Depletion of hypothalamic growth hormone-releasing hormone by neonatal monosodium glutamate treatment reveals an inhibitory effect of betamethasone on growth hormone secretion in adult rats

The methanol extract of Ceiba pentandra reverses monosodium glutamate-induced cardiometabolic syndrome in rats via the regulation of dyslipidemia, inflammation, oxidative stress, and insulin sensitization

The antidiabetic effects of the methanol extract of the stem bark of Ceiba pentandra (Cp) have been demonstrated in various experimental models. Besides, this extract is rich in 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthaquinone, 2,4,6-Trimethoxyphenol and vavain. However, it remains unknown whether Cp can mitigate cardiometabolic syndrome (CMS). The present study assessed the curative properties of Cp against Monosodium Glutamate (MSG)-induced CMS in rats. Male neonate Wistar rats were intraperitoneally administered with MSG (4 mg/g/day) during the first 5 days of life (postnatal days 2-6). They were kept under standard breeding conditions up to 5 months of age for the development of CMS. Diseased animals were then orally treated with atorvastatin (80 mg/kg/d) or Cp (75 and 150 mg/kg/day) for 28 days during which food intake, body mass, blood pressure, heart rate, glucose, and insulin tolerance were monitored. Plasma and tissues were collected on day 29th to assess the lipid profile, oxidative stress, and inflammatory parameters. The histomorphology of the adipose tissue was also evaluated. Cp significantly (p < 0.001) reduced the obesogenic and lipid profiles, adipocyte size, blood pressure, and oxidative and inflammatory status in MSG-treated rats. Cp also ameliorated glucose (p < 0.05) and insulin sensitivities (p < 0.001) hence, reducing animals' cardiometabolic risk score (p < 0.001). The curative effect of Cp on cardiometabolic syndrome is related to its capacity to reduce oxidative stress, inflammation, dyslipidemia, and increase insulin sensitivity. These results demonstrate the potential of Cp as a good candidate for alternative treatment of CMS.

Adipose cell-free DNA in diabetes

Cancer-associated necrosis is a well-known source of cell-free DNA (cfDNA). However, the origins of cfDNA are not strictly limited to cancer. Additionally, dietary exposure induces apoptosis-induced proliferation in adipocytes, leading to the release of cfDNA. The genetic information derived from cfDNA as a result of apoptosis-induced proliferation contains specific methylation patterns in adipose tissue that can be used as a marker to detect the risk of developing Type 2 diabetes Mellitus (T2DM) in the future. cfDNA is superior to peripheral blood leukocytes (PBL) and whole blood samples for reflecting tissue pathology due to the frequent use of PBL and whole blood samples that do not match tissue pathology. The difficulty of demonstrating that cfDNA is derived from adipose tissue. We propose several promising techniques by analyzing cfDNA derived from adipose tissue to detect T2DM risk. First, adipose-specific genes such as ADIPOQ and Leptin were utilized. Second, MCTA-Seq, EpiSCORE, deconvolution, multiplexing, and automated machine learning (AutoML) were used to determine the proportion of total methylation in related genes.

Galanin-like peptide stimulates food intake via activation of neuropeptide Y neurons in the hypothalamic dorsomedial nucleus of the rat

Galanin-like peptide (GALP), a 29-amino-acid neuropeptide, is located in the hypothalamic arcuate nucleus (ARC), binds to galanin receptor subtype 2, and induces food intake upon intracerebroventricular (icv) injection in rats. However, neural mechanisms underlying its orexigenic action remain unclear. We aimed to identify the nuclei and neuron species that mediate the food intake in response to icv GALP injection. Intracerebroventricular injection of GALP, as powerfully as that of neuropeptide Y (NYP), increased food intake for the initial 2 h. GALP injected focally into the dorsomedial nucleus (DMN), but not the ARC, lateral hypothalamus, or paraventricular nucleus (PVN), stimulated food intake for 2 h after injection. In contrast, galanin injected into the DMN had no effect. DMN-lesion rats that received icv GALP injection showed attenuated feeding compared with control rats. Intracerebroventricular GALP injection increased c-Fos expression in NPY-containing neurons in the DMN, but not the ARC. GALP increased the cytosolic calcium concentration ([Ca(2+)](i)) in NPY-immunoreactive neurons isolated from the DMN, but not the ARC. Furthermore, both anti-NPY IgG and NPY antagonists, when preinjected, counteracted the feeding induced by GALP injection. These data show that icv GALP injection induces a potent short-term stimulation of food intake mainly via activation of NPY-containing neurons in the DMN.

Ghrelin stimulates GH but not food intake in arcuate nucleus ablated rats

Ghrelin, an endogenous ligand for the GH secretagogue receptor 1a (GHS-R(1a)), was originally purified from the rat stomach. Ghrelin mRNA and peptide have also been detected in the hypothalamus and pituitary. Ghrelin is a novel acylated peptide that regulates GH release and energy metabolism. GHS-R(1a) mRNA is expressed in the pituitary gland as well as in several areas of the brain including the hypothalamus. In this study, we examined whether ghrelin could stimulate GH secretion and feeding in chronic GHRH, neuropeptide Y, and agouti-related protein deficient rats that were neonatally treated with monosodium glutamate (MSG), which destroys the neurons in the hypothalamic arcuate nucleus (ARC). Intravenous (iv) administration of rat ghrelin (10 micro g/kg body weight) increased plasma GH levels significantly in the normal adult male rats during a GH trough period of pulsatile GH secretion, while iv injection of ghrelin in MSG-treated rats resulted in a markedly attenuated GH response. When rat ghrelin (10 micro g/rat) was administered intracerebroventricular (icv), plasma GH levels were increased comparably in normal control and MSG-treated rats. However, the GH release after icv injection of ghrelin was markedly diminished compared with that after iv administration of a small amount of ghrelin in normal control rats (icv: 10 micro g/rat, iv: approximately 4.0 micro g/rat), indicating that the GH-releasing activity of exogenous ghrelin is route dependent and at least in part via hypothalamic ARC. The icv administration of 1 micro g of ghrelin increased significantly 4-h food intake in normal control, whereas the peptide did not increase food intake in MSG-treated rats, indicating that the feeding response to ghrelin requires intact ARC. Taken together, the primary action of ghrelin on appetite control and GH releasing activity is via the ARC even though it might act on another type of GHS-R besides GHS-R(1a).

Increase in mRNA concentrations of pituitary receptors for growth hormone-releasing hormone and growth hormone secretagogues after neonatal monosodium glutamate treatment

Previous studies have demonstrated that neonatal monosodium glutamate (MSG) treatment destroys growth hormone releasing-hormone (GHRH) neurones within the hypothalamic arcuate nucleus, decreases serum GH and insulin-like growth factor (IGF-I) concentrations, and retards linear growth. In the present study we investigated whether expression of pituitary GH, GHRH receptors (GHRH-R), growth hormone secretagogue receptors (GHS-R) and liver IGF-I is altered in this model of GHRH deficiency. In addition, we investigated if treatment of MSG-lesioned rats with the GHRH agonist, JI-38, would 'normalise' the GH-axis. Serum GH and IGF-I concentrations were determined by RIA, GH mRNA levels were evaluated by Northern blotting, and GHRH-R, GHS-R and IGF-I mRNA levels were measured by semiquantitative RT-PCR. In accord with previous reports, neonatal MSG treatment caused 50% and 76% decreases in serum GH and IGF-I concentrations, respectively, at 8 weeks of age. The decline in circulating GH was accompanied by a 56% reduction in total pituitary GH content, which was a reflection of the decrease in total pituitary protein. However, GH concentration (per mg protein) was unaltered. Despite the maintenance of a normal GH concentration, GH mRNA concentration (per microg total RNA) was suppressed by 42%, compared to saline-treated controls (P<0.05). These data indicate that a post-transcriptional mechanism, such as a reduction in the GH secretory rate, acts to maintain intracellular GH concentrations. The fall in circulating concentrations of GH leads to a 42% decrease in liver IGF-IB mRNA levels, while liver IGF-IA transcripts showed only a 27% suppression. In contrast, pituitary GHRH-R and GHS-R mRNA levels (per microg total RNA) were increased in MSG-lesioned rats by 96% and 180% of normal values (P<0.01), respectively. Twice daily treatment of MSG-lesioned rats (for 2 weeks) with the GHRH agonist, JI-38, increased serum GH and IGF-I levels, as measured 20 h after the last agonist injection. However, GH, IGF-I, GHRH-R and GHS-R mRNA levels were not altered at this time. These results demonstrate that intermittent GHRH agonist treatment stimulates pituitary GH secretion and GH in turn stimulates hepatic IGF-I but that effects on gene expression are not sustained. Collectively, our observations demonstrate a complex interplay between transcriptional, translational and post-translational mechanisms within each level of the GH-axis following destruction of GHRH neurones by neonatal MSG treatment.

Effects of continuous and repetitive administration of a potent analog of GH-RH(1-30)-NH2 on the GH release in rats treated with monosodium glutamate

To assess the efficacy of a potent GH-releasing hormone (GH-RH) analog (D-Ala2,Nle27,Gaba30-GH-RH-(1-30)-amide) in the treatment of GH deficiency, we investigated the effects of chronic administration of this analog (A-495) on growth responses in monosodium glutamate (MSG)-lesioned rats. Basal serum GH concentrations, GH responses to bolus injections of GH-RH, as well as acceleration of body gain and linear growth were compared after long-term continuous and repetitive administration of A-495. The effects of continuous and repetitive administration of the analog on GH responses in vitro were also compared using the superfused pituitary cell system method. Treatment with MSG reduced the body weight and linear growth of the animals (-22% and -11%, respectively), the basal serum GH concentration (-66%), and the GH-RH-induced absolute GH responses (-61%) but did not alter the relative GH responses (to basal GH concentrations). Repetitive administration of 10 micrograms daily doses of A-495 at 24 h intervals for 2 weeks highly increased the GH responsiveness to GH-RH and induced catch-up growth, by which MSG-treated animals achieved the growth rate of normal controls. However, basal serum GH concentrations were only modestly enhanced. Continuous infusion of A-495 at the same daily dose resulted in slight increases in the GH-RH-induced GH rises, moderate acceleration of body gain, and no change in linear growth. Basal serum GH concentrations were not significantly influenced by this treatment. These results demonstrate that exogenous GH-RH pulses administered at lower frequency than the frequency of the physiological GH secretion are able to fully restore the normal growth rate of the GH deficient rats. The effectivity of the treatment is rather dependent on the magnitude of GH rises than the basal GH level. Although continuous administrations of the GH-RH is also have some effect on the body gain, repetitive administration is more effective at the same daily dose. Our results from in vitro experiments show that, in addition to the low magnitude of the GH-RH-stimulated GH rises, desensitization of the GH secretory response might also be accounted for the low effectivity of the continuously administered GH-RH. Present results demonstrate the therapeutic usefulness of our new GH-RH analog and are the first to evidence that GH-RH need not be administered as frequently as the appearance of the endogenous GH pulses to restore the normal growth of the GH deficient rats.

Immunohistochemical evidence of neurons with GHRH or LHRH in the arcuate nucleus of male mice and their possible role in the postnatal development of adenohypophysial cells

BACKGROUND

The neonatal administration of monosodium L-glutamate (MSG) has been used in investigations of the possible role of the arcuate nucleus in neuroendocrine regulation during postnatal development. We used this method to examine whether the mouse arcuate contained cell bodies immunoreactive with antisera to growth hormone releasing hormone (GHRH) or luteinizing hormone releasing hormone (LHRH), and whether these hypothalamic peptides affect synthesis and secretion of growth hormone and gonadotropin and the testis.

METHODS

The hypothalamus, pituitary, and testes of adult male mice treated with MSG during the neonatal period were fixed in Bouin's fluid or 10% neutral formalin. The hypothalamus was used in immune staining, the pituitary was used in both morphometry and immune staining, and the testis was stained with hematoxylin and eosin.

RESULTS

Body weights in control and treated mice were not different. The treated mice had more subcutaneous adipose tissue and a shorter body than the control mice. The testes were heavier in the controls. Many perikarya immunoreactive with antisera to GHRH or LHRH were found in the arcuate nucleus in control mice, but few such perikarya were found in this nucleus in treated mice. The size of the anterior lobe and the number and size of GH cells, follicle stimulating hormone (FSH) cells, and prolactin (PRL) cells in treated mice were less than those of control mice.

CONCLUSIONS

GHRH and LHRH neurons in the arcuate nucleus in male mice may cause body and testis weight to increase via GH and LH cells, respectively, in the adenohypophysis during postnatal development. There are some differences in the hypothalamo-pituitary-testis axis of mice and rats.