprotein) appears to be necessary for the transport of diglyceride from the fat body cell into the hemolymph. This particular lipoprotein is also involved in the transport of cholesterol from the gut into the hemolymph. Thus, lipoprotein I appears to be the major neutral lipid and sterol transport agent in the insects studied and, in addition, plays a regulatory role in the release of both diglycerides and sterols. Hemolymph lipoprotein II (very high density lipoprotein) may be important in providing protein and lipid to the insect ovary during oogenesis. Ecdysone, the polyhydroxy steroidal insect molting hormone, is probably carried "free" in the hemolymph, although reports exist of specific hemolymph-binding proteins in some species. The other major insect growth hormone, juvenile hormone, is transported by hemolymph lipoproteins in silkmoths and locusts and by a lower molecular weight hemolymph protein in the tobacco hornworm.
许多昆虫物种几乎完全依赖脂质来满足其代谢需求，不过这通常取决于发育阶段。主要的储存器官是脂肪体，它可占昆虫鲜重的50%，并且还充当主要的代谢中心（类似于脊椎动物的脂肪组织和肝脏）。包围着脂肪体（以及所有其他组织和器官）的是血淋巴，其主要功能是将营养底物运输到利用部位，并将代谢废物输送到排泄系统。尽管中性脂质以甘油三酯的形式储存，但在需要时，在迄今为止研究的大多数昆虫（特别是蚕蛾和蝗虫）中，它们似乎以内能方式作为甘油二酯释放到血淋巴中。事实上，甘油二酯是蚕蛾、蝗虫、蟑螂、蝽等昆虫血淋巴中最大的中性脂质组分。在血淋巴中，甘油二酯是特定脂蛋白的组成成分，一种特定的脂蛋白类别（脂蛋白I；高密度脂蛋白）似乎是甘油二酯从脂肪体细胞运输到血淋巴所必需的。这种特殊的脂蛋白还参与胆固醇从肠道到血淋巴的运输。因此，脂蛋白I似乎是所研究昆虫中的主要中性脂质和固醇运输剂，此外，在甘油二酯和固醇的释放中起调节作用。血淋巴脂蛋白II（极高密度脂蛋白）在卵子发生期间为昆虫卵巢提供蛋白质和脂质方面可能很重要。蜕皮激素，即多羟基甾体昆虫蜕皮激素，可能以“游离”形式存在于血淋巴中，尽管在某些物种中有关于特定血淋巴结合蛋白的报道。另一种主要的昆虫生长激素，保幼激素，在蚕蛾和蝗虫中由血淋巴脂蛋白运输，在烟草天蛾中由分子量较低的血淋巴蛋白运输。
