Decrease In IGF-I Research Articles

Loss of sexually dimorphic liver gene expression upon hepatocyte-specific deletion of Stat5a-Stat5b locus.

Hepatocyte-specific, albumin-Cre recombinase-mediated deletion of the entire mouse Stat5a-Stat5b locus was carried out to evaluate the role of signal transducer and activator of transcription 5a and 5b (STAT5ab) in the sex-dependent transcriptional actions of GH in the liver. The resultant hepatocyte STAT5ab-deficient mice were fertile, and unlike global STAT5b-deficient male mice, postnatal body weight gain was normal, despite a 50% decrease in serum IGF-I. Whole-liver STAT5ab RNA decreased by approximately 65-85%, and residual STAT5 immunostaining was observed in a minority of the hepatocytes, indicating incomplete excision by Cre-recombinase. Quantitative PCR analysis of 20 sexually dimorphic, liver-expressed genes revealed significant down-regulation of 10 of 11 male-specific genes in livers of male hepatocyte STAT5ab-deficient mice. Class I female-specific liver genes were markedly up-regulated (de-repressed), whereas the expression of class II female genes, belonging to the Cyp3a subfamily, was unaffected by the loss of hepatocyte STAT5ab. STAT5ab is thus required in the liver for positive regulation of male-specific genes and for negative regulation of a subset of female-specific genes. Continuous GH infusion strongly induced (>500-fold) the class II female gene Cyp3a16 in both wild-type and hepatocyte STAT5ab-deficient male mice, indicating sex-specific transcriptional regulation by GH that is STAT5ab independent. In contrast, hepatocyte STAT5ab deficiency abolished the strong suppression of the male-specific Cyp2d9 by continuous GH seen in control mouse liver. Analysis of global STAT5a-deficient mice indicated no essential requirement of STAT5a for expression of these sex-specific liver Cyp genes. Thus, the major loss of liver sexual dimorphism in hepatocyte STAT5ab-deficient mice can primarily be attributed to the loss of STAT5b.

N‐terminal pro‐B‐type natriuretic peptide in patients with growth hormone disturbances

Acromegaly is associated with hypertrophic cardiomyopathy, hypertension and subsequent congestive heart failure. Impairment of cardiac function has also been associated with growth hormone deficiency (GHD). B-type natriuretic peptides (BNPs) have emerged as strong diagnostic and prognostic risk markers. They are cardioprotective hormones that compensate heart disease by promoting natriuresis and modulation of cardiac hypertrophy in response to volume expansion and ventricular wall stretch. To investigate N-terminal pro-BNP (NT-proBNP) in patients with GH disturbances before and after treatment, and in healthy gender- and age-matched controls. Ten acromegalic patients (age 48 +/- 12 years) and 10 patients with GHD (age 41 +/- 14 years) were studied. None had symptoms or signs of cardiovascular disease except for hypertension. Serum NT-proBNP was measured before and 3, 6, 12 and 24 months after treatment. Baseline NT-proBNP was lower in acromegalic patients [median (interquartile range) 24.3 (17.8-33.0) pg/ml] than in 20 healthy matched controls [57.9 (35.4-92.2) pg/ml; P < 0.001]. NT-proBNP increased during treatment (P = 0.002), concomitant with a decrease in IGF-I (P < 0.001). After 3 months of treatment NT-proBNP peaked, with a fourfold increase to 96.4 (57.8-113.2) pg/ml. NT-proBNP did not differ in patients with GHD compared with controls (P = 0.19), and did not change during treatment (P = 0.39). Untreated patients with acromegaly had low NT-proBNP levels that increased fourfold after treatment. This is in contrast to other conditions with cardiac hypertrophy. Further studies are required to determine the significance of this novel finding in relation to acromegalic cardiac disease.

Quantitative analysis of somatostatin receptor subtype (SSTR1–5) gene expression levels in somatotropinomas and non-functioning pituitary adenomas

It is believed that the variable effectiveness of somatostatin analogs in post-surgical management of somatotropinomas and non-functioning pituitary adenomas (NFPA) may be due in part to variable expression of somatostatin receptor isoforms (SSTR1-5), within and between pituitary tumor types. Quantitative real-time RT-PCR was used to compare absolute mRNA copy numbers for all five SSTR isoforms in 23 somatotropinomas and 19 NFPA. Somatostatin receptor subtype 5 mRNA was present at the highest level in somatotropinomas, followed by SSTR2>SSTR3>>SSTR1>>>SSTR4. In contrast, SSTR3 mRNA was present at the highest level in NFPA, followed by SSTR2, while SSTR1, SSTR4, and SSTR5 transcripts were only detectable in select tumors. Among somatotropinomas, a positive correlation was found between SSTR2 mRNA levels and the percent decrease of GH (%GH) after 3 and 6 months of therapy with octreotide long acting repeatable (LAR) (r=0.51 and r=0.66; P=0.05 and P=0.008). Also the percent decrease of IGF-I (%IGF-I) after 3 months of octreotide LAR was negatively correlated with SSTR5 and %IGF-I after 6 months of octreotide LAR was positively correlated with SSTR2. The present report is a large series examining SSTR mRNA levels in somatotropinomas and NFPA. These initial findings suggest that detailed knowledge of the SSTR mRNA expression profile in somatotropinomas can help to predict the hormonal response to therapy with LAR. Also, it appears that SSTR3 in NFPA may be a potential target for SSTR3 preferential or universal ligands such as pasireotide.

Nitric oxide production by hepatocytes contributes to the inhibitory effect of endotoxin on insulin-like growth factor I gene expression

We tested whether endotoxin (lipopolysaccharide, LPS) inhibits IGF-I gene expression in hepatocytes and the possible role of Kupffer cells and nitric oxide (NO) in this effect. LPS decreased IGF-I mRNA in hepatocyte cultures and increased the nitrite + nitrate levels in the culture medium. Furthermore, there was a negative correlation between the IGF-I mRNA and the nitrite+nitrate levels. When hepatocytes were cocultured with Kupffer cells, the inhibitory effect of LPS on IGF-I mRNA was higher than in hepatocyte cultures, but the stimulatory effect on nitrite+nitrate was similar in both conditions. The exogenous NO donated by S-nitroso-n-acetyl-d,l-penicillamide also decreased the IGF-I gene expression in hepatocyte cultures. In addition, two specific inducible NO synthase (iNOS) inhibitors, l-N6-(1-iminoethyl)lysine (l-NIL) and aminoguanidine, prevented the effect of LPS on nitrite+nitrate levels and on IGF-I gene expression in hepatocyte cultures. These data indicate that iNOS-derived NO may cause downregulation of IGF-I gene expression in hepatocytes. However, in cocultures, the iNOS inhibitor l-NIL prevented the effect of LPS on nitrite+nitrate levels, but only attenuated the LPS-induced decrease in IGF-I gene expression. We conclude that in hepatocytes, LPS-induced decrease in IGF-I is mainly due to induction of iNOS, whereas in the presence of Kupffer cells LPS inhibits IGF-I through NO release and through other inhibitory pathways.

Inverse correlation between serum free IGF-I and IGFBP-3 levels and blood pressure in patients affected with type 1 diabetes

Background Even though the gene encoding for IGF-I is considered of most importance amongst blood pressure-regulating genes in mouse models, little and discordant data are available in literature for what concerns a possible relationship between blood pressure and serum free IGF-I values in humans. In addition, no information is available on type 1 diabetes patients. Aim: Our aim is to analyze the relationship between systolic and diastolic blood pressure and serum free IGF-I and IGFBP-3 levels in subjects suffering from type 1 diabetes. Results: A highly significant inverse correlation was observed between serum free IGF-I levels and both systolic and diastolic blood pressure in subjects affected with type 1 diabetes. Similar but less significant relationships were observed for IGFBP-3, whose levels were also significantly and directly correlated with those of free IGF-I. The correlation between systolic and diastolic blood pressures with free IGF-I and between systolic blood pressure and IGFBP-3 levels were confirmed after adjusting for age, gender, age at diagnosis, disease duration, familial history, HBA1c, and amount of insulin administered by multivariate logistic regression analysis. A decrease in free IGF-I and IGFBP-3 levels, along with increases in blood pressure, significantly influenced the presence of diabetic complications, confirming how these molecules may be considered as severity markers for patients with type 1 diabetes as well as risk factors for altered pressure control linked diseases.

Effect of Protein Intake on IGF-I System Responses to a 7-Day Exercise-Induced Negative Energy Balance

IGF-I is an anabolic peptide responsive to changes in nutritional and physiological status. Energy and/or protein restriction decreases circulating IGF-I and increases IGF-I clearance from the circulation. Whether decreases in IGF-I associated with restricted energy intake can be attenuated by the intake of additional dietary protein is unclear. PURPOSE: To evaluate the effect of two different levels of protein intake on IGF-I system responses during seven days of negative energy balance achieved by increases in physical activity. METHODS: Fourteen men (age 23±6 yr, VO2max 60±9 ml kg−1. min−1, 14±7% body fat) completed a 4 day (D1-D4) baseline period of controlled energy balance followed by a 1,000 kcal.d-−1 exercise-induced energy deficit for 7 days (D5-D11). Seven volunteers received an adequate protein diet (AP) containing 0.9 g·kg−1 body weight, and seven volunteers received a high protein diet (HP) containing 1.8 g·kg−1 body weight. Daily energy expenditure was assessed periodically using closed circuit spirometry. Morning fasting blood draws were performed on days 3, 5, 6, 11, and 12 and IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3 were analyzed by immunoassays. A repeated measures ANOVA (p < 0.05) was used for statistical analysis. RESULTS: Mean energy intake for the entire 11 day period was 3,683±737 kcal d−1, while energy expenditure was 3,712±732 kcal·d−1 during D1-D4 and increased to 4,691±743 kcal·d−1 during D5-D11. Both the AP (D3: 63.3±5.2 kg vs. D12: 61.8±5.0 kg) and HP (D3: 73.1±7.5 kg vs. D12: 71.8±7.7 kg) groups lost 2.4% of lean body mass. No interaction or group effects were observed for the IGF-I system. Time effects were observed for IGF-I, IGFBP-1, IGFBP-2, and IGFBP-3.TableCONCLUSIONS: Exercise-induced negative energy balance resulted in a hierarchy of temporal changes within the IGF-I system (IGFBP-1>IGFBP-2=IGF-I>IGFBP-3). With a moderate, exercise induced energy deficit of 1,000 kcal·d−1, increasing dietary protein (0.9 vs. 1.8 g.kg−1 body mass) beyond adequate levels does not appear to affect the loss of lean body mass or attenuate alterations in the IGF-I system.

Growth hormone replacement therapy in growth hormone deficient children and adults: Effects on hemochrome

Several lines of evidence have suggested a role of the GH/IGF-I axis in the regulation of hemochrome. Many studies have been carried out in GH deficient children and adults about this topic, reporting predominantly a positive effect of recombinant human GH (rhGH) on red series, with no action on serum leucocytes and platelets counts. The aim of this study was to assess the impact of GH deficiency (GHD) and of rhGH replacement on blood cells count in 17 pre-pubertal children with idiopathic isolated GHD (11 males and 6 females, aged 9.1+/-0.8 yr) and in 18 patients with adult-onset GHD (12 males and 6 females, aged 47.9+/-3.0 yr). Evaluation of absolute and SD score (SDS) values of red blood cells, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelets and white blood cells was performed at baseline and after 12 months of rhGH treatment (0.045+/-0.001 mg/kg bw/day and 4.2+/-0.5 microg/kg bw/day for children and adults, respectively). At baseline, all patients showed low IGF-I levels. Effectiveness of rhGH therapy was documented by significant increase in height SDS, height velocity and serum IGF-I levels in children. In adults, adequacy of rhGH was demonstrated by significant increase in serum IGF-I and significant decrease in body fat. At baseline, about 25% of patients (4 of 17 children and 4 of 18 adults) showed normochromic normocytic anemia, while the other indices were normal. In 7 of the 8 anemic patients, normal levels of hemoglobin were restored on rhGH, while no change in all the other indices was observed. In conclusion, rhGH therapy at physiological doses has no effect on erythropoiesis in GHD children and adults with normal blood cells count, while in patients with normochromic normocytic anemia rhGH is able to restore normal hemoglobin levels.

Relative Impact of Androgen and Estrogen Receptor Activation in the Effects of Androgens on Trabecular and Cortical Bone in Growing Male Mice: A Study in the Androgen Receptor Knockout Mouse Model

The relative importance of AR and ER activation has been studied in pubertal male AR knockout and WT mice after orchidectomy and androgen replacement therapy, either with or without an aromatase inhibitor. AR activation dominates normal trabecular bone development and cortical bone modeling in male mice. Moreover, optimal periosteal bone expansion is only observed in the presence of both AR and ER activation. Androgen receptor (AR)-mediated androgen action has traditionally been considered a key determinant of male skeletal growth. Increasing evidence, however, suggests that estrogens are also essential for normal male bone growth. Therefore, the relative importance of AR-mediated and estrogen receptor (ER)-mediated androgen action after aromatization remains to be clarified. Trabecular and cortical bone was studied in intact or orchidectomized pubertal AR knockout (ARKO) and male wildtype (WT) mice, with or without replacement therapy (3-8 weeks of age). Nonaromatizable (dihydrotestosterone [DHT]) and aromatizable (testosterone [T]) androgens and T plus an aromatase inhibitor (anastrazole) were administered to orchidectomized ARKO and WT mice. Trabecular and cortical bone modeling were evaluated by static and dynamic histomorphometry, respectively. AR inactivation or orchidectomy induced a similar degree of trabecular bone loss (-68% and -71%, respectively). Both DHT and T prevented orchidectomy-induced bone loss in WT mice but not in ARKO mice. Administration of an aromatase inhibitor did not affect T action on trabecular bone. AR inactivation and orchidectomy had similar negative effects on cortical thickness (-13% and -8%, respectively) and periosteal bone formation (-50% and -26%, respectively). In orchidectomized WT mice, both DHT and T were found to stimulate periosteal bone formation and, as a result, to increase cortical thickness. In contrast, the periosteum of ARKO mice remained unresponsive to either DHT or T. Interestingly, administration of an aromatase inhibitor partly reduced T action on periosteal bone formation in orchidectomized WT mice (-34% versus orchidectomized WT mice on T), but not in ARKO mice. This effect was associated with a significant decrease in serum IGF-I (-21% versus orchidectomized WT mice on T). These findings suggest a major role for AR activation in normal development of trabecular bone and periosteal bone growth in male mice. Moreover, optimal stimulation of periosteal growth is only obtained in the presence of both AR and ER activation.

Predictors of Tumor Shrinkage after Primary Therapy with Somatostatin Analogs in Acromegaly: A Prospective Study in 99 Patients

Primary treatment with depot octreotide and lanreotide induces tumor shrinkage in newly diagnosed patients with acromegaly. The objective of the study was to evaluate clinical predictors of tumor shrinkage. This was an analytical, observational, open, prospective study. The study included 99 patients: 13 with microadenoma and 86 with macroadenoma (25 enclosed, 32 extrasellar, 29 invasive). Age, gender, estimated disease duration, body mass index, GH and IGF-I levels, and tumor volume at diagnosis and after 12 months of treatment were measured. Percentage of GH, IGF-I, and tumor size changes from baseline were also analyzed. Tumor changes were scored as absent (+/- 0-25%), mild (+/- 25.1-50%), moderate (+/- 50.1-75%), or notable (75%). Sixty patients (60.6%) received depot octreotide im (20-30 mg every 28 d), and 39 patients (39.4%) received lanreotide im (60-90 mg every 28 d). Basal tumor volume and maximal tumor diameter correlated with age, disease duration, and GH levels. After 12 months, GH levels were controlled (</=2.5 microg/liter) in 57.6%, IGF-I levels in 45.5%, and both in 42.4%. Shrinkage was absent in 22 patients (22.2%), mild in 31 (31.1%), moderate in 30 (30.3%), and notable in 14 patients (14.1%). Two patients (not responding to treatment) had a mild tumor increase (by 34 and 31.2%, respectively). Basal and posttreatment tumor volumes were highly correlated (r = 0.79, P < 0.0001). At the multistep regression analysis, the percent IGF-I decrease (t = 2.6; P = 0.011) was the best predictor of posttreatment tumor volume, followed by patients' age (t = 2.1; P = 0.042) and percent GH decrease (t = 2.0; P = 0.044). Most patients with acromegaly (75.5%) had 25% or greater tumor shrinkage after 12 months of primary somatostatin analog therapy: significant increase of tumor mass occurred in only 2.1% of patients (uncontrolled during treatment). Best predictor of tumor shrinkage was posttreatment IGF-I.

Overexpression of IGF‐I transgene rescued growth retardation of weaver mutant mice

IGF-I is an important growth factor for postnatal growth in mammals. To evaluate the relative contribution of IGF-1 in postnatal growth during pathological states, we used weaver mutant mouse. We found that, compared with their control littermates, the body weights of both male and female weaver (wv) mice were significantly decreased soon after birth and remained low later in life, although male wv mice showed a trend to catch-up to normal growth. Organ weights of wv mice also showed a proportional decrease. To determine if the growth retardation in wv mice is related to IGF-I deficiency, we measured circulating IGF-I levels by radioimmunoassay and hepatic IGF-I mRNA levels by Northern blot. Out data showed a parallel decrease of IGF-I and body weights in female and D21 male wv mice. After male wv mice entered puberty, their IGF-I levels caught-up to that of their wildtype littermates as well as their body weight. These data suggested that IGF-I deficiency may be the cause of postnatal growth retardation in wv mutant mice. After crossbred wv mice with IGF-I transgenic mice, wv mice carrying the IGF-I transgene restored their body weights to those of their wildtype littermates. Interestingly, among other organs, only brain, spleen and female liver showed significant weight increases. In summary, we demonstrated that the decrease in circulating IGF-I contributed to postnatal growth retardation in wv mutant mice, which was confirmed by the nearly normal growth pattern of wv mice in the presence of IGF-I transgene. Overall, our results support the notion that IGF-I plays an important role in postnatal growth in normal as well as neurodegenerative states.

Apoptosis is reduced in the colonic mucosa of patients with acromegaly

Patients with acromegaly have an increased risk of developing colonic tumours; reduced apoptosis is considered a leading mechanism in tumorigenesis. GH and IGF-1 decrease apoptosis in several cell lines including human colonic adenocarcinoma, but it is unknown whether epithelial cells of colonic mucosa of patients with acromegaly have reduced apoptosis. The aim of the study was to evaluate the degree of apoptosis in a cross-sectional study, in biopsy samples of colonic mucosa obtained from patients with acromegaly. Eleven patients with active, untreated acromegaly (AcroUntr), 16 patients with acromegaly in remission (AcroRem) and 23 controls were enrolled in the study. Samples of colonic mucosa were obtained during colonoscopy; apoptosis was evaluated by either DNA fragmentation or terminal deoxynucleotidyl transferase assay. Apoptotic cells were 60.0 +/- 2.5% in samples of colonic mucosa of controls, 62.0 +/- 3.4% in those from patients with AcroRem (P = ns vs. controls), and 39.0 +/- 4.1% in those from patients with AcroUntr (P < 0.0001 vs. the other groups). Apoptosis was inversely related to serum IGF-I (r = 0.771, P < 0.001) or GH (r = 0.404, P = 0.05) levels and less to the estimated duration of disease (r = 0.384, P = 0.07). PPARgamma is considered to be a tumour suppressor gene the expression of which might be involved in colonic tumorigenesis. The expression of PPARgamma was lower in the colonic mucosa of patients with AcroUntr (2845 +/- 947 transcripts) than in that of controls (35 200 +/- 2450 transcripts) or AcroRem (29 547 +/- 3650 transcripts) (P < 0.005). The recovery of PPARgamma expression was associated with apoptosis in most cells. The lower degree of apoptosis in patients with AcroUntr was associated with a reduced expression of the antiapoptotic Bax protein. In conclusion, patients with AcroUntr have reduced apoptosis in colonic mucosa that is apparently reversed after acromegaly is cured. It is conceivable that reduced apoptosis may represent an early event in colonic tumorigenesis of patients with acromegaly.

Pamidronate Prevents Bone Loss and Decreased Bone Strength in Adult Female and Male Rats Fed an Isocaloric Low-Protein Diet

Isocaloric dietary protein deficiency is associated with decreased BMD and bone strength as well as depressed somatotroph and gonadotroph axis. Inhibition of increased bone resorption by the bisphosphonate pamidronate in rats fed an isocaloric low-protein diet fully prevents bone loss and alteration of bone strength. Isocaloric dietary protein deficiency is associated with decreased BMD and bone strength as well as depressed somatotroph and gonadotroph axis. This negative bone balance is the consequence of increased bone resorption and decreased bone formation. Whether inhibition of bone resorption could prevent low-protein diet-induced bone loss and alteration of biomechanics is not known. The effect of the bisphosphonate pamidronate was studied in 5.5-month-old female or 6-month-old male rats pair-fed a control (15% casein) or an isocaloric low-protein (2.5% casein) diet for 19 and 26 weeks, respectively. Pamidronate (0.6 mg/kg) was given subcutaneously 5 days/month for 4 months in female rats or for 5 months in male rats. BMD, microarchitecture, and bone strength were measured at the level of the proximal and midshaft tibia. Urinary deoxypyridinoline excretion, serum osteocalcin, and IGF-I were also measured. The increase in bone resorption in female rats (+100%) and in male rats (+33%) fed a low-protein diet was prevented by pamidronate treatment. The reduced osteocalcin levels observed in rats fed a low-protein diet were further decreased in both female (-34%) and male (-30%) rats treated with pamidronate. The bone turnover decrease induced by pamidronate prevented bone strength reduction, trabecular bone loss, microarchitecture, and BMD alterations induced by the isocaloric low-protein diet. Similar effects were observed at the level of the midshaft tibia. Significant decrease of plasma IGF-I was observed in rats fed a low-protein diet independently of the pamidronate treatment. In conclusion, inhibition of increased bone resorption in rats fed an isocaloric low-protein diet fully prevents bone loss and alteration of bone strength.

Interactive responses in gut immunity, and systemic and local changes in the insulin-like growth factor system in nursery pigs in response to Salmonella enterica serovar Typhimurium,

Abstract In recent years, we have sought to understand how disparate endocrine and immune signals converge in response to Salmonella enterica serovar Typhimurium (ST) to affect growth and the IGF system in the nursery pig. The enteric pathogen ST interacts with gut epithelium to rapidly upregulate the chemoattractive chemokines IL-8 and chemokine ligand-20, and to selectively affect toll-like receptors. Activation of these components of the innate immune system seems to confine the immune response largely to the gut mucosa and mesenteric lymph nodes, as evidenced by the lack of systemic elevation of proinflammatory cytokines. Despite the apparent restriction of proinflammatory signals to the gut-associated lymphoid tissue, ST provokes peripheral sequelae consistent with danger signaling, including the febrile response and activation of the adrenal axis. In addition, pigs undergoing ST-induced febrile responses experience a consistent period of inappetence that is independent of changes in leptin. Moreover, this period of decreased intake is invariably accompanied by an unmistakable decrease in serum IGF-I and, less consistently, with parallel reductions in circulating IGFBP-3. More recently, we characterized changes in expression of components of the IGF system within skeletal muscle of pigs undergoing ST-associated enteric disease. Despite the characteristic decrease in circulating IGF-I, the relative abundance of skeletal muscle IGF-I and IGFBP-3 mRNA was unaffected by ST. However, mRNA for IGFBP-5 was decreased in the skeletal muscle of ST-challenged pigs, suggesting a possible effect of the enteric disease on IGF availability. Taken together, oral challenge with ST engages elements of the mucosal innate immune system that seem to contain the spread of systemic proinflammatory cytokine signals. Even so, ST challenge is associated with parallel changes in both systemic and local IGF systems that may affect pig growth.

Effect of cattle disease on carcass traits

Abstract The movement to price an increasing percentage of fed cattle on carcass merit grids has renewed interest in the effect of cattle disease on carcass traits. There is growing evidence that disease has the potential to affect not only carcass weight, but also the quantity, location, and ratio of muscle, fat, and water. A clear mechanistic pathway linking disease to changes in carcass traits has not been made. Three theories considered in this review are 1) a change in metabolic signals, such as cytokines and cortisol, could affect carcass composition through modification of hypothalamic secretions of thyrotropin-releasing hormone, by inhibition of IGF-I and insulin actions on muscle and fat tissues, and by direct protein catabolism and lipolysis; 2) disease-induced anorexia causing a decrease in serum IGF-I and an increase in serum GH, which induces a change in the partitioning of nutrients for tissue deposition; and 3) an indirect (and reversible) effect of anorexia, whereby sick cattle are on feed for fewer effective days than pen mates that do not become sick. Other pathogen or immune-mediated responses to disease, as well as interactions among hormones and cytokines, may influence nutrient partitioning and body composition but have yet to be described. The use of carcass merit to determine the value of fed cattle provides an improved economic signal of the cost of cattle disease. The value of disease avoidance as well as rapid diagnosis and treatment of disease increases when cattle are sold on carcass merit basis because of the negative effects of disease on carcass traits.

Feeding-unrelated factors influencing the plasma leptin level in ruminants

The triglyceride content of lipid depots associated with the current feeding level is the primary determinant of leptin gene expression and the circulating leptin level. In laboratory rodents and primates the plasma leptin is influenced also by the age, gender and physiological status (puberty, pregnancy, lactation, postpartum period), and by the health condition such as sepsis due to Gram-negative (GN) bacteria. Some pathologic conditions with intensive cytokine release evoke an increase in plasma leptin, which is thought to depress the subsequent feed intake. However, the effect of these secondary factors may be species-dependent, with still unknown clinical relevance in ruminants. In our ovine and bovine models plasma leptin increased after castration and dexamethasone treatment, decreased after experimental administration of synthetic androgens in castrated rams, but remained unchanged throughout the ovarian cycle and after ovariectomy. The circulating leptin level increased temporarily during synthetic progestin (fluorogestone) treatment in ewes, but similar changes were not seen in progesterone-supplemented ewes and norgestomet-treated cows. In a second trial on dairy cows we wanted to study whether elevated plasma leptin levels are induced by experimental endotoxin mastitis, or by natural outbreak of GN mastitis and puerperal metritis. Experimental endotoxin mastitis resulted in some-hour elevation in cortisol and insulin, with a simultaneous decrease in IGF-I and thyroid hormones. In the first 14 days of lactation GN mastitis induced the same endocrine alterations as the experimental endotoxin challenge, but in natural cases these changes varied within a wider range, and were more protracted and robust. Cows with puerperal metritis had more obvious catabolic changes in the early weeks of lactation, than their healthy counterparts. However, both mastitis and puerperal metritis failed to increase the circulating leptin level, showing that in cows the plasma leptin is not responsible for the anorexia associated with these inflammatory diseases.

Effects of combined estrogen/testosterone therapy on bone and body composition in oophorectomized women

Objective. To evaluate the effect of adding testosterone undecanoate 40 mg daily to estrogen therapy on bone markers, bone mineral density and body composition in oophorectomized women.Methods. Fifty women, 45–60 years old, who had undergone a hysterectomy and bilateral salpingo-oophorectomy for benign disorders, were randomly assigned to oral treatment with testosterone undecanoate 40 mg plus estradiol valerate 2 mg daily or placebo plus estradiol valerate 2 mg daily. Twenty-four weeks later, cross-over was performed to the other treatment regimen. Forty-four women completed the study. Their serum concentrations of insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3, osteocalcin, carboxyterminal telopeptide aminoterminal (ICTP), of type I collagen propeptide of type I procollagen (PICP) and interleukin (IL)-1 receptor antagonist were measured at baseline and after 24 weeks of both treatments, as were also their body mass index (BMI) and blood pressure. Bone mineral density of the total body, spine and hip and total body fat, total lean body mass, trunk fat and trunk lean mass were determined by dual-energy X-ray absorptiometry measurements at baseline and after 24 weeks of both regimens.Results. During treatment, the addition of testosterone counteracted the decrease in IGF-I and PICP seen with estrogen therapy alone. Osteocalcin and ICTP were significantly reduced to the same extent by both therapies. No change ocurred in the IL-1 receptor antagonist. A significant increase was seen in total lean body mass with the estrogen/testosterone regimen, but the total fat mass, trunk lean or fat mass remained unchanged after 24 weeks of both treatments. No effect was detected on total, hip or spinal bone mineral density after treatment with estrogen alone or estrogen/testosterone. Likewise, BMI and blood pressure were unaffected.Conclusions. The addition of testosterone to oral estrogen might have positive effects on bone as suggested by the fact that it counteracted the decline in IGF-I and PICP levels. An anabolic effect on muscle was reflected by an increase in the total lean body mass. No adverse effects were noted on BMI, fat distribution or blood pressure during the 6-month treatment with oral testosterone undecanoate.

Osteoprotegerin and Bone Mineral Density in Hemodiafiltration Patients

A newly identified cytokine, osteoprotegerin (OPG) appears to be involved in the regulation of bone remodeling. In vitro studies suggest that OPG, a soluble member of the TNF receptor family of proteins, inhibits osteoclastogenesis by interrupting the intercellular signaling between osteoblastic stromal cells and osteoclast progenitors. As patients with chronic renal failure (CRF) often have renal osteodystrophy (ROD), we investigated the role of osteoprotegerin (OPG) in ROD, and investigated whether there was any relationship between serum OPG, intact parathyroid (PTH) (iPTH), vitamin D, and trabecular bone. Serum OPG combined with iPTH might be a useful tool in the noninvasive diagnosis of ROD, at least in cases in which the range of PTH values compromises reliable diagnosis. Thirty-six patients on maintenance hemodiafiltration (HDF) and a control group of 36 age and sex matched healthy subjects with no known metabolic bone disease were studied. The following assays were made on serum: iPTH, osteocalcin (BGP), bone alkaline phosphatase, 25(OH)-cholecalciferol, calcium, phosphate, OPG, IGF-1, estradiol, and free testosterone. Serum Ca+ +, P, B-ALP, BGP, IGF-1, iPTH, and OPG levels were significantly higher in HDF patients than in controls, while DXA measurements and quantitative ultrasound (QUS) parameters were significantly lower. On grouping patients according to their mean OPG levels, we observed significantly lower serum IGF-1, vitamin D3 concentrations, and lumbar spine and hip bone mineral density in the high OPG groups. No correlation was found between OPG and bone turnover markers, whereas a negative correlation was found between serum OPG and IGF-1 levels (r= − 0.64, p = 0.032). Serum iPTH concentrations were positively correlated with bone alkaline phosphatase (B-ALP) (r = 0.69, p = 0.038) and BGP (r = 0.92, p < 0.001). The findings made suggest that an increase in OPG levels may be a compensatory response to elevated bone loss. The low bone mineral density (BMD) levels found in the high OPG group might have been due to the significant decrease in serum IGF-1 and vitamin D3 observed. In conclusion, the findings made in the present study demonstrate that increased OPG in hemodiafiltration patients is only partly due to decreased renal clearance. As it may partly reflect a compensatory response to increased bone loss, this parameter might be helpful in the identification of patients with a marked reduction in trabecular BMD.

Age-Related Femoral Bone Loss in Men: Evidence for Hyperparathyroidism and Insulin-Like Growth Factor-1 Deficiency

We sought to determine the extent to which the age-related decline of femoral neck (FN) bone mineral density (BMD) might be explained by the age-related change of body composition and biological parameters and the mechanisms by which these factors might influence FN BMD in men. The relationships between FN BMD and anthropometric, hormonal, and biochemical parameters and bone turnover markers were studied in 82 men aged 25-86 years. Age was associated with a decline of FN BMD and osteocalcin (OC), bone alkaline phosphatase (bALP), and urinary C-telopeptide (p <.05). The significant relationship between FN BMD and OC (p <.01) did not remain after adjustment for age. With use of multiple linear regression and adjusting for all significant variables associated with FN BMD in univariate analysis (p <.01) (age, weight, lean and fat mass, height, and levels of dehydroepiandrosterone sulfate, insulin-like growth factor [IGF-1], testosterone, and parathyroid hormone [PTH]), age accounted for 29.5% of FN BMD variance. When age was excluded from the model, PTH accounted for 19.5% and IGF-1 for 10% of the FN BMD variance. Bone turnover markers were significantly intercorrelated, and levels of IGF-1 were positively associated with those of bALP and OC (p <.05). These results show that age is a strong predictor of FN BMD in men, resulting in a decline of bone remodeling, especially of bone formation. The results also show that, after taking into account anthropometric and other biological factors possibly involved in bone aging, the major part of the effect of age on bone is explained by the age-related increase of PTH and decrease of IGF-1 in men, suggesting that all measures taken to limit these age-related changes may be effective in the prevention of the age-related decline of FN BMD in men.

63. Re-Directed Herpes Simplex Virus Infection by a Soluble, Bi-Specific Adapter Protein for gD in Combination with Nectin-1 Blocking Agents

One of the landmarks of advanced liver cirrhosis is the decrease of serum IGF-I levels probably due to its diminished synthesis from liver parenchyma. Patients with liver cirrhosis have a number of systemic derangements related to the reduced levels of circulating IGF-I. The administration of recombinant IGF-I in physiological doses reverts these symptoms and partially, the cirrhosis state. Recombinant viruses expressing a therapeutic protein are being used as an alternative for recombinant protein administration. We decided to study the efficiency of an IGF-I expressing recombinant vector based on Simian Virus 40 virus (SV40) to prevent liver cirrhosis in a rat model. Recombinant SV40 vectors have several advantages for this purpose. They efficiently infect hepatocytes, they have a long-term expression and they are non-immunogenic. We have produced recombinant viruses expressing firefly luciferase (rSVLuc) and rat IGFI-I (rSVIGF-I). Expression, secretion and activity of IGF-I by rSVIGF has been demonstrated in vitro by RIA and AKT activation in 3T3 cells. rSVLuc mouse liver infection has been visualised with a CCD camera for more than six moths. Luciferase liver expression in rSVLuc infected mice increased during liver regeneration, after CCl4 administration and in response to IGF-I. Healthy male Wistar rats were mock infected or intraportaly infected with rSVLuc or rSVIGF-I. Cirrhosis was induced by CCl4 inhalations during 36 weeks. rSVIGF-I infected rats had normal levels of transaminases, bilirubin and IGF-I binding proteins (IGFBPs) and a significant increase in IGFBP3, regulated by IGF-I. Control groups, saline and rSVLUC treated rats, had altered serum parameters, a significant decrease in testis weight and an increase in liver fibrosis formation. Quantitative RT-PCR from liver samples showed an increase in collagen, Timp1a and MIP1a expression and a decrease in IGF-I, HGF and IGFBP3 expression in control groups vs rSVIGF-I infected rats. These results indicate that the rSVIGF-I vector could be an efficient alternative for prevention and treatment of liver cirrhosis development.

The Effects of IL-6 Infusion on the GH???&gt;IGF-I System in Humans

1567 Recent investigations have revealed that the early response to exercise leads to a growth-hormone resistant state rather than the expected anabolic activation of the growth hormone—> insulin like growth factor-I (GH—>IGF-I) axis. This phenomenon is believed to be a result of exercise induced stimulation of proinflammatory cytokines [such as interleukin-6 (IL-6)] known to directly inhibit anabolic activity of the GH—>IGF-1 axis. PURPOSE: To test the hypothesis that an IV infusion of IL-6 will induce changes in the GH—> IGF-I axis mediators similar to those observed in acute exercise in humans. METHODS: Twelve young healthy volunteers were randomly assigned to receive a low dose of recombinant human (rh)IL-6 (n = 6) or saline (n = 6) for 3 h. IL-6, GH, IGF-I (total and free), IGFBP-1&3, GHBP and Insulin were measured at baseline, 30 minutes, 1, 2 and 3 hours during the infusion and 1, 2 and 5 hours after the infusion was stopped. Significance level was set at p<0.05. RESULTS: Plasma IL-6 levels during rhIL-6 infusion were 140 pg/ml, corresponding to the levels obtained during very strenuous exercise. No significant effects on body temperature, mean arterial pressure, or heart rate were noted. During the rhIL-6 infusion an increase in GH levels was observed at 1 hour. In addition, a decrease in IGF-I was noted at 3 hours. Two hours post-rhIL-6 infusion an increase in IGFBP-1 was noted, irrespective to changes in insulin. No significant changes were observed for GHBP, IGFBP-3. CONCLUSIONS: These findings supports the hypothesis that physiological concentrations of IL-6, equivalent to those seen following strenuous exercise play a major role in exercise-induced changes in the GH—>IGF-I axis.