Effect of trimethylamine-carbomethoxyborane on growth traits and lipid metabolism in lines of mice selected for high and low fat content.

The purpose of this study was to determine the effects of the amine carboxyborane, trimethylamine-carbomethoxyborane (B), on growth, body composition and lipid metabolism in lines of mice differing in fat content as a result of directional selection: high fat content (HF); low fat content (LF); and random control (RC). Mice were injected i.p. daily with either 20 mg/kg of B dissolved in 1% (w/v) carbomethoxycellulose as the vehicle or just vehicle (C) from 26 to 42 days of age. Growth rate, feed intake, feed efficiency, epididymal fat pad weight/BW and percentage body water were not affected by B treatment, but liver weight/BW was increased (P < 0.001). HF mice had larger epididymal fat pad weight/BW and less percentage body water when compared to LF mice (P < 0.001). Treatment with B lowered (P < 0.01) serum triglyceride and cholesterol levels, and selection for divergence in fat content led to positive divergence (P < 0.01, (HF-LF) > 0) in serum triglyceride and serum cholesterol levels; divergence x treatment interactions (P < 0.01) were due to administration of B eliminating the line differences present when C was administered. Treatment with B elevated (P < 0.001) HDL cholesterol level and lowered (P < 0.001) chylomicron, LDL and VLDL cholesterol levels, while positive divergence was found for all four fractions. Fecal triglyceride and cholesterol levels were increased (P < 0.01) by administering B, but were not affected by selection. Hepatic enzyme activity of cholesterol-7 alpha-hydroxylase was elevated (P < 0.001) by treatment with B while activities of other hepatic enzymes were depressed, e.g., acyl-CoA cholesterol acyltransferase. Line differences in activity of several hepatic enzymes also were found. These results indicate that B acts as a hypolipidemic agent in both high-fat and low-fat mouse genotypes, lowering serum cholesterol and triglyceride levels. However, at the administered dose, B had no affect on growth rate, feed intake, feed efficiency or body fat content.