Sharon TaySchool of Animal Biology

Sharon grew up in the city of Singapore where farms are almost non e istent She mo ed to Perth hen she as inalmost non-existent. She moved to Perth when she was in high school, and had her first taste of agriculture at a sheep

shearing demonstration. After completing a Molecular Biology degree at Murdoch University she did an honoursBiology degree at Murdoch University, she did an honours project which involved sequencing a gene associated with

skin and wool development, with the aim of identifying genetic markersgenetic markers.

Sharon was inducted into the world of agriculture when she was offered a PhD project investigating the effect of high-salt

diets during pregnancy in ewes and how this would affectdiets during pregnancy in ewes and how this would affect their offspring’s physiology. It is part of a national project

looking at innovative grazing systems that incorporate perennial plants that can provide the motivation and

Institute of

Agriculture

p p presources for improved agricultural landscapes.

Institute of

i lAgriculture

Physiology of lambs is altered by the high-salt y gy y gintake of their mothers during pregnancy

Sharon Tay

Institute of

Agriculture

Supervisors: Assoc/Prof Dominique Blache & Dr Dean Revell

A high-salt intake during pregnancy changed in the offspring:

• The ‘hardware’the number & size of functional units in the kidneykid ikidney size

• The ‘software’ that regulates salt balanceThe software that regulates salt balanceexpression of genes

hormonal control

Due to foetal programming

Institute of

Agriculture

Foetal Programming

• Maternal environment affects biology of offspringEg. nutrition

• Molecular mechanisms better understood

• My work - how high-salt intake programmes• My work - how high-salt intake programmes kidney function of the offspring

Why high-salt diets?Institute of

Agriculture

Why high-salt diets?

ProblemDryland salinityDryland salinity

M j bl i A t li• Major problem in Australia

• Affects ~1.8M Ha of land in WAarea increasing

• Affected areas turned intoAffected areas turned into wasteland

Institute of

Agriculture

Innovative solution

• Use saltbush (Atriplex spp.) to revegetate & regeneraterevegetate & regenerate

landscapes

• Food resource for livestockbut a high salt load (25%).… but a high salt load (25%)

• Capacity to excrete salt limits salt (& feed) intake

Saltbush in Yealering, WA

• Capacity to excrete salt limits salt (& feed) intakeenergy intake vs expenditure

affects animal productionInstitute of

Agriculture

affects animal production

Ewes consuming high-salt diet during pregnancy:

Did ff d i b• Did not affect reproduction but

H d ff t ff i• Had an effect on offspring

altered response to oral salt dose. i.e. l ti f lt/ t b lregulation of salt/water balance (Digby et al., 2009)

Ch d t h d d ft ?Change due to hardware and software?

Institute of

Agriculture

Programming of the hardware

Institute of

Agriculture

Nephron

• Structural & functional unit of kidneynephron

• Regulates concentration of water & soluble substances e g sodium salts

p

soluble substances e.g. sodium salts

• Functions regulated by hormones• Functions regulated by hormones (software)

• Control of blood pressure

Institute of

Agriculture

Glomerulus

• In the Bowman’s capsule glomerulusBlood enters via

renal arteryIn the Bowman s capsule

• Nephron’s initial filtering component

• Water, salts reabsorbed into bloodto maintain blood volumeto maintain blood volume

• Filters waste from blood & excreted &as urine ureter

Institute of

Agriculture

HypothesesH thHypothesesHypotheses

Feeding ewes a high salt diet during pregnancy:

• leads to histological changes in nephrons (kidney) of offspring

Effects observed in the young offspring persist into later life

Institute of

Agriculture

Experimental approach

Ewe fed control diet Ewe fed ‘salty’ dietEwe fed ‘salty’ dietEwe fed control diet during pregnancy

Ewe fed salty diet during pregnancy

Ewe fed salty diet during pregnancy

5 month old offspring

3 year old offspring

Institute of

Agriculture

HypothesesGl l b & i i l b

HypothesesGlomerular number & size in lambs

Glomerular number (per 10 transects)

Glomerular radius (µM)(per 10 transects) radius (µM)

Control offspring 185a 61a

High-salt offspring 154b 73b

~20% change

Institute of

Agriculture

HypothesesKid i h

HypothesesKidney weights

Lambs(g)

Adults(g)(g) (g)

Control offspring 122 175a

High-salt offspring 119 154b

10% decrease

Institute of

Agriculture

Programming of the software

Institute of

Agriculture

Renin Angiotensin System

A i t iRenin

Angiotensin I

Angiotensinogen

Angiotensin I-Converting Enzyme (ACE)

Angiotensin I

Angiotensin II

Vasopressin (antidiuretic hormone)Aldosterone

Sodium reabsorption & stimulation of thirst reflex

Water retention & stimulation of thirst reflexstimulation of thirst reflex stimulation of thirst reflex

Institute of

Agriculture

Regulation of water intake & urinary salt excretion

Renin Angiotensin System

A i t i* Renin

Angiotensin I

Angiotensinogen

salt

Angiotensin I-Converting Enzyme (ACE)

Angiotensin I

Angiotensin II

Vasopressin (antidiuretic hormone)* Aldosterone

Sodium reabsorption & stimulation of thirst reflex

Water retention & stimulation of thirst reflexstimulation of thirst reflex stimulation of thirst reflex

Institute of

Agriculture

Regulation of water intake & urinary salt excretion

HypothesesHypothesesHypothesesHypotheses

Feeding ewes a high salt diet during pregnancy:

• alters post natal expression of renin gene• alters post-natal expression of renin gene

• decreases plasma renin and aldosterone in offspring

Effects observed in the young offspring persist intoEffects observed in the young offspring persist into later life

Institute of

Agriculture

Experimental approach

Ewe fed control diet Ewe fed ‘salty’ dietEwe fed ‘salty’ dietEwe fed control diet during pregnancy

Ewe fed salty diet during pregnancy

Ewe fed salty diet during pregnancy

5 month old offspring

3 year old offspring

Institute of

Agriculture

R i iRenin gene expression

Institute of

Agriculture

R i iRenin gene expression

Lambs Adults

Control offspring 1.4a 1.2a

High-salt offspring 1.0b 0.5b

30-40% decrease

Institute of

Agriculture

Pl iPlasma renin

Lambs(ng/mL/hr)

Adults(ng/mL/hr)( g ) ( g )

Control offspring 10.0a 5.7a

High-salt offspring 8.0b 4.8b

15-20% decrease

Institute of

Agriculture

Plasma aldosteronePlasma aldosterone

Lambs(pg/mL)

Adults(pg/mL)

Control offspring 45a 12.6a

High-salt offspring 51b 15.5b

10-20% increase

Institute of

Agriculture

HypothesesDNA MethylationHypotheses• One of the mechanisms of foetal programming

• Changes gene expression but not DNA sequence

T T C G AT T A C G A C C

CHCH33CHCH33

AA AA TTTC C GGGG

CHCHCHCH

Institute of

Agriculture

CHCH33CHCH33

DNA methylation-kidneyDNA methylation kidney

Lambs(% methylation)

Adults(% methylation)

Control offspring 3.3a 2.5a

High-salt offspring 4.8b 3.7b

30-35% increase

Institute of

Agriculture

Experimental approachEwe fed control diet during pregnancy

Ewe fed ‘salty’ diet during pregnancy

Ewe fed ‘salty’ diet during pregnancyduring pregnancy during pregnancyduring pregnancy

5 month old offspring

3 year old offspring3 year old offspring

Dietary salt challenge

Institute of

Agriculture

Urinary sodium excretion adultsUrinary sodium excretion - adults

Control diet(g/day)

High-salt diet(g/day)(g y) (g y)

Control offspring 4 59

High-salt offspring 4 55

Institute of

Agriculture

Summary:

Foetal programming by high salt intake of:

y

• nephrogenesis in offspring

• regulation of renin-angiotensin system

• So, profound changes in soft and hardware for lifep g

But, no effect on offspring’s capacity to excrete saltBut, no effect on offspring s capacity to excrete salt

Are high salt offspring more metabolically efficient?Institute of

Agriculture

Are high salt offspring more metabolically efficient?

Practical consequences

• saltbush offspring fared better when grazed saltbush as adultsas adults

increased weight gain

increased fleece weight(Chadwick et al 2009)(Chadwick et al., 2009)

• long term animal performance?

metabolic efficiency

f t l i t t l?Institute of

Agriculture

foetal programming as a management tool?

Acknowledgements

Dr Dean Revell & Assoc/Prof Dominique BlacheDr Dean Revell & Assoc/Prof Dominique Blache

UWA School of Animal BiologyUWA School of Animal Biology

CSIRO Li t k I d t iCSIRO Livestock Industries

Future Farm Industries CRC

Institute of

Agriculture

Practical consequences

• saltbush offspring fared better when grazed saltbush as adultsas adults

increased weight gain

increased fleece weight(Chadwick et al 2009)(Chadwick et al., 2009)

• long term animal performance?

metabolic efficiency

f t l i t t l?Institute of

Agriculture

foetal programming as a management tool?