The role of IGF-1 resistance in obesity and type 2 diabetes-mellitus-related insulin resistance and vascular disease

Identification of hub genes associated with diabetic cardiomyopathy using integrated bioinformatics analysis

Diabetic cardiomyopathy (DCM) is a common cardiovascular complication of diabetes, which may threaten the quality of life and shorten life expectancy in the diabetic population. However, the molecular mechanisms underlying the diabetes cardiomyopathy are not fully elucidated. We analyzed two datasets from Gene Expression Omnibus (GEO). Differentially expressed and weighted gene correlation network analysis (WGCNA) was used to screen key genes and molecules. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and protein-protein interaction (PPI) network analysis were constructed to identify hub genes. The diagnostic value of the hub gene was evaluated using the receiver operating characteristic (ROC). Quantitative real-time PCR (RT-qPCR) was used to validate the hub genes. A total of 13 differentially co-expressed modules were selected by WGCNA and differential expression analysis. KEGG and GO analysis showed these DEGs were mainly enriched in lipid metabolism and myocardial hypertrophy pathway, cytomembrane, and mitochondrion. As a result, six genes were identified as hub genes. Finally, five genes (Pdk4, Lipe, Serpine1, Igf1r, and Bcl2l1) were found significantly changed in both the validation dataset and experimental mice with DCM. In conclusion, the present study identified five genes that may help provide novel targets for diagnosing and treating DCM.

Air Pollution in Cardio-Oncology and Unraveling the Environmental Nexus: JACC: CardioOncology State-of-the-Art Review

Although recent advancements in cancer therapies have extended the lifespan of patients with cancer, they have also introduced new challenges, including chronic health issues such as cardiovascular disease arising from pre-existing risk factors or cancer therapies. Consequently, cardiovascular disease has become a leading cause of non-cancer-related death among cancer patients, driving the rapid evolution of the cardio-oncology field. Environmental factors, particularly air pollution, significantly contribute to deaths associated with cardiovascular disease and specific cancers, such as lung cancer. Despite these statistics, the health impact of air pollution in the context of cardio-oncology has been largely overlooked in patient care and research. Notably, the impact of air pollution varies widely across geographic areas and among individuals, leading to diverse exposure consequences. This review aims to consolidate epidemiologic and preclinical evidence linking air pollution to cardio-oncology while also exploring associated health disparities and environmental justice issues.

Capn4 aggravates angiotensin II-induced cardiac hypertrophy by activating the IGF-AKT signaling pathway

Capn4 belongs to a family of calpains that participate in a wide variety of biological functions, but little is known about the role of Capn4 in cardiac disease. Here, we show that the expression of Capn4 was significantly increased in Angiotensin II (Ang II)-treated cardiomyocytes and Ang II-induced cardiac hypertrophic mouse hearts. Importantly, in agreement with the Capn4 expression patterns, the maximal calpain activity measured in heart homogenates was elevated in Ang II-treated mice, and oral coadministration of SNJ-1945 (calpain inhibitor) attenuated the total calpain activity measured in vitro. Functional assays indicated that overexpression of Capn4 obviously aggravated Ang II-induced cardiac hypertrophy, whereas Capn4 knockdown resulted in the opposite phenotypes. Further investigation demonstrated that Capn4 maintained the activation of the insulin-like growth factor (IGF)-AKT signaling pathway in cardiomyocytes by increasing c-Jun expression. Mechanistic investigations revealed that Capn4 directly bound and stabilized c-Jun, and knockdown of Capn4 increased the ubiquitination level of c-Jun in cardiomyocytes. Additionally, our results demonstrated that the antihypertrophic effect of Capn4 silencing was partially dependent on the inhibition of c-Jun. Overall, these data suggested that Capn4 contributes to cardiac hypertrophy by enhancing the c-Jun-mediated IGF-AKT signaling pathway and could be a potential therapeutic target for hypertrophic cardiomyopathy.

Association between insulin-like growth factor-1 and systolic blood pressure in children and adolescents with short stature

The relationship between insulin‐like growth factor‐1 (IGF‐1) and systolic blood pressure (SBP) is controversial in adults and children. The purpose of this study was to investigate the relationship between the IGF‐1 standard deviation score (IGF‐1 SDS) and SBP in children with short stature. A cross‐sectional analysis including 1315 children with short stature was conducted from March 2013 to October 2020. We estimated IGF‐1, blood pressure and other laboratory tests, and anthropometric indicators were also evaluated. Subgroup analyses of the pubertal stage, sex, growth hormone levels, thyroid hormone levels, fasting blood glucose levels, and triglyceride levels were performed. A positive association between the IGF‐1 SDS and SBP was observed by univariate analysis (p < .001). We further found a nonlinear association between the IGF‐1 SDS and SBP. The inflection point for the curve was found at an IGF‐1 SDS level of −2.91. In multivariate piecewise linear regression, there was a positive association between the IGF‐1 SDS and SBP when the IGF‐1 SDS was greater than −2.91 (β 1.56, 95% CI: 0.91, 2.22; p < .001). However, we did not observe a significant relationship between the IGF‐1 SDS and SBP when the IGF‐1 SDS level was less than −2.91 (β −0.95, 95% CI −3.17, 1.28; p = .379). This association was consistent across subgroup analyses. The present study demonstrated that there is a nonlinear relationship between the IGF‐1 SDS and SBP in children with short stature. Increased serum IGF‐1 levels were associated with elevated SBP when the IGF‐1 levels reached the inflection point.

Circulating IGF-1 Independently Predicts Blood Pressure in Children With Higher Calcium-Phosphorus Product Levels

OBJECTIVE

To study the association between insulin-like growth factor 1 (IGF-1) and blood pressure in children, in particular, the potential interaction with the serum calcium-phosphorus product (Ca*P).

METHODS

A longitudinal study included 521 children (age 8.8 ± 0.1) from northeastern Spain, of whom 158 were followed-up after 5 years. IGF-1, insulin-like growth factor-binding protein 3 (IGFBP-3), and serum calcium and phosphorus were measured at baseline. Anthropometric (body-mass index [BMI] and waist) and cardiometabolic variables (systolic [SBP] and diastolic blood pressure), pulse pressure, insulin, homeostatic model assessment of insulin resistance [HOMA-IR], high-density lipoprotein [HDL]-cholesterol, and triglycerides) were assessed at baseline and at the end of follow-up. Statistical analysis included Pearson correlations followed by multivariable linear regression analyses.

RESULTS

Baseline IGF-1 and IGF-1/IGFBP-3 molar ratio positively correlated with baseline and follow-up BMI, waist, SBP, pulse pressure, insulin, HOMA-IR and triglycerides (r 0.138-0.603; all P < 0.05). The associations with SBP were stronger with increasing Ca*P (r 0.261-0.625 for IGF-1; and r 0.174-0.583 for IGF-1/IGFBP-3). After adjusting for confounding variables, baseline IGF-1 and IGF-1/IGFBP-3 remained independently associated with both baseline and follow-up SBP in children in the highest Ca*P tertile (β = 0.245-0.381; P < 0.01; model R2 = 0.246-0.566).

CONCLUSIONS

Our results suggest that IGF-1 in childhood is an independent predictor of SBP in apparently healthy children, especially in those with high Ca*P levels.

The impact of type 2 diabetes on bone metabolism and growth after spinal fusion

BACKGROUND CONTEXT

Some clinical reports suggest diabetes may have a negative effect on spinal fusion outcomes, although no conclusive experimental research has been conducted to investigate the causality, impact, and inherent risks of this growing patient population.

PURPOSE

To analyze the hypothesis that type 2 diabetes (T2DM) inhibits the formation of a solid bony union after spinal fusion surgery by altering the local microenvironment at the fusion site through a reduction in growth factors critical for bone formation.

STUDY DESIGN/SETTING

In vivo rodent model of type 2 diabetes.

METHODS

Twenty control (Sprague Dawley, SD) and 30 diabetic (Zucker Diabetic Sprague Dawley, ZDSD) rats underwent posterolateral and laminar fusion surgery using a tailbone autograft implanted onto the L4/L5 transverse processes. A subset of animals was sacrificed 1-week postsurgery for growth factor analysis. Remaining rats were sacrificed 3-month postsurgery for fusion evaluation via manual palpation, micro-CT, and histology.

RESULTS

There was no significant difference in the manual palpation fusion rate between ZDSD rats and SD control rats. Growth factor assay of fusion site explants at early sacrifice demonstrated PDGF was upregulated in the ZDSD rats. TGFB, IGF, and VEGF were not statistically different between groups. Bone mineral density as determined by micro-CT was significantly lower in ZDSD rats compared to SD controls and was a significant function of HbA1c.

CONCLUSIONS

Data generated in this in vivo rat model of T2DM demonstrate that the metabolic dysregulation associated with the diabetic condition negatively impacts the quality and density of the formed fusion mass. Increased measures of diabetic status, as determined by blood glucose and HbA1c, were correlated with decreased quality of formed fusion, highlighting the importance of diabetic status monitoring and regulation to bone health, particularly during bone healing.

CLINICAL RELEVANCE

T2DM rats demonstrated increased rates of infection, metabolic dysregulation, and a reduction in spinal fusion consolidation. Clinicians should consider these negative effects during preoperative care and treatment of this growing patient population.

Insulin-Like Growth Factor 1 in the Cardiovascular System

Non-communicable diseases, such as cardiovascular diseases, are the leading cause of mortality worldwide. For this reason, a tremendous effort is being made worldwide to effectively circumvent these afflictions, where insulin-like growth factor 1 (IGF1) is being proposed both as a marker and as a central cornerstone in these diseases, making it an interesting molecule to focus on. Firstly, at the initiation of metabolic deregulation by overfeeding, IGF1 is decreased/inhibited. Secondly, such deficiency seems to be intimately related to the onset of MetS and establishment of vascular derangements leading to atherosclerosis and finally playing a definitive part in cerebrovascular and myocardial accidents, where IGF1 deficiency seems to render these organs vulnerable to oxidative and apoptotic/necrotic damage. Several human cohort correlations together with basic/translational experimental data seem to confirm deep IGF1 implication, albeit with controversy, which might, in part, be given by experimental design leading to blurred result interpretation.

Growth hormone and insulin-like growth factor-I axis in type 1 diabetes

The precise mechanisms relating type 1 diabetes (T1D) and poor glycemic control to the axis of growth hormone (GH), insulin like growth factor- I (IGF-I), and IGF binding protein-3 (IGFBP-3) remain to be definitively determined. GH resistance with low IGF-I as is frequently seen in patients with T1D is often related to portal hypoinsulization, and lack of upregulation of GH receptors. There are conflicting reports of the effect of a dysregulated GH/IGF-I axis on height in children and adolescents with T1D, as well as on chronic complications. This brief review discusses some of the interactions between the GH/IGF-I axis and T1D pathology, and vice-versa.

Peripheral insulin-like growth factor 1 in bipolar disorder

Bipolar disorder is a recurrent and highly incapacitating illness, related to inflammation and changes in the insulin-like growth factor 1 (IGF-1). The objective of this study was to evaluate serum levels of IGF-1 in bipolar disorder patients and its relation to inflammation. We included 31 patients with bipolar disorder and 33 healthy controls. Serum concentrations of IGF-1, growth hormone (GH), insulin and tumor necrosis factor α (TNF-α) were analyzed. The serum levels of IGF-1 seem to be increased in bipolar disorder patients (248.84±104.91ng/mL) compared to controls (169.18±74.16ng/mL). Comparing reference values of IGF serum concentrations between groups, we found that 32% of patients had increased IGF-1 serum concentrations while only 3% of subjects are above normal range. We did not find statistically significant differences between groups in the concentration of insulin, GH, and TNF-α. This study suggests an association between IGF-1 in the pathophysiology of bipolar disorder. It is possible that this peripheral increase is related to a central nervous system increased resistance to IGF-1, thus reducing its neuroprotective action.

Effects of Insulin and High Glucose on Human Meibomian Gland Epithelial Cells

PURPOSE

Type 2 diabetes is a risk factor for meibomian gland dysfunction (MGD). We hypothesize that this diabetic impact is due, at least in part, to the effects of insulin resistance/deficiency and hyperglycemia on human meibomian gland epithelial cells (HMGECs). To begin to test this hypothesis, we examined whether insulin and high glucose influence immortalized (I) HMGECs.

METHODS

Immortalized HMGECs were cultured in serum-containing or -free media and treated with insulin, insulin-like growth factor-1 (IGF-1), IGF-1 receptor (R) blocking antibody, and glucose or mannitol for varying time periods. Specific proteins were detected by Western blots, cell proliferation was evaluated by manual cell counting and lipids were assessed with LipidTOX and high performance thin layer chromatography.

RESULTS

We found that insulin induces a dose-dependent increase in phosphatidylinositide 3-kinase/Akt (AKT) signaling in IHMGECs. This effect involves the IGF-1R, but not the insulin receptor (IR), and is associated with a stimulation of cell proliferation and neutral lipid accumulation. In contrast, high glucose exposure alters cell morphology, causes a progressive cell loss, and significantly reduces the levels of IGF-1R, phospho (p)-AKT, Foxhead box protein O1 (FOXO1), and sterol-regulatory element binding protein (SREBP-1) in IHMGECs.

CONCLUSIONS

Our data show that insulin stimulates, and that high glucose is toxic for, IHMGECs. These results support our hypothesis that insulin resistance/deficiency and hyperglycemia are deleterious for HMGECs and may help explain why type II diabetes is a risk factor for MGD.

The hypertension of Cushing's syndrome: controversies in the pathophysiology and focus on cardiovascular complications

Cushing's syndrome is associated with increased mortality, mainly due to cardiovascular complications, which are sustained by the common development of systemic arterial hypertension and metabolic syndrome, which partially persist after the disease remission. Cardiovascular diseases and hypertension associated with endogenous hypercortisolism reveal underexplored peculiarities. The use of exogenous corticosteroids also impacts on hypertension and cardiovascular system, especially after prolonged treatment. The mechanisms involved in the development of hypertension differ, whether glucocorticoid excess is acute or chronic, and the source endogenous or exogenous, introducing inconsistencies among published studies. The pleiotropic effects of glucocorticoids and the overlap of the several regulatory mechanisms controlling blood pressure suggest that a rigorous comparison of in-vivo and in-vitro studies is necessary to draw reliable conclusions. This review, developed during the first ‘Altogether to Beat Cushing's syndrome’ workshop held in Capri in 2012, evaluates the most important peculiarities of hypertension associated with CS, with a particular focus on its pathophysiology. A critical appraisal of most significant animal and human studies is compared with a systematic review of the few available clinical trials. A special attention is dedicated to the description of the clinical features and cardiovascular damage secondary to glucocorticoid excess. On the basis of the consensus reached during the workshop, a pathophysiology-oriented therapeutic algorithm has been developed and it could serve as a first attempt to rationalize the treatment of hypertension in Cushing's syndrome.

Atypical Diabetic Foot Ulcer Keratinocyte Protein Signaling Correlates with Impaired Wound Healing

Diabetes mellitus is associated with chronic diabetic foot ulcers (DFUs) and wound infections often resulting in lower extremity amputations. The protein signaling architecture of the mechanisms responsible for impaired DFU healing has not been characterized. In this preliminary clinical study, the intracellular levels of proteins involved in signal transduction networks relevant to wound healing were non-biasedly measured using reverse-phase protein arrays (RPPA) in keratinocytes isolated from DFU wound biopsies. RPPA allows for the simultaneous documentation and assessment of the signaling pathways active in each DFU. Thus, RPPA provides for the accurate mapping of wound healing pathways associated with apoptosis, proliferation, senescence, survival, and angiogenesis. From the study data, we have identified potential diagnostic, or predictive, biomarkers for DFU wound healing derived from the ratios of quantified signaling protein expressions within interconnected pathways. These biomarkers may allow physicians to personalize therapeutic strategies for DFU management on an individual basis based upon the signaling architecture present in each wound. Additionally, we have identified altered, interconnected signaling pathways within DFU keratinocytes that may help guide the development of therapeutics to modulate these dysregulated pathways, many of which parallel the therapeutic targets which are the hallmarks of molecular therapies for treating cancer.

The insulin-like growth factor I system: physiological and pathophysiological implication in cardiovascular diseases associated with metabolic syndrome

Metabolic syndrome is a cluster of risk factors including obesity, dyslipidemia, hypertension, and insulin resistance. A number of theories have been speculated for the pathogenesis of metabolic syndrome including impaired glucose and lipid metabolism, lipotoxicity, oxidative stress, interrupted neurohormonal regulation and compromised intracellular Ca(2+) handling. Recent evidence has revealed that adults with severe growth hormone (GH) and insulin-like growth factor I (IGF-1) deficiency such as Laron syndrome display increased risk of stroke and cardiovascular diseases. IGF-1 signaling may regulate contractility, metabolism, hypertrophy, apoptosis, autophagy, stem cell regeneration and senescence in the heart to maintain cardiac homeostasis. An inverse relationship between plasma IGF-1 levels and prevalence of metabolic syndrome as well as associated cardiovascular complications has been identified, suggesting the clinical promises of IGF-1 analogues or IGF-1 receptor activation in the management of metabolic and cardiovascular diseases. However, the underlying pathophysiological mechanisms between IGF-1 and metabolic syndrome are still poorly understood. This mini-review will discuss the role of IGF-1 signaling cascade in the prevalence of metabolic syndrome in particular the susceptibility to overnutrition and sedentary life style-induced obesity, dyslipidemia, insulin resistance and other features of metabolic syndrome. Special attention will be dedicated in IGF-1-associated changes in cardiac responses in various metabolic syndrome components such as insulin resistance, obesity, hypertension and dyslipidemia. The potential risk of IGF-1 and IGF-1R stimulation such as tumorigenesis is discussed. Therapeutic promises of IGF-1 and IGF-1 analogues including mecasermin, mecasermin rinfabate and PEGylated IGF-1 will be discussed.

Influence of oxygen on wound healing dynamics in healing-impaired diabetic mice

A previous experiment using an in vivo mouse model has proved that hypoxia increased angiogenesis during wound healing. It was hypothesised that one of the mechanisms for wound healing impairment in diabetes includes insufficient angiogenic ability in response to hypoxia. The current study aims to investigate the influence of hypoxia on wound healing in diabetic mice. Oxygen-impermeable (hypoxic group) and -permeable membranes (normoxic group) were used to control topical oxygen tension. Membranes were applied to symmetrical excisional wounds on diabetic mice. Wound area, granulated tissue thickness, and vascular density were analyzed. As results, a decrease in wound size on day 7 was observed in the normoxic group (20.7 ± 3.64%) compared with the hypoxic group (34.1 ± 4.98%). The normoxic group also showed significantly thicker granulated tissue than the hypoxic group (225.7 ± 54.7 vs 128.7 ± 42.4 µm). There was no significant difference in mean vascular density between normoxic and hypoxic groups (0.046 ± 0.022 vs 0.038 ± 0.017 mm(2)/mm(2), p = 0.80). Contrary to healthy mice, diabetic mice have shown no enhancement of angiogenesis in hypoxic condition. The findings illustrate that neovascularisation in response to hypoxia is diminished in diabetic wounds.

Effects of growth hormone–releasing hormone on cognitive function in adults with mild cognitive impairment and healthy older adults: results of a controlled trial

BACKGROUND

Growth hormone–releasing hormone(GHRH), growth hormone, and insulin like growth factor 1 have potent effects on brain function, their levels decrease with advancing age, and they likely play a role in the pathogenesis of Alzheimer disease. Previously, we reported favorable cognitive effects of short-term GHRH administration in healthy older adults and provided preliminary evidence to suggest a similar benefit in adults with mild cognitive impairment (MCI).

OBJECTIVE

To examine the effects of GHRH on cognitive function in healthy older adults and in adults with MCI.

DESIGN

Randomized,double-blind,placebo-controlled trial.

SETTING

Clinical Research Center, University of Washington School of Medicine in Seattle.

PARTICIPANTS

A total of 152 adults (66 with MCI) ranging in age from 55 to 87 years (mean age, 68 years); 137 adults (76 healthy participants and 61 participants with MCI) successfully completed the study.

INTERVENTION

Participants self-administered daily subcutaneous injections of tesamorelin (Theratechnologies Inc),a stabilized analog of human GHRH (1 mg/d), or placebo 30 minutes before bedtime for 20 weeks. At baseline, at weeks 10 and 20 of treatment, and after a 10-week washout(week 30), blood samples were collected, and parallel versions of a cognitive battery were administered. Before and after the 20-week intervention, participants completed an oral glucose tolerance test and a dual-energy x-ray absorptiometry scan to measure body composition.

MAIN OUTCOME MEASURES

Primary cognitive outcomes were analyzed using analysis of variance and included 3 composites reflecting executive function, verbal memory, and visual memory. Executive function was assessed with Stroop Color-Word Interference,Task Switching, the Self-Ordered Pointing Test, and Word Fluency, verbal memory was assessed with Story Recall and the Hopkins Verbal Learning Test,and visual memory was assessed with the Visual-Spatial Learning Test and Delayed Match-to-Sample.

RESULTS

The intent-to-treat analysis indicated a favorable effect of GHRH on cognition (P=.03), which was comparable in adults with MCI and healthy older adults.The completer analysis showed a similar pattern, with a more robust GHRH effect (P=.002). Subsequent analyses indicated a positive GHRH effect on executive function (P=.005) and a trend showing a similar treatment-related benefit in verbal memory(P=.08). Treatment with GHRH increased insulin like growth factor 1 levels by 117 %(P.001), which remained within the physiological range, and reduced percent body fat by 7.4%(P.001). Treatment with GHRH increased fasting insulin levels within the normal range by 35%in adults with MCI (P.001) but not in healthy adults. Adverse events were mild and were reported by 68%of GHRH treated adults and 36% of those who received placebo.

CONCLUSIONS

Twenty weeks of GHRH administration had favorable effects on cognition in both adults with MCI and healthy older adults. Longer-duration treatment trials are needed to further examine the therapeutic potential of GHRH administration on brain health during normal aging and “pathological aging.”

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00257712

Effects of oral sodium bicarbonate in patients with CKD

BACKGROUND AND OBJECTIVES

Metabolic acidosis contributes to muscle breakdown in patients with CKD, but whether its treatment improves functional outcomes is unknown. The choice of dose and tolerability of high doses remain unclear. In CKD patients with mild acidosis, this study evaluated the dose-response relationship of alkali with serum bicarbonate, its side effect profile, and its effect on muscle strength.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this single-blinded pilot study from March of 2009 to August of 2010, 20 adults with estimated GFR 15-45 ml/min per 1.73 m(2) and serum bicarbonate 20-24 mEq/L were treated during successive 2-week periods with placebo followed by escalating oral NaHCO3 doses (0.3, 0.6, and 1.0 mEq/kg per day). At each visit, handgrip strength and time required to complete 5 and 10 repetitions of a sit-to-stand test were measured.

RESULTS

Each 0.1 mEq/kg per day increase in dose produced a 0.33 mEq/L (95% confidence interval=0.23-0.43 mEq/L) higher serum bicarbonate. Sit-to-stand time improved after 6 weeks of oral NaHCO3 (23.8±1.4 versus 22.2±1.6 seconds for 10 repetitions, P=0.002), and urinary nitrogen excretion decreased (-0.70 g/g creatinine [95% confidence interval=-1.11 to -0.30] per 0.1 mEq/kg per day higher dose). No statistically significant change was seen in handgrip strength (29.5±9.6 versus 28.4±9.4 kg, P=0.12). Higher NaHCO3 doses were not associated with increased BP or greater edema.

CONCLUSIONS

NaHCO3 supplementation produces a dose-dependent increase in serum bicarbonate and improves lower extremity muscle strength after a short-term intervention in CKD patients with mild acidosis. Long-term studies are needed to determine if this finding translates into improved functional status.

IGFBP-3 inhibits cytokine-induced insulin resistance and early manifestations of atherosclerosis

Metabolic syndrome is associated with visceral obesity, insulin resistance and an increased risk of cardiovascular diseases. Visceral fat tissue primarily consists of adipocytes that secrete cytokines leading to a state of systemic inflammation in obese conditions. One of the IGF-independent functions of IGFBP-3 is its role as an anti-inflammatory molecule. Our study in obese adolescents show a decrease in total IGFBP-3 levels and increase in proteolyzed IGFBP-3 in circulation when compared to their normal counterparts and establishes a positive correlation between IGFBP-3 proteolysis and adiposity parameters as well as insulin resistance. In human adipocytes, we show that IGFBP-3 inhibits TNF-α-induced NF-κB activity in an IGF-independent manner, thereby restoring the deregulated insulin signaling and negating TNF-α-induced inhibition of glucose uptake. IGFBP-3 further inhibits TNF-α, CRP and high glucose-induced NF-κB activity in human aortic endothelial cells (HAECs) and subsequently suppresses monocyte adhesion to HAEC through the IGFBP-3 receptor. In conclusion, these findings suggest that reduced levels of IGFBP-3 in circulation and reduced expression of IGFBP-3 in macrophages in obesity may result in suppression of its anti-inflammatory functions and therefore IGFBP-3 may present itself as a therapeutic for obesity-induced insulin resistance and for events occurring in the early stages of atherosclerosis.

The IGF-1 receptor and regulation of nitric oxide bioavailability and insulin signalling in the endothelium

The insulin-like growth factor-1 receptor (IGF-1R), like the insulin receptor (IR), plays a significant role in determining bioavailability of the critical signalling molecule nitric oxide (NO) and hence, modulates endothelial cell function, particularly in response to stimulation with insulin. In particular, the ability of the IGF-1R to form hybrid receptors with the IR appears to be highly significant in determining the sensitivity of the endothelial cell to insulin. This review will examine the structure of the IGF-1R and how this, with particular reference to the ability of the IGF-1R and the IR to form hybrid receptors, may have an effect both on endothelial cell function and the development of cardiovascular disease.

Diabetes mellitus and risk of prostate cancer: an updated meta-analysis based on 12 case-control and 25 cohort studies

The association between diabetes and risk of prostate cancer has been investigated widely. However, study results remain inconsistent and contradictory. Using a meta-analytic approach, the present study explore the relationship incorporating more recent studies and provide more powerful evidence without the limitations of any individual study. Relevant studies were identified by searching Pubmed and the Cochrane Central Register of Controlled Trials through May 18, 2012. The strength of the relationship between diabetes mellitus and risk of prostate cancer was assessed using relative risk (RR). Either a fixed effects or random effects model was used to calculate the pooled RRs. Stratification analyses and sensitivity analyses were conducted, and publication bias was assessed by Egger's test and Begg's test. Twelve case-control studies involving 9,767 cases and 19,790 controls, and 25 cohort studies involving 118,825 cases were included. The person-years of follow-up ranged from 29,963 to 6,264,890 among included cohort studies. Diabetes was not significantly associated with incidence of prostate cancer in our analysis of case-control studies only (RR = 0.846, 95 % CI [0.710, 1.009]) or that of cohort studies only (RR = 0.925, 95 % CI [0.811, 1.054]). However, through subgroup analyses, statistically significant associations between diabetes and prostate cancer were found when considering population-based studies only (RR = 0.719, 95 % CI [0.637, 0.812]), cohort studies conducted in the United States (RR = 0.789, 95 % CI [0.727, 0.857]), and studies with follow-up of more than 5 years. Compared to risk of prostate cancer among people without diabetes, diabetic patients using insulin treatment experienced reduced incidence of prostate cancer in both case-control and cohort studies. The results suggest that diabetes mellitus is associated with decreased incidence of prostate cancer, specifically in the population of the United States. In addition, the time since onset of diabetes was positively associated with decreasing incidence of prostate cancer. The present conclusions should be considered carefully, however, and confirmed with further studies.

The sirtuin SIRT6 blocks IGF-Akt signaling and development of cardiac hypertrophy by targeting c-Jun

Abnormal activation of insulin-like growth factor (IGF)-Akt signaling is implicated in the development of various diseases, including heart failure. However, the molecular mechanisms that regulate activation of this signaling pathway are not completely understood. Here we show that sirtuin 6 (SIRT6), a nuclear histone deacetylase, functions at the level of chromatin to directly attenuate IGF-Akt signaling. SIRT6-deficient mice developed cardiac hypertrophy and heart failure, whereas SIRT6 transgenic mice were protected from hypertrophic stimuli, indicating that SIRT6 acts as a negative regulator of cardiac hypertrophy. SIRT6-deficient mouse hearts showed hyperactivation of IGF signaling-related genes and their downstream targets. Mechanistically, SIRT6 binds to and suppresses the promoter of IGF signaling-related genes by interacting with c-Jun and deacetylating histone 3 at Lys9 (H3K9). We also found reduced SIRT6 expression in human failing hearts. These findings disclose a new link between SIRT6 and IGF-Akt signaling and implicate SIRT6 in the development of cardiac hypertrophy and failure.

Novel role of the IGF-1 receptor in endothelial function and repair: studies in endothelium-targeted IGF-1 receptor transgenic mice

We recently demonstrated that reducing IGF-1 receptor (IGF-1R) numbers in the endothelium enhances nitric oxide (NO) bioavailability and endothelial cell insulin sensitivity. In the present report, we aimed to examine the effect of increasing IGF-1R on endothelial cell function and repair. To examine the effect of increasing IGF-1R in the endothelium, we generated mice overexpressing human IGF-1R in the endothelium (human IGF-1R endothelium-overexpressing mice [hIGFREO]) under direction of the Tie2 promoter enhancer. hIGFREO aorta had reduced basal NO bioavailability (percent constriction to N(G)-monomethyl-l-arginine [mean (SEM) wild type 106% (30%); hIGFREO 48% (10%)]; P < 0.05). Endothelial cells from hIGFREO had reduced insulin-stimulated endothelial NO synthase activation (mean [SEM] wild type 170% [25%], hIGFREO 58% [3%]; P = 0.04) and insulin-stimulated NO release (mean [SEM] wild type 4,500 AU [1,000], hIGFREO 1,500 AU [700]; P < 0.05). hIGFREO mice had enhanced endothelium regeneration after denuding arterial injury (mean [SEM] percent recovered area, wild type 57% [2%], hIGFREO 47% [5%]; P < 0.05) and enhanced endothelial cell migration in vitro. The IGF-1R, although reducing NO bioavailability, enhances in situ endothelium regeneration. Manipulating IGF-1R in the endothelium may be a useful strategy to treat disorders of vascular growth and repair.

Antihyperglycemic and antihyperlipidemic effects of guar gum on streptozotocin-induced diabetes in male rats

BACKGROUND

Herbal medicine is widely used in the treatment of diseases like diabetes mellitus. We investigated the effects of guar gum in diabetic rats for the reduction of the risk of diabetes and cardiovascular disease. Dietary pattern emphasizing foods high in complex carbohydrates and fiber are associated with low blood glucose and cholesterol levels.

MATERIALS AND METHODS

Diet containing 0%, 5%, 10% and 20% (w/w) guar gum was fed to diabetic rats for 28 days. Blood serum glucose, triglycerides, cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol levels, atherogenic index levels, body weights and food intake were monitored at 0, 7.14 and 28 days after induction of diabetes.

RESULTS

In spite of the fact that diabetes elevated blood lipids in all rats after 14 days, the guar gum diet significantly decreased the serum concentration of cholesterol, triacylglicerols and LDL-C and atherogenic index. The most significant result in this study was the reduction of blood glucose in diabetic rats treated with the guar gum diet after 28 days versus non- and glibenclamide-treated rats. The gum promoted a general improvement in the condition of the diabetic rats in body weight and food intake in comparison with nontreated rats.

CONCLUSION

The results of this research suggest that guar gum was significantly effective in comparison with glibenclamide in the treatment of hyperlipidemia and hyperglycemia in diabetes rats. Therefore, it may be suggested as a reliable fiber in diabetic regimes in diabetic patients.

Insulin-like Growth Factor-1, Psoriasis, and Inflammation: A Ménage à Trois?

Psoriatic patients have an accumulation of metabolic syndrome (MS) and cardiovascular diseases (CVD), likely mediated by systemic inflammation, and exhibiting low circulating levels of insulin-like growth factor (IGF)-I, a marker of MS and CVD in the general population. The aim of this study is to determine the association of IGF-I and inflammation, and to assess the cardio-metabolic risk calculating the visceral adiposity index (VAI), in a group of psoriatic patients without MS. IGF-I, fibrinogen, C-reactive protein (CRP), and interleukin (IL)-6 levels were determined in 20 patients with moderate to severe psoriasis (age range 23–77 yrs) without MS, according to criteria of the National Cholesterol Education Program's Adult Panel III (ATP III), and 20 age- and BMI-matched controls. The standard deviation score (SDS) of IGF-I levels according to age (zSDS), the homeostasis model assessment of insulin resistance (HOMA-IR), the whole-body insulin sensitivity index (ISI), and VAI were also calculated. Psoriasis Area and Severity Index (PASI) mean value was 17.8±11. HDL cholesterol and IGF-I zSDS values were lower (p<0.001) and waist circumference (p<0.001), VAI, fibrinogen, and IL-6 (p<0.005) were higher compared with controls, while HOMA-IR and ISI were not statistically different. Lower IGF-I zSDS values were associated to higher values of BMI (p=0.04), waist circumference, VAI (p<0.001), PASI (p=0.011), or IL-6 (p<0.001). At the multivariate analysis PASI was the major determinant of IGF-I zSDS (p=0.016), accounting for 37% of its variability. In a subset of psoriatic patients without MS, chronic inflammation might be an important modulator of low IGF-I status, as a further possible mechanistic link between psoriasis and associated metabolic co-morbidities. The negative correlation between age-related IGF-I values and VAI suggest the involvement of adipocyte dysfunction in low IGF-I status more than MS per se. Further studies are needed to address whether these results are valid also for other psoriatic patients.

The insulin-like growth factor-1 receptor is a negative regulator of nitric oxide bioavailability and insulin sensitivity in the endothelium

OBJECTIVE

In mice, haploinsufficiency of the IGF-1 receptor (IGF-1R(+/-)), at a whole-body level, increases resistance to inflammation and oxidative stress, but the underlying mechanisms are unclear. We hypothesized that by forming insulin-resistant heterodimers composed of one IGF-1Rαβ and one insulin receptor (IR), IRαβ complex in endothelial cells (ECs), IGF-1R reduces free IR, which reduces EC insulin sensitivity and generation of the antioxidant/anti-inflammatory signaling radical nitric oxide (NO).

RESEARCH DESIGN AND METHODS

Using a number of complementary gene-modified mice with reduced IGF-1R at a whole-body level and specifically in EC, and complementary studies in EC in vitro, we examined the effect of changing IGF-1R/IR stoichiometry on EC insulin sensitivity and NO bioavailability.

RESULTS

IGF-1R(+/-) mice had enhanced insulin-mediated glucose lowering. Aortas from these mice were hypocontractile to phenylephrine (PE) and had increased basal NO generation and augmented insulin-mediated NO release from EC. To dissect EC from whole-body effects we generated mice with EC-specific knockdown of IGF-1R. Aortas from these mice were also hypocontractile to PE and had increased basal NO generation. Whole-body and EC deletion of IGF-1R reduced hybrid receptor formation. By reducing IGF-1R in IR-haploinsufficient mice we reduced hybrid formation, restored insulin-mediated vasorelaxation in aorta, and insulin stimulated NO release in EC. Complementary studies in human umbilical vein EC in which IGF-1R was reduced using siRNA confirmed that reducing IGF-1R has favorable effects on NO bioavailability and EC insulin sensitivity.

CONCLUSIONS

These data demonstrate that IGF-1R is a critical negative regulator of insulin sensitivity and NO bioavailability in the endothelium.