Morandat, Sandrine

The transcription factor Krüppel-like factor 10 (Klf10), also known as Tieg1 for TGFβ (Inducible Early Gene-1) is known to control numerous genes in many cell types that are involved in various key biological processes (differentiation, proliferation, apoptosis, inflammation), including cell metabolism and human disease. In skeletal muscle, particularly in the soleus, deletion of the Klf10 gene (Klf10 KO) resulted in ultrastructure fiber disorganization and mitochondrial metabolism deficiencies, characterized by muscular hypertrophy. To determine the metabolic profile related to loss of Klf10 expression, we analyzed blood and soleus tissue using UHPLC-Mass Spectrometry. Metabolomics analyses on both serum and soleus revealed profound differences between wild-type (WT) and KO animals. Klf10 deficient mice exhibited alterations in metabolites associated with energetic metabolism. Additionally, chemical classes of aromatic and amino-acid compounds were disrupted, together with Krebs cycle intermediates, lipids and phospholipids. From variable importance in projection (VIP) analyses, the Warburg effect, citric acid cycle, gluconeogenesis and transfer of acetyl groups into mitochondria appeared to be possible pathways involved in the metabolic alterations observed in Klf10 KO mice. These studies have revealed essential roles for Klf10 in regulating multiple metabolic pathways whose alterations may underlie the observed skeletal muscle defects as well as other diseases.

AbstractIntroduction/AimsKlf10 is a member of the Krüppel‐like family of transcription factors, which is implicated in mediating muscle structure (fiber size, organization of the sarcomere), muscle metabolic activity (respiratory chain), and passive force. The aim of this study was to further characterize the roles of Klf10 in the contractile properties of skeletal muscle fibers.MethodsFifty‐two single fibers were extracted from female wild‐type (WT) and Klf10 knockout (KO) oxidative (soleus) and glycolytic (extensor digitorum longus [EDL]) skinned muscles. Each fiber was immersed successively in relaxing (R), washing (W), and activating (A) solutions. Calcium was included in the activating solution to induce a maximum contraction of the fiber. The maximum force (Fmax) was measured and normalized to the cross‐sectional area to obtain the maximum stress (Stressmax). After a steady state in contraction was reached, a quick stretch‐release was performed; the force at the maximum stretch (Fstretch) was measured and the stiffness was assessed.ResultsDeletion of the Klf10 gene induced changes in the contractile parameters (Fmax, Stressmax, Stiffness), which were lower and higher for soleus and EDL fibers compared with littermates, respectively. These measurements also revealed changes in the proportion and resistance of attached cross‐bridges.DiscussionKlf10 plays a major role in the homeostasis of the contractile behavior of skeletal muscle fibers in a muscle fiber type–specific manner. These findings further implicate important roles for Klf10 in skeletal muscle function and shed new light on understanding the molecular processes regulating the contractility of skeletal muscle fibers.