May 13, 2014, Volume 60, No. 34
BMI: Direct Cause of Type 2 Diabetes & High Blood Pressure
Using new genetic evidence, an international team of scientists led by experts at the Perelman School of Medicine and Children’s Hospital of Philadelphia found that an increased body mass index (BMI) raised the risk for both type 2 diabetes and higher blood pressure. The results add to mounting evidence about the risks of obesity and are of major importance for the obesity pandemic that is affecting the United States—where two-thirds of adults are overweight or obese—and other countries. According to the findings, published online in The American Journal of Human Genetics, for every 1 kg/m2 increase in BMI—equivalent to a 196-pound, 40-year old man of average height gaining seven pounds—the risk of developing type 2 diabetes increases by 27 percent. The same rise in BMI also increases blood pressure by 0.7 mmHg.
“Our findings provide solid genetic support indicating that a higher body mass index causes a raised risk of type 2 diabetes and high blood pressure,” said the study’s lead author, Michael V. Holmes, research assistant professor of surgery in the division of transplant at Penn Medicine.
The research team used a recently developed statistical tool called Mendelian randomization (MR), which helps researchers identify genes responsible for particular diseases or conditions (such as obesity), independent of potentially confounding factors such as differences in behavior and lifestyle, which can lead to false-positive associations. In this case, the use of MR virtually rules out the possibility that both a high BMI and type 2 diabetes are caused by a third, unidentified factor.
“Whether high BMI raises the risk of adverse outcomes is of critical importance given that BMI is modifiable,” said Dr. Holmes. “Now that we know high BMI is indeed a direct cause of type 2 diabetes, we can reinforce to patients the importance of maintaining body mass within established benchmarks.”
Results of the study were based on the assessment of the genotypes for over 34,500 patients from previous studies. In addition, researches found that an elevated BMI has potentially harmful effects on several blood markers of inflammation.
“While this study has strong foundations and implications, there are many more BMI signals emerging,” said senior author Brendan Keating, research assistant professor of pediatrics and surgery at Penn Medicine and lead clinical data analyst in the Center for Applied Genomics at The Children’s Hospital of Philadelphia. “Future research will likely generate even more useful information about genetics and the associated risks for disease for both physicians and patients.”
Psychological Factors Turn Young Adults Away From HIV Intervention Counseling
Keeping young people in human immunodeficiency virus (HIV) prevention programs is a major goal in reducing the incidence of HIV, and multi-session interventions are often more effective than single-sessions. But according to a study from Penn’s Annenberg School for Communication, the way these programs are designed and implemented may turn off the very people they are trying to help.
The study, “Motivational barriers to retention of at-risk young adults in HIV-prevention interventions: perceived pressure and efficacy,” is published in AIDS Care: Psychological and Socio-medical Aspects of AIDS/HIV. Authors include Jiaying Liu, Christopher Jones, Kristina Wilson, Marta R. Durantini and Dolores Albarracín, all with the Annenberg School for Communication; and William Livingood, Florida Department of Health, Duval County, Jacksonville, FL.
The study is part of a larger research project on retention in HIV-prevention counseling conducted with community members at risk for HIV in northern Florida. Duval County remains fourth in sexually transmitted infection (STI) rates among Florida’s 67 counties. Presently, Duval is faced with a 25 percent increase in reported HIV/AIDS cases, escalating STI/HIV co-infections, increasing STI infections in pregnant women, increasing repeat STI infections and continued levels of unacceptable STI rates. The alarming rates of infection are complicated by high rates of poverty and racial segregation issues in Duval County.
Understanding barriers to retention is necessary to reduce morbidity and improve health outcomes for Duval residents. The study investigated three potential motivational barriers that might affect the likelihood of retention among a vulnerable population with high levels of risk behavior: perceived pressure, perceived efficacy and fear.
According to the study, when young adults (18-35 years old) feel pressured or coerced by HIV-prevention counselors to change their lifestyle and behaviors, they often become defensive and are less likely to return to recommended follow-up counseling sessions. This is especially the case with younger (18-22 years old) intervention recipients. Moreover, intervention program retention rates are also lower when participants view the initial intervention as ineffective or irrelevant to their life.
“Our findings suggest that practitioners make efforts to ensure younger clients in particular do not feel coerced, because such threats to autonomy can backfire,” wrote the authors. “Practitioners should also make efforts to explicitly communicate the efficacy of the intervention and to foster a sense of self-relevance [perhaps by] delivering tailored information about HIV risk in a personalized manner.”
The study also looked at the effect of HIV-related fear on retention rates and found no significant association. However, it did find an association between retention rates and both gender and age: Male clients and older clients were more likely to return for follow-up sessions than female clients and younger clients.
“It is important that practitioners understand the psychological factors that can turn clients away from interventions, and for whom these factors are especially likely to matter,” concluded the authors. “In this way, effective tailoring of interventions can be grounded in the collective experiences of successes and failures in retaining members of at-risk populations.”
Ability To Digest Milk and Development of Pastoralism
Babies are born with the ability to digest lactose, the sugar found in milk, but most humans lose this ability after infancy because of declining levels of the lactose-digesting enzyme lactase. People who do maintain high levels of lactase reap the nutritive benefits of milk, offering a potential evolutionary advantage to lactase persistence, or what is commonly known as lactose tolerance.
A study led by University of Pennsylvania researchers—constituting the largest examination ever of lactase persistence in geographically diverse populations of Africans—investigated the genetic origins of this trait and offers support to the idea that the ability to digest milk was a powerful selective force in a variety of African populations which raised cattle and consumed the animals’ fresh milk.
The research was led by David and Lyn Silfen University Professor Sarah Tishkoff, who holds appointments in the department of biology and Penn Medicine’s department of genetics, and Alessia Ranciaro, a postdoctoral fellow in the department of genetics.
Their analysis revealed strong evidence of recent positive selection affecting several variants associated with lactase persistence in African populations, likely in response to the cultural development of pastoralism. The distinct geographic patterns in which these variants were present correlate in many cases with historic human migrations, mixing between populations as well as the spread of cattle, camels or sheep.
Additional co-authors on the study included Michael C. Campbell, Jibril B. Hirbo and Wen-Ya Ko of Penn’s department of genetics; Alain Froment of the Musée de l’Homme in Paris; Paolo Anagnostou of Universita’ La Sapienzà and Istituto Italiano di Antropologia in Rome; Maritha J. Kotze of the University of Stellenbosch in South Africa; Muntaser Ibrahim of the University of Khartoum; Thomas Nyambo of Muhimbili University of Health and Allied Sciences in Tanzania; and Sabah A. Omar of the Kenya Medical Research Institute.
The paper was published in the American Journal of Human Genetics.
How Social Ties Influence Awards Given
When it comes to winning Oscars and other awards to gain recognition and success in Hollywood, who you know matters just as much as who is judging, according to a University of Pennsylvania collaborative study.
“Sociological theory suggests that the process of ‘making it’ in any field depends not only on individual merit but also on the kind of audience that makes the judgments,” said co-author Paul D. Allison, professor of sociology. “Specifically, peers are more likely to favor award candidates who are highly embedded in the field, whereas critics will not show such favoritism.”
“Insiders, Outsiders and the Struggle for Consecration in Cultural Fields: A Core-Periphery Perspective,” the study by Dr. Allison and his co-researchers Gino Cattani, of New York University, and Simone Ferriani, of the University of Bologna, is published in the American Sociological Review.
Film awards generally fall into two categories: those given by peers actively engaged in making movies and those given by critics who review movies for newspapers, magazines or other media outlets.
The research showed that awards given by peers more often go to people who are heavily embedded in the “core” of the social network. These core members have many social ties to other filmmakers.
Critics, on the other hand, show no favoritism toward core members and may even prefer those on the periphery of the industry.
“These patterns persisted even after taking into account other factors that influence who gets awards,” Dr. Allison said.
The researchers used data from the Internet Movie Database and Alan Goble Film Index covering many different awards and nominations given to actors, directors, screenwriters and others between 1992 and 2004.
While the study focused on the film industry, the researchers believe their findings may be useful outside of Hollywood.