Increasing Marbling Gene Expression in Beef Cattle with Dietary Lipids

Transcription

1 Increasing Marbling Gene Expression in Beef Cattle with Dietary Lipids Stephen B. Smith and Seong Ho Choi Texas A&M University Bradley J. Johnson Texas Tech University, Lubbock RMC 2012 June 18, 2012 Researchers acknowledge support from: The Beef Checkoff, Angus Research Foundation, Kansas Beef Council, South Korea National Institute of Animal Science, and Gordon W. Davis Regent s Chair Endowment

2 Does Marbling Matter? Premium Choice Hanwoo

3 Beef Eating Experience Tenderness Juiciness Flavor

4 What is Marbling? Marbling = Intramuscular Fat Adipose tissue stores extra calories as triglycerides To store extra calories you need a surplus of calories Moody and Cassens, 1968 Smith et al., 2012

5 Not All Fat Cells Are Created Equal!

6 Marbling adipocytes are different. Marbling adipocytes are smaller and less developed than subcutaneous or intermuscular (seam) adipocytes. Intermuscular Subcutaneous Intramuscular Moody and Cassens, 1968

7 Different substrates for adipose tissues The contributions of acetate, lactate, and glucose to de novo fatty acid biosynthesis in i.m. and s.c. adipose tissues (Smith and Crouse, 1984)

8 Marbling Adipocytes Glucose is a premium grade energy source for a ruminant due to the fermentation in the rumen Glucose preferred source of carbon for marbling adipocytes; other cells that make up backfat can utilize acetate

9 G protein-coupled receptors (GPRs) GPR40, 41, 43, and 120 are activated by free fatty acids. These receptors appear to be important for normal adipocyte differentiation.

10 GPR43 in IMAT, SCAT and MUSCLE 1. Western Blot Total Protein Commassie Staining GAPDH Western Blotting 2. Real Time PCR GPR43 GAPDH 1.2 Relative GPR43 mrna level GPR43/GAPDH i.m. AT s.c. AT mus T Bovine Tissues IM SC MUS Bovine Tissues GPR43 membrane protein is highly distributed in IMAT and muscle tissues but not in SCAT Relative GPR43 mrna level was greater in IMAT than SCAT or MUSCLE Funded by The Beef Checkoff and ARF

11 Bovine Preadipocyte Culture IM preadipocytes SC preadipocytes Subculture Proliferation (10%FBS/DMEM) Confluence Harvest Cells Differentiation (5%FBS/DMEM with DMI) -4 Day O Day 4 Day Time Frame of Cell Culture

12 Cont Diff Cont Diff IM adipocyte SC adipocyte a b c Cont IM Diff Cont SC Diff P-AMPKα AMPKα d e f pampkα/ampkα a Cont a Diff IM SC a b Relative PPARγ mrna level c a Cont IM SC d b Diff Relative SCD mrna level a c Cont b Diff IM SC d Relative GPR43 mrna level Cont IM SC Diff Funded by The Beef Checkoff and ARF

13 A B GPR43 GAPDH Level of GPR43/GAPDH protein Subcutaneous adipocytes C C+ O1 O10 O100 SC IM a ab abc bcd O500 Con- Cont+ O1 O10 O100 O500 Treatments cde e C Relative GPR43 mrna level Intramuscular adipocytes C C+ O1 O10 O100 O500 6 IM (P=0.098) 5 SC Cont- Cont+ O1 O10 O100 O500 Treatments A. Oleic acid increased amount of GPR43 protein in intramuscular and subcutaneous adipocyte cultures in a dosedependent fashion. B. Oleic acid increased GPR43/GAPDH protein level more in intramuscular adipocytes than in subcutaneous adipocytes. C. Oleic acid increased GPR43 mrna in intramuscular adipocytes but not in subcutaneous adipocytes. Funded by the Beef Checkoff and ARF

14 Saturated fatty acids stimulate C/EBPß and SCD gene expression in a preadipocyte culture system Relative level of C/EBPβ mrna in intramuscular adipocyte Relative level of SCD mrna in intramuscular adipocyte CON C16:0 C18:0 C18:1 C18:2 0.0 CON C16:0 C18:0 C18:1 C18:2 Single Co Single Co

15 Marbling Development Ligands Glucose Ligands Glucose GPR43 Intramuscular Adipocytes Subcutaneous Adipocytes Study on the effect of fatty acids on different adipose depots Development of GPR43 ligands for enhancing marbling in the beef cattle.

16 Role of β-aa and GPRs in Muscle and IMAT Ractopamine Clenbuterol Cimaterol LCFA SCFA ICI-118,551 Zilpaterol β-ar GPRs Exogenous Ligands G β G γ G s AC G i G γ G β ATP camp Muscle Response Protein Synthesis PKA P ppka P Protein Degradation Adipose Tissue Response HSL, ATGL activation Lipogenesis Lipolysis

17 Pasture feeding depresses marbling. Pasture-fed for 8 mo Wagyu Cornfed for 16 mo USDA Select Corn feeding promotes marbling. Corn-fed for 6 mo Corn-fed for 8 mo Super Prime USDA Choice USDA Prime

18 Hypotheses The polyunsaturated fatty acids in pasture depress adipogenesis. Supplementing finishing diets with saturated fatty acids will stimulate adiposity and carcass quality. Dietary saturated fatty acids also will enhance the deposition of oleic acid by stimulating 9 desaturase activity.

19 Materials and Methods Control Finishing diet Palm oil 3% palm oil Soybean oil 3% soybean oil 9-10 steers/treatment for 10 wk Oils fed as top dressing

20 Fatty acid composition of the test diet oils TABLE 6 Fatty acid composition of fats 1 Fatty acids Fats Palm oil Soybean oil Corn oil 14: : : : : :2n :3n :4n ãcopyright The Paleo diet No diet was supplemented with corn oil, but its composition is included to indicate the fatty acid profile of the corn-based control diet.

21 Experimental design Carcass quality Maturity, Marbling score Quality grade, fat thickness Yield grade Lipid metabolism Lipogenesis from glucose and acetate in vitro Fatty acid profiles Cellularity Lipogenic enzyme activity G-6-PDH, 6-PGDH, NADP-MDH and FAS

22 Sampling lipogenesis cellularity s.c. adipose tissue Enzyme activity Fatty acid profiles

23 Materials and Methods For in vitro measurements, groups were subsampled, n = 6/d for 3 d. Samples were removed immediately after hide removal. Subcutaneous adipose tissue was incubated for 3 h with radiolabeled acetate plus glucose.

24 Neither carcass weight nor marbling score was significantly affected by dietary palm oil or soybean oil. Carcass data

25 Plasma palmitic acid was increased by dietary palm oil. Plasma stearic acid and trans-vaccenic decreased over time. This was due to decreases in ruminal fatty acid biohydrogenation.

26 All plasma monounsaturated fatty acids increased over time. The greatest increase in MUFA was in the control steers. The soybean oil diet delayed the increase in plasma MUFA.

27 Soybean oil increased plasma polyunsaturated fatty acids. Soybean oil is enriched with linoleic acid and linolenic acid.

28 The plasma palmitoleic:stearic acid ratio The plasma palmitoleic:stearic acid ratio is an index of hepatic 9 desaturase activity. This ratio was unchanged by supplementary oils.

29 Palm oil did not increase palmitic acid in adipose tissue. Fatty acid Control Palm oil Soybean oil P-value Palmitic Palmitoleic Stearic Oleic cis-vaccenic Linoleic a-linolenic trans-10,cis Palm oil tended to increase stearic acid and signficantly decreased a-linolenic acid and trans-10, cis-12 CLA.

30 The adipose tissue palmitoleic:stearic acid ratio was depressed by palm oil. This indicates that palm oil depressed 9 desaturase activity in adipose tissue. This is opposite to what we predicted.

31 Lipogenesis was greatest in s.c. adipose tissue from palm oil-fed steers. Adipose tissue from soybean oilfed steers had the lowest rates of lipogenesis. Glucose and acetate incorporation into total lipids

32 There were no differences in s.c. adipose tissue MDH or FAS synthase activities across treatment groups. NADP-malate dehydrogenase and fatty acid synthase enzyme activities

33 G-6-PDH activity was significantly higher in s.c. adipose tissue of palm oil-fed steers than in control steers. 6-Phosphogluconate dehydrogenase and glucose-6-phoshate enzyme activities

34 Palm oil did not significantly affect s.c. fat thickness, but s.c. adipocyte size was greatest in palm oil-fed steers. Subcutaneous fat thickness and adipocyte size

35 Conclusions We had predicted that dietary palm oil would stimulate adipogenesis. Palm oil stimulated in vitro lipogenesis and increased adipocyte volume. Carcass adiposity was increased slightly by dietary palm oil. Dietary soybean oil depressed all measures of adipogenesis. We also predicted that dietary palm oil would stimulate 9 desaturase activity. This was hypothesis appears to have been incorrect.

36 How does these studies apply to marbling in beef cattle? Dietary or endogenous oleic acid may increase marbling by promoting trans-differentiation of muscle satellite cells. a-linolenic acid in pastures may be causative in depressing marbling development. Increasing the supply of saturated fatty acids for absorption may promote adipogenesis and carcass quality.

37 Thank You! MEAT SCIENCE & MUSCLE BIOLOGY Striving for Honor in the Pursuit of Excellence