Metabolic Disorders: Milk Fat Depression

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Metabolic DisordersMilk Fat Depression
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Enzymes Involved in Milk Fat Synthesis and
Secretion
Secretion
Translocation
Synthesis
Circulation
LPL
FABP
GPAT
UFA
DGAT
SCD
VLDL TAG
TAG synthesis
SFA (C16 - C18)
NEFA
FABP
Glycerol Glucose
Glycerol Glucose
Acetate ßHBA
FA synthesis de novo (C4 - C16)
ACC
FAS
Basal membrane
ER- membrane
Apical membrane
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Milk Fat DepressionHistorical Perspective
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Milk Fat Depression and forage to concentrate
ratio
Volatile fatty acids (VFA) produced in the rumen
Acetic Acid
Butyric Acid
Milk production and composition
What is the origin of milk fat depression?
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Jean Baptiste BOUSSINGAULT1802-1887 First to
describe milk fat depression Cows fed beets had
reduced milk fat and he attributed the MFD to low
fat content of beets
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New York Worlds Fair 1939

• Fed pelleted forage on the rotolactor
• Plan was scrapped when MFD was induced
• Powel showed feeding high grain or an all
  pelleted diet induced MFD

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Theories regarding milk fat depression

• Acetate deficiency
• Low acetate propionate ratio is not due to lower
  acetate, but rather an higher amount of
  propionate.
• Vitamin B12 deficiency
• Ruminal synthesis of vit. B12 is low under high
  grain diet. Vit B12 is required for propionate
  metabolism in the liver and elongation of fatty
  acid chains with acetic acid or
  b-hydroxy-butyrate (BHBA) in milk fat synthesis.
  
• Insulin and suppression of fat mobilization
• Hormonal messages, with high amount of propionate
  and possibly glucose absorption in the lower
  intestine eliciting an insulin response which
  tend to inhibit fat mobilization and the
  availability of ketones for fatty acids synthesis
  in the udder.
• Inhibition of the de novo synthesis of short and
  medium chain of fatty acids in the mammary gland
  by trans fatty acids (TFA).
• TFA are produced during ruminal hydrogenation of
  polyunsaturated fat supplements (vegetable oils)

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b-hydroxy butyrate Theory

• Van Soest and Allen 1959
• Theorized lack of BHBA was the cause of MFD
• Propionate inhibits CPT1
• Decreased ketone synthesis

• Palmquest et al. 1969
• Fed a high grain low roughage diet.
• BHBA levels unaltered in MFD
• BHBA contributes max 8 of milk fat carbons
• BHBA is not a factor in milk fat depression.

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Vitamin B12 Theory

• Frobish and Davis 1977
• High concentrate diets reduce Vit B12 rumen
  production
• Required for propionate metabolism into TCA cycle
• Deficiency results in build up of
  methylmalonyl-CoA.
• Methylmalonyl-Co exits the liver and decreases
  ACC and FAS in the mammary gland
• Croom et al. 1981
• Intramuscular injections of B12 resulted in no
  improvement of MFD

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• Energy partitioning between adipose and milk fat
• MFD diets will energetically increase adipose
  tissue accretion
• Insulin-glucogenic theory
• Increases propionate and reduces acetate
  production
• Increases glucose synthesis
• Increases insulin secretion
• Increases glucose uptake by adipose tissue, but
  not mammary gland
• Increases NADPH synthesis in adipose tissue
• Increases fatty acid synthesis in adipose tissue,
  making less acetate available for mammary gland
• Now believed that insulin plays a minor role in
  milk fat depression

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Trans Fatty Acid Theory

• Davis and Brown 1970
• Noted an increase in C181 mostly due to
  trans-C181 in MFD
• Rindsig and Shultz 1974
• No response when feeding 25 g of trans-9-C181.
• Selener and Shultz 1980
• MFD feeding 500g hydrogenated vegetable
  shortening.
• Gayor et al. 1994, Romo et al. 1996 showed
  similar results

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Conjugated Linoleic Acids (CLA)

• Many isomers (n24) found in ruminant food
  products
• C182 cis-9, trans- 11
• C182 trans-7, cis-9
• C182 trans-10, cis-12
• C182 cis-8, trans-10
• CLA has been shown to
• Anti-carcinogenic
• Anti-atherogenic
• Anti-diabetic
• Enhanced immune system
• Reduces severity of cachexia
• Alleviates symptoms of lupus
• Improved bone mineralization
• Alters lipid metabolism

c9, t11 CLA
t10, c12 CLA
c9, c12 C182
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Milk Fat CLA

• Due to the potential health benefits and because
  CLA is naturally found in dairy products
• Early work focused on
• Increasing CLA content in bovine milk (avg. 6
  mg/g)
• Identifying sources of variation (3 30 mg/g)
• Determining composition of milk fat CLA isomers
• In attempt to enhance milk fat CLA it was
  serendipitously discovered that exogenous CLA
  severely reduces milk fat synthesis (Chouinard et
  al., 1998)

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Serendipitous Discover?
Chouinard et al., 1998
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Which CLA Isomer is Responsible?

• CLA supplements contained many isomers
• Predominantly cis-9, trans-11 and trans-10,
  cis-12 CLA
• Diet-induced low milk fat content is associated
  with specific trans C181 isomer
• Low milk fat is a financial problem in the dairy
  industry as milk is frequently priced based on
  milk fat content
• Low milk fat is a phenomenon that has been
  troubling dairy scientists for over 150 years

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Change in rumen pH
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Milk Fat Response to trans-10, cis-12 CLA
Cows are eating 50 kg/d
Dose (g/d)
Baumgard et al., 2001 J. Nutr.
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trans-10, cis-12 CLA Dose Response
Baumgard et al., 2001 Peterson et al., 2002
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Conjugated Fatty Acids Milk Fat Synthesis
Active reduces milk fat synthesis
Inactive has no effect

• 182 cis-9, trans-11
• 182 trans-8, cis-10
• 182 cis-11, trans-13
• 182 trans-9, trans-11
• 183 cis-6, trans-10, cis-12
• 183 cis-6, trans-8, cis-12

• 182 trans-10, cis-12
• 182 trans-9, cis-11

Baumgard et al., 2000, 2002 Perfield et al.,
2004, 2005 Saebo et al., 2005
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CLA and Lactation in Other Species

• Feeding CLA supplements decrease milk fat
  synthesis in
• Nursing women
• Concern with neonatal energy intake
• Pigs
• Sheep
• Rodents

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Effective CLA Dose Body Fat vs. Lactation
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Identifying and Ruling Out Potential Mechanisms
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Baumgard et al., 2000, 2001, 2002 Mackle et al.,
2003
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Effect of trans-10, cis-12 CLA (10 g/d) on Fatty
Acid Composition
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4
1
2
Milk Fat Yield
-5
-18
-26
-45
Baumgard et al., 2000 Am. J. Phys.
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Effect of trans-10, cis-12 CLA on Milk Fatty Acid
Composition
Decrease in Milk Fat Yield (mmol)
Milk Fat Yield
-33
-25
-50
Baumgard et al., 2001 J. Nutr.
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Enzymes Involved in Milk Fat Synthesis and
Secretion
Secretion
Translocation
Synthesis
Circulation
LPL
FABP
GPAT
UFA
DGAT
SCD
VLDL TAG
TAG synthesis
SFA (C16 - C18)
NEFA
FABP
Glycerol Glucose
Glycerol Glucose
Acetate ßHBA
FA synthesis de novo (C4 - C16)
ACC
FAS
Basal membrane
ER- membrane
Apical membrane
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Effect of trans-10, cis-12 CLA on Metabolic Flux
Rates and Lipogenic Gene Expression
b
b
a
a
CO2
b
b
b
a
a
a
mRNA expression
Baumgard et al., 2002
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trans-10, cis-12 CLA and Mammary Triglyceride
Synthesis and Fatty Acid Transport
b
b
a
a
b
b
a
a
Baumgard et al., 2002
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trans-10, cis-12 CLA (48 h) Reduces Lipogenesis
in MAC-T Cells
Lipogenesis assessed by 14C-acetate incorporation
into total lipid
Peterson et al., 2004, J. Nutr. 1342523
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Bovine Mammary Cells 75 uM trans-10, cis-12 CLA
(48 h)
mRNA
Peterson et al., 2004 J. Nutr. 1342523
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Knowns Unknowns

• After 5 d, CLA decreases expression genes
  responsible for all aspects of milk fat synthesis
• Via a global common coordinator?
• I.e. PPAR, SREBP etc.?
• Or does CLA effect a specific gene and the
  effects on other genes are subsequent of/or lack
  of downstream feedback?
• I.e. ACC or the rate limiting enzyme

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Enzymes Involved in Milk Fat Synthesis and
Secretion
Secretion
Translocation
Synthesis
Circulation
LPL
FABP
GPAT
UFA
DGAT
SCD
VLDL TAG
TAG synthesis
SFA (C16 - C18)
NEFA
FABP
Glycerol Glucose
Glycerol Glucose
Acetate ßHBA
FA synthesis de novo (C4 - C16)
ACC
FAS
Basal membrane
ER- membrane
Apical membrane
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Temporal pattern of trans-10, cis 12 CLA in milk
fat
Mammary Biopsy
Mammary Biopsy
Kay and Baumgard, unpub
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Effect of trans-10, cis-12 CLA on Gene
Expression
12 hrs
24 hrs
72 hrs
Kay Baumgard unpubl
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Common Coordination

• Central coordinator of lipid gene expression?
• PPAR
• SREBP
• HNF
• NF?B

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Potential cellular and molecular mechanisms
Belury, 2002
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Sterol Response Element Binding Protein (SREBP)
Target Genes

• Fatty Acid/TG-Related
• Acetyl CoA carboxylase (ACC)
• Fatty acid synthase (FAS)
• Stearoyl CoA desaturase (SCD)
• Glycerol-P acyltransferase (GPAT)
• Lipoprotein lipase (LPL)
• Acyl CoA binding protein
• Acetyl CoA synthetase

• Cholesterol-Related
• LDL receptor
• HMG CoA reductase
• HMG CoA synthase
• Farnesyl di-P synthase
• Squalene synthase

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Bovine Mammary Cells 75 uM trans-10, cis-12 CLA
(48 h)
mRNA
Peterson et al., 2004 J. Nutr. 1342523
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SREBP-1 Activation in Bovine Mammary Cells
BSA
10,12
BSA
10,12
Control
CLA
Control
CLA
125
kDa
125
kDa
Membrane
-
Bound
Membrane
-
Bound
Precursor
Precursor
Percent of
Percent of
121
121
100
100
BSA Control
BSA Control
68
kDa
Mature
68
kDa
Mature
Nuclear Fragment
Nuclear Fragment
Percent of
Percent of
100
a
74
b
100
a
74
b
BSA Control
BSA Control
Peterson et al., 2004, J. Nutr. 1342523
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Summary

• trans-10, cis-12 CLA markedly reduces milk fat
  synthesis
• cis-9, trans-11 CLA has little or no effect on
  mammary lipid metabolism
• Effects most aspects of mammary lipid synthesis
  but especially pronounced on de novo fatty acid
  synthesis
• Little or no effect on systemic bioenergetic or
  metabolic indices
• Molecular events may be mediated by CLA ability
  to reduce SREBP activation

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CLA Effects on Milk Yield ?

• Preliminary evidence suggest that severe
  CLA-induced MFD causes a reduction in milk yield.
• References
• Chouinard et al., 1998
• Mackle et al., 2002
• Bell and Kennelly, 2003
• Kay et al., 2004
• Odens and Baumgard, unpublished

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CLA Pasture Transition Trial Milk Fat Content
and Milk Yield
Kay et al., 2004
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Decrease in Milk Fat Content vs. Change in Milk
Yield1
1RP-CLA compared to HYPRO
Kay et al., 2004
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CLA Effects on Fat Content
Mackle et al. 2002
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CLA Effects on Milk Yield
Kg/d
g CLA-60/d
Milk yield
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8
3
Mackle et al. 2002
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CLA-Induced Severe MFD Effects on Milk
Synthesis
Bell Kennelly, 2003
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Step-wise CLA Delivery

• Objective Maintain positive milk yield response
  as lactation progresses and mammary gland becomes
  more sensitive to CLA
• How Utilize a high CLA dose for the first 10
  days postpartum, then ½ the dose thereafter

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Milk Fat Content
000 g/d
000 g/d
600 g/d
300 g/d
600 g/d
600 g/d
Odens Baumgard, unpubl.
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Milk Yield
Odens Baumgard, unpubl.
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Overall Summary

• Little or no effect on mammary protein and
  carbohydrate metabolism
• CLA reduces milk fat synthesis in pigs, rodents,
  sheep and women
• Mammary gland lipid metabolism is much more
  sensitive ( 20 x) to CLA than adipose lipid
  metabolism

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Overall Summary Cont

• Effects of CLA are specific to the mammary gland,
  little or no effect to systemic physiology
• Reduces expression of most (if not all) genes
  responsible for milk fat synthesis
• Genes appear to be governed by a common
  coordinator
• Severe CLA induced MFD reduces milk synthesis

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Acknowledgements and Collaborators
The University of Arizona

• Dr. Dale Bauman
• Debbie Dwyer
• Dr. Ben Corl
• Jim Perfield
• Dr. Adam Lock
• Dr. Dan Peterson
• Dr. Elvina Matitashvili

• Sara Sanders
• Chel Moore
• Laura Odens
• Shannon Baker
• Dr. Rob Rhoads
• Dr. Shelly Rhoads

• Dexcel/Fontera
• Dr. Tim Mackle
• Dr. Eric Kolver
• Dr. John Roche
• Norm Thomson

• Travel Expenses
• NZSAP
• ISAT