HLA antigens and risk factors for nephropathy in type 1 (insulin-dependent) diabetes mellitus

Human Leukocyte Antigens (HLA) Genes Association in Type 1 Diabetic Nephropathy

BACKGROUND

Diabetic nephropathy is a common worldwide multifactorial disease where involvement of genetic factors is well etablished. The aim of this study was to investigate the HLA genes implication in the development of type 1 diabetic nephropathy.

METHODS

We performed a case- control study where one hundred and fifty subjects were examined. Patients were divided in two groups; with and without type 1 diabetic nephropathy. HLA typing was performed using Polymerase Chain Reaction- Sequence Specific Oligonucleotide (PCR- SSO) method. HLA association to clinical phenotype and HLA haplotype analysis was also investigated.

RESULTS

HLA B*51 is increased in patients without type 1 diabetic nephropathy (7.14% vs. 0 %, P <0.05, OR= 0), however no other studied alleles seem to have any effect (all P>0.05). Haplotype analysis also does not reveal any significant association, however, A*02-B*18-DRB1*03-DQA1*05- DQB1*03 haplotype shows a tendency to be associated with the development of diabetic nephropathy (P = 0.05).

CONCLUSION

These results suggest a protective effect of HLA B*51 allele from type 1 diabetic nephropathy. However, further studies are required in order to clarify its potential implication as a protective marker.

Determinants of albuminuria in people with Type 2 diabetes mellitus

This study sought to identify determinants of albuminuria in people with Type 2 diabetes. In 335 primary care patients, we assessed albumin-creatinine ratio (ACR) in two 24-h urine samples, and its cross-sectional associations with protein and alcohol intake, cigarette smoking, body weight and height, glycosuria, blood pressure, hypoglycaemic and antihypertensive treatment, gender, age, age at diagnosis, diabetes duration, family history of diabetes and cardiovascular diseases, ethnic origin, and education. The prevalence of micro- or macro-albuminuria (ACR> or =2.0 mg/mmol) was 33%. Among these patients, compared to those with normo-albuminuria, there were more men, protein intake (g/kg) estimated from urinary urea as well as systolic blood pressure and glycosuria were higher, there were more smokers, men were shorter, and a family history of diabetes was less prevalent (all P<0.05). In linear and logistic regression (n=270) albuminuria was independently associated (P<0.05 unless indicated otherwise) with systolic blood pressure (OR(10 mmHg)=1.32), smoking (OR(ex/never)=2.36, OR(current/never)=4.89), glycosuria (OR(> or =7/<1 g/l)=2.41), gender (OR(men/women)=2.50), age in men (OR(10 year)=1.60) (P<0.10) and, inversely, in women (OR(10 year)=0.63) (P>0.10). On aggregation, the modifiable determinants systolic blood pressure, smoking and glycosuria explained 12% of the variation in albuminuria. These factors thus are, although to a moderate extent only, potential determinants of albuminuria. We also observed an independent, inverse association with body height (OR(0.10 m)=0.47). This is in line with the hypothesis that development in utero or during early life influences kidney function in later life.

The 5' insulin gene polymorphism and the genetics of vascular complications in type 1 (insulin-dependent) diabetes mellitus

Recent data suggest genetic contributions to the microvascular complications of Type 1 (insulin-dependent) diabetes mellitus. Most research has focused on the HLA region, and the potential role of other genetic loci has not been adequately explored. We examined the possible relationship between DNA polymorphisms in the region 5' to the insulin gene on chromosome 11 and diabetic nephropathy. This was done by comparison of those diabetic patients homozygous for class 1 alleles at the 5' insulin gene polymorphism locus to 1/3 heterozygotes in a well-characterized series of 324 insulin-requiring diabetic patients from the Wisconsin Epidemiologic Study of Diabetic Retinopathy. Proteinuria (defined as greater than or equal to 0.3 g protein/l urine), was used as suggestive evidence for diabetic nephropathy. Hypertension, a frequent associated finding in diabetic patients with nephropathy, was defined as a blood pressure greater than 140/90 or a history of previous treatment of hypertension. The two genotypically defined groups did not differ from each other in regard to sex ratio, age at diagnosis, age at examination, duration of diabetes, body mass, HbAlc or C-peptide. The 1+1 group had a higher prevalence of proteinuria, 29% as compared to 16.2% in other genotypes (p less than 0.05). There was no significant difference in the frequency of hypertension between the two genotypic groups. This finding suggests that the 5' insulin gene polymorphism may be associated with risk for nephropathy, but the pathophysiologic mechanism remains unclear.

Prior long term glycaemic control and insulin therapy in insulin-dependent diabetic adolescents with microalbuminuria

Adolescence seems to be a period of increased risk for the initiation of diabetic renal disease in insulin-dependent diabetic children. Poor glycaemic control is a risk factor for diabetic nephropathy. We have therefore evaluated prior long-term glycaemic control in 23 diabetic adolescents with microalbuminuria (albumin excretion rate (AER) 20-200 micrograms/min, median 39.0 micrograms/min) and in 23 matched diabetic controls with AER less than 20 micrograms/min (median 9.3 micrograms/min). Glycaemic control was assessed by mean HbA1 and clinic blood glucose levels over a period ranging from 12 to 84 months (median 48 months). Mean HbA1 was 13.6 +/- 2.0% in the microalbuminuric subjects, compared to 11.5 +/- 2.2% in the controls (P less than 0.002); mean blood glucose levels were 13.5 +/- 3.0 and 11.4 +/- 3.0 mmol/l, respectively (P less than 0.02). There appeared to be a 'threshold effect' (mean HbA1 greater than 12.0%), above which the development of microalbuminuria was more likely. More patients with microalbuminuria than controls had been treated with a single rather than twice-daily insulin injections (P less than 0.001), and glycaemic control was significantly worse in patients treated with one injection. We conclude that poor long term glycaemic control is a risk factor for microalbuminuria, and that improving control during childhood is likely to reduce the prevalence of later microalbuminuria. Two insulin injections, of combined intermediate and short-acting preparations, are more likely to provide better control than a single daily insulin dose.

Genetic and metabolic risk factors for the development of late complications in type I (insulin-dependent) diabetes

The genetic background seems to be involved in the development of type I diabetes and it might also be involved in the development of diabetic complications, but studies carried out so far have yielded conflicting results. The aim of this study was to evaluate the influence of some genetic markers and metabolic factors in the development of late diabetic complications. One hundred and twenty-seven patients (69 males, 58 females) with type I diabetes were evaluated for ABO and Rh blood groups, chlorpropamide alcohol flush (CPAF) and acetylator phenotype (AP) as well as for life-habits (smoking, alcohol use, diet and drug compliance), metabolic indexes (M-value, HbA1, cholesterol and triglyceride levels) and late complications of diabetes [coronary heart disease (CHD), arterial hypertension (AH), retinopathy and nephropathy]. Diabetic patients were more frequently fast acetylators and CPAF positive than controls and CPAF was more frequent among females than among males. None of the genetic markers used in this study appeared as a risk factor for the development of diabetic complications. At multiple logistic analysis different risk factors appeared for each microangiopathic complication. For retinopathy: female sex, duration of disease and triglyceride levels; for nephropathy: male sex, cholesterol levels and hypertension. These risk factors have already been recognized in previous studies, while the genetic markers evaluated in our study do not identify a greater or smaller risk for the development of late complications.

The relationship between autonomic neuropathy and urinary sodium and albumin excretion in insulin-treated diabetics

There is evidence to suggest that renal function may alter in the presence of autonomic neuropathy. Albumin excretion rate (AER) and sodium excretion rate (NaER) in timed daytime (erect) and night-time (supine) urine collections were assessed in 20 insulin-treated diabetics with and in 20 without established autonomic neuropathy, matched for age, sex, duration of diabetes, diabetic control, and systolic blood pressure. All patients were free of proteinuria on albustix testing and had normal serum levels of urea and creatinine. AER based on daytime and pooled 24-hour collections was higher, but not significantly so, in the group with autonomic neuropathy. The nocturnal AER on the other hand was significantly elevated in the group with autonomic neuropathy (p less than 0.02) as was the nocturnal urine volume (p less than 0.01) and sodium excretion rate (p less than 0.05). The corrected nocturnal albumin/creatinine ratio was likewise greater in this group (p less than 0.02). These findings suggest that autonomic neuropathy can independently affect renal function and that nocturnal renal haemodynamics and glomerulotubular balance may be deranged in insulin-treated diabetics with autonomic neuropathy.

Glomerular membranopathy in adolescents with insulin-dependent diabetes

Kidney biopsy specimens from 15 patients ranging in age from 11 to 19 years with two- to 14-year histories of insulin-dependent diabetes mellitus were evaluated electron microscopically. Although the mean duration of disease was only eight years, the glomerular basement membrane (GBM) in these patients showed a variety of alterations typical of insulin-dependent diabetes mellitus. Saccular glomerular microaneurysms, previously little recognized, were seen in six of the specimens. These lesions, always associated with breaks in the paramesangial BM, were morphologically distinct from the ectatic capillary loops and glomerular capillary aneurysms described previously in diabetic glomerulopathy. All of the patients with such aneurysms also had other severe GBM alterations. Lytic or mechanical injury to the structurally and biochemically altered diabetic GBM may be responsible for the formation of microaneurysms.