To understand childhood obesity, researchers look to inactive, fat rats

July 24, 2012

BETHESDA, Md. (July 24, 2012)--Childhood obesity has nearly tripled in the past three decades, and by 2009, 17 percent of those 2-19 years of age were classified as obese. If actions against childhood obesity do not take place it is likely that today's children could be the first generation in over a century to experience a decline in life expectancy due to the epidemic of childhood obesity which leads to complications in later life. While little is known about how inactivity and obesity lead to undesirable side effects such as diabetes, cardiovascular disease and some cancers, scientists at the University of Missouri in Columbia have reviewed dozens of studies that look at childhood obesity using new animal models. The scientists suggest that the models could be key to better understanding the condition and its complex relationship to certain diseases.

The article is entitled "Potential Clinical Translation of Juvenile Rodent Inactivity Models to Study the Onset of Childhood Obesity." It appears in the online edition of the American Journal of Physiology - Regulatory, Integrative, and Comparative Physiology, published by the American Physiological Society.

Using Inactive, Fat Rats to Study Juvenile Obesity

Lead author Dr. Michael Roberts and his colleagues have written a review article outlining previous research, including some of their own studies, on various animal models that simulate childhood obesity through inactivity. The researchers concentrate specifically on a particular example, called the rodent wheel lock model, to study how different organ systems of young rats respond to a cessation of daily physical activity. This model houses rats in cages with running wheels starting at 28 days of age, which the animals voluntarily use for the next three to six weeks. After that period, the wheels are locked, preventing their primary source of physical activity.

Results

The researchers assert that findings from a variety of studies of juvenile obesity in humans show that children who are inactive in childhood are significantly more likely than those who engaged in exercise when young to continue this habit into adulthood. Additionally, they say, this inactivity in childhood initiates the mechanisms that lead to the consequences of obesity seen in adults. Using the wheel lock model and other animal models for studying childhood obesity is giving scientists more insight on exactly what happens when activity is restricted during youth, leading to obesity. For example, studies have shown that young, inactive rats have reduced insulin sensitivity (a precursor to type-2 diabetes), eat more and burn off fewer calories, and develop larger fat pads than animals who continue to exercise. Other studies show that fat cells multiply to a significantly greater extent in rats who aren't allowed to run on their wheels, while others show that such voluntary exercise in parents can stem positive transgenerational effects in offspring that are bred to be genetically predisposed to obesity (for instance, reduced body fat). Additionally, the wheel lock and other animal model suggest that exercise during youth may help preserve muscle mass over the course of aging and lower the activity of genes associated with cardiovascular disease.

Importance of the Findings

The authors suggest that the wheel lock model and other models that allow exercise, then block it later, are akin to modern-day living conditions in which children who are active during the summer become increasingly sedentary when the school year starts. For these children, voluntary exercise abruptly ends when they must ride in motorized vehicles to school, sit in classrooms, and have insufficient recess or physical education classes. By studying these conditions in rats and other animals, Roberts and his colleagues say, researchers can avoid the ethical conundrum involved in forcing active children to refrain from exercise, imposing biopsies and other tissue sampling techniques, or other parts of research that are possible in animals but not in humans. However, the authors note that animal research still has a long way to go. They suggest that future studies incorporating animal models of childhood obesity take place over longer periods to determine how inactivity during youth contributes to adult consequences of obesity and whether interventions, such as reintroducing exercise, can affect this trajectory. They also note that future studies should examine whether restricting exercise during childhood could affect future motivation to exercise in adulthood, something preliminary work in their lab and others' has suggested.

"Continuing to examine the effects of inactivity on physiological homeostasis during youth is crucial given that 58 percent of children between the ages of 6-11 fail to obtain the recommended 60 minutes per day of physical activity and 92 percent of adolescents fail to achieve this goal," the authors say. "Importantly we contend that using juvenile rodent inactivity models will continue to provide a powerful clinical translational tool that can be used for primordial prevention of human childhood obesity."
-end-
Study Team and Funding

In addition to Dr. Roberts, the article was written by Joseph M. Company, Jacob D. Brown, Ryan G. Toedebusch, Dr. Jaume Padilla, Dr. Nathan T. Jenkins, Dr. Harold Laughlin, and Dr. Frank Booth, all of the University of Missouri in Columbia. The work was supported in part by grants from the National Institutes of Health and the American Heart Association.

NOTE TO EDITORS: The article is available online at http://bit.ly/LdduDa For additional information, or to schedule an interview with Dr. Roberts, please contact Donna Krupa at dkrupa@the-aps.org, @Phyziochick, or 301.634.7209.

Physiology is the study of how molecules, cells, tissues and organs function to create health or disease. The American Physiological Society (APS; www.the-APS.org/press) has been an integral part of the discovery process for 125 years. To keep up with the science, follow @Phyziochick on Twitter.

American Physiological Society

Related Obesity Articles from Brightsurf:

11 years of data add to the evidence for using testosterone therapy to treat obesity, including as an alternative to obesity surgery
New research covering 11 years of data presented at this year's European and International Congress on Obesity (ECOICO 2020) show that, in obese men suffering from hypogonadism (low testosterone), treatment with testosterone injections lowers their weight and improves a wide range of other metabolic parameters.

Overlap between immunology of COVID-19 and obesity could explain the increased risk of death in people living with obesity, and also older patients
Data presented in a special COVID-19 session at the European and International Congress on Obesity (ECOICO 2020) suggests that there are overlaps between the immunological disturbances found in both COVID-19 disease and patients with obesity, which could explain the increased disease severity and mortality risk faced by obese patients, and also elderly patients, who are infected by the SARS-CoV-2 virus that causes COVID-19 disease.

New obesity guideline: Address root causes as foundation of obesity management
besity management should focus on outcomes that patients consider to be important, not weight loss alone, and include a holistic approach that addresses the root causes of obesity, according to a new clinical practice guideline published in CMAJ (Canadian Medical Association Journal) http://www.cmaj.ca/lookup/doi/10.1503/cmaj.191707.

Changing the debate around obesity
The UK's National Health Service (NHS) needs to do more to address the ingrained stigma and discrimination faced by people with obesity, says a leading health psychologist.

Study links longer exposure to obesity and earlier development of obesity to increased risk of type 2 diabetes
Cumulative exposure to obesity could be at least as important as actually being obese in terms of risk of developing type 2 diabetes (T2D), concludes new research published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]).

How much do obesity and addictions overlap?
A large analysis of personality studies has found that people with obesity behave somewhat like people with addictions to alcohol or drugs.

Should obesity be recognized as a disease?
With obesity now affecting almost a third (29%) of the population in England, and expected to rise to 35% by 2030, should we now recognize it as a disease?

Is obesity associated with risk of pediatric MS?
A single-center study of 453 children in Germany with multiple sclerosis (MS) investigated the association of obesity with pediatric MS risk and with the response of first-line therapy in children with MS.

Women with obesity prior to conception are more likely to have children with obesity
A systematic review and meta-analysis identified significantly increased odds of child obesity when mothers have obesity before conception, according to a study published June 11, 2019 in the open-access journal PLOS Medicine by Nicola Heslehurst of Newcastle University in the UK, and colleagues.

Obesity medicine association announces major updates to its adult obesity algorithm
The Obesity Medicine Association (OMA) announced the immediate availability of the 2019 OMA Adult Obesity Algorithm, with new information for clinicians including the relationship between Obesity and Cardiovascular Disease, Diabetes Mellitus, Dyslipidemia, and Cancer; information on investigational Anti-Obesity Pharmacotherapy; treatments for Lipodystrophy; and Pharmacokinetics and Obesity.

Read More: Obesity News and Obesity Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.