Prolonged aldose reductase inhibition in chronic peripheral diabetic neuropathy: effects on microangiopathy

A 2-year randomized placebo-controlled double-blind trial of 250 mg day-1 of the aldose reductase inhibitor Sorbinil in severe symptomatic chronic peripheral neuropathy was performed in 21 diabetic patients. Due to adverse reactions 8 patients completed the trial on Sorbinil and 6 patients on placebo. Despite differences in baseline neurophysiological parameters, duration of diabetes, and presence of retinopathy between the placebo and treatment groups, there were no initial differences in in vitro platelet aggregation, albumin excretion rate (AER) or muscle capillary basement membrane thickness. After 2 years the median deterioration in AER in the placebo group was 18.4 micrograms min-1 (range 2.6-64.8 micrograms min-1). This deterioration was significant (p less than 0.03). The change in AER in the Sorbinil group was +1.25 (-10.7 to +20.4) micrograms min-1, an insignificant change. In vitro platelet responsiveness to collagen and adenosine diphosphate (ADP) increased in the placebo group (median change max% collagen + 8 (+2 to +30)%; ADP +4.5 (0 to +20)% compared with a fall in the Sorbinil treated patients (median change; collagen -17.5 (-2 to -40)%, p less than 0.05; ADP, -4 (0 to -25)%, p less than 0.05). Muscle capillary basement membrane thickness was measured in only 3 patients in each group and did not alter significantly during the trial. All 12 neurophysiological measurements showed no significant changes between the treatment and placebo groups. The data suggest that aldose reductase inhibition has effects on platelet reactivity and microalbuminuria.

The immunogenetics of insulin-dependent (Type I) diabetes

Insulin-dependent diabetes develops when a genetically predisposed individual is exposed to an as-yet-unknown environmental insult. A major part of genetic susceptibility to the disorder is encoded close to or within the HLA-DQ region, but non-HLA-linked genes are also implicated.

The human red blood cell glyoxalase system in diabetes mellitus

Methylglyoxal and other alpha-oxoaldehydes are formed from glycolytic intermediates and may be involved in the development of diabetic microangiopathy. Glyoxalase I and glyoxalase II metabolise methylglyoxal to D-lactic acid, via the intermediate S-D-lactoylglutathione. The activities of the glyoxalase enzymes and the concentrations of methylglyoxal and S-D-lactoylglutathione were measured in erythrocytes of 45 control and 85 diabetic subjects (41 with retinopathy and 44 uncomplicated). The concentration of S-D-lactoylglutathione was increased in diabetic patients vs. controls (21.4 +/- 9.3 vs. 12.4 +/- 4.8 mumol/l, P less than 0.001), as was methylglyoxal (3.6 +/- 2.3 vs. 1.4 +/- 0.2 mumol/l, P less than 0.001). There were no significant differences in the activities of glyoxalase I and glyoxalase II between diabetic patients and controls. For insulin-dependent patients only, those without retinopathy had a higher activity of glyoxalase II than those with retinopathy (P less than 0.05). A group of age- and duration-matched insulin-dependent diabetic patients with retinopathy also had a higher activity of glyoxalase I compared with a group of diabetic patients without retinopathy (P less than 0.025). This study provides evidence for elevated concentrations of oxoaldehydes in diabetes mellitus which might have pathogenic significance.

Activity of the unstimulated renin-angiotensin-aldosterone system in type 1 diabetic patients with and without proteinuria

There have been conflicting reports of the activity of the renin-angiotensin-aldosterone system in diabetes. We studied the activity of the unstimulated renin-angiotensin-aldosterone system in 73 consecutive Type 1 diabetic patients with varying degrees of albuminuria. Patients with elevated albumin excretion rates had elevated median plasma renin activity (macroalbuminuric 2.2, range 0.5-8.2, p less than 0.05; microalbuminuric 2.3, 0.7-7.1, p less than 0.001; vs normoalbuminuric 1.0, 0.2-4.5 nmol l-1 h-1) and higher systolic blood pressure (macroalbuminuric 141 +/- 27 vs normoalbuminuric 116 +/- 13 mmHg, mean +/- SD, p less than 0.01) compared with those with normal albumin excretion rates. Aldosterone secretion and function were normal in all patients studied.

Serum fructosamine in diabetic pregnancy

Serum fructosamine was assessed in 41 previously diagnosed diabetic patients throughout pregnancy and compared with other standard measures of glycaemic control. Fructosamine was measured by a precise automated method using the reduction of nitro-blue tetrazolium at alkaline pH. Corrected serum fructosamine was calculated from serum fructosamine and serum protein concentrations in view of the falling protein concentrations during pregnancy. Serum fructosamine corrected for total serum protein was significantly lower at the end of pregnancy than at the initial visit. Clinic blood glucose, HbA1c and fructosamine corrected for serum albumin did not fall significantly. Fructosamine corrected for total protein concentration at all points through pregnancy showed positive correlations with birth weight ratio (r = 0.51-0.67). HbA1c did not show the same consistent pattern of results. The correlation of first and second trimester fructosamine values with birth weight ratio suggests that glucose control is a determinant of birth weight throughout pregnancy rather than just in the last trimester.

Identification of susceptibility loci for insulin-dependent diabetes mellitus by trans-racial gene mapping

INSULIN-dependent (type I) diabetes mellitus (IDDM) follows an autoimmune destruction of the insulin-producing beta-cells of the pancreas. Family and population studies indicate that predisposition is probably polygenic. At least one susceptibility gene lies within the major histocompatibility complex and is closely linked to the genes encoding the class II antigens, HLA-DR and HLA-DQ (refs 3, 4). Fine mapping of susceptibility genes by linkage analysis in families is not feasible because of infrequent recombination (linkage disequilibrium) between the DR and DQ genes. Recombination events in the past, however, have occurred and generated distinct DR-DQ haplotypes, whose frequencies vary between races. DNA sequencing and oligonucleotide dot-blot analysis of class II genes from two race-specific haplotypes indicate that susceptibility to IDDM is closely linked to the DQA1 locus and suggest that both the DQB1 (ref. 7) and DQA1 genes contribute to disease predisposition.

Pneumomediastinum in diabetic ketoacidosis

A 13-year-old girl was admitted with diabetic ketoacidosis. She was found to have a pneumomediastinum. This resolved spontaneously on correction of the metabolic disturbance. The condition is generally benign.

Diabetes in the UK West indian community: the Wolverhampton survey

A survey was carried out to determine the prevalence of known diabetes amongst West Indians living in Wolverhampton. Two hundred and fifty-one West Indians with diabetes were identified from a computerized register, which records all diabetic patients in the Wolverhampton area attending either the hospital diabetic clinic or general practitioner mini-clinics, and from questionnaire data obtained through local general practitioners. An estimated 4.4% of the Wolverhampton population are of West Indian origin determined by the 1981 census, giving a prevalence of known diabetes of 2.2% compared with 1.2% in the indigenous UK white Caucasian population. Only 4% of these patients were truly insulin-dependent but 38% were insulin-treated, 43% were on oral hypoglycaemic agents and 19% on diet alone. Only 1.6% were diagnosed below the age of 20 years, with peak frequency of diabetes occurring in the age group 45-64 years. Thirty-eight percent of all patients were obese, 40% were hypertensive, but only 4% had a history of angina or myocardial infarction. In UK West Indians non-insulin-dependent diabetes is common and is predominantly a disease of middle age, whereas insulin-dependent diabetes is relatively uncommon.

Trans-racial studies implicate HLA-DQ as a component of genetic susceptibility to type 1 (insulin-dependent) diabetes

Type 1 (insulin-dependent) diabetic patients and control subjects of Afro-Caribbean Negroid racial origin were investigated by serological HLA-DR-typing and restriction fragment length polymorphism analysis using DNA probes corresponding to the DQ alpha, DQ beta and DR beta chain genes. Combined analysis indicated that four DR antigens are positively associated with the condition in Negroid subjects - DR3, 4, 7 and w9. DR3 and 4 are also associated in Caucasians, but the relative risk for DR3 is lower in Negroid subjects. The DR7 association is specific for the Negroid race, and DRw9 is only weakly associated in Caucasoid subjects. Restriction fragment length polymorphism analysis demonstrated a DQ beta restriction pattern in Negroid subjects which is absent from Caucasoid subjects. This pattern was associated with DRw9 and a subset of DR7, and was markedly increased in frequency in diabetic patients compared with control subjects (48.7% vs 10.4%, respectively; p less than 10(-4). In the absence of this pattern, DR7 showed no positive association. DR3 in Negroid subjects was associated with two distinct DQ alpha-DQ beta patterns, only one of which was positively associated with diabetes. A DQ beta pattern, in linkage disequilibrium with different DR antigens in different races, conferred a consistent protective effect against the development of Type 1 diabetes. Trans-racial genetic analysis thus supports a primary role for DQ in susceptibility to Type 1 diabetes.

Effect of gliclazide on thromboxane B2, parameters of haemostasis, fluorescent IgG and lipid peroxides in non-insulin dependent diabetes mellitus

Abnormalities of platelet aggregation, and increased levels of lipid peroxides and denatured proteins have been implicated in the pathogenesis of diabetic microangiopathy. Seventeen non-insulin dependent diabetics (mean age 65.7) on established sulphonylurea therapy were converted to an equivalent dose of gliclazide. They were studied at baseline and intervals to 36 weeks. Thromboxane B2 (TXB2) and beta thromboglobulin (beta TG) were measured by radioimmunoassay. Lipid peroxides were measured as total diene conjugates (DC) by scanning UV spectrophotometry and thiobarbituric acid reactivity (TBA) by absorbance at 532 nm. Oxidation products of proteins were represented by fluorescence/UV ratio of immunoglobulin G (*IgG) separated from serum by HPLC. Glycaemic control remained stable throughout the study. TXB2 fell from 734 +/- 233 ng/l at 0 weeks to 488 +/- 155 at 36 weeks, p less than 0.001 and beta TG from 120 +/- 70 ng/ml to 48 +/- 18 at 24 weeks, p less than 0.005. Lipid peroxides fell between 0 and 36 weeks; DC from 0.71 +/- 0.28 to 0.32 +/- 0.09, p less than 0.001 and TBA from 29.6 +/- 22.4 to 4.0 +/- 2.2, p less than 0.001. Fluorescent IgG ratio fell from 1.44 +/- 0.36 to 0.32 +/- 0.07, p less than 0.001. This data provides evidence for a specific action of gliclazide on thromboxane synthesis and platelet aggregation. This is independent of glycaemic control and may in part be mediated by the observed fall in lipid peroxides.

Transfer factor for carbon monoxide in patients with diabetes with and without microangiopathy

The transfer coefficient (KCO) was significantly lower in diabetic patients with microangiopathy than in a matched group without this complication. This may reflect microangiopathy in the pulmonary circulation.

The fluorescence of serum proteins in diabetic patients with and without retinopathy

Non-enzymatic glycosylation of long-lived proteins results in a characteristic fluorescence, known as protein 'browning'. The degree of fluorescence of skin collagen correlates with retinopathy in diabetes. We have therefore measured the fluorescence of serum albumin and IgG by a sensitive HPLC technique in 69 diabetic patients, 38 with retinopathy and 31 without complications, and in 26 age-matched controls. The fluorescence of the IgG fraction, calculated as the ratio of fluorescence (excitation 360 nm, emission 454 nm) to optical density (280 nm), was elevated in diabetic patients with retinopathy (1.5 +/- 0.5) compared with those without retinopathy (1.1 +/- 0.2, p less than 0.005) and control subjects (1.1 +/- 0.2, p less than 0.005). The fluorescence ratio for the albumin fraction was increased in all diabetic patients (11.2 +/- 2.7) compared with control subjects (8.9 +/- 1.5, p less than 0.001). There was no significant difference in the fluorescence ratios of albumin in those with and without retinopathy. The fluorescence of serum albumin and IgG were not significantly correlated with serum protein glycosylation measured by the fructosamine method.

New referrals to a diabetic clinic

New referrals to a diabetic clinic were studied over 6 months. One hundred and twelve patients were referred from their General Practitioner (GP) and 49 from other hospital departments. Thirty percent of GP referrals and 10% of hospital referrals were made on the basis of glycosuria alone. From all the patients referred six were found to be non-diabetic and a further 19 had been prescribed drugs inappropriately (either the wrong drug or the right drug in excessive dose), some with potentially dangerous consequences. Almost half of the patients were given no dietary advice at all. There is, still much ignorance concerning diagnosis and initial management of diabetes in both general and hospital medical practice.

Class II HLA DNA polymorphisms in type 1 (insulin-dependent) diabetic patients of north Indian origin

Genetic associations with Type 1 (insulin-dependent) diabetes may be primary or secondary to linkage disequilibrium. Studies of different racial groups should allow these to be distinguished. We have reported that Type 1 diabetes is associated with HLA-DR3 and -DR4 in subjects of North Indian (Punjab) origin and now present the results of a study of HLA class II DNA polymorphisms in this group and in white caucasoid subjects. DR4 in North Indian Type 1 diabetic patients was associated with DQ beta and DX alpha DNA polymorphisms identical to those found in DR4-positive white caucasoid patients. This DQ beta/DX alpha pattern was increased in frequency in North Indian diabetic patients vs control subjects (33.3% vs 8.5%, p less than 0.001, relative risk = 5.12 (95% confidence limits: 1.96-13.4)). A DQ beta polymorphism with very low relative risk for Type 1 diabetes in white caucasoid subjects was also markedly reduced in North Indian diabetic patients vs control subjects (2.3% vs 24.7%, p less than 0.02, relative risk = 0.10 (95% confidence limits: 0.02-0.46)). This pattern was associated with DR2 in white caucasoid subjects, but with DRw6 in North Indians. A DR3-associated DR beta polymorphism was markedly increased in North Indian diabetic patients vs control subjects (90.2% vs 40.7%, p less than 10(-6), relative risk = 12.1 (95% confidence limits: 4.32-33.9)). The DQ subregion may be a primary site of genetic influence on susceptibility to Type 1 diabetes. Further studies in different racial groups will clarify the HLA associations of Type 1 diabetes.

Microalbuminuria in diabetic subjects with chronic peripheral neuropathy

Fifty-five patients with chronic peripheral neuropathy, 31 with and 24 without retinopathy, had albumin excretion rates determined on 2-h supine urine collections on three occasions by a radioimmunoassay method. Four patients with retinopathy had albustix-positive proteinuria and were excluded from subsequent analysis. Microalbuminuria was found in 20 of the 27 patients with retinopathy compared with 10 of the 24 patients with neuropathy alone. The mean albumin excretion rate (AER) was higher in neuropathic patients with retinopathy than in those patients with neuropathy alone (41.2 +/- 40.3 vs 18.8 +/- 33.2 micrograms/min, P less than 0.01). Multivariate analysis of the data was performed and this revealed a correlation coefficient of R2 = 0.33 (P less than 0.01) for AER as the dependent variable with respect to the independent variables HbA1, systolic blood pressure and known duration of diabetes. There was, however, no significant contribution separately of these individual variables to the regression equation. Microalbuminuria was significantly associated with retinopathy although almost half of the patients with neuropathy alone had microalbuminuria. The association between microalbuminuria and neuropathy even in the absence of retinopathy provides support for a microvascular element in the pathogenesis of diabetic neuropathy.

Pre-conception counselling in Asian women with non insulin dependent diabetes and impaired glucose tolerance

Asian patients comprise greater than 8% of our diabetic clinic. Retrospective analysis of the case notes of 22 Asian patients and 20 white patients with NIDDM or impaired glucose tolerance (IGT) attending our combined diabetic/antenatal clinic during 1985-1987 confirmed the reported advantages of pre-conception counselling. Those Asian patients with NIDDM or IGT had higher corrected birthweight than a parity matched Asian control group (3,472.3 +/- 595 g v 2,798.6 +/- 672.3 g p less than 0.001). Those Asian patients who had preconception counselling had, however, significantly smaller babies (3,270.8 +/- 445.1 g v 3,714.4 +/- 727.1 g p less than 0.05). An increase in foetal and maternal complications has been documented in cases of gestational diabetes, but the glucose levels that predict an increased risk have not been clearly defined. In the Asian patients with NIDDM/IGT there was one neonatal death and two congenital abnormalities, although these mothers did not have significantly higher glycosylated haemoglobin levels. HbA1 was not a good diagnostic test for glucose tolerance. Subjects with any degree of glucose intolerance should be managed as carefully as established diabetics and preconception counselling for high risk groups may be beneficial.

Autoantibodies in Indian-Asians with insulin-dependent diabetes in the UK

Classical insulin-dependent diabetes mellitus (IDDM) is relatively uncommon in Indian-Asians whether in India or in the UK and this may be related to immunogenetic factors. We have studied the presence or absence of islet cell antibodies and other auto-antibodies in 36 subjects with IDDM and 41 controls, all of Indian origin. Islet cell antibodies (ICA-IgG) were found in 8 subjects with IDDM but in none of the controls. Four of the 8 patients with ICA-IgG also possessed the complement fixing variety (CF-ICA). There was no definite association between possession of ICA and HLA-DR antigens. Thyroid antibodies were commoner in patients (22%) compared with controls (7%) as were parietal cell antibodies (8.3% vs 4.8%). None of the patients or controls had adrenal antibodies. The frequency of organ-specific antibodies in Indian-Asians with IDDM is similar to that of white Caucasians. The overall frequency of ICA is, however, lower than that reported for white Caucasians although the temporal distribution is similar. We conclude that even though the prevalence of IDDM in Indian-Asians is lower than in white Caucasians there is no evidence that different immunological mechanisms are involved in the pathogenesis of IDDM in the two groups.

HLA-DR and DQ DNA polymorphisms in subjects of Asian Indian and white Caucasian origin

There is a close correspondence between serologically defined DR types and DR beta chain restriction fragment length polymorphisms (RFLPs). There is also an association between DR types and DQ alpha and DQ beta RFLPs because of linkage disequilibrium. We present the results of an analysis of DR beta, DQ alpha and DQ beta RFLPs in Asian Indians and white Caucasian subjects. DR beta RFLPs were similar in the two groups. Clearly distinguishable DR beta patterns were observed for DR1, 2, 3, 4, 5, 7 and w10. The DR beta patterns associated with DR3 were, however, also found with w6. The DR7 DR beta patterns were also found with w9. For DR specificities 1, 3, 4, 5, 7 and w10, the associated DQ alpha and DQ beta RFLPs were similar in both racial groups, but for DR2, however, marked differences were found. The DR2-positive white Caucasian subjects all possessed a single DQ alpha/DQ beta combination whereas the DQ alpha/DQ beta patterns in DR2-positive Asian Indians showed considerable heterogeneity. The pattern seen in white subjects was present in only a minority of Asians. DR-DQ relationships clearly vary in different racial groups. RFLP analysis of HLA-linked diseases in different populations should prove to be an important technique in identifying the primary genetic factor(s) in these disorders.

Serum antioxidant activity in diabetes mellitus

Free radical medicated oxidative damage has previously been implicated in the pathogenesis of diabetic microangiopathy. Caeruloplasmin and transferrin act as antioxidants in serum by oxidizing and chelating ferrous iron which could otherwise act as a catalyst in free radical reactions. We have measured the serum anti-oxidant activity in 67 diabetics, 25 of whom had retinopathy and in 37 controls. Serum iron concentrations were normal in diabetics in comparison with controls (21.5 +/- 10 v 19.5 +/- 6.7 mumol/L) although transferrin and iron binding capacity were increased in the diabetics (3.7 +/- 0.8 v 2.9 +/- 0.9 g/L, p less than 0.001 and 69.9 +/- 10.8 v 59.0 +/- 14 mumol/L, p less than 0.002 respectively). Caeruloplasmin, measured by its ferroxidase activity, was increased in both male (46 +/- 11 v 36 +/- 9 mu/mL, p less than 0.002) and female diabetics (57 +/- 13 v 47 +/- 11 mu/mL, p less than 0.002). Ferritin was also increased in both male (124 +/- 113 v 44 +/- 38 ng/mL, p less than 0.001) and female diabetics (132 +/- 118 v 25 +/- 12 ng/mL, p less than 0.001). The presence of retinopathy, the degree of glycaemic control and duration of diabetes had no effect on these findings. We conclude that increased concentrations of iron-oxidizing and iron-binding proteins occur in diabetic serum, and that the increased serum antioxidant activity may be a response to oxidative stress.