DIAGNOSING PREDIABETES

Type 2 diabetes, formerly known as « non-insulin dependent diabetes mellitus » usually appears in middle age. It is emblematic of the Western lifestyle and of our plentiful societies: by abusing sweets and foods rich in hidden carbohydrates, we gradually disrupt our metabolism. Fortunately, before developing diabetes, one always goes through an asymptomatic phase, i.e. symptom-free, during which one doesn’t feel sick at all – indeed one isn’t, not yet… This phase called prediabetes may last between two and twenty-five years. At this stage, it is still possible to react in order to avoid becoming diabetic – and one should do so ASAP!

To determine whether you are prediabetic or to measure your prediabetes risk, physicians may use several tools.

Glycemia measurements

This is the most obvious as the first stage on the slippery slope leading to type 2 diabetes is impaired glucose tolerance. In healthy subjects, who metabolize glucose correctly, a surge in blood glucose triggers the release of insulin (a hypoglycemiant hormone) by the pancreas so as to bring the glycemia (blood glucose concentration) back to a normal level. But if these regulating mechanisms are triggered too often, they become dulled; the efficiency of insulin on the liver, the muscles, the adipocytes’ receptors and all the cells that absorb glucose from the blood diminishes: this is called impaired glucose tolerance (IGT). As a result of this loss of sensitivity, the pancreas produces larger quantities of insulin to maintain normal fasting glucose blood levels. The more insulin resistance settles in, the more the pancreas gets overworked and the more it incurs the risk, in time, of losing its capacity to compensate the tissues’ desensitization to insulin, which will sooner or later induce type 2 diabetes.

Prediabetes is defined by the presence of one of the following metabolic imbalances:

– a moderate fasting hyperglycemia (high blood sugar concentration), i.e. over 1.10 gram/liter but under 1.26 g/l (the normal fasting glycemia range being 0.7 to 1.05 g/l);

or impaired glucose tolerance (IGT), i.e. a glycemia between 1.40 and 2 g/l two hours after the oral ingestion of 75 grams of glucose;

or a glycated hemoglobin level (HbA1c) between 5.7 and 6.4%. Glycated hemoglobin measures the hemoglobin molecules altered by the fixation of glucose. It normally accounts for 4 to 5.6% of the circulating hemoglobin.

Risk scores

Physicians also use clinical risk scores that measure the risk of developing type 2 diabetes in the next decade of life, such as the Diabetes Risk Score devised by Finnish researchers[1]. This is based on the subject’s family history of diabetes, personal history of high blood pressure, exercise habits and also on clinical elements (age, weight, waist measurement), and gives a score out of 20.

The HOMA Index (Homeostasis Model Assessment)

The HOMA Index (Homeostasis Model Assessment)[2], which is based on a comparison of the glycemia and fasting insulinemia measurements, allows for an early diagnosis of the “peripheric” insulin resistance, i.e. in the liver and the muscles. It is therefore able to predict efficiently the prediabetes (and eventual type II diabetes) risk.

Measuring the tissues lipid levels

When a person develops impaired glucose tolerance (IGT), her liver is so busy dealing with sugar that it becomes unable to transform dietary fats, which therefore accumulate within it, thus promoting hepatic steatosis (fatty liver) as well as muscular steatosis (fatty deposits in muscles), which in turn promote insulin resistance.

Studies on animals have shown clearly that an increase in the lipid level in an organ or tissue increases the insulin resistance of the said organ or tissue. It does seem therefore that the fat content of our muscles is the best sign of insulin resistance, but as it is difficult to measure in humans, specialists still refer to the measure of blood glycemia and to the insulin levels to detect insulin resistance and prediabetes.

All these diagnosing tools aim to allow detecting prediabetes before it turns into type 2 diabetes and to offer patients diet and lifestyle changes in order to avoid their developing this severe metabolic disease.

[1] Lindström J., MSC, Tuomilehto J., MD, PHD. “The Diabetes Risk Score, A practical tool to predict type 2 diabetes risk”, Diabetes Care 26:725–731, 2003.

[2] Matthews Dr et al. Diabetologia. 1985 ; 28 : 412-9.

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