V. De Gennaro Colonna

Reduced growth hormone releasing factor (GHRF)-like immunoreactivity and GHRF gene expression in the hypothalamus of aged rats

Growth hormone releasing factor-like immunoreactivity (GHRF-LI) and GHRF mRNA levels were evaluated in the hypothalamus of aged (24 months) and young (3 months) rats by semiquantitative immunocytochemistry and slot blot hybridization technique, respectively. Simultaneous detection of reduced GHRF-LI and GHRF mRNA levels in aged rats as compared to young counterparts demonstrates the existence in aged rats of an impaired function of GHRF-producing neurons.

Effects of long-term disease-modifying antirheumatic drugs on endothelial function in patients with early rheumatoid arthritis.

Rheumatoid arthritis (RA) is associated with enhanced atherosclerosis and impaired endothelial function early after the onset of the disease and cardiovascular (CV) disease represents one of the leading causes of morbidity and mortality. It is well known that disease modifying antirheumatic drugs (DMARDs) are able to improve the course of the disease and the quality of life of these patients, but little is known about the effects of DMARDs on CV risk and endothelial dysfunction. Our goal was to examine the effects of long-term therapy with DMARDs on endothelial function and disease activity in early RA (ERA). Twenty-five ERA patients (mean age 52 ± 14.6 years, disease duration 6.24 ± 4.10 months) without evidence of CV involvement were evaluated for disease activity score (DAS-28), 2D-echo derived coronary flow reserve (CFR), common carotid intima-media thickness (IMT) and plasma asymmetric dimethylarginine (ADMA) levels at baseline and after 18 months of treatment with DMARDs (10 patients with methotrexate and 10 with adalimumab). DMARDs significantly reduced DAS-28 (6.0 ± 0.8 vs. 2.0 ± 0.7; P < 0.0001) and improved CFR (2.4 ± 0.2 vs. 2.7 ± 0.5; P < 0.01). Common carotid IMT and plasma ADMA levels did not show significant changes. The present study shows that DMARDs, beyond the well known antiphlogistic effects, are able to improve coronary microcirculation without a direct effect on IMT and ADMA, clinical markers of atherosclerosis. Treatment strategies in ERA patients with high inflammatory activity must be monitored to identify beneficial effects on preclinical markers of vascular function.

Sildenafil reduces L-NAME-induced severe hypertension and worsening of myocardial ischaemia-reperfusion damage in the rat.

Phosphodiesterase‐5 inhibitors are beneficial in pulmonary hypertension and congestive heart failure, the two conditions associated with coronary heart disease and ischaemia. We investigated whether sildenafil counteracts the cardiovascular alterations induced by N ω‐nitro‐L‐arginine methyl ester (L‐NAME) in the rat.

Growth hormone regulation of growth hormone-releasing hormone gene expression

Slot-blot hybridization technique was used to evaluate growth hormone-releasing hormone (GHRH) mRNA levels in the hypothalamus of long-term (14 days) hypophysectomized (HPX) rats treated or not with 125 micrograms hGH/rat, twice daily IP, since the first day postsurgery. In addition, mRNA levels were determined in the hypothalamus of short-term (4 days) GH-treated (250 micrograms hGH/rat, twice daily IP) intact rats. GHRH mRNA levels were increased in HPX rats, and GH treatment partially counteracted this rise. Short-term administration of GH decreased GHRH mRNA levels in intact rats. These results, evaluated together with previous findings showing decreased hypothalamic GHRH-like immunoreactivity in both HPX rats and intact rats given GH (6, 7, 9), indicate that GH exerts a negative feedback action on the synthesis and release of GHRH.

Hexarelin exhibits protective activity against cardiac ischaemia in hearts from growth hormone-deficient rats

Male rats were treated with growth hormone (GH)-releasing hormone antiserum to induce selective GH deficiency. The chronic administration of hexarelin to these GH-deficient rats had a pronounced protective effect against ischaemic and post-ischaemic ventricular dysfunction. Hexarelin prevented hyper-responsiveness of the coronary vascular bed to angiotensin II and also prevented the reduction in generation of 6-keto-prostaglandin F1alpha in perfused hearts from GH-deficient rats. The most plausible interpretation of these findings is that hexarelin acts via stimulation of specific cardiac and vascular receptors, triggering currently unknown cytoprotective mechanisms that are responsible for resistance to ischaemic insults and for the preservation of the integrity of the endothelial vasodilation function.

Worsening of ischemic damage in hearts from rats with selective growth hormone deficiency.

The effects of growth hormone (GH) deficiency on cardiac function were studied in young male rats administered an anti-GH-releasing hormone (GHRH) serum from postnatal day 20 to 40. Dependence of heart abnormalities on GH deficiency was ascertained by giving a group of anti-GHRH serum-treated rats GH replacement therapy. Heart preparations from anti-GHRH serum-treated rats, undergoing low-flow ischemia, showed a progressive increase in left ventricular end-diastolic pressure with poor recovery of mechanical activity and increased coronary perfusion pressure upon reperfusion. Hearts from anti-GHRH serum + GH-treated rats, undergoing global reduction to the flow, showed only a minimal increase of left ventricular end-diastolic pressure and, upon reperfusion, cardiac mechanical activity recovered almost completely. Similar findings were also observed in heart preparations from control (normal rabbit serum-treated) rats. Infusion of acetylcholine (10(-6) M) into heart preparations in the preischemic period increased coronary perfusion pressure values more markedly in hearts from normal rabbit serum- and anti-GHRH serum + GH-treated rats than in those from anti-GHRH serum-treated rats. These results indicate that selective GH deficiency in young male rats renders the heart more sensitive to ischemic damage and leads to an impairment of cardiac muscarinic receptor function.

Cardiovascular involvement in psoriatic arthritis

Psoriasis is a chronic, genetically determined and immunomediated inflammatory skin disease that affects 2-3% of the Caucasian population. A considerable proportion of these patients develop a form of inflammatory arthritis known as psoriatic arthritis (PsA), although the prevalence of this has not been well defined. Patients with PsA have a higher mortality rate than the general population and the risk of mortality is related to disease severity at the time of presentation. Endothelial dysfunction and early atherosclerosis have been found in patients with PsA without any cardiovascular disease (CVD) risk factors, and experts believe that CVD is one of the leading causes of death, as it is in patients with rheumatoid arthritis (RA). Various disease-related mechanisms may be involved in the development of premature vascular damage in both cases, including an increased synthesis of proinflammatory mediators (such as cytokines, chemokines and adhesion molecules), autoantibodies against endothelial cell components, perturbations in T-cell subsets, genetic polymorphisms, hyperhomocysteinemia, oxidative stress, abnormal vascular repair, and iatrogenic factors. In a recent study of 22 patients with PsA without any signs of CVD, we found that the plasma concentration of asymmetric dimethylarginine (ADMA) levels were significantly high and coronary flow reserve (CFR) was significantly reduced. Moreover, there was a significant correlation between CFR and plasma ADMA levels in the PsA group. The significant correlation between the reduced CRF and increased ADMA levels suggests that, like patients with early RA, PsA patients suffer from endothelial dysfunction and impaired coronary microcirculation. Active PsA is a risk factor for CVD, and so PsA patients should be screened for subclinical forms of the disease and its risk factors, and an early treatment approach should be adopted.

Effects of treatment strategy on endothelial function

A large body of evidence indicates that endothelial dysfunction is a characteristic of patients with arterial hypertension. As functional abnormalities lead to impaired endothelium-dependent vasodilation, this early step of atherogenesis is potentially reversible. In addition to reducing blood pressure, the major families of anti-hypertensive drugs have a number of pleiotropic effects that could improve endothelial function. In particular, the renin-angiotensin system plays an important role in the pathogenesis of both arterial hypertension and endothelial dysfunction, and so drugs capable of limiting the dangerous effects of this hormonal axis, such as angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers and renin inhibitors, could help prevent/delay/reverse the atherosclerotic process. New third-generation β-blockers and 5-phosphodiesterase inhibitors may affect endothelial function. Furthermore, the HMGCoA-reductase inhibitors currently used to reduce cholesterol levels have major pleiotropic anti-inflammatory and anti-hypertensive effects. The preservation or recovery of endothelial function in hypertensive patients is crucial to inhibit the development of atherosclerosis and the onset of cardiovascular events. This review focuses on the ancillary effects of hypertensive drugs and HMGCoA-reductase inhibitors that go beyond lowering blood pressure and cholesterol levels.

Growth Hormone Secretion Is Differently Affected in Genetically Obese Male and Female Rats

Growth hormone (GH) secretion is markedly blunted in obesity. Reportedly, genetically obese Zucker rats show a reduced GH secretion due to an impaired function of hypothalamic neurons producing the GH-releasing hormone (GHRH). The aim of this work was: (1) to compare the in vitro GH responsiveness to GHRH in genetically obese female versus male Zucker rats and, (2) to evaluate the function of hypothalamic GHRH and somatostatin and of pituitary receptors for these neurohormones as assessed by the effectiveness of GHRH and somatostatin on adenylate cyclase (AC) activity. Baseline GH secretion of pituitaries obtained from male and female obese rats was not different and similar to that present in lean counterparts. Stimulation with 10(-7) M GHRH elicited a significantly lower GH secretion from the pituitaries of obese male rats but induced a similar GH secretion from the pituitaries of lean and obese female rats. In these pituitaries, GH concentration was similar in obese versus lean male and female rats [corrected]. A sex-related difference was also evidenced when plasma concentrations of somatomedin C (IGF-I) were evaluated. Obese male rats had lower IGF-I concentrations than lean counterparts, while this was not the case for obese versus lean female rats. Evaluation of AC activity following GHRH disclosed a lower activation in obese than in lean male rats, whereas in the females the enzyme activation was higher in obese than in lean animals. Conversely, the inhibitory effect of somatostatin on forskolin-stimulated AC was similar in pituitary membranes of obese and lean rats of both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the Hypothalamic-Pituitary Somatotropic Function of Infant Hypothyroid Rats

Abstract The effects of the perturbation of the pituitary-thyroid axis induced during development on the functional activity of the growth hormone (GH) regulatory neuronal systems, GH-releasing hormone (GHRH), and somatostatin (SS) were studied in 14- and 21-day-old rats made hypothyroid by giving dams propylthiouracil in the drinking water since the day of parturition. Infant hypothyroid rats, both at 14 and 21 days of life, had elevated plasma thyroid-stimulating hormone levels and decreased pituitary and plasma GH levels. Simultaneous determination of hypothalamic GHRH/SS-like immunoreactivity (LI) and GHRH/SS mRNA levels did not reveal any difference in 14-day-old hypothyroid rats when compared with age-matched controls. In contrast, 21-day-old hypothyroid rats had decreased GHRH-LI content and a striking rise in GHRH mRNA levels, whereas SS-LI content and SS gene expression remained unaltered. These data indicate that in infant hypothyroid rats, changes in the functional activity of the GHRH neuronal system occur later than changes in GH secretion and are probably dependent on the GH deficiency. The functional activity of SS neurons was apparently unaltered in these hypothyroid rats, pointing to a lesser sensitivity of this system to the perturbation of the pituitary-thyroid axis.