Wednesday, April 15, 2009

All is infectious

One of my professors in medical school a few years back told me that, in the end, almost every disease will be proven to have some infectious trigger or component. We scoffed, being the know-it-all med students that we were, but the data is accumulating on his side.

The theories on coronary disease and chlamydia. Crohn's disease and mycobacteria. All of the cancer-causing viruses out there. No damning evidence yet for ALL diseases, but definitely something to consider in our microbe-laden world. Add diabetes to that list.

The first study I saw on this front was in JAMA last year, which looked at an interesting subtype of diabetes, mostly present in sub-saharan Africa. These patients would be especially prone to episodes of ketosis and severe hyperglycemia, with intervening periods where they wouldn't require insulin and have normal sugars. They found a fairly impressive rate of human herpes virus 8 infection at disease onset, compared with non-diabetic controls and controls with typical diabetes. It hasn't been replicated in other populations yet, but work on this is pending.

Adding to this are two studies discussed in an editorial in JAMA this week. The first found, from pancreas samples obtained at autopsy, much higher rates of enterovirus infection in the pancreases of type 1 diabetics compared with non-diabetics. The pancreatic protein expression profile was also consistent with a chronic viral infection. Further, the second study looked at rates of diabetes in a large sample of people, with those who have a variant in the gene IFIH1, a well-known enzyme that's involved, among other things, in our response to picornaviruses, of which enterovirus is one. Those who had a rare variant in this gene had a lower rate of type 1 diabetes.

Obviously, all of this holds tremendous implications, possibly further indicting a maladaptive immune response to a viral trigger as being a potential etiology for diabetes. We don't currently have any antivirals for the viruses implicated, so we can't fend off diabetes that way. Also, this is all for type I diabetes, what is now well-recognized to be a very different disease than type 2 diabetes, for which I have yet to see documented evidence of a known infectious trigger.

All this to say that it is an exciting time to be researching infectious diseases, since they seem to be the common pathway for so many different illnesses. The lesson: Wash your hands.


References:
Eugène Sobngwi, MD, PhD; Siméon Pierre Choukem, MD; Felix Agbalika, MD, MSc; Bertrand Blondeau, PhD; Lila-Sabrina Fetita, MD; Céleste Lebbe, MD, PhD; Doudou Thiam, MD; Pierre Cattan, MD, PhD; Jérôme Larghero, MD, PhD; Fabienne Foufelle, PhD; Pascal F (2008). Ketosis-Prone Type 2 Diabetes Mellitus and Human Herpesvirus 8 Infection in Sub-Saharan Africans JAMA, 299 (23), 2770-2776

Richardson, S., Willcox, A., Bone, A., Foulis, A., & Morgan, N. (2009). The prevalence of enteroviral capsid protein vp1 immunostaining in pancreatic islets in human type 1 diabetes Diabetologia DOI: 10.1007/s00125-009-1276-0

Nejentsev, S., Walker, N., Riches, D., Egholm, M., & Todd, J. (2009). Rare Variants of IFIH1, a Gene Implicated in Antiviral Responses, Protect Against Type 1 Diabetes Science DOI: 10.1126/science.1167728

2 comments:

  1. Well, people are certainly trying!
    At least in the field of cancer (my own), the progress seems to have slowed down significantly, though. It is likely that all major oncogenic viruses in humans have been discovered by now.

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  2. Nice Article....

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