Discovery of a series of nonpeptide small molecules that inhibit the binding of insulin-like growth factor (IGF) to IGF-binding proteins

Synthesis of 1-Aminoisoquinolines and Their Application in a Host-Guest Doped Strategy To Construct Ultralong Room-Temperature Phosphorescence Materials for Bioimaging

Organic ultralong room-temperature phosphorescence (RTP) materials have attracted great attention for their wide applications in optoelectronic devices and bioimaging. However, the development of these materials remains a challenging task, partially due to the lack of rational molecular design strategies and unclear luminescence mechanisms. Herein, we present a method for facile access to structurally diverse substituted 1-aminoisoquinoline derivatives through a copper-catalyzed one-pot three-component coupling reaction that provides a promising approach to rapidly assemble a library of 1-aminoisoquinolines for exploring the regularity of the host-guest doped system. A series of host-guest RTP materials with wide-ranging lifetimes from 4.4 to 299.3 ms were constructed by doping various substituted isoquinolines derivatives into benzophenone (BP). Furthermore, 4 r/BP nanoparticles could be used for in-vivo imaging with a signal-to-noise ratio value as high as 32, revealing the potential of the isoquinoline framework for the construction of high-performance RTP materials.

Synthesis of Isoquinoline-Derived Diene Esters and Quinolin-2(1H)-ylidene-Substituted 1,5-Diones from Enynones and (Iso) Quinoline N-Oxides

An efficient synthetic method was developed to access isoquinoline-derived diene esters from enynones and isoquinoline-N-oxides in an atom-economic manner. The isoquinoline-substituted diene esters were obtained in moderate to excellent yields via [3 + 2]-cycloaddition and isoxazole ring opening followed by a [1,5]-sigmatropic rearrangement reaction, which resulted in one C-C and two C-O bond formations. Further, quinolin-2(1H)-ylidene-substituted 1,5-diones were achieved by reaction of enynones with quinoline-N-oxides in very good to high yields.

Super-Electron-Donor 2-Azaallyl Anions Enable Construction of Isoquinolines

Herein is introduced the application of "super-electron-donor"(SED) 2-azaallyl anions in a tandem reduction/radical cyclization/radical coupling/aromatization protocol that enables the rapid construction of isoquinolines. The value of this transition-metal-free method is highlighted by the wide range of isoquinoline ethyl amines prepared with good functional group tolerance and yields. An operationally simple gram scale synthesis is also conducted, confirming the scalability.

Palladium-Catalyzed Isoquinoline Synthesis by Tandem C-H Allylation and Oxidative Cyclization of Benzylamines with Allyl Acetate

A novel approach to synthesize 3-methylisoquinolines via a one-pot, two-step, palladium(II)-catalyzed tandem C-H allylation/intermolecular amination and aromatization is reported. A wide series of 3-methylisoquinoline derivatives were obtained directly using this method in moderate to good yields, and we highlight the synthetic importance of this new transformation.

IGFBPs mediate IGF-1's functions in retinal lamination and photoreceptor development during pluripotent stem cell differentiation to retinal organoids

Development of the retina is regulated by growth factors, such as insulin-like growth factors 1 and 2 (IGF-1/2), which coordinate proliferation, differentiation, and maturation of the neuroepithelial precursors cells. In the circulation, IGF-1/2 are transported by the insulin growth factor binding proteins (IGFBPs) family members. IGFBPs can impact positively and negatively on IGF-1, by making it available or sequestering IGF-1 to or from its receptor. In this study, we investigated the expression of IGFBPs and their role in the generation of human retinal organoids from human pluripotent stem cells, showing a dynamic expression pattern suggestive of different IGFBPs being used in a stage-specific manner to mediate IGF-1 functions. Our data show that IGF-1 addition to culture media facilitated the generation of retinal organoids displaying the typical laminated structure and photoreceptor maturation. The organoids cultured in the absence of IGF-1, lacked the typical laminated structure at the early stages of differentiation and contained significantly less photoreceptors and more retinal ganglion cells at the later stages of differentiation, confirming the positive effects of IGF-1 on retinal lamination and photoreceptor development. The organoids cultured with the IGFBP inhibitor (NBI-31772) and IGF-1 showed lack of retinal lamination at the early stages of differentiation, an increased propensity to generate horizontal cells at mid-stages of differentiation and reduced photoreceptor development at the later stages of differentiation. Together these data suggest that IGFBPs enable IGF-1's role in retinal lamination and photoreceptor development in a stage-specific manner.

Metabolic Strategies for Inhibiting Cancer Development

The tumor microenvironment is a complex mix of cancerous and noncancerous cells (especially immune cells and fibroblasts) with distinct metabolisms. These cells interact with each other and are influenced by the metabolic disorders of the host. In this review, we discuss how metabolic pathways that sustain biosynthesis in cancer cells could be targeted to increase the effectiveness of cancer therapies by limiting the nutrient uptake of the cell, inactivating metabolic enzymes (key regulatory ones or those linked to cell cycle progression), and inhibiting ATP production to induce cell death. Furthermore, we describe how the microenvironment could be targeted to activate the immune response by redirecting nutrients toward cytotoxic immune cells or inhibiting the release of waste products by cancer cells that stimulate immunosuppressive cells. We also examine metabolic disorders in the host that could be targeted to inhibit cancer development. To create future personalized therapies for targeting each cancer tumor, novel techniques must be developed, such as new tracers for positron emission tomography/computed tomography scan and immunohistochemical markers to characterize the metabolic phenotype of cancer cells and their microenvironment. Pending personalized strategies that specifically target all metabolic components of cancer development in a patient, simple metabolic interventions could be tested in clinical trials in combination with standard cancer therapies, such as short cycles of fasting or the administration of sodium citrate or weakly toxic compounds (such as curcumin, metformin, lipoic acid) that target autophagy and biosynthetic or signaling pathways.

Synthetic applications of α,α-difluoroarylacetic acids and salts via decarboxylative functionalization

α,α-Difluoroarylacetic acids are stable, inexpensive and readily available building blocks which can be used to access various difluoromethylated aryl motifs via decarboxylative functionalization for the formation of carbon–carbon and carbon-heteroatom (F, O, S) bonds.

The metalloproteinase Papp-aa controls epithelial cell quiescence-proliferation transition

Human patients carrying PAPP-A2 inactivating mutations have low bone mineral density. The underlying mechanisms for this reduced calcification are poorly understood. Using a zebrafish model, we report that Papp-aa regulates bone calcification by promoting Ca2+-transporting epithelial cell (ionocyte) quiescence-proliferation transition. Ionocytes, which are normally quiescent, re-enter the cell cycle under low [Ca2+] stress. Genetic deletion of Papp-aa, but not the closely related Papp-ab, abolished ionocyte proliferation and reduced calcified bone mass. Loss of Papp-aa expression or activity resulted in diminished IGF1 receptor-Akt-Tor signaling in ionocytes. Under low Ca2+ stress, Papp-aa cleaved Igfbp5a. Under normal conditions, however, Papp-aa proteinase activity was suppressed and IGFs were sequestered in the IGF/Igfbp complex. Pharmacological disruption of the IGF/Igfbp complex or adding free IGF1 activated IGF signaling and promoted ionocyte proliferation. These findings suggest that Papp-aa-mediated local Igfbp5a cleavage functions as a [Ca2+]-regulated molecular switch linking IGF signaling to bone calcification by stimulating epithelial cell quiescence-proliferation transition under low Ca2+ stress.

Synthesis of rhodium(iii)-catalyzed isoquinoline derivatives from allyl carbonates and benzimidates with hydrogen evolution

A novel Rh(iii)-catalyzed cascade C-H activation/cyclization approach to access isoquinoline derivatives from benzimidates and available allyl carbonates with the liberation of H2 has been realized. Allyl carbonates were first used as a versatile and universal C2 synthon to synthesize this biological activity skeleton via an efficient and practical process just within 1 h.

The Exploration of Chirality for Improved Druggability within the Human Kinome

Chirality is important in drug discovery because stereoselective drugs can ameliorate therapeutic difficulties including adverse toxicity and poor pharmacokinetic profiles. The human kinome, a major druggable enzyme class has been exploited to treat a wide range of diseases. However, many kinase inhibitors are planar and overlap in chemical space, which leads to selectivity and toxicity issues. By exploring chirality within the kinome, a new iteration of kinase inhibitors is being developed to better utilize the three-dimensional nature of the kinase active site. Exploration into novel chemical space, in turn, will also improve drug solubility and pharmacokinetic profiles. This perspective explores the role of chirality to improve kinome druggability and will serve as a resource for pioneering kinase inhibitor development to address current therapeutic needs.

Ag-Catalyzed minisci C–H difluoromethylarylation of N-heteroarenes

A mild silver-catalyzed decarboxylative C–H difluoromethylarylation of electron-deficient N-heteroarenes.

Insulin-Like Growth Factor Binding Protein-5 in Physiology and Disease

Insulin-like growth factor (IGF) signaling is regulated by a conserved family of IGF binding proteins (IGFBPs) in vertebrates. Among the six distinct types of IGFBPs, IGFBP-5 is the most highly conserved across species and has the broadest range of biological activities. IGFBP-5 is expressed in diverse cell types, and its expression level is regulated by a variety of signaling pathways in different contexts. IGFBP-5 can exert a range of biological actions including prolonging the half-life of IGFs in the circulation, inhibition of IGF signaling by competing with the IGF-1 receptor for ligand binding, concentrating IGFs in certain cells and tissues, and potentiation of IGF signaling by delivery of IGFs to the IGF-1 receptor. IGFBP-5 also has IGF-independent activities and is even detected in the nucleus. Its broad biological activities make IGFBP-5 an excellent representative for understanding IGFBP functions. Despite its evolutionary conservation and numerous biological activities, knockout of IGFBP-5 in mice produced only a negligible phenotype. Recent research has begun to explain this paradox by demonstrating cell type-specific and physiological/pathological context-dependent roles for IGFBP-5. In this review, we survey and discuss what is currently known about IGFBP-5 in normal physiology and human disease. Based on recent in vivo genetic evidence, we suggest that IGFBP-5 is a multifunctional protein with the ability to act as a molecular switch to conditionally regulate IGF signaling.

Zebrafish heart regeneration: Factors that stimulate cardiomyocyte proliferation

Myocardial infarctions (MI) remain a leading cause of global morbidity and mortality, and a reason for this is the inability of adult, mammalian cardiomyocytes to divide post-MI. Recent studies demonstrate a limited population of cardiomyocytes retain their proliferative capacity and understanding how endogenous cardiomyocytes can be stimulated to re-enter the cell cycle is a focus of current research. In this review we discuss the history of zebrafish cardiac regeneration and highlight how different models reveal the molecular pathways important in driving cardiomyocyte proliferation after injury. Understanding the molecules that regulate cell cycle re-entry can provide insights into promoting cardiac repair in humans.

Tuneable access to isoquinolines via a transition-metal-free C(sp3)–C(sp3) bond cleavage rearrangement reaction

A novel divergent synthesis of multi-substituted isoquinolines via C(sp³)–C(sp³) bond cleavage rearrangement reactions was realized.

Tbx3-dependent amplifying stem cell progeny drives interfollicular epidermal expansion during pregnancy and regeneration

The skin surface area varies flexibly in response to body shape changes. Skin homeostasis is maintained by stem cells residing in the basal layer of the interfollicular epidermis. However, how the interfollicular epidermal stem cells response to physiological body shape changes remains elusive. Here, we identify a highly proliferative interfollicular epidermal basal cell population in the rapidly expanding abdominal skin of pregnant mice. These cells express Tbx3 that is necessary for their propagation to drive skin expansion. The Tbx3+ basal cells are generated from Axin2+ interfollicular epidermal stem cells through planar-oriented asymmetric or symmetric cell divisions, and express transit-amplifying cell marker CD71. This biased division of Axin2+ interfollicular epidermal stem cells is induced by Sfrp1 and Igfbp2 proteins secreted from dermal cells. The Tbx3+ basal cells promote wound repair, which is enhanced by Sfrp1 and Igfbp2. This study elucidates the interfollicular epidermal stem cell/progeny organisation during pregnancy and suggests its application in regenerative medicine.The abdominal skin expands rapidly during pregnancy. Here the authors show that a population of highly proliferative stem cell progenies expressing the transcription factor Tbx3 is required for abdominal skin expansion in pregnant mice.

Oxidant-Controlled C-sp2/sp3-H Cross-Dehydrogenative Coupling of N-Heterocycles with Benzylamines

Oxidant controlled ionic liquid mediated cross-dehydrogenative coupling (CDC) of benzylamines with N-heterocycles having sp² or sp³ carbon resulted in the formation of C-benzoylated or alkenylated products. Benzoylation of N-heterocycles occurs via (NH₄)₂S₂O₈ catalyzed benzoyl radical formation. An oxidative alkenylation of N-heterocycles having C-sp³ carbon (2-methylaza-arenes) occurs via deamination of benzylamine followed by C-sp³-H bond activation in high stereoselectivity. Both benzoylation and alkenylation protocols are metal-free, green, simple, efficient, and tolerate a wide variety of functional groups.

Follicle-Stimulating Hormone Regulates igfbp Gene Expression Directly or via Downstream Effectors to Modulate Igf3 Effects on Zebrafish Spermatogenesis

Previous work showed that pharmacological inactivation of Igf-binding proteins (Igfbps), modulators of Igf activity, resulted in an excessive differentiation of type A undifferentiated (A_und) spermatogonia in zebrafish testis in tissue culture when Fsh was present in the incubation medium. Using this testis tissue culture system, we studied here the regulation of igfbp transcript levels by Fsh and two of its downstream effectors, Igf3 and 11-ketotestosterone (11-KT). We also explored how Fsh-modulated igfbp expression affected spermatogonial proliferation by adding or removing the Igfbp inhibitor NBI-31772 at different times. Fsh (100 ng/mL) decreased the transcript levels of igfbp1a, -3, and -6a after 1 or 3 days, while increasing igfbp2a and -5b expression, but only after 5 days of incubation. Igf3 down-regulated the same igfbp transcripts as Fsh but with a delay of at least 4 days. 11-KT increased the transcripts (igfbp2a and 5b) that were elevated by Fsh and decreased those of igfbp6a, as did Fsh, while 11-KT did not change igfbp1a or -3 transcript levels. To evaluate Igfbps effects on spermatogenesis, we quantified under different conditions the mitotic indices and relative section areas occupied by the different spermatogonial generations (type A_und, type A differentiating (A_diff), or type B (B) spermatogonia). Igf3 (100 ng/mL) increased the area occupied by A_diff and B while decreasing the one for A_und. Interestingly, a concentration of Igf3 that was inactive by itself (25 ng/mL) became active in the presence of the Igfbp inhibitor NBI-31772 and mimicked the effect of 100 ng/mL Igf3 on spermatogonia. Studies exploiting the different dynamics of igfbp expression in response to Fsh and adding or removing NBI-31772 at different times showed that the quick downregulation of three igfbp as well as the delayed upregulated of two igfbps all support Igf3 bioactivity, namely the stimulation of spermatogonial differentiation. We conclude that Fsh modulates, directly or via androgens and Igf3, igfbp gene expression, supporting Igf3 bioactivity either by decreasing igfbp1a, -3, -6a or by increasing igfbp2a and -5b gene expression.

Igf Binding Proteins Protect Undifferentiated Spermatogonia in the Zebrafish Testis Against Excessive Differentiation

IGF binding proteins (IGFBPs) modulate the availability of IGFs for their cognate receptors. In zebrafish testes, IGF3 promotes the proliferation and differentiation of type A undifferentiated (A_und) spermatogonia, and igf3 expression is strongly elevated by FSH but also responds to T₃. Here we report the effects of FSH and T₃ on igfbp transcript levels in adult zebrafish testis. We then examined T₃ and FSH effects on zebrafish spermatogenesis and explored the relevance of IGFBPs in modulating these T₃ or FSH effects, using a primary tissue culture system for adult zebrafish testis. T₃ up-regulated igfbp1a and igfbp3 expression, whereas FSH reduced igfbp1a transcript levels. To quantify effects on spermatogenesis, we determined the mitotic index and relative section areas occupied by A_und, type A differentiating, or type B spermatogonia. In general, T₃ and FSH stimulated spermatogonial proliferation and increased the areas occupied by spermatogonia, suggesting that both self-renewal and differentiating divisions were stimulated. Preventing IGF/IGFBP interaction by NBI-31772 further increased T₃- or FSH-induced spermatogonial proliferation. However, under these conditions the more differentiated type A differentiating and B spermatogonia occupied larger surface areas at the expense of the area held by A_und spermatogonia. Clearly decreased nanos2 transcript levels are in agreement with this finding, and reduced amh expression may have facilitated spermatogonial differentiation. We conclude that elevating IGF3 bioactivity by blocking IGFBPs shifted T₃- or FSH-induced signaling from stimulating spermatogonial self-renewal as well as differentiation toward predominantly stimulating spermatogonial differentiation, which leads to a depletion of type A_und spermatogonia.

C1-Benzyl and benzoyl isoquinoline synthesis through direct oxidative cross-dehydrogenative coupling with methyl arenes

An oxidative cross-dehydrogenative coupling of isoquinolines with methyl arenes has been developed, yielding structurally diverse C₁-benzyl and -benzoyl isoquinolines selectively. The direct use of readily available methyl arenes as coupling partners avoids unproductive steps for preactivating functional group installation, and is thereby attractive.

TBHP/TFA mediated oxidative cross-dehydrogenative coupling of N-heterocycles with aldehydes

A metal-free oxidative cross-dehydrogenative coupling of N-heterocycles with diverse aldehydes has been established in the presence of TBHP/TFA.

Prenatal stress leads to changes in IGF-1 binding proteins network in the hippocampus and frontal cortex of adult male rat

Depression is a mental disorder of still unknown origin. Currently, much attention is paid to the potential influence of disturbances in the functioning of neurotrophic factors on the onset of this disease. Insulin-like growth factor 1 (IGF-1) is one of the most important growth agents affecting processes that are crucial for brain development. To date, there are no data showing the impact of prenatal stress on the family of six IGF binding proteins (IGFBP 1-6) that regulate IGF-1 bioactivity. The goal of this study was to investigate whether the decreased expression of IGF-1 in the frontal cortex (FCx) and hippocampus (Hp) of adult male rats following a prenatal stress procedure is related to changes in the IGFBP family. Our results show that rats exposed prenatally to stressful stimuli displayed depression-like behavior based on sucrose preference and elevated plus maze tests. In both cases, in the adult rat brain structures that were examined after the prenatal stress procedure, the IGF-1 protein level was reduced. Moreover, we observed changes of varying degrees in the levels of IGFBPs in stressed animals. A decrease in IGFBP-2 and IGFBP-3 accompanied by an increase in the IGFBP-4 concentration in the Hp and the FCx was detected. There were no differences in IGFBP-1 and IGFBP-6 brain levels between the stressed and control animals, whereas IGFBP-5 concentration was decreased in the Hp of prenatally stressed animals. This study demonstrated that stress during pregnancy may lead not only to behavioral disturbances but also to a decrease in IGF-1 level and the dysregulation of the IGF-1 binding protein network in adult rat offspring.

HTRA proteases: regulated proteolysis in protein quality control

Controlled proteolysis underlies a vast diversity of protective and regulatory processes that are of key importance to cell fate. The unique molecular architecture of the widely conserved high temperature requirement A (HTRA) proteases has evolved to mediate critical aspects of ATP-independent protein quality control. The simple combination of a classic Ser protease domain and a carboxy-terminal peptide-binding domain produces cellular factors of remarkable structural and functional plasticity that allow cells to rapidly respond to the presence of misfolded or mislocalized polypeptides.

Insulin-like growth factor system regulates oligodendroglial cell behavior: therapeutic potential in CNS

Amongst the many soluble extracellular factors stimulating intracellular signal transduction pathways and driving cellular processes such as proliferation, differentiation and survival, insulin-like growth factors (IGFs) stand out as indispensable factors for proper oligodendrocyte differentiation and accompanying myelin production. Owing to its potent myelinogenic capacity and its neuroprotective properties, IGFs hold therapeutic potential in demyelinating and neurodengenerative diseases. However, the IGF system is comprised of a complex molecular network involving regulatory binding proteins, proteases, cell surface and extracellular matrix components which orchestrate IGF-specific functions. Thus, the complexity by which these factors are tightly regulated makes a simplistic therapeutic approach towards treating demyelinating conditions unfeasible. In the present review, we address these issues and consider current therapeutic prospects of oligodendrocyte-targeted IGF-based therapies.

Increasing the levels of insulin-like growth factor-I by an IGF binding protein inhibitor produces anxiolytic and antidepressant-like effects

The present studies were conducted to determine if increasing central levels of the neurotrophic factor insulin-like growth factor-1 (IGF-I) either directly or indirectly produces anxiolytic and antidepressant-like effects in the mouse. Central levels of IGF-I can be increased directly, by administering IGF-I, or indirectly by blocking the insulin-like growth factor binding proteins (IGFBPs). The IGFBP family has the unique ability to regulate IGF-I levels by sequestering IGF-I into an inactive complex. Therefore, an IGFBP inhibitor increases the level of IGF-I available to bind to its receptor. Intracerebroventricular (icv) administration of the nonspecific IGFBP inhibitor NBI-31772 (10-30 microg) increases the number of punished crossings in the four-plate test and NBI-31772 (0.3-10 microg) increases time spent in the open quadrant of the elevated zero maze (EZM), indicative of anxiolytic-like effects. NBI-31772 (3-30 microg) also decreases immobility time in the tail suspension test, indicative of antidepressant-like effects. Similarly, icv administration of IGF-I (0.1 microg) produces anxiolytic-like effects in the four-plate test and IGF-1 (0.3-1 microg) produces anxiolytic-like effects in the EZM. IGF-I (10 microg) also produces antidepressant-like effects in the tail suspension test. Coadministration of the IGF-I receptor antagonist JB1 with NBI-31772 or IGF-I blocks the anxiolytic-like and antidepressant-like effects of these compounds. These results suggest that NBI-31772 produces behavioral effects by increasing levels of IGF-I that in turn activate the IGF-I receptor. The present studies demonstrate that an IGFBP inhibitor mimics the behavioral effects of IGF-I and that IGFBP inhibition may represent a novel mechanism by which to increase IGF-I to treat depression and anxiety.

Modifying IGF1 activity: an approach to treat endocrine disorders, atherosclerosis and cancer

Insulin-like growth factor 1 (IGF1) is a polypeptide hormone that has a high degree of structural similarity to human proinsulin. Owing to its ubiquitous nature and its role in promoting cell growth, strategies to inhibit IGF1 actions are being pursued as potential adjunctive measures for treating diseases such as short stature, atherosclerosis and diabetes. In addition, most tumour cell types possess IGF1 receptors and conditions in the tumour microenvironment, such as hypoxia, can lead to enhanced responsiveness to IGF1. Therefore, inhibiting IGF1 action has been proposed as a specific mechanism for potentiating the effects of existing anticancer therapies or for directly inhibiting tumour cell growth.

Modulation of insulin-like growth factor (IGF)-I and IGF-binding protein interactions enhances skeletal muscle regeneration and ameliorates the dystrophic pathology in mdx mice

Administration of recombinant human insulin-like growth factor-I (rhIGF-I) has beneficial effects in animal models of muscle injury and muscular dystrophy. However, the results of these studies may have been confounded by interactions of rhIGF-I with endogenous IGF-binding proteins (IGFBPs). To date, no study has examined whether inhibiting IGFBP interactions with endogenous IGF-I can improve muscle fiber regeneration or muscular pathologies. We tested the hypothesis that reducing IGFBP interactions with endogenous IGF-I would enhance muscle regeneration after myotoxic injury and improve the dystrophic pathology in mdx mice. We administered an IGF-I aptamer (NBI-31772; 6 mg/kg per day, continuous infusion) to C57BL/10 mice undergoing regeneration after myotoxic injury or to mdx dystrophic mice. NBI-31772 binds all six IGFBPs with high affinity and releases "free" endogenous IGF-I. NBI-31772 treatment increased the rate of functional repair in fast-twitch tibialis anterior muscles after notexin-induced injury as evidenced by an increase in maximum force producing capacity (P(o)) at 10 days after injury. In contrast, NBI-31772 administration for 28 days did not alter P(o) of extensor digitorum longus (EDL) and soleus muscles or normalized force of diaphragm muscle strips from mdx mice. Although IGFBP inhibition reduced the susceptibility of the fast-twitch EDL and the diaphragm muscle to contraction-mediated damage, it increased muscle fatigability during repeated maximal contractions. Although the results in the myotoxic injury model suggest IGF-I signaling is important in this model, the results in the mdx model are mixed.

The effects of the insulin-like growth factor-I aptamer, NBI-31772, on glucose homeostasis in the mouse

The majority of insulin-like growth factor-I (IGF-I) in the adult rodent circulation is bound to high affinity IGF binding proteins. We investigated the changes in IGF-I clearance, blood glucose and plasma insulin levels, and tissue 2-deoxyglucose uptake after intravenous administration of the IGF aptamer, NBI-31772, which selectively competes with IGF-I for binding to the IGFBPs, but has no effect at the IGF-I receptor. Clearance of 125I-IGF-I was significantly increased in NBI-31772-treated mice compared with vehicle-treated mice (t1/2 = 45.0 ± 1.9 vs. 56.3 ± 3.9 min, respectively; p = 0.021). However, NBI-31772 had no significant effect on glucose levels, and no insulin sparing effect was apparent neither under basal conditions nor during an intravenous glucose challenge. The decline in the specific activity after 3H-2-deoxyglucose administration was significantly less rapid in NBI-31772-treated mice compared with controls, suggesting that the IGF-I aptamer had an inhibitory effect on hepatic gluconeogenesis. In contrast, no insulin-like effect was apparent in other tissues examined. 3H-2-deoxyglucose accumulation was similar in all tissues analyzed, including skeletal muscle, which is thought to be particularly sensitive to IGF-I. These data suggest that the IGF-I aptamer affects clearance of radiolabeled IGF-I from the circulation, but has no marked effects on glucose nor insulin homeostasis. The search for hydrophilic IGF aptamers with longer duration of action that could be used in the treatment of diabetes may be rewarding. Key words: insulin resistance, gluconeogenesis, 2-deoxyglucose uptake, glucose clearance.

What's new in the IGF-binding proteins?

Since their initial discovery over 25 years ago as IGF carrier proteins, the insulin-like growth factor binding protein (IGFBP) family has grown to six members, ranging in size from 216 to 289 amino acids. The assumption over the years has been that this family of proteins, having higher affinities for IGF-I and IGF-II than does the IGF-IR, serves to block access of these ligands to the receptor. Although the need for such regulatory proteins is consistent with the constitutive secretion of IGFs from many cell types, it is not surprising that additional functions have begun to be uncovered for these proteins. This review will examine new and old actions of the IGFBPs from a biochemical and cell biological perspective.

Pharmacological disruption of insulin-like growth factor 1 binding to IGF-binding proteins restores anabolic responses in human osteoarthritic chondrocytes

Insulin-like growth factor 1 (IGF-1) has poor anabolic efficacy in cartilage in osteoarthritis (OA), partly because of its sequestration by abnormally high levels of extracellular IGF-binding proteins (IGFBPs). We studied the effect of NBI-31772, a small molecule that inhibits the binding of IGF-1 to IGFBPs, on the restoration of proteoglycan synthesis by human OA chondrocytes. IGFBPs secreted by human OA cartilage or cultured chondrocytes were analyzed by western ligand blot. The ability of NBI-31772 to displace IGF-1 from IGFBPs was measured by radiobinding assay. Anabolic responses in primary cultured chondrocytes were assessed by measuring the synthesis of proteoglycans in cetylpyridinium-chloride-precipitable fractions of cell-associated and secreted 35S-labeled macromolecules. The penetration of NBI-31772 into cartilage was measured by its ability to displace 125I-labeled IGF-1 from cartilage IGFBPs. We found that IGFBP-3 was the major IGFBP secreted by OA cartilage explants and cultured chondrocytes. NBI-31772 inhibited the binding of 125I-labeled IGF-1 to IGFBP-3 at nanomolar concentrations. It antagonized the inhibitory effect of IGFBP-3 on IGF-1-dependent proteoglycan synthesis by rabbit chondrocytes. The addition of NBI-31772 to human OA chondrocytes resulted in the restoration or potentiation of IGF-1-dependent proteoglycan synthesis, depending on the IGF-1 concentrations. However, NBI-31772 did not penetrate into cartilage explants. This study shows that a new pharmacological approach that uses a small molecule inhibiting IGF-1/IGFBP interaction could restore or potentiate proteoglycan synthesis in OA chondrocytes, thereby opening exciting possibilities for the treatment of OA and, potentially, of other joint-related diseases.

Neuroprotective effects of insulin-like growth factor-binding protein ligand inhibitors in vitro and in vivo

The role of brain insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) in neuroprotection was further investigated using in vitro and in vivo models of cerebral ischemia by assessing the effects of IGF-I, IGF-II, and high affinity IGFBP ligand inhibitors (the peptide [Leu24, 59, 60, Ala31]hIGF-I (IGFBP-LI) and the small molecule NBI-31772 (1-(3,4-dihydroxybenzoyl)-3-hydroxycarbonyl-6, 7-dihydroxyisoquinoline), which pharmacologically displace and elevate endogenous, bioactive IGFs from IGFBPs. Treatment with IGF-I, IGF-II, or IGFBP-LI (2 microg/mL) significantly (P < 0.05) reduced CA1 damage in organotypic hippocampal cultures resulting from 35 minutes of oxygen and glucose deprivation by 71%, 60%, and 40%, respectively. In the subtemporal middle cerebral artery occlusion (MCAO) model of focal ischemia, intracerebroventricular (icv) administration of IGF-I and IGF-II at the time of artery occlusion reduced ischemic brain damage in a dose-dependent manner, with maximum reductions in total infarct size of 37% (P < 0.01) and 38% (P < 0.01), respectively. In this model of MCAO, i.c.v. administration of NBI-31772 at the time of ischemia onset also dose-dependently reduced infarct size, and the highest dose (100 microg) significantly reduced both total (by 40%, P < 0.01) and cortical (by 43%, P < 0.05) infarct volume. In the intraluminal suture MCAO model, administration of NBI-31772 (50 microg i.c.v.) at the time of artery occlusion reduced both cortical infarct volume (by 40%, P < 0.01) and brain swelling (by 24%, P < 0.05), and it was still effective when treatment was delayed up to 3 hours after the induction of ischemia. These results further define the neuroprotective properties of IGFs and IGFBP ligand inhibitors in experimental models of cerebral ischemia.