Insulin Resistance and Endothelin: Another Pathway for Renal Injury in Patients With the Cardiometabolic Syndrome?

A Descriptive Review of the Action Mechanisms of Berberine, Quercetin and Silymarin on Insulin Resistance/Hyperinsulinemia and Cardiovascular Prevention

Insulin resistance (IR) and the associated hyperinsulinemia are early pathophysiological changes which, if not well treated, can lead to type 2 diabetes, endothelial dysfunction and cardiovascular disease. While diabetes care is fairly well standardized, the prevention and treatment of IR lacks a single pharmaceutical approach and many lifestyle and dietary interventions have been proposed, including a wide range of food supplements. Among the most interesting and well-known natural remedies, alkaloid berberine and the flavonol quercetin have particular relevance in the literature, while silymarin-the active principle of the Silybum marianum thistle-was traditionally used for lipid metabolism disorders and to sustain liver function. This review describes the major defects of insulin signaling leading to IR and the main properties of the three mentioned natural substances, their molecular targets and synergistic action mechanisms. The actions of berberine, quercetin and silymarin are partially superimposable as remedies against reactive oxygen intermediates generated by a high-lipid diet and by NADPH oxidase, which is triggered by phagocyte activation. Furthermore, these compounds inhibit the secretion of a battery of pro-inflammatory cytokines, modulate intestinal microbiota and are especially able to control the various disorders of the insulin receptor and post-receptor signaling systems. Although most of the evidence on the effects of berberine, quercetin and silymarin in modulating insulin resistance and preventing cardiovascular disease derive from experimental studies on animals, the amount of pre-clinical knowledge strongly suggests the need to investigate the therapeutic potential of these substances in human pathology.

An Update on the Current and Emerging Use of Thiazolidinediones for Type 2 Diabetes

Guidelines have increasingly stressed the concept that adequate glycemic control is required to prevent or decrease the macro- and microvascular complications of type 2 diabetes mellitus (T2DM). PPAR-gamma agonists (“glitazones”) are no longer prioritized due to their effects on heart failure. However, the association between these drugs and innovative therapies could be a valuable tool to attenuate the risk factors of the metabolic syndrome. Glitazones are used for the treatment of diabetes and associated comorbidities. There is substantial scientific evidence demonstrating the effect of glitazones at a cardiometabolic level, as well as on hematological and neurological pathologies that point to their usefulness. The use of glitazones has always been controversial both for the type of patients who must take these drugs and for the side effects associated with them. Unfortunately, the recent guidelines do not include them among the preferred drugs for the treatment of hyperglycemia and rosiglitazone is out of the market in many countries due to an adverse cardiovascular risk profile. Even though real-life studies have proven otherwise, and their pleiotropic effects have been highlighted, they have been unable to achieve primacy in the choice of antihyperglycemic drugs. It would be appropriate to demonstrate the usefulness of pioglitazone and its therapeutic benefit with further cardiovascular safety studies.

Proposal for standardizing normal insulin ranges in Brazilian patients and a new classification of metabolic syndrome

Background

Insulin resistance and/or hyperinsulinemia are closely linked to adiposity, metabolic syndrome (MetS) and prolonged inflammatory processes.

Methods

We retrospectively analyzed 1,018 adult individuals with a mean age of 46 years (74% male) and classified them as: Metabolically normal: without any of the five criteria of the International Diabetes Federation (IDF) used for the diagnosis of MetS, plus normal fasting insulin (Men < 8 mU/L, Women < 10 mU/L); Level 1 MetS: with one or two IDF criteria, plus hyperinsulinemia (Men: ≥ 8 mU/L), and Women: ≥ 10 mU/L); Level 2 MetS: with three or more IDF criteria, plus hyperinsulinemia.

Results

The mean values for fasting insulinemia in metabolically normal individuals was 4.6 ± 1.8 mU/L and 5.6 ± 2.3 mU/L, while their means for the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were 1.0 and 1.2 for men and women, respectively. In addition, the mean values for insulin (and HOMA-IR) for individuals with two normal anthropometric parameters (body mass index and waist girth), or two normal anthropometric parameters plus no IDF criteria, were similar to the metabolically normal group. Based on the obtained mean + 2 SD, we established the following insulin (and HOMA-IR) values as diagnostic cut-offs for hyperinsulinemia: Men: ≥ 8 mU/L (≥ 1.5), and Women: ≥ 10 mU/L (≥ 2.0). The mean serum insulin was significantly higher for individuals with Level 1 MetS (approx. 9 mU/L for both genders) compared with metabolically normal individuals, as was the prevalence of hepatic steatosis, which was more evident in men. Thus, the presence of one or two abnormal IDF criteria, combined with hyperinsulinemia and/or raised HOMA-IR, suggests the presence of MetS and insulin resistance. Patients of both genders with Level 2 MetS had higher serum insulin and/or HOMA-IR values than Level 1, as well as a higher prevalence of hypertension and hepatic steatosis, being more pronounced among men. The process was progressive and proportional to the degree of hyperinsulinemia.

Conclusion

It is proposed that intervention against MetS progression should be started in individuals with Level 1 MetS, rather than waiting for more criteria for diagnostic confirmation, which this should help to reduce the occurrence of known complications such as type 2 diabetes, atherosclerosis, hypertension, and chronic kidney disease, among others.

Metabolic Syndrome and Obesity-Related Indices Are Associated with Rapid Renal Function Decline in a Large Taiwanese Population Follow-Up Study

A rapid decline in renal function can cause many complications, and therefore it is important to detect associated risk factors. Few studies have evaluated the associations among obesity-related indices and metabolic syndrome (MetS) with renal function decline. This longitudinal study aimed to explore these relationships in a large cohort of Taiwanese participants. The studied obesity-related indices were waist-to-height ratio (WHtR), A body shape index (ABSI), visceral adiposity index (VAI), lipid accumulation product (LAP), waist-to-hip ratio (WHR), body roundness index (BRI), conicity index (CI), body mass index (BMI), body adiposity index (BAI) and abdominal volume index (AVI). We included 122,068 participants in the baseline study, of whom 27,033 were followed for a median of four years. The baseline prevalence of MetS was 17.7%. Multivariable analysis showed that the participants with MetS and high VAI, WHtR, WHR, LAP, CI, BRI, BMI, BAI, AVI, and ABSI values were significantly associated with a high baseline estimated glomerular filtration rate (eGFR) (all p < 0.001). In addition, the participants with MetS (p < 0.001), high WHtR (p = 0.007), low LAP (p < 0.001), high BRI (p = 0.002), high CI (p = 0.002), high AVI (p = 0.001), high VAI (p = 0.017), and high ABSI (p = 0.013) were significantly associated with a low △eGFR, indicating a rapid decline in renal function. These results showed associations between MetS and high values of obesity-related indices except LAP with high baseline eGFR and rapid decline in kidney function. These findings suggest that screening for MetS and obesity may help to slow the decline in renal function in high-risk populations.

Dapagliflozin Does Not Affect Short-Term Blood Pressure Variability in Patients With Type 2 Diabetes Mellitus

BACKGROUND

Increased blood pressure variability (BPV) is associated with increased cardiovascular and all-cause mortality in patients with type-2 diabetes mellitus (T2DM). Sodium-glucose co-transporter 2 (SGLT-2) inhibitors decrease the incidence of cardiovascular events, renal events, and death in this population. This study aimed to evaluate the effect of dapagliflozin on short-term BPV in patients with T2DM.

METHODS

This is a secondary analysis of a double-blind, randomized, placebo-controlled trial in 85 patients with T2DM. Subjects were randomized to dapagliflozin 10 mg/day or placebo for 12 weeks. All participants underwent 24-hour ambulatory blood pressure (BP) monitoring with Mobil-O-Graph-NG device at baseline and study-end. SD, weighted SD (wSD), coefficient of variation, average real variability (ARV), and variation independent of mean were calculated for the 24-hour, daytime and nighttime periods.

RESULTS

Dapagliflozin reduced 24-hour brachial BP compared with placebo. From baseline to study-end 24-hour brachial BPV indexes did not change with dapagliflozin (SBP-ARV: 11.51 ± 3.45 vs. 11.05 ± 3.35; P = 0.326, SBP-wSD: 13.59 ± 3.60 vs. 13.48 ± 3.33; P = 0.811) or placebo (SBP-ARV: 11.47 ± 3.63 vs. 11.05 ± 3.00; P = 0.388, SBP-wSD: 13.85 ± 4.38 vs. 13.97 ± 3.87; P = 0.308). Similarly, no significant changes in BPV indexes for daytime and nighttime were observed in any group. At study-end, no between-group differences were observed for any BPV index. Deltas (Δ) of all indexes during follow-up were minimal and not different between groups (SBP-wSD: dapagliflozin: -0.11 ± 3.05 vs. placebo: 0.12 ± 4.20; P = 0.227).

CONCLUSIONS

This study is the first to evaluate the effects of an SGLT-2 inhibitor on short-term BPV in T2DM, showing no effect of dapagliflozin on all BPV indexes studied.

CLINICAL TRIALS REGISTRATION

Trial Number NCT02887677.

Comparative Efficacy of Lobeglitazone Versus Pioglitazone on Albuminuria in Patients with Type 2 Diabetes Mellitus

INTRODUCTION

The aim of this analysis was to evaluate the efficacy of lobeglitazone on albuminuria at 24 weeks of follow-up in patients with type 2 diabetes mellitus (T2DM) compared with pioglitazone using data from a randomized, double-blinded phase III trial.

METHODS

In the phase III trial, patients who were inadequately controlled with metformin received 0.5 mg of lobeglitazone or 15 mg of pioglitazone for 24 weeks. Post hoc, exploratory analysis was used to investigate mean changes from baseline in the urine albumin-creatinine ratio (UACR) between the lobeglitazone (N = 104) and pioglitazone (N = 101) treatment groups.

RESULTS

After 24 weeks of treatment, UACR was slightly decreased in the lobeglitazone group (- 4.3 mg/g creatinine [Cr]) compared to baseline and slightly increased in the pioglitazone group (5.2 mg/g Cr), with no change in the estimated glomerular filtration rate in either group; this difference was not statistically significant (P = 0.476). The incidence of new-onset microalbuminuria (2.4%) and the progression of albuminuria by > 1 stage (2.9%) in the lobeglitazone group were lower than the respective values in the pioglitazone group (6.8 and 6.1%, respectively). Of the patients in the lobeglitazone group, 50% exhibited regression to normoalbuminuria, compared to 39.3% of the patients in the pioglitazone. In subjects in the lobeglitazone group with micro- and macroalbuminuria, UACR tended to be more decreased and HbA1c was more reduced compared to those with normoalbuminuria (P = 0.014).

CONCLUSION

Lobeglitazone had a tendency to improve albuminuria in patients with T2DM and had comparable effects on albuminuria as pioglitazone which has demonstrated beneficial effects.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT01106131.

Dapagliflozin decreases ambulatory central blood pressure and pulse wave velocity in patients with type 2 diabetes: a randomized, double-blind, placebo-controlled clinical trial

OBJECTIVES

Sodium-glucose co-transporter 2 (SGLT-2) inhibitors reduce the incidence of heart failure and death in patients with type-2 diabetes mellitus. Arterial stiffness is a prominent risk factor for heart failure and overall mortality. The aim of this study was to evaluate the effects of dapagliflozin on ambulatory brachial and central blood pressure (BP) levels and arterial stiffness parameters in patients with type-2 diabetes mellitus.

METHODS

This is a double-blind, randomized, placebo-controlled clinical trial including 85 adult patients with type-2 diabetes mellitus on monotherapy or combination therapy with two of: metformin, sulphonylurea, DPP-4 inhibitor, or insulin. Patients were randomized in a 1 : 1 ratio to oral dapagliflozin 10 mg per day or placebo for 12 weeks. Study participants underwent 24-h ambulatory BP monitoring with the Mobil-O-Graph NG monitor at baseline and study-end.

RESULTS

Baseline demographic, clinical and laboratory parameters were similar in the two groups. During follow-up, 24-h brachial SBP/DBP (129.0 ± 12.6/77.3 ± 7.3 vs. 123.2 ± 12.4/75.1 ± 6.4 mmHg; P < 0.001/P = 0.008) and central SBP/DBP (117.4 ± 10.5/78.9 ± 7.3 vs. 113.3 ± 8.8/77.3 ± 6.5 mmHg; P = 0.002/P = 0.047) significantly decreased in dapagliflozin but not in the placebo group. Corresponding reductions of 24-h brachial SBP (-5.8 ± 9.5 vs. -0.1 ± 8.7, P = 0.005) and central SBP (-4.1 ± 8.0 vs. -0.7 ± 7.8; P = 0.046) were greater with dapagliflozin than placebo. Twenty-four-hour heart-rate adjusted augmentation index significantly decreased with dapagliflozin and insignificantly with placebo. Importantly, there was a significant difference in change of estimated 24-h PWV (-0.16 ± 0.32 vs. 0.02 ± 0.27; P = 0.007) favoring dapagliflozin. In generalized linear mixed models including 24-h brachial SBP as a random covariate, the adjusted marginal means of delta 24-h central SBP and delta 24-h PWV were not significantly different between-groups.

CONCLUSION

Treatment with dapagliflozin significantly reduces ambulatory brachial and central BP levels and PWV in patients with type-2 diabetes mellitus. Improvement in these parameters may substantially contribute to the cardiovascular benefits of SGLT-2 inhibitors.

Pioglitazone for the Primary and Secondary Prevention of Cardiovascular and Renal Outcomes in Patients with or at High Risk of Type 2 Diabetes Mellitus: A Meta-Analysis

CONTEXT

The goal of the meta-analysis was to evaluate the effect of pioglitazone on the primary and secondary prevention of cardiovascular diseases (CVDs) and renal adverse events in patients with or at high risk of type 2 diabetes mellitus (T2DM).

DESIGN

Randomized controlled trials (RCTs) comparing pioglitazone with any control were identified through PubMed, Embase, and the Cochrane Library. Cardiovascular outcomes included major adverse cardiovascular events (MACEs, defined as the composite of nonfatal myocardial infarction, nonfatal stroke, and cardiovascular death), hospitalization for heart failure, and all-cause mortality. Renal outcomes included change in urinary albumin to creatinine ratio and 24-hour urinary protein excretion. Weighted mean difference (WMD) and risk ratio (RR) with 95% confidence intervals (CIs) were pooled.

RESULTS

A total of 26 studies with 19 645 participants were enrolled. Pioglitazone reduced the risk of MACE (RR, 0.8 [95% CI, 0.7-0.9]), with benefit only seen in patients with a history of established CVDs (0.8 [0.7-0.9]) and not in those without (1.0 [0.7-1.3]). Regarding the individual components, pioglitazone reduced the risk of nonfatal myocardial infarction (0.8 [0.6-1.0]) and nonfatal stroke (0.8 [0.7-0.9]), which was confined to patients with a history of established CVDs, whereas no treatment effect was found on cardiovascular death (1.0 [0.7-1.2]) regardless of the presence of established CVDs. Pioglitazone increased the risk of hospitalization for heart failure (1.3 [1.1-1.6]) and had no treatment effect on all-cause mortality (1.0 [0.8-1.1]). Pioglitazone reduced albuminuria by 18.5% (WMD 18.5% [95% CI, 21.1-16.0]), with a similar benefit in patients with different renal function categories.

CONCLUSIONS

Pioglitazone should be considered in patients with or at high risk of T2DM for the prevention of cardiovascular endpoints, especially in those with a history of established CVD who might benefit the most. Robust reductions in progression of renal disease are seen regardless of baseline renal function degree.

Long-term Body Weight Gain After Maturity is Associated With the Incidence of Chronic Kidney Disease (CKD), Independent of Current Body Weight, in Middle-aged and Older Men

BACKGROUND

This study investigated the relationship between long-term body weight gain after maturity and the incidence of chronic kidney disease (CKD).

METHODS

The participants were 303 men without a history of cardiovascular and cerebrovascular diseases, kidney dysfunction, or dialysis treatment. Their body weight gain after maturity was examined using a standardized self-administered questionnaire. The participants were divided into two groups based on the presence/absence of a body weight gain of ≥10 kg since 20 years of age.

RESULTS

After a 6-year follow-up, the cumulative incidence of CKD was significantly higher in participants with a body weight gain of ≥10 kg than in participants without body weight a body weight gain of ≥10 kg since 20 years of age (log-rank test: P = 0.041). After adjusting for the age, body mass index, estimated glomerular filtration rate levels, smoking and drinking habits, and the presence of hypertension, dyslipidemia, and hyperglycemia at baseline, the normal body weight participants with a body weight gain of ≥10 kg since 20 years of age was significantly related to the incidence of CKD (hazard ratio 2.47; 95% confidence of interval, 1.02-6.01, P = 0.045).

CONCLUSIONS

These results suggest that long-term body weight gain after maturity in normal body weight participants may be associated with the incidence of CKD, independent of current body weight.

An association of metabolic syndrome and chronic kidney disease from a 10-year prospective cohort study

OBJECTIVE

Although metabolic abnormalities have been considered important risk factors of chronic kidney disease (CKD), the impact of metabolic syndrome (MS) and insulin resistance on renal function deterioration is poorly understood. We investigated the association between MS and incident CKD/rapid decline of estimated glomerular filtration rate (eGFR) in a 10-year population-based longitudinal study.

MATERIAL AND METHODS

Among 10,030 subjects, 6065 without history of CKD or cardiovascular disease at baseline were analyzed using data generated from the Ansan-Ansung cohort of the Korean Genome Epidemiology Study. Participants were categorized into two groups based on the presence of MS at baseline. Incident CKD was defined as eGFR <60ml/min per 1.73m², and rapid decline of eGFR was defined as >3ml/min per 1.73m²/yr over 10years.

RESULTS

During the 10-year follow-up period, CKD developed in 893 subjects (14.7%). Compared to subjects without MS, the odds ratio (OR; 95% confidence interval, CI) of incident CKD in those with MS was 1.38 (1.16-1.64) after controlling for confounding factors. The risk of rapid decline of eGFR was also higher in subjects with MS than those without MS (OR: 1.20, 95% CI: 1.04-1.39). In addition, we found that higher levels of homeostatic model assessment of insulin resistance (HOMA-IR) were associated with incident CKD and rapid decline of eGFR independently of traditional CKD risk factors (OR: 1.24, 95% CI: 1.04-1.47).

CONCLUSION

Both MS and insulin resistance were independent risk factors of incident CKD and rapid decline of eGFR in healthy Korean population.

Prevalence of Chronic Kidney Disease in Turkish Adults With Obesity and Metabolic Syndrome: A Post Hoc Analysis from Chronic Renal Disease in Turkey Study

BACKGROUND

Obesity confers an increased risk of chronic kidney disease (CKD), which is increased further by accompanying metabolic abnormalities.

OBJECTIVE

To investigate the relationship of the risk of CKD with obesity and metabolic syndrome (MS) in adults by means of post hoc analysis of data from the Chronic Renal Disease in Turkey (CREDIT) study.

METHODS

The anthropometric measurements of a total of 9,100 adult participants in the CREDIT study were included in the analyses. Subjects were classified according to the presence or absence of obesity (body mass index [BMI] > 30) and MS. Logistic regression analyses were used to estimate odds ratio for CKD. Effect modification analyses were also performed.

RESULTS

The prevalence of obesity was 20.6% and that of MS was 31.3%. The prevalence of CKD was higher among obese subjects compared to those with a normal BMI (20.5% vs. 14%; P < .001). The odds ratio (OR) for CKD was 1.296 (95% confidence interval [CI], 1.121-1.498) for subjects who were overweight, 1.718 (95% CI, 1.444-2.044) for those with class I obesity, 1.983 (95% CI, 1.489-2.641) for those with class II obesity and 2.799 (95% CI, 1.719-4.557) for subjects with extreme obesity (P < .001 for each subgroup) compared to subjects with a normal BMI. CKD was significantly more prevalent in subjects with MS (21.9% vs. 12.3%, P < .001). The OR for CKD was higher in obese subjects with MS (adjusted OR, 1.321; 95% CI, 1.109-1.573; P = .002).

CONCLUSION

The stratification of obese individuals based on their metabolic phenotype is important for prevention and treatment of CKD.

Association of cardiac NT pro-β-type natriuretic peptide with metabolic and endothelial risk factors in young obese hypertensive patients: a perspective on the hypothalamic pituitary adrenal axis activation

BACKGROUND

In practice, there is increasing recognition of the importance of hypothalamic pituitary adrenal axis in the cardiovascular disease progression. The association of brain natriuretic peptide with obesity and characteristics of the metabolic syndrome in adults and aged patients is well established, but that in pediatrics needs thorough elucidation.

AIM

The aim of this study was to assess the association of hypothalamic pituitary adrenal axis mediators (cortisol and aldosterone) with plasma NT-pro β-type natriuretic peptide (NT-proBNP) levels on metabolic, immune-inflammatory and endothelial markers in young obese pediatric patients.

METHODS

This is achieved by recruitment of 60 young (13-17 years) obese pediatric cohorts who are further subclassified according to their stage of hypertension; normotensive, prehypertensive and hypertensive patients.

RESULTS

The study showed significant differences in the metabolic parameters (glucose, insulin and HOMA-index) among the three obese young patient groups. Levels of cortisol and aldosterone, as well as NT-proBNP levels are positively associated with characteristics of the metabolic syndrome; blood pressure, BMI, HOMA index in all three obese groups. However, their association to the lipid profile was insignificant. These increases aligned harmonically with the assessed immune-inflammatory markers; CRP, TNF-α, and IL-23, as well as levels of sICAM, sVCAM and p-selectin, reflecting the involvement of mast cells and inflammatory effects on the vascular endothelium. ROC analysis revealed their beneficial addition as promising biomarkers for a better prognostic profile of hypertension-induced cardiovascular risk.

CONCLUSION

Early detection of NT-proBNP, cortisol and aldosterone levels in pre-hypertension stage added to the immune-inflammatory mediators may improve the coronary risk assessment in young Egyptian patients.

Chronic kidney disease among overweight and obesity with and without metabolic syndrome in an urban Chinese cohort

BACKGROUND

It is widely accepted that metabolic syndrome is associated with an increased risk of chronic kidney disease (CKD). To investigate whether coexisting metabolic syndrome is a necessary condition for CKD in overweight and obese.

METHODS

A cohort study of 6852 Chinese individuals from August 2007 to December 2012. Examinations included a questionnaire, physical measurements, and blood sampling. Hazard ratios for incident CKD were estimated according to combinations of BMI category and absence or presence of metabolic syndrome.

RESULTS

For CKD, multivariable adjusted hazard ratios vs. normal weight individuals without metabolic syndrome were 1.31 (95% CI, 0.89-1.92) in overweight and 2.39 (95% CI, 1.27-4.52) in obese without metabolic syndrome and 1.54 (95% CI, 1.18-3.95) in normal weight, 2.06 (95% CI, 1.27-3.36) in overweight, and 2.77 (95% CI, 1.42-4.31) in obese with metabolic syndrome. There were no interactions between BMI and absence or presence of metabolic syndrome on risk of CKD when BMI was categorized (normal weight, overweight, obese) (P = 0.17). Among individuals both with and without metabolic syndrome there were increasing cumulative incidences of CKD from normal weight through overweight to obese individuals (log-rank trend P = 0.04 to P < 0.001). Although the multivariable adjusted hazard ratio for CKD in individuals with vs. without metabolic syndrome was 1.82 (95% CI, 1.20-2.78) within overweight and obese individuals (log-rank P = 0.005), only 26.1% of the increased risk observed for BMI is explained by metabolic syndrome.

CONCLUSIONS

These findings suggest overweight and obesity are risk factors for CKD regardless of the presence or absence of metabolic syndrome.

Longitudinal relationships of metabolic syndrome and obesity with kidney function: Healthy Twin Study

BACKGROUND

To examine cross-sectional and longitudinal relationships, including genetic and environmental correlations, of metabolic syndrome (MetS) and obesity with kidney function.

METHODS

Subjects were 3,437 Korean adults of the Healthy Twin Study for cross-sectional relationships and 1,881 participants for longitudinal relationships (follow-up interval 3.7 ± 1.4 years). Obesity (body mass index ≥ 25 vs. <25 kg/m(2)), MetS, and chronic kidney disease [CKD; estimated glomerular filtration rate (eGFR) (<60 mL/min/1.73 m(2) using the modification of diet in renal disease study equation)] were categorized at baseline and follow-up.

RESULTS

The prevalence and incidence of chronic kidney disease were 2.5 and 3.3 %, respectively. Compared to individuals without obesity and MetS, prevalent CKD was associated with MetS regardless of weight status [adjusted odds ratio (AOR) 4.19 for those with MetS but without obesity; AOR 4.63 for those with MetS and obesity]. Incident CKD was associated with obesity regardless of baseline metabolic status (AOR 2.03 for those with obesity but without MetS; AOR 2.85 for those with obesity and MetS). MetS at follow-up was associated with incident CKD regardless of baseline MetS (AOR 2.42-2.52). Sex-adjusted bivariate analyses show inverse environmental correlations of the number of MetS components and BMI at baseline, with eGFR at baseline and follow-up (ρ E, -0.26 to -0.42, P < 0.001).

CONCLUSIONS

MetS predicts prevalent CKD regardless of obesity, and obesity predicts incident CKD regardless of baseline MetS. Incident CKD is also associated with MetS at follow-up regardless of baseline MetS. These associations appear to be explained by shared environmental factors.

PPAR-γ agonism for cardiovascular and renal protection

Diabetes mellitus is an established risk factor for cardiovascular disease and the leading cause of end-stage renal disease in the Western World. Thiazolidinediones (TZDs) represent a class of antidiabetic agents that exert their glucose-lowering effects by reducing insulin resistance, through stimulation of a type of nuclear receptor, called peroxisome proliferator-activated receptor-γ. Apart from improving glycemic control, TZDs were shown to exert beneficial effects on several components of the metabolic syndrome and cardiovascular risk markers. Furthermore, background and human studies have shown that TZDs reduce urinary albumin and protein excretion and interfere with most of the pathogenentic pathways involved in the development and progression of diabetic nephropathy. On the other hand, currently used TZDs have side effects, most important of which is fluid retention leading to wait gain and heart failure deterioration. With regards to cardiovascular outcomes, the anticipated benefit of TZDs was demonstrated for pioglitazone, whereas a series of previous meta-analyses linking rosiglitazone treatment with increased risk of myocardial infarction and cardiovascular death raised uncertainty around the cardiovascular safety of rosiglitazone. This article will discuss the effects of TZDs on established and emerging cardiovascular risk factors, the data on possible beneficial renal effects of these compounds, and the existing evidence from large-scale clinical trials and meta-analyses on their effects on cardiovascular outcomes, aiming to provide an overview of the cardio- and renoprotective properties of these drugs.

Endothelin, hypertension and chronic kidney disease: new insights

PURPOSE OF REVIEW

Endothelin is important in the development of cardiorenal disease. This review discusses recent developments in understanding endothelin's role in hypertension and chronic kidney disease (CKD).

RECENT FINDINGS

Endothelin-1 production is increased in hypertension and CKD. Endothelin-1 stimulates vasoconstriction, inflammation and fibrosis, thereby promoting hypertension, atherosclerosis and CKD. These effects are closely linked to angiotensin II and reactive oxygen species. In preclinical studies, endothelin receptor antagonists were effective in treating hypertension (particularly with endothelial dysfunction) and CKD. In preclinical studies, endothelin A-selective, as opposed to combined endothelin A and B, receptor blockers have generally been more efficacious. Few clinical trials have been conducted in hypertension and/or kidney disease, partly due to concerns over side effects of testicular toxicity and fluid retention. Endothelin blockade reduces blood pressure in patients with resistant hypertension, with additional beneficial metabolic effects. Endothelin antagonism improves proteinuria in CKD (diabetic or not), particularly in patients taking inhibitors of angiotensin II action.

SUMMARY

Endothelin is a promising target in the treatment of resistant hypertension and CKD, with additional potential benefits on atherosclerosis and the metabolic syndrome. The nature and mechanisms of drug side effects require elucidation before the potential of this new class of drugs can be fully realized.

Effect of thiazolidinediones on albuminuria and proteinuria in diabetes: a meta-analysis

BACKGROUND

Because of the major clinical and economic burden of diabetic nephropathy, new therapeutic tools to delay its progression are needed. Recent studies suggest that thiazolidinediones have renal benefits. We aimed to evaluate the effect of thiazolidinediones on urinary albumin and protein excretion in patients with diabetes mellitus.

STUDY DESIGN

Systematic review and meta-analysis by searching MEDLINE/PubMed, EMBASE, and Cochrane CENTRAL databases (1991 to September 2009).

SETTING & POPULATION

Patients with diabetes mellitus.

SELECTION CRITERIA FOR STUDIES

Randomized controlled trials.

INTERVENTION

Thiazolidinediones (rosiglitazone and pioglitazone) compared with placebo or other antidiabetic agents.

OUTCOMES

Weighted (WMDs) and standardized mean differences (SMDs) for changes in urine albumin or protein excretion between the thiazolidinedione and control groups.

RESULTS

Of 171 originally identified articles, 15 studies (5 with rosiglitazone and 10 with pioglitazone) involving 2,860 patients were included in the analysis. In participants with baseline normo- or microalbuminuria, the WMD of proportional changes between the thiazolidinedione and control groups in urinary albumin excretion measured using time-specified collections was -64.8% (95% CI, -75.6 to -53.9) and the WMD of changes in albumin-creatinine ratio was -24.8% (95% CI, -39.6 to -10.0). Overall, in participants with normo- and microalbuminuria, thiazolidinedione treatment was associated with a significant decrease in urinary albumin excretion (SMD, -0.6 units of standard deviation [SD]; 95% CI, -0.8 to -0.4). Similarly, thiazolidinediones were associated with a significant decrease in urinary protein excretion in patients with proteinuria (SMD, -1.1 units of SD; 95% CI, -1.8 to -0.4).

LIMITATIONS

Significant heterogeneity across included studies in several subgroup analyses; patient-level data not available.

CONCLUSIONS

Treatment with thiazolidinediones significantly decreases urinary albumin and protein excretion in patients with diabetes. This finding calls for clinical trials with hard renal outcomes to elucidate the potential benefits of thiazolidinediones on diabetic nephropathy.

Clinical review: The pathogenetic role of cortisol in the metabolic syndrome: a hypothesis

CONTEXT

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities that increase the risk for type 2 diabetes mellitus and vascular disease. The common characteristics of MetS and hypercortisolemic conditions such as Cushing's syndrome (CS) suggest that the pathogenesis of MetS and central obesity might involve prolonged and excessive exposure to glucocorticoids. The present review summarizes the evidence on the potential role of cortisol in the pathogenesis of MetS and discusses new therapeutic approaches for these patients.

EVIDENCE ACQUISITION

Using PubMed, we searched for publications during the last 20 yr regarding the possible pathogenetic role of cortisol in the development of MetS.

EVIDENCE SYNTHESIS

Emerging data suggest that patients with MetS show hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a state of "functional hypercortisolism." The cause for this activation of the HPA axis remains uncertain but may be partly associated with chronic stress and/or low birth weight, which are both associated with increased circulating cortisol levels and greater responsiveness of the HPA axis. Increased exposure to cortisol contributes to increased fat accumulation in visceral depots. However, cortisol metabolism is not only centrally regulated. The action of 11beta-hydroxysteroid dehydrogenase-1 at the tissue level also modulates cortisol metabolism. Increased 11beta-hydroxysteroid dehydrogenase-1 activity in adipose tissue and liver might contribute to the development of several features of the MetS.

CONCLUSIONS

MetS shares many characteristics of CS, and cortisol might play a role in the development of MetS at both a central and a peripheral level.