Diabetes is associated with a high incidence of endothelial-binding antibodies which do not correlate with retinopathy, von Willebrand factor, angiotensin-converting enzyme or C-reactive protein.

Increasing evidence implicates endothelial cell dysfunction in the development of diabetic microvascular disease, but its precise nature is elusive. This study sought to extend previous observations on the association between diabetes and the endothelial cell-derived glycoprotein von Willebrand factor (vWF), in a study of 777 diabetic patients. Compared with a mean of 1.07 +/- 0.18 iu/ml in a non-diabetic population, vWF was found to be elevated to 1.59 +/- 0.14 iu/ml in the whole sample, but particularly in those with retinopathy or microalbuminuria. It was studied whether such an elevation is part of an acute phase response, or is accompanied by other indicators of endothelial cell dysfunction. Plasma samples were examined for vWF, and serum for angiotensin converting enzyme (ACE), C-Reactive protein (CRP), IgG and IgM endothelial cell-binding antibodies (anti-EC Ig). A strong positive association was found (p less than 0.005) between the extent of elevation of vWF and the presence of diabetic retinopathy. ACE and CRP were rarely raised, and their levels did not correlate with either diabetic retinopathy or vWF levels. However, 52% of the patients had circulating anti-EC IgG or IgM, although their presence did not correlate with retinopathy, or with vWF, ACE or CRP. Thus diabetic retinopathy and probably nephropathy is associated with a specific but generalised disturbance of vascular endothelial cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory blood pressure and heart rate in diabetic patients: an assessment of autonomic function.

In order to examine the physiological variation in blood pressure and heart rate that occurs during normal activities in patients with diabetes, 24-h profiles were constructed from continuous ambulatory recordings. Isometric and dynamic tests were also performed. The patients were subdivided into 25 uncomplicated cases, 11 with peripheral neuropathy and 6 with autonomic neuropathy. These were compared with a 'control' group of 22 normal subjects. Abnormal 24-h blood pressure profiles were found particularly in the patients with autonomic neuropathy. This group had attenuation or reversal of the usual diurnal rhythm, blood pressure often rising during the night and falling in the early morning. Diurnal heart rate variation was reduced in all three groups of patients. Blood pressure responses to both forms of exercise were also significantly reduced in the autonomic neuropathy group (maximum change in systolic blood pressure during isometric exercise was 10 +/- 4 mmHg vs 36 +/- 3 mmHg in the control group, p less than 0.003). Patients with peripheral neuropathy also had some impairment of exercise-induced blood pressure changes, but to a lesser degree.

Stimulation of endothelial cell growth by sera from diabetic patients with retinopathy.

An in-vitro proliferation assay has shown that sera from patients with diabetic retinopathy, particularly those with the proliferative form, are two to four times more effective than sera from non-diabetics at stimulating 3H-thymidine incorporation into both human umbilical vein and human omental microvascular endothelial cells, but not at stimulating incorporation into human dermal fibroblasts or 3T3 cells. The factor(s) is heat stable and of molecular weight greater than 15,000, and its presence is unrelated to metabolic control. It is not present in patients with other forms of diabetic vascular disease, which suggests that it is not related to carbohydrate or lipid metabolism. These results provide evidence against the hypothesis that metabolic disturbances are central to the development of diabetic microvascular disease, and raise possibilities of novel forms of therapeutic intervention.

Effects of a fish oil supplement on platelet function, haemostatic variables and albuminuria in insulin-dependent diabetics.

A randomised trial of the effects of 15 gm per day of a fish oil supplement (MaxEPA) on blood lipids, haemostatic variables (including platelet function) and albuminuria was undertaken in 41 insulin dependent diabetics. Compared with the control group there was a significant reduction in thromboxane production by platelets stimulated by collagen in vitro in the group who took the fish oil supplement. The extent of platelet aggregation was not altered but the lag phase before aggregation was prolonged. There were also statistically significant increases in plasma LDL cholesterol, fibrinogen and clotting factor X in the group who took the fish oil supplement. No other significant differences were noted.

A simple diabetic clinic information and audit system.

A simple method for managing the records of a diabetic clinic in a District General Hospital is described. It is based on a modified manual system in which selected items of data are recorded in a computer system. This provides a Diabetic Register, information for patient and clinical management and for research projects. It simplifies the management of the clinic, is easily used by medical staff inexperienced in the use of computers and causes minimal increase in the clinic workload.

Effect of poor diabetic control and obesity on whole body protein metabolism in man.

We have investigated whole body protein turnover in the fasted state in five normal men, five male Type 1 diabetic patients off insulin therapy, and five obese women, using IV 13C-leucine as a tracer. In diabetic patients, there was, as expected, a greater net loss of protein in the fasted state than in normal subjects. However, contrary to animal and studies in vitro, our diabetic patients in the fasted state showed a greater rate of protein synthesis than normal subjects (p less than 0.01). The increased net loss of protein in diabetic patients compared with normal subjects arose because, in the diabetic patients, protein breakdown was increased even more than protein synthesis under the conditions of this study. Plasma leucine concentration was higher in diabetic and in insulin-insensitive obese patients than in normal subjects (p less than 0.01), and higher in diabetic than in obese patients (p less than 0.05). The rate of protein synthesis per kg lean body mass was also higher in diabetic patients than in obese or normal subjects (p less than 0.01), and higher in obese than normal subjects (p less than 0.05). We conclude that, in human subjects, whole body leucine and protein metabolism are very sensitive to the action of insulin.

Improvement in insulin secretion in diabetes after diazoxide.

Diazoxide 5 mg/kg/day was administered to four normal subjects for five days and, together with insulin, to ten diabetic subjects for seven days. In every case there was a substantial increase in the insulin response to combined stimulation of the pancreatic beta cells with 1 mg of glucagon and 2 g of tolbutamide given intravenously. Similar increases were not seen in four diabetics who received placebo with insulin. It is likely that the observed improvements reflected increased insulin stores which resulted from diazoxide inhibition of insulin release. These findings suggest that poor insulin responses in diabetics may be due, at least in part, to chronic overstimulation of the beta cells. Pharmacological agents such as diazoxide, which inhibit glucose-induced insulin release, may have a place in preserving and restoring insulin secretion in diabetes.

Diabetic complications in a patient with coexisting anterior hypopituitarism.

We present a patient who developed insulin-requiring diabetes several years after the onset of symptoms of anterior hypopituitarism. It is likely that the hypopituitarism protected him against the development of diabetic retinopathy and glomerular basement membrane thickening but not against neuropathy and atheroma. The significance of this in relation to the growth-hormone-microangiopathy hypothesis is discussed.

Effect of phenylalanine and its metabolites on the metabolism of leucocytes and lymphocytes.

1. The pathogenesis of the mental retardation in phenylketonuria remains obscure. Leucocytes have proved of value in the study of other inborn errors of metabolism. The lymphocyte is a suitable model cell for the study of mammalian metabolism, because of its ability to divide in vitro in response to various stimuli. 2. We have examined the effects of phenylalanine, phenylpyruvate, phenyl-lactate and phenylacetate on the human leucocyte and the resting and phytohaemagglutinin-stimulated rabbit lymphocyte. 3. Phenylpyruvate and phenyl-lactate reduced acetate incorporation into leucocyte lipid by 38% and 48% respectively. Only phenyl-lactate reduced acetate incorporation into the resting and stimulated lymphocyte, by 20% and 34% respectively. 4. Glucose incorporation into leucocyte lipid was unaffected by phenylalanine, phenylpyruvate and phenyl-lactate. Only phenyl-lactate inhibited (46%) the production of CO2 from glucose. 5. Phenylalanine and leucine incorporation into trichloroacetic acid-insoluble material of resting and stimulated lymphocytes was inhibited by phenyl-lactate (10-42%), phenylpyruvate (27-57%) and phenylacetate (19-39%). 6. Uridine incorporation into resting and stimulated cells was inhibited by phenyl-lactate (22-26%), phenylpyruvate (42-52%) and phenylacetate (20%). 7. Thymidine incorporation into resting lymphocytes was reduced by phenyl-lactate, phenylpyruvate, phenylacetate and phenylalanine by 12-26%. Incorporation into the stimulated cell was inhibited by phenylpyruvate and phenyl-lactate (90%) and phenylacetate (66%). 8. Phenylalanine inhibited lymphocyte pyruvate kinase and phenylpyruvate inhibited citrate synthetase. 9. These results are compared with published data relating to experimental hyperphenylalaninaemia and the effects of these metabolites on nervous tissue in vitro.