The NEMP family supports metazoan fertility and nuclear envelope stiffness

Human genome-wide association studies have linked single-nucleotide polymorphisms (SNPs) in NEMP1 (nuclear envelope membrane protein 1) with early menopause; however, it is unclear whether NEMP1 has any role in fertility. We show that whole-animal loss of NEMP1 homologs in Drosophila, Caenorhabditis elegans, zebrafish, and mice leads to sterility or early loss of fertility. Loss of Nemp leads to nuclear shaping defects, most prominently in the germ line. Biochemical, biophysical, and genetic studies reveal that NEMP proteins support the mechanical stiffness of the germline nuclear envelope via formation of a NEMP-EMERIN complex. These data indicate that the germline nuclear envelope has specialized mechanical properties and that NEMP proteins play essential and conserved roles in fertility.

Cosmological Constraints from Multiple Probes in the Dark Energy Survey

The combination of multiple observational probes has long been advocated as a powerful technique to constrain cosmological parameters, in particular dark energy. The Dark Energy Survey has measured 207 spectroscopically confirmed type Ia supernova light curves, the baryon acoustic oscillation feature, weak gravitational lensing, and galaxy clustering. Here we present combined results from these probes, deriving constraints on the equation of state, w, of dark energy and its energy density in the Universe. Independently of other experiments, such as those that measure the cosmic microwave background, the probes from this single photometric survey rule out a Universe with no dark energy, finding w=-0.80_{-0.11}^{+0.09}. The geometry is shown to be consistent with a spatially flat Universe, and we obtain a constraint on the baryon density of Ω_{b}=0.069_{-0.012}^{+0.009} that is independent of early Universe measurements. These results demonstrate the potential power of large multiprobe photometric surveys and pave the way for order of magnitude advances in our constraints on properties of dark energy and cosmology over the next decade.

Prenatal course of metaphyseal anadysplasia associated with homozygous mutation in MMP9 identified by exome sequencing

Metaphyseal anadysplasia (MANDP) is a rare autosomal recessive form of skeletal dysplasia characterized by normal length at birth and transitory bowing of the legs. Although several families with MANDP have been reported, homozygous mutations in the matrix metalloproteinase type 9 (MMP9) gene have been described in only one consanguineous family, and thus the pre and postnatal phenotypic spectrum is still obscure. A clinically similar but more severe type is caused by autosomal-dominant inheritance and is caused by mutations in matrix metalloproteinase type 13 gene (MMP13). Here, we report the prenatal and early postnatal course of two affected sib fetuses with early sonographic evidence of long bone shortening and postnatally no metaphyseal changes. Whole-exome sequencing revealed homozygous mutation in MMP9 in both fetuses suggesting a diagnosis of MANDP. We propose that MANDP should be considered in pregnancies with early prenatal shortening of the long bones without associated finding of lethal skeletal dysplasias. In addition, the finding of homozygous mutation in non-consanguineous parents of Jewish-Caucasus ancestry may suggest unawareness of such relation or the occurrence of a founder mutation in this gene.

Efficacy of the Comprehensive Objective Mapping, Precise Image Guided Injection, Anti-Reflux Positioning and Sequential Sclerotherapy (COMPASS) Technique in the Management of Greater Saphenous Varicosities with Saphenofemoral Incompetence

Objective:

To evaluate the efficacy of the COMPASS technique in the management of greater saphenous varicosities with saphenofemoral incompetence.

Design:

Prospective open trial (2-6 year follow-up).

Patients:

One hundred and eighty-six limbs with refluxing greater saphenous vein (5.4–25.4 mm) and incompetent saphenofemoral junction (6.1–31.3 mm).

Main outcome measure:

Obliteration, recanalisation, residual veins, neovascularisation, venous dysfunction score.

Results:

Greater saphenous varicosity is commonly a disease of individuals in their forties, with morbid clinical presentations. Three stages of the COMPASS technique achieved 100% and 98% obliteration of the saphenofemoral junction and greater saphenous vein respectively. There was significant improvement in the venous dysfunction score. Residual refluxing veins were easily managed by sequential treatment. The results are sustained in the 3.4 SD 1.7 year follow up. There was no serious adverse experience reported.

Conclusion:

The COMPASS technique is safe and highly efficacious in the management of extensive large vein varicose disease.

GH safety workshop position paper: a critical appraisal of recombinant human GH therapy in children and adults

Recombinant human GH (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-term safety, including cancer risk, impact on glucose homeostasis, and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk, and the need for long-term surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS, and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement.

Insulin-like growth factor-I in growth and metabolism

Deficiency of insulin-like growth factor-I (IGF-I) results in growth failure. A variety of molecular defects have been found to underlie severe primary IGF-I deficiency (IGFD), in which serum IGF-I concentrations are substantially decreased and fail to respond to GH therapy. Identification of more patients with primary or secondary IGFD is likely with investigative and diagnostic progress, particularly in the assessment of children with idiopathic short stature. Diagnosis of IGFD requires accurate and reliable IGF-I assays, adequate normative data for reference, and knowledge of IGF-I physiology for proper interpretation of data. Recombinant human IGF-I (rhIGF-I) treatment improves stature in patients with severe primary IGFD, and has also been shown to improve glycaemic control and insulin sensitivity in patients with severe insulin resistance. Ongoing studies of patients receiving rhIGF-I will allow further evaluation of the clinical utility of this treatment, with concurrent increase in our understanding of IGF-I and conditions of IGFD.

Future e(+)e(-) colliders' sensitivity to Hbb coupling and CP violation

We perform a complete simulation of the process e(+)e(-)-->bbvv, where nu can be an electron, muon, or tau neutrino, in the context of a general Higgs coupling to b quarks. We parametrize the Hbb; coupling as (m(b)/v)(a+igamma(5)b). Taking into account interference effects between pure Higgs and Standard Model contributions, we find that sensitivities of the order of 2% and 20% can be obtained at a future e(+)e(-) collider for deviations of the a and b parameters, respectively, from their Standard Model values. Combining our analysis with an independent measurement of Gamma(H-->bb) can provide evidence about the CP nature of the Higgs sector.

The metabolic effects of short-term administration of physiological versus high doses of GH therapy in GH deficient adults

OBJECTIVE

GH treatment has demonstrated favourable effects on most features of GH deficiency in hypopituitary adults. However, most studies employed supraphysiological GH doses, resulting in deterioration in insulin sensitivity (SI). The short-term metabolic effects of physiological doses of GH therapy in GH deficient (GHD) adults are largely unknown. We therefore compared the effects of short-term administration of two 'physiological' ('lowest' dose: 0.0017 mg/kg/day; 'low' dose: 0.0033 mg/kg/day) with two 'supraphy-siological' ('high' dose: 0.010 mg/kg/day; 'highest' dose: 0.025 mg/kg/day) GH doses on SI, beta-cell function, IGF-1 and IGFBPs -1 and -3 in a group of GHD adults.

PATIENTS AND METHODS

Thirteen GHD adults were recruited (seven men, aged 23-63 years). For each of the four doses, six patients (three men) were allocated randomly to undergo a 7-day treatment phase. Fasting blood samples were collected daily (days 1-8), and SI and beta-cell function were calculated using the homeostasis model assessment (HOMA).

RESULTS

All four GH doses increased IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio, and decreased IGFBP-1 from day 3 onwards (P < 0.05). The highest dose increased fasting glucose (P < 0.001), insulin (P < 0.001) and beta-cell function (P < 0.001), but decreased SI (P < 0.001). The high and low doses did not modify fasting glucose and insulin, SI or beta-cell function, whereas the lowest dose enhanced beta-cell function (P < 0.05). The overall increase in the GH dose increased IGF-1, IGFBP-3, fasting glucose and insulin (P < 0.001), demonstrated a positive correlation with the final change in fasting glucose (r = 0.5, P < 0.05) and insulin (r = 0.8, P < 0.001) and a negative correlation with final SI (r = -0.5, P < 0.05).

CONCLUSIONS

Our results suggest that short-term administration of the highest GH dose induced insulin resistance, whereas the lowest dose (0.0017 mg/kg/day) could represent the optimal starting dose in GHD adults due to its beneficial effects on beta-cell function without compromising SI. It is, however, yet to be determined whether the positive effects of the lowest GH dose on beta-cell function can be demonstrated over a longer period of time.

A bicyclic and hsst2 selective somatostatin analogue: design, synthesis, conformational analysis and binding

A backbone bridged and disulfide bridged bicyclic somatostatin analogue, compound 1 (PTR-3205), was designed and synthesized by solid-phase methodology. The binding of compound 1 to the five different somatostatin receptors, expressed in CHO or COS-7 cells, indicate a high degree of selectivity towards hsstr2. The three-dimensional structure of this compound has been determined in DMSO-d(6) and in water by 1H NMR and by molecular dynamics simulations. Similar backbone conformations were observed in both solvents. We have established direct evidence that the backbone of this bicyclic somatostatin analogue assumes a 'folded' conformation in solution, where the lactam ring extends roughly in the plane of the beta-turn. The pharmacophoric region Phe-(D)-Trp-Lys-Thr of compound 1 is in accord with that of both the Veber compound L-363,301 (Merck) and sandostatin. We believe that the enhanced selectivity towards the hsst2 receptor, in comparison with other analogues, is due to its large hydrophobic region, composed of the lactam ring and the Phe side chains at positions 1 and 8.

Recommendations for the diagnosis and management of Turner syndrome

Comprehensive recommendations on the diagnosis of Turner syndrome (TS) and the care of affected individuals were published in 1994. In the light of recent advances in diagnosis and treatment of TS, an international multidisciplinary workshop was convened in March 2000, in Naples, Italy, in conjunction with the Fifth International Symposium on Turner Syndrome to update these recommendations. The present paper details the outcome from this workshop. The genetics and diagnosis of the syndrome are described, and practical treatment guidelines are presented.

Quality of life after great auricular nerve sacrifice during parotidectomy

OBJECTIVE

To determine the impact of great auricular nerve (GAN) sacrifice during parotidectomy on patients' quality of life.

DESIGN

Historical cohort survey of patients who had undergone GAN sacrifice during parotidectomy.

SETTING

Tertiary academic otolaryngologic practice.

PATIENTS AND METHODS

Fifty-three patients who had undergone GAN sacrifice during parotidectomy completed an 8-item quality-of-life survey with a 7-point response scale designed to measure outcome after GAN sacrifice during parotidectomy.

RESULTS

Thirty patients (57%) reported experiencing at least 1 abnormal symptom, but the mean number of symptoms decreased significantly with time, from a mean of 2.3 during the first year to 0.2 after 5 years (P<.001). Even among patients experiencing symptoms, 23 (77%) reported only a little or no bother caused by the symptoms, and 27 (90%) reported no interference or almost none with their daily activities. The degree of bother or interference reported had a moderate positive correlation with the number of abnormal sensations reported.

CONCLUSIONS

The results suggest that, while many patients experienced sensory deficits, the overall quality of life was not significantly affected after GAN sacrifice during parotidectomy. Patients who report multiple abnormal sensations, however, would benefit from additional counseling and from reassurance that the number of sensations will diminish with time. Further study evaluating the effect of preservation of the posterior branch of the GAN during parotidectomy on patients' quality of life is needed.

A fast algorithm for searching for molecules containing a pharmacophore in very large virtual combinatorial libraries

We present a new algorithm for identifying molecules that display a pharmacophore, or in general a structural motif, by efficiently constructing and screening huge virtual combinatorial libraries of diverse compounds. The uniqueness of this algorithm is its ability to build and screen libraries of ca. 10(18) 3D molecular conformations within a reasonable time scale, thereby increasing the chemical space that can be virtually screened by many orders of magnitude. The algorithm may be used to design new molecules that display a desired pharmacophore on predefined sets of chemical scaffolds. This is demonstrated herein by screening a library of backbone cyclic peptides to find candidate peptido- and proteinomimetics.

The rise and decline of homicide--and why

A dramatic rise in homicide in the latter half of the 1980s peaked during the 1990s and then declined at an equally dramatic rate. Such trends in homicide rates can be understood only by examining rates in specific age, sex, and racial groups. The increase primarily involved young males, especially black males, occurred first in the big cities, and was related to the sudden appearance of crack cocaine in the drug markets of the big cities around 1985. This development led to an increased need for and use of guns and was accompanied by a general diffusion of guns into the larger community. The decline in homicide since the early 1990s has been caused by changes in the drug markets, police response to gun carrying by young males, especially those under 18 years old, the economic expansion, and efforts to decrease general access to guns, as well as an increase in the prison population and a continued decline in homicide among those over age 24. The lessons learned from the recent homicide trends and the factors associated with them have important implications for public health and the criminal justice system.

Novel long-acting somatostatin analog with endocrine selectivity: potent suppression of growth hormone but not of insulin

Somatostatin, also known as somatotropin release-inhibiting factor (SRIF), is a natural cyclic peptide inhibitor of pituitary, pancreatic, and gastrointestinal secretion. Its long-acting analogs are in clinical use for treatment of various endocrine syndromes and gastrointestinal anomalies. These analogs are more potent inhibitors of the endocrine release of GH, glucagon, and insulin than the native SRIF; hence, they do not display considerable physiological selectivity. Our goal was to design effective and physiologically selective SRIF analogs with potential therapeutic value. We employed an integrated approach consisting of screening of backbone cyclic peptide libraries constructed on the basis of molecular modeling of known SRIF agonists and of high throughput receptor binding assays with each of the five cloned human SRIF receptors (hsst1-5). By using this approach, we identified a novel, high affinity, enzymatically stable, and long-acting SRIF analog, PTR-3173, which binds with nanomolar affinity to human SRIF receptors hsst2, hsst4, and hsst5. The hsst5 and the rat sst5 (rsst5) forms have the same nanomolar affinity for this analog. In the human carcinoid-derived cell line BON-1, PTR-3173 inhibits forskolin-stimulated cAMP accumulation as efficiently as the drug octreotide, indicating its agonistic effect in this human cell system. In hormone secretion studies with rats, we found that PTR-3173 is 1000-fold and more than 10,000-fold more potent in inhibiting GH release than glucagon and insulin release, respectively. These results suggest that PTR-3173 is the first highly selective somatostatinergic analog for the in vivo inhibition of GH secretion, with minimal or no effect on glucagon and insulin release, respectively.

Regulation of somatic growth by the p160 coactivator p/CIP

A family of p160 coactivators was initially identified based on ligand-dependent interactions with nuclear receptors and thought to function, in part, by recruiting CREB-binding protein/p300 to several classes of transcription factors. One of the p160 factors, p/CIP/AIB1, often amplified and overexpressed in breast cancer, also exhibits particularly strong interaction with CREB-binding protein/p300. In this manuscript, we report that p/CIP, which exhibits regulated transfer from cytoplasm to nucleus, is required for normal somatic growth from embryonic day 13.5 through maturity. Our data suggest that a short stature phenotype of p/CIP gene-deleted mice reflect both altered regulation of insulin-like growth factor-1 (IGF-1) gene expression in specific tissues and a cell-autonomous defect of response to IGF-1, including ineffective transcriptional activities by several classes of regulated transcription factors under specific conditions. The actions of p/CIP are therefore required for full expression of a subset of genes critical for regulating physiological patterns of somatic growth in mammals.

Study on the cyclization tendency of backbone cyclic tetrapeptides

The cyclization kinetics of five backbone-cyclic tetrapeptides was investigated both experimentally and computationally. The aim was to both accurately measure the cyclization rates in solution and develop a method that efficiently estimates the relative cyclization tendencies computationally. Progression of the cyclization reaction was monitored directly, yielding the kinetics of changes in the amounts of the linear precursor and the products. These measurements were used to calculate the reaction rates; the results were consistent with a first-order reaction kinetics. In order to predict the cyclization rates computationally, the conformation space of the linear precursors was mapped and used to construct an approximate partition function. We assumed that the cyclization tendency was correlated with the relative probability of being found in a cyclization-prone conformation of the backbone, this probability was estimated from the partition function. The results supported this assumption and demonstrated that, within reasonable accuracy, we are able to predict the relative cyclization tendencies of the peptides measured.

Growth hormone use in pediatric growth hormone deficiency and other pediatric growth disorders

The diagnosis and management of growth disorders in children, particularly disorders that respond to therapy with growth hormone (GH), raise challenging clinical and economic issues. Several such issues are presented in the following article in which Dr. Ron Rosenfeld examines the evaluation and diagnosis of the child with short stature; Dr. David B. Allen discusses the anabolic and metabolic indications for GH treatment in children; Dr. Margaret H. MacGillivray reviews GH dosing, height outcomes, and follow up; and Dr. Craig Alter presents the payer's perspective on the diagnosis and treatment of pediatric GH deficiency. In addressing the use of GH in other pediatric populations, Dr. Paul Saenger focuses on Turner syndrome, Dr. Henry Anhalt on chronic renal insufficiency of childhood, and Dr. Ray Hintz on idiopathic short stature. Dr. Harvey P. Katz presents one managed care organization's policy and implementation plan that is used to guide decisions regarding coverage for GH treatment.

Connective tissue growth factor (IGFBP-rP2) expression and regulation in cultured bovine endothelial cells

Media from large vessel endothelial cells (pulmonary artery, aorta) contained intact connective tissue growth factor (CTGF) and a dominant 19-kDa band. N-terminal analysis of the 19-kDa band showed sequence corresponding to CTGF amino acid 181-190, suggesting that the 19-kDa band represented a proteolytic fragment of CTGF. Intact CTGF was increased by cAMP but not by transforming growth factor-beta (TGFbeta). CTGF messenger RNA (mRNA) was not changed by cAMP nor TGFbeta. In two microvessel endothelial cells, mRNA was found at low levels by PCR and Northern analysis, but no CTGF protein was seen on Western analysis. In the microvessel cells, TGFbeta increased and cAMP did not change CTGF mRNA levels, with neither TGFbeta nor cAMP increasing CTGF protein. The discordance between protein and mRNA levels in large vessel and microvessel endothelial cells was mostly explained by the effects of cAMP and TGFbeta on media proteolytic activity; in large vessel cells, cAMP inhibited degradation of CTGF, whereas in microvessel cells, TGFbeta and cAMP stimulated proteolytic activity against CTGF. We conclude that in large vessel endothelial cells, cAMP increased intact CTGF protein by inhibiting degradation of CTGF, whereas TGFbeta stimulated neither CTGF mRNA nor protein; in microvessel cells, TGFbeta increased CTGF mRNA, while both TGFbeta and cAMP stimulated CTGF degradation.

Empirical modifications to the Amber/OPLS potential for predicting the solution conformations of cyclic peptides by vacuum calculations

BACKGROUND

Peptides have ubiquitous roles in all biological systems and are thus of interest in both basic and applied research. The rational design of bioactive peptides could be greatly enhanced by an efficient method for accurately predicting the conformations that these molecules can adopt in solution. As a design process inevitably requires testing numerous molecules, an efficient method would require the calculations to be performed in vacuum.

RESULTS

Attempts to predict the conformations of cyclic peptides using a simulated annealing protocol with the Amber/OPLS potential in vacuum resulted, not unexpectedly, in overly packed, non-native conformations. We therefore empirically modified the potential by several cycles of structure prediction and function refinement until a good fit between experimental and predicted conformations was obtained. Three major modifications to the potential were required in order to reproduce the solution structures of cyclic peptides: explicit torsional energies for the peptide backbone torsional angles; explicit hydrogen-bonding energies for backbone hydrogen bonds; and a penalty for close approaches between uncharged and charged atoms.

CONCLUSIONS

Using the modified potential, we predicted the solution conformations of cyclic peptides in the size range of 5-10 residues with reasonable accuracy.

Comparison of solution properties of human and rat ciliary neurotrophic factor

The solution structure and stability of rat and human ciliary neurotrophic factor (CNTF) were examined by circular dichroism (CD), Fourier transform infrared (FTIR) and fluorescence spectroscopy and sedimentation equilibrium analyses. The secondary structure of both proteins, as assessed by CD and FTIR, consists primarily of alpha-helix, consistent with CNTF being a member of the four-helical bundle family of cytokines and neurokines, with rat CNTF containing slightly less helix (about 10% less) and slightly more disordered structure. The environment of the tyrosine and tryptophan residues, assessed by intrinsic fluorescence emission spectroscopy, appears to be the same in both proteins. Binding of anilinonaphthalene sulfonate is identical for both proteins, indicating that these two proteins have similar surface hydrophobicities in the native state. The thermal stability of the human CNTF is significantly less than that of the rat CNTF, yet their stabilities to guanidine HCl-induced denaturation are equivalent. This apparent discrepancy in stability between the two proteins may be explained by solubility differences upon thermal unfolding. Although the human protein precipitates as it is denatured by heat, the rat protein does not. It thus appears that the unfolded state of human CNTF is less soluble and more prone to aggregation than that of the rat protein upon heating, although their conformational stability is similar. Both proteins remain largely folded at pH 3.0. Sedimentation equilibrium analysis demonstrates that both rat and human CNTF exist primarily as monomers; however, significant dimer formation occurs as the protein concentrations are increased to greater than 3 mg/mL, particularly in the presence of ammonium sulfate.

Preventing the generation of artifacts during peptide map analysis of recombinant human insulin-like growth factor-I

Peptide mapping using proteolytic enzymes is one useful technique to characterize proteins. However, developing an optimized peptide map is empirical. Some proteins are resistant to proteolysis and it is thereby difficult to obtain a good peptide map. In many cases, the protease-to-substrate ratio is the first modifier to improve the peptide map. As a consequence of increasing the amount of protease, some complications such as nonspecific cleavage, disulfide interchange, transpeptidation, and autolysis of the protease itself may occur. Recombinant human insulin-like growth factor-I (r-HuIGF-I) has been shown to generate a transpeptidation product and a nonspecifically cleaved product under the conditions reported in the literature. We describe here the completion of a peptide map using a combination of Asp-N and Glu-C (V8 strain) endoproteinases. No apparent transpeptidation, nonspecific cleavage, and disulfide exchange was observed. In situ digest of r-HuIGF-I on the probe was also analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and proved to be a quick method to analyze the sample.

Effect of intraperitoneal insulin delivery on growth hormone binding protein, insulin-like growth factor (IGF)-I, and IGF-binding protein-3 in IDDM

Low plasma insulin-like growth factor (IGF)-I despite high circulating growth hormone (GH) in insulin-dependent diabetes mellitus (IDDM) indicate a hepatic GH resistance. This state may be reflected by the reduction of the circulating GH binding protein (GHBP), corresponding to the extracellular domain of the GH receptor, and the reduction of insulin-like growth factor binding protein (IGFBP)-3, major IGF-I binding protein, upregulated by GH. We carried out two studies. In the first, plasma GHBP activity was compared in patients with IDDM on continuous subcutaneous insulin infusion (CSII) or on conventional therapy and in healthy subjects. In the second study, the 18 patients on CSII at baseline were then treated by continuous intraperitoneal insulin infusion with an implantable pump (CPII) and prospectively studied for GH-IGF-I axis. Although HbA1c was lower in patients on CSII than in those on conventional therapy, GHBP was similarly reduced in both when compared to control subjects (10.2 +/- 0.8 and 11.6 +/- 0.9% vs 21.0 +/- 1.3, p < 0.01). CPII for 12 months resulted in: a slight and transient improvement in HbA1c (Time (T)0: 7.6 +/- 0.2%, T3: 7.1 +/- 0.2%, T12: 7.5 +/- 0.2%, p < 0.02), improvement in GHBP (T0: 10.2 +/- 0.8%, T12: 15.5 +/- 1.5, p < 0.0001), near-normalization of IGF-I (T0: 89.4 +/- 8.8 ng/ml, T12: 146.9 +/- 15.6, p < 0.002) and normalization of IGFBP-3 (T0: 1974 +/- 121 ng/ml, T12: 3534 +/- 305, p < 0.0001). The hepatic GH resistance profile in IDDM does not seem to be related to glycaemic control, but partly to insufficient portal insulinization. Intraperitoneal insulin delivery, allowing primary portal venous absorption, may influence GH sensitivity, and improve hepatic IGF-I and IGFBP-3 generation.

Insulin therapy and GH-IGF-I axis disorders in diabetes: impact of glycaemic control and hepatic insulinization

In Type 1 diabetes, high circulating growth hormone (GH) in conjunction with low plasma insulin-like growth factor-I (IGF-I) is indicative of a hepatic GH-resistance profile since the liver is the main source of circulating IGF-I. The reduction in specific growth hormone binding protein (GHBP), corresponding to the extracellular domain of the GH receptor, provides an indirect indication of the hepatic density of GH receptors, as does the reduction in IGFBP-3, the major IGF binding protein, which is GH-dependent. Type 1 diabetes is also associated with high levels of IGFBP-1, a binding protein down-regulated by insulin. Although most of these abnormalities have been described in situations of poor glycaemic control, hyperglycaemia does not seem to be the predominant factor in their pathogenesis. Even intensified subcutaneous insulin therapy does not normalize GH, IGF-I, GHBP and IGFBP-3 plasma levels. Some indirect evidence suggests that portal insulinopenia plays a role in the hepatic GH-resistance profile of Type 1 diabetes, i.e. discrepancies between the abnormalities reported in Type 1 and Type 2 diabetes, and the inverse relationship between residual insulin secretion in Type 1 diabetes and some of these abnormalities. Intraperitoneal insulin therapy administered to Type 1 diabetic patients by implantable pumps (without modification of glycaemic control) can improve GHBP activity, practically normalize plasma IGF-I and normalize IGFBP-3. The improvement in GH-IGF-I axis disorders obtained with intraperitoneal insulin therapy (which allows primary portal insulin absorption) provides direct evidence of the central role of portal insulin in the regulation of this system.

Native and non-native structure in a protein-folding intermediate: spectroscopic studies of partially reduced IGF-I and an engineered alanine model

The structure of a metastable folding intermediate of human insulin-like growth factor I (IGF-I) and an engineered model are investigated by circular dichroism and two-dimensional 1H NMR spectroscopy. The intermediate, which contains two of three native disulfide bonds, was trapped by acid quenching and isolated by reverse-phase HPLC. The reduced cysteine residues were mapped to residues 47 and 52 (corresponding to A6-A11 in insulin). In the native state this disulfide bridge anchors an adjoining amphipathic alpha-helix (helix 2; residues 42 to 49) against the hydrophobic core. Comparison of CD and 1H-NMR spectra demonstrates that the acid-quenched intermediate is partially folded and contains elements of native secondary and tertiary structure. Spectra are similar to those of an equilibrium model in which the reduced cysteine residues are replaced by alanine. Complete 1H-NMR sequential assignment of the alanine model has been obtained and demonstrates that removal of the disulfide bond is associated with local unfolding of the adjoining alpha-helix. Native secondary structure (including helices 1 and 3) is otherwise retained and defines a folded subdomain. Long-range nuclear Overhauser effects (NOE) within this subdomain are similar to those of native IGF-I; no non-native NOE is observed. Our results support the hypothesis that folding of the insulin motif is directed by a subset of native structural elements and that these elements form at an early step in the pathway. Formation of helix 2, despite its prominence in the native state, is likely to represent a late step. Hydrophobic collapse of this segment appears to precede helix formation.

RNA loop structure prediction via bond scaling and relaxation

We have developed a method for predicting the structure of small RNA loops that can be used to augment already existing RNA modeling techniques. The method requires no input constraints on loop configuration other than end-to-end distance. Initial loop structures are generated by randomizing the torsion angles, beginning at one end of the polynucleotide chain and correlating each successive angle with the previous. The bond lengths of these structures are then scaled to fit within the known end constraints and the equilibrium bond lengths of the potential energy function are scaled accordingly. Through a series of rescaling and minimization steps the structures are allowed to relax to lower energy configurations with standard bond lengths and reduced van der Waals clashes. This algorithm has been tested on the variable loops of yeast tRNA-Asp and yeast tRNA-Phe, as well as the sarcin-ricin tetraloop and the anticodon loop of yeast tRNA-Phe. The results indicate good correlation between potential energy and the loop structure predictions that are closest to the variable loop crystal structures, but poorer correlation for the more isolated stem loops. The number of stacking interactions has proven to be a good objective measure of the best loop predictions. Selecting on the basis of energy and stacking, we obtain two structures with 0.65 and 0.75 A all-atom rms deviations (RMSD) from the crystal structure for the tRNA-Asp variable loop. The best structure prediction for the tRNA-Phe variable loop has an all-atom RMSD of 2.2 A and a backbone RMSD of 1.6 A, with a single base responsible for most of the deviation. For the sarcin-ricin loop from 28S ribosomal RNA, the predicted structure's all-atom RMSD from the nmr structure is 1.0 A. We obtain a 1.8 A RMSD structure for the tRNA-Phe anticodon loop.

Human neurotrophin-3: a one-step peptide mapping method and complete disulfide characterization of the recombinant protein

Human neurotrophin-3 (NT-3) is a member of the nerve growth factor (NGF) family of neurotrophic factors, and the recombinant protein is being developed as a therapeutic for neurodegenerative diseases. The final product purity and lot-to-lot variation are monitored routinely by peptide mapping. However, only the N-terminal region of NT-3 was susceptible to proteolysis under native conditions. Complete digestion required that the protein be chemically modified by reduction and S-alkylation prior to proteolysis. Complete proteolytic degradation of the protein was achieved simply by an initial denaturation of NT-3 in 6 M guanidinium chloride (pH6) for 2 hr at 37 degrees C, followed by a tenfold dilution with the digestion buffer (0.1 M Tris-HCl, 1 mM CaCl2 at pH 7.0) and immediate addition of chymotrypsin at 1% by weight. Direct comparison of the peptide map with an identical aliquot that had been reduced and alkylated also allowed the establishment of the cystine linkages present in NT-3: Cys14 to Cys79, Cys57 to Cys108, and Cys67 to Cys110. This disulfide structure is homologous to the NGF family of neurotrophic factors.