(Press-News.org) DURHAM, N.C. - The benefits of exercise are well known, but physical fitness becomes increasingly difficult as people age or develop ailments, creating a downward spiral into poor health.
Now researchers at Duke Medicine report there may be a way to improve exercise tolerance and, by extension, its positive effects.
Reporting in the July 7 issue of the journal Cell Metabolism, the research team describes a small molecule and its metabolic pathway that work together to optimize energy use in exercising muscles. In mouse studies, animals that received a nutrient supplement that increased activity of this pathway ran longer and farther than those that were not supplemented.
"We don't know yet if these results will hold true in humans," said senior author Deborah Muoio, Ph.D, director of basic research at the Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center.
"Exercise intolerance becomes a problem when reduced strength and stamina prevent normal, routine activities such as mowing the lawn or climbing stairs, or when physical activity causes extreme discomfort," Muoio said. "So finding ways to optimize exercise could have tremendous impact to improve overall health."
Muoio and colleagues focused on a metabolic enzyme called carnitine acetyltransferase, or CrAT, which uses the micronutrient carnitine to boost the energy economy within mitochondria, the tiny engines of cells. CrAT has been known for many years, but its role in exercise was unknown.
The Duke researchers engineered mice that lack the gene encoding CrAT, specifically in skeletal muscle, and evaluated their ability to perform exercise. The CrAT-deficient mice were compared against a control group of mice that were identical, except they had the CrAT gene.
As suspected, mice that lacked the CrAT gene tired earlier during various exercise tests because their muscles had more difficulty meeting the energy demands of the activity.
The researchers then introduced a carnitine supplement. Exercise tolerance improved only in animals with normal CrAT activity in muscle. Muoio said these results strongly imply that carnitine and the CrAT enzyme work together to optimize muscle energy metabolism during exercise.
"We were actually quite surprised that carnitine supplementation proved beneficial in young, healthy mice because our presumption was that carnitine availability was not a limiting factor under these circumstances," Muoio said. "We don't know yet if these results will hold true in humans."
Muoio said the findings suggest that CrAT and the metabolite it produces help the mitochondrial engines respond more efficiently when muscles transition from a low to higher work rate, and vice versa. She said more research is needed to fully understand how this system improves energy economy during exercise.
"Responses to any given exercise regimen or intervention can vary tremendously among individuals, which means that both genetic and environmental factors influence exercise-induced improvements in physical fitness and overall health," Muoio said. "Nutrition is one of those factors, and we are interested in identifying nutritional strategies to augment the positive effects of physical activity. Our recent studies suggest that the CrAT enzyme might be targetable through such strategies."
Clinical trials and additional animal studies are underway to define the role of CrAT in muscle energy metabolism. Muoio said the short-term goal is to determine whether carnitine supplementation enhances the benefits of exercise training in older individuals at risk of metabolic disease.
Long-term plans include efforts to identify other genes and metabolic pathways that influence individual responses to exercise intervention, with the goal of developing personalized programs to optimize the health benefits gained by physical activity.
"This work is not meant to imply that everyone should be taking carnitine supplements," Muoio said. "We need to consider underlying genetics, lifestyle factors and acquired conditions."
INFORMATION:
In addition to Muoio, study authors include Sarah E. Seiler; Timothy R. Koves; Jessica R. Gooding; Kari E. Wong; Robert D. Stevens; Olga R. Ilkayeva; April H. Wittmann; Karen L. DeBalsi; Michael N. Davies; Lucas Lindeboom; Patrick Schrauwen; and Vera B. Schrauwen-Hinderling.
The researchers received funding support in part from the United States Public Health Service (R01-DK089312, 2P01-DK058398, R01-HL101189R01, F32-DK-094573 F32-DK093256, and K01-GM1093200-01). A full list of grant support is included in the manuscript.
CLEVELAND - T cells from patients with melanoma can trigger a protective immune response against the disease according to a new study out of University Hospitals Case Medical Center Seidman Cancer Center and Case Western Reserve University School of Medicine.
Published in the July/August issue of Journal of Immunotherapy, these new findings demonstrate that T cells derived from lymph nodes of patients with melanoma can be expanded in number and activated in the laboratory for intravenous administration in the treatment of patients. Led by Julian Kim, MD, Chief Medical ...
If you're seeing more goat meat in grocery stores and on restaurant menus these days, you can probably chalk it up to a particular expression of ethnic identity--an expression that has important implications for immigrants, marketers, and policymakers, according to a recent study in the Journal of Public Policy & Marketing.
"Goat meat is becoming more popular in America, and in large part it's been due to the desire of immigrants to retain the tastes and preferences of their country of origin," write the authors of the study, Denver D'Rozario and Guang Yang (both at Howard ...
NASA's Aqua satellite passed over Typhoon Nangka on July 6 and took an infrared look at the large storm as it strengthened from a tropical storm into a typhoon.
The Atmospheric Infrared Sounder or AIRS instrument aboard NASA's Aqua satellite gathered infrared temperature data on Nangka on July 6 at 15:11 UTC (1:11 p.m. EDT). The infrared data showed a large storm with the bulk of thunderstorms east of the low-level center. The 20 nautical-mile-wide (23 miles/37 km) eye of the storm is also visible on the image.
Fragmented bands of powerful thunderstorms surrounded ...
Bringing reusable bags to the grocery store often means you are an environmentally friendly shopper. But it also influences the very things you buy. According to a new study in the Journal of Marketing, bringing your own bags makes you more likely to purchase organic food--and junk food as well.
"Grocery store shoppers who bring their own bags are more likely to purchase organic produce and other healthy food. But those same shoppers often feel virtuous, because they are acting in an environmentally responsible way. That feeling easily persuades them that, because they ...
The competition for customers in the service sector is fierce, and new customers are entering the market all the time. So when a company such as Time Warner, Travelocity, or AT&T loses a customer, is it worth it to try to win that customer back? Yes, says a new study in the Journal of Marketing.
"Our results show that lost customers, if won back, can be profitable to a company and that so-called win-back initiatives are worth the time and effort," write V. Kumar (Georgia State University), Yashoda Bhagwat , and Xi (Alan) Zhang (both Georgia State University). "In particular, ...
If you feel particularly annoyed when Michelin raises the prices of their tires, blame the Michelin Man. According to a new study in the Journal of Marketing, companies whose brands are represented by or associated with human or humanlike figures (think the Michelin Man or Colonel Sanders or Mrs. Paul) are often perceived to be taking advantage of consumers when they raise their prices.
"When brands are humanized, consumers attribute human motives to those brands. Consumers are more likely to see price increases in those brands as the result of a manager trying to see ...
Inside Gramercy maximum security prison, the market for nearly any kind of good or service is extremely limited, to say the least. But according to a new study in the Journal of Public Policy & Marketing, the severely restricted consumption choices faced by the 3,000 or so inmates at Gramercy create opportunities to pursue innovative and entrepreneurial business ventures.
"The men at Gramercy quickly come to understand that the formal system of exchange, from public provision of goods and services to the commissary, is primarily responsive to needs of third parties such ...
In the most inclusive study to date on friendship, Chapman University research looks at gender, age, and sexual orientation differences in the number of friends people rely on for support, to what extent they choose friends of the same gender, and overall life satisfaction. In a survey of more than 25,000 participants from all walks of life, this study examines at how U.S. adults rely on friends for expressive, instrumental and companionate support. Specifically, how many same-gender and cross-gender friends people have who they can talk to about their sex life, who they ...
Over a billion entrepreneurs in the world operate in subsistence economies, often living hand to mouth. Is there a relationship between such poverty and entrepreneurial activity? A new study in the Journal of Public Policy & Marketing says yes and sheds light on the way in which two kinds of constrained consumption spur--or in some cases impede--entrepreneurial activity.
"There is a complex interplay when it comes to entrepreneurship between what we define as 'chronic' constrained consumption and 'periodic' constrained consumption," write the authors of the study, Srinivas ...
In a study that included nearly 24,000 participants, those who experienced a stroke had an acute decline in cognitive function and also accelerated and persistent cognitive decline over 6 years, according to an article in the July 7 issue of JAMA.
Each year, approximately 795,000 U.S. residents experience a stroke. In 2010, almost 7 million adults were stroke survivors. Cognitive decline is a major cause of disability in stroke survivors. The magnitude of survivors' cognitive changes after stroke has been uncertain, according to background information in the article.
Deborah ...
