Transmethylation Activity In The Liver Of Rats Fed A Milk-yeast-barley Diet

Abstract

The protein quality of a Milk-Yeast-Barley (MYB) mixture employed in a school-lunch program in Kenya has been investigated by a rat growth assay method. Either casein or MYB were substituted isonitrogenously in a basal diet at the expense of corn starch. Rats receiving MYB protein gained significantly (P< .001) less weight than the controls, the daily weight gain being 1. 78 + 07 and 3.04 +07 g for MYB and casein groups respectively. Feed consumption was 8.24 + .2S and 9.82 +2:.18 g per day for the MYB and casein groups respectively. Accordingly, feed conversion was significantly (P< .(01) higher for the MYB group than for the casein group. The amino acid pattern of the MYB diet indicated a methionine deficiency and a nan-optimal Lysine/methionine Ratio. Improvement in the growth pattern of rats on the MYB diet. was observed when the diet was supplemented with methionine. A further Interesting observation was that liver weights showed significant1y (P< .001) greater values for MYB/methionine group than for the control casein group. Consequently further investigations were arranged to determine morphological and biochemical differences in the liver tissues of the animals on the different diet groups. Ultrastractural studies of the livers of the different diet groups of rats, showed a localized central-lobe fattyliver syndrome in the rats fed the MYB diet. The absence of the fatty-liver syndrome in the control casein and MYB/ methionine supplemented groups, led to the suggestion that the additional synthetic methionine to the MYB diet, did improve the diet with respect to the availability of labile methyl groups required for the synthesis of choline, an important Lipotiropic substiance, Biochemical studies employing both liver slices and isolated mitochondria pellets indicated that choline stimulated normal metaabolic processes in the liver. In this respect, the respiratory quotient (RQ) for the casein and MYB/methionine rats did not differ significantly, whereas the RQ for MYB rats was significantly different from the rest of the groups. The maximum rate for choline oxidation both in the presence and absence of added adenine nucleotides was lower in the MYB animals in comparison with the casein and MYB/methionine groups. This repressed rate of choline oxidation was partly attributed to reduced metabolic activities in the MYB Group of rats