Effects of chronic caffeine administration on blood glucose levels and on glucose tolerance in healthy and diabetic rats.

OBJECTIVE: To analyse the effect of chronic caffeine use on risk reduction and prognosis of diabetes mellitus. METHODS: In this 60-day study, five groups of 11 healthy male Wistar rats were selected to receive one of four doses (37.5, 56.2, 75.0 or 93.0 mg/kg per day) of caffeine orally or no caffeine (control). The effect of caffeine on glycaemia and glucose tolerance was evaluated. After 15 days, each group was treated with 60 mg/kg of streptozotocine to induce diabetes mellitus, and glycaemia and glucose tolerance were assessed for a further 45 days. RESULTS: In nondiabetic rats, caffeine had no effect on blood glucose. Compared with controls, the fasting blood glucose levels declined significantly in two caffeine-treated groups (93.0 mg/kg per day and 56.2 mg/kg per day) during the first 15 days following diabetes induction. Glucose tolerance was significantly improved 120 min after glucose loading in all caffeine-treated groups. The mean ± SE half-maximal effective concentration of caffeine was 35.79 ± 2.44 mg/dl. CONCLUSIONS: Blood glucose levels decreased, and glucose tolerance improved, in diabetic rats administered increasing doses of caffeine.

Forskolin compared with beclomethasone for prevention of asthma attacks: a single-blind clinical trial.

This single-blind study compared the efficacy of oral forskolin versus inhaled beclomethasone for mild or moderately persistent adult asthma. Patients were randomly assigned to receive forskolin (one 10-mg capsule orally per day; n = 30) or beclomethasone (two 50 microg inhalations every 12 h; n = 30) for 2 months. No statistically significant improvement occurred in any lung function parameter in the forskolin-treated patients. Subjects in the beclomethasone-treated group presented a slight but statistically significant improvement in percentage forced expiratory volume in 1 s (FEV(1)), percentage forced expiratory flow in the middle (25 - 75%) expiratory phase (FEF(25 - 75%)) and percentage forced vital capacity (FVC) after 2 months of treatment, though the improvement in absolute values for FEV(1), FEF(25 - 75%), FVC and FEV(1):FVC did not reach statistical significance. There was no statistically significant difference between the forskolin and beclomethasone treatment groups for any lung function parameter at baseline or after treatment. None of the beclomethasone-treated patients had an asthma attack and one forskolin-treated patient had a mild asthma attack during the 2-month study period. More studies are needed in adult asthma patients to confirm whether forskolin may be a useful preventive treatment for mild or moderately persistent adult asthma.