Soy protein and isoflavonoids in soybeans exhibit the improvement of insulin resistance. Our previous IN VITRO study showed that Chungkookjang (CKJ), fermented unsalted soybeans, had better antidiabetic actions than cooked unfermented soybeans (CSB) by increasing isoflavones aglycones and small peptides. We investigated whether 40% fat diets with different protein sources such as CSB, CKJ, and casein modulated peripheral insulin resistance in 90% pancreatectomized (Px) diabetic rats. The Px rats weighing 209+/-14 g were freely provided casein, CSB, or CKJ diets for 8 weeks. Both CKJ and CSB increased whole body glucose disposal rates and glucose uptake into skeletal muscles of Px rats as much as rosiglitazone plus casein treated rats during euglycemic hyperinsulinemic clamp. In addition, CKJ and CSB decreased hepatic glucose output at hyperinsulinemic clamped states, compared to the Casein group. The reduction of hepatic glucose output was greater in CKJ than CSB. This reduction was associated with enhanced tyrosine phosphorylation of IRS2 and serine (473) phosphporylation of Akt, indicating improved hepatic insulin signaling. This improved signaling led to decreased phosphoenolpyruvate carboxykinase expression to reduce hepatic glucose output. In conclusion, fermented soybeans mainly with BACILLUS SUBTILIS improved hepatic insulin sensitivity better than unfermented soybeans by enhancing hepatic insulin signaling cascade in diabetic rats.
The gradual disruption of the ozone layer in the stratosphere has resulted in increased exposure of plants to ultraviolet‐B (UV‐B, 280–315 nm) radiation. UV‐B radiation is known to affect crop growth and quality negatively. A study was conducted to determine the impact of elevated UV‐B radiation levels on the isoflavones and phenolic compound concentrations of seven soybean varieties. UV‐B radiation significantly reduced the concentration of most isoflavones and phenolic compounds in soybean seeds. Exposure to elevated UV‐B levels overall resulted in 35 % reduction in total isoflavones and 31 % in phenolic compounds concentrations. The effect on individual isoflavones and phenolic compounds depended on the compound and variety, but UV‐B overwhelmingly reduced concentrations. This study suggests that increased UV‐B radiation negatively impacted soybean quality by reducing the concentration of compounds that have health‐beneficial properties.
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