Convolvulus pluricaulis Choisy's Extraction, Chemical Characterization and Evaluation of the Potential Effects on Glycaemic Balance in a 3T3-L1 Adipocyte Cell Model

Abstract

Convolvulus pluricaulis (CP) is a common Indian herb, largely employed in Ayurvedic medicine and known for its neuroprotective and neuroinflammatory action. Its effectiveness against several pathologic/sub-pathologic conditions is widely accepted, but it is not yet completely chemically characterized. In recent years, several researchers have pointed out the involvement of CP and other Convolvulaceae in lipidic and glucidic metabolism, particularly in the control of hyperlipidaemia and diabetic conditions. In this scenario, the aim of the study was to chemically characterize the medium polarity part of the CP whole plant and its fractions and to shed light on their biological activity in adipocyte differentiation using the 3T3-L1 cell model. Our results demonstrated that the CP extract and fractions could upregulate the adipocyte differentiation through the modulation of the nuclear receptor PPARγ (Peroxisome Proliferator-Activated Receptor γ), broadly recognized as a key regulator of adipocyte differentiation, and the glucose transporter GLUT-4, which is fundamental for cellular glucose uptake and for metabolism control. CP also showed the ability to exert an anti-inflammatory effect, downregulating cytokines such as Rantes, MCP-1, KC, eotaxin, and GM-CSF, which are deeply involved in insulin resistance and glucose intolerance. Taken together, these data suggest that CP could exert a potential beneficial effect on glycemia and could be employed as an anti-diabetic adjuvant or, in any case, a means to better control glucose homeostasis.

Keywords: 3T3-L1; Convolvulus pluricaulis Choisy; GLUT-4; PPARγ; adipocyte differentiation.

Figure 1

Chromatographic analysis of CP: (A) chromatogram of the total extract of CP; (B–E) chromatograms of fractions 1 to 4, respectively, obtained by flash chromatography.

Figure 2

Effect of CP fractions and total extract on adipocyte differentiation. PPARγ mRNA level was evaluated, after the complete differentiation time, on 3T3-L1 cell line left untreated (UNTR) or treated with fractions 1, 2, and 4 (F1, F2, F4) or with the total extract (CP_TOT) at different concentrations (µg/mL) (A–D). Data are reported as mean ± SEM of at least three independent experiments performed in duplicate. * p < 0.05, **** p < 0.0001. Representative contrast phase images (E) and Oil Red O-stained cell images (F) in the same experimental conditions were shown, respectively. Magnification 20×.

Figure 3

Effect of CP fractions and total extract on GLUT-4 mRNA level. GLUT-4 mRNA level was evaluated by RT-PCR on the 3T3-L1 cell line at the end of the adipocyte differentiation time and after the contemporary treatment with the indicated concentration (µg/mL) of fractions 1 (F1, in (A)), 2 (F2, in (B)), and 4 (F4 in (C)) or of the total extract (CP_TOT, in (D)). Untreated cells (UNTR) did not receive any treatment. Results are reported as mean ± SEM of at least three independent experiments performed in duplicate. * p < 0.05, ** p < 0.01.

Figure 4

Effect of CP fractions and total extract on inflammatory cytokine release. Extracellular inflammatory cytokine release was evaluated in the culture medium at the end of adipocyte differentiation on 3T3-L1 cells left untreated (UNTR) or treated with the indicated concentration (µg/mL) of fractions 1, 2, or 4 (F1, F2, F4) or of the total extract (CP_TOT). The following cytokines’ modulation are shown: MCP-1 (A), KC (B), Rantes (C), IL5 (D), eotaxin (E) and GM-CSF (F). Results are expressed as mean ± SEM of at least two independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001.