Update on small intestinal stem cells

Among somatic stem cells, those residing in the intestine represent a fascinating and poorly explored research field. Particularly, somatic stem cells reside in the small intestine at the level of the crypt base, in a constant balance between self-renewal and differentiation. Aim of the present review is to delve into the mechanisms that regulate the delicate equilibrium through which intestinal stem cells orchestrate intestinal architecture. To this aim, special focus will be addressed to identify the integrating signals from the surrounding niche, supporting a model whereby distinct cell populations facilitate homeostatic vs injury-induced regeneration

The multikinase inhibitor Sorafenib enhances glycolysis and synergizes with glycolysis blockade for cancer cell killing

Although the only effective drug against primary hepatocarcinoma, the multikinase inhibitor Sorafenib (SFB) usually fails to eradicate liver cancer. Since SFB targets mitochondria, cell metabolic reprogramming may underlie intrinsic tumor resistance. To characterize cancer cell metabolic response to SFB, we measured oxygen consumption, generation of reactive oxygen species (ROS) and ATP content in rat LCSC (Liver Cancer Stem Cells) -2 cells exposed to the drug. Genome wide analysis of gene expression was performed by Affymetrix technology. SFB cytotoxicity was evaluated by multiple assays in the presence or absence of metabolic inhibitors, or in cells genetically depleted of mitochondria. We found that low concentrations (2.5-5 muM) of SFB had a relatively modest effect on LCSC-2 or 293 T cell growth, but damaged mitochondria and increased intracellular ROS. Gene expression profiling of SFB-treated cells was consistent with a shift toward aerobic glycolysis and, accordingly, SFB cytotoxicity was dramatically increased by glucose withdrawal or the glycolytic inhibitor 2-DG. Under metabolic stress, activation of the AMP dependent Protein Kinase (AMPK), but not ROS blockade, protected cells from death. We conclude that mitochondrial damage and ROS drive cell killing by SFB, while glycolytic cell reprogramming may represent a resistance strategy potentially targetable by combination therapies

Mammalian life-span determinant p66shcA mediates obesity-induced insulin resistance

Obesity and metabolic syndrome result from excess calorie intake and genetic predisposition and are mechanistically linked to type II diabetes and accelerated body aging; abnormal nutrient and insulin signaling participate in this pathologic process, yet the underlying molecular mechanisms are incompletely understood. Mice lacking the p66 kDa isoform of the Shc adaptor molecule live longer and are leaner than wild-type animals, suggesting that this molecule may have a role in metabolic derangement and premature senescence by overnutrition. We found that p66 deficiency exerts a modest but significant protective effect on fat accumulation and premature death in lepOb/Ob mice, an established genetic model of obesity and insulin resistance; strikingly, however, p66 inactivation improved glucose tolerance in these animals, without affecting (hyper)insulinaemia and independent of body weight. Protection from insulin resistance was cell autonomous, because isolated p66KO preadipocytes were relatively resistant to insulin desensitization by free fatty acids in vitro. Biochemical studies revealed that p66shc promotes the signal-inhibitory phosphorylation of the major insulin transducer IRS-1, by bridging IRS-1 and the mTOR effector p70S6 kinase, a molecule previously linked to obesity-induced insulin resistance. Importantly, IRS-1 was strongly up-regulated in the adipose tissue of p66KO lepOb/Ob mice, confirming that effects of p66 on tissue responsiveness to insulin are largely mediated by this molecule. Taken together, these findings identify p66shc as a major mediator of insulin resistance by excess nutrients, and by extension, as a potential molecular target against the spreading epidemic of obesity and type II diabetes