Growth hormone, somatomedin and prolactin--relationship to brain function

Multiple Effects of Growth Hormone in the Body: Is it Really the Hormone for Growth?

In this review, we analyze the effects of growth hormone on a number of tissues and organs and its putative role in the longitudinal growth of an organism. We conclude that the hormone plays a very important role in maintaining the homogeneity of tissues and organs during the normal development of the human body or after an injury. Its effects on growth do not seem to take place during the fetal period or during the early infancy and are mediated by insulin-like growth factor I (IGF-I) during childhood and puberty. In turn, IGF-I transcription is dependent on an adequate GH secretion, and in many tissues, it occurs independent of GH. We propose that GH may be a prohormone, rather than a hormone, since in many tissues and organs, it is proteolytically cleaved in a tissue-specific manner giving origin to shorter GH forms whose activity is still unknown.

The Role of Growth Hormone in Neural Development

Growth hormone (GH) is integrally involved in the development of the central nervous system (CNS), as well as during its recovery from injury, two processes that share many similarities and may influence CNS functionality. This review discusses some of the most recent findings in the field and, in particular, the ontogeny, distribution, regulation and putative functions of GH and its receptor within the CNS, particularly during development. The relative roles of peripheral GH, acting in part through insulin-like growth factor-I, and of the autocrine/paracrine GH system within the brain are considered. The potential role of GH as a therapeutic agent to influence brain development and function is discussed.

Antiapoptotic effects of leptin in human neuroblastoma cells

Many factors regulate nervous system development, including complex cross-talk between local neuroendocrine systems. The adipocyte-secreted hormone leptin, mainly known for its key roles in nutrition and reproductive balance, may also be involved in neuroanatomical organization, myelination processes, and neuronal/glia maturation. SK-N-SH-SY5Y neuroblastoma cells were employed as an in vitro model of human neuronal cells to determine whether leptin exerts neuroprotective activities. We show that SH-SY5Y cells express leptin, the long and short isoforms of the leptin receptor (ObRl, ObRs). In SH-SY5Y cells, leptin induced signal transducer and activator of transcription (STAT)-3 phosphorylation and suppressor of cytokine signaling-3 mRNA expression. Leptin dose-dependently increased cell number (up to 200% at 1 microm by 48 h, P < 0.01), and at 24-48 h, leptin at 100 nm increased SH-SY5Y cell number by 30-50%, respectively. SH-SY5Y cell viability was reduced in serum-free conditions at 24 h, and addition of leptin at 100 nm significantly reduced apoptosis by approximately 20% (P < 0.001). Leptin's antiapoptotic activity required Janus kinase/STAT, MAPK, and phosphatidylinositol-3-kinase activation because the antiapoptotic effects of leptin were abolished, and caspase-3 immunoreactivity increased in the presence of the specific blockers AG490, U0126, or LY294002. Gene array demonstrated that leptin inhibits apoptosis via potent down-regulation of caspase-10 and TNF-related apoptosis-inducing ligand. Our data thus demonstrate, for the first time, that leptin stimulates, in a time- and dose-dependent manner, neuroblastoma cell proliferation and that the underlying mechanisms involve suppression of apoptosis via the Janus kinase-STAT, phosphatidylinositol-3 kinase, and MAPK pathways that culminate altogether in the down-regulation of the apoptotic factors caspase-10 and TNF-related apoptosis-inducing ligand.

Abnormal cognitive function in treated congenital hypopituitarism

AIMS

To assess cognitive function in school age children with congenital pituitary hormone deficiency (PHD).

METHODS

Ten children with PHD (aged 6.0-15.6 years, mean 11.5 years) and sibling controls (aged 8.7-14.9 years, mean 12.1 years) were assessed using the Wechsler Intelligence Scale for Children (WISC-III UK).

RESULTS

The patients' full scale IQ scores were all below average (mean 75, 95% CI 70-80), but were not significantly different to those of sibling controls (mean 82, 95% CI 75-89). There was no difference in verbal IQ between patients and siblings, but performance IQ was significantly reduced (mean 75, 95% CI 68-82 in patients; mean 88, 95% CI 80-96 in sibling controls). The reduced performance IQ reflected a poorer performance in tasks assessing perceptual organisational skills.

CONCLUSIONS

Data suggest that children with PHD have an IQ that is below average when compared to the population norm and a reduced performance IQ when compared to sibling controls. This may reflect abnormal brain development or could be linked to the impact of hypoglycaemia or low thyroxine concentrations in early life. This information is of value when counselling parents and planning a child's care and education, although further, more extensive studies of patients and siblings are required.

Central nervous system actions of growth hormone on brain monoamine levels and behavior of juvenile rainbow trout

Growth hormone (GH) has been demonstrated to alter the behavior of juvenile salmonids. However, the mechanisms behind this action are not yet understood. In mammals and birds, peripheral GH treatment has been shown to affect monoaminergic activity in the central nervous system, which may be a mechanism whereby GH alters behavior. To investigate if GH may influence behavior directly at the central nervous system, juvenile rainbow trout were injected with GH into the third ventricle of the brain, whereupon physical activity and food intake were observed during 2 h. Thereafter, brains were sampled and the content of serotonin, dopamine, and noradrenaline and their metabolites were measured in hypothalamus, telencephalon, optic tectum, and brainstem. The GH-treated fish increased their swimming activity relative to sham-injected controls, while appetite remained unchanged, compared with sham-injected controls. Analysis of brain content of monoamines revealed that the GH treatment caused a decrease in the dopamine metabolite homovanillic acid in the hypothalamus, indicating a lowered dopaminergic activity. It is concluded that GH may alter behavior by acting directly on the central nervous system in juvenile rainbow trout. Furthermore, GH seems to alter the dopaminergic activity in the hypothalamus. Whether this is a mechanism whereby GH affects swimming activity remains to be clarified.

Influence of growth hormone (GH) and GH-releasing factor on locomotor activity in rats

Acute recombinant human growth hormone (r-hGH) administration (1-250 micrograms/kg; IP) decreased locomotor activity (LA) in a dose-dependent manner, F(5, 43) = 3.55, p < 0.009, with maximum effect at a dose of 10 micrograms/kg [control = 1655 +/- 659 inputs/outputs (I/O); r-hGH = 909 +/- 436 I/O; p < 0.05]. The daily treatment with r-hGH (10 micrograms/kg/day; 5 days; IP) reduced LA counts during the first trial, with no apparent changes in motor behavior after habituation. In contrast, growth hormone-releasing factor (GRF; 10 micrograms/rat/day; 5 days; IP) enhanced LA (control = 1045 +/- 566 I/O; GRF = 2284 +/- 894 I/O; p < 0.01) during the 5-day treatment period, inhibiting habituation. Moreover, the individual differences in LA persisted during the treatment period in response to GRF or r-hGH, but not in control rats. These results seem to indicate that the effects of GRF on LA are not mediated by the release of peripheral GH, and suggest that GRF might influence psychomotor behavior by a central mechanism.

Inverse correlation between right-paw use and body weight in right-pawed male cats and left-pawed female cats

The association between paw preference and body weight was studied in cats. In right-pawed males, the right minus left (R-L) paw use significantly decreased as the body weight increased. There was no significant correlation between these parameters in left-pawed males as well as in right-pawed females. In left-pawed females, the frequency of the left-paw use increased as the body weight increased. These results partly supported those in humans (Tan, in press). It was suggested that hormonal factors affecting body weight may also influence cerebral lateralization and consequently paw preference. The best possibility for these hormones appears to be testosterone.

The relation of body height to handedness in male and female right- and left-handed human subjects

The association between body size and the degree of hand preference was studied in male and female right- and left-handed human subjects. Hand preference was assessed by the Edinburgh Handedness Inventory. In left-handers (total sample), there was a significant, negative linear correlation between the degree of left-hand preference and body height. There was no significant correlation between these parameters if the males and females were considered separately. In right-handers (total sample), body height was found to be significantly and negatively linearly correlated with the degree of right-hand preference. A similar correlation was observed in males without familial sinistrality (FS-) and in FS+ females. There was no significant correlation between these parameters in FS+ right-handed males and FS- right-handed females. It was suggested that hormones affecting body height and brain size such as human growth hormone and testosterone would also contribute to the development of cerebral lateralization.