Nacre extract improves insulin resistance and cognitive functions in diabetic mice

ObjectivesChlorogenic acid (CGA) is an antioxidant dietary factor. We investigated the effects of CGA on endothelial cell dysfunction in diabetic mice and the mechanistic role of nuclear factor erythroid-related factor 2 (Nrf2) in the antioxidant effect of CGA.MethodsDiabetic (db/db) mice were fed normal chow or chow containing 0.02% CGA for 12 weeks. Human umbilical vein endothelial cells (HUVECs) and mouse aortas were treated with normal or high glucose.ResultsCGA treatment induced upregulation of Nrf2 in HUVECs in a dose-dependent manner. CGA pretreatment prevented reactive oxygen species generation and preserved nitric oxide bioavailability in HUVECs and aortas from wild-type but not Nrf2−/− mice. CGA improved endothelium-dependent relaxation in high glucose-treated aortas from wild-type and db/db mice, but not Nrf2−/− mice. Dietary CGA improved endothelium-dependent relaxation in db/db mice.ConclusionsCGA ameliorates endothelial dysfunction in diabetic mice through activation of the Nrf2 anti-oxidative pathway.

Background and ObjectiveInsulin resistance is well known to exhibit essential effects on the progression of diabetes mellitus (DM). Guava leaf was also reported to exhibit anti-diabetic effects including decreasing blood glucose. Therefore, this present study aims to explore the role guava leaf extract (GLE) plays in insulin resistance and its mechanism of action via the PI3K/Akt signaling pathway.MethodsKK-Ay mice is a spontaneous genetic type 2 diabetes mouse model induced by feeding a high fat and high sugar diet. Mice were randomly assigned into three groups: diabetic mice (DM), DM + MET (diabetic mice treated with metformin) and DM + GLE (diabetic mice treated with GLE) groups. After 8 weeks of treatment, body weight and levels of fasting plasma glucose (FPG), fasting insulin and lipids in plasma were measured. Mice were sacrificed and mRNA and protein expression of insulin receptor substrate1 (IRS1), phosphatidylinositol 3-kinase (PI3K) and serine/threonine kinase protein B (Akt) in livers were measured.ResultsGLE markedly reduced body weight, FPG, fasting insulin and insulin resistance index but increased the insulin sensitivity index of diabetic KK-Ay mice. Moreover, GLE upregulated the expression of IRS-1, PI3K and Akt mRNAs in livers of diabetic KK-Ay mice. In addition, GLE also elevated IRS-1, PI3K, Akt, p-PI3K and p-Akt protein expression in their livers. The results of the DM + MET group were similar to those of the DM + GLE group.ConclusionGLE plays anti-diabetic roles by ameliorating insulin resistance in KK-Ay diabetic mice and this is related to the activation of PI3K/Akt signaling pathway.

Cardiomyocyte-specific deletion of STING improves cardiac function, glucose homeostasis, and wound healing in diabetic mice.

Susceptibility of hippocampus and cerebral cortex to oxidative damage in streptozotocin treated mice: prevention by extracts of Withania somnifera and Aloe vera

BackgroundEvidence from our lab and others showed the vascular beneficial effects of dietary blueberries. However, dose‐ and time‐dependent effect of dietary blueberries on vascular complications in diabetes and the role of gut microbes in mediating this effect are unknown. We hypothesize that gut microbes are associated with the dose‐ and time‐dependent vascular beneficial effects of dietary blueberries.Methods7‐week‐old db/db male mice (Jackson Lab), a widely‐used type 2 diabetic animal model, were fed a diet with or without freeze‐dried wild blueberry powder (FD‐BB) for 4 or 8 or 12 weeks (D4, D8, and D12). Diets contained 0%, 1.23% (B1), 2.46% (B2) and 3.7% (B3) of FD‐BB, which is equivalent to 0, ½, 1, and 2 human servings of wild blueberries. Age‐matched, non‐diabetic db/+ mice fed a standard diet for 4 or 8 or 12 weeks (C4, C8, and C12) were used as controls. After the treatment period blood glucose, body composition, glucose tolerance, and insulin tolerance were assessed. Vascular inflammation was determined by the binding of fluorescent labelled mouse monocytic WEHI78/24 cells to vascular endothelium and mRNA expression of vascular inflammatory chemokines and adhesion molecules (IL8/KC, MCP1/JE, ICAM1, VCAM1 and E‐selectin). Microbial profiling of cecum was done by 16s rRNA amplification.ResultsDiabetic mice (D4, D8 and D12) had increased blood glucose, impaired glucose and insulin tolerance, increased body fat, decreased lean body mass, enhanced binding of monocytes to the aortic vessel, and increased expression of selected inflammatory molecules as compared to their respective control mice (C4, C8 and C12). Blueberry treatment at all levels didn’t improve the metabolic parameters in diabetic mice. However, 3.7% FD‐BB treatment reduced the binding of WEHI78/24 monocyte to vascular endothelium and suppressed the mRNA expression of selected inflammatory molecules in diabetic mice (D4B3 vs D4, D8B3 vs D8, and D12B3 vs D12). Microbial profiling showed an alteration in the relative abundance of gut microbes at different taxonomic levels in diabetic mice as compared to their respective control mice. At the genera level, 7, 9 and 10 genera were altered after 4‐, 8‐ and 12‐weeks treatment in diabetic vs control mice. Blueberry supplementation at different dosages improved the relative abundance of selected gut microbes in diabetic mice (>4 genera) at different time points. Specifically, blueberry treatment increased the abundance of commensal microbe Bifidobacterium and decreased the abundance of opportunistic Clostridium genera in diabetic mice.ConclusionThe beneficial effects of dietary blueberries on diabetic vasculature and gut microbiome varies with the doses and duration of treatment. In the present study, a dose of 3.7% FD‐BB in diet (equivalent to 1.5 human servings) was shown to exert potential beneficial effects on diabetic vasculature and is associated with specific gut microbes.

To examine the relationships between birthweight, current size, and fasting glucose and fasting insulin levels in Aboriginal adolescents. Longitudinal prospective study of a Northern Territory Aboriginal birth cohort of 686 Aboriginal babies born at the Royal Darwin Hospital between January 1987 and March 1990, and followed up between December 2006 and January 2008 in over 40 NT locations. Fasting insulin and glucose levels, adjusted for gestational age, sex and contemporary age. Among the 134 participants with complete data, those with fetal growth restriction (FGR) or low birthweight (LBW) at birth were not overweight at 18 2013s. In these circumstances, birthweight showed a significant positively directed association with fasting glucose levels (P = 0.002). Current weight showed a significant and positively directed association with both fasting insulin (P < 0.001) and fasting glucose levels (P = 0.001), and current height showed a significant and positively directed association with insulin levels (P = 0.006). Birthweight was only positively associated with fasting glucose levels, with no association with fasting insulin levels. The high-risk combination for type 2 diabetes of LBW or FGR with later overweight or obesity was rare in this adolescent Aboriginal population.

Sorafenib has been reported to reduce blood glucose levels in diabetic and non-diabetic patients in previous retrospective studies. However, the mechanism of which the hypoglycemic effects of sorafenib is not clearly explored. In this study, we investigated the effect of sorafenib on blood glucose levels in diabetic and normal mice and explored the possible mechanism. We established a mouse model of type 2 diabetes by a high-fat diet combined with a low-dose of streptozotocin (STZ), to identify the hypoglycemic effect of sorafenib in different mice. Glucose tolerance, insulin tolerance and pyruvate tolerance tests were done after daily gavage with sorafenib to diabetic and control mice. To explore the molecular mechanism by which sorafenib regulates blood glucose levels, hepatic glucose metabolism signaling was studied by a series of in vivo and in vitro experiments. Sorafenib reduced blood glucose levels in both control and diabetic mice, particularly in the latter. The diabetic mice exhibited improved glucose and insulin tolerance after sorafenib treatment. Further studies showed that the expressions of gluconeogenesis-related enzymes, such as PCK1, G6PC and PCB, were significantly decreased upon sorafenib treatment. Mechanistically, sorafenib downregulates the expression of c-MYC downstream targets PCK1, G6PC and PCB through blocking the ERK/c-MYC signaling pathway, thereby playing its hypoglycemic effect by impairing hepatic glucose metabolism. Sorafenib reduces blood glucose levels through downregulating gluconeogenic genes, especially in diabetic mice, suggesting the patients with T2DM when treated with sorafenib need more emphasis in monitoring blood glucose to avoid unnecessary hypoglycemia.

Introduction: Nicotinamide phosphoribosyltransferase (NAMPT) is a multitask peptide; extracellular NAMPT acts as a proinflammatory cytokine, and intracellular NAMPT participates in energy metabolism through NAD + production. Serum NAMPT level is increased in diabetic patients; however, the pathophysiological role of NAMPT in diabetic cardiovascular complications is poorly understood. This study aims to investigate the effect of NAMPT inhibition on coronary microvascular function in diabetes. Materials and Methods: We used two diabetic mouse models: inducible type 2 diabetic (T2D) mice generated by a single injection of low-dose STZ (75 mg/kg, i.p.) with a high-fat diet feeding, and spontaneous T2D mice, TALLYHO/JngJ. Cardiac endothelial cells (CECs) were isolated for molecular biological experiments. Coronary flow velocity reserve (CFVR) was used to determine coronary microvascular function. Results: T2D mice exhibited elevated NAMPT expression in CECs. There was no difference in glucose tolerance and body weight in diabetic NAMPT hetero knockout mice and FK866 (NAMPT inhibitor)-administered diabetic mice compared to their controls. However, CFVR was significantly increased by NAMPT inhibition in T2D mice, accompanied by increased capillary density and augmented endothelium-dependent relaxation (EDR). Chronic administration of neutralizing NAMPT antibody (Ab) also improved CFVR in T2D mice toward the level in control mice. RNA sequencing data in CECs revealed that NAMPT-Ab administration in T2D mice significantly restored the levels of genes related to angiogenesis. NAMPT (100 ng/ml) or NAD + (100 nM) treatment attenuated cell migration in control CECs and reduced EDR in control CAs. Furthermore, NAMPT or NAD + treatment increased mitochondrial ROS formation and decreased Gap junction activity in control CECs. Conclusion: Our data suggest that NAMPT inhibition increases capillary density via enhancing endothelial migration, arguments EDR through reducing mitochondrial ROS production and increasing gap junction activity, and results in restoration of coronary microvascular function in diabetic mice. Therefore, NAMPT inhibition could be a new therapeutic strategy for coronary microvascular disease in diabetes.

Recent evidence highlights the therapeutic potential of peroxisome proliferator–activated receptor-δ (PPARδ) agonists to increase insulin sensitivity in diabetes. However, the role of PPARδ in regulating vascular function is incompletely characterized. We investigate whether PPARδ activation improves endothelial function in diabetic and obese mice. PPARδ knockout (KO) and wild-type (WT) mice fed with high-fat diet and db/db mice were used as diabetic mouse models, compared with PPARδ KO and WT mice on normal diet and db/m+ mice. Endothelium-dependent relaxation (EDR) was measured by wire myograph. Flow-mediated vasodilatation (FMD) was measured by pressure myograph. Nitric oxide (NO) production was examined in primary endothelial cells from mouse aortae. PPARδ agonist GW1516 restored EDRs in mouse aortae under high-glucose conditions or in db/db mouse aortae ex vivo. After oral treatment with GW1516, EDRs in aortae and FMDs in mesenteric resistance arteries were improved in obese mice in a PPARδ-specific manner. The effects of GW1516 on endothelial function were mediated through phosphatidylinositol 3-kinase (PI3K) and Akt with a subsequent increase of endothelial nitric oxide synthase (eNOS) activity and NO production. The current study demonstrates an endothelial-protective effect of PPARδ agonists in diabetic mice through PI3K/Akt/eNOS signaling, suggesting the therapeutic potential of PPARδ agonists for diabetic vasculopathy.

GH therapy variably reduces the height deficit of short children born small for gestational age (SGA) but is associated with hyperinsulinemia. Intermittent, higher-dose GH regimens may be alternatives to continuous, lower-dose treatment. We examined whether the growth response to GH therapy is related to pre-treatment indices of endogenous somatotropic activity, and studied the reversibility of the insulin resistant state induced by GH. 13 non-GH deficient short SGA children were randomised to high-dose GH (100 mcg/kg/day) by daily sc injection (n = 9), or no GH treatment (n = 4) for 2 years (2/4 controls subsequently received GH treatment). Overnight GH profiles were performed at baseline; intravenous glucose tolerance tests were performed at baseline, yearly on GH treatment, and 3 months post-GH treatment. Fasting glucose, insulin and proinsulin levels were measured, insulin sensitivity estimated using Bergman's minimal model, and glucose tolerance calculated from rate of glucose disappearance. In all GH-treated children, gain in height SDS (mean gain yr 1 = +1.2 SDS) was inversely related to baseline peak overnight GH (r = -0.88, n = 10, p = 0.0008), IFG-I (r = -0.74, n = 11, p = 0.009), and fasting insulin levels (r = -0.71, n = 11, p = 0.014). GH treatment increased fasting glucose (means: baseline vs. yr 2: 3.7 vs. 4.4 mmol/l, p = 0.005), insulin (3.8 vs. 13.9 mU/l, p = 0.0002), and proinsulin levels (1.7 vs. 4.5 pmol/l, p = 0.004), and decreased insulin sensitivity (26.9 vs. 4.0 per min/mU/1 x 10(4), p = 0.002). Glucose tolerance initially decreased (baseline: 2.62 min(-1); yr 1: 2.18, p = 0.02; yr 2: 2.39, p = 0.12). However, by 3 months post-GH treatment significant improvements were seen in fasting insulin (post-GH: 5.2 mU/1, p = 0.0003 vs. yr 2), proinsulin (1.7 pmol/l, p = 0.002), and insulin sensitivity (17.6 per min/mU/1 x 10(4), p = 0.0001). Post-GH treatment, fasting glucose levels (4.1 mmol/l, p = 0.04) and glucose tolerance (2.49 min(-1), p = 0.4) were similar to baseline, and the slight increase in fasting insulin levels (5.2 mU/1, p = 0.04) was similar to that observed in non-GH treated children over the 2 yr study period (baseline vs. 2 years: 3.9 vs. 5.9 mU/1, n = 4). In conclusion, in this study of 13 short non-GH-deficient SGA children, high-dose GH therapy induced growth responses that were associated with reversible decreases in insulin sensitivity, and that were predicted by pretreatment markers of endogenous, but not stimulated, somatotropic activity.

Background: Severe hypoglycemia can cause cognitive impairment in diabetic patients, but the underlying molecular mechanism remains unclear.Objective: To assess the effect of severe hypoglycemia on cognitive function in diabetic mice to clarify the relationship between the mechanism and dysfunction of pericytes and the blood–brain barrier (BBB).Method: We established type 1 diabetes mellitus in 80 male C57BL/6J mice by intraperitoneal injection of streptozotocin (150 mg/kg). Further intraperitoneal injection of short-acting insulin induced severe hypoglycemia. The mice were divided into normal, diabetes, and diabetic + severe hypoglycemia groups, and their blood glucose and general weight index were examined. Pericyte and BBB morphology and function were detected by histological and western blot analyses, BBB permeability was detected by Evans blue staining, and cognitive function was detected with the Morris water maze.Results: Severe hypoglycemia aggravated the histological damage, BBB damage, brain edema, and pericyte loss in the diabetic mice. It also reduced the expression of the BBB tight junction proteins occludin and claudin-5, the expression of the pericyte-specific markers PDGFR-β (platelet-derived growth factor receptor-β) and α-SMA, and increased the expression of the inflammatory factor MMP9. At the same time, diabetic mice with severe hypoglycemia had significantly reduced cognitive function.Conclusion: Severe hypoglycemia leads to cognitive dysfunction in diabetic mice, and its possible mechanism is related to pericyte dysfunction and BBB destruction.

Prevalence of Elevated Alanine Aminotransferase Among US Adolescents and Associated Factors: NHANES 1999–2004

ABSTRACTBackground: Resveratrol, a phytoalexin, is reported to activate AMP-activated protein kinase (AMPK) in vascular cells. Whether resveratrol via activation of AMPK improves endothelial dysfunction in diabetes remains unknown. Here, we reported that activation of AMPK is required for resveratrol-induced improvement of endothelial function in diabetic mice. Methods: AMPK phosphorylation and activity, productions of reactive oxygen species, endothelium-dependent/independent relaxation were determined in vitro or in vivo. Results: Exposure of cultured human umbilical vein endothelial cells (HUVECs) to resveratrol activates AMPK by increasing the thr172 phosphorylation and its activities in time/dose-dependent manner. Loss function of liver kinase B1 by siRNA or mutant abolished resveratrol-induced AMPK activation. Incubation of endothelial cells with high glucose (HG) markedly induced oxidative stress of HUVECs, which was abolished by resveratrol in AMPK-dependent manner. In isolated mice aortas, resveratrol, AICAR or apocynin improved endothelium-dependent relaxation impaired by HG. In animal studies, streptozotocin-induced hyperglycemia dramatically increased oxidative stress and caused endothelial dysfunction, which were reversed by administration of resveratrol. Conclusions: We conclude that AMPK activation is required for resveratrol to improve endothelial function in diabetic mice.

Endothelial dysfunction plays an essential role in the pathogenesis of diabetic vascular diseases. Our previous studies showed exercise improves endothelial function in diabetic mice partially through AMPK pathway. MicroRNA 181b (miR-181b) was reported to inhibit NF-κB activity in endothelial cells. However, it is still unknown whether miR-181b is regulated by AMPK signaling and involved in the vasoprotective effect of exercise. The present study investigated the expression of miR-181b in aortas from diabetic mice with/without exercise and reveals a role of the AMPK in exercise-induced miR-181b expression. We first determined the miR-181b level in the aortas of diabetic db/db mice subjected to treadmill exercise (45 min/day for eight weeks). The results showed that exercise significantly increased miR-181b level in the endothelium of mouse aorta compared to the sedentary mice. To test whether the increased blood flow during exercise affects miR-181b expression, we tested the effect of laminar flow on miR-181b expression in Human Umbilical Vein Endothelial Cells (HUVECs). Laminar flow greatly increases miR-181b expression. To understand the mechanism for flow-induced miR-181b expression, we treated HUVECs with AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and found that AICAR-induced miR-181b expression is reversed by AMPK inhibitors. Furthermore, we infected db/db mice with the adenovirus over-expressing miR-181b. MiR-181b overexpression improved endothelial function in db/db mice accompanied by decreased vascular inflammation and increased eNOS expression in mouse arteries. In summary, exercise increases miR-181b level in mouse endothelium probably via shear stress-induced AMPK activation. MiR-181b improves endothelial function in diabetic mice by inhibiting vascular inflammation and increasing eNOS expression. The present results suggest the therapeutic potential of targeting miR-181b against diabetic vasculopathy. Disclosure W. Shang: None. Y. Wang: None. J. Luo: None. X. Tian: None. L. Wang: None. Y. Huang: None. Funding Hong Kong Research Grants Council/Collaborative Research Fund (C4024-16W); Hong Kong Health and Medical Research Fund (05161746)

To examine the effects of hydrogen water on retinal blood flow (RBF) dysregulation in diabetes, we evaluated changes in RBF in response to flicker stimulation and systemic hyperoxia in diabetic mice. Twelve type 2 diabetic mice were divided into a group that received non-hydrogen water (n = 6, control group) and the other that received hydrogen-rich water (0.6-0.8mM) (n = 6, HRW group) from six weeks of age. Body weight, blood glucose, intraocular pressure, and blood pressure were evaluated from eight to 14 weeks of age. RBF was measured in the vascular area of the optic disc as mean blur rate using laser speckle flowgraphy in the resting state and response to flicker stimulation and hyperoxia. We evaluated glial activation and oxidative stress based on immunofluorescence expression. At 14 weeks, blood glucose level was significantly lower in the HRW group, though still elevated. RBF changes improved significantly in the HRW group compared with the control group from eight weeks of age and persisted throughout the study. Immunofluorescent expression of glial fibrillary acidic protein, particularly in the outer plexiform layer, was significantly decreased in the HRW group. Among oxidative stress markers, 3-nitrotyrosine was significantly suppressed in the HRW group. Hydrogen-rich water intake significantly improved RBF dysregulation in diabetic mice. Hydrogen may improve impaired neurovascular coupling function in diabetic mice by suppressing gliosis and oxidative stress in the retina. This study highlights the potential of oral intake of hydrogen-rich water to mitigate retinal dysfunction in diabetic mice.