A Picrocrocin-Enriched Fraction from a Saffron Extract Affects Lipid Homeostasis in HepG2 Cells through a Non-Statin-like Mode

Abstract

Dyslipidemia is a lipid metabolism disorder associated with the loss of the physiological homeostasis that ensures safe levels of lipids in the organism. This metabolic disorder can trigger pathological conditions such as atherosclerosis and cardiovascular diseases. In this regard, statins currently represent the main pharmacological therapy, but their contraindications and side effects limit their use. This is stimulating the search for new therapeutic strategies. In this work, we investigated in HepG2 cells the hypolipidemic potential of a picrocrocin-enriched fraction, analyzed by high-resolution ¹H NMR and obtained from a saffron extract, the stigmas of Crocus sativus L., a precious spice that has already displayed interesting biological properties. Spectrophotometric assays, as well as expression level of the main enzymes involved in lipid metabolism, have highlighted the interesting hypolipidemic effects of this natural compound; they seem to be exerted through a non-statin-like mechanism. Overall, this work provides new insights into the metabolic effects of picrocrocin, thus confirming the biological potential of saffron and paving the way for in vivo studies that could validate this spice or its phytocomplexes as useful adjuvants in balancing blood lipid homeostasis.

Keywords: HepG2 cells; hypolipidemic activity; lipid metabolism; low-density lipoprotein receptor (LDLR); picrocrocin; saffron extract.

Figure 1

High-resolution ¹H NMR spectrum of PEF.

Figure 2

Picrocrocin inhibits the activity of the purified HMGR catalytic subunit. Results are expressed as percentage of enzymatic activity versus control (enzymatic assay without inhibitors); pravastatin was used as a positive control. Values represent mean ± SD of three independent experiments. * p value < 0.05; ** p value < 0.01; ns: non-significant.

Figure 3

Effects of picrocrocin in HepG2 cells. (A) Cell viability assessment of HepG2 cells after treatment for 72 h, with increasing concentrations (1 to 300 µg/mL) of PEF from saffron extract. (B) qPCR analysis of SREBP1 and SREBP2 transcription levels after treatment for 24 h. The relative expression of human SREBP1 and SREBP2 were determined by Sybr green qPCR. The ∆Ct of human PPIA was used as an internal calibrator. These results highlight PEF’s ability to increase mRNA levels of SREBP1 and SREBP2 in HepG2 cells without affecting cell viability. Values represent mean ± SD of three independent experiments. ** p value < 0.01; **** p value < 0.0001; ns: non-significant.

Figure 4

Effects of picrocrocin on the transcription of genes related to lipid metabolism. (A) qPCR analysis of the mRNA levels for the main proteins involved in lipid homeostasis after treatment of HepG2 for 24 and 48 h with PEF from our saffron extract (300 µg/mL). (B) qPCR analysis of mRNA levels after treatment of HepG2 cells for 24 and 48 h with pravastatin (5 µM). These results highlight PEF’s ability to modulate the mRNA levels of proteins involved in lipogenesis with a method different from that of pravastatin. Values represent mean ± SD of three independent experiments. * p value < 0.05; ** p value < 0.01; *** p value < 0.001; ns: non-significant.

Figure 5

Effects of picrocrocin on protein expression of enzymes related to lipid metabolism. (A) Immunoblot analysis of the main proteins involved in lipid homeostasis after treatment of HepG2 cells for 24 and 48 h with PEF from our saffron extract. (B) Quantification of protein expression levels by densitometry. Values represent mean ± SD of three independent experiments. * p value < 0.05; *** p value < 0.001; **** p value < 0.0001; ns: non-significant; nd: not detectable.