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    May 2015 Monthly Quiz

    Last month's question:

    In a study healthy volunteers are given 50 mls of 50% dextrose solution by one of two routes. Route A is intravenous and route B is via a nasogastric tube. Every 15 minutes the plasma insulin level and glucose are measured and plotted on a graph. Which of the following statements would best describe the likely results comparing route A to route B in this experiment?

    Answer: Insulin higher, glucose lower in route B


    Glucose given via the gut elicits a greater insulin response as compared to the same quantity given intravenously even though the plasma glucose peak is higher when it is given IV. This phenomenon is called the 'incretin effect'.

    The incretin effect denominates the phenomenon that oral glucose elicits a higher insulin response than does intravenous glucose.

    The two hormones responsible for the incretin effect, glucose-dependent insulinotropic hormone (GIP) and glucagon-like peptide-1 (GLP-1), are secreted after oral glucose loads and augment insulin secretion in response to hyperglycaemia.

    The investigation of the incretin effect is not usually performed using the same quantity of glucose as in this question. An 'isoglycaemic study' is often used where an infusion of glucose is designed to copy exactly the blood glucose profile generated in an individual or animal by a certain enteral glucose load.

    Exenatide (synthetic exendin-4) is a new agent for the treatment of type 2 diabetes. Exendin-4 occurs naturally in the saliva venom of the North American lizard called the Gila Monster. It mimics the action of the gut hormone GLP-1 (Glucagon-like peptide 1).


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