A new study conducted by a research team at MedUni Vienna’s Division of Endocrinology and Metabolism, has shown that cold ambient temperatures increase levels of Vitamin A in both mice and humans. This can help convert bad white adipose tissue into good brown adipose tissue which can then in turn stimulate heat generation and fat burning. Vitamin A is important for a variety of human processes – vision, cell growth, reproduction and the immune system.
Normally this fat transformation is accompanied by enhanced energy consumption therefore is considered a promising direction for developing novel obesity therapeutics.
In mammals and humans at least two types of fatty deposits are recognized – white and brown adipose tissue. When obesity develops, excess calories are mostly stored in white fat. In contrast to white fat, brown fat burns energy and thus generates heat. Over 90% of body fat deposits in humans are white which are mostly located at the bottom, abdomen and upper thighs. Converting white fat into brown fat might be a new therapeutic option for combating weight gain and obesity.
The research team demonstrated that moderate application of cold will increase levels of Vitamin A and its blood transporter retinol-binding protein in mice and humans. Most Vitamin A reserves are stored in the liver and exposure to cold seems to stimulate the redistribution of the vitamin towards the adipose tissue. This cold-induced increase in Vitamin A led to a conversion of white fat into brown fat or browning with a higher rate of fat burning.
When the team blocked the Vitamin A transporter in mice through genetic manipulation, both the cold mediated rise in Vitamin A and browning of the white fat were blunted. As a result, heat production and fat oxidation were disturbed so that the mice could no loner protect themselves against cold. In contrast, adding Vitamin A to white fat cells led to an expression of brown fat cell characteristics. This increased energy consumption and metabolic activity.
The team also examined humans although the study process was different. The team exposed 30 participants to cold temperatures and found increased levels of Vitamin A. They also extracted human cells from the belly fat of four of the participants. When they stimulated the cells with Vitamin A, the cells displayed browning behavior.
The results indicate that Vitamin A plays a vital role in the function of adipose tissue and also affects global energy consumption. This is not an argument for humans to begin consuming large amounts of Vitamin A supplements if they are not prescribed. It is critical that Vitamin A is transported at the right time to the right cells.
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