Lipoprotein lipase (LPL) hydrolyzes
lipoprotein triglyceride into
nonesterified fatty acids, which are then reesterified and stored in adipose tissue. Previous studies have demonstrated increases in LPL in response to
insulin-like growth factor I and GH when added in vitro. This study examined the effects of
acromegaly treatment on adipose tissue LPL. Ten patients with clinically active
acromegaly were recruited. A fasting adipose tissue biopsy was performed both before and 3 months
after treatment with
octreotide (8 patients) or surgery plus
octreotide (2 patients). With treatment, mean baseline
insulin-like growth factor I levels fell from 6.41 to 3.98 U/mL (normal, < 2.2 U/mL; P < 0.05), and serum
glycohemoglobin fell from 8.6 to 7.2 (normal, < 6.8). Adipose LPL was measured in the
heparin-released fraction as well as the cellular fraction extracted with nonionic
detergent (EXT).
After treatment of
acromegaly, there was no change in
heparin-released fraction LPL activity or immunoreactive mass. However, there was an increase in EXT activity from 0.73 +/- 0.33 to 1.83 +/- 0.58 nEq/min.10(6) cells (mean +/- SEM; P < 0.05) and an increase in EXT mass from 4.1 +/- 0.89 to 11.4 +/- 2.0 ng/10(6) cells (P < 0.05). There was no change in LPL messenger
ribonucleic acid levels with treatment, determined using both quantitative polymerase chain reaction and Northern blotting. Thus, treatment of
acromegaly resulted in an increase in the intracellular level of the LPL
protein, with no change in messenger
ribonucleic acid levels, suggesting posttranscriptional regulation of LPL. These changes in LPL may be due to improved
insulin sensitivity, or to other changes associated with
acromegaly treatment.