Effects Of Growth Hormone On Insulin Signal Transduction In The Rat Adipose Tissue Maintained In Vitro

Growth hormone treatment (GH) decreases adipose tissue sensitivity to insulin. However, the exact molecular mechanism(s) involved remains unclear. In the present study, we have evaluated the chronic effects of GH on adipose tissue explants cultured in a defined media. The objective was to determine the effects of GH treatment for 24 and 48 hours on the early steps of the insulin signal transduction, including IRS-3. The 24-hour culture media contained no hormones or 100 ng/ml GH. The 48-hour culture media contained insulin and dexamethasone supplemented with or without 100 ng/ml of GH. Results demonstrated a reduction in the cellular concentration of IRS-1 by around 30% when adipose tissue was chronically treated with growth hormone for either 24 or 48 hours. IRS-3 protein levels were also decreased by 15% after the 24-hour treatment, and by 27% after culture with GH for 48 hours in the presence of insulin and dexamethasone. PI 3-kinase concentrations were also reduced by GH in both experiments by around 25%. At the end of the 24-hour culture with GH adipose explants were stimulated with insulin in a short-term incubation, after which phosphorylation and association of the IRSs with PI 3-kinase were evaluated. After the insulin stimulus, the association of PI 3-kinase with IRS-1 and IRS-3 were decreased in explants chronically cultured with GH by 44 and 28%, respectively. After this short-term insulin stimulus, the IRS-3 phosphorylation was also lowered in GH-treated explants. The results with chronic cultures of adipose presented here are consistent with similar changes in IRS-1 and IRS-2 concentration and phosphorylation observed for liver and muscle after long-term (3-5 days) in vivo treatment with GH. The data suggest that chronic GH treatment alters the early steps of the insulin signal transduction pathway, and may explain the changes in adipose tissue sensitivity to insulin.302225238Etherton, T.D., Louveau, I., Somensen, M.T., Chaudhuri, S., Mechanisms by which somatotropin decreases adipose tissue growth (1993) Am J Clin Nutr, 58, pp. 287S-295SEtherton, T.D., Bauman, D.E., Biology of somatotropin in growth and lactation of domestic animals (1998) Physiol Rev, 78, pp. 745-761White, M.F., Kahn, C.R., The insulin signaling system (1994) J Biol Chem, 269, pp. 1-4Bauman, D.E., Vernon, R.G., Effects of exogenous bovine somatotropin on lactation (1993) Annu Rev Nutr, 13, pp. 437-461White, M.F., The insulin signalling system and the IRS proteins (1997) Diabetologia, 40, pp. S2-S17Lavan, B.E., Lane, S.W., Lienhard, G.E., The 60 kDa phosphotyrosine protein in insulin-treated adipocytes is a new member of the insulin receptor substrate family (1997) J Biol Chem, 272, pp. 11439-11443Sun, 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941-957Rice, K.M., Marilyn, A., Turnbow, M.A., Garner, C., Insulin stimulates the degradation of IRS-1 in 3T3-L1 adipocytes (1993) Biochem Biophys Res Commun, 190, pp. 961-967Tamemoto, H., Kadowaki, T., Tobe, K., Yagi, T., Sakura, H., Hayakawa, T., Terauchi, Y., Aizawa, S., Insulin resistance and growth retardation in mice lacking insulin receptor substrate-1 (1994) Nature, 372, pp. 182-186Araki, E., Lipes, M.A., Patti, M.-E., Bruning, J.C., Hagg III, B., Johnson, S.R., Kahn, C.R., Alternative pathway of insulin signalling in mice with targeted disruption of the IRS-1 gene (1994) Nature, 372, pp. 186-190Whiters, D.J., Gutierrez, J.S., Towery, H., Burks, D.J., Ren, J.-M., Previs, S., Zhang, Y., White, M.F., Disruption of IRS-2 causes type 2 diabetes in mice (1998) Nature, 391, pp. 900-904Smith, H.J., Pons, S., Patti, M.E., Burks, D.J., Yenush, L., Sun, X.J., Kahn, C.R., White, M.F., The 60kDa insulin receptor substrate functions like an IRS protein (pp60IRS-3) in adipose cells (1997) Biochemistry, 36, pp. 8304-8310Kaburagi, Y., Satoh, S., Tamemoto, H., Yamamoto-Honda, R., Tobe, K., Veki, K., Yamauchi, T., Kadowaki, Y., Role of the receptor substrate-1 and pp60 in the regulation of insulin-induced glucose transport and GLUT4 translocation in primary adipocytes (1997) J Biol Chem, 272, pp. 25839-25844Liu, S.C., Wang, Q., Lienhard, E.G., Keller, S.R., Insulin receptor substrate 3 is not essential for growth or glucose homeostasis (1999) J Biol Chem, 274, pp. 18093-18099Cheatham, B., Vlahos, C.J., Cheatham, L., Wang, L., Blenis, J., Kahn, C.R., Phosphatidylinositol 3-kinase activation is required for insulin stimulation of pp70 S6 kinase, DNA synthesis, and glucose transporter translocation (1994) Mol Cell Biol, 14, pp. 4902-4911Krook, A., Whitehead, J.P., Dobson, S.P., Griffiths, M.R., Ouwens, M., Baker, C., Hayward, A.C., O'Rahilly, S., Two naturally occurring insulin receptor tyrosine kinase domain mutants provide evidence that phosphoinositide 3-kinase activation alone is not sufficient for the mediation of insulin's metabolic and mitogenic effects (1997) J Biol Chem, 272 (48), pp. 30208-30214Yang, J., Clarke, J.F., Ester, C.J., Young, P.W., Kasuga, M., Holman, G.D., Phosphatidylinositol 3-kinase acts at an intracellular membrane site to enhance GLUT4 exocytosis in 3T3-L1 cells (1996) Biochem J, 313, pp. 125-131Zhou, L., Chen, H., Xu, P., Cong, L.N., Sciacchitano, S., Li, Y., Graham, D., Quon, M.J., Action of insulin receptor substrate-3 (IRS-3) and IRS-4 to stimulate translocation of GLUT4 in rat adipose cells (1999) Mol Endocrinol, 13, pp. 505-514Anai, M., Ono, H., Funaki, M., Fukushima, Y., Inukai, K., Ogihara, T., Sakoda, H., Asano, T., Different subcellular distribution and regulation of expression of insulin receptor substrate (IRS)-3 from those of IRS-1 and IRS-2 (1998) J Biol Chem, 273, pp. 29686-29692Razzini, G., Ingrosso, A., Brancaccio, A., Sciacchitano, S., Esposito, D.L., Falasca, M., Different subcellular localization and phosphoinositides binding of insulin receptor substrate protein pleckstrin homology domains (2000) Mol Endocrinol, 14, pp. 823-836Kabuta, T., Hakuno, F., Asano, T., Takahashi, Insulin receptor substrate-3 functions as transcriptional activator in the nucleus (2002) J Biol Chem, 277, pp. 6846-6851Laustsen, P.G., Michael, M.D., Crute, B.E., Cohen, S.E., Ueki, K., Kulkami, R.N., Keller, S.R., Kahn, R.C., Lipoatrophic diabetes in IRS1-/-/IRS3-/- double knockout mice (2002) Genes Dev, 16, pp. 3213-3222Quon, M.J., Butte, A.J., Zamowski, M.J., Yonezawa, K., Kasuga, M., Cushman, S.W., Taylor, S.I., Roles of 1-phosphatidylinositol 3-kinase and ras in regulating translocation of GLUT4 in transfected rat adipose cells (1995) Mol Cell Biol, 15, pp. 5403-5411Myers, M.G., White, M.F., Insulin signal transduction and the IRS proteins (1996) Annu Rev Pharmacol Toxicol, 36, pp. 615-658Pederson, T.M., Kramer, D.L., Rondine, C.M., Serine/Threonine phosphorylation of IRS1 triggers its degradation-possible regulation by tyrosine phosphorylation (2001) Diabetes, 50 (1), pp. 24-31Ranichandran, L.V., Esposito, D.L., Chen, J., Quon, J.M., Protein kinase C-zeta phosphorylates insulin receptor substrate 1 and impairs its ability to activate phosphatidylinositol 3-kinase in response to insulin (2001) J Biol Chem, 276, pp. 3543-3549Rui, L.Y., Aguirre, V., Kim, J.K., Shulman, G.I., Lee, A., Corbould, A., Dunaif, A., White, M.F., Insulin/IGF-I and TNF-alpha stimulate phosphorylation of IRS-1 at inhibitory Ser (307) via distinct pathways (2001) J Clin Invest, 107 (2), pp. 181-189Paz, K., Voliovitch, C., Hadari, Y.R., Roberts, C.T., LeRoith, D., Zick, Y., Interaction between the insulin receptor and its downstream effectors (1996) J Biol Chem, 271, pp. 6998-7003Paz, K., Hemi, R., LeRoith, R., Karasik, A., Elhanany, E., Kanety, H., Zick, Y., A molecular basis for insulin resistance. 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Microbiological risks of infant formulas

O objetivo desse trabalho foi discorrer sobre os principais perigos biológicos encontrados em fórmulas infantis a partir dos relatos da literatura, especialmente de registros de surtos. Este estudo é de cunho exploratório por meio de revisão bibliográfica, sendo utilizados como fontes de dados sites de busca científica. Dentre os principais micro-organismos causadores de doenças ligadas à ingestão de fórmulas infantis estão o Cronobacter sakazakii e a Salmonella enterica, porém outras bactérias, como Clostridium botulinum, Klebsiella pneumoniae, Staphylococcus aureus e Bacillus cereus, podem ser responsáveis por contaminações destas fórmulas. Visto que lactentes apresentam os sistemas imunológico e metabólico ainda em desenvolvimento, estes representam um público mais vulnerável a contaminantes, fazendo-se fundamental o oferecimento de alimentos seguros desde o processamento na indústria até a administração nas residências e unidades hospitalares22The objective of this paper was discuss the main biological hazards found in infant formulas from literature reports, especially from outbreak records. This study has an exploratory nature through a bibliographical review where scientific search sites were used as data sources. Cronobacter sakazakii and Salmonella enterica are among the main microorganisms that cause diseases associated with infant formulas ingestion; however, Clostridium botulinum, Klebsiella pneumoniae, Staphylococcus aureus and Bacillus cereus can also be responsible for infant formulas contaminations. Since infants have the immune and metabolic systems still in development, they represent a more vulnerable group to contaminants, making it essential to offer safe foods from processing in industry to administration in homes and hospital unit

A high-fructose diet induces insulin resistance but not blood pressure changes in normotensive rats

Rats fed a high-fructose diet represent an animal model for insulin resistance and hypertension. We recently showed that a high-fructose diet containing vegetable oil but a normal sodium/potassium ratio induced mild insulin resistance with decreased insulin receptor substrate-1 tyrosine phosphorylation in the liver and muscle of normal rats. In the present study, we examined the mean blood pressure, serum lipid levels and insulin sensitivity by estimating in vivo insulin activity using the 15-min intravenous insulin tolerance test (ITT, 0.5 ml of 6 µg insulin, iv) followed by calculation of the rate constant for plasma glucose disappearance (Kitt) in male Wistar-Hannover rats (110-130 g) randomly divided into four diet groups: control, 1:3 sodium/potassium ratio (R Na:K) diet (C 1:3 R Na:K); control, 1:1 sodium/potassium ratio diet (CNa 1:1 R Na:K); high-fructose, 1:3 sodium/potassium ratio diet (F 1:3 R Na:K), and high-fructose, 1:1 sodium/potassium ratio diet (FNa 1:1 R Na:K) for 28 days. The change in R Na:K for the control and high-fructose diets had no effect on insulin sensitivity measured by ITT. In contrast, the 1:1 R Na:K increased blood pressure in rats receiving the control and high-fructose diets from 117 ± 3 and 118 ± 3 mmHg to 141 ± 4 and 132 ± 4 mmHg (P<0.05), respectively. Triacylglycerol levels were higher in both groups treated with a high-fructose diet when compared to controls (C 1:3 R Na:K: 1.2 ± 0.1 mmol/l vs F 1:3 R Na:K: 2.3 ± 0.4 mmol/l and CNa 1:1 R Na:K: 1.2 ± 0.2 mmol/l vs FNa 1:1 R Na:K: 2.6 ± 0.4 mmol/l, P<0.05). These data suggest that fructose alone does not induce hyperinsulinemia or hypertension in rats fed a normal R Na:K diet, whereas an elevation of sodium in the diet may contribute to the elevated blood pressure in this animal model

Phenolic Composition, Antibacterial And Antioxidant Activities Of Brazilian Red Propolis [composição Fenólica, Atividade Antibacteriana E Antioxidante Da Própolis Vermelha Brasileira]

Propolis is a resinous hive product collected by honeybees from various plant sources. It has a complex chemical composition, constituted by various phenolic compounds. Extracts of increasing polarity (n-hexane, chloroform, and ethanol) were obtained from a sample of red propolis from the state of Alagoas. Assays were carried out for determination of contents of phenolics, along with antibacterial and antioxidant activities. The EEP, fractions and sub-fractions showed strong biological activities and were related with phenolic the content compounds contents. 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A high-fructose diet induces insulin resistance but not blood pressure changes in normotensive rats

FAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES – COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORRats fed a high-fructose diet represent an animal model for insulin resistance and hypertension. We recently showed that a high-fructose diet containing vegetable oil but a normal sodium/potassium ratio induced mild insulin resistance with decreased insulin receptor substrate-1 tyrosine phosphorylation in the liver and muscle of normal rats. In the present study, we examined the mean blood pressure, serum lipid levels and insulin sensitivity by estimating in vivo insulin activity using the 15-min intravenous insulin tolerance test (ITT, 0.5 ml of 6 µg insulin, iv) followed by calculation of the rate constant for plasma glucose disappearance (Kitt) in male Wistar-Hannover rats (110-130 g) randomly divided into four diet groups: control, 1:3 sodium/potassium ratio (R Na:K) diet (C 1:3 R Na:K); control, 1:1 sodium/potassium ratio diet (CNa 1:1 R Na:K); high-fructose, 1:3 sodium/potassium ratio diet (F 1:3 R Na:K), and high-fructose, 1:1 sodium/potassium ratio diet (FNa 1:1 R Na:K) for 28 days. The change in R Na:K for the control and high-fructose diets had no effect on insulin sensitivity measured by ITT. In contrast, the 1:1 R Na:K increased blood pressure in rats receiving the control and high-fructose diets from 117 ± 3 and 118 ± 3 mmHg to 141 ± 4 and 132 ± 4 mmHg (P<0.05), respectively. Triacylglycerol levels were higher in both groups treated with a high-fructose diet when compared to controls (C 1:3 R Na:K: 1.2 ± 0.1 mmol/l vs F 1:3 R Na:K: 2.3 ± 0.4 mmol/l and CNa 1:1 R Na:K: 1.2 ± 0.2 mmol/l vs FNa 1:1 R Na:K: 2.6 ± 0.4 mmol/l, P<0.05). These data suggest that fructose alone does not induce hyperinsulinemia or hypertension in rats fed a normal R Na:K diet, whereas an elevation of sodium in the diet may contribute to the elevated blood pressure in this animal model.Rats fed a high-fructose diet represent an animal model for insulin resistance and hypertension. We recently showed that a high-fructose diet containing vegetable oil but a normal sodium/potassium ratio induced mild insulin resistance with decreased insulin receptor substrate-1 tyrosine phosphorylation in the liver and muscle of normal rats. In the present study, we examined the mean blood pressure, serum lipid levels and insulin sensitivity by estimating in vivo insulin activity using the 15-min intravenous insulin tolerance test (ITT, 0.5 ml of 6 µg insulin, iv) followed by calculation of the rate constant for plasma glucose disappearance (Kitt) in male Wistar-Hannover rats (110-130 g) randomly divided into four diet groups: control, 1:3 sodium/potassium ratio (R Na:K) diet (C 1:3 R Na:K)control, 1:1 sodium/potassium ratio diet (CNa 1:1 R Na:K)high-fructose, 1:3 sodium/potassium ratio diet (F 1:3 R Na:K), and high-fructose, 1:1 sodium/potassium ratio diet (FNa 1:1 R Na:K) for 28 days. The change in R Na:K for the control and high-fructose diets had no effect on insulin sensitivity measured by ITT. In contrast, the 1:1 R Na:K increased blood pressure in rats receiving the control and high-fructose diets from 117 ± 3 and 118 ± 3 mmHg to 141 ± 4 and 132 ± 4 mmHg (P<0.05), respectively. Triacylglycerol levels were higher in both groups treated with a high-fructose diet when compared to controls (C 1:3 R Na:K: 1.2 ± 0.1 mmol/l vs F 1:3 R Na:K: 2.3 ± 0.4 mmol/l and CNa 1:1 R Na:K: 1.2 ± 0.2 mmol/l vs FNa 1:1 R Na:K: 2.6 ± 0.4 mmol/l, P<0.05). These data suggest that fructose alone does not induce hyperinsulinemia or hypertension in rats fed a normal R Na:K diet, whereas an elevation of sodium in the diet may contribute to the elevated blood pressure in this animal model34911551160FAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES – COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP – FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ – CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES – COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIO

Regulation of insulin signalling by hyperinsulinaemia: Role of IRS-1/2 serine phosphorylation and the mTOR/p70 S6K pathway

Aim/hypothesis: Several epidemiological studies have suggested an association between chronic hyperinsulinaemia and insulin resistance. However, the causality of this relationship remains uncertain. Methods: We performed chronic hyperinsulinaemic-euglycaemic clamps and delineated, by western blotting, an IR/IRSs/phosphatidylinositol 3-kinase(PI[3]K)/Akt pathway in insulin-responsive tissues of hyperinsulinaemic rats. IRS-1/2 serine phosphorylation, IR/protein tyrosine phosphatase 1B (PTP1B) association, and mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70 S6K) activity were also evaluated in the liver, skeletal muscle and white adipose tissue of hyperinsulinaemic animals. Results: We found that chronic hyperinsulinaemic rats have insulin resistance and reduced levels of glycogen content in liver and muscle. In addition, we demonstrated an impairment of the insulin-induced IR/IRSs/PI(3)K/Akt pathway in liver and muscle of chronic hyperinsulinaemic rats that parallels increases in IRS1/2 serine phosphorylation, IR/PTP1B association and mTOR activity. Despite a higher association of IR/PTP1B, there was an increase in white adipose tissue of chronic hyperinsulinaemic rats in IRS-1/2 protein levels, tyrosine phosphorylation and IRSs/PI(3)K association, which led to an increase in basal Akt serine phosphorylation. No increases in IRS-1/2 serine phosphorylation and mTOR activity were observed in white adipose tissue. Rapamycin reversed the insulin resistance and the changes induced by hyperinsulinaemia in the three tissues studied. Conclusions/interpretation: Our data provide evidence that chronic hyperinsulinaemia itself, imposed on normal rats, appears to have a dual effect, stimulating insulin signalling in white adipose tissue, whilst decreasing it in liver and muscle. The underlying mechanism of these differential effects may be related to the ability of hyperinsulinaemia to increase mTOR/p70 S6K pathway activity and IRS-1/2 serine phosphorylation in a tissue-specific fashion. In addition, we demonstrated that inhibition of the mTOR pathway with rapamycin can prevent insulin resistance caused by chronic hyperinsulinaemia in liver and muscle. These findings support the hypothesis that defective and tissue-selective insulin action contributes to the insulin resistance observed in hyperinsulinaemic states. \ua9 Springer-Verlag 2005