A trial to assess the amount of insulin antibodies in diabetic patients by surface plasmon resonance
ABSTRACT To measure the amount and affinity of insulin antibodies, we performed a trial to establish a new method for quantitative and qualitative analysis of these antibodies by using surface plasmon resonance (BIAcore system).
Real-time detection of insulin antibody interaction and kinetic analysis were performed using the BIAcore system.
Eight diabetic patients with insulin antibodies and whose fasting total immunoreactive insulin levels were more than 100 microU/ml were selected. The patients with and without recurrent hypoglycemia were classified into hypoglycemic episode-positive or hypoglycemic episode-negative groups, respectively. Seven diabetic patients without insulin antibodies were selected as controls.
In the 8 patients, the concentration of insulin antibodies ranged from 2.91 to 16.3 microg/ml and insulin antibodies were not detected in the control group. The apparent KD (dissociation constant) and kd (the dissociation rate constant) values of the patients were much larger than those seen for the anti-human insulin monoclonal antibody. The KD values were significantly higher in the hypoglycemic episode-positive group than in the hypoglycemic episode-negative group (p<0.05). No significant differences in the concentration, the ka (the association rate constant) and the kd values were noted between the groups.
The data suggests that insulin antibodies of the patients have an apparently lower affinity status in sera as compared with that for the anti-human insulin monoclonal antibody, and dissociate easily from the immune-complex in the sera, especially in cases where there is recurrent hypoglycemia in the patients. Therefore insulin antibody characteristics are one of the causative factors in hypoglycemic episodes.
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ABSTRACT: A lean 15-year-old girl was diagnosed with type 1 diabetes based on symptomatic hyperglycaemia and positive anti-islet cell antibodies. Glycaemia was initially stabilised on twice-daily mixed insulin. After 11 months from the time of diagnosis, she complained of hyperglycaemia and ketosis alternating with hypoglycaemia. This progressively worsened until prolonged hospital admission was required for treatment of refractory hypoglycaemia. A high titre of anti-insulin antibodies was detected associated with a very low recovery of immunoreactive (free) insulin from plasma after precipitation with polyethylene glycol, suggesting the presence of insulin in bound complexes. Insulin autoimmune syndrome was diagnosed and metabolic fluctuations were initially managed supportively. However, due to poor glucose control, immunosuppressive therapy was initiated first with steroids and plasmapheresis and later with anti-CD20 antibody therapy (Rituximab). This treatment was associated with a gradual disappearance of anti-insulin antibodies and her underlying type 1 diabetes has subsequently been successfully managed with an insulin pump. Anti-insulin antibodies may result in low levels of free insulin.Polyclonal anti-insulin antibodies can interfere with the pharmacological action of administered insulin, resulting in hypoglycaemia and insulin resistance, due to varying affinities and capacities.In this patient, rituximab administration was associated with a gradual disappearance of anti-insulin antibodies.It is hypothesised that this patient had subcutaneous insulin resistance (SIR) caused by insulin capture at the tissue level, either by antibodies or by sequestration.A prolonged tissue resistance protocol may be more appropriate in patients with immune-mediated SIR syndrome.01/2014; 2014:130086. DOI:10.1530/EDM-13-0086
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ABSTRACT: The advent of ultra-low-noise amplification has shifted the emphasis of low-noise design towards passive circuitry. Expressions for the noise parameters for a passive two-port are derived in terms of the scattering matrix and applied to the problem of design of power combining circuits. Simple guidelines for low-noise combiner design are presented