Presentation Notes on Insulin Resistance in type 2 diabetes with
symptoms & Treatment, metabolic syndrome in children, men & women for
medical & Biology students in word / .doc / ppt format
Insulin
Resistance:
Insulin resistance is
defined as resistance to the effects of insulin on glucose uptake, metabolism,
or storage. Insulin resistance is a characteristic feature of most patients
with type 2 diabetes and is an almost universal finding in diabetic individuals
who are obese. The role of insulin resistance in the pathogenesis of type 2
diabetes can be gauged from the finding that
(1) insulin resistance
is often detected 10 to 20 years before the onset of diabetes in predisposed
individuals (e.g., offspring of type 2 diabetics) and
(2) in prospective
studies, insulin resistance is the best predictor for subsequent progression to
diabetes.
Insulin resistance leads
to decreased uptake of glucose in muscle an adipose tissues and an inability of
the hormone to suppress hepatic gluconeogenesis.
Genetic
Defects of the Insulin Receptor and Insulin Signaling Pathway :
Loss of function
abnormalities of either the insulin receptor or its downstream intermediates
are obvious candidates for mediating insulin resistance in type 2 diabetes. In
mice, tissue specific knockout of genes encoding various insulin signaling
proteins has resulted in insulin resistance, hyperinsulinemia and
hyperglycemia, recapitulating human type 2 diabetes. Unfortunately, the
extrapolation of these single gene
knockout models to human disease has been less than gratifying. Point mutations
of the insulin receptor are relatively rare, accounting for no more than 1% to
5% of patients with insulin resistance.
Analysis of candidate
genes involved in insulin secretion or insulin action, as well as whole genome
linkage studies of affected families, have yielded many polymorphisms that
associate with the type 2 diabetic phenotype, but in most cases, the
associations have been weak, or the studies were not reproducible .From these
analyses, it appears that while the population risk associated with any particular
genetic variant (polymorphism) may be significant, the increased risk for
developing diabetes for a given individual harboring that variant is small at
best.
Obesity
and Insulin Resistance :
The association of
obesity with type 2 diabetes has been recognized for decades, visceral obesity
being a common phenomenon in the majority of type 2 diabetics. The link between
obesity and diabetes is mediated via effects on insulin resistance. Insulin
resistance is present even in simple obesity unaccompanied by hyperglycemia,
indicating a fundamental abnormality of insulin signaling in states of fatty
excess. The risk for diabetes increases as the body mass index (a measure of
body fat content) increases. It is not only the absolute amount but also the
distribution of body fat that has an effect on insulin sensitivity . Central
obesity (abdominal fat) is more likely to be linked with insulin resistance
than are peripheral (gluteal / subcutaneous) fat depots.
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