Telomeres are likely to impact on your life (indeed, most likely are already doing so), so for those who aren't familiar with them, telomeres are repeated segments of nucleotides found at the ends of chromosomes, and are described by Carol Greider, a professor here at Johns Hopkins and Nobel prize winner for her work on telomerase, the enzyme that helps form them, in this way: they're like the plastic ends of shoelaces, designed to protect the shoelace itself from unraveling. In the case of telomeres the assumption is they protect the actual chromosomal DNA during the process of replication, and as a cell replicates over its lifetime they get shorter and shorter. Turns out that how long these ends are is important in an increasing range of diseases, and in this week's PodMed, Rick and I discuss the impact of telomere length on susceptibility to an experimental model of the common cold, as published in JAMA.
Before describing the study, first of all let me say how much I admire these hearty souls who volunteer for such studies! While I have stepped forward for a range of studies here at Hopkins, I'm not sure what would induce me to voluntarily expose myself to a cold virus or other infectious disease. So to those 152 study subjects, thank you. All of the subjects lived in the Pittsburgh area and were 18 to 55 years of age, were in good health and took no regular medications outside of birth control pills, and had no chronic health problems.
All subjects had blood drawn for multitude of assessments, one of which was telomere length as seen in their leukocyte or white blood cell population, as these are the cells known to be involved in fighting off many infectious agents. Subjects were quarantined and administered nasal drops containing a common cold virus, and then monitored for 5 days to determine whether infection occurred. The study found that shorter telomere length was associated with greater susceptibility to infection, and advancing age was also associated with shorter telomeres, so older age and shorter telomere length conferred the greatest risk of infection.
Rick points out in the podcast that when researchers corrected for age, it turns out that shorter telomeres were independently associated with greater infection risk. This observation fits with other studies showing that short telomeres are also associated with some types of cancer and development of chronic illness. These conditions, of course, also increase in incidence as people age so clearly the question of the independent contribution short telomeres make to illness and disease susceptibility will remain under investigation. I predict in the podcast that telomere length assessment may some day soon be part of routine clinical testing to develop a composite picture of overall health, and perhaps may be a target for intervention at some point. You heard it here first, folks.
Other topics this week include a comparison of robotic hysterectomy with standard laparoscopic surgery in JAMA, and a new device for the treatment of GERD and volume resuscitation with starch in NEJM. Until next week, y'all live well.
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‘Spice’ is for Cooking
March 1st, 2013|Medical News Commentary|By Elizabeth Tracey
The active ingredients in 'Spice' were originally developed to help study drug receptor biology and came on the international drug scene in 2005 in the United Kingdom as a street legal means of mind-altering. The product is compounded of one or a number of these chemicals sprayed on plant material. The products appeared in the United States in 2009, most often marketed as 'K2' and sold largely in small, independent convenience stores or on the Internet. The packaging of these synthetic cannabinoids (SCs) is labeled to indicate that human consumption and smoking the material is not advisable, but the preparations have gained popularity for a number of reasons: in contrast to marijuana they are very easy to find and obtain, are less expensive, and metabolites are not tested for in routine drug screens. Most users say they also expect a more intense 'high' than that achieved with cannabis.
This issue of MMWR reports 16 cases of acute kidney injury secondary to smoking of SC products hours to days previous to development of symptoms. All 16 patients presented to the ED with abdominal pain, and all but one with nausea and vomiting. Fifteen of the 16 patients were male, with an age range of 15 to 33 years, and all were admitted to the hospital.
Serum creatinine concentrations peaked one to six days after symptom onset. Five of the 16 patients required hemodialysis, and 4 patients received corticosteroids, however, none died. Within 3 days of creatinine peak kidney function apparently recovered in all patients, but the authors caution that a propensity to the development of chronic kidney disease may exist secondary to this episode of acute injury.
Multiple attempts by drug enforcement authorities in the United States have been made to halt the use of SCs domestically, with the latest legislation enacted in July 2012 as the 'Synthetic Drug Abuse Prevention Act 2012,' specifically banning a number of the active compounds usually found in these products. However, sale and use continues apace, with authorities speculating that both sellers and users are unaware of the hazards. As Rick points out, physicians need to be aware of the potential for kidney injury in users of SCs and to ask about whether patients are smoking them.
Other studies this week include the USPSTF recommendations on vitamin D supplementation in Annals of Internal Medicine, a look at HIV infection and liver disease in the same journal, and medications for prevention of deep vein thrombosis (DVT) in the New England Journal of Medicine. Until next week, y'all live well.