| Popis: |
It is known that body composition, especially body fat content, determines plasma leptin (LEP) levels. Clinical observation confirms that glucocorticoids (GS) have a considerable impact on body composition and body fat distribution which leads to visceral fat accumulation and a decrease in muscle mass in limbs. On the other hand, in experimental models GS stimulate ob mRNA expression in adipose tissue and LEP secretion into bloodstream. The aim of the study was to evaluate changes in body composition and fat and fat-free mass distribution in the conditions of endogenous hypercortisolism as well as to determine whether changes in body composition parameters may influence plasma LEP levels in patients with Cushing's syndrome (CUS). The study group was composed of 14 patients (12 F, 2 M) with ACTH-dependent and ACTH-independent CUS (BMI 29,5 +/- 1,0 kg/m2, aged 41,6 +/- 2,9 yrs.). The control group (KON) included 14 overweight/obese subjects (12 F, 2 M; WHR0.8) matched for age, height, weight, and BMI with CUS group. Basal plasma LEP levels were measured by RIA kit. Total fat mass (BFM), fat-free mass (FFM), their regional depots (arms, legs, trunk) as well as bone mineral content (BMC) were determined by DEXA method (Lunar Co., USA). Values of BFM and %BF were comparable in both groups whereas the amount of FFM was lower in CUS group than in controls. Patients with CUS had less BF in limbs than controls whereas the difference in the amount of trunk BF in favour of CUS reached a borderline significance. Moreover, subjects with CUS exhibited decreased amount of FFM both in arms and legs when compared to controls, which may be explained by limb muscle and connective tissue wasting observed clinically. However, the amount of trunk FFM did not differ between both groups. Eventually, subjects with CUS had lower BMC values than controls. Absolute plasma LEP levels were 2-fold higher in CUS group than those in KON group (34,03 +/- 4,45 vs. 17,04 +/- 1,88, ng/ml; p=0.006), however, in both groups they were highly correlated with BFM and %BF. Multiple linear regression analysis revealed that in CUS group 64% of the variation of plasma LEP levels is explained by trunk BF and in KON group 92% of the variation of LEP levels is dependent of arms BF (+, 18%) and legs BF (+, 69%) and arms FFM (-, 5%). In conclusion, endogenous hypercortisolismus leads to the augmentation of truncal (visceral) fat accumulation as well as to a marked decrease in fat-free mass in limbs and in bone mineral content. In Cushing's syndrome, irrespectively of its cause (pituitary gland, adrenal glands), plasma LEP levels are elevated in relation to body fat content. Truncal (visceral) fat may have a relatively stronger influence on plasma LEP in Cushing's syndrome than in subjects with normal cortisolaemia, however, changes in body composition and tissue distribution do not fully account for the presence of markedly elevated LEP levels in this syndrome. |
