COMPARISON OF THE EFFECT OF MATERNAL HYPOTHYROIDISM ON CARBOHYDRATE METABOLISM IN YOUNG AND AGED MALE OFFSPRING IN RATS.

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Narges Karbalaee*,Saleh Zahediasl, Asghar Ghasemi, Farzaneh Faraji Shahrivar

Endocrine Research Center, Research Institute for Endocrine Sciences, Shaheed Beheshti University of Medical Sciences,

Tehran, Iran

IntroductionCritical periods of development (Composite data are from rodents and humans)

Introduction (cont.)Causes and consequences of intrauterine programming

Introduction (cont.)

Hyperlipidemia

Reproductive disorders

Insulin resistance

Hypertension

adulthood

Ischaemic heart disease

Renal failure Intrauterine growth

retardation

Glucose intolerance

Type 2 diabetes

Obstructive pulmonary disease

Introduction (cont.)

CNS

Metabolic Activities in Most Tissue

Cardiovascular

Hemodynamic

Reproductive system

Liver function

Immune System

Growth and

Development

There are evidences that maternal hormonal status markedly influence intra-uterine growth and developmen

Introduction (cont.)

Thyroid hormones act as metabolic and maturational signals, any changes in the levels of these hormones in uterus alters fetal development and has long term consequences for cardiovascular, reproductive,and metabolic function.

There is a relationship between serum thyroid hormone levels and diabetes risk and also various abnormalities in carbohydrate metabolism occur in patients with thyroid disease. So abnormalities in carbohydrate metabolism may take place in fetal hypothyroidism.

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Aim

This study aims to assess the glucose tolerance and insulin secretion capacity of islets in young and aged male offspring of mothers who were hypothyroid during pregnancy.

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Materials & MethodsAnimals and study design

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Pregnant femaleWistar rats

ControlPregnant rats consumed tap

water during gestation

Fetal HypothyroidPregnant rats received water containing 0.02 % of PTU

during gestation

Male offspring (3 and 12 month)

Delivery

Mother and Offspring (Blood)

Thyroid hormones (T3, T4) Assessed for

Male and female Wistar rats were crossed for 24 h

Material and Methods

Intravenous Glucose Tolerance Test (IVGTT) In young and old male offsprings, after over night fasting (12 h), IVGTT

was carried out by intravenous infusion of 50% glucose (0.5 g/kg body weight)

The plasma glucose and insulin levels of rats were assayed at 0, 5,10,15, 20, 30, and 60 minutes after an intravenous glucose load.

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Material and Methods

Glucose-stimulated insulin secretion (GSIS) ASSAY Islet isolation Incubation with different glucose concentrations (5.6, 8.3, 16.7 mM) ( 60

min, 37°C ,95 % O 2 / 5 % CO 2 ) Collection of supernatant for insulin determination

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Materials & Methods (cont.)

Measurements Weight

Plasma T3 & T4(ELISA kits )

Plasma Glucose concentration(glucose oxidase method )

Plasma Insulin concentration(ELISA method )

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Results

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Table I. Plasma T3 and T4 concentration in the fetal hypothyroid of control groups at birth and adulthood (3 and 12 months ), and their mothers at the time of delivery.

  

Offspring Mothers

At the time of birth Adulthood3 months 12 months

At the time of delivery

Hormones Control(n=10)

Fetal hypothyroid

(n=9)

Control(n=15)

Fetal hypothyroid

(n=15)

Control(n=7)

Fetalhypothyroid

(n=8)

Control(n=12)

Hypothyroid(n=12)

Triiodothyronine

(T 3 , ng /dl)

 69.1 ± 3.3

 40.1 ± 5.5**

 98.8 ± 4.03

 85.86 ± 5.6

 85.4 ±

3.3

 98.5 ± 7.0

 98.03 ± 5.7

 49.5 ± 4.9***

 Thyroxine

(T 4 , µg /dl) 

0.98 ± .07 

0.44 ± .06*

 3.5 ± 0.1

 3.3 ± 0.1

 

 2.5±0.08

 2.9 ± 0.2

 2.3 ± 0.3

 0.34 ± 0.03***

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Values are means ± SEM. * p< 0.05, *** p<0.0001 and *** p<0.0001 Significant difference compared to controls 

 

Table II. Effect of hypothyroid during pregnancy on reproductive performance.

Parameter (units) Control group FH group

Gestation length (day) 21.7 ± 0.2 22.8 ± 0.3

Percent maternal weight gain (%) a

49.2± 1.8 44.7 ± 2.0

Litter size 10.2±0.8 9.6±0.4

Offspring mortality rate (%) 10.8 43.7***

Birth weight (gr) b 6.0±0.0 4.6±0.1***

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a Percent weight gain relative to the weight on day 1 of pregnancy. Day 1 weight in all groups ranged from 180-220 g.bAll pups in a litter were weighed and the average pup weight of a litter computed and reported as a single point. This was done for all litters in a group and the mean of these points is reported as the group mean in the table. Values are means ± SEM. * p< 0.05 and *** p<0.001 Significantly from control

Body weight in control and Fetal hypothyroid (FH) male offspring rats. Values are mean ± SE ; n=14.

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Plasma glucose and insulin cocentrations and their AUC during intravenous glucose tolerance test in the young ( a , c n = 11) and old ( b , d n = 12) rats of fetal hypothyroid and control groups. Values are mean ± SE.

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Comparison of the islets insulin secretion in the fetal hypothyroid and control groups in old ( a) and young (b) rats. Values are means ± SE

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Conclusions

The results of this study have shown that maternal hypothyroid during pregnancy leads to: Intrauterine growth restriction in rat fetuses

Glucose intolerance and lower insulin secretion capacity in their adult off spring particularly in aged animals.

From the results of this study we can conclude that carbohydrate metabolism in the offspring of fetal hypothyroid subjects is a matter of concern particularly in the old ages.

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Definition of term `programming‘

A stimulus or insult during a critical or sensitive period of development can have long-term or lifetime effects on an organism’, as well as with the ‘predictive adaptive response’ . (Holness ,2000; Hales and Barker (2001 Lucas A, 2000; Gluckman PD,,2006)

Disturbance in the metabolic intrauterine environment alters the development of the endocrine pancreas and the insulin sensitive tissues.

lPerturbed nutritional and hormona environment are responsible for the altered β-cell mass.

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Diagram illustrating the relationships between nutritional state, hormone concentrations, metabolism and tissue accretion and differentiation in the fetus. (A L Fowden and A J Forhead(2004)