Lower muscle protein synthesis in humans with obesity concurrent with lower expression of muscle IGF1 splice variants.

Objective: This study tested the hypothesis that expression of insulin-like growth factor 1 (IGF-1) protein and mRNA splice variants is lower in skeletal muscle of humans with obesity who have a lower mixed-muscle protein fractional synthesis rate (MMP-FSR) when compared with individuals without obesity.

Methods: The study included nine participants with obesity (OB, mean [SD],  BMI = 35 [3] kg/m , MMP-FSR = 0.06%/h [0.

Lack of Increase in Muscle Mitochondrial Protein Synthesis During the Course of Aerobic Exercise and Its Recovery in the Fasting State Irrespective of Obesity.

Acute aerobic exercise induces skeletal muscle mitochondrial gene expression, which in turn can increase muscle mitochondrial protein synthesis. In this regard, the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), is a master regulator of mitochondrial biogenesis, and thus mitochondrial protein synthesis. However, PGC-1α expression is impaired in muscle of humans with obesity in response to acute aerobic exercise.

Subpopulation-specific differences in skeletal muscle mitochondria in humans with obesity: insights from studies employing acute nutritional and exercise stimuli.

Mitochondria from skeletal muscle of humans with obesity often display alterations with respect to their morphology, proteome, biogenesis, and function. These changes in muscle mitochondria are considered to contribute to metabolic abnormalities observed in humans with obesity. Most of the evidence describing alterations in muscle mitochondria in humans with obesity, however, lacks reference to a specific subcellular location.

Adenosine Triphosphate Production of Muscle Mitochondria after Acute Exercise in Lean and Obese Humans.

Introduction: Current evidence indicates mitochondrial dysfunction in humans with obesity. Acute exercise appears to enhance mitochondrial function in the muscle of nonobese humans, but its effects on mitochondrial function in muscle of humans with obesity are not known. We sought to determine whether acute aerobic exercise stimulates mitochondrial function in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in humans with obesity.

Obesity modifies the stoichiometry of mitochondrial proteins in a way that is distinct to the subcellular localization of the mitochondria in skeletal muscle.

Background: Skeletal muscle mitochondrial content and function appear to be altered in obesity. Mitochondria in muscle are found in well-defined regions within cells, and they are arranged in a way that form distinct subpopulations of subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria. We sought to investigate differences in the proteomes of SS and IMF mitochondria between lean subjects and subjects with obesity.

Lower Fasted-State but Greater Increase in Muscle Protein Synthesis in Response to Elevated Plasma Amino Acids in Obesity.

Objective: Obesity alters protein metabolism in skeletal muscle, but consistent evidence is lacking. This study compared muscle protein synthesis in adults with obesity and in lean controls in the fasted state and during an amino acid infusion.

Methods: Ten subjects with obesity (age: 36 ± 3 years; BMI: 34 ± 1 kg/m ) and ten controls (age: 35 ± 3 years; BMI: 23 ± 1 kg/m ) received an infusion of L-[2,3,3,4,5,5,5,6,6,6- H ]leucine (0.

Plasma Amino Acids Stimulate Uncoupled Respiration of Muscle Subsarcolemmal Mitochondria in Lean but Not Obese Humans.

Context: Obesity is associated with mitochondrial dysfunction in skeletal muscle. Increasing the plasma amino acid (AA) concentrations stimulates mitochondrial adenosine triphosphate (ATP) production in lean individuals.

Objective: To determine whether acute elevation in plasma AAs enhances muscle mitochondrial respiration and ATP production in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in obese adults.

Subsarcolemmal mitochondria isolated with the proteolytic enzyme nagarse exhibit greater protein specific activities and functional coupling.

Skeletal muscle mitochondria are arranged as a reticulum. Insight into the functional characteristics of such structure is achieved by viewing the network as consisting of "subsarcolemmal" (SS) and "intermyofibrillar" (IMF) regions. During the decades, most, but not all, published studies have reported higher (sometimes over 2-fold) enzyme and enzyme-pathway protein-specific activities in IMF compared to SS mitochondria.