Glucocorticoid-dependent stimulation of adiposity and appetite by a ghrelin mimetic in the rat

OBJECTIVE

Chronic administration of GH secretagogues (GHSs) induces a state of positive energy balance in rodents by a GH-independent mechanism. Here we sought to determine to what extent the GHS effects to increase food intake and increase fat accumulation are glucocorticoid-dependent.

DESIGN

The effects of twice-daily s.c. injections of GH-releasing peptide-6 (GHRP-6) (250 microg/kg) for 2 weeks on body weight, food intake and fat pad weight were determined in both adrenalectomised (ADX) rats (with or without basal corticosterone replacement) and adrenal-intact rats.

RESULTS

All GHS-injected rats had a significantly increased body weight at the end of 2 weeks of treatment compared with saline controls. However, increased fat accumulation was only seen in adrenal-intact rats, with a 15% increase in s.c. inguinal (P<0.05 vs saline controls) and 20% increase in visceral mesenteric (P<0.05) fat pad weights following GHS treatment. The increased body weight observed in ADX rats following GHS treatment was not due to increased fat mass or increased weight of other organs measured. Food intake was increased for up to 7 h following a single injection of GHRP-6 in both the adrenal-intact (P<0.01) and corticosterone-replacement groups (P<0.05). This stimulating effect on food intake was not observed at any time point in the ADX rats without corticosterone replacement.

CONCLUSION

These data suggest that GHS-induced body weight gain is glucocorticoid-independent. However, basal levels of glucocorticoids are permissive for the GHS-induced increase in food intake whilst activation of the hypothalamo-pituitary-adrenal axis appears to contribute to the GHS-induced accumulation of fat mass.

Neutrophil chemiluminescence in burned patients

Phagocytic and bactericidal assays showed that a close correlation was present between bactericidal activity and neutrophil chemiluminescence (PMN-CL) (r = 0.81; p less than 0.01). This suggested that the microbicidal action of the neutrophil depends metabolically on the generation of oxygenating agents. PMN-CL and opsonic index (OI) were measured in 36 burned patients. The levels of serum transferrin (Tf) were examined simultaneously by nephelometric method in order to determine the correlation between humoral-phagocyte axis of immune system and nutritional status. It was found that PMN-CL and OI were generally lower in the greater than 35% TBSA burn group (PMN-CL, 1.85 +/- 0.21 cpm X 10(3), OI, 0.69 +/- 0.06) compared with control subjects (PMN-CL, 3.55 +/- 0.15 cpm X 10(3), OI, 1.05 +/- 0.04). It suggested that both neutrophil oxygenation activity and opsonic activity were impaired following severe burns. PMN-CL was higher in the smaller than 30% TBSA burn group during infection phase as compared with control subjects (5.61 +/- 0.26 cpm X 10(3) vs. 3.55 +/- 01.5 cpm X 10(3); p less than 0.01). It remained high in patients with persistent infection, but fell to normal if appropriate therapy was instituted. This result indicated that the neutrophils of the majority of patients with minor burns during acute infection were in an activated state both metabolically and functionally. The occurrence of sepsis was associated with a marked lowering of PMN-CL and OI values, but no difference was noted before and after the development of sepsis. The incidence of sepsis was 85.7% when PMN-CL was lower than 2 cpm X 10(3).(ABSTRACT TRUNCATED AT 250 WORDS)