Flavonols Induce Adipose Browning
Compared with white adipose tissue, brown adipose tissue BAT has more mitochondria, subcellular organelles associated with energy production, which allows it to burn calories and produce heat by activating the mitochondrial uncoupling protein 1 (Ucp-1).
The stimulation of the sympathetic nervous system (SNS) after cold exposure, exercise, and calorie restriction is well known to induce fat browning. Dietary polyphenols may also activate BAT, causing heat to be dissipated from our bodies.
The authors of this study had previously discovered that a single oral dose of FLs caused fat burning and increased skeletal muscle blood flow. Here, Ishii et al. investigated the effects of single and multiple dose administration of FLs in mouse adipose tissue and found that FLs activate fat browning via the SNS, which secretes "catecholamine" neurotransmitters such as adrenaline (AD) and noradrenaline (NA).
They fed cocoa-derived FLs to distinct groups of mice in two independent sets of experiments. One group was given a single dose of FLs over the course of 24 hours, and their urine was collected for testing. The other group received repeated doses for 14 days before being dissected for the collection of brown and white fat. All adipose samples were tested for gene and protein markers that indicate fat browning, while the urine samples were tested specifically for AD and NA levels.
Higher concentrations of AD and NA in the urine following a single dose of FL clearly demonstrated SNS activation.
The team then used the obtained adipose tissue to investigate the effects of long-term FL treatment. They were thrilled to discover that the white fat of mice who were fed FLs for 14 days eventually turned brown. Some of these cells also had notable structural changes, such as "multilocular phenotype," and appeared to be smaller than normal cells.
Since BAT dissipates heat energy, does long-term FL consumption change the amounts of heat-related proteins? To answer this question, the scientists showed that Ucp-1 levels, as well as other high temperature-linked proteins, increased in mice fed repeated doses of FLs. Browning markers, referred to as "beige markers" in this study, were also abundant in these mice.
"Although the mechanism of adipose browning is not fully understood, it is possible that repeated administration of FLs may produce browning via catecholamines and its receptors," explains Prof. Osakabe. "Further studies will be required to understand how this process is induced by FL-rich foods," she concludes.
Adipose browning will be discussed in detail in the 13th World Annual Meeting of WMS on Targeting Mitochondria will be held on October 2022 in Berlin.
Targeting Mitochondria 2022 Congress
October 26-28, 2022 - Berlin, Germany
wms-site.com
