What exactly is insulin resistance? One of insulin’s jobs is to help move glucose from the blood into the cells for energy. When blood glucose remains elevated despite normal or high levels of insulin, this is called insulin resistance. The cells are resisting insulin’s pleas to take up glucose. But why is this happening? What causes insulin resistance?
The current paradigm of understanding insulin resistance is the ‘lock and key’ model. The hormone insulin acts upon a cell surface receptor to do its job. The insulin receptor is like a lock keeping the gates to the cell closed. Insulin is like the proper key. When inserted, the gate opens to let glucose from the blood inside the cell for energy. Once you remove the key (insulin), the gate closes back up and blood glucose can no longer enter the cell.
During the phenomenon of insulin resistance, we imagine that the lock and key no longer fit together very well. The key (insulin) only partially opens the lock (receptor) and not very easily. Glucose cannot pass through the gate normally, and as a result, less gets into the cell. The blood glucose piles up outside the gate, becoming detectable as the clinical diagnosis of type 2 diabetes is made.
This past fall, Gary Taubes took his wife and two sons on a trip to a wildlife preserve in Sonoma County, California, the kind of place where guests learn firsthand about the species of the Serengeti. They slept in tents and spent the day among giraffes, zebras, antelope, and the like. One morning, Taubes and his boys awoke early. “It was 50 degrees out — freezing by our standards,” he recalls. “I took the kids to breakfast, and” — his face takes on a pained expression — “how can I not give them hot chocolate?”
For most parents, indulging the kids with some cocoa would pose no dilemma. But Taubes, one of America’s leading and most strident nutrition writers, is no ordinary father. His new book, The Case Against Sugar, seems destined to strike fear into the hearts of children everywhere. Taubes’ argument is simple: Sugar is likely poison, and it’s what is making our country fat. And not just fat but sick. So don’t eat it. Ever.
When I was a medical student at McGill in the late 1970s, we learned a straightforward explanation for the cause of Type 2 diabetes, the most common form of diabetes in adults, accounting for about 90 per cent of all diabetes cases. We were told the insulin resistance responsible for Type 2 diabetes was caused by high levels of insulin. Hyperinsulinemia–increased insulin levels in the blood–was said to “downregulate” insulin receptors, making cells with those receptors less responsive to the insulin message. From a physiology point of view, this makes perfect sense. It’s analogous to the development of tolerance that can happen with regular heroin use when a person no longer responds to the drug in the way they did initially.
Sometime in the 1980s this explanation for the cause of insulin resistance was abandoned. Instead, the medical community adopted a new theory that insulin resistance comes first, and is behind high insulin levels in Type 2 diabetes. To overcome insulin resistance, the pancreas secretes larger-than-normal amounts of insulin, resulting in so-called “reactive hyperinsulinemia.” The cause of this insulin resistance is never clearly explained, although obesity, chronic inflammation, and genes are all said to contribute.
UT Southwestern Medical Center researchers have found that intermittent fasting inhibits the development and progression of the most common type of childhood leukaemia.
This strategy was not effective, however, in another type of blood cancer that commonly strikes adults.
“This study using mouse models indicates that the effects of fasting on blood cancers are type-dependent and provides a platform for identifying new targets for leukaemia treatments,” said Dr. Chengcheng “Alec” Zhang, Associate Professor of Physiology at UT Southwestern and senior author of the study, published online today by Nature Medicine. “We also identified a mechanism responsible for the differing response to the fasting treatment,” he added.
The researchers found that fasting both inhibits the initiation and reverses the progression of two sub-types of acute lymphoblastic leukaemia, or ALL – B-cell ALL and T-cell ALL. The same method did not work with acute myeloid leukaemia (AML), the type that is more common in adults.