Our major hypothesis is that type 2 diabetes mellitus (DM2) induced alterations in skeletal muscle (SkM) mitochondria limit tissue growth and thus, facilitate muscle dysfunction. Specifically, this project will characterize DM2 induced perturbations in SkM mitochondria and their relationship with changes in mediators of muscle growth and differentiation. We intend to demonstrate that the preservation and/or enhancement of mitochondria structure/function will improve SkM growth and consequently, exercise capacity. Currently supported by a 1 year NIDDK seed R24 proposal ("Targeting cellular bioenergetics for the prevention and treatment of diabetes") this research team has characterized the positive effects of the primary flavanol present in cacao, (-)-epicatechin (Epi) on mitochondria related endpoints. Thus, the use of this class of compounds can serve as a powerful tool to pursue our major objective and generate evidence for their therapeutic potential. Our studies in mice and primary human cells demonstrate that Epi, stimulates SkM mitochondrial mass/volume and increases maximal mitochondrial respiratory rate. Further, mice treated with 1 mg/kg BID Epi by gavage for 15 days demonstrate enhanced SkM function, endurance, mitochondrial volume, cristae density and capillarity. We recently published the results of a study performed in heart failure DM2 patients in which Epi rich cocoa administration restored SkM (quadriceps) mitochondrial cristae density and increased protein and activity levels of multiple indicators of mitochondria biogenesis. We have also documented at baseline, severe perturbations in SkM structure and sarcomere organization. Interestingly, perturbations in mitochondrial biogenesis are linked to disruptions in muscle regeneration and differentiation. Indeed, following treatment with Epi rich cocoa sarcomere organization was improved as well as markers of muscle growth/regeneration including myostatin, follistatin and MyoD amongst others. Through our collaborative efforts, we have also synthetized more potent Epi isomer forms and novel derivatives active in the low nM range. These results pave the way for the future use of Epi (and patentable related compounds) as therapeutic agents for the treatment DM2 induced SkM related pathologies which are also likely to improve disease profile. To reveal the mechanisms responsible for these responses, we will test the following hypotheses:
Aim 1. Hypothesis: The presence of DM2 leads to perturbations in SkM mitochondria structure/function, which adversely impacts regulators of growth and differentiation.
Aim 2. Hypothesis: The in vitro stimulation of mitochondria structure/function restores DM2 induced loss of SkM differentiation and growth potential.
Aim 3. Hypothesis: The in vivo stimulation of mitochondria structure/function reverses DM2 induced loss of SkM growth and function. This translational proposal is to further the R24 supported ongoing collaboration of Epi biology, diabetology and muscle physiology experts to provide rigorous pre-clinical results to be used for the planning and implementation of relevant clinical trials in DM2 patients.

Public Health Relevance

The major goal of this proposal is to determine the role that mitochondria play in allowing for muscle growth to occur in the setting of type 2 diabetes. We propose to test this hypothesis by using a class of novel and effective compounds that stimulate mitochondria formation and thus, likely muscle growth. Thus, the science advanced by this proposal may allow us to develop safe and effective new therapies to treat diabetes.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Skeletal Muscle and Exercise Physiology Study Section (SMEP)
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Pawlyk, Aaron
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University of California San Diego
Internal Medicine/Medicine
Schools of Medicine
La Jolla
United States
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Ramirez-Sanchez, Israel; De los Santos, Sergio; Gonzalez-Basurto, Silvia et al. (2014) (-)-Epicatechin improves mitochondrial-related protein levels and ameliorates oxidative stress in dystrophic ?-sarcoglycan null mouse striated muscle. FEBS J 281:5567-80
Gutiérrez-Salmeán, Gabriel; Ortiz-Vilchis, Pilar; Vacaseydel, Claudia Maria et al. (2014) Effects of (-)-epicatechin on a diet-induced rat model of cardiometabolic risk factors. Eur J Pharmacol 728:24-30
Gutiérrez-Salmeán, Gabriela; Ortiz-Vilchis, Pilar; Vacaseydel, Claudia M et al. (2014) Acute effects of an oral supplement of (-)-epicatechin on postprandial fat and carbohydrate metabolism in normal and overweight subjects. Food Funct 5:521-7