Microinjection of galanin-like peptide into the medial preoptic area stimulates food intake in adult male rats.

Galanin-like peptide (GALP) is a neuropeptide implicated in the regulation of feeding behaviour, metabolism and reproduction. GALP is an endogenous ligand of the galanin receptors, which are widely expressed in the hypothalamus. GALP is predominantly expressed in arcuate nucleus (ARC) neurones, which project to the paraventricular nucleus (PVN) and medial preoptic area (mPOA). Intracerebroventricular or intraparaventricular (iPVN) injection of GALP acutely increases food intake in rats. The effect of GALP injection into the mPOA on feeding behaviour has not previously been studied. In the present study, intra-mPOA (imPOA) injection of GALP potently increased 0-1-h food intake in rats. The dose-response effect of imPOA GALP administration on food intake was similar to that previously observed following iPVN administration. The effects of GALP (1 nmol) or galanin (1 nmol) on food intake were then compared following injection into the PVN, mPOA, ARC, dorsal medial nucleus (DMN), lateral hypothalamus and rostral preoptic area (rPOA). GALP (1 nmol) increased food intake to a similar degree when injected into the imPOA or iPVN, but produced no significant effect when injected into the ARC, DMN, lateral hypothalamus or rPOA. Similarly, galanin (1 nmol) significantly increased food intake following injection imPOA and iPVN. However, the effect was significantly smaller than that following administration of GALP (1 nmol). Galanin also had no significant effect on food intake when administered into the ARC, DMN, lateral hypothalamus and rPOA. These data suggest that the mPOA and the PVN may have specific roles in mediating the orexigenic effect of GALP and galanin.

Cortisol-binding globulin is important in the interpretation of dynamic tests of the hypothalamic--pituitary--adrenal axis.

OBJECTIVE: Assessment of the hypothalamic--pituitary--adrenal (HPA) axis relies on the interpretation of serum (total) cortisol in response to dynamic tests of the HPA axis. Most cortisol is bound to cortisol-binding globulin (CBG) and serum total cortisol levels are significantly affected by variation in CBG. We hypothesised that CBG variation significantly affects interpretation of dynamic tests of the HPA axis. DESIGN: We investigated the effect of CBG variation on the outcome of the 250 microg short Synacthen test (SST) in 30 healthy adults. METHODS: Blood was sampled at time -30, 0 (at which point Synacthen was given) and +30 min. CBG and total cortisol were measured at each time-point. Integrity of the HPA axis was confirmed by measurement of urine cortisol. RESULTS: We found that CBG varied significantly within individuals, falling from 51+/-3.4 to 43 +/-3.2 microg/ml (P<0.0001) on changing from standing to lying. Total cortisol levels strongly correlated with CBG (r=0.88, P<0.0001). Thirteen subjects had a +30 min total cortisol <550 nmol/l. In these subjects, the CBG levels at each time-point were significantly lower compared with subjects who had a +30 min total cortisol of >550 nmol/l (P<0.05). To correct for variation in CBG we calculated the total cortisol:CBG ratio and found no significant difference in the +30 min ratio between these two groups. CONCLUSION: CBG varies significantly within and between individuals. This is accompanied by changes in serum total cortisol large enough to affect the outcome of an SST and, by implication, other tests of the HPA axis.

Neuropeptide Y induced feeding in the rat is mediated by a novel receptor.

There are now six recognized neuropeptide Y (NPY) receptor subtypes (Y1-Y4 and two recently cloned distinct receptors labeled Y5), of which Y1 and one of the Y5's have been suggested could mediate the effect of NPY on feeding. The fragments NPY(2-36) and NPY(3-36), which bind Y1 only poorly, were injected intracerebroventricularly (icv) and found to have similar dose-response relationships to NPY in the stimulation of feeding. However NPY (13-36), which stimulates both Y2 and Y5, caused no increase in food intake, even at high doses. Maximal stimulation with the classical Y1 agonist [Pro34]-NPY produced only 50% of the maximum effect of NPY itself despite fully inhibiting adenylyl cyclase activity in vitro in a Y1 system. The novel fragment [Pro34]-NPY(3-36) is as effective at stimulating food intake as the classical Y1 analogue [Pro34]-NPY but bound to the Y1 receptor with only 1/20th of the affinity of NPY and failed to inhibit adenylyl cyclase through this receptor. [Pro34]-NPY(3-36) is therefore a relatively appetite-selective ligand. Coadministration of high dose NPY(13-36) and [Pro34]NPY did not enhance feeding compared with [Pro34]-NPY alone. In addition, the NPY Y1 receptor antagonist BIBP-3226, which does not bind Y2, Y4, or Y5 receptors, significantly reduced NPY induced feeding. These results indicate that the feeding effect of icv NPY involves a novel receptor and that it is functionally distinct from the recognized receptor subtypes.

Oral and inhaled corticosteroids reduce bone formation as shown by plasma osteocalcin levels.

Osteoporosis is a well-known, serious complication of long-term high-dose corticosteroid therapy. This study was performed to determine the effects of commonly used doses of oral and inhaled steroids on biochemical indices of bone formation. Initially we examined the long-term effects of oral steroids. Thirty-four outpatients with symptomatic asthma or chronic obstructive airways disease (COAD) receiving long-term oral prednisolone (mean 10.1 mg daily) were compared with 34 control subjects with asthma or COAD matched individually for age, sex, and menopausal status who were not taking oral steroids. Plasma osteocalcin concentrations were significantly lower (patients 6.3 +/- 0.1 ng/ml; control subjects 8.6 +/- 0.5 ng/ml, mean +/- SEM; p < 0.01) in patients on steroids with no difference in alkaline phosphatase. To examine the short-term effects of oral and inhaled corticosteroids, healthy male volunteers were given a 7-d course of either 15 mg oral prednisolone daily (n = 10) or 500 micrograms inhaled beclomethasone twice daily (n = 20). After 1 wk of oral prednisolone, mean plasma osteocalcin decreased from 11.8 +/- 1.1 ng/ml to 6.9 +/- 0.8 ng/ml (p < 0.001). With inhaled beclomethasone mean plasma osteocalcin decreased from 11.6 +/- 0.6 ng/ml to 9.6 +/- 0.6 ng/ml (p < 0.001) with no change in alkaline phosphatase. In doses routinely prescribed for the prophylaxis and treatment of asthma, oral and inhaled steroids suppress osteocalcin levels and may therefore inhibit bone formation. This effect is seen with short courses of steroids and also with chronic administration.(ABSTRACT TRUNCATED AT 250 WORDS)