Plasma progesterone concentration in beef heifers receiving exogenous glucose, insulin, or bovine somatotropin

Three experiments were conducted to evaluate plasma concentrations of glucose, insulin, IGF-I, and progesterone (P4) in pubertal beef heifers receiving exogenous glucose, insulin, or sometribove zinc. All heifers used had no luteal P4 synthesis but received a controlled internal drug-releasing device containing 1.38 g of P4 to estimate treatment effects on hepatic P4 degradation. In Exp. 1, 8 pubertal, nulliparous Angus x Hereford heifers (initial BW = 442 +/- 14 kg; initial age = 656 +/- 7 d) were randomly assigned to receive, in a crossover design containing 2 periods of 10 h, intravenous (i.v.) infusions (10 mL) of insulin (1 mu g/kg of BW; INS) or saline (0.9%; SAL). Treatments were administered via jugular venipuncture in 7 applications (0.15 mu g insulin/kg BW per application) 45 min apart (from 0 to 270 min). Blood samples were collected immediately before each infusion as well as at -120, -60, 330, 390, and 450 min relative to the first infusion. Heifers receiving INS had greater (P < 0.01) plasma insulin, reduced (P <= 0.04) plasma glucose and IGF-I, and similar (P = 0.62) plasma P4 concentrations compared with SAL heifers. In Exp. 2, the same heifers were assigned to receive, in a similar experimental design as Exp. 1, i.v. infusions (10 mL) of 1) insulin (1 mu g/kg BW) and glucose (0.5 g/kg BW; INS+G) or 2) SAL. Heifers receiving INS+G had greater (P <= 0.02) plasma insulin, glucose, and P4 but reduced (P = 0.01) plasma IGF-I concentrations compared with SAL heifers. In Exp. 3, the same heifers were assigned to receive, in a crossover design containing 2 periods of 14 d, subcutaneous (s.c.) injections of 1) 250 mg of sometribove zinc (BST) or 2) SAL. Blood samples were collected 3 h apart (0900, 1200, 1500, and 1800 h) from heifers on d 6, 8, and 10 relative to treatment administration (d 1). Heifers receiving BST had greater (P < 0.01) plasma glucose and IGF-I and similar (P >= 0.67) plasma insulin and P4 concentrations compared with SAL heifers. Results from this series of experiments suggested that concurrent increases in glucose and insulin are required to reduce hepatic catabolism and increase plasma concentrations of P4 in bovine females.

Growth hormone and heart failure: Oxidative stress and energetic metabolism in rats

Several evidences point for beneficial effects of growth hormone (GH) in heart failure (HF). Taking into account that HF is related with changes in myocardial oxidative stress and in energy generation from metabolic pathways, it is important to clarify whether GH increase or decrease myocardial oxidative stress and what is its effect on energetic metabolism in HF condition. Thus, this study investigated the effects of two different doses of GH on energetic metabolism and oxidative stress in myocardium of rats with HF. Male Wistar rats (n = 25) were submitted to aortic stenosis (AS). The HF was evidenced by tachypnea and echocardiographic criteria around 28 weeks of AS. The rats were then randomly divided into three groups: (HF) with HF, treated with saline (0.9% NaCl); (HF-GHI), treated with 1 mk/kg/day recombinant human growth hormone (rhGH), and (HF-GH2) treated with 2 mg/kg/day rhGH. GH was injected, subcutaneously, daily for 2 weeks. A control group (sham; n = 12), with the same age of the others rats was evaluated to confirm data for AS. HF had lower IGF-I (insulin-like growth factor-I) than sham-operated rats, and both GH treatments normalized IGF-I level. HF-GH1 animals had lower lipid hydroperoxide (LH), LH/total antioxidant substances (TAS) and glutathione-reductase than HF. Glutathione peroxidase (GSH-Px), hydroxyacyl coenzyme-A dehydrogenase, lactate dehydrogenase(LDH) were higher in HF-GH1 than in HF. HF-GH2 compared with HF, had increased LH/TAS ratio, as well as decreased oxidized glutathione and LDH activity. Comparing the two GH doses, GSH-Px, superoxide dismutase and LDH were lower in HF-GH2 than in HF-GHI. In conclusion, GH effects were dose-dependent and both tested doses did not aggravate the heart dysfunction. The higher GH dose, 2 mg/kg exerted detrimental effects related to energy metabolism and oxidative stress. The lower dose, 1 mg/kg GH exerted beneficial effects enhancing antioxidant defences, reducing oxidative stress and improving energy generation in myocardium of rats with heart failure. (c) 2007 Elsevier Ltd. All rights reserved.

Effects of short-term physical training on the liver IGF-I in diabetic rats

To investigate the influence of short-term physical training on IGF-I concentrations in diabetic rats, male wistar rats were distributed into four groups: sedentary control, trained control, sedentary diabetic and trained diabetic. Diabetes was induced by Alloxan (32 mg/kg b.w.) and training protocol consisted of swimming 1 h/day, 5 days/week, during 4 weeks, supporting 5% b.w. At the end of this period, rats were sacrificed and blood was collected for determinations of serum glucose, insulin, albumin, IGF-I and hematocrit. Liver samples were used to determine glycogen, protein, DNA and IGF-I concentrations. Diabetes reduced insulin and IGF-I concentrations in blood and liver protein, ratio protein/DNA and IGF-I concentrations in liver and increased glycemia. Physical training reduced serum glucose and recovered hepatic glycogen stores in diabetic rats and reduced serum and liver IGF-I concentrations. In conclusion, short-term physical training improved the metabolic conditions of diabetic rats, despite of impairing liver and blood IGF-I concentrations.

Growth factors and glucose homeostasis in diabetic rats: effects of exercise training

To investigate the alterations of glucose homeostasis and variables of the insulin-like growth factor-I (IGF- 1) growth system in sedentary and trained diabetic (TD) rats, Wistar rats were divided into sedentary control (SC), trained control (TC), sedentary diabetic (SD), and TD groups. Diabetes was induced by Alloxan (35 mg kg(-1) b.w.). Training program consisted of swimming 5 days week(-1), 1 h day(-1), during 8 weeks. Rats were sacrificed and blood was collected for determinations of serum glucose, insulin, growth hormone (GH), IGF-1, and IGF binding protein-3(IGFBP-3). Muscle and liver were removed to evaluate glycogen content. Cerebellum was extracted to determinate IGF-1 content. Diabetes decreased serum GH, IGF-1, IGFBP-3, liver glycogen, and cerebellum IGF-1 peptide content in baseline condition. Physical training recovered liver glycogen and increased serum and cerebellum IGF-1 peptide in diabetic rats. Physical training induces important metabolic and hormonal alterations that are associated with an improvement in glucose homeostasis and serum and cerebellum IGF-1 concentrations. Copyright (C) 2009 John Wiley & Sons, Ltd.

Long-term physical training increases liver IGF-I in diabetic rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do fator de crescimento semelhante à insulina I (IGF-I) adicionado ao meio fluido sintético de tuba uterina (SOF) sobre a maturação in vitro de oócitos caninos (Canis familiaris)

The follicular growth and oocyte maturation knowledge are very important to the development and improvement of new biotechnologies such as in vitro fertilization and somatic cell nuclear transfer. In order to the necessity of clarify the basic mechanisms related to canine oocyte maturation, this investigation focuses on the evaluation of the effect of insulin-like growth factor-i (IGF-I), added to synthetic oviductal fluid medium (SOF) on the in vitro maturation of domestic dog oocytes. Thirty-seven bitches undergoing ovariohysterectomy for castration or due to pathological conditions of the uterus were selected as oocytes' donors (n=875). The oocytes were allocated in the following groups: MO (stained in the collection's time), Control (72h in SOF) and Experimental (72h in SOF plus 100 ng IGF-I). After 72 hours of maturation the oocytes' nuclear status were assessed by Hoechst 33342 dye. The best results in terms of oocyte harvest were observed in those juvenile donors,, females in estrus, nuliparous and pure breeds. No significant differences were observed between treatments control (SOF) or experimental (IGF-I).

Metabolic disturbances in male broilers of different strains. 2. Relationship between the thyroid and somatotropic axes with growth rate and mortality

Seven male broiler strains (Arbor Acres, Avian Farms, Cobb-500, Hubbard-Peterson, ISA, Naked Neck, and Ross) were compared for their growth rate, feed efficiency, and mortality due to sudden death and ascites. In addition, weekly plasma levels of thyroid hormones [3,3′,5-triiodothyronine (T3) thyroxine (T4), T3: T4 ratio, growth hormone (GH), and insulin-like growth factor-I (IGF-I)] were determined. The highly productive, commercial strains were very similar in their endocrine profiles but differed markedly from the Naked Neck chickens. Naked Neck chickens were characterized by higher plasma T3 and lower T4 levels at similar ages as well as when compared on the same body weight basis. The present findings support the hypothesis that the slightly hypothyroid state of high productive broilers renders them more sensitive to metabolic disorders. Naked Neck chickens also had higher plasma GH levels than those of their age-matched commercial broilers. The coefficient of variation for GH was highest for Naked Neck chickens, which is indicative for an amplified GH burst amplitude. It may be stated that changes in plasma thyroid hormone concentration in indirect response to selection for low feed conversion and fast growth may be causatively linked to susceptibility for metabolic disturbances such as sudden death syndrome and ascites.

Application of a serum/protein-free medium for the growth of mammalian cell lines and high level production of classical, variant and very virulent strain of infectious bursal disease virus (IBDV)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Myogenin, MyoD and IGF-I regulate muscle mass but not fiber-type conversion during resistance training in rats

The purpose of this study was to test the hypothesis that skeletal muscle adaptations induced by long-term resistance training (RT) are associated with increased myogenic regulatory factors (MRF) and insulin-like growth factor-I (IGF-I) mRNA expression in rats skeletal muscle. Male Wistar rats were divided into 4 groups: 8-week control (C8), 8-week trained (T8), 12-week control (C12) and 12-week trained (T12). Trained rats were submitted to a progressive RT program (4 sets of 10-12 repetitions at 65-75% of the 1RM, 3 day/week), using a squat-training apparatus with electric stimulation. Muscle hypertrophy was determined by measurement of muscle fiber cross-sectional area (CSA) of the muscle fibers, and myogenin, MyoD and IGF-I mRNA expression were measured by RT-qPCR. A hypertrophic stabilization occurred between 8 and 12 weeks of RT (control-relative % area increase, T8: 29% vs. T12: 35%; p>0.05) and was accompanied by the stabilization of myogenin (control-relative % increase, T8: 44.8% vs. T12: 37.7%, p>0.05) and MyoD (control-relative % increase, T8: 22.9% vs. T12: 22.3%, p>0.05) mRNA expression and the return of IGF-I mRNA levels to the baseline (control-relative % increase, T8: 30.1% vs. T12: 1.5%, p<0.05). Moreover, there were significant positive correlations between the muscle fiber CSA and mRNA expression for MyoD (r=0.85, p=0.0001), myogenin (r=0.87, p=0.0001), and IGF-I (r=0.88, p=0.0001). The significant (p<0.05) increase in myogenin, MyoD and IGF-I mRNA expression after 8 weeks was not associated with changes in the fiber-type frequency. In addition, there was a type IIX/D-to-IIA fiber conversion at 12 weeks, even with the stabilization of MyoD and myogenin expression and the return of IGF-I levels to baseline. These results indicate a possible interaction between MRFs and IGF-I in the control of muscle hypertrophy during long-term RT and suggest that these factors are involved more in the regulation of muscle mass than in fiber-type conversion. © Georg Thieme Verlag KG Stuttgart · New York.

Effects of bovine somatotropin administration on growth, physiological, and reproductive responses of replacement beef heifers

This experiment compared growth, body composition, plasma IGF-I and leptin, and reproductive development of beef heifers receiving or not recombinant bovine ST (BST) beginning after weaning until the first breeding season. Fifty Angus × Hereford heifers (initial BW = 219 ± 2 kg; initial age = 208 ± 2 d), weaned at approximately 6 mo of age, were assigned to the experiment (d 0 to 210). On d 0, heifers were ranked by initial BW and age and assigned to 1) treatment with BST or 2) saline control. Heifers assigned to the BST treatment received subcutaneous (s.c.) injections containing 250 mg of sometribove zinc whereas control heifers received a 5-mL s.c. injection of 0.9% saline every 14 d. Treatments were initiated on d 14 and last administered on d 196. Heifers were maintained on separate pastures harvested for hay the previous summer according to treatment and received grass and alfalfa hay at a rate to provide a daily amount of 7.0 and 1.0 kg of DM per heifer, respectively. Heifer shrunk BW was collected on d 1 and 211 for heifer ADG calculation. Blood samples were collected weekly from d 0 to 210 for determination of plasma progesterone to estimate puberty attainment as well as plasma concentrations of IGF-I and leptin in selected samples. On d 0, 63, 133, and 189, heifers were evaluated for intramuscular marbling, LM depth, and backfat thickness via real-time ultrasonography. No treatment effects were detected (P = 0.27) for heifer ADG (0.49 vs. 0.51 kg/d for control and BST heifers, respectively; SEM = 0.02). Mean backfat thickness was lesser (P < 0.01) in BST heifers compared with control cohorts (3.56 vs. 3.92 mm, respectively; SEM = 0.08). Heifers receiving BST had greater plasma IGF-I concentrations compared with control cohorts 7 d after treatment administration (treatment × day interaction; P < 0.01). Mean plasma leptin concentrations were lesser (P = 0.05) in BST heifers compared with control cohorts (1.82 vs. 2.03 ng/mL, respectively; SEM = 0.07). Onset of puberty was hastened in BST heifers compared with control cohorts (treatment x day interaction; P = 0.04). In summary, a greater proportion of BST heifers reached puberty during the experiment compared with control cohorts, despite lesser plasma leptin concentrations, backfat thickness, and similar ADG. Hence, circulating IGF-I was positively associated with hastened puberty attainment independently of growth rate, circulating leptin concentrations, and body fat content of replacement beef heifers. © 2013 American Society of Animal Science. All rights reserved.

Efeito do fator de crescimento IGF-I sobre a maturação in vitro de oócitos caninos (Canis familiaris): avaliação da maturação nuclear e citoplasmática

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O efeito do fator de crescimento semelhante à insulina-I em oócitos de vacas Bos indicus e Bos taurus expostas ao estresse térmico un vitro

Pós-graduação em Ciências Biológicas (Farmacologia) - IBB

Fibronectin glycation increases IGF-I induced proliferation of human aortic smooth muscle cells

The advanced glycation end products, namely AGEs, contribute to long-termed complications of diabetes mellitus, including macroangiopathy, where smooth muscle cells (SMC) proliferation stimulated by platelet-derived growth factor (PDGF) isoforms and insulin-like growth factor-I (IGF-I) plays an important role. The objective of the present study was to investigate the effect of an AGE-modified extracellular matrix protein on IGF-I induced SMC proliferation and on the IGF-I-IGF binding protein 4 (IGFBP-4) axis under basal conditions and after stimulation with PDGF-BB. IGF-I resulted in significantly higher thymidine incorporation in SMC seeded on AGE-modified fibronectin (AGE-FN) in comparison to cells seeded on fibronectin (FN). This augmented proliferation could not be accounted for by increased expression of IGF-IR, by decreased secretion of IGFBP-4, a binding protein that inhibits IGF-I mitogenic effects or by increased IGF-IR autophosphorylation. PDGF-BB did not modulate IGF-IR and IGFBP-4 mRNA expression in any of the substrata, however, this growth factor elicited opposite effects on the IGFBP-4 content in the conditioned media, increasing it in cells plated on FN and diminishing it in cells plated on AGE-FN. These findings suggest that one mechanism by which AGE-modified proteins is involved in the pathogenesis of diabetes-associated atherosclerosis might be by increasing SMC susceptibility to IGF-I mitogenic effects.

Differential expression of IGF-I mRNA and peptide in the male and female gonad during early development of a bony fish, the tilapia Oreochromis niloticus

Insulin-like growth factor I (IGF-I) plays a key role in the complex system that regulates bony fish growth, differentiation, and reproduction. The major source of circulating IGF-I is liver, but IGF-I-producing cells also occur in other organs, including the gonads. Because no data are available on the potential production sites of IGF-I in gonad development, developmental stages of monosex breedings of male and female tilapia from 0 day postfertilization (DPF) to 90 DPF were investigated for the production sites of IGF-I at the peptide (immunohistochemistry) and mRNA (in situ hybridization) level. IGF-I mRNA first appeared in somatic cells of the male and female gonad anlage at 7 DPF followed by IGF-I peptide around 9-10 DPF. Gonad anlagen were detected from 7 DPF. Starting at 7 DPF, IGF-I peptide but no IGF-I mRNA was observed in male and female primordial germ cells (PGCs) provided that IGF-I mRNA was not under the detection level, this observation may suggest that IGF-I originates from the somatic cells and is transferred to the PGCs or is of maternal origin. While in female germ cells IGF-I mRNA and peptide appeared at 29 DPF, in male germ cells both were detected as late as at 51-53 DPF. It is assumed that the production of IGF-I in the germ cells is linked to the onset of meiosis that in tilapia ovary starts at around 28 DPF and in testes at around 52-53 DPF. In adult testis, IGF-I mRNA and peptide occurred in the majority of spermatogonia and spermatocytes as well as in Leydig cells, the latter indicating a role of IGF-I in the synthesis of male sex steroids. In adult ovary, IGF-I mRNA and IGF-I peptide were always present in small and previtellogenic oocytes but only IGF-I peptide infrequently occurred in oocytes at the later stages. IGF-I expression appeared in numerous granulosa and some theca cells of follicles at the lipid stage and persisted in follicles with mature oocytes. The results suggest a crucial role of local IGF-I in the formation, differentiation and function of tilapia gonads.

Insulin-like growth factors (IGFs), IGF binding proteins, and other endocrine factors in milk: role in the newborn

The role of colostrum and milk in the neonate has been chiefly recognized as a comprehensive nutrient foodstuff. In addition, the provision of colostrum-the first milk-for early immune capacity has been well documented for several species. Colostrum is additionally a rich and concentrated source of various factors that demonstrate biological activity in vitro. Three hypotheses have been proposed for the phenotypic function of these secreted bioactive components: (1) only mammary disposal, (2) mammary cell regulation, and (3) neonatal function [gastrointestinal tract (GIT) or systemic]. Traditionally, it was assumed that the development of the GIT is preprogrammed and not influenced by events occurring in the intestinal lumen. However, a large volume of research has demonstrated that colostrum (or milk-borne) bioactive components can basically contribute to the regulation of GIT growth and differentiation, while their role in postnatal development at physiological concentrations has remained elusive. Much of our current understanding is derived from cell culture and laboratory animals, but experimentation with agriculturally important species is taking place. This chapter provides an overview of work conducted primarily in neonatal calves and secondarily in other species on the effects on neonates of selected peptide endocrine factors (hormones, growth factors, in part cytokines) in colostrum. The primary focus will be on insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) and other bioactive peptides, but new interest and concern about steroids (especially estrogens) in milk are considered as well.