Date:September 18, 2015
Source:University of Kansas
Summary:The brains of endurance trainers communicate with muscles differently than those of strength trainers or sedentary individuals, new research shows. While it is not immediately clear why the communication between the brain and muscle was different as a result of different types of exercise, one researcher said it offers leads for new means of research into neuromechanical differences in muscle function, muscle performance, muscle stiffness and other areas.
A University of Kansas study shows that the communication between the brain and quadriceps muscles of people who take part in endurance training, such as running long distances, is different than those who regularly took part in resistance training and those who were sedentary. The findings may offer clues to the type of physical activity humans are most naturally suited to.
Trent Herda, assistant professor of health, sport and exercise sciences, and Michael Trevino, a doctoral student, conducted studies in which they measured muscle responses of five people who regularly run long distances, five who regularly lift weights and five sedentary individuals who regularly do neither. The studies have been published in the Journal of Sports Sciences and Muscle and Nerve.
Among the findings, Herda and Trevino showed that the quadriceps muscle fibers of the endurance trainers were able to fire more rapidly.
“The communication between the brains and their muscles was slightly different than the resistance trainers and sedentary individuals,” Herda said of endurance trainers. “This information also suggested that resistance trainers and those who are sedentary were more likely to fatigue sooner, among other things.”
Survey participants were 15 healthy volunteers. The endurance trainers had consistently taken part in a structured running program for at least three years prior to the study and ran an average of 61 miles a week and did not take part in resistance training. The resistance trainers had consistently taken part in a weight-training program for at least four years prior to the study. They took part in resistance training four to eight hours per week and reported doing at least one repetition of a back squat of twice their body mass. One reported doing a squat of 1.5 times his or her body weight, but none engaged in aerobic activity such as swimming, jogging or cycling. The sedentary participants did not take part in any structured physical exercise for three years prior to the study.
Participants wore mechanomyographic and electromyographic electrode sensors on their quadriceps muscle and extended their leg while seated. The researchers measured submaximal contraction and total force by having participants extend their leg, then exert more force, attempting to achieve from 40 to 70 percent of total force, which they could see represented in real time on a computer screen.
While it is not immediately clear why the communication between the brain and muscle was different as a result of different types of exercise as evidenced by the difference in rates of muscle fibers firing, Herda said it offers leads for new means of research into neuromechanical differences in muscle function, muscle performance, muscle stiffness and other areas. It also provides several clues into the type of exercise humans are more naturally built for. While not claiming that one type of exercise or sport is superior to another, Herda said the findings suggest that the human body’s neuromuscular system may be more naturally inclined to adapt to aerobic exercise than resistance training for strength as the communication between the brain and muscles was similar between resistance training and sedentary individuals.
- Trent J. Herda, Jacob A. Siedlik, Michael A. Trevino, Michael A. Cooper, Joseph P. Weir. Motor unit control strategies of endurance- versus resistance-trained individuals. Muscle & Nerve, 2015; DOI: 10.1002/mus.24597
- Michael A. Trevino, Trent J. Herda. The effects of chronic exercise training status on motor unit activation and deactivation control strategies. Journal of Sports Sciences, 2015; 1 DOI: 10.1080/02640414.2015.1046396
Feb. 6, 2013 — Columbia University Medical Center (CUMC) researchers have identified a protein trafficking defect within brain cells that may underlie common non-familial forms of Parkinson’s disease. The defect is at a point of convergence for the action of at least three different genes that had been implicated in prior studies of Parkinson’s disease. Whereas most molecular studies focus on mutations associated with rare familial forms of the disease, these findings relate directly to the common non-familial form of Parkinson’s.
The study was published today in the online edition of the journalNeuron.
The defective pathway is called the “retromer” pathway, in part because it can guide the reutilization of key molecules by moving them back from the cell surface to internal stores. In this study, defects in the retromer pathway also appear to have profound effects on the cell’s disposal machinery, which may explain why Parkinson’s disease brain cells ultimately accumulate large protein aggregates. The trafficking defects associated with Parkinson’s can be reversed by increasing retromer pathway activity, suggesting a possible therapeutic strategy. No current therapies for Parkinson’s alter the progression of the disease.
The researchers also found evidence that, even in unaffected individuals who simply carry common genetic variants associated with an increased risk of Parkinson’s disease, these molecular changes are at work. This supports the notion that early treatment approaches will be important in tackling Parkinson’s disease.
“Taken together, the findings suggest that drugs that target the retromer pathway could help prevent or treat Parkinson’s,” said study leader Asa Abeliovich, MD, PhD, associate professor of pathology and cell biology and of neurology in the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at CUMC.
In recent years, through genome-wide association studies (GWAS), researchers have identified about 10 common genetic variants that appear to have small effects on the risk of non-familial Parkinson’s, However, it has been hard to delve deeper into the impact of these variants. “When you look at patient brain tissue at autopsy, it’s usually too late — all the critical dopamine neurons are long gone and the damage has been done,” said Dr. Abeliovich.
In the current study, Dr. Abeliovich and his CUMC colleagues used an unusually broad array of approaches — including analyses of Parkinson’s disease-associated genetic variations, patient brain tissue, in vitro tissue culture studies of brain neurons, and fruit fly (Drosophila) models that harbor genetic variants related to those associated with Parkinson’s disease.
The researchers found that common variants in two genes previously linked to Parkinson’s disease, LRRK2 and RAB7L1, led to an unexpectedly similar impact on human brain tissue. The effects of the variants were found to be highly overlapping, pointing to a common pathway of action. Prominent cellular changes were observed in the retromer pathway, which is involved in the trafficking of proteins from the Golgi apparatus (which packages proteins for delivery to other cell components) to the lysosomes (which recycle proteins and other molecules). Mutations that affect the retromer pathway have also been found in familial Parkinson’s disease. Earlier studies from Columbia’s Taub Institute have shown that genetic variants in genes associated with retromer function are linked to Alzheimer’s disease and retromer component levels appear altered in Alzheimer’s disease brains, suggesting a broader role for retromer dysfunction in neurodegenerative diseases of aging, according to Dr. Abeliovich.
The impact of the RAB7L1 and LRRK2 variants was apparent even in individuals with no signs or symptoms of Parkinson’s disease. This suggests that there is a pre-disease state in unaffected carriers of the two genetic variants that favors early disease onset and that, in theory, could be targeted therapeutically.
The CUMC researchers also demonstrated that overexpression of one of the variants, RAB7L1, can overcome the effects of the other variant. Similarly, expression of VPS35, a gene involved in the retromer pathway, can suppress LRRK2 mutant pathology. “It will be interesting to look for drugs that directly target these retromer components or that more generally promote flow through the pathway,” said Dr. Abeliovich.
The title of the paper is “RAB7L1 interacts with LRRK2 to modify intraneuronal protein sorting and Parkinson’s disease risk.” The other contributors are David A. Macleod, Herve Rhinn, Tomoki Kuwahara, Ari Zolin, Gilbert Di Paolo, Brian D. McCabe, Lorraine N. Clark, and Scott A. Small, all at CUMC.
The study was supported by grants from the Michael J. Fox Foundation and the National Institutes of Health (NS064433, NS060876, NS060113, A6008702, AG025161, and AG08702-21.
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- David A. MacLeod, Herve Rhinn, Tomoki Kuwahara, Ari Zolin, Gilbert Di Paolo, Brian D. MacCabe, Karen S. Marder, Lawrence S. Honig, Lorraine N. Clark, Scott A. Small, Asa Abeliovich. RAB7L1 Interacts with LRRK2 to Modify Intraneuronal Protein Sorting and Parkinson’s Disease Risk. Neuron, 2013; 77 (3): 425 DOI:10.1016/j.neuron.2012.11.033
Feb. 5, 2013 — The overall pattern of food that a person eats is more important to a healthy diet than focusing on single foods or individual nutrients, according to the Academy of Nutrition and Dietetics in its newly updated position paper “Total Diet Approach to Healthy Eating.”
According to the position paper: “In contrast to the total diet approach, classification of specific foods as ‘good’ or ‘bad’ is overly simplistic and may foster unhealthy eating behaviors.” The Academy’s position paper stresses that moderation, portion size and exercise are the key concepts for balancing food and beverage intakes.
The position paper has been published in the February Journal of the Academy of Nutrition and Dietetics and can be found on the Academy’s website. It states: It is the position of the Academy of Nutrition and Dietetics that the total diet or overall pattern of food eaten is the most important focus of healthy eating. All foods can fit within this pattern, if consumed in moderation with appropriate portion size and combined with physical activity. The Academy strives to communicate healthy eating messages that emphasize a balance of food and beverages within energy needs, rather than any one food or meal.
The Academy’s position paper has been updated to reflect the most current nutrition guidance, such as the 2010 Dietary Guidelines for Americans and the USDA’s MyPlate food guidance system; the White House’s Let’s Move! campaign to reduce childhood obesity and Healthy People 2020. Each of these public policies and dietary patterns supports the total diet approach.
According to the position paper, while studies including the Academy’s “Nutrition and You” national consumer survey show Americans are “conscious of the importance of healthy diets and physical activity,” most people do not meet the recommendations of the Dietary Guidelines. For example, large majorities do not eat fruit (68 percent) or vegetables (74 percent) more than twice a day, and a substantial number (36 percent) engage in no leisure-time physical activity.
In that environment, according to the Academy: “Labeling specific foods in an overly simplistic manner as ‘good foods’ and ‘bad foods’ is not only inconsistent with the total diet approach, but it may cause many people to abandon efforts to make dietary improvements.”
The position paper adds: “In 2011, 82 percent of U.S. adults cited not wanting to give up foods they like as a reason for not eating healthier. For these reasons, the concepts of moderation and proportionality are necessary components of a practical, action-oriented understanding of the total diet approach.”
The Academy’s position paper notes that the most recent Dietary Reference Intakes use a total diet approach because it allows for a broad range of foods to meet a person’s nutrition needs over time. Therefore, a person can make diet choices based on individual preferences, genetic background, personal health status and food availability.
The position paper was written by registered dietitians Jeanne Freeland-Graves, Bess Heflin Centennial Professor in the department of nutritional sciences at the University of Texas — Austin; and Susan Nitzke, professor emerita and extension specialist in nutritional sciences at the University of Wisconsin — Madison.
The Academy’s position paper contains advice and recommendations for health professionals as well as consumers. It explains how food and nutrition practitioners can use behavioral theories and models to develop effective nutrition communications; and how food and beverage choices are affected by multiple factors that influence people’s ability to make use of expert advice on healthy eating.
Updated sections of the position paper look at new indicators of nutrient quality, such as the Nutrient Rich Food Index, the European Union Nutrient Profiling System and the Overall Nutrient Quality Index. In addition, the Social Ecological model, used in the Dietary Guidelines, is incorporated into the Academy’s position as “a guide for understanding why we eat what we do.”
According to the Academy’s position paper: “Food and nutrition practitioners have a responsibility to communicate unbiased food and nutrition information that is culturally sensitive, scientifically accurate, medically appropriate and tailored to the needs and preferences of the target audience. Some health and nutrition professionals and many ‘pseudo-experts’ promote specific types of foods to choose or avoid. A more responsible and effective approach is to help consumers understand and apply the principles of healthy diet and lifestyle choices. Unless there are extenuating circumstances (severe cognitive or physical limitations), the total diet approach is preferred because it is more consistent with research on effective communication and inclusive of cultural/personal differences.”
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