Mini MCAT passage: Diabetes and hyperglycemia

Diabetes mellitus, or diabetes, is a metabolic disease that is characterized by “hyperglycemia” or elevated blood glucose levels. Diabetes is further classified into type 1 diabetes (T1D) and type 2 diabetes (T2D). There are various differences between the causes and symptoms of T1D and T2D, but the primary difference is that type 1 diabetics cannot produce insulin whereas type 2 diabetics suffer from insulin resistance.

Of note, untreated type 1 diabetics are susceptible to ketoacidosis - an increase in blood ketone levels. The ketone levels can change the pH of the blood, specifically making it more acidic. Interestingly, type 2 diabetics are not as susceptible to ketoacidosis.

The synthesis of ketone bodies (hydroxybutyrate and acetoacetate) from acetyl CoA is shown in Figure 1. Notably, acetone forms from the spontaneous decarboxylation of acetoacetate. Although acetone does not serve as a ketone fuel (because it cannot be converted back to acetyl CoA), it contributes to the “sweet and fruity” odor that patients have when ketone levels are elevated.

Adapted from upload.wikimedia.org/wikipedia/commons/thumb/d/db/Ketone_bodies_synthesis.svg/585px-Ketone_bodies_synthesis.svg.png

Figure 1 Synthesis of ketone bodies hydroxybutyrate and acetoacetate from acetyl Co-A