Reduced somatostatin in hypothalamus of young male mouse increases local but not circulatory GH

The effect of pasireotide on intestinal anastomotic healing with and without whole-body irradiation in a rat model

OBJECTIVE

To examine pasireotide's effect on intestinal anastomotic healing under physiological conditions and following preoperative whole-body irradiation.

MATERIAL AND METHODS

Forty-five male Wistar rats received an ileoileal end-to-end anastomosis. Group 1 (Co, n = 9) served as control. Group 2 (SOM, n = 10) received pasireotide (60 mg/kg) 6 days preoperatively. Group 3 (R-Co, n = 13) was subjected to 8 Gy whole-body irradiation 4 days preoperatively. Finally, group 4 (R-SOM, n = 13) received pasireotide 6 days preoperatively and whole-body irradiation 4 days preoperatively. On postoperative day 4, anastomotic bursting pressure, histology, IGF-1 staining, and collagen density were examined.

RESULTS

Mortality was higher in irradiated animals (30.8% vs. 5.3%, p = 0.021), and anastomotic bursting pressure was significantly lower (median, R-Co = 83 mmHg; R-SOM = 101 mmHg; Co = 149.5 mmHg; SOM = 169 mmHg). Inflammation measured by leukocyte infiltration following irradiation was reduced (p = 0.023), and less collagen was observed, though this was not statistically significant. Bursting pressure did not significantly differ between Co and SOM and between R-Co and R-SOM animals respectively. Semi-quantitative scoring of IGF-1, fibroblast bridging, or collagen density did not reveal significant differences among the groups.

CONCLUSION

Whole-body irradiation decreases the quality of intestinal anastomotic wound healing and increases mortality. Pasireotide does not significantly lessen this detrimental effect.

Somatostatin system: molecular mechanisms regulating anterior pituitary hormones

The somatostatin (SRIF) system, which includes the SRIF ligand and receptors, regulates anterior pituitary gland function, mainly inhibiting hormone secretion and to some extent pituitary tumor cell growth. SRIF-14 via its cognate G-protein-coupled receptors (subtypes 1-5) activates multiple cellular signaling pathways including adenylate cyclase/cAMP, MAPK, ion channel-dependent pathways, and others. In addition, recent data have suggested SRIF-independent constitutive SRIF receptor activity responsible for GH and ACTH inhibition in vitro. This review summarizes current knowledge on ligand-dependent and independent SRIF receptor molecular and functional effects on hormone-secreting cells in the anterior pituitary gland.

Whey protein isolate counteracts the effects of a high-fat diet on energy intake and hypothalamic and adipose tissue expression of energy balance-related genes

The intake of whey protein isolate (WPI) is known to reduce high-fat diet (HFD)-induced body-weight gain and adiposity. However, the molecular mechanisms are not fully understood. To this end, we fed C57BL/6J mice for 8 weeks with diets containing 10 % energy as fat (low-fat diet, LFD) or 45 % energy as fat (HFD) enriched with either 20 % energy as casein (LFD and HFD) or WPI (high-fat WPI). Metabolic parameters and the hypothalamic and epididymal adipose tissue expression of energy balance-related genes were investigated. The HFD increased fat mass and plasma leptin levels and decreased the dark-phase energy intake, meal number, RER, and metabolic (VO₂ and heat) and locomotor activities compared with the LFD. The HFD increased the hypothalamic tissue mRNA expression of the leptin receptor, insulin receptor (INSR) and carnitine palmitoyltransferase 1b (CPT1b). The HFD also reduced the adipose tissue mRNA expression of GLUT4 and INSR. In contrast, WPI reduced fat mass, normalised dark-phase energy intake and increased meal size in HFD-fed mice. The dietary protein did not have an impact on plasma leptin, insulin, glucose or glucagon-like peptide 1 levels, but increased plasma TAG levels in HFD-fed mice. At a cellular level, WPI significantly reduced the HFD-associated increase in the hypothalamic tissue mRNA expression of the leptin receptor, INSR and CPT1b. Also, WPI prevented the HFD-induced reduction in the adipose tissue mRNA expression of INSR and GLUT4. In comparison with casein, the effects of WPI on energy intake and hypothalamic and adipose tissue gene expression may thus represent a state of reduced susceptibility to weight gain on a HFD.

Construction of porcine growth hormone eukaryotic expression vector and its transfection mediated by cationic liposome in mice

The present study was designed to construct the eukaryotic expression vector for pGH mature peptide (mpGH) and to investigate its transfection mediated by cationic liposome (CLs) in COS-7 cells and mice. The cDNA of mpGH ORF was successfully cloned by reverse transcription-PCR (RT-PCR) using the adult pig pituitary gland RNA. The recombinant eukaryotic expression vector, VmpGH, was constructed by ligating the cDNA fragment to the vector VR1020. The successful construction was confirmed by restriction enzyme digestion, and the expression of mpGH was confirmed by RT-PCR, immunofluorescence analyses (IFA), and ELISA in COS-7 cells. The VmpGH and VR1020 plasmids were entrapped with CLs, and four experimental groups of male Kunming mice were administrated with VmpGH / lipoplex or naked VmpGH plasmids at two dosages (0.5 and 1.0 mg/kg), while the mice injected with VR1020-lipoplex at the dosage of 0.5 mg/kg body weight (BW) were used as control. The BWs of the mice administrated with VmpGH-lipoplex at both dosages were significantly higher than not only those of the control (P < 0.01) but also those of mice injected with naked plasmids (P < 0.01), from 30 to 60 days post-transfection. The transcription of VmpGH was detected by RT-PCR in six tissues, including the liver, kidney, spleen, heart, muscle, and blood, of the mice injected with VmpGH-lipoplex, but not in the same tissues of control mice. Furthermore, the mice injected with VmpGH-lipoplex showed higher plasma GH contents than the control mice (P < 0.05), although their IgG contents did not show much difference. Our study demonstrates that the VmpGH plasmids' transfection mediated by CLs can significantly promote the growth of mice, which may be used to improve the livestock production.

Isolated GH deficiency type II: knockdown of the harmful Delta3GH recovers wt-GH secretion in rat tumor pituitary cells

Isolated GH deficiency type II (IGHD II) is the autosomal dominant form of GHD. In the majority of the cases, this disorder is due to specific GH-1 gene mutations that lead to mRNA missplicing and subsequent loss of exon 3 sequences. When misspliced RNA is translated, it produces a toxic 17.5-kDa GH (Delta3GH) isoform that reduces the accumulation and secretion of wild-type-GH. At present, patients suffering from this type of disease are treated with daily injections of recombinant human GH in order to maintain normal growth. However, this type of replacement therapy does not prevent toxic effects of the Delta3GH mutant on the pituitary gland, which can eventually lead to other hormonal deficiencies. We developed a strategy involving Delta3GH isoform knockdown mediated by expression of a microRNA-30-adapted short hairpin RNA (shRNA) specifically targeting the Delta3GH mRNA of human (shRNAmir-Delta3). Rat pituitary tumor GC cells expressing Delta3GH upon doxycycline induction were transduced with shRNAmir-Delta3 lentiviral vectors, which significantly reduced Delta3GH protein levels and improved human wild-type-GH secretion in comparison with a shRNAmir targeting a scrambled sequence. No toxicity due to shRNAmir expression could be observed in cell proliferation assays. Confocal microscopy strongly suggested that shRNAmir-Delta3 enabled the recovery of GH granule storage and secretory capacity. These viral vectors have shown their ability to stably integrate, express shRNAmir, and rescue IGHD II phenotype in rat pituitary tumor GC cells, a methodology that opens new perspectives for the development of gene therapy to treat IGHD patients.