Effects of acetylsalicylic acid and indomethacin on growth hormone secretion in man

Potential role of salicylates in type 2 diabetes

OBJECTIVE

To review the evidence base supporting the use of salicylates for glucose level control in patients with type 2 diabetes and provide a comprehensive review of available information describing the potential role of salicylates and, in particular, salsalate, for glucose control in type 2 diabetes prevention and treatment.

DATA SOURCES

A literature search using MEDLINE (1966-March 2010), PubMed, and Google Scholar was conducted using the search terms salicylates, salicylic acid, aspirin, salsalate, acetylsalicylic acid, insulin, glucose, glycemic control, diabetes, hyperglycemia, and nuclear factor. The bibliographies of identified articles were reviewed for additional citations.

STUDY SELECTION AND DATA EXTRACTION

All relevant English-language information on the pharmacology, efficacy, and safety of salicylates for glucose control related to insulin resistance or diabetes prevention were reviewed. Preclinical data, clinical trials, and case reports were identified, evaluated, and included in this systematic review.

DATA SYNTHESIS

Treatment of inflammation may be a potential novel strategy in prevention and treatment of type 2 diabetes, in which the body is resistant to the effects of insulin. Previous and recent studies reveal a possible relationship between inflammation and obesity. The chronic activation of the immune system due to low-grade inflammation was found in several studies to be associated with obesity, and this, in turn, can promote development of insulin resistance and impaired glucose tolerance. Administration of salicylates was shown over a century ago to lower glucose levels in patients with diabetes. Many in vitro and in vivo pharmacologic studies have demonstrated a glucose-lowering effect of salicylates. Salicylates, especially salsalate, were found in several clinical studies and case reports to be potential agents for diabetes treatment with a favorable safety profile. Although these studies had inherent limitations, such as small numbers of patients and short duration, the vast majority showed significant glucose-lowering effects. A large randomized trial, the National Institute of Diabetes and Digestive and Kidney Diseases-sponsored Targeting Inflammation with Salsalate in Type 2 Diabetes (TINSAL-T2D) trial, recently concluded that salsalate lowers hemoglobin A(1c) levels and improves glycemic control in patients with type 2 diabetes.

CONCLUSIONS

Salicylates, especially salsalate, appear to be a promising treatment option for prevention or treatment of diabetes by lowering glucose levels. More extensive studies are needed to confirm the mechanisms involved and whether the effects are sustainable with continued administration of these agents. Further studies are warranted.

Hormonal influences of early postnatal indomethacin and ibuprofen in neonatal rats

OBJECTIVE

Indomethacin and ibuprofen are administered to preterm neonates for symptomatic patent ductus arteriosus. The drugs suppress prostaglandins (PGs) which modulate growth and secretion of various hormones. We examined the hypothesis that early postnatal indomethacin and ibuprofen influence growth and GH-IGF-I-insulin and HPA axes in neonatal rats.

DESIGN

Rat pups received IP injections of saline (Sal) on P1, P2, and P3; 10mg/kg ibuprofen on P1 followed by 5mg/kg on P2 and P3; or 0.2mg/kg indomethacin on P1 followed by 0.1mg/kg on P2 and P3. Serum and hepatic GH, GHBP and IGF-I; and serum corticosterone and insulin levels were determined.

RESULTS

Ibuprofen suppressed somatic growth in the sucking rats, but the effect was transient, resolving by P14. Indomethacin had an opposite, latent effect on body weight and liver to body weight ratios in weanling rats. Both indomethacin and ibuprofen had profound hormonal effects that differed in magnitude and timing. Indomethacin resulted in a sustained elevation in corticosterone levels at P21, while ibuprofen increased serum and hepatic GH levels. Both drugs suppressed GHBP in serum at P7 and P14; and liver at P4 and P7, but a rebound increase in serum GHBP was noted at P21 with Ibuprofen only. Both drugs increased serum IGF-I at P7. The effect remained sustained with indomethacin.

CONCLUSIONS

These results provide evidence for an involvement of PGs in the regulation of growth as well as the GH-IGF and HPA axes. Therefore, early postnatal exposure to PG inhibitors may further exacerbate postnatal growth restriction and ability to cope with stress.

Modulation of the growth hormone-insulin-like growth factor (GH-IGF) axis by pharmaceutical, nutraceutical and environmental xenobiotics: an emerging role for xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. A review

The growth hormone-insulin-like growth factor (GH-IGF) axis has gained considerable focus over recent years. One cause of this increased interest is due to a correlation of age-related decline in plasma GH/IGF levels with age-related degenerative processes, and it has led to the prescribing of GH replacement therapy by some practitioners. On the other hand, however, research has also focused on the pro-carcinogenic effects of high GH-IGF levels, providing strong impetus for finding regimes that reduce its activity. Whereas the effects of GH/IGF activity on the action of xenobiotic-metabolizing enzyme systems is reasonably well appreciated, the effects of xenobiotic exposure on the GH-IGF axis has not received substantial review. Relevant xenobiotics are derived from pharmaceutical, nutraceutical and environmental exposure, and many of the mechanisms involved are highly complex in nature, not easily predictable from existing in vitro tests and do not always predict well from in vivo animal models. After a review of the human and animal in vivo and in vitro literature, a framework for considering the different levels of direct and indirect modulation by xenobiotics is developed herein, and areas that still require further investigation are highlighted, i.e. the actions of common endocrine disruptors such as pesticides and phytoestrogens, as well as the role of xenobiotic-metabolizing enzymes and the transcription factors regulating their expression. It is anticipated that a fuller appreciation of the existing human paradigms for GH-IGF axis modulation gained through this review may help explain some of the variation in levels of plasma IGF-1 and its binding proteins in the population, aid in the prescription of particular dietary regimens to certain individuals such as those with particular medical conditions, guide the direction of long-term drug/nutraceutical safety trials, and stimulate ideas for future research. It also serves to warn athletes that using compounds touted as performance enhancing because they promote short-term GH release could in fact be detrimental to performance in the long-run.

Endocrine Function Is Altered in Chronic Migraine Patients with Medication-Overuse

OBJECTIVE

To evaluate the effects of analgesic overuse on endocrine function in patients with chronic migraine and medication-overuse headache (CM-MOH).

BACKGROUND

Chronic migraine is frequently associated with an overuse of symptomatic medications. Drugs currently used in acute migraine attacks are associated with several endocrine effects. At present, the endocrine effects of medication overuse in chronic migraine patients are unknown.

METHODS

Eighteen patients with CM-MOH, diagnosed according to the ICHD-II criteria, and 18 healthy controls received an intravenous administration of GHRH, hCRH, and TRH. Plasma concentrations of GH, TSH, ACTH, and cortisol were measured for a 90-minute period after administration of the specific releasing hormones.

RESULTS

Hormonal basal concentrations were similar in both groups. GH response to GHRH was significantly reduced in patients with CM-MOH in comparison with controls. TRH induced a reduction of TSH concentrations only at the end of the test. After hCRH administration, ACTH and cortisol concentrations were significantly higher in cases than in controls. A significant correlation between duration of the disease and altered hormonal response was found.

CONCLUSIONS

Our study shows that both corticotropic and somatotropic functions are significantly impaired in CM-MOH patients and suggests a role for hormones in the development of chronic migraine.

Acetylsalicylic acid inhibits the pituitary response to exercise-related stress in humans

PURPOSE

Prostaglandins (PGs) modulate the activity of the hypothalamus-pituitary axis, and pituitary hormones are largely involved in the physiological responses to exercise. The purpose of this study was to analyze the effects of acetylsalicylic acid (ASA), an inhibitor of PGs synthesis, in the pituitary responses to physical stress in humans.

METHODS

Adrenocorticotropin (ACTH), beta-endorphin, cortisol, growth hormone (GH), and prolactin (PRL) responses to exercise were evaluated after administration of either placebo or ASA. Blood samples for hormone evaluations before (-30, -15, and 0 pre) and after (0 post, +15, +30, +45, +60, and +90 min) a 30-min treadmill exercise (75% of .VO(2max)) were taken from 12 male athletes during two exercise trials. One tablet of ASA (800 mg), or placebo, was administered two times daily for 3 d before and on the morning of each exercise-test.

RESULTS

The results clearly show that, compared with placebo, ASA ingestion significantly blunted the increased serum ACTH, beta-endorphin, cortisol, and GH levels before exercise (anticipatory response) and was associated with reduced cortisol concentrations after exercise. Furthermore, although no differences in the GH response to exercise were shown, a significantly reduced total PRL response to stress condition was observed after ASA.

CONCLUSION

ASA influences ACTH, beta-endorphin, cortisol, GH, and PRL responses to exercise-related stress in humans (preexercise activation/exercise-linked response). Even though it is not possible to exclude direct action for ASA, our data indirectly confirm a role of PGs in these responses. We have to further evaluate the nature of the preexercise endocrine activation and, because of the large use of anti-inflammatory drugs in athletes, whether the interaction between ASA and hormones might positively or negatively influence health status, performance, and/or recovery.

Ibuprofen fails to increase plasma growth hormone levels in humans

In eight healthy volunteers, basal and arginine-stimulated plasma glucose and growth hormone levels were determined during administration of a placebo and after 3 days of ibuprofen (800 mg four times daily). Ibuprofen had no significant effect on basal or stimulated plasma glucose or growth hormone levels. As is not the case with indomethacin, ibuprofen fails to increase basal and arginine-stimulated plasma growth hormone levels. This suggests that the effect of indomethacin on growth hormone secretion is due to a mechanism unrelated to inhibition of prostaglandin synthesis.

Indomethacin increases plasma growth hormone levels in man

In seven normal volunteers, the basal and arginine-stimulated levels of plasma growth hormone, glucose, glucagon, and free fatty acids and serum insulin was determined during placebo and during indomethacin 25 mg four times daily. Basal plasma growth hormone was higher during indomethacin (5.4 +/- 1 vs 1.7 +/- 2 ng/ml, p less than 0.005), as was the mean integrated response to intravenous arginine (40 +/- 14 vs 6 +/- 4 ng.min/ml, p less than 0.05). Despite lack of effect on plasma glucagon, indomethacin decreased the insulin response to arginine. The fall in free fatty acids during arginine infusion was decreased by indomethacin, which may in part be due to increased plasma growth hormone levels. In view of the many patients treated with indomethacin, the effect on growth hormone may be of clinical importance.

Hormonal, haemodynamic, and subjective effects of intravenously infused indomethacin: no change in the physiological response to hypertonic saline challenge

This double-blind, placebo-controlled human study was performed to determine the endocrine responses to intravenously administered indomethacin at two dose rates (0.36 or 0.72 mg/kg bolus followed by 0.071 or 0.143 mg/kg/hr for 150 min.). A 5% hypertonic saline infusion was used for further assess the hormonal systems regulating body fluid and electrolyte balance. Plasma renin activity (PRA) and concentrations of aldosterone and vasopressin (AVP) were unaffected by indomethacin. Hypertonic saline caused a 5% increase in plasma sodium and a 4.2% increase in serum osmolality, with a concomitant two-fold rise in plasma AVP levels and significant declines in PRA and aldosterone. Indomethacin had no effects on these responses, and did not affect plasma catecholamine concentrations, but the hypertonic saline infusion doubled the noradrenaline levels in plasma. Atrial natriuretic peptide (ANP)-like immunoreactivity in plasma was not affected by indomethacin nor by hypertonic saline. The higher dose rate of indomethacin resulted in significant stimulation of growth hormone release, but plasma prolactin levels were not influenced. Thus acute intravenous administration of indomethacin proved to be devoid of significant effects on the multihormonal system regulating fluid and electrolyte balance.

Different effects of prostaglandins E2 and F2 alpha on triglyceride levels in uterine smooth muscle from diabetic diestrous rats

Triglyceride (TG) concentrations in uterine strips isolated from diestrous normal rats, from diestrous streptozotocin (single iv. injection of 65 mg X Kg body weight-1)-diabetic rats and from diestrous diabetic animals, treated in vivo with insulin (protamine zinc insulin 4U X day-1, 6 days, sc.), were measured. Determinations were made immediately following killing (0 min, or postisolation) as well as after an incubation period in glucose-free medium (60 min, or postincubation), with or without additions. The basal or postisolation levels of TGs (0 min) in the uterus from control normal rats (TGs: 17.0 +/- 0.5 mumol X g-1, d.w.; blood glucose: 100.4 +/- 4.8 mg X dl-1) were lower (P less than 0.001) than in streptozotocin-diabetics (TGs: 28.5 +/- 0.6 mumol X g-1, d.w.; blood glucose: 302.0 +/- 10.1 mg X dl-1) and the treatment with insulin (blood glucose: 165.0 +/- 14.7 mg X dl-1), restored TGs towards normal (19.3 +/- 1.3 mumol X g-1, d.w.). The postisolation levels of TGs (0 min) in the uterus from normal controls did not differ in comparison with postincubation values (60 min), either without additions or in presence of indomethacin (5 X 10(-6)M) or of prostaglandins (PGs) E2 or F2 alpha, at 10(-9)M. On the contrary, in uteri from diabetic animals, the higher initial TG levels diminished spontaneously in comparison to controls (P less than 0.001) following 60 min of incubation without additions; this decrement being antagonized by indomethacin or by propranolol (10(-6)M). Moreover, exogenous PGE2 failed to alter the effect of indomethacin, whereas PGF2 alpha evoked its abolition. In addition, propranolol, which effectively blocked the spontaneous decrement of TGs as did indomethacin, prevented also the influence of PGF2 alpha on the action of the cyclo-oxygenase inhibitor. In the case of uteri from diabetic rats treated in vivo with insulin, TG levels remained unaltered at the end of an incubating period of 60 min without additions and so they did following the administration of indomethacin or PGF2 alpha. The results document that the regulation of TGs in the diestrous rat uteri, suspended in glucose-free solution, is affected differently by PGE2 and F2 alpha, depending on the existence or not of an untreated diabetic condition. They also suggest that the action of PGF2 alpha may involve the activation of tissue beta-adrenoreceptors.

Prostaglandin E2 and prostaglandin F2 regulation of triglyceride levels in uterine smooth muscle from restricted-diet estrous and diestrous rats

Triglyceride concentrations in uterine strips isolated from estrous and diestrous normal-fed or restricted-diet (50% food intake for 15 days) rats, were measured. Determinations were made immediately following killing (0 min, or postisolation) as well as after a period in glucose-free medium, (60 min or post-incubation) with or without additions. The postisolation levels of triglycerides (0 min) in the uterus from normal-fed estrous animals were lower than in diestrus but in each group did not differ in comparison with postincubation values (60 min), either without additions or in the presence of indomethacin (10-6M). Initial (0 min) tissue triglycerides of estrous and diestrous partially-starved rats were significantly higher than in their respective fed controls and exhibited different modifications depending on the stage of the sex cycle. In estrus, levels remained unaltered at the end of an incubating period without additions and declined in the presence of indomethacin. This influence of indomethacin was not modified by added PGF2 (10(-9)M) but was effectively abolished by PGE2 (10(-9)M). On the contrary, in diestrus, initial triglyceride levels diminished spontaneously following 60 min without additions, this being antagonized by indomethacin or propranolol (10(-6)M). Furthermore, exogenous PGE2 failed to alter the effect of indomethacin whereas PGF2 evoked its abolition. Propranolol, which effectively blocked the spontaneous decrement of triglycerides as did indomethacin, prevented also the influence of PGF2 on the action of indomethacin. The foregoing results are compatible with the notion that the regulation of triglycerides in rat uteri suspended in the absence of exogenous substrate, is affected differently by prostaglandin E2 and F2 alpha depending on the state of the sex cycle. They also suggest that the phenomenon may involve the activation of the beta adrenoreceptors.

Increased secretion of insulin but unchanged secretion of growth hormone in hyperglycaemic type II diabetics treated with acetyl-salicylic acid

The effect of acetyl-salicylic acid (ASA, 3 g/d for three days) on basal and arginine-stimulated concentrations of insulin and growth hormone was studied in seven type II diabetics. From 120 min before until 120 min after the infusion of arginine-hydrochloride (30 g/30 min) blood glucose concentrations were clamped at hyperglycaemic levels both during treatment with ASA (blood glucose: 12.7 +/- 1.2 mmol/l) and during a control experiment without ASA (blood glucose: 12.9 +/- 1.3 mmol/l). Concentrations of serum insulin in the hyperglycaemic state prior to arginine infusion were increased during treatment with ASA, whereas increments of serum insulin induced by i.v. arginine were unaffected. No difference was seen in either basal or stimulated concentrations of growth hormone. Thus, ASA enhances glucose-induced secretion of insulin in type II diabetics but fails to potentiate the glucose-dependent suppression of arginine-stimulated growth hormone release. In contrast to the pancreatic beta-cell the glucose-sensitive regulatory mechanism of growth hormone release appears to be unaffected by the inhibition of endogenous prostaglandin synthesis.

Effect of indomethacin on the metabolic and hormonal response to a standardized breakfast in normal subjects

We have investigated the influence of a single oral administration of indomethacin on blood glucose, plasma free fatty acids (FFA), alpha-amino-nitrogen, insulin and glucagon concentrations in young healthy subjects. Two groups of 6 subjects were studied, the first received a standardized 500 kcal mixed meal without any previous drug administration (controls) whereas the second group received 50 mg indomethacin 2 h before ingesting an identical meal. Plasma indomethacin concentration reached its maximum (2.36 +/- 0.36 micro g/ml) 15 min after administration and declined to 0.45 +/- 0.04 micro g/ml after 2 h. Indomethacin ingestion was followed by a significant increase in blood glucose and plasma FFA reaching their maximum value at 45 min and returning to basal levels at 120 min. No simultaneous changes in plasma alpha-amino-nitrogen, insulin or glucagon levels were detected during this period. The meal was followed by a rise in blood glucose and plasma insulin as well as by a decrease in plasma FFA concentration. No significant differences were detected between the controls and the subjects receiving indomethacin. In controls, the meal was followed by a rise in plasma alpha-amino-nitrogen and a modest although significant increase in glucagon levels. In indomethacin-treated subjects, the increment of alpha-amino-nitrogen was less marked and the increase in plasma glucagon was not observed. Thus, indomethacin by itself can exert several metabolic effects; however, it does not deteriorate the blood glucose or insulin profile after a regular meal. The present work is the first to demonstrate that an inhibitor of prostaglandin synthesis inhibits the plasma glucagon rise occurring after a physiological stimulus such as a normal meal. On the basis of previous in vitro experiments, we suggest that this effect results from an inhibition of glucagon secretion by the PG synthesis inhibitor.

Prostaglandins and the alpha-cell

Experimental evidence has recently accumulated indicating that administration of some prostaglandins (PGs), particularly those of the E series, can evoke release of glucagon by the pancreatic alpha-cells. Virtually, all the in vitro studies (isolated perfused rat pancreas, isolated guinea-pig islets) agree that PGs can increase both basal and stimulated glucagon release. On the other hand, inhibition of PG synthesis with indomethacin blocks glucagon release. In rats and in normal humans, PGE1, but not PGA2 or PGF2a, causes a progressive rise of plasma glucagon levels. While in the rat this response seems independent of the adrenergic nervous system, in man the hyperglucagonemia induced by PGE1 is easily suppressed by propranolol, suggesting an interaction between the prostaglandin and the beta-receptors of the alpha-cell. Studies with inhibitors of PG synthesis in vivo have yielded conflicting results, depending on the particular experimental protocol used and on the type of inhibitor tested. In normal humans, it seems that acetylsalicylic acid (ASA) has no effect on glucagon response to arginine, tolbutamide and insulin-induced hypoglycemia. Conversely, a stimulator of PG synthesis, such as furosemide, increases glucagon response to an arginine pulse in man. In insulin-dependent diabetics, who present an exaggerated glucagon response to stimulants, ASA fails to alter glucagon response to arginine, but completely blunts the glucagon response to salbutamol, a weak beta-2 receptor agonist. In conclusion, these observations provide evidence in support to a role for PGs, at least PGE, in the contro of glucagon release.

Neuroendocrine tests of monoamine function in man: a review of basic theory and its application to the study of depressive illness

Neuroendocrine tests are now available for studying monoamine function in the brains of patients with mental illness. Great care is required in the selection of drugs which act upon specific monoamine receptors to produce specific hormonal responses. Equal care is required in the control of biological variables which may influence hormonal release. Recently reported neuroendocrine studies of depressive illness are assessed in these terms. The results of these studies support the hypothesis that there is defective noradrenergic function in the brains of some patients with depressive illness.

Influence of acetylsalicylic acid on plasma glucose, insulin, glucagon, and growth hormone levels following tolbutamide stimulation in man

The effects of acetylsalicylic acid (ASA), a known inhibitor of prostaglandin (PG) synthesis, on plasma glucose, insulin, glucagon and growth hormone (GH) responses to tolbutamide were examined in ten normal volunteers. Treatment with 3.2 g ASA daily for 3 days caused a significant reduction in basal plasma glucose levels (p less than 0.05); by contrast, basal insulin rose from 23 +/- 2 to 31 +/- 2 microU/ml (p less than 0.01). No significant changes in the basal concentrations of glucagon and GH were found after ASA. Insulin response to tolbutamide was significantly augmented after ASA (p less than 0.01) while GH response to hypoglycemia was reduced (p less than 0.05). The pattern of plasma glucose and glucagon was not significantly modified by the treatment. Since ASA seems to have an action opposite to PGE on insulin and GH secretion, it is possible that the ASA may work through inhibition of PG synthesis.

The prostaglandins system and insulin release. Studies with the isolated perfused rat pancreas

Using the isolated perfused rat pancreas PGE2 (1 MUM and 10 muM) had no effect on basal or glucose (10 and 20 mM)-induced insulin release (IR). PGF2 alpha stimulated basal IR at 1 muM and inhibited IR at 10 muM. The glucose-induced IR was unaffected by this PG. Furosemide (5 and 10 mM) led to a monophastic IR at low glucose (glu) and to a potentiation of IR at high glu. Only high indomethacin (Indo) (50 microgram/ml) inhibited glu-induced IR. The stimulatory effect of furosemide on IR could not be inhibited by indomethacin. However mepacrine (0.1 mM) abolished the furosemide effect. Also glu-induced IR was inhibited by mepacrine. Acetylsalicylic acid (30 mg/100 ml) had no significant influence on glu-induced IR. These findings provide evidence that phospholipase activation rather than increased PG synthesis might primarily be involved in the secretory process of insulin.

A possible short-term prediction of potential carcinogenicity of chemical compounds in vivo by means of a promoting activity test (PAT)

Carcinogens of chemically unrelated structure and different organotropism cause a mitotic stimulation of adrenocortical epithelia in vivo. A similar response is observed in liver regenerating rats following partial hepatectomy or intoxication by carbon tetrachloride. It is very probable from these and other results that the short-term effect (48 hours p. applic.) is brought about by the emergence of humoral growth stimulators which are evidenced in restorative regeneration and, therefore, accounts for the promoting activity of carcinogens. Special problems resulting from false positive (indomethacin, sodium nitrite) and false negative (7,12-dimethylbenz(a)anthracene, ethionine) findings as well as such of the role of solvents are discussed. The proof of the "contradictory" test result by long-term treatment in the case of trinitroso-trimethylene-triamine, nitroso-ethyltert-butylamine or nitroso-diallylamine has shown the accuracy of this short-term test.