Abstract
Quercetin, a flavonoid found in fruits and vegetables, is widely distributed as a secondary metabolite in the plant kingdom. Oxidative stress plays a role in the pathogenesis of diabetes mellitus (DM). The present study investigated the effects of quercetin dietary supplementation on streptozotocin- (STZ-) induced hyperglycemic Arbor Acre (AA) broilers by determining the levels of fasting blood glucose (FBG), fasting insulin (FINS), biochemical indicators, oxidative stress markers, inflammatory cytokines content, antioxidant enzymes activities in tissues, and mRNA expression of genes relating to the insulin signaling pathway. Three hundred one-day-old healthy AA broilers were randomly assigned into 5 treatments; A, control healthy broilers; B, STZ-induced broilers; C, STZ-induced broiler dietary supplemented with 0.02% quercetin; D, STZ-induced broiler dietary supplemented with 0.04% quercetin; and E, STZ-induced broiler dietary supplemented with 0.06% quercetin. The results showed that quercetin supplementation relieved the side effects of STZ-induced oxidative stress by changing activities of antioxidant enzymes, decreasing malondialdehyde (MDA) and nitric oxide (NO) levels, activating expression of genes relating to PI3K/PKB signaling pathway that modulate glucose metabolism and reduce oxidative damage, thereby decreasing FBG and increasing FINS levels. These findings suggest that quercetin exhibits a protective effect in STZ-induced hyperglycemic AA broilers via decreasing oxidative stress.
Highlights
Diabetes mellitus (DM) is a disease characterized by hyperglycemia, resulting in severe metabolic imbalances and nonphysiologic changes in many tissues [1]
STZ significantly increased the fasting blood glucose (FBG) levels of broilers (34.4%, P < 0:01) that were decreased by 0.04%
STZ administration significantly decreased fasting insulin (FINS) levels compared to that of normal broilers (17.4%, P < 0:05) and dietary supplementation with 0.04% and 0.06% quercetin significantly increased FINS by 17.58% and 20.85%, respectively (P < 0:05) (Figure 1(b))
Summary
Diabetes mellitus (DM) is a disease characterized by hyperglycemia, resulting in severe metabolic imbalances and nonphysiologic changes in many tissues [1]. Oxidative stress (OS) is involved in the pathogenesis of DM partly via reactive oxygen species (ROS) generation in diabetic human and animal models [4]. The balance between ROS and antioxidants is a major mechanism in preventing the damages from oxidative stress. Various experimental diabetes models have been proved to induce animal characteristic function and structural changes These models include rats and mice that become diabetic after the administration of alloxan and STZ [7, 8]. Intraperitoneal administration of STZ (4555 mg/kg body weight) decreased insulin sensitivity and Oxidative Medicine and Cellular Longevity induced hyperglycemia and diabetes mellitus in mice and rats [13, 14]. The present study was conducted to confirm the relationship between oxidative stress, glucose metabolism, and insulin signaling pathway in STZ-induced AA broilers. An effort was made to understand the underlying mechanisms of these actions
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