الفهرس 
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Abstract
Fructose consumption has increased in the last three decades, especially as a
sweetener in carbonated beverages. Long term fructose intake adversely affected several
metabolic parameters resulting in IR. IR is one important feature of metabolic syndrome
that might account for renal injury.
The purpose of the present study is to evaluate the level of osteopontin as a marker of
kidney function in a rat model of insulin resistance, with and without metformin treatment.
It also aimed at gaining information about the histological changes occurring in kidneys of
all studied groups.
The present study included 70 male adult albino rats weighing 100–120 g. They were
classified into 7 groups, each group containing 10 rats:
Group I: Control animals (C) received the control diet and tap water ad libitum.
Group II: Control animals received the control diet and tap water ad libitum for
four weeks. Metformin was administered during the third and fourth
weeks of the experimental period (CM).
Group III: Fructose drinking rats (F) received the control diet and 10 % fructose
solution for four weeks.
Group IV: Fructose drinking rats received the control diet and 10 % fructose
solution for four weeks. Metformin was given during the third and
fourth weeks (FM).
Group V: Control animals received the control diet and tap water ad libitum for
eight weeks. Metformin was administered during the fifth, sixth,
seventh and eighth weeks of the experimental period (CM).
Group VI: Fructose drinking rats (F) received the control diet and 10 % fructose
solution for eight weeks.
Group VII: Fructose drinking rats received the control diet and 10 % fructose
solution for eight weeks. Metformin was given during the fifth, sixth,
seventh and eighth weeks (FM).
At the end of four and eight weeks of experiment, rats were deprived of food and
placed in individual metabolic cages for a 24-h urine collection for assaying urine
creatinine levels. Animals were then weighed and anesthetized with ether. 5 ml of blood
were taken from each rat by cardiopuncture. The blood samples were centrifuged after
clotting at 4000 r.p.m for 15 minutes and the serum was separated for assaying fasting
glucose, creatinine and urea nitrogen. The remaining serum was divided into several
aliquots and stored at – 20 °C for assaying fasting insulin and osteopontin using ELISA
technique. After collecting the blood, each rat was dissected and the kidneys were
immediately removed, blotted, weighed and fixed in 10 % neutral formalin for histological
processing. The insulin resistance and insulin sensitivity were assessed by HOMA-IR score
Summary
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and QUICKI respectively. Creatinine clearance was determined and expressed per gram of
kidney weight.
At the end of four weeks of experiment, the data showed a marked increase in serum
levels of insulin without a significant change in blood glucose levels, elevated HOMA-IR
index and lower insulin sensitivity (QUICKI).
Administration of rats with longer duration of fructose in drinking water for eight
weeks, leads to insulin resistance as demonstrated by hyperglycemia, hyperinsulinemia,
elevated IR index and lower insulin sensitivity (QUICKI).
Two weeks treatment of fructose drinking rats (FDR) with metformin eliminated
hyperinsulinemia without affecting the normal serum glucose levels. At the end of eight
weeks experiment, metformin was able to improve fasting hyperglycemia, significantly
declined hyperinsulinemia, greatly improved elevated HOMA-IR index and increased
insulin sensitivity (QUICKI).
Serum creatinine values in FDR after four weeks of experiment were found to be
within the normal range and not affected by the fructose sugar. However prolonged
administration of fructose for eight weeks, revealed a significant elevation in serum levels
of creatinine than normal control level. Metformin did not show any effect on serum
creatinine levels at eight weeks of experiment.
Creatinine clearance levels in FDR at four and eight weeks experiment were found to
be statistically higher than that in control group. Metformin treatment improved creatinine
clearance levels significantly at four week experiment and insignificantly at eight week
experiment.
It was found that BUN is significantly higher in both fructose drinking rats groups
compared to normal control group. After metformin treatment, the levels of BUN in both
FDR groups were declined and become within the normal range.
The present study revealed that OPN serum levels in FDR at the end of four weeks
experiment was significantly higher than control group. Moreover, the levels of this
parameter become more obvious with longer duration of fructose administration in
drinking water for eight weeks. It is of interest to notice that OPN level is not affected by
metformin treatment for two weeks, whereas at four weeks of treatment, this parameter
was highly significantly increased.
In this study, it is of interest to compare the diagnostic value of serum OPN with
those of BUN and serum creatinine. This comparison was carried out using the ROC curve
analysis in such a way that the greater area under the curve (AUC), corresponds to a better
diagnostic test. Serum OPN showed the greater AUC (93.5%) followed by BUN (84.8%)
then serum creatinine (79.0%). The sensitivity, specificity and cutoff value for diagnosing
CKD in FDR-induced IR were 90.0%, 100.0 %, 49.308 ng/ml for OPN, 85.0%, 80 %,
19.4 mg/dl for BUN and 85.0%, 70.0 %, 0.68 mg/dl for creatinine. These results led us to
predict that the cytokine OPN is superior to BUN and serum creatinine respectively, and
can be used as a sensitive and specific biomarker for early detection of renal injury.