Peroxisome proliferator-activated receptor gamma upregulation and dietary fat levels in laying hens
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The present study was conducted to investigate the effect of feeding the different levels of the dietary fat on the expression of genes encoding proteins involving energy metabolism, oxidative phosphorylation, and lipid synthesis including peroxisome proliferator-activated receptor gamma (PPARγ) of laying hens in the intestine. Birds fed diets with 3 levels of fat, that is, low (LF), medium (MF), and high fat (HF) were reared from 22 to 42 wk of age. Jejunum tissue was collected at week 42 for gene expression analysis. Dietary fat content as ether extract, net energy to AME ratio, and CP content of 3 treatment groups were as follows: LF: 25, 0.735, 187 (g/kg, DM); MF: 61, 0.739, 185 (g/kg, DM); HF: 73, 0.752, 181 (g/kg, DM). The BW, fat pad weight (g), fat pad–to–BW ratio (%) was the same for all the treatments (P > 0·05). Birds fed a diet containing HF increased the AME daily intake per metabolic BW (BW0.75) (P < 0.05). The expression of jejunal PPARγ was increased in the birds fed MF than that fed LF (P < 0.05). Dietary fat level did not affect the expression of other genes: protein kinase AMP-activated noncatalytic subunit gamma 2, NADH dehydrogenase subunit 2, succinate dehydrogenase complex flavoprotein subunit A, ubiquinol-cytochrome c reductase Rieske iron-sulfur polypeptide 1, cytochrome c oxidase subunit III, ATP synthase subunit alpha, avian adenine nucleotide translocator, and acetyl-CoA carboxylase alpha (P > 0·05). The mitochondrial count per cell showed no difference among the 3 groups with different dietary treatments (P > 0·05). The results suggest that PPARγ may be important to the energy expenditure during nutrient absorption, digestion, and metabolism, and respiratory chain complexes, and other genes involving mitochondrial energy metabolism and lipogenesis may be less responsive to dietary treatment.Keywords:
Jejunum
Microbody
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Zellweger syndrome
Glyoxysome
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Lipogenesis
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Aim To investigate difference expression of peroxisome proliferator-activated receptor α (PPAR α) during aging and explore the molecular mechanism of perturbation in lipid metabolism during aging. Methods We used two-group SD rats to estimate the lipid level of young (6～8 weeks) and aged (24 months) groups. The levels of triglyceride (TG) and total cholesterol (TC) were examined. The levels of liver PPAR α and target genes mRNA were measured by reverse transcription-polymerse chain reaction (RT-PCR) and PPAR α protein were determined by western blotting respectively. Results The TG and TC level of the aged group increased significantly. The PPAR α mRNA and protein level of the aged group significantly decreased compared with the young group. Target gene levels were changed during aging. Conclusion The mechanism of lipid dysfunction during aging is probably associated with the decreased expression of PPAR α.
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Abstract We analyzed all four Pex23 family proteins of the yeast Hansenula polymorpha , which localize to the ER. Of these Pex24 and Pex32, but not Pex23 and Pex29, accumulate at peroxisome-ER contacts, where they are important for normal peroxisome biogenesis and proliferation and contribute to organelle positioning and segregation. Upon deletion of PEX24 and PEX32 - and to a lesser extent of PEX23 and PEX29 - peroxisome-ER contacts are disrupted, concomitant with peroxisomal defects. These defects are suppressed upon introduction of an artificial peroxisome-ER tether. Accumulation of Pex32 at peroxisomes-ER contacts is lost in the absence of the peroxisomal membrane protein Pex11. At the same time peroxisome-ER contacts are disrupted, indicating that Pex11 contributes to Pex32-dependent peroxisome-ER contact formation. Summarizing, our data indicate that H. polymorpha Pex24 and Pex32 are tethers at peroxisome-ER contacts that are important for normal peroxisome biogenesis and dynamics. Summary Two Hansenula polymorpha ER proteins, Pex24 and Pex32, are tethers at peroxisome-ER contacts and function together with the peroxisomal protein Pex11. Their absence disturbs these contacts leading to multiple peroxisomal defects, which can be restored by an artificial tether.
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Peroxisomes are compartments in cells called organelles that perform many different functions. In humans, peroxisomal defects result in serious disorders, leading to early death. Peroxisomes need proteins to perform their function but they cannot make these proteins themselves. Therefore, peroxisomes take up (import) proteins from the cytosol, which is the fluid that surrounds organelles inside cells. Under certain conditions, peroxisome numbers need to be increased in cells, and one way to achieve this is by the division of pre-existing ones. This process is termed ‘fission’ but we do not understand fully how this occurs. In this thesis, we have studied details of the peroxisomal fission and import processes by analysing them in yeast. Pex11p is a protein which is important for peroxisome fission. Pex11p reshapes the peroxisomal membrane so that peroxisomes can start dividing. We investigated how Pex11p is stimulated to perform this function and how it interacts with the peroxisomal membrane. Our studies indicate that membrane reshaping occurs due to Pex11p interacting with specific regions of the membrane. Proteins destined for peroxisomes contain Peroxisome Targeting Signals (PTS) that are recognized by proteins Pex5p and Pex7p. These receptors transport PTS containing proteins from the cytosol, where they are made, into peroxisomes. We have identified that Aspartate aminotransferase-2 (Aat2p) localises to peroxisomes despite lacking a classical PTS. Peroxisomal localisation persisted in the absence of Pex5p and Pex7p. Instead, Pex20p is required for targeting. Functional analysis suggests that Aat2p may contribute to the regulation of metabolism inside peroxisomes.
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Peroxisomal targeting signal
Transport protein
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Microbody
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Zellweger syndrome
Peroxisomal disorder
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Adrenoleukodystrophy
Cell function
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More than half a century of research on peroxisomes has revealed unique features of this ubiquitous subcellular organelle, which have often been in disagreement with existing dogmas in cell biology. About 50 peroxisomal enzymes have so far been identified, which contribute to several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, and render peroxisomes indispensable for human health and development. It became obvious that peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. However, many aspects of peroxisome biology are still mysterious. This review addresses recent exciting discoveries on the biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross talk of peroxisomes with other subcellular compartments. Furthermore, recent advances on the role of peroxisomes in medicine and in the identification of novel peroxisomal proteins are discussed.
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Zellweger syndrome
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Peroxisome proliferator activated receptors (PPAR) belong to a family of nuclear receptors broadly distributed in the organism. Their pleiotropic role has been recently proved as well as their pathogenic significance in diabetes, obesity, cell cycle controlling, carcinogenesis, inflammation and atherosclerosis. The three types of PPAR identified until today have different tissue localization. PPARgamma, primarily identified in macrophages and adipocytes, play an important role in the expression of proteins essential for lipid metabolism and adipogenesis. PPARalpha are localized predominantly in hepatocytes and have also an important role in lipid metabolism. PPAR are though to be lipid sensors in organism. Carbohydrate metabolism is also under the control of PPAR and their exogenous ligands, (ie: thiasolidinediones), are important antidiabetic drugs.
Carbohydrate Metabolism
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