Type 2 diabetes is also associated with an increase in glucagon
secretion, which is frequently forgotten, but which has
important consequences on hepatic glucose production both in
the postabsorptive and the postprandial states. Insulin resistance
is characterized by an overproduction of glucose by the
liver and a reduction of glucose utilization by skeletal muscle.
Insulin resistance results from a defect in insulin signalling
pathway in target tissues, secondarily to a dysfunction of adipose
tissue. Type 2 diabetes never occurs as long as pancreatic
β-cells are able to compensate for insulin resistance by an oversecretion
of insulin (prediabetic state). The passage from prediabetic
state to patent type 2 diabetes is characterized by three
major changes. The first one is a reduction of pancreatic β-cells
and of compensatory insulin secretion. It is not known whether
if this functional defect in β-cells is genetically programmed
and/or acquired (glucotoxicity and/or lipotoxicity). This transition
is crucial in the natural history of type 2 diabetes. The
second one is an overproduction of glucose by the liver, probably
secondarily to the oversecretion of glucagon, to an excessive
release of free fatty acids and adipocytokines by the adipose
tissue. The third one is an increase of insulin resistance in
skeletal muscles, frequently linked to the presence of obesity
and an excessive release of free fatty acids and adipocytokines.
The aim of the present chapter is to summarize the knowledge
of biochemical mechanisms responsible for the anomalies of
pancreatic hormone secretion and of insulin action and to try
to identify the cellular steps, which should be the basis for a
pharmacological approach for the treatment of type 2 diabetes
Type 2 diabetes is also associated with an increase in glucagon
secretion, which is frequently forgotten, but which has
important consequences on hepatic glucose production both in
the postabsorptive and the postprandial states. Insulin resistance
is characterized by an overproduction of glucose by the
liver and a reduction of glucose utilization by skeletal muscle.
Insulin resistance results from a defect in insulin signalling
pathway in target tissues, secondarily to a dysfunction of adipose
tissue. Type 2 diabetes never occurs as long as pancreatic
β-cells are able to compensate for insulin resistance by an oversecretion
of insulin (prediabetic state). The passage from prediabetic
state to patent type 2 diabetes is characterized by three
major changes. The first one is a reduction of pancreatic β-cells
and of compensatory insulin secretion. It is not known whether
if this functional defect in β-cells is genetically programmed
and/or acquired (glucotoxicity and/or lipotoxicity). This transition
is crucial in the natural history of type 2 diabetes. The
second one is an overproduction of glucose by the liver, probably
secondarily to the oversecretion of glucagon, to an excessive
release of free fatty acids and adipocytokines by the adipose
tissue. The third one is an increase of insulin resistance in
skeletal muscles, frequently linked to the presence of obesity
and an excessive release of free fatty acids and adipocytokines.
The aim of the present chapter is to summarize the knowledge
of biochemical mechanisms responsible for the anomalies of
pancreatic hormone secretion and of insulin action and to try
to identify the cellular steps, which should be the basis for a
pharmacological approach for the treatment of type 2 diabetes
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