Ethnic Differences in Fatty Acid Oxidation
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INTRODUCTION: Triglyceride levels of African Americans are significantly lower than those of Caucasians. This discrepancy complicates the recognition and diagnosis of metabolic disease in African Americans and represents a paradox in the metabolic health of African Americans. Many reasons for this difference have been explored including increased lipoprotein lipase activity, decreased hepatic lipase activity, and increased suppression of adipocyte lipolysis. Another possible explanation for this triglyceride discrepancy that has been sparsely explored is a difference in fatty acid oxidation between the two groups. The hypothesis of the present study is that the discrepancy in triglycerides can be explained, at least in part, by more efficient beta oxidation of fatty acids in the African American population. METHODS: A pilot study was initiated to examine whether a difference in beta oxidation of fatty acids between the two groups exists by examining the ratio of downstream metabolites of beta oxidation (beta hydroxybutyrate; BHB) to upstream metabolites (nonesterified fatty acids; NEFA). Healthy lean African American and Caucasian males were given a fat bolus (200 mg/kg Schepp's dairy heavy cream) hourly over a ten hour time period (fat tolerance test). BHB, NEFA, and plasma triglycerides were measured throughout the test. The data were plotted against time and area under the curve (AUC) was calculated for each plot using the trapezoid rule. The ratio of BHB to NEFA total AUC was calculated and compared between groups. One volunteer from the Caucasian group was excluded from analysis as an outlier based on fasting BHB levels (Grubb's test p<0.01). Groups were compared using 2 sample t-tests. RESULTS: Preliminary results (n=9 African Americans, n=8 Caucasians) demonstrate a trend, as predicted, for the ratio of BHB AUC to NEFA AUC to be higher in African Americans compared to Caucasians (p<0.05). Additionally, the BHB AUC is significantly higher in African Americans (p<0.05), further supporting the study hypothesis. CONCLUSIONS: Initial results suggest that healthy lean African American men may be more efficient oxidizers of fatty acids when compared to healthy lean Caucasian men. This difference could be a contributing factor to the triglyceride difference observed in African Americans and Caucasians. The study is still ongoing and further recruitment and analysis remains to be done.