Uien voor betere insuline tolerantie bij diabetes*
Derivaten van quercetine in uien worden beschouwd als de belangrijkste bioactieve stoffen voor een betere
insulinetolerantie bij diabetici. In deze studie werd naar alle
bioactieve stoffen in uien gekeken en nu eens niet alleen naar quercetine, dat maar 16% van die bioactieve stoffen uitmaakt. Speciale ratten kregen 8 welen lang of gewone voeding of voeding met een extract van de buitenste laag van uien, of voeding met quercetine. De voeding met het uienextract bleek het meeste effectief te zijn in bestrijding van ontstekingen en het flink verbeteren van de insulinetolerantie, duidelijk beter nog als voeding met extra quercetine.
Onion peel extracts ameliorate hyperglycemia and insulin resistance in high fat diet/streptozotocin-induced diabetic rats
Ji Young Jung, Yeni Lim, Min Sun Moon, Ji Yeon Kim and Oran Kwon
Nutrition & Metabolism 2011, 8:18 doi:10.1186/1743-7075-8-18
Abstract (provisional)
Background
Quercetin derivatives in onions have been regarded as the most important flavonoids to improve diabetic status in cells and animal models. These studies are generally carried out using highly purified quercetin rather than onion and the mechanisms of action still remain unclear. The present study was aimed to examine the hypoglycemic and insulin-sensitizing capacity of onion peel extract (OPE) in high fat diet/streptozotocin-induced diabetic rats and to elucidate the mechanism of its insulin-sensitizing effect.
Methods
Male Sprague-Dawley rats were fed the AIN-93G diet modified to contain 41.2% fat and intraperitoneally injected with a single dose of streptozotocin (40 mg/kg body weight). One week after injection, the rats with fasting blood glucose levels above 126 mg/dL were randomly divided into 4 groups to treat with 0 (diabetic control), 0.5, or 1% OPE or with 0.1% pure quercetin (positive control, quercetin equivalent to 1% OPE) for 8 weeks.
Results
Compared to the diabetic control, hypoglycemic and insulin-sensitizing capability of 1% OPE were demonstrated by significant improvement of glucose tolerance as expressed in incremental area under the curve (P=0.0148). The insulin-sensitizing effect of OPE was further supported by increased glycogen levels in peripheral tissues like liver and skeletal muscle (P<0.0001 and P=0.0089, respectively). Quantitative RT-PCR analysis showed increased expression of insulin receptor (P=0.0408) and GLUT4 (P=0.0346) in muscle tissues. The oxidative stress, as assessed by superoxide dismutase activity and malondialdehyde formation, plasma free fatty acids, and hepatic protein expressions of IL-6 were significantly reduced by 1% OPE administration (P=0.0393, 0.0237, 0.0148 and 0.0025, respectively).
Conclusion
Taken together, OPE might improve glucose response and insulin resistance associated with type 2 diabetes by alleviating metabolic dysregulation of free fatty acids, suppressing oxidative stress, up-regulating glucose uptake at peripheral tissues, and/or down-regulating inflammatory gene expression in liver. Moreover, in most cases, OPE showed greater potency than pure quercetin equivalent. These findings provide a basis for the use of onion peel to improve insulin insensitivity in type 2 diabetes.
The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in
production. (Maart 2011)
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