The cellularity of normal and lipomatous adipose tissue and its response to different lipolytic agents have been studied in a group of 10 patients with
multiple symmetric lipomatosis (MSL). In MSL patients, fat cells from lipomatous tissue are smaller than normal, uninvolved adipocytes. Fat cells from
lipomata show minimal variations in size following conspicuous increase of lipomatous masses. These findings suggest that the growth of
lipomata can be attributed to the neoformation of adipocytes rather than to an enlargement in the single fat cells. The incidence of reduced
glucose tolerance and of
hyperlipoproteinemia is similar in MSL patients and in controls. A significant reduction in plasma
free fatty acids was observed in MSL patients after a 24-h fast as well as after
noradrenaline infusion. A specific insensitivity of lipomatous tissue to the lipolytic effect of
noradrenaline and
isoprenaline was observed in vitro, as indicated by
glycerol release in the medium, whereas response to
theophylline and to
dibutyryl cyclic AMP was retained. The lipolytic response to
catecholamines was retained. The lipolytic response to
catecholamines was normal in the nonlipomatous adipose tissue of MSL patients. In basal conditions
ATP concentrations were similar in normal and in lipomatous adipose tissue. However, incubation with
noradrenaline induced a significant fall in intracellular
ATP levels in normal tissue, whereas no variations were observed in lipomatous tissue.
Theophylline, instead, induced a prompt and significant decrease in intracellular
ATP levels in lipomatous tissue. These observations indicate that the block in
catecholamine-stimulated lipolysis in lipomatous tissue of MSL patients can be localized at a level preceding the formation of
cyclic AMP.