Age-Related Alterations of B-Group Vitamin Contents in Urine, Blood and Liver from Rats

Abstract

SummaryTo investigate how aging alters B-group vitamin metabolism, rats were fed with niacin-free 20% casein diet from 3 to 80 wk old, and the urinary excretions of the B group vitamins were periodically measured. The blood and liver B-group vitamin levels in 80-wk-old rats were also compared with those in 8-wk-old rats. The urinary excretion of thiamin, riboflavin, vitamin B 6 metabolite 4-pyridoxic acid, pantothenic acid, folic acid and biotin were not altered during 540 d. The urinary vitamin B 12 increased by 8-fold at 29 wk old, and further increased at 80 wk old. Conversion of nicotinamide from tryptophan gradually decreased to 60% from 29 to 48 wk old. Plasma PLP, vitamin B 12 and folate levels in 80-wk-old rats were lower than those in 8-wk-old rats, consistent with lower liver vitamin B 6 and folate levels in aged rats. Plasma and liver biotin levels in aged rats were higher than those in young rats. Other B-group vitamins such as vitamin B 1 , vitamin B 2 , niacin and pantothenic acid levels in blood and liver from aged rats were same as those from young rats. Alteration of vitamin B 6 metabolism in particular is similar to the observations in eldery humans reported previously. Our findings suggest that aged rats can be useful models to investigate aging-related B-group vitamin metabolism. Key Words aging, vitamin B 2 , vitamin B 6 , folate, biomarker The precise cascade of pathological age-related events is still not clearly understood, but enhanced production of free radicals and its deleterious effects on macro-biomolecules such as proteins and DNA ( 1 , 2 ) as well as polyunsaturated fatty acids ( 3 ) are well known during aging. Aging is a major risk factor for various chronic disorders including cancer. It is well known that taking in nutrients suitable for life stages is important to prevent the aging process and chronic disorders. Food, namely nutrient intake, is a key factor affecting aging and the incidence of many chronic disorders ( 4 -6 ). Decreased food intake and a sedentary lifestyle reduce energy expenditure and may alter their metabolism in elderly adults, and alteration of metabolism may cause alteration of nutrient requirement. However, there is not sufficient information on how aging alters vitamin metabolism ( 7 , 8 ). To investigate age-related alterations of B-group vitamins, rats were kept for 540 d from 3 to 80 wk old, and the urinary excretions of the B group vitamins were periodically measured. The blood and liver B-group vitamin levels in 80-wk-old rats were also compared with those in 8-wk-old rats.

The Cardiac Effects of Prolonged Vitamin B12 and Folate Deficiency in Rats

“…Since folate and B 12 serum concentrations in rats are strongly dependent on the intake of these vitamins via food and the age of the animals, reference ranges have to be calculated individually for each experimental setting. However, our vitamin concentrations correspond well with those recorded in previous studies [24,25]. Since the circulating HCY concentration also depends on folate and B12 levels, the same condition applies for HCY.…”

Urinary excretion of B-group vitamins reflects the nutritional status of B-group vitamins in rats

“…Preparation and measurement of the extracts of B-group vitamins from urine and blood were as previously described ( 14 , 31 , 32 ) .…”

Nutritional Aspect of Tryptophan Metabolism

“…This diet contains enough niacin and tryptophan to maintain niacin nutrition. We investigated whether rats can maintain their niacin nutrition from nicotinamide supplied only from tryptophan with no dietary niacin 7. Rats were fed a niacin-free 20% casein diet starting from the age of 3 weeks until the age of 80 weeks.…”