Bergamot Polyphenolic Extract Combined with Albedo and Pulp Fibres Counteracts Changes in Gut Microbiota Associated with High-Fat Diet: Implications for Lipoprotein Size Re-Arrangement

Abstract

Evidence exists that the gut microbiota contributes to the alterations of lipid metabolism associated with high-fat diet (HFD). Moreover, the gut microbiota has been found to modulate the metabolism and absorption of dietary lipids, thereby affecting the formation of lipoproteins occurring at the intestinal level as well as systemically, though the pathophysiological implication of altered microbiota composition in HFD and its role in the development of atherosclerotic vascular disease (ATVD) remain to be better clarified. Recently, evidence has been collected indicating that supplementation with natural polyphenols and fibres accounts for an improvement of HFD-associated intestinal dysbiosis, thereby leading to improved lipidaemic profile. This study aimed to investigate the protective effect of a bergamot polyphenolic extract (BPE) containing 48% polyphenols enriched with albedo and pulp-derived micronized fibres (BMF) in the gut microbiota of HFD-induced dyslipidaemia. In particular, rats that received an HFD over a period of four consecutive weeks showed a significant increase in plasma cholesterol, triglycerides and plasma glucose compared to a normal-fat diet (NFD) group. This effect was accompanied by body weight increase and alteration of lipoprotein size and concentration, followed by high levels of MDA, a biomarker of lipid peroxidation. Treatment with a combination of BPE plus BMF (50/50%) resulted in a significant reduction in alterations of the metabolic parameters found in HFD-fed rats, an effect associated with increased size of lipoproteins. Furthermore, the effect of BPE plus BMF treatment on metabolic balance and lipoprotein size re-arrangement was associated with reduced gut-derived lipopolysaccharide (LPS) levels, an effect subsequent to improved gut microbiota as expressed by modulation of the Gram-negative bacteria Proteobacteria, as well as Firmicutes and Bacteroidetes. This study suggests that nutraceutical supplementation of HFD-fed rats with BPE and BMP or with their combination product leads to restored gut microbiota, an effect associated with lipoprotein size re-arrangement and better lipidaemic and metabolic profiles.

Keywords: atherosclerotic vascular disease; bergamot extract; gut microbiota; high-fat diet; lipid metabolism; lipoprotein assembly; polyphenols; prebiotics.

Figure 1

The effect of BPE, BMF or BPE + BMF (20 mg/Kg daily given orally over a period of 4 weeks on (A) plasma glucose (a), total cholesterol (b), LDL cholesterol (c), HDL cholesterol (d), triglycerides (e) and MDA (f) and on (B) body weight in NFD and HFD groups. Data are expressed as means ± SEs. *: p < 0.05 vs. NFD; §: p < 0.05 vs. HFD.

Figure 1

The effect of BPE, BMF or BPE + BMF (20 mg/Kg daily given orally over a period of 4 weeks on (A) plasma glucose (a), total cholesterol (b), LDL cholesterol (c), HDL cholesterol (d), triglycerides (e) and MDA (f) and on (B) body weight in NFD and HFD groups. Data are expressed as means ± SEs. *: p < 0.05 vs. NFD; §: p < 0.05 vs. HFD.

Figure 2

The effect of BPF, BMF or BPF + BMF (20 mg/Kg daily given orally over a period of 4 weeks) on lipoprotein diameter (a) and concentration (nmol/L) in NFD and HFD groups. Plasma total HDL (b); plasma total VLDL (c); plasma total LDL (d); plasma lipoprotein VLDL (large, medium and small) (e); plasma lipoprotein LDL (large, intermediate and small) (f). Data are expressed as means ± SEs. *: p < 0.05 vs. NFD; §: p < 0.05 vs. HFD.

Figure 3

The modulatory effect of BPE, BMF or BPE + BMF on the gut microbiota composition (determined by sequencing the V3–V4 region of the 16S rRNA gene using the MiSeq Illumina system) expressed as relative community abundance at the phylum level. Among the identifiable bacterial phyla with ≥1% abundance in all samples, Firmicutes was the most abundant, followed by Bacteroidota and Actinobacteroidota.

Figure 4

The effect of BPE, BMF or BPE + BMF on the relative abundances of Firmicutes, Bacteroidetes and Proteobacteria in NFD and HFD groups. Data are expressed as means ± SEs (n = 6). *: p < 0.05 vs. the NFD group; §: p < 0.05 vs. the HFD group.

Figure 5

The effect of BPF, BMF or BPF + BMF (20 mg/Kg daily given orally over a period of 4 weeks) on plasma LPS (EU/L) concentration in NFD and HFD groups. Data are expressed as means ± SE. *: p < 0.05 HFD vs. NFD; §: p < 0.05 HFD.