Pilot and Exploratory Projects Core

Core Director: Monty Montano, Ph.D.
Core Co-director: Shalender Bhasin, M.D.

The overall goal of the Pilot/Exploratory Studies Core (PESC) is to support the expeditious translation of early innovative research ideas that have potential for important discoveries but which carry a higher risk premium than incremental science into full-fledged projects by providing funding for the following:

The PESC projects target leading candidates in the discovery of function promoting therapies. The field of function promoting therapies has witnessed considerable excitement in recent years and this is reflected in the progression of a number of candidate drugs through the drug discovery process. The leading candidates include androgens, selective androgen receptor modulators, GH/IGH secretagogues, myostatin antagonists, and mGF. It is becoming apparent that a small number of signaling pathways are crucial for inducing skeletal muscle growth through their effects on mesenchymal stem cell differentiation (Wnt signaling pathway) and/or muscle progenitor cell proliferation (TGFb/Notch pathway), and immunomyogenic interactions. We posit that pharmacophores that selectively activate these signaling pathways in the skeletal muscle would be attractive candidates as function promoting anabolic therapies. Indeed, the data presented in this application provide evidence of the effectiveness of this innovative approach in identifying novel targets for drug discovery (e.g., BJS-1 in pilot project 2). The proposed pilot projects explore each of these leading signaling pathways (TGFb, Wnt); other extant projects that are a part of this OAIC (e.g., Mechanisms of Androgen Action, Bhasin, PI) will explore the role of androgens in regulating Notch signaling in satellite cells and of Wnt signaling in regulating mesenchymal stem cell differentiation). In addition, the OAIC includes efficacy trials of leading function promoting therapies (Testosterone Therapy in Older Men with Functional Limitations) and physical exercise modalities (Fielding). Thus, the proposed OAIC projects represent the cutting edge of science in the field of function promoting anabolic therapies.

Pilot Announcements: 

The Center is currently accepting PESC applications for inclusion in the overall Center renewal grant.The RFA can be accessed here: Boston OAIC PESC RFA November 2011 

Deadline for Submission: December 14, 2011

 

Current Pilot/Exploratory Studies: 

Biomarkers of Androgen Action on the Muscle
Primary Investigator: Monty Montano, PhD  

The purpose of this pilot is to evaluate the hypothesis that there are biomarkers (based on gene expression, cell subsets and serum circulating factors) that can be identified in muscle and blood that can be used to predict gains in muscle mass and strength in older men with mild or moderate physical impairment. There is a strong motivation to develop SARM agonists that promote muscle mass accretion, but do not promote androgen-associated prostate growth. Because accumulating evidence also supports a role for immune modulators in myogenesis, the identification of specific initiators of myogenesis mediated by immune factors could provide new targets for the design of what may be termed selective immuno-myogenic modulators (SIMMs).

A better understanding of the overlap between SARMs/SIMMs gene networks, myogenic differentiation and biomarkers for anabolic effects represents an important new area worthy of further investigation. The identification of a functional linkage between soluble biomarkers and an androgen-responsive gene network would assist in future studies that attempt to dissect and identify finely tailored therapies using anabolic drugs, such as SARMs, which are designed to both promote the beneficial function promoting effects of testosterone supplementation and minimize undesirable effects like androgen associated mediators of prostate cancer. A major challenge in early phase I and II clinical trials is development of biomarkers that can provide early leads to the efficacy of the drug; thus, availability of such biomarkers of anabolic effects of testosterone would be useful in the development of androgens and SARMs as function-promoting anabolic therapies.
 

The Role of Testosterone in the Regeneration of Young and Aged Skeletal Muscles and the Synergy with the Notch and TGF-b Pathways
Primary Investigator: Carlo Serra, Ph.D.

The natural process of aging decreases the stimuli that sustain muscle regeneration; for this, human aging is characterized by the reduction of muscle mass and strength, a condition generally termed sarcopenia.

Several studies in human subjects of different ages indicated that androgens supplementation increases muscle mass and strength, by activating the satellite cells, a muscle-restricted stem-like cell population.
The main goal of this project is to explore if testosterone treatment ameliorates the regeneration of both young and aged skeletal muscles, and if the Notch and transforming growth factor-b (TGF-b) signaling modulate this effect. The experiments will be conducted in vivo, on injured and uninjured skeletal muscles of mice of various ages and in vitro, by using mouse muscle satellite cells and fibers. Mice will be treated with or without testosterone, and its effects on muscle regeneration will be assessed by immunohistochemical means, gene expression profiles and signaling analysis. The new information gathered from this project will provide critical inputs to better define an androgen-based pharmacological strategy aimed to counteract the progressive skeletal muscle atrophy associated with human aging. 

Mechanism of Skeletal Muscle Anabolism in Response to Resistance Exercise
Primary Investigator: Roger Fielding, PhD 

The age-related loss of skeletal muscle mass (1) is associated with well-characterized functional limitations and physical disability (4). Reductions in muscle fiber size, contractile and metabolic properties underlie the observed age-related changes in whole body function. The cellular processes that signal these changes in skeletal muscle and the extent to which they are affected by exercise or physical activity and nutrition are not well understood, particularly in older humans.

The 70 kDa ribosomal protein S6 kinase (p70S6K) is a member of the protein kinase B/mammalian target of rapamycin (Akt/mTOR) pathway; a fundamental regulator of muscle size during overload and contraction-induced hypertrophy (3, 6, 32). p70S6K and other kinases of the Akt/mTOR pathway direct protein translation by phosphorylating key ribosomal proteins, influencing the availability of eukaryotic initiation factors (eIF’s), and regulating glycogen synthase kinase-3 (GSK-3). We have recently shown that contraction-mediated activation of these specific signaling kinases is significantly blunted in older animals (17, 30). We posit that impaired activation of these kinases result in the observed attenuation of muscle hypertrophy that has been reported in older humans and animals in response to exercise training (5, 14, 21, 25). In addition, that specific nutrients, particularly branched-chain amino acids, may also mediate activation of these signaling kinases.

Thus, the objective of this proposal is to determine in humans whether exercise and dietary intake of a essential amino acid supplement (15 g) synergistically activates this key signaling pathway. Specifically, we propose to examine the influence of an acute bout of high intensity resistance exercise (RE) in combination with 15 g of essential amino acids in older adults with defined sarcopenia and functional limitations. We hypothesize that the anabolic effects of RE in older sarcopenic adults will be augmented by the post-exercise availability of dietary amino acids. Intake of an essential amino acid supplement (EAA) following RE will activate Akt/mTOR signaling compared to RE plus placebo administration in older adults with sarcopenia and functional limitations. Elucidating the mechanisms by which exercise and amino acid intake exert their function promoting effects in humans will extend our understanding of the role of nutrition and exercise on the maintenance of skeletal muscle mass with advancing age.

To examine these hypotheses, we propose to evaluate the following specific aims: 

Physical Function and Cardiovascular Risk Factors in Elderly Men taking OpioidAnalgesics for Chronic Non-Cancer Pain
Primary Investigator: Shezhad Basaria, MD 

The treatment of pain has received increasing attention over the past decade. Many have labeled pain as the “5th vital sign” and questioning about pain has become a common practice in medical clinics. Data suggest that the prevalence of chronic non-cancer pain is common and affects up to 15-30% of the US population. A recent survey showed that prescription of potent opioids have increased significantly with 5.9 million prescriptions given to patients with chronic pain in 2000 compared to 1.3 million in 1980. Pharmacy claims data show that older patients have more claims for opioid analgesics than younger subjects, suggesting that the consumption of opioids have significantly increased in the elderly population.

Testosterone levels decline with natural aging. About 20-50% of men >60 years old have testosterone levels that are lower than levels seen in young men (3). To make matters worse, hypogonadism is a known complication of opioid use. Indeed, men on opioids have been shown to have very low testosterone levels, sometimes reaching castrate levels. This suggests that older men on opioids are at risk of developing more profound hypogonadism. The prevalence of hypogonadism in men on opioids is about 75%, with estimates suggesting that approximately 5 million men in the US have opioid-induced hypogonadism. These men have higher prevalence of sexual dysfunction, decreased quality of life (QOL) and osteoporosis. A recent study showed that sexual function and QOL improves on testosterone therapy. However, no information exists on body composition, physical function or cardiovascular (CV) risk factors in these men.

Recent data show that low testosterone in men is an independent risk factor for diabetes, metabolic syndrome and cardiovascular mortality. These CV complications are seen even in men who have testosterone levels that are slightly below the normal range (9). Since men on opioids have very low testosterone levels (5), this may predispose them to even higher metabolic burden. To make matters worse, opioids themselves have been associated with insulin resistance, diabetes and hyperlipidemia irrespective of testosterone levels. Indeed, a recent large study showed that opiates are an independent risk factor for coronary artery disease and the amount of opiate consumption is directly associated with the degree of coronary atherosclerosis. Hence, it is possible that opiates increase a subject’s CV risk directly (due to their drug effect) and indirectly by inducing hypogonadism.
The goal of this pilot study is to evaluate the prevalence of adverse body composition, physical function and cardiovascular risk factors in men ≥60 years who are taking opioids for >6 months. 

Anabolic Effects of a Novel Signaling Molecule (BJS1) on Skeletal Muscle Aging and Function
Primary Investigator: Ravi Jasuja, PhD 

A growing body of evidence has established that androgen administration to men increases skeletal muscle mass, muscle strength, and power, and reduces fat mass. Although these anabolic effects of androgens are well supported by in vivo and in vitro studies, concerns about prostatic side effects have limited enthusiasm about the clinical use of androgens for age-related functional limitations. The stimulatory side effects of androgens on benign and cancerous prostate tissue have provided the impetus for the development of more selective therapies that increase muscle mass and physical function while sparing the prostate. Similarly, virilizing effects of testosterone inherently limit its use in women.

We posit that the signaling transcripts that are androgen regulated, but that exert their pro-myogenic effects downstream of androgen receptor signaling will display muscle anabolism without affecting prostate growth. Accordingly, we explored a series of molecules that are activated by testosterone and are downstream of AR/b-catenin and TCF4 in the Wnt cascade, which led to identification of BJS1. In preliminary studies in young castrated mice, recombinant BJS1 treatment restored the castration-induced loss of LBM and decreased fat mass. As BJS1 acts downstream of AR, we don’t expect recombinant BJS1 to activate androgen-related prostate growth. In this project we will conduct studies to examine the molecular mechanisms of action of BJS1 in muscle and prostate and contrast it with androgen supplemented states in older mice. 

Cognitive and functional correlates of minimally-invasive coronary artery bypass Angela Jefferson, PhDgrafting (CABG). 
Primary Investigator: Angela L. Jefferson, PhD 

The study, which is in collaboration with Dr. Robert Poston, Chief of Cardiothoracic Surgery at Boston Medical Center, compares cognitive and functional outcomes of patients undergoing minimally invasive versus traditional open-heart CABG procedures. Minimally invasive CABG involves the use of a robotic surgical technique that is less invasive than traditional CABG and may yield better post-operative cognitive and functional results. The project is a unique opportunity to explore the potential cognitive and functional benefits of a cutting-edge surgical technique that may benefit future older Americans undergoing cardiac surgery. 

Defective ankle joint performance and myostatin deficiency.
Primary Investigator: Wen Guo, PhD
Co-Investigator: Andrew D. Miller, DVM 

Myostatin is a negative regulator for muscle development. Knockout of myostatin resulted in doubled muscle and diminished fat mass. This phenotype sustains through life. However, we discovered that a large percentage of myostatin null mice would loss the ankle flexibility beginning at middle age. Histological analysis shows increased tendon calcification especially in the tendon-bone insertion region. This change is coupled with increased skeletal and limb bone density as well as ectopic bone formation around the knee at older age. Plasma analysis showed a profound increase in serum osteogenic protein levels. We hypothesize that loss of myostatin may disturb the balance of the signaling network of TGFbeta family members and leads to hyper-activation of BMP signaling that cause calcification in tendon and other soft tissue surrounding the joint. Current studies are focused around the following three areas:

Dietary protein and functional decline in the Framingham offspring study.
Primary Investigator: Lynn L. Moore 

The specific aims for this project are to complete the following analyses in the Framingham Offspring Study: (1) to estimate the independent effects of the amount, type (various animal vs. plant sources), and sources (e.g., dairy, red meat, soy) of dietary protein on the risk of functional decline in adults over the age of 55 years; (2) to determine whether the above protein effects are independent of or modified by the type and amount dietary fats consumed; (3) to determine whether the effects of dietary protein are modified by other risk factors for functional decline (especially physical activity levels, BMI, smoking status, other dietary patterns); and (4) to determine the extent to which the effects of these dietary protein exposures on the above outcomes are mediated through intermediate health effects including such as diabetes or cardiovascular disease. 

Role of skeletal muscle stem cells in age-related muscle dysfunction.
Primary Investigator: Simone Hettmer, M.D. 

Lifelong maintenance of skeletal muscle function relies critically on preserving the regenerative capacity of muscle fibers through a highly regulated process that begins with activation of normally quiescent muscle satellite cells. Age-related deficits in the number and function of muscle satellite cells have been linked to reduced muscle regenerative activity in aged individuals and may contribute to progressive muscle weakness and functional decline. In mice, combinatorial analysis of cell surface markers has allowed direct discrimination and isolation by fluorescence-activated cell sorting (FACS) of highly regenerative muscle satellite cells. However, cell sorting strategies to isolate analogous populations of human skeletal muscle stem cells have yet to be developed. Thus, the goal of this work is to establish robust methodologies for the prospective isolation and functional assessment of human satellite cells, based on expression of cell surface antigens. We will then use this methodology to evaluate the frequency, muscle regenerative capacity and transcriptional profile of human skeletal muscle precursor cells isolated from the skeletal muscle of healthy young and old donors. These analyses will inform the selection of novel molecular targets to reverse hSMP dysfunction in aged skeletal muscle.

Role of HIV Invection in Accelerating Mechanisms that Promote Subclinical Declines in Physical Function
Primary Investigator: Amy Baranoski, MD, MSc

 

Innovations in Late-Life Disability Assessment
Primary Investigator: Christine M. McDonough, PhD, PT,MS

 

Assessment of multi-hormonal dysregulation for joint prediction of cardiometabolic disease, loss of physical function and mortality in aging populations
Primary Investigator: Thomas G. Travison, PhD