Figure 7 illustrates the physiology measures of plasma glucose, insulin sensitivity and secretion, and secretion and activity levels of the incretins glucose-dependent insulinotropic hormone (GIP) and glucagon-like peptide (GLP-1) in the 12 years prior to diagnosis of diabetes and in the 20 years following diagnosis.[5]
Typically during the 4 to 12 years prior to a diagnosis of diabetes there are many physiologic changes occurring in the future patient. The top panel shows that for the 12 years prior to diagnosis the postprandial glucose levels are starting to rise while the fasting glucose levels are relatively normal, but in the few years before the disease is finally diagnosed the post-prandial glucose levels have almost double the fasting levels.
The middle panel shows that insulin secretion is slightly elevated before the diabetes is diagnosed, but then in the year following diagnoses secretion of insulin from the pancreas falls by at least 50%. Insulin sensitivity, on the other hand, is slightly lower than normal prior to diagnosis, and this trend continues after the diabetes is diagnosed. In other words, the patients may still be producing insulin, but their bodies are not using it efficiently at the cellular level.
Finally the bottom panel shows that secretion of incretins (GIP and GLP-1) is relatively normal until the diabetes is evident enough to be diagnosed, but once the disease reaches that stage the secretion of these enzymes begins declining significantly before leveling off after about 8 years. Harms D. J Nurse Pract. 2014; 00:00 – 00.