Abstract
The effects of substances extracted from Toona sinensis leaves, using 50% alcohol/water, on cellular [3H]‐2‐deoxyglucose uptake in differentiated cultured 3T3‐L1 adipocytes were investigated. Following treatment of cells with 0.001, 0.01, or 0.1 mg/mL extracts for 60 minutes, [3H]‐2‐deoxyglucose uptake increased from a basal value of 0.23 nmol/min/mg protein to 0.30, 0.33, and 0.38 nmol/min/mg protein, respectively. In insulin‐stimulated cells, cellular [3H]‐2‐deoxyglucose uptake was enhanced by Toona sinensis leaf extract from a basal value of 0.35 nmol/min/mg protein to 0.41, 0.46, and 0.52 nmol/min/mg protein, respectively. Cellular glucose uptake was also enhanced by Toona sinensis leaf extract after incubation of cells with 20 mM glucose for 48 hours. Cellular glucose uptake with a combination of Toona sinensis leaf extract and insulin was significantly inhibited by pretreatment of cells with the protein synthesis inhibitor cycloheximide and the protein kinase C inhibitor calphostin C in normal‐, medium‐ and high‐glucose media. However, the glucose uptake‐enhancing effect of Toona sinensis leaf extract was not diminished by cycloheximide and calphostin C in the absence of insulin. These results indicate that enhancement of cellular glucose uptake by Toona sinensis leaf extract in basal and insulin‐stimulated 3T3‐L1 adipocytes may be mediated by distinct mechanisms.
Keywords: 2‐deoxyglucose uptake, 3T3‐L1 adipocytes, Toona sinensis leaf
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