Coenzyme Q10 protects against β-cell toxicity induced by pravastatin treatment of hypercholesterolemia

New onset of diabetes is associated with the use of statins. We have recently demonstrated that pravastatin-treated hypercholesterolemic LDL receptor knockout (LDLr^−/−) mice exhibit reductions in insulin secretion and increased islet cell death and oxidative stress. Here, we hypothesized that these diabetogenic effects of pravastatin could be counteracted by treatment with the antioxidant coenzyme Q ₁₀ (CoQ ₁₀), an intermediate generated in the cholesterol synthesis pathway. LDLr ^−/− mice were treated with pravastatin and/or CoQ ₁₀ for 2 months. Pravastatin treatment resulted in a 75% decrease of liver CoQ ₁₀ content. Dietary CoQ ₁₀ supplementation of pravastatin-treated mice reversed fasting hyperglycemia, improved glucose tolerance (20%) and insulin sensitivity (>2-fold), and fully restored islet glucose-stimulated insulin secretion impaired by pravastatin (40%). Pravastatin had no effect on insulin secretion of wild-type mice. In vitro, insulin-secreting INS1E cells cotreated with CoQ ₁₀ were protected from cell death and oxidative stress induced by pravastatin. Simvastatin and atorvastatin were more potent in inducing dose-dependent INS1E cell death (10–15-fold), which were also attenuated by CoQ ₁₀ cotreatment. Together, these results demonstrate that statins impair β-cell redox balance, function and viability. However, CoQ ₁₀ supplementation can protect the statins detrimental effects on the endocrine pancreas.     

Integrated network reconstruction,visualization and analysis using YANAsquare

Background  

Modeling of metabolic networks includes tasks such as network assembly, network overview, calculation of metabolic fluxes and testing the robustness of the network.     

Taurine supplementation prevents morpho-physiological alterations in high-fat diet mice pancreatic β-cells

Taurine (Tau) is involved in beta (β)-cell function and insulin action regulation. Here, we verified the possible preventive effect of Tau in high-fat diet (HFD)-induced obesity and glucose intolerance and in the disruption of pancreatic β-cell morpho-physiology. Weaning Swiss mice were distributed into four groups: mice fed on HFD diet (36 % of saturated fat, HFD group); HTAU, mice fed on HFD diet and supplemented with 5 % Tau; control (CTL); and CTAU. After 19 weeks of diet and Tau treatments, glucose tolerance, insulin sensitivity and islet morpho-physiology were evaluated. HFD mice presented higher body weight and fat depots, and were hyperglycemic, hyperinsulinemic, glucose intolerant and insulin resistant. Their pancreatic islets secreted high levels of insulin in the presence of increasing glucose concentrations and 30 mM K⁺. Tau supplementation improved glucose tolerance and insulin sensitivity with a higher ratio of Akt phosphorylated (pAkt) related to Akt total protein content (pAkt/Akt) following insulin administration in the liver without altering body weight and fat deposition in HTAU mice. Isolated islets from HTAU mice released insulin similarly to CTL islets. HFD intake induced islet hypertrophy, increased β-cell/islet area and islet and β-cell mass content in the pancreas. Tau prevented islet and β-cell/islet area, and islet and β-cell mass alterations induced by HFD. The total insulin content in HFD islets was higher than that of CTL islets, and was not altered in HTAU islets. In conclusion, for the first time, we showed that Tau enhances liver Akt activation and prevents β-cell compensatory morpho-functional adaptations induced by HFD.     

Insight into the role of HSPG in the cellular uptake of apolipoprotein E-derived peptide micelles and liposomes

Liposomes and micellar carriers equipped with targeting and cellular uptake mediating peptides have attracted attention for numerous applications. The optimization of the carrier requires an understanding of how their properties influence target cell recognition and uptake. We developed a dipalmitoylated apolipoprotein E-derived peptide, named P2A2 as promising vector to mediate cellular uptake of potential micellar and liposomal carriers. Confocal laser scanning microscopy (CLSM) and fluorescence-activated cell sorting (FACS) were used to get insight into the internalization mediated by carboxyfluoresceine-labeled P2fA2 and the all-D amino acid analogue P2fa2 into brain capillary endothelial cells. Both peptide micelles and liposomes entered cells via endocytosis. Cell surface heparan sulfate proteoglycans (HSPGs) were involved in the internalization process of peptide-bearing liposomes characterized by a diameter of 100 nm, a low surface density of 100 peptide molecules per vesicle and a helical conformation of the vector. In contrast, peptide micelles characterized by a diameter of about 10 nm, a high peptide density caused by 19 associated molecules and a high conformational flexibility of the vector sequence did not address HSPG. Unspecific interactions between the carriers and membrane constituents predominate the two uptake processes but stereospecific components seem to be involved. Both routes differ with respect to transport efficiency. The results provide a prospective basis to optimize liposomes and micelles as drug delivery systems.     

ArfGAP1 restricts Mycobacterium tuberculosis entry by controlling the actin cytoskeleton

The interaction of Mycobacterium tuberculosis (Mtb) with pulmonary epithelial cells is critical for early stages of bacillus colonization and during the progression of tuberculosis. Entry of Mtb into epithelial cells has been shown to depend on F‐actin polymerization, though the molecular mechanisms are still unclear. Here, we demonstrate that mycobacterial uptake into epithelial cells requires rearrangements of the actin cytoskeleton, which are regulated by ADP‐ribosylation factor 1 (Arf1) and phospholipase D1 (PLD1), and is dependent on the M3 muscarinic receptor (M₃R). We show that this pathway is controlled by Arf GTPase‐activating protein 1 (ArfGAP1), as its silencing has an impact on actin cytoskeleton reorganization leading to uncontrolled uptake and replication of Mtb. Furthermore, we provide evidence that this pathway is critical for mycobacterial entry, while the cellular infection with other pathogens, such as Shigella flexneri and Yersinia pseudotuberculosis, is not affected. Altogether, these results reveal how cortical actin plays the role of a barrier to prevent mycobacterial entry into epithelial cells and indicate a novel role for ArfGAP1 as a restriction factor of host–pathogen interactions.     

Taurine supplementation increases KATP channel protein content,improving Ca2+ handling and insulin secretion in islets from malnourished mice fed on a high-fat diet

Pancreatic β-cells are highly sensitive to suboptimal or excess nutrients, as occurs in protein-malnutrition and obesity. Taurine (Tau) improves insulin secretion in response to nutrients and depolarizing agents. Here, we assessed the expression and function of Cav and K_ATP channels in islets from malnourished mice fed on a high-fat diet (HFD) and supplemented with Tau. Weaned mice received a normal (C) or a low-protein diet (R) for 6 weeks. Half of each group were fed a HFD for 8 weeks without (CH, RH) or with 5 % Tau since weaning (CHT, RHT). Isolated islets from R mice showed lower insulin release with glucose and depolarizing stimuli. In CH islets, insulin secretion was increased and this was associated with enhanced K_ATP inhibition and Cav activity. RH islets secreted less insulin at high K⁺ concentration and showed enhanced K_ATP activity. Tau supplementation normalized K⁺-induced secretion and enhanced glucose-induced Ca²⁺ influx in RHT islets. R islets presented lower Ca²⁺ influx in response to tolbutamide, and higher protein content and activity of the Kir6.2 subunit of the K_ATP. Tau increased the protein content of the α1.2 subunit of the Cav channels and the SNARE proteins SNAP-25 and Synt-1 in CHT islets, whereas in RHT, Kir6.2 and Synt-1 proteins were increased. In conclusion, impaired islet function in R islets is related to higher content and activity of the K_ATP channels. Tau treatment enhanced RHT islet secretory capacity by improving the protein expression and inhibition of the K_ATP channels and enhancing Synt-1 islet content.     

Amino acid restriction increases β-cell death under challenging conditions

Malnutrition programs metabolism, favor dysfunction of β cells. We aimed to establish an in vitro protocol of malnutrition, assessing the effect of amino acid restriction upon the β cells. Insulin-producing cells INS-1E and pancreatic islets were maintained in RPMI 1640 medium containing 1× (Ctl) or 0.25× (AaR) of amino acids. We evaluated several markers of β-cell function and viability. AaR Insulin secretion was reduced, whereas cell viability was unaltered. Calcium oscillations in response to glucose increased in AaR. AaR showed lower Ins1 RNAm, snap 25, and PKC (protein kinase C) protein content, whereas phospho-eIF2α was increased. AaR cells exposed to nutrient or chemical challenges displayed higher apoptosis rates. We showed that amino acid restriction programmed β cell and induced functional changes. This model might be useful for the study of molecular mechanisms involved with β-cell programming helping to establish novel therapeutic targets to prevent harmful outcomes of malnutrition.