- Email: [email protected]
The GH response to ghrelin in humans is impaired in conditions of hyper- and hypothyroidism
Abstracts / Frontiers in Neuroendocrinology 27 (2006) 32–37
analyzed in the presence of 30 mM K+ and 100 nM of ghrelin. The perfusate levels of met-enkephalin, leptin, and ghrelin were assayed by RIA. Short fasting decreased the basal secretion of all tested hormones by 30–90%, but a single injection of ghrelin partially reversed this drop for leptin and met-enkephalin. Naltrexone, an opioid receptor antagonist, significantly lowered the effect of in vivo ghrelin. On the other hand, ghrelin added to incubated tissue strongly changed the secretion of leptin (decrease from 0.8 ± 0.01 to 0.6 ± 0.02 ng/mg/20 min), met-enkephalin (increase from 0.145 ± 0.01 to 0.293 ± 0.04 pmol/mg/20 min) and endogenous ghrelin (increase from 90 ± 8 to 135 ± 11) from the hypothalamus of fasted animals. The obtained results clearly showed the presence of opioids, ghrelin, and leptin in the hypothalamus of mice. Also, it may be postulated that ghrelin is involved in regulation of opioids and leptin release in fed as well as in fasted animals. (Supported by grant given to K.P.K.)
35
mone (LH) release from gonadotropes. However, in these cells, it reduced the expression levels of the receptor to their primary hypothalamic regulator, the GnRH receptor. Taken together, these results indicate that the pituitary constitutes a relevant site of action for adiponectin. Furthermore, we observed that both adiponectin and its receptors are expressed in the rat pituitary and that this adipokine increases its own expression in the short-term (4 h) in pituitary cell cultures, while reducing AdipoR1 mRNA levels in the long-term (24 h). In sum, our results show that adiponectin, produced locally or from other sources, can regulate hormone secretion and gene expression in both somatotropes and gonadotropes, thereby adding a new component for the functional relationship between the regulation of metabolism, growth, and reproduction at the pituitary level. (Financial support: CVI-139 (J. Andalucia) and BFU2004-03883 (MEC/FEDER), Spain.) doi:10.1016/j.yfrne.2006.03.071
doi:10.1016/j.yfrne.2006.03.070
Regulation of pituitary cell function by the adipokine adiponectin M.M. Malago´n a, F. Rodrı´guez-Pacheco a, A.J. Martı´nezFuentes a, S. Tovar b, L. Pinilla a, M. Tena-Sempere a, C. Die´guez b, J.P. Castan˜o a a Department of Cell Biology, Physiology, and Immunology, University of Co´rdoba, Spain b Department of Physiology, University of Santiago de Compostela, Spain Adiponectin, which is a member of the family of adipose tissue-specific or enriched hormones known as adipokines, is considered as an insulin-sensitizing agent because it reduces glucose production and enhances insulin action in the liver. Adiponectin actions are primarily mediated through its binding to two distinct receptors, AdipoR1 and AdipoR2. A recent report has shown that adiponectin is expressed in the anterior pituitary in birds. Interestingly, treatment of cultured human adipocytes with growth hormone (GH) decreased both adiponectin secretion and AdipoR2 expression. Based on these results, in the present study, we aimed at investigating whether adiponectin acts on pituitary somatotropes. Additionally, and in view of the relationship between the control of energy metabolism and reproduction, we also sought to analyze the effect of adiponectin on gonadotropes. To this end, dispersed anterior pituitary cells from adult male rats were treated with adiponectin (107–109 M). Results show that adiponectin inhibited GH release and also regulated the expression of two key receptors of somatotropes, the GH secretagogue/ ghrelin receptor and the GH-releasing hormone receptor. Specifically, it increased mRNA levels of both receptors. As for somatotropes, adiponectin inhibited luteinizing hor-
The GH response to ghrelin in humans is impaired in conditions of hyper- and hypothyroidism Fabio Broglio, Flavia Prodam, Fabrizio Riganti, Elena Gramaglia, Ezio Ghigo Department of Internal Medicine, University of Turin, Italy Both hyper- and hypothyroidisms show a reduced spontaneous and GHRH-stimulated GH secretion. Although an impaired GHRH secretion and activity as well as a reduced GH pituitary synthesis have been reported in these pathological conditions, a definitive description of the underlying pathophysiological mechanisms have not been provided yet. Ghrelin elicits a potent GH-releasing effect partially mediated by a functional somatostatin antagonism and a synergic interaction with GHRH. Specifically, the functional integrity of GHRH neurons is essential for ghrelin’s GH releasing effect. We aimed to investigate the GH releasing effect of ghrelin in conditions of naı¨ve overt altered thyroid function. To this aim, in eight patients with primary autoimmune hypothyroidism (HYPO; age [mean ± SEM]: 41.8 ± 6.9 year; BMI: 27.1 ± 2.2 kg/m2; TSH: 16.5 ± 5.8 mU/ml; fT3: 3.1 ± 1.2 ng/L; fT4: 8.7 ± 1.6 ng/L), eight patients with thyrotoxicosis due to Basedow Disease (HYPER; age: 45.3 ± 7.6 year; BMI: 23.5 ± 3.0 kg/m2; TSH: 0.0 ± 0.0 mU/L; fT3: 6.5 ± 3.0 ng/L; fT4: 25.0 ± 6.4 ng/L; TRAb: 47.5 ± 7.6 U/L) and eight control subjects (NS; age: 35.1 ± 5.9 year; BMI: 22.1 ± 1.9 kg/m2) we studied the effects of the acute iv bolus administration at 0 0 of acylated ghrelin (AG; 1.0 lg/kg) and placebo (saline; 3 ml) on circulating GH levels assayed every 15 0 up to 90 0 . In all the subjects, AG increased GH levels (p < 0.01). Notably, both in HYPO (Dpeak: 30.4 ± 6.2 lg/L; DAUC: 1458.7 ± 364.0 lg/L/h) and in HYPER (Dpeak: 39.6 ± 4.1 lg/L; DAUC: 1924.9 ± 252.7 lg/L/h) the GH response to AG was lower (p < 0.01) than in NS (Dpeak: 79.8 ± 8.2 lg/L;
36
Abstracts / Frontiers in Neuroendocrinology 27 (2006) 32–37
DAUC: 4360.3 ± 552.5 lg/L/h). This study shows that in the presence of altered thyroid function, the GH response to ghrelin is reduced. Such an impairment could result from the above mentioned functional alterations of the GHRH/ GH axis, nevertheless the existence of a specific reduced sensitivity to the GH releasing effect of ghrelin as an adjunctive mechanism of hyposomatotropism in thyroid disease is worthy of being further investigated. doi:10.1016/j.yfrne.2006.03.072
Effects of dietary rhIGF-1 on epithelial growth and mRNA expression of Na+/H+ exchanger in rumen epithelium of neonatal goat lambs Zan-Ming Shen a, Yue-Ju Su a, Qiu-Sheng Zeng a, Ling-Zhi Sun a, Hao-Long Huang a, Jie Chen a, Holger Martens b a Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, China b Institute of Veterinary Physiology, Free University Berlin, Germany E-mail address: [email protected] (Z.-M. Shen) Introduction: The ruminal postnatal development of papillary morphology and absorptive function is diet-dependent. We reported an increment of rumen papillae size and ruminal Na+ transport caused by an energy-rich diet, which is associated with increased IGF type 1 receptor in rumen epithelium and IGF-1 concentration in plasma of young goats (Shen et al. 2004a). In vitro IGF-1 stimulated rumen epithelial proliferation of neonatal calves (Shen et al. 2004b). The activity of electroneutral Na+ transport (Martens, et al. 1991), carried by Na+/H+ exchanger (NHE), was observed in rumen epithelium of adult (Gaebel et al.1996) and suckling ruminants (Breves et al. 2002). Furthermore, the messenger RNA of NHE-1 and NHE-3 was detected in rumen epithelium (Schweigel et al. 2005). The present study investigated influences of dietary rhIGF-1 on papillae growth and NHE mRNA expression in rumen epithelium of neonatal goat lambs. Methods: (A) Eight suckling Chinese goat lambs (14days old), supplied with milk powder, were randomly allocated into two groups (n = 4). The crude rhIGF-1 (containing rhIGF-1 200 lg g1) of 5 g BW kg1 d1 was mixed with milk powder and orally administered to EXP lambs for 10 days. At d 11, the lambs were slaughtered and the rumen epithelium was sampled for morphology observation and NHEs mRNA analysis. (B) An in vitro study determined the direct effect of IGF-1 on rumen epithelial proliferation and NHEs (1 and 3) mRNA expression by incubation of rumen epithelial cells, collected from young goats, without (Con, n = 4) or with (EXP, n = 4) IGF-1 (Sigma, 25 ng ml1) treatment for 30 h. The cell cycle was assayed by flow cytometry, and NHE mRNA was measured by semi-quantitative reverse transcriptionpolymerase chain reaction (RT-PCR).
Results: (A) In suckling lambs treated with dietary rhIGF-1 an increase of papillae numbers/surface cm2, from atrium ruminis, dorsal rumen sac and ventral blind sac, was observed. It is accompanied by a higher ratio of papillary DNA/RNA (p < 0.05). Simultaneously the mRNA abundances of both HNE-1 and -3 were greater (p < 0.05) in dietary rhIGF-1administered lambs. (B) In vitro, the epithelial cell cycle in rumen of EXP lambs, characterized by a greater number of cells in S-phase (p < 0.05), was promoted by IGF-1. The HNE-3 mRNA abundances was 32% higher (p < 0.05) in EXP epithelium than that in Con. Taken together, this study demonstrates that dietary rhIGF-1 stimulates papillae growth and mRNA expression of NHE-1 and NHE-3 in rumen epithelium of neonatal lambs and is associated with a direct stimulating action of IGF-1 on rumen papillae. (Supported by Chinese National Nature Science Foundation (No. 30270972) and German–Chinese cooperative project in Agricultural research.) doi:10.1016/j.yfrne.2006.03.073
Effects of chronic treatment with an oral growth hormone (GH) secretagogue on nocturnal GH and IGF-I in older men and women G.R. Merriam a, M.R. Blackman b, A.R. Hoffman c, R. Salvatori d, J.Y. Wei e, H.K. White f, M. Kletke a, A.E. Taylor g, W. Landschulz g a VA/University of Washington, USA b NCCAM/NIH, USA c VA/Stanford University, USA d Johns Hopkins University, USA e University of Arkansas, USA f VA/Duke University, USA g Pfizer, Inc., USA Aging is characterized by a progressive decline in lean body (muscle) mass, strength, and exercise capacity, leading eventually to loss of capability for independent living, or frailty. GH secretion also declines with aging, and many age-related changes resemble those of adult GH deficiency. These similarities have raised interest in the potential benefits of replacing or stimulating GH in older adults. Use of orally active ghrelin-mimetic GH secretagogues (GHS) could provide convenient and more physiologic GH replacement than GH injections. We studied the endocrine and physical effects of chronic oral treatment with the GHS capromorelin in 395 men and women ages 65–84 with mild functional limitations. Subjects were randomized to receive placebo, or one of four GHS dosing groups (10 mg tiw, 3 mg bid, 10 mg qhs, or 10 mg bid) for up to 12 months. In a subset of subjects, GH was measured at 20 min intervals from 8 p.m.–8 a.m. before and after 2 months of treatment, beginning just before the time of an evening dose of active GHS or placebo. Serum IGF-I levels were measured on the same evenings.
analyzed in the presence of 30 mM K+ and 100 nM of ghrelin. The perfusate levels of met-enkephalin, leptin, and ghrelin were assayed by RIA. Short fasting decreased the basal secretion of all tested hormones by 30–90%, but a single injection of ghrelin partially reversed this drop for leptin and met-enkephalin. Naltrexone, an opioid receptor antagonist, significantly lowered the effect of in vivo ghrelin. On the other hand, ghrelin added to incubated tissue strongly changed the secretion of leptin (decrease from 0.8 ± 0.01 to 0.6 ± 0.02 ng/mg/20 min), met-enkephalin (increase from 0.145 ± 0.01 to 0.293 ± 0.04 pmol/mg/20 min) and endogenous ghrelin (increase from 90 ± 8 to 135 ± 11) from the hypothalamus of fasted animals. The obtained results clearly showed the presence of opioids, ghrelin, and leptin in the hypothalamus of mice. Also, it may be postulated that ghrelin is involved in regulation of opioids and leptin release in fed as well as in fasted animals. (Supported by grant given to K.P.K.)
35
mone (LH) release from gonadotropes. However, in these cells, it reduced the expression levels of the receptor to their primary hypothalamic regulator, the GnRH receptor. Taken together, these results indicate that the pituitary constitutes a relevant site of action for adiponectin. Furthermore, we observed that both adiponectin and its receptors are expressed in the rat pituitary and that this adipokine increases its own expression in the short-term (4 h) in pituitary cell cultures, while reducing AdipoR1 mRNA levels in the long-term (24 h). In sum, our results show that adiponectin, produced locally or from other sources, can regulate hormone secretion and gene expression in both somatotropes and gonadotropes, thereby adding a new component for the functional relationship between the regulation of metabolism, growth, and reproduction at the pituitary level. (Financial support: CVI-139 (J. Andalucia) and BFU2004-03883 (MEC/FEDER), Spain.) doi:10.1016/j.yfrne.2006.03.071
doi:10.1016/j.yfrne.2006.03.070
Regulation of pituitary cell function by the adipokine adiponectin M.M. Malago´n a, F. Rodrı´guez-Pacheco a, A.J. Martı´nezFuentes a, S. Tovar b, L. Pinilla a, M. Tena-Sempere a, C. Die´guez b, J.P. Castan˜o a a Department of Cell Biology, Physiology, and Immunology, University of Co´rdoba, Spain b Department of Physiology, University of Santiago de Compostela, Spain Adiponectin, which is a member of the family of adipose tissue-specific or enriched hormones known as adipokines, is considered as an insulin-sensitizing agent because it reduces glucose production and enhances insulin action in the liver. Adiponectin actions are primarily mediated through its binding to two distinct receptors, AdipoR1 and AdipoR2. A recent report has shown that adiponectin is expressed in the anterior pituitary in birds. Interestingly, treatment of cultured human adipocytes with growth hormone (GH) decreased both adiponectin secretion and AdipoR2 expression. Based on these results, in the present study, we aimed at investigating whether adiponectin acts on pituitary somatotropes. Additionally, and in view of the relationship between the control of energy metabolism and reproduction, we also sought to analyze the effect of adiponectin on gonadotropes. To this end, dispersed anterior pituitary cells from adult male rats were treated with adiponectin (107–109 M). Results show that adiponectin inhibited GH release and also regulated the expression of two key receptors of somatotropes, the GH secretagogue/ ghrelin receptor and the GH-releasing hormone receptor. Specifically, it increased mRNA levels of both receptors. As for somatotropes, adiponectin inhibited luteinizing hor-
The GH response to ghrelin in humans is impaired in conditions of hyper- and hypothyroidism Fabio Broglio, Flavia Prodam, Fabrizio Riganti, Elena Gramaglia, Ezio Ghigo Department of Internal Medicine, University of Turin, Italy Both hyper- and hypothyroidisms show a reduced spontaneous and GHRH-stimulated GH secretion. Although an impaired GHRH secretion and activity as well as a reduced GH pituitary synthesis have been reported in these pathological conditions, a definitive description of the underlying pathophysiological mechanisms have not been provided yet. Ghrelin elicits a potent GH-releasing effect partially mediated by a functional somatostatin antagonism and a synergic interaction with GHRH. Specifically, the functional integrity of GHRH neurons is essential for ghrelin’s GH releasing effect. We aimed to investigate the GH releasing effect of ghrelin in conditions of naı¨ve overt altered thyroid function. To this aim, in eight patients with primary autoimmune hypothyroidism (HYPO; age [mean ± SEM]: 41.8 ± 6.9 year; BMI: 27.1 ± 2.2 kg/m2; TSH: 16.5 ± 5.8 mU/ml; fT3: 3.1 ± 1.2 ng/L; fT4: 8.7 ± 1.6 ng/L), eight patients with thyrotoxicosis due to Basedow Disease (HYPER; age: 45.3 ± 7.6 year; BMI: 23.5 ± 3.0 kg/m2; TSH: 0.0 ± 0.0 mU/L; fT3: 6.5 ± 3.0 ng/L; fT4: 25.0 ± 6.4 ng/L; TRAb: 47.5 ± 7.6 U/L) and eight control subjects (NS; age: 35.1 ± 5.9 year; BMI: 22.1 ± 1.9 kg/m2) we studied the effects of the acute iv bolus administration at 0 0 of acylated ghrelin (AG; 1.0 lg/kg) and placebo (saline; 3 ml) on circulating GH levels assayed every 15 0 up to 90 0 . In all the subjects, AG increased GH levels (p < 0.01). Notably, both in HYPO (Dpeak: 30.4 ± 6.2 lg/L; DAUC: 1458.7 ± 364.0 lg/L/h) and in HYPER (Dpeak: 39.6 ± 4.1 lg/L; DAUC: 1924.9 ± 252.7 lg/L/h) the GH response to AG was lower (p < 0.01) than in NS (Dpeak: 79.8 ± 8.2 lg/L;
36
Abstracts / Frontiers in Neuroendocrinology 27 (2006) 32–37
DAUC: 4360.3 ± 552.5 lg/L/h). This study shows that in the presence of altered thyroid function, the GH response to ghrelin is reduced. Such an impairment could result from the above mentioned functional alterations of the GHRH/ GH axis, nevertheless the existence of a specific reduced sensitivity to the GH releasing effect of ghrelin as an adjunctive mechanism of hyposomatotropism in thyroid disease is worthy of being further investigated. doi:10.1016/j.yfrne.2006.03.072
Effects of dietary rhIGF-1 on epithelial growth and mRNA expression of Na+/H+ exchanger in rumen epithelium of neonatal goat lambs Zan-Ming Shen a, Yue-Ju Su a, Qiu-Sheng Zeng a, Ling-Zhi Sun a, Hao-Long Huang a, Jie Chen a, Holger Martens b a Key Laboratory of Animal Physiology and Biochemistry, Nanjing Agricultural University, China b Institute of Veterinary Physiology, Free University Berlin, Germany E-mail address: [email protected] (Z.-M. Shen) Introduction: The ruminal postnatal development of papillary morphology and absorptive function is diet-dependent. We reported an increment of rumen papillae size and ruminal Na+ transport caused by an energy-rich diet, which is associated with increased IGF type 1 receptor in rumen epithelium and IGF-1 concentration in plasma of young goats (Shen et al. 2004a). In vitro IGF-1 stimulated rumen epithelial proliferation of neonatal calves (Shen et al. 2004b). The activity of electroneutral Na+ transport (Martens, et al. 1991), carried by Na+/H+ exchanger (NHE), was observed in rumen epithelium of adult (Gaebel et al.1996) and suckling ruminants (Breves et al. 2002). Furthermore, the messenger RNA of NHE-1 and NHE-3 was detected in rumen epithelium (Schweigel et al. 2005). The present study investigated influences of dietary rhIGF-1 on papillae growth and NHE mRNA expression in rumen epithelium of neonatal goat lambs. Methods: (A) Eight suckling Chinese goat lambs (14days old), supplied with milk powder, were randomly allocated into two groups (n = 4). The crude rhIGF-1 (containing rhIGF-1 200 lg g1) of 5 g BW kg1 d1 was mixed with milk powder and orally administered to EXP lambs for 10 days. At d 11, the lambs were slaughtered and the rumen epithelium was sampled for morphology observation and NHEs mRNA analysis. (B) An in vitro study determined the direct effect of IGF-1 on rumen epithelial proliferation and NHEs (1 and 3) mRNA expression by incubation of rumen epithelial cells, collected from young goats, without (Con, n = 4) or with (EXP, n = 4) IGF-1 (Sigma, 25 ng ml1) treatment for 30 h. The cell cycle was assayed by flow cytometry, and NHE mRNA was measured by semi-quantitative reverse transcriptionpolymerase chain reaction (RT-PCR).
Results: (A) In suckling lambs treated with dietary rhIGF-1 an increase of papillae numbers/surface cm2, from atrium ruminis, dorsal rumen sac and ventral blind sac, was observed. It is accompanied by a higher ratio of papillary DNA/RNA (p < 0.05). Simultaneously the mRNA abundances of both HNE-1 and -3 were greater (p < 0.05) in dietary rhIGF-1administered lambs. (B) In vitro, the epithelial cell cycle in rumen of EXP lambs, characterized by a greater number of cells in S-phase (p < 0.05), was promoted by IGF-1. The HNE-3 mRNA abundances was 32% higher (p < 0.05) in EXP epithelium than that in Con. Taken together, this study demonstrates that dietary rhIGF-1 stimulates papillae growth and mRNA expression of NHE-1 and NHE-3 in rumen epithelium of neonatal lambs and is associated with a direct stimulating action of IGF-1 on rumen papillae. (Supported by Chinese National Nature Science Foundation (No. 30270972) and German–Chinese cooperative project in Agricultural research.) doi:10.1016/j.yfrne.2006.03.073
Effects of chronic treatment with an oral growth hormone (GH) secretagogue on nocturnal GH and IGF-I in older men and women G.R. Merriam a, M.R. Blackman b, A.R. Hoffman c, R. Salvatori d, J.Y. Wei e, H.K. White f, M. Kletke a, A.E. Taylor g, W. Landschulz g a VA/University of Washington, USA b NCCAM/NIH, USA c VA/Stanford University, USA d Johns Hopkins University, USA e University of Arkansas, USA f VA/Duke University, USA g Pfizer, Inc., USA Aging is characterized by a progressive decline in lean body (muscle) mass, strength, and exercise capacity, leading eventually to loss of capability for independent living, or frailty. GH secretion also declines with aging, and many age-related changes resemble those of adult GH deficiency. These similarities have raised interest in the potential benefits of replacing or stimulating GH in older adults. Use of orally active ghrelin-mimetic GH secretagogues (GHS) could provide convenient and more physiologic GH replacement than GH injections. We studied the endocrine and physical effects of chronic oral treatment with the GHS capromorelin in 395 men and women ages 65–84 with mild functional limitations. Subjects were randomized to receive placebo, or one of four GHS dosing groups (10 mg tiw, 3 mg bid, 10 mg qhs, or 10 mg bid) for up to 12 months. In a subset of subjects, GH was measured at 20 min intervals from 8 p.m.–8 a.m. before and after 2 months of treatment, beginning just before the time of an evening dose of active GHS or placebo. Serum IGF-I levels were measured on the same evenings.