Insulin-like growth factor I, growth hormone and insulin in white adipose tissue

IGF-1 and its receptor in esophageal cancer: association with adenocarcinoma and visceral obesity

OBJECTIVES

The insulin-like growth factor (IGF) pathway and visceral obesity have been independently linked with esophageal cancer. This study aimed to delineate the differential and interlinked role of visceral obesity and the IGF-1 system in esophageal adenocarcinoma and esophageal squamous-cell carcinoma (SCC).

METHODS

IGF-1 receptor (IGF-1R) mRNA and protein were examined in esophageal SCC (KYSE 410, OE21) and esophageal adenocarcinoma (OE19, OE33) cell lines by western blotting. Tumor cell proliferation in response to IGF-1 was assessed by bromodeoxyuridine incorporation assay. In esophageal tumor sections, expression of IGF-1R and CD68(+) cell numbers were assessed by immunohistochemistry. IGF-1 was measured in serum from esophageal cancer patients, Barrett's esophagus patients, and healthy controls by enzyme-linked immunosorbent assay.

RESULTS

Higher IGF-1R protein expressions were observed in SCC cells compared with esophageal adenocarcinoma cells however only adenocarcinoma cell lines significantly increased proliferation in response to IGF-1 (P<0.01). Serum IGF-1 levels were highest in esophageal adenocarcinoma patients (P<0.01) and higher in viscerally obese vs. nonobese (P<0.05) patients. In resected esophageal cancer, increased expression of IGF-1R was observed in the tumor and invasive edge compared with tumor-associated stroma (P<0.05), which coincided with increased CD68(+) cells in stromal tissue surrounding invasive tumor edge (P<0.01).

CONCLUSIONS

This novel study examined the differential role of the IGF system in esophageal adenocarcinoma and SCC, and its association with visceral obesity. These results indicate that the IGF-1 axis has a key role in malignant progression of esophageal cancer, and represents a plausible mechanism through which visceral obesity impacts on esophageal adenocarcinoma risk and tumor biology.

Necdin-E2F4 interaction provides insulin-sensitizing effect after weight loss induced by gastric bypass surgery

BACKGROUND

The insulin-like growth factor-1 (IGF-1) signaling pathway promotes adipocyte differentiation and, therefore, insulin sensitivity by suppression of necdin expression, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4 in mouse adipocytes. The aim of the present study was to test the hypothesis that this pathway represents one of the mechanisms by which Roux-en-Y gastric bypass surgery (RYGB) induces resolution of insulin resistance.

METHODS

Clinical samples were collected and the key biomarkers measured to test the hypothesis that the IGF-1 pathway represents 1 of the mechanisms by which RYGB induces resolution of insulin resistance in obese individuals.

RESULTS

Free IGF-1 levels were significantly greater in the post-RYGB patients than in the pre-RYGB obese patients (2.55 ± 1.54 versus 1.32 ± .65 μg/L, P = .03) and similar to that in normal weight controls (2.54 ± 1.27 μg/L). Necdin and E2F4 gene expression in the adipose tissue was significantly downregulated after RYGB compared with obese and were similar to the levels observed in the controls. In mature human adipocytes cultured in vitro, treatment with des-IGF-1 induced downregulation of necdin and E2F4 gene expression in a dose-dependent manner (P = .01).

CONCLUSION

After RYGB, the insulin/IGF-1 signaling pathway is activated and could account for the observed decrease in the expression of necdin, which represses peroxisome proliferator-activated receptor-gamma promoter activity by interaction with E2F4. This could represent one of the mechanisms that induce resolution of insulin resistance after RYGB.

Body composition and hormonal effects following exposure to mycotoxin deoxynivalenol in the high-fat diet-induced obese mouse

SCOPE

To characterize the effects of ingesting the common foodborne mycotoxin deoxynivalenol (DON) on body weight and composition in the high-fat (HF) diet-induced obese mice, a model of human obesity.

METHODS AND RESULTS

Female B6C3F1 mice were initially fed HF diets containing 45% kcal (HF45) or 60% kcal (HF60) as fat for 94 days to induce obesity. Half of each group was either continued on unamended HF diets or fed HF diets containing 10 mg/kg DON (DON-HF45 or DON-HF60) for another 54 days. Additional control mice were fed a low-fat (LF) diet containing 10%  kcal as fat for the entire 148-day period. DON induced rapid decreases in body weights and fat mass, which stabilized to those of the LF control within 11 days. These effects corresponded closely to a robust transient decrease in food consumption. While lean body mass did not decline in DON-fed groups, further increases were suppressed. DON exposure reduced plasma insulin, leptin, insulin-like growth factor 1, and insulin-like growth factor acid labile subunit as well as increased hypothalamic mRNA level of the orexigenic agouti-related protein.

CONCLUSION

DON-mediated effects on body weight, fat mass, food intake, and hormonal levels in obese mice were consistent with a state of chronic energy restriction.

Interleukin 1 receptor antagonist is associated with changes in body composition during physiological GH substitution in patients with adult-onset growth hormone deficiency

OBJECTIVE

We examined the effect of GH substitution on adipose tissue-derived hormones and cytokines and sought to identify predictors for changes in body composition during therapy. Long-standing adult-onset GH deficiency (AO-GHD) is associated with increased body fat mass (FM) which, through production of hormones and inflammatory cytokines from adipose tissue, may contribute to different manifestations of the metabolic syndrome.

DESIGN, PATIENTS AND MEASUREMENTS

Fifty-five patients with AO-GHD (24 women, 31 men, mean age 49 years) were enrolled in a placebo-controlled, double-blind crossover study. GH therapy was individually dosed to obtain an IGF-I concentration within the normal range for age and sex. GH and placebo were administered for 9 months each, separated by a 4-month washout period. Adipose tissue-derived cytokines were measured by enzyme immunoassay.

RESULTS

GH treatment was associated with a significant decrease in IL-1 receptor antagonist (IL-1Ra) compared to placebo, which correlated with declining body FM (truncal and total) after GH substitution. The change in IL-1Ra was the strongest predictor of the variation in BFM in regression models. No changes were observed for leptin, adiponectin, soluble TNF receptor 1 or interleukin (IL)-8.

CONCLUSION

The data indicate a possible unrecognized association between IL-1Ra and changes in body composition during GH substitution and suggest further research on the interaction between the GH-IGF axis and the IL-1 system.

Erythropoietin improves the survival of fat tissue after its transplantation in nude mice

Background

Autologous transplanted fat has a high resorption rate, providing a clinical challenge for the means to reduce it. Erythropoietin (EPO) has non-hematopoietic targets, and we hypothesized that EPO may improve long-term fat graft survival because it has both pro-angiogenic and anti-apoptotic properties. We aimed to determine the effect of EPO on the survival of human fat tissue after its transplantation in nude mice.

Methodology/Principal Findings

Human fat tissue was injected subcutaneously into immunologically-compromised nude mice, and the grafts were then treated with either 20 IU or 100 IU EPO. At the end of the 15-week study period, the extent of angiogenesis, apoptosis, and histology were assessed in the fat grafts. The results were compared to vascular endothelial growth factor (VEGF)-treated and phosphate-buffered saline (PBS)-treated fat grafts. The weight and volume of the EPO-treated grafts were higher than those of the PBS-treated grafts, whose weights and volumes were not different from those of the VEGF-treated grafts. EPO treatment also increased the expression of angiogenic factors and microvascular density, and reduced inflammation and apoptosis in a dose-dependent manner in the fat grafts.

Conclusions/Significance

Our data suggest that stimulation of angiogenesis by a cluster of angiogenic factors and decreased fat cell apoptosis account for potential mechanisms that underlie the improved long-term survival of fat transplants following EPO treatment.

Flow-regulated glucose and lipid metabolism in adipose tissue, endothelial cell and hepatocyte cultures in a modular bioreactor

Static cell culture has serious limitations in its ability to represent cellular behaviour within a live organism. In vivo, cells are constantly exposed to the flow of bodily fluids and contact with other cell types. Bioreactors provide the opportunity to study cells in an environment that more closely resembles the in vivo setting because cell cultures can be exposed to dynamic flow in contact with or in proximity to other cell types. In this study we compared the metabolic profile of a dynamic cell culture system to that of a static cell culture in three different cellular phenotypes: adipocytes, endothelial cells and hepatocytes. Albumin, glucose, free fatty acids, glycerol, and lactate were measured over 48 h. We show that all three cell types have increased glucose uptake in the presence of flow; lactate release was also significantly affected. We provide robust evidence that the presence of flow significantly modifies cellular metabolism. While flow provides a more uniform nutrient distribution and increases metabolite turnover, our results indicate that different cell types have specific metabolic responses to flow, suggesting cell-specific flow-regulated activation of metabolite signalling pathways.

Long-term IGF-I exposure decreases autophagy and cell viability

A reduction in IGF-I signaling has been found to increase lifespan in multiple organisms despite the fact that IGF-I is a trophic factor for many cell types and has been found to have protective effects against multiple forms of damage in acute settings. The increase in longevity seen in response to reduced IGF-I signaling suggests that there may be differences between the acute and chronic impact of IGF-I signaling. We have examined the possibility that long-term stimulation with IGF-I may have a negative impact at the cellular level using quiescent human fibroblasts. We find that fibroblast cells exposed to IGF-I for 14 days have reduced long-term viability as judged by colony forming assays, which is accompanied by an accumulation of senescent cells. In addition we observe an accumulation of cells with depolarized mitochondria and a reduction in autophagy in the long-term IGF-I treated cultures. An examination of mice with reduced IGF-I levels reveals evidence of enhanced autophagy and fibroblast cells derived from these mice have a larger mitochondrial mass relative to controls indicating that changes in mitochondrial turnover occurs in animals with reduced IGF-I. The results indicate that chronic IGF-I stimulation leads to mitochondrial dysfunction and reduced cell viability.

Regulation of human adipose-derived stromal cell osteogenic differentiation by insulin-like growth factor-1 and platelet-derived growth factor-alpha

BACKGROUND

Human adipose-derived stromal cells possess a great potential for tissue engineering purposes. The authors' laboratory is interested in harnessing human adipose-derived stromal cells for skeletal tissue regeneration and identifying those factors that enhance human adipose-derived stromal cell osteogenic differentiation. The authors hypothesized that insulin-like growth factor (IGF) and platelet-derived growth factor (PDGF) would stimulate human adipose-derived stromal cell osteogenesis and that IGF would stimulate adipogenesis.

METHODS

Adipose-derived stromal cells were harvested from human lipoaspirate. Previously, a microarray analysis examined gene expression throughout osteogenic differentiation. In a candidate fashion, the authors added recombinant IGF-1 and PDGF-alpha individually and in combination. Osteogenesis and adipogenesis were assessed by alkaline phosphatase, alizarin red, and oil red O staining, and quantitative real-time polymerase chain reaction (RUNX2, ALP, OCN, IGF1, PPARG, LPL, AP2, and GCP1). Finally, intersection between IGF and PDGF signaling pathways was evaluated.

RESULTS

IGF-1 was observed to increase osteogenic differentiation by all markers (p < 0.01). However, PDGF-alpha when added alone primarily did not affect osteogenic markers. PDGF-alpha positively regulated transcription of IGF1. Addition of PDGF-alpha in combination with or before IGF-1 enhanced osteogenesis more than either alone. IGF-1 increased whereas PDGF-alpha diminished human adipose-derived stromal cell adipogenesis.

CONCLUSIONS

IGF signaling significantly increased osteogenesis in human adipose-derived stromal cells and may be used for tissue-engineering purposes. The combination of PDGF and IGF may be more beneficial than either alone in driving adipose-derived stromal cell osteogenesis. Future in vivo applications will focus on the combination of adipose-derived stromal cells, biomimetic scaffolds, and recombinant IGF.

Insulin and insulin-like growth factor I signaling pathways in rainbow trout (Oncorhynchus mykiss) during adipogenesis and their implication in glucose uptake

Primary cultures of rainbow trout ( Oncorhynchus mykiss ) adipocytes were used to examine the main signaling pathways of insulin and insulin-like growth factor I (IGF-I) during adipogenesis. We first determined the presence of IGF-I receptors (IGF-IR) and insulin receptors (IR) in trout preadipocytes ( day 5) and adipocytes ( day 14). IGF-IRs were more abundant and appeared to be in higher levels in differentiated cells than in preadipocytes, whereas IRs were detected in lower but constant levels throughout the culture. The cells were immunoreactive against ERK1/2 MAPK, and AKT/PI3K, components of the two main signal transduction pathways for insulin and IGF-I receptors. Stimulation of MAPK phosphorylation by IGF-I was higher in preadipocytes than in adipocytes, while no effects were observed in MAPK phosphorylation after incubation of cells with insulin. AKT phosphorylation increased in the presence of both insulin and IGF-I, with higher levels of stimulation in adipocytes than in preadipocytes. Activation of both pathways was blocked by the use of specific inhibitors of MAPK (PD98059) and AKT (wortmannin). We describe here, for the first time, the effects of IGF-I and insulin on 2-deoxyglucose uptake in primary culture of trout adipocytes. IGF-I was more potent in stimulating glucose uptake than insulin, and PD98059 and wortmannin inhibited the stimulation of glucose uptake by this growth factor, suggesting that IGF-I plays an important metabolic role in trout adipocytes. Our results suggest that differential activation of the MAPK and AKT pathways are involved in the IGF-I- and insulin-induced effects of trout adipocytes during the various stages of adipogenesis.

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<r<0.45; P<0.05). In all subjects, BMI correlated with IGF-II/M6P-R (r=0.57; P<0.001) and IGF-II (r=0.39; P<0.005). IGF-II/M6P-R and IGF-II were not associated.

CONCLUSION

Serum IGF-II/M6P-R is up-regulated in morbid obesity, down-regulated by weight loss and elevated in moderately obese T2D. However, although plasma IGF-II was also reduced following GB, the two peptides were not statistically correlated. No acute effect of insulin was seen. These findings indicate that the IGF-II/M6P-R is nutritionally regulated, independently of IGF-II.

Pleiotropic role of IGF-I in obesity hypoventilation syndrome

CONTEXT

Obesity hypoventilation syndrome (OHS) is defined by the association between obesity and daytime arterial hypercapnia. The syndrome includes in variable proportion impaired diaphragmatic weakness, decreased central ventilatory drive and nearly systematically occurrence of sleep apnea. An increased cardio-vascular risk has been demonstrated compared to normocapnic obesity. IGF-I has a pleiotropic role in metabolism, ventilatory control, muscle function and cardiovascular protection.

OBJECTIVES AND DESIGN

We performed a case control study comparing somatotropic axis changes including IGF-I in obese with or without OHS.

METHODS

Patients underwent respiratory function tests, CO(2) ventilatory responses, polysomnography and somatotropic axis exploration (GH, IGF-I and IGFBP-3).

RESULTS

15 OHS (BMI: 41+/-5.6 kg/m(2), PaCO(2): 6.13+/-0.39 kPa, age: 55.6+/-5.9 years) and 15 matched obese without hypercapnia (BMI: 42+/-6.7 kg/m(2), PaCO(2): 5.13+/-0.27 kPa, age: 55.0+/-7.5 years) were compared. IGF-I and IGFBP-3 were significantly lowered in OHS, and negatively correlated with PaCO(2) (r=-0.615; P<0.001 and r=-0.452; P=0.016, respectively). Inspiratory capacity and forced vital capacity reflecting respiratory muscle strength decreased significantly with IGF-I (r=0.408; P=0.038). Triglycerides levels were higher in OHS (1.64+/-0.58 versus 1.13+/-0.56 g/L; P<0.01), and negatively associated with IGF-I (r=-0.418; P=0.027).

CONCLUSION

A low IGF-I level is associated with hypercapnia presumably by reducing ventilatory drive and favouring muscle weakness. The relationship between increased triglycerides and low IGF-I may represent one of mechanisms involved in the OHS increased cardio-vascular risk.

Establishment of a mammary stromal fibroblastic cell line for in vitro studies in mice of mammary adipocyte differentiation

Mammary stromal adipose tissue remodeling is important for appropriate mammary gland development during pregnancy, lactation, and involution. However, the precise mechanisms underlying mammary stromal adipose tissue remodeling remain unclear. We have established a mammary stromal, fibroblastlike cell line (MSF) from primary mouse mammary culture by introducing a temperature-sensitive simian virus-40 large tumor antigen. Among several hormones related to mammary gland development, hydrocortisone was found to commit MSF cells to a preadipocyte lineage, whereas insulin was found to induce extracellular matrix-dependent adipogenic differentiation of the cells, as assessed by lipid accumulation and marker gene expression. Interestingly, such hormone-induced adipogenic differentiation of MSF cells, but not 3T3-L1 cells, was suppressed by prolactin through its receptor and downstream STAT5. Furthermore, coculture of MSF cells with mammary epithelial HC11 cells and culture in HC11-conditioned medium also suppressed adipogenic differentiation of MSF cells. We have demonstrated that adipogenic differentiation of at least some populations of mammary stromal cells is modulated by lactogenic hormones and humoral factors from epithelial cells, suggesting that the response of these mammary cells may differ from adipocytes at other sites. We believe that the MSF cell line will prove a useful model to elucidate mammary stromal adipose development in vitro as well as represent an important first step toward developing stable adipocyte cell lines that faithfully represent their site of origin.

Anthropometry, carbohydrate and lipid metabolism in the East Flanders Prospective Twin Survey: linkage of candidate genes using two sib-pair based variance components analyses

Insulin resistance and obesity are underlying causes of type 2 diabetes and therefore much interest is focused on the potential genes involved. A series of anthropometric and metabolic characteristic were measured in 240 MZ and 112 DZ twin pairs recruited from the East Flanders Prospective Twin Survey. Microsatellite markers located close to ABCC8, ADIPOQ, GCK, IGF1, IGFBP1, INSR, LEP, LEPR, PPARgamma and the RETN gene were genotyped. Univariate single point variance components linkage analyses were performed using two methods: (1) the standard method, only comprising the phenotypic and genotypic data of the DZ twin pairs and (2) the extended method, also incorporating the phenotypic data of the MZ twin pairs. Suggestive linkages (LOD > 1) were observed between the ABCC8 marker and waist-to-hip ratio and HDL-cholesterol levels. Both markers flanking ADIPOQ showed suggestive linkage with triglycerides levels, the upstream marker also with body mass and HDL-cholesterol levels. The IGFBP1 marker showed suggestive linkage with fat mass, fasting insulin and leptin levels and the LEP marker showed suggestive linkage with birth weight. This study suggests that DNA variants in ABCC8, ADIPOQ, IGFBP1 and LEP gene region may predispose to type 2 diabetes. In addition, the two methods used to perform linkage analyses yielded similar results. This was however not the case for birth weight where chorionicity seems to be an important confounder.

The mixed-lineage kinase DLK is a key regulator of 3T3-L1 adipocyte differentiation

BACKGROUND

The mixed-lineage kinase (MLK) family member DLK has been proposed to serve as a regulator of differentiation in various cell types; however, its role in adipogenesis has not been investigated. In this study, we used the 3T3-L1 preadipocyte cell line as a model to examine the function of DLK in adipocyte differentiation.

METHODS AND FINDINGS

Immunoblot analyses and kinase assays performed on 3T3-L1 cells showed that the expression and activity of DLK substantially increase as differentiation occurs. Interestingly, DLK appears crucial for differentiation since its depletion by RNA interference impairs lipid accumulation as well as expression of the master regulators of adipogenesis C/EBPalpha and PPARgamma2 at both the mRNA and protein levels. In contrast, neither the expression nor the DNA binding activity of C/EBPbeta, an activator for C/EBPalpha and PPARgamma, is affected by DLK loss.

CONCLUSIONS

Taken together, these results suggest that DLK is important for expression of mature adipocyte markers and that its action most likely takes place via regulation of C/EBPbeta transcriptional activity and/or initiation of C/EBPalpha and PPARgamma2 gene transcription.

Milk--the promoter of chronic Western diseases

Common chronic diseases of Western societies, such as coronary heart disease, diabetes mellitus, cancer, hypertension, obesity, dementia, and allergic diseases are significantly influenced by dietary habits. Cow's milk and dairy products are nutritional staples in most Western societies. Milk and dairy product consumption is recommended by most nutritional societies because of their beneficial effects for calcium uptake and bone mineralization and as a source of valuable protein. However, the adverse long-term effects of milk and milk protein consumption on human health have been neglected. A hypothesis is presented, showing for the first time that milk protein consumption is an essential adverse environmental factor promoting most chronic diseases of Western societies. Milk protein consumption induces postprandial hyperinsulinaemia and shifts the growth hormone/insulin-like growth factor-1 (IGF-1) axis to permanently increased IGF-1 serum levels. Insulin/IGF-1 signalling is involved in the regulation of fetal growth, T-cell maturation in the thymus, linear growth, pathogenesis of acne, atherosclerosis, diabetes mellitus, obesity, cancer and neurodegenerative diseases, thus affecting most chronic diseases of Western societies. Of special concern is the possibility that milk intake during pregnancy adversely affects the early fetal programming of the IGF-1 axis which will influence health risks later in life. An accumulated body of evidence for the adverse effects of cow's milk consumption from fetal life to childhood, adolescence, adulthood and senescence will be provided which strengthens the presented hypothesis.

Growing in Antarctica, a challenge for white adipose tissue development in Adelie penguin chicks (Pygoscelis adeliae)

Rapid growth is of crucial importance for Adélie penguin chicks reared during the short Antarctic summer. It partly depends on the rapid ontogenesis of fat stores that are virtually null at hatching but then develop considerably (x40) within a month to constitute both an isolative layer against cold and an energy store to fuel thermogenic and growth processes. The present study was aimed at identifying by RT-PCR the major transcriptional events that chronologically underlie the morphological transformation of adipocyte precursors into mature adipocytes from hatching to 30 days of age. The peak expression of GATA binding protein 3, a marker of preadipocytes, at day 7 posthatch indicates a key proliferation step, possibly in relation to the expression of C/EBPalpha (C/EBPalpha). High plasma total 3,5,3'-triiodo-l-thyronine (T(3)) levels and high levels of growth hormone receptor transcripts at hatching suggested that growth hormone and T(3) play early activating roles to favor proliferation of preadipocyte precursors. Differentiation and growth of preadipocytes may occur around day 15 in connection with increased abundance of transcripts encoding IGF-1, proliferator-activated receptor-gamma, and C/EBPbeta, gradually leading to functional maturation of metabolic features of adipocytes including lipid uptake and storage (lipoprotein lipase, fatty-acid synthase) and late endocrine functions (adiponectin) by day 30. Present results show a close correlation between adipose tissue development and chick biology and a difference in the scheduled expression of regulatory factors controlling adipogenesis compared with in vitro studies using cell lines emphasizing the importance of in vivo approaches.

Nutrition-induced catch-up growth at the growth plate

The effect of 40% food restriction (FR) and replenishment on the growth hormone (GH) and insulin-like growth factor-I (IGF-I) axis in the epiphyseal growth plate (EGP) was examined in a mouse model. Changes in RNA and protein levels were evaluated with real time PCR and immunohistochemistry, respectively, and serum levels of IGF-I and leptin were measured with radioimmunoassay. Dramatic changes in weight, tibial length and EGP height were observed following 10 days of 40% FR. The protein levels of IGF-I receptor (IGF-IR) and GH receptor (GHR), which were reduced during FR, increased during catch-up growth without an apparent change in the level of their RNA. The levels of type II and X collagens were unchanged. Serum IGF-I and leptin levels were reduced during FR and increased during catch-up growth. Following 40% FR, there was a significant decrease in the level of GHR and IGF-IR in the EGP which may explain the reduced effect of GH treatment in malnourished animals and children.

Associations of circulating C-reactive protein and interleukin-6 with cancer risk: findings from two prospective cohorts and a meta-analysis

OBJECTIVE

We investigated the associations of circulating C-reactive protein (CRP) and interleukin-6 (IL-6) with cancer risk.

METHODS

We examined the associations of CRP and IL-6 with incident cancer in two prospective cohorts, the British Women's Heart and Health Study (4,286 women aged 60-80) and the Caerphilly Cohort (2,398 men aged 45-59) using Cox regression and pooled our findings with previous prospective studies' in fixed and random effects meta-analyses.

RESULTS

CRP and IL-6 were associated with some incident cancers in our cohorts, but the numbers of cancer cases were small. In our meta-analyses elevated CRP was associated with an increased overall risk of cancer (random effects estimate (RE): 1.10, 95% CI: 1.02, 1.18) and lung cancer (RE: 1.32, 95% CI: 1.08, 1.61). Its associations with colorectal (RE: 1.09, 95% CI: 0.98, 1.21) and breast cancer risks (RE: 1.10, 95% CI: 0.97, 1.26) were weaker. CRP appeared unrelated to prostate cancer risk (RE: 1.00 0.88, 1.13). IL-6 was associated with increased lung and breast cancer risks and decreased prostate cancer risk, and was unrelated to colorectal cancer risk.

CONCLUSIONS

Our findings suggest an etiological role for CRP and IL-6 in some cancers. Further large prospective and genetic studies would help to better understand this role.

Altered metabolism of growth hormone receptor mutant mice: a combined NMR metabonomics and microarray study

Background

Growth hormone is an important regulator of post-natal growth and metabolism. We have investigated the metabolic consequences of altered growth hormone signalling in mutant mice that have truncations at position 569 and 391 of the intracellular domain of the growth hormone receptor, and thus exhibit either low (around 30% maximum) or no growth hormone-dependent STAT5 signalling respectively. These mutations result in altered liver metabolism, obesity and insulin resistance.

Methodology/Principal Findings

The analysis of metabolic changes was performed using microarray analysis of liver tissue and NMR metabonomics of urine and liver tissue. Data were analyzed using multivariate statistics and Gene Ontology tools. The metabolic profiles characteristic for each of the two mutant groups and wild-type mice were identified with NMR metabonomics. We found decreased urinary levels of taurine, citrate and 2-oxoglutarate, and increased levels of trimethylamine, creatine and creatinine when compared to wild-type mice. These results indicate significant changes in lipid and choline metabolism, and were coupled with increased fat deposition, leading to obesity. The microarray analysis identified changes in expression of metabolic enzymes correlating with alterations in metabolite concentration both in urine and liver. Similarity of mutant 569 to the wild-type was seen in young mice, but the pattern of metabolites shifted to that of the 391 mutant as the 569 mice became obese after six months age.

Conclusions/Significance

The metabonomic observations were consistent with the parallel analysis of gene expression and pathway mapping using microarray data, identifying metabolites and gene transcripts involved in hepatic metabolism, especially for taurine, choline and creatinine metabolism. The systems biology approach applied in this study provides a coherent picture of metabolic changes resulting from impaired STAT5 signalling by the growth hormone receptor, and supports a potentially important role for taurine in enhancing β-oxidation.

Lower visceral and subcutaneous but higher intermuscular adipose tissue depots in patients with growth hormone and insulin-like growth factor I excess due to acromegaly

CONTEXT

GH and IGF-I are important regulators of metabolism and body composition. In acromegaly, a state of GH and IGF-I excess, the lipolytic and insulin antagonistic effects of GH may alter adipose tissue (AT) distribution.

OBJECTIVES

Our objective was to test the hypothesis that in acromegaly whole-body AT mass is less and to examine for the first time the relationship between GH/IGF-I excess and intermuscular AT (IMAT), an AT depot associated with insulin resistance in other populations.

DESIGN, SETTING, AND PATIENTS

We conducted a cross-sectional study in 24 adults with active acromegaly compared with predicted models developed in 315 healthy non-acromegaly subjects.

OUTCOME MEASURES

Mass of AT in the visceral AT (VAT), sc AT (SAT), and IMAT compartments from whole-body magnetic resonance imaging and serum levels of GH, IGF-I, insulin, and glucose were measured.

RESULTS

VAT and SAT were less in active acromegaly (P < 0.0001); these were 68.2 +/- 27% and 79.5 +/- 15% of predicted values, respectively. By contrast, IMAT was greater (P = 0.0052) by 185.6 +/- 84% of predicted. VAT/trunk AT ratios were inversely related to IGF-I levels (r = 0.544; P = 0.0054). Acromegaly subjects were insulin resistant.

CONCLUSIONS

VAT and SAT, most markedly VAT, are less in acromegaly. The proportion of trunk AT that is VAT is less with greater disease activity. IMAT is greater in acromegaly, a novel finding, which suggests that increased AT in muscle could be associated with GH-induced insulin resistance. These findings have implications for understanding the role of GH in body composition and metabolic risk in acromegaly and other clinical settings of GH use.

Gene expression analyses in cynomolgus monkeys provides mechanistic insight into high-density lipoprotein-cholesterol reduction by androgens in primates

Androgens increase muscle mass, decrease fat mass, and reduce high-density lipoprotein cholesterol (HDL), but the relationship between body composition, lipoprotein metabolism, and androgens has not been explained. Here we treated ovariectomized cynomolgus monkeys with 5alpha-dihydrotestosterone (DHT) or vehicle for 14 d and measured lipoprotein and triglycerides. Nuclear magnetic resonance analysis revealed that DHT dose-dependently reduced the cholesterol content of large HDL particles and decreased mean HDL particle size (P < 0.01) and also tended to lower low-density lipoprotein cholesterol without altering other lipoprotein particles. Liver and visceral fat biopsies taken before and after DHT treatment for 1 or 14 d were analyzed by genome-wide microarrays. In liver, DHT did not alter the expression of most genes involved in cholesterol synthesis or uptake but rapidly increased small heterodimer partner (SHP) RNA, along with concomitant repression of CYP7A1, a target of SHP transcriptional repression and the rate-limiting enzyme in bile acid synthesis. DHT regulation of SHP and CYP7A1 also occurs in rats, indicating a conserved mechanism. In adipose tissue, pathway analyses suggested coordinate regulation of adipogenesis, tissue remodeling, and lipid homeostasis. Genes encoding IGF-I and beta-catenin were induced, as were extracellular matrix, cell adhesion, and cytoskeletal components, whereas there was consistent down-regulation of genes involved in triacylglycerol metabolism. Interestingly, cholesterol ester transfer protein RNA was induced rapidly in monkey adipose tissue, whereas its inhibitor apolipoprotein CI was repressed. These data provide insight into the androgenic regulation of lipoprotein homeostasis and suggest that changes in adipose lipoprotein metabolism could contribute to HDL cholesterol reduction.

Milk consumption: aggravating factor of acne and promoter of chronic diseases of Western societies

Consumption of cow's milk and cow's milk protein result in changes of the hormonal axis of insulin, growth hormone and insulin-like growth factor-1(IGF-1) in humans. Milk consumption raises IGF-1 serum levels in the perinatal period, adolescence and adulthood. During puberty with the physiological onset of increased secretion of growth hormone, IGF-1 serum levels increase and are further enhanced by milk consumption. IGF-1 is a potent mitogen; after binding to its receptor in various tissues, it induces cell proliferation and inhibits apoptosis. Keratinocytes and sebocytes, as well as the androgen-synthesizing adrenals and gonads, are stimulated by IGF-1. The epidemic incidence of adolescent acne in Western milk-consuming societies can be explained by the increased insulin- and IGF-1-stimulation of sebaceous glands mediated by milk consumption. Acne can be regarded as a model for chronic Western diseases with pathologically increased IGF-1-stimulation. Many other organs, such as the thymus, bones, all glands, and vascular smooth muscle cells as well as neurons are subject to this abnormally increased hormonal stimulation. The milk-induced change of the IGF-1-axis most likely contributes to the development of fetal macrosomia, induction of atopy, accelerated linear growth, atherosclerosis, carcinogenesis and neurodegenerative diseases. Observations of molecular biology are supported by epidemiologic data and unmask milk consumption as a promoter of chronic diseases of Western societies.

Adipocytes and adipose tissue

An epidemic of obesity is taking place in most societies around the world. Overall obesity substantially increases the risk of subsequent morbidity. In children and adolescents the degree of body fat mass depends upon ethnic background, gender, developmental stage and age. Obesity is characterized by increases in the number or size of fat cells, or a combination of both. It is generally believed that the number of fat cells depends on age of onset and degree of obesity. This chapter provides information on intrauterine growth of fetal adipose tissue, the earliest period of onset of proliferation, and some of the factors that interact to enhance or suppress development. Fetal adipose tissue development is regulated by the complex interaction of transcription factors, nutrients and adipocytokines. Maternal, endocrine, and paracrine factors also influence specific changes in angiogenesis, adipogenesis, and metabolism. During embryogenesis and in fetal life, leptin and adiponectin, two important adipocytokines, are present at high concentrations in the circulation and in tissues. Developmental stages and metabolic processes influenced by specific hormones and paracrine factors have been identified through examination of the offspring of obese and diabetic pregnancies, hormonal manipulation during late pregnancy in animal models, and the use of cell cultures. Collectively, the results of the studies cited herein delineate the basis for imprinting or conditioning of fetal pre-adipocytes at the paracrine/autocrine level, and of fetal adipose tissue development and metabolism.

Hibiscus sabdariffa L. water extract inhibits the adipocyte differentiation through the PI3-K and MAPK pathway

Hibiscus sabdariffa L., a tropical beverage material and medical herb, is used commonly as in folk medicines against hypertension, pyrexia, inflammation, liver disorders, and obesity. This report was designed to investigate the inhibitory mechanisms of hibiscus extract on adipocyte differentiation in 3T3-L1 preadipocytes. The possible inhibitory pathways that regulate the adipocyte differentiation contain the adipogenic transcription factors, C/EBPalpha and PPARgamma, PI3-kinase, and MAPK pathway. In this study, we examined whether hibiscus extract affected the adipogenesis via these three pathways. To differentiate preadipocyte in adipocyte, confluent 3T3-L1 preadipocytes were treated with the hormone mixture including isobutylmethylxanthine, dexamethasone, and insulin (MDI). Hibiscus extract inhibited significantly the lipid droplet accumulation by MDI in a dose-dependent manner and attenuated dramatically the protein and mRNA expressions of adipogenic transcriptional factors, C/EBPalpha and PPARgamma, during adipogenesis. The increase of phosphorylation and expression of PI3-K/Akt during adipocytic differentiation was markedly inhibited by treatment with hibiscus extract or PI3-K inhibitors. Furthermore, the phosphorylation and expression of MEK-1/ERK known to regulate the early phase of adipogenesis were clearly decreased with the addition of hibiscus extract. Taken together, this report suggests that hibiscus extract inhibits the adipocyte differentiation through the modulation of PI3-K/Akt and ERK pathway that play pivotal roles during adipogenesis.

PPARgamma and GLUT-4 expression as developmental regulators/markers for preadipocyte differentiation into an adipocyte

In this document, we have integrated knowledge about two major cellular markers found in cells of the adipocyte lineage (an adipogenic marker and a metabolic marker). This review provides information as to how differentiation of a cell (such as an adipofibroblast, fibroblast or preadipocyte) to become a viable (and new) adipocyte is under different regulation than that experienced by an immature adipocyte that is just beginning to accumulate lipid. The differentiation, prior to lipid-filling, involves PPARgamma. Subsequently, lipid-filling of the adipocyte relies on a late subset of genes and, depending on depot specificity, involves GLUT-4 or any number of other metabolic markers.

Influence of hormones on osteogenic differentiation processes of mesenchymal stem cells

Bone development, regeneration and maintenance are governed by osteogenic differentiation processes from mesenchymal stem cells through to mature bone cells, which are directed by local growth and differentiation factors and modulated strongly by hormones. Mesenchymal stem cells develop from both mesoderm and neural crest and can give rise to development, regeneration and maintenance of mesenchymal tissues, such as bone, cartilage, muscle, tendons and discs. There are only limited data regarding the effects of hormones on early events, such as regulation of stemness and maintenance of the mesenchymal stem cell pool. Hormones, such as estrogens, vitamin D-hormone and parathyroid hormone, besides others, are important modulators of osteogenic differentiation processes and bone formation, starting off with fate decision and the development of osteogenic offspring from mesenchymal stem cells, which end up in osteoblasts and osteocytes. Hormones are involved in fetal bone development and regeneration and, in childhood, adolescence and adulthood, they control adaptive needs for growth and reproduction, nutrition, physical power and crisis adaptation. As in other tissues, aging in mesenchymal stem cells and their osteogenic offspring is accompanied by the accumulation of genomic and proteomic damage caused by oxidative burden and insufficient repair. Failsafe programs, such as apoptosis and cellular senescence avoid tumorigenesis. Hormones can influence the pace of such events, thus supporting the quality of tissue regeneration in aging organisms in vivo; for example, by delaying osteoporosis development. The potential for hormones in systemic therapeutic strategies is well appreciated and some concepts are approved for clinical use already. Their potential for cell-based therapeutic strategies for tissue regeneration is probably underestimated and could enhance the quality of tissue-engineering constructs for transplantation and the concept of in situ-guided tissue regeneration.

IGF-1 protects intestinal epithelial cells from oxidative stress-induced apoptosis

BACKGROUND

Reactive oxygen species (ROS) are involved in the pathogenesis of necrotizing enterocolitis (NEC) in premature infants. We have recently found that activation of multiple cellular signaling transduction pathways occurs during ROS-induced intestinal cell apoptosis; the phosphatidylinositol 3-kinase (PI3-K) pathway plays an anti-apoptotic role during this process. Insulin-like growth factor (IGF)-1 activates PI3-K pathway to promote cell survival; however, the effects of IGF-1 treatment during gut injury are not clearly defined. The purpose of this study was to determine whether IGF-1 protects intestinal cells from ROS-induced apoptosis.

MATERIALS AND METHODS

Rat intestinal epithelial (RIE)-1 cells were treated with either IGF-1 (100 nm), hydrogen peroxide (H2O2; 500 microm), or combination. Western blotting was performed to assess phosphorylation of Akt, a downstream effector of PI3-K. Cell Death Detection ELISA, DCHF, and JC-1 assays were performed to demonstrate protective effects of IGF-1. Wortmannin, an inhibitor of PI3-K, was used to show PI3-K-dependent mechanism of action for IGF-1.

RESULTS

H2O2 treatment resulted in increased intestinal epithelial cell apoptosis with intracellular ROS generation and mitochondrial membrane depolarization; IGF-1 pre-treatment attenuated this response without affecting ROS production. H2O2-induced phosphorylation of Akt was further increased with IGF-1 treatment; wortmannin abolished these effects in RIE-1 cells.

CONCLUSIONS

PI3-K pathway is activated during ROS-induced intestinal epithelial cell injury; IGF-1 exerted an anti-apoptotic effect during this response by PI3-K activation. A better understanding of the exact role of IGF-1-mediated activation of PI3-K may allow us to facilitate the development of novel therapy against NEC.