Effect of methylxanthines on lactational performance

Hart, Alexandra Data (1987) Effect of methylxanthines on lactational performance. University of Southampton, Doctoral Thesis.

Abstract

Caffeine, theophylline and theobromine constitute a group of purine alkaloids designated methylxanthines. These are consumed in coffee, tea, chocolates, cola beverages and some patent drugs, presenting diverse metabolic actions such as stimulation of the central nervous system, diuresis and increased metabolic rate. Methylxanthines are easily transferred through the placenta, breast milk and all tissue fluids. With the resurgence in breast feeding, this project was designed to investigate the effect of such pharmacologically active substances on lactational performance, based on measurement of pup growth in relation to maternal milk production and composition, and metabolic adaptations in terms of energy utilization, mammary enzyme activities and mammary protein synthetic rate. The drug doses administered were 50 : 1 : 2 mg caffeine, theophylline or theobromine/kg body weight, or a mixture of all three drugs. Initial studies indicated that caffeine stimulated increased fluid intake. Pup growth was also enhanced by caffeine and theobromine, partly as a result of increased food intake with subsequently enhanced milk volume in the case of caffeine. Lack of differences in maternal carcass fat and fatty acid profile of the milk indicated there was no contribution to pup growth from extra lipid mobilization. The mixture of all three methylxanthines failed to produce any of the favourable effects observed with caffeine or theobromine. Subsequent studies to investigate factors mediating improved pup growth yielded non-reproducible results. While caffeine failed to stimulate pup growth, enhanced growth by the theobromine group was unrelated to increased food intake, milk yield or mammary enzyme activities. Owing to the erratic responses observed, it was difficult to establish whether pup growth in previous studies was due to increased mammary protein sythesis or mammary enzyme activities (lactose sythetase and galactosyltransferase). In view of the reported thermogenic action of methylxanthines, the mechanism of energy utilization was investigated by measuring brown adipose tissue (BAT) mitochondrial GDP binding, an index of BAT thermogenic capacity. Results showed a clear inhibition of thermogenesis during lactation. A parallel study on well-nourished Hampshire mothers showed no influence of coffee or chocolate on milk nutrient composition. In conclusion, although rats exhibited variable and erractic responses to methylxanthine treatment, there is no adverse effect of a reasonably high consumption on lactational performance.(D75610/87)

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