Taxifolin-3-O-glucoside from Osbeckia nepalensis Hook. mediates antihyperglycemic activity in CC1 hepatocytes and in diabetic Wistar rats via regulating AMPK/G6Pase/PEPCK signaling axis

Hypoglycemic effect and intestinal transport of phenolics-rich extract from digested mulberry leaves in Caco-2/insulin-resistant HepG2 co-culture model

Phenolics of mulberry (Morus alba L.) leaves (MLs) have potential anti-diabetic effects, but they may be chemically modified during gastrointestinal digestion so affect their biological activity. In this study, an in vitro digestion model coupled with Caco-2 monolayer and Caco-2/insulin-resistant HepG2 coculture model were used to study the transport and hypoglycemic effects of phenolics in raw MLs (U-MLs) and solid-fermented MLs (F-MLs). The results of LC-MS/MS analysis showed that the Papp (apparent permeability coefficient, 10-6cm/s) of phenolics in digested MLs ranged from 0.002 ± 0.00 (quercetin 3-O-glucoside) to 60.19 ± 0.67 (ferulic acid), indicating higher phenolic acids absorbability and poor flavonoids absorbability. The Papp values of phenolic extracts of F-MLs in Caco-2 monolayer were significantly higher (p > 0.05) than that of U-MLs. Digested phenolic extracts inhibited the activities of sucrase (60.13 ± 2.03 %) and maltase (82.35 ± 0.78 %) and decreased 9.28 ± 0.84 % of glucose uptake in Caco-2 monolayer. Furthermore, a decrease in the mRNA expression of glucose transporters SGLT1 (0.64 ± 0.18), GLUT2 (0.14 ± 0.02) and the sucrase-isomaltase (0.59 ± 0.00) was observed. In Caco-2/insulin-resistant HepG2 co-culture model, phenolic extracts regulated glucose metabolism by up-regulating the mRNA expressions of IRS1 (9.32-fold), Akt (17.07-fold) and GYS2 (1.5-fold), and down-regulating the GSK-3β (0.22-fold), PEPCK (0.49-fold) and FOXO1 (0.10-fold) mRNA levels. Both U-MLs and F-MLs could improve glucose metabolism, and the partial least squares (PLS) analysis showed that luteoforol and p-coumaric acid were the primary phenolics that strongly correlated with the hypoglycemic ability of MLs. Results suggested that phenolics of MLs can be used as dietary supplements to regulate glucose metabolism.

Mild Intermittent Cold Stimulation Affects Cardiac Substance Metabolism via the Neuroendocrine Pathway in Broilers

This study aimed to investigate the impact of cold adaptation on the neuroendocrine and cardiac substance metabolism pathways in broilers. The broilers were divided into the control group (CC), cold adaptation group (C3), and cold-stressed group (C9), and experimental period was divided into the training period (d 1-35), recovery period (d 36-43), and cold stress period (d 43-44). During the training period, the CC group was reared at ambient temperature, while C3 and C9 groups were reared at 3 °C and 9 °C lower than the ambient temperature, respectively, for 5 h/d at 1 d intervals. During the recovery period, all the groups were maintained at 20 °C. Lastly, during the cold stress period, the groups were divided into two sub-groups, and each sub-group was placed at 10 °C for 12 h (Y12) or 24 h (Y24) for acute cold stimulation. The blood, hypothalamic, and cardiac tissues samples were obtained from all the groups during the training, recovery, and acute stress periods. The results revealed that the transcription of calcium voltage-gated channel subunit alpha 1 C (CACNAIC) was increased in the hypothalamic tissues of the C3 group (p < 0.05). Moreover, compared to the CC group, the serum norepinephrine (NE) was increased in the C9 group (p < 0.05), but insulin (INS) was decreased in the C9 group (p < 0.05). In addition, the transcription of the phosphoinositide-3 kinase (PI3K), protein kinase B (Akt), mammalian target of rapamycin (mTOR), SREBP1c, FASN, ACC1, and SCD genes was down-regulated in the C3 and C9 groups (p < 0.05); however, their expression increased in the C3 and C9 groups after acute cold stimulation (p < 0.05). Compared to the CC group, the transcription of forkhead box O1 (FoxO1), PEPCK, G6Pase, GLUT1, HK1, PFK, and LDHB genes was up-regulated in the C3 and C9 groups (p < 0.05. Furthermore, compared to the CC and C9 groups, the protein and mRNA expressions of heat shock protein (HSP) 70 and HSP90 were significantly increased in the C3 group (p < 0.05). These results indicate that intermittent cold training can enhance cold stress tolerance in broilers by regulating their neuroendocrine and cardiac substance metabolism pathways.

Antidiabetic Effect of Collagen Peptides from Harpadon nehereus Bones in Streptozotocin-Induced Diabetes Mice by Regulating Oxidative Stress and Glucose Metabolism

Oxidative stress and abnormal glucose metabolism are the important physiological mechanisms in the occurrence and development of diabetes. Antioxidant peptides have been reported to attenuate diabetes complications by regulating levels of oxidative stress, but few studies have focused on peptides from marine bone collagen. In this study, we prepared the peptides with a molecular weight of less than 1 kD (HNCP) by enzymolysis and ultrafiltration derived from Harpadon nehereus bone collagen. Furthermore, the effects of HNCP on blood glucose, blood lipid, liver structure and function, oxidative stress, and glucose metabolism were studied using HE staining, kit detection, and Western blotting experiment in streptozocin-induced type 1 diabetes mice. After the 240 mg/kg HNCP treatment, the levels of blood glucose, triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) in streptozotocin-induced diabetes mice decreased by 32.8%, 42.2%, and 43.2%, respectively, while the levels of serum insulin and hepatic glycogen increased by 142.0% and 96.4%, respectively. The antioxidant enzymes levels and liver function in the diabetic mice were markedly improved after HNCP intervention. In addition, the levels of nuclear factor E2-related factor 2 (Nrf2), glucokinase (GK), and phosphorylation of glycogen synthase kinase-3 (p-GSK3β) in the liver were markedly up-regulated after HNCP treatment, but the glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase1 (PEPCK1) were down-regulated. In conclusion, HNCP could attenuate oxidative stress, reduce blood glucose, and improve glycolipid metabolism in streptozocin-induced type 1 diabetes mice.