Improved insulin responsiveness in rat adipose tissue pieces cultured with charcoal-treated albumin and oxygen.

R S Bernstein

doi:10.1016/s0022-2275(20)38155-4

Abstract

In an effort tao simulate the effects of insulin on fat cells prepared from fresh adipose tissue, pieces of epididymal adipose tissue were cultured in a medium containing charcoal-treated bovine serum albumin (BSA) with a gas phase of 100% O2. Using this system, the insulin effect on [1-14C]glucose oxidation was retained, in contrast to previous results in culture with untreated BSA in room air. Basal [1-14C]glucose oxidation was similar to fresh tissue, and insulin stimulated oxidation by 137%. In contrast to the effects of this culture system on [1-14C]glucose oxidation, tissue cultured with charcoal-treated BSA had lower basal rates of [U-14C]glucose utilization and 2-deoxyglucose uptake than either cells from fresh tissue or from tissue cultured with untreated BSA. The insulin effect on both of these measures was similar for the two culture systems and lower than for fresh tissues. Rates of lipolysis were increased in both types of cultured fat cells. Thus the improvement in [1-14C]glucose oxidation is presumably an effect on the pentose phosphate shunt, does not reflect a change in glucose transport or overall glucose utilization, and is not caused by a reduction in free fatty acid levels.

Highlights

The cells cultured with the charcoal-treated bovine serum albumin (BSA) contrast with those cultured with untreated BSA [4], in which basal oxidation was identical to fresh cells but there was no response to insulin
Rates of lipolysis were measured in order to determine whether the improved insulin effect on [ l-14C]glucose oxidation after culture with charcoal-treated BSA and O2 is mediated by a reduction in the high levels of cellassociated and extracellular free fatty acids previously observed in cultured cells [4]
A similar enhancement of both [ 1-'4C]glucose oxidation and fatty acid synthesis can be seen after culture with 20% human serum despite an atmosphere of room air [8]

Summary

MATERIALS AND METHODS

Summary In an effort to simulate the effects of insulin on fat cells prepared from fresh adipose tissue, pieces of epididymal adipose tissue were cultured in a medium containing charcoaltreated bovine serum albumin (BSA) with a gas phase of 100% 02U. sing this system, the insulin effect on [ l-'4C]glucose oxidation was retained, in contrast to previous results in culture with untreated BSA in room air. Summary In an effort to simulate the effects of insulin on fat cells prepared from fresh adipose tissue, pieces of epididymal adipose tissue were cultured in a medium containing charcoaltreated bovine serum albumin (BSA) with a gas phase of 100% 02U. In contrast to the effects of this culture system on [l''C]glucose oxidation, tissue cultured with charcoal-treated BSA had lower basal rates of [U-'4C]glucose utilization and 2deoxyglucose uptake than either cells from fresh tissue or from tissue cultured with untreated BSA. S. Improved insulin responsiveness in rat adipose tissue pieces cultured with charcoal-treated albumin and oxygen. The distal two-thirds of the epididymal fat pads from 6-8 rats were cut into approximately 50-mg pieces, pooled, and distributed to flasks containing 10 ml of TC-199 medium supplemented with HEPES, 0.3 mg/ml; glucose, 3 mg/ml; penicillin, 5000 U/ml; streptomycin, 50 mg/ml; and 4% BSA (either untreated or charcoal-treated).

RESULTS

Medium free fatty acid

DISCUSSION