What is the clinical evidence from this study?

Study design: Other. Population: Morbid obesity (n=62). Intervention: Insulin and dexamethasone vs. Basal (no hormone additions). Primary outcome: Lipoprotein lipase (LPL) activity and mRNA levels.

November 1, 1993Open Access

Lipoprotein lipase regulation by insulin and glucocorticoid in subcutaneous and omental adipose tissues of obese women and men.

SFSusan K. FriedRutgers Sexual and Reproductive Health and Rights CRColleen D. RussellColumbia University NGN L GrausoRutgers, The State University of New Jersey

Key Result

Insulin increased lipoprotein lipase activity approximately fivefold in subcutaneous adipose tissue but had little to no effect in omental tissue, whereas dexamethasone increased activity more markedly in the omental depot.

Structured PICO

Do insulin and dexamethasone regulate LPL activity and mRNA expression differently in subcutaneous versus omental adipose tissue of obese men and women?

Population

62 obese or formerly obese adults undergoing gastrointestinal surgery who provided omental and subcutaneous adipose tissue samples for 7-day in vitro culture.

Intervention

Organ culture of adipose tissue fragments with varying concentrations of insulin (0-7 nM) and/or dexamethasone (0-250 nM) for 7-8 days.

Comparator

Organ culture of adipose tissue fragments in serum-free medium without hormonal additions (basal).

Outcome

Lipoprotein lipase (LPL) activity and LPL mRNA expression levels.surrogate

Insulin and glucocorticoids regulate human adipose tissue LPL activity at the level of gene expression and posttranslationally, with responsiveness dependent on adipose depot and gender.

Limitations

In vitro study using tissue from severely obese subjects may not fully extrapolate to lean or moderately obese subjects.
Difficulty in determining whether observed changes in LPL mRNA levels fully account for observed differences in activity because recovery of RNA cannot be quantified per cell.

Abstract

There are marked variations in the activity of lipoprotein lipase (LPL) among adipose depots, particularly in women. Consistent with data on LPL activity, the level of expression of LPL mRNA was lower in omental (OM) than subcutaneous (SQ) adipose tissue of women. To investigate the cellular basis of these differences, OM and SQ adipose tissues obtained at surgery from obese men and women were placed in organ culture for 7 d with varying concentrations of insulin and dexamethasone. Insulin increased levels of LPL mRNA and LPL activity in abdominal SQ but not OM adipose tissue. Dexamethasone also increased LPL mRNA and LPL activity, and these effects were more marked in the OM adipose tissue, particularly in men. When insulin and dexamethasone were added together, synergistic increases in LPL activity were seen in both depots, and this was in part explained at the level of LPL mRNA. The SQ depot was more sensitive to the effects of submaximal doses of dexamethasone in the presence of insulin. The maximum activity of LPL induced by insulin or insulin plus dexamethasone was higher in the SQ than in the OM depot of women, and this was associated with higher levels of LPL mRNA. Rates of LPL synthesis paralleled LPL mRNA levels. These data show that insulin and glucocorticoids influence human adipose tissue LPL activity at the level of LPL gene expression, as well as posttranslationally, and that responsiveness to these hormonal effects is dependent on adipose depot and gender.

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