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STAT

An MUSC blog
Keyword: diabetes

External carotidIn an article published ahead of print on November 24, 2015 in the journal Diabetes (available at http://dx.doi.org/10.2337/db15-0930), researchers from the Medical University of South Carolina (MUSC), the American University of Beirut (AUB), and Case Western Reserve University report that a molecule called pre-kallikrein (PK) could be a target for the vascular complications associated with type 1 diabetes. PK has been formerly suggested as a marker for diabetic vascular disease of the kidneys, but the new work supports the idea that increased plasma PK levels are an independent risk factor for whole-body diabetic vascular disease, similar to the risks of high triglycerides or high blood pressure in heart disease. Ayad A. Jaffa, Ph.D., who holds a dual appointment at MUSC and AUB, led the study. Other MUSC investigators included Miran A Jaffa, Ph.D., Deirdre Luttrell, Ph.D., Richard L. Klein, Ph.D., Maria Lopes-Virella, M.D., Ph.D., and Louis M Luttrell, M.D., Ph.D.  

PK is a member of the kallikrein-kinin system, a group of molecules that frequent the walls of blood vessels. In healthy vessels, circulating PK reaches the vessel surface and activates a sequence of molecular signals that travel inward to the inner vessel layers, called the intima-media, causing momentary changes in dilation and tension. The types of blood vessel malfunction seen in patients with diabetes causes the cells of the intima-media to spread to the surface, allowing PK to contact them directly. This contact closes the circuit of an alternative pathway of chronic inflammation. Scientists who study the kallikrein-kinin system suspect that this chronic inflammation is responsible for the blood vessel thickening observed in diabetic kidney disease, retinopathy, and atherosclerosis.

Jaffa’s team wanted to know if these suspicions were relevant to patients. Specifically, are levels of PK in the blood associated with the blood vessel thickening commonly seen in people with type 1 diabetes?

They started by examining patient samples housed at MUSC and collected as part of a multi-center observational study, called the Epidemiology of Diabetes Interventions and Complications, designed to track the complications and progression of vascular disease in hundreds of people with diabetes. They focused on levels of PK in blood samples paired with ultrasounds taken to measure the thickness of the intima-media of their carotid arteries.

Relevance was found: patients with higher levels of PK in their blood do have thicker layers of intima-media in the vasculature of their carotids.

It isn’t clear if high levels of PK cause arteries to thicken or if thicker arteries release more PK. In other words, Jaffa’s group can’t say yet if PK causes vascular disease or not. Their work, though, is an important first step to developing a treatment for the vascular complications that seem unavoidable for patients with type 1 diabetes. Their next steps involve developing drug candidates to target PK in preclinical experiments. “These preclinical studies not only will give us insights into the involvement of plasma PK in vascular disease,” says Jaffa, “but will also contribute to development of novel treatment strategies for diabetic vascular disease.”

Image Caption: Arteries of the neck - right side. The external carotid artery arises from the common carotid artery - labeled Common caroti on the figure. From Gray's Anatomy 1918. Public Domain Available at http://www.bartleby.com/107/Images/large/image520.gif

photo of a box of fruits and vegetablesA recent study led by MUSC professor David P. Turner, Ph.D. finds that lifestyle habits such as diet and exercise could affect the progression of cancer and the rate of survival, but so could race. According to the study published in Cancer Research in May, our bodies have to metabolize food to obtain the sugars we need, thus leaving behind a reactive-metabolite waste product. These leftovers are referred to as advanced glycation end-products (AGE), and this study addresses the apparent correlation between AGE levels and the prevalence of age-related diseases among non-Hispanic whites and African Americans. 

High levels of AGE are associated with diabetes, cardiovascular disease, Alzheimer’s, and cancer. These levels are highest in African American men with prostate cancer—they are 1.5 times more likely to be diagnosed with this cancer and twice as likely to die from it than non-Hispanic whites. Consumption of sugar and processed food can contribute to AGE levels. Food preparation (i.e., browning) also plays a large role in these levels. They are higher in the West, where the diet commonly consists of red meat, refined grains, and high sugar and fatty foods.

 When analyzing serum from cancer patients, Turner found that AGE levels were significantly higher in patients with cancer than those without. Breast and prostate immortalized cancer cell lines grew more, migrated farther, and invaded more when treated with AGE. In conjunction with higher AGE levels, African Americans have more C-reactive protein (CRP), making them more susceptible to chronic inflammation. Chronic inflammation is one of the key factors implicated in the development of cancer, along with oxidative stress, an increased immune response, and the presence of AGE.

AGE cannot be completely eliminated, but levels of circulating AGE can be lowered. Simply changing lifestyle habits can slow down the accumulation of AGE in the body. Avoid food with high protein, sugar, and fat, as well as processed foods. Then increase your intake of natural grains, fruits, and vegetables. Change the way you prepare your food by cooking meats at a lower temperature for a longer period of time, skipping the browning step of a dish. You can also replace high-sugar, oil-based marinades with lemon juice, vinegar, and tomato juice. The last big step of lowering your AGE levels is exercise. A sedentary lifestyle only allows for more AGE to accumulate.

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