American Journal of Clinical Nutrition, Vol 36, 115-121, Copyright © 1982 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Carnitine metabolism in Macaca arctoides: the effects of dietary change and fasting on serum triglycerides, unesterified carnitine, esterified (acyl) carnitine, and beta-hydroxybutyrate

FP Bell, A DeLucia, LR Bryant, CS Patt and HS Greenberg

Serum triglycerides and serum total, esterified, and free (unesterified) carnitine were measured in 21 male Macaca arctoides that were switched from a low fat (5.2% w/w), high carbohydrate diet to a high fat (15.9% w/w), low carbohydrate diet for 90 days and then returned to the original low fat diet for a subsequent 76-day period. Serum triglycerides and total carnitine levels fell significantly (p less than 0.05) during the initial 2 wk of feeding the high fat diet and the ratio of esterified/unesterified carnitine rose significantly (P less than 0.05) on the high fat diet. A return to the low fat diet reversed these changes; triglycerides rose significantly (p less than 0.05) within 3 days and the ratio of esterified/unesterified carnitine fell significantly (p less than 0.05) within 3 days and the ratio of esterified/unesterified carnitine fell significantly (p less than 0.05) during the same period. A return of total carnitine levels to those initially observed on the low fat diet was slower to develop. Fasting for 24 to 48 h resulted in increases of 65 to 75% in total serum carnitine. This increase reflected elevations of both the esterified and unesterified carnitine fractions but was largely attributable to increases in esterified carnitine which rose from 10 to 41 nmol/ml by 48 h while unesterified carnitine rose from 55 to 72 nmol/ml during the same period. In addition, the ratio of esterified/unesterified carnitine ratio rose from 0.183 +/- 0.023 to 0.583 +/- 0.069 (n = 8) with a 48-h fast and was significantly correlated with serum beta- hydroxybutyrate levels at both 24 and 48 h.