AIMTo study the protection of casein and protamine against degradation of insulin (INS) by proteolysis enzymes and the effect of these two kinds of protein on the hypoglycemic action of INS solution and enteric-microspheres after administrated orally to rats.

METHODSHPLC was used to determine the remained INS in the solution of alpha-chymotrypsin and trypsin with or without casein or protamine; INS solution and enteric-microspheres were prepared and adiministrated orally to rats together with the absorption enhancer sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC). At the same time, casein or protamine or both of these two kinds of protein were administrated together in order to study their influence on the hypoglycemic effect of INS and microspheres.

RESULTSCasein had a good protection against degradation of INS by alpha-chymotrypsin, but protamine had no protection effect. However, the degradation of INS by trypsin is concerned, the protection effect of protamine on INS was better that of casein. Both of protamine and casein can increase the hypoglycemic effect of INS solution and enteric-microspheres. Co-administrated these two kinds of protein had a better effect. In addition, co-administrated with SNAC, casein and protamine, INS enteric-microspheres had a longer and more potent hypoglycemic effect than that of the solution.

CONCLUSIONCasein and protamine can increase the stability of INS in the intestinal fluid by the mechanism of competition and combine with proteolysis enzymes, which will benefit to INS oral administration.

Administration, Oral ; Animals ; Blood Glucose ; metabolism ; Caprylates ; Caseins ; pharmacology ; Chymotrypsin ; antagonists & inhibitors ; Drug Delivery Systems ; Hypoglycemic Agents ; administration & dosage ; pharmacokinetics ; Insulin ; administration & dosage ; pharmacokinetics ; Male ; Microspheres ; Protamines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Solutions ; Trypsin ; pharmacology

PURPOSE: Premixed insulin is effective to improve glycemic control; however, clinicians may be less likely to know which premixed insulin is appropriate for which patients. This study aimed to evaluate the effects of twice-daily injections of premixed insulin lispro on glycemic control in type 2 diabetic patients. MATERIALS AND METHODS: Forty type 2 diabetic patients, who had been treated with twice-daily injections of human protamine mixture 30/70 insulin for at least 12 months, were divided into two groups; one group whose blood glucose 2 hours after breakfast was greater than 200 mg/dL, was switched to lispro mix50, and the other group whose blood glucose 2 hours after breakfast < 200 was switched to lispro mix25. RESULTS: Glycated haemoglobin (HbA1c) significantly improved in the Mix50 group from 8.3% to 7.5% (at 12 weeks; p < 0.05), and to 7.5% (at 24 weeks; p < 0.05). On the other hand, HbA1c levels in the Mix25 group were slightly decreased from 8.1% to 7.7% at 12 weeks (p < 0.05), and to 7.9% at 24 weeks (not significant). Both postprandial plasma glucose and fasting plasma glucose levels were significantly improved in the Mix50 group, but not in the Mix25 group. Overall, 95% of subjects preferred premixed lispro insulin from human insulin in the viewpoint of the timing of insulin injection by questionnaire analysis. CONCLUSION: Switching from human protamine mixture 30/70 insulin to lispro mix50 twice-daily injection therapy in patients with high postprandial plasma glucose could improve their glycemic control and quality of life.
Aged ; Blood Glucose/*analysis ; Body Mass Index ; Body Weight ; Diabetes Mellitus, Type 2/*drug therapy ; Female ; Hemoglobin A, Glycosylated/metabolism ; Humans ; Insulin/administration & dosage/*analogs & derivatives ; Male ; Middle Aged ; Postprandial Period ; Protamines/administration & dosage ; Treatment Outcome

PURPOSE: Adenosine triphosphate (ATP) from the urothelium acts as a sensory neurotransmitter and is augmented in many diseases, such as overactive bladder. We investigated the effects of intravesical instillation of oxybutynin on ATP-induced bladder overactivity to determine whether this effect is mediated by effects on urothelial muscarinic receptors. MATERIALS AND METHODS: Cystometry (at rate of 0.04 ml/min) was performed in female Sprague-Dawley rats (body weight 250 g) under urethane anesthesia (1.2 g/kg). After a 2-hour baseline period, protamine sulfate (10 mg/ml) was instilled for 1 hour, and then ATP (60 mM, pH 6.0) or a mixture of oxybutynin (10(-6) M) and ATP (60 mM, pH 6.0) was instilled intravesically. We performed experiments with 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP) and methoctramine by the same methods. Cystometric parameters, such as the intercontraction interval (ICI), pressure threshold (PT), and maximal voiding pressure (MVP), were compared. RESULTS: With intravesical instillation of ATP after protamine sulfate treatment, the ICI was decreased compared with baseline (ICI: baseline, 487.1+/-64.8 s; protamine, 450.6+/-56.1 s; ATP, 229.7+/-35.3 s; p<0.05). Addition of oxybutynin, 4-DAMP, or methoctramine in the ATP solution did not significantly change the ICI compared with ATP solution alone (ICI: oxybutynin, 189.1+/-32.3 s; 4-DAMP, 161.1+/-22.8 s; methoctramine, 341.0+/-113.3 s; p>0.05). Intravesical instillation of ATP decreased MVP and PT significantly compared with baseline, but MVP and PT were not changed significantly with oxybutynin, 4-DAMP, or methoctramine compared with ATP. CONCLUSIONS: Bladder overactivity induced by intravesical instillation of ATP was not suppressed by intravesical instillation of antimuscarinics. Suppression of ATP-induced bladder overactivity by intravenous oxybutynin is not mediated by urothelial muscarinic receptors.
Adenosine ; Adenosine Triphosphate ; Administration, Intravesical ; Anesthesia ; Animals ; Diamines ; Female ; Humans ; Hydrogen-Ion Concentration ; Mandelic Acids ; Muscarinic Antagonists ; Neurotransmitter Agents ; Piperidines ; Polyphosphates ; Protamines ; Rats ; Rats, Sprague-Dawley ; Receptors, Muscarinic ; Urethane ; Urinary Bladder ; Urinary Bladder, Overactive ; Urothelium