Figure 4. Starvation-mediated dynamics of plasma phospholipids.

(A) Spaghetti plot of phospholipids for each subject, color-coded by phospholipid class. SM, sphingomyelin; PC, phosphatidylcholines; PE, phosphatidylethanolamines; PS, phosphatidylserines; LPC, lysophosphatidylcholines; LPE, lysophosphatidylethanolamines. (B) Mean phosphatidylethanolamine and phosphatidylcholine values relative to baseline (dashed line). (C) Mean lysophosphatidylethanolamine and lysophosphatidylcholine values relative to baseline (dashed line). Lysophosphatidylethanolamines/lysophosphatidylcholines are catabolic products resulting from fatty acid release from phosphatidylethanolamine and phosphatidylcholine, respectively (shown in B). (D) Mean ceramide levels relative to baseline (dashed line), which, together with PC and PE, serve as substrate for sphingomyelin synthesis. (E) Mean diacylglycerol (DAG) levels relative to baseline. Diacylglycerol is a byproduct of sphingomyelin synthesis. (F) Mean sphingomyelin levels relative to baseline (dashed line). (G) Mean phosphatidylcholine and phosphatidylethanolamine plasmalogen values relative to baseline (dashed line). (B–G) Blue dots signify negative levels relative to baseline; red dots signify positive levels relative to baseline. Dots become progressively darker as a function of fasting duration. Phospholipids listed on the x axis are ordered with an increasing number of double bonds from left to right. *P < 0.05, comparing day 10 value to baseline (false discovery rate adjustment for multiple comparisons).