Is GIP a glucagon cell constituent?

Summary Gastric inhibitory peptide or glucose-dependent insulin-releasing peptide (GIP) is a member of the gut hormone family. Its physiological action is thought to be related to its insulinotrophic effect.The occurrence and distribution of GIP was studied by immunohistochemistry. In all species examined including man, GIP immunoreactivity was found to reside in the glucagon cells of the pancreas and gut. Three pancreatic glucagonomas were found to contain numerous cells displaying GIP and glucagon immunoreactivity.The GIP antiserum used did not cross react with either pancreatic-type or gut-type glucagon (GLI).     

Two incretin hormones GLP-1 and GIP: comparison of their actions in insulin secretion and β cell preservation

Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the two primary incretin hormones secreted from the intestine upon ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic β cells. GIP and GLP-1 exert their effects by binding to their specific receptors, the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R), which belong to the G-protein coupled receptor family. Receptor binding activates and increases the level of intracellular cAMP in pancreatic β cells, thereby stimulating insulin secretion glucose-dependently. In addition to their insulinotropic effects, GIP and GLP-1 have been shown to preserve pancreatic β cell mass by inhibiting apoptosis of β cells and enhancing their proliferation. Due to such characteristics, incretin hormones have been gaining mush attention as attractive targets for treatment of type 2 diabetes, and indeed incretin-based therapeutics have been rapidly disseminated worldwide. However, despites of plethora of rigorous studies, molecular mechanisms underlying how GIPR and GLP-1R activation leads to enhancement of glucose-dependent insulin secretion are still largely unknown. Here, we summarize the similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic actions and their effects on pancreatic β cell preservation. We then try to discuss potential of GLP-1 and GIP in treatment of type 2 diabetes.     

Is GIP a glucagon cell constituent?

"Gastric inhibitory peptide" or "glucose-dependent insulin-releasing peptide" (GIP) is a member of the gut hormone family. Its physiological action is thought to be related to its insulinotrophic effect. The occurrence and distribution of GIP was studied by immunohistochemistry. In all species examined including man, GIP immunoreactivity was found to reside in the glucagon cells of the pancrease and gut. Three pancreatic glucagonomas were found to contain numerous cells displaying GIP and glucagon immunoreactivity. The GIP antiserum used did not cross react with either pancreatic-type or gut-type glucagon (GLI).     

GIP受体激动剂类药物筛选模型的构建

目的:GIP受体激动剂类药物筛选模型的构建。方法:GIP受体激动剂能刺激胰岛素分泌,可作为治疗Ⅱ型糖尿病的潜在药物,因此,GIP受体激动剂的筛选模型十分重要。本研究采用PCR的方法扩增GIPR基因,将扩增产物酶切回收后与表达载体pCMV6-AC-GFP连接,构建pCMV6-AC-GIPR-GFP重组质粒,转化大肠杆菌DH5α经菌落扩增、质粒提取及序列测序重组质粒;利用脂质体lipofectamine2000转染重组质粒到RIN-m5F细胞中,通过抗生素G418筛选,挑单克隆得到稳定的RIN-m5F/GIPR-GFP细胞株。结果:结果表明PCR扩增获得长度为1 319 bp的GIPR基因,克隆至pCMV6-AC-GFP真核表达载体,经菌落PCR酶切鉴定及序列分析后,证实质粒pCMV6-AC-GIPR-GFP构建成功;通过荧光显微镜观察到细胞内荧光分布均匀,表明重组质粒成功转到RINm5F细胞中。该细胞株经阳性对照(D-Ala~2)GIP处理后,与对照组对比,具有荧光斑点聚集。结论:因此,GIP受体激动剂筛选模型RIN-m5F/GIPR-GFP成功构建,可用于筛选新的GIP受体激动剂,为糖尿病药物开发提供新的筛选模型。     

重组GIP蛋白的原核优化表达及其生物活性的研究

葡萄糖依赖性促胰岛素多肽或抑胃肽(glucose-dependentinsulinotropicpolypeptideorgastricinhibitorypeptide,GIP)是由42个氨基酸组成的胃肠调节肽,在高血糖背景下能够刺激胰岛素释放,能够抑制胃酸分泌、促进神经细胞增生,具有广泛的临床应用价值.化学提取或人工合成GIP,成本过高,不宜规模化生产,故应用基因工程技术研制重组人GIP(rhGIP)并探讨其生物活性有积极的现实意义.人工合成具有大肠杆菌偏爱密码子的编码GIP成熟肽的cDNA序列,利用pET32a( )系统进行原核表达;在小规模发酵条件下,进行优化诱导表达和目的蛋白的亲和纯化;通过检测SD大鼠胃酸分泌和血糖浓度,对纯化后的rhGIP进行生理活性研究;通过形态学观察和培养基中NO含量测定,检测rhGIP对PC12细胞NO自由基生成量的影响;应用Aβ25-35加入培养基造成PC12细胞神经损伤模型,分别以高、中、低剂量rhGIP作用于此模型,通过MTT(2-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyltetrazoliumbromide)法测定PC12细胞的活性.结果显示,成功克隆了人GIP基因,诱导表达的rhGIP占细胞总蛋白质的35%,部分可溶,部分以包涵体形式存在.经过诱导表达的重组蛋白质分子质量约为26ku,与理论值相符.纯化后的rhGIP具有免疫活性.优化诱导表达条件为表达菌生长密度A600值0.50,IPTG浓度0.5mmol/L,温度37℃,诱导表达时间4h.裂解上清液经固定化金属亲和层析一步法层析后,表达的水溶性rhGIP融合蛋白的最后得率为1.2mg/L菌液,纯度为85%.纯化后的rhGIP能够使SD大鼠胃液pH值增高,其抑制胃酸分泌作用与生理盐水对照组比较差异有显著性(P<0.05),而rhGIP组和标准品GIP组比较差异无显著性.在高血糖背景下,注射rhGIP15min后,大鼠血浆血糖浓度较基础血糖显著降低(P<0.05),30min时与单独注射葡萄糖的模型对照组比较,差异无显著性,而rhGIP组和标准品GIP组其差异不显著.在rhGIP对神经细胞的营养和对PC12细胞免受神经损伤和缺氧损伤影响的研究中发现,用rhGIP培养PC12细胞32h后,rhGIP组NO含量极显著低于正常对照组(P<0.01),细胞存活较多,神经突起延伸较好,中、高剂量rhGIP组均较神经损伤和缺氧损伤组活性显著升高(P<0.05),且细胞活性呈剂量依赖关系,rhGIP组与标准品GIP组差异不显著,与正常对照组亦无显著差异.研究结果表明,已得到高效表达的rhGIP融合蛋白,该蛋白质具有免疫活性,具有抑制胃酸分泌和降低大鼠血浆血糖浓度的生理活性,并且对神经细胞有营养和保护作用.     

Sex, Death, and Evolution in Proto- and Metazoa, 1876–1913

In the period 1875–1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rates of entry and oxidation of acetate,glucose, d(?)-β-hydroxybutyrate,palmitate, oleate and stearate,and rates of production and oxidation of propionate and butyrate in fed and starved sheep

1. Rates of entry and oxidation of a range of metabolites have been measured in tracheostomized sheep (diet, 800g. of lucerne chaff and 100g. of maize/day) by combining isotope-dilution techniques with the continuous measurement of total respiratory gas exchange, and ¹⁴CO₂ production during the intravenous or intraruminal infusion of ¹⁴C-labelled substrates. 2. Mean entry rates in fed and starved (24hr.) sheep respectively, expressed as mg./min./kg. body wt.^0·75, were: glucose, 5·0 (range 4·8–5·1, 2 observations) and 3·8 (3·2–4·2, 4); acetate, 10·8 (9·1–13·5, 4) and 5·8 (1); d(−)-β-hydroxybutyrate, 1·4 (1) and 1·5 (0·8–2·4, 4); palmitate, oleate and stearate (starved sheep only) 1·0 (0·6–1·9, 7), 0·9 (0·2–1·6, 10) and 0·9 (0·5–1·1, 11) respectively. 3. Production rates of propionate and butyrate in continuously feeding sheep were 6·4 (4·7–8·3, 4) and 4·3 (3·4–6·1, 4) mg./min./kg.^0·75 respectively, and in starved (24hr.) sheep were 2·5 (2·2–2·9, 2) and 1·0 (0·8–1·2, 2) mg./min./kg.^0·75 respectively. 4. Calculated terminal values for the specific radioactivity of respiratory ¹⁴CO₂ during measurements of entry rates and production rates were used to calculate the contributions of individual substrates to overall oxidative metabolism. Mean values for fed and starved sheep respectively were: glucose, 9·1 (8·6–9·6, 2) and 11·2 (5·9–15·1, 4)%; acetate, 31·6 (26·8–38·1, 4) and 22·1 (1)%; d(−)-β-hydroxybutyrate, 10·4 (1) and 4·8 (1·9–7·7, 4)%; propionate, 23·0 (13·8–29·9, 4) and 7·1 (6·8–7·4, 2)%; butyrate, 16·5 (13·7–20·5, 4) and 5·3 (5·2–5·3, 2)%; palmitate, oleate and stearate (starved sheep only), 4·7 (2·0–7·7, 7), 4·0 (1·2–6·6, 10) and 4·4 (3·8–5·8, 9)% respectively. The sum of these values for individual substrates in fed and starved sheep, excluding that of β-hydroxybutyrate and after correction of the glucose value for the known interrelations of this substrate with propionate, accounted for 76% and 58% respectively of total production of carbon dioxide. 5. Calculations based on the proportion of substrate entry directly oxidized indicated that the substrates studied accounted for 63% (fed sheep) and 43% (starved sheep) of total energy expenditure measured by oxygen uptake. The contribution of β-hydroxybutyrate was excluded, and corrections were made for glucose–propionate interrelations, and for the different rates of oxidation of the methyl and carboxyl fragments of acetate. 6. The present results have been combined with those obtained earlier in this Laboratory to examine the relationships between rates of substrate entry and oxidation, and concentrations of substrate in blood. Rates of entry of acetate, glucose, d(−)-β-hydroxybutyrate, palmitate and oleate (but not stearate) were well correlated with concentration in blood, and substrate contribution to production of carbon dioxide showed a similar correlation to blood concentration, except with glucose. 7. It was concluded that the general technique is of potential value in providing valid quantitative parameters of animal metabolism.     

HIV and HCV： from Co-infection to Epidemiology, Transmission, Pathogenesis, and Treatment

Human immunodeficiency virus (HIV) is the infectious agent causing acquired immu-nodeficiency syndrome (AIDS),a deadliest scourge of human society. Hepatitis C virus (HCV) is a major causative agent of chronic liver disease and infects an estimated 170 million people worldwide,resulting in a serious public health burden. Due to shared routes of transmission,co-infection with HIV and HCV has become common among individuals who had high risks of blood exposures. Among hemophiliacs the co-infection rate accounts for 85%; while among injection drug users (IDU) the rate can be as high as 90%. HIV can accelerate the progression of HCV-related liver disease,particularly when immunodeficiency has developed. Although the effect of HCV on HIV infection is controversial,most studies showed an increase in mortality due to liver disease. HCV may act as a direct cofactor to fasten the progression of AIDS and decrease the tolerance of highly active antiretroviral therapy (HARRT). Conversely,HAART-related hepatotoxicity may enhance the progression of liver fibrosis. Due to above complications,co-infection with HCV and HIV-1 has imposed a critical challenge in the management of these patients. In this review,we focus on the epidemiology and transmission of HIV and HCV,the impact of the two viruses on each other,and their treatment.     

重组人GIP衍生物的克隆、表达、纯化及活性研究

葡萄糖依赖性促胰岛素释放肽(glucose-dependent insulinotropic polypeptide,GIP)具有促胰岛素分泌的作用,但因体内半衰期短而限制了其应用。对二肽酶4(dipeptidase IV,DPP IV)识别位点等氨基酸进行改造可有效延长其半衰期。通过人工合成基因或PCR定点突变的方法合成GIP不同突变体基因,将其克隆到大肠杆菌表达载体pET32a(+)中进行诱导表达,通过亲和层析,纯化获得各对应的多肽。经肠激酶酶切后,分别在昆明鼠及糖尿病模型鼠体内研究其生物活性。结果显示突变体mGIP243在昆明鼠体内具有显著的降血糖活性,当给药剂量为48nmol/kg时,其体内降血糖活性可延长至90分钟,相对于将第二位上的丙氨酸突变成丝氨酸的mGIP2和天然GIP半衰期显著延长。GIP类似物mGIP243在2型糖尿病模型鼠中也有降血糖活性,使其可能成为治疗糖尿病的候选药物。     

The Cell and Protoplasm as Container,Object, and Substance, 1835–1861

This article revisits the development of the protoplasm concept as it originally arose from critiques of the cell theory, and examines how the term “protoplasm” transformed from a botanical term of art in the 1840s to the so-called “living substance” and “the physical basis of life” two decades later. I show that there were two major shifts in biological materialism that needed to occur before protoplasm theory could be elevated to have equal status with cell theory in the nineteenth century. First, I argue that biologists had to accept that life could inhere in matter alone, regardless of form. Second, I argue that in the 1840s, ideas of what formless, biological matter was capable of dramatically changed: going from a “coagulation paradigm” (Pickstone, 1973) that had existed since Theophrastus, to a more robust conception of matter that was itself capable of movement and self-maintenance. In addition to revisiting Schleiden and Schwann’s original writings on cell theory, this article looks especially closely at Hugo von Mohl’s definition of the protoplasm concept in 1846, how it differed from his primordial utricle theory of cell structure two years earlier. This article draws on Lakoff and Johnson’s theory of “ontological metaphors” to show that the cell, primordial utricle, and protoplasm can be understood as material container, object, and substance, and that these overlapping distinctions help explain the chaotic and confusing early history of cell theory.     

Biosynthesis,isolation, purification and separation of nivalenol,fusarenone — X and zearalenone

Fusarium, graminearum KF 370 isolate is able to simultaneous biosynthesis of three toxic metabolites, namely: fusarenone-X (FUS), nivalenol (NIV) and zearalenone (F-2). After metabolites extraction with methanol — water (3:1) and defatting with n-heptane toxins were partitioned into chloroform layer. Purification of the? compounds was performed on Celite 545 — charcoal — Aluminiumoxid 90 column then metabolites were separated on Kieselgel 60 (200–300 mesh) column with developing solvent chloroform — methanol. This way FUS, NIV and F-2 were obtained as crystalline or high purity standards.     

When Do Allocations and Constructs Respect Material,Energy, Financial,and Production Balances in LCA and EEIO?

Conservation of mass and energy are essential to physical accounting, just as price and market balances are essential to economic accounting. These principles guide data collection and inventory compilation in industrial ecology. The resulting balanced surveys, however, can rarely be used directly for life cycle assessment (LCA) or environmentally extended input‐output (EEIO) analysis; some modeling is necessary to recast coproductions by multifunctional activities as monofunctional unit processes (a.k.a. Leontief production functions or technical “recipes”). This modeling is done with allocations in LCA and constructs in input‐output. In this article, we ask how these models respect or perturb the balances of the original inventory. Which allocations or constructs, applied to what type of data set, have the potential to simultaneously respect its multiple physical, financial, and market balances? Our analysis builds upon the recent harmonization of allocations and constructs and the ongoing development of multilayered supply and use inventory tables. We derive the necessary and sufficient conditions for balanced models, investigate the role of data aggregation, and clarify these models' relation to system expansion. We find that none of the modeling families in LCA and EEIO are balanced in general, but special data characteristics can allow for the respect of multiple balances. An analysis of these special cases allows for clear guidance for data compilation and methods integration.     

A GIP Receptor Agonist Exhibits β-Cell Anti-Apoptotic Actions in Rat Models of Diabetes Resulting in Improved β-Cell Function and Glycemic Control

Aims

The gastrointestinal hormone GIP promotes pancreatic islet function and exerts pro-survival actions on cultured β-cells. However, GIP also promotes lipogenesis, thus potentially restricting its therapeutic use. The current studies evaluated the effects of a truncated GIP analog, D-Ala²-GIP_1–30 (D-GIP_1–30), on glucose homeostasis and β-cell mass in rat models of diabetes.

Materials and Methods

The insulinotropic and pro-survival potency of D-GIP_1–30 was evaluated in perfused pancreas preparations and cultured INS-1 β-cells, respectively, and receptor selectivity evaluated using wild type and GIP receptor knockout mice. Effects of D-GIP_1–30 on β-cell function and glucose homeostasis, in vivo, were determined using Lean Zucker rats, obese Vancouver diabetic fatty rats, streptozotocin treated rats, and obese Zucker diabetic fatty rats, with effects on β-cell mass determined in histological studies of pancreatic tissue. Lipogenic effects of D-GIP_1–30 were evaluated on cultured 3T3-L1 adipocytes.

Results

Acutely, D-GIP_1–30 improved glucose tolerance and insulin secretion. Chronic treatment with D-GIP_1–30 reduced levels of islet pro-apoptotic proteins in Vancouver diabetic fatty rats and preserved β-cell mass in streptozotocin treated rats and Zucker diabetic fatty rats, resulting in improved insulin responses and glycemic control in each animal model, with no change in body weight. In in vitro studies, D-GIP_1–30 exhibited equivalent potency to GIP_1–42 on β-cell function and survival, but greatly reduced action on lipoprotein lipase activity in 3T3-L1 adipocytes.

Conclusions

These findings demonstrate that truncated forms of GIP exhibit potent anti-diabetic actions, without pro-obesity effects, and that the C-terminus contributes to the lipogenic actions of GIP.     

Partial sequence homologies between cytoskeletal proteins,c-myc,Rous sarcoma virus and adenovirus proteins,transducin, and β- and γ-crystallins

Computer based sequence comparisons indicate partial sequence homology between human c-myc, Rous sarcoma virus, adenovirus 7, and simian sarcoma virus proteins and the cytoskeletal proteins desmin, keratin and vimentin. In addition, sections of the oncogene proteins showed partial but significant homology to and subunits of transducin, -II and -BP crystallins showed partial but significant homology to the cytoskeletal proteins keratin, vimentin, desmin, and -tubulin, and to adenovirus 7 and simian sarcoma virus transforming gene proteins. -BP crystallin showed partial but significant homology to Rous sarcoma virus protein, and to and y subunits of transducin. Both crystallins showed partial sequence homology to the GTP-binding protein elongation factor TU fromEscherichia coli . These sequence homologies suggest a link between the mechanisms of normal lens cell differentiation, involving modifications to the cytoskeleton and subsequent changes to the pattern of protein synthesis, and mechanisms of neoplastic transformation. Furthermore the transducin-like region on -crystallin may be important for its interaction with lens membranes and the maintenance of short-range order for lens transparency.     

Pollen morphology and ultrastructure of Australian Monimiaceae ‐ Austromatthaea,Hedycarya, Kibara,Leviera, Steganthera and Tetrasynandra

The pollen morphology and ultrastructure of Austromatthaea elegans, Hedycarya angustifolia, H. loxocarya, Kibara rigidifolia, Leviera acuminata, Steganthera macooraia and Tetrasynandra laxiflora, are described. All are Australian members of the Monimiaceae sensu stricto of the order Laurales, subclass Magnoliidae. Except for Hedycarya angustifolia, which has pollen grains in permanent tetrads, all species have small, globose, apolar, inaperturate pollen. They can be identified under SEM by their surface ornamentation: Austromatthaea has fossulate sculpturing; Hedycarya angustifolia has tetrads with a warty configuration; H. loxocarya has echinate pollen; Kibara has spherical gemmae with nipple‐like projections; Leviera has stellate sculpturing; Steganthera has a verrucose surface with small spherical projections on each verruca, and Tetrasynandra is gemmate with one to several spiny projections on each gemma. The pollen grains of all genera of Australian Monimiaceae sensu stricto, some the results of previous studies, are summarized in tabular form. The exine has no columellae, foot layer or endexine, in contrast to the family Atherospermataceae (syn. subfamily Atherospermatoideae of the Monimiaceae, sensu lato). The most elaborate type of wall structure consists of radial elements ("radial processes") with white line‐centered regions extending from beyond the intine to the tectal region and a two‐layered intine with an outer channelled part (onciform zone). Trends of evolution from this type are discussed and comparisons are made with other Monimiaceae, Lauraceae, Amborellaceae and Trimeniaceae.     

Eicosanoids, β-cell function, and diabetes

Arachidonic acid (AA) is metabolized by cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) enzymes into eicosanoids, which are involved in diverse diseases, including type 1 and type 2 diabetes. During the last 30 years, evidence has been accumulated that suggests important functions for eicosanoids in the control of pancreatic β-cell function and destruction. AA metabolites of the COX pathway, especially prostaglandin E(2) (PGE(2)), appear to be significant factors to β-cell dysfunction and destruction, participating in the pathogenesis of diabetes and its complications. Several elegant studies have contributed to the sorting out of the importance of 12-LOX eicosanoids in cytokine-mediated inflammation in pancreatic β cells. The role of CYP eicosanoids in diabetes is yet to be explored. A recent publication has demonstrated that stabilizing the levels of epoxyeicosatrienoic acids (EETs), CYP eicosanoids, by inhibiting or deleting soluble epoxide hydrolase (sEH) improves β-cell function and reduces β-cell apoptosis in diabetes. In this review we summarize recent findings implicating these eicosanoid pathways in diabetes and its complications. We also discuss the development of animal models with targeted gene deletion and specific enzymatic inhibitors in each pathway to identify potential targets for the treatment of diabetes and its complications.