Metformin improves healthspan and lifespan in mice

Metformin is a drug commonly prescribed to treat patients with type 2 diabetes. Here we show that long-term treatment with metformin (0.1% w/w in diet) starting at middle age extends healthspan and lifespan in male mice, while a higher dose (1% w/w) was toxic. Treatment with metformin mimics some of the benefits of calorie restriction, such as improved physical performance, increased insulin sensitivity, and reduced LDL and cholesterol levels without a decrease in caloric intake. At a molecular level, metformin increases AMP-activated protein kinase activity and increases antioxidant protection, resulting in reductions in both oxidative damage accumulation and chronic inflammation. Our results indicate that these actions may contribute to the beneficial effects of metformin on healthspan and lifespan. These findings are in agreement with current epidemiological data and raise the possibility of metformin-based interventions to promote healthy aging

Identification and Characterization of Anaplasma phagocytophilum Proteins Involved in Infection of the Tick Vector, Ixodes scapularis

Anaplasma phagocytophilum is an emerging zoonotic pathogen transmitted by Ixodes scapularis that causes human granulocytic anaplasmosis. Here, a high throughput quantitative proteomics approach was used to characterize A. phagocytophilum proteome during rickettsial multiplication and identify proteins involved in infection of the tick vector, I. scapularis. The first step in this research was focused on tick cells infected with A. phagocytophilum and sampled at two time points containing 10–15% and 65–71% infected cells, respectively to identify key bacterial proteins over-represented in high percentage infected cells. The second step was focused on adult female tick guts and salivary glands infected with A. phagocytophilum to compare in vitro results with those occurring during bacterial infection in vivo. The results showed differences in the proteome of A. phagocytophilum in infected ticks with higher impact on protein synthesis and processing than on bacterial replication in tick salivary glands. These results correlated well with the developmental cycle of A. phagocytophilum, in which cells convert from an intracellular reticulated, replicative form to the nondividing infectious dense-core form. The analysis of A. phagocytophilum differentially represented proteins identified stress response (GroEL, HSP70) and surface (MSP4) proteins that were over-represented in high percentage infected tick cells and salivary glands when compared to low percentage infected cells and guts, respectively. The results demonstrated that MSP4, GroEL and HSP70 interact and bind to tick cells, thus playing a role in rickettsia-tick interactions. The most important finding of these studies is the increase in the level of certain bacterial stress response and surface proteins in A. phagocytophilum-infected tick cells and salivary glands with functional implication in tick-pathogen interactions. These results gave a new dimension to the role of these stress response and surface proteins during A. phagocytophilum infection in ticks. Characterization of Anaplasma proteome contributes information on host-pathogen interactions and provides targets for development of novel control strategies for pathogen infection and transmission. (Résumé d'auteur

Stimulation of MC38 tumor growth by insulin analog X10 involves the serine synthesis pathway

Recent evidence suggests that type II diabetes is associated with increased risk and/or aggressive behavior of several cancers, including those arising from the colon. Concerns have been raised that endogenous hyperinsulinemia and/or exogenous insulin and insulin analogs might stimulate proliferation of neoplastic cells. However, the mechanisms underlying possible growth-promoting effects of insulin and insulin analogs in cancer cells in vivo, such as changes in gene expression, are incompletely described. We observed that administration of the insulin analog X10 significantly increased tumor growth and proliferation in a murine colon cancer model (MC38 cell allografts). Insulin and X10 altered gene expression in MC38 tumors in a similar fashion, but X10 was more potent in terms of the number of genes influenced and the magnitude of changes in gene expression. Many of the affected genes were annotated to metabolism, nutrient uptake, and protein synthesis. Strikingly, expression of genes encoding enzymes in the serine synthesis pathway, recently shown to be critical for neoplastic proliferation, was increased following treatment with insulin and X10. Using stable isotopic tracers and mass spectrometry, we confirmed that insulin and X10 increased glucose contribution to serine synthesis in MC38 cells. The data demonstrate that the tumor growth-promoting effects of insulin and X10 are associated with changes in expression of genes involved in cellular energy metabolism and reveal previously unrecognized effects of insulin and X10 on serine synthesis.status: publishe

Treatment with Insulin Analog X10 and IGF-1 Increases Growth of Colon Cancer Allografts

<div><p>Obesity and type 2 diabetes are associated with an increased risk for development of certain forms of cancer, including colon cancer. The publication of highly controversial epidemiological studies in 2009 raised the possibility that use of the insulin analog glargine increases this risk further. However, it is not clear how mitogenic effects of insulin and insulin analogs measured <i>in vitro</i> correlate with tumor growth-promoting effects <i>in vivo</i>. The aim of this study was to examine possible growth-promoting effects of native human insulin, insulin X10 and IGF-1, which are considered positive controls <i>in vitro</i>, in a short-term animal model of an obesity- and diabetes-relevant cancer. We characterized insulin and IGF-1 receptor expression and the response to treatment with insulin, X10 and IGF-1 in the murine colon cancer cell line (MC38 cells) <i>in vitro</i> and <i>in vivo</i>. Furthermore, we examined pharmacokinetics and pharmacodynamics and monitored growth of MC38 cell allografts in mice with diet-induced obesity treated with human insulin, X10 and IGF-1. Treatment with X10 and IGF-1 significantly increased growth of MC38 cell allografts in mice with diet-induced obesity and we can therefore conclude that supra-pharmacological doses of the insulin analog X10, which is super-mitogenic <i>in vitro</i> and increased the incidence of mammary tumors in female rats in a 12-month toxicity study, also increase growth of tumor allografts in a short-term animal model.</p></div

Tumor growth <i>in vivo</i>.

<p>95% CI = 95% confidence interval.</p>†<p>fold change, i.e., mean value for a given treatment expressed relative to the mean value of the vehicle-treated group.</p>*<p>, ** and *** indicates <i>P</i><0.05, <0.001 and <0.0001 respectively.</p

Effect of treatment with HI/X10/IGF-1 on tumor growth.

<p>A: Data for tumor volume day 14 in experiment A–E. Treatment with IGF-1 significantly increased tumor volume compared to all other treatments and treatment with X10 increased tumor growth compared to vehicle. B: Area under the tumor growth curves day 0–14 in experiment A–E. These data were in excellent agreement with the data describing tumor volume at day 14; treatment with IGF-1 increased tumor growth compared to all other treatments and treatment with X10 increased tumor growth compared to the vehicle-treated group. Open circles: observations from individual animals, horizontal bars: group mean, error bars: SEM. * and *** indicates <i>P</i><0.05 and 0.0001, respectively.</p

Mean values ± SEM of selected metabolic parameters in DIO-mice and lean, age-matched controls.

†<p>Area under blood glucose curves during a glucose tolerance test was calculated as described previously <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079710#pone.0079710-Andrikopoulos1" target="_blank">[52]</a>.</p>††<p>Whole-body insulin sensitivity indices during a glucose tolerance test was calculated as described in a previous study <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079710#pone.0079710-Matsuda1" target="_blank">[43]</a>.</p>*<p>, ** and *** indicate <i>P</i><0.05, <0.001 and <0.0001, respectively, when the difference between DIO-mice and lean mice was analyzed (student t-test).</p

Effect of HI, X10 and IGF-1 on proliferation <i>in vitro</i>.

<p>MCF-7 cells (A) and MC38 cells (B) were exposed to HI/X10/IGF for 24 h in medium with low serum content (MCF-7; 0.1% (v/v), MC38; 0.25% (v/v)). At the end of the treatment period relative cell numbers were assessed with an MTT assay. Panel A and B shows the mean of three independent experiments, each with four replicates per condition, error bars indicate SEM. HI, X10 and IGF-1 increased proliferation in MCF-7 and MC38 cells. In agreement with previously published data and receptor expression profile, the ranking of the test compounds according to mitogenic potency in MCF-7 cells was IGF-1>X10>HI. In the MC38 cells the ranking was X10≥IGF-1>HI. This suggests IR and IGF-1R are expressed at roughly comparable levels in MC38 cells.</p

Overview and aims of the animal experiments.

<p>Overview and aims of the animal experiments.</p