Why is there still disagreement over insulin secretion in non-insulin-dependent diabetes?

Fasting, postprandial and postprandial plus glucagon-stimulated plasma C-peptide levels in non-insulin-dependent diabetics and in control subjects

We have studied fasting, postprandial and postprandial plus glucagon-stimulated plasma C-peptide levels in 149 non-insulin-dependent diabetics treated either with diet or oral drugs and in 101 non-diabetic control subjects. Diet-treated diabetics showed the highest fasting, postprandial and post-glucagon C-peptide levels in both sexes. In men, diabetics treated with oral drugs showed lower postprandial and glucagon-stimulated C-peptide levels than control subjects, while in women C-peptide levels in this group of diabetics were similar to those in control subjects. The distribution of individual plasma C-peptide levels was wide in non-insulin-dependent diabetics and control subjects and there was considerable overlapping in plasma C-peptide distribution for diabetics and control subjects. Fasting and post-glucagon plasma C-peptide levels in diabetics showed an inverse association to plasma glucose levels and a positive association to degree of obesity, but no association with the known duration of diabetes.

Prevention of type 2 (non-insulin-dependent) diabetes mellitus by diet and physical exercise. The 6-year Malmö feasibility study

From a previously reported 5-year screening programme of 6,956 47-49-year-old Malmö males, a series of 41 subjects with early-stage Type 2 (non-insulin-dependent) diabetes mellitus and 181 subjects with impaired glucose tolerance were selected for prospective study and to test the feasibility aspect of long-term intervention with an emphasis on life-style changes. A 5-year protocol, including an initial 6-months (randomised) pilot study, consisting of dietary treatment and/or increase of physical activity or training with annual check-ups, was completed by 90% of subjects. Body weight was reduced by 2.3-3.7% among participants, whereas values increased by 0.5-1.7% in non-intervened subjects with impaired glucose tolerance and in normal control subjects (p less than 0.0001); maximal oxygen uptake (ml.min-1.kg-1) was increased by 10-14% vs decreased by 5-9%, respectively (p less than 0.0001). Glucose tolerance was normalized in greater than 50% of subjects with impaired glucose tolerance, the accumulated incidence of diabetes was 10.6%, and more than 50% of the diabetic patients were in remission after a mean follow-up of 6 years. Blood pressure, lipids, and hyperinsulinaemia were reduced and early insulin responsiveness to glucose loading preserved. Improvement in glucose tolerance was correlated to weight reduction (r = 0.19, p less than 0.02) and increased fitness (r = 0.22, p less than 0.02). Treatment was safe, and mortality was low (in fact 33% lower than in the remainder of the cohort).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of indices of islet B-cell function in type 2 diabetes in relation to insulin effectiveness and clinical outcome

The most appropriate way to estimate islet B-cell function in Type 2 diabetes is unclear, and this has led to many different techniques of measurement being used. We have examined the associations to two fasting and four glucose-stimulated indices of islet B-cell function in members of a group of 249 Type 2 patients, seeking correlations with concurrent glucose tolerance and antilipolytic effect, and with subsequent clinical outcome. The six B-cell indices were interrelated to variable degrees (rs -0.21 to +0.92). Early glucose-stimulated insulin output (incremental 1st-phase insulin area) was not significantly positively correlated with the fasting plasma concentration of immunoreactive insulin at any time. Fasting immunoreactive insulin and 'minimal model' islet B-cell parameters were poorly related to the rate constant for glucose clearance and the degree of antilipolysis (rs values between -0.13 and +0.40). Homeostatic model assessment of the fasting islet B-cell function was more consistently related to these metabolic effects. Incremental first-phase insulin area was the islet B-cell index most consistently related to metabolic abnormalities (rs up to +0.56), and to subsequent need for oral hypoglycaemic or exogenous insulin therapy. No index of islet B-cell function was consistently associated with the subsequent development of diabetic tissue damage.

First-phase insulin response to glucose in nonobese or obese subjects with glucose intolerance: analysis by C-peptide secretion rate

This study was proposed to clarify the impairment of first-phase insulin response to glucose in subjects with glucose intolerance by analysis of C-peptide secretion rate after glucose or glucagon injection. The rate was calculated from kinetic analysis of peripheral C-peptide behavior. The rate reached the peak two minutes after glucose injection and then rapidly declined (first-phase secretion) in control subjects. In nonobese subjects with impaired glucose tolerance (IGT) or non-insulin-dependent diabetes mellitus (NIDDM), the rate promptly increased in response to glucose and was followed by a second phase increase. The time course of the rate in the subjects was slightly different from that in control subjects. There was a progressively greater deficit in the first-phase increase with increasing severity of glucose intolerance. The time course of the rate in the obese subjects with NIDDM was different from that in control subjects. The first-phase increase was reduced in the obese subjects with NIDDM. The glucose disappearance rate was correlated with the first-phase increase. Since the time course of the rate after glucagon injection in all subjects did correspond well with that in the control subjects, variation of metabolic clearance rate of endogenous C-peptide among the subjects may be negligible for this study. This study provides the precise time course of first- and second-phase insulin response to glucose injection in nonobese and obese subjects with IGT or NIDDM as well as convincing evidence of the progressive reduction of first-phase insulin response with increasing severity of glucose intolerance. First-phase insulin response to glucose might be slightly delayed in some obese subjects with NIDDM.

The relationship between the pharmacokinetics and pharmacodynamic effects of oral hypoglycaemic drugs

Oral hypoglycaemic drugs have widely differing pharmacokinetic properties. Possible pharmacodynamic benefits include greater efficacy and fewer adverse effects. In general, it has not been possible to demonstrate unequivocal differences in clinical efficacy between the sulphonylureas during long term use, although there are clear differences in potency. These differences have been emphasised to the extent that the term 'second-generation' has been used for the most potent sulphonylureas, but there is little to suggest that potency is of any therapeutic significance. Trials to study differences in efficacy have rarely been of acceptable design. They have often used fixed doses of drugs, begging the question of whether true potency ratios have been established for chronic treatment. They have rarely involved substantial numbers of patients in double-blind crossover studies with a suitable washout period. Trials which show that there is a clear relationship between drug concentrations in blood and drug effects (whether therapeutic effects or adverse effects such as severe hypoglycaemia) are generally lacking. Qualitative and semiquantitative analysis of adverse effects supports the concept that drugs with a long half-life (e.g. chlorpropamide), renally excreted active metabolites (e.g. acetohexamide) or unusual properties (e.g. glibenclamide, which accumulates progressively in islet tissue) are more likely to cause prolonged hypoglycaemia, which may be fatal. The major adverse effect of treatment with biguanides is lactic acidosis, and this probably occurs more commonly in patients treated with phenformin than those treated with metformin because of pharmacogenetic variation in phenformin metabolism. The available evidence therefore favours the use of drugs with a short elimination half-life which are extensively metabolised and which have no active metabolites.