The role of insulin-like growth factor in Acrochordon Etiopathology.

BACKGROUND: There are reports that acrochordon (skin tag), the most common fibroepithelial tumor of the skin, may be associated with metabolic syndrome components, particularly insulin metabolism disorders. However, to the best of our knowledge, there is no study examining its association with insulin resistance and tissue levels of insulin-like growth factor 1 receptor (IGF-1R) and insulin-like growth factor 2 receptor (IGF-2R). METHODS: Thirty patients with at least one acrochordon in their body who had no known history of diabetes mellitus and a control group comprised 30 individuals who had no acrochordon or no known history of diabetes mellitus were included. The tissue expression of IGF-1R and IGF-2R were investigated via immunohistochemical assessment in both groups. RESULTS: In the group with acrochordon, IGF-1R and IGF-2R expression was found to be significantly higher compared to the control group (p < 0,01). Using logistic regression analysis, an increase in serum insulin, serum IGF-1 and HOMA-IR levels was found to be associated with the expression levels of IGF-1R and IGF-2R. CONCLUSION: These findings support the view that insulin metabolism disorders should be evaluated in patients with acrochordon. Our study indicates that IGF receptors may have an effect on acrochordon pathogenesis and that acrochordon etiology and related conditions can be clarified by detection of parameters that influence receptor levels.

Chronic prenatal ethanol exposure alters expression of central and peripheral insulin signaling molecules in adult guinea pig offspring.

Maternal ethanol consumption during pregnancy can produce a range of teratogenic outcomes in offspring. The mechanism of ethanol teratogenicity is multi-faceted, but may involve alterations in insulin and insulin-like growth factor (IGF) signaling pathways. These pathways are not only important for metabolism, but are also critically involved in neuronal survival and plasticity, and they can be altered by chronic prenatal ethanol exposure (CPEE). The objective of this study was to test the hypothesis that CPEE alters expression of insulin and IGF signaling molecules in the prefrontal cortex and liver of adult guinea pig offspring. Pregnant Dunkin-Hartley-strain guinea pigs received ethanol (4 g/kg maternal body weight/day) or isocaloric-sucrose/pair-feeding (nutritional control) throughout gestation. Fasting blood glucose concentration was measured in male and female offspring at postnatal day 150-200, followed by euthanasia, collection of prefrontal cortex and liver, and RNA extraction. IGF-1, IGF-1 receptor (IGF-1R), IGF-2, IGF-2 receptor (IGF-2R), insulin receptor substrate (IRS)-1, IRS-2, and insulin receptor (INSR) mRNA expression levels were measured in tissues using quantitative real-time PCR. The mean maternal blood ethanol concentration was 281 ± 15 mg/dL at 1 h after the second divided dose of ethanol on GD 57. CPEE resulted in increased liver weight in adult offspring, but produced no difference in fasting blood glucose concentration compared with nutritional control. In the liver, CPEE decreased mRNA expression of IGF-1, IGF-1R, and IGF-2, and increased IRS-2 mRNA expression in male offspring only compared with nutritional control. Female CPEE offspring had decreased INSR hepatic mRNA expression compared with male CPEE offspring. In the prefrontal cortex, IRS-2 mRNA expression was increased in CPEE offspring compared with nutritional control. The data demonstrate that CPEE alters both central and peripheral expression of insulin and IGF signaling molecules at the mRNA level, which may be related to metabolic dysregulation in adult offspring. Furthermore, altered insulin and IGF signaling may be a mechanism of ethanol neurobehavioral teratogenicity.

Development of IGF signaling antibody arrays for the identification of hepatocellular carcinoma biomarkers.

PURPOSE: Our objective was to develop a system to simultaneously and quantitatively measure the expression levels of the insulin-like growth factor (IGF) family proteins in numerous samples and to apply this approach to profile the IGF family proteins levels in cancer and adjacent tissues from patients with hepatocellular carcinoma (HCC). EXPERIMENTAL DESIGN: Antibodies against ten IGF family proteins (IGF-1, IGF-1R, IGF-2, IGF-2R, IGFBP-1, IGFBP-2, IGFBP-3, IGFBP-4, IGFBP-6, and Insulin) were immobilized on the surface of a glass slide in an array format to create an IGF signaling antibody array. Tissue lysates prepared from patient's liver cancer tissues and adjacent tissues were then applied to the arrays. The proteins captured by antibodies on the arrays were then incubated with a cocktail of biotinylated detection antibodies and visualized with a fluorescence detection system. By comparison with standard protein amount, the exact protein concentrations in the samples can be determined. The expression levels of the ten IGF family proteins in 25 pairs of HCC and adjacent tissues were quantitatively measured using this novel antibody array technology. The differential expression levels between cancer tissues and adjacent tissues were statistically analyzed. RESULTS: A novel IGF signaling antibody array was developed which allows the researcher to simultaneously detect ten proteins involved in IGF signal pathway with high sensitivity and specificity. Using this approach, we found that the levels of IGF-2R and IGFBP-2 in HCC tissues were higher than those in adjacent tissues. CONCLUSION: Our IGF signaling antibody array which can detect the expression of ten IGF family members with high sensitivity and specificity will undoubtedly prove a powerful tool for drug and biomarker discovery.

Aliskiren affects fatty-acid uptake and lipid-related genes in rodent and human cardiomyocytes.

PURPOSE: We investigated whether the direct renin inhibitor aliskiren can affect metabolism in cardiomyocytes from rat, mouse and human sources. METHODS AND RESULTS: At 10-50 µmol/L, aliskiren significantly increased medium-chain-fatty-acid uptake in primary-cultured neonatal-rat and HL-1 adult-mouse-derived cardiomyocytes (BODIPY-induced fluorescence intensity). The fatty-acid transporter CD-36 was correspondingly translocated to, but the glucose transporter Glut-4 away from, the sarcoplasmic reticulum/plasma membrane, in primary-cultured neonatal-rat (CD-36, Glut-4) and adult-human (CD-36) cardiomyocytes (confocal immunocytochemistry). Immunoblotting showed that aliskiren induced phosphorylation of ERK1/2 in cardiomyocytes from all three sources; responses were dose- and time-dependent, unaffected by renin treatment, and did not cause alterations in expression of (P)R or Igf2/M6P receptors. Microarray analysis of the complete genome of aliskiren-treated neonatal-rat cardiomyocytes, with RT-qPCR and immunoblot confirmation assays in rat and human primary cardiomyocytes, showed that aliskiren up-regulated mRNA and increased protein expression of several enzymes important in lipid and glucose metabolism and in cholesterol biosynthesis. Cardiomyocyte cell-cycle and viability were unaffected by aliskiren. CONCLUSIONS: Aliskiren can induce changes in fatty-acid and glucose uptake and expression of key enzymes of lipid and cholesterol metabolism, which are not associated with increased expression of (P)R or Igf2/M6P receptors, in cultured cardiomyocytes.

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

OBJECTIVE: The extracellular domain of the insulin-like growth factor II/mannose-6-phosphate receptor (IGF-II/M6P-R) is present in the circulation, but its relationship with plasma IGF-II is largely unknown. As IGF-II appears to be nutritionally regulated, we studied the impact of obesity, type 2 diabetes (T2D) and weight loss on circulating levels of IGF-II and its soluble receptor. METHODS: Twenty-three morbidly obese non-diabetic subjects were studied before and after gastric banding (GB), reducing their BMI from 59.3+/-1.8 to 52.7+/-1.6 kg/m(2). Lean controls (n=10, BMI 24.2+/-0.5 kg/m(2)), moderately obese controls (n=21, BMI 31.8+/-1.0 kg/m(2)) and obese T2D patients (n=20, BMI 32.3+/-0.8 kg/m(2)) were studied before and after a hyperinsulinaemic euglycaemic clamp. RESULTS: Morbidly obese subjects had elevated IGF-II/M6P-R and IGF-II levels, which both decreased following GB (IGF-II/M6P-R: from 0.97+/-0.038 to 0.87+/-0.030 nmol/l, P=0.001; IGF-II: from 134+/-7 to 125+/-6 nmol/l, P=0.01), as did fasting plasma glucose and insulin (P<0.05). However, the metabolic parameters correlated with neither IGF-II nor IGF-II/M6P-R. Obese diabetics had increased IGF-II/M6P-R as compared with lean and obese controls (0.82+/-0.031 vs. 0.70+/-0.033 vs. 0.74+/-0.026 nmol/l; P<0.03) and levels were unaffected by clamp. In the latter cohort, IGF-II/M6P-R but not IGF-II correlated with HbA1c, and fasting plasma C-peptide, insulin and glucose (0.34

Levels of insulin-like growth factors and their receptors in placenta in relation to macrosomia.

OBJECTIVE: To investigate the associations between mRNA levels that encodes for insulin-like growth factors (IGFS) and their receptors in term placenta, and the risk of macrosomia. METHODS: Term placentas were collected from 37 neonates with macrosomia and 37 neonates with normal birth weight in Changzhou Women and Children Health Hospital from March 1 to June 30, 2008. The IGF mRNA levels and their receptors in those placentas were measured by Real-time PCR. RESULTS: The placental weight was positively correlated with the birth weight both in the macrosomia group (r=0.550, p=0.004) and the control group (r=0.678, p=0.000). After adjusting for potential confounders, multivariable adjusted ORs of neonates with macrosomia for those in the increasing two tertiles were 17.3 (95%CI: 2.50-19.2) and 5.94 (95%CI: 0.96, 36.8), respectively, compared with those in the lowest tertile in terms of IGF-IImRNA level. Similarly, multivariable adjusted ORs of neonates with macrosomia for those in the increasing two tertiles of IGF-IR mRNA were 25.3 (95%CI: 3.43-187) and 43.0 (95%CI: 4.89, 378), respectively. CONCLUSION: These results indicate that the levels of placental IGF-IIand IGF-IR mRNA may be involved in the development of macrosomia.

The mannose 6-phosphate/insulin-like growth factor II receptor restricts the tumourigenicity and invasiveness of squamous cell carcinoma cells.

The mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) mediates biosynthetic sorting and endocytosis of various factors that impinge on the proliferation, migration and invasiveness of tumour cells. The gene encoding M6P/IGF2R is frequently lost or mutated in a wide range of malignant tumours including squamous cell carcinomas. We have previously shown that M6P/IGF2R-deficient SCC-VII murine squamous cell carcinoma cells secrete large amounts of pro-invasive lysosomal proteinases. Furthermore, the formation of mature lysosomes is impaired in SCC-VII cells. To assess the link between M6P/IGF2R status and tumour invasion, we have now generated SCC-VII lines stably transfected with human M6P/IGF2R cDNA. Reconstitution of functional M6P/IGF2R expression in SCC-VII cells strongly improves the intracellular retention of lysosomal proteinases and restores the formation of mature lysosomes. In addition, the presence of heterologous M6P/IGF2R compromises the growth of SCC-VII cells both in vitro and in vivo. Remarkably, M6P/IGF2R expression also reduces the invasive capacity of SCC-VII cells in response to various chemoattractants. These results indicate that the M6P/IGF2R status influences the metastatic propensity of squamous cell carcinomas.

Immunolocalization of insulin-like growth factors and their receptors in the diabetic mouse oviduct and uterine tissues during the preimplantation period.

The aim of the present study was to analyze the immunolocalization of insulin-like growth factor (IGF)-1 and IGF-2 and their receptors in the oviduct and uterus of control and diabetic mice. Sexually mature female ICR mice aged 6-8 weeks were rendered diabetic by streptozotocin (200 mg/kg, administered intraperitoneally). Oviductal and uterine tissues were obtained from the superovulated control and diabetic mice at 48, 72 and 96 h post-human chorionic gonadotropin (hCG) treatment. Localization of IGF-1, IGF-2, IGF-1R and IGF-2R was determined by immunohistochemistry and a semi-quantitative scoring of immunolabelling was performed using a standardized 5-point system. The immunohistochemical scorings for both IGF-1 and IGF-1R were significantly decreased in the oviducts of diabetic mice at 96 h post-hCG treatment. The scores for IGF-2 were significantly increased in the oviducts of diabetic mice at 48 and 72 h post-hCG treatment, and for IGF-2R at 72 h post-hCG treatment. However, there was no significant difference in the scores of IGFs and their receptors in the uterus of control and diabetic mice. In conclusion, the oviductal immunolabelling for IGFs and their receptors was significantly altered by maternal diabetes, which may be of importance in the pathogenesis of preimplantation diabetic embryopathy.

IGF-II/mannose-6-phosphate receptor signaling induced cell hypertrophy and atrial natriuretic peptide/BNP expression via Galphaq interaction and protein kinase C-alpha/CaMKII activation in H9c2 cardiomyoblast cells.

The role played by IGF-II in signal transduction through the IGF-II/mannose-6-phosphate receptor (IGF2R) in heart tissue has been poorly understood. In our previous studies, we detected an increased expression of IGF-II and IGF2R in cardiomyocytes that had undergone pathological hypertrophy. We hypothesized that after binding with IGF-II, IGF2R may trigger intracellular signaling cascades involved in the progression of pathologically cardiac hypertrophy. In this study, we used immunohistochemical analysis of the human cardiovascular tissue array to detect expression of IGF2R. In our study of H9c2 cardiomyoblast cell cultures, we used the rhodamine phalloidin staining to measure the cell hypertrophy and western blot to measure the expression of cardiac hypertrophy markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in cells treated with IGF-II. We found that a significant association between IGF2R overexpression and myocardial infarction. The treatment of H9c2 cardiomyoblast cells with IGF-II not only induced cell hypertrophy but also increased the protein level of ANP and BNP. Using Leu27IGF-II, an analog of IGF-II which interacts selectively with the IGF2R, to specifically activate IGF2R signaling cascades, we found that binding of Leu27IGF-II to IGF2R led to an increase in the phosphorylation of protein Kinase C (PKC)-alpha and calcium/calmodulin-dependent protein kinase II (CaMKII) in a Galphaq-dependent manner. By the inhibition of PKC-alpha/CaMKII activity, we found that IGF-II and Leu27IGF-II-induced cell hypertrophy and upregulation of ANP and BNP were significantly suppressed. Taken together, this study provides a new insight into the effects of the IGF2R and its downstream signaling in cardiac hypertrophy. The suppression of IGF2R signaling pathways may be a good strategy to prevent the progression of pathological hypertrophy.

Insulin-like growth factors 1 and 2 induce lymphangiogenesis in vivo.

Lymphangiogenesis is an important process that contributes to the spread of cancer. Here we show that insulin-like growth factors 1 (IGF-1) and 2 (IGF-2) induce lymphangiogenesis in vivo. In a mouse cornea assay, IGF-1 and IGF-2 induce lymphangiogenesis as detected with LYVE-1, a specific marker for lymphatic endothelium. Interestingly, IGF-1-induced lymphangiogenesis could not be blocked by a soluble vascular endothelial growth factor receptor 3, suggesting that the vascular endothelial growth factor receptor 3-signaling pathway is not required for IGF-induced lymphangiogenesis. In vitro, IGF-1 and IGF-2 significantly stimulated proliferation and migration of primary lymphatic endothelial cells. IGF-1 and IGF-2 induced phosphorylation of intracellular signaling components, such as Akt, Src, and extracellular signal-regulated kinase in lymphatic endothelial cells. Immunohistochemistry, RT-PCR, and Affymetrix GeneChip microarray analysis showed that the receptors for IGFs are present in lymphatic endothelium. Together, our findings suggest that IGFs might act as direct lymphangiogenic factors, although any indirect roles in the induction of lymphangiogenesis cannot be excluded. Because members of the IGF ligand and receptor families are widely expressed in various types of solid tumors, our findings suggest that these factors are likely to contribute to lymphatic metastasis.

Characterization of the TGN exit signal of the human mannose 6-phosphate uncovering enzyme.

The human mannose 6-phosphate uncovering enzyme participates in the uncovering of the mannose 6-phosphate recognition tag on lysosomal enzymes, a process that facilitates recognition of those enzymes by mannose 6-phosphate receptors to ensure delivery to lysosomes. Uncovering enzyme has been identified on the trans-Golgi network at steady state. It has been shown to traffic to the plasma membrane from where it is rapidly internalized via endosomal structures, the process being mediated by a tyrosine-based internalization motif, Y488HPL, in its cytoplasmic tail. Using immunogold electron microscopy a GFP-uncovering enzyme fusion construct was found to be colocalized with the cation-dependent mannose 6-phosphate receptor in regions of the trans-Golgi network, suggesting that uncovering enzyme might follow a similar pathway of exit from the trans-Golgi network as that of the cation-dependent mannose 6-phosphate receptor. In this study, we identified the signal sequence in the cytoplasmic tail of uncovering enzyme responsible for its exit from the trans-Golgi network. Using GFP fusion constructs of the transmembrane and cytoplasmic domains of uncovering enzyme, we could show, by automated analysis of confocal immunofluorescence images, that residues Q492EMN in the cytoplasmic tail of uncovering enzyme are involved in its exit from the trans-Golgi network. Detailed characterization of the exit signal revealed that residue Q492 is the most important to the exit function while M494 and N495 also contribute. The cytoplasmic tail of the uncovering enzyme does not possess any of the known canonical signal sequences for interaction with Golgi-associated gamma ear-containing adaptor proteins. The identification of a trans-Golgi network exit signal in its cytoplasmic tail elucidates the trafficking pathway of uncovering enzyme, a crucial player in the process of lysosomal biogenesis.

The cellular repressor of E1A-stimulated genes mediates glucocorticoid-induced loss of the type-2 IGF receptor in ileal epithelial cells.

Glucocorticoids induce hypertrophy of the neonatal ileal mucosa but the molecular mechanisms behind this growth induction remain poorly understood. Ileal epithelial cells (IECs) are dependent upon IGF-II for proliferation both in vivo and in culture. The type-2 IGF receptor (IGFR-2) is a lysosomal transport protein that attenuates IGF-II-driven growth and is highly abundant in the ileum. The cellular repressor of E1A-stimulated genes (CREG) is a secreted phosphoglycoprotein that affects cell fate via ligand binding with IGFR-2, although the mechanism by which it does so is unknown. We hypothesized that glucocorticoids might facilitate IGF-mediated hypertrophy through CREG-mediated degradation of IGFR-2. To test this hypothesis, confluent rat IECs (IEC-18) were cultured for 72 h with or without dexamethasone (DEX) and harvested for Western blot, immunocytochemistry, gene array and CREG immunoneutralization experiments. IGFR-2 and CREG immunohistochemistry were also performed in archived ileal specimens from control and DEX-exposed newborn mice and extremely premature infants to investigate in vivo and clinical relevance. DEX exposure was found to diminish IGFR-2 immunolocalization in cultured rat IECs, newborn mouse ileal mucosa and human neonatal ileal mucosa. Gene array data indicated that IGFR-2 expression was unchanged with DEX treatment, suggesting a mechanism of protein degradation. CREG immunolocalization and abundance was found to be increased by DEX and immunoneutralization of CREG resulted in the abolition of IGFR-2 degradation. We have concluded that CREG is a secreted mediator by which DEX induces degradation of IGFR-2 and speculate that this is a fundamental mechanism of mucosal growth induction.

Effects of diet consistency on the expression of insulin-like growth factors (IGFs), IGF receptors and IGF binding proteins during the development of rat masseter muscle soon after weaning.

A soft diet facilitates the development of faster-type fibres in rat masseter muscle in the 9 days after weaning compared with a hard diet. To determine whether insulin-like growth factors (IGFs), IGF receptors (IGFRs) and IGF binding proteins (IGFBPs) are involved in this fibre-type alteration, the expression of myosin heavy chain (MHC), IGF, IGFR and IGFBP mRNAs in the masseter muscle of rats fed a hard or soft diet for 9 days after weaning was analysed using competitive, reverse transcriptase-polymerase chain reaction. A soft diet decreased the expression of MHC IIa (slower type) by 70%, but increased the expression of MHC IIx (intermediate type) and IIb (faster type) by 80 and 582%, respectively, compared with a hard diet. These findings verified that a soft diet facilitates the development of faster-type fibres in rat masseter muscle compared with a hard diet. A soft diet induced reductions of 25-76% (P < 0.05-0.01) in the expression of IGF-I, IGF-II, IGFR2, IGFBP4 and IGFBP6 compared with a hard diet, but induced a 25% (P < 0.05) increase only in expression of IGFBP3. These findings suggest that the changes in expression of IGF-I, IGF-II, IGFR2, IGFBP3, IGFBP4 and IGFBP6 are associated with the fibre-type alteration of rat masseter muscle in response to diet consistency soon after weaning.

Expression of insulin-like growth factors (IGF)-1 and -2, IGF-binding proteins-2 and -3, and receptors for growth hormone, IGF type-1 and -2 and insulin in the gastrointestinal tract of neonatal calves.

Growth hormone (GH), insulin-like growth factors (IGFs) and insulin influence post-natal gastrointestinal development and function. We have measured by real-time PCR the mRNA levels of IGF-1 and -2, IGF-binding proteins (IGFBPs)-2 and -3, and receptors for GH, IGF type-1 and -2, and insulin in esophagus, rumen, fundus, pylorus, duodenum, jejunum, ileum and colon of calves on days 1 and 5 of life. Levels of mRNA of measured traits were different (P < 0.05) at different gastrointestinal sites. Furthermore, mRNA levels of IGFs, IGFBPs and of receptors for GH and IGF type-1 and -2 and insulin differed (P < 0.05) on days 1 and 5. Differences in mRNA abundance of IGFs, IGFBPs and of receptors for GH, IGFs, and insulin among gastrointestinal sites on days 1 and 5 of life suggest site-specific functional importance and demonstrate that changes are the consequence of ontogenetic development and/or due to feeding.

Gastric cancer: the role of insulin-like growth factor 2 (IGF 2) and its receptors (IGF 1R and M6-P/IGF 2R).

Insulin-like growth factor 2 (IGF 2) appears to be involved in the progression of many tumours. It binds to at least two different types of receptor: IGF type 1 (IGF 1R) and mannose 6-phosphate/IGF type 2 (M6-P/IGF 2R). Ligand binding to IGF 1R provokes mitogenic and anti-apoptotic effects. M6-P/IGF 2R has a tumour suppressor function--it mediates IGF 2 degradation. Mutation of M6-P/IGF 2R causes both diminished growth suppression and augmented growth stimulation. The aim of this study was to investigate the role of IGF 2 and its receptors (IGF 1R and IGF 2R) in human gastric cancer. The expression of IGF 2 and its receptors was measured in order to analyse the possible correlation between the activity of these genes and cell proliferation in two different gastric tumour types: diffuse and intestinal. The effect of IGF 1 receptor blockage on cell proliferation and anchorage-independent cell growth was also examined. Increased expression of IGF 2 and IGF 1R genes (at the mRNA and protein level) was found in gastric cancer when compared with non-tumour tissue. Furthermore, there was a significant difference between IGF 2 expression in the more aggressive diffuse type and that in the intestinal type of gastric cancer. Moreover, the IGF 2 peptide level in the culture media obtained from the diffuse type of cancer cells was significantly higher when compared with the intestinal type. The level of IGF 2 peptide in the conditioned media strongly correlated with [3H]thymidine incorporation and cell proliferation. On the contrary, IGF 2R mRNA expression was much higher in the intestinal type of cancer than in the diffuse type. In addition, IGF 2R protein expression was substantially lower with progression of the diffuse cancer type to a higher stage. The alphaIR3 monoclonal antibody strongly inhibited [3H]thymidine incorporation and decreased the number of colonies in soft agar of cells overexpressing IGF 2. These findings suggest that members of the IGF family are involved in the pathogenesis of gastric cancer, probably by autocrine/paracrine stimulation of cell growth. Such tumours might be excellent candidates for therapeutic strategies aimed at interference with this pathway.

Abundance of message for insulin-like growth factors-I and -II and for receptors for growth hormone, insulin-like growth factors-I and -II, and insulin in the intestine and liver of pre- and full-term calves.

The somatotropic axis and insulin are involved in pre- and postnatal development. In pre- and full-term calves (GrP0 and GrN0; born after 277 and 290 d of pregnancy, respectively) and in preterm calves on d 8 of life after being fed for 7 d (GrP8), we studied whether there are differences in the abundance of messenger RNA (mRNA) of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin among different intestinal sites (duodenum, jejunum, ileum, and colon) and whether there are ontogenetic differences during the perinatal period in intestine and liver. Intestinal site differences (P < 0.05) existed in mRNA levels of IGF-I and IGF-II and receptors for GH, IGF-I, IGF-II, and insulin. Abundance of mRNA of IGF-I and -II and of receptors for IGF-I and GH was highest (P < 0.05) in the colon, abundance of the receptor for IGF-II was comparably high in the colon and ileum, and that of the receptor for insulin was similarly high in colon, ileum, and jejunum. Among GrP0, GrN0, and GrP8 groups, there were differences (P < 0.05) in mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin. Abundance of mRNA of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II and insulin was highest (P < 0.05) in GrP0 calves immediately after birth and was primarily seen in the ileum. In liver, the mRNA levels differed (P < 0.05) among groups for IGF-II and receptors for IGF-I, IGF-II, and insulin, and were highest (P < 0.05) for IGF-II in GrP0, for receptors of IGF-I in GrN0, and were higher (P < 0.05) in GrP0 than GrP8 for receptors of IGF-II. In conclusion, mRNA levels of IGF-I and IGF-II and of receptors for GH, IGF-I, IGF-II, and insulin were different at different intestinal sites and in intestine and liver and changed during the perinatal period.

Distribution and trafficking of MPR300 is normal in cells with cholesterol accumulated in late endocytic compartments: evidence for early endosome-to-TGN trafficking of MPR300.

It has been reported that an accumulation of cholesterol within late endosomes/lysosomes in Niemann-Pick type C (NPC) fibroblasts and U18666A-treated cells causes impairment of retrograde trafficking of the cation-independent mannose 6-phosphate/IGF-II receptor (MPR300) from late endosomes to the trans-Golgi network (TGN). In apparent conflict with these results, here we show that as in normal fibroblasts, MPR300 localizes exclusively to the TGN in NPC fibroblasts as well as in normal fibroblasts treated with U18666A. This localization can explain why several lysosomal properties and functions, such as intracellular lysosomal enzyme activity and localization, the biosynthesis of cathepsin D, and protein degradation, are all normal in NPC fibroblasts. These results, therefore, suggest that the accumulation of cholesterol in late endosomes/lysosomes does not affect the retrieval of MPR300 from endosomes to the TGN. Furthermore, treatment of normal and NPC fibroblasts with chloroquine, which inhibits membrane traffic from early endosomes to the TGN, resulted in a redistribution of MPR300 to EEA1 and internalized transferrin-positive, but LAMP-2-negative, early-recycling endosomes. We propose that in normal and NPC fibroblasts, MPR300 is exclusively targeted from the TGN to early endosomes, from where it rapidly recycles back to the TGN without being delivered to late endosomes. This notion provides important insights into the definition of late endosomes, as well as the biogenesis of lysosomes.

Insulin-like growth factor-II/mannose-6-phosphate receptor: widespread distribution in neurons of the central nervous system including those expressing cholinergic phenotype.

The insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor is single transmembrane glycoprotein that plays a critical role in the trafficking of lysosomal enzymes and the internalization of circulating IGF-II. At present, there is little information regarding the cellular distribution of the IGF-II/M6P receptor within the adult rat brain. With the use of immunoblotting and immunocytochemical methods, we found that the IGF-II/M6P receptor is widely but selectively expressed in all major brain areas, including the olfactory bulb, striatum, cortex, hippocampus, thalamus, hypothalamus, cerebellum, brainstem, and spinal cord. Intense IGF-II/M6P receptor immunoreactivity was apparent on neuronal cell bodies within the striatum, deeper layers (layers IV and V) of the cortex, pyramidal and granule cell layers of the hippocampal formation, selected thalamic nuclei, Purkinje cells of the cerebellum, pontine nucleus and motoneurons of the brainstem as well as in the spinal cord. Moderate neuronal labeling was evident in the olfactory bulb, basal forebrain areas, hypothalamus, superior colliculus, midbrain areas, granule cells of the cerebellum and in the intermediate regions of the spinal gray matter. We also observed dense neuropil labeling in many regions, suggesting that this receptor is localized in dendrites and/or axon terminals. Double-labeling studies further indicated that a subset of IGF-II/M6P receptor colocalizes with cholinergic cell bodies and fibers in the septum, striatum, diagonal band complex, nucleus basalis, cortex, hippocampus, and motoneurons of the brainstem and spinal cord. The observed widespread distribution and colocalization of IGF-II/M6P receptor in the adult rat brain provide an anatomic basis to suggest a multifunctional role for the receptor in a wide-spectrum of central nervous system neurons, including those expressing a cholinergic phenotype.

M6P/IGF2R tumor suppressor gene mutated in hepatocellular carcinomas in Japan.

Mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) tumor suppressor- gene mutation is an early event in human hepatocellular carcinoma (HCC) formation in the United States, but its role in hepatocarcinogenesis in Japan is unclear. We therefore determined M6P/IGF2R mutation frequency in HCCs from patients who resided in the southern, central, and northern regions of Japan. Ten single nucleotide polymorphisms were used to identify HCCs and dysplastic liver nodules with M6P/IGF2R loss of heterozygosity. The retained allele in these tumors was also assessed for point mutations and deletions in the M6P/IGF2R ligand binding domains by direct sequencing of polymerase chain reaction (PCR) amplified DNA products. Fifty-eight percent (54 of 93) of the patients were heterozygous at the M6P/IGF2R locus, and 67% (43 of 64) of the HCCs and 75% (3 of 4) of the dysplastic nodules had loss of heterozygosity. The remaining allele in 21% of the HCCs contained either M6P/IGF2R missense mutations or deletions, whereas such mutations were not found in the dysplastic lesions. In conclusion, M6P/IGF2R is mutated in HCCs from throughout Japan with a frequency similar to that in the United States. Loss of heterozygosity in dysplastic liver nodules provides additional evidence that M6P/IGF2R haploid insufficiency is an early event in human hepatocarcinogenesis.

Feeding different amounts of colostrum or only milk replacer modify receptors of intestinal insulin-like growth factors and insulin in neonatal calves.

Colostrum intake influences growth and development of the gastrointestinal tract (GIT) in several species and colostral insulin-like growth factors I and II (IGF-I and IGF-II), and insulin are involved in neonatal intestinal tissue growth. We have studied IGF type 1, IGF type 2, and insulin receptors in the intestine of 8-day-old calves fed different amounts of colostrum or only milk replacer. Calves were fed colostrum of the first six milkings on the first 3 days and then milk replacer (GrC(6)) or colostrum only once and then milk replacer (GrC(1)) or they were fed only milk replacer from the beginning, i.e., no colostrum (GrM). Competitive binding studies and ligand blots confirmed the presence of IGF type 1, IGF type 2, and insulin receptors in mucosal cell membranes of duodenum, jejunum, ileum, and colon. The IGF type 1 receptor number in ileum and total intestine in GrC(6) was greater (P<0.05) than in GrC(1) and in GrM, and IGF type 2 receptor number in total intestine was greater (P<0.05) in GrC(6) than in GrM. Insulin binding was best fitted by a model with two binding sites. High affinity insulin receptor numbers in duodenum, ileum, and total intestine were greater (P<0.05) in GrC(6) than in GrM. The data demonstrate that IGF type 1, IGF type 2, and insulin receptors in intestinal mucosa of neonatal calves are influenced by feeding.