Improvements in stage of change correlate to changes in dietary intake and clinical outcomes in a 5-year lifestyle intervention in young high-risk Sri Lankans

The objectives of a stage-matched approach to lifestyle change are that individuals progress forward through the stages of change. It also posits that progression through the stages of change is associated with positive changes in lifestyle behaviours. Measuring the relationship between stage of change and food intake is challenging due to the plurality of dietary behaviours. Furthermore, it is not clear whether changes in behaviour are sustained long-term. In this study we assess the movement through stages of change in the intensive (visits every 3months) and control groups (visits annually) of a large-scale primary prevention study in cardiovascular disease, carried out in 2637 children and young adults in Sri Lanka between 2007 and 2012. We also examine their relationship to dietary behaviours and clinical outcomes. We demonstrate that individuals in both groups continue to progress through stages of change over the course of the study and that measures of dietary behaviours improved from baseline to final follow-up. We also demonstrate that stage of change positively correlates to dietary behaviours including the ratio of recommended:not-recommended items, unpolished:polished starches and low-fat:high-fat food items throughout each year of the study. Finally, participants in the later stages of change at Y2, Y3 and Y4, had a significantly attenuated increase in weight and waist circumference at the final visit in both groups. We therefore demonstrate the usefulness of stage-matched approach in modifying complex dietary behaviours, and that stage of change is a valid measure of dietary behaviours across a large population over time.

Cancer outcomes and all-cause mortality in adults allocated to metformin: systematic review and collaborative meta-analysis of randomised clinical trials

AIMS/HYPOTHESIS

Observational studies suggest that metformin may reduce cancer risk by approximately one-third. We examined cancer outcomes and all-cause mortality in published randomised controlled trials (RCTs).

METHODS

RCTs comparing metformin with active glucose-lowering therapy or placebo/usual care, with minimum 500 participants and 1-year follow-up, were identified by systematic review. Data on cancer incidence and all-cause mortality were obtained from publications or by contacting investigators. For two trials, cancer incidence data were not available; cancer mortality was used as a surrogate. Summary RRs, 95% CIs and I (2)statistics for heterogeneity were calculated by fixed effects meta-analysis.

RESULTS

Of 4,039 abstracts identified, 94 publications described 14 eligible studies. RRs for cancer were available from 11 RCTs with 398 cancers during 51,681 person-years. RRs for all-cause mortality were available from 13 RCTs with 552 deaths during 66,447 person-years. Summary RRs for cancer outcomes in people randomised to metformin compared with any comparator were 1.02 (95% CI 0.82, 1.26) across all trials, 0.98 (95% CI 0.77, 1.23) in a subgroup analysis of active-comparator trials and 1.36 (95% CI 0.74, 2.49) in a subgroup analysis of placebo/usual care comparator trials. The summary RR for all-cause mortality was 0.94 (95% CI 0.79, 1.12) across all trials.

CONCLUSIONS/INTERPRETATION

Meta-analysis of currently available RCT data does not support the hypothesis that metformin lowers cancer risk by one-third. Eligible trials also showed no significant effect of metformin on all-cause mortality. However, limitations include heterogeneous comparator types, absent cancer data from two trials, and short follow-up, especially for mortality.

Experience of malignancies with oral glucose-lowering drugs in the randomised controlled ADOPT (A Diabetes Outcome Progression Trial) and RECORD (Rosiglitazone Evaluated for Cardiovascular Outcomes and Regulation of Glycaemia in Diabetes) clinical trials

AIMS/HYPOTHESIS

Observational and mechanistic studies have suggested a possible relationship between treatment with metformin and decreased incidence of cancer in participants with type 2 diabetes. We extracted data for malignancies from the ADOPT (A Diabetes Outcome Progression Trial) and RECORD (Rosiglitazone Evaluated for Cardiovascular Outcomes and Regulation of Glycaemia in Diabetes) randomised controlled clinical trials, in which the efficacy and/or safety of metformin was assessed in comparison with sulfonylureas and rosiglitazone.

METHODS

Neoplasm occurrences were collected as adverse events in these studies. We reviewed and re-analysed the individual participant data in both studies for serious adverse events, malignancies reported as adverse events and related neoplasms of special interest.

RESULTS

In ADOPT, 50 participants (3.4%) on metformin and 55 (3.8%) on each of rosiglitazone and glibenclamide (known as glyburide in the USA and Canada) developed serious adverse event malignancies (excluding non-melanoma skin cancers). This corresponds to 1.03, 1.12 and 1.31 per 100 person-years, giving hazard ratios for metformin of 0.92 (95% CI 0.63-1.35) vs rosiglitazone and 0.78 (0.53-1.14) vs glibenclamide. In RECORD, on a background of sulfonylurea, 69 (6.1%) participants developed malignant neoplasms in the metformin group, compared with 56 (5.1%) in the rosiglitazone group (HR 1.22 [0.86-1.74]). On a background of metformin, 74 (6.7%) participants in the sulfonylurea group developed malignant neoplasms, compared with 57 (5.1%) in the rosiglitazone group (HR 1.33 [0.94-1.88]).

CONCLUSIONS/INTERPRETATION

The malignancy rates in these two randomised controlled clinical trials do not support a view that metformin offers any particular protection against malignancy compared with rosiglitazone. However, they do not refute the possibility of a difference compared with sulfonylureas.

Rosiglitazone is more effective than metformin in improving fasting indexes of glucose metabolism in severely obese, non-diabetic patients

AIM

In obese patients, the diet-induced weight loss markedly improves glucose tolerance with an increase in insulin sensitivity and a partial reduction of insulin secretion. The association with metformin treatment might potentiate the effect of diet alone.

METHODS

From patients admitted to our Nutritional Division for diet programme, we selected obese, non-diabetic, uncomplicated patients with age 18-65 years and body mass index 35-50 kg/m(2) and studied the effects of a 6-month pharmacological treatment with either metformin (850 mg twice daily) or rosiglitazone (4 mg twice daily) on possible changes in body weight, fat mass, glucose and lipids metabolism.

RESULTS

A significant weight loss and reduction of fat mass was demonstrated with metformin (-9.7 +/- 1.8 kg and -6.6 +/- 1.1 kg) and also with rosiglitazone (-11.0 +/- 1.9 kg and -7.2 +/- 1.8 kg), without fluid retention in either treatment group. Rosiglitazone administration induced a significant decrease in glucose concentration (4.7 +/- 0.1 vs. 4.4 +/- 0.1 mmol/l, p < 0.005) and insulin-circulating level (13.6 +/- 1.5 vs. 8.0 +/- 0.,7 microU/ml, p < 0.005), an increase in insulin sensitivity as measured by homeostatic model assessment (HOMA) of insulin sensitivity (68.9 +/- 8.8 vs. 109.9 +/- 10.3, p < 0.005) with a concomitant decrease in beta-cell function as measured by HOMA of beta-cell function (163.2 +/- 16.1 vs. 127.4 +/- 8.4, p < 0.005). In contrast, metformin did not produce any significant effect on blood glucose concentration, insulin level and HOMA2 indexes. No adverse events were registered with pharmacological treatments.

CONCLUSION

Our study shows that in severely obese, non-diabetic, hyperinsulinaemic patients undergoing a nutritional programme, rosiglitazone is more effective than metformin in producing favourable changes in fasting-based indexes of glucose metabolism, with a reduction of both insulin resistance and hyperinsulinaemia. In spite of previous studies reporting rosiglitazone-induced body weight gain, in our study the joint treatment with diet and rosiglitazone was accompanied by weight loss and fat mass reduction.

Hyperhomocysteinemia in winter elite athletes: a longitudinal study

Hyperhomocysteinemia is a well-established risk factor for cardiovascular diseases. The aims of this study were to longitudinally investigate, in a group of elite athletes, plasma homocysteine levels and to search for relationships with the muscular workload and the vitamin status. One hundred and three athletes (59 males and 44 females, respectively) were evaluated in different periods: namely the recovery period, the training period, and the competition period; 84 subjects (37 males and 47 females), served as controls. The evaluation sessions consisted in blood sampling and medical examination. The percentages of athletes with normal and elevated homocysteine levels, defined by levels below or above the limit of 15 mumol/l, were 68.0% and 32.0%, respectively, in the recovery period, and these percentages remained unchanged during the following periods. In the control group, relevant percentages were 92.9% and 7.1%, respectively. The comparison between plasma homocysteine of male and female, evaluated in the recovery period, showed significantly higher levels in the former group (18.8+/-18.0 micromol/l vs 10.7+/-5.9 micromol/l, p<0.001 respectively), as well as a higher proportion of individuals with hyperhomocysteinemia (24/59 vs 9/44, p<0.05). The correlation analyses showed a weak but significant negative correlation between homocysteine and folate in the three periods considered, while no significant relationship was observed between homocysteine and creatine-kinase. We found excess prevalence of hyperhomocysteinemia in elite athletes of winter sports. A strategy to understand which mechanisms in these athletes subserve hyperhomocysteinemia is essential in order to reduce the potential risk for future cardio-vascular morbidity and mortality.

A Diabetes Outcome Progression Trial (ADOPT): baseline characteristics of Type 2 diabetic patients in North America and Europe

AIMS

To examine baseline characteristics of patients recruited into ADOPT, a multinational trial comparing three oral glucose-lowering monotherapies.

METHODS

Between April 2000 and June 2002, 4360 patients aged 30-75 years with Type 2 diabetes diagnosed for < 3 years and remaining on diet therapy alone with fasting plasma glucose levels (FPG) between 7.0 and 10.0 mmol/l were enrolled by 488 North American and European centres. Medical histories, anthropometric data and laboratory measurements were determined using common methodologies.

RESULTS

The mean (SD) age of the patients was 57 (10) years, body mass index 32.2 (6.4) kg/m(2), HbA(1c) 7.4 (0.9)%; 58% were male, 88% Caucasian and 15% smoked. North American Caucasians (NAC) were younger, more obese, and more insulin resistant than European Caucasians (EUC), but had better pancreatic B-cell function. NAC had lower total, low-density lipoprotein- and high-density liporpotein-cholesterol concentrations with higher triglyceride concentrations and were more often on lipid-lowering treatment. They had lower blood pressure levels but were equally likely to be on antihypertensive treatment. Metabolic syndrome was more frequent and microalbuminuria less frequent in NAC. Within North America, NAC had lower HbA(1c) concentrations than Blacks, Hispanics and Asians despite similar or higher FPG and 30-min postchallenge glucose concentrations.

CONCLUSIONS

Caucasian North American and European ADOPT patients differ with respect to adiposity, insulin resistance and metabolic syndrome prevalence. North American Blacks, Hispanics and Asians had lower HbA(1c) concentrations than NAC despite similar or higher glucose concentrations. These phenotypic differences may influence the progression of Type 2 diabetes and the response to initial oral glucose-lowering monotherapy.

Evidence for renoprotection by blockade of the renin-angiotensin-aldosterone system in hypertension and diabetes

The incidence of end-stage renal disease (ESRD) is rising worldwide, accompanied by corresponding increases in the risk of morbidity and mortality. Underlying this trend are increasing rates of hypertension and diabetes mellitus, the two most common causes of ESRD. In addition to the adverse haemodynamic effects of hypertension on the kidney, elevated blood pressure (BP) can activate components of the renin-angiotensin-aldosterone system (RAAS), which, in turn, activate mediators of inflammation, oxidative stress, cell growth, and matrix accumulation. Lowering BP reduces the risk of cardiovascular events and renal damage. Accumulating evidence from clinical and laboratory studies suggests that interrupting the RAAS with therapies such as angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, and aldosterone receptor blockers can interfere with the mechanisms that promote diabetic and non-diabetic renal damage. Moreover, clinical trials of RAAS blockade have demonstrated reductions in microalbuminuria, a predictor of increased cardiorenal risk and overt nephropathy in patients with and without diabetes and/or hypertension. In this way, agents that block the RAAS should be considered the drugs of first choice as they provide enhanced renoprotection compared with other classes of antihypertensive agents such as calcium channel blockers and beta-blockers.

The MCP-1/CCR2 system has direct proinflammatory effects in human mesangial cells

Both inflammatory and haemodynamic factors have been implicated in the pathogenesis of diabetic and other progressive glomerulopathies. Mesangial cell exposure to mechanical stretch induces both intercellular adhesion molecule 1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression. CC Chemokine receptor 2 (CCR2), the cognate MCP-1 receptor, has been recently demonstrated in human mesangial cells (HMCs). We tested whether MCP-1 binding to CCR2 affects ICAM-1 expression in HMCs and, secondly, if stretch-induced ICAM-1 is mediated by MCP-1 via an autocrine mechanism. Serum-deprived HMCs were exposed to either rh-MCP-1 (0.1-1-10-50-100 ng/ml) or mechanical stretch in the presence and in the absence of RS102895, a specific CCR2 inhibitor. ICAM-1 expression was assessed both by immunofluorescence and cytofluorimetry. Monocyte-HMC interaction was tested by adhesion assay. CCR2 expression was studied by reverse transcriptase-polymerase chain reaction, immunoblotting, and flow cytometry. HMCs exposure to rh-MCP-1 induced a significant twofold increase in ICAM-1 expression at 24 h, leading to enhanced monocyte adhesion. This effect occurred via the CCR2 receptor as CCR2 was expressed in HMCs and CCR2 blockade prevented ICAM-1 upregulation. Stretch-induced ICAM-1 expression was not altered by CCR2 blockade and stretch significantly reduced CCR2 mRNA and protein expression via an MCP-1-independent mechanism. In conclusion, stretch and MCP-1 independently induce ICAM-1 expression in HMCs. Stretch-induced CCR2 downregulation may favour MCP-1 paracrine activity.

Direct regulation of insulin secretion by angiotensin II in human islets of Langerhans

AIMS/HYPOTHESIS

This study aimed to identify the expression of angiotensin II receptors in isolated human islets and beta cells and to examine the functional consequences of their activation.

MATERIALS AND METHODS

Single-cell RT-PCR was used to identify whether human islet cells express mRNA for type 1 angiotensin II receptors (AT(1)), and western blotting was used to determine AT(1) protein expression by human islets and MIN6 beta cells. We measured changes in intracellular calcium by microfluorimetry using Fura 2-loaded MIN6 cells and human islet cells. Dynamic insulin secretory responses were determined by RIA following perifusion of human islets and MIN6 cells.

RESULTS

Human islets expressed mRNAs for both the angiotensin precursor, angiotensinogen, and for angiotensin-converting enzyme. In addition, human and mouse beta cells expressed AT(1). These were functionally coupled to increases in intracellular calcium, which occurred at least in part through phospholipase-C-sensitive mechanisms and calcium influx through voltage-operated calcium channels. Short-term exposure of human islets and MIN6 cells to angiotensin II caused a rapid, short-lived initiation of insulin secretion at 2 mmol/l glucose and potentiation of insulin secretion induced by glucose (at 8 and 16.7 mmol/l).

CONCLUSIONS/INTERPRETATION

These data demonstrate that the AT(1) is expressed by beta cells and that angiotensin II effects a short-lived and direct stimulation of human and mouse beta cells to promote insulin secretion, most probably through elevations in intracellular calcium. Locally produced angiotensin II may be important in regulating a coordinated insulin secretory response from beta cells.

Rosiglitazone reduces urinary albumin excretion in type II diabetes

This study examines the effect of rosiglitazone on urinary albumin excretion (UAE) in patients with type II diabetes. Urinary albumin: creatinine ratio (ACR) was measured in a 52-week, open-label, cardiac safety study comparing rosiglitazone and glyburide. Patients were randomised to treatment with rosiglitazone 4 mg b.i.d. or glyburide. ACR was measured at baseline and after 28 and 52 weeks of treatment. Statistically significant reductions from baseline in ACR were observed in both treatment groups at week 28. By week 52, only the rosiglitazone group showed a significant reduction from baseline. Similar results were observed for the overall study population and for the subset of patients with baseline microalbuminuria. For patients with microalbuminuria at baseline, reductions in ACR did not correlate strongly with reductions in glycosylated haemoglobin, or fasting plasma glucose, but showed strong correlation with changes in mean 24-h systolic and diastolic blood pressure for rosiglitazone-treated patients (deltaACR vs deltamean 24-h systolic blood pressure, r=0.875; deltaACR vs deltamean 24-h diastolic blood pressure, r=0.755; P < 0.05 for both). No such correlation was observed for glyburide-treated patients. In conclusion, rosiglitazone treatment was associated with a decrease in urinary albumin excretion. These findings suggest a potential beneficial effect of rosiglitazone in the treatment or prevention of renal and vascular complications of type II diabetes.

[The need for strict control of cardiovascular risk factors in type 2 diabetic patients]

HIGH CARDIOVASCULAR RISK: The clinical and metabolic anomalies observed in patients with type 2 diabetes are associated with high risk of cardiovascular disease (particularly coronary heart disease), which is responsible for 75% of all deaths in diabetic patients. CLASSICAL RISK FACTORS: Several large-scale surveys have demonstrated the role of classic risk factors such as hypercholesterolemia, smoking and hypertension in the development of ischemic heart disease compared with the general population. OTHER RISK FACTORS: Other risk factors in the diabetic patient include risk associated with the metabolic anomalies (blood glucose levels, insulin resistance) as well as to left ventricular hypertrophy and microalbuminuria, which are often found together in hypertensive diabetics. INTERNATIONAL GUIDELINES: The importance of these risks has led several organizations to issue guidelines, particularly regarding the need for stricter blood pressure control. Regular screening for microalbuminuria and renal dysfunction (creatinine clearance) is also recommended, as well as more rigorous objectives for lipid levels.

Pathogenesis of diabetic nephropathy

Diabetic Nephropathy (DN) is the commonest cause of end-stage renal failure (ESRF) in the Western world. Diabetic nephropathy follows a well outline clinical course, starting with microalbuminuria through proteinuria, azotaemia and culminating in ESRF. Before the onset of overt proteinuria, there are various renal functional changes including renal hyperfiltration, hyperperfusion, and increasing capillary permeability to macromolecules. Basement-membrane thickening and mesangial expansion have long been recognized as pathological hallmark of diabetes. It has been postulated that DN occurs as a result of the interplay of metabolic and hemodynamic factors in the renal microcirculation. There is no doubt that there is a positive relationship between hyperglycaemia, which is necessary but not sufficient, and microvascular complications. The accumulation of advanced glycosylated end-products (AGEs), the activation of isoform(s) of protein kinase C (PKC) and the acceleration of the aldose reductase pathway may explain how hyperglycemia damages tissue. PKC is one of the key signaling molecules in the induction of the vascular pathology of diabetes. The balance between extracellular matrix production and degradation is important in this context. Transforming growth factor-beta (TGF-beta) appears to play a pivotal role in accumulation in the diabetic kidney. Hemodynamic disturbances are believed to be directly responsible for the development of glomerulosclerosis and its attendant proteinuria. There is familial clustering of diabetic kidney disease. A number of gene loci have been investigated to try to explain the genetic susceptibility to diabetic nephropathy. The genes coding for components of renin-angiotensin system have drawn special attention, due to the central role that this system plays in the regulation of blood pressure, sodium metabolism, and renal hemodynamics. Endothelial dysfunction is closely associated with the development of diabetic retinopathy, nephropathy and atherosclerosis, both in IDDM and in NIDDM. The pathogenesis of diabetic nephropathy is not clarified completely yet.

Interaction of angiotensin II and mechanical stretch on vascular endothelial growth factor production by human mesangial cells

The antiproteinuric effect of angiotensin-converting enzyme inhibitors underscores the importance of a hemodynamic injury and the renin-angiotensin system in the proteinuria of various glomerular diseases. Vascular endothelial growth factor (VEGF), a potent promoter of vascular permeability, is induced in mesangial cells by both mechanical stretch and TGF-beta1. This study investigates the effect of TGF-beta blockade, angiotensin II (AngII), and the interaction between AngII and stretch on human mesangial cell VEGF production. Exposure to AngII (1 microM) induced a significant increase in VEGF mRNA and protein levels (1.5+/-0.1 and 1.7+/-0.3, respectively, fold increase over control, P<0.05). The AngII receptor (AT1) antagonist Losartan (10 microM) prevented AngII-induced, but not stretch-induced, VEGF protein secretion (AngII 1.7+/-0.3, AngII + Losartan 1.0+/-0.1, P<0.05; stretch 2.4+/-0.4, stretch + Losartan 2.6+/-0.5). Stretch-induced VEGF production was also unaffected by the addition of an anti-TGF-beta neutralizing antibody (stretch 2.85+/-0.82 versus stretch + anti-TGF-beta 2.84+/-0.01, fold increase over control). Simultaneous exposure to both AngII and stretch for 12 h had an additive effect on VEGF production (AngII 1.6+/-0.1, stretch 2.6+/-0.27, AngII + stretch 3.1+/-0.35). Conversely, preexposure to stretch magnified AngII-induced VEGF protein secretion (unstretched + AngII 1.3+/-0.0, stretched + AngII 1.9+/-0.1, P<0.01) with a parallel 1.5-fold increase in AT1 receptor levels. AngII and stretch can both independently induce VEGF production; in addition, mechanical stretch upregulates the AT1 receptor, enhancing the cellular response to AngII.

Microalbuminuria and coronary heart disease in NIDDM: an incidence study

In most survival studies in NIDDM, microalbuminuria (urinary albumin excretion rate 20-200 microg/min) predicts early mortality; in cross-sectional studies, it is associated with coronary heart disease (CHD) morbidity. It is unclear, however, whether microalbuminuria is a risk factor for the development of CHD or the result of it, and little is known of the factors that predispose to the development of microalbuminuria in NIDDM. We examined these issues in a 7-year prospective study of a hospital-based cohort comprising 146 white NIDDM patients without clinical albuminuria. Microalbuminuria was a significant risk factor for both all-cause mortality (relative risk 3.94, 95% CI 2.04-7.62) and CHD mortality (relative risk 7.40, 95% CI 2.94-18.7) when adjusted for age only. Its independent predictive power did not persist, however, in age-adjusted multivariable survival analysis that allowed for the other significant risk factors: male sex, preexisting CHD, high levels of glycated hemoglobin, and high serum cholesterol. Among men free of CHD at baseline, the independent risk factors for CHD morbidity and mortality were microalbuminuria, current smoking, high diastolic blood pressure, and high serum cholesterol (all P < 0.05). For the 100 NIDDM patients with normoalbuminuria at baseline, the incidence of microalbuminuria was 29% over the 7-year period. In that group, fasting plasma glucose, current smoking, preexisting CHD, and high initial urinary albumin excretion rate were risk factors for the development of microalbuminuria (all P < 0.05). When men and women were analyzed separately, preexisting CHD was a significant risk factor in men only. These results demonstrate that microalbuminuria predicts incident clinical CHD in men with NIDDM. Preexisting CHD is also a risk factor for incident microalbuminuria in men, however, suggesting that microalbuminuria and CHD are not causally related but rather reflect common determinants.

Glutathione reverses the growth abnormalities of skin fibroblasts from insulin-dependent diabetic patients with nephropathy

Oxidative stress has been proposed as a possible pathogenic factor for diabetic complications. It is relevant in determining cell replicative capacity and life span, and in vitro antioxidant treatment is able to reverse the impaired proliferative activity of different cell types. It was recently demonstrated that cultured skin fibroblasts from insulin-dependent diabetic patients with nephropathy age prematurely and have a shorter life cell cycle. To test whether the growth phenotype of cells from patients with diabetic nephropathy was related to a lack of protection from oxidative stress, the effect of reduced glutathione (GSH) on cultured skin fibroblasts from 13 insulin-dependent diabetes mellitus (IDDM) patients with nephropathy (DN), 10 IDDM patients without kidney disease (D), and 10 nondiabetic control subjects (C), in normal (5 mM) glucose (NG) and high (22 mM) glucose (HG) medium was studied. After 6 to 8 passages, fibroblasts from DN showed impaired growth both in NG (mean +/- SD fold increase over baseline counts in DN 1.17 +/- 0.6 versus D 1.7 +/- 0.5 versus C 1.95 +/- 0.8; P = 0.04 by ANOVA) and in HG (mean +/- SD fold increase over baseline counts DN 1.16 +/- 0.41 versus D 1.89 +/- 0.66 versus C 2.24 +/- 0.9; P = 0.003 by ANOVA). GSH prevented the growth abnormalities of cells from DN restoring it to values similar to that of the other two groups (mean +/- SD fold increase over baseline counts NG +/- GSH: DN 1.68 +/- 0.9 versus D 1.78 +/- 0.49 versus C 1.99 +/- 0.7, P = 0.6; and in HG + GSH: DN 1.66 +/- 0.69 versus D 1.87 +/- 0.75 versus C 2.2 +/- 0.9, P = 0.3). Growth rates were not affected by the addition of GSH in fibroblasts from D and C. The treatment of fibroblasts from D and C with the inhibitor of the gamma-glutamylcysteine synthetase activity, L-buthionine-S,R-sulfoximine, resulted in growth impairment, and the addition to the culture medium of another antioxidant, superoxide dismutase, corrected the growth abnormalities in fibroblasts from DN. The impaired growth of cultured fibroblasts from IDDM patients with nephropathy is prevented by GSH and superoxide dismutase and is independent of prevailing glucose concentrations. This suggests that oxidative stress is an important mechanism of intrinsic cell dysfunction in these patients.

Angiotensin converting enzyme inhibitors in diabetic patients with microalbuminuria or normoalbuminuria

In adult diabetic patients microalbuminuria is a marker of early vascular damage in the micro- and macrocirculation. Microalbuminuria is a powerful predictor of renal and cardiovascular disease outcome and is associated with other, potentially modifiable, risk factors of vascular damage. Studies of secondary prevention have shown that blood pressure lowering drugs effectively reduce albumin excretion rate. Angiotensin converting enzyme (ACE) inhibitors seem particularly effective in reducing the risk of progression to clinical albuminuria in both insulin dependent and non-insulin dependent diabetic patients and this beneficial effect appears to be long-lasting. Whether this postpones the onset of end-stage renal failure and/or reduces early mortality in these patients remains to be established. Recent studies of primary prevention in insulin-dependent diabetic patients predominantly with normoalbuminuria demonstrate that ACE inhibition reduces significantly the rate of progression of albumin excretion rate and, of great interest, seems to affect beneficially the progression of retinopathy. These results compare favorably with the beneficial effect of intensified insulin therapy and strict blood glucose control in this same group of patients. Thus, ACE inhibitors are a powerful tool to prevent progression of microalbuminuria in diabetes and may prove useful as an adjunct therapy to intensified insulin therapy in the prevention of development of microalbuminuria and of retinopathy progression in insulin dependent diabetes.

Glomerular volume and the glomerular vascular pole area in patients with insulin-dependent diabetes mellitus

The vascular pole area (VPA) and glomerular volume were measured in renal biopsies from 9 insulin-dependent diabetes mellitus (IDDM) patients with normal albumin excretion rate (IDDM group 1), 38 IDDM patients with albumin excretion rate > 15 micrograms/min (IDDM group 2) and 10 living kidney donors (ND). The volume of individual glomeruli was estimated as the sum of profile areas factored by the measured distance between levels, t approximately 10 microns, and VPA as the sum of chords multiplied by t. Mean glomerular volume was increased in IDDM patients but reached statistical significance only in IDDM group 2 (P = 0.002 vs ND). VPA was significantly different among the groups, mean (CV%) was 2036 (29) microns2 in ND, 3555 (34) micron2 in IDDM group 1, and 3528 (48) microns2 in IDDM group 2, p = 0.004 and 0.001, IDDM versus ND. VPA calculated as a percentage of the surface area of the corresponding glomerulus was 2.4 (23)% in ND, 3.4 (27)% in IDDM group 1, and 3.3 (42)% in IDDM group 2; P = 0.007 and 0.01, IDDM versus ND. The intra-biopsy coefficient of variation was high (20-35%) and of the same order in all groups for all three measurements. Glomerular volume and absolute as well as relative size of VPA showed a positive correlation with estimates of mesangial expansion in IDDM group 2 and the VPA showed a negative correlation with GFR. Thus, part of the enlargement may represent a compensatory phenomenon triggered by the development of structural and functional abnormalities in the diabetic kidney.

Mechanical stretch induces vascular permeability factor in human mesangial cells: mechanisms of signal transduction

Hemodynamic abnormalities have been implicated in the pathogenesis of the increased glomerular permeability to protein of diabetic and other glomerulopathies. Vascular permeability factor (VPF) is one of the most powerful promoters of vascular permeability. We studied the effect of stretch on VPF production by human mesangial cells and the intracellular signaling pathways involved. The application of mechanical stretch (elongation 10%) for 6 h induced a 2.4-fold increase over control in the VPF mRNA level (P < 0.05). There was a corresponding 3-fold increase in VPF protein level by 12 h (P < 0. 001), returning to the baseline by 24 h. Stretch-induced VPF secretion was partially prevented both by the protein kinase C (PKC) inhibitor H7 (50 microM: 72% inhibition, P < 0.05) and by pretreatment with phorbol ester (phorbol-12-myristate-13 acetate 10(-)7 M: 77% inhibition, P < 0.05). A variety of protein tyrosine kinase (PTK) inhibitors, genistein (20 microg/ml), herbimycin A (3.4 microM), and a specific pp60(src) peptide inhibitor (21 microM) also significantly reduced, but did not entirely prevent, stretch-induced VPF protein secretion (respectively 63%, 80%, and 75% inhibition; P < 0.05 for all). The combination of both PKC and PTK inhibition completely abolished the VPF response to mechanical stretch (100% inhibition, P < 0.05). Stretch induces VPF gene expression and protein secretion in human mesangial cells via PKC- and PTK-dependent mechanisms.

Regulation of the epithelial brush border Na+/H+ exchanger isoform 3 stably expressed in fibroblasts by fibroblast growth factor and phorbol esters is not through changes in phosphorylation of the exchanger

The epithelial brush border Na+/H+ exchanger isoform 3 (NHE3) is regulated by growth factors and protein kinases. When stably expressed in PS120 fibroblasts, NHE3 is stimulated by serum and fibroblast growth factor (FGF) and inhibited by phorbol esters. To examine the role of phosphorylation of NHE3 in growth factor/protein kinase regulation, NHE3 was C-terminally tagged with an 11-amino acid epitope of the vesicular stomatitis virus glycoprotein (VSVG) and stably expressed in Na+/H+ exchanger null PS120 fibroblasts (PS120/NHE3V). NHE3V was regulated by serum, FGF, and phorbol ester in a manner identical to wild type non-VSVG-tagged NHE3. Phosphorylation of NHE3V was evaluated via immunoprecipitation with anti-VSVG antibody after in vivo labeling of PS120/NHE3V cells with [32P]orthophosphate. NHE3V was phosphorylated under basal conditions. However, FGF and PMA, under conditions in which these agonists regulate NHE3V, altered neither the amount of phosphorylation of NHE3V as analyzed by one-dimensional SDS-polyacrylamide gel electrophoresis and autoradiography nor two-dimensional phosphopeptide maps of tryptic digests of NHE3V. In contrast, while changes in NHE3V phosphorylation were not observed with serum exposure by one-dimensional SDS-polyacrylamide gel electrophoresis, two-dimensional studies showed increases in two phosphopeptides. Under all these conditions, phosphoamino acid analysis showed that NHE3V was phosphorylated only on serine residues. By cell surface protein biotinylation studies under basal conditions, at least 27% of the NHE3V was expressed on the cell surface. To further analyze the phosphorylation status of the surface and intracellular forms of NHE3V under basal conditions and determine whether the amount of phosphorylation of the surface form changes upon serum, FGF, and PMA regulation, the surface form of NHE3V was separated from intracellular form by biotinylation/avidin-agarose precipitation. Under basal conditions, both intracellular and surface forms of NHE3V were phosphorylated. However, the amount of phosphorylation of the surface form of NHE3V did not change upon stimulation by serum and FGF and inhibition by PMA based on one-dimensional SDS-polyacrylamide gel electrophoresis and autoradiography. Thus, we conclude that when expressed in PS120 cells, while NHE3 is a phosphoprotein under basal conditions, its regulation by FGF and PMA is not by changes in the phosphorylation of NHE3, while regulation by serum may involve changes in its phosphorylation. Regulation of NHE3 probably involves intermediate associated regulatory proteins. The function of basal phosphorylation of NHE3 is not known.

Enhanced collagen synthesis in cultured skin fibroblasts from insulin-dependent diabetic patients with nephropathy

Excessive production and deposition of extracellular matrix proteins are characteristic features of diabetic nephropathy. This study tests the hypothesis that cells from diabetic patients who develop nephropathy have a disturbance in collagen metabolism compared with cells from diabetic patients without complications. Kinetics of overall collagen metabolism and total protein synthesis were examined in serially passaged, subconfluent, quiescent skin fibroblasts cultured in either normal (5 mM) or high (25 mM) glucose concentrations from 14 insulin-dependent diabetic (IDDM) patients with nephropathy; 14 IDDM patients without nephropathy matched for age, diabetes duration, and body mass index; and 14 healthy subjects. Fibroblasts were incubated in the presence of 2 microCi/ml [3H]proline, and after labeling the incorporation of [3H]proline into total protein, collagen (collagenase-sensitive material), and noncollagen proteins (collagenase-resistant material) was determined at different time points. Collagen degradation was determined in pulse-chase experiments by following the residual collagen-bound radioactivity after incubation for 8 h with 10 microCi/ml [3H]proline. In high glucose concentrations (25 mM), overall collagen synthesis (measured as [3H]proline incorporation into extracellular and intracellular collagenase-sensitive material) was significantly greater in the patients with nephropathy (mean +/- SEM after a 24-h labeling period: 7189 +/- 671 dpm/10(6) cells) than in the patients without (4341 +/- 267 dpm/10(6) cells; P < 0.01) or healthy control subjects (3836 +/- 234 dpm/10(6) cells; P < 0.01). No significant differences were observed in noncollagen protein production or in collagen degradation rates among the three groups of subjects. In the presence of normal glucose concentrations (5 mM), collagen synthesis was lower in all groups studied, but the differences between IDDM patients with nephropathy and those without remained unaltered. These results suggest that long-term cultured fibroblasts derived from diabetic patients with nephropathy exhibit an abnormality in collagen metabolism. Cells from long-standing diabetic patients without nephropathy have normal collagen metabolism. The increased collagen synthesis is likely to be intrinsic to those diabetic patients susceptible to nephropathy and may play an important role in the sclerotic processes that occur in the kidneys, arteries, and heart.

Sodium-hydrogen antiporter: its possible role in the genesis of diabetic nephropathy

The epidemiological evidence that only a subset of diabetic patients are susceptible to renal damage and the demonstration of clear familiar clustering of diabetic nephropathy are consistent with the possibility that genetic factors may explain the liability to or protection from renal disease of diabetic patients. A predisposition to hypertension and cardiovascular disease may be an important determinant of susceptibility to renal disease and its cardiovascular complications in diabetes since raised blood pressure [1] and an increased frequency of cardiovascular disease [2] are more prevalent in parents of diabetic patients with nephropathy. These results have raised growing interest in the search for intermediate phenotypes significantly associated with diabetic nephropathy, poorly influenced by environment, stable with age, easy to quantify and possibly dependent upon a single major gene effect. Such intermediate phenotypes can be useful for early diagnosis and would help clarify the molecular mechanisms leading to diabetic nephropathy. An elevation of Na+/H+ antiporter activity has consistently been associated with diabetic renal disease both in insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) patients, making this cell membrane exchanger system an ideal intermediate phenotype for the study of diabetic nephropathy.

Permissive role of hypertension in the development of proteinuria and progression of renal disease in insulin-dependent diabetic patients

BACKGROUND

In insulin-dependent diabetic subjects, heritable factors related to hypertension and cardiovascular disease are associated with nephropathy.

OBJECTIVE

To determine the relationship of blood pressure, glycaemic control, family history of cardiovascular disease and sodium-lithium countertransport activity to the onset of proteinuria and decline in glomerular filtration.

DESIGN

A retrospective analysis of the rate of onset of proteinuria and a longitudinal study of the progression of established renal disease.

SETTING

Guy's Hospital Diabetes Renal Clinic, a secondary referral centre.

PATIENTS

Fifty-four insulin-dependent diabetic patients with nephropathy, persistent total protein excretion rate > 500 mg/24 h, enrolled between 1978 and 1992.

MAIN OUTCOME MEASURES

Rate of decline in glomerular filtration rate. Duration of diabetes at onset of nephropathy (time to proteinuria). Blood pressure and glycosylated haemoglobin at the time of diagnosis of nephropathy (baseline). Family history of cardiovascular disease and hypertension. Erythrocyte sodium-lithium countertransport activity in a subset of patients (n = 41) not being administered renal replacement therapy in 1992.

RESULTS

The estimated (95% confidence interval) time to proteinuria was shortened in relation to increments in diastolic blood pressure at baseline and to a family history of cardiovascular disease in both parents [1.9 (0.2-3.2) years/10 mmHg, P < 0.05 and 6.7 (-0.3-13.7) years, P < 0.07, respectively]. During follow-up 15% (n = 8) of the patients who did not require antihypertensive therapy had slower rates of decline in glomerular filtration and lower rates of sodium-lithium countertransport activity than did those who had been administered treatment [median (range): 2.88 (0.2 to -11.28) versus 7.8 (0.1 to -20.4) ml/min per 1.73 m2/year, P < 0.05 and 0.28 (0.14-0.54) versus 0.43 (0.18-0.88) mmol/l per erythrocyte/h, P < 0.03, respectively]. In this group there was an inverse relationship between the time to proteinuria and glycosylated haemoglobin (r = -0.79, P = 0.018). For the whole group a multivariate analysis showed hypertension and initial glomerular filtration rate to be related independently to the rate of decline in renal function; glycaemic control just failed to attain statistical significance (P < 0.06).

CONCLUSION

Elevation of blood pressure accelerates the onset of nephropathy and its progression; its absence, a reduced familial predisposition to cardiovascular disease, low sodium-lithium countertransport activity and good blood glucose control favour a more benign prognosis.

Glomerular hyperfiltration in the prediction of nephropathy in IDDM: a 10-year follow-up study

Glomerular hyperfiltration has been proposed as an independent risk factor for the development of diabetic nephropathy in patients with IDDM. In a case-controlled prospective study of IDDM patients without albuminuria, serial glomerular filtration rate (GFR) measurements were performed over an observation period of 10 years. A group of 25 IDDM patients (20 men, 5 women; initial age, 29 [17-49] years) with glomerular hyperfiltration (GFR >135 ml x min(-1) x 1.73 m(-2)) were matched for age, sex, and duration of diabetes with 25 IDDM patients (20 men, 5 women; initial age, 30 [17-48] years) with glomerular normofiltration (GFR 83-135 ml x min(-1) x 1.73 m(-2)). GFR, urinary albumin excretion rate (AER), blood pressure, and glycated hemoglobin were measured at baseline and at 5, 8, and 10 years. The two groups had similar entry levels of blood pressure, AER, and glycated hemoglobin. Metabolic control was similar in the two groups during follow-up. The final GFR remained higher in the group with hyperfiltration (122 [109-135] vs. 103 [95-111] ml x min(-1) x 1.73 m(-2); P = 0.02) despite a nonsignificantly faster rate of fall of GFR compared with that of the control group (2.54 [1.20-3.88] vs. 1.50 [1.01-1.99] ml x min(-1) x year(-1); P = 0.14). A similar number of patients in each group progressed to either microalbuminuria or macroalbuminuria (n = 4 vs. n = 3) or developed hypertension (blood pressure, >160/95 mmHg; n = 3 vs. n = 4). End-of-study AER was, however, higher in the group with hyperfiltration (geometric mean [95% CI]: 18.9 [11.3-31.6] vs. 11.0 [8.1-15.0]; P = 0.05), and baseline glomerular hyperfiltration was an independent determinant of end-of-study blood pressure (P = 0.04). The strongest predictors of end-of-study AER and blood pressure were their baseline values (P < 0.04 and P < 0.01, respectively). In conclusion, levels of AER and blood pressure are the main risk factors for renal outcome, while glomerular hyperfiltration appears to play a lesser role.

Premature senescence of skin fibroblasts from insulin-dependent diabetic patients with kidney disease

Diabetic glomerulopathy develops in a subset only of patients with insulin-dependent diabetes (IDDM) and early, in its course, is characterized by cell hypertrophy and by excessive extracellular matrix production. These observations suggest that an alteration in the control of cell growth processes may contribute to its pathogenesis and be related to the susceptibility to kidney disease. We therefore investigated whether the development of diabetic nephropathy is associated with abnormalities of cell growth and morphology. Cultured skin fibroblasts from 14 IDDM patients with nephropathy (DN) were compared with those of 10 IDDM patients without nephropathy (D) and of 14 control non-diabetic subjects (C). Cell volume (in arbitrary units) and total protein content (microgram/10, 000 cells) were increased in serially passaged skin fibroblasts of IDDM patients with nephropathy (DN = 809.5 +/- 33.1 and 1.93 +/- 0.38 vs. D = 764.4 +/- 31.5 and 1.5 +/- 0.37, P = 0.005 and P = 0.03, respectively; vs. C = 756.2 +/- 36.3 and 1.5 +/- 0.38, P = 0.0006 and P = 0.03, respectively). These hypertrophic cells had a tendency to a slower duplication rate and exhibited a dissociation of the DNA and cytoplasmic cell-cycles, resulting in a higher proportion of tetraploid cells (DN = 25 +/- 15% vs. D = 6 +/- 4%, P = 0.005; and vs. C = 10 +/- 8%, P = 0.04). The frequency of terminally differentiated post-mitotic fibrocytes, cells specialized for extracellular matrix production, was higher in patients with nephropathy compared to that of patients without nephropathy and normal controls (DN = 34 +/- 14% vs. D = 21 +/- 10%, P = 0.02; and vs. C = 19 +/- 12%, P = 0.008). That early differentiation was a specific feature of cells derived from patients with diabetic nephropathy was confirmed by the study of cell life-span which demonstrated that these cells aged prematurely (log rank test, chi 2 = 10,012; P = 0.0067). We conclude that an acceleration of cell aging is a peculiar feature of diabetic kidney disease and may contribute to its pathological tissue changes.

A quantitative ultrastructural study of juxtaglomerular arterioles in IDDM patients with micro- and normoalbuminuria

Hyalinization of juxtaglomerular arterioles is prominent in advanced diabetic nephropathy and may have important functional consequences. We studied the early stages of diabetic renal disease using kidney biopsy material from insulin-dependent diabetic patients, 8 with normal albumin excretion rate (< 15 micrograms/min) and 16 with microalbuminuria (15-200 micrograms/min). Ten living non-diabetic kidney donors served as a control group. Median duration of diabetes was 9.5 years (range 5-31) in patients with normoalbuminuria, and 12 years (7-22) in patients with microalbuminuria (p = 0.27). The tissue was sectioned systematically, 1-micron thick sections for light microscopy at 10-micron intervals, and thin sections for electron microscopy taken at 60-micron intervals. The arterioles were identified as afferent or efferent, and total profiles were photographed (magnification 7500x), providing a systematic independent sample for measurements using standard stereological methods. Patients with microalbuminuria had significantly increased arteriole parameters compared with the control group: for afferent and efferent arterioles the volume fraction of matrix/media, means and (co-efficient of variation, CV), was 0.47 (0.16) vs 0.33 (0.19) (p = 0.0009), and 0.62 (0.14) vs 0.45 (0.23) (p = 0.0004) and matrix-T, expressing amount of matrix per unit arteriolar surface, 2.38 (0.38) micron vs 1.44 (0.30) micron (p = 0.004), and 1.62 (0.28) micron vs. 1.03 (0.34) (p = 0.0009). Patients with normoalbuminuria showed no significant differences from the control group, and had lower values than microalbuminuric patients for all parameters except the afferent matrix-T. In the normoalbuminuric group a correlation was found between parameters for afferent arterioles and those for glomerular structure. In conclusion there is arteriolar accumulation of extracellular material in the early phase of diabetic nephropathy, concomitant with early glomerulopathy.

Renal functional reserve in subjects with diabetes mellitus

Diabetic nephropathy develops in approximately 35% of patients with insulin-dependent diabetes mellitus (IDDM) and in a similar proportion of patients with non-insulin-dependent diabetes mellitus (NIDDM). However, we remain at present unable to identify the susceptible subset prior to the development of microalbuminuria. Up to 25% of IDDM patients and a variable proportion of NIDDM patients manifest glomerular hyperfiltration in the first few years of diabetes. It has been debated whether this basal hyperfiltration is predictive of future renal disease and whether better prediction can be achieved by the use of the renal haemodynamic response to a protein meal, defined by some authors as renal reserve. The concept of renal functional reserve in patients with diabetes mellitus is complicated by the dependence of the GFR response on basal GFR, the influence of the prevailing metabolic conditions, and because the response differs to different stimuli. We review the factors affecting renal hemodynamics and renal hemodynamic responses in the context of supranormal, normal, and impaired renal function in diabetes. We conclude that although the measurement of renal functional reserve may help clarify important pathophysiological mechanisms, the assessment of basal GFR in clinical practice is all that is required for predictive and monitoring purposes.

Single-blind studies of the effects of improved periodontal health on metabolic control in type 1 diabetes mellitus

Uncontrolled studies have suggested a beneficial effect of periodontal treatment on metabolic control of insulin-dependent diabetes mellitus (IDDM). We therefore conducted controlled single-blind studies, using current metabolic status indicators in IDDM subjects free of significant complications other than periodontal diseases. In the 1st study, 41 IDDM subjects with gingivitis and early periodontitis were randomly assigned to treatment (oral hygiene and scaling) or control groups. The study was completed by 16 experimental and 15 control subjects. Reassessment after 2 months showed a Hawthorne effect in the control group, and no difference between groups. However, further analysis showed a relationship between individual metabolic control variation and gingival inflammation. A 2nd study enrolled 23 IDDM subjects with advanced periodontitis, who were randomised to treatment (full initial therapy including root planning) or control groups. Only 1 subject failed to complete the study, owing to illness. In this study, a significant response to periodontal treatment was not accompanied by any improvement in metabolic control. These results support the concept that the effect of metabolic control may be predominant in the relationship between IDDM and periodontal health.

Prognostic significance of microalbuminuria

Diabetic nephropathy is the only increasing cause of renal failure in the Western world. It affects a large proportion of both insulin-dependent (IDDM) and non-insulin-dependent diabetic (NIDDM) patients. A critical stage in the development of diabetic renal disease is the onset of microalbuminuria, defined as an albumin excretion rate of 30 to 300 mg/day. Microalbuminuria predicts progression to renal failure and early cardiovascular mortality in both IDDM and NIDDM patients. Microalbuminuria is associated with a constellation of other risk factors for small and large vessel damage which include raised blood pressure, poor glycemic control, plasma lipid and clotting factor abnormalities, left ventricular hypertrophy, and insulin resistance. Treatment with angiotensin-converting enzyme inhibitors corrects microalbuminuria and prevents progression to persistent proteinuria. Good blood glucose control significantly reduces the risk of progression from normoalbuminuria to microalbuminuria. The treatment of microalbuminuria appears highly cost-beneficial and substantially increases life expectancy. The development of microalbuminuria, for which all diabetic patients aged 12 to 70 years should be screened, should alert the physician to set in motion a program of assessment, monitoring, and correction of all risk factors for renal and cardiovascular disease.

Plasma cholesteryl ester transfer protein and its relationship to plasma lipoproteins and apolipoprotein A-I-containing lipoproteins in IDDM patients with microalbuminuria and clinical nephropathy

OBJECTIVE

To study the distribution of high-density lipoprotein (HDL) subclasses in insulin-dependent diabetes mellitus (IDDM) patients with nephropathy and factors involved in the regulation of HDL, including plasma cholesteryl ester transfer protein (CETP) and postheparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities.

RESEARCH DESIGN AND METHODS

Participants included 52 microalbuminuric IDDM patients (with a urinary albumin excretion rate [UAER] of 20-200 micrograms/min), 37 macroalbuminuric IDDM patients (UAER > 200 micrograms/min), and 64 normoalbuminuric IDDM patients (UAER < 20 micrograms/min). Groups were matched for age, body mass index, duration of diabetes, and glycemic control (HbA1).

RESULTS

Median concentrations of HDL and HDL2 cholesterol were 11.6 (P = 0.01) and 22.7% (P = 0.01) less in microalbuminuric patients and 5.1 and 15.5% less in macroalbuminuric patients compared with normoalbuminuric patients. No significant differences were observed in the concentrations of apoA-I, apoA-II (apolipoprotein) or LpA-I or LpA-I:A-II (lipoprotein) particles between the groups. HDL cholesterol: apoA-I+apoA-II ratio was significantly lower in micro- (19.7 +/- 4.2 (+/- SD); P < 0.01) and macroalbuminuric patients (20.0 +/- 3.7, P < 0.05) than in normoalbuminuric patients (22.1 +/- 4.4). Postheparin plasma LPL:HL ratio was lower in microalbuminuric patients compared with normoalbuminuric patients (1.65 vs. 1.05 [median], P < 0.01). Plasma CETP activity was higher in the macroalbuminuric patients than in micro- (P < 0.05) and normoalbuminuric patients (P < 0.05) but did not correlate with HDL, HDL2, or HDL3 cholesterol. LPL:HL ratio correlated positively with HDL cholesterol (r = 0.372, P < 0.001), HDL2 cholesterol (r = 0.413, P < 0.001) and with LpA-I particles (r = 0.355, P < 0.001) but not with LpA-I:A-II particles (r = -0.065, NS).

CONCLUSIONS

IDDM patients with micro- and macroalbuminuria show only trivial changes in concentrations of different HDL parameters, which cannot explain the excess risk of coronary heart disease in these patients. Data also indicate that elevation of CETP activity in IDDM patients with nephropathy is probably not responsible for the lowering of HDL cholesterol.

Serum sialic acid, a risk factor for cardiovascular disease, is increased in IDDM patients with microalbuminuria and clinical proteinuria

OBJECTIVE

An elevated serum sialic acid concentration has recently been shown to be a potent cardiovascular risk factor in the general population. Because clinical proteinuria is associated with a high frequency of cardiovascular disease, and because microalbuminuria predicts the development of renal and cardiovascular disease in diabetes, we investigated whether serum sialic acid levels are increased in insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria or clinical proteinuria.

RESEARCH DESIGN AND METHODS

We studied 23 patients with IDDM who had a normal urinary albumin excretion rate, 23 patients who had microalbuminuria, and 23 patients with clinical proteinuria. The patients were matched for age, sex, duration of diabetes, GHb levels, and body mass index (BMI). Fasting blood samples were taken for measurement of sialic acid, cholesterol, triglyceride, creatinine, and GHb.

RESULTS

Serum sialic acid was significantly higher in the microalbuminuric patients compared with the normoalbuminuric group (mean +/- SD: 1.93 +/- 0.26 vs. 1.76 +/- 0.27 mM, P < 0.01). Moreover, serum sialic acid was also significantly higher in the group with clinical proteinuria compared with the microalbuminuric patients (2.34 +/- 0.24 vs. 1.93 +/- 0.26 mM, P < 0.001). Serum sialic acid was not related independently to age, BMI, diabetes duration, GHb, blood pressure, serum cholesterol, triglyceride, or creatinine concentration in any of the diabetic groups.

CONCLUSIONS

These observations suggest that the serum sialic acid concentration is raised in IDDM patients with both microalbuminuria and clinical proteinuria and may play a role as a cardiovascular risk factor or disease marker in these conditions.

Effect of captopril on progression to clinical proteinuria in patients with insulin-dependent diabetes mellitus and microalbuminuria. European Microalbuminuria Captopril Study Group

OBJECTIVES

To study the effect of angiotensin converting enzyme inhibition on the rate of progression to clinical proteinuria and the rate of change of albumin excretion rates in patients with insulin-dependent diabetes mellitus and persistent microalbuminuria.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled clinical trial of 2 years' duration at 12 hospital-based diabetes centers.

PATIENTS

Ninety-two patients with insulin-dependent diabetes mellitus and persistent microalbuminuria but no hypertension.

INTERVENTION

The patients were randomly allocated in blocks of two to receive either captopril, 50 mg, or placebo twice per day.

MEASUREMENTS

Albumin excretion rate, blood pressure, glycosylated hemoglobin level, and fructosamine level every 3 months; urinary urea nitrogen excretion every 6 months; and glomerular filtration rate every 12 months.

RESULTS

Twelve patients receiving placebo and four receiving captopril progressed to clinical proteinuria, defined as an albumin excretion rate persistently greater than 200 micrograms/min and at least a 30% increase from baseline (P = .05). The probability of progression to clinical proteinuria was significantly reduced by captopril therapy (P = .03 by log-rank test). Albumin excretion rate rose from a geometric mean (95% confidence interval) of 52 (39 to 68) to 76 (47 to 122) micrograms/min in the placebo group but fell from 52 (41 to 65) to 41 (28 to 60) micrograms/min in the captopril group, a significant difference (P < .01). Mean blood pressure was similar at baseline in the two groups and remained unchanged in the placebo group but fell significantly, by 3 to 7 mm Hg, in the captopril group. Glycosylated hemoglobin levels and glomerular filtration rate remained stable in the two groups.

CONCLUSIONS

Captopril therapy significantly impeded progression to clinical proteinuria and prevented the increase in albumin excretion rate in nonhypertensive patients with insulin-dependent diabetes mellitus and persistent microalbuminuria.

Insulin resistance in insulin-dependent diabetic patients with microalbuminuria

In insulin-dependent diabetes, microalbuminuria increases the risk of cardiovascular and renal disease. By means of a euglycaemic hyperinsulinaemic clamp method, we measured total-body glucose utilisation rate and studied the interaction of this measure of insulin sensitivity with known risk factors for cardiovascular disease in 14 diabetic patients with microalbuminuria and 14 with normal albumin excretion (median albumin excretion rate [AER] 56.2 [range 39.2-80.6] vs 8.8 [7.4-10.7] micrograms per min). The two groups were of similar age, duration of diabetes, and body-mass index. Total-body glucose disposal rate was significantly lower in the patients with microalbuminuria than in those without (mean 7.86 [SD 1.40] vs 9.04 [0.90] mg/kg per min; p < 0.05). There were also significant differences between the groups in the daily insulin dose needed for equivalent glucose control (0.76 [0.20] vs 0.65 [0.10] U/kg, p < 0.05), mean systolic blood pressure over 24 h ambulatory monitoring (134 [7] vs 127 [7] mm Hg; p < 0.05), and various plasma lipid concentrations, contributing to a more atherogenic profile in the microalbuminuric group. Total-body glucose disposal rate was inversely correlated with body-mass index and log10 AER. The insulin sensitivity of the microalbuminuric group remained impaired after adjustment for blood pressure and body-mass index. Impaired insulin sensitivity is a feature of insulin-dependent diabetic patients with microalbuminuria, which adds, with other factors, to the increased risks of renal and cardiovascular disease in these patients.

Relationship between insulin resistance and coronary heart disease in diabetes mellitus and the general population: a critical appraisal

The hypothesis that a causal relationship exists between insulin resistance and atherogenesis was first proposed over 23 years ago, and has given rise to a vast literature. Biological plausibility has been lent to the hypothesis by studies in which insulin has produced some effects in cell and tissue culture, and in vivo in arterial tissue, consistent with our understanding of the pathogenesis of atherosclerosis. Clinical studies demonstrating a complex interrelationship between insulin resistance-hyperinsulinaemia and established risk factors for CHD--hypertension, hypertriglyceridaemia, low HDL cholesterol levels and abdominal obesity--are reviewed. A review of the studies examining an independent association between hyperinsulinaemia and coronary heart disease is presented. Cross-sectional studies in both the general population and diabetes support the relationship; however, prospective studies in the general population provide limited and inconsistent support for this hypothesis and highlight the confounding effects of blood pressure, dyslipidaemia and obesity on the effects of hyperinsulinaemia. In subjects with NIDDM and impaired glucose tolerance, prospective studies have not shown a deleterious effect of insulin treatment per se, nor have they consistently shown a significantly increased risk for those with higher endogenous insulin levels. The therapeutic implications of the evidence to date are less complex and involve weight reduction by diet and exercise, the lowering of elevated blood pressure with metabolically neutral agents, the judicious use of lipid lowering drugs and, in diabetes, the use of insulin where clinically indicated.