Fructose- and sucrose- but not glucose-sweetened beverages promote hepatic de novo lipogenesis: A randomized controlled trial

It has been known that high-fructose consumption increases hepatic de novo lipogenesis and hepatic fat content. Additionally, it reduces hepatic insulin sensitivity independently from weight gain. There are little data to support whether moderate amounts of sugar sustainably increase the irregularity of the FA synthesis pathway or if they dysregulate basal FFA delivery and oxidation. Additionally, whether fructose exerts adverse effects on hepatic lipid metabolism when consumed alone or in combination with glucose i. e. as sucrose or high fructose corn syrup (HFCS) is not known. Bettina Geidl-Flueck and colleague conducted a trial under the title “Fructose- and sucrose- but not glucose-sweetened beverages promote hepatic de novo lipogenesis: A randomized controlled trial” published in the Journal of Hepatology. The summary of the study is given below:

Objective:

1.  To investigate hexose-specific metabolic effects free from confounding factors such as CHO overfeeding or ways of presentation of sugars or differences in the degree of complexity.
2.  To identify the effects of fructose-containing sugar-sweetened beverages (SSB).

Method:

This double-blind, randomized trial included 94 subjects. They were assigned to daily consumption of SSB containing moderate amounts of fructose, sucrose, or glucose (80g/day) along with their usual diet or restrict SSB consumption (control group) for seven weeks. Tracer methodology was used to assess De novo FA and triglyceride (TAG) synthesis, lipolysis, and plasma-free FA (FFA) oxidation.

Findings:

The study reports that daily consumption of beverages that don’t contain glucose but moderate amounts of either fructose or sucrose increases hepatic FA synthesis in healthy individuals in a basal state. SSB consumption affects macronutrient intake such as it decreases fat and protein intake and did not increase total energy intake. Similar to previous studies, this study confirms that SSB intake containing fructose changes LDL composition. Additionally, frequent consumption of fructose-containing beverages elevates hepatic basal lipogenic activity. The study found a comparable outcome for increasing basal hepatic FA synthesis for pure fructose i.e. 80g fructose/day and sucrose i.e. 40g fructose plus 40g glucose/day.
Hence, the study concludes that increased basal hepatic FA synthesis might be the first metabolic change caused by regular SSB intake containing fructose.

Limitation:

Some inherent limitation from this study is: first, there was little control for adherence to the protocol of individual subjects. Secondly, there are unknown intestinal capacities of the subjects to tolerate fructose. Additionally, there is a chance of underestimation of de novo fatty acid synthesis as the study used 13C acetate as tracer and mass isotopomer distribution analysis (MIDA). Lastly, the contribution of VLDL-TAG with glycerol originating from the glycolytic or glyceroneogenic pathway has not been investigated in the study.

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