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)

Comparison of insulin analogue B9AspB27Glu and soluble human insulin in insulin-treated diabetes

Postprandial plasma glucose excursions and plasma levels of free insulin after subcutaneous bolus injection of a rapidly absorbed monomeric insulin analogue (B9AspB27Glu) or soluble human insulin ('Actrapid HM' U100) were studied in six insulin-treated diabetic subjects. 10 U actrapid or an equimolar amount of the analogue were injected, in random order with an interval of 1 week, immediately before a 500 kcal test meal. Basal insulin levels were similar on the 2 study days (mean 74.1 [SE 5.1] pmol/l, actrapid; 79.7 [13.0] pmol/l, analogue). After injection of actrapid plasma free insulin levels rose slowly, reaching a plateau by 105 min at 222 (19) pmol/l. Injection of the analogue resulted in a rapid early peak at 30 min (798 [112] pmol/l), and levels were significantly higher than those after actrapid between 15 and 210 min. The more physiological plasma insulin levels achieved with the analogue were accompanied by a substantial reduction in postprandial plasma glucose excursions; the integrated area under the incremental plasma glucose curve was 45% lower after the analogue than after actrapid.

A streptokinase dependent plasma factor (SKDF) induces leucocyte tissue factor activity

Various inducers endow human leucocytes with a procoagulant activity of tissue factor type. We have observed a novel plasma factor which in combination with streptokinase induces powerful leucocyte procoagulant activity. This streptokinase dependent factor (SKDF) is present in normal plasma or serum albeit quantitatively different in individual donors. The generation of tissue factor activity as a function of streptokinase-plasma complex shows a specific and saturable sigmoidal dose-response curve. The Hill plot shows a straight line with Hill coefficient, H = 2.2, suggesting a strong positive cooperativity for the binding of this streptokinase-plasma complex to the leucocyte surface receptor for the signal transduction leading to the biosynthesis of tissue factor apoprotein. It also suggests that the leucocyte surface receptor for streptokinase-plasma complex differs from that for endotoxin lipopolysaccharides. SKDF is of apparent high molecular weight. It does not appear to be an antibody to streptokinase since its level does not correlate with the level of antibodies to streptokinase, and it does not correlate with the antistreptolysin titre. Furthermore, SKDF does not bind to protein A. It has a narrow pH range of stability, and is destroyed at 56 degrees C, or at freeze-drying, Urokinase, another plasminogen activator, or plasmin were unable to activate SKDF to induce the leucocyte procoagulant activity. SKDF may play a role in thrombolytic therapy.

Recombinant DNA derived monomeric insulin analogue: comparison with soluble human insulin in normal subjects

OBJECTIVE

To compare the rate of absorption from subcutaneous tissue and the resulting hypoglycaemic effect of iodine-125 labelled soluble human insulin and a monomeric insulin analogue derived by recombinant DNA technology.

DESIGN

Single blind randomised comparison of equimolar doses of 125I labelled soluble human insulin and insulin analogue.

SETTING

Study in normal people at a diabetes research unit and a university department of medical physics.

SUBJECTS

Seven healthy male volunteers aged 20-39 not receiving any other drugs.

INTERVENTIONS

After an overnight fast and a basal period of one hour two doses (0.05 and 0.1 U/kg) of 125I labelled soluble human insulin and insulin analogue were injected subcutaneously into the anterior abdominal wall on four separate days.

END POINT

To find a fast acting insulin for meal related requirements in insulin dependent diabetics. MEASUREMENTS and main results--Residual radioactivity at the injection site was measured continuously for the first two hours after injection of the 125I labelled preparations and thereafter for five minutes simultaneously with blood sampling. Frequent venous blood samples were obtained over six hours for determination of plasma immunoreactive insulin, insulin analogue, glucose, and glucagon values. Time to 50% of initial radioactivity at the injection site for the insulin analogue compared with soluble insulin was 61 v 135 minutes (p less than 0.05) with 0.05 U/kg and 67 v 145 minutes (p less than 0.001) with 0.1 U/kg. Concentrations in plasma increased faster after the insulin analogue compared with soluble insulin, resulting in higher plasma concentrations between 10 and 150 minutes (0.001 less than p less than 0.05) after 0.05 U/kg and between 40 and 360 minutes (0.001 less than p less than 0.05) after 0.1 U/kg. The hypoglycaemic response to insulin analogue was a plasma glucose nadir at 60 minutes with both doses compared with 90 and 120 minutes with soluble insulin at 0.5 and 0.1 U/kg respectively. The response of glucagon substantiated the earlier and more dramatic hypoglycaemic effect with the insulin analogue.

CONCLUSIONS

The much faster absorption from subcutaneous tissue of the disubstituted monomeric insulin analogue compared with soluble insulin suggests that the analogue may be a potential candidate for rapid insulin delivery after subcutaneous bolus injection.

Purification of human brain tissue factor

Tissue factor (thromboplastin or Factor III), a glycoprotein cofactor, is required for Factor VII to express its catalytic activity, thereby initiating the extrinsic as well as intrinsic pathway of blood coagulation. Human brain tissue factor was purified 2,500-fold to 98% homogeneity from 2% Triton X-100 extraction of acetone dried brain powder with an overall yield of 36%. The method was based upon affinity chromatography utilizing the high affinity binding of tissue factor to Factor VII noncovalently complexed to immobilized anti-Factor VII-agarose beads. The apparent molecular weight of the purified tissue factor is 45,000 as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its isoelectric point is 4.8-5.1 by column chromatofocussing and flat bed agarose isoelectric focussing.

Glucose and insulin responses are improved in patients with psoriasis during therapy with etretinate

Since lipemia is commonly induced by retinoid therapy, we investigated the effects of etretinate administration on glucose metabolism by obtaining five-hour oral glucose tolerance tests in 23 patients before and after 20 weeks of etretinate therapy for psoriasis. Compared with pretreatment values, peak and aggregate levels for serum glucose and aggregate levels for serum insulin were significantly lower during therapy. The changes were not associated with obesity, weight loss during treatment, or pretherapy glucose tolerance or insulin secretion level. Of 11 patients with impaired or diabetic glucose tolerance prior to therapy, eight patients had improved glucose tolerance after 20 weeks of etretinate treatment. Despite inducing hypertriglyceridemia in most patients, etretinate therapy is associated with a reduction in glucose levels in response to a glucose load.

Topical application of nonsteroidal anti-inflammatory drugs prevents vehicle-induced improvement of psoriasis

In a double-blind fashion, we compared the effect of topical application of 1% indomethacin cream or 1% meclofenamate cream with the effect of vehicle therapy alone in thirty patients with psoriasis. After 4 weeks' treatment of bilaterally symmetric psoriatic plaques, the indomethacin-treated sides were worse than the vehicle-treated sides in fourteen of twenty patients (p less than 0.01); the meclofenamate-treated sides were worse than the vehicle-treated sides in seven of ten patients (p less than 0.05). We suspect that the nonsteroidal anti-inflammatory drugs contributed to the maintenance of our patients' psoriasis by altering the arachidonic acid transformation cascade.

Etretinate therapy reduces polymorphonuclear leukocyte chemotaxis--enhancing properties of psoriatic serum

Using a Boyden chamber technic, we measured the directed chemotaxis of polymorphonuclear leukocytes obtained from control subjects or psoriasis patients when the leukocytes were placed in sera obtained from control subjects or psoriasis patients. The samples from patients were obtained before therapy and after 2 and 4 weeks of etretinate administration. Compared with control sera, the sera from seven untreated psoriasis patients significantly enhanced the chemotaxis of polymorphonuclear leukocytes from control subjects toward a chemotaxin (p less than 0.05). After 4 weeks of etretinate therapy, the chemotaxis-stimulating ability of the sera from psoriasis patients was no longer significantly greater than that of the control sera. This decline in the chemotaxis-stimulating activity of our patients' sera preceded significant clearing of their psoriasis. The levels of circulating etretinate in the blood of our patients could not account for the reduction. Etretinate therapy had no apparent direct effect on the chemotactic activity of polymorphonuclear leukocytes from the psoriasis patients but may act in part by reducing the inflammatory effects of psoriatic sera.

Etretinate therapy for psoriasis. Reduction of antibody-dependent cell-mediated cytotoxicity of polymorphonuclear leukocytes

We monitored the antibody-dependent cell-mediated cytotoxicity of polymorphonuclear leukocytes from 14 patients with psoriasis before and during etretinate therapy. Neutrophils obtained from the patients with psoriasis at pretherapy demonstrated significantly greater cytotoxic activity than control cells. After four weeks of etretinate therapy, the cytotoxicity of neutrophils from the psoriatic patients decreased significantly and was no longer significantly different from the control value (at a 1:1 effector-to-target ratio). The decline in neutrophil cytotoxicity preceded significant clearing of our patients' psoriasis. The reduction in the antibody-dependent cell-mediated cytotoxicity of polymorphonuclear leukocytes from patients with psoriasis occurs early during therapy and may represent one of the mechanisms of action of etretinate.

Disseminated bone and joint tuberculosis 25 years after development of lupus vulgaris

A case of extensive bone and joint tuberculosis is reported in a 62-year-old caucasian woman who had a 25 year history of inadequately treated facial lupus vulgaris. In spite of a good response to standard anti-tuberculosis chemotherapy there was extensive residual joint destruction.

Oral ibuprofen and tetracycline for the treatment of acne vulgaris

A prospective evaluation of the efficacy and safety of oral ibuprofen and tetracycline hydrochloride was conducted for 8 weeks in patients with moderately severe acne. Sixty-eight patients were randomly assigned in a double-blind fashion to one of four regimens: (1) one 600 mg ibuprofen tablet plus one 250 mg tetracycline capsule four times daily; (2) one 600 mg ibuprofen tablet plus one placebo capsule four times daily; (3) one 250 mg tetracycline capsule plus one placebo tablet four times daily; and (4) one placebo tablet and one placebo capsule four times daily. Sixty patients completed the 8-week study. The mean percent improvement in the groups treated with ibuprofen and tetracycline (56% +/- 5 SE), ibuprofen alone (26% +/- 13 SE), or tetracycline alone (26% +/- 9 SE) was statistically significant. However, only the combination of ibuprofen and tetracycline therapy had an effect statistically better than the placebo response (16+ +/- 11 SE). Adverse effects were transient and were similar in all four groups.

Topical minoxidil for hair regrowth

Minoxidil, a potent peripheral vasodilator used orally for refractory hypertension, has produced hypertrichosis. To determine the efficacy and safety of 1% or 5% topical minoxidil for the stimulation of scalp hair regrowth, we studied fifteen normotensive patients, five with androgenic alopecia and ten with alopecia areata diagnosed clinically and by biopsy, for 12 months. Three of five patients with androgenic alopecia using 5% minoxidil for 12 months noted hair regrowth, ranging from minimally observable hair to an appreciable restoration of larger, pigmented, terminal hair in one patient. Among the patients with androgenic alopecia, regrowth response corresponded to the serum minoxidil blood levels. None of the patients with alopecia areata receiving either 1% or 5% minoxidil noted hair regrowth despite comparable minoxidil blood levels. Improved local absorption of topical minoxidil solution may promote hair regrowth in androgenic alopecia.