- Lipid metabolism in peripheral tissue pre/post treatment by 1./analyzing bioactive lipid composition of red-blood cell membranes, 2./measuring phospholipase A2 (cPLA2) activity in serum (the enzyme responsible for the cleavage of arachidonic acid (AA) and other precursors of bioactive lipids from glycerophospholipids (GPL) and 3./the topical niacin flush test (a clinical test of the AA-prostaglandin D2 cascade).