[Degenerative diabetic complications. Is persistent hyperglycemia more dangerous than wide glycemic fluctuations?...

Consistant data drawn from animal experiments and from clinical statistics have shown the diabetic specific complications (neuropathy and microangiopathy) to be closely related to the hyperglycemic component of diabetes mellitus. Working directly or through more complicated biochemical disorders, high levels of blood glucose interfer with the metabolism of the lens, the retina and the peripheral axon (leading to cataracts, retinopahy, and neuropathy). High blood sugar also alters the metabolism of endothelial and blood cells as well as the composition of plasma proteins. Wall and content of the minute vessels are both affected resulting in disturbed local blood flows and hypoxic areas. Various intertricated mechanisms have been discovered. Some of them initiate vicious circles leading to self-supported functional and later on, morphological abnormalities of diabetic microangiopathy (retinopathy, glomerulosclerosis, etc., etc.). High blood sugar exerts its influence (directly or not) in terms of duration and intensity (hours per day, days per year). There are good reasons to believe that persistent hyperglycemia uninterrupted throughout the day is much more harmful than high peaks alternating with periods of normo- and even hypoglycemia. There is no experimental nor clinical data pointing to glycemic instability as a risk factor for the minute vessels and the nerves, and opinion still often hold in some quarters. Although undesirable, frequent bouts of hypoglycemia associated with insulin treatment are indices that a rather good glycemic control has been achieved. And this can greatly delay the development of specific complications.