Hesperidin is an abundant and

Hesperidin is an abundant and inexpensive plant flavonoid, largely derived from citrus species including sweet orange and lemon. Hesperetin (Hst) is the aglycone of hesperidin. Hesperidin and hesperetin have been reported to show a battery of pharmacological properties, including anti-hyperlipidemic, anti-inflammatory, anti-oxidative, anti-diabetic, anti-hypertensive, and anti-atherogenic potentials [[14], [15], [16], [17]]. Hesperetin has been reported to attenuate the symptoms of diabetic retinopathy [18,19], while hesperidin can mitigate diabetic neuropathy [20] and nephropathy [21]. Moreover, hesperetin alleviates renal interstitial fibrosis in a unilateral ureteral obstruction model of mice [22]. Most importantly, Xue et al. report that hesperetin can improve metabolic and vascular health in overweight and obese subjects as a small-molecule Glo-1 inducer screened within nontoxic dietary bioactive compounds [23], and they firstly verify that Glo-1 is also regulated and controlled by Nrf2/ARE pathway [24]. Our recent report indicated that Glo-1 down-regulation was associated with inactivation of Nrf2/ARE pathway in high-glucose cultured neurons [8]. Furthermore, hesperidin or hesperetin can activate Nrf2/ARE pathway and up-regulates mRNA and protein levels of the downstream target HTH-01-015 receptor in some diseases [25,26]. However, there is no report whether hesperetin can ameliorate DN through enhancement of Glo-1 functions and activation of Nrf2/ARE pathway.
Methods and methods
Results
Discussion Increasing evidences verify that induction of Glo-1, a polyfunctional phase Ⅱ detoxication enzyme, plays a pivotal role in the treatment and prevention of diabetic complications, including DN. The current study demonstrated that hesperetin remarkably delayed the pathological process of DN, and this action was related to the enhancement of Glo-1, which was mediated by the activation of Nrf2/ARE pathway. Furthermore, a review paper also emphasizes the defense efficacy of Glo-1 against glycative stress in the pathogenesis of nephropathy [28]. Flavonoids are a large group of phenolic compounds that are widely distributed in plants. Hesperidin and its aglycone hesperetin are two flavonoids isolated from citrus species that have numerous biological properties. In the present study, we found that hesperetin improved the renal functions of diabetic rats, as evidenced by the decreases in urinary protein excretion, serum creatinin, BUN, and uric acid levels. Meanwhile, hesperetin ameliorated the renal morphological changes of diabetic rats reflected by the decreased FN and CoIV protein expressions as well as the reduced PAS-stained positive area. A report from Wang et al. [22] shows that hesperetin decreases BUN and serum creatinine levels, FN and collagen I protein levels in kidney, as well as some indices of tubular epithelial-mesenchymal transition in a unilateral ureteral obstruction model of mice, indicating the alleviations of renal functions and interstitial fibrosis by hesperetin. Hesperetin attenuates cisplatin-induced renal injury in rats through the inhibition of oxidative stress, lipid peroxidation, and inflammatory cytokines [29]. Additionally, our study also showed that hesperetin mitigated foot process fusion and foot process widening as well as glomerular basement membrane thickening in the kidney of diabetic rats by electron microscope observation. These results demonstrate that hesperetin is beneficial to the therapy of nephropathy, including diabetic nephropathy. A mass of researches confirm that Glo-1 is an important therapeutic target for DN [5,11,12]. Many natural products are reported to induce Glo-1, such as fisetin, mangiferin, resveratrol, hesperetin [4,5,8,10,23]. In the present study, we found that hesperetin significantly elevated Glo-1 enzymatic activity, protein expression, and mRNA levels in the kidney of diabetic rats, accompanied by the increased GSH levels, an integrant cofactor of Glo-1 activity. As we know, Glo-1 can promptly clear methylglyoxal and then reduces AGEs formation and accumulation, for methylglyoxal is a major precursor of AGEs formation, and Glo-1 can also directly inhibit AGEs formation in endothelial cells [30,31]. Actually, Glo-1 over-expression reduces hyperglycemia-induced levels of AGEs and RAGE in diabetic rats [7]. Our study showed that hesperetin reversed the increases in AGEs levels and RAGE expressions in the renal cortex of diabetic rats, which further reflected the enhanced effects of hesperetin on Glo-1. Interestingly, it is found that hesperidin and its aglycon hesperetin possess relatively strong activity against the formation of AGEs [32], suggesting a potential direct inhibitory efficacy of hesperetin on AGEs formation under the diabetic condition.