PMC

Comparative effects of fructose-sweetened (red) and glucose-sweetened beverages (blue). Data from Teff, et al. [] were merged. Insulin-sensitive (−□-) and insulin-resistant (−○-) sub-groups were separately analyzed from the original populations.

Control of glucokinase. Binding of glucokinase-regulatory protein (RP) reduces the activity of glucokinase (GK). Fructose-1-P relieves the inhibition by stabilizing the dissociated RP, while F-6-P furthers inhibition by stabilizing the complex. Not shown in the figure: the GK-RP complex is transported to the nucleus []. Dissociation leads to transport from the nucleus.

Effect of sugar on percentage of palmitate (16:0) in VLDL TG before and after OGTT (glucose, 75 g; average, 0.8 g/kg) and indicated levels of fructose (F) and glucose (G). Redrawn from reference [].

Hepatic insulin sensitivity (100/(glucose production × fasting insulin)). Male subjects consumed weight maintenance diets for 6–7 days and then the indicated amount of sugar was added to the same diet. Data from reference [].

24-hour circulating triacylglycerol before (black) or after 2, 8 and 10 weeks of consuming glucose-sweetened (blue) or fructose-sweetened beverages (red) providing 25% of energy. Superposition of Figures A and B, redrawn from Stanhope, et al. [].

Effect of diet on postprandial lipemic responses in subjects with atherogenic dyslipidemia. Absolute TAG values in subjects who consumed a very low carbohydrate ketogenic diet (VLCKD) or a low-fat diet (LF) for 12 weeks. Redrawn from Volek, et al. [].

Incorporation of labeled glucose or fructose as a function of concentration of the labeled sugar and effect of presence of other (cold) sugar. Incorporation of labeled sugar in the absence of the other is shown by the blue symbol and the unbroken gray line. When the other (unlabeled) sugar is added there is a shift in the incorporation as shown by the red symbol and the gray broken line). All the effects are enhanced upon addition of insulin (heavy black lines). Figure redrawn from Parniak & Kalant [].

Overview of the major aspects of hepatic metabolism of glucose and fructose. Key points emphasized in the text: the two sugars converge at the level of the triose-phosphates (dihydroxyacetone-phosphate (DHAP) and glyceraldehyde-3-P (Ga-3-P)). Conversion of fructose to the triose-phosphates is unidirectional but fructose-1-phosphate is a positive effector of glucokinase and regulates glycogen synthesis by activating the synthase and inhibiting phosphorylase. The last effect may be different between species. Light blue arrows show the path of gluconeogenesis from fructose leading to glucose-6-P which, in turn, can produce glucose or be incorporated into glycogen.