>Magister Scientiae - MSc / The incidence of type 2 diabetes (T2D) is persistently increasing globally. T2D is associated
with pancreatic β cell dysfunction and insulin resistance in peripheral tissues such as the liver
and skeletal muscle. Skeletal muscle is the major site for insulin stimulated glucose uptake.
Maintenance on a gestational high fat diet may programme insulin resistance. Programming
is induced by the exposure of organisms to either a stimulus or insult during foetal and/or
early neonatal life and alters offspring physiology and metabolism. The aim of the present
study was therefore to investigate the effects of maternal diets, varying in fat content, on
neonatal hepatic and skeletal muscle gene (mRNA) and protein (immunoreactivity)
expression of proximal insulin signalling factors: insulin receptor alpha (IRα), insulin
receptor substrate 2 (IRS2) and phosphoinositide 3-kinase-p110 alpha (PI3K-p110α), and to
assess the therapeutic potential of Aspalathus linearis extract after high fat programming.
Pregnant rats were randomised into groups maintained on diets with varying fat proportions:
10% (control), 20% (20F), 30% (30F) and 40% (40F) fat as energy throughout gestation.
Neonatal liver and skeletal muscle were collected to determine the proximal insulin signalling
expression profiles of the target factors: IRα, IRS2 and PI3K-p110α. Quantitative polymerase
chain reaction (qPCR) was applied to determine mRNA expression of these target insulin
signalling factors. Immunostaining of the target proteins in the liver and skeletal muscle was
performed followed by relative quantification with image analysis software. Further,
Aspalathus linearis (Al) extract was orally administered to mothers during gestation in the
10% (Control-Al) and 40% (HFD-Al) diets at a dose of 150 mg/kg. Body weight, food intake
and blood glucose concentrations were monitored throughout gestation in mothers.
Maternal diets, varying in the percentage of fat content, showed no significant effect on
neonatal hepatic IR and IRS2 mRNA expression. However, hepatic PI3K mRNA expression
was elevated in 30F neonates compared to 20F neonates. Skeletal muscle IR and PI3K
mRNA expression were reduced in the 30F and 40F neonates compared to 20F neonates.
There was reduced hepatic IRα immunoreactivity in 40F neonates compared to control and
20F neonates. Further, skeletal muscle IRα immunoreactivity was significantly reduced in
30F and 40F neonates compared to control neonates. Therefore foetal high fat programming reduced IRα in both the liver and skeletal muscle which may impair proximal insulin
signalling in these glucose recipient organs. Aspalathus linearis had no effect on maternal
serum insulin and glucagon concentrations. In addition, maternal caloric intake, body weight
and organ weights (liver, brain and pancreas) were not altered amongst the groups. Further,
HFD-Al neonates were heavier than control neonates. In conclusion, Aspalathus linearis, at a
dose of 150 mg/kg, had neither harmful nor ameliorative effects in pregnant mothers fed high
fat diet during gestation. In addition, Aspalathus linearis treatment had no ameliorative
effects on neonates from mothers fed high fat diet throughout gestation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uwc/oai:etd.uwc.ac.za:11394/4311 |
| Date | January 2013 |
| Creators | Ndlovu, Zibele |
| Contributors | Syce, James, Cerf, Marlon E. |
| Publisher | University of the Western Cape |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of the Western Cape |
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