Folate induces stemness and increases oxygen consumption under glucose deprivation by notch-1 pathway activation in colorectal cancer cell.

Evidence for folate's protective effects on neural tube defects led the USA and Chile to start mandatory folic acid (FA) fortification programs, decreasing up to 50%. However, ∼30% of the population consuming fortified foods reach supraphysiologic serum levels. Although controversial, several epidemiological and clinical observations suggest that folate increases cancer risk, giving concern about the risks of FA supplementation. The Cancer stem cells (CSCs) model has been used to explain survival to anticancer therapies. The Notch-1 pathway plays a role in several cancers and is associated with the stemness process. Different studies show that modulation of metabolic pathways regulates stemness capacity in cancer. Supraphysiologic concentrations of FA increase the proliferation of HT-29 cells by Notch-1 activation. However, whether folate can induce a stemness-like phenotype in cancer is not known. We hypothesized that FA protects from glucose deprivation-induced cell death through Notch-1 activation. HT-29 cells were challenged with glucose deprivation at basal (20 nM) and supraphysiological (400 nM) FA and 5-MTHF concentrations. We analyzed changes in stemness-like gene expression, cell death and different energetic metabolic functions. Supraphysiological concentrations of FA increased stemness-like genes, and improved survival and oxygen consumption, inducing AMPK phosphorylation and HSP-70 protein expression. We evaluated the Notch-1 pathway using the DAPT and siRNA as inhibitors, decreasing the stemness-like gene expression and preventing the FA protection against glucose deprivation-induced cell death. Moreover, they decreased oxygen consumption and AMPK phosphorylation. These results suggest that FA protects against glucose deprivation. These effects were associated with AMPK activation, a critical metabolic mediator in nutrient consumption and availability that activates the Notch-1 pathway.

The CB1 cannabinoid receptor regulates autophagy in the tibialis anterior skeletal muscle in mice

The endocannabinoid system (ECS) regulates energy metabolism, has been implicated in the pathogenesis of metabolic diseases and exerts its actions mainly through the type 1 cannabinoid receptor (CB1). Likewise, autophagy is involved in several cellular processes. It is required for the normal development of muscle mass and metabolism, and its deregulation is associated with diseases. It is known that the CB1 regulates signaling pathways that control autophagy, however, it is currently unknown whether the ECS could regulate autophagy in the skeletal muscle of obese mice. This study aimed to investigate the role of the CB1 in regulating autophagy in skeletal muscle. We found concomitant deregulation in the ECS and autophagy markers in high-fat diet-induced obesity. In obese CB1-KO mice, the autophagy-associated protein LC3 II does not accumulate when mTOR and AMPK phosphorylation levels do not change. Acute inhibition of the CB1 with JD-5037 decreased LC3 II protein accumulation and autophagic flux. Our results suggest that the CB1 regulates autophagy in the tibialis anterior skeletal muscle in both lean and obese mice.

Hydrogen sulfide disrupts insulin-induced glucose uptake in L6 skeletal muscle cells.

Hydrogen sulfide (H2S) has been known for its toxicity. However, recent studies have focused on the mechanisms involved in endogenous production and function. To date, the H2S role in insulin signaling and glucose homeostasis is unclear. This uncertainty is even more evident in skeletal muscle, a physiological niche highly relevant for regulating glycemia in response to insulin. This study aimed to investigate the role of H2S on insulin signaling and glucose uptake in the L6 skeletal muscle cell line. We evaluated the endogenous synthesis with the fluorescent dye, 7-azido-4-methyl coumarin (7-AzMC). Glucose restriction-induced an increase in the endogenous levels of H2S, likely through stimulation of cystathionine γ-lyase activity, as its specific inhibitor, PAG (5 mM) prevented this increase, and mRNA levels of CSE decreased with glucose and amino acid restriction. Exogenous H2S reduced insulin-induced glucose uptake at 0.5 up to 24 h, an effect dissociated from the level of Akt phosphorylation. Our results show that glucose restriction induces endogenous production of H2S via CSE. In addition, H2S disrupts insulin-induced glucose uptake independent of the Akt pathway. These results suggest that H2S antagonism over insulin-induced glucose uptake could help maintain the plasmatic glucose levels in conditions that provoke hypoglycemia, which could serve as an H2S-regulated mechanism for maintaining glucose plasmatic levels through the inhibition of the skeletal muscle insulin-depended glucose uptake.

Mifepristone enhances insulin-stimulated Akt phosphorylation and glucose uptake in skeletal muscle cells.

Mifepristone is the only FDA-approved drug for glycaemia control in patients with Cushing's syndrome and type 2 diabetes. Mifepristone also has beneficial effects in animal models of diabetes and patients with antipsychotic treatment-induced obesity. However, the mechanisms through which Mifepristone produces its beneficial effects are not completely elucidated. PURPOSE: To determine the effects of mifepristone on insulin-stimulated glucose uptake on a model of L6 rat-derived skeletal muscle cells. RESULTS: Mifepristone enhanced insulin-dependent glucose uptake, GLUT4 translocation to the plasma membrane and Akt Ser473 phosphorylation in L6 myotubes. In addition, mifepristone reduced oxygen consumption and ATP levels and increased AMPK Thr172 phosphorylation. The knockdown of AMPK prevented the effects of mifepristone on insulin response. CONCLUSIONS: Mifepristone enhanced insulin-stimulated glucose uptake through a mechanism that involves a decrease in mitochondrial function and AMPK activation in skeletal muscle cells.