The Role of Glucokinase in NonInsulinDependent Type 2 Diabetes

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The Role of Glucokinase in Non-Insulin-Dependent
(Type 2) Diabetes
Presenter Beth Prentice
Slosberg E, Desai U, Fanelli B, St. Denny B,
Connelly S, Kaleko M, Boettcher B, Caplan S.
2001. Treatment of type 2 diabetes by
adenoviral-mediated overexpression of the
glucokinase regulatory protein. Diabetes
501813-20.
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Presentation Outline

• INTRODUCTION
• Types of Diabetes
• Understanding Type 2 Diabetes
• Symptoms and Complications
• Treatment for Type 2 Diabetes
• Patient Self-Care
• PRIMARY ARTICLE - RESEARCH/DATA
• What is glucokinase (GK)? GKRP?
• Treatment of Type 2 Diabetes by
  Adenoviral-Mediated Overexpression of the
  Glucokinase Regulating Proteins
• CONCLUSION
• Summary

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Types of Diabetes
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Two primary types of diabetes affecting 16
million people in the United States
Type 1 diabetes (insulin-dependent diabetes
mellitus) accounts for of those affected

• Type 2 diabetes (non-insulin-dependent diabetes
  mellitus) accounts for
• of those affected

10
90
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Type 1 diabetes insulin production stops

• Insulin helps glucose (sugar) move into cells,
  where it is used to produce energy
• Without insulin, glucose cannot enter the cells
• Cells quickly waste away from lack of glucose

INSULIN
INSULIN
CELL
INSULIN
CELL
CELL
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Type 2 diabetes insulin production and
effectiveness are impaired

• Insulin helps glucose move into cells, where it
  is used to produce energy
• If not enough insulin is produced (insulin
  deficiency), not enough glucose can move into
  cells
• When insulin is not used properly (insulin
  resistance), cells do not respond by taking in
  glucose
• Cells slowly waste away from lack of glucose

INSULIN
INSULIN
CELL
INSULIN
INSULIN
CELL
INSULIN
CELL
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Understanding Type 2 Diabetes
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Normally, the body regulates blood glucose levels
by removing excess glucose after a meal...

• Ingested carbohydrates are metabolized into
  glucose and absorbed into the blood, causing high
  blood sugar (hyperglycemia)

The pancreas produces and secretes insulin, which
helps move glucose into cells
Blood glucose levels return to normal
Muscle, fat, and liver cells take up glucose from
the blood
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and releasing stored glucose back into the blood
between meals

• Gastrointestinal
• tract is empty glucose must be supplied by the
  body for energy

The pancreas produces and secretes glucagon,
stimulating the liver to release the glucose
stored during meals
The liver releases glucose in response to low
blood sugar (hypoglycemia)
Blood glucose levels return to normal
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Normally, the body keeps glucose levels from
rising too high...
Too High
Normal
Too Low

• Carbohydrates, metabolized into glucose, are
  absorbed into the blood

Blood glucose increases to higher than normal
levels (hypergly-cemia)
The pancreas secretes insulin, helping uptake of
glucose by muscle, fat, and liver cells
Glucose moves quickly out of the blood into the
cells
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and falling too low
Too High
Normal
Too Low
Gastrointestinal tract is empty glucose must be
supplied by the body
Blood glucose decreases to lower than normal
levels (hypogly-cemia)
The pancreas secretes glucagon, stimulating the
liver to release glucose
Glucose is released from the liver into the blood
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Type 2 diabetes evolves from 2 primary defects
insulin deficiency and insulin resistance
Progression of untreated type 2 diabetes

• Glucose is absorbed into the blood, causing
  hyperglycemia

Pancreatic dysfunction leads to insulin deficiency
Muscle, liver, and fat cells develop insulin
resistance
Blood glucose levels remain high
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With type 2 diabetes, glucose levels stay high
for a longer time...
Too High
Normal
Too Low
Carbohydrates are metabolized into glucose and
absorbed into the blood
Muscle, fat, and liver cells are insulin
resistant glucose stays in the blood
Due to an increase in blood glucose
concentration, the liver produces glucose
Because it moves slowly into the cells, glucose
levels stay high for longer than normal
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and fall more slowly
Too High
Normal
Too Low
Hyperinsulinemia results from a release of too
much insulin in response to glucose levels that
remain high from the previous meal
Movement of glucose out of the blood into cells
eventually outpaces the release of glucose from
the liver
Gastro-intestinal tract is empty glucose is
supplied by the liver
Glucose levels do not return to normal
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Symptoms and Complications
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Early symptoms are unpleasant...

• Excessive eating (polyphagia) and drinking
  (polydipsia)

Excessive urination (polyuria)
Dramatic weight changes (sudden loss or excessive
gain)
Genital itching and infections in women
impotence in men
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and can be significant

• Blurred vision

Weakness, tiredness, or dizziness inability to
concentrate loss of coordination loss of
consciousness
Slow-healing cuts or sores frequent skin and
urinary tract infections
Nausea and vomiting
Numbness or tingling in hands or feet
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Later complications can be quite serious...
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and can often be life threatening

• Myocardial infarction, congestive heart failure,
  hypertension

Peripheral vascular disease, stroke
Kidney disease (nephropathy)
Gangrene and amputations
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Treatment for Type 2 Diabetes
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Patients nutrition therapy is an essential part
of total diabetes care

• Restrict caloric intake (by 250 to 500 calories
  per day)

Limit salt intake (lt3000 mg sodium per day)
Limit fat intake (total fat lt30 of total
calories saturated fat lt10 of total calories)
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Increased physical activity is vital to diabetes
management

• Physical activity (such as walking) may improve
  insulin sensitivity

Physical activity can lower blood glucose to
normal levels
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Drug therapy is needed in addition when diet and
physical activity fail to correct hyperglycemia
Oral hypoglycemic agents for type 2 diabetes

• Insulin for type 1 or type 2 diabetes

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Follow the Food Pyramid
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Treatment of Type 2 Diabetes by
Adenoviral-Mediated Overexpression of the
Glucokinase Regulating Proteins
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What is Glucokinase?
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What is Glucokinase?

• Glucokinase is produced in the liver.
• It is an important component in maintaining
  glucose homeostasis in the entire body.
• Glucokinase does this by catalyzing the
  phosphorylation of glucose in cells that express
  this enzyme.
• ? pancreatic ß cells

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The Role of Glucokinase

• Glucokinase is critical in maintaining normal
  blood glucose and insulin levels.
• Non-insulin-dependent patients have a reported
  decrease in glucokinase enzymatic activity.
• Slight alterations in glucokinase protein levels
  has a great effect on maintaining normal blood
  glucose levels.

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What is GKRP?

• Glucokinase Regulatory Protein
• In the liver, glucokinase activity is regulated
  by binding to the glucokinase regulatory protein
  (GKRP).
• Function GKRP inhibits GK activity under
• low-glucose conditions
• GKRP has been identified in the regulation of
  glucokinase, and has been postulated as a
  candidate gene for type-2 diabetes.

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Treatment of Type 2 Diabetes by
Adenoviral-Mediated Overexpression of the
Glucokinase Regulating Proteins
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Objective of Study

• Slosberg, et al. were interested in looking at
  the effect of increasing the hepatic levels of
  glucokinase regulatory protein (GKRP) on the
  diabetic phenotype of mice maintained on a
  high-fat diet.

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Structure and Function of the Av3hGKRP vector
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The Schematic Structure of Av3hGKRP
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Western Blot Analysis
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The Effect of GKRP Over-Expression on the Rate of
Glucose Phosphorylation
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Fasting Blood Glucose Values in Vector-Treated
Mice
HBSS
Null
300
GKRP
LF HBSS
250
200
Fasting blood sugar glucose (mg/dl)
150
100
50
0
Pre-inject
1 week
3 weeks
2 weeks
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Null mice had lower fasting blood sugar levels
than HBSS mice at all times tested.
HBSS
Null
300
GKRP
LF HBSS
250
200
Fasting blood sugar glucose (mg/dl)
150
100
50
0
Pre-inject
1 week
3 weeks
2 weeks
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GKRP mice showed significant decrease in fasting
glucose levels compared with both null and HBSS
mice at all times tested.
HBSS
Null
300
GKRP
LF HBSS
250
200
Fasting blood sugar glucose (mg/dl)
150
100
50
0
Pre-inject
1 week
3 weeks
2 weeks
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At the end of the experiment GKRP mice were
indistinguishable from non-diabetic LF-HBSS mice.
HBSS
Null
300
GKRP
LF HBSS
250
200
Fasting blood sugar glucose (mg/dl)
150
100
50
0
Pre-inject
1 week
3 weeks
2 weeks
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The Effect of Av3hGKRP Treatment on GK Protein
and Activity in vitro
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The effect of Av3hGKRP treatment on GK protein
and activity
60
50
40
GK Activity
30
20
10
0
Av3Null
Av3hGKRP
Av3hGKRP Av3hGK
Av3hGK
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Western Blot Analysis
GKRP
GK
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Thank-You!