Fixed ratio dosing of pramlintide with regular insulin before a standard meal in patients with type 1 diabetes

Amylin is co-secreted with insulin and is therefore lacking in patients with type 1 diabetes. Replacement with fixed ratio co-administration of insulin and the amylin analogue pramlintide may be superior to separate dosing. This concept was evaluated in a ratio-finding study. Patients with type 1 diabetes were enrolled in a randomized, single-masked, standard breakfast crossover study using regular human insulin injected simultaneously with pramlintide 6, 9 or 12 mcg/unit insulin or placebo. Insulin dosage was reduced by 30% from patients' usual estimates. Plasma glucose, glucagon and pramlintide and adverse events were assessed. All ratios reduced 0-3-h glucose and glucagon increments by >50%. No hypoglycaemia occurred. Adverse events were infrequent and generally mild. All pramlintide/insulin ratios markedly and safely reduced glycaemic excursions and suppressed glucagon secretion in the immediate postprandial state. Further study using one of these ratios to explore the efficacy and safety of longer-term meal-time and basal hormone replacement is warranted.

Pramlintide improved measures of glycemic control and body weight in patients with type 1 diabetes mellitus undergoing continuous subcutaneous insulin infusion therapy

OBJECTIVE

To assess the safety and efficacy of the addition of pramlintide to continuous subcutaneous insulin infusion (CSII) therapy in patients with type 1 diabetes mellitus (T1DM).

RESEARCH DESIGN AND METHODS

We conducted a post hoc analysis of 2 studies: a 29-week, multicenter, randomized, double-blind, placebo-controlled trial (referred to as RCT) (pramlintide, n = 82; placebo, n = 73) and an open-ended, multicenter, open-label, single-arm, observational study (referred to as clinical practice trial) (n = 150), which assessed the addition of pramlintide to CSII therapy in patients with T1DM. Pramlintide was initiated at 15 μg and titrated to 30 or 60 μg with major meals. The mealtime insulin dose was reduced by 30% to 50% at initiation, and then adjusted to optimize glycemic control. Endpoints at 29 weeks (RCT) and 6 months (clinical practice trial) included change in glycated hemoglobin (HbA1c) level, insulin dose, body weight, pre- and postprandial blood glucose level, and tolerability and safety.

RESULTS

In both studies, mean baseline age was approximately 42 years, duration of diabetes was 20 to 24 years, and HbA1c level was approximately 8%. Pramlintide reduced blood glucose excursions and improved the percentage of recorded postprandial blood glucose levels < 180 mg/dL. Mean (± standard deviation) reduction in HbA1c level in the clinical practice trial was -0.3% ± 0.1% (P < 0.0001), and in the RCT was similar between pramlintide- and placebo-treated patients (-0.4% ± 0.1% and -0.3% ± 0.1%, respectively). Glycemic improvements were accomplished, with reductions in mealtime insulin doses (RCT: pramlintide, -23.8% ± 5.2%; placebo, -3.2% ± 4.1%; P < 0.0005; clinical practice trial: -27.5% ± 2.9%; P < 0.0001) and body weight (RCT: pramlintide, -2.2 kg ± 0.5 kg; placebo, +1.4 kg ± 0.3 kg; P < 0.0001; clinical practice trial: -3.2 kg ± 0.4 kg; P < 0.0001). Short-lived nausea, primarily mild to moderate in intensity, was the most common adverse event associated with pramlintide therapy. Severe hypoglycemic events occurred at a rate of 0.56 and 0.34 events per patient-year in pramlintide- and placebo-treated patients, respectively, in the RCT, and at a rate of 0.12 events per patient-year in the clinical practice trial.

CONCLUSION

Addition of pramlintide to CSII therapy was safe and effective in patients with T1DM. Pramlintide should be considered for patients who are not able to optimize glycemic control with CSII therapy alone, particularly those with difficulty controlling postprandial blood glucose levels and/or body weight.

TRIAL REGISTRATION

www.ClinicalTrials.gov identifiers: NCT00042458, NCT00108004.

Effect of Pramlintide on Weight in Overweight and Obese Insulin-Treated Type 2 Diabetes Patients

OBJECTIVE

Several randomized, placebo-controlled, double-blind trials in insulin-treated patients with type 2 diabetes have shown that adjunctive therapy with pramlintide reduces hemoglobin (Hb)A1c with concomitant weight loss. This analysis further characterizes the weight-lowering effect of pramlintide in this patient population.

RESEARCH METHODS AND PROCEDURES

This pooled post hoc analysis of two long-term trials included all patients who were overweight/obese at baseline (BMI > 25 kg/m2), and who were treated with either 120 microg pramlintide BID (n = 254; HbA1c 9.2%; weight, 96.1 kg) or placebo (n = 244; HbA1c 9.4%; weight, 95.0 kg). Statistical endpoints included changes from baseline to week 26 in HbA1c, body weight, and insulin use.

RESULTS

Pramlintide treatment resulted in significant reductions from baseline to week 26, compared with placebo, in HbA1c and body weight (both, p < 0.0001), for placebo-corrected reductions of -0.41% and -1.8 kg, respectively. Approximately three times the number of patients using pramlintide experienced a > or = 5% reduction of body weight than with placebo (9% vs. 3%, p = 0.0005). Patients using pramlintide also experienced a proportionate decrease in total daily insulin use (r = 0.39, p < 0.0001). The greatest placebo-corrected reductions in weight at week 26 were observed in pramlintide-treated patients with a BMI >40 kg/m2 and in those concomitantly treated with metformin (both, p < 0.001), for placebo-corrected reductions of -3.2 kg and -2.5 kg, respectively.

DISCUSSION

These findings support further evaluation of the weight-lowering potential of pramlintide in obese patients with type 2 diabetes.

Pharmacometrics and the transition to model-based development

As the transition to model-based drug development continues, pharmacometric analysis will have an increasingly important role across the entire life cycle of drug discovery, development, regulatory approval, and commercialization. For this reason, pharmacometrics can--and should--have an integrating function in the transformation to model-based development. This essay describes an approach for formalizing the pharmacometrics process using the disciplines encompassed by enterprise engineering.

The effect of pramlintide on hormonal, metabolic or symptomatic responses to insulin-induced hypoglycaemia in patients with type 1 diabetes

BACKGROUND

Pramlintide, a human amylin analogue, is a potential new adjunctive therapy to insulin for patients with type 1 diabetes and insulin-using patients with type 2 diabetes. Early clinical trials have shown a transient increased risk of hypoglycaemia in some patients at the time of initiating pramlintide therapy. This may be the result of combining the postprandial glucose, lowering effect of pramlintide with the existing hypoglycaemic potential of insulin without appropriate adjustment of insulin doses. However, the possibility that pramlintide may exert an independent detrimental effect on the physiological responses to insulin-induced hypoglycaemia needs to be excluded.

METHODS

We conducted three separate randomized, placebo-controlled studies in patients with type 1 diabetes treated with adjunctive pramlintide. These studies utilized pramlintide at high doses (either 0.1-1 mg pramlintide daily or 0.1-0.8 mg pramlintide four times a day for 5 or 6 days) as well as doses closer to those anticipated for therapeutic usage (30, 100 or 300 microg three times daily for 14 days), and examined the hormonal, metabolic and symptomatic responses to an insulin-infusion hypoglycaemic challenge conducted at baseline and after days of therapy.

RESULTS AND CONCLUSION

Pramlintide had no effect on the counter-regulatory hormonal, metabolic and symptomatic responses to hypoglycaemia. These findings demonstrated that pramlintide, when used as adjunctive therapy to insulin in patients with type 1 diabetes, has no independent effect on the response to hypoglycaemia.

Properties of pramlintide and insulin upon mixing

PURPOSE

The pharmacokinetics, pharmacodynamics, and safety of pramlintide and various insulin formulations in patients with type 1 diabetes mellitus (DM) when given as separate injections or mixed in the same syringe before injection were studied.

METHODS

In two randomized, open-label, placebo-controlled, five-period-crossover studies, patients with type 1 DM received preprandial injections of pramlintide, short-acting insulin, and long-acting insulin administered either by separate injections or after mixing in various combinations. Serum free insulin and plasma glucose concentrations were measured for 10 hours and plasma pramlintide concentrations for 5 hours after injection.

RESULTS

Blood samples were collected from a total of 51 patients. All treatments involving mixtures were comparable to separate injections with respect to the area under the concentration-versus-time curve (AUC) and the maximum concentration (Cmax) of serum free insulin. There were some minor differences in the AUC and Cmax of pramlintide. No injection-site reactions or other unexpected adverse events were observed.

CONCLUSION

Mixing pramlintide with short- or long-acting insulin in the same syringe before subcutaneous injection did not affect the pharmacodynamics of glucose or the pharmacokinetics of insulin or pramlintide in a clinically significant manner.

Adjunctive Therapy with Pramlintide Lowers HbA1c without Concomitant Weight Gain and Increased Risk of Severe Hypoglycemia in Patients with Type 1 Diabetes Approaching Glycemic Targets

AIMS

In long-term clinical trials in patients with type 1 diabetes spanning a wide range of HbA1c, addition of pramlintide to existing insulin regimens led to reductions in HbA1c that were accompanied by weight loss and no increase in overall severe hypoglycemia event rates. Given that weight gain and increased hypoglycemia risk contribute to the difficulty of attaining HbA1c targets (<7 %), the question arose whether pramlintide could benefit patients approaching, but not reaching glycemic targets with insulin alone. To address this question, we conducted a pooled analysis from 3 long-term clinical trials, including all patients with an entry HbA1c between 7.0 % and 8.5 %.

METHODS

Within the subset of patients with an entry HbA1c between 7.0 % and 8.5 % (approximately 28 % of all patients enrolled in the 3 studies), 196 were treated with placebo + insulin (baseline HbA1c 7.9+/-0.4 %, body weight 76.0+/-14.3 kg [mean+/-SD]) and 281 with pramlintide+insulin (baseline HbA1c 7.9+/-0.4 %, body weight 75.4+/-13.1 kg). Endpoints included placebo-corrected changes from baseline to week 26 in HbA1c, body weight, and the event rate of severe hypoglycemia.

RESULTS

Adjunctive therapy with pramlintide resulted in significant reductions in HbA1c and body weight from baseline to week 26 (0.3 % and 1.8 kg, placebo-corrected treatment differences, respectively, both p<or=0.0009). These changes occurred without an increase in the overall risk of severe hypoglycemia (1.40 pramlintide vs. 1.86 placebo, events/patient-year of exposure).

CONCLUSIONS

Addition of pramlintide to insulin therapy may help patients with type 1 diabetes who are approaching, but not yet reaching, glycemic targets with insulin alone to achieve further reductions in HbA1c without concomitant weight gain and increased risk of severe hypoglycemia.

Pharmacokinetics, pharmacodynamics, and safety of exenatide in patients with type 2 diabetes mellitus

PURPOSE

The pharmacology and tolerability of exenatide in patients with type 2 diabetes mellitus were studied.

METHODS

Two randomized, single-blind, placebo-controlled studies were conducted. Treatment with oral antidiabetic agents was stopped 14 days before study initiation. In the first study (study A), eight subjects received placebo, 0.1-, 0.2-, 0.3-, and either 0.4-microg/kg exenatide or placebo five minutes before a meal combined with liquid acetaminophen (to assess the rate of gastric emptying) on days 1, 3, 5, 7, and 9. In the second study (study B), subjects received a single s.c. dose of exenatide or placebo on consecutive days. Part 1 of study B used exenatide doses of 0.01 and 0.1 microg/ kg; 0.02-, 0.05-, and 0.1-microg/kg doses were given in part 2. After an overnight fast, the study drug was injected 15 minutes before a meal (part 1) and before a meal and acetaminophen (part 2). Parts 1 and 2 of study B enrolled six and eight patients, respectively.

RESULTS

In both studies, plasma exenatide pharmacokinetic profiles appeared dose proportional. Exenatide doses of 0.02-0.2 microg/kg dose-dependently lowered postprandial glucose excursions. Exenatide suppressed postprandial plasma glucagon and slowed gastric emptying. There were no serious adverse events and no patient withdrawals related to treatment. Nausea and vomiting were the most common adverse events and were mild to moderate in severity at doses ranging from 0.02 to 0.2 microg/kg.

CONCLUSION

Administration of preprandial exenatide by s.c. injection resulted in dose-proportional exenatide pharmacokinetics and antidiabetic pharmacodynamic activity. At doses ranging from 0.02 to 0.2 microg/kg, exenatide dose-dependently reduced postprandial plasma glucose excursion by insulinotropism, suppression of plasma glucagon, and slowing of gastric emptying.

Amylin replacement with pramlintide as an adjunct to insulin therapy improves long-term glycaemic and weight control in Type 1 diabetes mellitus: a 1-year, randomized controlled trial

AIMS

The autoimmune-mediated destruction of pancreatic beta-cells in Type 1 diabetes mellitus renders patients deficient in two glucoregulatory peptide hormones, insulin and amylin. With insulin replacement alone, most patients do not achieve glycaemic goals. We aimed to determine the long-term efficacy and safety of adjunctive therapy with pramlintide, a synthetic human amylin analogue, in patients with Type 1 diabetes.

METHODS

In a double-blind, placebo-controlled, parallel-group, multicentre study, 651 patients with Type 1 diabetes (age 41 +/- 13 years, HbA(1c) 8.9 +/- 1.0%, mean +/- sd) were randomized to mealtime injections of placebo or varying doses of pramlintide, in addition to their insulin therapy, for 52 weeks.

RESULTS

Addition of pramlintide [60 microg three times daily (TID) or four times daily (QID)] to insulin led to significant reductions in HbA(1c) from baseline to Week 52 of 0.29% (P < 0.011) and 0.34% (P < 0.001), respectively, compared with a 0.04% reduction in placebo group. Three times the proportion of pramlintide- than placebo-treated patients achieved an HbA(1c) of < 7%. The greater reduction in HbA(1c) with pramlintide was achieved without an increase in concomitant insulin use and was accompanied by a significant reduction in body weight from baseline to Week 52 of 0.4 kg in the 60 microg TID (P < 0.027) or QID (P < 0.040) pramlintide treatment groups, compared with a 0.8-kg gain in body weight in the placebo group. The most common adverse event in pramlintide-treated patients was transient, mild-to-moderate nausea.

CONCLUSIONS

These results show that mealtime amylin replacement with pramlintide, as an adjunct to insulin therapy, improves long-term glycaemic and weight control in patients with Type 1 diabetes.

Pramlintide reduces postprandial glucose excursions when added to insulin lispro in subjects with type 2 diabetes: a dose-timing study

BACKGROUND

To assess the postprandial glucose-lowering effect of the human amylin analog pramlintide when given with insulin lispro in subjects with type 2 diabetes, with an emphasis on the optimal dose timing relative to meals.

METHODS

In this randomized, single-blind, placebo-controlled, five-way crossover study, 19 subjects with type 2 diabetes using insulin lispro underwent five consecutive mixed-meal tests. In randomized order, subjects received subcutaneous injections of placebo at -15 min or 120-microg pramlintide at -15, 0, +15, or +30 min relative to the standardized breakfast after an overnight fast. Insulin lispro was injected at 0 min at doses that were adjusted appropriately for both the content of the standardized meal and the anticipated effects of pramlintide. Plasma glucose concentrations were measured before and during the 4-h postmeal period.

RESULTS

When injected at 0 min, pramlintide reduced the postprandial glucose excursion by 81% compared to insulin lispro + placebo (incremental AUC(0-4 h) (mean +/- SE) 2.0 +/- 1.5 vs. 10.4 +/- 2.2 mmol/h/L, P<0.05). When pramlintide was injected at -15, +15, and +30 min, the postprandial incremental glucose AUC(0-4 h) was also significantly reduced (P<0.05), but to a lesser extent (42 to 73%). Pramlintide treatment was well tolerated and no serious adverse events were reported.

CONCLUSIONS

Administration of pramlintide either at or just prior to a meal caused a greater reduction in postprandial glucose than either administration of placebo or postmeal pramlintide injections in subjects with type 2 diabetes treated with a rapid-acting insulin analog, insulin lispro.

Pramlintide reduces postprandial glucose excursions when added to regular insulin or insulin lispro in subjects with type 1 diabetes: a dose-timing study

OBJECTIVE

To assess the postprandial glucose-lowering effect of the human amylin analog pramlintide when given with either regular insulin or insulin lispro in subjects with type 1 diabetes, with an emphasis on the optimal dose timing relative to meals.

RESEARCH DESIGN AND METHODS

In this randomized, single-blind, placebo-controlled, five-way crossover study, 19 subjects with type 1 diabetes using regular insulin and 21 subjects with type 1 diabetes using insulin lispro underwent five consecutive mixed meal tests. In randomized order, subjects received subcutaneous injections of placebo at -15 min or 60 microg pramlintide at -15, 0, +15, or +30 min relative to the meal after an overnight fast. Regular insulin or insulin lispro was injected at -30 and 0 min, respectively, at doses that were adjusted appropriately for both the content of the standardized meal and the anticipated effects of pramlintide. Plasma glucose concentrations were measured before and during the 4-h postmeal period.

RESULTS

In both the regular insulin and insulin lispro groups, pramlintide injections at all four time points lowered the postprandial glucose excursion (36 to >100% reduction in incremental area under the concentration time curve from 0 to 4 h (AUC(0-4 h)) compared with placebo. However, only preprandial injections of pramlintide (-15 and 0 min) were able to prevent the initial postprandial surge in glucose. The optimal time for pramlintide injection was 0 min, which reduced the postprandial glucose excursion by >100% compared with regular insulin plus placebo (incremental AUC(0-4 h): -0.6 +/- 2.5 vs. 11.0 +/- 2.9 mmolx h(-1) x l(-1), P < 0.0007) and by 75% compared with insulin lispro plus placebo (incremental AUC(0-4 h): 2.5 +/- 2.1 vs. 10.0 +/- 2.5 mmol x h(-1) x l(-1), P < 0.0098). No serious adverse events were reported.

CONCLUSIONS

Pramlintide, given at or just before a meal, reduces the postprandial glucose excursion in subjects with type 1 diabetes, regardless of whether added to regular insulin or a rapid-acting insulin analog.

Synthetic exendin-4 (exenatide) significantly reduces postprandial and fasting plasma glucose in subjects with type 2 diabetes

Despite the advent of new treatments, glucose control in the type 2 diabetes population is unsatisfactory. AC2993 (synthetic exendin-4; exenatide), a novel glucose-dependent insulinotropic agent, exhibited notable antidiabetic potential in two clinical studies in patients with type 2 diabetes. In study A, 24 subjects received sc injections of study medication (0.1 micro g/kg AC2993 or placebo) twice daily with meals for 5 d. Statistically significant reductions in mean postprandial circulating concentrations of glucose, insulin, and glucagon occurred following treatment with AC2993. In study B, 13 subjects receiving a single dose of study medication (0.05, 0.1, or 0.2 micro g/kg AC2993 or placebo) following an overnight fast had reduced fasting plasma glucose concentrations during the subsequent 8-h period. The relative glucose and insulin concentration profiles were consistent with glucose-dependent insulinotropism. AC2993 was well tolerated. Mild transient headache, nausea, and vomiting were the main adverse events. In conclusion, AC2993 acutely and markedly reduces fasting and postprandial glucose concentrations in patients with type 2 diabetes. During fasting, glucose-dependent enhancement of insulin secretion and suppression of glucagon secretion are the predominant mechanisms, and postprandially, slowing of gastric emptying is additionally operative. This robust antidiabetic effect warrants further evaluation of AC2993.

Pramlintide as an adjunct to insulin therapy improves long-term glycemic and weight control in patients with type 2 diabetes: a 1-year randomized controlled trial

OBJECTIVE

Mealtime amylin replacement with the human amylin analog pramlintide, as an adjunct to mealtime insulin replacement, reduces postprandial glucose excursions in patients with type 2 diabetes. The aim of the present study was to assess the long-term efficacy and safety of pramlintide in this patient population.

RESEARCH DESIGN AND METHODS

In a 52-week, double-blind, placebo-controlled, parallel-group, multicenter study, 656 patients with type 2 diabetes (age 57 +/- 10 years, diabetes duration 12 +/- 7 years, BMI 34.0 +/- 7.0 kg/m(2), HbA(1c) 9.1 +/- 1.2%, mean +/- SD) treated with insulin (alone or in combination with sulfonylureas and/or metformin) were randomized to receive additional preprandial subcutaneous injections of either placebo or pramlintide (60 micro g TID, 90 microg BID, or 120 microg BID).

RESULTS

Treatment with pramlintide 120 micro g BID led to a sustained reduction from baseline in HbA(1c) (-0.68 and -0.62% at weeks 26 and 52, respectively), which was significantly greater than that seen with placebo (P < 0.05). The proportion of patients achieving an HbA(1c) <8% was approximately twofold greater with pramlintide (120 microg BID) than with placebo (46 vs. 28%, P < 0.05). The glycemic improvement with pramlintide 120 micro g BID was accompanied by a mean weight loss (-1.4 kg vs. +0.7 kg with placebo at week 52, P < 0.05) and occurred without an overall increase in the severe hypoglycemia event rate. The most common adverse event associated with pramlintide use was transient, mild-to-moderate nausea.

CONCLUSIONS

Mealtime amylin replacement with pramlintide 120 microg BID, as an adjunct to insulin therapy, improves long-term glycemic and weight control in patients with type 2 diabetes.

Impact of pramlintide on glucose fluctuations and postprandial glucose, glucagon, and triglyceride excursions among patients with type 1 diabetes intensively treated with insulin pumps

OBJECTIVE

To assess the effects of adjunctive treatment with pramlintide, an analog of the beta-cell hormone amylin, on 24-h glucose fluctuations and postprandial glucose, glucagon, and triglyceride excursions in patients with type 1 diabetes intensively treated with continuous subcutaneous insulin infusion (CSII).

RESEARCH DESIGN AND METHODS

In this study, 18 patients (16 of whom could be evaluated) with type 1 diabetes (age 44 +/- 11 years, HbA(1c) 8.2 +/- 1.3% [mean +/- SD]) were given mealtime injections of 30 micro g pramlintide t.i.d. for 4 weeks in addition to their preexisting CSII regimen (16 lispro, 2 regular insulin). Mealtime insulin boluses were reduced by a minimum of 10% during the first 3 days, and re-adjusted thereafter based on clinical judgment. At weeks 0 (baseline), 4 (on treatment), and 6 (2 weeks off treatment), 24-h interstitial glucose concentrations were measured using a continuous glucose monitoring system (CGMS), and postprandial plasma glucose, glucagon, and triglyceride concentrations were measured in response to a standardized test meal.

RESULTS

At baseline, patients had excessive 24-h glucose fluctuations, with 59% of the CGMS measurements >140 mg/dl, 13% <80 mg/dl, and only 28% in the euglycemic range (80-140 mg/dl). After 4 weeks on pramlintide, measurements in the hyperglycemic range declined to 48% and measurements within the euglycemic range increased to 37%. This shift from the hyperglycemic to the euglycemic range occurred with a concomitant 17% reduction in mealtime insulin dosages and without relevant increases in measurements below the euglycemic range (15%) or any severe hypoglycemic events. After 4 weeks on pramlintide, postprandial glucose, glucagon, and triglyceride excursions were reduced by approximately 86, approximately 87, and approximately 72%, respectively (incremental areas under the curve, all P < 0.05 vs. baseline). At week 6 (off treatment), the 24-h glucose profile and postprandial glucose, glucagon, and triglyceride excursions approached pretreatment values.

CONCLUSIONS

In this study, the addition of pramlintide to insulin therapy reduced excessive 24-h glucose fluctuations as well as postprandial glucose, glucagon, and triglyceride excursions in patients with type 1 diabetes intensively treated with insulin pumps.

The human amylin analog, pramlintide, reduces postprandial hyperglucagonemia in patients with type 2 diabetes mellitus

AIMS

Amylin is a second beta-cell hormone that is normally co-secreted with insulin in response to meals; it complements the effects of insulin in postprandial glucose control, in part by suppressing glucagon secretion. In patients with type 2 diabetes, mealtime administration of the human amylin analog pramlintide markedly improves postprandial glucose excursions. The aim of this study was to examine whether pramlintide reduces the postprandial hyperglucagonemia that is often seen in this patient population.

METHODS

Utilizing a single-blind, placebo-controlled crossover design, 24 patients with type 2 diabetes, 12 insulin-treated and 12 non-insulin-treated, underwent a standardized mixed meal test on 2 occasions during which they received, in randomized order, a five-hour intravenous infusion of placebo or pramlintide (100 microg/h).

RESULTS

During the placebo infusion, plasma glucose and plasma glucagon concentrations increased substantially after the meal. During the pramlintide infusion, postprandial plasma glucose and plasma glucagon responses were significantly (p < 0.05, all) reduced following ingestion of the same meal, both in the insulin-treated and non-insulin-treated subgroups.

CONCLUSION

Supplementation of mealtime amylin with pramlintide reduces postprandial hyperglucagonemia in patients with type 2 diabetes, a mechanism that likely contributes to pramlintide's postprandial glucose-lowering effect.

The human amylin analog, pramlintide, corrects postprandial hyperglucagonemia in patients with type 1 diabetes

Mealtime amylin replacement with the human amylin analog pramlintide as an adjunct to insulin therapy improves postprandial glycemia and long-term glycemic control in type 1 diabetes. Preclinical animal studies indicate that these complementary effects may result from at least 2 independent mechanisms: a slowing of nutrient delivery to the small intestine and a suppression of nutrient-stimulated glucagon secretion. The former effect of pramlintide has previously been demonstrated in patients with type 1 diabetes. The present studies characterize the effect of pramlintide on postprandial glucagon secretion in this patient population. Plasma glucagon and glucose concentrations were measured before and after a standardized liquid meal in 2 separate randomized, double-blind, placebo-controlled studies of pramlintide administration to patients with type 1 diabetes. In a 2-day crossover study, 18 patients received a 5-hour intravenous infusion of pramlintide (25 microg/h or 50 microg/h) or placebo in addition to subcutaneous (SC) insulin injections. In a 14-day parallel-group study, 84 patients received SC injections of 30, 100, or 300 microg of pramlintide or placebo 3 times daily in addition to SC injections of insulin. In both studies plasma glucagon concentrations increased in response to the meal in the placebo-plus-insulin group but not in any of the pramlintide-treated groups (all pramlintide treatment arms v placebo, P <.05). We conclude that mealtime amylin replacement with pramlintide prevents the abnormal meal-related rise in glucagonemia in insulin-treated patients with type 1 diabetes, an effect that likely contributes to its ability to improve postprandial glucose homeostasis and long-term glycemic control.

A randomized study and open-label extension evaluating the long-term efficacy of pramlintide as an adjunct to insulin therapy in type 1 diabetes

OBJECTIVE

To assess the effect of mealtime amylin replacement with pramlintide on long-term glycemic and weight control in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

In a 52-week, double-blind, placebo-controlled, multicenter study, 480 patients with type 1 diabetes were randomized to receive preprandial injections of placebo or 30 microg pramlintide q.i.d., in addition to existing insulin regimens. At week 20, pramlintide-treated patients were re-randomized to 30 or 60 microg pramlintide q.i.d. if decreases from baseline in HbA(1c) were <1% at week 13. Of the 342 patients who completed the 52-week study, 236 individuals ( approximately 70%) elected to participate in a 1-year open-label extension in which all patients received 30 or 60 microg pramlintide q.i.d.

RESULTS

Treatment with pramlintide led to a mean reduction in HbA(1c) of 0.67% from baseline to week 13 that was significantly (P < 0.0001) greater than the placebo reduction (0.16%), and a significant placebo-corrected treatment difference was sustained through week 52 (P = 0.0071). The greater HbA(1c) reduction was associated with an average weight loss, rather than weight gain, and was not accompanied by an increased overall event rate of severe hypoglycemia. In the open-label extension, mean HbA(1c) levels decreased rapidly in patients receiving pramlintide for the first time and remained at reduced levels in patients who continued pramlintide treatment. The most common adverse events reported by the pramlintide group were mild nausea and anorexia, which both occurred during the initial weeks of treatment and dissipated over time.

CONCLUSIONS

Mealtime pramlintide treatment as an adjunct to insulin improved long-term glycemic control without inducing weight gain or increasing the overall risk of severe hypoglycemia in patients with type 1 diabetes.

Adjunctive therapy with the amylin analogue pramlintide leads to a combined improvement in glycemic and weight control in insulin-treated subjects with type 2 diabetes

The objective of this study was to assess the effect of mealtime amylin replacement with pramlintide on long-term glycemic and weight control in subjects with type 2 diabetes. This 52-week, randomized, placebo-controlled, multicenter, double-blind, dose-ranging study in 538 insulin-treated subjects with type 2 diabetes compared the efficacy and safety of 30-, 75-, or 150-microg doses of pramlintide, a synthetic analogue of the beta-cell hormone amylin, to placebo when injected subcutaneously three times daily (TID) with major meals. Pramlintide therapy led to a mean reduction in HbA1c of 0.9% and 1.0% from baseline to week 13 in the 75- and 150-microg dose groups, which was significant compared to placebo (p = 0.0004 and p = 0.0002, respectively). In the 150-microg dose group, there was a mean reduction in HbA1c of 0.6% from baseline to week 52 (p = 0.0068 compared to placebo). The greater reduction in HbA1c with pramlintide was achieved without increases in insulin use or severe hypoglycemia, and was accompanied by a significant (p < 0.05) reduction in body weight in all dose groups compared to placebo. Three times the proportion of subjects in the 150-microg pramlintide group compared to the placebo group achieved a concomitant reduction in both HbA1c and body weight from baseline to week 52 (48% versus 16%). The most common adverse event reported with pramlintide treatment was nausea, which was mild to moderate and dissipated early in treatment. The results from this study support the safety and efficacy of pramlintide administered three times a day with major meals, in conjunction with insulin therapy, for improving long-term glycemic and weight control in subjects with type 2 diabetes.

Amylin replacement with pramlintide as an adjunct to insulin therapy in type 1 and type 2 diabetes mellitus: a physiological approach toward improved metabolic control

Destruction and dysfunction of pancreatic beta-cells, resulting in absolute and relative insulin deficiency, represent key abnormalities in the pathogenesis of type 1 and type 2 diabetes, respectively. Following the discovery of amylin, a second beta-cell hormone that is co-secreted with insulin in response to nutrient stimuli, it was realized that diabetes represents a state of bihormonal beta cell deficiency and that lack of amylin action may contribute to abnormal glucose homeostasis. Experimental studies show that amylin acts as a neuroendocrine hormone that complements the effects of insulin in postprandial glucose regulation through several centrally mediated effects. These include a suppression of postprandial glucagon secretion and a vagus-mediated regulation of gastric emptying, thereby helping to control the influx of endogenous and exogenous glucose, respectively. In animal studies, amylin has also been shown to reduce food intake and body weight, consistent with an additional satiety effect. Pramlintide is a soluble, non-aggregating, injectable, synthetic analog of human amylin currently under development for the treatment of type 1 and insulin-using type 2 diabetes. Long-term clinical studies have consistently demonstrated that pre-prandial s.c. injections of pramlintide, in addition to the current insulin regimen, reduce HbA(1c) and body weight in type 1 and type 2 diabetic patients, without an increase in insulin use or in the event rate of severe hypoglycemia. The most commonly observed side effects were gastrointestinal-related, mainly mild nausea, which typically occurred upon initiation of treatment and resolved within days or weeks. Amylin replacement with pramlintide as an adjunct to insulin therapy is a novel physiological approach toward improved long-term glycemic and weight control in patients with type 1 and type 2 diabetes.

Pramlintide, a synthetic analog of human amylin, improves the metabolic profile of patients with type 2 diabetes using insulin. The Pramlintide in Type 2 Diabetes Group

OBJECTIVE

To examine the effects of 4 weeks of subcutaneous administration of pramlintide, a synthetic analog of human amylin, on metabolic control in patients with type 2 diabetes using insulin.

RESEARCH DESIGN AND METHODS

Serum fructosamine, HbA1c, and fasting plasma lipids were measured in 203 patients in a randomized double-blind placebo-controlled parallel-group multicenter trial using doses of 30 micrograms q.i.d., 60 micrograms t.i.d., and 60 micrograms q.i.d.

RESULTS

Statistically significant reductions in serum fructosamine concentrations were observed in the pramlintide 30 micrograms q.i.d. group (17.5 +/- 4.9 mumol/l, P = 0.029), the pramlintide 60 micrograms t.i.d. group (24.1 +/- 4.9 mumol/l, P = 0.003), and the 60 micrograms q.i.d. group (22.6 +/- 4.1 mumol/l, P = 0.001) compared with the placebo group (3.5 +/- 3.8 mumol/l). There were also statistically significant shifts in the proportion of patients with an abnormal serum fructosamine concentration at baseline that normalized at week 4 within the pramlintide 60 micrograms t.i.d. group and the 60 micrograms q.i.d. group. Consistent with the fructosamine results, there were statistically significant reductions in HbA1c in the pramlintide 30 micrograms q.i.d. group (0.53 +/- 0.07%, P = 0.0447), the pramlintide 60 micrograms t.i.d. group (0.58 +/- 0.07%, P < 0.0217), and the pramlintide 60 micrograms q.i.d. group (0.51 +/- 0.08%, P = 0.0242) compared with the placebo group (0.27 +/- 0.08%). Total cholesterol concentrations were also statistically significantly reduced in both the pramlintide 60 micrograms t.i.d. group (8.4 mg/dl, P < 0.01) and 60 micrograms q.i.d. group (10.5 mg/dl, P < 0.01) compared with placebo (1.2 mg/dl). Body weight decreased in both of the pramlintide 60 micrograms groups, but the trend did not achieve statistical significance. The incidence of hypoglycemia was similar in all treatment groups.

CONCLUSIONS

Reductions in serum fructosamine, plasma total and LDL cholesterol concentrations, and HbA1c support the hypothesis that pramlintide may improve metabolic control in patients with type 2 diabetes using insulin.

Effects of 4 weeks' administration of pramlintide, a human amylin analogue, on glycaemia control in patients with IDDM: effects on plasma glucose profiles and serum fructosamine concentrations

The effects of 4 weeks' administration of pramlintide, an analogue of the human hormone amylin, on blood glucose control in 215 patients with insulin-dependent diabetes mellitus were examined in a 4-week, randomized, double-blind, placebo-controlled, parallel-group trial. Pramlintide was administered subcutaneously prior to meals in four dosing regimens: 30 microg four times per day (breakfast, lunch, dinner, and evening snack), 30 microg three times per day (breakfast, lunch and dinner [BLD]), 30 microg three times per day (breakfast, dinner and evening snack [BDS]), and 60 microg twice per day (breakfast and dinner). After 4 weeks of pramlintide 30 microg four times per day administration, there was a statistically significant reduction in the mean 24 h plasma glucose concentration when compared to placebo (-1.4 +/- 0.5 vs 0.3 +/- 0.5 micromol/l, p = 0.009). Serum fructosamine concentrations were reduced 62 +/- 10 micromol/l in the pramlintide 30 mg four times per day group, 43 +/- 7 micromol/l in the pramlintide 30 microg three times per day (BLD) group, 47 +/- 6 micromol/l in the pramlintide 30 microg three times per day (BDS) group, 46 +/- 7 micromol/l in the pramlintide 60 microg twice per day group, and 29 +/- 8 micromol/l by placebo. The incidence of hypoglycaemia was not different in any pramlintide group compared to the placebo group. Nausea, the most frequent adverse event, subsided after the first week of treatment in the majority of patients. In conclusion, pramlintide improved blood glucose control over a 4-week period without increased hypoglycaemia and was well tolerated. Future studies using a longer period of pramlintide administration with assessment of HbA1c as the measurement of glycaemic control are warranted.

Pramlintide: a human amylin analogue reduced postprandial plasma glucose, insulin, and C-peptide concentrations in patients with type 2 diabetes

In order to determine the influence of a 5 h infusion of pramlintide compared to placebo on postprandial glucose, lactate, insulin, and C-peptide concentrations in patients with Type 2 diabetes, a single-blind, randomized, cross-over study was conducted in 24 patients; 12 treated with exogenous insulin and 12 managed with diet and/or oral hypoglycaemic agents. One hour after initiation of infusion, patients consumed a Sustacal test meal. The protocol was repeated on the following day with each patient receiving the alternate study medication. Pramlintide infusion in the insulin-treated patients resulted in statistically significant reductions in mean glucose, insulin, C-peptide, and lactate concentrations during the 4-h period after the Sustacal test meal. Pramlintide infusion also resulted in significant reductions of mean insulin, C-peptide, and lactate concentrations, but not glucose concentrations, in the patients treated with diet and/or oral hypoglycaemic agents. Within this latter group, reduction in postprandial glucose concentrations in individual patients correlated with glycated haemoglobin values. These results suggest that administration of pramlintide may improve glycaemic control in patients with Type 2 diabetes treated with insulin or poorly controlled on diet and/or oral hypoglycaemic agents.

Amylin and glycaemic regulation: a possible role for the human amylin analogue pramlintide

Clinical studies with the human amylin analogue, pramlintide, suggest that it may help to improve glycaemic control in patients with diabetes mellitus using insulin. This has been demonstrated by reductions in postprandial glycaemic excursion, 24-h glucose profile and serum fructosamine concentrations following administration of pramlintide for periods of up to 28 days in patients with Type 1 diabetes. Additionally, preliminary studies with pramlintide in patients with Type 2 diabetes using insulin have indicated its ability to reduce postprandial hyperglycaemia in this population. Thus, this data set suggests a potential role for pramlintide as a partner to insulin for the optimization of glycaemic control in patients with diabetes using insulin.

Self-care behaviors in insulin-dependent diabetes: evaluative tools and their associations with glycemic control

Clarified the relationships between self-care behaviors and illness-specific outcomes in approximately 270 youths with IDDM. Youths were assessed at three points in time using a semistructured interview measure and multiple indices of dietary intake and physical activity with two different methodologies (i.e., recalls, logs). Glycemic control was most strongly related to the semistructured Self-Care Adherence Interview (SCAI); and second to the overall quality of the youth's dietary intake. The SCAI also predicted glycemic control over time. Physical activity levels and specific nutritional components from the logs and recalls were generally unrelated to glycemic control.

Effect of 14 days' subcutaneous administration of the human amylin analogue, pramlintide (AC137), on an intravenous insulin challenge and response to a standard liquid meal in patients with IDDM

Individuals with insulin-dependent diabetes mellitus (IDDM or type 1 diabetes) are deficient in both insulin and amylin, peptides secreted by the beta cell. We have investigated the effects of amylin replacement therapy employing the human amylin analogue, pramlintide (25, 28, 29-pro-human amylin, previously referred to as AC137), upon the responses to a standardized insulin infusion (40 mU. kg-1. h-1) for 100 min and a liquid Sustacal meal (360 kcal) in 84 healthy IDDM patients. Following baseline evaluations, patients were randomly assigned to receive subcutaneous injections of placebo, 30, 100 or 300 micrograms pramlintide 30 min before meals for 14 days. There was no meaningful difference between adverse events reported by the 30-micrograms pramlintide and the placebo groups, but ten subjects withdrew due to nausea, eight of these in the 300-micrograms dose group. Peak plasma pramlintide concentrations for the 30-micrograms group were 21 +/- 3 and 29 +/- 5 pmol/l on Days 1 and 14, respectively. These values are similar to postprandial plasma amylin concentrations in normal volunteers. The plasma glucose, free insulin, glucagon, epinephrine and norepinephrine concentrations during the insulin infusion test before and after therapy were identical in each of the group. Prior to pramlintide therapy, Sustacal ingestion produced a 4.0-4.8 mmol/l rise in plasma glucose concentrations in each of the groups. Pramlintide therapy reduced postprandial hyperglycaemia as reflected by the 3-h incremental AUCglucose (AUCglucose above or below fasting glucose concentration) Day 1 vs Day 14: 30 micrograms, 322 +/- 92 vs -38 +/- 161 mmol/l.min, p = 0.010; 100 micrograms, 317 +/- 92 vs -39 +/- 76 mmol/l.min, p = 0.001; and 300 micrograms, 268 +/- 96 vs -245 +/- 189 mmol/l.min, p = 0.077. Thus, pramlintide therapy with these regimens did not appear to impair either in vivo insulin action or the counter-regulatory response to hypoglycaemia but did show a clear effect of blunting postprandial hyperglycaemia following a standardized meal.

Pharmacokinetics and pharmacodynamics of AC137 (25,28,29 tripro-amylin, human) after intravenous bolus and infusion doses in patients with insulin-dependent diabetes

A study was conducted to evaluate the effect of 30-mug, 100-mug, and 300-mug 2-minute bolus doses and 2-hour infusion doses of AC137 (25,28,29 tripro-amylin, human) on plasma AC137 concentrations and plasma glucose and lactate responses in patients with insulin-dependent diabetes mellitus (IDDM). The study design was an imbedded two-way cross-over wherein patients received placebo and active boluses in one period and placebo and active infusions in the other period. Two patients in each dose group received placebo throughout the two periods. Pharmacokinetics and pharmacodynamics (PK/PD) were determined during the 6-hour period after initiation of dosing. Data were fitted with a linked PK/PD model. Pharmacokinetics were linear over the dose range studied, and attenuation of glucose and lactate responses to a mixed meal was dose and concentration dependent. The results of the PK/PD model indicate that the attenuation of glucose and lactate responses was greater after AC137 infusion doses than after the same doses given as a bolus. Glucose and lactate responses to a mixed meal were essentially negated by the 300-mug infusion dose.

Empirical validation for a family-centered model of care

OBJECTIVE

To examine whether family relations and family-life stress predict adherence behaviors and metabolic control in youths by testing a theoretically- and empirically-based model.

RESEARCH DESIGN AND METHODS

HbA1c levels of 157 youths 12-20 years of age with insulin-dependent diabetes mellitus (IDDM) were evaluated, along with treatment adherence and psychosocial family data based on interviews and self-reports. A family-centered model for IDDM care was analyzed with the EQS structural modeling statistical program. An additional exploratory model including HbA1c levels 6 months earlier was also tested.

RESULTS

Positive family relations (high family cohesion and low family conflict), especially during the first years of illness, indirectly related to good metabolic control through positive adherence behaviors. High levels of family-life stress related to worse metabolic control directly, and also indirectly via poor family relations, which in turn related to poor adherence to treatment. Longer illness duration related indirectly to metabolic control via adherence to treatment. Longer illness duration also related to maternal perceptions of higher family-life stress. Older youths perceived more family-life stress as well. The older age of the youths related indirectly to poor metabolic control through its association with poor adherence behaviors and less cohesive and more conflictual family relations. Results were consistent when earlier levels of metabolic control were included in the model, except that the direct relationship between family-life stress and metabolic control became nonsignificant.

CONCLUSIONS

The findings suggest that a family-centered approach to diabetes care that facilitates positive family functioning and leads to lower levels of family-life stress may be useful in promoting optimal health outcomes.

Low-carbohydrate diet alters intracellular glucose metabolism but not overall glucose disposal in exercise-trained subjects

Dietary composition has been strongly implicated as an important determinant of in vivo insulin sensitivity. However, the metabolic alterations associated with extreme changes in diet have not been well described. We compared glucose metabolism after a standard diet ([STD] 35% fat, 51% carbohydrate, and 14% protein) with the effects of a 3-week adaptation to a low-carbohydrate, high-fat diet ([LCD] 75% fat, 8% carbohydrate, and 17% protein). Ten healthy men were studied using the euglycemic clamp technique, indirect calorimetry, and percutaneous vastus lateralis muscle biopsies for analysis of glycogen synthase (GS) and pyruvate dehydrogenase (PDH) activities in the basal and insulin-stimulated states. Insulin-stimulated glucose disposal was unchanged (STD 46.1 +/- 4.3 v LCD 46.0 +/- 4.3 mumol/kg.min, P = NS), but marked alterations in the routes of glucose disposal were noted. Insulin-stimulated glucose oxidation (Gox) was markedly reduced following LCD (STD 18.6 +/- 1.9 v LCD 8.23 +/- 1.9 mumol/kg.min, P = .0001), and nonoxidative glucose metabolism (Gnox) was enhanced by LCD (STD 24.9 +/- 0.9 v LCD 38.9 +/- 4.3 mumol/kg.min, P = .03). Following LCD, both the total and active forms of PDH (PDHt and PDHa) were significantly depressed. After LCD, GS activates (FV0.1, %I, and A0.5) were unaffected in the basal state, but were greater than for STD (P = .004) after insulin stimulation. The apparent increase in the sensitivity of GS to activation by insulin following LCD correlated strongly with maximal O2 consumption ([VO2max] r = .97, P = .001), suggesting that physical conditioning interacted with the metabolic impact of LCD. In summary, LCD did not induce changes in net glucose disposal.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of postprandial hyperglycemia in subjects with IDDM by intravenous infusion of AC137, a human amylin analogue

OBJECTIVE

To demonstrate that intravenous administration of AC137 (25,28,29 tripro-human amylin), a human amylin analogue, modulates the rate of appearance of glucose derived from a standard oral meal in the peripheral circulation of patients with insulin-dependent diabetes mellitus (IDDM).

RESEARCH DESIGN AND METHODS

After the observation that a 2-h infusion of AC137 at a rate of 150 micrograms/h, in conjunction with the subjects' usual morning insulin dose, decreased postprandial hyperglycemia in 6 subjects with IDDM, a double-blind placebo-controlled two-period crossover design in an additional 18 IDDM patients was undertaken to confirm and extend the observation. Based on reasoning that an effect to modulate the appearance of orally administered glucose would have no impact on the disposition of an intravenous glucose load, nine patients were challenged with an intravenous glucose loads (300 mg/kg), while another nine patients were challenged with a standardized Sustacal meal (350 kcal) during a 5-h infusion of AC137 (50 micrograms/h). On each occasion, the subjects received their usual morning doses of insulin subcutaneously. The impact of the AC137 infusion on the plasma glucose responses to these different challenges was assessed.

RESULTS

Intravenous infusion of AC137 yielding steady state plasma concentrations of 225 +/- 15 pmol/l (mean +/- SE) reduced postprandial plasma glucose concentrations after the standardized Sustacal meal challenge. The mean area under the glucose curve, corrected for baseline, was reduced from -1,869 +/- 5,562 mg.dl-1.min during placebo infusion to -28,872 +/- 4,812 mg.dl-1.min during AC137 infusion, P = 0.0015. In contrast, an AC137 infusion producing steady-state concentrations of 234 +/- 16 pmol/l had no effect on the plasma glucose profile after administration of an intravenous glucose load.

CONCLUSIONS

AC137 administration, in these patients with IDDM, reduced postprandial hyperglycemia apparently by affecting the delivery rate of glucose from the gastrointestinal tract. AC137 may prove to be a clinically useful addition to insulin regimens to facilitate the achievement of glycemic control.

Glyburide in non-insulin-dependent diabetes: an update

Recent data suggest that non-insulin-dependent diabetes mellitus (NIDDM) may evolve in genetically predisposed individuals beginning with impaired peripheral glucose metabolism followed by insulin deficiency. Glyburide is an effective, long-acting, second-generation oral sulfonylurea introduced in the United States in 1984. In comparison with the first-generation sulfonylureas, glyburide is at least as effective, has a lower incidence of side effects, and may enhance postreceptor insulin activity to a greater degree. Glyburide can improve glycemic control, as evidenced by reduced fasting blood glucose concentrations and glycohemoglobin levels, without the inconvenience of insulin injections, the higher plasma insulin concentrations, and the additional training required to administer insulin. Because of its ability to enhance target tissue insulin action, glyburide also improves glycemic control in many NIDDM patients who have previously failed therapy with other sulfonylurea agents. Gluburide, as adjunctive therapy, may reduce the daily dosage needed by those who require insulin. Favorable pharmacokinetics and high inherent potency of glyburide often allow effective therapy when the drug is administered once a day.

Elevated insulin, norepinephrine, and neuropeptide Y in hypertension

To investigate the relationship between insulin and sympathetic activity, plasma norepinephrine, neuropeptide Y, serum glucose and insulin concentrations were measured in ten age-, weight-, and sex-matched normotensive and untreated hypertensive subjects at fasting and 2 h following ingestion of a 75 g oral glucose dose. Hypertensives had higher fasting serum insulin (27 +/- 6 v 12 +/- 2 microU/mL; P = .02) and plasma norepinephrine (356 +/- 38 v 235 +/- 35 pg/mL; P = .03) concentrations than normotensives. Glucose load increased serum insulin (P less than .001) and plasma norepinephrine concentrations (P = .001) in both groups and hypertensives had still higher postglucose insulin (P = .003) and norepinephrine levels (P = .003) than normotensives. Fasting neuropeptide Y was higher in hypertensives than in normotensives (P = .03) and correlated with age in both groups (r = 0.7; r = 0.77). Postglucose serum insulin correlated positively with plasma norepinephrine (r = 0.75; P = .013) in normotensives, but these parameters correlated negatively in hypertensives (r = -0.7; P = .036). We hypothesize that elevated plasma norepinephrine and neuropeptide Y levels reflect an increased level of sympathetic nervous activity in hypertensives, which in turn may be responsible for the abnormal relationship between plasma NE and insulin levels.

Day-long integrated serum insulin and C-peptide profiles in patients with NIDDM. Correlation with urinary C-peptide excretion

To determine whether non-insulin-dependent diabetes mellitus (NIDDM) is characterized by day-long hypoinsulinemia, we measured 24-h serum profiles for glucose, insulin, and C-peptide by use of a constant-rate blood-withdrawal technique in diabetic and control subjects fed isocaloric meals. When only lean subjects were considered, diabetic subjects (relative body weight 0.99 +/- 0.3) and control subjects (relative body weight 0.95 +/- 0.03) had similar 24-h integrated serum insulin concentrations (13.4 +/- 2.5 vs. 16.1 +/- 2.0 microU/ml, P NS) due to the offsetting effects of increased basal levels and decreased postprandial responses in NIDDM. In contrast, both basal and meal-stimulated insulin levels were decreased in obese NIDDM subjects (relative body weight 1.39 +/- 0.07) compared with obese control subjects (relative body weight 1.60 +/- 0.08), resulting in a 61% reduction in the 24-h integrated insulin value (18.7 +/- 1.5 vs. 48.4 +/- 13.7 microU/ml). Thus, the capacity to increase 24-h integrated serum insulin as a function of relative body weight was impaired in NIDDM subjects (r = 0.27, P NS) compared with control subjects (r = .70, P less than .01). In contrast, 24-h integrated C-peptide was decreased (P less than .01) in both lean (0.92 +/- 0.13 pM/ml) and obese (1.52 +/- 0.19 pM/ml) NIDDM patients compared with the respective control groups (1.50 +/- 0.13 and 3.03 +/- 0.44 pM/ml). The molar ratio of 24-h integrated C-peptide to insulin was diminished in lean but not obese NIDDM compared with control subjects. A 3-wk period of intensive insulin therapy led to normalization of the mean 24-h integrated insulin (but not integrated serum C-peptide) value in NIDDM compared with a control group that had an identical mean relative body weight. The 24-h urinary C-peptide measured on the same day as the serum profile was correlated (P less than .01) with both the 24-h integrated serum insulin (r = .69) and C-peptide (r = .67) concentrations in control subjects but not in NIDDM subjects (r = .20 and .04, respectively, P NS). Additionally, the urinary clearance of C-peptide was increased in NIDDM (38.1 +/- 7.8 vs. 20.4 +/- 1.7 ml/min in control subjects, P less than .05) and varied with treatment status (26.0 +/- 4.6 ml/min after insulin therapy).(ABSTRACT TRUNCATED AT 400 WORDS)

Decreased activation of skeletal muscle glycogen synthase by mixed-meal ingestion in NIDDM

Glycogen synthase (GS) catalyzes the formation of glycogen in human skeletal muscle, the tissue responsible for disposal of a significant portion of an oral carbohydrate load. Non-insulin-dependent diabetes mellitus (NIDDM) is characterized by fasting and postprandial hyperglycemia in conjunction with reduced rates of insulin-stimulated glucose disposal and storage in peripheral tissues, including muscle. Our objectives in this study were to determine whether ingestion of a mixed meal activates GS in control nondiabetic subjects and whether meal-related GS activation is reduced in NIDDM. To accomplish this, mixed formula meals were administered to 11 NIDDM and 9 age- and weight-matched nondiabetic control subjects. Plasma glucose and insulin values were measured before and for 90 min after meal ingestion. Skeletal muscle biopsies were performed just before and 90 min after meal ingestion for measurement of GS activity. Compared with control subjects, NIDDM subjects had significantly higher postprandial hyperglycemia and reduced postprandial hyperinsulinemia. GS was activated by meal ingestion in control subjects to a significantly greater extent than in NIDDM subjects. In NIDDM subjects, activation of GS was inversely correlated with fasting plasma glucose (r = .69, P less than .05). Therefore, NIDDM is characterized by reduced activation of a key step in the process of muscle glycogen repletion after a meal. Reduced activation of GS by a mixed meal in NIDDM may contribute to the reduced glucose disposal after a meal, thus contributing to the hyperglycemia observed in these subjects.

Effects of insulin infusion on human skeletal muscle pyruvate dehydrogenase, phosphofructokinase, and glycogen synthase. Evidence for their role in oxidative and nonoxidative glucose metabolism

To determine whether activation by insulin of glycogen synthase (GS), phosphofructokinase (PFK), or pyruvate dehydrogenase (PDH) in skeletal muscle regulates intracellular glucose metabolism, subjects were studied basally and during euglycemic insulin infusions of 12, 30, and 240 mU/m2 X min. Glucose disposal, oxidative and nonoxidative glucose metabolism were determined. GS, PFK, and PDH were assayed in skeletal muscle under each condition. Glucose disposal rates were 2.37 +/- 0.11, 3.15 +/- 0.19, 6.71 +/- 0.44, and 11.7 +/- 1.73 mg/kg X min; glucose oxidation rates were 1.96 +/- 0.18, 2.81 +/- 0.28, 4.43 +/- 0.32, and 5.22 +/- 0.52. Nonoxidative glucose metabolism was 0.39 +/- 0.13, 0.34 +/- 0.26, 2.28 +/- 0.40, and 6.52 +/- 1.21 mg/kg X min. Both the proportion of active GS and the proportion of active PDH were increased by hyperinsulinemia. PFK activity was unaffected. Activation of GS was correlated with nonoxidative glucose metabolism, while activation of PDH was correlated with glucose oxidation. Sensitivity to insulin of GS was similar to that of nonoxidative glucose metabolism, while the sensitivity to insulin of PDH was similar to that of glucose oxidation. Therefore, the activation of these enzymes in muscle may regulate nonoxidative and oxidative glucose metabolism.

The effect of short-term alpha-glucosidase inhibition on carbohydrate and lipid metabolism in type II (noninsulin-dependent) diabetics

With use of the alpha-glucosidase inhibitor bay g 5421 (acarbose), it is possible to improve glycemic profiles in diabetics without a concomitant increase in insulin levels or weight reduction. We have taken advantage of this feature to test whether an improvement in glycemic control alone can ameliorate some of the known abnormalities of type II diabetes (ie, impaired insulin secretion, elevated rate of basal hepatic glucose output, peripheral insulin resistance). We have studied eight type II diabetics (mean +/- SE fasting serum glucose 193 +/- 25 mg/dL) before and after 2 weeks of acarbose therapy (100 mg with each meal). Assessment of endogenous insulin secretion, peripheral and hepatic insulin sensitivity, and adipose tissue lipoprotein lipase (ATLPL) activity were performed. Results showed significant lowering of postprandial glucose excursions above basal but no change in basal serum glucose levels, marked reduction in fasting and day-long triglyceride levels and in spite of a reduction in ATLPL activity, an increase in hepatic sensitivity to insulin's ability to suppress hepatic glucose output, and no effect on peripheral insulin sensitivity. In conclusion, inhibition of carbohydrate digestion with alpha-glucosidase inhibitors ameliorates many of the metabolic abnormalities in type II (noninsulin-dependent diabetics), suggesting that agents of this type can be of therapeutic value.

The impact of sulfonylureas on hepatic glucose metabolism in type II diabetics

Fasting hyperglycemia in subjects with NIDDM appears to be the final result of abnormalities in endogenous insulin secretion combined with diminished peripheral insulin action secondary to a combined receptor and postbinding defect in cellular insulin action and accelerated hepatic glucose production. Of these various abnormalities, the accelerated rate of hepatic glucose production appears to be of major importance in determining the overall severity of the hyperglycemia. The hyperglycemia, which is maintained by the accelerated rate of hepatic glucose release, appears to compensate for the decrease in insulin action at the level of the peripheral tissues, as well as the liver. Although this compensatory effect of hyperglycemia appears to match the decrease in insulin action in the peripheral tissues rather precisely, the compensation at the level of the liver does not totally restore normal homeostasis. These observations suggest that the liver and peripheral tissues are intimately linked via mechanisms that remain to be delineated. Recent observations of alterations in the activities of key rate-limiting enzymes in the pathway for oxidiative glucose metabolism suggest that an abundance of glucose precursors may be made in peripheral tissues, which then recycle to the liver to support and/or drive the accelerated rates of hepatic glucose production. Additional studies are clearly needed in these areas to further delineate these crucial issues. In a similar manner, the role of the liver in determining the success of various therapeutic modalities in these subjects appears to be of paramount importance. The data reviewed regarding the mechanisms of action of sulfonylurea agents indicate that the quality of glycemic control achieved in subjects treated with these agents is largely determined by the ability of the drug to lower the elevated rates of hepatic glucose production. This suggests that new compounds that are more effective in this regard will prove to be more efficacious.

Role of hyperglucagonemia in maintenance of increased rates of hepatic glucose output in type II diabetics

Elevated rates of basal hepatic glucose output (bHGO) are significantly correlated with the fasting serum glucose (FSG) level in subjects with non-insulin-dependent diabetes mellitus (NIDDM). This observation suggests that bHGO is a major determinant of the severity of the diabetic state in these subjects. In addition, basal glucagon levels (bGL) are higher in these diabetics than in control subjects, despite the concurrent basal hyperglycemia and hyperinsulinemia, two factors known to suppress glucagon secretion. Although bGL is responsible for sustaining two-thirds of bHGO in normal humans, its role in sustaining elevated rates of bHGO in NIDDM has not been previously defined. To this end, we have studied 13 normal and 10 NIDDM subjects; mean FSG levels were 90 +/- 2 and 262 +/- 21 mg/dl, respectively (P less than .001). The mean fasting serum insulin and glucagon levels were higher in the diabetics than in the controls: 17 +/- 2 vs. 9 +/- 1 microU/ml (P less than .01) and 208 +/- 37 vs. 104 +/- 15 pg/ml (P less than .01), respectively. On separate days, HGO was assessed isotopically (with 3-[3H]glucose) in the basal state and during infusion of somatostatin (SRIF) (600 micrograms/h) alone and in conjunction with replacement infusions of glucose and insulin. The results demonstrate that bHGO is higher in diabetics than in controls (145 +/- 12 vs. 89 +/- 3 mg X m-2 X min-1, P less than .01); during infusion of SRIF alone, HGO was suppressed by 25% (P less than .05) and 34% (P less than .05) of the basal value in controls and diabetics, respectively; when the studies were repeated with glucose levels held constant at or near the FSG level by the glucose-clamp technique, the pattern and degree of HGO suppression was similar to that obtained by infusion of SRIF alone; during isolated glucagon deficiency (SRIF + insulin, 5 mU X m-2 min-1, with serum glucose maintained at basal level), HGO was suppressed by 71 +/- 8% of the basal value in controls (P less than .001) and by 58 +/- 7% in diabetics (P less than .001); and when isolated glucagon deficiency with similar hyperglycemia was created in control subjects, HGO was suppressed by 87% of the basal value.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipocyte glycogen synthase and pyruvate dehydrogenase in obese and type II diabetic subjects

To determine whether 1) insulin stimulates pyruvate dehydrogenase (PDH) and glycogen synthase (GS) in isolated human adipocytes and 2) adipocytes from subjects with obesity or noninsulin-dependent diabetes mellitus (NIDDM) are resistant to the effects of insulin, PDH and GS were assayed in adipocytes from 11 control, 8 obese, and 9 NIDDM subjects. Basal PDH activities were 123 +/- 20, 129 +/- 21, and 128 +/- 25 pmol pyruvate oxidized/min per 2 X 10(5) adipocytes in these groups. Insulin stimulated PDH activity to a maximum of 223 +/- 38 pmol/min per 2 X 10(5) in adipocytes from control subjects, but did not significantly increase values from obese subjects. Insulin significantly decreased PDH activity in cells from NIDDM subjects (99 +/- 20 pmol/min per 2 X 10(5) cells, P less than 0.05). PDH activity assayed with high magnesium and calcium concentrations was significantly stimulated by insulin in adipocytes from control, but not obese or NIDDM subjects. GS assayed with 1 mM glucose 6-phosphate did not differ significantly among control, obese, or NIDDM subjects (446 +/- 110, 451 +/- 156, and 291 +/- 35 pmol incorporated into glycogen, respectively). Insulin significantly stimulated glycogen synthase in all three groups (827 +/- 179, 764 +/- 177, and 569 +/- 51 pmol incorporated) to a similar extent. Glycogen synthase assayed with 10 mM glucose 6-phosphate was decreased in NIDDM (1,335 +/- 131 pmol incorporated) compared with obese or control subjects (2,512 +/- 451 and 2,239 +/- 230 pmol incorporated, respectively, P less than 0.01).

Antiinsulin receptor antibodies in an insulin-dependent diabetic may arise as autoantiidiotypes

An insulin-requiring diabetic patient with intermittent periods of increased insulin requirements and insulin resistance was studied. The patient was found to have high titers of antiinsulin antibodies; subfractionation of the patient's serum revealed several populations of antiinsulin antibodies with differing affinities and titers for insulin. The ability of one of the insulin antibody fractions to bind [125I]iodoinsulin was markedly inhibited by the patient's serum (insulin depleted) and by purified total immunoglobulin G from which antiinsulin antibodies and insulin were removed. These findings suggested an antiidiotypic antibody in the patient's immunoglobulin G fraction reacting specifically with the antiinsulin antibody subfraction. Finally, the patient's serum contained an antiinsulin receptor antibody, as demonstrated by the ability of serum to specifically immunoprecipitate covalently labeled soluble insulin receptors. In conclusion, these results suggest that this patient generated a widespread polyclonal response to insulin, with the development of several populations of antiinsulin antibodies. An antiidiotypic antibody to a specific insulin antibody subfraction was present in the patient's serum which we believe had structural similarity to the binding site of the insulin molecule, accounting for the reactivity of the antiidiotypic antibody with the insulin receptor.

Metabolic consequence of two-week fructose feeding in diabetic subjects

We studied the metabolic effects of 2-wk fructose feeding as the sweetener in the diet of seven non-insulin-dependent diabetic individuals. The data demonstrated reduced postprandial hyperglycemia to an oral glucose challenge after 14 days without a significant difference in insulin response. There was no change in the markedly blunted glucose response to a fructose challenge but a significantly lower insulin response (area under the 3-h curve) was observed after 14 days of fructose feeding. There was reduced postprandial hyperglycemia after 14 days of fructose feeding with test meals as compared with baseline, without significant differences in insulin response. We also found no significant difference in free fatty acids, cholesterol, high-density lipoprotein (HDL) cholesterol, pyruvate, lactate, or uric acid after fructose feedings. There was a 13% increase in triglyceride levels after 14 days in 5 subjects with initial fasting hypertriglyceridemia (greater than 150 mg/dl). Insulin receptor binding to isolated adipocytes did not change after 14 days of fructose feeding.

In vivo deactivation of proinsulin action on glucose disposal and hepatic glucose production in normal man

We have studied the deactivation of the in vivo actions of insulin and biosynthetic human proinsulin (recombinant DNA) to stimulate the glucose disposal rate (GDR) and to inhibit hepatic glucose output (HGO) in man. Twelve healthy, lean, young subjects were studied using a modification of the euglycemic glucose clamp technique. Subjects received 4-h infusions on separate occasions of insulin (15 mU/m2/min equivalent to 0.54 microgram/m2/min) or proinsulin (2.75 micrograms/m2/min), achieving steady-state serum levels of 32 +/- 3 microU/ml (equivalent to 0.23 +/- 0.02 pmol/ml) and 3.7 +/- 0.2 pmol/ml, respectively. Suppression of HGO was similar (83-84%) with proinsulin and insulin, but stimulation of GDR above basal was greater with insulin (3.41 +/- 0.43 versus 1.98 +/- 0.28 mg/kg/min, P less than 0.001). Following cessation of the hormone infusions, serum proinsulin concentration fell in a biphasic fashion with half-times of 25 and 146 min for the two phases. Serum half-disappearance time for insulin was 5 min. Deactivation of the hormone's effects to stimulate GDR was 50% complete by 35 min after insulin and 71 min after proinsulin. In contrast, 50% of the recovery times for the effect on suppression of HGO were 55 min after insulin and 188 min after proinsulin. Serum glucagon levels did not differ significantly after the insulin and proinsulin infusions. In summary: (1) Deactivation of proinsulin and insulin's effects to suppress HGO proceeds more slowly than deactivation of their effects to stimulate GDR; and (2) There is a markedly prolonged and disproportionately delayed deactivation of proinsulin's effects on suppression of HGO. This later finding may prove of therapeutic value in the treatment of diabetes mellitus.

Metabolic consequences of very-low-calorie diet therapy in obese non-insulin-dependent diabetic and nondiabetic subjects

To determine the effects of very-low-calorie diets on the metabolic abnormalities of diabetes and obesity, we have studied 10 obese, non-insulin-dependent diabetic (NIDDM) and 5 obese, nondiabetic subjects for 36 days on a metabolic ward during consumption of a liquid diet of 300 kcal/day with 30 g of protein. Rapid improvement occurred in the glycemic indices of the diabetic subjects, with mean (+/- SEM) fasting plasma glucose falling from 291 +/- 21 to 95 +/- 6 mg/dl (P less than 0.001) and total glycosylated hemoglobin from 13.1 +/- 0.7% to 8.8 +/- 0.3% (P less than 0.001) (normal reference range 5.5-8.5%). Lipid elevations were normalized with plasma triglycerides reduced to less than 100 mg/dl and total plasma cholesterol to less than 150 mg/dl in both groups. Hormonal and substrate responses were also comparable between groups with reductions in insulin and triiodothyronine and moderate elevations in blood and urinary ketoacid levels without a corresponding rise in free fatty acids. Electrolyte balance for sodium, potassium, calcium, and phosphorus was initially negative but approached equilibrium by completion of the study. Magnesium, in contrast, remained in positive balance in both groups throughout. Total nitrogen loss varied widely among all subjects, ranging from 70 to 367 g, and showed a strong positive correlation with initial lean body mass (N = 0.83, P less than 0.001) and total weight loss (N = 0.87, P less than 0.001). The nondiabetic group, which had a significantly greater initial body weight and lean body mass than the diabetic group, also had a significantly greater weight loss of 450 +/- 31 g/day compared with 308 +/- 19 g/day (P less than 0.01) in the diabetic subjects. The composition of the weight lost at completion was similar in both groups and ranged from 21.6% to 31.3% water, 3.9% to 7.8% protein, and 60.9% to 74.5% fat. The contribution of both water and protein progressively decreased and fat increased, resulting in unchanged caloric requirements during the diet. This study demonstrates that short-term treatment with a very-low-calorie diet in both obese diabetic and nondiabetic subjects results in: safe and effective weight loss associated with the normalization of elevated glucose and lipid levels, a large individual variability in total nitrogen loss determined principally by the initial lean body mass, and progressive increments in the contribution of fat to weight loss with stable caloric requirements and no evidence of a hypometabolic response.

Rates of noninsulin-mediated glucose uptake are elevated in type II diabetic subjects

Although insulin is extremely potent in regulating glucose transport in insulin-sensitive tissues, all tissues are capable of taking up glucose by facilitated diffusion by means of a noninsulin-mediated glucose uptake (NIMGU) system. Several reports have estimated that in the postabsorptive state the majority of glucose disposal occurs via a NIMGU mechanism. However, these estimates have been either derived or extrapolated in normal humans. In the present study we have directly measured NIMGU rates in 11 normal (C) and 7 Type II noninsulin-dependent diabetic subjects (NIDDM; mean +/- SE fasting serum glucose, 249 +/- 24 mg/dl). To accomplish this, the serum glucose was clamped at a desired level during a period of insulin deficiency induced by a somatostatin infusion (SRIF, 550 micrograms/h). With a concomitant [3-3H]glucose infusion, we could isotopically quantitate glucose disposal rates (Rd) during basal (basal insulin present) and insulin-deficient (SRIF) conditions. With this approach we found that (a) basal Rd was greater in NIDDM than in C, 274 +/- 31 vs. 150 +/- 7 mg/min, due to elevated hepatic glucose output, (b) NIMGU composes 75 +/- 5% of basal Rd in C and 71 +/- 4% in NIDDM, (c) NIDDMS have absolute basal NIMGU rates that are twice that of C (195 +/- 23 vs. 113 +/- 8 mg/min, P less than 0.05), (d) when C were studied under conditions of insulin deficiency (SRIF infusion) and at a serum glucose level comparable to that of the NIDDM group (250 mg/dl), their rates of NIMGU were the same as that of the NIDDM group (186 +/- 19 vs. 195 +/- 23 mg/min; NS). We conclude that (a) in the postabsorptive state, NIMGU is the major pathway for glucose disposal for both C and NIDDM; (b) for a given glucose level the efficiency of NIMGU (NIMGU divided by serum glucose level) is equal in C and NIDDM, but since basal Rd is elevated in NIDDMs their absolute basal rates of NIMGU are higher; and (c) elevated basal rates of NIMGU in NIDDM may play a role in the pathogenesis of the late complications of diabetes.

Longitudinal evaluation of the effects of sulfonylurea therapy in subjects with type II diabetes mellitus

Despite more than a quarter of a century of use in managing type II diabetes, the mechanism responsible for the hypoglycemic action of sulfonylurea agents remains controversial. To identify factors responsible for the clinical response to the drug, glycemic control, endogenous insulin secretion in response to mixed meals, adipocyte insulin binding, insulin-mediated peripheral glucose disposal as well as basal hepatic glucose output were assessed in 17 type II diabetic subjects before and after three months of therapy with glyburide, a second-generation sulfonylurea. To determine if the response to the drug changed with time, nine of the subjects were treated for an additional 15 months. Glyburide therapy increased endogenous insulin secretion, increased adipocyte insulin binding after 18 but not three months of therapy, enhanced peripheral insulin action by acting primarily at a post-receptor site, and reduced basal hepatic glucose output. The increase in post-receptor function and the reduction of basal hepatic glucose output appear to be the crucial determinants of the clinical response to the sulfonylurea; the response pattern to sulfonylurea compounds can vary as a function of the duration of treatment. An accelerated rate of basal hepatic glucose output appears to be the major cause of secondary failure in glyburide-treated patients.

Mechanisms of insulin resistance in non-insulin-dependent (type II) diabetes

Characteristic of both obesity and non-insulin-dependent diabetes mellitus, insulin resistance is triggered at the level of the target tissue and can be induced by three general categories of causes: (1) an abnormal beta cell secretory product, (2) circulating insulin antagonists, or (3) a target tissue defect in insulin action. Decreased numbers of insulin receptors and a post-receptor defect in insulin action both play relative roles in insulin resistance. A general trend, however, indicates that as insulin resistance increases, the post-receptor defect becomes more prominent. Impaired glucose uptake and subsequent increased hepatic glucose oxidation in non-insulin-dependent diabetes mellitus are major contributing factors to fasting hyperglycemia.

The metabolic clearance of insulin and the feedback inhibition of insulin secretion are altered with aging

Elevated basal and stimulated insulin levels have been previously demonstrated in elderly human subjects. To see whether these elevated insulin levels are due to alterations in either the metabolic clearance rate (MCR) for insulin or the feedback inhibition of insulin secretion, we have studied 14 elderly and 19 nonelderly subjects, mean age 70 +/- 2 and 35 +/- 2 yr, respectively. Fasting serum insulin and C-peptide levels were elevated in the elderly compared with the nonelderly, 17 +/- 2 versus 11 +/- 1 microU/ml, P less than 0.01 and 0.95 +/- 0.12 versus 0.47 +/- 0.07 pmol/ml, P less than 0.001. Euglycemic hyperinsulinemia created by insulin infusion rates of 15, 40, and 1200 mU/m2/min with glucose held constant resulted in steady-state serum insulin levels of 65 +/- 4, 109 +/- 8, and 11,316 +/- 890 versus 34 +/- 2, 96 +/- 5, and 11,083 +/- 1079 microU/ml in the elderly and nonelderly subjects, respectively. The MCR of insulin was decreased by 46% in the elderly compared with the nonelderly (10.1 +/- 0.7 versus 18.7 +/- 1.4 ml/kg/min) at the insulin infusion rate of 15 mU/m2/min with no difference observed between the two groups at the higher insulin infusions. Steady-state suppression of C-peptide by exogenous insulin was similar, 73 +/- 2% versus 72 +/- 2% and 70 +/- 3% versus 64 +/- 5% in the nonelderly and elderly groups during the 15 and 40 mU/m2/min insulin infusions, respectively. However, 50% suppression was achieved within 30 min in the nonelderly group compared with 70 min in the elderly group during the low-dose infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of insulin treatment on insulin secretion and insulin action in type II diabetes mellitus

We have studied the effects of 3 wk of continuous subcutaneous insulin infusion (CSII) on endogenous insulin secretion and action in a group of 14 type II diabetic subjects with a mean (+/-SEM) fasting glucose level of 286 +/- 17 mg/dl. Normal basal and postprandial glucose levels were achieved during insulin therapy at the expense of marked peripheral hyperinsulinemia. During the week of posttreatment evaluation, the subjects maintained a mean fasting glucose level of 155 +/- 11 mg/dl off insulin therapy, indicating a persistent improvement in carbohydrate homeostasis. Adipocyte insulin binding and in vivo insulin dose-response curves for glucose disposal using the euglycemic clamp technique were measured before and after therapy to assess the effect on receptor and postreceptor insulin action. Adipocyte insulin binding did not change. The insulin dose-response curve for overall glucose disposal remained right-shifted compared with age-matched controls, but the mean maximal glucose disposal rate increased by 74% from 160 +/- 14 to 278 +/- 18 mg/m2/min (P less than 0.0005). The effect of insulin treatment on basal hepatic glucose output was also assessed; the mean rate was initially elevated at 159 +/- 8 mg/m2/min but fell to 90 +/- 5 mg/m2/min in the posttreatment period (P less than 0.001), a value similar to that in control subjects. Endogenous insulin secretion was assessed in detail and found to be improved after exogenous insulin therapy. Mean 24-h integrated serum insulin and C-peptide concentrations were increased from 21,377 +/- 2766 to 35,584 +/- 4549 microU/ml/min (P less than 0.01) and from 1653 +/- 215 to 2112 +/- 188 pmol/ml/min (P less than 0.05), respectively, despite lower glycemia. Second-phase insulin response to an intravenous (i.v.) glucose challenge was enhanced from 170 +/- 53 to 1022 +/- 376 microU/ml/min (P less than 0.025), although first-phase response remained minimal. Finally, the mean insulin and C-peptide responses to an i.v. glucagon pulse were unchanged in the posttreatment period, but when glucose levels were increased by exogenous glucose infusion to approximate the levels observed before therapy and the glucagon pulse repeated, responses were markedly enhanced. Simple and multivariate correlation analysis showed that only measures of basal hepatic glucose output and the magnitude of the postbinding defect in the untreated state could be related to the respective fasting glucose levels in individual subjects.(ABSTRACT TRUNCATED AT 400 WORDS)