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Dietary Fat Modulation of Murine Mammary Tumor Metabolism Studied by in Vivo ³¹P-Nuclear Magnetic Resonance Spectroscopy¹

Department of Human Anatomy, School of Medicine [D. K. B., K. L. E.], and NMR Facility [B. D. R.], University of California, Davis, California 95616

The effect of dietary fat concentration and saturation on high energy phosphate metabolites and phospholipid turnover in transplanted line 168 murine mammary tumors was studied using surface coil ³¹P-nuclear magnetic resonance spectroscopy. Female BALB/c mice were fed one of five diets each containing at least the minimum of essential fatty acids (EFA). Four diets contained additional safflower or palm oil for a total fat concentration of 5 or 20% by weight. The growth rate of tumors from mice fed the high safflower oil diet was significantly greater than the growth rate of tumors for mice fed all the other diets including the one which contained the minimal EFA. ³¹P-nuclear magnetic resonance-observable phosphate metabolite ratios, ATP/P_i, ATP/phosphomonoester (ATP/PME), and PME/P_i, and tumor pH of line 168 tumors decreased with increasing tumor volume, indicating a shift from active to inactive tumor metabolism. The rates of those decreases with progressive tumor growth differed significantly among tumors of mice fed the different diets. Decreases in ATP/P_i, ATP/PME, and pH were the most rapid in the tumors of mice fed the high safflower oil diet and significantly faster than tumors of mice fed the diet containing minimum EFA. In addition, the decrease in the PME/P_i ratio of tumors was significantly greater in mice fed the high fat (high palm oil and high safflower oil) diets than mice fed the diet containing the minimum of EFA. The rate of decline of ATP/P_i and ATP/PME with progressive tumor growth was directly correlated with levels of linoleic acid as well as total unsaturated fat. High levels of a polyunsaturated fat had a significant effect on mammary tumor metabolism particularly during early stages of tumor growth. Differences in high energy phosphate metabolite dynamics relative to dietary fat were present in tumors of equal volume. Thus, dietary fat influences on mammary tumorigenesis may be related to high energy phosphate metabolites.

¹ This research was supported by grants from the National Live Stock and Meat Board, The Gustavus and Louis Pfeiffer Research Foundation, and the NIH Regional Resource for in Vivo NMR, RR02479.

² To whom requests for reprints should be addressed.

Received 11/18/86. Revised 6/11/87. Accepted 8/ 6/87.