Difference In Fatty Acid Oxidation Research Articles

Differences in Fatty Acid Oxidation between Nab-Paclitaxel- and Solvent-Based Paclitaxel-Treated A549 Cells Based on Metabolomics.

The pharmacokinetics, safety, and anticancer efficacy profiles of nanoparticle albumin-bound (nab)-paclitaxel formulations are superior to those of solvent-based paclitaxel formulations. The aims of the present study were to study the effects of nab-paclitaxel and solvent-based paclitaxel formulations on the metabolic profiles of the model cell line (A549) and attempt to elucidate the associated metabolic pathways. A mass spectrometry-based cell metabolomics approach and viability evaluation were used to explore the potential difference. Western blotting was utilized to measure the levels of relevant proteins, and carnitine palmitoyltransferase 1 (CPT1) activities were quantified. Fold changes normalized to controls in levels of carnitine and several acylcarnitines were significantly different (p < 0.05) between A549 cells treated with nab-paclitaxel and those treated with solvent-based paclitaxel. Relative to the controls, there were also significant fold change differences in palmitic and linoleic acid levels in the cell lysates, mitochondrial CPT1 activities, and mitochondrial medium-chain acyl-CoA dehydrogenase (MCAD) protein levels in the A549 cells subjected to the nab-paclitaxel and solvent-based paclitaxel formulations. Results suggested that the two formulations differentially modulated fatty acid oxidation in the A549 cells. While cell viability results did not reveal significant differences, the findings implied that a mass spectrometry-based cell metabolomics approach could be a sensitive tool to explore the differences caused by formulation changes without using animals. Since uncertainties of products containing nanomaterials warrant holistic screening to address safety concerns, the aforementioned approach may be of regulatory importance and is worth further investigation.

SAT-137 The Effect of Hypertriglyceridemia on Triple Negative Breast Cancer Progression

Obesity is associated with increased cancer risk and cancer-associated mortality1,2. Hypertriglyceridemia (HTG), a component of the metabolic syndrome which frequently co-exists with obesity, has been associated with increased breast cancer risk and mortality in triple negative breast cancer (TNBC)3,4. To determine if HTG is causally related to enhanced TNBC progression in the absence of other obesity-associated characteristics, TNBC growth and metastasis in a mouse model of HTG was examined. Mice overexpressing human apolipoprotein C3 (AC3) were backcrossed onto FVB/N background and crossed with recombination-activating gene 1 (Rag1) knockout mice to generate immunodeficient HTG mice. AC3 mice relative to wild-type (WT) littermates showed a 20-fold higher circulating triglycerides (p < 0.0001) and elevated very low density lipoprotein (VLDL) cholesterol (p = 0.001). No differences in body weight, body composition, blood glucose or plasma insulin levels were observed between the two groups, allowing for investigation on the influence of HTG on TNBC without confounders such as hyperinsulinemia or hyperglycemia. AC3 mice orthotopically implanted with the mouse mammary tumor cell line, Mvt1, showed both increased tumor growth (AC3 vs WT: 1157.0 ± 84.2 vs 707.2 ± 58.6 mm3, p = 0.0009) and lung metastasis (AC3 vs WT: 57.3 ± 3.0 vs 32.9 ± 5.3 mm3, p = 0.001) relative to WT mice. Immunodeficient Rag1/AC3 mice likewise, showed increased tumor growth compared to WT controls when implanted with human TNBC MDA-MB-231 cells (AC3 vs WT: 363.2 ± 113.9 vs 92.95 ± 16.2 mm3, p = 0.038). To investigate how HTG affects tumor lipid metabolism, serum and tumors from both groups were analyzed by liquid chromatography/mass spectrometry. Total alkyl-acyl, di-acyl-phosphatidylcholines and sphingomyelin concentrations were higher in the serum of AC3 mice relative to WT. In contrast, no overall difference in tumor phospholipid or acylcarnitine content was noted between AC3 and WT mice, suggesting no difference in fatty acid oxidation in the setting of HTG. Mvt1 tumors from AC3 and WT mice were analyzed by RNA sequencing. Decreased expression of genes associated with cholesterol synthesis (Fdft1, Pvmk, Acss2) were found in tumors from AC3 mice. Tumors from AC3 mice also showed decreased protein expression of LDLR, which is associated with LDL cholesterol uptake. Overall, these findings suggest that HTG, independently of other obesity-associated characteristics such as hyperinsulinemia and hyperglycemia, leads to changes in intracellular lipid metabolism and promotes TNBC progression.

Metabolic Response of Visceral White Adipose Tissue of Obese Mice Exposed for 5 Days to Human Room Temperature Compared to Mouse Thermoneutrality.

Housing of laboratory mice at room temperature (22°C) might be considered a constant cold stress, which induces a thermogenic program in brown adipose tissue (BAT). However, the early adaptive response of white adipose tissue (WAT), the fat storage organ of the body, to a change from thermoneutrality to room temperature is not known. This was investigated here for various WAT depots, focusing on epididymal WAT (eWAT), widely used as reference depot. Male adult diet-induced obese (DIO) C57BL/6JOlaHsd mice housed at thermoneutrality (29°C), were for 5 days either switched to room temperature (22°C) or remained at thermoneutrality. Energy metabolism was continuously measured using indirect calorimetry. At the end of the study, serum metabolomics and WAT transcriptomics were performed. We confirmed activation of the thermogenic program in 22°C housed mice. Body weight and total fat mass were reduced. Whole body energy expenditure (EE) was increased, with a higher fatty acid to carbohydrate oxidation ratio and increased serum acylcarnitine levels, while energy intake was not significantly different between the two groups. Transcriptome analysis of eWAT identified tissue remodeling and inflammation as the most affected processes. Expression of pro-inflammatory M1 macrophage-related genes, and M1 over M2 macrophage ratio were decreased, which might be linked to an increased insulin sensitivity. Markers of thermogenesis were not altered in eWAT. Decreased expression of tryptophan hydroxylase 2 (Tph2) and cholecystokinin (Cck) might represent altered neuroendocrine signaling. eWAT itself does not show increased fatty acid oxidation. The three measured WATs, epididymal, mesenteric, and retroperitoneal, showed mainly similar responses; reduced inflammation (s100a8), decreased carbohydrate oxidation, and no or small differences in fatty acid oxidation. However, Ucp1 was only expressed and increased in rWAT in 22°C housed mice. Cck expression was decreased in the three WATs, significantly in eWAT and rWAT, in contrast to Tph2, which was decreased in eWAT while not expressed in mWAT and rWAT. Our data show that tissue remodeling, inflammation and neuroendocrine signaling are early responses in WAT to a moderate decrease in environmental temperature.

Long-Term exposure of INS-1 cells to cis and trans fatty acids influences insulin release and fatty acid oxidation differentially

The importance of elevated levels of fatty acids in the pathogenesis of the deteriorated β-cell function present in type 2 diabetes has been established. Long-term exposure of the β-cell to high levels of fatty acids causes enhanced insulin secretion at low glucose (basal insulin release), while glucose-stimulated insulin secretion (GSIS) is decreased or unchanged. We have previously demonstrated that the spatial configuration of fatty acids ( cis and trans isomers) is of importance for the acute impact on the β-cell function. In this study we aimed to elucidate whether the spatial configuration also influenced β-cell function after long-term exposure. Thus, we compared the effect of 3 days culture of INS-1 cells with cis ( cis C 18:1–11) and trans vaccenic acid ( trans C 18:1–11), as well as oleic ( cis C 18:1–9) and elaidic acid ( trans C 18:1–9), on basal and glucose-stimulated insulin release. All fatty acids tested increased basal insulin release; however, a significantly lower basal insulin release was demonstrated for cells cultured with 0.3 to 0.4 mmol/L trans vaccenic acid compared to equimolar levels of the cis isomer. GSIS was not changed by cis or trans vaccenic acid or by oleic acid, whereas it was stimulated by 0.3 to 0.4 mmol/L elaidic acid. The mechanisms behind the fatty acid-induced changes in the β cells have been linked to changes in glucose and fatty acid oxidation. We demonstrated an increased fatty acid oxidation in β cells after long-term exposure to all of the tested fatty acids. Interestingly, both trans isomers ( trans vaccenic and elaidic acid) induced higher fatty acid oxidation than the cis isomers ( cis vaccenic and oleic acid, respectively). No changes in glucose oxidation were found when INS-1 cells were cultured with either of the fatty acids. The increased fatty acid oxidation was associated with an increased content of carnitine palmitoyltransferase I (CPT-I) mRNA, but no difference in the content of CPT-I mRNA to the different fatty acids was found. Insulin mRNA expression in β cells was not affected by the fatty acids. In conclusion, we have demonstrated that the pathological changes in insulin secretion from INS-1 cells to long-term culture with elevated levels of fatty acids are more pronounced for the cis ( cis vaccenic acid and oleic acid) rather than the trans isomers ( trans vaccenic acid and elaidic acid). We suggest that this, at least in part, may be explained by a lower fatty acid oxidation in cells cultured with the cis compared to the trans fatty acid isomers. Apparently, the difference in fatty acid oxidation was not caused by an increased induction of CPT-I mRNA, nor by changes in glucose oxidation or insulin mRNA in β cells chronically exposed to the fatty acids.

Fat metabolism during high-intensity exercise in endurance-trained and untrained men

To determine whether trained individuals rely more on fat than untrained persons during high-intensity exercise, six endurance-trained men and six untrained men were studied during 30 minutes of exercise at 75% to 80% maximal oxygen consumption (VO2max). The rates of appearance (Ra) and disappearance (Rd) of glycerol and free fatty acids (FFAs) were determined using [1,1,2,3,3-2H]glycerol and [1-13C]palmitate, respectively, whereas the overall rate of fatty acid oxidation was determined using indirect calorimetry. During exercise, the whole-body rate of lipolysis (ie, glycerol Ra) was higher in the trained group (7.1 +/- 1.2 v 4.5 +/- 0.7 micromol x min(-1) x kg(-1), P < .05), as was the Ra (approximately Rd) of FFA (9.0 +/- 0.9 v 5.0 +/- 1.0 micromol x min(-1) x kg(-1), P < .001). FFA utilization was higher in trained subjects even when expressed as a percentage of total energy expenditure (10% +/- 1% v 7% +/- 1%, P < .05). However, this difference in plasma FFA flux could not account for all of the difference in fatty acid oxidation between trained and untrained subjects (20.8 +/- 3.3 v 7.9 +/- 1.6 micromol x min(-1) x kg(-1), or 23% +/- 3% v 13% +/- 2% of total energy expenditure, both P < .05). Thus, the oxidation of fatty acids derived from some other source also must have been greater in the trained men. We conclude that trained athletes use more fat than untrained individuals even during intense exercise performed at the same percentage of VO2max. The additional fatty acids appear to be derived from both adipose tissue and, presumably, intramuscular triglyceride stores.

Regulation of fatty acid oxidation in untrained vs. trained men during exercise.

We have recently shown that increased carbohydrate flux decreases fat oxidation during exercise by inhibition of fatty acid entry into the mitochondria. Because endurance training reduces the rate of carbohydrate flux during exercise, we hypothesized that training increases fat oxidation by relieving this inhibition. To test this hypothesis, five sedentary and five endurance-trained men exercised on a cycle ergometer at an oxygen consumption (VO2) of approximately 2.0 l/min, representing 80 and 40% peak VO2, respectively. [1-13C]oleate and [1-14C]octanoate, long- and medium-chain fatty acids, respectively, were infused for the duration of the studies. Carbohydrate oxidation was significantly higher in the sedentary group (196 +/- 9 vs. 102 +/- 17 mumol.kg-1.min-1, P < 0.05). Oleate oxidation was higher in the trained group (3.8 +/- 0.6 vs. 1.9 +/- 0.3 mumol.kg-1.min-1, P < 0.05), whereas octanoate oxidation was not different between the two groups. The percentage of oleate that was taken up by tissues and oxidized was higher in the trained group (76 +/- 7 vs. 58 +/- 3%, P < 0.05). However, the percentage of octanoate taken up and oxidized was not different (82 +/- 3 vs. 85 +/- 4%, not significant). Because octanoate, unlike oleate, can freely diffuse across the mitochondrial membrane, the present results suggest that the difference in fatty acid oxidation between trained and untrained individuals may be due to enhanced fatty acid entry into the mitochondria.

Reversible, highly localized alterations in fatty acid metabolism in the chronically ischemic canine myocardium

Acute myocardial ischemia is accompanied by a marked decrease in the oxidation of fatty acids. Whether similar changes occur during chronic ischemia was studied in 13 beagles. In 10 dogs, an ameroid constrictor was implanted about the left circumflex artery; 3 others served as sham-operated controls. Mitochondrial and peroxisomal fatty acid oxidation of (1− 14C)oleate were measured and compared in affected (posterobasal left ventricular endocardial [posterior LV endo]) and unaffected (anteroapical LV epicardial [anterior LV epi]) tissues of control and experimental dogs. Five experimental and 3 control dogs were killed after 3 weeks. The posterior LV endo sections of experimental dogs at 3 weeks showed increased fatty acid oxidation due to peroxisomal (KCN-insensitive) β oxidation (p <0.01). The anterior LV epi sections showed no difference in fatty acid oxidation between shamoperated and experimental dogs. Five dogs were studied after 3 months; fatty acid oxidation of the posterior LV endo section was normal. Thus, under a slowly evolving state of myocardial ischemia, highly localized and reversible adaptive changes in fatty acid oxidation occur that enable the affected tissue to cope with a fatty acid load. When collateralization is accomplished, fatty acid metabolism reverts to normal.