Wednesday, March 14, 2012

C-peptide a useful waste product of insulin production


    Making sense out of Facebook conversations is still a mystery to me, they seem like disjointed comments about various unrelated subjects. 
    I was struggling through my FaceBook discussions yesterday and saw a reference for the use of urine C peptide test in people over the age of 30 to help distinguish between people with type 1 and type 2 diabetes.  They discussed a lady who was able to discontinue her insulin as a result of this " simple urine test that can be done at home ". I was unable to find the article today but I will keep looking.
    A word of caution
    This caught my attention and my recall of an obese patient over the age of 30 lady who  discontinued her insulin and went into ketoacidosis after getting a positive test for C-peptide.
    What is c-peptide

    C-peptide is basically a waste product of insulin production.   
There is one molecule of C-peptide produced for each molecule of insulin. C-peptide can be measured in the blood and urine and can be used to determine if someone  is making insulin. The problem is that people with Type 1 and Type 2 Diabetes can continue making small amounts of insulin and C-peptide for a long time. Remember , people with Type 1 Diabetes are not the only ones with insulin deficiency. Insulin deficiency is also the primary problem for people with type 2 diabetes.


 I have attached an article abstract from Diabetes Care on this subject.


Tomorrow- C-peptide , a clue for the " Doctor / Detective ".


Have Fun , Be Smart and buy my book, ebook ,1phone or iPad App Diabetes Office Visit
David Calder, MD



    Diabetes Care
  1. Denise L. Faustman, MD, PHD
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Author Affiliations
  1. Immunobiology Laboratories, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
  1. Corresponding author: Denise L. Faustman, faustman@helix.mgh.harvard.edu.

Abstract

OBJECTIVE To examine persistence of C-peptide production by ultrasensitive assay years after onset of type 1 diabetes and factors associated with preserving β-cell function.
RESEARCH DESIGN AND METHODS Serum C-peptide levels, a marker of insulin production and surviving β-cells, were measured in human subjects (n = 182) by ultrasensitive assay, as was β-cell functioning. Twenty-two times more sensitive than standard assays, this assay’s lower detection limit is 1.5 pmol/L. Disease duration, age at onset, age, sex, and autoantibody titers were analyzed by regression analysis to determine their relationship to C-peptide production. Another group of four patients was serially studied for up to 20 weeks to examine C-peptide levels and functioning.
RESULTS The ultrasensitive assay detected C-peptide in 10% of individuals 31–40 years after disease onset and with percentages higher at shorter duration. Levels as low as 2.8 ± 1.1 pmol/L responded to hyperglycemia with increased C-peptide production, indicating residual β-cell functioning. Several other analyses showed that β-cells, whose C-peptide production was formerly undetectable, were capable of functioning. Multivariate analysis found disease duration (β = −2.721; P = 0.005) and level of zinc transporter 8 autoantibodies (β = 0.127; P = 0.015) significantly associated with C-peptide production. Unexpectedly, onset at >40 years of age was associated with low C-peptide production, despite short disease duration.
CONCLUSIONS The ultrasensitive assay revealed that C-peptide production persists for decades after disease onset and remains functionally responsive. These findings suggest that patients with advanced disease, whose β-cell function was thought to have long ceased, may benefit from interventions to preserve β-cell function or to prevent complications.


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Your comments and questions are appreciated. David Calder,MD