Intrauterine Growth Retardation in Livestock:Implications, Mechanisms, and Solutions

Guoyao Wu

Departments of Animal ScienceTexas A&M University

College Station, TX 77843, USA

E mail: g wu@tamu eduE-mail: g-wu@tamu.edu

I. REGULATION OF FETAL GROWTHAND DEVELOPMENT

--- Fetal growth and development is regulated by genetics, epigenetics,maternal maturity, and environmental factors (e.g., nutrition).

--- IUGR is defined as impaired growth and development of the mammalian embryo/fetus or its organs during pregnancy.

Wu et al. J Anim Sci 84: 2316-2337, 2006

DNA methylationHistone methylation & acetylationHistone methylation & acetylation

Genes of Epigenetic E i t lGenes of both parents

Epigeneticstate

Environmentalfactors

(nutrition, stressdisease & toxins)disease & toxins)Maternal

maturity

Placental growth(including placental angiogenesis

d l th)and vascular growth)

Transfer of nutrients from mother to fetus

Fetal growthWu et al. J Anim Sci 84: 2316-2337, 2006

IUGR in Livestock SpeciesIUGR in Livestock Species

Naturally occurring IUGR(e g litter-bearing animals)(e.g., litter-bearing animals)

Environmentally-induced IUGR(e g over- and undernutrition heat(e.g., over- and undernutrition, heat stress, disease, and toxins)

Production-imposed uterine pinsufficiency (e.g., twining through reproductive technologies and early breeding at 70-80% of mature BW)breeding at 70 80% of mature BW)

Wu et al. J Anim Sci 84: 2316-2337, 2006.

Uterine Insufficiency and IUGRy

When an embryo is transferred from a genetically larger mother to a recipient dam with a lower uterine capacity.

IUGR

When an embryo is transferred from a genetically smaller motherWhen an embryo is transferred from a genetically smaller mother to a recipient dam with a higher uterine capacity.

↑ Growth

Wu et al. J Anim Sci 84: 2316-2337, 2006

Experimentally-induced undernutritionExperimentally-induced undernutrition

Well-controlled experimental studies have demonstrated that maternal undernutrition during the peri-breeding or gestation period reduces fetal growth in animals (sheep, cows, pigs, and horses).

Undernutrition IUGR

Available evidence shows that prenatal growth of all species is sensitive to maternal nutrition at all stages between oocytesensitive to maternal nutrition at all stages between oocyte maturation and birth.

Wu et al. J Anim Sci 84: 2316-2337, 2006

Overnutrition and IUGR

Increasing energy and protein intake during a short period of time (termed “flushing”) around conception can increase the number of(termed flushing ) around conception can increase the number of embryos/fetuses, but often results in increased porcine embryo and fetal mortality.

IUGRIUGR Lamb

Obese Sheep

Overconditioning of cows during the dry period still occurs on many farms, particularly among high-producing herds.

Wu et al. J Anim Sci 84: 2316-2337, 2006

Overnutrition and IUGR

Overfeeding during all or part of the gestation has a detrimental effect on pregnancy outcomes in animals, including sheep, cows, pigs and horsespigs, and horses.

Overnutrition IUGR

Wu et al. J Anim Sci 84: 2316-2337, 2006

II. IMPLICATIONS OF IUGR FOR ANIMAL AGRICULTUREAGRICULTURE

Body and tissue composition↑Whole-body and intramuscular fat mass↑Whole body and intramuscular fat mass↑ Connective tissue content↓ Skeletal muscle fiber number↓ Skeletal muscle fiber number↓ Meat quality (in animal science)

Cardiovascular disorders↑ C h t di↑ Coronary heart disease ↑ Hypertension ↓ E d th li l f ti↓ Endothelial function

Wu et al. J Anim Sci 84: 2316-2337, 2006.

Postnatal Growth↓ Whole-body and skeletal muscle growth rates↓ Efficiency of nutrient utilization↓ Athletic performance

Hormonal imbalance↑ Plasma levels of glucocorticoids and renin↑ Plasma levels of glucocorticoids and renin ↓ Plasma levels of thyroid hormones and anabolic hormones

(e.g., insulin, growth hormone, and IGF-I)( g , , g , )

Wu G. et al. J Nutr 134: 2169-2172, 2004.

Metabolic disordersMetabolic disorders

Insulin resistanceβ C ll d f tiβ-Cell dysfunctionDyslipidemiaGlucose intoleranceImpaired energy homeostasisObesityType-II diabetes

Glucose

FatCO2yp

Oxidative stressMitochondrial dysfunction

Fat

Barker DJP and Clark PM. Rev Reprod 2: 105-112, 1997.

Neonatal mortality, health and adjustmenty, j

↑ Stillbirths (In humans, IUGR is responsible for ~50% of non-malformed tillbi th )stillbirths.)

↑Morbidity and mortality (In livestock, most IUGR neonates die in the↑Morbidity and mortality (In livestock, most IUGR neonates die in thefirst wk of life. Infants < 2.5 kg at birth have perinatal mortality rates that are 5 to 30 times higher than those with average birth weights, while infants < 1 5 kg have rates that are 70 to 100 times higher )while infants < 1.5 kg have rates that are 70 to 100 times higher.)

↓ Adjustment to the extrauterine life ↓ j

McMillen IC and Robinson JS. Physiol Rev 85: 571-633, 2005.

Organ dysfunction and abnormal development

TestesOvaries IUGR ↓ M lti l S tBrainHeartSkeletal muscle

IUGR ↓ Multiple Systems

Skeletal muscleLiverThymusSmall intestineSmall intestineWool folliclesMammary gland

Wu G. et al. J Nutr 134: 2169-2172, 2004.

Fetal programmingFetal programming

The intrauterine environment of the conceptus (e.g., fetal nutritionand endocrine status) may alter expression of the fetal genome andhave life-long consequences. This phenomenon is termed “fetalhave life long consequences. This phenomenon is termed fetal programming”.

StructureEndocrine

GrowthDevelopment

MetabolismPhysiology

HealthDisease

III. MECHANISMS OF IUGR

Placental growth and uteroplacental blood flows

The placenta is the organ that transports nutrients, respiratory gases, and the products of metabolism between maternal and fetal circulationand the products of metabolism between maternal and fetal circulation.

Placental growth (including vascular growth) is crucial for fetal growthand developmentand development.

Mother Fetus

PlacentaPlacenta

Reynolds et al. J Physiol 572: 51-58, 2006.

Uteroplacental blood flow is a major factor that influences theUteroplacental blood flow is a major factor that influences the availability of nutrients for fetal growth and development.

Mother FetusUMV

Placenta

UMA

Placenta

Fetal nutrient uptake = (UMV-UMA) x Blood flow

Available evidence from well-controlled studies shows that

Fetal nutrient uptake = (UMV-UMA) x Blood flow

impaired placental growth is associated with IUGR.

UMV umbilical vein; UMA umbilical arteryUMV, umbilical vein; UMA, umbilical artery.

Rates of uteroplacental blood flows depend, in large part,p p g pon placental vascular growth, which results fromangiogenesis (the growth of new vessels from existing

) d l t l l i tiones) and placental vascularization.

Placental growth

Placental vascularizationUteroplacental blood flows

Placental vascularization

Reynolds et al. J Physiol 572: 51-58, 2006.

Impaired placental blood flow in IUGR

Insufficient uteroplacental blood flows and reduced transportactivity in natural uterine insufficiency.

Both undernutrition of adult ewes and overnutrition of adolescent ewes during pregnancy reduced placental proliferation and placental expression of angiogenic factors.

Wallace at al. J Physiol 565: 19-26, 2005.

Arginine

NO

Placental PlacentalPlacental vascular growth

Placentalblood flow

Nutrient transfer

from motherfrom mother to fetus

Wu et al. J Nutr 134: 2169-2172, 2004.

Arginine in porcine allantoic fluidg e po c e a a to c u d

5 Arginine Ornithine Glutamine

3

4

5

/L

g

1

2

3

mm

ol/

0

1

30 35 40 45 60 90 11030 35 0 5 60 90 0

Day of Pregnancy

Wu et al. Biol Reprod 54: 1261-1265, 1996.

Arginine in ovine allantoic fluidg e o e a a to c u d

8

10Arginine Ornithine Citrulline

4

6

8

mol

/L

0

2

4mm

030 40 60 80 100 120 140

Day of PregnancyDay of Pregnancy

Kwon et al. Biol Reprod 68: 1813-1820, 2003.

I i d NO th i i IUGRImpaired NO synthesis in IUGR

Evidence from studies with pregnant pigs and sheep indicatesimpaired syntheses of NO and polyamines in the conceptusesof underfed and overfed dams.

Maternal undernutrition impairs NO-dependent vasodilation andincreases arterial blood pressure in the ovine fetus.

Kwon et al. Biol Reprod 71: 901-908, 2004.

HypothesisHypothesis

Impaired placental syntheses of NO and polyaminesfrom arginine may provide a unified explanation for thesame pregnancy outcome (IUGR) in response to bothsame pregnancy outcome (IUGR) in response to bothundernutrition and overnutrition.

Wu et al. J Nutr 134: 2169-2172, 2004.

Citrulline ProlineGln

Arginine Ornithine

Citrulline ProlineGln

Arginase

AS-AL PO-OAT

Arginine Ornithine

BH4 NOS

NO

SAM

Polyamines

ODC

NO PolyaminesLeucineGlucose

Embryogenesis Placental growthmTORsignaling

ArginineGlutamine

Placental-fetal blood flow

Nutrient and O supplies from mother to fetusNutrient and O2 supplies from mother to fetus

Fetal growth and development

Wu et al. J Anim Sci 84: 2316-2337, 2006.

IV MECHANISMS OF FETAL PROGRAMMINGIV. MECHANISMS OF FETAL PROGRAMMING

Genomic imprinting: Parental influence on the genome of progeny.

Maternal or fetal nutritional status can alter the epigenetic state of the fetal genome and expression of imprinted genes (eg, Igf2 and H19).

(Igf2 is paternally expressed and maternally silent, whereas H19 is paternally silent and preferentially expressed from the maternal allele.)p y p y p )

I i dNutrition Imprinted genes

Two mechanisms mediating epigenetic effects

1) DNA methylation1) DNA methylation(occurring in 5’-positions of cytosine residues within CpG dinucleotides throughout the mammalian genome).

DNA Methylase

SAM SAHM

CH3-DNA Genomic imprinting

2) Histone modification(acetylation and methylation)(acetylation and methylation)

Histone Acetylase Actyl-Histone Genomic imprintingAcetyl-CoA CoA

Jaenisch R and Bird A. Nature Genet 33 (Suppl.) 245-254, 2003.

CpG methylation can regulate gene expression by modulating the binding of methyl-sensitive DNA-binding proteins. This affectsbinding of methyl sensitive DNA binding proteins. This affects regional chromatin conformation.

Histone acetylation or methylation can alter the positioning of histone-DNA interactions and the affinity of histone binding to DNA. This affects gene expression.

Jaenisch R and Bird A. Nature Genet 33 (Suppl.) 245-254, 2003.

DihydrofolateFolic Acid

NADPH+H+

NADP+

NADPH+H+ NADP+

THF

Gly

Ser

B6

MethionineHis

Glu

5,10-MTFDNA

y

B12

5-FTFGlu

H+

NH3

5-MTF

MTHFNADPH+H+

NADP+Homocysteine

FAD

Homocysteine

Wu et al. J Anim Sci 84: 2316-2337, 2006.

Protein Methylthioadenosine

Mg-ATP Mg-PPi+Pi DCAM

SPD + SPM

Putrescine

Methionine

Mg ATP Mg PPi Pi

S-Adenosylmethionine

DimethyleGA DNA

Dimethyle-glycine

Betaine Choline

Creatine CH3-DNA

Homocysteine S-AdenosylhomocysteineHomocysteine S Adenosylhomocysteine

Wu et al. J Anim Sci 84: 2316-2337, 2006.

V POTENTIAL SOLUTIONS TOV. POTENTIAL SOLUTIONS TO PREVENTING IUGR

Hormone therapy (Progesterone and placental lactogen)

Dietary supplementation with energy and/or proteinconcentratesconcentrates

Adequate nutritional support for immature pregnant damsAdequate nutritional support for immature pregnant dams

Provision of antioxidant nutrients

Manipulations of the arginine-NO/polyamine pathway

Wu et al. J Anim Sci 84: 2316-2337, 2006.

Standard Diet for Gestating Gilts and Sows(Corn- and Soybean Meal-Based)

Crude Protein: 12% Di tibl E 3 400 k l/k di tDigestible Energy: 3,400 kcal/kg dietFeed Intake: 2 kg/day

NRC 1998.

Dietary L-Arginine Supplementation Enhanced Fetal Growth in Pigs

ArginineAlanine* P=0.10

1412

141618

g

* ** **

** P<0.03

8

10

12

lets 8

10

12

Pigl

ets

10121416

kg

* **

2

4

6Pigl

2

4

6T

otal

2468k

0Total Piglets Born

0Total Piglets Born Alive

02

Ave. Litter Weight

Gilts (n = 53) were fed a corn- and soybean meal-based diet supplemented with 1% L-arginine-HCl or isonitrogenous L-alanine between Days 30 and 114 of gestation.

Mateo et al. (2007) J. Nutr. 137: 652-656.

Viagra Administration Enhanced Fetal Growth In Both Adequately-Fed and Underfed Ewes

0 mg Viagra 75 mg Viagra 150 mg Viagra

q y

66.5

y 11

2

0 mg Viagra 75 mg Viagra 150 mg Viagra

a

aba-b: P < 0.05

55.5

6bs

) at D

ay abb

aab

b

44.5

wei

ght (

lb b

33.5

100% NRC 50% NRC

Feta

l

100% NRC 50% NRC

Between Days 28 and 112 of gestation, ewes were fed diets providing 100 or 50% NRC nutrient requirements and received i.m. administration of Viagra (0, 25 or 50 mg) three q g ( , g)times daily. Fetal weight was measured at Day 112.

Satterfield C, FW Bazer, TE Spencer & G Wu (2007)

Intravenous Arginine Infusion Increased Fetal Growth in Underfed Ewes

A B

g

200

250

ol/m

l)

789

10

lbs)

aa

aa

b

a-b: P < 0.05 a-b: P < 0.05

100

150

ma

Arg

(nm

o

34567

rth

wei

ght (

b

0

50

100% NRC 50% NRC 50% NRC +

Plas

m

012

100% NRC 50% NRC 50% NRC +

Bir

Arginine Arginine

Beginning at Day 60 of gestation, underfed ewes received i.v. infusion of 0 or 27 mg L-arginineper kg body wt three times daily until Day 147 (term). Birth weight at term was measured.

Lassala A, FW Bazer & TE Spencer & G Wu (2007)

Prolific ewes (Booroola Rambouillet ewes)

IUGR model: ewes gestating multiple fetusesIUGR model: ewes gestating multiple fetuses

Bi th i ht f l b f t i t i l t d d l tBirth weights of lambs from twin, triplet and quadruplet pregnancies from control and arginine infused ewes

Birth weight (Kg)(Kg)

Group Twins Triplets Quadruplets

Control 4 30 ± 0 38a 3 06 ± 0 17b 2 47 ± 0 22cControl 4.30 ± 0.38 3.06 ± 0.17 2.47 ± 0.22

Arginine 4.11 ± 0.21a 3.39 ± 0.22b 3.03 ± 0.14bg

Lassala A, FW Bazer & TE Spencer & G Wu (2008)

CONCLUSION

Fetal growth is controlled by complex interactions among genetic, g y p g g ,epigenetic, and environmental factors, as well as maternal maturity.

These factors regulate placental growth (including placentalThese factors regulate placental growth (including placental angiogenesis and vascular growth) and, therefore, utero-placental blood flows and the transfer of nutrients from mother to fetus.

IUGR results from disturbances of these maternal and fetal homeostatic mechanisms. It has important implications for both h h lth d i l i lthuman health and animal agriculture.

Modulating the arginine-NO pathway may provide an effectivemeans to prevent and treat IUGR in humans and livestock.

ACKNOWLEDGMENTS

Grant support: NIH Pfizer Texas A&M University and USDAGrant support: NIH, Pfizer, Texas A&M University, and USDA.

Colleagues: Drs. Fuller Bazer, Tim Cudd, Steve Ford, Laurie Jaeger, G J h D ll K b S Ki C thiGreg Johnson, Darrell Knabe, Sungwoo Kim, Cynthia Meininger, Tom Spencer, Troy Ott, and Wenbin Tuo.

Assistants: Graduate Students, Postdoc Fellows, and Technicians