Therapeutic Potential of Insulin-Like Growth Factor-1 in Patients with Diabetes Mellitus

Methods to predict heart failure in diabetes patients

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is one of the leading causes of cardiovascular disease and powerful predictor for new-onset heart failure (HF).

AREAS COVERED

We focus on the relevant literature covering evidence of risk stratification based on imaging predictors and circulating biomarkers to optimize approaches to preventing HF in DM patients.

EXPERT OPINION

Multiple diagnostic algorithms based on echocardiographic parameters of cardiac remodeling including global longitudinal strain/strain rate are likely to be promising approach to justify individuals at higher risk of incident HF. Signature of cardiometabolic status may justify HF risk among T2DM individuals with low levels of natriuretic peptides, which preserve their significance in HF with clinical presentation. However, diagnostic and predictive values of conventional guideline-directed biomarker HF strategy may be non-optimal in patients with obesity and T2DM. Alternative biomarkers affecting cardiac fibrosis, inflammation, myopathy, and adipose tissue dysfunction are plausible tools for improving accuracy natriuretic peptides among T2DM patients at higher HF risk. In summary, risk identification and management of the patients with T2DM with established HF require conventional biomarkers monitoring, while the role of alternative biomarker approach among patients with multiple CV and metabolic risk factors appears to be plausible tool for improving clinical outcomes.

Cross-Domain Text Mining of Pathophysiological Processes Associated with Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide. This study's goal was to identify the signaling drivers and pathways that modulate glomerular endothelial dysfunction in DKD via artificial intelligence-enabled literature-based discovery. Cross-domain text mining of 33+ million PubMed articles was performed with SemNet 2.0 to identify and rank multi-scalar and multi-factorial pathophysiological concepts related to DKD. A set of identified relevant genes and proteins that regulate different pathological events associated with DKD were analyzed and ranked using normalized mean HeteSim scores. High-ranking genes and proteins intersected three domains-DKD, the immune response, and glomerular endothelial cells. The top 10% of ranked concepts were mapped to the following biological functions: angiogenesis, apoptotic processes, cell adhesion, chemotaxis, growth factor signaling, vascular permeability, the nitric oxide response, oxidative stress, the cytokine response, macrophage signaling, NFκB factor activity, the TLR pathway, glucose metabolism, the inflammatory response, the ERK/MAPK signaling response, the JAK/STAT pathway, the T-cell-mediated response, the WNT/β-catenin pathway, the renin-angiotensin system, and NADPH oxidase activity. High-ranking genes and proteins were used to generate a protein-protein interaction network. The study results prioritized interactions or molecules involved in dysregulated signaling in DKD, which can be further assessed through biochemical network models or experiments.

Effects of Type 1 Diabetes Mellitus on Linear Growth: A Comprehensive Review

Type 1 diabetes mellitus (T1DM) has a significant effect on the growth of children. The disease has a negative effect on growth when considered in relation to the time period and metabolic control. Studies in this review have suggested debilitated growth in children with T1DM and have a few anomalies in the growth hormone (GH)-insulin-like growth factor-1 (IGF-1) axis when compared to fit children. Some studies show that children with T1DM were taller before the onset of the disease and during early diagnosis. Moreover, the linear growth depends on the interaction between the gonadotropin hormone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and sex steroid hormones axis and GH-IGF-1; there's a rise in GH during puberty, which has an effect on the estrogen and testosterone, which leads to the pulsatile secretion of GH, this increment leads to insulin resistance. These studies suggest short stature in girls, and some suggest in both. The final height in boys was unchanged, but a slight decline was observed in girls. This review aims to provide the latest understanding of impaired height in children with T1DM. The most accepted and effective treatment of impaired growth is the administration of long-acting insulin or continuous rapid-acting insulin. However, height was affected by the administration of good basal insulin at puberty and was unaffected by the continuous subcutaneous insulin injection. Hence, new technologies are the therapeutic regimen in children, especially the prepubertal age group; it will be interesting to see their effects on growth patterns in these children with T1DM.

IGFBP-4 Proteolysis by PAPP-A in a Primary Culture of Rat Neonatal Cardiomyocytes under Normal and Hypertrophic Conditions

Cardiovascular diseases (CVD) are among the leading causes of death and disability worldwide. Pregnancy-associated plasma protein-A (PAPP-A) is a matrix metalloprotease localized on the cell surface. One of the substrates that PAPP-A cleaves is the insulin-like growth factor binding protein-4 (IGFBP-4), a member of the family of proteins that bind insulin-like growth factor (IGF). Proteolysis of IGFBP-4 by PAPP-A occurs at a specific site resulting in formation of two proteolytic fragments - N-terminal IGFBP-4 (NT-IGFBP-4) and C-terminal IGFBP-4 (CT-IGFBP-4), and leads to the release of IGF activating various cellular processes including migration, proliferation, and cell growth. Increased levels of the proteolytic IGFBP-4 fragments correlate with the development of CVD complications and increased risk of death in patients with the coronary heart disease, acute coronary syndrome, and heart failure. However, there is no direct evidence that PAPP-A specifically cleaves IGFBP-4 in the cardiac tissue under normal and pathological conditions. In the present study, using a primary culture of rat neonatal cardiomyocytes as a model, we have demonstrated that: 1) proteolysis of IGFBP-4 by PAPP-A occurs in the conditioned medium of cardiomyocytes, 2) PAPP-A-specific IGFBP-4 proteolysis is increased when cardiomyocytes are transformed to a hypertrophic state. Thus, it can be assumed that the enhancement of IGFBP-4 cleavage by PAPP-A and hypertrophic changes in cardiomyocytes accompanying CVD are interrelated, and PAPP-A appears to be one of the activators of the IGF-dependent processes in normal and hypertrophic-state cardiomyocytes.

Linear Growth in Children and Adolescents with Type 1 Diabetes Mellitus

Ensuring normal linear growth is one of the major therapeutic aims in the management of type one diabetes mellitus (T1DM) in children and adolescents. Many studies in the literature have shown that pediatric patients with T1DM frequently present some abnormalities in their growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis compared to their healthy peers. Data on the growth of T1DM children and adolescents are still discordant: Some studies have reported that T1DM populations, especially those whose diabetes began in early childhood, are taller than healthy pediatric populations at diagnosis, while other studies have not found any difference. Moreover, many reports have highlighted a growth impairment in T1DM patients of prepubertal and pubertal age, and this impairment seems to be influenced by suboptimal glycemic control and disease duration. However, the most recent data showed that children treated with modern intensive insulin therapies reach a normal final adult height. This narrative review aims to provide current knowledge regarding linear growth in children and adolescents with T1DM. Currently, the choice of the most appropriate therapeutic regimen to achieve a good insulin level and the best metabolic control for each patient, together with the regular measurement of growth parameters, remains the most important available tool for a pediatric diabetologist. Nevertheless, since new technologies are the therapy of choice in young children, especially those of pre-school age, it would be of great interest to evaluate their effects on the growth pattern of children with T1DM.

Supramolecular Nanofibers with Superior Bioactivity to Insulin-Like Growth Factor-I

Bioactive peptides derived from proteins generally need to be folded into secondary structures to activate downstream signaling pathways. However, synthetic peptides typically form random-coils, thus losing their bioactivities. Here, we show that by introducing a self-assembling peptide motif and using different preparation pathways, a peptide from insulin-like growth factor-I (IGF-1) can be folded into an α-helix and β-sheet. The β-sheet one exhibits a low dissociation constant to the IGF-1 receptor (IGF-1R, 11.5 nM), which is only about 3 times higher than that of IGF-1 (4.3 nM). However, the α-helical one and the peptide without self-assembling motif show weak affinities to IGF-1R ( K_D = 179.1 and 321.6 nM, respectively). At 10 nM, the β-sheet one efficiently activates the IGF-1 downstream pathway, significantly enhancing HUVEC proliferation and preventing cell apoptosis. The β-sheet peptide shows superior performance to IGF-1 in vivo, and it improves ischemic hind-limb salvage by significantly reducing muscle degradation and enhancing limb vascularization. Our study provides a useful strategy to constrain peptides into different conformations, which may lead to the development of supramolecular nanomaterials mimicking biofunctional proteins.

The Prospective Association Between Plasma Concentrations of Cellular Growth Factors and Risk of Heart Failure Mortality in Japanese Population

Background

Limited evidence is available on the association of insulin-like growth factors (IGFs) and risk of heart failure in population-based samples. We investigated whether serum IGFs concentrations can predict mortality from heart failure.

Methods

We conducted a nested case-control study of 39,242 subjects aged 40–79 years who participated in the JACC study, a large Japanese prospective cohort study; participants provided serum samples and were followed up for 9 years. In heart failure cases and age-, sex-, community-, and year of blood withdrawal-matched controls, we measured serum concentrations of IGF-I, IGF-II, and IGF binding protein 3 (IGFBP3) and transforming growth factor (TGF-β1).

Results

During the follow-up, there were 88 heart failure deaths (44 men and 44 women). Each increment of 1 standard deviation [SD] of IGF-II (120.0 ng/mL in women and 143.7 ng/mL in men) was associated with a 47% reduced risk of mortality from heart failure; multivariable odds ratio was 0.53 (95% confidence interval [CI], 0.30–0.94, P-trend = 0.03). The multivariable odds ratio in the highest quartile of IGFBP3 serum concentrations (≥3.29 µg/mL in women and ≥3.31 µg/mL in men) compared with the lowest (<2.11 µg/mL in women and <2.56 µg/mL in men) was 0.24 (95% CI, 0.05–1.11; P-trend = 0.12). No association was found between serum concentrations of IGF-I or TGF-β1 and risk of heart failure.

Conclusions

Higher serum concentrations of IGF-II were associated with lower mortality from heart failure, which might suggest a possible role of IGF-II in the occurrence or prognosis of heart failure.

The role of cadmium in obesity and diabetes

Multiple studies have shown an association between environmental exposure to hazardous chemicals including toxic metals and obesity, diabetes, and metabolic syndrome. At the same time, the existing data on the impact of cadmium exposure on obesity and diabetes are contradictory. Therefore, the aim of the present work was to review the impact of cadmium exposure and status on the risk and potential etiologic mechanisms of obesity and diabetes. In addition, since an effect of cadmium exposure on incidence of diabetes mellitus and insulin resistance was suggested by several epidemiologic studies, we carried out a meta-analysis of all studies assessing risk of prevalence and incidence of diabetes. By comparing the highest versus the lowest cadmium exposure category, we found a high risk of diabetes incidence (odds ratio=1.38, 95% confidence interval 1.12-1.71), which was higher for studies using urine as exposure assessment. On the converse, results of epidemiologic studies linking cadmium exposure and overweight or obesity are far less consistent and even conflicting, also depending on differences in exposure levels and the specific marker of exposure (blood, urine, hair, nails). In turn, laboratory studies demonstrated that cadmium adversely affects adipose tissue physiopathology through several mechanisms, thus contributing to increased insulin resistance and enhancing diabetes. However, intimate biological mechanisms linking Cd exposure with obesity and diabetes are still to be adequately investigated.

Insulin-like growth factor-1 receptor-mediated inhibition of A-type K(+) current induces sensory neuronal hyperexcitability through the phosphatidylinositol 3-kinase and extracellular signal-regulated kinase 1/2 pathways, independently of Akt

Although IGF-1 has been implicated in mediating hypersensitivity to pain, the underlying mechanisms remain unclear. We identified a novel functional of the IGF-1 receptor (IGF-1R) in regulating A-type K(+) currents (IA) as well as membrane excitability in small trigeminal ganglion neurons. Our results showed that IGF-1 reversibly decreased IA, whereas the sustained delayed rectifier K(+) current was unaffected. This IGF-1-induced IA decrease was associated with a hyperpolarizing shift in the voltage dependence of inactivation and was blocked by the IGF-1R antagonist PQ-401; an insulin receptor tyrosine kinase inhibitor had no such effect. An small interfering RNA targeting the IGF-1R, or pretreatment of neurons with specific phosphatidylinositol 3-kinase (PI3K) inhibitors abolished the IGF-1-induced IA decrease. Surprisingly, IGF-1-induced effects on IA were not regulated by Akt, a common downstream target of PI3K. The MAPK/ERK kinase inhibitor U0126, but not its inactive analog U0124, as well as the c-Raf-specific inhibitor GW5074, blocked the IGF-1-induced IA response. Analysis of phospho-ERK (p-ERK) showed that IGF-1 significantly activated ERK1/2 whereas p-JNK and p-p38 were unaffected. Moreover, the IGF-1-induced p-ERK1/2 increase was attenuated by PI3K and c-Raf inhibition, but not by Akt blockade. Functionally, we observed a significantly increased action potential firing rate induced by IGF-1; pretreatment with 4-aminopyridine abolished this effect. Taken together, our results indicate that IGF-1 attenuates IA through sequential activation of the PI3K- and c-Raf-dependent ERK1/2 signaling cascade. This occurred via the activation of IGF-1R and might contribute to neuronal hyperexcitability in small trigeminal ganglion neurons.

IGF-1 restores visual cortex plasticity in adult life by reducing local GABA levels

The central nervous system architecture is markedly modified by sensory experience during early life, but a decline of plasticity occurs with age. Recent studies have challenged this dogma providing evidence that both pharmacological treatments and paradigms based on the manipulation of environmental stimulation levels can be successfully employed as strategies for enhancing plasticity in the adult nervous system. Insulin-like growth factor 1 (IGF-1) is a peptide implicated in prenatal and postnatal phases of brain development such as neurogenesis, neuronal differentiation, synaptogenesis, and experience-dependent plasticity. Here, using the visual system as a paradigmatic model, we report that IGF-1 reactivates neural plasticity in the adult brain. Exogenous administration of IGF-1 in the adult visual cortex, indeed, restores the susceptibility of cortical neurons to monocular deprivation and promotes the recovery of normal visual functions in adult amblyopic animals. These effects were accompanied by a marked reduction of intracortical GABA levels. Moreover, we show that a transitory increase of IGF-1 expression is associated to the plasticity reinstatement induced by environmental enrichment (EE) and that blocking IGF-1 action by means of the IGF-1 receptor antagonist JB1 prevents EE effects on plasticity processes.

Metabolic imbalance of the insulin-like growth factor-I axis in Zucker diabetic fatty rats

In healthy conditions, insulin-like growth factor-I (IGF-I) acts in a coordinated fashion with insulin to lower glycemia, mainly by increasing insulin sensitivity in peripheral tissues. The aim of this study was to explore the relationship between glucose homeostasis and the endocrine IGF-I axis in Zucker diabetic fatty (ZDF) rats. The plasma levels of glucose, insulin, growth hormone, free IGF-I, total IGF-I (associated to insulin-like growth factor binding proteins plus free), and corticosterone were measured in 13-week-old ZDF rats and in age-matched controls under fasting and postprandial conditions. The plasma IGF-I binding capacity was measured by radioligand binding. In ZDF rats, fasting total and free IGF-I levels were reduced by 22% and 92%, respectively, compared with controls. Postprandial free IGF-I was reduced by 35%, whereas total IGF-I was unaffected. The plasma IGF-I binding capacity in ZDF rats was reduced by 24% after fasting and by 13% under postprandial conditions. A clear correlation between free IGF-I and insulin was observed in postprandial controls but not in ZDF rats. A principal component analysis clearly separated ZDF and control rats into 2 main components under both fasting and postprandial conditions. The first component was determined equally by total IGF-I, bound IGF-I, the free to total IGF-I ratio, and the IGF-I binding capacity. The second component was determined mostly by glucose and insulin. Our results show a marked alteration of the plasma IGF-I levels and of the capacity of plasma to bind IGF-I, and a disturbed relationship between IGF-I and postprandial insulinemia in a rat model of type 2 diabetes mellitus.

Noninsulin pharmacological management of type 1 diabetes mellitus

The injectable nature and other shortcomings of insulin have stimulated interest in studying the noninsulin pharmacological therapies to manage type 1 diabetes mellitus (T1DM). The purpose of this study is to conduct a systematic literature review of noninsulin pharmacological therapies for the management of T1DM. For this, the following PubMed search was conducted: Diabetes Mellitus, Type 1/therapy"[Mesh]

LIMITS

Review Sort by: Publication Date. After applying various inclusion and exclusion criteria, a total of 63 studies were reviewed. Based on this review, noninsulin pharmacological therapies can be divided into following classes: (1) Insulin-sensitizing agents (biguanides and thiazolidinediones), (2) gastrointestinal nutrient absorption modulators (α-Glucosidase inhibitors and amylin), (3) immunotherapeutic agents, (4) incretin-based therapies, (5) recombinant human insulin-like growth factors, and (6) other promising therapeutics. Some of these are already used either as monotherapy or adjuvant to insulin, whereas, to manage T1DM, the benefits and risks of the others are still under evaluation. Nonetheless, insulin still remains the cornerstone to manage the T1DM.

Peripheral sensitization caused by insulin-like growth factor 1 contributes to pain hypersensitivity after tissue injury

Sensitization of primary afferent neurons is one of the most important components of pain hypersensitivity after tissue injury. Insulin-like growth factor 1 (IGF-1), involved in wound repair in injured tissue, also plays an important role in maintaining neuronal function. In the present study, we investigated the effect of tissue IGF-1 on nociceptive sensitivity of primary afferent neurons. Local administration of IGF-1 induced thermal and mechanical pain hypersensitivity in a dose-dependent manner, and was attenuated by IGF-1 receptor (IGF1R) inhibition. Tissue but not plasma IGF-1 levels, as determined by enzyme-linked immunosorbent assay, significantly increased after plantar incision. Immunohistochemistry revealed that IGF1R was predominantly expressed in neurons as well as in satellite glial cells in the dorsal root ganglion (DRG). Double-labeling immunohistochemistry showed that IGF1R expression colocalized with peripherin and TRPV1, but not with NF200 in DRG neurons. The IGF1R inhibitor successfully alleviated mechanical allodynia, heat hyperalgesia, and spontaneous pain behavior observed after plantar incision. Expression of phosphorylated Akt in DRG neurons significantly increased after plantar incision and was suppressed by IGF1R inhibition. These results demonstrate that increased tissue IGF-1 production sensitizes primary afferent neurons via the IGF1R/Akt pathway to facilitate pain hypersensitivity after tissue damage.

Molecular mechanisms and treatment strategies for Dupuytren's disease

Dupuytren’s disease (DD) is a common disease of the hand and is characterized by thickening of the palmar fascia and formation of tight collagenous disease cords. At present, the disease is incurable and the molecular pathophysiology of DD is unknown. Surgery remains the most commonly used treatment for DD, but this requires extensive postoperative therapy and is associated with high rates of recurrence. Over the past decades, more indepth exploration of the molecular basis of DD has raised the hopes of developing new treatment modalities. This paper reviews the clinical presentation and molecular pathophysiology of this disease, as well as current and emerging treatment. It also explores the implications of new findings in the laboratory for future treatment.

Diabetes, insulin, and development of acute lung injury

OBJECTIVES

Recently, many studies have investigated the immunomodulatory effects of insulin and glucose control in critical illness. This review examines evidence regarding the relationship between diabetes and the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS), reviews studies of lung injury related to glycemic and nonglycemic metabolic features of diabetes, and examines the effect of diabetic therapies.

DATA SOURCES AND STUDY SELECTION

A MEDLINE/PubMed search from inception to August 1, 2008, was conducted using the search terms acute lung injury, acute respiratory distress syndrome, hyperglycemia, diabetes mellitus, insulin, hydroxymethylglutaryl-CoA reductase inhibitors (statins), angiotensin-converting enzyme inhibitor, and peroxisome proliferator-activated receptors, including combinations of these terms. Bibliographies of retrieved articles were manually reviewed.

DATA EXTRACTION AND SYNTHESIS

Available studies were critically reviewed, and data were extracted with special attention to the human and animal studies that explored a) diabetes and ALI; b) hyperglycemia and ALI; c) metabolic nonhyperglycemic features of diabetes and ALI; and d) diabetic therapies and ALI.

CONCLUSIONS

Clinical and experimental data indicate that diabetes is protective against the development of ALI/ARDS. The pathways involved are complex and likely include effects of hyperglycemia on the inflammatory response, metabolic abnormalities in diabetes, and the interactions of therapeutic agents given to diabetic patients. Multidisciplinary, multifaceted studies, involving both animal models and clinical and molecular epidemiology techniques, are essential.

Increased renal Akt/mTOR and MAPK signaling in type I diabetes in the absence of IGF type 1 receptor activation

Growth hormone (GH) and IGF-I have been implicated in the pathogenesis of type I diabetic (DM) nephropathy. We investigated renal GH receptor (GHR) and IGF-type 1 receptor (IGF1R) signaling in an animal model of type I DM. Kidney tissue was examined for GHR and IGF1R key signaling molecules. GHR levels were unchanged and IGF-I mRNA levels were decreased in the diabetic group (D). Basal and GH stimulated phosphorylated (p-) JAK2 and STAT5 levels were similar in controls (C) and D. The levels of p-IGF1R were similar in the two groups at baseline, while pAkt, pGSK3, p-mTOR, p-rpS6, p-erk1/2 (Mapk), and pSTAT-3 were increased in D. Following IGF-I administration p-Akt, p-rpS6, p-Mapk, and p-GSK levels increased more pronouncedly in D versus C. In conclusion, the lack of JAK2-STAT5 activation and the decrease in kidney IGF-I mRNA levels in D argue against a role for the GH activated JAK2-STAT5 pathway in the pathogenesis of diabetic nephropathy. On the other hand while IGF1R phosphorylation was unchanged, Akt/mTOR and MAPK signaling were hyperactivate in DM, suggesting their involvement. The increase in baseline activated Akt, mTOR, rpS6, and MAPK cannot be explained by activation of the IGF1R, but may be triggered by other growth factors and nutrients.

Serum IGF-I levels are similar in Samoan, Māori and European populations despite differences in body composition

OBJECTIVE

To determine if serum IGF-I concentrations are similar in healthy adult subjects from the Samoan, Māori and European populations in New Zealand.

DESIGN

Serum IGF-I concentration was measured in 75 healthy adults, aged 18-50 years, of Samoan (n=23), Māori (n=22) and European (n=30) descent. Body composition was assessed using standard anthropomorphic measures. In addition all subjects had body composition assessed by Dual energy X-ray absorptiometry (DXA).

RESULTS

Weight, body mass index (BMI), and fat mass were significantly greater in Māori and Samoan subjects than European subjects (ANOVA p=0.006, p=0.0003, p=0.03, respectively). However, serum IGF-I concentration was similar between the groups (European 186.8 SEM 14.9 microg/l, Māori 204.8 SEM 17.1 microg/l, Samoan 180.0 SEM 17.5 microg/l, p=0.58). IGF-I levels were similar between ethnic groups after adjustment (ANCOVA) for age, sex or BMI (p=0.5) or age, sex and fat mass (p=0.44). In multivariate analysis the only independent predictor of IGF-I was age (p<0.001) and explained 22% of the variance in IGF-I level.

CONCLUSIONS

Serum IGF-I concentrations were similar in Māori, Samoan and European population groups in New Zealand, despite significant differences in anthropomorphic variables and body composition.