Carnosol Increases Skeletal Muscle Cell Glucose Uptake via AMPK-Dependent GLUT4 Glucose Transporter Translocation.

Skeletal muscle is a major insulin-target tissue and plays an important role in glucose homeostasis. Insulin action in muscle activates the phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway causing the translocation of intracellularly stored GLUT4 glucose transporters to the plasma membrane and increased glucose uptake. Impaired insulin action in muscle results in insulin resistance and type 2 diabetes mellitus (T2DM). Activation of the energy sensor AMP-activated kinase (AMPK) increases muscle glucose uptake and the use of AMPK activators is viewed as an effective strategy to combat insulin resistance. Rosemary extract (RE) has been shown to stimulate muscle AMPK and glucose uptake, but the exact components responsible for these effects are unknown. In the current study, we investigated the effect of carnosol, a RE polyphenol, in L6 rat muscle cells. Carnosol stimulated glucose uptake in L6 myotubes in a dose- and time-dependent manner, did not affect Akt, increased AMPK phosphorylation and plasma membrane GLUT4 levels. The carnosol-stimulated glucose uptake and GLUT4 translocation was significantly reduced by the AMPK inhibitor compound C (CC). Our study is the first to show an AMPK-dependent increase in muscle glucose uptake by carnosol. Carnosol has potential as a glucose homeostasis regulating agent and deserves further study.

Effects of Resveratrol against Lung Cancer: In Vitro and In Vivo Studies.

Uncontrolled cell growth and resistance to apoptosis characterize cancer cells. These two main features are initiated in cancer cells through mutations in key signaling molecules, which regulate pathways that are directly involved in controlling cell proliferation and apoptosis. Resveratrol (RSV), a naturally occurring plant polyphenol, has been shown to have biological effects counteracting different diseases. It has been found to provide cardio-protective, neuro-protective, immuno-modulatory, and anti-cancer health benefits. RSV has been found to inhibit cancer cell proliferation, induce cell cycle arrest and apoptosis, and these anticancer effects may be due to its ability to modulate signaling molecules involved in these processes. The present review summarizes the existing in vitro and in vivo studies on resveratrol and its anti-lung cancer properties.

Dual effect of chloramphenicol peptides on ribosome inhibition.

Chloramphenicol peptides were recently established as useful tools for probing nascent polypeptide chain interaction with the ribosome, either biochemically, or structurally. Here, we present a new 10mer chloramphenicol peptide, which exerts a dual inhibition effect on the ribosome function affecting two distinct areas of the ribosome, namely the peptidyl transferase center and the polypeptide exit tunnel. According to our data, the chloramphenicol peptide bound on the chloramphenicol binding site inhibits the formation of both acetyl-phenylalanine-puromycin and acetyl-lysine-puromycin, showing, however, a decreased peptidyl transferase inhibition compared to chloramphenicol-mediated inhibition per se. Additionally, we found that the same compound is a strong inhibitor of green fluorescent protein synthesis in a coupled in vitro transcription-translation assay as well as a potent inhibitor of lysine polymerization in a poly(A)-programmed ribosome, showing that an additional inhibitory effect may exist. Since chemical protection data supported the interaction of the antibiotic with bases A2058 and A2059 near the entrance of the tunnel, we concluded that the extra inhibition effect on the synthesis of longer peptides is coming from interactions of the peptide moiety of the drug with residues comprising the ribosomal tunnel, and by filling up the tunnel and blocking nascent chain progression through the restricted tunnel. Therefore, the dual interaction of the chloramphenicol peptide with the ribosome increases its inhibitory effect and opens a new window for improving the antimicrobial potency of classical antibiotics or designing new ones.

Chloramphenicol Derivatives as Antibacterial and Anticancer Agents: Historic Problems and Current Solutions.

Chloramphenicol (CAM) is the D-threo isomer of a small molecule, consisting of a p-nitrobenzene ring connected to a dichloroacetyl tail through a 2-amino-1,3-propanediol moiety. CAM displays a broad-spectrum bacteriostatic activity by specifically inhibiting the bacterial protein synthesis. In certain but important cases, it also exhibits bactericidal activity, namely against the three most common causes of meningitis, Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. Resistance to CAM has been frequently reported and ascribed to a variety of mechanisms. However, the most important concerns that limit its clinical utility relate to side effects such as neurotoxicity and hematologic disorders. In this review, we present previous and current efforts to synthesize CAM derivatives with improved pharmacological properties. In addition, we highlight potentially broader roles of these derivatives in investigating the plasticity of the ribosomal catalytic center, the main target of CAM.