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Hepatic 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) activity, which converts cortisone (inactive) to cortisol, is downregulated in obesity. However, this compensation fails in obese with metabolic abnormalities, such as diabetes. To further characterize the tissue-specific cortisol regeneration in obesity, we have investigated the mRNA expression of genes related to local cortisol production, i.e., 11β-HSD1, hexose-6-phosphate dehydrogenase (H6PDH) and cortisol action, glucocorticoid receptor (GR) and a cortisol target gene, phosphoenolpyruvate carboxykinase (PEPCK) in the liver, and visceral (VAT) and subcutaneous (SAT) adipose tissues from morbidly obese patients with and without metabolic syndrome (MS).Fifty morbidly obese patients undergoing bariatric surgery, 14 men (mean age, 41.3 ± 3.5 years; BMI, 48.0 ± 3.6 kg/m(2)) and 36 women (mean age, 44.6 ± 1.9 years; BMI, 44.9 ± 1.2 kg/m(2)), were classified as having MS (MS+, n = 20) or not (MS-, n = 30). Tissue mRNA levels were measured by real-time polymerase chain reaction.Hepatic mRNA levels of these genes were higher in obese patients with MS (11β-HSD1, P = 0.002; H6PDH, P = 0.043; GR, P = 0.033; PEPCK, P = 0.032) and positively correlated with the number of clinical characteristics that define the MS. The expression of the four genes positively correlated among them. In contrast to the liver, these genes were not differently expressed in VAT or SAT, when MS+ and MS- obese patients were compared.Coordinated liver-specific upregulation of genes involved in local cortisol regeneration and action support the concept that local hepatic hypercortisolism contributes to development of MS in morbidly obese patients.

Appropriate expression of the GnRH receptor (GnRH-R) in gonadotrophs is critical for GnRH signaling and hence for gonadotropin secretion and sexual development. In the present work, we have studied the ontogeny of the steady-state GnRH-R mRNA levels in pituitaries of female rats from Day 5 to Day 55, when sexual maturity is attained. Developmental changes of gonadotropin subunit (alpha, FSHbeta, and LHbeta) mRNA levels were also assessed. In addition, the role of the endogenous GnRH on the maturational changes of GnRH-R and gonadotropin subunit gene expression was investigated. Messenger RNA levels were determined by Northern blot analysis of total RNA from anterior pituitaries. Amounts of the most abundant (5.0 kilobase [kb]) GnRH-R mRNA increased slowly from Day 5 through the infantile period, to peak at Day 20 ( approximately 4-fold increase vs. Day 5). Thereafter the levels of the GnRH-R mRNA decline abruptly by Day 25 (75% decrease vs. Day 20) and then fell slightly until Day 35. Parallel changes were observed on the 4.5-kb transcript of the GnRH-R gene. Alpha subunit mRNA was easily detected at Day 5 and its levels increased quickly through the beginning of the infantile period to peak at Day 10 (3.2-fold increase vs. Day 5); then it decreased by 85% at Day 35. FSHbeta and LHbeta mRNA levels rose slowly until Days 15-20, a short time before GnRH-R. Thereafter, the levels of both mRNAs fell until Day 35 (90% decrease vs. Day 15 for FSHbeta and 50% decrease vs. Day 20 for LHbeta). To ascertain whether developmental activation of the GnRH-R and gonadotropin subunit gene expression is GnRH dependent, we have studied the effect of blocking the endogenous GnRH action by treating developing female rats with the specific GnRH antagonist cetrorelix (1.5 mg/kg body weight/wk, s.c.) through the infantile (Days 5-20) and the juvenile period (Days 20-35). Cetrorelix completely blocked the rise of levels of the two most abundant species, 5.0 kb and 4.5 kb, of GnRH-R mRNA during the infantile phase and dropped them to almost undetectable levels during the juvenile prepubertal period. Cetrorelix also abolished the developmental rise of gonadotropin beta subunit mRNAs during the two periods of the study. In contrast, alpha subunit gene expression tended to decrease, but not significantly, with cetrorelix treatment during the two periods. These data demonstrate that sexual maturation of female rats is advanced by an early and strong induction of GnRH-R and gonadotropin subunit gene expression during the infantile period, followed by weaker persistent activation during puberty. Developmental GnRH-R and gonadotropin beta subunit gene expression is almost entirely GnRH dependent, not only in the juvenile prepubertal stage but also during the infantile period.

Appropriate expression of the GnRH receptor (GnRH-R) in gonadotropes is critical for GnRH signaling and hence for gonadotropin secretion and sexual development. In the present work, we have studied the ontogeny of the steady-state GnRH-R mRNA levels in pituitaries of male rats from Day 5 to Day 55, when sexual maturity is attained. Developmental changes of gonadotropin subunit (alpha, FSHbeta, and LHbeta) mRNA levels were also assessed. In addition, the role of the endogenous GnRH on the maturational changes of GnRH-R and gonadotropin subunit gene expression was investigated. Messenger RNA levels were determined by Northern blot analysis of total RNA from anterior pituitaries. Amounts of the most abundant (5.0 kb) GnRH-R mRNA increased slowly from Day 5 through the infantile and the juvenile periods, to peak at Day 35 (12-fold increase vs. Day 5). Thereafter, the levels of the GnRH-R mRNA decline slightly until Day 55 (33% decrease vs. Day 35). Parallel changes were observed on the 4.5-kb transcript of the GnRH-R gene. Alpha subunit mRNA was easily detected at Day 5, and its levels increased progressively through the infantile period (2.5-fold increase) and peaked at Day 25 (3.3-fold increase vs. Day 5) with a smooth nonstatistically significant increment until Day 35; then it decreased by 41.5% at Day 55. FSHbeta and LHbeta mRNA levels rose slowly until Day 25. A sharp rise occurred thereafter to reach maximum levels at Day 35 (5.8-fold for FSHbeta and 3.8-fold for LHbeta vs. Day 25). Thereafter, the levels of both mRNAs fell until Day 55 (44.1% decrease for FSHbeta and 37.1% decrease for LHbeta vs. Day 35). To ascertain whether developmental activation of the GnRH-R and gonadotropin subunit gene expression is GnRH dependent, we have studied the effect of blocking the endogenous GnRH action by treating developing male rats with the specific GnRH antagonist cetrorelix (1.5 mg/kg body weight/week, s.c.) through the infantile (Days 5-20) and the juvenile periods (Days 20-35). Cetrorelix completely blocked the rise of levels of the two most abundant species, 5.0 kb and 4.5 kb, of the GnRH-R mRNA, during both the infantile and the juvenile periods. Cetrorelix also abolished the developmental rise of the gonadotropin beta subunit mRNAs during the two periods of the study. In contrast, the alpha subunit gene expression was not altered by cetrorelix treatment during any of the two periods. These data demonstrate that sexual maturation of male rats is accompanied by a progressive and concerted induction of GnRH-R and gonadotropin subunit gene expression. Developmental activation of GnRH-R and gonadotropin beta subunit genes is GnRH dependent. The apparent GnRH-independent regulation of the alpha-glycoprotein subunit mRNA levels may be due to the contribution of thyrotropes and perhaps to the presence of exclusive regulatory signals for this gene.

BACKGROUND: IGF-I gene expression and IGF-I plasma concentration decline with age. A decreased sensitivity to GH has been suggested to be a contributory mechanism to this, in addition to attenuated GH secretion. OBJECTIVE: This study focuses on the sensitivity to exogenous GH and the reversibility of the reduced IGF-I gene expression in aging male rats. DESIGN: Three groups of male Wistar rats aged 3 months (young adult), 11 months (middle-aged) and 27 months (old), received recombinant human GH (rhGH) (150 microg/12 h s.c.) for seven consecutive days. RESULTS: This rhGH treatment completely reversed plasma immunoreactive IGF-I (IR-IGF-I) and hepatic IGF-I mRNA levels in 11-month-old and 27-month-old animals to the levels of the young group of animals. The sensitivity in the old group (percentage of increment after the same or lower dose of rhGH per body weight) was increased for both parameters; serum IGF-I increment: 15% in 3-month-old, 42.6% in 11-month-old and 119.1% in 27-month-old rats; and hepatic IGF-Ib mRNA increase: 45% in 3-month-old, 27.8% in 11-month-old and 64.3% in 27-month-old rats. IGF binding protein-3 (IGFBP-3) mRNA level in the liver was significantly decreased in the old group and only a partial reversion occurred in this group after rhGH treatment; the percentage of increment was also higher in the old group of rats. In extrahepatic tissues IGF-I mRNA was not significantly different in the kidney and the testis of the three groups, and the rhGH treatment produced a significant and similar increase of IGF-I mRNA level in the kidney of the three groups of rats and in the testis of the 27-month-old animals. The GHr/GHBP mRNA remained unchanged in the liver and in the kidney or the testis of the three groups, and was not influenced by the rhGH treatment. Exogenous rhGH decreased pituitary GH mRNA accumulation in a more intense manner in the old group versus control of each group: young adult, 25%; middle-aged, 41.2%; and old rats, 55%. The action of rhGH on pituitary immunoreactive GH (IR-GH) content was only significantly evident in the young group. CONCLUSIONS: These results establish that exogenous rhGH recovers the attenuated liver IGF-I gene expression and the diminished plasma IR-IGF-I in old rats to the levels of young adult animals. They also indicate that the hepatic and extrahepatic (kidney and testis) sensitivity to one established dose per weight of exogenous rhGH is not altered in old animals, or could be potentially increased in some tissues.

It is well known that chronic supraphysiological doses of glucocorticoids (GC) inhibit GH secretion in vivo, and stimulate GH secretion from the somatotropes in vitro. It has been suggested that GC exert an inhibitory role in the hypothalamus surpassing the GC-positive effect at the somatotrope level. To test the hypothesis that GC can affect growth hormone-releasing releasing factor (GRF) and somatostatin (SS) at the hypothalamic level, we studied the effect of corticosterone on the immunoreactive content of GRF (IR-GRF) and SS (IR-SS) in cells and media of fetal hypothalamic cells in culture. After 20 days in culture, cells were incubated with serum-free medium containing corticosterone (from 0.3 to 300 nM) for 48 h. Corticosterone had a dual effect on IR-GRF. Concentrations in the range of the glucocorticoid receptor Kd (3 nM) increased peptide content, whereas higher concentrations (30 and 300 nM) decreased IR-GRF content in cells and media. Conversely, corticosterone increased SS cell content, only at a concentration of 3 nM, inducing a 2- to 3-fold increment in media content with the highest doses (30 and 300 nM). These results demonstrated that both GRF and SS are modulated by corticosterone in primary fetal rat hypothalamic cultures. Whereas GRF exhibited a dual response, stimulatory and inhibitory, at low and high corticosterone doses, respectively, SS showed a parallel increase with the corticosterone concentrations.