DNA polymorphisms in the ACE gene, serum ACE activity and the risk of nephropathy in insulin-dependent diabetes mellitus.

BACKGROUND: To determine the relationship between DNA polymorphisms in the angiotensin I converting enzyme (ACE) gene, serum ACE activity and the risk of diabetic nephropathy. METHODS: A case-control study was carried out in a population of Jewish insulin-dependent diabetes mellitus (IDDM) patients. Cases (77 IDDM patients with diabetic nephropathy) and controls (89 IDDM patients with normoalbuminuria) were genotyped with PCR protocols for detecting two DNA polymorphisms in the ACE gene: one in intron 7 detected with the restriction enzyme PstI and the other in intron 16 identified as an insertion/deletion (I/D). RESULTS: The risk of nephropathy was increased only in patients homozygous for the allele with the PstI site. These homozygotes had a nephropathy risk that was 2.3 times (95% C.I.: 1.2-4.5) that of the other genotypes. Furthermore, these individuals did not have elevated serum ACE activity. CONCLUSIONS: The results of this study are evidence that the risk of diabetic nephropathy in IDDM is influenced by genetic variability at the ACE locus, but the responsible variant is not the I/D polymorphism in intron 16. Our findings require further studies in other populations.

Gender-specific association of M235T polymorphism in angiotensinogen gene and diabetic nephropathy in NIDDM.

This study examined the association between the development of nephropathy in non-insulin-dependent diabetes mellitus (NIDDM) patients and M235T polymorphism in the angiotensinogen gene. White NIDDM patients with diabetic nephropathy (case subjects, n = 117) and patients without any evidence of nephropathy and > or = 10 years of NIDDM (control subjects, n = 125) were selected from among patients of the Joslin Diabetes Center and examined. In addition to a standardized examination, blood was drawn for DNA and determination of M235T genotypes at the angiotensinogen locus. For the angiotensinogen gene, the frequency of the genotype 235T/235T, known to be associated with essential hypertension, was higher among case subjects with nephropathy than in control subjects without this complication. This difference, expressed as the odds ratio for nephropathy among 235T/235T homozygotes in comparison with all other genotypes, was 2.2 (95% confidence interval, 1.1 to 4.4). The difference, however, was confined to men (odds ratio, 4.8; 95% confidence interval, 1.5 to 14.9), with the distribution of genotypes in case and control subjects being equal among women (odds ratio, 1.1). DNA polymorphism M235T in the angiotensinogen gene, which is associated with higher expression of this gene, contributes to the risk of diabetic nephropathy in NIDDM men but not in women.

Diabetic nephropathy is associated with AGT polymorphism T235: results of a family-based study.

Diabetic nephropathy is a serious and frequent complication of insulin-dependent diabetes mellitus (IDDM) that has a strong genetic component. Several case-control studies have reported conflicting results with regard to the role of angiotensinogen gene polymorphisms, specifically the M235T T allele, in the development of diabetic nephropathy. The primary limitation of the case-control approach is that bias may be introduced by unrecognized differences in the populations selected for cases and control subjects. In contrast, family-based approaches, such as the transmission/disequilibrium test, assess whether a particular variant, or allele, is transmitted preferentially from a parent having a single copy of that allele. Thus each family provides its own control, thereby eliminating spurious results caused by mismatched population samples. To take advantage of this study design for further investigation of M235T, we collected from the Joslin Diabetes Center in Boston 148 IDDM patients with diabetic nephropathy, 62 nephropathy-free patients with long-duration IDDM, and, very importantly, parents of all these individuals. We found that among males (but not females) the T allele of the M235T polymorphism was transmitted preferentially to those with nephropathy compared with IDDM patients without nephropathy (P=.05). Moreover, the T allele was transmitted preferentially to patients with the most severe manifestation of nephropathy, end-stage renal disease (P=.04). In conclusion, results obtained in our family-based study support a role of the angiotensinogen gene M235T polymorphism, and specifically the T allele, in the development of diabetic nephropathy in IDDM.

Microangiopathic complications in type 1 diabetes mellitus: differences in severity when isolated or associated with autoimmune polyendocrinopathies.

CONTEXT: The development and evolution of different chronic diabetic complications may present variations among the different types and conditions of this disease. OBJECTIVE: To evaluate the degree of microangiopathy in Type 1 diabetes mellitus (DM1) associated with autoimmune polyendocrinopathies (OSAD) or isolated DM1 (iDM1). PATIENTS: OSAD (n = 17) and iDM1 (n = 13) were over 15 years old at diagnosis of DM and were matched for diabetes duration (13.9 +/- 8.2 and 13.2 +/- 5.9 years respectively) and metabolic control (HbA1c: 6.4 +/- 1.9 and 6.8 +/- 1.4%). MAIN OUTCOME MEASURES: Urinary albumin excretion (UAE; ELISA), the inversion of serum creatinine (1/C) level and indirect ophthalmoscopy. RESULTS: Although the prevalence of hypertension was similar in both groups, the OSAD had inferior levels of UAE (7.4 +/- 2.5 vs. 17.3 +/- 9.2 micrograms/min; p < 0.05). Nephropathy was detected in 12% of the OSAD (none of them macroproteinuric) and in 39% of the iDM1. The UAE in the iDM1 correlated negatively with 1/C values (r = -0.7, p < 0.005), but the same did not occur in the OSAD (r = 0.2, ns). Among patients with retinopathy, the severe form was found in 29% of the OSAD and in 46% of the iDM1. CONCLUSIONS: OSAD was associated with a lower degree of microangiopathy, in spite of age at diagnosis, duration of diabetes and the metabolic control. In contrast with the iDM1, the increase in UAE of OSAD was not associated with reductions in GFR.

Epidemiology of late diabetic complications. A basis for the development and evaluation of preventive programs.

This article examines the relationship between duration and level of glycemia in patients with diabetes and the occurrence of complications in the eyes, kidneys, and heart. Emphasis is placed on those aspects that are relevant to the development and evaluation of preventive and therapeutic programs against these complications. Data on patients with insulin-dependent diabetes mellitus are reviewed, and the similarities and differences with the data on patients with non-insulin-dependent diabetes mellitus are discussed.

Angiotensinogen polymorphism M235T, hypertension, and nephropathy in insulin-dependent diabetes.

The allele 235T (a threonine in place of a methionine at position 235) of angiotensinogen has been found to be associated with a predisposition to essential hypertension. We investigated whether this allele also confers increased susceptibility to nephropathy in patients with insulin-dependent diabetes mellitus (IDDM). A group of 380 patients who had had IDDM for 15 to 20 years were genotyped at the angiotensinogen 235 locus. Included were 75 patients with normoalbuminuria (albumin excretion rate < 30 micrograms/min), two series of patients with microalbuminuria (n = 30 and n = 136), and two series with overt proteinuria (n = 41 and n = 98). Allele 235T frequency was higher among cases with microalbuminuria (0.41 in the two series combined) or overt proteinuria (0.40) than in the normoalbuminuria group (0.36). However, this difference was not statistically significant with this sample size (chi 2 = 1.2, P = NS with 2 df). Under a recessive model, allele 235T homozygotes had a 1.6-fold risk of developing nephropathy relative to carriers of other genotypes, but this value was not significantly different from 1(95% CI = 0.8 to 3.5). The strength of the association did not improve after stratification by degree of glycemic control. With respect to the hypertension in these IDDM patients, no association with allele 235T was found. Allele 235T frequencies in normotensive and hypertensive individuals were 0.363 and 0.353, respectively, among normoalbuminuric IDDM individuals (chi 2 = 0.01, P = NS) and 0.411 and 0.414 among microalbuminuric IDDM subjects (chi 2 = 0.0, P = NS). We conclude that the angiotensinogen polymorphism M235T might influence susceptibility to nephropathy in insulin-dependent diabetes, but its effect, if any, is rather small and independent of hypertension.

Effect of improved glycemic control on blood pressure and albuminuria of insulin-dependent diabetes without nephropathy.

To assess the effect of glycemic control on blood pressure (BP) and albumin excretion rate (AER) in insulin-dependent diabetes, 35 patients (age 12.6 +/- 2.7 years) and 45 matched control subjects (11.9 +/- 1.8 years) were studied at an educational camp (Study I). They were evaluated at the beginning and at the end of a 9-day program of adequate diet and exercise twice daily, which induced statistically significant reductions in urinary glucose (18 +/- 21 to 5 +/- 7 g/12 h, P < 0.01) and in insulin requirement (42 +/- 20 to 31 +/- 12 U/day, P < 0.01) in the diabetic group. The mean BP and AER of the diabetic patients fell from 74 +/- 11 to 69 +/- 11 mmHg, P < 0.001, and from 4.9 +/- 6.0 to 2.1 +/- 2.0 micrograms/min, P < 0.01, and a correlation was found between AER and urinary glucose. In contrast, controls showed a lower reduction in BP and no change in AER. To evaluate the mechanisms involved in BP fall another group of 39 diabetics (age 12.7 +/- 2.1 years) was submitted to the same 9-day program and also to improved glycemic control (Study II). Changes in BP (79 +/- 11 to 76 +/- 11 mmHg, P < 0.05) were slighter than in the previous study. Initial creatinine clearance was high and fell to the normal range at the end of the study (159 +/- 99 to 127 +/- 42 ml min-1 (1.73 m2)-1, P < 0.05). Urinary aldosterone decreased from 5.3 +/- 3.9 to 3.4 +/- 2.4 micrograms/24 h (P < 0.05), and fractional Na+ excretion tended to increase. Initial and final metanephrine values did not differ. Changes in mean BP did not correlate with changes in aldosterone, insulin requirement or urinary glucose. The decreases in hyperfiltration and AER may have been due to the improved glycemic control induced by this educational program. Exercise may be responsible for BP reduction in diabetics and controls. BP changes particularly in diabetics could be attributed to the inhibition of the renin-angiotensin-aldosterone system and/or to decreased insulin requirement. The contribution of a negative Na+ balance consequent to decreased plasma insulin levels to the BP fall cannot be excluded.

Effect of improved glycemic control on blood pressure and albuminuria of insulin-dependent diabetes without nephropathy

To assess the effect of glycemic control on blood pressure (BP) and albumin excretion rate (AER) in insulin-dependent diabetes, 35 patients (age 12.6 ñ 2.7 years) and 45 matched control subjects (11.9 ñ 1.8 years) were studied at an educational camp (Study I). They were evaluated at the beginning and at the end of a 9-day program of adequate diet and exercise twice daily, which induced statistically significant reductions in urinary glucose (18 ñ 21 to 5 ñ 7 g/12 h, P<0.01) and in insulin requirement (42 ñ 20 to 31 ñ 12 U/day, P<0.01) in the diabetic group. The mean BP and AER of the diabetic patients fell from 74 ñ 11 to 69ñ 11 mmHg,P<0.001, and from 4.9ñ 6.0 to 2.1 ñ 2.0 mug/min, P<0.01, and a correlation was found between AER and urinary glucose. In contrast, controls showed a lower reduction in BP and no change in AER. To evaluate the mechanisms involved in BP fall another group of 39 diabetics (age 12.7 ñ 2.1 years) was submitted to the same 9-day program and also to improved glycemic control (Study II). Changes in BP (79 ñ 11 to 76 ñ 11 mmHg, P<0.05) were slighter than in the previous study. Initial creatinine clearance was high and fell to the normal range at the end of the study (159 ñ 99 to 127 ñ 42 ml min(-1)(1.73 M2) (-1), P<0.05). Urinary aldosterone decreased from 5.3 ñ 3.9 to 3.4 ñ 2.4 mug/24 h (P<0.05), and fractional Na+ excretion tended to increase. Initial and final metanephrine values did not differ. Changes in mean BP did not correlate with changes in aldosterone, insulin requirement or urinary glucose. The decreases in hyperflltration and AER may have been due to the improved glycemic control induced by this educational program. Exercise may be responsible for BP reduction in diabetics and controls. BP changes particularly in diabetics could be attributed to the inhibition of the renin-angiotensin-aldosterone system and/or to decreased insulin requirement. The contribution of a negative Na+ balance consequent to decreased plasma insulin levels to the BP fall cannot be excluded.

Detection of insulin antibodies by radioassay and ELISA: interrelation and correlation with metabolic control in type I diabetes.

1. The literature suggests that the radioassay (RA) and ELISA detect different types of insulin antibodies (IA) (Wilkin et al., 1989. Diabetes, 38: 172-181). 2. In the present study we evaluated the relationship between these two antibodies and their involvement in the metabolic control of Type I diabetic (DMI) patients. 3. IA were measured by RA and ELISA in sera obtained from 34 patients (age: 9-16 years, median = 12.5 years; clinical duration of DMI: 0.1-11.0 years, median = 1.7 years) treated with different types of insulin [purified (bovine + porcine) N = 18, and monocomponent (porcine or human) N = 16] and submitted to various degrees of metabolic control as assessed by glycosylated serum protein (GSP) levels: range, 3.4-13.5%; median = 8.7%; normal value, 0.8-2.4%. 4. Insulin antibody levels measured by RA were: 3264 +/- 300 nU/ml (mean +/- SEM, normal value < 60 nU/ml) and by ELISA: 0.74 +/- 0.11 ELISA index (EI) (normal value, < 0.53). No correlation was found between IA levels measured by RA and ELISA, or between duration of the disease or insulin daily necessity and IA by either method. GSP was positively correlated with IA determined by ELISA (rS = 0.43, P < 0.01) but not with IA determined by RA. 5. The patients on purified bovine + porcine insulin had higher titers of IA by ELISA, compared to those of patients on monocomponent (0.96 +/- 0.15 vs 0.50 +/- 0.13 EI, P < 0.03, while IA levels measured by RA did not differ between groups. 6. These data show that RA or ELISA assays provide different serum titers of IA in insulin-treated diabetics and data obtained with ELISA correlated best with the metabolic control of Type I diabetic patients.

Detection of insulin antibodies by radioassay and ELISA: interrelation and correlation with metabolic control in type I diabetes

1. The literature suggests that the radioassay (RA) and ELISA detect different types of insulin antibodies (IA) (Wilkin et al., 1989. Diabetes, 38: 172-181). 2. In the present study we evaluated the relationship between these two antibodies and their involvement in the metabolic control of Type I diabetic (DMI) patients. 3. IA were measured by RA and ELISA in sera obtained from 34 patients (age: 9-16 years, median = 12.5 years; clinical duration of DMI: 0.1-11.0 years, median = 1.7 years) treated with different types of insulin [purified (bovine + porcine) N = 18, and monocomponent (porcine or human) N = 16] and submitted to various degrees of metabolic control as assessed by glycosylated serum protein (GSP) levels: range, 3.4-13.5; median = 8.7; normal value, 0.8-2.4. 4. Insulin antibody levels measured by RA were: 3264 +/- 300 nU/ml (mean +/- SEM, normal value < 60 nU/ml) and by ELISA: 0.74 +/- 0.11 ELISA index (EI) (normal value, < 0.53). No correlation was found between IA levels measured by RA and ELISA, or between duration of the disease or insulin daily necessity and IA by either method. GSP was positively correlated with IA determined by ELISA (rS = 0.43, P < 0.01) but not with IA determined by RA. 5. The patients on purified bovine + porcine insulin had higher titers of IA by ELISA, compared to those of patients on monocomponent (0.96 +/- 0.15 vs 0.50 +/- 0.13 EI, P < 0.03, while IA levels measured by RA did not differ between groups. 6. These data show that RA or ELISA assays provide different serum titers of IA in insulin-treated diabetics and data obtained with ELISA correlated best with the metabolic control of Type I diabetic patients.

Familial hypertension and albuminuria in normotensive type I diabetic patients.

An inherited predisposition to hypertension may increase susceptibility to nephropathy in type I diabetes. We evaluated the influence of a family history of essential hypertension on albuminuria in normotensive, normoalbuminuric type I diabetic patients. Forty-two diabetics (12.9 +/- 2.04 years) were divided into three groups according to tertiles of albumin excretion rate (group 1, 1.27 +/- 0.35; group 2, 2.43 +/- 0.49; group 3, 6.37 +/- 3.43 micrograms/min; P < .001). Familial hypertension was considered to be present if the patient had one parent or grandparent on antihypertensive therapy. The three groups did not differ concerning age, diabetes duration, insulin requirement, body mass index, blood pressure, and urinary glucose excretion. Albumin excretion rate did not correlate with any parameter studied. The frequency of hypertension was significantly lower among the relatives of the patients from group 1 compared with those from groups 2 and 3 (28.6% versus 64.3% versus 78.6%, P < .03). Our data suggest that a familial antecedent of hypertension in normoalbuminuric type I diabetic patients is associated with a high normal albumin excretion rate not related to increases in blood pressure. Early changes in renal hemodynamics, seen in patients with a predisposition to hypertension, may contribute to increments in albuminuria even within the normal range.

Blood pressure disturbance in diabetes mellitus.

BACKGROUND: Arterial hypertension and, less often, postural hypotension are frequently associated with diabetes mellitus, and with diabetic complications and death. AIM: To review data on the relationship between hypertension and nephropathy in diabetes mellitus. METHODS: We reviewed data on both retinopathy and nephropathy in hypertensive diabetic patients. Data suggesting that vasopressin levels might affect blood pressure in upright patients with postural hypotension due to cardiocirculatory diabetic neuropathy were also examined. Antihypertensive treatment during different phases of diabetic nephropathy in insulin-dependent diabetes was reviewed. RESULTS: The data showed that hydrochlorothiazide and nitrendipine reduce urinary protein excretion in parallel with a reduction in blood pressure. However, the decreases in urinary protein excretion induced by captopril are not correlated with a reduction in blood pressure and may be related to decreases in intraglomerular pressure found in patients with mild renal failure taking furosemide. Domperidone, a peripherally acting dopaminergic antagonist is an additional therapeutic option for the treatment of diabetic postural hypotension.

Microalbuminuria, arterial blood pressure and retinopathy in insulin dependent diabetes

In order to evaluate the relationship between urinary albumin excretion, arterial blood pressure and diabetic retinopathy in insulin dependent diabetics we examined 55 patients without clinical proteinuria and whose disease had started before the age of 30. Each patient was asked to collect at least one overnight timed urine sample for albumin analysis by an ELISA method. Normoalbuminuria was defined as urinary albumin excretion (UAE) of < 20 mug/min (n = 32) and microalbuminuria as 21-200 mug/min (n = 23). Patients with microalbuminuria showed higher levels of blood pressure, serum creatinine and glicosylated haemoglobin as compared to normoalbuminuric patients. Significant correlation was observed between diastolic blood pressure and UAE (r = 0.52; p < O.001).Preproliferative and proliferative diabetic retinopathy was detected in 9 patients (l6.4 per cent). All of them had diabetes for more than 10 years, elevated UAE and diastolic blood pressure equal or higher than 85 mmHg. In our population of insulin dependent diabetics we found a high prevalence of microalbuminuria which is considered to be predictive of the latter development of diabetic nephropathy. Microalbuminuria is associated with elevated blood pressure and diabetic retinal lesions. We conclude that urinary albumin excretion should be monitored in patients with insulin dependent diabetes to detect those who should be considered at risk of developing nephropathy and retinopathy.