Phospholipid Composition of Liver Homogenates and Microsomes of the Lean and Obese Hyperglycemic (OB/OB) Mouse 1

Summary The phospholipid composition of livers obtained from obese-hyperglycemic (ob/ob) male mice and from their lean mates was compared. In unfractionated liver ho-mogenates, the content (percentage of the total lipid phosphorus) of phosphatidyl-choline, phosphatidylinositol, lysophospha-tidylcholine, phosphatidic acid, phosphati-dylethanolamine, and cardiolipin was similar in obese and lean mice; the content of sphingomyelin was 38% lower (P≤0.01)in the obese liver than in the lean liver. In the microsomal fractions, the obese mouse liver contained a 20% lower content of phospha-tidylethanolamine (P ≤ 0.001) and a 46% higher content of phosphatidic acid (P≤ 0.005) than the lean mouse liver; the content of the remaining four phospholipids was similar in the two groups. The total phospholipid (micrograms per milligram of protein) concentrations in lean and obese livers were 127 and 124 for unfractionated homogenates (without statistical significance) and 422 and 373 for the microsomal fraction (P < 0.005), respectively. The possibility is discussed that the alterations in the phospholipid composition of obese liver mi-crosomes might be partly responsible for the greater amount of a latent form of the insulin-degrading enzyme, glutathione-insulin transhydrogenase, in the obese liver micro-somes.