Effects of hyperglycaemia and sorbitol accumulation on erythrocyte deformability in diabetes mellitus

Erythrocyte deformability was studied in a total of 83 poorly controlled diabetics (mean blood glucose 12.2 mmol/l) who were divided into three groups, each with matched healthy controls. There was no appreciable difference between diabetics and matched controls regarding the filtration of erythrocytes through 3 micron diameter straight channel pores (25 diabetics) or tortuous channel pores (28 diabetics), or for the measurement of erythrocyte elongation over a range of osmolalities in the Ektacytometer (30 diabetics). When erythrocytes from 17 additional diabetics and 17 healthy controls were incubated for two hours at 37 degrees C in hyperglycaemic (50 mmol glucose/l) buffer, however, there was a considerable reduction in erythrocyte filterability for both diabetics and controls in parallel with an increase in erythrocyte sorbitol concentration. This loss of filterability was prevented by the addition of an aldose reductase inhibitor (Sorbinil). High glucose concentrations (congruent to 50 mmol/l) impair the filterability of erythrocytes through 3 micron pores, and the intracellular accumulation of sorbitol in poorly controlled outpatients is therefore unlikely to have a major adverse effect on erythrocyte rheology in diabetes mellitus.

Low molecular weight proteinuria in insulin-dependent diabetes

Although the protein leak of early diabetic nephropathy is said to be purely a glomerular lesion, there is still controversy as to the existence of a tubular component. We have, therefore, assessed the urine of insulin-dependent diabetics for tubular proteinuria as a feature of early diabetic nephropathy. The urine of 25 patients with increased albumin excretion rate was analyzed by sodium dodecyl polyacrylamide gel electrophoresis. One patient showed high molecular weight proteinuria, 2 showed low molecular weight proteinuria and 2 patients showed both low and high molecular weight proteinuria. The urine was also analyzed for 3 tubular proteins by single radial immunodiffusion. No patient showed elevated beta-2-microglobulin, but alpha-1-microglobulin (A1M) (corrected for creatinine excretion) was elevated in 3 out of 25 patients including 2 of the 4 patients with a low molecular weight pattern. One of the patients with raised A1M also had raised retinol-binding protein concentration. We conclude that, in early diabetic nephropathy, proteinuria can have a proximal tubular, as well as a glomerular, component.

Abnormal platelet aggregation in chronic symptomatic diabetic peripheral neuropathy

Both diabetic nephropathy and retinopathy result from microangiopathic processes although there is controversy as to whether this is true for neuropathy. Increased platelet aggregation has been reported in diabetics with nephropathy and retinopathy. The presence of increased platelet aggregation in diabetics with neuropathy could be due to the other coincident microvascular complications. We have, therefore, studied in vitro platelet aggregation in 10 diabetics with chronic symptomatic neuropathy but no other complications, 10 with neuropathy and severe retinopathy, 17 with retinopathy alone, and 23 diabetics with no complications. Increased platelet aggregation to adenosine diphosphate (ADP) and adrenaline was seen in diabetics with neuropathy alone (peak responses 85.0 +/- 5.5% and 82.9 +/- 6.2%, respectively) when compared with uncomplicated diabetics (peak response 74.9 +/- 10.1%, p less than 0.005, and 74.3 +/- 12.5%, p less than 0.01, respectively). The increased platelet aggregation in the patients with neuropathy alone was similar to that found in the diabetics with severe retinopathy. We conclude that increased platelet aggregation is associated with established microangiopathy and is also present in otherwise uncomplicated patients with neuropathy, and this may have pathogenic and therapeutic implications.

Specific thromboxane synthetase inhibition and retinopathy in insulin-dependent diabetics

We have previously reported that specific thromboxane synthetase inhibition may be associated with a reduction in albumin excretion rate in insulin-dependent diabetics (IDD). We now report studies of retinal morphology assessed by serial fluorescein angiography in 25 insulin-dependent diabetics during a 16-week double-blind, randomized, placebo-controlled study of the specific thromboxane synthetase inhibitor UK-38,485. Assessment of angiograms was by, computerized image analysis indicating the percentage area of vascularization and, panel scoring by 4 ophthalmologists who scored the posterior pole in each of the 4 angiograms "blind" according to a prearranged system. There was no significant change in percentage area of vascularization in either placebo or "active" group during the study. Panel scoring, however, suggested that some patients deteriorated whilst others remained unchanged or improved. There was, however, no significant difference in these parameters between those subjects on UK-38,485 and those on placebo. We conclude that specific thromboxane synthetase inhibition is not associated with any significant change in diabetic retinopathy over a 4-month period of study.

Phenotypes of the heavy chains of immunoglobulins in patients with diabetic microangiopathy: evidence for an immunogenetic predisposition

The B3 allotype of the fourth component of complement (C4B3) is associated with microangiopathy. As C4 is important in the humoral immune response phenotypic variation of other inherited components of the response such as the immunoglobulins could also be associated with microangiopathy. Phenotypes of the heavy chains of immunoglobulins (Gm) were compared in 48 insulin dependent diabetics with and 74 without microangiopathic complications. The Gm(zafnbg) phenotype was found significantly more often in insulin dependent diabetics with complications than in those without (16 (33%) out of 48 v 7 (9%) out of 74, respectively, p less than 0.01). Insulin dependent diabetics with both C4B3 and Gm(zafnbg) had an increased risk of complications compared with insulin dependent diabetics with neither or only one factor. Statistical analysis suggested that these two associations were additive, indicating that they increased risk by independent mechanisms. These findings suggest that susceptibility to diabetic microangiopathy is influenced by genes at or in linkage disequilibrium with both the major histocompatibility complex and the Gm loci.

Dissociation of changes in sodium transport in erythrocytes from changes in blood pressure

There is considerable evidence to suggest that the transport of Na+ ions across cell membranes is reduced in essential hypertension. The contribution of this abnormality to the development of elevated blood pressure remains unknown. We have observed similar abnormalities in erythrocytes from normotensive patients with diabetes mellitus and suggest that they may not be of aetiological significance in hypertension.

Sulbactam/ampicillin: effects on glucose metabolism in diabetics with soft tissue infection

Rats and dogs chronically treated with high doses of sulbactam are known to sequester protein-bound glycogen in their hepatocytes. As a result, previous UK studies of sulbactam/ampicillin excluded patients suffering from diabetes mellitus. This study examined the effects of sulbactam/ampicillin compared to flucloxacillin/ampicillin on diabetic control, the ability to mobilize glycogen and the pancreatic beta cell response to glucagon, in diabetic patients suffering from soft tissue infection. There was no significant effect between treatment groups on any of these parameters. Sulbactam/ampicillin is unlikely to have an adverse effect on diabetic control in clinical practice when used short term in the doses employed in this study.

Relation of gene expression (allotypes) of the fourth component of complement to insulin dependent diabetes and its microangiopathic complications

About a quarter of insulin dependent diabetics have low concentrations of the fourth component of complement (C4), and a low concentration of C4 is associated with diabetic microangiopathy. The variability of the expression of the C4 gene was compared in insulin dependent diabetics with and without microangiopathy and controls. Of the two genes coding for C4, the A gene (C4A) was not expressed--that is, C4A null--in 16 (13%) of the 126 insulin dependent diabetics compared with none of the 93 controls (p less than 0.001), and all these 16 subjects had low concentrations of C4. Lack of expression of the other C4 gene (C4B) was not associated with insulin dependent diabetes, but a rare variant, C4B3, was significantly increased in the diabetics (21/126; 17%) compared with the controls (none) (p less than 0.001). The prevalence of C4B3 was also increased in the diabetics with complications when compared with those without (14/50 (28%) v 7/76 (9%), p less than 0.01). Low plasma C4 concentrations in insulin dependent diabetics are at least partly due to variation in the expression of the C4 gene. The association of the rare C4B3 variant with microangiopathy suggests a genetic component of its aetiology.

Asian patients attending a diabetic clinic

Patients of Asian origin comprised 8% of the patients attending a diabetic clinic. Of the 201 Asian patients (120 male), 110 had been diabetic for more than five years, and although 141 were 40 to 60 years old, over one quarter had been aged under 40 at diagnosis. Thirty patients were being treated with insulin, but only eight were truly dependent on insulin compared with 18% of the white patients attending the clinic. Insulin was stopped in eight patients who were receiving insulin inappropriately; control was achieved by diet plus oral hypoglycaemics or diet alone. Over three years 37 patients were admitted with ketoacidosis but none was Asian. During the same period, however, five Asians were admitted in hyperosmolar coma. Asian diabetics have a low prevalence of insulin dependence, possibly related to genetic and environmental factors, and some may be treated with insulin inappropriately.

Diabetic control and the effect of changing a diabetic clinic to modern management

The feasibility and effects of changeover from traditional to modern methods of diabetic management in insulin-dependent diabetics (IDDs) are described. Patients were asked to switch from urine testing to home blood glucose monitoring, from carbohydrate restricted to high carbohydrate-high fibre diets and from one to two injections of insulin per day with the help of a diabetic education sister. Most patients (81%) changed immediately to blood glucose monitoring and after 6 months none wanted to go back to urine tests and 58% changed to a high fibre diet. Subjects in the 'monitoring' group had a significant improvement in HbA1 (mean +/- S.E.M. 14.1 +/- 0.4% to 11.4 +/- 0.5% and 11.8 +/- 0.5% at 4 and 8 months, respectively, p less than 0.01), without any increase in frequency of hypoglycaemia, whereas the rest showed no change. No subject was hospitalized for hyperglycaemia. In conclusion, these newer management techniques can be successful in the majority of IDDs. They are easy to apply, highly acceptable and effective.

Low plasma C4 concentrations: association with microangiopathy in insulin dependent diabetes

Plasma C4 concentrations were measured in insulin dependent diabetics with and without microangiopathy and in controls. The diabetics had significantly lower C4 values than controls (p less than 0.001), and patients with insulin dependent diabetes and microangiopathy had lower values than those without this complication (p less than 0.001). There was a 7.1-fold increase in the prevalence of complications in the diabetics with low C4 values. Of 41 diabetics whose rate of albumin excretion was measured, 13 had increased rates and 11 of these had low C4 concentrations. Low plasma C4 concentration in insulin dependent diabetes is strongly associated with microvascular disease and may identify diabetics with a particular propensity to develop this complication.

Specific thromboxane synthetase inhibition and albumin excretion rate in insulin-dependent diabetes

Albumin excretion rates (AER) were measured in 30 insulin-dependent diabetics during a 16-week double-blind, randomised, placebo-controlled study of the specific thromboxane synthetase inhibitor UK-38,485.6 of 15 subjects in the active group had microalbuminuria (defined as mean pretreatment AER 20-150 micrograms/min); in these patients AER fell from 32 +/- 3 micrograms/min to 11 +/- 1 micrograms/min at 8 weeks and 9 +/- 1 micrograms/min at 16 weeks. The AER rose again (to 29 +/- 8 micrograms/min) within 12 weeks of stopping the drug. There was no significant change in the 10 patients with microalbuminuria who received placebo. There was a strong correlation between change from baseline values and the baseline values themselves in the active, but not in the placebo group, and the change from baseline differed significantly between the two groups. There was no change in glycosylated haemoglobin or mean blood glucose levels during the study. In a separate study UK-38,485 caused significant suppression of thromboxane B2 synthesis in diabetic and non-diabetic subjects.

Insulin secretory capacity in newly diagnosed non-insulin dependent diabetics

Plasma insulin was measured fasting and after iv glucose in fifteen newly diagnosed non-grossly obese non-insulin dependent diabetics. Two-thirds had normal fasting insulin (less than 13 mU/L) and all had sub-normal responses to iv glucose. There was no significant correlation between fasting or stimulated insulin concentrations and body weight. Six subjects with totally "flat" response to iv glucose were tested after a standard 4MJ meal and after 75 g oral glucose. They now showed normal profiles of later phase insulin release to the meal test or oral glucose and a significant increase in early phase insulin concentration, but this response was still blunted when compared with control subjects. We conclude that for non-grossly obese NIDDs (1) insulin deficiency is a common and important disorder and (2) there may be a loss of beta cell sensitivity to blood glucose with retention of sensitivity to gut mediated factors.

Muscle capillary basement membrane in identical twins discordant for insulin-dependent diabetes

Although hereditary factors clearly modulate susceptibility to develop diabetes, their role as determinants of vascular complications associated with diabetes remains unclear. These studies were undertaken to further assess the extent to which capillary basement membrane thickening (CBMT) is governed by metabolic derangements associated with relative or absolute insulin deficiency versus genetic determinants of vascular disease closely linked to but independent of those modulating susceptibility to develop relative or absolute insulin deficiency. Quadriceps muscle capillary basement membranes obtained by needle biopsy were examined in eight pairs of identical twins discordant for insulin-dependent diabetes (IDD) for 11-29 yr. Biopsy material from one of the diabetic twins was technically unsuitable for study. The average CBM width of the IDD twins was found to be significantly thicker than that of their nondiabetic (ND) twin mates (t = 2.50, P less than 0.025). Three IDD, but none of the ND twins, had basement membrane width values in excess of 95% upper tolerance intervals for age- and sex-matched controls with no family history of diabetes. The absence of CBMT in all of the ND twins and in four of the IDD twins with diabetes of 15-24 yr duration argues against the existence, in this group of subjects, of hereditary determinants of diabetic vascular disease linked to those governing susceptibility to develop diabetes. In addition, the absence of CBMT in four subjects with IDD of 15-24 yr duration is consistent with evidence from other studies indicating that diabetic microangiopathy is not an inevitable consequence of the diabetic milieu.(ABSTRACT TRUNCATED AT 250 WORDS)

Low serum C4 concentrations: an inherited predisposition to insulin dependent diabetes?

Twenty two out of 86 insulin dependent diabetics had serum C4 concentrations below the normal range. None of 41 non-insulin dependent diabetics tested had low concentrations. Low C4 values were seen in insulin dependent diabetes irrespective of the duration of the disease and did not appear to correlate with complement activation. There was a close correlation in C4 values between identical cotwins, even when only one was diabetic. These results suggest that a low serum C4 concentration is an inherited phenomenon and may predispose towards the development of insulin dependent diabetes.

Comparison of preoperative and postoperative ACTH concentrations after bilateral adrenalectomy in Cushing's disease

Up to one-third of subjects who have had bilateral adrenalectomy for treatment of Cushing's disease will develop Nelson's syndrome. To examine the value of pre-operative ACTH assays in predicting outcome, we have studied fifteen cases of Cushing's disease treated by bilateral adrenalectomy and pituitary irradiation. Three patients developed Nelson's syndrome. There was no significant correlation between preoperative ACTH level, either 8 am 'basal' or during metyrapone testing, and ACTH concentration post-treatment. Plasma ACTH concentration in the first year after treatment, however, showed a highly significant correlation with the latest postoperative value (n = 14, r = 0.684, P less than 0.01), even more marked when subjects with duration of follow-up less than 3 years were excluded (n = 11, r = 0.836, P less than 0.002). In nine of fifteen patients, plasma ACTH showed either no change or a definite fall during subsequent follow-up. We conclude that plasma ACTH measurement in the first post-operative year is a good indicator of eventual outcome. The continued fall in plasma ACTH shown in many patients after the first year of treatment suggests an effect of irradiation on the pituitary.

Metabolic studies in chlorpropamide-alcohol flush positive and negative Type 2 (non-insulin dependent) diabetic patients with and without retinopathy

Serum insulin and blood metabolite responses to oral glucose with and without intravenous naloxone were measured in 24 chlorpropamide-alcohol flush positive and negative Type 2 (non-insulin dependent) diabetic patients with and without retinopathy. In the chlorpropamide-alcohol flush positive patients with retinopathy, fasting blood glucose was increased greater than 40% and the serum triglycerides were increased over twofold compared with each of the other three groups. Following oral glucose (50 g), the chlorpropamide-alcohol flush positive diabetic patients with complications had a lower serum insulin and higher blood glycerol than the other three groups. Thus, chlorpropamide-alcohol flush positive subjects with retinopathy showed distinct metabolic differences from the other three groups. There was no evidence that opiate-receptors influenced the metabolic response to oral glucose in the Type 2 diabetic patients since the infusion of intravenous naloxone produced no effect on the serum insulin or blood metabolites.

Insulin secretory capacity, beta-thromboglobulin and blood viscosity in long standing, non-insulin dependent diabetics with and without microangiopathy

A comparison was made of insulin secretion in response to i.v. glucose between noninsulin dependent diabetics with and without severe microangiopathy. During i.v. glucose tolerance testing those with complications had significantly lower serum insulin concentration (at 40 and 60 min 15.2 +/- 2.9 and 11.7 +/- 2.5 mU-1 respectively) than those without (26.1 +/- 4.7 and 24.3 +/- 3.6 mU-1, p less than 0.01). The differences were also significant when insulin increment above basal was determined. All subjects had raised plasma beta-thromboglobulin concentration (indicating increased tendency to platelet aggregation), but with no significant difference between the two groups. There was also no difference in fasting glucose, kg values, HbAl or blood viscosity. We conclude that non-insulin dependent diabetics with severe microangiopathy have significantly reduced insulin secretory capacity in response to i.v. glucose when compared with those without.

Patients presenting with Addison's disease need not be pigmented

Three consecutive cases of Addison's disease without increased pigmentation are described. We suggest that the absence of this important physical sign contributed to serious delays in diagnosis and markedly increased morbidity. We emphasize that, despite the usual textbook description, excess pigmentation is not necessarily a feature of Addison's disease.

Opiate receptors and the metabolic response to intravenous glucose

The role of opiate receptors in the metabolic response to an intravenous glucose load was determined in eight non-diabetic subjects (four of whom showed a positive chlorpropamide alcohol flush response and four who did not). Subjects were studied in a double blind randomised fashion receiving either a saline control or the specific opiate receptor antagonist, naloxone (0.4 mg/min), as an infusion for 5 minutes before and 20 minutes after an intravenous bolus of glucose (0.5 g/kg body weight). Naloxone decreased the early plasma glucose peak in all subjects by increasing the distribution volume but did not alter the fractional glucose clearance. Insulin and glucagon responses to glucose were not altered by naloxone. Naloxone delayed the normal post-glucose rise in the levels of the gluconeogenic precursors alanine, lactate, pyruvate and glycerol suggesting a delay in the usual inhibition in gluconeogenesis following a glucose load. There was no difference in the metabolic response between those subjects who were liable to chlorpropamide alcohol flushing and those who were not either with or without naloxone. We conclude that opiate receptors may influence distribution volume and gluconeogenesis but do not play a major role in either insulin or glucagon secretion or in glucose disposal following an intravenous glucose load.