Ingestion of
high-fructose corn syrup (HFCS) is associated with the risk of both diabetes and
obesity. Rare
sugar syrup (RSS) has been developed by alkaline isomerization of HFCS and has anti-
obesity and anti-diabetic effects. However, the influence of RSS on
glucose metabolism has not been explored. We investigated whether long-term administration of RSS maintains
glucose tolerance and whether the underlying mechanism involves hepatic
glucokinase translocation. Wistar rats were administered water, RSS, or HFCS in
drinking water for 10 weeks and then evaluated for
glucose tolerance,
insulin tolerance,
liver glycogen content, and subcellular distribution of liver
glucokinase. RSS significantly suppressed
body weight gain and abdominal fat mass (p < 0.05). The
glucose tolerance test revealed significantly higher
blood glucose levels in the HFCS group compared to the water group, whereas the RSS group had significantly lower
blood glucose levels from 90 to 180 min (p < 0.05). At 30, 60, and 90 min, the levels of
insulin in the RSS group were significantly lower than those in the water group (p < 0.05). The amount of
hepatic glycogen was more than 3 times higher in the RSS group than that in the other groups. After
glucose loading, the nuclear export of
glucokinase was significantly increased in the RSS group compared to the water group. These results imply that RSS maintains
glucose tolerance and
insulin sensitivity, at least partly, by enhancing nuclear export of hepatic
glucokinase.