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Mark Huising Part 1, The Difference Delta Cells Make in Glucose Control

In part 1 of this Exclusive Interview, Dr. Mark Huising talks with Diabetes in Control Publisher Steve Freed during the ADA meeting in San Diego, California about the function of delta cells and what precipitated his work in this field.

Dr. Mark O. Huising, PhD, is an assistant professor at UC Davis in California. His work has been focused on the evolution of immune and endocrine systems in early vertebrates.

Transcript of this video segment:

Steve Freed: This is Steve Freed with Diabetes in Control and we’re here at the American Diabetes Association 77 scientific session 2017. We are here to present you some really exciting interviews with some of the top endos from all across the world. We have a special guest with us and I’m going to let you tell us a little bit about yourself and what you do.

Mark Huising: Okay so my name is Mark Huising. I am a basic scientist. I work at the University of California at Davis and I study physiology of pancreatic islets.

Steve Freed: You presented a symposium here and the title is “Neglected Delta Cell:The Difference Delta Cells Make in Glucose Control.” I consider myself fairly knowledgeable about diabetes but between the alpha and the beta cell, and know we are getting to the delta and maybe the gamma…what is the delta cell?

Mark Huising: So the delta cell is really nothing new and all of us and probably some of the folks watching also will know delta cells and they know that they are endocrine cells that sit in islets and around 1 to 10 percent of the islet cells are delta cells and they make somatostatin and that’s where we’ve stopped knowing and learning about them. Somatostatin was discovered actually right here in the San Diego area in my former lab back in the 70’s and back in those times when it was established that somatostatin is a really powerful way to inhibit insulin secretion from beta cells and glucagon secretion from alpha cells. But we haven’t really followed up and tried to understand how this works in a normal healthy person and potentially how the control afforded by delta cells breaks down in diabetes. In the last couple of years, we’ve really started to make inroads, to be able to understand those aspects of delta cells that we’ve not known before.

Steve Freed: So maybe you can describe some of your research interests. I know that when it comes to diabetes, most people involved are very passionate about what they do and a lot of people have diabetes.

Mark Huising: Right.

Steve Freed: Let me ask you, do you have type 1 diabetes?

Mark Huising: I have no personal connection with diabetes.

Steve Freed: Then what generated your interest?

Mark Huising: So, the way I started in this field is I was at the lab that discovered many of the peptide hormones that I work with. The lab was headed by Wiley Vail and he discovered, as I said, somatostatin but he also discovered a peptide that’s called urocortin 3 that is becoming better and better studied for reasons that we will talk about. Urocortin 3 is a wonderful way to mark mature beta cells. Basically, if a beta cell makes and expresses urocortin 3, it’s a real beta cell and we know this now. When we started this, we didn’t know this though. We discovered this peptide urocortin 3, not knowing anything about it, and it turned out that one of the main sites that expresses urocortin 3 is the beta cell, and the pancreas and the question became “well if the beta cell makes large amounts of this urocortin peptide, what is it doing?” and that’s what I’ve been studying ever since.

Steve Freed: So obviously you presented here. What were the most important points of your presentation that you wanted people to take away?

Mark Huising: The most important points are that delta cells are there for a reason. They participate in the accurate control of insulin secretion from beta cells and glucagon secretion from alpha cells. If you do not have delta cells and the direct feedback they provide, minute to minute, second to second, beta cells and alpha cells don’t know when to stop secreting. Like everything in biology, what comes up has to come down, and the feedback by delta cells helps beta cells come back down after they have secreted insulin, after insulin has told the body to store glucose away and keeping insulin secretion high will be detrimental, so it needs to be shut down and delta cells are important to help beta cells timely attenuate insulin secretion.

Steve Freed: What percentage of the beta cells are delta cells?

Mark Huising: So, in mice it’s about 60 to 70%, in humans 50 to 60% of the endocrine cells are beta cells and depending on the islet, between 1 and 10% of the endocrine cells are delta cells. Now the big difference here is that beta cells have to release enough insulin to serve almost every other cell in the body, so they need to release a lot of insulin for the insulin to reach basically all the other tissues in the body. Delta cells have only to supply enough somatostatin to target the beta cells in the same islet. So there is a reason why there are not as many delta cells. Their audience, if you will, is more limited to the cells in their immediate surrounding.

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