Interference of a nonmetabolized analogue of L-leucine with lipid metabolism in tumoral pancreatic islet cells

The nonmetabolized analogue of L-leucine, 2-aminobicyclo2,2,1]heptane-2-carboxylic acid (BCH), was recently found to inhibit O2 uptake and insulin release from tumoral islet cells of the RINm5F line. BCH inhibited lipogenesis, stimulated lipolysis, and severely decreased the oxidation of endogenous U-14C]palmitate in prelabelled RINm5F cells. D-Glucose exerted metabolic effects which were sometimes opposite to those caused by BCH and, within limits, protected the islet cells against the inhibitor action of BCH. Since BCH augments NH4+ production and facilitated the catabolism of 14C-labelled amino acids in the prelabelled cells, it is proposed that the unexpected inhibition of O2 uptake by BCH is mainly attributable to a decrease in the oxidation of endogenous fatty acids.