Optimizing Nutritional Strategies to Promote Growth in Newborns

Teresa A. Davis, Ph.D.

Professor of Pediatrics

USDA/ARS Children’s Nutrition Research Center,

Baylor College of Medicine, Houston, TX

Disclosure Statement

Affiliation/Financial Interest Organization

Editor-in-Chief The Journal of Nutrition

Board of Directors American Society of Animal Science

Research Funding NIH 5R01HD072891

NIH 9R01HD085573

USDA NIFA 2013-67015-20438

USDA CRIS 6250-51000-055

Abbott Nutrition

LOW BIRTH WEIGHT INFANTS

• 10% Births in U.S. and 15-20% worldwide

• LBW = <2500 g or <5.5 pounds

• Most are born preterm = <37 weeks gestation

• Preterm birth is leading cause of child death

Optimizing the nutritional management of LBW infants is crucial for their immediate and long-term health

• Most are extrauterine growth restricted and small at hospital discharge

• Adverse long-term developmental outcomes are incurred

• Cognitive deficit

• Motor impairment

• Altered body composition – high fat to lean body mass ratio

• Obesity, insulin resistance, Type 2 diabetes

• Metabolic syndrome, cardiovascular disease

LOW BIRTH WEIGHT

INFANTS

• Extrauterine growth restriction of LBW infants is frequently due to our inability to provide adequate nutrition

• Initially fed total parenteral nutrition (TPN) due to intolerance to oral feeds

• Advanced gradually from TPN to enteral feeding

LOW BIRTH WEIGHT

INFANTS

Orogastric Tube Feeding

Bolus Continuous

?Which feeding pattern is more beneficial for promoting lean growth in infants is unknown

Pulsatile pattern ofhormones and substrates

Low, constant level of hormones and substrates

Neonatal Piglet Model• To identify new strategies to optimize the nutritional

management and improve the growth of low birth weight infants

• Ethical considerations limit human infant studies

• Anatomy and metabolism similar to infants

• Body size enables many experimental approaches

o repeated sampling

o tracer kinetics

o feeding modality

Feeding Stimulates Muscle Protein Synthesis by Eliciting a Rise in Circulating Insulin and Amino Acids that Activate Insulin and Amino Acid Signaling Pathways

Food

Insulin Amino Acids

Muscle Protein Synthesis

PI3-K

PDK

PKB

IRS-1

FoodInsulin

PAT-1SNAT-2

Amino Acids AA

Gln

Gln

LeuLAT-1

Gln

Gln

Na+

Na+

Rag A-D

mTORC1

eIF4E • eIF4G

eIF4E • 4EBP1

AAAAA

60S

40S

Met-tRNA

Initiation Elongation Termination

Protein Synthesis

Newly synthesized proteineIF2

eIF2B

eEF2 kinase

eEF2

S6K1

rpS6

Rheb

PRAS40

FKBP38

mTORGβLRaptor

PAT-1

Leu

PTEN

PTP1B

TSC1

TSC2

Insulin Receptor

AMPK

AA

AA

Insulin and Amino Acid Signaling Pathways that Regulate Protein Synthesis

mRNA

60S

40S

mRNA

Ragulator

Is bolus feeding more beneficial than continuous feeding because it activates the signaling components that

regulate protein synthesis?

Question

• Neonatal pigs

• Gastric tube for 24 h

• Formula (240 mL•kg-1 BW•d-1)

0 4 8 12 16 20 24Hours

Continuous 10 mL•kg-1 BW•h-1

Bolus 40 mL•kg-1 BW

q4h

Methods

0

200

400

600

800

1000

1200

0 4 8 12 16 20 24

nmol•mL

-1

Hours

µU•m

L-1

0

20

40

60

80

0 4 8 12 16 20 24Hours

Intermittent

Continuous

tinuousMeal

Amino AcidsInsulinBolus

Gazzaneo et al, J Nutr,

141: 2152, 2011.%/d

Continuous Bolus

0

5

10

15

20

25

30

35

AU

Continuous Bolus

0

0.5

1.0

1.5

2.0* *

Translation initiation Protein synthesis

Bolus Feeding Compared to Continuous Feeding

Increases Lean Growth

0 3 6 9 12 15 18 21

0

2

3

4

5

6

Bolus

Continuous

. B

od

y w

eig

ht,

kg

Days

**

*

**

0

1

2

3

Lean m

ass,

kg

Body weight Lean gain

*

Continuous Bolus

Conclusion:Orogastric Tube Feeding

Bolus Continuous

Pulsatile pattern ofamino acids & insulin

Low, constant level of amino acids & insulin

Activates amino acid & insulin signaling pathways

Mutes amino acid & insulin signaling pathways

Stimulates protein synthesis Blunts protein synthesis

Increases lean growth Restricts lean growth

Perspectives

Intermittent bolus feeding is the preferable feeding method to enhance lean growth during

gastric tube feeding.

• Some low birth weight infants must be fed continuously because of meal feeding intolerance.

• Can strategies be developed to improve the growth of infants who must be continuously fed?

Leucine• Essential amino acid

• Signaling molecule that stimulates intracellular signaling pathways that regulate protein synthesis

• Primary driver of the increase in protein synthesis in skeletal muscle after a meal

*

0

5

10

15

20

Pro

tein

syn

the

sis

(%

/da

y)

Control Leu Ile Val

Leucine Is a Primary Driver of the Rapid Increase in Protein Synthesis after a Meal

24

0

6

12

18 *

eIF

4Ge

IF4

E(A

U)

Translation Initiation

Control Leu Ile Val

Escobar et al, J Nutr 140:1418, 2010.

Protein Synthesis

Can pulsatile delivery of a leucine supplement during continuous feeding enhance lean growth

by mimicing the pulse of leucine that occurs after a meal?

Methods

CONT + alanine

CONT + leucine

• Neonatal pigs, 2.3± 0.1 kg

• Continuous infusion of formula by orogastric tube for 21 d (10 mL•kg-1 BW•h-1)

• Parenterally pulsed with leucine (800 μmol•kg-1 BW•h-1) or alanine (isonitrogenous control) at 4 h intervals

Control Leucine

Pulse

0.0

0.4

0.8

1.2

1.6*

Le

an

ga

in (

kg)

Pulses of leucine during continuous feeding for 21 days increased lean growth

Continuous Feeding in Days

0 3 6 9 12 15 18 210.0

2.0

3.0

4.0

Control

Leucine pulse*

Bo

dy w

eig

ht

(kg)

Fat gain

Control Leucine

Pulse

0.0

0.1

0.2

*

Fa

t ga

in (

kg)

Lean GainBody Weight

Boutry et al, Am J Physiol, 310: E699, 2016.

LD

Control Leucine

We

igh

t (g

)

a

b

Gastrocnemius

Leucine pulses increased muscle weight

0

20

40

60

We

igh

t (g

)

Control Leucine

a

b

0

1

2

3

4

Control Leucine

a

b

We

igh

t (g

)

Soleus

Boutry et al, Am J Physiol, 310: E699, 2016.

SoleusLD

Pro

tein

Syn

thesis

(%

.d-1

)

Gastrocnemius

Leucine pulses increased muscle protein synthesis

Control Leucine

Pro

tein

Syn

thesis

(%

.d-1

)

Control Leucine

Pro

tein

Syn

thesis

(%

.d-1

)

Control Leucine

a

b

0

2

4

6

8

10

0

2

4

6

8 a

b

0

2

4

6

8

10

a

b

Boutry et al, Am J Physiol, 310: E699, 2016.

Leucine pulses increased the activation of translation

initiation factors

0.0

0.4

0.8

1.2

S6

K1 P

ho

sp

ho

ryla

tio

n (

AU

)

Control Leucine

4E

BP

1 P

ho

sp

ho

ryla

tio

n (

AU

)

Control Leucine

eIF

4G

•eIF

4E

Co

mp

lex

(A

U)

Control Leucine

a

b

a

b

a

b

0.0

0.5

1.0

1.5

2.0

0.0

0.5

1.0

1.5

Boutry et al, Am J Physiol, 310: E699, 2016.

Conclusions• Pulsatile delivery of a leucine supplement during

continuous enteral feeding in neonates activates the translation initiation pathway that increases protein synthesis in skeletal muscle.

• This stimulatory effect of leucine supplementation on muscle protein synthesis leads to an increase in lean growth.

Can supplementation with leucine metabolites enhance protein synthesis in the

neonate?

Nissen et al, J Nutr 130:1937, 2000.

Leucine

Branched Chain Amino Acid Transferase

α-Ketoglutarate

Glutamate

Alanine

GlutaminePyruvate

α-Ketoisocaproate (KIC)

O2

CO2Urine

(10-40%)

HMB-CoA

HMG-CoA

MC-CoA

MG-CoA

Mevalonate

Cholesterol Acetoacetyl-CoA

Branched Chain α-ketoacid

Dehydrogenase (mitochondria)Isovaleryl-CoA

β-methyl-crotonyl-CoA

(MC-CoA)

Enol-CoA hydrase

(when biotin is deficient)

Isovaleryl-CoA

dehydrogenase

β-methyl-gluconyl-CoA

(MG-CoA)

β-hydroxy-β-methylglutaryl-CoA

(HMG-CoA)

Acetyl-CoA Acetoacetate

MC-CoA carboxylaseCO2

Biotin

MG-CoA lyase

(liver)

H2O

CO2CO2

HMG-CoA reductase

HMG-CoA synthase

KIC-dioxygenase (cytosol)CO2

β-Hydroxy-

β-Methylbutyrate

(HMB)

QuestionCan supplementation with the leucine metabolite, β-

hydroxy-β-methylbutyrate (HMB), stimulate protein

synthesis in neonates?

HMB may promote lean gain and strength in adults.

Methods• Treatment groups (n = 7-9/treatment; 5-7 d-old):

1) Fasted (F)

2) Low Protein Diet (LP)

3) Low Protein Diet + HMB 4 µmol/kg/day (HMB-4)

4) Low Protein Diet + HMB 40 µmol/kg/day (HMB-40)

5) Low Protein Diet + HMB 80 µmol/kg/day (HMB-80)

6) High Protein Diet (HP)

• Gastric tube feeding every 4 hours for 24 hours

HMB Increases the Activation of Regulators of Translation Initiation in Skeletal Muscle

Association of eIF4E with eIF4G

Kao et al, Am J Physiol, 310:E1072, 2016.

Enteral HMB Supplementation Increases Muscle Protein Synthesis

Kao et al, Am J Physiol, 310:E1072, 2016.

myofibril

Neonatemature myofiber

Adult

satellite cell division

protein accretion

myonuclear accretion

protein synthesis

Perinatal Muscle Growth

Hypertrophy

Kao et al, Am J Physiol, 310:E1072, 2016.

HMB Supplementation Stimulates Satellite Cell Proliferation in Muscle

CONCLUSIONS

Enteral HMB supplementation in neonatal piglets:

• Increases skeletal muscle protein synthesis by enhancing the activation of translation initiation via the mTOR pathway

• Increases satellite cell proliferation

Perspectives

Supplementation with leucine or its metabolite, HMB may be useful adjuncts to the nutritional management of

LBW infants to promote their growth.

Thank you!