Artemisia dracunculus L. extract ameliorates insulin sensitivity by attenuating inflammatory signalling in human skeletal muscle culture.

AIMS: Bioactives of Artemisia dracunculus L. (termed PMI 5011) have been shown to improve insulin action by increasing insulin signalling in skeletal muscle. However, it was not known if PMI 5011's effects are retained during an inflammatory condition. We examined the attenuation of insulin action and whether PMI 5011 enhances insulin signalling in the inflammatory environment with elevated cytokines. METHODS: Muscle cell cultures derived from lean, overweight and diabetic-obese subjects were used. Expression of pro-inflammatory genes and inflammatory response of human myotubes were evaluated by real-time polymerase chain reaction (RT-PCR). Insulin signalling and activation of inflammatory pathways in human myotubes were evaluated by multiplex protein assays. RESULTS: We found increased gene expression of monocyte chemoattractant protein 1 (MCP1) and TNFα (tumour necrosis factor alpha), and basal activity of the NFkB (nuclear factor kappa-light-chain-enhancer of activated B cells) pathway in myotubes derived from diabetic-obese subjects as compared with myotubes derived from normal-lean subjects. In line with this, basal Akt phosphorylation (Ser473) was significantly higher, while insulin-stimulated phosphorylation of Akt (Ser473) was lower in myotubes from normal-overweight and diabetic-obese subjects compared with normal-lean subjects. PMI 5011 treatment reduced basal phosphorylation of Akt and enhanced insulin-stimulated phosphorylation of Akt in the presence of cytokines in human myotubes. PMI 5011 treatment led to an inhibition of cytokine-induced activation of inflammatory signalling pathways such as Erk1/2 and IkBα (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha)-NFkB and moreover, NFkB target gene expression, possibly by preventing further propagation of the inflammatory response within muscle tissue. CONCLUSIONS: PMI 5011 improved insulin sensitivity in diabetic-obese myotubes to the level of normal-lean myotubes despite the presence of pro-inflammatory cytokines.

Inhibition of carnitine palymitoyltransferase1b induces cardiac hypertrophy and mortality in mice.

Recent reports suggest that short-term pharmacological carnitine palmitoyltransferase 1 (Cpt1) inhibition improves skeletal muscle glucose tolerance and insulin sensitivity. Although this appears promising for the treatment of diabetes, these Cpt1 inhibitors are not specific to skeletal muscle and target multiple Cpt1 isoforms. To assess the effects of inhibiting the Cpt1b isoform we generated mice with a heart- and skeletal muscle-specific deletion of the Cpt1b, Cpt1b(HM-/-). These mice seem to develop normally with similar bodyweights as control mice. However, premature mortality was observed by 15 weeks of age in the Cpt1b(HM-/-) mice. The hearts of Cpt1b(HM-/-) mice were four times the size of controls. Cpt1b(HM-/-) mice were also subject to stress-induced seizures that accompanied an increased risk for premature mortality. Our data suggests that prolonged Cpt1b inhibition poses severe cardiac risk and emphasizes that attempts to improve insulin sensitivity by targeting Cpt1 with current inhibitors is not viable.