ENDO V Flashcards
A cells/α cells -
Glucagon
B cells/β cells -
Insulin
D cells/δ cells -
Somatostatin
F Cells –
Pancreatic Polypeptide
The pancreas
contains ~–
million islets of
Langerhans.
1-2
α cells and β
constitute about
–% of the cells in
the islets.
85
he majority of the
pancreas is composed of
Acinar Cells produce
Digestive Enzymes
Exocrine Portion
Insulin secretion is associated
with
energy abundance.
Insulin is composed of
two amino acid
chains, connected by disulfide
linkages.
When A & B chains are —,
functional activity of insulin
molecule is lost
split
The proinsulin and C peptide
have virtually
no insulin activity
Insulin circulates entirely in
unbound form. T1/2 =
6min
Formation of Insulin occurs in –
cells. It is first made as proinsulin.
β
In the Golgi, proinsulin is
cleaved to form
C
peptide and insulin
Incretins are
hormones produced by the digestive system that work to
stimulate insulin secretion BEFORE plasma glucose is elevated.
incretins include (2)
Glucagon-like Peptide-1 (GLP-1)
Glucose-dependent Insulinotropic Polypeptide (GIP).
The sulfonylurea receptor (SUR) receptor (KATP channel) is the binding site for some drugs that act as
insulin secretagogues (ex. Glimepiride/Amaryl) for treatment of type 2 Diabetes Mellitus.
Glucose is the key regulator of insulin secretion; glucose levels >-- mmol/L (70 mg/dL) stimulate insulin synthesis.
3.9
(5) also
influence insulin secretion.
Amino acids, ketones, various nutrients, gastrointestinal peptides, and neurotransmitters
Tyrosine Kinase-linked receptor
• Target cells responses: (3)
1. Fast (seconds): Increased glucose uptake, especially by muscle cells and adipocytes due to translocation of vesicles containing GLUT-4 to the membrane. The membrane also becomes more permeable to many amino acids along with potassium and phosphate ions.
- Slower (10-15 minutes): Change
in enzyme activity leading to
changes in metabolism. - Slowest (hours-days): Changes
in gene expression and growth.
Insulin promotes muscle glucose — and metabolism-
anabolic effect
uptake
– Resting muscle
membrane only
slightly
permeable to glucose
– Insulin stimulation
increases
glucose
transport
Effects of Insulin on Muscle
increase (2)
– Increases glycogen storage in skeletal muscle – Increases protein synthesis and inhibits protein degradation
Effect of Insulin on Protein Metabolism & Growth
Promotes — — and
Storage Inhibits — —
Protein Synthesis
Protein Degradation
Lack of insulin
causes protein
depletion &
increased
plasma amino
acids.
Insulin promotes the uptake and storage of
glucose (as
glycogen) by the liver
nsulin promotes the uptake and storage of glucose (as
glycogen) by the liver
Mechanisms: (3)
• increases glucose uptake (glucokinase)
• increase glycogen synthase lead to increased glycogen synthesis
• decrease breakdown of glycogen by inhibiting liver
phosphorylase
Insulin promotes conversion of excess glucose into
fatty
acids
insulin inhibits
gluconeogenesis
