Effect Of Insulin Concentration Research Articles

Association of Insulin Secretion Level on Lipid Fractions and Risk of Arterial Hypertension

Background: The existing literature reports results on the association of lipid parameters with the level of insulin secretion and the risk of arterial hypertension. Objective: This study evaluated the role of the insulin dosage and lipid fractions in the risk of arterial hypertension in type 2 diabetic patients in Western Algeria. Methods: This was a cross-sectional observational study involving 101 subjects with type 2 diabetes mellitus. The data collected was about the biodemographic profile of the participants. We performed multiple regressions to test the effect of insulin concentration on the parameters studied. Results: The multiple regression analytical study showed that HOMA-IR, BMI and waist circumference were predictors for the insulinemia response variable (P<0.05). It should be noted that in insulinopenia, insulin secretion is positively and significantly correlated with non-HDL-C (P=0.037), and it is also significantly and positively correlated with LDL-C (P=0.042). Multiple regression also shows that SBP and DBP are significantly and positively related to insulin resistance. Our data suggest a possible direct relationship between fasting insulin and blood pressure. Conclusion: Monitoring of circulating insulin concentrations is critically important in a population of type 2 diabetics.

Impact of insulin concentration and mode of FSH addition on the in vitro survival and development of isolated bovine preantral follicles

The insulin and FSH are two important substances in the folliculogenesis process. Thus, the hypothesis of this experiment is that insulin concentration and the form of FSH addition affect the in vitro survival, growth, and estradiol production after culture of isolated bovine preantral follicles. The effects of insulin concentration (experiment 1) and the influence of both fixed and sequential concentrations of FSH (experiment 2) on the in vitro survival and development of bovine preantral follicles were investigated in this study by IVC for 18 days. In experiment 1, on Day 18 of culture, the addition of insulin at all concentrations promoted follicular survival rates significantly higher than that of the control, with the 10-ng/mL insulin treatment showing values significantly higher than the other treatments. The addition of 5- and 10-ng/mL insulin promoted higher follicular growth than the control and other treatments. In experiment 2, FSH 100 had a higher percentage of follicular viability compared with the control. FSH 100 produced follicle diameters significantly higher than those of the control and FSH seq. treatment. Estradiol levels in the presence of FSH (fixed concentration) were significantly higher than the other treatments. In conclusion, the association of insulin (10 ng/mL) and fixed concentration FSH (100 ng/mL) provides high rates of survival, growth, and estradiol production in bovine preantral follicles.

Sustained release of insulin through skin by intradermal microdelivery system

An intradermal microdelivery system comprising a wafer having 150-mum long microneedles and an applicator was used for controlled release of insulin. Insulin was topically applied on microneedle-pretreated skin. In vitro percutaneous studies showed that the penetration amount of FITC-Insulin following microneedle pretreatment was enhanced significantly and continued to increase for several hours after the removal of donor phase. In vivo studies on diabetic rats confirmed that the pharmacodynamic profile of percutaneously administrated regular insulin was smooth, with the duration of action comparable to that of subcutaneously injected biphasic insulin. The effects of insulin concentration, duration and area of microneedle treatment on blood glucose lowering were studied in vivo. The results indicated that the duration of microneedle treatment and insulin concentration were key influencing factors to optimize blood glucose control. The extent of blood glucose lowering was in proportion to the area of microneedle treatment.

Elution behavior of insulin on high-performance size exclusion chromatography at neutral pH

The pharmacopoeia protocol for HP-SEC of insulin, using an acidic non-physiological eluent, does not represent insulin's association state in the formulation. This study aimed to evaluate insulin's elution behavior in HP-SEC in a “physiological” (aqueous, neutral pH) eluent, using on-line UV absorption and multi-angle laser light scattering detection. The effect of insulin concentration and association state in the formulation (monitored by circular dichroism) and eluent composition (zinc ion, arginine) on its elution behavior was assessed. We showed that the elution behavior of insulin in “physiological” HP-SEC is affected by both dynamic association–dissociation of insulin molecules and insulin–column interactions. Insulin molecules re-equilibrated in the HP-SEC eluent, making its elution behavior practically insensitive to the association state of insulin in the formulation. Zinc ions in the eluent promoted association of insulin to hexamers, whereas arginine overruled the effect of zinc ions and induced on-column dissociation of insulin to dimers and monomers. Combined results from “physiological” and compendial HP-SEC were shown to provide a better view of the aggregation state of heat-stressed insulin than either of the single methods. The insights obtained with this study are crucial for a proper evaluation of HP-SEC data of insulin.

Effects of insulin concentration and self-association on the partitioning of its A-21 cyclic anhydride intermediate to desamido insulin and covalent dimer.

In the pH range 2-5, human insulin degrades via deamidation at the A-21 asn and covalent dimerization. Both products form via a common cyclic anhydride intermediate, a product of intramolecular neucleophilic attack by the A-21 carboxyl terminus. This study examines the influence of [insulin] and self-association on the partitioning of the intermediate to products. Insulin self-association was characterized (pH 2-4) by concentration difference spectroscopy. Deamination rates (pH 2-4) and concurrent rates of covalent dimer formation (pH 4) were determined versus [insulin] at 35 degrees C by initial rates. A mathematical model was developed to account for the overall rate and product composition profile versus pH and [insulin]. Between pH 2-4, insulin self-associates to form non-covalent dimers with a pH independent association constant of 1.8 x 10(4) M-1. The overall rate of degradation is governed by intermediate formation, while product distribution is determined by competition between water and the phe B-1 amino group of insulin for the anhydride. In dilute solutions, deamidation is first-order in [insulin] while covalent dimerization is second-order. Thus, deamidation predominates in dilute solutions but the fraction of covalent dimer formed increases with [insulin]. At high [insulin], self-association inhibits covalent dimer formation, preventing exclusive degradation via this pathway. The model accurately predicts a maximum in covalent dimer formation near pH 4. A mechanism is described which accounts for the complex dependence of insulin's degradation rate and product distribution profile on pH (between 2-5) and [insulin]. If these results can be generalized, they suggest that covalent aggregation in proteins may be inhibited by self-association.

Effect of insulin concentration, subcutaneous fat thickness and skin temperature on subcutaneous insulin absorption in healthy subjects

Effect of insulin concentration, subcutaneous fat thickness and skin temperature on subcutaneous insulin absorption in healthy subjects

Effect of insulin concentration, subcutaneous fat thickness and skin temperature on subcutaneous insulin absorption in healthy subjects.

Subcutaneous insulin absorption kinetics were assessed in 50 healthy study subjects (21 female, 29 male; age 26 +/- 3 years, BMI 22.5 +/- 1.8 kg/m2; mean +/- SD) during 45 min after periumbilical injection of soluble human U40- or U100-insulin (0.15 IU/kg). Subcutaneous fat thickness was measured by ultrasound, and skin temperature at the injection site was registered. Serum insulin concentrations increased within 30 min from basal values of 37 +/- 15 to 140 +/- 46 pmol/l after U40-insulin and from 36 +/- 10 to 116 +/- 37 pmol/l after U100-insulin (p < 0.001). After 45 min serum insulin concentrations were 164 +/- 43 pmol/l with U40-insulin and 128 +/- 35 pmol/l with U100-insulin (p < 0.001). Decline in blood glucose levels and suppression of C-peptide were comparable. The serum insulin levels reached 30 and 45 min after U40- and U100-insulin injection were positively correlated with skin temperature (p < 0.0008), and negatively correlated with subcutaneous fat thickness (p < 0.009). In conclusion, the lower insulin concentration of U40-insulin, higher skin temperature, and a thinner subcutaneous fat tissue at the injection site are associated with accelerated and enhanced subcutaneous insulin absorption.

Monomeric Insulins and Their Experimental and Clinical Implications

Due to the inherent pharmacokinetic properties of available insulins, normoglycemia is rarely, if ever, achieved in insulin-dependent diabetic patients without compromising their quality of life. Subcutaneous insulin absorption is influenced by many factors, among which the associated state of insulin (hexameric) in pharmaceutical formulation may be of importance. This review describes the development of a series of human insulin analogues with reduced tendency to self-association that, because of more rapid absorption, are better suited to meal-related therapy. DNA technology has made it possible to prepare insulins that remain dimeric or even monomeric at high concentration by introducing one or a few amino acid substitutions into human insulin. These analogues were characterized and used for elucidating the mechanisms involved in subcutaneous absorption and were investigated in preliminary clinical studies. Their relative receptor binding and in vitro potency (free-fat cell assay), ranging from 0.05 to 600% relative to human insulin, were strongly correlated (r = 0.97). In vivo, most of the analogues exhibited approximately 100% activity, explainable by a dominating receptor-mediated clearance. This was confirmed by clamp studies in which correlation between receptor binding and clearance was observed. Thus, an analogue with reduced binding and clearance gives higher circulating concentrations, counterbalancing the reduced potency at the cellular level. Absorption studies in pigs revealed a strong inverse correlation (r = 0.96) between the rate of subcutaneous absorption and the mean association state of the insulin analogues. These studies also demonstrated that monomeric insulins were absorbed three times faster than human insulin. In healthy subjects, rates of disappearance from subcutis were two to three times faster for dimeric and monomeric analogues than for human insulin. Concomitantly, a more rapid rise in plasma insulin concentration and an earlier hypoglycemic response with the analogues were observed. The monomeric insulin had no lag phase and followed a monoexponential course throughout the absorption process. In contrast, two phases in rate of absorption were identified for the dimer and three for the normal hexameric human insulin. The initial lag phase and the subsequent accelerated absorption of soluble insulin can now be explained by the associated state of native insulin in pharmaceutical formulation and its progressive dissociation into smaller units during the absorption process. In the light of these results, the effects of insulin concentration, injected volume, temperature, and massage on the absorption process are now also understood.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of insulin concentration on retroendocytosis in isolated rat adipocytes.

After internalization by isolated rat adipocytes, insulin can be degraded or released intact from the cell, a process termed retroendocytosis. To determine whether the amount of ligand entering the cell could modulate its ultimate intracellular disposition, adipocytes were incubated with 0.4-25 ng/ml radiolabeled insulin for 20 min at 37 C to reach steady state binding and internalization. After this, surface bound insulin was removed by acid extraction and the cells were reincubated in insulin-free 37 C buffer. The fractional rate of release of internalized cell associated radioactivity was similar at all insulin concentrations. However, insulin enhanced the appearance of trichloroacetic acid (TCA)-precipitable material in a dose-dependent manner reaching a maximum at an insulin concentration of 10 ng/ml. At 0.4 ng/ml insulin, 18 +/- 2% of the released radioactivity was TCA precipitable whereas 36 +/- 3% was precipitable at 25 ng/ml. Sephadex G-50 gel chromatography and reverse phase HPLC analysis of the reincubation medium confirmed TCA-precipitable material was intact insulin. To further investigate the dual pathways of intracellular insulin processing, adipocytes were incubated with 0.4 and 25 ng/ml insulin for 20 min, acid extracted to remove surface receptor insulin, and solubilized. Sephadex G-50 and HPLC analysis revealed that proportionately less insulin intermediates and low molecular weight degradation products are found in cells incubated at the higher insulin concentrations. In conclusion, as adipocytes internalize more insulin, less is converted into insulin intermediates and low molecular weight degradation products and more is diverted to retroendocytosis.

The physiologic action of insulin on glucose uptake and its relevance to the interpretation of the metabolic clearance rate of glucose

Glucose uptake (Ru) is dependent upon the concentrations of both glucose and insulin. The metabolic clearance rate of glucose (MCR G), has been used as an in vivo measure of insulin action, because it was said to be independent of the prevailing glucose concentration. The validity of this assumption has recently been challenged. In this study, the effect of insulin concentration on the rate of glucose uptake (Ru) and on the MCR G was studied during euglycemia (5.1 ± 0.3 mmol/L) and moderate hyperglycemia (10.4 ± 0.5 mmol/L) in 17 experiments on nine normal ambulant volunteers. Stable plasma insulin levels were maintained with fixed infusion rates of insulin (0–300 mU/kg/h) and somatostatin (7.5 μg/min). At low insulin concentrations (less than 5 μU/mL) the increase in glucose uptake in response to hyperglycemia was small (5.3 ± 2.3 μmol/kg/min). In contrast, with insulin levels more than 25 μU/mL, there was a steep rise in glucose uptake with hyperglycemia (55 ± 3 μmol/kg/min; range: 44–47 μmol/kg/min). The metabolic clearance rate of glucose fell by an average of 32% with hyperglycemia in the studies at the lowest insulin levels (2.2 ± 0.6 v 1.5 ± 0.1mL/kg/min; 0.15 > P > 0.1). There was no change in the MCR G in the subjects studied at higher insulin levels. It is concluded that (1) low concentrations of insulin are essential for the increase in glucose disposal during hyperglycemia; and (2) provided insulin levels are more than 25 μU/mL and plasma glucose less than 11 mmol/L, MCR G is independent of the plasma glucose concentration and is therefore a valid measure of insulin-mediated glucose uptake.

Factors affecting insulin adherence to type I glass bottles

Some physicochemical factors that could account for insulin adherence to type I glass bottles from admixtures of insulin with 5% dextrose (D5W) and 0.9% sodium chloride (NS) injections were studied. Samples of three volumes of NS or D5W containing insulin I 125 were mixed in three sizes of bottles to test the effect of surface area and volume. Appropriate volumes of insulin were combined with insulin I 125 and D5W or NS to yield solutions containing nine concentrations of insulin to test the effect of insulin concentration. Appropriate volumes of KCl injection to yield six concentrations were combined with insulin I 125 and NS or D5W to test the effect of KCl concentration. All samples were assayed by gamma scintillation. In general, there was a direct relationship between the percentage of insulin adhering and the container surface area. In D5W admixtures, as the fill volume at constant insulin I 125 concentration was doubled and quadrupled, the adherence of insulin decreased in all three bottle sizes (200, 250, and 500 ml). In NS admixtures, however, this effect was seen only with the 250-ml bottle. Increasing insulin concentrations over the range of 50-300 units/liter in D5W and 0-50 units/liter in NS resulted in decreased adherence. The addition of 1-60 meq/liter of KCl resulted in a significant decrease of insulin adhering from D5W and an insignificant decrease from NS admixtures. The percentage of insulin adhering to type I glass surfaces may be reduced to 25% or less by preparing i.v. admixtures in full bottles of D5W or NS at insulin concentrations of 25 to 300 units/liter. The addition of KCl, when therapeutically appropriate, will further decrease the extent of insulin adherence.