Proteome-wide muscle protein fractional synthesis rates predict muscle mass gain in response to a selective androgen receptor modulator in rats

Abstract

. Proteome-wide muscle protein fractional synthesis rates predict muscle mass gain in response to a selective androgen receptor modulator in rats. Am J Physiol Endocrinol Metab 310: E405-E417, 2016. First published December 29, 2015 doi:10.1152/ajpendo.00257.2015.-Biomarkers of muscle protein synthesis rate could provide early data demonstrating anabolic efficacy for treating muscle-wasting conditions. Androgenic therapies have been shown to increase muscle mass primarily by increasing the rate of muscle protein synthesis. We hypothesized that the synthesis rate of large numbers of individual muscle proteins could serve as early response biomarkers and potentially treatment-specific signaling for predicting the effect of anabolic treatments on muscle mass. Utilizing selective androgen receptor modulator (SARM) treatment in the ovariectomized (OVX) rat, we applied an unbiased, dynamic proteomics approach to measure the fractional synthesis rates (FSR) of 167-201 individual skeletal muscle proteins in triceps, EDL, and soleus. OVX rats treated with a SARM molecule (GSK212A at 0.1, 0.3, or 1 mg/kg) for 10 or 28 days showed significant, dose-related increases in body weight, lean body mass, and individual triceps but not EDL or soleus weights. Thirty-four out of the 94 proteins measured from the triceps of all rats exhibited a significant, dose-related increase in FSR after 10 days of SARM treatment. For several cytoplasmic proteins, including carbonic anhydrase 3, creatine kinase M-type (CK-M), pyruvate kinase, and aldolase-A, a change in 10-day FSR was strongly correlated (r 2 ϭ 0.90 -0.99) to the 28-day change in lean body mass and triceps weight gains, suggesting a noninvasive measurement of SARM effects. In summary, FSR of multiple muscle proteins measured by dynamics of moderate-to high-abundance proteins provides early biomarkers of the anabolic response of skeletal muscle to SARM. fractional synthesis rate; protein synthesis; selective androgen receptor modulator; skeletal muscle; anabolism; dynamic proteomics; stable isotope; biomarkers of muscle anabolism LOSS OF SKELETAL MUSCLE MASS with age (sarcopenia) or chronic disease (cachexia) is associated with reduced functional capacity, disability, and increased mortality (8). Androgen receptor (AR) stimulation via testosterone or other anabolic steroids is an established intervention for increasing muscle mass, strength, and functional performance in a dose-responsive way in many clinical settings (3, 15). Selective androgen receptor modulators (SARMs) represent a promising class of smallmolecule therapeutics for stimulating muscle anabolism through AR activation. SARM molecules have been under development for decades, and several compounds have proven to be effective at increasing muscle mass in several animal models and in humans (2,16,31).AR stimulation increases muscle mass primarily by increasing the synthesis rates of muscle proteins (10, 11). Changes in muscle mass or function that may result from an anabolic agent are also related to a number of addit...

On the Rate of Synthesis of Individual Proteins within and between Different Striated Muscles of the Rat

“…Table 5 provides a comparison between our 7-day data and equivalent data reported in Table 2 of Shankaran et al . [32]. In most cases, we report less protein synthesis in the hindlimb muscles than Shankaran et al report in the triceps.…”

“…[31] reports the half-life of cardiac ATPA is approximately 27–30 days which is equivalent to the values estimated here in the diaphragm and EDL (Table 2). More recently, 2 H 2 O labelling in vivo has been used to investigate synthesis in the triceps of ovariectomised rats exposed to a selective androgen receptor modulator or vehicle control [32]. Rats were administered deuterium oxide for a period of 7 days prior to muscle harvesting and peptide mass spectrometry was used to calculate the synthesis of individual proteins.…”

Dynamic proteome profiling of individual proteins in human skeletal muscle after a high‐fat diet and resistance exercise

“…9) has not previously been captured and is a unique aspect of the current investigation. New techniques have recently been developed that incorporate D 2 O labeling with proteomic analyses, including peptide mass spectrometry, which measures the rate constant (k) for synthesis on a protein-by-protein basis in the muscle of animals (33)(34)(35)(36) and humans (20). Collectively, these works and our current data (Fig.…”

Circulating protein synthesis rates reveal skeletal muscle proteome dynamics

“…Changes in the FSR of muscle proteins have been reported within 5 days of starting anabolic treatments (8) and predict subsequent changes in muscle mass and strength in humans (5, 9) and rodents (72), while the latter typically require 4-20 weeks to be observable. Indeed, a general principle of dynamic systems is that changes in synthesis or breakdown rates within a molecular pool typically precede and are more sensitive than changes in the pool size (73).…”