Conclusions
A single oral bolus of fructose and glucose rapidly increases serum TG and TG palmitate in overweight subjects. A dual sugar challenge test could prove useful to identify individuals at risk for carbohydrate-induced dyslipidemia and other adverse effects of increased DNL.
Objective
The aim of the study was to develop a simple outpatient tolerance test for lipogenic sensitivity to dietary sugar. Design and setting: In inpatients given repeated doses of fructose, protocol 1 compared the acute increase in DNL determined from the percentage of palmitate ("new palmitate") and the percentage of isotopically labeled palmitate ("%DNL") in very low-density lipoprotein triglyceride (TG). Protocol 2 compared the increase in new palmitate in outpatients given three different sugar beverages in a randomized crossover design. Participants: There were 15 lean and overweight volunteers in protocol 1 and 15 overweight volunteers in protocol 2. Interventions: In protocol 1, subjects received 1.4 g/kg fructose in divided oral doses over 6 h; in protocol 2, subjects received 0.5 g/kg fructose, 0.5 g/kg fructose plus 0.5 g/kg glucose, or 1 g/kg fructose plus 1 g/kg glucose each as a single oral bolus. Main outcome measures: We measured the increase in DNL by two
Results
After repeated doses of fructose, new palmitate was significantly correlated with the increase in %DNL (Δ, r = 0.814; P < 0.001) and with fasting insulin levels (area under the curve, r = 0.754; P = 0.001). After a single sugar dose, new palmitate showed a dose effect and was greater after fructose plus glucose. Very low-density lipoprotein TG and total TG significantly increased in both protocols. Conclusions: A single oral bolus of fructose and glucose rapidly increases serum TG and TG palmitate in overweight subjects. A dual sugar challenge test could prove useful to identify individuals at risk for carbohydrate-induced dyslipidemia and other adverse effects of increased DNL.
Trial registration
ClinicalTrials.gov NCT00234156 NCT00535535.