Effect of cucurbitaceae extracts on glucose and lipid metabolism in 3T3-L1 adipocytes

Abstract

The use of herbal remedies in the prevention of disease conditions has been the focus of many studies due to their multiple health benefits. One such condition is a state of hyperglycemia which may be altered with the use of natural products originating from herbs, fruits or vegetables. Three of the proclaimed vegetables were used in this study, a commonly consumed gourds belonging to the Cucurbitaceae family, namely: Momordica charantia (also known as Bitter gourd, Karela or Peria Katak), Trichosanthes cucumerina (known as Snake gourd or Labu Ular) and Lagenaria siceraria (known as Bottle Gourd, Opo squash or Calabash). Water and ethanol extracts from whole vegetable, peels and seeds were assessed for antioxidant activities using 2, 2-diphenyl-l-picrylhydrazyl assay (DPPH assay), total phenolic assay (TPC assay) and total flavonoid assay (TFC). The total phenolic contents were highest in the ethanol extract of Lagenaria Siceraria peels (LSPe), the water extract of Momordica charantia seeds (MCSw) and the ethanol extract of Trichosanthes cucumerina peels (TCPe) being 35.58±1.2, 33.03±1.4 and 20.70±1.26 mg GAE/g, respectively. Total flavonoid contents were highest in the seeds of all three vegetables for the ethanol extract of Lagenaria Siceraria seeds (LSSe), the water extract of Trichosanthes cucumerina seeds (TCSw) and the ethanol extract of Momordica charantia seeds (MCSe) being 0.73±0.01, 0.67±0.02 and 0.65±0.02 mg QE/g, respectively in accordance with the high total phenol content. The extracts exhibited high free radical scavenging activity with the highest inhibition for DPPH being 79.80, 73.92 and 71.97% for LSPe, TCPe and MCSw, respectively. Cell viability assay for water and ethanol extracts revealed that 3T3-L1 adipocytes maximum toleration concentration was 0.063 mg/ml. The extracts were further tested on adipocytes’ differentiation and showed a stimulation of lipid droplets formation during adipogenesis. The extracts significantly (p<0.001) increased glycerol release levels during adipolysis compared to the control and were higher in all three sources for the ethanol extracts of Trichosanthes cucumerina whole vegetable (TCWe), Lagenaria siceraria whole vegetable (LSWe) and Momordica charantia peels (MCPe), respectively. The extracts also significantly (p<0.001) promoted the uptake of glucose in the cells for the ethanol extract of Lagenaria siceraria whole vegetable (LSWe), ethanol extract of Trichosanthes cucumerina whole vegetable (TCWe) and water extract of Momordica charantia seeds (MCSw) for up to 81.31, 71,24 and 56.18%, respectively. The effect of the extracts was further tested on adiponectin and leptin concentrations in adipocytes using ELISA kit assay where it indicated a significant (p<0.01) increase in adiponectin concentrations for the water extract of Lagenaria siceraria peels (LSPw), the water extract of Momordica charantia peels (MCPw) and the water extract of Trichosanthes cucumerina seeds (TCSw) with 5405±1557, 4966±1097 and 3593±225 ng/ml, respectively and a decrease in leptin concentrations for the extracts LSPw and MCSe with 14633±612 and 17578±1536 pg/ml, respectively. The present study data showed that there is a beneficial effect of the extracts on adipogenesis, adipolysis and glucose uptake in 3T3-L1 adipocytes. Furthermore, the observed adipocytes concentrations of adiponectin and leptin could be of clinical importance in energy regulation which is a key factor in diabetes, obesity and metabolic syndrome.