Prevention of Type 2 Diabetes: Evidence and Strategies
Xenical
Xenical is a gastrointestinal lipase inhibitor approved for use for weight reduction and maintenance. A possible diabetes prevention benefit of xenical was initially suggested by a retrospective analysis of xenical treatment effects on obese patients with IGT [68]. This finding was subsequently confirmed by a multicenter randomized placebo-controlled study, XENical in the prevention of Diabetes in Obese Subjects (XENDOS), where 3305 obese subjects, with normal glucose tolerance or IGT were randomly assigned to either xenical 120 mg 3 times a day or placebo, in addition to lifestyle changes for all participants [69]. In the group of patients with IGT (694 subjects), xenical treatment was associated with a 45% risk reduction of progression to diabetes at 4 years (18.8% versus 28.8% in placebo), whereas participants with baseline normal glucose tolerance had no significant change in incidence of diabetes. On the other hand, weight reduction at 4 years was significantly greater in all patients who received xenical (5.8 kg in intervention group vs 3 kg in control group). The beneficial effect of xenical in diabetes prevention seems to be additive to the benefit of weight loss. As in many weight reduction trials, this study was limited by the high discontinuation rate in both groups (48% in xenical group and 66% in control group), probably related to insufficient clinical response.
Fibric Acid Derivatives (Bezafibrate)
Bezafibrate, a nonselective ligand/activator for PPAR-α, was found to reduce not only triglycerides, but also FPG, fructosamine, and A1C levels significantly in T2DM patients with hyperlipidemia [70]. Different mechanisms of glucose lowering have been suggested with bezafibrate: nonselective activation of PPAR-γ, improving insulin sensitivity, and enhancing glucose disposal in adipose tissue and skeletal muscles [71]. Furthermore, bezafibrate treatment was associated with decreased incidence of diabetes in patients with IFG and in obese non-diabetic patients with normal glycemic levels [72,73]. In a posthoc analysis of the Bezafibrate Infarction Prevention study, 303 patients with IFG received either 400 mg of bezafibrate daily or placebo [73]. Over a mean follow-up of 6.2 years, development of diabetes was less prevalent (54.4% vs 42.3%, relative risk reduction of 22%) and delayed (mean 10 months) in the bezafibrate group compared to placebo. Multivariate analysis identified bezafibrate as an independent predictor of decreased risk of new diabetes development, regardless of BMI and lipid profile.
Surgery
Over the past decade, bariatric surgery has become one of the most effective interventions for inducing and sustaining weight reduction in severely obese patients, leading to a significant benefit in diabetes prevention or remission. The Swedish Obese Subject Study is a large ongoing prospective nonrandomized cohort study that between 1987 and 2001 enrolled 4047 nondiabetic obese participants who underwent gastric surgery or were matched obese control, with diabetes incidence measured at 2, 10 and 15 years [74–76]. At 15 years, analysis of the available cohort of the initial group showed that T2DM developed in 392 of 1658 control participants and in 110 of 1771 bariatric-surgery participants, corresponding to incidence rates of 28.4 and 6.8 cases per 1000 person-years, respectively (P < 0.001). The treatment effects on the incidence of T2DM were at least as strong after 2 years and 10 years of follow-up as after 15 years. This effect was most prominent among the 591 patients who had IFG at baseline, with a number needed to treat as low as 1.3. The surgery group maintained an average 20-kg weight loss at 15 years.
In another study of the effects of bariatric surgery, 150 of 152 obese participants with IGT who underwent gastric bypass achieved and maintained a normal glycemic profile at 14 years of follow-up [77]. Similarly, in a follow-up of 136 obese participants with IGT, 109 of whom underwent bariatric surgery, 1 participant in the surgical group developed diabetes, as compared with 6 out of 27 in the control group [78]. In a meta-analysis including studies involving 22,094 patients who underwent bariatric surgery, 76.8% had complete resolution of their diabetes [79]. The rapid improvement of glycemic profile after bariatric surgery is thought to be due to oral intake restriction as well as acute hormonal changes related to the exclusion of the upper gastrointestinal tract (eg, incretin and ghrelin levels variations) [80].
Conclusions and Recommendations
The natural history of T2DM allows identification of patients at risk for diabetes and implementation of prevention strategies, which seems to be a public health need given the alarming increase in diabetes incidence. Indeed, the onset of T2DM is typically preceded by many years of beta cell dysfunction translating into carbohydrate metabolism abnormalities such as IFG and IGT, providing an excellent window of opportunity to identify persons at risk and prevent progression to diabetes. Numerous randomized controlled trials established lifestyle modifications, including dietary changes, moderate weight loss, and moderate intensity physical activity, as safe and effective interventions to prevent diabetes. This protective effect has been consistently shown to be sustained for more than 10 years after the initial intervention. Pharmacologic agents such as metformin, thiazolidinediones, alpha-glucosidase inhibitors, xenical, liraglutide, and insulin have also been associated with diabetes prevention in patients at risk. However, except for metformin, safety concerns or lack of durable efficacy or tolerability seem to outweigh their potential diabetes prevention benefit.
Given their favorable glycemic effect, RAS blockade and fibrates should be considered, when indicated, as reasonable treatment options for hypertension and hyperlipidemia in prediabetic patients. Bariatric surgery has been associated with a dramatic reduction in diabetes incidence in obese prediabetic patients and can be considered an alternative prevention measure in patients with severe obesity and prediabetes.
The recently updated ADA guidelines recommend referring patients with prediabetes to an intensive diet and physical activity behavioral counseling program; diet and activity goals should adhere to the tenets of the DPP, with a loss of 7% of body weight and at least 150 minutes of moderate physical activity (eg, brisk walking) per week [8]. Metformin therapy for diabetes prevention should be considered in patients with prediabetes, especially in those with BMI greater than 35 kg/m2, those younger than 60 years of age, women with history of gestational diabetes, and/or those with rapidly rising A1C despite lifestyle modifications. Monitoring for development of diabetes, at least annually, and screening for and treatment of modifiable cardiovascular risk factors are suggested in patients with prediabetes [8].
Many lessons have been learned through the studies of diabetes prevention interventions. The challenge that remains is how to apply these interventions, especially the lifestyle modifications, in real world medical practice, at both the individual and public health level.
Corresponding author: Jocelyne Karam, MD, 4802 10th Avenue, Brooklyn, NY 11219, jkaram@maimonidesmed.org.
Financial disclosures: None reported.
