Vitamin B-6 metabolism during pregnancy and lactation

Hsiu-Chen Wang, Purdue University

Abstract

Three studies presented in this thesis were conducted to better understand the vitamin B-6 metabolism and requirements during pregnancy and lactation. In the first study, $\beta$-glucosidase activity, that catalyzes the hydrolysis of pyridoxine-5$\sp\prime$-$\beta$-D-glucoside (PNG) to pyridoxme, was investigated in vitro in various tissues of male, non-pregnant and pregnant rats. Enzyme activity was measured by the rate of disappearance of PNG. In the liver and the small intestine, the highest to the lowest of enzyme activity, in order, was in pregnant, non-pregnant and male rats. Results showed that both gender and pregnancy differences during pregnancy affect the utilization of PNG. In the second study, secretion of vitamin B-6 in human milk was investigated in supplemented and nonsupplemented, one-month postpartum, lactating women. Controlled diets were provided to subjects for six consecutive days (4-day adjustment and 2-day experimental phases). The baseline vitamin B-6 status after 4-day adjustment period was measured by the combination of plasma phosphopyridoxal (PLP) and pyridoxal (PL). The supplemented women were provided PN-HCl (1 mg PN equivalent) at breakfast on the first experimental day. No difference was found in the concentration of vitamin B-6 in breast-milk between the supplemented and nonsupplemented women. The portion of maternal dietary vitamin B-6 that was secreted into the milk was 2.3-2.9%. PNG was detectable in breast-milk. The third study involved measuring the concentrations of total vitamin B-6 and the individual vitamins and the extent of their binding capacity in breast-milk and three different types of commercially prepared cow milk (pasteurized, evaporated and Ultra-High-Temperature processed). PL and PLP were the major forms of vitamin B-6 in human and cow milk, respectively. A greater level of PL and a lower level of pyridoxamine was observed in sterilized milk compared to pasteurized milk, although the total vitamin B-6 concentration was not different among three types of cow milk. Sterilization of cow milk yielded a greater percentage of bound vitamin B-6. Although the level of vitamin B-6 was lower in human milk compared to the cow milk, the portion of the vitamin that was free was greater.

Degree

Ph.D.

Advisors

Trumbo, Purdue University.

Subject Area

Nutrition|Obstetrics|Gynecology|Anatomy & physiology|Animals

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