Department of Nephrology, Hypertension, Diabetology, Endocrinology and Metabolism, Fukushima Medical University, Fukushima, Japan.
Nutr Diabetes. 2013 May 27;3(5):e70. doi: 10.1038/nutd.2013.11.
Yacon is a perennial plant forming a clump of >20 big, edible underground tubers. Yacon, which originates from South America, has become increasingly popular in the Japanese diet for tubers have a lower caloric value and a high fiber content. Recent studies have suggested that yacon feeding ameliorates diabetes as indicated by reduced blood glucose.
We fed male Zucker fa/fa rats for 5 weeks with isocaloric normal chow diet containing from 6.5% control aroid or 6.5% yacon. Insulin sensitivity was evaluated by euglycemic-hyperinsulinemic clamp study.
Body weight was comparable between yacon- and aroid-fed rats. In the basal state, yacon feeding had an effect to lower fasting glucose levels from 184.1±4.1 to 167.8±2.7 mg dl(-1) (P<0.01), as well as basal hepatic glucose output (HGO) from 9.9±0.4 to 7.4 ± 0.2 mg kg(-1) per min (P<0.01). During the clamp studies, the glucose infusion rate required to maintain euglycemia was increased by 12.3% in yacon-fed rat. The insulin suppression of HGO was also increased in yacon-fed rats compared with control rats (85.3±2.4% vs 77.0±3.0%; P<0.05), whereas the glucose disposal rate was not different between the two groups. Consistent with the clamp data, the insulin-stimulated phosphorylation of Akt was significantly enhanced in liver but not in skeletal muscle. Furthermore, tribbles 3 (Trb3) expression, which is a negative regulator of Akt activity, was markedly reduced in the liver of yacon-fed rats compared with control rats.
These results indicate that the effect of yacon feeding to reduce blood glucose is likely due to its beneficial effects on hepatic insulin sensitivity in the insulin resistant state.
雅甘是一种多年生植物，形成一簇 20 多个大的、可食用的地下块茎。雅甘原产于南美洲，由于块茎的热量值较低，纤维含量较高，在日本饮食中越来越受欢迎。最近的研究表明，雅甘喂养可以改善糖尿病，表现为血糖降低。
我们用等热量的正常饲料喂养雄性 Zucker fa/fa 大鼠 5 周，饲料中含有 6.5%的对照块茎或 6.5%的雅甘。通过正葡萄糖高胰岛素钳夹研究评估胰岛素敏感性。
雅甘和块茎喂养的大鼠体重相当。在基础状态下，雅甘喂养可使空腹血糖水平从 184.1±4.1 降至 167.8±2.7mg/dl（P<0.01），基础肝葡萄糖输出（HGO）从 9.9±0.4 降至 7.4±0.2mg/kg/min（P<0.01）。在钳夹研究中，维持血糖正常所需的葡萄糖输注率在雅甘喂养的大鼠中增加了 12.3%。与对照组相比，雅甘喂养的大鼠胰岛素抑制 HGO 的作用也增强（85.3±2.4%比 77.0±3.0%；P<0.05），而两组的葡萄糖处置率没有差异。与钳夹数据一致的是，雅甘喂养大鼠肝脏中 Akt 的胰岛素刺激磷酸化明显增强，但骨骼肌中没有。此外，雅甘喂养大鼠肝脏中的 Tribbles 3（Trb3）表达，作为 Akt 活性的负调节因子，明显低于对照组。
这些结果表明，雅甘喂养降低血糖的作用可能是由于其对胰岛素抵抗状态下肝胰岛素敏感性的有益影响。
