help needed about insulin sensitivity

Discussion in 'Health and medical' started by Jackson, Mar 7, 2004.

  1. Jackson

    Jackson Guest

    Hey, dear all,

    I am a Ph.D. student working on diabetes research using
    mouse model, this is my first time being here in this forum,
    this is great place. I have now a problem in calculating the
    insulin sensitivity index, any help from you is highly
    appreciated:

    A: There are many ways to calculate the insulin sensitivity
    index, which way is mostly authorized and accepted?

    B: In details, we have two groups of mice A and B(all fully
    diabetic with 18-hour fasting glucose >210 mg/dl ), which
    are fully equivalent. Same strain, same food... After
    overnight fasting we did the GTT (glucose tolerance
    test)in timepoints of 0, 30,60, and 120 minutes. The
    group A has significantly higher glucose level in all
    time points of GTT; In terms of insulin level, group A is
    significantly higher than B in 0 minute (before injection
    glucoe); However, in the timepoints of 30,60,120 (after
    glucose injection), Group B has significantly higher
    level of insulin.

    C: Based on above situation, can we make any decision to say
    that which group has higher insulin sensitivity? why?

    I do not know if any of you have met the same situation, any
    of your ideas, suggestion and help are highly appreciated!!!
    In all the literatures I read do not release any situation
    like we have: In GTT, one group is significantly higher in
    glucose level (p<0.001), while significantly lower (P<0.001)
    in insulin level (except in 0 minute significant higher).

    best regards!

    Jackson
     
    Tags:


  2. Did you try a search on "hyperinsulinima" on Medscape?
    Best of luck in your research. Your answer would depend on
    how you define insulin sensitivity. BTW - it would be
    great to have a simple blood test to find people who are
    developing insulin insensitivity - which may be the
    precursor to IGT then T2.

    [email protected] (Jackson) wrote in message
    news:<[email protected]>...
    > Hey, dear all,
    >
    > I am a Ph.D. student working on diabetes research using
    > mouse model, this is my first time being here in this
    > forum, this is great place. I have now a problem in
    > calculating the insulin sensitivity index, any help from
    > you is highly appreciated:
    >
    > A: There are many ways to calculate the insulin
    > sensitivity index, which way is mostly authorized and
    > accepted?
    >
    > B: In details, we have two groups of mice A and B(all
    > fully diabetic with 18-hour fasting glucose >210 mg/dl
    > ), which are fully equivalent. Same strain, same
    > food... After overnight fasting we did the GTT (glucose
    > tolerance test)in timepoints of 0, 30,60, and 120
    > minutes. The group A has significantly higher glucose
    > level in all time points of GTT; In terms of insulin
    > level, group A is significantly higher than B in 0
    > minute (before injection glucoe); However, in the
    > timepoints of 30,60,120 (after glucose injection),
    > Group B has significantly higher level of insulin.
    >
    > C: Based on above situation, can we make any decision
    > to say that which group has higher insulin
    > sensitivity? why?
    >
    > I do not know if any of you have met the same situation,
    > any of your ideas, suggestion and help are highly
    > appreciated!!! In all the literatures I read do not
    > release any situation like we have: In GTT, one group is
    > significantly higher in glucose level (p<0.001), while
    > significantly lower (P<0.001) in insulin level (except in
    > 0 minute significant higher).
    >
    > best regards!
    >
    > Jackson
     
  3. Frank Roy

    Frank Roy Guest

    Jackson wrote:
    >
    > Hey, dear all,
    >
    > I am a Ph.D. student working on diabetes research using
    > mouse model, this is my first time being here in this
    > forum, this is great place. I have now a problem in
    > calculating the insulin sensitivity index, any help from
    > you is highly appreciated:
    >
    > A: There are many ways to calculate the insulin
    > sensitivity index, which way is mostly authorized and
    > accepted?
    "Measurements of insulin sensitivity index, glucose
    effectiveness, and acute insulin response and C-
    peptide response.

    Each subject underwent an intravenous glucose tolerance test
    (IVGTT) after the overnight fasting period of 12 h. After
    insertion of a cannula into the antecubital vein each
    subject rested in a quiet room for at least 20 min. Baseline
    values of serum insulin, serum C-peptide, and plasma glucose
    were taken in duplicate with 5-min intervals. Glucose was
    injected intravenously in the contralateral antecubital vein
    over a period of 60 s (0.3 grams/kg body weight of 50%
    glucose). At 20 min after the end of the glucose injection,
    a bolus of 3 mg tolbutamide/kg body weight (Rastinon,
    Hoechst, Germany) was injected during 5 s to elicit a
    secondary pancreatic -cell response. Venous blood was
    sampled at 2, 4, 8, 19, 22, 30, 40, 50, 70, 90, and 180 min,
    timed from the end of the glucose injection for measurements
    of plasma glucose, serum insulin and serum C-peptide. All
    the IVGTTs were done by the same investigator. Insulin
    sensitivity index and glucose effectiveness were calculated
    using the Bergman MINIMOD computer program developed
    specifically for the combined intravenous glucose and
    tolbutamide tolerance test (26, 27, 28, 29, 30). The insulin
    sensitivity index represents the increase in net fractional
    glucose clearance rate per unit change in serum insulin
    concentration after the intravenous glucose load. Glucose
    effectiveness represents the net fractional glucose
    clearance rate due to the increase in glucose itself without
    any increase in circulating insulin concentration above
    baseline. Furthermore, glucose effectiveness includes a
    lesser contribution mediated by the preexisting basal
    insulin status. Importantly, both the insulin sensitivity
    index and glucose effectiveness involve an inhibition of
    hepatic glucose output (26, 27). Acute phase insulin and C-
    peptide responses (0-8 min) were calculated by means of the
    trapezoidal rule as the incremental values (areas under the
    curve when expressed above basal values). Glucose
    disappearance constant (Kg) was calculated as the slope of
    the line relating the natural logarithm of the glucose
    concentration to the time between 8 and 19 min after the
    glucose bolus administered as a part of the IVGTT (31). The
    disposition index was calculated as the product of insulin
    sensitivity index and first phase insulin responses (0-8
    min) (32, 33).

    Validation of the IVGTT with reduced sampling for
    measurements of insulin sensitivity index and glucose
    effectiveness.

    The tolbutamide-boosted protocol for frequently sampled
    IVGTT with minimal model analysis has been validated
    previously against the euglycemic, hyperinsulinemic clamp in
    normal subjects (34, 35). To validate the reduced sampling
    protocol of the tolbutamide-modified IVGTT, 18 of the study
    participants volunteered for a study to compare the
    frequently sampled protocol (33 samples) with the present
    protocol (12 samples). Highly significant correlations
    considering insulin sensitivity index (r = 0.98, 95%
    confidence interval 0.95-0.99) and considering glucose
    effectiveness (r = 0.93, 95% confidence interval .82- 0.97)
    were found between the IVGTT method using 33 samples and the
    present method using 12 samples. The difference between the
    two IVGTT methods was plotted against the average of the two
    methods for each participant to give an estimate of the
    agreement between the two methods (Bland-Altman plot) (36).
    Limits of agreement were calculated as mean difference±1.96
    × SD of the difference. Limits of agreement between the
    method using 33 samples and the method using 12 samples were
    from 3.2 to
    2.1 × 105 (min × pmol/liter)1 considering insulin
    sensitivity index and from 0.7 to 0.6 × 102 × min1
    considering glucose effectiveness. Thus, the 12-sample
    protocol may estimate insulin sensitivity index 3.2 × 105
    (min × pmol/liter)1 below or 2.1 × 105 (min × pmol/liter)1
    above the values obtained with the 33-sample schedule. As
    the limits of agreement are narrower than the variation of
    both insulin sensitivity index (mean value = 15.3 × 105
    (min × pmol/liter)1 and SD = 9.3) and glucose
    effectiveness (mean value = 2.1 × 102 × min1 and SD =
    0.6), the reduced sampling schedule during the IVGTT as
    applied here provides an acceptable estimate of both the
    insulin sensitivity index and the glucose effectiveness in
    population studies. Similar results have been obtained in
    a recent comparative study (27)." Source: Insulin
    Sensitivity Index, Acute Insulin Response, and Glucose
    Effectiveness in a Population-based Sample of 380 Young
    Healthy Caucasians
    http://www.jci.org/cgi/content/full/98/5/1195

    Assessment of insulin sensitivity with minimal model: role
    of model assumptions http://ajpendo.physiology.org/cgi/cont-
    ent/abstract/272/5/E925

    A Google search using "Measurement of insulin sensitivity
    index" - http://tinyurl.com/34a5s

    The following is an old article. If you have access to the
    full article, you may find more recent citations that have
    reference to this article.: Quantitative estimation of
    insulin sensitivity
    http://ajpgi.physiology.org/cgi/content/abstract/236/6/G667

    The following are two High-Wire search across multiple
    journals: The first using search terms "insulin sensitivity
    index"+definition - http://tinyurl.com/2qyot The second
    using the search terms "insulin sensitivity"+definition -
    http://tinyurl.com/2u558

    This group has a few professional MDs and scientist. I am
    not one of them.

    Frank

    >
    > B: In details, we have two groups of mice A and B(all
    > fully diabetic with 18-hour fasting glucose >210 mg/dl
    > ), which are fully equivalent. Same strain, same
    > food... After overnight fasting we did the GTT (glucose
    > tolerance test)in timepoints of 0, 30,60, and 120
    > minutes. The group A has significantly higher glucose
    > level in all time points of GTT; In terms of insulin
    > level, group A is significantly higher than B in 0
    > minute (before injection glucoe); However, in the
    > timepoints of 30,60,120 (after glucose injection),
    > Group B has significantly higher level of insulin.
    >
    > C: Based on above situation, can we make any decision
    > to say that which group has higher insulin
    > sensitivity? why?
    >
    > I do not know if any of you have met the same situation,
    > any of your ideas, suggestion and help are highly
    > appreciated!!! In all the literatures I read do not
    > release any situation like we have: In GTT, one group is
    > significantly higher in glucose level (p<0.001), while
    > significantly lower (P<0.001) in insulin level (except in
    > 0 minute significant higher).
     
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