Prevention of type 2 diabetes in prediabetic patients by using functional olive oil enriched in oleanolic acid: The PREDIABOLE study, a randomized controlled trial.

AIM: To assess whether the regular intake of an oleanolic acid (OA)-enriched olive oil is effective in the prevention of diabetes. METHODS: In the PREDIABOLE study, prediabetic individuals (impaired fasting glucose and impaired glucose tolerance) of both sexes (176 patients, aged 30-80 years) were randomized to receive 55 mL/day of OA-enriched olive oil (equivalent dose 30 mg OA/day) [intervention group (IG)] or the same oil not enriched [control group (CG)]. The main outcome was the incidence of new-onset type 2 diabetes in both groups. RESULTS: Forty-eight new diabetes cases occurred, 31 in the CG and 17 in the IG. The multivariate-adjusted hazard ratio was 0.45 (95% CI, 0.24-0.83) for the IG compared with the CG. Intervention-related adverse effects were not reported. CONCLUSIONS: The intake of OA-enriched olive oil reduces the risk of developing diabetes in prediabetic patients. The results of the PREDIABOLE study promote the use of OA in new functional foods and drugs for the prevention of diabetes in individuals at risk of developing it.

Biochemical basis of the antidiabetic activity of oleanolic acid and related pentacyclic triterpenes.

Oleanolic acid (OA), a natural component of many plant food and medicinal herbs, is endowed with a wide range of pharmacological properties whose therapeutic potential has only partly been exploited until now. Throughout complex and multifactorial mechanisms, OA exerts beneficial effects against diabetes and metabolic syndrome. It improves insulin response, preserves functionality and survival of ß-cells, and protects against diabetes complications. OA may directly modulate enzymes connected to insulin biosynthesis, secretion, and signaling. However, its major contributions appear to be derived from the interaction with important transduction pathways, and many of its effects are consistently related to activation of the transcription factor Nrf2. Doing that, OA induces the expression of antioxidant enzymes and phase II response genes, blocks NF-κB, and represses the polyol pathway, AGEs production, and hyperlipidemia. The management of type 2 diabetes requires an integrated approach, which includes the early intervention to prevent or delay the disease progression, and the use of therapies to control glycemia and lipidemia in its late stages. In this sense, the use of functional foods or drugs containing OA is, undoubtedly, an interesting path.

Reduction of virgin olive oil bitterness by fruit cold storage.

Green mature olives (Olea europaea L. cv. 'Manzanilla', 'Picual', and 'Verdial') were stored at 5 degrees C, and the oil extracted from them showed a middle intensity level of sensory-evaluated bitterness. The storage times necessary for this reduction were different for the three varieties tested, requiring 4, 6, and 8 weeks, respectively, for 'Manzanilla', 'Picual', and 'Verdial' olives. The level of commercial quality of the extracted oil did not deteriorate as a consequence of previous fruit storage. Olives matured during refrigeration at 5 degrees C, as the increase of maturation index and the decrease of color index and fruit firmness indicated. Similarly, as the fruit storage period progressed, the total phenolic compound content of the extracted oils decreased. Although the use of green mature olives may require a more prolonged storage time, it allows for a better postharvest handling of the fruits, which are more resistant to physical damage or fungal infections than the riper ones.