Growth hormone increases mRNA levels of PPARdelta and Foxo1 in skeletal muscle of growth hormone deficient lit/lit mice.

GH plays an important role in lipid metabolism as a partitioning hormone. PPARdelta regulates lipid oxidation in skeletal muscle and is activated by several physiological ligands including fatty acids. To investigate whether GH has an effect on the regulation of transcription of PPARdelta and other genes involved in energy metabolism in skeletal muscle, mRNA levels were studied by real-time RT-PCR in lit/lit mice (isolated GH deficiency) and lit/+ mice controls (normal GH levels). Mice received either a single bolus (120 ng/g) of rat GH or vehicle, and skeletal muscle was collected 4h later. PPARdelta mRNA was increased in vehicle-treated lit/lit mice compared to vehicle-treated lit/+ mice (1.67 fold, P<0.05). lit/lit mice treated with GH showed a further increase in PPARdelta mRNA levels (2.83 fold vs. vehicle-treated lit/+ mice, P<0.001). mRNA levels of Foxo1 were increased in vehicle-treated lit/lit mice compared to vehicle-treated lit/+ mice (1.74 fold, P<0.05). lit/lit mice treated with GH showed a further increase in Foxo1 mRNA levels (6.30 fold vs. vehicle-treated lit/+ mice, P<0.001). mRNA levels of acyl CoA-oxidase showed a trend to be higher in vehicle-treated lit/lit mice compared to vehicle-treated lit/+ mice. This reached statistical significance in GH-treated lit/lit mice compared to vehicle-treated lit/+ mice (2.11 fold, P<0.05). In summary, mRNA levels of PPARdelta and Foxo1 were increased in skeletal muscle of GH-deficient mice, and further acutely increased by GH administration. These results suggest that GH plays a relevant role in the lipid catabolism in skeletal muscle.

Tissue-specific regulation of growth hormone (GH) receptor and insulin-like growth factor-I gene expression in the pituitary and liver of GH-deficient (lit/lit) mice and transgenic mice that overexpress bovine GH (bGH) or a bGH antagonist.

GH has diverse biological actions that are mediated by binding to a specific, high-affinity cell surface receptor (GHR). Expression of GHR is tissue specific and a requirement for cellular responsiveness to GH. IGF-I is produced in multiple tissues and regulated in part by GH through GHR. In this study, we evaluated GHR and IGF-I mRNA expression in pituitary gland and compared the levels with those derived from liver of bovine GH transgenic, GH antagonist transgenic, lit/lit mice, and their respective controls using real-time RT-PCR. In liver, both GHR and IGF-I mRNA expressions were regulated in parallel with GH action in all three animal models, and there was a strong correlation between GHR and IGF-I mRNA levels. In the pituitary gland, increased expression of IGF-I mRNA in the pituitary of bovine GH transgenic mice was observed, whereas IGF-I expression in GH antagonist transgenic or lit/lit mice was similar to that observed in control animals. There were no differences of GHR mRNA levels in pituitary gland of any groups we examined. There was also no correlation between GHR and IGF-I mRNA levels in any group in the pituitary gland. In conclusion, we found that hepatic GHR and IGF-I mRNA levels were strongly correlated with each other in chronic GH excess or deficient state, and that regulation and correlation between local GHR and IGF-I mRNA levels induced by GH is different between liver and pituitary gland.

Serum adiponectin levels in adult growth hormone deficiency and acromegaly.

Atherosclerosis and insulin resistance are common complications of adult growth hormone deficiency (GHD) and acromegaly. Circulating adiponectin, an adipocyte-derived protein, has both anti-atherogenic and insulin-sensitising effects. In this study, we measured serum adiponectin levels in patients with either adult GHD or acromegaly to clarify the impact of GH secretory states on the regulation of serum adiponectin levels. Serum adiponectin level was measured by radioimmunoassay in 32 patients with adult GHD, 49 patients with acromegaly and 25 normal subjects. The relationships between adiponectin and insulin sensitivity index assessed as quantitative insulin sensitivity check index (QUICKI), BMI, and serum GH and IGF-I levels were then investigated. The values of QUICKI were significantly lower in patients with acromegaly or adult GHD compared to normal subjects (0.33 +/- 0.03, P < 0.01, 0.35 +/- 0.04, P < 0.05 and 0.36 +/- 0.01, respectively). While patients with adult GHD had significantly lower serum adiponectin levels than patients with acromegaly (6.5 +/- 3.9, 9.2 +/- 5.0, P < 0.01) these levels were not significantly different from those found in normal subjects (7.8 +/- 4.3 mug/ml). There was an inverse correlation between serum adiponectin levels and BMI in both patient groups (GHD r = -0.39, P < 0.05; Acromegaly r = -0.35, P < 0.05). However, serum adiponectin levels correlated positively with QUICKI (R(s) = 0.37, P < 0.05) only in patients with adult GHD. In patients with acromegaly, the levels of circulating adiponectin showed an inverse correlation with serum IGF-I levels (R(s) = -0.34, P < 0.05), but not with basal GH levels. These results demonstrate that adiponectin levels are significantly lower in patients with adult GHD than in patients with acromegaly. Adiponectin levels are similar in patients with GHD and healthy controls, whereas in patients with acromegaly, insulin resistance appears to be not closely related to adiponectin levels compared with BMI. The different relationship between adiponectin and QUICKI observed in the adult GHD and acromegaly groups presumably reflects differences in the mechanisms of insulin resistance under states of GH deficiency or excess.

Lack of contribution of 11betaHSD1 and glucocorticoid action to reduced muscle mass associated with reduced growth hormone action.

11Beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) is expressed in several tissues and converts inactive glucocorticoids (GC) to active GC. 11betaHSD1 activity, evaluated by urine cortisol metabolites, is increased in patients with hypopituitarism and decreased by GH replacement. Skeletal muscle wasting is one of the major characteristics of GH deficiency (GHD). We hypothesized that increased 11betaHSD1 activity and increased GC action in skeletal muscle may play a role in the development of muscle atrophy observed in GHD patients. Glutamine synthetase (GS) mRNA in muscle has been reported to be related to GC-induced muscle atrophy. In this study, we measured mRNA levels of 11betaHSD1 and GS in skeletal muscle of GH receptor gene disrupted (GHR-/-) mice and of their age-matched wild-type mice controls to elucidate the physiological significance of 11betaHSD1 and GC in the development of GHD-associated muscle atrophy in vivo. We also measured the expression of these genes in hypertrophied muscles of giant, bovine GH transgenic mice. In skeletal muscle, although IGF-I mRNA levels were decreased in GHR-/- mice, 11betaHSD1 mRNA levels were not significantly changed compared to wild-type mice. In addition, expression level of 11betaHSD1 in muscle was lower compared to that seen in liver. GS mRNA in skeletal muscle of GHR-/- mice was not significantly different from that of controls. In bGH mice, 11betaHSD1 and GS mRNA levels were not altered compared to control mice. These data do not support a significant role of 11betaHSD1 and GC action in skeletal muscle in the development of muscle atrophy associated with GHD.

Metabolic disorders in adult growth hormone deficiency: A study of 110 patients at a single institute in Japan.

The purpose of this study carried out at a single institute in Japan was to investigate the clinical characteristics and complications of patients with adult growth hormone deficiency (GHD). Clinical and biochemical data of 110 patients (50 males, 60 females; mean age 42 +/- 17 yr) with adult GHD who attended Tokyo Women's Medical University between 1990 and 1999 were analyzed retrospectively from medical records. This retrospective analysis demonstrated that 109 patients had multiple pituitary hormone deficiencies, with 98 patients having a deficiency of more than three hormones. Sixty-one patients had childhood onset GHD (COGHD) while the remaining 49 patients had adulthood onset GHD (AOGHD). Body mass index (BMI) ranged from 16.9 to 35.9 with a mean of 23.9 +/- 4.1 (kg/m2), with BMI being > or = 25 kg/m2 in 38 patients (31% of COGHD and 38% of AOGHD). Forty-one percent of the patients had hypercholesterolemia, 41% had hypertriglyceridemia, 47% had decreased levels of HDL cholesterol and 48% had increased levels of LDL cholesterol. Intima-media thickness (IMT) of the carotid arteries was investigated in 33 patients, with abnormal findings including increased IMT or plaque being observed in 4 of 18 COGHD patients and 4 of 15 AOGHD patients. Diabetes mellitus and impaired glucose tolerance was found in 4 COGHD patients and 16 AOGHD patients. Insulin resistance was assessed in 36 patients by the homeostasis model insulin resistance index (HOMA-R) and ranged from 0.65 to 10.58 with a mean of 2.80 +/- 0.37. This mean value of HOMA-R was significantly greater than that measured in normal subjects (1.58 +/- 0.05: P < 0.05). These data suggest that abnormal lipid and glucose metabolism, and atherosclerotic changes occur frequently in adult patients with GHD. Insulin resistance may play a role in glucose and lipid metabolism disorders associated with GHD.

Diurnal variation in growth hormone receptor messenger ribonucleic acid in liver and skeletal muscle of lit/+ and lit/lit mice.

The present study investigated the diurnal variation in GH receptor (GHR) mRNA in liver and skeletal muscle of 3-month-old GH-deficient and -sufficient mice using quantitative real-time RT-PCR. lit/lit (GH deficient) or lit/+ (GH sufficient) mice were fed ad libitum and lights were on between 0600 and 2000. Tissues were collected at 0800-1000, 1200-1400 and 2000-2200. Hepatic GHR mRNA levels of lit/+ mice at 0800-1000 were significantly lower than those at 1200-1400 and 2000-2200. There was no significant variation in hepatic GHR mRNA of lit/lit mice. In skeletal muscle, GHR mRNA levels of both lit/+ and lit/lit mice at 1200-1400 were significantly higher than those at 0800-1000 and 2000-2200. There was also a diurnal change in hepatic IGF-I mRNA levels of lit/+ but not of lit/lit mice; the levels were lowest at 0800-1000 in lit/+ mice. On the other hand, there was no variation in IGF-I mRNA levels in skeletal muscle. These results suggest that 1) there is a diurnal variation in GHR expression in liver and skeletal muscle and the pattern of the variation is tissue specific; 2) GH deficiency blunted the diurnal variation in GHR mRNA in liver but not that in skeletal muscle; 3) IGF-I mRNA expression in liver is more closely related to GHR mRNA expression than that in skeletal muscle.

Acid-labile subunit in growth hormone excess and deficiency in adults: evaluation of its diagnostic value in comparison with insulin-like growth factor (IGF)-I and IGF-binding protein-3.

In serum, insulin-like growth factors (IGFs) are primarily present as a approximately 150 kDa ternary protein complex, which consists of IGFs, IGF binding protein-3 (IGFBP-3), and acid-labile subunit (ALS). Like IGF-I and IGFBP-3, serum levels of ALS depend on growth hormone (GH). To date, the diagnostic relevance of ALS in adult GH deficiency (GHD) has remained uncertain. To clarify the clinical utility of ALS measurement in adults, we measured serum ALS levels in patients with adult GHD or acromegaly. We also measured the levels of serum IGF-I and IGFBP-3 in these patients to compare the utility of ALS with IGF-I and IGFBP-3 as a marker of GH secretion. Serum ALS was measured by radioimmunoassay (RIA) kit, and serum IGF-I and IGFBP-3 were measured by immunoradiometric assay (IRMA) kits in 56 patients with adult GHD (adult-onset (AO)/child-onset (CO), 13/43) and 43 patients with acromegaly. Serum ALS levels were less than 5th percentile in 40 of 56 (71%) patients with adult GHD (32/43 (74%) for CO and 8/13 (62%) for AO), and more than 95th percentile in 38 of 43 (88%) patients with acromegaly, respectively. Serum IGF-I levels were less than -1.96 SD in 43 of 56 (77%) patients with adult GHD (35/43 (81%) for CO and 8/13 (62%) for AO) and more than +1.96 SD in 42 of 43 (98%) patients with acromegaly, respectively. Serum IGFBP-3 levels were less than -1.96 SD in 51 of 56 (91%) patients with adult GHD (42/43 (98%) for CO and 9/13 (69%) for AO) and more than +1.96 SD in 31 of 43 (72%) patients with acromegaly, respectively. These data suggested that measurement of ALS offers no advantage over measurements of serum IGF-I and IGFBP-3. Furthermore, our results indicate that serum IGFBP-3 is the most suitable marker of GH secretion for adult GHD, especially CO, while IGF-I may be the most useful in acromegaly.

Muscle mechano growth factor is preferentially induced by growth hormone in growth hormone-deficient lit/lit mice.

Two muscle insulin-like growth factor-I (IGF-I) mRNA splice variants (IGF-IEa and IGF-IEb) have been identified in rodents. IGF-IEb, also called mechano growth factor (MGF) has been found to be upregulated by exercise or muscle damage. Growth hormone (GH) is the principal regulator of IGF-I expression in several tissues including skeletal muscle. Therefore, we investigated the effect of chronic GH excess or disruption of GH receptor (GHR) signalling, and the acute effect of GH administration on expression of muscle IGF-I isoforms using transgenic mice that express bovine GH (bGH), GHR gene-disrupted (GHR-/-) mice and GH-deficient lit/lit mice before and after exogenous GH administration. MGF mRNA in skeletal muscle was increased in bGH mice whereas it was decreased in GHR-/- mice compared with control animals. Exogenous GH administration to dwarf lit/lit mice significantly increased muscle MGF but not IGF-IEa mRNA 4 h after treatment. Twelve hours after GH treatment, both MGF and IGF-IEa mRNAs in muscle were increased compared with vehicle-treated lit/lit mice. In contrast in GH-sufficient lit/+ mice, both MGF and IGF-IEa mRNAs were increased 4 h after and returned to the basal level 12 h after GH treatment. Hepatic IGF-I isoforms were regulated in parallel by GH. Thus, our results demonstrated that: (1) MGF mRNA in skeletal muscle is expressed in parallel with GH action; (2) MGF mRNA in muscle is produced preferentially in the situation of GH deficiency in contrast to the pattern in the GH-sufficient state; and (3) the induction of IGF-I isoforms by GH is tissue-specific.

Regulation of full-length and truncated growth hormone (GH) receptor by GH in tissues of lit/lit or bovine GH transgenic mice.

Two truncated isoforms of growth hormone (GH) receptor (GHR) were identified in mice and in humans. The proteins encoded by these isoforms lack most of the intracellular domain of the GHR and inhibit GH action in a dominant negative fashion. We have quantified the mRNAs encoding the GHR isoforms in mouse tissues by use of real-time RT-PCR and examined the effect of GH excess or deficiency on regulation of mRNA levels of the GHR isoforms in vivo. In the liver, the truncated GHR mRNAs (mGHR-282 and mGHR-280) were 0.5 and <0.1%, respectively, the level of full-length GHR (mGHR-fl). In skeletal muscle, the values were 2-3 and 0.1-0.5% of mGHR-fl, respectively, and in subcutaneous fat, the values were 3-5 and 0.1-0.5% of mGHR-fl, respectively. The bovine GH transgenic mice showed a significant increase of mGHR-fl in liver but a significant decrease in skeletal muscle, with no difference in subcutaneous fat when compared with control mice. The lit/lit mice showed a significant decrease of mGHR-fl in liver, no difference of mGHR-fl in muscle, and a significant increase of mGHR-fl in subcutaneous fat when compared with lit/+ mice. The mRNA of mGHR-282 was regulated in parallel with mGHR-fl in all tissues of all mice examined, whereas that of mGHR-280 was not changed in either GH-excess or GH-deficient states. In conclusion, two truncated isoforms of GHR mRNAs were detected in liver, skeletal muscle, and subcutaneous fat of mice. The ratio of GHR-tr to GHR-fl mRNA was tissue specific and not affected by chronic excess or deficiency of GH.