Enzyme site-specific changes in hepatic microsomal fatty acid chain elongation in streptozotocin-induced diabetic rats

Suneja, Sanoj K.; Osei, Peter; Cook, Lynda; Nagi, Mahmoud N.; Cinti, Dominick L.

doi:10.1016/0005-2760(90)90059-7

Cited by 13 publications

(8 citation statements)

References 22 publications

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“…Early studies showed that PCE activity increased concomitantly with an increase in SCD activity by administration of clofibric acid (11,24,31), diethylhexylphthalate (10), refeeding of a fat-free diet after fasting, and treatment of diabetic rats with insulin (10,11); in contrast, a diabetic state and starvation reduced the activities of both SCD and PCE (5,10,15). These findings suggest that both PCE and SCD are regulated by similar mechanisms.…”

Section: Induction Of Pce By Glucose and Fructosementioning

confidence: 69%

“…By contrast, information on FA chain elongation has been limited, although several lines of indirect evidence have suggested that the endoplasmic reticulum contains at least three different enzymes catalyzing the elongation of FA (1,(10)(11)(12)(13). Among them, palmitoyl-CoA chain elongation (PCE), which catalyzes stearic acid (18:0) formation from palmitic acid (16:0), was regulated by refeeding after fasting, insulin, and PUFA (10,11,(14)(15)(16). In addition, various xenobiotics such as clofibric acid and diethylhexylphthalate induced the activities of both SCD and PCE (10,11,17,18), although the mechanism of the induction has not yet been clarified.…”

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confidence: 93%

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Regulation by carbohydrate and clofibric acid of palmitoyl‐CoA chain elongation in the liver of rats

Kudo

Toyama

Mitsumoto

et al. 2003

Lipids

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Regulation of palmitoyl-CoA chain elongation (PCE) and its contribution to oleic acid formation were investigated in rat liver in comparison with stearoyl-CoA desaturase (SCD). Hepatic PCE activity was induced by the administration of 20% wt/vol glucose or fructose in the drinking water of normal rats. In streptozotocin-induced diabetic rats, the activities of both PCE and SCD were suppressed, and fructose, but not glucose, feeding caused an increase in the activities of both enzymes. Treatment of normal rats with clofibric acid in combination with carbohydrate further increased PCE, but not SCD, activity. FA analysis of hepatic lipids revealed that the proportion of oleic acid (18:1 n-9) increased upon administration of carbohydrate or clofibric acid. The treatment of rats with clofibric acid in combination with carbohydrate greatly increased the proportion of 18:1 n-9. A significant correlation was observed between PCE activity and the hepatic proportion of 18:1 n-9 (r2 = 0.874, P < 0.01), whereas the relationship between SCD activity and the proportion of 18:1 n-9 was not significant (r2 = 0.552, P > 0.05). Taken together, these results suggest that carbohydrate induces PCE as well as SCD activity to increase the hepatic 18:1 content in rat liver, and the increased PCE activity seems to be responsible for the further increase in 18:1 n-9 when carbohydrate is administered in combination with clofibric acid.

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Section: Induction Of Pce By Glucose and Fructosementioning

confidence: 69%

mentioning

confidence: 93%

Regulation by carbohydrate and clofibric acid of palmitoyl‐CoA chain elongation in the liver of rats

Kudo

Toyama

Mitsumoto

et al. 2003

Lipids

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“…The results from the transgenic and knockout mice would suggest that KAR and TER are not regulated by insulin in a manner similar to other lipogenic genes (32,33). The activities of the four microsomal elongation enzymes previously have been measured under conditions of high and low insulin (34). These studies demonstrated that only the initial condensation reaction catalyzed by LCE is regulated by insulin.…”

Section: Discussionmentioning

confidence: 89%

Identification of Two Mammalian Reductases Involved in the Two-carbon Fatty Acyl Elongation Cascade

Moon¹,

Horton²

2003

Journal of Biological Chemistry

188

150

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The de novo synthesis of fatty acids occurs in two distinct cellular compartments. Palmitate (16:0) is synthesized from acetyl-CoA and malonyl-CoA in the cytoplasm by the enzymes acetyl-CoA carboxylase 1 and fatty acid synthase. The synthesis of fatty acids longer than 16 carbons takes place in microsomes and utilizes malonyl-CoA as the carbon source. Each two-carbon addition requires four sequential reactions: condensation, reduction, dehydration, and a final reduction to form the elongated fatty acyl-CoA. The initial condensation reaction is the regulated and rate-controlling step in microsomal fatty acyl elongation. We previously reported the cDNA cloning and characterization of a murine long chain fatty acyl elongase (LCE) (1). Overexpression of LCE in cells resulted in the enhanced addition of two-carbon units to C12-C16 fatty acids, and evidence was provided that LCE catalyzed the initial condensation reaction of long chain fatty acid elongation. The remaining three enzymes in the elongation reaction have not been identified in mammals. Here, we report the identification and characterization of two mammalian enzymes that catalyze the 3-ketoacyl-CoA and trans-2,3-enoyl-CoA reduction reactions in long and very long chain fatty acid elongation, respectively.

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“…It has been known that these enzyme activities are modulated by nutritional and hormonal status through the altered levels of blood sugar and insulin as well as lipids including cholesterol. 1,23,29) The changes in these nutritional parameters also exert a modulation of the gene expression of fatty acid synthase that supplies C16:0.…”

Section: Discussionmentioning

confidence: 99%

Identification and Expression of a Rat Fatty Acid Elongase Involved in the Biosynthesis of C18 Fatty Acids

Inagaki

Aki

Fukuda

et al. 2002

Bioscience, Biotechnology, and Biochemistry

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A major part of the palmitic acid (C16:0) generated by fatty acid synthase is converted into stearic acid (C18:0) via carbon chain elongation. Here, we describe the cloning and expression of a rat hepatic enzyme, rELO2, responsible for the elongation of C16:0, presumably at the condensing reaction. Heterologous expression experiments in a yeast, Saccharomyces cerevisiae, demonstrated the elongation activity of rELO2 on C16:0 and to a lesser extent, C18:0 and fatty acids with low desaturation degree. This was distinct from that rELO1, a rat homolog of HELO1, which preferably catalyzed the elongation of mono-and polyunsaturated fatty acids of C16-C20. The Northern analysis showed that the expression of rELO2, but not rELO1, in hepatocytes was activated by the cycles of fasting and refeeding rats on a fat-free diet. Under these conditions, the rELO1 was expressed constitutively in various tissues but the rELO2 transcripts were detected predominantly in liver.

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Enzyme site-specific changes in hepatic microsomal fatty acid chain elongation in streptozotocin-induced diabetic rats

Cited by 13 publications

References 22 publications

Regulation by carbohydrate and clofibric acid of palmitoyl‐CoA chain elongation in the liver of rats

Regulation by carbohydrate and clofibric acid of palmitoyl‐CoA chain elongation in the liver of rats

Identification of Two Mammalian Reductases Involved in the Two-carbon Fatty Acyl Elongation Cascade

Identification and Expression of a Rat Fatty Acid Elongase Involved in the Biosynthesis of C18 Fatty Acids

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