Insulin resistance in microalbuminuric hypertension. Sites and mechanisms

Association between Food Label Unawareness and Loss of Renal Function in Diabetes: A Cross-Sectional Study in South Korea

Objectives: To examine sex differences in the association between food label unawareness and loss of renal function among South Korean diabetic patients aged ≥30 year and determine whether reading food labels when choosing which food products to consume plays a potential role in slowing the progression of renal disease. Methods: Data from the 2016–2017 Korea National Health and Nutrition Examination Survey were used for the analysis. Renal function was determined by the Modification of Diet in Renal Disease estimated glomerular filtration rate, and food label unawareness was defined as being unaware of the food label when choosing a food product for consumption. Multiple regression analysis was used to investigate the association between food label unawareness and loss of renal function among South Korean diabetic patients. Results: Four hundred and eighty-seven diabetic patients (men: 274; women: 213) were enrolled. Loss of renal function was associated with food label unawareness in only male diabetic patients (men: β = –10.01, standard error (SE) = 5.08, p = 0.0506; women: β = –0.30, SE = 5.14, p = 0.9528). A strong association was found between loss of renal function and food label unawareness among socially isolated male diabetic patients who lived in a one-generational household, did not have a spouse, and ate alone. Conclusion: Cultivating habits of reading food labels and inducing social facilitation may play a potential role in managing loss of renal function among male diabetic patients.

Hypertension and microalbuminuria: the new detrimental duo

Excretion of albumin with urine (UAE) in small amounts, i.e. microalbuminuria (MAU), also referred to as "incipient nephropathy", has long been considered a marker of early nephropathy and increased cardiovascular risk in the specific setting of diabetes mellitus. However, numerous clinical studies found an association between MAU and other cardiovascular risk factors, target organ damage and risk of cardiovascular disease in clinical contexts different from diabetes and including arterial hypertension. The present article reviews the available evidence on the clinical value of MAU in subjects with primary hypertension. In these subjects, prevalence of MAU varied from about 4% to 46% across different studies and these differences may be explained by the huge intra-individual variability in UAE, discrepancies in the technique of measurement and different definitions of MAU. A direct and continuous association between UAE and blood pressure (BP) has been found in many studies. A continuous association between UAE and left ventricular mass has also been found in most studies. In contrast, it is not yet clear whether the association between UAE and other factors including age, gender, smoking, ethnicity, insulin resistance, lipids and obesity is independent or mediated by confounders, particularly BP. From a prognostic standpoint, several longitudinal studies showed an association between MAU and the risk of future cardiovascular disease. Of particular note, in some of these studies the incidence of major cardiovascular events progressively increased with UAE starting below the conventional MAU thresholds. Thus, besides being a direct risk factor for progressive renal damage, MAU can be considered a marker, which integrates and reflects the long-term level of activity of several other detrimental factors on cardiovascular system. Antihypertensive treatment reduces UAE and such effect may be detected after just a few days of treatment. Among available antihypertensive drugs, angiotensin-converting enzyme (ACE) inhibitors and the angiotensin II receptor antagonists seem to be superior to other antihypertensive drugs in reducing UAE. The dual blockade of the renin-angiotensin system with an ACE inhibitor and an angiotensin II receptor antagonist is a new and promising approach to control UAE in hypertensive patients. Determination of MAU is recommended in the initial work-up of subjects with primary hypertension.

Association of urinary albumin excretion with insulin resistance in Japanese subjects: impact of gender difference on insulin resistance

OBJECTIVE

To investigate the relationship between homeostasis model assessment for insulin resistance (HOMA-R) and urinary albumin excretion in Japanese and clarify gender difference in albuminuria-related insulin resistance.

METHODS

The subject group consisted of 752 Japanese who had no history of diabetes, hypertension or dyslipidemia. After anthropometric examination, fasting blood samples were obtained to determine plasma glucose (FPG), lipids and HOMA-R. The urinary excretion of albumin in the first void urine was expressed as the creatinine ratio (ACR, mg/gCr). Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine using the formula for Japanese.

RESULTS

HOMA-R showed a significant correlation with ACR, and the correlation between HOMA-R and ACR was evident in the subjects with central obesity, whereas no significant correlation was found in the non-obese subjects. There was no correlation between HOMA-R and eGFR. HOMA-R increased according to the quintile of ACR and followed a significant trend. This association was obvious in males; however, in females there was no significant trend. Multiple regression analysis revealed that HOMA-R showed a significant correlation with age, waist circumference, blood pressure and serum triglyceride. In addition, ACR exhibited an independent association with HOMA-R. The association of HOMA-R and ACR was observed only in males, and was not present in females.

CONCLUSION

Microalbuminuria is associated with insulin resistance in Japanese, where central obesity might play an essential role. This association is gender-specific suggesting the involvement of sex hormones in the pathogenesis of albuminuria-related insulin resistance.

Evidence for no global effect of metabolic syndrome per se on early hypertensive sequelae

OBJECTIVE

In the present study we assessed the impact of metabolic syndrome (MS) and its components on markers of cardiovascular and renal damage in a population of essential hypertensives.

METHODS

A total of 651 consecutive, untreated and non-diabetic hypertensives (age 54 +/- 12 years, 340 males) who were included in the 3H Study, an ongoing registry of hypertension-related target organ damage, were considered for analysis. Left ventricular mass was indexed both for body surface area (LVMBSA) and for height2.7 (LVMheight2.7). Diastolic function was estimated by means of both conventional and tissue Doppler imaging (TDI) methods. Arterial stiffness was evaluated on the basis of carotid to femoral pulse wave velocity (c-f PWV) and microalbuminuria (MA) as albumin to creatinine ratio (ACR) 22-300 mg/g in men and 31-300 mg/g in women in two non-consecutive morning spot urine samples.

RESULTS

MS (Adult Treatment Panel III criteria) was present in 201 hypertensives (30.9%). Hypertensives with MS had increased logACR (by 10%, P = 0.01) and higher prevalence of MA (17 versus 8%, P < 0.001). Both groups exhibited similar values of LVMBSA, transmitral and TDI-derived indexes and c-f PWV (NS for all) while LVMheight2.7 was significantly higher in hypertensives with MS (by 2.6 g/m2.7, P = 0.023). Multiple regression analysis revealed that MS was an independent predictor only of logACR (beta = 0.110, P = 0.007) and MA (odds ratio = 2.577, P < 0.001), while components of blood pressure affected all studied indices of organ damage.

CONCLUSIONS

MS per se does not deteriorate cardiac adaptations and aortic stiffness beyond haemodynamic load in hypertension. The MS-related unfavourable effect is limited to the level of the glomerulus.

Increased cardiovascular events in hypertensive patients with insulin resistance: a 13-year follow-up

Insulin resistance (IR) is commonly associated with other cardiovascular risk factors and is considered an independent risk factor for cardiovascular disease and events. The hyperinsulinemic euglycemic clamp technique is considered the gold standard for evaluating IR, but this technique is cumbersome and not easily applicable in large studies. Therefore, there are no long-term follow-up published studies on the relationship between IR determined by this technique and cardiovascular outcome. Thirteen years ago we performed a hyperinsulinemic euglycemic clamp in 31 hypertensive patients, 16 of whom manifested IR and 15 had normal insulin sensitivity. Thirteen years later we were able to re-evaluate or obtain medical records for all these patients. Over these years, 11 of the 16 insulin resistant patients developed cardiovascular disease and events, including two cardiovascular deaths, two myocardial infarctions, one angina pectoris, one peripheral vascular disease, and five carotid plaques or stenosis. Moreover, two patients developed new onset diabetes, one proteinuria and two impaired kidney function. Among insulin-sensitive patients, one developed peripheral vascular disease, one new onset diabetes and one proteinuria. In conclusion, this is the first longitudinal study of the relationship between insulin resistance, measured by the hyperinsulinemic euglycemic clamp and cardiovascular disease and events in a small cohort of patients with essential hypertension. The data suggest that hypertensive patients with IR are at greater risk of developing cardiovascular disease and events than hypertensive patients with normal insulin sensitivity.

Albumin excretion rate in normal adolescents: relation to insulin resistance and cardiovascular risk factors and comparisons to type 1 diabetes mellitus patients

BACKGROUND AND OBJECTIVES

Although albumin excretion rates have been related to cardiovascular morbidity and mortality in both diabetic and nondiabetic adults, little is known about the relation between albuminuria and either cardiovascular risk factors or the insulin resistance syndrome in adolescents. A normal range for albumin excretion in adolescents was established, correlations between albumin excretion and cardiovascular risk factors were evaluated, and albumin excretion in normal adolescents was compared with that in type 1 diabetes mellitus adolescents.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Albumin excretion rate was measured in 368 normal and 175 diabetic adolescents. Multiple regression analysis was used to predict the relation of age, sex, Tanner stage, body mass index, and systolic blood pressure to albumin excretion in both cohorts. In addition, correlations between albumin excretion and age, blood pressure, body mass index, lipids, and measurements of insulin resistance were performed in the normal adolescents.

RESULTS

Mean albumin excretion was significantly lower in normal adolescents (4.0 microg/min) than in type 1 diabetic adolescents (5.0 microg/min). Albumin excretion increased with age in diabetics. Albumin excretion did not significantly correlate with any measure of cardiovascular risk or insulin resistance but did significantly correlate with fasting insulin.

CONCLUSIONS

Albumin excretion rate is not related to insulin resistance or traditional cardiovascular risk factors in adolescence but is related to fasting insulin. Diabetic adolescents have increased albumin excretion compared with normal adolescents.

Microalbuminuria in pediatric obesity: prevalence and relation to other cardiovascular risk factors

BACKGROUND

Microalbuminuria (MA) has emerged as a strong predictor of cardiovascular (CV) events, even in nondiabetic adults. While the mechanisms behind this association remain to be established, most studies suggest that MA is the result of increased vascular leakage denoting endothelial dysfunction associated with early vasculopathy.

OBJECTIVE

To examine if a urine albumin creatinine ratio (UACR) in the microalbuminuric range is related to metabolic markers of CV risk in obese and pre-diabetic youth recruited from an obesity clinic.

METHODS

MA was defined as a UACR between 2.0 and 20 mg/mmol. Subjects with gross proteinuria (UACR>20 mg/mmol) were excluded from the study. Analyses were performed to assess the relationship of MA and markers of CV risk, including body mass index (BMI), % body fat, blood pressure (BP), lipid profile, inflammatory markers, insulin sensitivity indexes and degrees of oral glucose tolerance. MA was also correlated with risk factor constellations unique to the metabolic syndrome, a distinct CV risk entity.

RESULTS

Postchallenge alterations in glucose metabolism and overall loss in insulin sensitivity were strongly and positively correlated with the presence of MA (P = 0.002 and 0.01, respectively). Neither the metabolic syndrome nor any of the individual CV risk factors examined were associated with MA.

CONCLUSIONS

These data suggest that early glucose toxicity, as reflected by postchallenge elevations in plasma glucose even below the diagnostic cutoff for diabetes mellitus may contribute to the presence of MA. Whether MA is equally as predictive of CV disease in youth, as in adulthood, remains to be investigated.

[Proteinuria]

Several health organizations recommend that people be regularly checked for proteinuria to detect and treat kidney disease before it progresses. Proteinuria detected by a simple dipstick test should be confirmed by a quantitative measurement to assess persistent proteinuria. Most proteins are too big to pass through the kidneys' filters into the urine unless the kidneys are damaged. Markers of kidney damage in addition to proteinuria include abnormalities in the urine sediment, ultrasound of the kidneys and estimation of kidney function (creatinemia to calculate glomerular filtration rate). These assessments provide clues to the type (diagnosis) of chronic kidney disease and will the risk for developing progressive kidney failure. Thus, early detection of kidney disease will result in a more timely introduction of therapy that may slow the course of kidney disease. Microalbuminuria (albumin excretion above the normal range) that a marker of microvascular lesions in diabetes and hypertension is associated with a worth cardiovascular prognosis. Level of proteinuria in excess of 3,0 g/d in glomerular disease strongly determines the extent of kidney damage and renal prognosis.

Proteinuria and metabolic syndrome as predictors of cardiovascular death in non-diabetic and type 2 diabetic men and women

AIMS/HYPOTHESIS

Proteinuria predicts cardiovascular disease (CVD), but it is unclear whether this is explained by the association of the metabolic syndrome with proteinuria. Therefore, we investigated proteinuria and the metabolic syndrome as independent predictors of CVD death in men and women.

METHODS

The cohort comprised 574 non-diabetic men, 707 non-diabetic women, 371 diabetic men and 349 diabetic women, all free of CVD at baseline. Modified World Health Organization criteria were used to define the metabolic syndrome, and a urinary protein concentration of >or=0.1 g/l (or >or=0.2 g/l) to define proteinuria. The endpoint was CVD mortality during the 18-year follow-up.

RESULTS

Among non-diabetic men, CVD mortality per 1,000 person-years was as follows: no metabolic syndrome, no urinary protein group: 5.3; no metabolic syndrome, positive for urinary protein: 8.9; positive for metabolic syndrome, no urinary protein: 13.3; and positive for metabolic syndrome and urinary protein: 14.9. For non-diabetic women the corresponding values were: 0.9, 2.3, 4.9 and 7.9, respectively. Among diabetic men, CVD mortality per 1,000 person-years was 15.2, 32.5, 23.6 and 42.0 for the respective groups. Among diabetic women it was 25.3, 38.0, 26.3 and 40.3 (urinary protein in all cases defined as >or=0.1 g/l). In multivariate Cox models including both urinary protein and metabolic syndrome, the hazard ratios (HRs, 95% CI) of proteinuria for CVD mortality were 1.5 (0.9-2.4) in non-diabetic men, 1.8 (0.8-4.2) in non-diabetic women, 1.6 (1.0-2.6) in diabetic men and 1.6 (1.1-2.3) in diabetic women. Urinary protein as a continuous variable was associated with CVD mortality in all groups. The corresponding HRs for metabolic syndrome were: 1.6 (0.9-2.7), 4.0 (1.7-9.7), 1.5 (1.1-2.0) and 1.1 (0.8-1.5).

CONCLUSIONS/INTERPRETATION

Proteinuria predicted CVD mortality independently of the presence of metabolic syndrome in non-diabetic and diabetic subjects. Metabolic syndrome predicted CVD mortality in non-diabetic women and in diabetic men, independently of the presence of proteinuria.

The Cardiometabolic Syndrome as a Cardiovascular Risk Factor

The cardiometabolic syndrome (CMS) is associated with cardiovascular disease (CVD) and includes a constellation of risk factors such as central obesity, hypertension, insulin resistance, dyslipidemia, microalbuminuria, and hypercoagulability. Collectively, these risk factors increase CVD endpoints such as stroke, congestive heart failure, chronic kidney disease (CKD), and overall mortality. The CMS is associated with endothelial dysfunction, inflammation, abnormal thrombolysis, and increased oxidative stress that accentuate progression of CVD. We will review how the varying components of the CMS relate to an increased CVD and renal disease risk.

Proteinuria is a prognostic marker for cardiovascular mortality: NIPPON DATA 80, 1980-1999

BACKGROUND: Proteinuria has been considered to be a prognostic marker for persons with diabetes mellitus, but only a limited number of studies about the relationship between proteinuria and mortality among general population has been available.

METHODS: The subjects were 10,897 individuals who participated in the National Cardiovascular Survey conducted in 1980 and who were aged 30 years or older living in 300 districts that had been randomly selected throughout Japan. The vital records were confirmed in 1999 and 7,203 subjects (3,180 males and 4,023 females) without a history of hypertension, stroke, heart disease, renal disease, or diabetes mellitus at the start of the study were investigated.

RESULTS: There were 126,825 person-years of follow-up. During the observed period of time, 371 died of cardiovascular causes, including 171 stroke deaths and 74 coronary deaths. The risk of proteinuria for cardiovascular mortality was greater than unity for those with a normal serum creatinine level, after adjusting for age and other cardiovascular disease risk factors.

CONCLUSIONS: When contrasted with other cardiovascular disease risk factors, urinary protein is an independent risk factor for cardiovascular death among the Japanese population.

Influence of metabolic syndrome on hypertension-related target organ damage

OBJECTIVES

The aim of our study was to analyse, in a wide group of essential hypertensive patients without diabetes mellitus, the influence of metabolic syndrome (MS) (defined according to the criteria laid down in the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults) on markers of preclinical cardiac, renal and retinal damage.

DESIGN

Cross-sectional study.

SETTING

Outpatient hypertension clinic.

SUBJECTS AND METHODS

A total of 353 young and middle-aged hypertensives, free from cardiovascular and renal diseases (and 37% of whom had MS), underwent echocardiographic examination, microalbuminuria determination and non-mydriatic retinography.

RESULTS

When compared with subjects without MS, hypertensive patients with MS exhibited more elevated left ventricular (LV) mass (either normalized by body surface area or by height elevated by a power of 2.7), higher myocardial relative wall thickness, albumin excretion rate (AER) and a greater prevalence of LV hypertrophy (57.7% vs. 25.1%; P < 0.00001), of microalbuminuria (36.2% vs. 19.3%; P = 0.002) and of hypertensive retinopathy (87.7% vs. 48.4%; P < 0.00001). These results held even after correction for age, 24-h blood pressures, duration of hypertension, previous antihypertensive therapy, and gender distribution. The independent relationships between LV mass and MS, and between AER and MS, were confirmed in multivariate regression models including MS together with its individual components.

CONCLUSIONS

MS may amplify hypertension-related cardiac and renal changes, over and above the potential contribution of each single component of this syndrome. As these markers of target organ damage are well-known predictors of cardiovascular events, our results may partly explain the enhanced cardiovascular risk associated with MS.

Impact of statins in microalbuminuric subjects with the metabolic syndrome: a substudy of the PREVEND Intervention Trial

AIMS

Microalbuminuria frequently clusters with the metabolic syndrome and may identify subjects at increased coronary risk. Statin treatment may reduce the incidence of major adverse cardiac events in subjects with the metabolic syndrome, but evidence is limited. We evaluated the impact of pravastatin treatment on the incidence of major adverse cardiac events in microalbuminuric subjects with the metabolic syndrome.

METHODS AND RESULTS

This substudy of the PREVEND Intervention Trial (a randomized, placebo-controlled trial with a 2x2 factorial design) included 864 microalbuminuric subjects, who were randomized to fosinopril 20 mg or matching placebo and pravastatin 40 mg or matching placebo (mean follow-up 46 months). The metabolic syndrome was defined according to the NCEP ATPIII-report. Subjects with or without the metabolic syndrome were characterized by a higher age, male sex, and increased albuminuria. The incidence of major adverse cardiac events in subjects with the metabolic syndrome [9.1%; 95% confidence interval (CI) 6.0-13.0%] was increased vs. those without [3.6%; 95% CI 2.3-5.5%; P=0.007). Pravastatin treatment lowered the incidence of major adverse cardiac events in subjects with the metabolic syndrome after adjustment for age and sex (hazard ratio=0.39; 95% CI 0.17-0.89; P=0.025).

CONCLUSION

This study supports the use of statins in microalbuminuric subjects with the metabolic syndrome to reduce the incidence of major adverse cardiac events.

Effect of sodium intake on blood pressure and albuminuria in Type 2 diabetic patients: the role of insulin resistance

AIMS/HYPOTHESIS

This study was done to measure the effect of Na+ intake on blood pressure and albuminuria, in relation with insulin sensitivity and kidney haemodynamics, in Type 2 diabetic patients with and without microalbuminuria.

METHODS

Type 2 diabetic patients, 20 with microalbuminuria, 21 without, spent two consecutive 7-day periods, one on a high (250 mmol), the other on a low-Na+ (20 mmol) diet. Body weight, 24-h blood pressure and albuminuria were measured at the end of each period. At the end of high-Na+ diet insulin sensitivity (euglycaemic insulin clamp; 2 mU.kg(-1).min(-1)) and kidney haemodynamics were measured in nine patients from each group.

RESULTS

Switching from low to high-Na+ diet resulted in an increase in blood pressure (7.4+/-4.7 mmHg; p<0.001), body weight (1.9+/-0.4 kg; p<0.05) and albuminuria [from 80 (31-183) microg/min to 101 (27-965) microg/min; p<0.01) in patients with microalbuminuria. No changes occurred in patients without microalbuminuria. Patients with microalbuminuria also had greater intraglomerular pressure (44+/-1 mmHg vs 36+/-1; p<0.001), calculated from glomerular filtration rate, renal plasma flow, plasma protein concentration and the relationship between pressure and natriuresis. In these patients insulin sensitivity was lower (5.16+/-49 vs 7.36+/-0.63 mg.kg(-1).min(-1); p=0.007). Urinary albumin excretion (r=0.40; p=0.009) and insulin sensitivity (r=-0.59; p=0.01) were correlated with intraglomerular pressure.

CONCLUSION/INTERPRETATION

High salt intake increases blood pressure and albuminuria in Type 2 diabetic patients with microalbuminuria. These responses are associated with insulin resistance and increased glomerular pressure. Insulin resistance could contribute to greater salt sensitivity, increased glomerular pressure and albuminuria.

Is it time to measure microalbuminuria in hypertension?

Former guidelines on hypertension never made a commitment to the detection of microalbuminuria for screening or follow-up of hypertensive patients. On the other hand, growing evidence support the contributory role of microalbuminuria in the prediction of absolute cardiovascular risk in hypertension and document the potential relevance of this parameter to the initial choice of antihypertensive treatment. Upcoming new guidelines and diagnostic algorithms in hypertension need to underscore the clinical positioning of microalbuminuria for stratification of risk and follow-up purposes.

Microalbuminuria, a parameter independent of metabolic influences in hypertensive men

OBJECTIVE

To evaluate the relationship of albuminuria and microalbuminuria (overnight urine albumin > or = 15 micro g/min) with insulin resistance and related metabolic abnormalities in patients with essential hypertension.

DESIGN

Cross-sectional evaluation of 271 (age range, 19-77 years) never-treated, non-diabetic, uncomplicated hypertensive men.

MAIN OUTCOME MEASURES

Triplicate overnight urine albumin determination and homeostasis model assessment (HOMA) of insulin resistance as a surrogate measure of insulin sensitivity. Additional parameters were fasting and post-load circulating glucose and insulin, lipids, body mass index, blood pressure and echocardiographic left ventricular mass.

RESULTS

HOMA, fasting and post-challenge glucose and insulin, percentages of glucose-intolerant patients, triglycerides and high-density lipoprotein cholesterol levels did not differ across ascending urine albumin quartiles. Body mass index, blood pressure and ventricular mass were significantly greater in the upper quartiles, and the prevalence of obesity fivefold more frequent in the top as compared with the bottom urine albumin fourth. The statistical trend was unchanged after adjustment for HOMA, while accounting for systolic blood pressure and left ventricular mass by co-variance analysis abolished it. Eighty-eight patients bearing the phenotypic traits of the metabolic syndrome and a striking degree of insulin resistance and hyperinsulinemia showed urine albumin rates and prevalence of microalbuminuria comparable with the 183 patients who were not affected by that syndrome.

CONCLUSIONS

Albuminuria is independent of insulin resistance and other phenotypic components of the metabolic syndrome in never-treated, non-diabetic essential hypertensive men. Microalbuminuria is more frequent in obese hypertensives but this association is explained by higher blood pressure more than insulin resistance.

Silent ischemia is more prevalent among hypertensive patients with microalbuminuria and salt sensitivity

Some patients with essential hypertension manifest greater than normal urinary albumin excretion (UAE). Salt-sensitive hypertensives also manifest greater UAE compared to salt-resistant individuals. Although the significance of these associations is not well established, several lines of evidence suggest that microalbuminuria and/or salt sensitivity may be associated with greater prevalence of cardiovascular risks and events. In this study, we have evaluated by ergometric exercise 42 subjects with microalbuminuria and 42 matched individuals with normal UAE. All these subjects also underwent a standardized protocol to determine blood pressure sensitivity to a high salt intake. Patients with microalbuminuria displayed greater levels of ambulatory blood pressure and a greater rise in systolic blood pressure during exercise compared to patients with normal UAE (33.1 +/- 1.56 vs 26.4 +/- 1.7 mmHg, P < 0.001). Seven hypertensive patients with microalbuminuria developed ST segment depression during exercise compared to only one subject with normal UAE. Salt-sensitive patients manifested greater UAE than salt-resistant subjects (58 and 14 mg, 24 h, P < 0.001) and greater prevalence of silent ischemia (6 vs 2) than salt-resistant individuals. In conclusion, these studies have shown that hypertensive individuals with microalbuminuria and/or salt sensitivity manifest an increased prevalence of silent ischemia.

Update on the cardiometabolic syndrome

An array of metabolic, hemodynamic, and renal abnormalities constitutes the cardiometabolic syndrome. A hallmark of this syndrome is visceral obesity and associated insulin resistance/hyperinsulinemia. The syndrome is also associated with essential hypertension, abnormalities in the circadian rhythm of blood pressure and heart rate, the diabetic dyslipidemic syndrome, hypercoagulability, hyperuricemia, increased cardiovascular inflammation, and microalbuminuria, all of which contribute to an increased risk of cardiovascular disease morbidity and mortality. This article reviews current knowledge about the interrelationship of the various factors that make up the cardiometabolic syndrome and its implications for individuals with and without diabetes mellitus.

Association between high-normal albuminuria and risk factors for cardiovascular and renal disease in essential hypertensive men

BACKGROUND

Microalbuminuria (overnight urinary albumin excretion [UAE] > 15 microg/min) is associated with cardiovascular risk factors and predicts morbid events in hypertensive subjects. However, albuminuria is not a dichotomous variable, and a relationship with cardiovascular risk factors may extend below that conventional threshold.

METHODS

We studied 186 never-treated, glucose-tolerant, normalbuminuric (overnight UAE < or = 15 microg/min), essential hypertensive men with normal renal function (serum creatinine < 1.4 mg/dL). Study variables were 24-hour ambulatory blood pressure (BP), cardiac structure and geometry (by echocardiography), body weight, fasting insulin levels, insulin sensitivity (the Homeostasis Model Assessment index), and creatinine clearance (from overnight collections or through the Cockcroft formula) analyzed as a function of ascending urine albumin quartiles (cutoff values, 4.3, 6.3, and 9.4 microg/min; n = 47, 45, 47, and 47, respectively).

RESULTS

As compared with the three bottom fourths, patients with high-normal albuminuria (albumin, 9.4 to 15 microg/min) had a greater 24-hour BP, greater relative wall thickness, more frequent concentric left ventricular hypertrophy, heavier body size, increased fasting insulin levels, reduced insulin sensitivity, and greater creatinine clearance.

CONCLUSIONS

High-normal albuminuria in uncomplicated essential hypertensive men is associated with an adverse cardiovascular and metabolic risk profile. Furthermore, hyperfiltration in the presence of minimally increased albuminuria may underlie an augmented glomerular blood flow and hydraulic pressure conducive to glomerular hypertension and, eventually, renal insufficiency. Overall, these data confirm the appropriateness to shift downward the limits for diagnosing microalbuminuria in essential hypertension, as indicated from previous prospective studies.

Microalbuminuria in diabetes: focus on cardiovascular and renal risk reduction

Albuminuria has long been recognized as a harbinger for the progression of diabetic nephropathy. Recently, it has become increasingly recognized that albuminuria is a powerful risk factor for cardiovascular disease and stroke. In this article we explore evidence for albuminuria being an integral component of the cardiometabolic syndrome and a risk factor for cardiovascular disease and stroke.

Microalbuminuria in hypertension is not a determinant of insulin resistance

BACKGROUND

Microalbuminuria (MA) clusters with metabolic derangements linked to the insulin resistance syndrome, and is associated with increased risk of cardiovascular disease in both diabetes and hypertension. This study questioned if MA, reflecting endothelial damage, is directly linked to impaired insulin action.

METHODS

MA was measured in two 24-hour urine samples in 84 persons with untreated hypertension recruited from a population survey (diastolic blood pressures 90 to 105 mm Hg). Thirty-one percent had MA values>20 microg/min (MA group, N = 26), and these were matched according to age, gender, and body-mass index with hypertensive persons without MA (non-MA group, N = 32) for comparison of the metabolic profile. Insulin sensitivity was measured with clamp techniques.

RESULTS

The MA and non-MA groups were similar in their fasting and post-load glucose and insulin levels, in the first (930 +/- 594 vs. 1097 +/- 707 pmol/L) and second (1111 +/- 662 vs. 1163 +/- 702 pmol/L) phases of insulin release during a hyperglycemic clamp, and in their insulin sensitivity indices (0.16 +/- 0.10 vs. 0.17 +/- 0.13, P> 0.3 for all). The MA group had higher systolic blood pressure (157 +/- 13 vs. 150 +/- 12 mm Hg, P = 0.05) and a higher serum level of circulating advanced glycation end products (AGEs; 11.0 +/- 3.0 vs. 7.9 +/- 3.5 U/mL, P = 0.05) than the controls. No associations were found between MA and the insulin sensitivity index, or glucose and insulin levels. Weak associations were found with systolic blood pressure (r = 0.25, P = 0.05), AGEs (r = 0.27, P = 0.05), and smoking habits (r = 0.39, P = 0.01).

CONCLUSION

In hypertension, MA is not a determinant of insulin resistance, provided confounding factors such as degree of adiposity are carefully controlled.

Microalbuminuria, an integrated marker of cardiovascular risk in essential hypertension

This paper reviews the existing epidemiological and clinical evidence about the relationships of non-diabetic microalbuminuria with cardiovascular risk factors such as elevated blood pressure (BP), systolic particularly, cardiac hypertrophy, adverse metabolic status, smoking habits, elevated angiotensin II levels, endothelial dysfunction, acute and perhaps subclinical inflammation. Because of that unique property of reflecting the influence of so many clinically relevant parameters, microalbuminuria may legitimately be defined as an integrated marker of cardiovascular risk, an unique profile among the several prognostic predictors available to stratify risk in hypertensive patients. Recent cohort studies also showed associations with cardiovascular morbidity and mortality independently from conventional atherogenic factors. This behaviour, whose understanding still needs further elucidation, suggests to measure albuminuria and to screen patients at a higher absolute risk in whom preventive treatment is expected to be more beneficial than in those with a lower absolute risk.

Frequency and determinants of microalbuminuria in mild hypertension: a primary-care-based study

OBJECTIVE

To evaluate the frequency of microalbuminuria and its relationship with several risk factors and left ventricular mass in a population of mildly hypertensive subjects attended in a primary-care setting.

DESIGN

Cross-sectional study.

SETTING

Eight primary-care centres.

PATIENTS

Two hundred and twenty-three non-diabetic patients recently diagnosed with mild hypertension were included in the study. None of them had clinical evidence of target-organ damage or had received prior antihypertensive treatment.

INTERVENTIONS

Subjects included in the study underwent clinical interview, measurement of blood pressure (BP) on three visits, blood analysis, measurement of albumin by immunonephelometry in three overnight urine collections, 24 h BP monitoring and M-mode and Doppler echocardiography.

MAIN OUTCOME MEASURES

Tobacco habit, clinic BP, body mass index, serum lipids and uric acid, glycaemia, urinary albumin excretion (UAE), ambulatory BP and left ventricular mass index.

RESULTS

The frequency of microalbuminuria was 7.2%. Microalbuminuric patients were more likely to be men and to be characterized by higher ambulatory BP, body mass index and uric acid levels. Regression analysis demonstrated that male sex and 24 h systolic BP were determinants of UAE. Patients with white-coat hypertension showed lower UAE than did subjects with sustained hypertension. Although a certain relationship between UAE and left ventricular mass index was found, these variables were not significantly correlated.

CONCLUSIONS

A low proportion of mildly hypertensive patients attended in a primary care setting are microalbuminuric. In this population, UAE is an expression of BP values over 24 h and correlates with several risk factors.

[Factors associated with changes in microalbuminuria during antihypertensive treatment]

BACKGROUND

The objective of the present study was to analyze the factors related with changes of microalbuminuria during antihypertensive treatment in patients with essential hypertension.

METHODS

One hundred and six patients (57 men, mean age 40.8 [SD 6.6] years) never treated with antihypertensive treatment were included. At the beginning and after one year, blood pressure biochemical profile and urinary albumin excretion (UAE) were measured. After the initial evaluation, 53 patients received angiotensin converting enzyme inhibitors (ACEi) and 53 beta-blockers (BB). Hydrochlorothiazide was added to achieve the blood pressure target < 140/90 mmHg.

RESULTS

The average of UAE was 32.1 (43.1) mg/24 h, and 41 (39%) patients had microalbuminuretics. After 12 months of treatment, a significative fall of systolic BP (-20.6 [8.03] mmHg, p < 0.001), and diastolic BP (-14.18 [10.34] mmHg, p < 0.001) were observed, whereas baseline glucose increases (3.08 [11.07] mg/dl, p = 0.006). The changes of UAE were only related with the baseline UAE values. Neither, age, sex, baseline diastolic BP and changes in diastolic BP were significantly related with the changes in UAE. In spite of similar mean BP reduction (medial BP 17.4 [10.9] vs 14.8 [10.4] mmHg), UAE only was reduced in patients treated with ACEi (LogUAE: 0.203 [0.872] mg/24 h; p < 0.04). In addition, in patients treated with BB a significative increase in baseline glucose (4.4 [12.3] mg/dl; p = 0.013) and uric acid (1.18 [4.18]; p = 0.031) were observed.

CONCLUSIONS

In patients with essential hypertension, changes in microalbuminuria depends of the initial UAE values and the kind of antihypertensive treatment. ACEi produced higher UAE reduction and lower derangement of the glucose metabolism than BB.

Microalbuminuria in essential hypertension: significance, pathophysiology, and therapeutic implications

Some patients with essential hypertension manifest greater than normal urinary albumin excretion (UAE). The significance of this association, which is the object of this review, is not well established. Hypertensive patients with microalbuminuria manifest greater levels of blood pressure, particularly at night, and higher serum levels of cholesterol, triglycerides, and uric acid than patients with normal UAE. Levels of high-density lipoprotein cholesterol, on the other hand, were lower in patients with microalbuminuria than in those with normal UAE. Patients with microalbuminuria manifested greater incidence of insulin resistance and thicker carotid arteries than patients with normal UAE. After a follow-up of 7 years, we observed that 12 cardiovascular events occurred among 54 (21.3%) patients with microalbuminuria and only two such events among 87 patients with normal UAE (P < 0.0002). Stepwise logistic regression analysis showed that UAE, cholesterol level, and diastolic blood pressure were independent predictors of the cardiovascular outcome. Rate of creatinine clearance from patients with microalbuminuria decreased more than that from those with normal UAE. In conclusion, these studies suggest that hypertensive individuals with microalbuminuria manifest a variety of biochemical and hormonal derangements with pathogenic potential, which results in hypertensive patients having a greater incidence of cardiovascular events and a greater decline in renal function than patients with normal UAE.

Erectile dysfunction in patients with diabetes

Erectile dysfunction, which is common among men with diabetes, leads to significant reduction in quality of life, and as with other complications of diabetes deserves to be treated on the NHS. This article explores the problem of erectile dysfunction and diabetes and the role of sildenafil, which is likely to be the first choice treatment of patients presenting with erectile dysfunction.

Urinary platelet-activating factor excretion is elevated in non-insulin dependent diabetes mellitus

Proteinuria is currently considered a very sensitive predictor of diabetic nephropathy, but 20-25% of all diabetic patients with negative Albustix reaction excrete higher than normal (< 20 mg/24 h) amounts of albumin in their urine. It is our hypothesis that platelet-activating factor (PAF), a potent glycerophospholipid that acts as a chemical mediator for a wide spectrum of biological activities, including increased vascular permeability, may be produced in significant amounts during periods preceding microalbuminuria. In this study, we compared urinary PAF excretion in Mexican-American subjects who were diagnosed with non-insulin dependent diabetes mellitus (NIDDM) with their healthy control counterparts. The age of the NIDDM subjects (45.9 +/- 2.1 years) was not significantly different from the healthy control group, which was 39.4 +/- 2.7 years (P < 0.0672). The NIDDM subjects (body mass index, 29.9 +/- 1.1 compared to 26.1 +/- 0.9 kg/m2 in healthy controls) were characterized by significantly increased (P < 0.05) fasting plasma glucose (192 +/- 11 vs. 97 +/- 4 mg/dl in healthy controls), fasting insulin (20.9 +/- 2.4 vs. 12.3 +/- 1.6 microU/ml), fasting C-peptide (2.93 +/- 1.26 vs. 1.48 +/- 0.51 ng/ml), and hemoglobin A1c (10.3 +/- 0.7 vs. 5.6 +/- 0.3%), respectively. The urine output for the NIDDM and control subjects were 1942 +/- 191 ml/24 h and 1032 +/- 94 ml/24 h, respectively, and urinary albumin excretion (UAE) rates were estimated to be 38 +/- 7 micrograms/min and 11 +/- 1 micrograms/min, respectively. The NIDDM subjects produced significantly increased levels of urinary PAF (2606.3 +/- 513.1 ng/24 h compared with 77.9 +/- 14.1 ng/24 h in controls (or 1706.3 +/- 420.8 ng/ml compared with 85.4 +/- 17.8 pg/ml of urine, in NIDDM and control subjects, respectively). We found that urinary PAF excretion was significantly correlated with microalbumin excretion (r = 0.7) especially at UAE rates greater than 30 mg/day and more importantly, some NIDDM patients with negative Albustix reaction (i.e. normal UAE) produced significantly more PAF, suggesting that PAF excretion may precede microalbuminuria and that subtle injury to the kidneys are present in NIDDM long before overt albuminuria ensues, urinary PAF measurements could potentially therefore serve as a sensitive indicator of renal injury in diabetes mellitus. These results lend further credence to our hypothesis that PAF may be the biochemical compound linking the various members of the insulin resistance syndrome.

Microalbuminuria in essential hypertension

Urinary excretion of albumin exceeds normal values in 10 to 25% of patients with essential hypertension. The level of albuminuria is highly correlated with arterial pressure, and more closely with ambulatory arterial pressure. The interaction between albuminuria and arterial pressure is enhanced by overweight, smoking, protein intake, insulin resistance, lipid abnormalities, and possibly genotypes of the components of the renin-angiotensin system. The renal mechanisms of microalbuminuria are not well elucidated. Notably, an increase in filtration fraction suggestive of intraglomerular hypertension was observed in patients with hyperfiltration. Microalbuminuria may be a marker of diffuse vascular abnormalities predisposing to cardiovascular disease and/or hypertensive renal disease heralding future renal failure, but its predictive value needs to be tested in more long-term follow-up studies. Antihypertensive treatment has a varied influence on albuminuria; angiotensin-converting enzyme inhibitors may correct this abnormality (at least partially) better than other agents.

Blood pressure control, microalbuminuria and cardiovascular risk in Type 2 diabetes mellitus

Type 2 (noninsulin-dependent) diabetes mellitus (DM) affects about 3% of the UK population. Diabetes often coexists with a cluster of other potent cardiovascular risk factors, including hypertension, dyslipidaemia and increased tendency for thrombosis, and increases the risk of early death from cardiovascular causes by about threefold. Microalbuminuria or proteinuria also may be present, further increasing the risk of cardiovascular mortality. Cardiovascular risk factors must be treated aggressively in patients with Type 2 diabetes and control of blood pressure at 140/85 mm Hg or lower is a priority. The management of hypertension in patients from some ethnic groups demands special consideration because they have a high incidence of diabetes and hypertensive complications. Patients must be urged to adopt appropriate lifestyle changes in the first instance but additional drug treatment for hypertension is usually required. All the major classes of antihypertensive agents lower blood pressure in Type 2 diabetic patients but have different effects on metabolic risk factors in different ways. Low-dose thiazide diuretics, beta-blockers, calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors have been shown to reduce cardiovascular risk. Individually, the effects of low-dose thiazide diuretics and beta-blockers on glucose and lipid metabolism is clinically insignificant, though in combination much larger metabolic effects are seen. ACE inhibitors and calcium channel blockers have no, or small, beneficial effects on glucose and lipid metabolism, while the greater beneficial effects of alpha1-blockers on lipid profiles may render them especially useful in the Type 2 diabetic patient. Long-acting calcium-channel blockers and ACE inhibitors protect renal function and are suitable as first line therapy in patients with microalbuminuria or proteinuria. Until results from the current batch of randomized, placebo-controlled trials comparing different classes of antihypertensive agents are available, the choice of antihypertensive agent is difficult. Addressing overall cardiovascular risk factors, rather than hypertension alone, is essential in the management of the hypertensive Type 2 diabetic patient.

Renal protection by antihypertensive drugs: insights from microalbuminuria studies

During the last few years there has been a renewed interest in blood-pressure (BP)-induced kidney damage, owing to a progressive increase in the incidence and prevalence of hypertension and vascular diseases as a cause of end-stage renal disease (ESRD). The need to prevent ESRD demands continued efforts so as to identify early those people with hypertension who are at risk and to provide them with effective antihypertensive therapy. This review analyses what is needed in terms of surrogate endpoints for monitoring kidney damage and what is known about the impact of antihypertensive treatments in reducing the BP burden on the kidney in non-diabetic subjects. Although glomerular filtration rate (GFR) and proteinuria are useful surrogate endpoints for patients with nephropathy and GFR below or close to the threshold value for renal insufficiency, it is clear that monitoring changes in either GFR or proteinuria does not provide a sensitive endpoint for subjects with the mildest forms of renal disease, e.g. essential hypertensive patients who are at risk of developing kidney damage. In this case microalbuminuria may be useful, although unequivocal evidence demonstrating that microalbuminuria is a risk marker for developing renal insufficiency in non-diabetic renal diseases has not existed until now, and whether a decrease in microalbuminuria is of prognostic significance in patients with essential hypertension remains to be demonstrated. The beneficial effects of the antihypertensive agents on microalbuminuria are also proportional to BP reduction. If a large enough BP reduction is achieved there seem to be, at most, only minimal differences among the antihypertensive drug classes. Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers have additional beneficial effects on microalbuminuria independent of the BP reduction, owing to their direct role in glomerular haemodynamics. The heterogeneity in the changes in urinary albumin excretion during antihypertensive treatment may be related to the different factors involved in the presence of microalbuminuria or structural end-organ damage, or both.

Simultaneous gradient-echo/spin-echo EPI of graded ischemia in human skeletal muscle

The goal of this study was to evaluate the usefulness of blood oxygenation level-dependent (BOLD) methodologies to provide temporal and spatial information about skeletal muscle perfusion. A simultaneous gradient echo (GE) and spin-echo (SE) imaging sequence (GE/SE) with alternating TE was used to acquire images of leg skeletal muscle throughout a stepped reactive hyperemia paradigm. The change in both the GE and SE relaxation rates (deltaR2*, deltaR2) measured during ischemia and reactive hyperemia scaled with the duration of cuff inflation (the ischemic period) plateaued for cuff inflations lasting longer than 120 seconds and were greater in soleus muscle than in gastrocnemius. The ratio deltaR2*/deltaR2 was found to be less during the reactive hyperemia period relative to ischemia. Considering that a greater proportion of capillary vessels are perfused during reactive hyperemia than during ischemia, this finding suggests that magnetic susceptibility methodologies, with their dependence on compartment size, may provide a measure of the relative distribution of small and large vessels in skeletal muscle.

Microalbuminuria predicts cardiovascular events and renal insufficiency in patients with essential hypertension

BACKGROUND

Some patients with essential hypertension manifest greater than normal urinary excretion of albumin (UAE). Authors of a few retrospective studies have suggested that there is an association between microalbuminuria and cardiovascular risk.

OBJECTIVE

To evaluate whether microalbuminuria is associated with a greater than normal risk of cardiovascular and renal events.

METHODS

We performed a retrospective cohort analysis of 141 hypertensive individuals followed up for approximately 7 years. Hypertensive patients were defined as having microalbuminuria if the baseline average UAE of three urine collections was in the range 30-300 mg/24 h.

RESULTS

Fifty-four patients had microalbuminuria and 87 had normal UAE. At baseline, the two groups were similar for age, weight, blood pressure, and rate of clearance of creatinine. Serum levels of cholesterol, triglycerides, and uric acid in patients with microalbuminuria were higher than levels in those with normal UAE, whereas levels of high-density lipoprotein cholesterol in patients with microalbuminuria were lower than levels in patient with normal UAE. During follow-up, 12 cardiovascular events occurred among the 54 (21.3%) patients with microalbuminuria and only two such events among the 87 patients with normal UAE (P < 0.0002). Stepwise logistic regression analysis showed that UAE (P = 0.003), cholesterol level (P = 0.047) and diastolic blood pressure (P = 0.03) were independent predictors of the cardiovascular outcome. Rate of clearance of creatinine from patients with microalbuminuria decreased more than did that from those with normal UAE (decrease of 12.1 +/- 2.77 versus 7.1 +/- 0.88 ml/min, P < 0.03).

CONCLUSIONS

This study suggests that hypertensive individuals with microalbuminuria manifest a greater incidence of cardiovascular events and a greater decline in renal function than do patients with normal UAE.

Treatment of patients with essential hypertension and microalbuminuria

There has been increasing interest in the question of whether microalbuminuria can be used in the risk stratification of patients with essential hypertension. A cluster of cardiovascular and/or renal risk factors may be associated with microalbuminuria in hypertension. Despite this, prospective data about the potential role of microalbuminuria as a prognostic marker of cardiovascular and/or renal risk have been sparse and inconclusive until now. Blood pressure values have been considered the most important determinant of microalbuminuria in essential hypertension; however, hyperinsulinaemia--a metabolic component-was noted to be present in conjunction with high blood pressure. Furthermore, 2 other factors may be also related to microalbuminuria: salt sensitivity and renal structural changes (nephrosclerosis). We are now aware that the clinical and physiological implications of abnormal urinary albumin excretion (UAE) are much broader than anticipated, possibly involving haemodynamic, metabolic and vascular components overlapping several clinical syndromes. Achievement of short term UAE reduction with antihypertensive treatment depends on structural abnormalities established in the glomerulus, the extent of blood pressure reduction and the antihypertensive drug class used. In terms of UAE reduction, better results are obtained with ACE inhibitors or angiotensin II antagonists such as losartan and valsartan, than with other antihypertensive classes, although their true impact in preserving renal function needs to be assessed. The capacity of new calcium antagonists, such as amlodipine, lacidipine or mibefradil, to reduce UAE also needs to be assessed further. Thus, microalbuminuria may be seen as an integrated marker of risk and should be assessed in recently diagnosed patients with essential hypertension. In microalbuminuric patients, the target should be to decrease blood pressure < 135/85 mm Hg, reduce salt intake to around 100 mmol/day and prescribe a low-calorie diet if obesity is present. ACE inhibitors or angiotensin II antagonists have more potential benefits than the other classes of antihypertensive drugs in reducing UAE. Finally, a yearly assessment of microalbuminuria is recommended during treatment, to monitor the impact of therapy.

Plasma PAF acetylhydrolase in non-insulin dependent diabetes mellitus and obesity: effect of hyperinsulinemia and lovastatin treatment

Insulin resistance is characterized principally by impaired insulin-mediated glucose uptake which provokes a compensatory increase in pancreatic beta-cell secretory activity. For a time this may produce well-controlled plasma glucose levels but as the insulin resistance worsens the augmented insulin production becomes inadequate to keep plasma glucose at euglycemia leading to the development of non-insulin dependent diabetes mellitus (NIDDM), accompanied by hyperinsulinemia and hyperglycemia. A number of metabolic defects are associated with NIDDM including obesity, hypercoagulability, cardiovascular disease risk factors such as hypertension and dyslipidemia and these constitute the insulin resistance syndrome. The identity of the biochemical factor that might link all these defects is not yet known. We have hypothesized that platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) may be such a link. In this study, we measured plasma acetylhydrolase (EC.1.1.48), which degrades PAF to the inactive metabolise lyso-PAF, as a surrogate for PAF activity in three groups of hypercholesterolemic subjects: lean controls (n = 9), non-diabetic obese (n = 6) and NIDDM subjects (n = 6). The ages and body mass indices of the subjects were 46 +/- 3.1 and 24.2 +/- 2.2 for the lean controls, 52 +/- 2.5 and 28.7 +/- 0.9 for the NIDDM subjects and 60 +/- 2 and 27.6 +/- 2.1 for the obese, non-diabetic subjects (mean +/- S.E.M.). The measurements were made before and after therapy with the cholesterol-lowering drug lovastatin, a 3-hydroxy 3 methylglutaryl (HMG) coenzyme. A reductase inhibitor (40 mg/day) for 3 months. Fasting plasma glucose (FPG) levels were 91 +/- 11, 96 +/- 3 and 146 +/- 11 mg/dl, for the lean, obese and NIDDM subjects, respectively, before therapy began. Lovastatin did not affect FPG in any of the three subject groups. Before treatment, the fasting plasma insulin (FPI) levels were 6.1 +/- 0.92, 10.83 +/- 2.03 and 14.68 +/- 3.64 mU/l for the lean, non-diabetic obese and NIDDM subjects, respectively. After lovastatin therapy only the obese group exhibited a significant change in FPI (15.35 +/- 2.47 mU/l) (P < 0.05). Total cholesterol levels were similar in all three groups both before and after lovastatin therapy but within each group lovastatin therapy significantly reduced the total cholesterol by 32, 29 and 34% in the lean, obese and NIDDM subject groups respectively (P < 0.0001). Lovastatin therapy reduced LDL-cholesterol levels by 40, 32 and 46% in the lean, obese and NIDDM subjects, respectively, but produced no significant effect on HDL or triglyceride levels. Before therapy, the plasma acetylyhydrolase activities were 104 +/- 7, 164 +/- 7 and 179 +/- 7 nmol/ml per min in the lean, obese and NIDDM subjects, respectively. Lovastatin therapy reduced plasma acetylhydrolase levels to 70 +/- 7, 87 +/- 6 and 86 +/- 7 nmol/ml per min in the lean, obese and NIDDM subjects, respectively. Plasma acetylhydrolase activity was predominantly (> 80%) associated with LDL cholesterol both before and after lovastatin treatment. Also, plasma acetylhydrolase activity significantly correlated with fasting plasma insulin levels before lovastatin therapy but not after. Taken together, this study clearly implicates PAF metabolism in three defects associated with the insulin resistance syndrome: hypercholesterolemia, obesity and NIDDM. Additionally, we conclude that chronic hyperinsulinemia may play a significant role in the production of plasma acetylhydrolase.

Predictors of renal and cardiovascular mortality in patients with non-insulin-dependent diabetes: a brief overview of microalbuminuria and insulin resistance

Both microalbuminuria and insulin resistance are present at some stage in the natural history of non-insulin-dependent diabetes mellitus (NIDDM). Microalbuminuria predicts both progression to endstage renal disease and an increase in cardiovascular mortality compared to diabetic patients without microalbuminuria. Conversely, microalbuminuria is not a strong predictor of either renal or cardiovascular mortality in hypertensive nondiabetic subjects. This difference in risk may relate to the presence of glycated albumin in patients with diabetes. Glycation of albumin occurs because of persistent hyperglycemia. Glycated albumin is directly toxic to both renal and vascular tissue through stimulation of reactive oxygen species by both renal and immune protective cells. Blunting the rise in microalbuminuria with either aggressive blood glucose control or angiotensin-converting enzyme (ACE) inhibition, early in the course of the disease, markedly reduces renal mortality. In contrast to microalbuminuria, which is a reflection of renal injury, insulin resistance is a genetically determined problem that directly relates to peripheral glucose utilization. In most cases, insulin resistance is phenotypically expressed as diabetes as a result of environmental factors such as obesity. Insulin resistance is associated with an increased risk for development of both hypertension and NIDDM as well as atherosclerosis. Diabetic or hypertensive subjects with insulin resistance have an increased risk of cardiovascular but not renal mortality. Sustained weight loss is the best way to reduce insulin resistance and arterial pressure. Additionally, alpha blockers, more than other antihypertensive agents reduce insulin resistance. This class of drugs, however, has not been shown to reduce either microalbuminuria or overall cardio-renal mortality.

Peripheral but not hepatic insulin resistance in mice with one disrupted allele of the glucose transporter type 4 (GLUT4) gene

Glucose transporter type 4 (GLUT4) is insulin responsive and is expressed in striated muscle and adipose tissue. To investigate the impact of a partial deficiency in the level of GLUT4 on in vivo insulin action, we examined glucose disposal and hepatic glucose production (HGP) during hyperinsulinemic clamp studies in 4-5-mo-old conscious mice with one disrupted GLUT4 allele [GLUT4 (+/-)], compared with wild-type control mice [WT (+/+)]. GLUT4 (+/-) mice were studied before the onset of hyperglycemia and had normal plasma glucose levels and a 50% increase in the fasting (6 h) plasma insulin concentrations. GLUT4 protein in muscle was approximately 45% less in GLUT4 (+/-) than in WT (+/+). Euglycemic hyperinsulinemic clamp studies were performed in combination with [3-3H]glucose to measure the rate of appearance of glucose and HGP, with [U-14C]-2-deoxyglucose to estimate muscle glucose transport in vivo, and with [U-14C]lactate to assess hepatic glucose fluxes. During the clamp studies, the rates of glucose infusion, glucose disappearance, glycolysis, glycogen synthesis, and muscle glucose uptake were approximately 55% decreased in GLUT4 (+/-), compared with WT (+/+) mice. The decreased rate of in vivo glycogen synthesis was due to decreased stimulation of glucose transport since insulin's activation of muscle glycogen synthase was similar in GLUT4 (+/-) and in WT (+/+) mice. By contrast, the ability of hyperinsulinemia to inhibit HGP was unaffected in GLUT4 (+/-). The normal regulation of hepatic glucose metabolism in GLUT4 (+/-) mice was further supported by the similar intrahepatic distribution of liver glucose fluxes through glucose cycling, gluconeogenesis, and glycogenolysis. We conclude that the disruption of one allele of the GLUT4 gene leads to severe peripheral but not hepatic insulin resistance. Thus, varying levels of GLUT4 protein in striated muscle and adipose tissue can markedly alter whole body glucose disposal. These differences most likely account for the interindividual variations in peripheral insulin action.

Microalbuminuria in essential hypertension

The prevalence of microalbuminuria in patients with essential hypertension ranges between 10 and 25%. The level of albuminuria is highly correlated with arterial pressure and more closely ambulatory arterial pressure. The interaction between albuminuria and arterial pressure is enhanced by overweight and smoking. The renal mechanisms of microalbuminuria are not well elucidated; however, an increase in filtration fraction suggestive of intraglomerular hypertension was observed in patients with hyperfiltration. The significance of microalbuminuria as a marker of cardiovascular risk or hypertensive renal damage needs to be confirmed through long-term follow-up studies. Antihypertensive treatment has variable influence on albuminuria; and angiotensin-converting enzyme inhibitors and to a lesser extent other agents, tend to partially correct this abnormality.

Hyperinsulinemia as a determinant of microalbuminuria in essential hypertension

OBJECTIVE

To analyze the relationship between insulinemia and urinary albumin excretion in a group of nonobese, young adult hypertensive patients, who had never been treated with antihypertensive drugs.

PATIENTS AND METHODS

Forty-nine patients who fulfilled the inclusion criteria were included. Twenty-four-hour ambulatory blood pressure monitorings, urinary albumin excretion (UAE) measurements, and an oral glucose-tolerance test measuring glucose and insulin, were performed, and left ventricular mass was measured by echocardiography. Hypertensive patients were classified as normoalbuminuric when their UAE was < 30 mg/24 h (40 patients; mean UAE 13.4 +/- 7.0 mg/24 h), and as microalbuminuric when their UAE was 30-300 mg/24 h (nine patients; mean UAE 90.5 +/- 86.6 mg/24 h).

RESULTS

In comparison with that of the normoalbuminuric group, the fasting plasma glucose concentration for the microalbuminuric group was only slightly higher (100 +/- 9 versus 95 +/- 8 mg/dl, NS). In contrast, the fasting insulin concentration in the microalbuminuric group was significantly higher than that observed in the normoalbuminuric group (25.2 +/- 6.7 versus 16.6 +/- 5.2 microU/ml, P<0.0001). During the oral glucose-tolerance test, the area under the curve (AUC) for glucose (317 +/- 41 versus 253 +/- 53 mg/dl x 2/h, P<0.001) and the AUC for insulin (253 +/- 171 versus 124 +/- 43 microU/ml x 2/h, P<0.001) were significantly higher in the microalbuminuric group than were those AUC observed in the normoalbuminuric group. After adjustments for age, sex, body mass index and average 24 h ambulatory mean blood pressure were made, the fasting insulin level was associated independently with an increase in UAE in a multiple regression model with base 10 logarithm of the UAE as the dependent variable. Variations in fasting insulin level alone accounted for 33% of the UAE variance. In contrast, the 24 h ambulatory mean blood pressure, rather than the insulin level, was the strongest predictor of the left ventricular mass index.

CONCLUSIONS

Mild hypertensive patients with microalbuminuria were hyperinsulinemic in the absence of obesity, and their insulin level was the main determinant of microalbuminuria in these patients. Microalbuminuria in essential hypertension seems to identify patients with a cluster of cardiovascular risk factors and a bad risk profile. Thus, assessment of microalbuminuria may be useful in the stratification of risk in essential hypertension.