Radiosynthesis of 1‐[ 11 C] polyhomoallylic fatty acids

This article is available online at http://www.jlr.org "methyl-end" FA desaturases. Therefore, linoleic acid and ␣ -linolenic acid must be provided by the diet ( 3 ). These dietary essential FAs then serve as precursors for longer PUFAs of the n-6 and n-3 series, including arachidonic acid (20:4 n-6) and docosahexaenoic acid (22:6 n-3) required for many important physiological functions in humans ( 4,5 ). In this PUFA biosynthesis, only "front-end" desaturases ( ⌬ 5-and ⌬ 6-desaturases) are involved to introduce new double bonds between the preexisting double bonds and the carboxyl end of FAs ( 6 ).In 2000, the genomic structure of the fatty acid desaturase (FADS) cluster, located on chromosome 11 in humans, was reported ( 7 ). This cluster includes the FADS1 and FADS2 genes that code, respectively, for the well-known ⌬ 5-and ⌬ 6-desaturases involved in PUFA biosynthesis ( 8-10 ). A third gene was identifi ed on this cluster with high degree of nucleotide sequence homology with both FADS1 (62%) and FADS2 (70%) and was therefore named FADS3. Since its fi rst description in humans ( 7 ), FADS3 has been identifi ed in rats ( 11 ), baboons ( 12 ), mice ( 3 ), and many other mammals showing a similar nucleotide sequence and intron/exon organization ( 12 ). When analyzing the peptide sequence deduced from the FADS3 nucleotide sequence, FADS3 protein was identifi ed as a putative desaturase, according to its similarity with FADS1 and FADS2. Indeed, the predicted structure of FADS3 is composed of an N-terminal cytochrome b5-like domain characterized by a HPGG motif shown to be essential for the ⌬ 6-desaturase activity of FADS2 ( 13 ) QIEHH in the rat) characteristic of front-end-desaturases ( 14 ). According to its amino acid sequence, FADS3 was thereafter supposed to Abstract Fatty acid desaturases play critical roles in regulating the biosynthesis of unsaturated fatty acids in all biological kingdoms. As opposed to plants, mammals are so far characterized by the absence of desaturases introducing additional double bonds at the methyl-end site of fatty acids. However, the function of the mammalian fatty acid desaturase 3 (FADS3) gene remains unknown. This gene is located within the FADS cluster and presents a high nucleotide sequence homology with FADS1 ( ⌬ 5-desaturase) and FADS2 ( ⌬ 6-desaturase). Here, we show that rat FADS3 displays no common ⌬ 5-, ⌬ 6-or ⌬ 9-desaturase activity but is able to catalyze the unexpected ⌬ 13-desaturation of trans -vaccenate. Although there is no standard for complete conclusive identifi cation, structural characterization strongly suggests that the ⌬ 11,13-conjugated linoleic acid (CLA) produced by FADS3 from trans -vaccenate is the trans 11, cis 13-CLA isomer. In rat hepatocytes, knockdown of FADS3 expression specifically reduces trans -vaccenate ⌬ 13-desaturation. Evidence is presented that FADS3 is the fi rst "methyl-end" fatty acid desaturase functionally characterized in mammals. FA desaturases introduce double bonds between defi ned carbons of the fatty acyl chain and catalyze ...

Section: Incubation Of Cells With Fatty Acidsmentioning

confidence: 99%

Trans-vaccenate is Δ13-desaturated by FADS3 in rodents

Rioux

Pédrono

Blanchard

et al. 2013

“…Radiochemistry of [1][2][3][4][5][6][7][8][9][10][11] C]DHA [1-11 C]DHA was synthesized by the Grignard reaction as previously described, with a specific activity .500 mCi/nmol (34). HPLC analysis of aliquots of the final product revealed .98.6 6 0.9% (n 5 8) radiochemical purity.…”

Section: Human Subjectsmentioning

confidence: 99%

“…To do this, we first developed a radiosynthetic method for positron-emitting [1-11 C]polyhomoallylic acids, including ARA and DHA (33,34). We then used intravenously injected [1-11 C]ARA together with positron emission tomography (PET) to image regional brain incorporation coefficients K* and calculate regional incorporation rates J in of ARA in monkey and humans in the resting state (35,36) and following functional activation (37).…”

mentioning

confidence: 99%

Imaging incorporation of circulating docosahexaenoic acid into the human brain using positron emission tomography

Umhau

Zhou

Carson

et al. 2009

165

152

Docosahexaenoic acid (DHA; 22:6n-3) is a critical constituent of the brain, but its metabolism has not been measured in the human brain in vivo. In monkeys, using positron emission tomography (PET), we first showed that intravenously injected [1-11 C]DHA mostly entered nonbrain organs, with ?0.5% entering the brain. Then, using PET and intravenous [1-11 C]DHA in 14 healthy adult humans, we quantitatively imaged regional rates of incorporation (K*) of DHA. We also imaged regional cerebral blood flow (rCBF) using PET and intravenous [15 O]water. Values of K* for DHA were higher in gray than white matter regions and correlated significantly with values of rCBF in 12 of 14 subjects despite evidence that rCBF does not directly influence K*. For the entire human brain, the net DHA incorporation rate J in , the product of K*, and the unesterified plasma DHA concentration equaled 3.8 6 1.7 mg/day. This net rate is equivalent to the net rate of DHA consumption by brain and, considering the reported amount of DHA in brain, indicates that the half-life of DHA in the human brain approximates 2.5 years. Thus, PET with [1-11 C]DHA can be used to quantify regional and global human brain DHA metabolism in relation to health and

“…Muscle fatty acid oxidative capacity (study 2) C]vaccenic and elaidic acids were prepared using well-established procedures (29,30). Briefly, the bromo precursors were synthesized from unlabeled fatty acids according to the procedure of Barton, Crich, and Motherwell (30).…”

Section: Intraperitoneal Glucose Tolerance Test (Study 1)mentioning

confidence: 99%

Effects of trans MUFA from dairy and industrial sources on muscle mitochondrial function and insulin sensitivity

Tardy

Giraudet

Rousset

et al. 2008

Epidemiological studies suggest that chronic consumption of trans MUFA may alter muscle insulin sensitivity. The major sources of dietary trans MUFA (dairy fat vs. industrially hydrogenated oils) have different isomeric profiles and thus probably different metabolic consequences. These effects may involve alterations in muscle mitochondrial oxidative capacity, which may in turn promote insulin resistance if fatty acid oxidation is reduced. We report that in Wistar rats, an 8 week diet enriched (4% of energy intake) in either dairy, industrial, or control MUFA did not alter insulin and glucose responses to an intraperitoneal glucose tolerance test (1g/kg). In C2C12 myotubes, vaccenic and elaidic acids did not modify insulin sensitivity compared with oleic acid. Furthermore, the ex vivo total, mitochondrial and peroxisomal oxidation rates of [1-14 C]oleic, vaccenic, and elaidic acids were similar in soleus and tibialis anterior rat muscle. Finally, an 8 week diet enriched in either dairy or industrial trans MUFA did not alter mitochondrial oxidative capacity in these two muscles compared with control MUFA but did induce a specific reduction in soleus mitochondrial ATP and superoxide anion production (P , 0.01 vs. control). In conclusion, dietary trans MUFA of dairy or industrial origin have similar effects and do not impair muscle mitochondrial capacity and insulin sensitivity. Plurimetabolic syndrome (syndrome X) affects 40% of men and 25% of women over the age of 55 in Europe (1). One of the features of this metabolic disorder is impaired insulin sensitivity 10 to 20 years before the development of type 2 diabetes, with a concomitant increased risk of cardiovascular disease (2). Several observational studies suggest that insulin resistance is primarily a lifestyle disorder (3), because overweight and low physical activity are the greatest risk factors for type 2 diabetes (4). Evidence is now emerging that the incidence of this metabolic disorder could also be affected by diet composition. High energy intake is a factor contributing to the development of insulin resistance by increasing body weight and fat deposition (5, 6), whereas several studies have shown that weight loss is very effective in reducing the prevalence of type 2 diabetes in overweight individuals (7,8). Among all the macronutrients, dietary fatty acids have received particular attention as potential inductors of insulin resistance. Changes in the fatty acid composition of blood and muscle have been shown to correlate with insulin resistance in humans (9, 10). Furthermore, epidemiological studies have reported that mono-and polyunsaturated fat may reduce the risk of developing type 2 diabetes, whereas saturated fat has been reported to have a potentially adverse effect (11-13). These effects are independent of changes in body weight and composition. The KANWU (Kuopio, Aarhus, Naples, Wollong and Uppsala) interventional study confirms these effects, but only when total dietary fat consumption is lower than 37% of total energy intake (14)....