[Insulin sensitivity, blood pressure and cardiovascular diseases]

Essential hypertension is one of the main components of the insulin resistance syndrome. Blood pressure levels are especially critical for the cardiovascular prognosis of patients with diabetes. However, whether the relationship between blood pressure levels and insulin sensitivity is causal, or just an association, remains debatable. In this study, this relationship is explored through the data of currently available clinical trials.

Interest of Clinitek Microalbumin in screening for microalbuminuria: results of a multicentre study in 302 diabetic patients

A prospective survey was performed in 302 consecutive diabetic outpatients from 3 French diabetic centres to study the sensitivity and specificity of screening for microalbuminuria using Clinitek Microalbumin. Urinary samples with positive (at least one +) proteinuria, hematuria, leucocyturia, or nitrates using the Multistix strip were excluded from the study. Results obtained with Clinitek Microalbumin were compared to those observed with the reference method of the biological laboratory of the centre on the same urinary sample. A positive result was defined as an albumin-to-creatinine ratio > or =30 mg/g. Results were described in terms of sensitivity, specificity, positive and negative predictive values and likelihood ratio. Agreement rates were compared with the Kappa test. In the study population, 48 patients (17%) had a positive microalbuminuria with reference assay. However, different rates were found in each site (25%, 11%, and 15%, respectively, p<0.001). Using the Clinitek Microalbumin, a positive result was found among 86 patients (29%), (39%, 26%, and 23%, respectively). A good agreement was observed in the population as a whole (81%, K=0.47 +/- 0.06) and in each site (77%, 81%, 84%, respectively). Sensitivity was 79% (82%, 80%, 75%), specificity 81% (76%, 81%, 85%), positive predictive value 46% (53%, 35%, 46%), negative predictive value 95% (93%, 97%, 95%), and positive likelihood ratio 4.2 (3.4, 4.3, 5.0, respectively). Due to the excellent negative predictive value, these results suggest that Clinitek Microalbumin is a good screening test for microalbuminuria. Positive results should be confirmed using a reference assay.

Microalbuminuria and markers of the atherosclerotic process: the D.E. S.I.R. study

The relationship between microalbuminuria and tissue-type plasminogen activator antigen (tPA-ag) and fibrinogen was evaluated in non-diabetic subjects. Subjects were participants of the D.E.S.I. R. (Data from an Epidemiological Study on the Insulin Resistance syndrome) Study. Analyses were carried out on 2248 women and 2402 men for fibrinogen and on 272 women and 284 men for tPA-ag. Microalbuminuria was defined as urinary albumin concentration greater than 20 mg/l. Men with microalbuminuria had a 6% higher fibrinogen concentration than those without (3.07 g/l (95% confidence interval: 2.99,3.15) vs. 2.89 g/l (2.87,2.91), adjusted for age and smoking). This relationship existed in hypertensive as well as non-hypertensive subjects. The association between microalbuminuria and tPA-ag existed only in hypertensive men, those with microalbuminuria having a 21% higher tPA-ag than those without (4.39 ng/ml (3.70,5.08) vs. 3.63 ng/ml (3.32,3.94), adjusted for age and smoking). Adjustment for other risk markers for cardiovascular disease did not change the results. There was no relationship between microalbuminuria and these haemostatic factors in women. The results of this study suggest that in non-diabetic men, microalbuminuria is associated with fibrinogen, but with tPA-ag only when concomitant with hypertension.

Lack of relationship in long-term type 1 diabetic patients between diabetic nephropathy and polymorphisms in apolipoprotein epsilon, lipoprotein lipase and cholesteryl ester transfer protein. Genétique de la Nephropathie Diabétique Study Group. Données Epidémiologiques sur le Syndrome d'Insulino-Résistance Study Group

BACKGROUND

Genetic susceptibility contributes to the risk of diabetic nephropathy. Lipid disorders may favour diabetic nephropathy. Thus polymorphisms in lipid metabolism are candidates for the genetic component of risk for diabetic nephropathy.

METHODS

We searched for a contribution of the genetic polymorphisms of lipoprotein lipase (LPL), cholesteryl ester transfer protein (CETP) and apolipoprotein epsilon (Apo E) to the development of diabetic nephropathy by studying 494 type 1 diabetic patients with proliferative retinopathy and various stages of diabetic nephropathy (GENEDIAB Study). The selection process ensured that all patients had expressed their risk of chronic complications due to uncontrolled diabetes. Thus the nephropathy stages were largely influenced by genetic background. The lipid profile included fasting plasma total cholesterol (TC), triglycerides (TG), apolipoprotein A1 (Apo A1) and B (Apo B), and lipoprotein (a) (Lp(a)). Genetic polymorphisms were determined by PCR-based detection of Apo epsilon (e2/e3/e4), LPL (mutation Asn 291 Ser) and CETP (TAQ:IB B1/B2).

RESULTS

One hundred and fifty-seven patients (32%) had no nephropathy, 104 (21%) incipient nephropathy, 126 (25%) established nephropathy and 107 (22%) advanced nephropathy. There was a significant relationship between the stages of diabetic nephropathy and TC (P=0.002), TG (P<0.0001), Apo B (P=0.0007) or Lp(a) (P=0. 038), but not Apo A1. However the genetic polymorphism distributions of LPL, CETP and Apo epsilon did not differ in terms of renal complications. The study power to reject the null hypothesis was 58% for the Apo epsilon genotypes.

CONCLUSION

These results support no or only marginal effects of a genetic basis for lipid disturbances encountered in diabetic nephropathy.

[Hypertension and diabetes]

Hypertension is often associated with diabetes mellitus. Its physiopathology is different when it's a question of type 1 or type 2 diabetes mellitus. In the case of type 1 diabetes mellitus, hypertension is often the result of a underlying nephropathy. In the case of type 2 diabetes mellitus, hypertension is more often essential and it lies within a plurimetabolic syndrome and insulin resistance context. In all cases, hypertension worsens the patients' prognostics, increasing the risk of macrovascular and microvascular complications. The optimal blood pressure control allows to limit their evolution. It is necessary to fight against all cardiovascular risks like sedentary lifestyle, obesity, tabacco or hyperlipemia. ANAES recommends a blood pressure control lower or equal to 140/80 mmHg. In type 1 diabetes mellitus, the angiotensin converting enzyme inhibitors (ACE) are the first recommended treatment because of their action in case of nephropathy. In type 2 diabetes mellitus, besides ACE, diuretics. beta-blockers can be used in first line. Often, therapeutic associations are necessary.

[Microabluminuria in arterial hypertension. Measurement, variables, interpretation, recommendations]

Permanent hypertension is frequently associated with increased glomerular permeability to albumin at an early stage, indicating renal involvement and endothelial dysfunction. The definition of microalbuminuria is an urinary albumin excretion of 30-300 mg/24 hrs, confirmed on two occasions over a 3 month period. It may also be expressed in microgram/min, m/l or mg/mmol of creatinine. Radio-immunological, immunonephelometric methods and Elisa are specific and the most sensitive methods of measurement. There is a large intra-individual variability (25-60%) making it essential to repeat measurements always by the same technique. The prevalence of microalbuminuria is 5-8% in the general population and 6-24% in hypertensive patients. When present, it is a marker of increased cardiovascular risk. Clinical recommendations suggest adaptation of urinary collection according to the context: screening, diagnosis or clinical research. It is always necessary to start by dip-stick detection of proteinuria, haematuria or urinary infection. Clinical research requires repeated measurement of 24 hour microalbuminuria, sometimes divided into two periods of day and night, often associated with ambulatory blood pressure recordings and renal function tests. Studies of the effects of anti-hypertensive drugs on microalbuminuria could provide better evaluation. In conclusion, measurement of microalbuminuria remains a tool of clinical research allowing an assessment of cardiovascular and renal risk of hypertensive patients.

[Normal and abnormal daily variability of urinary excretion of albumin]

Urinary albumin excretion (UAE) is very variable from day to day. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE < 30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z = log(log(k+ UAE)) where k is an integer. We found that z has a gaussian distribution for k = 2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z = 1.25, corresponding to UAE = 30.8 mg/24 h, which is precisely the level currently used to define microalbuminuria in diabetic subjects.

The non-insulin-dependent diabetes, hypertension, microalbuminuria or proteinuria, cardiovascular events, and ramipril (DIABHYCAR) study: design, organization, and patient recruitment. DIABHYCAR Study Group

The non-insulin-dependent DIABetes, HYpertension, microalbuminuria or proteinuria, CARdiovascular events, and Ramipril (DIABHYCAR) study is a randomized, prospective, double-blind, placebo-controlled, multicenter international trial of the ACE inhibitor ramipril (1.25 mg/day) in patients with type II diabetes and micro- or macroalbuminuria. The main outcome of the study is the time to first occurrence of either death from a cardiovascular origin, including sudden death, nonfatal myocardial infarction, stroke, or congestive heart failure, or requirement of hemodialysis or renal transplantation. The study was launched in France in early 1995 with the participation of general practitioners only, but had to be extended to 15 other countries in 1997 due to difficulties in recruitment. Since 2.5 years after the beginning of the trial the observed event rate was much less than anticipated, it was decided to increase recruitment and follow-up duration and to include congestive heart failure in the definition of the main outcome to keep the study power at a satisfactory level. Recruitment ended on April 1, 1998 with 4937 randomized patients. Following the early discontinuation for efficacy of another study of ramipril in high cardiovascular risk patients, the Heart Outcomes Prevention Evaluation study (HOPE), the second interim analysis of DIABHYCAR was performed early (when 406 instead of 500 patients presented a main outcome) and the Data Safety and Monitoring Board recommended that the study continue. Follow-up is planned to end on March 31, 2001.

[Differences in glycemic balance (but not weight) correlate positively with changes in absolute cardiovascular risk in diabetic patients]

Coronary Risk Profile (CRP), assessed according to the Framingham equation takes the presence of diabetes into account, but not the glycaemic control or the body overweight. We have performed an observational survey to study the respective roles of changes in body weight or glycaemic control on calculated CRP, in a given subject, by an effect on several items of the CRP equation (systolic blood pressure, total and HDL cholesterol) which can be modified by blood glucose or weight. We have studied the CRP of 179 type 1 and 208 type 2 diabetes patients, admitted in the department of diabetology of the Angers Hospital, twice (interval < 3 years; 1.6 +/- 0.8 yr). The patients yielded no coronary heart disease, their age ranged from 30 to 74 yr (mean +/- SD: 53 +/- 13), they were not on antihypertensive or lipid lowering medication. Glycaemic control was assessed by glyco-haemoglobin (HbA1c), systolic blood pressure (SBP) was measured with an automatic device (Dinamap). Total and HDL cholesterol were determined by an enzymatic method, in fasting patients. Only age at first examination was taken into account to compute CRP. Initially, SBP was 131 +/- 17 mmHg, total and HDL cholesterol were 2.20 +/- 0.47 et 0.56 +/- 0.20 g/L, respectively. SBP was positively correlated with body weight (Rho = 0.310; p < 0.0001), but not with HbA1c. Median 5 yr CRP was 5% (range: < 1%-25%). Between both admissions, mean change in body weight, HbA1c and 5 yr CRP was +1.0 kg (range: -27 à +29), -0.2% (range: -4.5 à +7.6) et -0.01% (range: -10 à +13) respectively. Change in CRP between both admissions was associated with change in HbA1c (Rho = 0.109; p = 0.0315) but not in body weight (Rho = 0.072; p = 0.1588). This result was explained by the effect of the change in HbA1c on total cholesterol (Rho = 0.151; p = 0.003), (no effect on SBP or HDL cholesterol: Rho = 0.008 and Rho = 0.019; NS, respectively). These results suggest that, in diabetic patients, changes in glycaemic control affect their CRP by an effect on total cholesterol, but the changes in body weight do not affect their CRP.

Hereditary factors in the development of diabetic renal disease

The role of genetics in diabetic renal disease has been suspected on the basis of follow-up and familial studies. Barely half of Type 1 patients who develop a diabetic retinopathy also develop nephropathy, and the relative risk of nephropathy for a diabetic proband is around 3 if a sib is affected. Candidate genes for diabetic nephropathy can be divided into two categories: those affecting glucose metabolism in target organs of diabetic microangiopathy, and those affecting renal changes in response to hyperglycaemia. The role of angiotensin-I-converting enzyme (ACE) insertion/deletion (I/D) polymorphism has been suspected for several years. Evidence of its possible role in the development and progression of diabetic renal disease is presented here.

Efficacy of diuretics and beta-blockers in diabetic hypertensive patients. Results from a meta-analysis. The INDANA Steering Committee

OBJECTIVE

To review the effectiveness of diuretic or beta-blocker-based treatment of hypertension in diabetic patients.

RESEARCH DESIGN AND METHODS

A meta-analysis on individual patient data was performed on four trials of the treatment of hypertension in which diabetic patients were included and treated with first-line diuretics or beta-blockers. The main outcomes were the relative risk of death, fatal or nonfatal stroke, fatal or nonfatal coronary events, and major cardiovascular events.

RESULTS

There were 92 diabetic patients who received first-line beta-blockers and 1,008 who received diuretics. In the control groups, diabetic patients had nearly twice the risk of any outcome when compared with nondiabetic patients. The same blood pressure reduction was achieved under treatment in the diabetic and nondiabetic patients, except for systolic pressure, which decreased more in the nondiabetic patients at 1 year. In the 15,843 nondiabetic patients, the risk of all four outcomes was reduced significantly in the treated group. In the 2,254 diabetic patients, the risk reduction was significant only for fatal and nonfatal stroke (36%, P = 0.011) and major cardiovascular events (20%, P = 0.032), but not for death (5%, P = 0.65) and fatal or nonfatal coronary events (15%, P = 0.23). However, no heterogeneity was detected between diabetic patients and nondiabetic patients for any outcome. The numbers of outcomes avoided for 1,000 patients treated for 5 years were higher in diabetic patients (e.g., 38 major cardiovascular events) than with nondiabetic patients (e.g., 28 major cardiovascular events).

CONCLUSIONS

These results show that hypertensive diabetic patients benefit from first-line treatment with diuretics. No conclusion can be drawn for beta-blockers, owing to the small sample size.

Association between high von willebrand factor levels and the Thr789Ala vWF gene polymorphism but not with nephropathy in type I diabetes. The GENEDIAB Study Group and the DESIR Study Group

BACKGROUND

A genetic susceptibility for diabetic kidney disease is suspected since diabetic nephropathy occurs in only 30 to 40% of type I diabetic patients. As elevated von Willebrand factor (vWF) plasma concentrations have been reported to precede the development of microalbuminuria in type I diabetes, we addressed a possible implication of vWF as a genetic determinant for diabetic nephropathy.

METHODS

Three known vWF gene polymorphisms were genotyped in a group of 493 type I diabetic subjects, all showing proliferative retinopathy, but with various stages of renal involvement, which ranged from no microalbuminuria, despite a mean duration of diabetes of 31 years, to advanced nephropathy (GENEDIAB Study): Thr789Ala (Rsa I), M-/M+ (Msp I) (intron 19), and Ala1381Thr (Hph I). Plasma vWF and factor VIII (F VIII) levels were also measured in this population.

RESULTS

Plasma vWF and F VIII levels were increased in diabetic subjects with nephropathy (P < 0.001) or with coronary heart disease (CHD; P < 0.001), but there was no interaction of both conditions on plasma levels. The Msp I polymorphism (M-/M+) was weakly associated with nephropathy (P = 0. 04), but this association was not more significant when other risk factors were used in a logistic regression analysis. The vWF Thr789Ala polymorphism was associated with CHD (P = 0.002) and with plasma vWF levels. Logistic regression analysis indicated an independent and codominant effect of the Thr789Ala polymorphism on CHD, but not on nephropathy, with a maximal risk for Ala/Ala homozygotes (OR = 4.2, 95% CI, 1.8 to 9.9, P = 0.0008).

CONCLUSION

It is unlikely that polymorphisms in the vWF gene contribute to the risk for nephropathy in type I diabetic patients. However, the Thr789Ala polymorphism might affect the risk for CHD in this population through modulation of plasma vWF levels.

Determinants of elevated urinary albumin in the 4,937 type 2 diabetic subjects recruited for the DIABHYCAR Study in Western Europe and North Africa

OBJECTIVE

Whether ACE inhibition is useful for type 2 diabetic patients with micro- and macroalbuminuria remains unknown. The Non-Insulin-Dependent Diabetes, Hypertension, Microalbuminuria, Cardiovascular Events and Ramipril (DIABHYCAR) Study was set up to address this issue through a multicenter double-blind parallel placebo-controlled > or = 3-year trial in Europe and North Africa. In this article, we report the characteristics of the randomized patients.

RESEARCH DESIGN AND METHODS

The main selection criteria were as follows: men or women aged > or = 50 years with type 2 diabetes treated with oral antidiabetic drugs, with or without hypertension, with a plasma creatinine level < 150 mumol/l, and with persistent micro- or macroalbuminuria, as assessed centrally by two successive urine samples containing a urinary albumin concentration > or = 20 mg/l. Patient characteristics were studied by comparing patients who were randomized to those who were not, taking their geographical origin into account.

RESULTS

There were 25,455 patients screened for urinary albumin (20,296 from France, 918 from Germany, 1,019 from Northwest Europe, 969 from Central Europe, 959 from Mediterranean Europe, and 1,294 from North Africa). Of these patients, 4,937 were randomized. Compared with the nonrandomized patients, the randomized patients were older, more often men, more obese, had higher systolic/diastolic blood pressure and plasma glucose, smoked more tobacco, drank more alcohol, and had complications more frequently. Using a logistic regression analysis, all the above-mentioned items appeared as independent determinants for randomization into the study, with the exception of alcohol intake. The contribution of each item varied slightly from one geographical origin to another.

CONCLUSIONS

The physical, biological, and behavioral characteristics create a poor renal and cardiovascular prognosis for the type 2 diabetic patients randomized to the DIABHYCAR Study because of micro- and macroalbuminuria. Testing the usefulness of ACE inhibition for the type 2 diabetic patients with microalbuminuria seems feasible through the DIABHYCAR Study.

Normal and abnormal day-to-day variability of urinary albumin excretion in control and diabetic subjects

Urinary albumin excretion (UAE) is very variable from day to day. This variability, more or less potent, might by itself have a patho-physiological significance. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE<30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z=log (log (k + UAE)) where k is an integer and looked for a k value for which z might be normally distributed. We found that z was actually normally distributed for k=2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z=1.25, corresponding to UAE=30.8 mg/24 h. This value is precisely the level currently used to define microalbuminuria in diabetic subjects. It is remarkable that the day-to-day variability of UAE collapses when UAE crosses the level which has been used to define microalbuminuria.

Relationships between abdominal body fat distribution and cardiovascular risk factors: an explanation for women's healthier cardiovascular risk profile. The D.E.S.I.R. Study

OBJECTIVE

To assess whether the extent of abdominal fat distribution, as measured by the waist to hip ratio (WHR), might account for the sex differences in the levels of cardiovascular risk factors.

DESIGN

Cross-sectional age-matched study.

SUBJECTS

1264 men and 1264 premenopausal women, aged 30-49 y, free from known cardiovascular diseases and diabetes, included in the prospective study, D.E.S.I.R.

MEASUREMENTS

(1) body mass index (BMI), WHR and blood pressures; (2) fasting concentrations of blood glucose, insulin, lipids and lipoprotein subfractions, and apolipoproteins; and (3) smoking status, physical activity, and alcohol consumption.

RESULTS

After taking into account age and BMI, there were gradual relationships, within and across sexes, between WHR and the levels of most lipids and lipoproteins, of fasting glucose and insulin, and, to a lesser extent, of blood pressures. In particular, men and women with similar BMI and WHR had similar levels of triglycerides. Multivariate regression analysis showed that the variance of cardiovascular risk factors explained by the model was increased when sex was included, after controlling for age, BMI and lifestyle habits (all P<0.01). If WHR was included in the model, sex had no additional effect on total cholesterol (P>0.09 for change in total r2 ) or triglycerides (P>0.40 for change in total r2). In contrast, for other cardiovascular risk factors, adjustment for covariates and WHR did not fully eliminate the sex differences, although WHR increased the variance explained with or without additional control for sex (all P<0.01).

CONCLUSION

The continuous increase of cardiovascular risk factors with WHR, especially for lipids and lipoproteins, suggests that the abdominal body fat distribution may partially explain the relative unhealthier cardiovascular risk profile of men.

[Metabolic mechanisms of renal fibrosis: diabetes]

Diabetic nephropathy, a cause for renal fibrosis, results from glomerular haemodynamic abnormalities: intra-glomerular hypertension is provoked by pre-glomerular vasodilatation (a consequence of hyperglycaemia) facing to constitutive, post-glomerular, vascular resistances. Pre-glomerular vasodilatation is due to abnormal glucose metabolism during hyperglycaemia. Studies on pathophysiology, genetics, and treatment of diabetic nephropathy are oriented by these latter two components of risk for renal fibrosis.

[Contribution of arterial hypertension to vascular risk in diabetic patients]

Hypertension is a major cardiovascular risk factor in diabetic subjects. Recent trials have suggested that blood pressure objectives should be < or = 140/80 mmHg. However, there is currently no evidence supporting any particular preferential drug strategy for this treatment objective.

Relationship between glomerular hyperfiltration and ACE insertion/deletion polymorphism in type 1 diabetic children and adolescents

OBJECTIVE

Glomerular hyperfiltration may predict diabetic nephropathy in type 1 diabetes, and some studies suggest that the ACE D allele is associated with diabetic nephropathy. The aim of this study was to examine a possible relationship between glomerular hyperfiltration and ACE insertion/deletion (I/D) polymorphism in type 1 diabetic children and adolescents.

RESEARCH DESIGN AND METHODS

A cross-sectional study was conducted to examine the relationship between glomerular hyperfiltration and ACE (I/D) polymorphism in 76 type 1 diabetic children and adolescents without diabetic nephropathy (mean +/- SD: age 16 +/- 3 years; diabetes duration 7 +/- 4 years; age at diabetes onset 9 +/- 4 years; HbA1c 9.5 +/- 1.9%). Glomerular hyperfiltration (defined as a glomerular filtration rate [GFR] > or = 135 ml.min-1. 1.73 m-2 and by 51Cr-labeled EDTA plasma disappearance technique) and ACE I/D genotypes and plasma levels (enzyme-linked immunosorbent assay [ELISA] method) were determined.

RESULTS

Of the patients, 29 (38%) displayed glomerular hyperfiltration. An association between glomerular hyperfiltration and ACE (I/D) polymorphism was observed (chi 2 = 7.09, P = 0.029) because of a reduced proportion of DD genotypes among patients with glomerular hyperfiltration (4 vs. 19; chi 2 = 6.03, P = 0.014) and not because of an excess of the II genotype (5 vs. 9; chi 2 = 0.04, P = 0.83). Age, diabetes duration, age at diabetes onset, and HbA1c were not different according to genotype. Patients with glomerular hyperfiltration had low plasma ACE levels, compared with those with normal glomerular filtration (457 +/- 157 vs. 553 +/- 186 micrograms/l; P = 0.027).

CONCLUSIONS

These results suggest an unexpected association between glomerular hyperfiltration and ACE (I/D) polymorphism, characterized by a defect of the DD genotype among type 1 diabetic children and adolescents with glomerular hyperfiltration.

Genetics and the prediction of complications in type 1 diabetes

OBJECTIVE

Epidemiological evidence suggests that genetic factors can affect the course of type 1 diabetes complications produced by long-lasting hyperglycemia. In this review, the current strategies applicable to identifying these genetic factors are examined, as are recent findings on the genetics of diabetic nephropathy and whether these are applicable to type 1 diabetes patient care.

RESEARCH DESIGN AND METHODS

Whole-genome screening and candidate gene strategies can be applied to the genetics of type 1 diabetes complications. The search for candidate genes can focus on enzymes involved in glucose metabolism or on those affecting non-glycemic-dependent vascular risk. For each candidate, the level of evidence may vary from case-control to intervention studies. Literature on diabetic complications and a possible role for genetics was examined systematically.

RESULTS

The most significant results were obtained regarding a role for polymorphisms of the renin-angiotensin system in diabetic nephropathy. Several studies suggest a role for angiotensin I converting enzyme insertion/deletion polymorphism in the development of renal complications. However, the level of evidence is currently not sufficient to recommend treatment strategy based on this or any other polymorphism.

CONCLUSIONS

The search for a genetic basis of type 1 diabetes complications is an important avenue to examine their pathophysiologies. However, it is still premature to apply the current findings in this domain to type 1 diabetes patient care.

Renal changes on hyperglycemia and angiotensin-converting enzyme in type 1 diabetes

Hyperglycemia causes capillary vasodilation and high glomerular capillary hydraulic pressure, which lead to glomerulosclerosis and hypertension in type 1 diabetic subjects. The insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene can modulate risk of nephropathy due to hyperglycemia, and the II genotype (producing low plasma ACE concentrations and probably reduced renal angiotensin II generation and kinin inactivation) may protect against diabetic nephropathy. We tested the possible interaction between ACE I/D polymorphism and uncontrolled type 1 diabetes by measuring glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) during normoglycemia ( approximately 5 mmol/L) and hyperglycemia ( approximately 15 mmol/L) in 9 normoalbuminuric, normotensive type 1 diabetic subjects with the II genotype and 18 matched controls with the ID or DD genotype. Baseline GFR (145+/-22 mL/min per 1.73 m2) and ERPF (636+/-69 mL/min per 1.73 m2) of II subjects declined by 8+/-10% and 10+/-9%, respectively, during hyperglycemia; whereas baseline GFR (138+/-16 mL/min per 1.73 m2) and ERPF (607+/-93 mL/min per 1.73 m2) increased by 4+/-7% and 6+/-11%, respectively, in ID and DD subjects (II versus ID or DD subjects: P=0.0007 and P=0.0005, for GFR and ERPF, respectively). The changes in renal hemodynamics of subjects carrying 1 or 2 D alleles were compatible, with a mainly preglomerular vasodilation induced by hyperglycemia, proportional to plasma ACE concentration (P=0.024); this was not observed in subjects with the II genotype. Thus, type 1 diabetic individuals with the II genotype are resistant to glomerular changes induced by hyperglycemia, providing a basis for their reduced risk of nephropathy.

[Type 2 diabetes: new therapeutic perspectives]

UKPDS: The results of the United Kingdom Prospective Diabetes Study (UKPDS) were reported in 1998. This multi-center, prospective, randomized, intervention trial of 5102 newly-diagnosed patients with type 2 diabetes mellitus was aimed at determining whether improved blood glucose control can prevent complications and reduce associated morbidity and mortality.

THE RESULTS

Improved blood glucose control was shown to reduce the number of complications, mainly by reducing the effect of microangiopathy. There was however no reduction in the number of diabetes-related deaths nor in the risk of myocardial infarction or sudden death.

CONTROVERSY OVER CALCIUM ANTAGONISTS

Calcium antagonists are suspected of increasing the risk of cardiovascular disease. On the basis of published reports, the JNC VI guidelines are recommended: calcium antagonists should not be used as first line treatment in diabetics.

RECENT DRUGS

Acarbose, an alpha-glucosidase inhibitor, lowers post-prandial blood glucose level. It has marketing approval for single-drug regimens in France. Miglitol, another alpha-glucosidase inhibitor, would have the same therapeutic effect. Orliatort, an gastro-intestinal lipase inhibitor, is indicated in obese patients but long-term results are lacking to evaluate effects in diabetics.

Ambulatory blood pressure and urinary albumin excretion in diabetic (non-insulin-dependent and insulin-dependent) hypertensive patients: relationships at baseline and after treatment by the angiotensin converting enzyme inhibitor trandolapril

The aim of the present study was to examine the relationships between ambulatory blood pressure (ABPM) and urinary albumin excretion (UAE) in diabetic (non-insulin dependent [NIDDM] and insulin-dependent [IDDM]) hypertensives at baseline and after treatment by an angiotensin converting enzyme (ACE) inhibitor. After a 3-week placebo period, patients were treated for 16 weeks with trandolapril, 2 to 4 mg/day. The UAE and blood pressure (mercury sphygmomanometer and 24-h ABPM) were measured at baseline and repeated on trandolapril. Predictive factors of abnormal UAE (24-h UAE > or = 30 mg) were determined using univariate and multivariate analysis (logistic regression). Predictors of UAE decrease were also searched. One hundred seventy-one patients entered the analysis. Baseline office BP was 164+/-14 / 97+/-6 mm Hg and 24-h BP was 142+/-17 / 83+/-10 mm Hg. Seventy-four patients (43%) had UAE > or = 30 mg. Independent risk factors for abnormal UAE were nighttime diastolic BP (odds ratio [OR] = 4.1, confidence interval [CI] = 2.0 to 8.6, P = .0001), diabetes duration (OR = 2.4, CI = 1.1 to 5.0, P = .025), and presence of retinopathy (OR = 3.2, CI = 1.0 to 10.0, P = .047). Conversely, office BP level was not significantly related to UAE. On treatment, office BP levels decreased to 143+/-13 / 82+/-8 mm Hg (P < .0001) and 24-h BP levels to 134+/-17 / 78+/-9 mm Hg (P < .0001). In the abnormal UAE group, UAE significantly decreased from 76 to 50 mg/day (P = .006). After treatment, independent predictive factors of abnormal UAE were: on-drug fasting plasma glucose (OR = 3.5, CI = 1.7 to 7.4, P = .0009) and on-drug nighttime diastolic BP (OR = 3.5, CI = 1.7 to 7.4, P = .001). The only predictor of UAE decrease was a 24-h systolic BP decrease (OR = 2.3, CI = 1.3 to 4.3, P = .007). We conclude that in diabetic hypertensives with abnormal UAE, trandolapril exhibited a sustained 24-h antihypertensive effect and provided a consistent reduction of microalbuminuria. This study confirmed the superiority of ABPM over clinical BP to predict target organ damage.