Oxygen, hypoxia, oxygen tension in human obesity
A new review published from current opinion clinical nutrition and metabolism. And this is worth attention.
There is a growing number of studies investigating on the role of oxygen in development of obesity. In obese mice, its been reported that there are changes in morphology of mithocondria, reduction on mitochondrial biogenesis and mass and more importantly, lower oxygen consumption of the cell. This oxygen consumtion (pergram) also seen in obese individual. Before more talk about more about oxygen, i would like to describe some term in this field.
Adipose tissue oxygen tension or PO2 is the result of balance between adipose tissue blood flow (ATBF) and metabolic rate. Decreased ATBF might affect lipid buffering capacity of adipocyte. That would lead to reduction of clearence of circulating TG and increase re-esterification of FA.
Other from ATBF, oxygen consumption should also be considered as important factor. In obese subjects, there is a reduction of mitochondrial function and in vivo oxygen consumption. Thus, decreased mitochondrial consumption could affect adipose tissue oxygen tension. The reduction of oxygen level in the cells, animal model or human measuring expression of HIF-1alpha could be an alternative. We can also directly oxygen tension at the adipose tissue as performed by Gossens et al.
Mostly data that we have today is came from animal model or in vitro study. That is why, it is very important to consider that animal model cant really mimic human for adipose tissue formation. Relatively, body fat of human is higher in mouse model compared to human. And mouse model have higher rate on body fat gain than human. In real life situation, human dont become obese just for several weeks.
Talking about real life, the real hypoxia in human is different with hypoxia induction in the plate, in vitro. As the comparison, hypoxia treatment which is mostly given to adipocyte cell line is 1%. However, the real hypoxia condition in adipose subcutaneous tissue only range between 3 until 11%.
Gosseens GH, Blaak EE. Adipose tissue oxygen tension: implications for chronic metabolic and inflammatory disease. Curr Opin Clin Nutr Metab Care, 2012, 15:539-546.