Key result
Recombinant tumour necrosis factor decreased lipoprotein lipase activity by approximately 50% and mRNA levels by 30% in rat epididymal adipose tissue in vitro, but had no effect on isolated adipocytes.
Why the study?
Does recombinant human TNF alter LPL activity and mRNA levels in rat epididymal adipose tissue in vitro?
Does recombinant human TNF alter LPL activity and mRNA levels in rat epididymal adipose tissue in vitro?
Recombinant human TNF decreases LPL activity and mRNA levels in intact rat adipose tissue in vitro, but not in isolated adipocytes.
Supports further investigation of TNF in adipose lipid regulation; leaves open clinical relevance in humans due to animal model limitations.
Tumour necrosis factor (TNF) has previously been shown to decrease lipoprotein lipase (LPL) activity and mRNA levels in 3T3-L1 cells and in adipose tissue from rats and guinea pigs when injected in vivo, but not to alter LPL activity in human adipocytes incubated in vitro. The effect of recombinant human TNF on LPL activity and mRNA levels in rat epididymal adipose tissue incubated in vitro was examined. LPL activity and mRNA levels fell in adipose tissue taken from fed rats and incubated in Krebs-Henseleit bicarbonate medium with glucose. The addition of insulin and dexamethasone prevented these falls. TNF (400 ng/ml) produced a fall of approx. 50% in LPL activity after 2 h of incubation and of approx. 30% in LPL mRNA levels after 3 h. TNF did not decrease LPL activity in isolated adipocytes. These results demonstrate that rat adipose tissue incubated in vitro is responsive to TNF whereas isolated adipocytes are not.
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Mackay et al. (1990) studied this question. Recombinant human tumour necrosis factor (TNF) vs. Control (no TNF) was evaluated on Lipoprotein lipase (LPL) activity at 2 hours (p=<0.01). Recombinant tumour necrosis factor decreased lipoprotein lipase activity by approximately 50% and mRNA levels by 30% in rat epididymal adipose tissue in vitro, but had no effect on isolated adipocytes.
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