Glucose Counterregulation, Hypoglycemia, and Intensive Insulin Therapy in Diabetes Mellitus

GLUCOSE is an optional fuel for tissues such as muscle, fat, and liver that can also use fatty acids and other substrates to satisfy their energy needs. However, glucose is an obligate fuel for the central nervous system, since under physiologic conditions, alternative substrates either are excluded by the blood–brain barrier or circulate at concentrations too low to be taken up in substantial quantities.¹ Because the brain can neither synthesize nor store more than a few minutes' supply of it, normal cerebral function requires a continuous supply of glucose from the circulation. Consequently, maintenance of the plasma glucose concentration above.