Stopping insulin treatment in middle-aged diabetic patients with high postglucagon plasma C-peptide. Effect on glycaemic control, serum lipids and lipoproteins

Assessment of endogenous insulin secretion in insulin treated diabetes predicts postprandial glucose and treatment response to prandial insulin

BACKGROUND

In patients with both Type 1 and Type 2 diabetes endogenous insulin secretion falls with time which changes treatment requirements, however direct measurement of endogenous insulin secretion is rarely performed. We aimed to assess the impact of endogenous insulin secretion on postprandial glucose increase and the effectiveness of prandial exogenous insulin.

METHODS

We assessed endogenous insulin secretion in 102 participants with insulin treated diabetes (58 Type 1) following a standardised mixed meal without exogenous insulin. We tested the relationship between endogenous insulin secretion and post meal hyperglycaemia. In 80 participants treated with fast acting breakfast insulin we repeated the mixed meal with participants' usual insulin given and assessed the impact of endogenous insulin secretion on response to exogenous prandial insulin.

RESULTS

Post meal glucose increment (90 minute - fasting) was inversely correlated with endogenous insulin secretion (90 minute C-peptide) (Spearman's r = -0.70, p < 0.001). Similar doses of exogenous prandial insulin lowered glucose increment more when patients had less endogenous insulin; by 6.4(4.2-11.1) verses 1.2(0.03-2.88) mmol/L (p < 0.001) for patients in the lowest verses highest tertiles of endogenous insulin.

CONCLUSIONS

In insulin treated patients the measurement of endogenous insulin secretion may help predict the degree of postprandial hyperglycaemia and the likely response to prandial insulin.

Urine C-peptide creatinine ratio is an alternative to stimulated serum C-peptide measurement in late-onset, insulin-treated diabetes

AIMS

Serum C-peptide measurement can assist clinical management of diabetes, but practicalities of collection limit widespread use. Urine C-peptide creatinine ratio may be a non-invasive practical alternative. The stability of C-peptide in urine allows outpatient or community testing. We aimed to assess how urine C-peptide creatinine ratio compared with serum C-peptide measurement during a mixed-meal tolerance test in individuals with late-onset, insulin-treated diabetes.

METHODS

We correlated the gold standard of a stimulated serum C-peptide in a mixed-meal tolerance test with fasting and stimulated (mixed-meal tolerance test, standard home meal and largest home meal) urine C-peptide creatinine ratio in 51 subjects with insulin-treated diabetes (diagnosis after age 30 years, median age 66 years, median age at diagnosis 54, 42 with Type 2 diabetes, estimated glomerular filtration rate > 60 ml min(-1) 1.73 m(-2) ).

RESULTS

Ninety-minute mixed-meal tolerance test serum C-peptide is correlated with mixed-meal tolerance test-stimulated urine C-peptide creatinine ratio (r = 0.82), urine C-peptide creatinine ratio after a standard breakfast at home (r = 0.73) and urine C-peptide creatinine ratio after largest home meal (r = 0.71). A stimulated (largest home meal) urine C-peptide creatinine ratio cut-off of 0.3 nmol/mmol had a 100% sensitivity and 96% specificity (area under receiver operating characteristic curve = 0.99) in identifying subjects without clinically significant endogenous insulin secretion (mixed-meal tolerance test-stimulated C-peptide < 0.2 nmol/l). In detecting a proposed serum C-peptide threshold for insulin requirement (stimulated serum C-peptide < 0.6 nmol/l), a stimulated (largest home meal) urine C-peptide creatinine ratio cut-off of 0.6 nmol/mmol had a sensitivity and specificity of 92%.

CONCLUSION

In patients with insulin-treated diabetes diagnosed after age 30 years, urine C-peptide creatinine ratio is well correlated with serum C-peptide and may provide a practical alternative measure to detect insulin deficiency for use in routine clinical practice.

Classification of type 2 diabetes by clinical response to metformin-troglitazone combination and C-Peptide criteria

OBJECTIVE

To assess the ability of basal and stimulated C-peptide levels and stimulated glucose values after oral administration of glucose to predict a successful response to metformin and troglitazone combination therapy after discontinuation of insulin therapy.

METHODS

At the onset of the study, plasma glucose and C-peptide levels were measured in a group of 64 obese patients with insulin-treated type 2 diabetes while they were fasting and 2 hours after a challenge of 100 g of glucose administered orally. Then combination metformin-troglitazone treatment was initiated while insulin therapy was gradually tapered over 8 to 12 weeks. Subjects who successfully tolerated insulin withdrawal after the metformin-troglitazone combination were categorized as non-insulin-requiring responders, whereas those who needed insulin to obtain glycemic control were categorized as insulin-requiring nonresponders. Basal and glucose-stimulated C-peptide levels as well as stimulated glucose values were contrasted in the responder versus nonresponder groups. In a second protocol, eight obese patients with insulin-treated type 2 diabetes who successfully stopped insulin therapy were reassessed for C-peptide and glucose variables during the 2-hour oral glucose tolerance test. This reassessment followed a 12-week period of therapy to determine whether treatment of insulin resistance with the combination of metformin and troglitazone could normalize the impaired glucose tolerance in type 2 diabetes.

RESULTS

After metformin-troglitazone therapy, 48 study subjects (75%) could later be managed without insulin, whereas 16 (25%) needed insulin to achieve acceptable glycemic control. In a comparison of the non-insulin-requiring responder and insulin-requiring nonresponder groups, the responder group had significantly higher glucose-stimulated C-peptide levels and much lower stimulated glucose levels. The mean basal plasma C-peptide level was higher in the responder than in the nonresponder group, but a small degree of overlap was found between the two groups. Combination treatment with metformin and troglitazone for 12 weeks resulted in a significant reduction in the C-peptide response and glucose variables after the glucose load.

CONCLUSION

The results of this study indicate that stimulated C-peptide and glucose levels may be useful criteria to identify whether combination metformin-troglitazone treatment can successfully replace insulin therapy in the management of obese patients with type 2 diabetes. Inability to normalize glucose intolerance after restoring insulin resistance with insulin sensitizers is supportive of the presence of both disturbed beta-cell function and insulin resistance in patients with type 2 diabetes.

One-hour meal tolerance test to assess withdrawal of insulin therapy in overweight patients with type 2 diabetes

OBJECTIVE

To evaluate the clinical usefulness of a 1-hour meal tolerance test to determine the feasibility and safety of discontinuation of insulin therapy in overweight, insulin-treated patients with type 2 diabetes mellitus.

METHODS

Overweight patients who presented with metabolic decompensation at initial diagnosis of type 2 diabetes were hospitalized and treated with insulin. A 1-hour meal tolerance test was performed in an outpatient setting when patients had maintained a stable metabolic status with decreasing daily insulin requirement and the possibility of withdrawal of insulin therapy was considered. After an overnight fast, venous blood samples were collected before and 1 hour after consumption of an oral liquid meal (240 mL, 240 kcal, approximately 30 g of sucrose) to measure glucose and C-peptide levels. If the postmeal glucose level was < or = 10 mmol/L, the insulin therapy was discontinued. Patients underwent follow-up to validate the clinical decision.

RESULTS

Twenty-four overweight adult Mexican American patients (8 of whom had ketoacidosis) were treated with insulin at initial diagnosis of type 2 diabetes. The mean insulin dosages were reduced progressively from 71 +/- 8 U/day to 31 +/- 3 U/day during a period of 4 +/- 0.5 months. At that stage, the mean fasting and 1-hour postmeal blood glucose levels were 5.0 +/- 0.2 mmol/L and 8.4 +/- 0.4 mmol/L, respectively. Meal-induced plasma C-peptide levels showed 1.9- to 4-fold increases, confirming substantial endogenous insulin secretion. The C-peptide responses were similar in the two subgroups of patients with or without initial ketoacidosis. On the basis of postmeal blood glucose levels, the insulin therapy was discontinued in all cases. After 3 months of follow-up, all patients were in good metabolic control. Fourteen patients underwent follow-up for >12 months; 10 of them were maintained without antidiabetic medications for 21.4 +/- 2.8 months. Two patients were treated with sulfonylurea drugs after 4 months, and another two required insulin therapy by the 4th and 18th months, respectively.

CONCLUSION

A 1-hour postmeal blood glucose level is helpful for deciding the withdrawal of insulin therapy in overweight, insulin-treated patients with type 2 diabetes.

Management of elderly diabetic patients in the subacute care setting

Type 2 diabetes is a commonly encountered condition in the subacute care setting. The results of the landmark UK prospective studies have confirmed that aggressive glycemic and blood pressure control delayed diabetes-related microvascular and macrovascular complications and significantly improved diabetic outcomes. Within the past few years, new drugs have been developed to address both aspects of the type 2 diabetes syndrome: insulin resistance and insulin secretory defect. C-peptide analysis may be useful to predict a successful response to therapy with insulin sensitizers or the need to initiate therapy with insulin or insulin stimulators. The issues regarding the general approach to elderly diabetics and the strategies of dealing with diabetic complications encountered in the subacute care program are discussed and updated. It is hoped that diabetic management can be improved and that suggested alternate therapies can be used in the subacute care facilities.

Relationships between diabetes duration, metabolic control and beta-cell function in a representative population of type 2 diabetic patients in Sweden

To clarify whether metabolic control and beta-cell function deteriorate with increasing duration of diabetes, we investigated in a cross-sectional study Type 2 diabetic patients in an area-based population. Type 2 diabetic patients (n = 231: 112 males, 119 females) were identified by age at onset > or = 35 years, fasting levels of C-peptide > 0.04 nmol l-1, and absence of islet cell antibodies. Body weight was slightly elevated (BMI 26.8 +/- 0.3 kg m-2), however 76/210 (36%), had normal weight (BMI < 25 kg m-2). Fasting blood glucose rose significantly during the first 10 years of known diabetes from 8.2 +/- 0.3 mmol l-1 in patients with 0-5 years of duration to 9.9 +/- 0.7 mmol l-1 in those with 5-10 years of duration, p < 0.01 and HbA1c from 6.4 +/- 0.2 to 7.4 +/- 0.4%, p < 0.05. Fasting C-peptide levels decreased after 10 years duration from 0.90 +/- 0.06 nmol l-1 during 5-10 to 0.69 +/- 0.08 nmol l-1 during 10-15 years of diabetes, p < 0.05. The proportion of insulin treated patients increased from 13% (12/94) with 0-5 years of duration to 33% (13/39) with 10-15 years and 60% (18/30) with more than 15 years of duration. In conclusion in Type 2 diabetic patients without signs of autoimmunity, metabolic control, and beta-cell function deteriorate with increasing duration of diabetes, leading to common but not inevitable occurrence of 'secondary failure'.