Consumption of a low protein diet increases norepinephrine turnover in brown adipose tissue of adult rats.

Adult rats were fed diets containing 5 or 15% casein to determine effects of low protein intake on efficiency of energy retention and on brown adipose tissue metabolism. Efficiency of energy retention of rats fed the 5% casein diet for 4 or 8 weeks was approximately 40% lower than was efficiency of energy retention of rats fed the 15% casein diet. Rats fed the 5% casein diet also exhibited an enhanced norepinephrine (NE)-stimulated metabolic rate and an accelerated NE turnover in their brown adipose tissue relative to responses of rats fed the 15% casein diet. Additionally, NE turnover in white adipose tissue, but not heart, was accelerated in rats fed the 5% casein diet. The reduced efficiency of energy retention in rats fed the low protein diet may be linked to accelerated NE turnover and heat production by their brown adipose tissue.