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The present study cloned successfully two lipid-metabolism genes, lipoprotein lipase (LPL) and fatty acid binding protein (FABPs) from cobia and studied the mRNA expressions of the two genes and their upstream gene PPARs when the cobia were fed diets containing 15% lipid. Among the lipids, 6% was fish oil and the remaining 9% were supplemented by fish oil (FO, rich in n-3 HUFA), perilla oil (PE, rich in 18:2 n-6), safflower oil (SA, rich in 18:2 n-6), olive oil (OL, rich in 18:1 n-9) or palm oil (PA, rich in 16:0). The whole sequences of LPL, liver-FABP (L-FABP) and muscle-FABP (M-FABP) encode 520, 126 and 133 amino acids, respectively. RT-PCR and real time PCR analyses based on these gene sequences show that the mRNA expressions of L-FABP and M-FABP in the tissue of the cobia were diet-specific. The mRNA expression of LPL, on the other hand, did not respond to the treatments, except in visceral fat depot. Linear regression analysis shows that the mRNA expression of LPL in the liver and muscle was positively (P<0.05) related to dietary fatty acids and ther concentration, but that in the visceral fat depot was negatively related. The mRNA expression of FABPs was also positively correlated with dietary fatty acid levels. Among all fatty acids, the levels of C14:0, C20:1 n-9, EPA and DHA were positively correlated with the mRNA expression of PPAR£^and also with FABPs mRNA expression in the visceral fat depot and LPL mRNA expression in the muscle. Thus, LPL, L-FABP and M-FABP mRNA expression of the cobia were highly influenced by the kind and amount of dietary fatty acids. The role of PPARs was not clearly demonstrated.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Nutritional Sciences." Includes bibliographical references (p. 149-161).

published_or_final_version / Medicine / Master / Master of Philosophy

published_or_final_version / Pharmacology and Pharmacy / Master / Master of Philosophy

Background and objectives: Growing bodies of evidence demonstrate that adipocyte fatty acid binding protein (A-FABP) mediates the pathogenesis of atherosclerosis through its direct impacts on macrophages. Loss-of-function study was conducted by utilizing peritoneal macrophages derived from A-FABP knockout (KO) mice, to investigate the role of A-FABP in autophagy and macrophage foam cell formation. Key findings: 1. No morphological changes between the peritoneal macrophages derived from A-FABP knockout (KO) or their wild-type (WT) littermates. 2. Foam cell formation was successfully induced by the treatment of acetylated low-density lipoproteins (LDL) in peritoneal macrophages derived from A-FABP WT and KO mice. 3. LDL treatment induces autophagy in peritoneal macrophages from both A-FABP WT and KO mice. 4. The extent of LDL-induced autophagy is reduced in peritoneal macrophages of WT mice and is accompanied by increased lipid droplet accumulation when compared with A-FABP KO mice. Conclusions: A-FABP is a suppressor of autophagy and contributes to the attenuation of cholesterol efflux, subsequently resulting in enhancement of lipid droplets accumulation in peritoneal macrophages. A-FABP mediates the formation of macrophage foam cell via the suppression of autophagy. The results suggest that A-FABP is a potential therapeutic target to suspend the progression of atherosclerosis and remit the atherosclerotic lesion. / published_or_final_version / Medicine / Master / Master of Medical Sciences

Liver fatty acid binding protein (L-FABP) binds and translocates many lipophilic substrates within the cytoplasm including long chain fatty acids. Moreover it was reported that L-FABP possesses antioxidative properties within hepatocytes. However, the mechanism of L-FABP’s antioxidative activity remains to be determined. Peroxisome proliferator activated receptor (PPAR) agonists and antagonists can regulate L-FABP levels. However, it needs to be investigated how PPAR agonists and antagonists regulate L-FABP expression. And whether the altered expression of L-FABP by these agents will affect its antioxidative properties within hepatocytes remains unclear. In this thesis we employed clofibrate (PPARα agonist), MK886 (PPARα antagonist), and GW9662 (PPARγ antagonist) to elucidate the mechanism whereby PPAR regulate L-FABP expression and what effect such expression has on the antioxidant activity of L-FABP in CRL-1548 hepatoma cells. Clofibrate served to upregulate L-FABP expression while MK886 and GW9662 were employed to inhibit L-FABP expression. The principal findings revealed that clofibrate treatment enhanced L-FABP mRNA stability and transcription, which resulted in increased L-FABP levels, while MK866 and GW9662 reduced these levels. We also demonstrated that increases in L-FABP levels were associated with reduced cytosolic reactive oxygen species (ROS), while L-FABP siRNA knockdown resulted in a decrease in L-FABP expression and an associated increase in ROS levels. The antioxidant mechanism of recombinant rat L-FABP in the presence of a hydrophilic (AAPH) and lipophilic (AMVN) free radical generators was also evaluated. Recombinant rat L-FABP was produced in E. coli and its amino acid sequence was confirmed by MALDI QqTOF MS. Antioxidant activity was assayed using the thiobarbituric acid method. Ascorbic acid served as a positive control for the AAPH reaction while α-tocopherol was used as a positive control for the AMVN reaction. The antioxidant activity of recombinant L-FABP was greater when free radicals were generated with AAPH than AMVN. Oxidative modification of L-FABP included up to five methionine oxidative peptides with a total of 80 Da mass shift compared to native L-FABP. These findings suggest that the mechanism of L-FABP’s antioxidant activity involved the reaction of methionine with free radicals. In conclusion, L-FABP expression is regulated by PPAR agonists and antagonists through transcription and mRNA stability. Moreover, methionine residues appear to play an important role in the antioxidative activity of L-FABP.

Liver fatty acid binding protein (L-FABP) binds and translocates many lipophilic substrates within the cytoplasm including long chain fatty acids. Moreover it was reported that L-FABP possesses antioxidative properties within hepatocytes. However, the mechanism of L-FABP’s antioxidative activity remains to be determined. Peroxisome proliferator activated receptor (PPAR) agonists and antagonists can regulate L-FABP levels. However, it needs to be investigated how PPAR agonists and antagonists regulate L-FABP expression. And whether the altered expression of L-FABP by these agents will affect its antioxidative properties within hepatocytes remains unclear. In this thesis we employed clofibrate (PPARα agonist), MK886 (PPARα antagonist), and GW9662 (PPARγ antagonist) to elucidate the mechanism whereby PPAR regulate L-FABP expression and what effect such expression has on the antioxidant activity of L-FABP in CRL-1548 hepatoma cells. Clofibrate served to upregulate L-FABP expression while MK886 and GW9662 were employed to inhibit L-FABP expression. The principal findings revealed that clofibrate treatment enhanced L-FABP mRNA stability and transcription, which resulted in increased L-FABP levels, while MK866 and GW9662 reduced these levels. We also demonstrated that increases in L-FABP levels were associated with reduced cytosolic reactive oxygen species (ROS), while L-FABP siRNA knockdown resulted in a decrease in L-FABP expression and an associated increase in ROS levels. The antioxidant mechanism of recombinant rat L-FABP in the presence of a hydrophilic (AAPH) and lipophilic (AMVN) free radical generators was also evaluated. Recombinant rat L-FABP was produced in E. coli and its amino acid sequence was confirmed by MALDI QqTOF MS. Antioxidant activity was assayed using the thiobarbituric acid method. Ascorbic acid served as a positive control for the AAPH reaction while α-tocopherol was used as a positive control for the AMVN reaction. The antioxidant activity of recombinant L-FABP was greater when free radicals were generated with AAPH than AMVN. Oxidative modification of L-FABP included up to five methionine oxidative peptides with a total of 80 Da mass shift compared to native L-FABP. These findings suggest that the mechanism of L-FABP’s antioxidant activity involved the reaction of methionine with free radicals. In conclusion, L-FABP expression is regulated by PPAR agonists and antagonists through transcription and mRNA stability. Moreover, methionine residues appear to play an important role in the antioxidative activity of L-FABP.

The triglyceride-free fatty acid (TG-FFA) cycle was studied in white adipose tissue. The major aims of the study were 1) to see if the rate of TG-FFA cycling (i.e. FFA reesterification) and the sensitivity properties (see Newsholme and Crabtree, 1976, Biochem. Soc. Symp. 41, 61-109) were affected by various treatments, and 2) to measure the rate of cycling in vivo and assess its contribution to the metabolic rate of an animal. There are two ways of estimating the rate of TG-FFA cycling; the first is based on the release of glycerol and FFA from the tissue, and the second on the synthesis of the glycerol and FFA moieties of triglyceride. Experimental agreement between the two methods is very good. It is shown that the rate of TG glycerol synthesis can be estimated by measuring the incorporation of tritium from tritiated water into the TG-glycerol moiety; this method is used to study the TG-FFA cycle in vivo. Experimental results indicated that the rate of TG-FFA cycling in white adipose tissue in vitro and in vivo is affected by various short- and long-term treatments. However, the reesterification of FFA in adipose tissue can only account for perhaps ~1% of the basal metabolic rate of a mouse, and perhaps 4% of the increase in osygen consumption observed in fenoterol-treated mice. The equations of Newsholme and Crabtree (1976) describing the sensitivity properties of substrate cycles are extended and used to show that the TG-FFA cycle increases the sensitivity of control of FFA release from adipose tissue. The degree of sensitivity attainable is variable depending on the treatment used. The use of tritiated water for estimating TG-FFA cycling is tentatively extended to brown adipose tissue. It is suggested that the rate of cycling could be used as an indicator of sympathetic activity in brown and white adipose tissue.

Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 46-54). / x, 54 leaves, bound ill. 29 cm