Abstract

A hallmark of type 2 diabetes (T2D) is β-cell dysfunction and the eventual loss of functional β-cell mass. Therefore, mechanisms that improve or preserve β-cell function could be used to improve the quality of life of individuals with T2D. Studies have shown that monomeric, oligomeric and polymeric cocoa flavanols have different effects on obesity, insulin resistance and glucose tolerance. We hypothesized that these cocoa flavanols may have beneficial effects on β-cell function. INS-1 832/13 derived β-cells and primary rat islets cultured with a monomeric catechin-rich cocoa flavanol fraction demonstrated enhanced glucose-stimulated insulin secretion, while cells cultured with total cocoa extract, oligomeric, or polymeric procyanidin-rich fractions demonstrated no improvement. The increased glucose-stimulated insulin secretion in the presence of the monomeric catechin-rich fraction corresponded with enhanced mitochondrial respiration, suggesting improvements in β-cell fuel utilization. Mitochondrial complex III, IV and V components were upregulated after culture with the monomer-rich fraction, corresponding with increased cellular ATP production. The monomer-rich fraction improved cellular redox state and increased glutathione concentration, which corresponds with Nrf2 nuclear localization and expression of Nrf2 target genes, including NRF-1 and GABPA, essential genes for increasing mitochondrial function. We propose a model by which monomeric cocoa catechins improve the cellular redox state, resulting in Nrf2 nuclear migration and upregulation of genes critical for mitochondrial respiration, and, ultimately, enhanced glucose-stimulated insulin secretion and β-cell function. These results suggest a mechanism by which monomeric cocoa catechins exert their effects as an effective complementary strategy to benefit T2D patients.

Degree

MS

College and Department

Life Sciences; Nutrition, Dietetics, and Food Science

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2017-08-01

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd9516

Keywords

cocoa; β-cell; catechin; insulin secretion; mitochondrial respiration; Nrf2

Included in

Nutrition Commons

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