인슐린(insulin)과 insulin-like growth factor-1 (IGF-1)은 척추동물에서 대사, 생장, 수명 등의 여러 생리대사를 조절하는 중요한 호르몬 이다. 곤충에서도 IGF-1과 구조적으로 유사한 insulin-like peptide (ILP)들이 존재하며 이들이 곤충 생리 조절에 중요하게 관여함이 밝혀졌다. 이번 총설에서 곤충 ILP 및 초파리(Drosophila melanogaster) 유전체 분석을 통해 척추동물에 존재하는 인슐린 및 IGF-1 수용체 신호전달계와 유 사하다고 확인된 ILP 수용체 신호전달계에 대해 설명하고자 한다. 추가적으로, 곤충 체내의 영양 상태에 따라 조절되는 뇌에서의 ILP의 합성과 분비, ILP에 의한 대사의 생리적 조절에 대해 논한다. 또한 ILP가 생장, 발달, 생식, 휴면에 기여하는 바도 논의하고, 마지막으로 ILP 수용체 신 호전달계 제어를 통한 해충 방제에의 이용 가능성에 대해 제안하고자 한다.

The production of therapeutic protein from transgenic domestic animal is the major technology of biotechnology. Insulin-like growth factor-1 (IGF-1) is known to play an important role in the growth of the animal. The objective of this study is construction of knock-in vector that bovine IGF-1 gene is inserted into the exon 7 locus of β-casein gene and expressed using the gene regulatory DNA sequence of bovine β-casein gene. The knock-in vector consists of 5’ arm region (1.02 kb), bIGF-1 cDNA, CMV-EGFP, and 3’ arm region (1.81 kb). To express bIGF-1 gene as transgene, the F2A sequence was fused to the 5’ terminal of bIGF-1 gene and inserted into exon 7 of the β-casein gene. As a result, the knock-in vector is confirmed that the amino acids are synthesized without termination from the β-casein exon 7 region to the bIGF-1 gene by DNA sequence. These knock-in vectors may help to create transgenic dairy cattle expressing bovine bIGF-1 protein in the mammary gland via the expression system of the bovine β-casein gene.

Colony collapse disorder (CCD), a phenomenon of honeybees disappearance, has been reported since 2006. Chronic exposure to neonicotinoid insecticides, particularly imidacloprid, has been suggested to impair forager’s ability for foraging and be a main cause of CCD. Recently, it has been reported that imidacloprid induces insulin resistance in animal cell line by blocking glucose uptake. Similarly to human insulin, insulin-like peptide (ILP) of insects is involved in maintaining blood glucose contents in hemolymph by regulating the concentration of trehalose and glycogen. Therefore, we have hypothesized that sublethal concentration of neonicotinoid may affect the metabolic pathway of honey bees as well. We investigated the transcription levels of the genes involved in the insulin/insulin-like signaling (IIS) pathway, such as AmILP and AmInR, following an acute or a chronic dietary exposure of sublethal concentrations of imidacloprid to foragers. In both experiments, honeybees showed increased expression levels of ILP and InR in a dose-dependent manner. Our results suggest that sublethal dose of imidacloprid likely upregulates IIS pathway, thereby rendering honey bees to become resistant to insulin.

Like vertebrate insulins, insulin-like peptides (ILPs) play crucial roles in controlling immature growth, adult lifespan, and plasma sugar level in some insects. An ILP gene (SeILP1) was predicted from a transcription database of Spodoptera exigua. SeILP1 encodes 95 amino acid sequence, which shares sequence homologies (33~83%) with other insects ILPs. The predicted B and A chains possess six cysteine residences. SeILP1 was expressed in all developmental stages of S. exigua. However, its expression was detected in fat body, gut and epidermis, but not in hemocytes. Its expression increased with feeding activity. Plasma trehalose levels of fifth instar larvae maintained at relatively stable concentration of 2.31±0.62 mM. However, starvation induced a significant increase of plasma trehalose level by more than two fold in 48 h, at which SeILP1 expression kept at a low level. RNA interference of SeILP1 induced a significant increase of plasma trehalose level. Interestingly, a bovine insulin decreased plasma trehalose level in a dose-dependent manner. These results indicate mat SeILP1 plays a role in suppressing plasma trehalose level in S. exigua.

Recently, with the increase of meat production, high quality and safety of meat have been strongly emphasized by Korean consumers. Marbling in beef has been regarded as an important criterion deciding meat quality in Korea. The purpose of this study was to identify the transcriptional level of insulin-like growth factor-1 (IGF-1) in longissimus muscle samples of 46 Hanwoo. The level of IGF-1 transcripts was measured by real-time polymerase chain reaction (PCR) and molecular connection of IGF-1 was analyzed using the Pathway Studio program (Ver 9.0). Increase of marbling score (MS) induced increase of IGF-1 transcripts level in the muscle and there is a significant correlation (p<0.05) between IGF-1 mRNA expression and MS. The pathway study showed that IGF-1 genes are regulated in insulin, fatty acid synthase, leptin, and corticotrophin releasing hormone. These results suggest that IGF-1 might be used as a useful marker for the improvement of economic traits in Hanwoo.

Insulin in vertebrates plays a crucial role in maintaining homeostasis of blood sugar level. Insulin-like peptide (ILP) has been identified in insects, such as Drosophila melanogaster and Aedes aegypti. Plasma sugars and polyols of the diamondback moth, Plutella xylostella were separated by a Bio-LC. Among seven peaks, trehalose was the most predominant blood sugar and maintained at approximately 3.5 mM in the larval plasma. However, the feeding activity affected the plasma trehalose level, in which starvation significantly up-regulated the trehalose level. Analysis of ILP expression upon feeding indicated that feeding stimulated the gene expression of ILP. Interestingly, an injection of a vertebrate insulin significantly suppressed the hypertrehalosemia induced by starvation. These results suggest that ILP is a endocrine signal to down-regulate the plasma trehalose level in P. xylostella.

Insulin/insulin-like peptide-binding protein (IBP) is abundantly found in venom of the solitary hunting wasp, Eumenes pomiformis (Hymenoptera: Eumenidae). E. pomiformis IBP (EpIBP) is most similar to insect IBP-like proteins that are known to inhibit insect growth and insulin signaling. To investigate the toxicity and target protein, EpIBP was in vivo expressed by Escherichia coli. Spodoptera exigua (Lepidoptera: Noctuidae) larvae injected with EpIBP showed a 20% lower pupation rate than the control larvae, although their body weight was not significantly different from the control when the larvae were provided artificial diet after the injection. EpIBP extended the larval stage without inducing paralysis of S. exigua larvae. To investigate the effects of EpIBP on caterpillar under a starvation condition, survivorship and body weight of the EpIBP-injected were evaluated without providing artificial diet until all the larvae died. The survivorship of the EpIBP-injected larvae was 24-36% higher than the control larvae at 4-5 d post-injection. The body weight of the control larvae reduced to 59% that is approximately 10% lower than the body weight of the EpIBP-injected larvae. These results suggest that EpIBP might inhibit the metabolism of the caterpillars, which is likely related with insulin-like peptide signaling pathway, suppress the loss of body weight and eventually extend the larval stage. An EpIBP-binding protein (EpIBPBP) isolated by immunoprecipitation was matched with a coiled-coil domain-containing protein of the fruit fly. The full-length sequence analysis of EpIBPBP is in progress.

Differential capacity of the parthenogenetic embryonic stem cells (PESCs) is still under controversy and the mechanisms of its neural induction are yet poorly understood. Here we demonstrated neural lineage induction of PESCs by addition of insulin-like growth factor-2 (Igf2), which is an important factor for embryo organ development and a paternally expressed imprinting gene. Murine PESCs were aggregated to embryoid bodies (EBs) by suspension culture under the leukemia inhibitory factor-free condition for 4 days. To test the effect of exogenous Igf2, 30 ng/ml of Igf2 was supplemented to EBs induction medium. Then neural induction was carried out with serum-free medium containing insulin, transferrin, selenium, and fibronectin complex (ITSFn) for 12 days. Normal murine embryonic stem cells derived from fertilized embryos (ESCs) were used as the control group. Neural potential of differentiated PESCs and ESCs were analyzed by immunofluorescent labeling and real-time PCR assay (Nestin, neural progenitor marker; Tuj1, neuronal cell marker; GFAP, glial cell marker). The differentiated cells from both ESC and PESC showed heterogeneous population of Nestin, Tuj1, and GFAP positive cells. In terms of the level of gene expression, PESC showed 4 times higher level of GFAP expression than ESCs. After exposure to Igf2, the expression level of GFAP decreased both in derivatives of PESCs and ESCs. Interestingly, the expression level of Tuj1 increased only in ESCs, not in PESCs. The results show that IGF2 is a positive effector for suppressing over-expressed glial differentiation during neural induction of PESCs and for promoting neuronal differentiation of ESCs, while exogenous Igf2 could not accelerate the neuronal differentiation of PESCs. Although exogenous Igf2 promotes neuronal differentiation of normal ESCs, expression of endogenous Igf2 may be critical for initiating neuronal differentiation of pluripotent stem cells. The findings may contribute to understanding of the relationship between imprinting mechanism and neural differentiation and its application to neural tissue repair in the future.

Agi ng adversely affects the structure and function of the saliva ry gla nd and leads to ma rked insulin resis t ance that correlates with red uced ins ulin s ignal t ra nsduction, lnsulin-like g rowth factors are k.nown to be regulator involved in embryonic a nd postnatal development with sequences 62% identical t o that of proins ulin , To determine whether i n suli n- like growth facto l' - l, -2, - 1 receptor a l'e involved in the changes in rat salival'y gland by aging, we a na lyzecl the qua nti tation of 19f - 1, -2, - 1 rece ptor mRNA in l'at salivary glancl between 2 weeks and 26 months after bir th using the competiti ve reverse t ra nscriptase-polymerase chain reaction(RT-PCR) methocl Between 2 weeks ancl 2 months age, sharp falls in the qua nt ities of Igf-2 mRNA were observed, W11ereas Igf- 1 receptor mRNA rose by aging, but not sig nifïcantly, The quanti t ies of 19f- l kept by aging, These change seem to be involvecl a role fol' the Igf-2 in sali va ry c1evelopment a ncl earl y growth is incli ca ted, Thus, t he dras tic changes in the qua ntities of Igf-2 mRNA in the ra t sali va ry gla nd by aging seem to be in volved in the development, early growth and homeostasis of sali vary gla nd,

To deterrnine the effects of insulin-like growth factor system in the aging process of the rat submandibular gland, expression pattems of 19f-1, 19f-2 and 19f-1 receptor were investigated by immunohistochem엽따. 1n addition, age-related changes of 19f-1 and 19f-2 concentrations in serum were deterrnined by radioimmunoassay 19f-1, 19f-2 and 19f-1 receptor were principally expressed 띠 the duct cells. 19f-1 receptors were strongly expre잃ed in 2-week-old group but were gradually decreased with advancing age. 19f-1 expressions were the strongest in the excretory and striated ducts of 7-month-old and 17-month-old groups. 19f-1 expressions, however, were weakiy expressed in the cells of granular convoluted tubules of 7-month잉ld ， 17-month-old and 27-month-old groups. 19f-2 expressions were found in some cells around duαs of 2-week-old group but were persisted relatively weak. The concentrations of 19f-1 and 1향2 in serum were the highest in 2-week-old group but were decreased and maintained at low level with advancing age. These results show that all components of 19f system were expressed in the rat submandibular giand in an age-related manner. Serum concentrations of all components of 19f system were not dosely related with the intra-밍and비ar expresslon patterns 까lerefore ， 1양 systerns may play important roles in the aging process of the rat submandibular gland in an autocrine/paracrine manner