Insulin antibodies do not influence the absorption rate of subcutaneously injected insulin

Insulin aspart pharmacokinetics: an assessment of its variability and underlying mechanisms

BACKGROUND

Insulin aspart (IAsp) is used by many diabetics as a meal-time insulin to control post-prandial glucose levels. As is the case with many other insulin types, the pharmacokinetics (PK), and consequently the pharmacodynamics (PD), is associated with clinical variability, both between and within individuals. The present article identifies the main physiological mechanisms that govern the PK of IAsp following subcutaneous administration and quantifies them in terms of their contribution to the overall variability.

MATERIAL AND METHODS

CT scanning data from Thomsen et al. (2012) are used to investigate and quantify the properties of the subcutaneous depot. Data from Brange et al. (1990) are used to determine the effects of insulin chemistry in subcutis on the absorption rate. Intravenous (i.v.) bolus and infusion PK data for human insulin are used to understand and quantify the systemic distribution and elimination (Pørksen et al., 1997; Sjöstrand et al., 2002). PK and PD profiles for type 1 diabetics from Chen et al. (2005) are analyzed to demonstrate the effects of IAsp antibodies in terms of bound and unbound insulin. PK profiles from Thorisdottir et al. (2009) and Ma et al. (2012b) are analyzed in the nonlinear mixed effects software Monolix® to determine the presence and effects of the mechanisms described in this article.

RESULTS

The distribution of IAsp in the subcutaneous depot show an initial dilution of approximately a factor of two in a single experiment. Injected insulin hexamers exist in a chemical equilibrium with monomers and dimers, which depends strongly on the degree of dilution in subcutis, the presence of auxiliary substances, and a variety of other factors. Sensitivity to the initial dilution in subcutis can thus be a cause of some of the variability. Temporal variations in the PK are explained by variations in the subcutaneous blood flow. IAsp antibodies are found to be a large contributor to the variability of total insulin PK in a study by Chen et al. (2005), since only the free fraction is eliminated via the receptors. The contribution of these and other sources of variability to the total variability is quantified via a population PK analysis and two recent clinical studies (Thorisdottir et al., 2009; Ma et al., 2012b), which support the presence and significance of the identified mechanisms.

CONCLUSIONS

IAsp antibody binding, oligomeric transitions in subcutis, and blood flow dependent variations in absorption rate seem to dominate the PK variability of IAsp. It may be possible via e.g. formulation design to reduce some of these variability factors.

Reproducibility of plasma insulin kinetics during intraperitoneal insulin treatment by programmable pumps

OBJECTIVE

To study the reproducibility of plasma insulin kinetics during intraperitoneal (IP) insulin therapy using an implanted programmable pump in patients with type 1, insulin dependent, diabetes mellitus (IDDM).

RESEARCH DESIGN AND METHODS

In a group of ten type 1 IDDM patients beginning chronic IP insulin treatment with an implanted pump, plasma free insulin profiles were determined from 12: 00 am to 12: 30 pm on two separate test days, one month apart. Anti-insulin antibody (AIA) levels were measured on each test day.

RESULTS

From test day 1 to test day 2, no difference was observed in morning fasting free insulin levels (m +/- SD): 9.7 +/- 5.4 mU/L versus 9.8 +/- 5.3 mU/L, insulin peak values: 19.1 +/- 17 mU/L versus 20.8 +/- 9.9 mU/L, time to peak: 40 +/- 15 versus 42.8 +/- 16 minutes or post-bolus area under the plasma free insulin curve (AUC): 40.7 +/- 29 mU/L.h versus 45.5 +/- 29 mU/L.h. The intrapatient coefficient of variation was 14.4 +/- 13% for insulin peaks and 16.9 +/- 9.2% for post-bolus AUC. A significant increase in AIA levels (m +/- SD) was observed from 16.5 +/- 18% on test day 1 to 28.1 +/- 28% on test day 2.

CONCLUSIONS

The reproducibility of plasma free insulin profiles is highly satisfactory during insulin delivery by the IP route using an implanted device.

Inhaled insulin and insulin antibodies: a new twist to an old debate

The recent development of inhaled insulin for the treatment of diabetes has the potential to significantly improve patient compliance and diabetes control. Preliminary studies have shown inhaled insulin to be effective in lowering blood glucose and HbA(1c) levels. However, inhaled insulin may stimulate insulin antibody production more than is commonly observed with highly purified human insulin administered subcutaneously. The significance of insulin antibodies in patient care has been a topic of frequent debate and has been studied extensively. This review will discuss the potential implications of elevated insulin antibody levels, the role insulin antibodies play in the metabolic control of diabetes and the effect inhaled insulin may have on the immune system.