Nephropathy in non-insulin-dependent diabetes mellitus

Cigarette smoking is associated with low glomerular filtration rate in male patients with type 2 diabetes

OBJECTIVE

The relationship between cigarette smoking and renal dysfunction in diabetes has predominantly been documented in patients with type 1 diabetes. The aim of the present study was to explore the relationship between cigarette smoking and glomerular filtration rate (GFR) in a large cross-sectional study carried out in male subjects with type 2 diabetes. The role of metabolic syndrome in modulating this relationship was also investigated.

RESEARCH DESIGN AND METHODS

One hundred fifty-eight current smokers and 158 never smokers with type 2 diabetes were consecutively recruited. Low GFR was defined as GFR <60 ml/min per 1.73 m(2).

RESULTS

The proportion of patients affected by low GFR was significantly higher in current smokers (20.9 vs. 12.0%, P = 0.03). The adjusted risk (odds ratio [OR]) of low GFR in current smokers was 2.20 (95% CI 1.14-4.26, P = 0.02) and markedly higher in patients from the first tertile of disease duration (4.27 [1.26-14.40], P = 0.02). When metabolic syndrome was added to the statistical model exploring the relationship between smoking and low GFR, the risk of low GFR showed a small change, although it did not become any more significant (1.84 [0.98-3.45], P = 0.06). Current smokers showed even higher free oxygen radical test unit values (560.0 +/- 91.5 vs. 442.7 +/- 87.2, P < 0.0001).

CONCLUSIONS

In a large population of male patients with type 2 diabetes, the risk of low GFR is markedly enhanced by smoking and is at least partially mediated by metabolic syndrome.

Frequency of proteinuria in type 2 diabetes mellitus seen at a diabetes centre in southern India

The frequency of proteinuria was assessed in a cohort of 1848 diabetic patients attending a diabetes centre in south India. A total of 127 (6.9%) patients had evidence of macroproteinuria and 49 (2.5%) patients had microproteinuria. Thus overall 9.4% of patients had diabetes related proteinuria. In addition, 70 patients (3.8%) had evidence of proteinuria with no evidence of retinopathy. The frequency of both microproteinuria and macroproteinuria increased linearly with duration of diabetes. Multiple logistic regression analysis showed that duration of diabetes, serum creatinine, and glycated haemoglobin were risk factors for macroproteinuria.

Renal function in the noninsulin-dependent diabetic rat: effects of unilateral nephrectomy

A new model of noninsulin-dependent diabetic (NIDD) is described which exhibits more prominent defects in renal function than does the standard neonatal NIDD model. To produce this model, 2-day-old neonatal male Wistar Kyoto (WKY) rats were injected intraperitoneally with streptozotocin (90 mg/kg; NIDD), while their corresponding nondiabetic controls were administered vehicle (citrate buffer, pH: 4.5; control). At 3 weeks of age, the animals were weaned, and 1 week later, under ether anesthesia, the animals underwent a right nephrectomy or a sham operation. Diabetes was confirmed by intraperitoneal administration of a glucose load (2g/kg), which resulted in significantly higher blood glucose concentration in the NIDD, compared to the nondiabetic rats. Surgical reduction of renal mass had no effect on the glycemic response to a glucose tolerance test in either group. Intravenous administration of an isotonic saline load resulted in a similar pattern of enhanced sodium and fluid excretion in the two-kidney sham-operated nondiabetic and NIDD rats. These responses were significantly higher than those observed in their counterparts with one remaining kidney. Yet, the natriuretic and diuretic responses to the saline load were significantly lower in the nephrectomized NIDD, compared to the nephrectomized nondiabetic rats. The glomerular filtration rate was similar in the sham-operated (two kidneys) NIDD and nondiabetic rats. In contrast, both the basal and saline-stimulated glomerular filtration rate were lower in the nephrectomized NIDD rats compared to the nephrectomized nondiabetic group. Mean arterial pressure was similar between the two nephrectomized groups, thereby ruling out a significant contribution from the pressure-diuresis-natriuresis mechanism to the reduction in sodium and fluid excretion in the nephrectomized NIDD rats. Thus, unilateral nephrectomy is an effective method of accelerating the manifestation of NIDD-related renal alterations. The mild, but progressive, nature of diabetes in this model should facilitate the investigation of temporal changes in renal function in NIDDM.

Systolic blood pressure relates to the rate of progression of albuminuria in NIDDM

We prospectively followed a cohort of 278 non-insulin-dependent (NIDDM) patients for a 6-year period, intending to estimate the rate of increase of albuminuria and to identify clinical variables that influence this increase. At baseline, normo-albuminuria (N) was seen in 74%, microalbuminuria (M) in 19% and 7% presented with proteinuria (P). A total of 80 patients died; they were older (p < 0.001) and had higher albumin excretion both at baseline and as an average during follow-up (p < 0.01). At baseline, patients with proteinuria had higher blood pressures (systolic and diastolic), whereas there was no difference between patients with normo-and microalbuminuria. Glycaemic control was increasingly poor throughout the three groups. At follow-up, an average relative rate of increase of albuminuria (slope) of 17% per year was seen both for patients with complete 6 years, follow-up (n - 135) and patients with at least 4 years follow-up (n = 178). Slope correlated significantly with systolic blood pressure (r = 0.26 and 0.29) in both groups, diastolic blood pressure only in the 4-year group (r = 0.22) and average albuminuria in both (r = 0.31 and 0.24). By multiple regression analyses systolic blood pressure and average albuminuria remained with significant influence on slope. Progression was defined as an increase in the category (e.g. normo- to microalbuminuria) as well as an increase of more than 20% in albumin excretion, and was seen in 46 patients with at least 4 years' follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)

High mortality and poor quality of life during predialysis period in type II diabetic patients with diabetic nephropathy

We investigated the rate of decline in GFR and the changing prevalences of micro- and macrovascular complications in 20 type II diabetic patients [mean age 58 (46-71) years, female:male = 7:13, duration of diabetes 16 (12-30) years] from the stage of macroproteinuria with GFRs which were still normal until the beginning of dialysis or the time of death. Controls of renal function, proteinuria, HbAlc, serum lipids, and blood pressure were performed every 6 months at the beginning of the study and later on at 3-month intervals. Fundoscopy, electrocardiogram at rest and in case of need a symptom-limited treadmill ECG, a Duplex ultrasound examination of the carotid vessels, and a Doppler sonographic examination of the femoral arteries were repeated each year. The creatinine clearance (mean +/- SD) of the patients was 81 +/- 6 mL/min/1.73 m2 at the beginning of the study. The rate of decline in creatinine clearance was 1.01 +/- 0.38 mL/min/month during the whole period of observation. Twelve patients (group A) required dialysis after a mean time of 74 (40-119) months; their creatinine clearance was 7 +/- 2 mL/min/month at the beginning of renal replacement therapy. Eight patients (group B) died a short time before the beginning of dialysis treatment; their creatinine clearance was 13 +/- 5 mL/min/1.73 m2. The causes of death were sudden death (n = 4), cardiac failure (n = 1), and stroke (n = 2); in one case it was unknown. The two patient groups did not differ in respect to the mean age, duration of diabetes, HbAlc values, serum cholesterol levels, and blood pressure. The decline in the creatinine clearance was also similar in both patient groups, with 1.07 +/- 0.35 versus 0.98 +/- 0.41 mL/min/month. Only the mean serum triglyceride concentration was significantly higher in the patients who died before dialysis. At the start of the study, cerebrovascular disturbances (including plaques in the carotid vessels) were found in 30%, cardiovascular disturbances (including pathologic ECG findings) in 45%, a peripheral vascular disease in 15%, and diabetic retinopathy (grade I and II) in 75%. At the beginning of dialysis treatment or the time of death, respectively, the prevalence of cerebrovascular diseases was increased to 70% and the prevalence of cardiovascular diseases to 90%; peripheral vascular disease was present in 50% and diabetic retinopathy in all of the cases. We conclude that type II diabetic patients show high mortality (40%) and poor quality of life, not only when they require dialysis treatment, but also in the predialysis phase.

Glomerular structure and function in proteinuric type 2 (non-insulin-dependent) diabetic patients

Glomerular ultrastructure was examined in a series of 20 Type 2 (non-insulin-dependent) diabetic patients with proteinuria. Reference was made to data previously obtained in non-diabetic kidney donors and in Type 1 (insulin-dependent) diabetic patients with similar degrees of proteinuria. The Type 2 diabetic patients demonstrated the changes which characterize the diabetic glomerulopathy seen in Type 1 diabetic patients: basement membrane thickening, and increase in the mesangium and mesangial matrix expressed as fraction of the glomerular volume. Among the Type 2 diabetic patients there was more variation than among the Type 1 diabetic patients, as this group included subjects with normal parameters. The group means and coefficients of variation (= SD/mean) of the glomerulopathy parameters combined in the glomerulopathy index = basement membrane thickness/10+ Vv(matrix/glom).100 were 81 (0.30) and 92 (0.15) in the two diabetic groups, clearly different from the non-diabetic index, 42 (0.16). All Type 2 diabetic patients who also had retinopathy had a glomerulopathy index above the normal range. Similar changes in glomerular composition were seen in the two diabetic groups: with increasing glomerulopathy the volume of matrix dominated over the peripheral basement membrane, and a shift in the ratio of interfaces was seen: mesangial surface towards capillary lumen increased relative to the urinary surface, and peripheral capillary surface comprised less of the total capillary surface. Data indicated marked glomerular hypertrophy, which correlated with the mesangial volume fraction, thus encompassing preserved filtration surface per glomerulus.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective study of clinical and metabolic associates of proteinuria in patients with type 2 diabetes mellitus

Urinary protein excretion rate and clinical and metabolic associates were investigated in a group of 108 patients with Type 2 diabetes mellitus at the time of diagnosis and after 5 years, and also 121 control subjects. The presence of coronary heart disease, neuropathy and retinopathy, cardiovascular risk factors and 24-h urinary excretion rate of albumin, beta-2-microglobulin, and IgG were examined. At the 5-year examination, urinary excretion rate of albumin was higher in diabetic patients than in control subjects (39 +/- 75 vs 16 +/- 28 mg 24 h-1 for men, p < 0.05; 38 +/- 57 vs 22 +/- 42 mg 24(-1) h for women, p < 0.01). Furthermore, increased beta-2-microglobulin excretion rate, a marker of tubular impairment, was observed in diabetic men as compared to control men (0.17 +/- 0.15 vs 0.14 +/- 0.21 mg 24 h-1, p < 0.05). Diabetic patients with increased albumin excretion rate (> 30 mg 24 h-1) showed poorer metabolic control than those with normal albumin excretion rate, but no significant differences in body mass index or in the frequencies of smoking, hypertension, coronary heart disease or retinopathy and neuropathy were observed between the groups. Baseline hyperinsulinaemia was closely associated with increasing albuminuria at the 5-year examination.

A charge selectivity impairment in protein permselectivity is present in type 2 diabetes

A possible loss in kidney charge permselectivity of proteins before any manifestation of nephropathy has been sought in type 2 (non-insulin-dependent) diabetes by assessing the clearances of proteins differing in charge and/or size (anionic and cationic immunoglobulins, albumin). Eighty-five consecutive outpatients with type 2 diabetes were studied and compared with 101 normal subjects. Of the patients, 14.1% were microalbuminuric and 2.3% macroalbuminuric. A significant increase in protein clearances was observed in diabetic patients in comparison with normal subjects: the median of albumin clearance was 0.09 ml/min, interquartile range (IR) 0.04-0.31 (P < 0.01 vs normals); that of anionic immunoglobulins (IgG4) 0.02 ml/min, IR 0.04-0.05 (P < 0.005 vs normals); and that of neutral/cationic immunoglobulins (IgG) 0.13 ml/min, IR 0.07-0.19 (P < 0.01 vs normals). The anionic/cationic immunoglobulin ratio median was 0.22, IR 0.11-0.43, and exceeded the upper limit of normal values in 29.4% of all patients. IgG4 clearance was positively correlated with albumin clearance (r = 0.72) and with IgG clearance (r = 0.98). Nevertheless anionic immunoglobulin clearance was increased in a number of patients (17.3%) with normal IgG excretion and even in patients (15.1%) with normal albumin clearance. Clearances of IgG4 and IgG, but not that of albumin, were correlated with the duration of diabetes. Thus, an increased anionic/cationic IgG ratio in type 2 diabetes highlights a charge selectivity defect in protein permselectivity; this selective proteinuria may reflect more accurately than does microalbuminuria an early kidney abnormality in this form of diabetes.

Vascular risk factors in Japanese non-insulin-dependent diabetic patients with microalbuminuria

To determine if non-insulin-dependent diabetes mellitus (NIDDM) patients with microalbuminuria would have augmented vascular risk factors, we studied the relationships between blood pressure, serum lipids, plasma fibrinogen, and uric acid concentrations and plasma lipoprotein (a) level in 25 Japanese NIDDM patients with microalbuminuria [albumin excretion rate (AER) 20-200 micrograms/min] and 25 individually pair-matched NIDDM patients with normal urinary albumin excretion (AER less than 20 micrograms/min), matched for age, sex, body mass index, treatment and HbAlc level. Microalbuminuric patients had significantly higher systolic blood pressure (p less than 0.05) and plasma fibrinogen level (p less than 0.05) and lower high-density lipoprotein (HDL) cholesterol concentration (p less than 0.05) as compared with those in normoalbuminuric patients, respectively, while there were no differences in serum triglycerides and uric acid levels between the two groups. Plasma lipoprotein (a) level, assessed in 15 microalbuminuric and 15 normoalbuminuric patients, was comparable in the two groups. The results suggest that some of the vascular risk factors are already present in microalbuminuric NIDDM patients when compared with normoalbuminuric patients.

Renal disease in noninsulin-dependent diabetes mellitus

Diabetic nephropathy now accounts for approximately one-third of all patients who develop end-stage renal disease. The estimated cost to supply renal replacement therapy for this population now exceeds $750 million. The relatively recent realization that half of these individuals suffer from noninsulin-dependent diabetes mellitus has sparked increased interest in attempts to understand the pathologic processes involved and how they may be similar or different from those alterations seen in insulin-dependent diabetes mellitus. Basic and clinical investigation continues in an attempt to solve the puzzle of pathogenesis, as well as answer questions about the clinical usefulness of microalbuminuria and the appropriate management of hypertension in this population.

Kidney function and cardiovascular risk factors in non-insulin-dependent diabetics (NIDDM) with microalbuminuria

Microalbuminuria in non-insulin-dependent diabetes (NIDDM) is a strong predictor of increased mortality. The major causes of death are cardiovascular, whereas end-stage renal failure is of low frequency. To define kidney function and the presence of some assumed cardiovascular risk factors, we compared a group of 19 microalbuminuric NIDDM patients (M), of mean age (+/- SD) 65 +/- 4 years, and known duration of diabetes 8 +/- 7 years, with 19 randomly selected matched normoalbuminuric patients (N). Seven microalbuminuric patients (P) were also studied. Glomerular filtration rate (GFR) did not differ between N and M, whereas kidney volume was increased in M (260.3 +/- 54.1 ml 1.73 m-2) compared to N (220.4 +/- 44.8 ml 1.73 m-2; P = 0.018). The frequency of cardiac disease increased with increasing albuminuria. Glycaemic control did not differ between the groups, but fasting plasma C-peptide levels increased from 2.8 +/- 1.1 micrograms l-1 in N, to 3.7 +/- 1.7 micrograms l-1 in M (P = 0.08), and to 4.2 +/- 1.9 micrograms l-1 (P = 0.03) in P. The lipoprotein profile showed no significant differences, although the LDLcholesterol/HDLcholesterol (LDL-C/HDL-C) ratio tended to rise. A significant correlation was found between C-peptide and LDL-C/HDL-C (r = 0.5; P less than 10(-3]. In conclusion, GFR was not increased, and did not differ between N and M, whereas kidney volume was enhanced in M. Several assumed cardiovascular risk factors showed values of M intermediate between those of N and P.

Clinical characteristics associated with microalbuminuria in an adult diabetic population

A study was conducted to identify clinical characteristics which might distinguish individuals at risk for diabetic nephropathy. A cross-sectional survey measuring microalbuminuria in a population of 140 diabetic adults was performed and several clinical parameters among subgroups with different clinical types of diabetes, based upon age of onset and insulin treatment, were examined. In 67 insulin-treated patients with onset of diabetes at or after the age of 30 who had elevated albumin excretion rates, significantly greater duration of diabetes, age, blood pressure, serum creatinine, body mass index, and serum triglycerides were found. In this group of maturity onset insulin-treated diabetic patients, there was a significantly smaller proportion of smokers in the microalbuminuria group than in the group with normal excretion. No such distinctions were seen in 58 maturity onset patients with and without microalbuminuria who were not receiving insulin. In 15 insulin dependent patients with onset in early adulthood, only age and duration distinguished those with, or without, microalbuminuria. Analysis of microalbuminuria, taking into account diabetes therapy and other clinical and demographic data, may provide clues to the pathophysiology of renal disease in diabetes mellitus.