Low level of Lemon Balm (Melissa officinalis) essential oils showed hypoglycemic effects by altering the expression of glucose metabolism genes in db/db mice

Abstract

The effects of the lemon balm essential oils (LBEO) in the db/db mice were examined. Mice were divided into four groups and the LBEO was orally administered for 6 weeks: saline, control; 0.15mg/d, LBEO1; 0.05mg/d, LBEO2; 0.0125mg/d, LBEO3. The LBEO showed biphasic effects on plasma glucose levels; the low level feeding was hypoglycemic but the medium and the high levels exerted hyperglycemic effects. The LBEO3 group showed reduced fasting glucose (65%, P<0.05) and triglyceride concentrations compared with the controls. Glucose tolerance, assessed by oral glucose tolerance test, was improved in this group accordingly. However, in the LBEO1 and the LBEO2 groups, glucose tolerance was worsened according to the elevated fasting glucose levels compared with the controls (33% and 27% elevation in the LBEO1 and the LBEO2, respectively P<0.05). Plasma GOT and GPT levels were elevated in these groups as well. The hypoglycemic mechanism of low level feeding of the LBEO was further investigated with quantifying the expression of the glucose metabolism genes by real time PCR. The glucokinase and the GLUT 4 gene expressions were significantly upregulated, however, the expression of glucose‐6‐phosphase and phosphoenolpyruvate carboxykinase were downregulated in the mouse livers of the LBEO3 group. The results suggest that the LBEO may be hypoglycemic when administered at low concentration. These effects may be due to the enhanced glucose uptake and the inhibition of gluconeogenesis in the livers.