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Reduced Suppression of Plasma Saturated Fatty Acid Mobilization and Oxidation by Feeding in Lymphoma-bearing Mice¹

Liver Research Laboratory, Medical and Research Services, Veterans Administration Wadsworth Medical Center, and UCLA School of Medicine, Los Angeles, California 90073 [R. K., M. G-E., N. B.], and John Muir Cancer and Aging Research Institute, Walnut Creek, California 94596 [N. B.]

Lymphoma-bearing mice have a circulating lipid-mobilizing factor, but increased plasma free fatty acid (FFA) turnover has not been demonstrable in earlier studies using postabsorptive tumor-bearing mice. We hypothesized that FFA mobilization in lymphoma-bearing mice is only elevated in fed mice and may best be observed at night (dark, reversed light cycle). AKR mice with early and advanced tumors (10⁶ SL-3 lymphoma cells, i.p.) and controls were fed ad libitum (reversed light cycle, dark) or fasted 4 h (daylight, regular cycle), given injections of [¹⁴C]bicarbonate or [1-¹⁴C]palmitate-mouse serum albumin, i.v., and plasma [¹⁴C]FFA disappearance and/or breath ¹⁴CO₂ were monitored. Plasma FFA mobilization, estimated by multicompartmental analysis (SAAM) of the oxidation rate was lower in fasted mice with advanced tumors [tumor, 9.5 ± 6.0% (%SE); controls, 14 ± 4.4% µg-atoms fatty acid-carbon/min/30 g body weight, n = 3 to 6 mice/time point/group]. Feeding reduced these rates 90% in control mice and 53% in mice with early tumors, but only 14% in mice with advanced tumors. Plasma FFA fractional catabolic rates were 2.5 times faster in fed mice with advanced tumors than in controls. Diminished suppression of fatty acid mobilization in fed tumor-bearing mice (at night) probably accounts partially for the body fat loss.

¹ This research project was supported by National Cancer Institute Grant CA15813.

² To whom requests for reprints should be addressed at the John Muir Cancer and Aging Research Institute, 2055 North Broadway, Walnut Creek, CA 94596.

Received 6/14/89. Revised 12/11/89.