The obesogenic effects of polyunsaturated fatty acids are dependent ...

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was used as the liver cytosolic fraction and total glutathione (GSH) content was determined by a colorimetric assay, Bioxytech GSH-400 (OXISResarch TM , Portland, OR, USA). Adipose tissue fatty acid oxidation capacity – samples from eWAT and iBAT was homogenized in a glycine-glycine buffer as previously described (44). The homogenates were centrifuged at 1000 g for 5 minutes and the supernatant was collected (post-nuclear fraction). Fatty acid oxidation capacity was measured in the post-nuclear fractions by the acid-soluble product method using radiolabeled palmitoyl-Coenzyme A as the substrate, as previously described in detail (30). In vitro adipocyte differentiation and fatty acid oxidation – The stromal vascular fraction was isolated from eWAT dissected out from rats as earlier described (37). Contaminating erythrocytes were eliminated from the stromalvascular fraction by a wash with sterile distilled water. Cells were plated and induced to differentiate as described (37). Differentiated cells were treated with increasing concentrations of taurocholic acid in the medium for 24h. Afterwards, the cells were scraped and homogenized in a buffer containing 0.25 M sucrose, 2 mM EGTA and 10 mM Tris/HCl, pH 7.4. Fatty acid oxidation capacity was evaluated by the total amount of acid-soluble products using radio-labeled palmitoyl-Coenzyme A as the substrate, as previously described in detail (30). Energy in faeces and diets - The gross energy content was determined in a bomb calorimeter following the manufacturer’s instruction (Parr Instruments, Moline, IL, USA). Statistical analysis – Data are presented as mean+S.E. Analysis of variance was performed by post-hoc pairwise comparison Student’s t-test or Tukey’s HSD test. Data that failed to show homogeneity in variance by Levenes’ test were tested by the nonparametric tests Mann-Whitney U test or Kruskal-Wallis test. Data were considered statistically different at P
the SPH+c’am treated groups (Fig 1I). However, the lean body mass including bones was borderline reduced in the SPH-treated (231±4 g, P = 0.052) but was significantly reduced in the SPH+cholestyramine-treated (223±1 g, P = 0.005), relative to the casein-fed rats (259±7 g). Since bile acids are known to increase energy expenditure and energy dissipation in the form of heat (20), we considered it likely that the reduced fat content in the SPH-treated rats was accompanied by higher energy dissipation. To demonstrate this we determined energy expenditure in the rats by indirect calorimetry. Indeed, SPH-treated rats had significantly higher O 2 consumption and heat production, as well as CO 2 elimination relative to the casein treated rats (Fig 1K-M). Importantly, and providing further evidence for a role of the increased plasma BA concentration with regard to the increased energy expenditure, pharmacological lowering of plasma BAs attenuated heat production, and led to higher body fat content at an equal energy intake (Fig 1J-M). The higher CO 2 production in the SPH-treated rats was independent of the reduced bodyweight in these animals, as total CO 2 production (Liter/24h) was higher in the SPH, relative to the casein fed rats, 8.69 ± 0.15 and 8.09 ± 0.11, respectively (P = 0.03). The corresponding value for the SPH+c’am treated rats was 8.31 ± 0.18, which was not statistically different from neither the SPH nor the casein treated rats. Nutritional regulation of endogenous BA metabolism modulates fat oxidation capacity in brown and white adipose tissues. Mice ingesting cholic acid supplemented diets have increased fat oxidation and energy dissipation as heat in iBAT, which is important to prevent high-fat diet-induced adiposity (20). To elucidate whether nutritional modulation of plasma BAs could induce fat oxidation in iBAT, we measured ex vivo fatty acid oxidation capacity in iBAT. In agreement with the increased whole-body heat production, fatty acid oxidation capacity was significantly higher in iBAT from SPH fed rats compared with rats fed casein (Fig 2A). The metabolic effect of bile acids on energy expenditure is critically dependent on the cAMP-inducible thyroid activating enzyme type 2 6 iodothyronine deiodinase (Dio2) and is lost in Dio2 -/- mice (20). Expression of Dio2 has been linked to expression of the thyroid-responsive gene, uncoupling protein 1 (Ucp1) (45). Exogenously added bile acids have also been shown to increase the expression of peroxisome proliferator-activated receptor γ coactivator 1α (Pgc-1α) in brown adipose tissue (20), a key regulator of mitochondrial biogenesis and energy expenditure (46,47). Here we show that the higher heat production and fatty acid oxidation capacity in iBAT was accompanied by induction of genes encoding Ucp1 and Dio2 whereas Pgc-1α expression was not significantly increased (Fig. 2B-D). Even though brown adipose tissue is considered the major adipose tissue to dissipate chemical energy in the form of heat (48), white adipose tissue is plastic and under certain conditions the expression of Pgc-1α and Ucp1 can be induced (49-51). Under conditions with increased intracellular cAMP signaling, studies in mice suggest that induced expression of Ucp1 in white adipose tissues is associated with a lean and healthy phenotype (40,52-54). As BAs are known to increase intracellular cAMP levels, we speculated whether the increased plasma BA concentrations could also alter the phenotype of WAT. Indeed, the SPHtreated rats displayed higher expressions of Ucp1, Dio2 and Pgc-1α in white adipose tissues of subcutaneous origin (inguinal, iWAT) and of abdominal origin, eWAT and MeWAT (Fig. 2E-G). These data supported the idea that not only iBAT, but also white adipose tissues contributed to the lean phenotype in the SPH-treated rats. To further corroborate the hypothesis that nutritional regulation of plasma BA levels was of importance for the WAT phenotype, we investigated WAT from the rats treated with SPH and SPH+c’am. Pharmacological removal of BAs from circulation attenuated the reduction in abdominal WAT mass (eWAT + MeWAT + perirenal/retroperitoneal WAT) (Fig. 2H). Furthermore, ex vivo fat oxidation capacity and expression of Ucp1, Dio2 and Pgc-1α were lower in eWAT from SPH+c’am, relative to the SPH treated rats, even though the difference did not reach significant levels (Fig. 2I, J). The lower plasma BA concentrations were also accompanied by larger adipocyte cell sizes in eWAT (Fig. 2K). Downloaded from www.jbc.org by guest, on July 7, 2011
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The obesogenic effects of polyunsat
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Table of Contents Acknowledgement .
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Abstract in Danish Polyumættede n-
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Polyunsaturated fatty acids in the
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was more than 3 times higher in the
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gluconeogenesis and ureagenesis (Fi
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high dietary PUFAs, the modulation
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In a pair of population studies, an
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18. Massiera, F. et al. Arachidonic
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54. Xu, J. et al. Polyunsaturated f
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Annexes 1. Ma T, Liaset B, Hao Q, P
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Fish Oil, Sucrose and Obesity Obesi
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Fish Oil, Sucrose and Obesity Figur
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Fish Oil, Sucrose and Obesity Table
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Fish Oil, Sucrose and Obesity 6. Ma
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Carbohydrate source and insulin sec
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20 21 22 23 24 25 26 27 28 29 30 31
Page 39 and 40: 68 69 70 71 72 73 74 75 76 77 78 79
Page 41 and 42: 114 115 116 117 118 119 120 121 122
Page 43 and 44: 160 161 162 163 164 165 166 167 168
Page 45 and 46: 208 209 210 211 212 213 214 215 216
Page 47 and 48: 256 257 258 259 260 261 262 263 264
Page 49 and 50: 302 303 304 305 306 307 308 309 310
Page 51 and 52: 350 351 FIGURE LEGENDS 352 353 354
Page 53 and 54: 398 399 400 401 402 403 404 subunit
Page 55 and 56: 446 447 448 449 450 451 gamma, coac
Page 57 and 58: 484 485 486 TABLE 1. Macronutrient
Page 59 and 60: Energy (kJ/g) 17.16 25.12 25.12 25.
Page 61 and 62: 561 562 563 564 565 566 567 568 569
Page 63 and 64: 635 636 637 638 639 640 641 642 643
Page 65: 711 712 713 714 715 716 717 718 719
Page 74 and 75: Cyclooxygenases and UCP1 Although i
Page 76 and 77: Cyclooxygenases and UCP1 Figure 2.
Page 78 and 79: Cyclooxygenases and UCP1 Figure 4.
Page 80 and 81: Cyclooxygenases and UCP1 PLoS ONE |
Page 82 and 83: Cyclooxygenases and UCP1 E synthase
Page 84 and 85: Cyclooxygenases and UCP1 29. Granne
Page 86 and 87: JBC Papers in Press. Published on J
Page 88 and 89: hydrolysate (SPH), would be protect
Page 92 and 93: In order to demonstrate that bile a
Page 94 and 95: Nutritional regulation of endogenou
Page 96 and 97: in increased whole body energy expe
Page 98 and 99: 38. Kanehisa M, and Goto S. (2000)
Page 100 and 101: FOOTNOTES This work was carried out
Page 102 and 103: fed the same diets, plus the SPH-di
Page 104 and 105: Figure 2 A nmol/ min/ mg prot 2,4 1
Page 106 and 107: Figure 4 A 6 Liver Pparα B 21 Live
Page 108 and 109: Figure 7 A Plasma ALAT B Liver Ucp2
Page 110 and 111: Ruzzin et al. investigated the meta
Page 112 and 113: Ruzzin et al. CD14, and rho kinases
Page 114 and 115: Ruzzin et al. salmon oil induced a
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