EFFECT OF LIPECTOMY AND LONG-TERM DEXAMETHASONE ON VISCERAL FAT AND METABOLIC VARIABLES IN RATS

Intraperitoneal (IP) fat accumulation in humans is a risk factor for a number of diseases. We tried to increase this particular adipose mass in rats by long-term administration of low-dose dexamethasone (Dex) a nd/or elimination of other fat depots. Male adult Wistar rats were lip ectomized (Lip) or sham-operated (Sh). Bilateral lipectomy of retroper itoneal and inguinal fat pads was performed under anesthesia with Na p entobarbital 40 mg/kg supplemented with ether. After 8 days, half the animals of each group received Dex in their drinking water (0.1 mu g/m L) while the other half received water (W), for a total of four groups : Sh-W Lip-W, Sh-Dex, and Lip-Dex. Body weight (BW) and food and water intake were measured throughout the treatment period. A glucose toler ance test was performed 34 days after starting Dex treatment, and then rats were killed, fat depots were weighed, and plasma and liver were obtained for metabolic determinations. Dex rats ate the same amount of food as W controls, but gained significantly less weight (2.02 +/- 0. 18 v 3.82 +/- 0.10 g/d, P <.01). Mean daily W intake was approximately 40 mL/d in all groups, which means that Dex rats ingested approximate ly 4 mu g/d Dex. Average glycemic values during the 180-minute glucose tolerance test were as follows: Sh-W, 162 +/- 13; Lip-W, 166 +/- 7; S h-Dex, 118 +/- 6; and Lip-Dex, 229 +/- 27 mg/dL. These values show tha t glucose tolerance was improved by Dex treatment alone, but was impai red in Lip-Dex animals. The same trend was evident for the relative we ights (percent of BW) of two intact adipose depots: IP and epididymal (EPI) (Sh-W, 2.08 +/- 0.13 and 1.35 +/- 0.11, respectively; Lip-W, 1.6 7 +/- 0.15 and 1.17 +/- 0.11; Sh-Dex, 1.66 +/- 0.10 and 1.28 +/- 0.07; Lip-Dex, 2.41 +/- 0.11 and 1.53 +/- 0.09). Average glycemia for all r ats was significantly correlated with IP (r =.55, P <.01) but not with EPI; moreover, it was also correlated in the Sh-W control group (r =. 81, P <.05), suggesting a normal relation between these variables. Liv er triglycerides (LTG), which were elevated in Dex rats, were also cor related with IP (r =.51, P <.02 for all rats and r =.82, P <.05 for Sh -W rats). The results show that long-term administration of low-dose D ex has some different effects in normal versus Lip rats concerning mai nly the IP fat depot, the relative mass of which seems to significantl y affect glucose tolerance. Copyright (C) 1995 by W.B. Saunders Compan y