November 16 Research Roundup: Obesity and Pancreatic Cancer, the Mighty Mitochondria, and Weightlifting and Heart Attack Risk
There are plenty of great scientific research stories out this week. Here’s a look at just a few of them.
Adolescent Obesity Linked to Four-Fold Increased Risk of Pancreatic Cancer
Obesity is often linked to an increased risk of cancer, although the reasons for this are not completely understood. Researchers at Rabin Medical Center and Tel Aviv University recently conducted a study published in the journal Cancer that found obese adolescents had a four-fold greater risk of pancreatic cancer later in life.
Zohar Levi and colleagues analyzed 1,087,358 Israeli Jewish men and 707,212 Jewish women who had compulsory physical exams between the ages of 16 and 19 years from 1967 to 2002. They linked this data to incidence of pancreatic cancer through 2012 to the Israel National Cancer Registry. Compared to normal weight, obesity was linked to a 3.67-times higher cancer risk among men and a 4.07-times higher risk among women.
“The overall population attributable fraction of pancreatic cancer due to adolescent overweight and obesity was 11 percent among this Israeli Jewish population,” Levi stated.
An editorial that accompanied the article by Chanan Meydan, of the Mayanei Hayeshua Medical Center in Israel, cited systemic inflammation caused by obesity as a potential driver in the development of pancreatic cancer.
Cellphone Tech to Detect HIV
Sometimes it really does seem like “there’s an app for that”—or almost everything. Researchers at Brigham and Women's Hospital designed a portable and inexpensive mobile diagnostic tool that uses a cellphone and nanotechnology that can detect HIV viruses. The technology opens the possibility of disease management in resource-limited regions. The research was published in the journal Nature Communications.
“Early detection of HIV is critical to prevent disease progression and transmission, and it requires long-term monitoring, which can be a burden for families that have to travel to reach a clinic or hospital,” stated senior author Hadi Shafiee, principal investigator in the Division of Engineering in Medicine and Renal Division of Medicine at the Brigham. “This rapid and low-cost cellphone system represents a new method for detecting acute infection, which would reduce the risk of virus transmission and could also be used to detect early treatment failure.”
How the Mighty Mitochondria Fluences Metabolism and Gene Expression
Mitochondria, small organelles found in the cytoplasm of cells, are known as the powerplants of the cells because of their role in energy production. But more and more is being found out about mitochondria. Mitochondria have their own DNA, but only 13 genes; they also have peptides, tRNAs and rRNAs. Although they tend to be overpowered by the 20,000 or so genes in the human nucleus, recent research by Scott Ballinger at the University of Alabama at Birmingham outlined just how big a factor mitochondria can have. The research was published in the journal EBioMedicine.
Although nuclear DNA is inherited from both mom and dad, mitochondrial DNA comes from the mother, via her egg. The mitochondrial DNA also evolved distinct haplotypes, each which has variations inherited together. By exchanging mitochondrial DNA in mice, the researchers looked for changes in metabolism and nuclear gene expression. They found a significant impact on adiposity, whole body metabolism and nuclear gene expression.
“These results are clearly consistent with the notion that different nuclear-mitochondrial genetic combinations influence metabolism, adiposity and gene expression in different ways,” Ballinger stated. “The overall implication of this work is that it can provide a new framework for understanding complex genetic disease susceptibility—that both an individual’s nuclear and mitochondrial genomes, in combination, can affect disease development.”
Mitochondria Attack MRSA
Researchers at the University of Michigan published research in the journal Cell Host & Microbe describing how mitochondria play a role in the immune system’s response to methicillin-resistantStaphylococcus aureus(MRSA).
When microbes infect the body, immune cells called macrophages surround and swallow bacteria. They “quarantine” them in something called the phagosome. The cell then uses reactive oxygen species (ROS) to destroy them. An example of an ROS is bleach. Mary O’Riordan, professor of microbiology and immunology at U of M and the study’s principal investigator, stated, “Just like you don’t want bleach on your skin, bacteria don’t want reactive oxygen to damage their outside surface.”
ROS’s get dumped into phagosome. But some bacteria, such as MRSA and salmonella, have evolved ways to avoid these attacks. O’Riordan and colleagues Basel Abduaita and Tracey Schultz were studying those backup systems, and in doing so, discovered something expected—mitochondria’s role. “We discovered that macrophages sense invading MRSA and turn on the machinery to increase mitochondrial development of ROS,” stated Abuaita.
Essentially, when placed under stress, such as invasion by a bacterium, the endoplasmic reticulum sends out chemical signals notifying mitochondria to increase production of ROS. What remained to be determined, however, was how the mitochondria delivered their ROS. “ROS are also damaging to our own cells,” stated O’Riordan, “so we hypothesized that there must be some delivery mechanism. Mitochondria have not traditionally been known to package and deliver substances to different parts of the cell.”
What they found was the ROS were delivered in mitochondrial vesicles. It appears to be a redundant system for delivering ROS. But it may also provide ways for researchers to develop therapeutics that boost the immune system.
At Least 4 Different Subgroups of Obese Patients Identified
Researchers at Brown University analyzed data from more than 2,400 obese patients who had bariatric weight-loss surgery. In the study, they identified at least four different patient subgroups. The subgroups varied significantly in eating behaviors, rate of diabetes, and weight loss. Their work was published in the journal Obesity.
Alison Field, lead author of the study and chair of the department of epidemiology at the Brown University School of Public Health, stated, “There probably isn’t one magic bullet for obesity—if there is a magic bullet, it’s going to be different for different groups of people.”
She went on to say, “There’s a really diverse mix of people who get put into one group. A child who becomes very obese by age 5 is going to be very different from someone who gradually gains weight over time and at age 65 is obese. We need to recognize this diversity, as it may help us to develop more personalized approaches to treating obesity.”
Group 1 had low levels of high-density lipoprotein and very high levels of blood glucose. Most were diabetic.
Group 2 had disordered eating behaviors, such as a binge eating disorder.
Group 3 were metabolically average but had very low levels of disordered eating. “Interestingly,” the authors stated in the paper, “no other factors distinguished this group from the other classes.”
Group 4 were people who had been obese since childhood. They had the highest body mass index (BMI) at age 18 with an average of 32.
Weightlifting Less Than an Hour a Week Can Reduce Heart Attack/Stroke Risk by 40-70%
Researchers at Iowa State University analyzed data from almost 13,000 adults in the Aerobics Center Longitudinal Study. They found that lifting weights for less than an hour a week could cut the risk of a heart attack or stroke by 40 to 70 percent. They published their research in Medicine and Science in Sports and Medicine.
“People may think they need to spend a lot of time lifting weights, but just two sets of bench presses that take less than five minutes could be effective,” stated DC (Duck-chul) Lee, associate professor of kinesiology.
In the study, Lee and colleagues measured three health outcomes: cardiovascular events like heart attack and strokes that didn’t kill the patient, all cardiovascular events that involved death, and any type of death. They found that resistance training cut the risk for all three.
There is a tendency to think of—and for researchers to study—the benefits of cardiovascular exercises such as walking, running, swimming and bicycling in reducing the risk of cardiovascular disease. This study suggests that weight lifting may be as good for the heart and include other benefits.
Lee stated, “The results are encouraging, but will people make weightlifting part of their lifestyle? Will they do it and stick with it? That’s the million-dollar question.”