full issue - Association of Biotechnology and Pharmacy

Current Trends in Biotechnology and Pharmacy
Vol. 5 (3) 1338 -1345 July 2011, ISSN 0973-8916 (Print), 2230-7303 (Online)
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in the blood so that the brain, muscle and red
blood cells have sufficient glucose to meet their
metabolic demands. Gluconeogenesis is often
associated with ketosis. Gluconeogenesis is also
a target of therapy for type II diabetes, such as
metformin, which inhibits glucose formation and
stimulates glucose uptake by cells (2).
During the development of drugs and
formulations (3) intended for oral administration,
it is of considerable value to have reliable and
predictive in vitro methods to quantify drug
transport across the intestinal epithelium. Several
in vitro models are available to determine
permeability, such as human Colon Carcinoma
(Caco-2) cells, Madin Darby Canine Kidney
(MDCK) cells, Immobilized Artificial
Membrane (IAM) columns, Parallel Artificial
Membrane Permeation Assay (PAMPA), excised
animal tissues in using chambers and everted gut
sacs.
The everted gut sac model, especially the
improved technique offers advantages as it is
easy and inexpensive to perform and offers the
possibility of conducting regional and
mechanistic studies. The everted gut sac of the
rat small intestine can be used to determine
various aspects of drug absorption with high
reliability and reproducibility in early stages of
drug discovery. It was suggested that fasting
intestine contributes in two ways to maintain
blood glucose level, directly by absorbing more
glucose and indirectly by providing lactate and
alanine (4). In catheterized rat model, portal vein
draining the gut did not show any increase in the
substrates of gluconeogenesis (5). An increase
in the content of gluconeogenic enzymes and
glucose transporter levels in the rat intestine after
prolonged fasting was observed (6). Glucose-6-
phosphatase gene is expressed in the small
intestine of rats and humans and that it is induced
in insulinopenic states such as fasting and
diabetes (7). In the small intestine, glutamine and,
Gajalakshmi et al
to a much lesser extent, glycerol is the precursor
of glucose, whereas alanine and lactate are the
main precursors in liver. A recent report
suggested that glucose-6-phosphatase and
Phosphoenolpyruvate carboxykinase genes are
expressed in rat small intestine and are strongly
induced in fasted and diabetic states (8, 9). This
contributes to 20–25% of systemic endogenous
glucose production in insulinopenic rats. In
addition, glucose production in small intestine
may be suppressed by insulin. This identifies
small intestine as a new insulin-sensitive tissue.
Recent work has clearly indicated that glucose
uptake and lactic acid output by the everted
jejunal sacs of 4 days fasted rats was significantly
increased indicating that the glycolytic pathway
of metabolism was enhanced (10). However, the
provision of intestinal substrates for hepatic
gluconeogenesis is less documented and hence
this lacuna forms the focus of this study.
Materials and Methods
The study was approved by the
Institute’s Animal Ethical Committee and the
Committee for the Purpose of Control and
Supervision of Experiments on Animals
(CPCSEA). Healthy adult male Swiss albino rats
weighing about 180- 200g have been used for
this study and allowed to have food and water
ad libitum. Fasting rats were deprived of food
for 4 and 6 days before experiments and were
allowed to have free access to water only.
Animals were divided into three groups, each
group consisting of six animals. Group 1 serves
as control animals, Group 2 as 4 days fasted
animals and Group 3 acts as 6 days fasted
animals.
Surgical procedure: On the day of experiment,
rats were sacrificed by cervical dislocation. The
abdomen was opened by a midline incision. The
entire small intestine was removed quickly by
cutting across the upper end of the duodenum
and the lower end of the ileum, and by stripping