Evaluation of the effect of A. unedo L. extracts on blood indices and microelements status in high-fat STZ-induced diabetic rats

• Autor(a) principal: Lemos, Virgínia Carvalho
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/15469
• topic: Bioquímica; Medronheiro; Fenóis; Diabetes

The strawberry tree (Arbutus unedo L.) is an endemic shrub, which grows in the Mediterranean region. In Portugal, it can be found through all the country but mostly in the south. The fruit is used to produce hams and jellies and firewater, reason why the fruit’s chemical composition is relatively well known, when compared to the leaves. Until now, there are only a few studies concerning the leaves’ chemical composition and the existing mainly focus on their phenolic content. This plant has long been used in folk medicine to treat a vast amount of illnesses like gastrointestinal disorders, gastritis, dermatologic and urological problems, kidney problems and cardiovascular diseases. However, very few studies in vivo have been performed about these medicinal properties until now. Diabetes is a pandemic disease that affects millions of people. There are only two studies about A. unedo root’s aqueous extract antidiabetic properties. This study evaluated the anti-diabetic effect of strawberry tree (Arbutus unedo L.) fruit and leaf aqueous extracts in streptozotocin (STZ) induced diabetic rats fed with a high-fat diet. Firstly the optimal parameters to obtain the fruit aqueous extract were established. After that, the leaves and fruits aqueous extracts were characterized in terms of total phenolic content (TPC). Leaf aqueous extracts presented a higher TPC concentration than the fruit aqueous extract. Male Wistar rats were injected with STZ, after a 2 week feeding with high-fat diet in order to induce non-insulin dependent type 2 diabetes. After confirmation of the rats’ diabetic state, the animals were fed with Arbutus unedo L. fruit aqueous extract or leaf aqueous extract added to the high-fat diet for 4 weeks. The extracts were given in the following doses: 1.25g /kg b.w./day for leaf extract and 0.5g /kg b.w./day for fruit extract. After the animals were sacrificed analyses were perform for blood indices, haematological indices, mineral tissular status and gene expression. Arbutus unedo L. fruit extract presented a tendency to lower blood glucose levels. More beneficial effects were seen for this extract in terms of regulating TNF-α gene expression in muscular tissue. Some effects in zinc renal homeostasis were also shown, although they were not very significant. The leaf extract, appeared to be more efficient in regulating insulin levels and improving HOMA-IR index. It also presented a tendency towards lowering blood glucose levels. Both extracts proved to efficiently improve insulin sensitivity (leaf extract in a larger extent). In this study, there were also some good preliminary results, as the groups supplemented with this extracts showed a tendency in decreasing serum creatinine and/or phosphatase concentration, improving the Red Cell Distribution Width measured with standard deviation (RDW-SD) and lymphocytes concentration. Positive antidiabetic and anti-inflammatory aspects were found for both aqueous extracts. The results obtained confirm the mid-therapeutically effects of A. unedo as the plant’s material effectively improved insulin sensitivity (HOMA-IR index) although failed to significantly modulate glucose metabolism. This study was the first in vivo trial on a type 2 diabetes animal model that evaluated the antidiabetic potential of Arbutus unedo L. fruits and leaves aqueous extracts.