Circadian misalignment, such as in shift work, has been associated with obesity and type 2 diabetes, however, direct effects of circadian misalignment on skeletal muscle insulin sensitivity and muscle molecular circadian clock have never been investigated in humans. Here we investigated insulin sensitivity and muscle metabolism in fourteen healthy young lean men (age 22.4 2.8 years; BMI 22.3 2.1 kg/m2 [mean SD]) after a 3-day control protocol and a 3.5-day misalignment protocol induced by a 12-h rapid shift of the behavioral cycle. We show that circadian misalignment results in a significant decrease in peripheral insulin sensitivity due to a reduced skeletal muscle non-oxidative glucose disposal (Rate of disappearance: 23.7 2.4 vs. 18.4 1.4 mg/kg/min; control vs. misalignment; p=0.024). Fasting glucose and FFA levels as well as sleeping metabolic rate were higher during circadian misalignment. Molecular analysis of skeletal muscle biopsies revealed that the molecular circadian clock was not aligned to the new behavourial rhythm, and microarray analysis revealed the human PPAR pathway as a key player in the disturbed energy metabolism upon circadian misallignement. Our findings may provide a mechanism underlying the increased risk of type 2 diabetes among shift workers.
Circadian misalignment induces fatty acid metabolism gene profiles and compromises insulin sensitivity in human skeletal muscle.
Sex, Subject
View SamplesEmbryonal Tumors with Multilayered Rosettes (ETMRs) have recently been described as a new entity of rare pediatric brain tumors with fatal outcome. We show here that ETMRs are characterized by a parallel activation of Shh- and Wnt-signaling. Co-activation of these pathways in murine neural precursors is sufficient to induce ETMR-like tumors in vivo that resemble their human counterparts based on histology and global gene expression analyses, and point to apical radial glia cells as the possible tumor cell-of-origin. Overexpression of LIN28A, which is a hallmark of human ETMRs, augments Sonic Hedgehog (Shh)- and Wnt-signaling in these precursor cells through downregulation of let7-miRNA, and LIN28A/let7a interaction with the Shh-pathway was detected at the level of Gli mRNA. Finally, human ETMR cells that were transplanted into immunocompromised host mice were responsive to the Shh-inhibitor Arsenic trioxide (ATO). Our findings provide a novel mouse model to study this tumor type, demonstrate the driving role of Wnt- and Shh-activation in the growth of ETMRs and propose downstream inhibition of Shh-signaling as a therapeutic option for patients with ETMRs.
A mouse model for embryonal tumors with multilayered rosettes uncovers the therapeutic potential of Sonic-hedgehog inhibitors.
Specimen part
View Samples