Inhibition of mTOR prevents glucotoxicity-mediated increase of SA-beta-gal, p16INK4a, and insulin hypersecretion, without restoring electrical features of mouse pancreatic islets.

An over-activation of the mechanistic target of rapamycin (mTOR) pathway promotes senescence and age-related diseases like type 2 diabetes. Besides, the regenerative potential of pancreatic islets deteriorates with aging. Nevertheless, the role of mTOR on senescence promoted by metabolic stress in islet cells as well as its relevance for electrophysiological aspects is not yet known. Here, we investigated whether parameters suggested to be indicative for senescence are induced in vitro in mouse islet cells by glucotoxicity and if mTOR inhibition plays a protective role against this. Islet cells exhibit a significant increase (~ 76%) in senescence-associated beta-galactosidase (SA-beta-gal) activity after exposure to glucotoxicity for 72 h. Glucotoxicity does not markedly influence p16INK4a protein within 72 h, but p16INK4a levels increase significantly after a 7-days incubation period. mTOR inhibition with a low rapamycin concentration (1 nM) entirely prevents the glucotoxicity-mediated increase of SA-beta-gal and p16INK4a. At the functional level, reactive oxygen species, calcium homeostasis, and electrical activity are disturbed by glucotoxicity, and rapamycin fails to prevent this. In contrast, rapamycin significantly attenuates the insulin hypersecretion promoted by glucotoxicity by modifying the mRNA levels of Vamp2 and Snap25 genes, related to insulin exocytosis. Our data indicate an influence of glucotoxicity on pancreatic islet-cell senescence and a reduction of the senescence markers by mTOR inhibition, which is relevant to preserve the regenerative potential of the islets. Decreasing the influence of mTOR on islet cells exposed to glucotoxicity attenuates insulin hypersecretion, but is not sufficient to prevent electrophysiological disturbances, indicating the involvement of mTOR-independent mechanisms.

Comparative Screening of the Liver Gene Expression Profiles from Type 1 and Type 2 Diabetes Rat Models.

Experimental animal models of diabetes can be useful for identifying novel targets related to disease, for understanding its physiopathology, and for evaluating emerging antidiabetic treatments. This study aimed to characterize two rat diabetes models: HFD + STZ, a high-fat diet (60% fat) combined with streptozotocin administration (STZ, 35 mg/kg BW), and a model with a single STZ dose (65 mg/kg BW) in comparison with healthy rats. HFD + STZ- induced animals demonstrated a stable hyperglycemia range (350-450 mg/dL), whereas in the STZ-induced rats, we found glucose concentration values with a greater dispersion, ranging from 270 to 510 mg/dL. Moreover, in the HFD + STZ group, the AUC value of the insulin tolerance test (ITT) was found to be remarkably augmented by 6.2-fold higher than in healthy animals (33,687.0 ± 1705.7 mg/dL/min vs. 5469.0 ± 267.6, respectively), indicating insulin resistance (IR). In contrast, a more moderate AUC value was observed in the STZ group (19,059.0 ± 3037.4 mg/dL/min) resulting in a value 2.5-fold higher than the average exhibited by the control group. After microarray experiments on liver tissue from all animals, we analyzed genes exhibiting a fold change value in gene expression <-2 or >2 (p-value <0.05). We found 27,686 differentially expressed genes (DEG), identified the top 10 DEGs and detected 849 coding genes that exhibited opposite expression patterns between both diabetes models (491 upregulated genes in the STZ model and 358 upregulated genes in HFD + STZ animals). Finally, we performed an enrichment analysis of the 849 selected genes. Whereas in the STZ model we found cellular pathways related to lipid biosynthesis and metabolism, in the HFD + STZ model we identified pathways related to immunometabolism. Some phenotypic differences observed in the models could be explained by transcriptomic results; however, further studies are needed to corroborate these findings. Our data confirm that the STZ and the HFD + STZ models are reliable experimental models for human T1D and T2D, respectively. These results also provide insight into alterations in the expression of specific liver genes and could be utilized in future studies focusing on diabetes complications associated with impaired liver function.

Combined Gamma Conglutin and Lupanine Treatment Exhibits In Vivo an Enhanced Antidiabetic Effect by Modulating the Liver Gene Expression Profile.

Previous studies have individually shown the antidiabetic potential of gamma conglutin (Cγ) and lupanine from lupins. Until now, the influence of combining both compounds and the effective dose of the combination have not been assessed. Moreover, the resulting gene expression profile from this novel combination remains to be explored. Therefore, we aimed to evaluate different dose combinations of Cγ and lupanine by the oral glucose tolerance test (OGTT) to identify the higher antidiabetic effect on a T2D rat model. Later, we administered the selected dose combination during a week. Lastly, we evaluated biochemical parameters and liver gene expression profile using DNA microarrays and bioinformatic analysis. We found that the combination of 28 mg/kg BW Cγ + 20 mg/kg BW lupanine significantly reduced glycemia and lipid levels. Moreover, this treatment positively influenced the expression of Pdk4, G6pc, Foxo1, Foxo3, Ppargc1a, Serpine1, Myc, Slc37a4, Irs2, and Igfbp1 genes. The biological processes associated with these genes are oxidative stress, apoptosis regulation, and glucose and fatty-acid homeostasis. For the first time, we report the beneficial in vivo effect of the combination of two functional lupin compounds. Nevertheless, further studies are needed to investigate the pharmacokinetics and pharmacodynamics of the Cγ + lupanine combined treatment.

Maize Flavonoid Biosynthesis, Regulation, and Human Health Relevance: A Review.

Maize is one of the most important crops for human and animal consumption and contains a chemical arsenal essential for survival: flavonoids. Moreover, flavonoids are well known for their beneficial effects on human health. In this review, we decided to organize the information about maize flavonoids into three sections. In the first section, we include updated information about the enzymatic pathway of maize flavonoids. We describe a total of twenty-one genes for the flavonoid pathway of maize. The first three genes participate in the general phenylpropanoid pathway. Four genes are common biosynthetic early genes for flavonoids, and fourteen are specific genes for the flavonoid subgroups, the anthocyanins, and flavone C-glycosides. The second section explains the tissue accumulation and regulation of flavonoids by environmental factors affecting the expression of the MYB-bHLH-WD40 (MBW) transcriptional complex. The study of transcription factors of the MBW complex is fundamental for understanding how the flavonoid profiles generate a palette of colors in the plant tissues. Finally, we also include an update of the biological activities of C3G, the major maize anthocyanin, including anticancer, antidiabetic, and antioxidant effects, among others. This review intends to disclose and integrate the existing knowledge regarding maize flavonoid pigmentation and its relevance in the human health sector.

Lupin γ-conglutin protects against cell death induced by oxidative stress and lipotoxicity, but transiently inhibits in vitro insulin secretion by increasing KATP channel currents.

Lupin γ-conglutin beneficially modulates glycemia, but whether it protects against oxidative and lipotoxic damage remains unknown. Here, we studied the effects of γ-conglutin on cell death provoked by hydrogen peroxide and palmitate in HepG2 hepatocytes and insulin-producing MIN6 cells, and if a modulation of mitochondrial potential and reactive oxygen species (ROS) levels was involved. We also investigated how γ-conglutin influences insulin secretion and electrical activity of ß-cells. The increased apoptosis of HepG2 cells exposed to hydrogen peroxide was prevented by γ-conglutin, and the viability and ROS content in γ-conglutin-treated cells was similar to that of non-exposed cells. Additionally, γ-conglutin partially protected MIN6 cells against hydrogen peroxide-induced death. This was associated with a marked reduction in ROS. No significant changes were found in the mitochondrial potential of γ-conglutin-treated cells. Besides, we observed a partial protection against lipotoxicity only in hepatocytes. Unexpectedly, we found a transient inhibition of insulin secretion, plasma membrane hyperpolarization, and higher KATP channel currents in ß-cells treated with γ-conglutin. Our data show that γ-conglutin protects against cell death induced by oxidative stress or lipotoxicity by decreasing ROS and might also indicate that γ-conglutin promotes a ß-cell rest, which could be useful for preventing ß-cell exhaustion in chronic hyperglycemia.

Glucokinase activation as antidiabetic therapy: effect of nutraceuticals and phytochemicals on glucokinase gene expression and enzymatic activity.

Diabetes represents an important public health problem. Recently, new molecular targets have been identified and exploited to treat this disease. Due to its pivotal role in glucose homeostasis, glucokinase (GCK) is a promising target for the development of novel antidiabetic drugs; however, pharmacological agents that modulate GCK activity have been linked to undesirable side-effects, limiting its use. Interestingly, plants might be a valuable source of new therapeutic compounds with GCK-activating properties and presumably no adverse effects. In this review, we describe biochemical characteristics related to the physiological and pathological importance of GCK, as well as the mechanisms involved in its regulation at different molecular levels. Posteriorly, we present a compendium of findings supporting the potential use of nutraceuticals and phytochemicals in the management of diabetes through modulation of GCK expression and activity. Finally, we propose critical aspects to keep in mind when designing experiments to evaluate GCK modulation properly.

Effect of the acute and chronic administration of Lupinus albus ß-conglutin on glycaemia, circulating cholesterol, and genes potentially involved.

Constituents of lupin seeds, like γ-conglutin and lupanine, have gained attention as potential complementary treatments for dysglycaemia management. Notwithstanding, the effect of other lupin components on carbohydrate metabolism, including ß-conglutin protein, has received little attention. Here, we investigated the influence of the acute and chronic administration of ß-conglutin on glycaemia modulation in normal and streptozotocin induced-to-diabetes rats. We analysed the liver transcriptome modulation exerted by ß-conglutin in diabetes-induced rats using DNA microarrays to scout for potential molecular targets and pathways involved in this biological response. The acute administration of ß-conglutin reduced the incremental area under the curve of glycaemia in normal and diabetes-induced animals. In a seven-day study with diabetic animals, glycaemia increased significantly in non-treated animals but remained unchanged in animals treated with a daily dose of ß-conglutin. Total cholesterol was significantly lower at the end of the experimental period (-21.8 %, p = 0.039). The microarray and gene ontology analyses revealed several targets and pathways potentially modulated by ß-conglutin treatment, including a possible down-regulation of Jun kinase activity. Moreover, our data indicate that targets related to oxidative stress, inflammation, and estrogenic activity might orchestrate these metabolic effects. In conclusion, our findings show that ß-conglutin may help manage postprandial glycaemia and reduce cholesterol levels under the dysglycaemia stage. We identified and proposed new potential molecular targets for further research related to the mechanism of action of ß-conglutin.

Lupin gamma conglutin protein: effect on Slc2a2, Gck and Pdx-1 gene expression and GLUT2 levels in diabetic rats

ABSTRACT Recently, lupin seed (Lupinus albus L., Fabaceae) products have emerged as a functional food due to their nutritional and health benefits. Numerous reports have demonstrated the hypoglycemic effects of lupin's gamma conglutin protein; nonetheless, its mechanism of action remains elusive. To understand the role of this protein on glucose metabolism, we evaluated the effect of administering L. albus' gamma conglutin on Slc2a2, Gck, and Pdx-1 gene expression as well as GLUT2 protein tissue levels in streptozotocin-induced diabetic rats. While consuming their regular diet, animals received a daily gamma conglutin dose (120 mg/kg per body weight) for seven consecutive days. Serum glucose levels were measured at the beginning and at the end of the experimental period. At the end of the trial, we quantified gene expression in pancreatic and hepatic tissues as well as GLUT2 immunopositivity in Langerhans islets. Gamma conglutin administration lowered serum glucose concentration by 17.7%, slightly increased Slc2a2 and Pdx-1 mRNA levels in pancreas, up-regulated Slc2a2 expression in the liver, but it had no effect on hepatic Gck expression. After gamma conglutin administration, GLUT2 immunopositivity in Langerhans islets of diabetic animals resembled that of healthy rats. In conclusion, our results indicate that gamma conglutin up-regulates Slc2a2 gene expression in liver and normalizes GLUT2 protein content in pancreas of streptozotocin-induced rats.