In vivo and in vitro antidiabetic effects of aqueous cinnamon extract and cinnamon polyphenol-enhanced food matrix

Abstract

Cinnamon has a long history of medicinal use and continues to be valued for its therapeutic potential for improving metabolic disorders such as type 2 diabetes. In this study, a phytochemically-enhanced functional food ingredient that captures water soluble polyphenols from aqueous cinnamon extract (CE) onto a protein rich matrix was developed. CE and cinnamon polyphenol-enriched defatted soy flour (CDSF) were effective in acutely lowering fasting blood glucose levels in diet induced obese hyperglycemic mice at 300 and 600 mg/kg, respectively. To determine mechanisms of action, rat hepatoma cells were treated with CE and eluates of CDSF at a range of 1-25 μg/ml. CE and eluates of CDSF demonstrated dose-dependent inhibition of hepatic glucose production with significant levels of inhibition at 25 μg/ml. Furthermore, CE decreased the gene expression of two major regulators of hepatic gluconeogenesis, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. The hypoglycemic and insulin-like effects of CE and CDSF may help to ameliorate type 2 diabetes conditions.

Copyright © 2012 Elsevier Ltd. All rights reserved.

Figures

Fig. 1

Representative UPLC-ESI-MS chromatograms and mass spectrographs of [M-H] ion masses from cinnamon extract. (a) Chromatogram of m/z 577, [M-H] ion scan and corresponding mass spectrographs of the two major peaks at A: 8.369 min and B: 9.732 min. Peak B corresponds to procyanidin B2. (b) Chromatogram of m/z 863, [M-H] ion scan and corresponding mass spectrographs of the two major peaks at A: 10.317 min and B: 10.634 min. Peak B corresponds to cinnamtannin B1.

Fig. 1

Representative UPLC-ESI-MS chromatograms and mass spectrographs of [M-H] ion masses from cinnamon extract. (a) Chromatogram of m/z 577, [M-H] ion scan and corresponding mass spectrographs of the two major peaks at A: 8.369 min and B: 9.732 min. Peak B corresponds to procyanidin B2. (b) Chromatogram of m/z 863, [M-H] ion scan and corresponding mass spectrographs of the two major peaks at A: 10.317 min and B: 10.634 min. Peak B corresponds to cinnamtannin B1.

Fig. 2

Effect of acute oral administration of cinnamon extract and cinnamon sorbed to defatted soy flour (CDSF) on fasting blood glucose. (a) Fasting blood glucose (FBG) levels of diet induced hyperglycemic mice prior to (black bars) and 6 hours after (gray bars) oral administration of water vehicle (VEH), Metformin® (300 mg/kg), or cinnamon extract (500, 300, or 100 mg/kg). (b) Diet induced hyperglycemic mice were treated with Metformin® (300 mg/kg), cinnamon extract (CE, 300 mg/kg), cinnamon-DSF (CDSF, 600 mg/kg) and DSF (600 mg/kg). Values are the means +/− SEM (n= 8–15). Significant differences were determined by paired t-tests of FBG before and after treatment *** p< 0.001, ** p<0.01, *p<0.05.

Fig. 3

Inhibition of glucose production in H4IIE rat hepatoma cells by cinnamon extract, cinnamon-defatted soy flour (cinnamon-DSF) eluate, and defatted soy flour (DSF) eluate. Cells were serum-starved overnight prior to treatment with Metformin® (2 mM), insulin (50 nM), cinnamon extract (25, 6.25, 1.56 µg/ml), cinnamon- DSF (25, 6.25, 1.56 µg/ml), or DSF eluate (25 µg/ml) for 8 h. Cellular glucose output was measured by Amplex Red® Glucose Assay, standardized to total protein content and normalized to control (vehicle). Results are the means +/− SEM of three independent experiments. Treatments were compared to control (media alone) and significant differences were determine by Dunnett’s multiple comparisons test *** p< 0.001, ** p<0.01, *p<0.05.

Fig. 4

Inhibition of (a) glucose production (b) PEPCK and (c) G6Pase gene expression in H4IIE rat hepatoma cells by cinnamon extract. Cells were serum-starved overnight prior to treatment with insulin (50 nM) or cinnamon extract (25, 10, 5 or 1 µg/ml) for 8 h. Cellular glucose output was measured by Amplex Red® Glucose Assay and standardized to total protein content and normalized to control. Results are the means +/− SEM of three independent experiments. Expression of PEPCK and G6Pase were stimulated with Dex-cAMP treatment in all wells, except control (white). Dex-cAMP stimulated cells were treated with insulin (10 nM) or cinnamon extract (25, 10, 5 or 1 µg/ml) for 8 h. The levels of gene expression were measured by qRT-PCR and presented as the fold change ratio of gene expression normalized to Dex-cAMP control using the comparative ΔΔCt method. Results are the means +/− SEM of four independent experiments. Treatments were compared to Dex-cAMP control and significant differences were determine by Dunnett’s multiple comparisons test *** p< 0.001, ** p<0.01, *p<0.05.

Fig. 5

Effect of cinnamon extract on H4IIE cell viability. Cells were treated identically to glucose production assay or gluconeogenic gene expression assay followed by 3 h of incubation with MTT reagent. A representative figure is presented showing no differences in cell viability under Dex-cAMP stimulated conditions.