Does a central MHC gene in linkage disequilibrium with HLA-DRB1*0401 affect susceptibility to type 1 diabetes?

Subtypes of HLA-DR4 are associated with susceptibility or protection against type 1 diabetes (T1DM). We addressed whether this reflects linkage disequilibrium with the true susceptibility locus by studying broader MHC haplotypes marked by alleles of HLA-B, IKBL (adjacent to TNFA) and complement C4. The study used a largely Caucasian cohort from Western Australia. HLA-DRB1*0401 and HLA-DRB1*0405 marked susceptibility to T1DM. In Caucasians, DRB1*0401 occurs predominantly in the 44.1 ancestral haplotype (AH; HLA-A2,B44, DRB1*0401,DQB1*0301) and the 62.1AH (HLA-A2,B15(62),DRB1*0401,DQB1*0302). HLA-B15 marked susceptibility and HLA-B44 marked with resistance to T1DM in patients and controls preselected for HLA-DRB1*0401. A gene between TNFA and HLA-B on the 8.1AH (HLA-A1,B8,;DR3,DQ2) modifies the effects of the class II alleles. Here, alleles characteristic of the 62.1AH (C4B3, IKBL+446*T and HLA-A2,B15) were screened in donors preselected for HLA-DRB1*0401. C4B3 was associated with diabetes, consistent with a diabetes gene telomeric of MHC class II. However, increases in carriage of IKBL+446*T and HLA-A2,B15 were marginal, as too few control subjects were available with the diabetogenic alleles. However, with these tools, selection of HLA-DRB1*0401, DQB1*0302 donors who are positive and negative for C4B3 will allow bidirectional mapping of diabetes genes in the central MHC.

Can MHC class II genes mediate resistance to type 1 diabetes?

Numerous studies have associated carriage of HLA-DRB1*1501, DQA1*0102 and DQB1*0602 (DR15, DQ6) with dominant resistance to type 1 diabetes and have concluded that one or more of the component HLA class II molecules mediate this effect. Mechanisms for MHC class II-mediated resistance to diabetes have been proposed from studies of transgenic mice, usually using the diabetes-prone non-obese diabetic (NOD) strain. However, these studies have not reached any consensus on a plausible mechanism. In this study we question why the role of central MHC genes in resistance to diabetes has not been addressed, as the central MHC carries markers of susceptibility to diabetes in linkage disequilibrium with several genes with known or putative immunoregulatory functions. To illustrate the type of studies required to address this issue, we selected diabetes patients and control subjects for carriage of HLA-DR15 and the C allele at position +738 in the inhibitor of kappa B-like gene (IKBL). These alleles mark the 7.1 haplotype (HLA-A3, B7, IKBL738*C, DR15, DQ6). HLA-DR15 was the most effective marker of resistance, but an effect may be evident with IKBL738*C in a larger study. Moreover, carriage of the entire haplotype was particularly rare in patients. The best explanation for this is that the critical gene lies between IKBL and HLA-DRB1, and is more closely linked to HLA-DRB1. Candidate genes at the centromeric end of the central MHC are reviewed, highlighting the need for further study.

Localization of central MHC genes influencing type I diabetes.

The contribution of MHC class II haplotypes to susceptibility to type I diabetes has been clearly established, and interest has now focused on the effects of additional genes in the MHC region. We have investigated the central MHC alleles on 8.1 ancestral haplotype (HLA-A1, B8, DR3, DQ2), as it is well conserved in Caucasian populations. The HLA-DR3-DQ2 genotype is a recognized risk factor for type I diabetes. Single nucleotide polymorphisms and microsatellites in the MHC were used to map segments of the 8.1 ancestral haplotype carried by type I diabetic and control subjects expressing either HLA-B8 or DR3, but not both these markers. In this way we controlled for the diabetogenic effect of carriage of DR3. Alleles of the 8.1 ancestral haplotype between TNFA-308/D6STNFa and HLA-B were carried with significantly greater frequency in B8(-), DR3(+) type I diabetic patients compared with B8(-), DR3(+) controls. This interval was marked by a BAT1 gene polymorphism and a MIB microsatellite allele.

Does the eating match the teaching? Food habits in people with non insulin dependent diabetes.

Three-day food records were used to assess the dietary intake of 50 patients with non insulin dependent diabetes; body mass index (BMI) exceeded 25 in 74% and exceeded 30 in 20%. Present nutrient intake was determined by the food compositional analysis package known as SODA III analysis. Two at-risk micronutrients were used as markers of food intake quality, namely calcium and thiamin. Calcium intake prior to diagnosis of diabetes by retrospective questionnaire. Serum and red cell thiamin levels were measured. All patients had received nutrition education. Results showed fat intake less than 35% in 50% of subjects and carbohydrate intake greater than 50% in 18% of subjects. Seventy-two percent of subjects had a saturated fat intake greater than 10%. Cholesterol intake exceeded 300mg in 16% of subjects. Dietary thiamin intake was adequate in 98% and did not correlate with serum or red cell thiamin levels. Only 24% of subjects had an adequate calcium intake. Previous to diagnosis of diabetes, 50% of subjects had had adequate calcium intakes. Calcium intake was related to age, increasing with increasing age (p<0.05) and saturated fat intake (p<0.01). This group had an excess intake of fat and calcium intake was largely inadequate.

Microalbuminuria in type 2 diabetes: an independent predictor of cardiovascular mortality.

BACKGROUND: Microalbuminuria has been shown to be associated with cardiovascular mortality in type 2 diabetic subjects. It is unclear to what extent this is due to the increased prevalence of other cardiac risk factors. AIMS: To examine the relationship of urine albumin excretion to cardiovascular mortality and to determine its status as an independent risk factor. METHODS: In a prospective longitudinal study from 1986-1993 we followed 666 type 2 diabetic subjects from a diabetes outpatient service. Cardiovascular risk factors including urine albumin concentration were measured at study entry. Cox proportional hazards regression was used to determine risk factors for mortality. The hazard ratios of microalbuminuria and macroalbuminuria for all cause, cardiovascular and coronary heart disease mortality were determined after accounting for other cardiac risk factors including blood pressure, glycated haemoglobin, total cholesterol, HDL cholesterol, triglycerides, urea, smoking, body mass index, patient age and disease duration. RESULTS: The prevalence of urine albumin of 30-300 mg/L at study entry was 31.7%. A total of 167 deaths occurred (80 from cardiovascular disease). Mortality hazard ratios in subjects with urine albumin of 30-300 mg/L as compared to < 30 mg/L, adjusted for age, sex and other cardiovascular risk factors were 1.77 (95% CI 1.22-2.57, p = 0.002) for all causes, 2.34 (95% CI 1.38-3.99, p = 0.002) for cardiovascular and 1.78 (95% CI 0.97-3.26, p = 0.061) for coronary heart disease (CHD) mortality. Other factors significantly associated with cardiovascular mortality included diastolic blood pressure, HDL cholesterol and glycated haemoglobin. Total cholesterol and log triglyceride were significantly associated with CHD mortality. Disease duration, age at diagnosis, smoking and body mass index were not related to cardiovascular or CHD mortality. CONCLUSIONS: We confirm microalbuminuria as an independent predictor of mortality in type 2 diabetes despite its association with a number of conventional cardiovascular risk factors.

A computerized technique for analyzing lateral bending behavior of subjects with normal and impaired lumbar spine. A pilot study.

STUDY DESIGN: A computerized technique, employing a motion analysis system and a force platform, was developed to analyze lateral bending behavior of subjects with normal and painful spines. METHODS: Lateral bending was quantified using motion (angle and speed of rotation), force (ground reaction kinetics), and biomechanical behavior ("compliance" and "transfer mobility") characteristics of four discrete spinal segments measured during standing, range of bending, and bending at normal and maximum speeds. RESULTS: For subjects with pain, there were reductions in the range of lateral bend (43%) and speed of rotation (39%). Ground reaction moment about the medial-lateral axis was greater (58%), whereas that about the anterior-posterior axis was less (28%). "Compliance" was less (25%), whereas "transfer mobility" was greater (24%). CONCLUSIONS: The findings suggest that the characteristics of lateral bending, rather than range of motion, is most affected in subjects with pain.

Mortality and coronary heart disease in diabetes mellitus.

A clinic-based study of 1,063 patients with Type 2 diabetes recruited from 1973 to 1982 identified 533 deaths (attributed to coronary heart disease in 268 cases) by 31 December 1989. When compared to the general population of Australia the overall standardised mortality ratio was 1.42 (95 per cent confidence interval (CI) 1.26 to 1.58) for females and 1.19 (CI 1.03 to 1.35) for males. Cox regression analysis showed that having coronary heart disease or absence of foot pulses at the time of entrance to the study were the major independent risk factors for overall mortality after adjustment for initial age. Elevated cholesterol and blood pressure were found to be major independent risk factors for death from coronary heart disease.

Type 1 diabetes and latent pernicious anaemia.

OBJECTIVE: To determine the prevalence of latent pernicious anaemia (PA) in Type 1 diabetics. DESIGN: Patients with Type 1 diabetes were screened at two yearly intervals on a continuing basis. SETTING: Diabetic Unit, Royal Perth Hospital, Western Australia. PATIENTS: Three hundred and seventy-one patients, 156 females and 215 males, attending a diabetic clinic. They were classified as having Type 1 diabetes on the basis of age of onset less than 40 years and requiring insulin from the start. MAIN OUTCOME MEASURES: Serum cobalamin levels were measured and studies of thyroid function and a blood count were done. Patients with a reduced serum level of cobalamin had tests for cobalamin absorption. RESULTS: Six patients had a low serum cobalamin level; five showed malabsorption of the vitamin which could be corrected by the addition of intrinsic factor. Four of these patients had no clinical signs of PA. The fifth was mildly anaemic (haemoglobin level 111 g/L) and had megaloblastic bone marrow. He was classified as having frank PA. The sixth patient was not available for further testing. These results give a prevalence of latent PA of 11 per 1000 in Type 1 diabetics, compared with 3.9 per 1000 in diabetics with clinically manifest disease and 1.27 per 1000 in the general population. All four patients with latent PA had hypothyroidism, based on low thyroxine levels, increased levels of thyroid stimulating hormone and the presence of thyroid antibodies. CONCLUSION: Latent PA is not uncommon in Type 1 diabetics. It has a long preclinical course and occurs in those patients with thyroid disease. The screening of Type 1 diabetics for latent PA has worthwhile benefits as a "preventive" health measure.

Ancestral haplotypes reveal the role of the central MHC in the immunogenetics of IDDM.

The major histocompatibility complex (MHC) contains multiple and diverse genes which may be relevant to the induction and regulation of autoimmune responses in insulin dependent diabetes mellitus (IDDM). In addition to HLA class I and II, the possible candidates include TNF, C4, and several other poorly defined polymorphic genes in the central MHC region. This study describes two approaches which take advantage of the fact that the relevant genes are carried by highly conserved ancestral haplotypes such as 8.1 (HLA-B8, TNFS, C4AQ0, C4B1, DR3, DQ2). First, three "diabetogenic" haplotypes (two Caucasoid and one Mongoloid) have been compared and it has been shown that all three share a rare allele of BAT3 as well as sharing DR3, DQ2. In 43 sequential patients with IDDM the cross product ratio for BAT3S was 4.8 (p less than 0.01) and 6.9 for HLA-B8 plus BAT3S (p less than 0.001). Second, partial or recombinant ancestral haplotypes with either HLA class I (HLA-B8) or II (HLA-DR3, DQ2) alleles were identified. Third, using haplotypic polymorphisms such as the one in BAT3, we have shown that all the patients carrying recombinants of the 8.1 ancestral haplotype share the central region adjacent to HLA-B. These findings suggest that both HLA and non-HLA genes are involved in conferring susceptibility to IDDM, and that the region between HLA-B and BAT3 contains some of the relevant genes. By contrast, similar approaches suggest that protective genes map to the HLA class II region.

The evaluation of group education for patients with non-insulin dependent diabetes at Hollywood Repatriation Hospital in Western Australia.

OBJECTIVES: To enable effective use of hospital resources in relation to staff time and diabetes education; to ensure that all patients have access to a standard level of education; and to maintain and/or improve diabetes control. METHOD: Multiple choice questionnaire to test knowledge; check of individual biochemical status. RESULTS: Diabetes knowledge and control were assessed in 51 persons with non-insulin dependent diabetes mellitus (NIDDM) attending diabetes group education sessions at Hollywood Repatriation Hospital in Western Australia. The programme comprising three 2.5 hour sessions at weekly intervals, was conducted by the physician, dietitian, nurse educator, podiatrist and physio-therapist. Groups consisted of 7-14 patients, with partners encouraged to attend, and aimed to promote and stimulate discussion on diabetes self-care among participants. After group education there was a significant improvement in knowledge of diabetes, blood sugar control and energy balance. This was achieved with a reduction in staff time, when compared with individual education, and a more efficient use of hospital resources. Thus, the objectives were realized. It is concluded that diabetes group education is useful in patients with NIDDM attending Hollywood Repatriation Hospital.

Prevalence of diabetic complications in relation to risk factors.

The prevalence of diabetic complications is reported from a cross-sectional study of rural diabetic subjects in Western Australia. Logistic-regression analysis has been used to discover potential risk factors associated with each complication. A distinction has been made between time-related variables (age, age at diagnosis, duration of diabetes) and other risk variables. We have attempted to identify the major time-related risk variables for each complication and then examined the effect of other risk variables after accounting for the major time-related variables. The important time-related variables were found to be duration of diabetes for retinopathy, age for macrovascular disease, duration and age at diagnosis of diabetes for sensory neuropathy, and age for renal impairment. When matched on these important time-related variables, the overall prevalences of complications for insulin-dependent (IDDM) compared with non-insulin-dependent (NIDDM) diabetic patients were essentially the same. An exception is renal impairment, for which IDDM patients had a higher prevalence than did NIDDM patients of the same age. After allowing for time-related variables, the analysis also demonstrates positive independent associations between diabetic control (glycosylated hemoglobin) and retinopathy and between diabetic control and macrovascular disease. Plasma cholesterol (positively) and high-density lipoprotein cholesterol (negatively) were related independently to both macrovascular disease and renal impairment. Very few differences in the risk-factor profiles for complications were found for IDDM compared with NIDDM patients after allowing for time-related variables.

An unusual case of cutaneous listeriosis.

Listeria monocytogenes was identified as the etiological agent in the cutaneous and febrile illness of a 64-year-old male who acquired the organism as a result of contact with the genital tract of a cow while assisting in the delivery of a stillborn calf.

Reference ranges for serum C4 concentrations in subjects with and without C4 null alleles.

Serum C4 concentrations were measured in 102 healthy subjects and 90 subjects with type I diabetes mellitus. A wide range was observed in the group as a whole (0.08-0.67 g/l; mean = 0.26 g/l; SEM = 0.01 g/l). After C4 allotyping it was possible to subgroup 134 of these subjects according to the number of C4 null alleles present. C4 concentrations in the group with two null alleles were lower than in the group without null alleles (mean 0.2 v 0.37 g/l; p less than 0.001). C4 concentrations in the group with one C4 null allele were intermediate and significantly different from those of the group without null alleles (mean 0.24 v 0.37 g/l; p less than 0.001). Appropriate analysis has defined reference ranges for serum C4 concentrations in subjects with two, one, or zero C4 null alleles. Interpretation of low serum C4 concentrations should take account of the number of C4 null alleles present.

Endodontic considerations in the design of acid-etched anterior splints for patients with reduced periodontal support.

A modification of existing designs for resin-bonded retainers has been introduced. This new design is appropriate for the extracoronal splinting of anterior teeth with reduced periodontal support. The design of the splint will accommodate the increased risk of these teeth for endodontic failure. The versatility and advantages of this design have been presented and compared with other anterior splinting techniques. At present, there appears to be no clinically significant difference in the retentiveness of perforated and nonperforated etched metal retainers.

Susceptibility to IDDM is marked by MHC supratypes rather than individual alleles.

107 patients with insulin-dependent diabetes mellitus (IDDM) were typed for HLA A, B, C-, and DR antigens, and for complement C4A, C4B, and Bf alleles, and the results were compared with those of a combined reference group of 332 appropriately matched healthy subjects. Supratypes (allelic combinations) were identified from the phenotype of each group, and it was shown that the frequency of several supratypes is increased in patients with IDDM, in particular supratypes (A1 Cw7) B8 C4AQ0 C4B1 BfS DR3 (P = 0.0001), (A30 Cw-) B18 C4A3 C4BQ0 BfF1 DR3 (P = 0.0003), (A2 Cw3) B62 C4AR C4B2.9 BfS DR4 (P = 0.0002), and three other supratypes including DR4. It was also shown that increases in the frequency of individual alleles are secondary to increases in supratype frequency. Moreover, supratypes appeared to interact; the presence of two relevant supratypes being particularly important. The absolute risk of IDDM was approximately 0.5 in subjects who were homozygous for B18 C4A3 C4BQ0 BfF1 DR3. We concluded that genetic susceptibility is best recognized by MHC supratypes rather than isolated alleles, and that supratype combinations make the identification of even greater disease risk possible.

Diabetes in part-aborigines of Western Australia.

One thousand, two hundred and eighteen diabetic subjects living in and around country towns of Western Australia were screened for complications of diabetes. This population included 134 subjects of Aboriginal descent, who were compared with the Caucasoids taking part. In the Aboriginal group there was a greater proportion of Type 2 (non-insulin-dependent) diabetic patients, a relative female preponderance (69% compared with 51%) and a tendency to present at an earlier age of onset than their Caucasoid counterparts. Diabetic complications were at least as common in the Aboriginal group as in the Caucasoid patients. Indeed, retinopathy within 10 years of onset of diabetes was more common in the Aborigines. Peripheral neuropathy was more prevalent in Aborigines treated by diet alone or oral hypoglycaemic agents than in Caucasoids. A much greater prevalence of proteinuria was an additional feature of the Aboriginal subgroup (29% versus 4%).