Abstract
BackgroundHigh carbohydrate feeding is known to increase plasma triglycerides as well as hepatic de novo lipogenesis (DNL) and may be implicated in the development of hepatic insulin resistance and fatty liver. Unfortunately, it is technically challenging to determine what proportion of circulating plasma triglycerides have been derived from the newly synthesized fatty acids in the postprandial period. The aims of this study were to 1) characterize the changes in the plasma postprandial total fatty acid pool in beagles following the consumption of meals containing 44% (Control) and 74% (High Sucrose) carbohydrate and 2) determine if changes in plasma fatty acid concentration and delta-9 desaturation index (DI) would be useful as simple and easy to measure biomarkers of systemic DNL.FindingsNo differences in plasma total palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) concentrations or delta-9 DI for the total 18:0 and 18:1 pools between High Sucrose and Controls were observed. However, newly synthesized 16:0 (2.6 ± 0.2% vs. 8.8 ± 2.0%; p = 0.016), 18:0 (0.93 ± 0.2% vs. 4.1 ± 1.7%; p = 0.007) and 18:1 (0.29 ± 0.09% vs. 3.5 ± 1.2%; p = 0.017) were higher in High Sucrose versus Control animals, respectively. Also, the delta-9 DI for the newly synthesized 18:0 and 18:1 pools was higher at 2 and 6 hours postprandial, with a pattern of change which supports the increased stearoyl-CoA desaturase (SCD-1) activity following high carbohydrate feeding followed by a down regulation of this enzyme.ConclusionsOur data show that high sucrose meals increase the relative contribution of systemic DNL produced fatty acids to the total postprandial plasma fatty acid pool. These data also show that a different pattern of both fatty acid synthesis and disposal occurs depending on energy and macronutrient profile of the meal. These changes are in spite of no observable changes in the plasma concentrations or ratios of the total fatty acid pool opposed to the observed changes in the newly synthesized fatty acid pool.
Highlights
High carbohydrate feeding is known to increase plasma triglycerides as well as hepatic de novo lipogenesis (DNL) and may be implicated in the development of hepatic insulin resistance and fatty liver
Our data show that high sucrose meals increase the relative contribution of systemic DNL produced fatty acids to the total postprandial plasma fatty acid pool
These changes are in spite of no observable changes in the plasma concentrations or ratios of the total fatty acid pool opposed to the observed changes in the newly synthesized fatty acid pool
Summary
High carbohydrate feeding is known to increase plasma triglycerides as well as hepatic de novo lipogenesis (DNL) and may be implicated in the development of hepatic insulin resistance and fatty liver. Because the main driver of the serum TG levels following high carbohydrate feeding tends to be DNL [13], changes in the relative proportion of newly synthesized fatty acids in the plasma are reflective of the DNL contribution to postprandial lipemia. Because of this direct relationship between dietary carbohydrate and the rate of postprandial DNL there is much interest in how this relationship contributes to the development of lipemia [14], obesity [2] and diabetes [15]
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