Decrease of antibodies to insulin, proinsulin and contaminating hormones after changing treatment from conventional beef to purified pork insulin
Decrease of Antibodies to Insulin, Proinsulin and Contaminating Hormones after Changing Treatment from Conventional Beef to Purified Pork Insulin
A. B. Kurtz 0
J. A. Matthews 0
B. E. Mustaffa 0
P. R. Daggett 0
J. D. N. N a b a r r o 0
0 Department of Nuclear Medicine and Cobbold Laboratories, Thorn Institute of Clinical Science, The MiddlesexHospital Medical School , London, England
Summary. T h e sera of 30 patients who h a d b e e n t r e a t e d with conventional b e e f insulin were tested for binding of insulin and other pancreatic hormones. All showed antibody binding of insulin, 29 binding of proinsulin, 29 binding of pancreatic polypeptide, two binding of glucagon but n o n e of the sera b o u n d vasoactive intestinal peptide or somatostatin. A f t e r changing t h e r a p y to highly purified p o r k insulin the binding capacity of sera for insulin and the other horm o n e s was m o n i t o r e d for up to 35 m o n t h s and a steady fall was f o u n d in nearly all cases. In eight of the patients conventional b e e f insulin t r e a t m e n t was resumed: in one m o n t h binding of insulin and of the o t h e r h o r m o n e s increased b a c k to the initial levels. In eighteen subjects w h o h a d only received highly purified p o r k insulin low levels of insulin binding were found with no binding of proinsulin or other h o r m o n e s . T h e a m o u n t s of proinsulin and contaminating h o r m o n e s in highly purified p o r k insulin are so low that they are not immunogenic; conventional b e e f insulin not only contains i m m u n o g e n i c a m o u n t s of proinsulin and the contaminating horm o n e s pancreatic p o l y p e p t i d e and glucagon but also is m o r e i m m u n o g e n i c than purified p o r k insulin.
Insulin; proinsulin; pancreatic p o l y p e p tide; glucagon; antibodies
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Conventional b e e f insulin p r e p a r a t i o n s are m o r e
i m m u n o g e n i c than highly purified p o r k insulin [
1
].
T h e y contain appreciable quantities of proinsulin,
pancreatic p o l y p e p t i d e (PP), glucagon, somatostatin
and vasoactive intestinal peptide (VIP) [
2
]. T h e
g r e a t e r immunogenicity of the conventional b e e f
insulins has b e e n attributed to the contaminants
although o t h e r factors such as alteration or p o l y m e r
isation of the insulin m a y be m o r e important. A
change of t h e r a p y f r o m b e e f to purified p o r k insulin
involves b o t h a change in the species of insulin origin
and an increase in purity as well as a possible change
in the physical or chemical state of the insulin.
In the present study the antibodies to insulin,
proinsulin, PP, glucagon, somatostatin and V I P have
b e e n m e a s u r e d in patients t r e a t e d with conventional
beef insulin b e f o r e and at intervals after a change to
highly purified p o r k insulin.
Materials and Methods
Patients
Thirty insulin treated patients were studied; 17 males and 13
females with an average age at the start of the study of 33 years
(range 12-67) and an average duration of diabetes of 12 years
(range 5-38).
For at least six months before the start of this study all the
patients were treated with twice daily soluble and isophane beef
insulin with an average daily dose of 55 U (range 24-84): before
this some had received other beef insulin preparations including
beef/pork mixtures. None of the patients were regarded as
"britfie" or insulin resistant, their antibody status was not known when
they entered this study and none were taking immunosuppressive
drugs or steroids.
An initial blood sample was collected and then, after
changeover to highly purified pork insulin (twice daily Leo
Neutral| and Leo Retard| insulins), blood samples were collected at
approximately monthly intervals for six months and thereafter at
4-6 monthly intervals. The group was followed for an average of
30 months (range 23-35): twenty two patients have continued on
the purified pork insulin while eight patients, at their own request,
have changed back to conventional beef insulin after an average of
8.4 months (range 6-12) on the purified pork insulin.
For comparison with this group of patients the sera from 18
subjects never treated with other than highly purified pork insulin
were checked for antibody binding. This group had been on insulin
for an average of 13 months (range 2-24).
Blood samples were collected at routine diabetic clinic visits and
the plasma or serum stored deep-frozen until studied.
For all the ligands tested the same general method was used to
measure antibody binding. Ten ul of plasma was incubated for 24 h
100
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