ABSTRACT
Carnitine has two main functions, i.e., transporting long-chain fatty acids into the mitochondrial matrix for beta-oxidation to provide cellular energy and modulating the rise in intramitochondrial acyl-CoA/CoA ratio, which relieves the inhibition of many intramitochondrial enzymes involving glucose and amino acid catabolism. The present study examined the acid soluble carnitine (ASCAR) acid insoluble carnitine (AICAR) and total carnitine (TCAR) concentrations of 50 human brain tumor tissues and 11 normal brain tissues. The ASCAR levels significantly higher in gliomas and meningiomas than brain, however similar to brain in metastatic adenocarcinomas. AICAR levels were lower than brain in all tumors with the exception of a medullablastoma. TCAR levels were similar to brain in all tumor types. Decreased AICAR levels may be due to increased utilization of lipids or enhanced phospholipid and cholesterol synthesis which is need for increased membrane synthesis or formation of eicosanoids. Also decreased concentrations may be a reflection of camitine and its acylesters role in preserving the physiologic membrane structure function from oxidative damage.
Subject(s)
Brain Neoplasms/chemistry , Carnitine/isolation & purification , Medulloblastoma/chemistry , Meningeal Neoplasms/chemistry , Perchlorates/pharmacology , Solvents/pharmacology , Adenocarcinoma/chemistry , Adenocarcinoma/secondary , Astrocytoma/chemistry , Brain Neoplasms/secondary , Carnitine/chemistry , Carnitine/physiology , Energy Metabolism , Glioma/chemistry , Humans , Hydrogen-Ion Concentration , Lipid Metabolism , Membrane Lipids/metabolism , Meningioma/chemistry , Mitochondria/metabolism , Neoplasm Recurrence, Local , Neurilemmoma/chemistry , Oxidation-Reduction , SolubilityABSTRACT
Several studies demonstrated that certain fatty acids have specific effects on tumor cells. n-3 series fatty acids (alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid) may suppress the carcinogenesis, whereas n-6 series fatty acids (arachidonic acid, linoleic acid) may exert tumor promoting effects. In this study, 19 patients with various brain tumors and 12 control brain tissues were studied. n-3, n-6, n-9 unsaturated fatty acids and certain saturated fatty acids levels were measured in the plasma membrane of tumor or control brain tissues by capillary gas chromatography. We found that the level of docosahexaenoic acid from n-3 series fatty acids was significantly lower in gliomas and meningiomas than controls (p = 0.000). Total n-3 fatty acids level was also significantly lower in tumors than controls (p = 0.000). The levels of linoleic acid, arachidonic acid and dihomogamma linolenic acid from n-6 series were significantly higher in gliomas and meningiomas compared with controls (p = 0.000). Total n-6 fatty acids level was also significantly higher in tumors than controls (p = 0.000). Furthermore, in total n-9 fatty acids, total unsaturated fatty acids and total saturated fatty acids levels, there were no significant differences in gliomas and meningiomas compared with controls (p = 0.6840, p = 0.4388 and p = 0.4343, respectively). This findings suggest that n-6 fatty acids can act as a tumor-promoting agent in human brain tumors.
Subject(s)
Brain Chemistry , Brain Neoplasms/chemistry , Fatty Acids, Nonesterified/analysis , Fatty Acids, Unsaturated/analysis , Membrane Lipids/analysis , Brain Neoplasms/secondary , Brain Neoplasms/surgery , Cell Membrane/chemistry , Cerebellar Neoplasms/chemistry , Chromatography, Gas/methods , Humans , Medulloblastoma/chemistry , Meningeal Neoplasms/chemistry , Meningioma/chemistry , Myristic Acid/analysis , Neurilemmoma/chemistry , Palmitic Acid/analysis , Reference Values , Stearic Acids/analysisABSTRACT
Arachidonic acid is stored in the cell membrane and released when the cell is activated by appropriate stimuli. It is the substrate for prostaglandins. Both experimental and human tumors often synthesize high levels of prostaglandins, most notably prostaglandin E2 (PGE2). Some experiments suggest that these compounds increase tumor growth through their actions on host immunocytes. In this study, 22 patients with various brain tumors and 12 control brain tissues were studied. PGE2 levels in tissue samples were measured by ELISA. Arachidonic acid levels in the plasma membrane of tissue samples were analyzed by capillary gas chromatography. The levels of PGE2 were significantly higher in gliomas (n = 10) and meningiomas (n = 7) compared with control tissues (P = 0.000 and P = 0.000, respectively). Also, PGE2 levels in meningiomas were significantly higher than in gliomas (P = 0.000). Arachidonic acid levels in the plasma membrane of gliomas (n = 9) and meningiomas (n = 6) were significantly higher than in the control tissues (P = 0.000 and P = 0.000, respectively). These results suggest that the increased production of PGE2 may suppress the immune system and play an important role in tumor growth.
