Increased systolic blood pressure in rats induced by a maternal low-protein diet is reversed by dietary supplementation with glycine

When rat dams consume a diet low in protein during pregnancy, their offspring develop high blood pressure. On a low-protein diet, the endogenous formation of the amino acid glycine is thought to become constrained. Glycine may become conditionally essential, as its rate of endogenous formation is inadequate to meet metabolic needs, and may be limiting for the normal development of the fetus. In the present study, five groups of Wistar rats were provided during pregnancy with one of five diets: a control diet containing 18% (w/w) casein (CON), a low-protein diet containing 9% casein (MLP), or the low-protein diet supplemented with 3% glycine (MLPG), alanine (MLPA) or urea (MIPU). The offspring were weaned on to standard laboratory chow, and blood pressure was measured at 4 weeks of age. Blood pressure was significantly increased in the MLP, MLPA and MLPU groups compared with the CON group, but for the MLPG group blood pressure was not significantly different from CON. Compared with the CON group, body weight was significantly reduced for the MLP, MLPA and MLPG groups, but for the MLPU group body weight was not different from CON. These data show that different forms of non-essential dietary nitrogen, when consumed during pregnancy, exert different effects upon the growth and function of the offspring. The availability of glycine appears to be of critical importance for normal cardiovascular development.