More on Glucose and Diabetes, September 23, 2015

Joseph Dixon ♦ September 23, 2015 ♦ Leave a comment

Last time I gave more information on glucose transporters in order to answer two questions that were asked in class.  There was another question that was asked by a student that I couldn’t think of the answer right away.  The question was, “Why does the intestinal brush border glucose transporter requires sodium as a co-transporter?”  This is a why question, and I’ll do my best to answer it.  We already know that the sodium gradient provides energy for the transport of glucose into the enterocyte. There is very little sodium in the cytoplasm of the enterocyte, and so the flow of sodium ions into the enterocyte flows from a high concentration in the lumen to a very low concentration inside the enterocyte.  But why is glucose transport linked to sodium transport in the small intestine and no where else in the body?

Answer:  This answer requires imagination. We will never be able to go back in time and observe if the following is exactly the reason. When all cells were unicellular organisms, they most likely existed in the ocean, which is high in sea salt (sodium chloride). Therefore, when glucose transporters were first developing, they used the high salt in seawater to flow down a concentration gradient from high to low sodium. Then these first unicellular cells linked up together to become an early intestine, and it turned out that using the sodium gradient for energy was still a good strategy.  But then when multi-tissue organisms began to develop, it was no longer feasible to use the sodium gradient for efficient energy, so glucose transporters lost this part of this mechanism and developed other strategies to bring glucose into cells.  All of this changing was done under the mechanism of natural selection.

Another question asked by a student in class related to how long a Type I diabetic patient could live without insulin injections. In class I said a month, but the answer depends upon how many residual Beta cells are still working in the pancreas of the patient.  I was thinking of the Type 1 diabetic who had recently lost most of their beta cells and was getting to the point where they make very little insulin. If this condition is allowed to proceed they will in fact die with the time being based upon how long the last Beta cells hold out.  But if the patient is already in End Stage Type 1 Diabetes and has absolutely no insulin produced, they will have complications on a much quicker time frame and require insulin injections every day or else they will feel very ill and will die quickly.  

A comparison of Type 1 Diabetes and Type 2 Diabetes is shown below: