Polysaccharide IV from Lycium barbarum L. Improves Lipid Profiles of Gestational Diabetes Mellitus of Pregnancy by Upregulating ABCA1 and Downregulating Sterol Regulatory Element-Binding Transcription 1 via miR-33

Abstract

Lycium barbarum L. (LBL) has beneficial effects on gestational diabetes mellitus (GDM) but the related mechanism remains unclear. Polysaccharides of LBL (LBLP) are the main bioactive components of LBL. miR-33, ATP-binding cassette transporter A1 (ABCA1) and sterol regulatory element-binding transcription 1 (SREBF1) affect lipid profiles, which are associated with GDM risk. LBLP may exert protective against GDM by affecting these molecules. Four LBLP fractions: LBLP-I, LBLP-II, LBLP-III, and LBLP-IV were isolated from LBL and further purified by using DEAE-Sephadex column. The effects of purified each fraction on pancreatic beta cells were comparatively evaluated. A total of 158 GDM patients were recruited and randomly divided into LBL group (LG) and placebo group (CG). miR-33 levels, lipid profiles, insulin resistance and secretory functions were measured. The association between serum miR-33 levels and lipid profiles were evaluated by using Spearman's rank-order correlation test. After 4-week therapy, LBL reduced miR-33 level, insulin resistance and increased insulin secretion of GDM patients. LBL increased the levels of ABCA1, high-density lipoprotein cholesterol (HDL-C) and reduced miR-33, SREBF1, low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), triglyceride (TG), and malondialdehyde. Homeostatic model assessment of β-cell function and insulin resistance was lower in LG than in CG, whereas homeostatic model assessment of β-cell function and insulin secretory function was higher in LG than in CG. There was a strong positive association between miR-33 level and TG, or TC and or LDL-C, and a strong negative association between miR-33 level and HDL-C. The levels of miR-33 had negative relation with ABCA1 and positive relation with SREBF1. ABCA1 has negative relation with TG, TC, and LDL-C and positive relation with HDL-C. Inversely, SREBF1 had positive relation with TG, TC, and LDL-C and negative relation with HDL-C. The main bioactive compound LBLP-IV of LBL increased insulin secretion of beta cells and the levels of ABCA1, and reduced miR-33 levels and SREBF1 in beta cells. However, LBLP-IV could not change the levels of these molecules anymore when miR-33 was overexpressed or silenced. LBLP-IV had the similar effects with LBL on beta cells while other components had no such effects. Thus, LBLP-IV from LBL improves lipid profiles by upregulating ABCA1 and downregulating SREBF1 via miR-33.

Keywords: ATP-binding cassette transporter A1; Lycium barbarum L.; gestational diabetes mellitus; miR-33; sterol regulatory element-binding transcription.

Figure 1

Flowchart of the study population. ABCA1, ATP-binding cassette transporter A1. SREBF1, sterol regulatory element-binding transcription. The whole period was 4 weeks.

Figure 2

The polysaccharides of the extracts of Lycium barbarum L. (LBL) are purified by using a DEAE SephadexA-25 column. (A) There are four main polysaccharides [polysaccharides of LBL (LBLP) I, II, III, and IV] in the extracts of LBL (B) High-performance gel-permeation chromatography (HP-GPC) analysis of LBLP I. (C) HP-GPC analysis of LBLP II. (D) HP-GPC analysis of LBLP III. (E) HP-GPC analysis of LBLP IV.

Figure 3

Lycium barbarum L. (LBL) consumption significantly reduces miR-33 level and the level of sterol regulatory element-binding transcription 1 (SREBPF1) and increases the level of ABCA1 in gestational diabetes mellitus (GDM) patients. (A) The effects of LBL on miR-33 level. (B) The effects of LBL on relative mRNA levels of ABCA1 and SREBF1. LG-B, the GDM patients before receiving LBL treatment. CG-B, the GDM patients before receiving placebo. LG-A, the GDM patients after receiving 4-week LBL treatment. CG-A, the GDM patients after receiving 4-week placebo. (C) LBL consumption significantly reduces protein level of SREBPF1 and increases the level of ABCA1 in GDM patients. All data were presented as mean values ± SD. There were statistically significant differences if *P < 0.05 vs. a control group.

Figure 4

The analysis of spearman’s rank correlation coefficient for the relationship between serum miR-33 level and serum lipid profiles. (A) The relationship between serum miR-33 level and triglyceride (TG) concentrations. (B) The relationship between serum miR-33 level and total cholesterol (TC) concentrations. (C) The relationship between serum miR-33 level and high-density lipoprotein cholesterol (HDL-C) concentrations. (D) The relationship between serum miR-33 level and low-density lipoprotein cholesterol (LDL-C) concentrations. Spearman’s Rho is used to measure the strength of association between two variables, where the value r falls between 0.5 and 1 means a strong positive correlation and the value r falls between −1 and −0.5 means a strong negative correlation.

Figure 5

Polysaccharides of Lycium barbarum L. (LBL) activate insulin secretion in SW1990 cells. Values were represented as the means ± SD. from eight experiments. There were statistically significant differences if *P < 0.05. LBL, the extracts of LBL with four main polysaccharides (LBLP I, II, III, and IV).

Figure 6

LBLP IV reduces miR-33 level and mRNA level of SREBPF1 and increases the level of ABCA1 in human pancreatic carcinoma cell SW1990. (A) The effects of different polysaccharide on miR-33 level. (B) The effects of different polysaccharides on relative mRNA levels of ABCA1 and SREBF1. (C) The effects of scrambled miRNA on miR-33 level. (D) The effects of scrambled miRNA on relative mRNA levels of ABCA1 and SREBF1. (E) The effects of miR-33 overexpression on miR-33 level. (F) The effects of miR-33 overexpression on relative mRNA levels of ABCA1 and SREBF1. (G) The effects of miR-33 silence on miR-33 level. (H) The effects of miR-33 silence on relative mRNA levels of ABCA1 and SREBF1. All data were presented as mean values ± SD. There were statistically significant differences if *P < 0.05 and **P < 0.001 vs. a control group.

Figure 7

Polysaccharides of Lycium barbarum L. (LBLP) IV reduces protein level of sterol regulatory element-binding transcription 1 (SREBPF1) and increases the level of ABCA1 in human pancreatic carcinoma cell SW1990. (A) The effects of different polysaccharide on relative protein levels of ABCA1 and SREBF1. (B) The effects of scrambled miRNA on protein levels of ABCA1 and SREBF1. (C) The effects of miR-33 overexpression on protein levels of ABCA1 and SREBF1. (D) The effects of miR-33 silence on protein levels of ABCA1 and SREBF1. All data were presented as mean values ± SD. There were statistically significant differences if *P < 0.05 and **P < 0.001 vs. a control group.