What is prediabetes?
Prediabetes is defined as the state where a patient does not have all of the symptoms required to label them as diabetic, but their blood sugar is abnormally high. There are three ways to diagnose prediabetes: if the patient has impaired fasting glucose values (IFG), i.e., fasting plasma glucose (PG) levels of 100–125 mg/dL (5.6–6.9 mmol/L); if the patient has impaired glucose tolerance (IGT), i.e., PG values 2 hours after an OGTT with 75 g glucose of 140–199 mg/dL (7.8–11.0 mmol/L); or an A1C threshold greater than or equal to 6.5% (as recently defined by an international expert committee). Subjects with IGT or IFG have an increased risk of developing type 2 diabetes, so they are an important target group for interventions aimed at preventing diabetes.
What is metabolic syndrome?
Metabolic syndrome is a cluster of cardiovascular risk factors with a very high prevalence. According to the International Diabetes Federation (IDF), about 25% of adults globally suffer from it. People with metabolic syndrome have a 3-fold higher risk for myocardial infarction or stroke and their mortality rate for these conditions is twice as high as that for people without metabolic syndrome. Furthermore, people with metabolic syndrome have a 5-fold greater risk of developing type 2 diabetes.
Metabolic syndrome is linked to or caused by insulin resistance, i.e., reduced insulin action. Glucose does not enter the cells as easily as usual, the glucose production of the liver in the fasting state is not suppressed as strongly as in a healthy state, and the lipid-lowering effect of insulin (in particular concerning triglycerides) is also reduced as are the other effects of insulin, e.g., the dilation of on blood vessels.
The World Health Organization (WHO) diagnostic criteria for metabolic syndrome consist of diabetes mellitus, IGT, IFG or insulin resistance, plus two of the following conditions: elevated blood pressure, hyperlipidemia (elevated triglycerides and decreased LDL-cholesterol), central obesity, or microalbuminuria, hypertension, hyperglycemia, and dyslipidemia involving elevated triglycerides. Metabolic syndrome is associated with high cardiovascular risk and increased all-cause mortality. Other definitions of metabolic syndrome have been put forward, in reports published by the IDF, the US National Cholesterol Education Program (NCEP) and the European Group for the Study of Insulin Resistance (EGIR).
Prevention of type 2 diabetes in people with prediabetes
A number of clinical trials have demonstrated that changes in lifestyle can prevent the occurrence of type 2 diabetes in a high-risk population, i.e., people with prediabetes. The Finnish Diabetes Prevention Study Group demonstrated that an intervention with individualized counseling aimed at reducing weight, total fat intake and saturated fat intake and increasing fiber intake and physical activity reduced the incidence of diabetes by 58% versus a control group that received general oral and written information about diet and exercise annually without individualized counseling. Interestingly, the difference in weight change between intervention and control was fairly modest (about 4 kg), indicating that in many patients even small changes in body weight are sufficient to prevent or delay the onset of type 2 diabetes.
In line with these findings, the Diabetes Prevention Program (DPP) demonstrated the same relative risk reduction (58%) in patients who had elevated fasting and post-OGTT plasma glucose concentrations and took on a lifestyle-modification program with the goals of at least a 7 percent weight loss and at least 150 minutes of physical activity per week versus a control group. By contrast, an intervention with 850 mg metformin twice daily was less effective, reducing the incidence of type 2 diabetes by 31%. Thus, type 2 diabetes can be best prevented with lifestyle interventions. However, in a daily clinical setting, these can prove difficult for patients to adhere to over a longer period of time.