Sodium Selenite Improves Folliculogenesis in Radiation-Induced Ovarian Failure: A Mechanistic Approach

Radiotherapy is a major factor contributing to female infertility by inducing premature ovarian failure (POF). Therefore, the need for an effective radioprotective agent is evident. The present study investigated the mechanism of potential radioprotective effect of sodium selenite on radiation-induced ovarian failure and whether sodium selenite can stimulate in-vivo follicular development in experimental rats. Immature female Sprague-Dawely rats were either exposed to gamma-radiation (3.2 Gy, LD₂₀), once and/or treated with sodium selenite (0.5 mg/kg), once daily for one week before irradiation. Follicular and oocyte development, apoptotic markers, proliferation marker as well as oxidative stress markers were assessed 24-h after irradiation. In addition, fertility assessment was performed after female rats became completely mature at two months of age. Sodium selenite significantly enhanced follicular development as compared to the irradiated group. Sodium selenite significantly reversed the oxidative stress effects of radiation that was evidenced by increasing in lipid peroxide level and decreasing in glutathione level, and glutathione peroxidase (GPx) activity. Assessment of apoptosis and cell proliferation markers revealed that caspase 3 and cytochrome c expressions markedly-increased, whereas, PCNA expression markedly-decreased in the irradiated group; in contrast, sodium selenite treatment prevented these alterations. Histopathological examination further confirmed the radioprotective efficacy of sodium selenite and its in-vivo effect on ovarian follicles’ maturation. In conclusion, sodium selenite showed a radioprotective effect and improved folliculogenesis through increasing ovarian granulosa cells proliferation, estradiol and FSH secretion, and GPx activity, whilst decreasing lipid peroxidation and oxidative stress, leading to inhibition of the apoptosis pathway through decreasing the expressions of caspase 3 and cytochrome c.     

Relationship of liver and skeletal muscle IGF-1 mRNA to plasma GH profile, production of IGF-1 by liver, plasma IGF-1 concentrations, and growth rates of cattle

Growth hormone (GH), insulin-like growth factor-1 (IGF-1), and thyroid hormone (T3 and T4) concentrations in blood plasma of 18 crossbred cattle (six bulls, six steers, and six heifers) were measured over an 8-hr period. One week later at slaughter, IGF-1 production by liver slices and IGF-1 mRNA concentrations in skeletal muscle and liver were measured. Bulls had higher (P less than 0.05) mean plasma GH and GH peak amplitudes (P less than 0.01) than heifers, and values for steers were intermediate between bulls and heifers. Baseline GH concentrations and number of GH peaks were not significantly different for the three groups. Bulls had 1.6-fold (P less than 0.01) and 3.0-fold (P less than 0.01) greater liver IGF-1 mRNA concentrations than steers or heifers, respectively, whereas the steers had 1.8-fold (P less than 0.05) greater IGF-1 mRNA in liver than heifers. Production of IGF-1 by liver slices was greater (P less than 0.05) in bulls than steers or heifers. Bulls had 1.3-fold greater plasma IGF-1 than steers (P less than 0.01), whereas steers had 1.8-fold greater plasma IGF-1 than heifers (P less than 0.01). There were no significant differences in concentrations of skeletal muscle IGF-1 mRNA between the three groups of animals. Liver IGF-1 mRNA, liver IGF-1 production, and plasma IGF-1 were all significantly correlated with gain and mean GH peak amplitude, but not with GH baseline, GH peak frequency, or concentrations of T3 and T4. Concentrations if IGF-1 mRNA in skeletal muscle were not correlated to gain or any parameter of the GH profile. Plasma concentrations of T3 were significantly (P less than 0.05) negatively correlated to plasma GH baseline concentrations. Muscle IGF-1 mRNA concentration was negatively related to plasma T4 and T3. The results of this study suggest that the cascade of events starting with secretion of GH from the pituitary, expression of liver IGF-1 mRNA, and secretion of IGF-1 by the liver are important phenomena for growth of cattle.     

Secretion of IGF-1 by ovine granulosa cells: effects of growth hormone and follicle stimulating hormone

Insulin-like growth factor-1 (IGF-1) is implicated in follicle development and is considered to mediate the actions of growth hormone (GH) and gonadotrophins at the ovarian level. However, the expression and secretion of IGF-1 by the ovary are controversial, partly because of species and cell-type specificity. The present study investigated whether IGF-1 is produced by ovine granulosa cells and whether its production is regulated by GH and follicle stimulating hormone (FSH). Follicles (>/=4.0 mm) were obtained from ewes during seasonal anoestrus. Granulosa cells were cultured for a total period of 96 h in Dulbecco's modified Eagle's medium (DMEM)/Ham's F-12 medium supplemented with BSA (0.1%, w:v), transferrin (0.5 microg/ml) and testosterone (100 ng/ml). In the first set of experiments, cells were incubated in the presence of bovine calf serum (BCS) (2.5%) for the initial 48 h of culture. The cells were then cultured for the next 48 h in medium without BCS, but containing either GH (0, 2, 20, and 200 ng/ml) or FSH (0, 20, 200, and 2000 ng/ml). The medium was assayed for oestradiol (E), progesterone (P) and IGF-1. There were six wells per treatment and the experiment was carried out four times. Control granulosa cells maintained both IGF-1 and E secretion, with only low levels of progesterone output. In all experiments, both GH and FSH produced significant (P<0.001) dose-related increases in E, IGF-1 and P secretion into the medium. The maximum responses to GH (20 or 200 ng/ml) were 402% for E and 528% for IGF-1 compared with controls. The maximum responses to FSH (200 or 2000 ng/ml) were 460% for E and 514% for IGF-1. The objective of the second set of experiments was to determine the effect of the progestogenic status of cells on IGF-1 production. Granulosa cells were cultured both in the presence and absence of BCS (2.5% in the medium) during the initial 48 h of culture. For the next 48 h, cells were cultured in serum-free medium. Addition of BCS to the medium during the initial 48 h of culture stimulated progesterone production. However, it did not affect either IGF-1 or oestradiol secretion between 49 and 96 h of culture, or the cell numbers at the end of culture. In conclusion, (1) IGF-1 is secreted by granulosa cells irrespective of their progestogenic status and (2) concomitant increases in E and IGF-1 production by granulosa cells as a result of GH and/or FSH treatment suggest a role for GH and FSH in the regulation of ovarian function.     

Renoprotective Effect of Lactoferrin against Chromium-Induced Acute Kidney Injury in Rats: Involvement of IL-18 and IGF-1 Inhibition

Hexavalent chromium (CrVI) is a heavy metal widely used in more than 50 industries. Nephrotoxicity is a major adverse effect of chromium poisoning. The present study investigated the potential renoprotective effect of lactoferrin (Lf) against potassium dichromate (PDC)-induced acute kidney injury (AKI) in rats. Beside, because previous studies suggest that interlukin-18 (IL-18) and insulin-like growth factor-1 (IGF-1) play important roles in promoting kidney damage, the present work aimed to evaluate the involvement of these two cytokines in PDC model of AKI and in the potential renoprotective effect of lactoferrin. Adult male albino Wistar rats were pretreated with Lf (200mg/kg/day, p.o.) or (300mg/kg/day, p.o.); the doses that are usually used in the experiment studies, for 14 days followed by a single dose of PDC (15mg/kg, s.c.). PDC caused significant increase in serum urea, creatinine, and total protein levels. This was accompanied with decreased renal glutathione content, and increased renal malondialdehyde, IL-18, IL-4, nuclear factor kappa B (NFκB), IGF-1, and the phosphorylated form of forkhead box protein O1 (FoxO1) levels. Moreover, normal expression IFN-γ mRNA and enhanced expression of TNF-α mRNA was demonstrated in renal tissues. Histopathological investigations provoked deleterious changes in the renal tissues. Tubular epithelial hyperplasia and apoptosis were demonstrated immunohistochemically by positive proliferating cell nuclear antigen (PCNA), Bax, and Caspase-3 expression, respectively. Pretreatment of rats with Lf in both doses significantly corrected all previously mentioned PDC-induced changes with no significant difference between both doses. In conclusion, the findings of the present study demonstrated the involvement of oxidative stress, inflammatory reactions, tubular hyperplasia and apoptosis in PDC-induced AKI. It suggested a role of IL-18 through stimulation of IL-4-induced inflammatory pathway, and IGF-1 through triggering FoxO1-induced cell proliferation. Moreover, the study revealed that Lf protected the kidney against Cr-induced AKI in rats and significantly showed antioxidant, anti-inflammatory, and anti-proliferative properties with down-regulation of IL-18 and IGF-1.     

Single nucleotide polymorphisms in the growth hormone and insulin-like growth factor-1 genes are associated with milk production, body condition score and fertility traits in dairy cows

The somatotrophic axis (GH-IGF) is a key regulator of animal growth and development, affecting performance traits that include milk production, growth rate, body composition, and fertility. The aim of this study was to quantify the association of previously identified SNPs in bovine growth hormone (GH1) and insulin-like growth factor 1 (IGF-1) genes with direct performance trait measurements of lactation and fertility in Holstein-Friesian lactating dairy cows. Sixteen SNPs in both IGF-1 and GH1 were genotyped across 610 cows and association analyses were carried out with traits of economic importance including calving interval, pregnancy rate to first service and 305-day milk production, using animal linear mixed models accounting for additive genetic effects. Two IGF-1 SNPs, IGF1i1 and IGF1i2, were significantly associated with body condition score at calving, while a single IGF-1 SNP, IGF1i3, was significantly associated with milk production, including milk yield (means ± SEM; 751.3 ± 262.0 kg), fat yield (21.3 ± 10.2 kg) and protein yield (16.5 ± 8.0 kg) per lactation. Only one GH1 SNP, GH33, was significantly associated with milk protein yield in the second lactation (allele substitution effect of 9.8 ± 5.0 kg). Several GH1 SNPs were significantly associated with fertility, including GH32, GH35 and GH38 with calving to third parity (22.4 ± 11.3 days) (GH32 and GH38 only), pregnancy rate to first service (0.1%) and overall pregnancy rate (0.05%). The results of this study demonstrate the effects of variants of the somatotrophic axis on milk production and fertility traits in commercial dairy cattle.     

Expression of insulin-like growth factor-1 and insulin-like growth factor-1 receptors in EL4 lymphoma cells overexpressing growth hormone

Almost all of the previous studies with growth hormone (GH) have been done with exogenously supplied GH and, therefore, involve actions of the hormone through its receptor. However, the actions of endogenous or lymphocyte GH are still unclear. In a previous study, we showed that overexpression of GH (GHo) in a lymphoid cell line resulted in protection of the cells to apoptosis mediated by nitric oxide (NO). In the present study, we show that the protection from apoptosis could be transferred to control cells with culture fluids obtained from GHo cells and blocked by antibodies to the insulin-like growth factor-1 (IGF-1) or antibodies to the IGF-1-receptor (IGF-1R). Northern and Western blot analysis detected significantly higher levels of IGF-1 in cells overexpressing GH. An increase in the expression of the IGF-1R in GHo cells was also detected by Western blot analysis, (125)I-IGF-1 binding and analysis of IGF-1R promoter luciferase constructs. Transfection of GHo cells with a dominant negative IGF-1R mutant construct blocked the generation of NO and activation of Akt seen in GHo cells compared to vector alone control EL4 cells. The results suggest that one of the consequences of the overexpression of GH, in cells lacking the GH receptor, is an increase in the expression of IGF-1 and the IGF-1R which mediate the protection of EL4 lymphoma cells from apoptosis.     

A critical analysis of the role of growth hormone and IGF-1 in aging and lifespan

Studies in Caenorhabditis elegans demonstrate that disruption of the daf-2 signaling pathways extends lifespan. Similarities among the daf-2 pathway, insulin-like signaling in flies and yeast, and the mammalian insulin-like growth factor 1 (IGF-1) signaling cascade raise the possibility that modifications to IGF-1 signaling could also extend lifespan in mammals. In fact, growth hormone (GH)/IGF-1-deficient dwarf mice do live significantly longer than their wild-type counterparts. However, multiple endocrine deficiencies and developmental anomalies inherent in these models confound this interpretation. Here, we critique the current mammalian models of GH/IGF-1 deficiency and discuss the actions of GH/IGF-1 on biological aging and lifespan.     

Cardiomyocyte protective effects of thyroid hormone during hypoxia/reoxygenation injury through activating of IGF-1-mediated PI3K/Akt signalling

Ischaemia/reperfusion (I/R) injury is a common clinical condition that results in apoptosis and oxidative stress injury. Thyroid hormone was previously reported to elicit cardiac myocyte hypertrophy and promote cardiac function after cardiac injury. We used an in vivo mouse model of I/R injury and in vitro primary cardiomyocyte culture assays to investigate the effects of thyroid hormone on cardiomyocytes during hypoxia/reoxygenation (H/R) injury. The results showed that T3 pretreatment in vivo significantly improved left ventricular function after I/R injury. In vitro, T3 pretreatment decreased cell apoptosis rate, inhibited caspase-3 activity and decreased the Bax/Bcl-2 ration induced by H/R injury. T3 pretreatment significantly attenuated the loss of mitochondrial membrane potential. Furthermore, it was observed that T3 diminished the expression of NCX1 protein and decreased SERCA2a protein expression in H/R-induced cardiomyocytes, and T3 prevented intracellular Ca²⁺ increase during H/R injury. Also, T3 increased the expression of IGF-1, and PI3K/Akt signalling in cardiomyocytes under H/R-induced injury, and that the protective effect of T3 against H/R-induced injury was blocked by the PI3K inhibitor LY294002. IGF-1 receptor (IGF-1R) inhibitor GSK1904529A significantly inhibited the expression of IGF-1R and PI3K/Akt signalling. In summary, T3 pretreatment protects cardiomyocytes against H/R-induced injury by activating the IGF-1-mediated PI3K/Akt signalling pathway.     

Effects of growth hormone and insulin-like growth factor-1 on hepatocyte antioxidative enzymes

The physiological decline that occurs in aging is thought to result, in part, from accumulation of oxidative damage generated by reactive oxygen species during normal metabolic processes. Elevated levels of antioxidative enzymes in liver tissues are present in the Ames dwarf, a growth hormone (GH)-deficient mouse that lives more than 1 year longer than wild-type mice from the same line. In contrast, transgenic mice that overexpress GH exhibit depressed hepatic levels of catalase and have significantly shortened life spans. In this study, we evaluated the in vitro effects of GH and insulin-like growth factor 1 (IGF-1) on antioxidative enzymes in mouse hepatocytes. Hepatocytes were isolated from wild-type mice following perfusion of livers with a collagenase-based buffer. Dispersed cells were plated on Matrigel and treated with rat GH (0.1, 1.0, or 10 microg/ml) or IGF-1 (0.5, 5.0, or 50 nM) for 24 hr. Hepatocytes were recovered and protein was extracted for immunoblotting and enzyme activity assays of catalase (CAT), glutathione peroxidase (GPX), and manganese superoxide dismutase (MnSOD). A 41% and 27% decrease in catalase activity was detected in cells treated with GH, whereas IGF-1 reduced CAT activity levels to a greater extent than GH (P < 0.0001). The activity and protein levels of GPX were also significantly depressed in cells treated with GH, whereas activity alone was decreased in cells treated with IGF-1 (P < 0.04). GH significantly suppressed MnSOD levels by 40% and 66% in 1.0 and 0.1 microg/ml concentrations, respectively. Similarly, IGF-1 decreased MnSOD protein levels (5 nM; P < 0.05). These results suggest that GH and IGF-1 may decrease the ability of hepatocytes to counter oxidative stress. In addition, these experiments provide an explanation for the differing antioxidative defense capacity of GH-deficient versus GH-overexpressing mice, and they suggest that GH is directly involved in antioxidant regulation and the aging process.     

Mitochondrial involvement in IGF-1 induced protection of cardiomyocytes against hypoxia/reoxygenation injury

Studies in animal models of myocardial ischemia-reperfusion revealed that the administration of insulin-like growth factor (IGF-1) can provide substantial cardioprotective effect. However, the mechanisms by which IGF-1 prevents myocardial ischemia-reperfusion injury are not fully understood. This study addresses whether mitochondrial bioenergetic pathways are involved in the cardioprotective effects of IGF-1. Single cardiomyocytes from adult rats were incubated in the absence or presence of IGF-1 for 60 min and subjected to 60 min hypoxia followed by 30 min reoxygenation at 37°C. Mitochondrial function was evaluated by assessment of enzyme activities of oxidative phosphorylation and Krebs cycle pathways. Hypoxia/reoxygenation (HR) caused significant inhibition of mitochondrial respiratory complex IV and V activities and of the Krebs cycle enzyme citrate synthase, whereas pretreatment with IGF-1 maintained enzyme activities in myocytes at or near control levels. Mitochondrial membrane potential, evaluated with JC-1 staining, was significantly higher in IGF-1 + HR- treated myocytes than in HR alone, with levels similar to those found in normal control cardiomyocytes. In addition, IGF-1 reduced both HR-induced lactate dehydrogenase (LDH) release and malondialdehyde production (an indicator of lipid peroxidation) in cardiomyocytes. These results suggest that IGF-1 protects cardiomyocytes from HR injury via stabilizing mitochondria and reducing reactive oxidative species (ROS) damage.     

Control of ceramide-induced apoptosis by IGF-1: involvement of PI-3 kinase,caspase-3 and catalase

Insulin-like growth factor-1 (IGF-1) inhibited N-acetylsphingosine (C2-ceramide)-induced HL-60 cell apoptosis via relieving oxidative damage. This inhibitory action of IGF-1 was blocked by a phosphatidylinositol-3 (PI-3) kinase inhibitor wortmannin and enhanced by overexpression of the p110 catalytic subunit of PI-3 kinase. Either IGF-1 pretreatment or PI-3 kinase overexpression restored ceramide-depleted catalase function, and this restoration was inhibited by wortmannin. A catalase inhibitor 3-amino-1h-1, 2, 4-triazole (ATZ) blocked the inhibitory action of IGF-1 on ceramide-induced apoptosis, whereas exogenous purified catalase enhanced it. Ceramide-activated caspase-3 was inhibited by IGF-1/PI-3 kinase and enhanced by wortmannin, while the addition of a specific caspase-3 inhibitor DMQD-CHO significantly enhanced the restoration by IGF-1 of ceramide-depleted catalase function. Moreover, IGF-1 inhibited C2-ceramide-induced decrease of mitochondrial membrane potential, and increase of cytochrome c release, caspase-3 cleavage and caspase-3 activity as judged by PhiPhiLux cleaving method. In summary, these results suggest that IGF-1/PI-3 kinase inhibited C2-ceramide-induced apoptosis due to relieving oxidative damage, which resulted from the inhibition of catalase by activated caspase-3.     

IGF-1 prevents oxidative stress induced-apoptosis in induced pluripotent stem cells which is mediated by microRNA-1

Oxidative stress contributes to tissue injury and cell death during the development of various diseases. The present study aims at investigating whether oxidative stress triggered by the exposure to hydrogen peroxide (H₂O₂) can induce apoptosis of induced pluripotent stem cells (iPS cells) in a mechanism mediated by insulin-like growth factor (IGF-1) and microRNA-1 (miR-1). iPS cells treated with H₂O₂ showed increases in miR-1 expression, mitochondria dysfunction, cytochrome-c release and apoptosis, Addition of IGF-1 into the iPS cell cultures reduced the H₂O₂ cytotoxicity. Prediction algorithms showed that 3′-untranslated regions of IGF-1 gene as a target of miR-1. Moreover, miR-1 mimic, but not miR-1 mimic negative control, diminished the protective effect of IGF-1 on H₂O₂-induced mitochondrial dysfunction, cytochrome-c release and apoptosis in iPS cells. In conclusion, IGF-1 inhibits H₂O₂-induced mitochondrial dysfunction, cytochrome-c release and apoptosis. IGF-1′s effect is, at least partially, regulated by miR-1 in iPS cells.     

Effect of somatostatin on repair of ionizing radiation-induced DNA damage in pituitary adenoma cells GH3

Ionizing radiation and somatostatin analogues are used for acromegaly treatment to achieve normalization or reduction of growth hormone hypersecretion and tumor shrinkage. In this study, we investigated a combination of somatostatin (SS14) with ionizing radiation of (60)Co and its effect on reparation of radiation-induced damage and cell death of somatomammotroph pituitary cells GH3. Doses of gamma-radiation 20-50 Gy were shown to inhibit proliferation and induce apoptosis in GH3 cells regardless of somatostatin presence. It has been found that the D(0) value for GH3 cells was 2.5 Gy. Somatostatin treatment increased radiosensitivity of GH3 cells, so that D(0) value decreased to 2.2 Gy. We detected quick phosphorylation of histone H2A.X upon irradiation by the dose 20 Gy and its colocalization with phosphorylated protein Nbs-1 in the site of double strand break of DNA (DSB). Number of DSB decreased significantly 24 h after irradiation, however, clearly distinguished foci persisted, indicating non repaired DSB, after irradiation alone or after combined treatment by irradiation and SS14. We found that SS14 alone triggers phosphorylation of Nbs1 (p-Nbs1), which correlates with antiproliferative effect of SS14. Irradiation also increased the presence of p-Nbs1. Most intensive phosphorylation of Nbs1 was detected after combined treatment of irradiation and SS14. The decrease of the number of the DSB foci 24 h after treatment shows a significant capacity of repair systems of GH3 cells. In spite of this, large number of unrepaired DSB persists for 24 h after the treatment. We conclude that SS14 does not have a radioprotective effect on somatomammotroph GH3 cells.     

Differential requirement for nitric oxide in IGF-1-induced anti-apoptotic, anti-oxidant and anti-atherosclerotic effects

We have shown previously that insulin like-growth factor I (IGF-1) suppressed atherosclerosis in Apoe(-/-) mice and activated endothelial nitric oxide (NO) synthase. To determine whether IGF-1-induced atheroprotection depends on NO, IGF-1- or saline-infused mice were treated with l-NAME, the pan-NO synthase inhibitor or with d-NAME (control). IGF-1 reduced atherosclerosis in both the d-NAME and l-NAME groups suggesting that IGF-1's anti-atherogenic effect was NO-independent. IGF-1 increased plaque smooth muscle cells, suppressed cell apoptosis and downregulated lipoprotein lipase and these effects were also NO-independent. On the contrary, IGF-1 decreased oxidative stress and suppressed TNF-α levels and these effects were blocked by l-NAME. Thus IGF-1's anti-oxidant effect is dependent on its ability to increase NO but is distinct from its anti-atherosclerotic effect which is NO-independent.     

Comparative effects of insulin and insulin-like growth factor-1 on follicle-stimulating hormone-induced responses in porcine granulosa cells

The effect of insulin and insulin-like growth factor-1 (IGF-1) on progesterone secretion by porcine granulosa cells and their modulatory effect on follicle-stimulating hormone (FSH)-induced responses were examined. For comparative purposes, growth hormone (GH), previously shown to stimulate IGF-1 secretion, was also included. Granulosa cells from ovarian follicles (3 to 5 mm) were cultured in multiwell plates for the first 48 hours, either in the presence or absence of 1% fetal bovine serum (FBS). Following plating, all cultures were maintained in serum-free media. The addition of only insulin, but not IGF-1 or GH, enhanced progesterone secretion under both culture conditions. When low-density lipoprotein was provided as steroid substrate, a stimulatory effect of insulin on progesterone accumulation was observed with a minimum dose of 10 ng/ml. Granulosa cells cultured in serum-free media from the time of plating secreted less progesterone and were less responsive to FSH compared with cultures plated with 1% FBS. Only insulin, but not IGF-1, enhanced FSH responses to threefold in cells cultured with 1% FBS. However, when cells were cultured in serum-free media from the time of plating, both insulin and IGF-1, but not GH, potentiated the responses to FSH, but insulin was more potent than IGF-1. Insulin-like growth-factor-1 binding studies with granulosa cells indicate the presence of specific high-affinity binding sites (Kd 3.96 nM). A dose of 100 ng/ml of insulin had negligible cross-reactivity with IGF-1 receptors.     

Fatty Liver Index Associates with Relative Sarcopenia and GH/ IGF- 1 Status in Obese Subjects

Introduction

Recently the association between hepatic steatosis and sarcopenia has been described. GH/IGF-1 axis has been postulated to play a role in linking fatty liver and low muscle mass. The aim of our study was to explore the association between fatty liver index, sarcopenic obesity, insulin sensitivity, and GH/IGF-1 status.

Methods

427 subjects [age: 45.65±13.94 years, BMI: 36.92±6.43 kg/m²] were enrolled. Participants were divided into three groups: fatty liver index (FLI) <20, 20≥FLI<60, and FLI≥60. Body composition was assessed by DXA. The truncal fat mass (TrFM) to appendicular skeletal muscle (ASM) ratio was used as an indicator of sarcopenic obesity. ISI-Matsuda index was used.

Results

BMI, fat mass, and the TrFM/ASM ratio were higher in subjects with FLI≥60. GH, IGF-1 and ISI-Matsuda were lower in the high FLI group (all p<0.05). A significantly positive correlation between FLI and TrFM/ ASM ratio (r = 0.221, p<0.001) was found, whereas FLI levels were negatively correlated with ISI- Matsuda (r = -0.335, p<0.001), GH (r = -0.200, p = 0.006), and IGF- 1 levels (r = -0.157, p = 0.028). Stepwise linear regression analysis showed that GH levels were significantly negatively correlated with FLI, while the TrFM/ ASM ratio was positively associated with FLI, after adjustment for age, BMI, total fat mass, truncal fat mass, fat- free mass, and ISI- Matsuda.

Conclusions

Impairment of GH/IGF-1 axis seems to be associated to the risk of the development of sarcopenic obesity and ectopic fat deposition in the liver. Metabolic and hormonal derangements as determinants of ectopic fat deposition and body composition deserve to be evaluated in obese subjects.     

Mode of growth hormone action in osteoblasts

Growth hormone (GH) affects bone size and mass in part through stimulating insulin-like growth factor type 1 (IGF-1) production in liver and bone. Whether GH acts independent of IGF-1 in bone remains unclear. To define the mode of GH action in bone, we have used a Cre/loxP system in which the type 1 IGF-1 receptor (Igf1r) has been disrupted specifically in osteoblasts in vitro and in vivo. Calvarial osteoblasts from mice homozygous for the floxed IGF-1R allele (IGF-1R(flox/flox)) were infected with adenoviral vectors expressing Cre. Disruption of IGF-1R mRNA (>90%) was accompanied by near elimination of IGF-1R protein but retention of GHR protein. GH-induced STAT5 activation was consistently greater in osteoblasts with an intact IGF-1R. Osteoblasts lacking IGF-1R retained GH-induced ERK and Akt phosphorylation and GH-stimulated IGF-1 and IGFBP-3 mRNA expression. GH-induced osteoblast proliferation was abolished by Cre-mediated disruption of the IGF-1R or co-incubation of cells with an IGF-1-neutralizing antibody. By contrast, GH inhibited apoptosis in osteoblasts lacking the IGF-1R. To examine the effects of GH on osteoblasts in vivo, mice wild type for the IGF-1R treated with GH subcutaneously for 7 days showed a doubling in the number of osteoblasts lining trabecular bone, whereas osteoblast numbers in similarly treated mice lacking the IGF-1R in osteoblasts were not significantly affected. These results indicate that although direct IGF-1R-independent actions of GH on osteoblast apoptosis can be demonstrated in vitro, IGF-1R is required for anabolic effects of GH in osteoblasts in vivo.     

Glucose induces apoptosis of cardiomyocytes via microRNA-1 and IGF-1

Glucose toxicity is an important initiator of cardiovascular disease, contributing to the development of cardiomyocyte death and diabetic complications. The present study investigated whether high glucose state could induce apoptosis of rat cardiomyocyte cell line H9C2 through microRNA regulated insulin-like growth factor (IGF-1) signaling pathway. Our data showed that H9C2 cells exposed to high glucose have increased miR-1 expression level, decreased mitochondrial membrane potential, increased cytochrome-c release, and increased apoptosis. Glucose induced mitochondrial dysfunction, cytochrome-c release and apoptosis was blocked by IGF-1. Using prediction algorithms, we identified 3′-untranslated regions of IGF-1 gene are the target of miR-1. miR-1 mimics, but not mutant miR-1, blocked the capacity of IGF-1 to prevent glucose-induced mitochondrial dysfunction, cytochrome-c release and apoptosis. In conclusion, our data demonstrate that IGF-1 inhibits glucose-induced mitochondrial dysfunction, cytochrome-c release and apoptosis and IGF-1’s effect is regulated by miR-1.