Thesis defence in the University of Oulu

Doctoral Candidate

Master of Pharmacy Ghulam Shere Raza

Faculty and research unit

University of Oulu Graduate School, Faculty of Medicine, Research Unit of Biomedicine
+358294485280

Field of study

Physiology

Date and time of the thesis defence

23.8.2019 12:00

Place of the thesis defence

Auditorium F202 Faculty of medicine

Topic of the dissertation

The role of dietary fibers in metabolic diseases

Opponent

Professor Riitta Korpela, University of Helsinki

Custos

Professor Karl-Heinz Herzig, University of Oulu

The role of dietary fibers in metabolic diseases

Obesity and dyslipidemia are major risk factors for type 2 diabetes, cardiovascular diseases, cancer, and musculoskeletal disorders. In prevention, the major goal is to limit calorie consumption and to reduce low-density lipoprotein cholesterol (LDL-C) and triglyceride. Dietary fiber intake is inversely related to body weight gain, insulin resistance, dyslipidemia, and cardiovascular diseases. This thesis investigated the effects of the dietary fibers polydextrose and lignin-rich insoluble residue from brewer’s spent grain on lipid metabolism and obesity in diet-induced obese mice. Polydextrose was also studied on food intake and appetite-related parameters in healthy and overweight females.

Polydextrose is a well-known dietary fiber supplement used in several countries in various foods and beverages. We found that polydextrose reduced fasting plasma cholesterol and triglyceride and inhibited food intake in Western diet fed mice. These changes in the plasma lipids are due to the increase in beneficial gut microbiota. We suggest that reduction in plasma lipids with polydextrose is exerted via diet-induced modification of gut microbiota and gene expression. A midmorning preload of 12.5 g PDX reduced hunger by 31.4% during satiation period and lowered plasma insulin and increase glucagon like peptide-1 (GLP-1) in healthy/overweight females.

Brewer’s spent grain is the main by-product from the brewing industry and mainly used in animal feed. The lignin-rich insoluble residue from brewer’s spent grain is abundant in lignin, β-glucan and arabinoxylan, well-known dietary fiber constituents. We found that lignin-rich insoluble residue from brewer’s spent grain was partially degraded in mice and the major metabolite in mouse urine was 4-methylcatechol. Lignin-rich insoluble residue from brewer’s spent grain, reduced plasma cholesterol, body weight and hepatic steatosis in high fat diet fed mice. The present results suggest that lignin-rich insoluble residue from brewer’s spent grain induced beneficial systemic changes via bile acid binding and gut microbiota.

Polydextrose reduced fasting plasma lipids and could be used as an adjunct to lipid-lowering drugs or as monotherapy for dyslipidemia and to lower the risk of cardiovascular diseases. The reduction in body weight gain, total cholesterol with lignin-rich insoluble residue from brewer’s spent grain may reduce the risk of obesity and cardiovascular diseases.

Dissertation

Last updated: 15.8.2019