We spend a lot of time on this blog discussing insulin resistance. It's important for cardiovascular health.
Illness, injury, toxic exposure, or genetics, or some combination of all four, change cells so they protect themselves from sugar by turning off receptor sites for insulin. Usually we talk about insulin resistance in the liver, or in fat cells, or in the muscles, but it turns out our arteries can become insulin resistant, too. When arteries become insulin resistant, they tend to accumulate hardened cholesterol deposits that raise blood pressure and increase the risk of heart attacks.
In type 2 diabetes, at least in the early stages, the pancreas produces more and more insulin to try to compensate for insulin resistance and keep blood sugar levels normal, and the process usually works. Eventually, however, blood sugar levels go higher and higher despite the extra insulin, and full-fledged type 2 sets in. At the end of this process, arteries tend to get "clogged" with cholesterol. But until recently scientists didn't know whether it was the extra insulin or the high blood sugars that cause artery problems.
It turns out it is high blood sugar levels, not high insulin levels. When blood sugar levels go higher and higher, the arteries also have to protect themselves from absorbing so much sugar they would "flame out" on a molecular level. They do this by shutting off the docking portals on the outside of the cell that would otherwise respond to insulin. But when the cells in the lining of the arteries stop responding to insulin, they also don't activate the protective mechanisms that keep cholesterol soft and safe. Instead cholesterol becomes hard and dangerous to cardiovascular health.
What's the significance of this recent research? There are several things diabetics need to know.
1. If you keep your blood sugar levels normal, you keep your arteries healthy.
2. If you need to use insulin to keep blood sugar levels normal, you won't be harming your cardiovascular health.
3. If you don't keep your blood sugar levels normal by diet, exercise, pills, or insulin, you will be harming your cardiovascular health.
It's not all about total cholesterol. Your cardiovascular health is also about what happens to the cholesterol. Doing whatever you have to do to keep your blood sugar levels from soaring will keep your heart and arteries safer. You have to diet, however, to do all of this without gaining weight. And if you take blood pressure medication, your doctor needs to know that beta-blockers increase insulin resistance (and cholesterol damage) to the arteries, while other blood pressure medications do not.
Kveiborg B, Hermann TS, Major-Pedersen A, Christiansen B, Rask-Madsen C, Raunsø J, Køber L, Torp-Pedersen C, Dominguez H.Metoprolol compared to carvedilol deteriorates insulin-stimulated endothelial function in patients with type 2 diabetes - a randomized study. Cardiovasc Diabetol. 2010 May 25;9:21.
Rask-Madsen C, Li Q, Freund B, Feather D, Abramov R, Wu IH, Chen K, Yamamoto-Hiraoka J, Goldenbogen J, Sotiropoulos KB, Clermont A, Geraldes P, Dall'Osso C, Wagers AJ, Huang PL, Rekhter M, Scalia R, Kahn CR, King GL. Loss of insulin signaling in vascular endothelial cells accelerates atherosclerosis in apolipoprotein E null mice. Cell Metab. 2010 May 5;11(5):379-89.