Effect of β-glucan molecular weight and viscosity on the mechanism of cholesterol lowering in humans
| dc.contributor.author | Wang, Yanan | |
| dc.contributor.examiningcommittee | Taylor, Carla (Human Nutritional Sciences) Alfa, Michelle (Medical Microbiology) Khafipour, Ehsan (Animal Science) Marquart, Leonard (University of Minnesota) | en_US |
| dc.contributor.supervisor | Ames, Nancy (Human Nutritional Sciences) Jones, Peter (Food Science) | en_US |
| dc.date.accessioned | 2016-01-13T16:26:54Z | |
| dc.date.available | 2016-01-13T16:26:54Z | |
| dc.date.issued | 2015 | |
| dc.degree.discipline | Human Nutritional Sciences | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | The cholesterol-lowering effect of mixed linkage (1→3) (1→4)-β-D-glucans (β-glucan) from barley has been documented, yet the underlying mechanism responsible for this action and factors influencing it, such as physicochemical properties of β-glucan and genetic background of an individual, remain unclear.As a component of dietary fibre, β-glucan also has the potential to shift the gut microbial community, however, whether alterations in the gut microbiota are associated with the physiological effects of β-glucan have yet to be determined. This study was designed to assess the effects of β-glucan molecular weight (MW) and dose on loweringserum cholesterol levels and to elucidate its mechanism of action in human subjects. Additionally, this study examined gene-diet interactions as well as changes in the gut microbiota profile following consumption of barley foods. In a controlled four phase crossover trial, mildly hypercholesterolemic but otherwise healthy subjects (n =30) were randomly assigned to receive breakfasts containing 3g high MW (HMW), 5g low molecular weight (LMW), 3g LMW barley β-glucan or a control diet with wheat and rice (WR control), each for 5 weeks. The washout period between the phases was 4 weeks. The consumption of 3g/d HMW diet lowered total cholesterol (TC) compared with WR control diet (P =0.0046), but not the LMW diet at either 3g/d or 5g/d. Individuals with the SNP rs3808607-G allele of CYP7A1 had greater TC reduction in response to 3g/d HMW β-glucan diet compared to the individuals carrying homozygous TT alleles (P<0.01). Cholesterol absorption and synthesis were not changed, but bile acid synthesis increased by 3g/d HMW diet compared to the control. Consuming 3g HMW/d β-glucan altered gut microbiota at the phylum and genus levels and the impacted microbial members was correlated with favorable shifts of cardiovascular disease risk factors. In conclusion, physicochemical properties of β-glucan play critical roles in the cholesterol-lowering effect and gut microbiota alteration ability of β-glucan. The results suggest the increasing bile acid synthesis rather than inhibiting cholesterol absorption and synthesis is the mechanism responsible for the cholesterol reducing property of β-glucan.The altered microbiota profile by HMW β-glucan is associated with its physiological effect. | en_US |
| dc.description.note | February 2016 | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/31048 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | β-glucan | en_US |
| dc.subject | molecular weight | en_US |
| dc.subject | viscosity | en_US |
| dc.subject | cholesterol | en_US |
| dc.subject | CYP7A1 | en_US |
| dc.subject | bile acid | en_US |
| dc.subject | mechanism | en_US |
| dc.subject | microbiota | en_US |
| dc.subject | cardiovascular disease | en_US |
| dc.subject | cholesterol absorption | en_US |
| dc.subject | cholesterol synthesis | en_US |
| dc.title | Effect of β-glucan molecular weight and viscosity on the mechanism of cholesterol lowering in humans | en_US |
| dc.type | doctoral thesis | en_US |