Heritability of albumin excretion rate in families of patients with Type II diabetes.

AIMS/HYPOTHESIS: To study whether albumin excretion rate is an inherited trait in families of patients with Type II (non-insulin-dependent) diabetes mellitus. METHODS: We used three different approaches. Heritability of albumin excretion rate was studied in 267 nuclear families from the Botnia Study in Western Finland using parent-offspring regression. Albumin excretion rate was also measured in 206 non-diabetic offspring of 119 Type II diabetic parents with or without albuminuria (albumin excretion rate > 20 microg/min). Finally, albumin excretion rate was measured in altogether 652 siblings of 74 microalbuminuric and 320 normoalbuminuric probands. To study the potential confounding effect of blood pressure, the heritability of blood pressure was estimated in 718 nuclear families. RESULTS: Using parent-offspring regression, the heritability of albumin excretion rate was about 30 %, being the strongest from mothers to sons (35-39 % resemblance). The heritability for systolic blood pressure ranged from 10 to 20 % and for diastolic blood pressure from 10 to 27 %. Offspring of albuminuric Type II diabetic parents had higher albumin excretion rates (median 5.4 [range 1.0-195] vs 4.0 [1.0-23] microg/min, p = 0. 0001) and a higher frequency of microalbuminuria (11 vs 2 %, p = 0. 012) than offspring of normoalbuminuric parents. Further, siblings of microalbuminuric probands had higher albumin excretion rates than siblings of normoalbuminuric probands (4.1 [0.6-14.5] vs 3.6 [0.2-14. 4] microg/min, p < 0.01). CONCLUSION/INTERPRETATION: The data suggest that albumin excretion rate is an inherited trait in families of patients with Type II diabetes. [Diabetologia (1999) 42: 1359-1366]

Risk factors for mortality in Type II (non-insulin-dependent) diabetes: evidence of a role for neuropathy and a protective effect of HLA-DR4.

To test the hypothesis that interaction between genetic, immunological, clinical and metabolic risk factors influences the outcome of Type II (non-insulin-dependent) diabetes mellitus, we examined which of the above factors present at baseline were associated with mortality in 134 Type II diabetic patients followed for 9 years. Thirty-eight patients (29%) died during the follow-up period; the majority of whom (68%) died from cardiovascular disease. At baseline, the deceased patients had higher HbA1c values (p = 0.002), higher LDL-triglycerides (p = 0.007), lower HDL-cholesterol (p = 0.007), higher non-esterified fatty acid (NEFA) concentrations (p = 0.014), and higher albumin excretion rate (p < 0.0001) than the patients who survived. In addition, the frequency of HLA-DR4 (21 vs 39%, p = 0.048) and of parietal cell antibodies (5 vs 14%, p = 0.016) were decreased in the deceased as compared to the living patients. Patients who died during follow-up also had more retinopathy (42 vs 16%, p = 0.002), neuropathy (57 vs 23%, p < 0.001), microalbuminuria (45 vs 6%, p < 0.0001), coronary heart disease (50 vs 13%, p < 0.0001), and peripheral vascular disease (27 vs 9%, p = 0.005) at baseline than patients who survived. In a multiple logistic regression analysis macroangiopathy (p = 0.004), neuropathy (p = 0.007), HbA1c (p = 0.018) and albumin excretion rate (p = 0.016) were independent risk factors for death. In patients free of cardiovascular disease at baseline, conventional risk factors such as LDL-cholesterol (p = 0.005) and age (p = 0.003) were associated with subsequent development of cardiovascular disease. In conclusion, in addition to coexisting macroangiopathy, increased albumin excretion rate, poor glycaemic control and neuropathy are risk factors for cardiovascular mortality in patients with Type II diabetes. The presence of HLA-DR4 and signs of autoimmunity may be associated with decreased risk of cardiovascular disease.

Predictors of progression from normoalbuminuria to microalbuminuria in NIDDM.

OBJECTIVE: Our objective was to establish the clinical, genetic, metabolic, and immunologic risk factors for the progression of the albumin excretion rate (AER) in normoalbuminuric NIDDM patients. RESEARCH DESIGN AND METHODS: We recruited 108 NIDDM patients with normal AER after a diabetes duration of 9 years to participate in a prospective 9-year follow-up. In addition to conventional clinical and metabolic variables, we assessed microvascular (retinopathy, nephropathy, neuropathy) and macrovascular (coronary heart disease, peripheral vascular disease) diabetic complications, genetic markers (HLA genotypes), and organ-specific autoimmune markers, including islet cell antibodies. Multiple logistic regression was used to determine independent predictors of progression of AER. RESULTS: A total of 21 patients (19%) died during the follow-up. There was an overrepresentation of men (61 vs. 39%; P = 0.044) and smokers (55 vs. 27%; P = 0.01) in patients who progressed to micro- or macroalbuminuria versus those who did not progress. In addition, progressors had higher fasting plasma glucose (P = 0.002) and HbA1 (P = 0.0002) concentrations at baseline than did nonprogressors. Neuropathy was more often seen in progressors than in nonprogressors at baseline (53 vs. 16%; P = 0.0004). Frequency of HLA genotypes and autoimmune markers did not differ between progressors and nonprogressors. In a multiple logistic regression analysis, HbA1 (P = 0.0005) and a history of smoking (P = 0.011) were independent predictors of progression of AER. CONCLUSIONS: This study reemphasizes the importance of poor glycemic control and smoking as independent risk factors for progression of AER. Furthermore, development of micro- or macroalbuminuria in NIDDM was associated with neuropathy and male sex.

Novel mutations and a mutational hotspot in the MODY3 gene.

Maturity-onset diabetes of the young 3 (MODY3) is a type of NIDDM caused by mutations in the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha) located on chromosome 12q. We have identified four novel HNF-1alpha missense mutations in MODY3 families. In four additional and unrelated families, we observed an identical insertion mutation that had occurred in a polycytidine tract in exon 4. Among those families, one exhibited a de novo mutation at this location. We propose that instability of this sequence represents a general mutational mechanism in MODY3. We observed no HNF-1alpha mutations among 86 unrelated late-onset diabetic patients with relative insulin deficiency. Hence mutations in this gene appear to be most strongly associated with early-onset diabetes.

Insulin resistance and abnormal albumin excretion in non-diabetic first-degree relatives of patients with NIDDM.

Microalbuminuria has recently been associated with insulin resistance in both insulin-dependent and non-insulin-dependent (NIDDM) diabetes mellitus. To establish whether microalbuminuria in non-diabetic subjects as well is associated with insulin resistance and associated abnormalities in glucose and lipid metabolism, oral glucose tolerance tests were performed with measurement of urinary albumin excretion rate, lipids and lipoproteins in 582 male non-diabetic first-degree relatives of patients with NIDDM. In addition, insulin sensitivity was assessed in 20 of these subjects with the euglycaemic hyperinsulinaemic clamp technique. Abnormal albumin excretion rate (AER), defined as AER 15-200 micrograms/min, was associated with higher systolic blood pressure (p < 0.05), higher fasting glucose values (p < 0.05), lower HDL-cholesterol (p < 0.05) and lower apolipoprotein A-I (p < 0.05) concentrations than observed in subjects with normal AER. The rate of glucose metabolism was lower in subjects with abnormal compared to subjects with normal albumin excretion rate (38.0 +/- 2.8 vs 47.3 +/- 2.4 mumol.kg lean body mass-1.min-1; p = 0.028). This difference was almost completely accounted for by a reduction in non-oxidative glucose metabolism (17.7 +/- 1.9 vs 27.4 +/- 2.7 mumol.kg lean body mass-1.min-1; p = 0.010), which correlated inversely with the AER (r = -0.543; p = 0.013). These results suggest that in non-diabetic individuals genetically predisposed to NIDDM, abnormal AER is associated with insulin resistance and abnormalities in glucose and lipid metabolism.

Predictive value of microalbuminuria in patients with insulin-dependent diabetes of long duration.

OBJECTIVE: To investigate the predictive value of microalbuminuria (albumin excretion rate 30-300 mg/24 h) as a risk factor for overt diabetic nephropathy in patients with longstanding insulin dependent diabetes. DESIGN: 10 year follow up of patients with normoalbuminuria (albumin excretion rate < 30 mg/24 h), microalbuminuria (30-300 mg/24 h), and macroalbuminuria (> 300 mg/24 h) based on two out of three timed overnight urine samples. SETTING: Outpatient clinic of Helsinki University Hospital. SUBJECTS: 72 consecutive patients who had had insulin dependent diabetes for over 15 years. MAIN OUTCOME MEASURES: Urinary albumin excretion rate, mortality, and prevalence of diabetic complications after 10 years. RESULTS: 56 patients were re-examined at 10 year follow up, 10 had died, five were lost to follow up, and one was excluded because of non-diabetic kidney disease. At initial screening 22 patients had macroalbuminuria, 18 had microalbuminuria, and 26 had normal albumin excretion. Only five (28%, 95% confidence interval 10% to 54%) of the microalbuminuric patients developed macroalbuminuria during the 10 year follow up and none developed end stage renal failure. Two (8%, 1% to 25%) normoalbuminuric patients developed macroalbuminuria and four (15%, 4% to 35%) became microalbuminuric. Seven (32%, 14% to 55%) of the macroalbuminuric patients developed end stage renal failure and six (27%, 11% to 50%) died of cardiovascular complications. CONCLUSION: Microalbuminuria is not a good predictor of progression to overt nephropathy in patients with longstanding insulin dependent diabetes.