Research Digest

Imaging Device may Predict Diabetes

Researchers at the University of Michigan Kellogg Eye Center have developed a vision imaging device that provides an early warning for diabetes.¹ A non-invasive camera that is linked to computer software detects metabolic stress and tissue damage by measuring levels of flavoprotein autofluorescence (FA), which the researchers have previously shown to be an indicator of eye disease. It requires only about 5 minutes to photograph both eyes.

Victor M. Elner, M.D., Ph.D., and Howard R. Petty, M.D., who developed the device, measured the FA levels in 21 patients diagnosed with diabetes. Patients were broken down into three groups according to age: 30 to 39 years, 40 to 49 years and 50 to 59 years. Each was compared with aged-matched control groups.

Twelve individuals in the study had previously been diagnosed with diabetic retinopathy in at least one eye. These patients had significantly higher FA activity than those with diabetes who did not have any detectable eye disease. Further, Elner and Petty found that those with diabetes had significantly higher FA activity, regardless of the severity of the disease, than those who did not. This finding held for each of the three age groups studied.

"Increased FA is the earliest indicator that cell death has occurred and tissue is beginning to break down," says Petty. "FA serves as a ‘spectral-biomarker’ for metabolism gone awry and we can use the results to detect and monitor disease."

The new device could offer significant advantages over blood glucose testing. Petty claims that a test with their device could cost as little as $20, comapred to approximately $120 for blood glucose testing. It would also eliminate the need for fasting and three blood drawings that the standard oral glucose test requires.

"So much damage occurs before [diabetes] can be detected by a doctor," says Elner. "Early diagnosis will allow us to reduce organ damage and prevent many complications that accompany this disease."

The imaging device awaits federal approval. OM

Reference

1. Matthew G. Field, B.A.; Victor M. Elner, MD., Ph.D.; Donald G. Puro, M.D., Ph.D.; Jason M. Feuerman, BS; David C. Musch, PhD, MPH; Howard R. Petty, PhD , et al. Rapid, Noninvasive Detection of Diabetes-Induced Retinal Metabolic Stress. Arch Ophthalmol. 2008;12:934-938.

Polymorphism Influences IOP Response to Beta Blockers

Researchers at the Marshfield Clinic Research Foundation in Wisconsin have found that a coding single-nucleotide polymorphism is associated with an increased likelihood of a "meaningful" IOP response to topical beta blockers.

The researchers examined the medical records of 18,773 adults in the foundation's Personalized Medicine Research Project, documenting all IOP measure ments for subjects who had been prescribed a topical beta blocker. They genotyped five single-nucleotide polymorphisms in the B1-, B2- and B3-adrenergic receptor genes, and six polymorphisms in the CYP2D6 gene.

The mean age of subjects was 63.8 years; 58.1% were female. Topical beta blockers were prescribed for 343 eyes of 215 subjects. An IOP reduction of 20% or more in one or both eyes was found in 61% of subjects, with men signif icantly more likely to show an IOP decrease of 20% or more (69.3% of men vs. 54.9% of women).

The researchers report that after adjusting for gender, family history of glaucoma and use of systemic beta blockers, subjects with the CC genotype at coding single-nucleotide polymorphism rs1042714 in the ADRB2 gene were approximately twice as likely to show an IOP decrease of 20% or more. Lead investigator Catherine A. McCarty, Ph.D., MPH, says that rs1042714 was present in 32% of their study subjects who had used a beta blocker.

"Prostaglandin analogs are the most commonly prescribed IOP-lowering agent initially, and once started, patients may be on these agents for the rest of their lives," Dr. McCarty says. "If we could perform a simple genetic test to determine who would respond clinically to the much cheaper generic beta blocker, the potential cost savings over a lifetime would be huge." OM

Reference

1. McCarty CA, Burmester JK, Mukesh BN, Patchett RB, Wilke RA. Intraocular Pressure Response to Topical B-Blockers Associated With an ADRB2 Single-Nucleotide Polymorphism. Arch Ophthalmol. 2008;126:959-963.