Effects of Ethanolic Extracts from Azadirachta indica and Gymnema inodorum Leaves on Anti-Inflammation in Macrophage and Anti-Insulin Resistance in Adipocyte

Abstract

The leaves of Azadirachta indica (AI) and Gymnema inodorum (GI) have been reported on their anti-inflammatory and anti-diabetic potentials in animal model. However, there was no report studying the mechanism of bioactivities of AI and GI on adipocyte which directly involves in obesity and insulin resistance. Obesity induces a chronic local inflammation in adipose tissue, while macrophages also play a crucial role in adipocyte inflammation and systemic metabolic abnormalities. Subsequently, several inflammatory cytokines, especially TNF- can induce the insulin resistance in adipocyte. The purpose of this study is to determine whether AI and GI have inhibitory effect on both inflammation and insulin resistance in macrophage and adipocyte, respectively. Crude exthanolic extracts of AI and GI leaves were prepared and then analyzed for their phytochemical composition, and antioxidant activities. The results showed that total phenolic and flavonoid contents were more intensive both in the GI and AI extracts. The ethanolic extracts exhibited higher free radical scavenging effect on the DPPH assay. Next, the extract from these plant leaves were tested for their anti-inflammatory activity in RAW 264.7 macrophage and anti-insulin resistant activity in 3T3-L1 adipocyte. AI and GI exhibited the inhibitory effect against the nitric oxide production in LPS-activated macrophage in a dose-dependent manner. The extracts were not toxic to 3T3-L1 adipocyte as determined by WST-1 assay. Using a co-culture model, insulin resistance was induced in 3T3-L1 by the inflamed RAW 264.7 cells. Both AI and GI (12.5 and 25 g/ml) significantly improved the insulin response of 3T3L-1 by increasing the cellular uptake of glucose, and decreasing the lipolysis closed to the basal levels. Moreover, using RT-qPCR analysis, both AI and GI (25g/mL) reduced the expression of several pro-inflammatory cytokines (IL-1 and TNF). Finally, the results of this study likely demonstrate their anti-inflammatory and anti-insulin resistant activities for a possible use of Azadirachta indica and Gymnema inodorum leaves as an effective herbal medicine for prevention and treatment of diabetes.