It is expected that the number and variety of engineered nanoparticles will increase rapidly over the next few years, and there is a need for new methods to quickly test the potential toxicity of these materials. Because experimental evaluation of the safety of chemicals is expensive and time-consuming, computational methods have been found to be efficient alternatives for predicting the potential toxicity and environmental impact of new nanomaterials before mass production. Here, we show that the quantitative structure-activity relationship (QSAR) method commonly used to predict the physicochemical properties of chemical compounds can be applied to predict the toxicity of various metal oxides. Based on experimental testing, we have developed a model to describe the cytotoxicity of 17 different types of metal oxide nanoparticles to bacteria Escherichia coli. The model reliably predicts the toxicity of all considered compounds, and the methodology is expected to provide guidance for the future design of safe nanomaterials.

Hyperinsulinemia is associated with obesity and pancreatic islet hyperplasia, but whether insulin causes these phenomena or is a compensatory response has remained unsettled for decades. We examined the role of insulin hypersecretion in diet-induced obesity by varying the pancreas-specific Ins1 gene dosage in mice lacking Ins2 gene expression in the pancreas, thymus, and brain. Age-dependent increases in fasting insulin and β cell mass were absent in Ins1(+/-):Ins2(-/-) mice fed a high-fat diet when compared to Ins1(+/+):Ins2(-/-) littermate controls. Remarkably, Ins1(+/-):Ins2(-/-) mice were completely protected from diet-induced obesity. Genetic prevention of chronic hyperinsulinemia in this model reprogrammed white adipose tissue to express uncoupling protein 1 and increase energy expenditure. Normalization of adipocyte size and activation of energy expenditure genes in white adipose tissue was associated with reduced inflammation, reduced fatty acid spillover, and reduced hepatic steatosis. Thus, we provide genetic evidence that pathological circulating hyperinsulinemia drives diet-induced obesity and its complications.

Random copolymers based on poly(N-ethyl glycine) and poly(N-butyl glycine) have been synthesized by NHC-mediated or primary amine-initiated copolymerization of the corresponding Nsubstituted N-carboxyanhydride monomers (i.e., Et-NCA and Bu-NCA), respectively. The copolymers are thermally responsive and exhibit reversible phase transitions with tunable cloud point temperature (T cp ) in aqueous solution. The T cp can be readily tuned in the temperature range 20−60 °C by controlling the copoly(α-peptoid) composition and the architecture (i.e., cyclic vs linear). The copoly(α-peptoid)s are noncytotoxic (similar to poly(ethylene glycol) (PEG), a benchmark biocompatible polymer), suggesting their potential use in biotechnology and biomedicine.

Obesity is a principal risk factor for type 2 diabetes, and elevated fatty acids reduce ␤-cell function and survival. An unbiased proteomic screen was used to identify targets of palmitate in ␤-cell death. The most significantly altered protein in both human islets and MIN6 ␤-cells treated with palmitate was carboxypeptidase E (CPE). Palmitate reduced CPE protein levels within 2 h, preceding endoplasmic reticulum (ER) stress and cell death, by a mechanism involving CPE translocation to Golgi and lysosomal degradation. Palmitate metabolism and Ca 2؉ flux were also required for CPE proteolysis and ␤-cell death. Chronic palmitate exposure increased the ratio of proinsulin to insulin. CPE null islets had increased apoptosis in vivo and in vitro. Reducing CPE by Ϸ30% using shRNA also increased ER stress and apoptosis. Conversely, overexpression of CPE partially rescued ␤-cells from palmitate-induced ER stress and apoptosis. Thus, carboxypeptidase E degradation contributes to palmitate-induced ␤-cell ER stress and apoptosis. CPE is a major link between hyperlipidemia and ␤-cell death pathways in diabetes.2D difference gel electrophoresis proteomics ͉ free fatty acids ͉ hyperproinsulinemia ͉ mechanisms of ␤-cell lipotoxicity ͉ type 2 diabetes T here is a strong association between type 2 diabetes and obesity.High levels of circulating lipids, including free fatty acids, are a prominent clinical feature of type 2 diabetes and represent an important risk factor for this disease (1, 2). But exactly how elevated lipids might lead to diabetes remains unresolved. Fatty acids increase basal insulin secretion (3) and the relative levels of circulating proinsulin (4). Chronic exposure to the free fatty acid palmitate has been shown to impair glucose-stimulated insulin release (i.e., lipotoxicity) (5-10). ␤-Cell apoptosis can be initiated by high levels of palmitate (6,7,(11)(12)(13)(14), which may account in part for alterations in insulin secretory function (13). A number of studies have established palmitate targets in the ␤-cell, including lipid metabolism (15, 16), mitochondrial function (17-23), and prosurvival transcription factors such as Pdx1 (24,25). Recently, a role for endoplasmic reticulum (ER) stress in lipotoxicity has been demonstrated in multiple cell types, including ␤-cells (11,26,27). The effects of palmitate on ␤-cell survival are likely mediated by a number of mechanisms.In the present study, we conducted unbiased proteomic screens using human islets and MIN6 ␤-cells to elucidate targets of palmitate. Carboxypeptidase E (CPE) was the most significantly changed protein in both screens. Mice lacking CPE develop hyperproinsulinemia and hyperglycemia (28), but the involvement of this protein in ␤-cell apoptosis has not been reported. Palmitate caused the rapid intracellular redistribution and degradation of CPE via mechanisms that required palmitate metabolism, K ATP channel closure, Ca 2ϩ influx, and protease activity. We further showed that CPE levels control ␤-cell ER stress and apoptosis. Thus, CPE is a cri...

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Human embryonic stem cells (hESCs) were used as a model system of human pancreas development to study characteristics of the polyhormonal cells that arise during fetal pancreas development. HESCs were differentiated into fetal-like pancreatic cells in vitro using a 33-day, 7-stage protocol. Cultures were ~90-95% PDX1-positive by day (d) 11 and 70-75% NKX6.1-positive by d17. Polyhormonal cells were scattered at d17, but developed into islet-like clusters that expressed key transcription factors by d33. Human C-peptide and glucagon secretion were first detected at d17 and increased thereafter in parallel with INS and GCG transcript levels. HESC-derived cells were responsive to KCl and arginine, but not glucose in perifusion studies. Compared to adult human islets, hESC-derived cells expressed ~10-fold higher levels of glucose transporter 1 (GLUT1) mRNA, but similar levels of glucokinase (GCK). In situ hybridization confirmed the presence of GLUT1 transcript within endocrine cells. However, GLUT1 protein was excluded from this population and was instead observed predominantly in non-endocrine cells, whereas GCK was co-expressed in insulin-positive cells. In rubidium efflux assays, hESC-derived cells displayed mild potassium channel activity, but no responsiveness to glucose, metabolic inhibitors or glibenclamide. Western blotting experiments revealed that the higher molecular weight SUR1 band was absent in hESC-derived cells, suggesting a lack of functional KATP channels at the cell surface. In addition, KATP channel subunit transcript levels were not at a 1:1 ratio, as would be expected (SUR1 levels were ~5-fold lower than KIR6.2). Various ratios of SUR1:KIR6.2 plasmids were transfected into COSM6 cells and rubidium efflux was found to be particularly sensitive to a reduction in SUR1. These data suggest that an impaired ratio of SUR1:KIR6.2 may contribute to the observed KATP channel defects in hESC-derived islet endocrine cells, and along with lack of GLUT1, may explain the absence of glucose-stimulated insulin secretion.

Four phthalocyanine (Pc)–peptide conjugates designed to target the epidermal growth factor receptor (EGFR) were synthesized and evaluated in vitro using four cell lines: human carcinoma A431 and HEp2, human colorectal HT-29, and kidney Vero (negative control) cells. Two peptide ligands for EGFR were investigated: EGFR-L1 and -L2, bearing 6 and 13 amino acid residues, respectively. The peptides and Pc-conjugates were shown to bind to EGFR using both theoretical (Autodock) and experimental (SPR) investigations. The Pc–EGFR-L1 conjugates 5a and 5b efficiently targeted EGFR and were internalized, in part due to their cationic charge, whereas the uncharged Pc–EGFR-L2 conjugates 4b and 6a poorly targeted EGFR maybe due to their low aqueous solubility. All conjugates were nontoxic (IC50 > 100 μM) to HT-29 cells, both in the dark and upon light activation (1 J/cm2). Intravenous (iv) administration of conjugate 5b into nude mice bearing A431 and HT-29 human tumor xenografts resulted in a near-IR fluorescence signal at ca. 700 nm, 24 h after administration. Our studies show that Pc–EGFR-L1 conjugates are promising near-IR fluorescent contrast agents for CRC and potentially other EGFR overexpressing cancers.

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