Effects of conjugated linoleic acid on adipogenic genes regulation in chickens
Modern commercial chickens exhibit excessive fat accumulation in the abdominal area. The major goals of the poultry industry are to increase the carcass yield and to reduce carcass fatness. Excessive fat deposition in chicken is detrimental for human consumption. Increasing the leanness of meat w...
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| Format: | Thesis |
| Language: | English |
| Published: |
2015
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/85595/1/fpv%202015%2011%20ir.pdf |
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| Summary: | Modern commercial chickens exhibit excessive fat accumulation in the abdominal
area. The major goals of the poultry industry are to increase the carcass yield and to
reduce carcass fatness. Excessive fat deposition in chicken is detrimental for human
consumption. Increasing the leanness of meat will improve the meat quality, and thus
makes animals more valuable. Conjugated linoleic acid (CLA) consists of a complex
mixture of geometrical (cis and trans) and positional isomers which consist of two
major isomers; cis-9, trans-II CLA and trans-In, cis-I2 CLA. Animal studies have
reported that dietary intake of CLA changes animal body composition by preventing
obesity development. This study was performed with the hypothesis that CLA
modified adipose tissue through alteration of the adipocyte genes. Therefore the general
objective of current study was to evaluate the effects of CLA on lipid metabolism,
cellular morphology and transcription of regulatory genes that were involved in
adipogenesis of chickens. Cis-9, trans-l l CLA and trans-In, cis-TZ CLA isomers were
evaluated individually for their effects on morphological changes, and adipogenic
genes expressions on primary adipose tissue isolated from chicken Adipose tissue
isolated from specific pathogen-free (SPF) chicken was cultured in induction media
containing Dulbecco's Modified Eagle Medium (DMEM: HEM's (50:50); 1.5% bovine
serum albumin; lOOnlM HEPES (4-(2-hydro>..)'ethyl)-1-piperazineethanesulfonic acid);
2mglmL collagenease type I, and 1% penicillin/streptomycin. The media were
incorporated with two concentrations of both CLA isomers at 1.51% and 2.56% with a
CONTROL group (without CLA isomers). After day 7, adipose tissues differentiation
was monitored morphologically using ImageJ software, and adipogenic genes
expressions were analyzed by real time polymerase chain reaction (PCR). It was
observed that the efficacy of cis-9, trans-ll CLA isomer was more pronounced than
trans-In, cis-12 CLA isomer in the in vitro study. Adipose tissue morphology data
presented in this work revealed that the domination of cis-9, trans-l l isomer CLA
effect was observed at higher concentration in the abdominal fat of broiler chickens.
This was associated with a lower transcriptional level of peroxisome proliferator activated
receptor gamma (PP AR y), and adipocyte protein 2 (aP2), together with lesser
abdominal adipocyte volume and smaller amount of fat. The acyl-Coenzyme A binding
domain containing 5 (ACBD 5), and lipoprotein lipase (LPL) were down-regulated by
cis-9, trans-ll CLA isomer. The primary adipose tissue treated with trans-In, cis-I2
concentrations had no changes on the adipose cellularity and adipogenic genes. The influences of CLA supplementation on growth performance, fatty acid composition,
lipid peroxidation, meat colour and plasma lipids in broiler chicken were investigated
in this study. The CLA used in this study was of commercial feed grade (Lutrell®
BSAF, SE, Ludwigshafen, Germany). A total of 180 broiler chickens were allocated to
3 dietary treatments (0,2.5 and 5% CLA), and given a standard broiler starter diet from
1 to 21 days, and finisher diet from 22 to 42 days. Body weight of chickens and feed
intake were recorded weekly. After slaughter, the breast meat was aged at 4°C for 0, 3
and 6 days. The fatty acid composition was measured in the breast meat. The dietary
CLA supplementation significantly (P<0.05) increased the content of CLA in chicken
meat. The predominant CLA in meat from birds with supplemented diets was trans-It),
cis-9. The proportion of monounsaturated (MUFA) fatty acid in meat decreased
significantly (P<0.05) with increasing CLA supplementation. Dietary CLA also
increased the thiobarbituric acid reactive substances (TBARS) values in breast meat.
Conjugated linoleic acid feeding also resulted in the reduction of plasma total
cholesterol, low-density protein, and the ratio of high-density protein, particularly
among the 5% CLA fed-chickens. The effects of CLA on adipocytes morphology, fatty
acid profile and PPARs associated genes were performed in CLA-fed chickens. The
adipocyte morphology was analyzed using ImageJ software. It was also observed that
the content of cis-9, trans-Ll CLA in abdominal fat tissue was higher than that of trans-
10, cis-12 CLA. The CLA feeding increased total saturated fatty acid and decreased the
MUFA in concentration in broilers compared to the control group. Conjugated linoleic
acid fed-chickens have lesser mean abdominal adipocyte volume and a smaller amount
of fat because of reduced capacities to store fats. The influence on body composition
appears to be dependent on PPAR a (alpha). Current study demonstrated that CLA
down-regulated aP2 transcription, which was parallel to PPAR Y transcription in
adipose tissue of broiler chickens. Adipocyte protein 2 (aP2) was regulated by PPAR Y
as PP AR y is regarded as ,,master regulator" of adipocyte differentiation. The
upregulation of LPL suggested that tins gene might play an independent role in
regulation of adipogenesis in chicken model. The upregulation of ACBD 5 seems to be
novel; therefore, more studies need to be done on this gene. However, LPL gene was
not altered which indicates that the ex-pression of LPL occurs spontaneously at
confluence and is independent. Therefore, tile current results supported the hypotheses
that CLA modified adipose tissue through alteration of the adipocyte genes. It is
evident that the CLA down-regulated PPAR y and aP2, which subsequently resulted in
decreased adipocyte size, number and area of abdominal fat cells. The comparatively
lower CLA content in poultry species could be mitigated through the use of feed and
biotechnology approach to enhance CLA content. In conclusion, tile present results
proved that CLA feeding is a practical strategy to reduce fat deposition in broiler
chicken, while increasing its appeal to the general populace consuming chicken meat. |
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