Circulating levels of insulin-like growth factor-II/mannose-6-phosphate receptor in obesity and type 2 diabetes

The associations of IGF2, IGF2R and IGF2BP2 gene polymorphisms with gestational diabetes mellitus: A case-control study

OBJECTIVE

To investigate the associations of Insulin-like growth factor-II (IGF2) gene, Insulin-like growth factor-II receptor (IGF2R) gene and Insulin-like growth factor-II binding protein 2 (IGF2BP2) gene polymorphisms with the susceptibility to gestational diabetes mellitus (GDM) in Chinese population.

METHODS

A total of 1703 pregnant women (835 GDM and 868 Non-GDM) were recruited in this case-control study. All participants underwent prenatal 75 g oral glucose tolerance test (OGTT) examinations during 24-28 gestational weeks at the Maternal and Child Health Hospital of Hubei Province from January 15, 2018 to March 31, 2019. Genotyping of candidate SNPs (IGF2 rs680, IGF2R rs416572, IGF2BP2 rs4402960, rs1470579, rs1374910, rs11705701, rs6777038, rs16860234, rs7651090) was performed on Sequenom MassARRAY platform. Logistic regression analysis was conducted to investigate the associations between candidate SNPs and risk of GDM. In addition, multifactor dimensionality reduction (MDR) method was applied to explore the effects of gene-gene interactions on GDM risk.

RESULTS

There were significant distribution differences between GDM group and non-GDM group in age, pre-pregnancy BMI, education level and family history of diabetes (P < 0.05). After adjusted for age, pre-pregnancy BMI, education level and family history of diabetes, there were no significant associations of the candidate SNPs polymorphisms and GDM risk (P > 0.05). Furthermore, there were no gene-gene interactions on the GDM risk among the candidate SNPs (P > 0.05). However, the fasting blood glucose (FBG) levels of rs6777038 CT carriers were significantly lower than TT carriers (4.69±0.69 vs. 5.03±1.57 mmol/L, P < 0.01), and the OGTT-2h levels of rs6777038 CC and CT genotype carriers were significantly lower than TT genotype carriers (8.10±1.91 and 8.08±1.87 vs. 8.99±2.90 mmol/L, P < 0.01).

CONCLUSIONS

IGF2 rs680, IGF2R rs416572, IGF2BP2 rs4402960, rs1470579, rs11705701, rs6777038, rs16860234, rs7651090 polymorphisms were not significantly associated with GDM risk in Wuhan, China. Further lager multicenter researches are needed to confirm these results.

The Role of Obesity in Breast Cancer Pathogenesis

Research has shown that obesity increases the risk for type 2 diabetes mellitus (Type 2 DM) by promoting insulin resistance, increases serum estrogen levels by the upregulation of aromatase, and promotes the release of reactive oxygen species (ROS) by macrophages. Increased circulating glucose has been shown to activate mammalian target of rapamycin (mTOR), a significant signaling pathway in breast cancer pathogenesis. Estrogen plays an instrumental role in estrogen-receptor-positive breast cancers. The role of ROS in breast cancer warrants continued investigation, in relation to both pathogenesis and treatment of breast cancer. We aim to review the role of obesity in breast cancer pathogenesis and novel therapies mediating obesity-associated breast cancer development. We explore the association between body mass index (BMI) and breast cancer incidence and the mechanisms by which oxidative stress modulates breast cancer pathogenesis. We discuss the role of glutathione, a ubiquitous antioxidant, in breast cancer therapy. Lastly, we review breast cancer therapies targeting mTOR signaling, leptin signaling, blood sugar reduction, and novel immunotherapy targets.

DHA Supplementation during Pregnancy in Women with Obesity Normalizes IGF2R Levels in the Placenta of Male Newborns

Introduction

Insulin-like growth factor receptor 2 (IGF2R) regulates placental nutrient transport, and its soluble form is related to obesity in adults. If the placental expression of IGF2R is altered in women with obesity is unknown. Whether maternal supplementation with docosahexaenoic acid (DHA), a polyunsaturated fatty acid with anti-inflammatory properties, has a modulatory role in IGF2R's function has not been elucidated. We hypothesized that maternal obesity (Ob) would be associated with alterations in placental IGF2R expression, which may be prevented with DHA supplementation during pregnancy.

Methods

At delivery, we obtained placentas from women with Ob (BMI ≥ 30 kg/m², n = 17), Ob supplemented with 800 mg/day of DHA during pregnancy (Ob + DHA, n = 13), and normal-weight women (Nw, BMI ≥ 18.5 ≤ 24.9 kg/m², n = 14). The IGF2R mRNA and protein were determined by RT-PCR and western blotting, respectively. Moreover, we quantified the gene expression of molecules that modulate the IGF2R function in the extracellular domain, such as TACE/ADAM17, PLAU, and IGF2. Mann-Whitney and Kruskal-Wallis nonparametric tests were used to compare results between two or three groups accordingly.

Results

The IGF2R levels in the Ob placentas of the male offspring were higher than in the Nw group. The DHA supplementation prevented this effect, suggesting an unknown relationship between IGF2R-Ob-DHA in placental tissues.

Conclusion

We report, for the first time, that DHA supplementation during pregnancy in women with obesity normalizes the increased IGF2R levels in male placentas, reducing the risk of adverse outcomes related to the IGF2/IGF2R system in male newborns.

Insulin-like growth factor role in determining the anti-cancer effect of metformin: RCT in prostate cancer patients

OBJECTIVE

Androgen deprivation therapy (ADT), a principal therapy in patients with prostate cancer, is associated with the development of obesity, insulin resistance, and hyperinsulinemia. Recent evidence indicates that metformin may slow cancer progression and improves survival in prostate cancer patients, but the mechanism is not well understood. Circulating insulin-like growth factors (IGFs) are bound to high-affinity binding proteins, which not only modulate the bioavailability and signalling of IGFs but also have independent actions on cell growth and survival. The aim of this study was to investigate whether metformin modulates IGFs, IGF-binding proteins (IGFBPs), and the pregnancy-associated plasma protein A (PAPP-A) - stanniocalcin 2 (STC2) axis.

DESIGN AND METHODS

In a blinded, randomised, cross-over design, 15 patients with prostate cancer on stable ADT received metformin and placebo treatment for 6 weeks each. Glucose metabolism along with circulating IGFs and IGFBPs was assessed.

RESULTS

Metformin significantly reduced the homeostasis model assessment as an index of insulin resistance (HOMA IR) and hepatic insulin resistance. Metformin also reduced circulating IGF-2 (P < 0.05) and IGFBP-3 (P < 0.01) but increased IGF bioactivity (P < 0.05). At baseline, IGF-2 correlated significantly with the hepatic insulin resistance (r2= 0.28, P < 0.05). PAPP-A remained unchanged but STC2 declined significantly (P < 0.05) following metformin administration. During metformin treatment, change in HOMA IR correlated with the change in STC2 (r2= 0.35, P < 0.05).

CONCLUSION

Metformin administration alters many components of the circulating IGF system, either directly or indirectly via improved insulin sensitivity. Reduction in IGF-2 and STC2 may provide a novel mechanism for a potential metformin-induced antineoplastic effect.

Activation of Cx43 Hemichannels Induces the Generation of Ca2+ Oscillations in White Adipocytes and Stimulates Lipolysis

The aim of the study was to investigate the mechanisms of Ca²⁺ oscillation generation upon activation of connexin-43 and regulation of the lipolysis/lipogenesis balance in white adipocytes through vesicular ATP release. With fluorescence microscopy it was revealed that a decrease in the concentration of extracellular calcium ([Ca²⁺]_ex) results in two types of Ca²⁺ responses in white adipocytes: Ca²⁺ oscillations and transient Ca²⁺ signals. It was found that activation of the connexin half-channels is involved in the generation of Ca²⁺ oscillations, since the blockers of the connexin hemichannels-carbenoxolone, octanol, proadifen and Gap26-as well as Cx43 gene knockdown led to complete suppression of these signals. The activation of Cx43 in response to the reduction of [Ca²⁺]_ex was confirmed by TIRF microscopy. It was shown that in response to the activation of Cx43, ATP-containing vesicles were released from the adipocytes. This process was suppressed by knockdown of the Cx43 gene and by bafilomycin A1, an inhibitor of vacuolar ATPase. At the level of intracellular signaling, the generation of Ca²⁺ oscillations in white adipocytes in response to a decrease in [Ca²⁺]_ex occurred due to the mobilization of the Ca²⁺ ions from the thapsigargin-sensitive Ca²⁺ pool of IP₃R as a result of activation of the purinergic P2Y1 receptors and phosphoinositide signaling pathway. After activation of Cx43 and generation of the Ca²⁺ oscillations, changes in the expression levels of key genes and their encoding proteins involved in the regulation of lipolysis were observed in white adipocytes. This effect was accompanied by a decrease in the number of adipocytes containing lipid droplets, while inhibition or knockdown of Cx43 led to inhibition of lipolysis and accumulation of lipid droplets. In this study, we investigated the mechanism of Ca²⁺ oscillation generation in white adipocytes in response to a decrease in the concentration of Ca²⁺ ions in the external environment and established an interplay between periodic Ca²⁺ modes and the regulation of the lipolysis/lipogenesis balance.

Investigating IGF-II and IGF2R serum markers as predictors of body weight loss following an 8-week acute weight loss intervention: PREVIEW sub-study

BACKGROUND

Weight reduction is effective in preventing T2D however, weight reduction and maintenance is difficult to achieve on a population scale. Serum insulin-like growth factor II (IGF-II) and IGF-II receptor (IGF2R) have been associated with diabetic status and body weight in prior studies and, in addition, IGF-II has been indicated as predictive of future weight change. We measured these serum markers in participants with obesity/overweight and prediabetes from the New Zealand arm of the PREVIEW lifestyle intervention randomised trial before and after an 8-week low energy diet (LED).

METHODS

Total IGF-II (n = 223) and soluble IGF2R (n = 151) were measured using commercial ELISA kits on fasted serum samples taken prior to an 8-week LED and also from participants completing the LED.

RESULTS

IGF-II levels were not correlated with baseline body weight although mean levels did significantly decrease following the LED. Change in IGF-II serum level was correlated to fasting glucose change (p = 0.04) but not to weight change. Baseline serum IGF2R was correlated with BMI (p = 0.007) and was significantly higher in Māori compared to European Caucasian participants independent of body weight (p = 0.0016). Following LED, IGF2R change was positively associated with weight change (p = 0.02) when corrected for ethnicity. Pre-LED levels of these serum markers were not predictive of the magnitude of weight loss over the 8 weeks.

CONCLUSION

Neither marker was useful in predicting magnitude of short-term weight loss. IGF2R is positively associated with BMI and is higher in Māori compared to European Caucasian individuals.

The Neglected Insulin: IGF-II, a Metabolic Regulator with Implications for Diabetes, Obesity, and Cancer

When originally discovered, one of the initial observations was that, when all of the insulin peptide was depleted from serum, the vast majority of the insulin activity remained and this was due to a single additional peptide, IGF-II. The IGF-II gene is adjacent to the insulin gene, which is a result of gene duplication, but has evolved to be considerably more complicated. It was one of the first genes recognised to be imprinted and expressed in a parent-of-origin specific manner. The gene codes for IGF-II mRNA, but, in addition, also codes for antisense RNA, long non-coding RNA, and several micro RNA. Recent evidence suggests that each of these have important independent roles in metabolic regulation. It has also become clear that an alternatively spliced form of the insulin receptor may be the principle IGF-II receptor. These recent discoveries have important implications for metabolic disorders and also for cancer, for which there is renewed acknowledgement of the importance of metabolic reprogramming.

The insulin like growth factor and binding protein family: Novel therapeutic targets in obesity & diabetes

Background

Recent changes in nutrition and lifestyle have provoked an unprecedented increase in the prevalence of obesity and metabolic disorders. Recognition of the adverse effects on health has prompted intense efforts to understand the molecular determinants of insulin sensitivity and dysglycemia. In many respects, actions of insulin-like growth factors (IGFs) mirror those of insulin in metabolic regulation. Unlike insulin, however, the bioactivity of IGFs is regulated by a family of seven high-affinity binding proteins (IGFBPs) which confer temporospatial modulation with implications for metabolic homeostasis. In addition, evidence is accumulating that IGF-independent actions of certain of the IGFBPs can directly modulate insulin sensitivity.

Scope of review

In this review, we discuss the experimental data indicating a critical role for IGF/IGFBP axis in metabolic regulation. We highlight key discoveries through which IGFBPs have emerged as biomarkers or putative therapeutic targets in obesity and diabetes.

Major conclusions

Growing evidence suggests that several components of the IGF-IGFBP system could be explored for therapeutic potential in metabolic disorders. Both IGFBP-1 and IGFBP-2 have been favorably linked with insulin sensitivity in humans and preclinical data implicate direct involvement in the molecular regulation of insulin signaling and adiposity respectively. Further studies are warranted to evaluate clinical translation of these findings.

Insulin-like factor-2 receptor rs9456497 G genotype overrepresents in males of average population and its correlation with cardiovascular risks

OBJECTIVES

To look at the possible effect of IGF2R rs9456497 on cardiovascular risks in a long-lived population.

METHODS

IGF-2R rs9456497 was genotyped by iMLDR for 496 long-lived Zhuang Chinese (90-107 y/o) and their offspring (n = 723, 60-75 y/o) and healthy controls (n = 611, 60-75 y/o). Association analyses were then conducted among genotypes and cardiovascular risks.

RESULTS

The G genotype (GA/GG) was found to represent more frequently in males of general population. No significantly difference was detected among genotypes in each group except that G genotype tended to reduce the systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels in longevity group. However, after sex stratification, total cholesterol (TC) of each genotype in offspring males was elevated versus relevant genotype in longevity and control group; the triglyceride (TG), fasting plasma glucose (FPG) and BMI of each genotype in longevity group were lower while SBP and DBP were higher than that of the relevant genotype in offspring and controls. After stratified by lipid status, the frequency of G allele was markedly increased in the dyslipidemic subgroup in the combined population and controls. Linear regressive analyses showed that HDL was positively correlated to rs9456497 GA genotype while BMI was negatively correlated to AA genotype in offspring group, whereas TC and TG were reversely while BMI was positively associated with AA genotype in CG.

CONCLUSIONS

IGF-2R rs9456497 G genotype correlates to detrimental cardiovascular risks in ordinary population which might partially interpret their less preservation of health as compared to long-lived cohort.

Unravelling novel functions of the endosomal transporter mannose 6-phosphate/insulin-like growth factor receptor (CD222) in health and disease: An emerging regulator of the immune system

Properly balanced cellular responses require both the mutual interactions of soluble factors with cell surface receptors and the crosstalk of intracellular molecules. In particular, immune cells exposed unceasingly to an array of positive and negative stimuli must distinguish between what has to be tolerated and attacked. Protein trafficking is one of crucial pathways involved in this labour. The approximately >270-kDa protein transporter called mannose 6- phosphate/insulin-like growth factor 2 receptor (M6P/IGF2R, CD222) is a type I transmembrane glycoprotein present largely intracellularly in the Golgi apparatus and endosomal compartments, but also at the cell surface. It is expressed ubiquitously in a vast majority of higher eukaryotic cell types. Through binding and trafficking multiple unrelated extracellular and intracellular ligands, CD222 is involved in the regulation of a plethora of functions, and thus implicated in many physiological but also pathophysiological conditions. This review describes, first, general features of CD222, such as its evolution, genomic structure and regulation, protein structure and ligands; and second, its specific functions with a special focus on the immune system.

Obesity and Cancer Mechanisms: Cancer Metabolism

Obesity is a risk factor for cancer development and is associated with poor prognosis in multiple tumor types. The positive energy balance linked with obesity induces a variety of systemic changes including altered levels of insulin, insulin-like growth factor-1, leptin, adiponectin, steroid hormones, and cytokines. Each of these factors alters the nutritional milieu and has the potential to create an environment that favors tumor initiation and progression. Although the complete ramifications of obesity as it relates to cancer are still unclear, there is convincing evidence that reducing the magnitude of the systemic hormonal and inflammatory changes has significant clinical benefits. This review will examine the changes that occur in the obese state and review the biologic mechanisms that connect these changes to increased cancer risk. Understanding the metabolic changes that occur in obese individuals may also help to elucidate more effective treatment options for these patients when they develop cancer. Moving forward, targeted clinical trials examining the effects of behavioral modifications such as reduced carbohydrate intake, caloric restriction, structured exercise, and/or pharmacologic interventions such as the use of metformin, in obese populations may help to reduce their cancer risk.

Increased plasma dipeptidyl peptidase-4 activities are associated with high prevalence of diabetic nephropathy in Chinese patients with newly diagnosed type 2 diabetes: A cross-sectional study

OBJECTIVE

To investigate the association between plasma Dipeptidyl peptidase-4 (DPP4) activities and diabetic nephropathy in type 2 diabetes.

RESEARCH DESIGN AND METHODS

A total of 1193 newly diagnosed type 2 diabetic subjects were studied. Plasma DPP4 activity, mannose 6-phosphate receptor, inflammatory markers and oxidative stress parameters were measured in all participants. Diabetic nephropathy was defined as the presence of albuminuria or an estimated glomerular filtration rate < 60 mL/min/1.73 m(2).

RESULTS

Participants in the highest quartile of DPP4 activity had higher HbA1c, homeostatic model assessment of insulin resistance, nitrotyrosine, 8-iso-PGF2a, interleukin-6, high-sensitivity C-reactive protein, mannose 6-phosphate receptor, urinary albumin-to-creatinine ratio and lower estimated glomerular filtration rate compared with participants in the lowest quartile (all p < 0.001). DPP4 activities were associated positively with HbA1c, homeostatic model assessment of insulin resistance, nitrotyrosine, 8-iso-PGF2a, interleukin-6, high-sensitivity C-reactive protein, mannose 6-phosphate receptor, urinary albumin-to-creatinine ratio and negatively with estimated glomerular filtration rate (all p < 0.001). In the highest DPP4 quartile, diabetic nephropathy risk was significantly higher (odds ratio: 3.77; 95% confidence interval: 2.34-6.07) than in the lowest quartile after adjustment for potential confounders. This association remained strong (2.85; 1.74-4.68) after further controlling for HbA1c, homeostatic model assessment of insulin resistance, nitrotyrosine and high-sensitivity C-reactive protein.

CONCLUSION

This study shows that increased DPP4 activities are strongly and independently associated with diabetic nephropathy in type 2 diabetes. The associations between DPP4 and diabetic nephropathy, although strong, do not imply causality. There are however plausible mechanisms which could explain such a link.

Soluble M6P/IGFIIR in the circulation

Soluble M6P/IGFIIR has the potential to be a significant carrier of IGF-II and mannose 6-P proteins in the circulation and play an important role as an antagonist to the cellular receptor. Evidence suggests that soluble receptor plays a role in fetal and childhood growth by opposing the growth stimulatory effects of IGF-II. Maternal serum levels of M6P/IGFIIR are elevated in late pregnancy and the IGF-II:soluble M6P/IGFIIR ratio in cord blood correlates strongly with weight at birth and placental weight suggesting an important role in fetal growth and development. However, elevated soluble receptor levels may also be indicative of disease in later life, such as liver cirrhosis and some tumor types and may be a useful marker for monitoring treatment and progression of the disease. Further investigation of the regulation of this soluble receptor in health and disease is required to fully elucidate its role in the circulation.

Increased plasma dipeptidyl peptidase-4 activities are associated with high prevalence of subclinical atherosclerosis in Chinese patients with newly diagnosed type 2 diabetes: a cross-sectional study

OBJECTIVE

Hyperglycemia, insulin resistance, dislipidemia, oxidative stress and inflammation are well-documented risk factors for subclinical atherosclerosis. Dipeptidyl peptidase-4(DPP4) is a newly identified adipokine related to these risk factors. Hence, we aimed to investigate the association between plasma DPP4 activities and subclinical atherosclerosis in type 2 diabetes.

METHODS

A total of 985 newly diagnosed type 2 diabetic subjects were studied. Plasma DPP4 activity, mannose 6-phosphate receptor (M6P-R), oxidative stress parameters, inflammatory markers and common carotid artery Intima-Media Thickness (c-IMT) were measured in all participants.

RESULTS

Participants in the highest quartile of DPP4 activity had higher HbA1c, homeostatic model assessment of insulin resistance(HOMA-IR), triglyceride, low-density lipoprotein cholesterol(LDL-C), oxidized LDL, nitrotyrosine, 8-iso-PGF2a, interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), M6P-R, c-IMT compared with participants in the lowest quartile (all P < 0.001). DPP4 activities were associated positively with HbA1c, HOMA-IR, triglyceride, LDL-C, oxidized LDL, nitrotyrosine, 8-iso-PGF2a, IL-6, hs-CRP, M6P-R and c-IMT (all P < 0.05). The ORs for insulin resistance, dislipidemia, oxidative stress and inflammation were higher with increasing DPP4 quartiles (P < 0.001 for trend). In the highest DPP4 quartile, subclinical atherosclerosis risk was significantly higher (OR 4.97; 95% CI 3.03-8.17) than in the lowest quartile. This association remained strong (2.17; 1.21-3.89) after further controlling for HbA1c, HOMA-IR, triglyceride, oxidized LDL, nitrotyrosine, and IL-6.

CONCLUSIONS

This study shows that increased DPP4 activities are positively and independently associated with subclinical atherosclerosis in type 2 diabetes. Our findings suggest of potential role of DPP4 in the pathogenesis of subclinical atherosclerosis and in the prevention and management of this disease.

Insulin-like growth factors and related proteins in plasma and cerebrospinal fluids of HIV-positive individuals

Background

Clinically significant dysregulation of the insulin-like growth factor (IGF) family proteins occurs in HIV-infected individuals, but the details including whether the deficiencies in IGFs contribute to CNS dysfunction are unknown.

Methods

We measured the levels of IGF1, IGF2, IGFBP1, IGFBP2, and IGF2 receptor (IGF2R) in matching plasma and cerebrospinal fluid (CSF) samples of 107 HIV+ individuals from CNS HIV Antiretroviral Therapy Effects Research (CHARTER) and analyzed their associations with demographic and disease characteristics, as well as levels of several soluble inflammatory mediators (TNFα, IL-6, IL-10, IL-17, IP-10, MCP-1, and progranulin). We also determined whether IGF1 or IGF2 deficiency is associated with HIV-associated neurocognitive disorder (HAND) and whether the levels of soluble IGF2R (an IGF scavenging receptor, which we also have found to be a cofactor for HIV infection in vitro) correlate with HIV viral load (VL).

Results

There was a positive correlation between the levels of IGF-binding proteins (IGFBPs) and those of inflammatory mediators: between plasma IGFBP1 and IL-17 (β coefficient 0.28, P = 0.009), plasma IGFBP2 and IL-6 (β coefficient 0.209, P = 0.021), CSF IGFBP1 and TNFα (β coefficient 0.394, P < 0.001), and CSF IGFBP2 and TNF-α (β coefficient 0.14, P < 0.001). As IGFBPs limit IGF availability, these results suggest that inflammation is a significant factor that modulates IGF protein expression/availability in the setting of HIV infection. However, there was no significant association between HAND and the reduced levels of plasma IGF1, IGF2, or CSF IGF1, suggesting a limited power of our study. Interestingly, plasma IGF1 was significantly reduced in subjects on non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy (ART) compared to protease inhibitor-based therapy (174.1 ± 59.8 vs. 202.8 ± 47.3 ng/ml, P = 0.008), suggesting a scenario in which ART regimen-related toxicity can contribute to HAND. Plasma IGF2R levels were positively correlated with plasma VL (β coefficient 0.37, P = 0.021) and inversely correlated with current CD4+ T cell counts (β coefficient −0.04, P = 0.021), supporting our previous findings in vitro.

Conclusions

Together, these results strongly implicate (1) an inverse relationship between inflammation and IGF growth factor availability and the contribution of IGF deficiencies to HAND and (2) the role of IGF2R in HIV infection and as a surrogate biomarker for HIV VL.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0288-6) contains supplementary material, which is available to authorized users.

Increased plasma DPP4 activities predict new-onset hyperglycemia in Chinese over a four-year period: possible associations with inflammation

OBJECTIVE

DPP4, a novel proinflammatory cytokine, is involved in the inflammatory process through its interaction with the IGF-II/M6P receptor. Our objective was to determine whether DPP4 acts as a link between low-grade chronic inflammation and hyperglycemia.

DESIGN AND METHODS

A prospective cohort study was conducted with 486 adults (177 men and 309 women) aged 18 to 70years without hyperglycemia examined in 2007 (baseline) and 2011 (follow-up). Circulating DPP4 activity, IGF-II/M6P receptor, and inflammatory markers were measured at baseline and four years later.

RESULTS

After a four-year follow-up period, 111 individuals developed hyperglycemia (71 prediabetes and 40 type 2 diabetes). According to the multiple linear regression analysis, the baseline DPP4 activity was an independent predictor of an increase in the IGF-II/M6P receptor, inflammatory markers, and insulin resistance over the four-year period (all P <0.05). In the multivariable-adjusted models, the odds ratio (OR) for incident hyperglycemia comparing the highest and lowest quartiles of DPP4 activity was 2.90 (95% CI 1.47-5.73) after adjustment for confounding risk factors (P=0.002). The incidence of hyperglycemia because of DPP4 activity increased by 9.47%. Furthermore, the plasma DPP4 activity significantly improved the area under the ROC curve for predicting new-onset hyperglycemia based on the information from the baseline levels of the risk factors (P=0.036).

CONCLUSIONS

DPP4 activity is an important predictor of the onset of insulin resistance and hyperglycemia in apparently healthy Chinese. This finding may have important implications for understanding the proinflammatory role of DPP-4 in the development and pathogenesis of hyperglycemia.

The association of soluble IGF2R and IGF2R gene polymorphism with type 2 diabetes

The aim of this study is to investigate the insulin-like growth factor type 2 (IGF2R) gene and circulating soluble IGF2R in relation to type 2 diabetes (T2DM). Six hundred fifty-four subjects without history of diabetes were screened for diabetes by oral glucose tolerance test. In addition, 145 subjects with known diabetes were recruited from a local diabetes clinic. Circulating IGF2R levels were measured by ELISA method; plasma glucose was measured by colorimetric method; insulin levels were determined by chemiluminescent method; IGF2R gene rs416572 was genotyped using real-time PCR. The distributions of IGF2R genotypes were 69.2% CC, 27.8% CT, and 3.0% TT. The C allele was more commonly found in diabetes subjects, with a significant difference (P < 0.01). In the presence of the T allele, circulating IGF2R levels were significantly lower (P < 0.05). There was no significant difference in other potential confounders including age, sex, and BMI. Only circulating IGF2R, age, and BMI were independently associated with the degree of insulin resistance, as assessed by the HOMA model. It was found that age, sex, and BMI were associated with beta cell function. In conclusion, IGF2R gene polymorphism and circulating IGF2R are associated with T2DM.

The Insulin-Like Growth Factor System in Obesity, Insulin Resistance and Type 2 Diabetes Mellitus

The insulin-like growth factor (IGF) system, acting in concert with other hormone axes, is important in normal metabolism. In obesity, the hyperinsulinaemia that accompanies peripheral insulin resistance leads to reduced growth hormone (GH) secretion, while total IGF-I levels are relatively unchanged due to increased hepatic GH sensitivity. IGF-binding protein (IGFBP)-1 levels are suppressed in relation to the increase in insulin levels in obesity and low levels predict the development of type 2 diabetes several years later. Visceral adiposity and hepatic steatosis, along with a chronic inflammation, contribute to the IGF system phenotype in individuals with metabolic syndrome and type 2 diabetes mellitus, including changes in the normal inverse relationship between IGFBP-1 and insulin, with IGFBP-1 concentrations that are inappropriately normal or elevated. The IGF system is implicated in the vascular and other complications of these disorders and is therefore a potential therapeutic target.

Increased plasma DPP4 activity predicts new-onset hypertension in Chinese over a 4-year period: possible associations with inflammation and oxidative stress

To investigate whether increased dipeptidyl peptidase 4 (DPP4) activity predicts new-onset hypertension in Chinese patients. A prospective study was conducted for 1884 adults (804 men/1080 women) aged 18-70 years without hypertension. Participants were examined in 2007 (baseline) and 2011 (follow-up) and circulating DPP4 activity, mannose 6-phosphate receptor (M6P-R) concentration, inflammatory markers and oxidative stress parameters were measured. After a 4-year follow-up, 296 individuals developed hypertension with an incidence of 39 per 1000 patient years. In multiple linear regression analyses, baseline DPP4 activity was an independent predictor of an increase in M6P-R, inflammatory markers and oxidative stress parameters over a 4-year period (all P < 0.01). Cox proportional hazards models revealed that DPP4 activity independently predicted the risk of developing hypertension (relative risk 2.68 (95% confidence interval 1.71-4.21) P < 0.01). Our results indicate that DPP4 activity is an important predictor of hypertension onset in apparently healthy Chinese individuals. This finding may have important implications for understanding the effects of DPP4 in promoting inflammation and oxidative stress in the pathogenesis of hypertension.

Increased plasma DPP4 activities predict new-onset atherosclerosis in association with its proinflammatory effects in Chinese over a four year period: A prospective study

OBJECTIVE

DPP4, a novel proinflammatory cytokine, is involved in the inflammatory process through its interaction with IGF-II/M6P receptor. We aimed to investigate whether it could predict new-onset atherosclerosis in Chinese.

METHODS

A prospective study was conducted of 590 adults (213 men and 377 women) aged 18-70 years without atherosclerosis examined in 2007(baseline) and 2011(follow-up). Circulating DPP4 activity, inflammatory markers, IGF-II/M6P receptor and common carotid artery Intima-Media Thickness (C-IMT) were measured at baseline and four years later.

RESULTS

At baseline, individuals in the highest quartile of DPP4 activity had higher age, WHR, BMI, SBP, fasting insulin, 2h-PG, TG, LDL-C, IL-6, hs-CRP, IGF-II/M6P-R, C-IMT and lower HDL-C compared with individuals in the lowest quartile. After a 4-year follow-up, 71 individuals developed atherosclerosis. In multiple linear regression analysis, baseline DPP4 activity was an independent predictor of an increase in inflammatory markers, IGF-II/M6P receptor, and C-IMT over a 4-year period (all P < 0.01). In multivariable-adjusted models, the odds ratio (OR) for incident atherosclerosis comparing the highest with the lowest quartiles of DPP4 activity was 3.17 (95%CI 1.33-7.58) after adjustment for confounding risk factors (P = 0.009). The incidence of atherosclerosis owing to DPP4 activity increased by 12.41%.

CONCLUSIONS

DPP4 activity is an important predictor of the onset of inflammation and atherosclerosis in apparently healthy Chinese. This finding may have important implications for understanding the proinflammatory role of DPP-4 in the pathogenesis of atherosclerosis.

Insulin-like growth factor-II: its role in metabolic and endocrine disease

Insulin-like growth factor-II (IGF-II) is a widely expressed 7·5 kDa mitogenic peptide hormone. Although it is abundant in serum, understanding of its physiological role is limited compared with that of IGF-I. IGF-II regulates foetal development and differentiation, but its role in adults is less well understood. Evidence suggests roles in a number of tissues including skeletal muscle, adipose tissue, bone and ovary. Altered IGF-II expression has been observed in metabolic conditions, notably obesity, diabetes and the polycystic ovary syndrome. This article summarizes what is known about the actions of IGF-II and its dysregulation in metabolic and endocrine diseases. The possible causes and consequences of dysregulation are discussed along with the implications for diagnostic tests and future research.

Characterization of IGF-II isoforms in binge eating disorder and its group psychological treatment

Intro

Binge eating disorder (BED) affects 3.5% of the population and is characterized by binge eating for at least 2 days a week for 6 months. Treatment options include cognitive behavioral therapy, interpersonal psychotherapy, and pharmacotherapy which are associated with varied success.

Little is known about the biology of BED. Since there is evidence that the insulin like growth factor system is implicated in regulation of body weight, insulin sensitivity and feeding behavior, we speculated it may be involved in BED.

Methods

A cross-sectional comparison was made between three groups of women: overweight with BED, overweight without BED and normal weight without BED. Women were assigned to Group Psychodynamic Interpersonal Psychotherapy. Blood was collected before therapy, at completion and at 6months follow up for evaluation of IGF-II using Western blot.

Results

97 overweight women with BED contributed to the cross-sectional comparison. The two control groups comprised 53 overweight women without BED, and 50 age matched normal weight women without BED. Obese women had significantly lower Big IGF-II than normal weight women, p = .028; Overweight women with BED had higher Mature IGF-II than normal weight women, p<.05.

Big IGF-II showed a significant decreasing slope from pre- to post- to six months post-group psychological treatment, unrelated to changes in BMI (p = .008).

Conclusion

Levels of IGF-II isoforms differed significantly between overweight and normal weight women. Overweight women with BED display abnormal levels of circulating IGF-II isoforms. BED is characterized by elevated mature IGF-II, an isoform shown to carry significant bioactivity. This finding is not related to BMI or to changes in body weight. The results also provide preliminary evidence that BIG IGF-II is sensitive to change due to group psychological treatment. We suggest that abnormalities in IGF-II processing may be involved in the neurobiology of BED.

IGF2 and cancer

Insulin-like growth factor 2 (IGF2) is a 7.5  kDa mitogenic peptide hormone expressed by liver and many other tissues. It is three times more abundant in serum than IGF1, but our understanding of its physiological and pathological roles has lagged behind that of IGF1. Expression of the IGF2 gene is strictly regulated. Over-expression occurs in many cancers and is associated with a poor prognosis. Elevated serum IGF2 is also associated with increased risk of developing various cancers including colorectal, breast, prostate and lung. There is established clinical utility for IGF2 measurement in the diagnosis of non-islet cell tumour hypoglycaemia, a condition characterised by a molar IGF2:IGF1 ratio >10. Recent advances in understanding of the pathophysiology of IGF2 in cancer have suggested much novel clinical utility for its measurement. Measurement of IGF2 in blood and genetic and epigenetic tests of the IGF2 gene may help assess cancer risk and prognosis. Further studies will determine whether these tests enter clinical practice. New therapeutic approaches are being developed to target IGF2 action. This review provides a clinical perspective on IGF2 and an update on recent research findings.

The insulin receptor and the kidney

PURPOSE OF REVIEW

In recent years, it has become clear that the insulin receptor is important in a variety of renal cell types. It is through this transmembrane receptor that insulin, and to a lesser extent insulin-like growth factor, hormones bind and can control important cellular functions. This review will summarize the advances in our understanding of the role of the insulin receptor and insulin signalling in the glomeruli and tubules of the kidney.

RECENT FINDINGS

The insulin receptor is important for podocyte function and when lost results in a number of features resembling diabetic nephropathy. Exciting recent data also highlight the importance of mammalian target of rapamycin in nutrient sensing and protein biosynthesis in the podocyte, which may also be regulated by the insulin receptor. The insulin receptor has also been shown to perform an important role in the distal regions of the renal tubules, regulating sodium excretion and blood pressure control here.

SUMMARY

The insulin receptor is crucial for renal function in glomeruli and tubules. When signalling is diminished here, as may occur in insulin-resistant states, it may be responsible for a number of important renal complications including albuminuric glomerular disease and hypertension.

Insulin-like growth factor physiology: what we have learned from human studies

Although very similar to insulin and its receptor; the modus operandi of the insulin-like growth factors (IGFs) within the body is very different from that of the traditional peptide hormone. The IGF-binding proteins bind the IGFs with greater affinity than the cell surface receptors, enabling them to tightly control tissue activity. In addition to their role in fetal and childhood growth, IGFs play an important role in metabolic regulation. This article describes the basic underlying human physiology of IGFs, how this differs from that of experimental models, and why some information can only be learned from human clinical studies.

Targeting the insulin growth factor receptor 1

The IGF axis is a tightly controlled endocrine system that regulates cell growth and development, known to have an important function in cancer biology. IGF1 and IGF2 can promote cancer growth in a GH-independent manner both through paracrine and autocrine secretion and can also confer resistance to chemotherapy and radiation. Many alterations of this system have been found in neoplasias, including increased expression of ligands and receptors, loss of heterozygosity of the IGF2 locus and increased IGF1R gene copy number. The IGF1 network is an attractive candidate for targeted therapy, including receptor blockade with monoclonal antibodies and small molecule inhibitors of receptor downstream signaling. This article reviews the role of the IGF axis in the initiation and progression of cancer, and describes the recent advances in IGF inhibition as a therapeutic tool.