Caveolin 1 Modulates Aldosterone-Mediated Pathways of Glucose and Lipid Homeostasis

Increased Salt Sensitive Blood Pressure in Women Versus men: Is Relative Hyperaldosteronism the Mechanism?

CONTEXT

Women versus men have more Salt sensitive blood pressure (SSBP) and higher stimulated aldosterone (ALDO) levels, suggesting that their increased SSBP is secondary to a relative hyper-ALDO state. Contrariwise, men versus women have higher sedentary ALDO levels.

OBJECTIVE

Thus, the present project was designed to address the question are women versus men in a relatively hyper-ALDO state?

METHODS

363 women, and 483 men were selected from HyperPATH cohort to assess the potential underlying mechanism for observed sex differences.

RESULTS

Women had greater SSBP, greater ALDO and vasculature response to Ang II, and higher upright ALDO/plasma renin activity, but men on both restricted and liberal salt diets had higher basal levels of supine ALDO, PRA levels, and other ALDO secretagogues. Using 24-hour urine ALDOs to assess overall production, ALDO did not differ by sex regardless of salt intake, except when assessed in subsets. Normotensive women vs men had greater urine ALDO, and women vs men younger than 51 had higher urine ALDO.

CONCLUSION

1) Lower Ang II responsiveness in Ang II targeted organs was observed in men vs women. 2) Similar 24-hour urine ALDO levels in women and men do not support the concept that relative hyper-ALDO is the mechanism for sex difference in SSBP.The data also suggest that the SSBP in women, in some cases, may be benign since it is secondary to a BP reduction on the restricted salt diet not an increase on the liberal salt diet.

Understanding Diabetic Cardiomyopathy: Insulin Resistance and Beyond

Background: Diabetic cardiomyopathy (DC) is a syndrome of heart failure occurring in patients with diabetes mellitus (DM), independent of other risk factors. It is a relatively underdiagnosed condition with a prolonged subclinical phase. There is an abundance of studies put forward to explain the underlying pathogenic mechanisms observed in this condition. This review aims to summarize the evidence available in contemporary medical literature with regard to the molecular mechanisms, abnormalities in signalling and metabolism and structural and functional abnormalities manifesting as DC. Methods: We conducted a literature search using the terms 'diabetic cardiomyopathy', 'heart failure AND Diabetes mellitus', 'Cardiomyopathy AND Diabetes mellitus'. We searched the reference lists of included studies and relevant systematic reviews. Results: In this review, we elucidate all the mechanisms that have been postulated to have a role in the pathogenesis of DC, in addition to insulin resistance, such as inflammation, renin-angiotensin-aldosterone system activation and deranged protein homeostasis. Conclusions: DC is an underrecognized cardiac complication of DM. A comprehensive knowledge of all the pathways and mediators will aid in the development of diagnostic and prognostic markers, screening protocols and novel management strategies.

Involvement of a battery of investigated genes in lipid droplet pathophysiology and associated comorbidities

Lipid droplets (LDs) are highly specialized energy storage organelles involved in the maintenance of lipid homoeostasis by regulating lipid flux within white adipose tissue (WAT). The physiological function of adipocytes and LDs can be compromised by mutations in several genes, leading to NEFA-induced lipotoxicity, which ultimately manifests as metabolic complications, predominantly in the form of dyslipidemia, ectopic fat accumulation, and insulin resistance. In this review, we delineate the effects of mutations and deficiencies in genes - CIDEC, PPARG, BSCL2, AGPAT2, PLIN1, LIPE, LMNA, CAV1, CEACAM1, and INSR - involved in lipid droplet metabolism and their associated pathophysiological impairments, highlighting their roles in the development of lipodystrophies and metabolic dysfunction.

A prevalent caveolin-1 gene rs926198 variant is associated with type 2 diabetes mellitus in the Thai population

This study investigated the associations between CAV1 variants and metabolic syndrome (MetS), type 2 diabetes mellitus (T2DM), and cardiometabolic risk factors, as well as the influence of CAV1 variants on CAV1 mRNA expression. We genotyped 743 T2DM patients for CAV1 variants. Multiple logistic regression was conducted to adjust for sex, age, and body mass index (BMI), and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. The expression of mRNA was measured by reverse transcription polymerase chain reaction. The rs926198 variant, but not the rs3807989 variant, was associated with T2DM. Crude ORs were 1.87 (95% CI: 1.32-2.69, p = 0.0005) and adjusted ORs were 1.81 (95% CI: 1.12-2.96, p = 0.016), respectively. Additionally, patients with Mets and T2DM who had the rs926198 variant exhibited a significant 44.3% reduction in CAV1 mRNA expression (P < 0.05). Clinical samples revealed that the rs926198 variant is strongly linked to T2DM, with significantly reduced CAV1 mRNA. Our findings suggest a crucial role for the rs926198 variant in T2DM, indicating its potential for prevention, diagnosis, and intervention purposes.

Dietary Insulin Index (DII) and Dietary Insulin load (DIL) and Caveolin gene variant interaction on cardiometabolic risk factors among overweight and obese women: a cross-sectional study

BACKGROUND AND OBJECTIVE

Studies have shown that Caveolin gene polymorphisms (CAV-1) are involved in chronic diseases, such as metabolic syndrome. Moreover, the dietary insulin index (DII) and dietary insulin load (DIL) have been shown to potentially elicit favorable effects on cardiovascular disease (CVD) risk. Therefore, this study sought to investigate the effect of DII DIL and CAV-1 interaction on CVD risk factors.

METHODS

This cross-sectional study consisted of 333 overweight and obese women aged 18-48 years. Dietary intakes, DII, and DIL were evaluated using the 147-item food frequency questionnaire (FFQ). Serum profiles were measured by standard protocols. The CAV-1 rs 3,807,992 and anthropometric data were measured by the PCR-RFLP method and bioelectrical impedance analysis (BIA), respectively. Participants were also divided into three groups based on DII, DIL score, and rs3807992 genotype.

RESULTS

This comparative cross-sectional study was conducted on 333 women classified as overweight or obese. Participants with A allele for the caveolin genotype and higher DII score showed significant interactions with high-density lipoprotein (HDL) (P for AA = 0.006 and P for AG = 0.019) and CRI-I (P for AA < 0.001 and P for AG = 0.024). In participants with AA genotype and greater DII score, interactions were observed in weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, CRI-II, fat-free mass (FFM), and skeletal muscle mass (SMM) (P < 0.079). Those with higher DIL scores and AA genotype had higher weight (P = 0.033), FFM (P = 0.022), and SMM (P = 0.024). In addition, DIL interactions for waist/hip ratio (WHR), waist circumference (WC), triglyceride (TG), CRI-I, and body fat mass (BFM) among individuals with AA genotype, while an HDL interaction was observed in individuals with AG and AA (P < 0.066).

CONCLUSION

The findings of the present study indicate that people who carry the caveolin rs3807992 (A) allele and have greater DII and DIL scores are at higher risk for several cardiovascular disease and metabolic syndrome biomarkers. These results highlight that diet, gene variants, and their interaction, should be considered in the risk evaluation of developing CVD.

Caveolin-1 protein expression as a prognostic biomarker of gastrointestinal tumours: A systematic review and meta-analysis

BACKGROUND

Gastrointestinal (GI) cancers remain a major threat worldwide, accounting for over 30% of cancer deaths. The identification of novel prognostic biomarkers remains a challenge despite significant advances in the field. The CAV1 gene, encoding the caveolin-1 protein, remains enigmatic in cancer and carcinogenesis, as it has been proposed to act as both a tumour promoter and a tumour suppressor.

METHODS

To analyse the differential role of caveolin-1 expression in both tumour cells and stroma in relation to prognosis in GI tumours, we performed a systematic review and meta-analysis according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines; PROSPERO registration number: CRD42022299148.

RESULTS

Our analysis showed that high levels of caveolin-1 in tumour cells were associated with poor prognosis and inferior overall survival (OS) in oesophageal and pancreatic cancer and hepatocellular carcinoma (HCC), but not in gastric and colorectal cancer. Importantly, our study showed that higher stromal caveolin-1 expression was associated with significantly longer OS and disease-free survival in colorectal cancer. Analysis of stromal caveolin-1 expression in the remaining tumours showed a similar trend, although it did not reach statistical significance.

CONCLUSIONS

The data suggest that caveolin-1 expression in the tumour cells of oesophageal, pancreatic cancer and HCC and in the stroma of colorectal cancer may be an important novel predictive biomarker for the clinical management of these diseases in a curative setting. However, the main conclusion of our analysis is that caveolin-1 expression should always be assessed separately in stroma and tumour cells.

A study to investigate genetic factors associated with weight gain in people with diabetes: analysis of polymorphisms in four relevant genes

BACKGROUND

Weight change is often seen in people with diabetes. We investigated the effects of genes associated with weight change/glucose handling/insulin-signalling.

MATERIALS/METHODS

DNA from diabetes individuals and non-diabetes individuals, plus clinical data, were available from the DARE study (n = 379 individuals: T1D n = 111; T2D n = 222; controls n = 46). Weight gain was assessed by temporal change of Body Mass Index (BMI). Genotyping was performed for CAV1rs926198, LEPRrs1137101, BDNFrs6265 and FTOrs9939609.

RESULTS

No differences in genotype distributions were observed for the four SNPs in all groups un-stratified by weight gain. Following stratification differences in genotype distribution were observed. For those BMI relatively stable; controls showed a difference in genotype distributions versus T1D (CAV1rs926198, LEPRrs1137101). In T2D vs controls, significant differences were observed in genotype distribution for all four genes. For BMI increase, the only difference by category was LEPRrs1137101 (bothT1D/T2D vs controls). In BMI-stable groups, CAV1rs926198, T1D individuals showed lower T allele frequency (p=0.004) vs non-diabetes and for LEPRrs1137101 a higher G allele frequency versus controls (p=0.002). For T2D, CAV1rs926198, T allele frequency was lower in T2D than controls (p=0.005). For LEPR rs1137101, the G allele frequency was higher than in controls (p=0.004). In those with BMI increase, LEPRrs1137101 T1D individuals had higher G allele frequency versus controls (p=0.002) as did T2D vs controls (p=0.03).

CONCLUSION

Differences in allele frequency were seen between diabetes individuals and non-diabetes diagnosed at baseline in relation to the likelihood of BMI increase of >10%. It is established that the G allele of LEPRrs1137101 is associated with weight gain/obesity. However, this is the first report of CAV1rs926198 polymorphism being associated with weight stability/gain in diabetes.

Caveolin-1 rs1997623 variant and adult metabolic syndrome—Assessing the association in three ethnic cohorts of Arabs, South Asians and South East Asians

Background: Animal and cell model studies have implicated CAV1 in the pathophysiology of metabolic disorders. Our previous studies demonstrated a potential association of CAV1 rs1997623 C/A variant with pediatric metabolic syndrome (MetS) in Arab children. In the present study, we evaluate whether the CAV1 variant associates with MetS Arab adults as well. The association signal is further examined for ancestry-specific variation by considering cohorts of other ethnicities.

Method: The CAV1 rs1997623 was genotyped in three cohorts of Arab (n = 479), South Asian (n = 660), and South East Asian (n = 362) ethnic adults from Kuwait. MetS status of the individuals was diagnosed using the IDF criteria (presence of central obesity and at least two abnormalities out of: elevated TG, low HDL, hypertension, or T2D). The quantitative measure of MetS was calculated as siMS = 2 × WC/Height + FBG/5.6 + TG/1.7 + SBP/130–HDL/1.02 for males or HDL/1.28 for females. Allelic associations with quantitative and dichotomous MetS traits were assessed using linear and logistic regression models adjusted for age and sex. In addition, empirical p-values (P_emp) were generated using max(T) permutation procedure based on 10,000 permutations.

Results: The CAV1 variant was significantly associated with MetS status (OR = 1.811 [1.25–2.61]; p-value = 0.0015; P_emp = 0.0013) and with siMS (Effect size = 0.206; p-value = 0.0035; P_emp = 0.0028) in the cohort of Arab individuals. The association was weak and insignificant in the South Asian and South East Asian cohorts (OR = 1.19 and 1.11; p-values = 0.25 and 0.67, respectively).

Conclusion: The reported association of CAV1 rs1997623 C/A with MetS in Arab pediatric population is now demonstrated in an adult Arab cohort as well. The weak association signal seen in the Asian cohorts lead us to propose a certain extent of ethnic-specificity in CAV1 rs1997623 association with MetS.

Unraveling and Targeting Myocardial Regeneration Deficit in Diabetes

Cardiomyopathy is a common complication in diabetic patients. Ventricular dysfunction without coronary atherosclerosis and hypertension is driven by hyperglycemia, hyperinsulinemia and impaired insulin signaling. Cardiomyocyte death, hypertrophy, fibrosis, and cell signaling defects underlie cardiomyopathy. Notably, detrimental effects of the diabetic milieu are not limited to cardiomyocytes and vascular cells. The diabetic heart acquires a senescent phenotype and also suffers from altered cellular homeostasis and the insufficient replacement of dying cells. Chronic inflammation, oxidative stress, and metabolic dysregulation damage the population of endogenous cardiac stem cells, which contribute to myocardial cell turnover and repair after injury. Therefore, deficient myocardial repair and the progressive senescence and dysfunction of stem cells in the diabetic heart can represent potential therapeutic targets. While our knowledge of the effects of diabetes on stem cells is growing, several strategies to preserve, activate or restore cardiac stem cell compartments await to be tested in diabetic cardiomyopathy.

Caveolin-1 Regulates Cellular Metabolism: A Potential Therapeutic Target in Kidney Disease

The kidney is an energy-consuming organ, and cellular metabolism plays an indispensable role in kidney-related diseases. Caveolin-1 (Cav-1), a multifunctional membrane protein, is the main component of caveolae on the plasma membrane. Caveolae are represented by tiny invaginations that are abundant on the plasma membrane and that serve as a platform to regulate cellular endocytosis, stress responses, and signal transduction. However, caveolae have received increasing attention as a metabolic platform that mediates the endocytosis of albumin, cholesterol, and glucose, participates in cellular metabolic reprogramming and is involved in the progression of kidney disease. It is worth noting that caveolae mainly depend on Cav-1 to perform the abovementioned cellular functions. Furthermore, the mechanism by which Cav-1 regulates cellular metabolism and participates in the pathophysiology of kidney diseases has not been completely elucidated. In this review, we introduce the structure and function of Cav-1 and its functions in regulating cellular metabolism, autophagy, and oxidative stress, focusing on the relationship between Cav-1 in cellular metabolism and kidney disease; in addition, Cav-1 that serves as a potential therapeutic target for treatment of kidney disease is also described.

Mediation role of body fat distribution (FD) on the relationship between CAV1 rs3807992 polymorphism and metabolic syndrome in overweight and obese women

BACKGROUND

Metabolic syndrome (MetS) is associated with an increased risk of morbidity and mortality in almost all chronic diseases. The most frequent methods for the calculation of a continuous MetS (cMetS) score have used the standardized residuals in linear regression (z-score). Recently, emerging data suggest that one of the main genetic targets is the CAV1, which plays a crucial role in regulating body fat distribution. This study is designed to investigate the relationship between CAV1 rs3807992 genotypes and cMetS, and to determine whether body fat distribution plays a mediating role in this regard.

METHODS

The current cross-sectional study was conducted on 386 overweight and obese females. The CAV1 rs3807992 and body composition were measured by the PCR-RFLP method and bioelectrical impedance analysis, respectively. Serum profile of HDL-C, TGs, FPG, and Insulin were measured by standard protocols.

RESULTS

GG allele carriers had significantly lowered Z-MAP (p = 0.02), total cMetS (p = 0.03) and higher Z-HDL (p = 0.001) compared with (A) allele carriers. There was a significant specific indirect effect (standardized coefficient = 0.19; 95% CI 0.01-0.4) of Visceral fat level (VFL). Although, total body fat was significantly associated with CAV1 rs3807992 and cMetS, the specific indirect effect was not significant (standardized coefficient = 0.21; 95% CI - 0.006, 0.44). VFL contributed to significant indirect effects of 35% on the relationship between CAV1 and cMetS.

CONCLUSION

Higher visceral adipose tissue may affect the relationship between CAV1 and cMetS. Although CAV1 rs3807992 is linked to VFL in our study, the influence of this polymorphism on MetS is not via total fat.

The Interface of Nuclear and Membrane Steroid Signaling

Steroid hormones bind receptors in the cell nucleus and in the cell membrane. The most widely studied class of steroid hormone receptors are the nuclear receptors, named for their function as ligand-dependent transcription factors in the cell nucleus. Nuclear receptors, such as estrogen receptor alpha, can also be anchored to the plasma membrane, where they respond to steroids by activating signaling pathways independent of their function as transcription factors. Steroids can also bind integral membrane proteins, such as the G protein-coupled estrogen receptor. Membrane estrogen and progestin receptors have been cloned and characterized in vitro and influence the development and function of many organ systems. Membrane androgen receptors were cloned and characterized in vitro, but their function as androgen receptors in vivo is unresolved. We review the identity and function of membrane proteins that bind estrogens, progestins, and androgens. We discuss evidence that membrane glucocorticoid and mineralocorticoid receptors exist, and whether glucocorticoid and mineralocorticoid nuclear receptors act at the cell membrane. In many cases, integral membrane steroid receptors act independently of nuclear steroid receptors, even though they may share a ligand.

Role of AMP-activated protein kinase on cardio-metabolic abnormalities in the development of diabetic cardiomyopathy: A molecular landscape

Cardiovascular complications associated with diabetes mellitus remains a leading cause of morbidity and mortality across the world. Diabetic cardiomyopathy is a descriptive pathology that in absence of co-morbidities such as hypertension, dyslipidemia initially characterized by cardiac stiffness, myocardial fibrosis, ventricular hypertrophy, and remodeling. These abnormalities further contribute to diastolic dysfunctions followed by systolic dysfunctions and eventually results in clinical heart failure (HF). The clinical outcomes associated with HF are considerably worse in patients with diabetes. The complexity of the pathogenesis and clinical features of diabetic cardiomyopathy raises serious questions in developing a therapeutic strategy to manage cardio-metabolic abnormalities. Despite extensive research in the past decade the compelling approaches to manage and treat diabetic cardiomyopathy are limited. AMP-Activated Protein Kinase (AMPK), a serine-threonine kinase, often referred to as cellular "metabolic master switch". During the development and progression of diabetic cardiomyopathy, a plethora of evidence demonstrate the beneficial role of AMPK on cardio-metabolic abnormalities including altered substrate utilization, impaired cardiac insulin metabolic signaling, mitochondrial dysfunction and oxidative stress, myocardial inflammation, increased accumulation of advanced glycation end-products, impaired cardiac calcium handling, maladaptive activation of the renin-angiotensin-aldosterone system, endoplasmic reticulum stress, myocardial fibrosis, ventricular hypertrophy, cardiac apoptosis, and impaired autophagy. Therefore, in this review, we have summarized the findings from pre-clinical and clinical studies and provided a collective overview of the pathophysiological mechanism and the regulatory role of AMPK on cardio-metabolic abnormalities during the development of diabetic cardiomyopathy.

Novel Targets in Glucose Homeostasis and Obesity-Lesson from Rare Mutations

PURPOSE OF REVIEW

Obesity and diabetes have already become the second largest risk factor for cardiovascular disease. During the last decade, remarkable advances have been made in understanding the human genome's contribution to glucose homeostasis disorders and obesity. A few studies on rare mutations of candidate genes provide potential genetic targets for the treatment of diabetes and obesity. In this review, we discussed the detailed findings of these studies and the possible causalities between specific genetic variations and dysfunctions in energy or glucose homeostasis. We are optimistic that novel therapeutic strategies targeting these specific mutants for treating and preventing diabetes and obesity will be developed in the near future.

RECENT FINDINGS

Studies on rare genetic mutation-caused obesity or diabetes have identified potential genetic targets to decrease body weight or reduce the risk of diabetes. Rare mutations observed in lipodystrophy, obese, or diabetic human patients are promising targets in the treatment of diabetes and obesity.

MicroRNA-451a targets caveolin-1 in stomach cancer cells

MicroRNA-451 (miR-451) is lowly expressed in stomach cancer cells and improves their metastatic ability by down-regulating extracellular signal-regulated kinase 2 (ERK2). Many studies have found that caveolin-1 (CAV1) plays an important role in cancer progression. Additionally, miR-451 has been reported to regulate the expression of CAV1 in chronic obstructive pulmonary disease. Therefore, this study aims to determine if miR-451 regulates the biological functions of stomach cancer cells by regulating CAV1 expression. Through a bioinformatics analysis, we found that miR-451a regulates CAV1 expression, and miR-451a expression is relatively low in stomach cancer cells. Next, we confirmed that miR-451a negatively regulates CAV1 expression using a dual-luciferase reporter assay. Then MTT, 5-ethynyl-2'-deoxyuridine (EdU), propidium iodide (PI), an Annexin V-FITC/PI apoptosis kit, and transwell assays were used to measure the changes in cell proliferation, the cell cycle, apoptosis, cell migration, and invasiveness in stomach cancer cells overexpressing miR-451a or both miR-451a and CAV1. It was found that increasing the miR-451a expression in stomach cancer cells inhibits cell growth, migration, and invasiveness, and promotes apoptosis. After restoring the CAV1 expression, these biological processes resumed. In summary, in stomach cancer cells, the overexpression of miR-451a can restrain cell growth and promote apoptosis, so it is a potential treatment for stomach cancer.

Interplay Between Statins, Cav1 (Caveolin-1), and Aldosterone

Statin use is associated with lower aldosterone levels. We hypothesized that caveolin-1 may be important for the uptake of statins into the adrenal gland and would affect statin’s aldosterone-lowering effects. The aim of this study was to test whether the caveolin-1 risk allele (rs926198) would affect aldosterone levels associated with statin use. The Hypertensive Pathotype database includes healthy and hypertensive individuals who have undergone assessment of adrenal hormones. Individuals were studied off antihypertensive medications but were maintained on statins if prescribed by their personal physician. Adrenal hormones were measured at baseline and after 1 hour of angiotensin II stimulation on both high- and low-sodium diets. A mixed-model repeated-measures analysis was employed with a priori selected covariates of age, sex, body mass index, and protocol (low versus high sodium, baseline versus angiotensin II stimulated aldosterone). A total of 250 individuals were included in the study; 31 individuals were taking statins (12.4%) and 219 were not. Among statin users, carrying a caveolin-1 risk allele resulted in a 25% (95% CI, 1–43.2) lower aldosterone level (P=0.04). However, among nonstatin users, carrying a caveolin-1 risk allele resulted in no significant effect on aldosterone levels (P=0.38). Additionally, the interaction between caveolin-1 risk allele and statin use on aldosterone levels was significant (P=0.03). These findings suggest caveolin-1 risk allele carrying individuals are likely to receive the most benefit from statin’s aldosterone-lowering properties; however, due to the observational nature of this study, these findings need further investigation.

Loss of Caveolin-1 Is Associated with a Decrease in Beta Cell Death in Mice on a High Fat Diet

Elevated free fatty acids (FFAs) impair beta cell function and reduce beta cell mass as a consequence of the lipotoxicity that occurs in type 2 diabetes (T2D). We previously reported that the membrane protein caveolin-1 (CAV1) sensitizes to palmitate-induced apoptosis in the beta pancreatic cell line MIN6. Thus, our hypothesis was that CAV1 knock-out (CAV1 KO) mice subjected to a high fat diet (HFD) should suffer less damage to beta cells than wild type (WT) mice. Here, we evaluated the in vivo response of beta cells in the pancreatic islets of 8-week-old C57Bl/6J CAV1 KO mice subjected to a control diet (CD, 14% kcal fat) or a HFD (60% kcal fat) for 12 weeks. We observed that CAV1 KO mice were resistant to weight gain when on HFD, although they had high serum cholesterol and FFA levels, impaired glucose tolerance and were insulin resistant. Some of these alterations were also observed in mice on CD. Interestingly, KO mice fed with HFD showed an adaptive response of the pancreatic beta cells and exhibited a significant decrease in beta cell apoptosis in their islets compared to WT mice. These in vivo results suggest that although the CAV1 KO mice are metabolically unhealthy, they adapt better to a HFD than WT mice. To shed light on the possible signaling pathway(s) involved, MIN6 murine beta cells expressing (MIN6 CAV) or not expressing (MIN6 Mock) CAV1 were incubated with the saturated fatty acid palmitate in the presence of mitogen-activated protein kinase inhibitors. Western blot analysis revealed that CAV1 enhanced palmitate-induced JNK, p38 and ERK phosphorylation in MIN6 CAV1 cells. Moreover, all the MAPK inhibitors partially restored MIN6 viability, but the effect was most notable with the ERK inhibitor. In conclusion, our results suggest that CAV1 KO mice adapted better to a HFD despite their altered metabolic state and that this may at least in part be due to reduced beta cell damage. Moreover, they indicate that the ability of CAV1 to increase sensitivity to FFAs may be mediated by MAPK and particularly ERK activation.

mTORC1 Deficiency Modifies Volume Homeostatic Responses to Dietary Sodium in a Sex-Specific Manner

The mechanistic target of the rapamycin (mTOR) pathway plays a role in features common to both excess salt/aldosterone and cardiovascular/renal diseases. Dietary sodium can upregulate mTORC1 signaling in cardiac and renal tissue, and the inhibition of mTOR can prevent aldosterone-associated, salt-induced hypertension. The impact of sex and age on mTOR's role in volume homeostasis and the regulation of aldosterone secretion is largely unknown. We hypothesize that both age and sex modify mTOR's interaction with volume homeostatic mechanisms. The activity of 3 volume homeostatic mechanisms-cardiovascular, renal, and hormonal (aldosterone [sodium retaining] and brain natriuretic peptide [BNP; sodium losing])-were assessed in mTORC1 deficient (Raptor+/-) and wild-type male and female littermates at 2 different ages. The mice were volume stressed by being given a liberal salt (LibS) diet. Raptor+/-mice of both sexes when they aged: (1) reduced their blood pressure, (2) increased left ventricular internal diameter during diastole, (3) decreased renal blood flow, and (4) increased mineralocorticoid receptor expression. Aldosterone levels did not differ by sex in young Raptor+/- mice. However, as they aged, compared to their littermates, aldosterone decreased in males but increased in females. Finally, given the level of Na+ intake, BNP was inappropriately suppressed, but only in Raptor+/- males. These data indicate that Raptor+/- mice, when stressed with a LibS diet, display inappropriate volume homeostatic responses, particularly with aging, and the mechanisms altered, differing by sex.

Poor Renal and Cardiovascular Outcomes in Patients with Biopsy-Proven Diabetic Nephropathy

BACKGROUND

Despite the high mortality of cardiovascular disease (CVD) in diabetic patients with renal injury, few studies have compared cardiovascular characteristics and outcomes between patients with diabetic nephropathy (DN) and non-diabetic renal disease (NDRD).

METHODS

A total of 326 type 2 diabetes mellitus patients with renal biopsy were assigned to DN and NDRD groups. Echocardiography and Doppler ultrasound were performed to evaluate left ventricular hypertrophy (LVH) and peripheral atherosclerosis disease (PAD). Renal and cardiovascular survival rates were compared between the DN and NDRD groups by Kaplan-Meier analysis. Risk factors for renal and cardiovascular events in DN patients were identified by a Cox proportional hazards model.

RESULTS

In total, 179 patients entered the DN group (54.9%) and 147 made up the NDRD group (45.1%). The presence of diabetic retinopathy, family history of diabetes, and dependence on insulin therapy were associated with the presence of DN. DN patients had more CVD with more severe LVH and PAD. Poorer renal (log-rank χ2 = 26.534, p < 0.001) and cardiovascular (log-rank χ2 = 16.257, p < 0.001) prognoses were seen in the DN group. DR (HR 1.539, 95% CI 1.332-1.842), eGFR (HR 0.943, 95% CI 0.919-0.961), and 24-h proteinuria (HR 1.211, 95% CI 1.132-1.387) were identified as risk factors for renal endpoints. Age (HR 1.672, 95% CI 1.487-1.821), HbA1C (HR 1.398, 95% CI 1.197-1.876), and 24-h proteinuria (HR 1.453, 95% CI 1.289-1.672) were associated with cardiovascular endpoints.

CONCLUSION

Patients with DN had more severe CVD along with poorer renal and cardiovascular prognoses than those with NDRD.

Hepatocyte caveolin-1 modulates metabolic gene profiles and functions in non-alcoholic fatty liver disease

Caveolin-1 (CAV1) is a crucial regulator of lipid accumulation and metabolism. Previous studies have shown that global Cav1 deficiency affects lipid metabolism and hepatic steatosis. We aimed to analyze the consequences of hepatocyte-specific Cav1 knockout under healthy conditions and upon non-alcoholic fatty liver disease (NAFLD) development. Male and female hepatocyte-specific Cav1 knockout (HepCAV1ko) mice were fed a methionine/choline (MCD) deficient diet for 4 weeks. MCD feeding caused severe hepatic steatosis and slight fibrosis. In addition, liver function parameters, i.e., ALT, AST, and GLDH, were elevated, while cholesterol and glucose level were reduced upon MCD feeding. These differences were not affected by hepatocyte-specific Cav1 knockout. Microarray analysis showed strong differences in gene expression profiles of livers from HepCAV1ko mice compared those of global Cav1 knockout animals. Pathway enrichment analysis identified that metabolic alterations were sex-dimorphically regulated by hepatocyte-specific CAV1. In male HepCAV1ko mice, metabolic pathways were suppressed in NAFLD, whereas in female knockout mice induced. Moreover, gender-specific transcription profiles were modulated in healthy animals. In conclusion, our results demonstrate that hepatocyte-specific Cav1 knockout significantly altered gene profiles, did not affect liver steatosis and fibrosis in NAFLD and that gender had severe impact on gene expression patterns in healthy and diseased hepatocyte-specific Cav1 knockout mice.

LncRNA Gm12664-001 ameliorates nonalcoholic fatty liver through modulating miR-295-5p and CAV1 expression

Background

Our study aims to investigate the mechanisms of lncRNA Gm12664–001 improved hepatic lipid accumulation-initiated NAFLD via regulating miR-295-5p and CAV1 in AML12 cells.

Methods

The animals were divided into normal control (NC) group and high fat diet (HFD) group (20 mice per group) for 8w. The steatotic liver was measured by hematoxylin eosin (HE) staining and kits. We performed systematical analyses on hepatic expression profiles of long noncoding RNAs (lncRNAs) and microRNAs in a high-fat diet (HFD)-induced steatotic animal model. The expression profile of targets was confirmed by bioinformatics analysis, luciferase assay, RT-PCR and western blot in AML12 cells.

Results

HFD treatment markedly observed hepatic fatty degeneration with primarily fat vacuoles, and increased TG level compared with control. According to microarray data, we found that transfection of Gm12664–001 siRNA (siRNA-118,306) obviously enhanced TG accumulation and repressed CAV1 in AML12 cells. Furthermore, the TG accumulation markedly increased by siRNA-mediated knockdown of CAV1 in AML12 cells. By bioinformatics prediction, AML12 cells were transfected of siRNA-118,306 obviously upregulated miR-295-5p. Transfection of miR-295-5p mimics significantly increased TG accumulation and obviously suppressed the target CAV1.

Conclusions

The results revealed that lncRNA Gm12664–001 attenuated hepatic lipid accumulation through negatively regulating miR-295-5p and enhancing CAV1 expression in AML12 cells.

Sex-specific differences in endoplasmic reticulum aminopeptidase 1 modulation influence blood pressure and renin-angiotensin system responses

Salt sensitivity of blood pressure (SSBP) and hypertension are common, but the underlying mechanisms remain unclear. Endoplasmic reticulum aminopeptidase 1 (ERAP1) degrades angiotensin II (ANGII). We hypothesized that decreasing ERAP1 increases BP via ANGII-mediated effects on aldosterone (ALDO) production and/or renovascular function. Compared with WT littermate mice, ERAP1-deficient (ERAP1+/-) mice had increased tissue ANGII, systolic and diastolic BP, and SSBP, indicating that ERAP1 deficiency leads to volume expansion. However, the mechanisms underlying the volume expansion differed according to sex. Male ERAP1+/- mice had increased ALDO levels and normal renovascular responses to volume expansion (decreased resistive and pulsatility indices and increased glomerular volume). In contrast, female ERAP1+/- mice had normal ALDO levels but lacked normal renovascular responses. In humans, ERAP1 rs30187, a loss-of-function gene variant that reduces ANGII degradation in vitro, is associated with hypertension. In our cohort from the Hypertensive Pathotype (HyperPATH) Consortium, there was a significant dose-response association between rs30187 risk alleles and systolic and diastolic BP as well as renal plasma flow in men, but not in women. Thus, lowering ERAP1 led to volume expansion and increased BP. In males, the volume expansion was due to elevated ALDO with normal renovascular function, whereas in females the volume expansion was due to impaired renovascular function with normal ALDO levels.

Aldosterone Rapidly Enhances Levels of the Striatin and Caveolin-1 Proteins in Rat Kidney: The Role of the Mineralocorticoid Receptor

BACKGROUND

Striatin and caveolin-1 (cav-1) are scaffolding/regulating proteins that are associated with salt-sensitive high blood pressure and promote renal sodium and water reabsorption, respectively. The mineralocorticoid receptor (MR) interacts with striatin and cav-1, while aldosterone increases striatin and cav-1 levels. However, no in vivo data have been reported for the levels of these proteins in the kidney.

METHODS

Male Wistar rats were intraperitoneally injected with normal saline solution, aldosterone alone (Aldo: 150 μg/kg body weight), or aldosterone after pretreatment with eplerenone, an MR blocker, 30 minutes before the aldosterone injection (eplerenone [Ep.]+Aldo). Thirty minutes after the aldosterone injection, the amount and localization of striatin and cav-1 were determined by Western blot analysis and immunohistochemistry, respectively.

RESULTS

Aldosterone increased striatin levels by 150% (P<0.05), and cav-1 levels by 200% (P<0.001). Eplerenone had no significant effect on striatin levels, but partially blocked the aldosterone-induced increase in cav-1 levels. Aldosterone stimulated striatin and cav-1 immunoreactivity in both the cortex and medulla. Eplerenone reduced cav-1 immunostaining in both areas; however, striatin intensity was reduced in the cortex, but increased in the medulla.

CONCLUSION

This is the first in vivo study demonstrating that aldosterone rapidly enhances renal levels of striatin and cav-1. Aldosterone increases striatin levels via an MR-independent pathway, whereas cav-1 is partially regulated through MR.

Diabetic Cardiomyopathy: An Update of Mechanisms Contributing to This Clinical Entity

Heart failure and related morbidity and mortality are increasing at an alarming rate, in large part, because of increases in aging, obesity, and diabetes mellitus. The clinical outcomes associated with heart failure are considerably worse for patients with diabetes mellitus than for those without diabetes mellitus. In people with diabetes mellitus, the presence of myocardial dysfunction in the absence of overt clinical coronary artery disease, valvular disease, and other conventional cardiovascular risk factors, such as hypertension and dyslipidemia, has led to the descriptive terminology, diabetic cardiomyopathy. The prevalence of diabetic cardiomyopathy is increasing in parallel with the increase in diabetes mellitus. Diabetic cardiomyopathy is initially characterized by myocardial fibrosis, dysfunctional remodeling, and associated diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure. Impaired cardiac insulin metabolic signaling, mitochondrial dysfunction, increases in oxidative stress, reduced nitric oxide bioavailability, elevations in advanced glycation end products and collagen-based cardiomyocyte and extracellular matrix stiffness, impaired mitochondrial and cardiomyocyte calcium handling, inflammation, renin-angiotensin-aldosterone system activation, cardiac autonomic neuropathy, endoplasmic reticulum stress, microvascular dysfunction, and a myriad of cardiac metabolic abnormalities have all been implicated in the development and progression of diabetic cardiomyopathy. Molecular mechanisms linked to the underlying pathophysiological changes include abnormalities in AMP-activated protein kinase, peroxisome proliferator-activated receptors, O-linked N-acetylglucosamine, protein kinase C, microRNA, and exosome pathways. The aim of this review is to provide a contemporary view of these instigators of diabetic cardiomyopathy, as well as mechanistically based strategies for the prevention and treatment of diabetic cardiomyopathy.

Higher urinary cortisol levels associate with increased cardiovascular risk

There are conflicting data on whether variations of physiologic cortisol levels associated with cardiovascular risk. We hypothesize that prior discordant findings are related to problems associated with varying sample size, techniques for assessing cardiovascular risk and failure to adequately account for environmental factors. To address these issues, we utilized a large sample size, selected the Framingham risk score to compute cardiovascular risk and performed the study in a highly controlled setting. We had two main objectives: determine whether higher, yet physiologic, cortisol levels associated with increased cardiovascular risk and determine whether caveolin-1 (rs926198) risk allele carriers associated with increased cardiovascular risk. This was a cross-sectional study of 574 non-diabetic individuals who completed a common protocol. Data collection included fasting blood samples, blood pressure measurements and a 24-h urine-free cortisol collection. Five hundred seventeen of these participants also completed caveolin-1 genotyping. Subjects were classified as belonging to either the low-mode or high-mode urine-free cortisol groups, based on the bimodal distribution of urine-free cortisol. In multivariate analysis, Framingham risk score was statistically higher in the high-mode cortisol group (10.22 (mean) ± 0.43 (s.e.m.)) compared to the low-mode cortisol group (7.73 ± 0.34), P < 0.001. Framingham risk score was also statistically higher in the caveolin-1 risk allele carriers (8.91 ± 0.37) compared to caveolin-1 non-risk allele carriers (7.59 ± 0.48), P = 0.034. Overall, the estimated effect on Framingham risk score of carrying the caveolin-1 risk allele was 1.33 ± 0.61, P = 0.029. Both urinary cortisol and caveolin-1 risk allele status are independent predictors of Framingham risk score.

Genetics of Human Primary Hypertension: Focus on Hormonal Mechanisms

Increasingly, primary hypertension is being considered a syndrome and not a disease, with the individual causes (diseases) having a common sign-an elevated blood pressure. To determine these causes, genetic tools are increasingly employed. This review identified 62 proposed genes. However, only 21 of them met our inclusion criteria: (i) primary hypertension, (ii) two or more supporting cohorts from different publications or within a single publication or one supporting cohort with a confirmatory genetically modified animal study, and (iii) 600 or more subjects in the primary cohort; when including our exclusion criteria: (i) meta-analyses or reviews, (ii) secondary and monogenic hypertension, (iii) only hypertensive complications, (iv) genes related to blood pressure but not hypertension per se, (v) nonsupporting studies more common than supporting ones, and (vi) studies that did not perform a Bonferroni or similar multiassessment correction. These 21 genes were organized in a four-tiered structure: distant phenotype (hypertension); intermediate phenotype [salt-sensitive (18) or salt-resistant (0)]; subintermediate phenotypes under salt-sensitive hypertension [normal renin (4), low renin (8), and unclassified renin (6)]; and proximate phenotypes (specific genetically driven hypertensive subgroup). Many proximate hypertensive phenotypes had a substantial endocrine component. In conclusion, primary hypertension is a syndrome; many proposed genes are likely to be false positives; and deep phenotyping will be required to determine the utility of genetics in the treatment of hypertension. However, to date, the positive genes are associated with nearly 50% of primary hypertensives, suggesting that in the near term precise, mechanistically driven treatment and prevention strategies for the specific primary hypertension subgroups are feasible.

Dietary Fatty Acid Saturation Modulates Sphingosine-1-Phosphate-Mediated Vascular Function

Sphingolipids, modified by dietary fatty acids, are integral components of plasma membrane and caveolae that are also vasoactive compounds. We hypothesized that dietary fatty acid saturation affects vasoconstriction to sphingosine-1-phosphate (S1P) through caveolar regulation of rho kinase. Wild type (WT) and caveolin-1-deficient (cav-1 KO) mice which lack vascular caveolae were fed a low-fat diet (LF), 60% high-saturated fat diet (lard, HF), or 60% fat diet with equal amounts of lard and n-3 polyunsaturated menhaden oil (MO). Weight gain of WT on HF and MO diets was similar while markedly blunted in cav-1 KO. Neither high-fat diet affected the expression of cav-1, rho, or rho kinase in arteries from WT. In cav-1 KO, MO increased the vascular expression of rho but had no effect on rho kinase. HF had no effect on rho or rho kinase expression in cav-1 KO. S1P produced a concentration-dependent constriction of gracilis arteries from WT on LF that was reduced with HF and restored to normal with MO. Constriction to S1P was reduced in cav-1 KO and no longer affected by a high-saturated fat diet. Inhibition of rho kinase which reduced constriction to PE independent of diet in arteries from WT and cav-1 KO only reduced constriction to S1P in arteries from WT fed MO. The data suggest that dietary fatty acids modify vascular responses to S1P by a caveolar-dependent mechanism which is enhanced by dietary n-3 polyunsaturated fats.

Diabetic Cardiomyopathy: Current and Future Therapies. Beyond Glycemic Control

Diabetes mellitus and the associated complications represent a global burden on human health and economics. Cardiovascular diseases are the leading cause of death in diabetic patients, who have a 2–5 times higher risk of developing heart failure than age-matched non-diabetic patients, independent of other comorbidities. Diabetic cardiomyopathy is defined as the presence of abnormal cardiac structure and performance in the absence of other cardiac risk factors, such coronary artery disease, hypertension, and significant valvular disease. Hyperglycemia, hyperinsulinemia, and insulin resistance mediate the pathological remodeling of the heart, characterized by left ventricle concentric hypertrophy and perivascular and interstitial fibrosis leading to diastolic dysfunction. A change in the metabolic status, impaired calcium homeostasis and energy production, increased inflammation and oxidative stress, as well as an accumulation of advanced glycation end products are among the mechanisms implicated in the pathogenesis of diabetic cardiomyopathy. Despite a growing interest in the pathophysiology of diabetic cardiomyopathy, there are no specific guidelines for diagnosing patients or structuring a treatment strategy in clinical practice. Anti-hyperglycemic drugs are crucial in the management of diabetes by effectively reducing microvascular complications, preventing renal failure, retinopathy, and nerve damage. Interestingly, several drugs currently in use can improve cardiac health beyond their ability to control glycemia. GLP-1 receptor agonists and sodium-glucose co-transporter 2 inhibitors have been shown to have a beneficial effect on the cardiovascular system through a direct effect on myocardium, beyond their ability to lower blood glucose levels. In recent years, great improvements have been made toward the possibility of modulating the expression of specific cardiac genes or non-coding RNAs in vivo for therapeutic purpose, opening up the possibility to regulate the expression of key players in the development/progression of diabetic cardiomyopathy. This review summarizes the pathogenesis of diabetic cardiomyopathy, with particular focus on structural and molecular abnormalities occurring during its progression, as well as both current and potential future therapies.

Caloric restriction improves glucose homeostasis, yet increases cardiometabolic risk in caveolin-1-deficient mice

BACKGROUND AND PURPOSE

The plasma membrane protein caveolin-1 (CAV-1) has been shown to be involved in modulating glucose homeostasis and the actions of the renin-angiotensin-aldosterone system (RAAS). Caloric restriction (CR) is widely accepted as an effective therapeutic approach to improve insulin sensitivity and reduce the severity of diabetes. Recent data indicate that polymorphisms of the CAV-1 gene are strongly associated with insulin resistance, hypertension and metabolic abnormalities in non-obese individuals. Therefore, we sought to determine whether CR improves the metabolic and cardiovascular (CV) risk factors in the lean CAV-1 KO mice.

MATERIALS/METHODS

Twelve- to fourteen-week-old CAV-1 knockout (KO) and genetically matched wild-type (WT) male mice were randomized by genotype to one of two dietary regimens: ad libitum (ad lib) food intake or 40% CR for 4 weeks. Three weeks following the onset of dietary restriction, all groups were assessed for insulin sensitivity. At the end of the study, all groups were assessed for fasting glucose, insulin, HOMA-IR, lipids, corticosterone levels and blood pressure (BP). Aldosterone secretion was determined from acutely isolated Zona Glomerulosa cells.

RESULTS

We confirmed that the CAV-1 KO mice on the ad lib diet display a phenotype consistent with the cardiometabolic syndrome, as shown by higher systolic BP (SBP), plasma glucose, HOMA-IR and aldosterone levels despite lower body weight compared with WT mice on the ad lib diet. CAV-1 KO mice maintained their body weight on the ad lib diet, but had substantially greater weight loss with CR, as compared to caloric restricted WT mice. CR-mediated changes in weight were associated with dramatic improvements in glucose and insulin tolerance in both genotypes. These responses to CR, however, were more robust in CAV-1KO vs. WT mice and were accompanied by reductions in plasma glucose, insulin and HOMA-IR in CAV-1KO but not WT mice. Surprisingly, in the CAV-1 KO, but not in WT mice, CR was associated with increased SBP and aldosterone levels, suggesting that in CAV-1 KO mice CR induced an increase in some CV risk factors.

CONCLUSIONS

CR improved the metabolic phenotype in CAV-1 KO mice by increasing insulin sensitivity; nevertheless, this intervention also increased CV risk by inappropriate adaptive responses in the RAAS and BP.

Randomized, Placebo-Controlled Trial to Evaluate Effects of Eplerenone on Metabolic and Inflammatory Indices in HIV

CONTEXT

HIV-infected individuals demonstrate increased renin-angiotensin-aldosterone system activation in association with visceral adiposity, insulin resistance, and inflammation. A physiologically based treatment approach targeting mineralocorticoid receptor (MR) blockade may improve metabolic and inflammatory indices in HIV.

OBJECTIVE

To investigate effects of eplerenone on insulin sensitivity, inflammatory indices, and other metabolic parameters in HIV.

DESIGN

Six-month, double-blind, randomized, placebo-controlled trial.

SETTING

Academic clinical research center.

PARTICIPANTS

HIV-infected individuals with increased waist circumference and abnormal glucose homeostasis.

INTERVENTION

Eplerenone 50 mg or placebo daily.

OUTCOME

The primary end point was change in insulin sensitivity measured by the euglycemic-hyperinsulinemic clamp technique. Secondary end points included change in body composition and inflammatory markers.

RESULTS

Forty-six individuals were randomized to eplerenone (n = 25) vs placebo (n = 21). Eplerenone did not improve insulin sensitivity [0.48 (-1.28 to 1.48) vs 0.43 (-1.95 to 2.55) mg/min/μIU/mL insulin; P = 0.71, eplerenone vs placebo] when measured by the gold standard euglycemic-hyperinsulinemic clamp technique. Intramyocellular lipids (P = 0.04), monocyte chemoattractant protein-1 (P = 0.04), and high-density lipoprotein (P = 0.04) improved among those randomized to eplerenone vs placebo. Trends toward decreases in interleukin-6 (P = 0.10) and high-sensitivity C-reactive protein (P = 0.10) were also seen with eplerenone vs placebo. Plasma renin activity and aldosterone levels increased in the eplerenone vs placebo-treated group, demonstrating expected physiology. MR antagonism with eplerenone was well tolerated among the HIV population, with no considerable changes in blood pressure or potassium.

CONCLUSION

MR blockade may improve selected metabolic and inflammatory indices in HIV-infected individuals. Further studies are necessary to understand the clinical potential of MR antagonism in HIV.

Biological Sex Modulates the Adrenal and Blood Pressure Responses to Angiotensin II

The relationship between biological sex and aldosterone on blood pressure (BP) is unclear. We hypothesized that sex would modify the interaction between aldosterone and vascular responses to salt intake and angiotensin II (AngII). To test this hypothesis, in 1592 subjects from the well-controlled Hypertensive Pathotype cohort, we compared responses of women and men to chronic (BP and aldosterone levels in response to dietary salt) and acute (BP, renal plasma flow, and aldosterone responses to AngII infusion) manipulations. Women had a 30% higher salt sensitivity of BP than men (P<0.0005) regardless of age or hypertension status, a greater BP response to AngII, and a 15% greater aldosterone response to AngII on both restricted and liberal salt diets (P<0.005). Furthermore, there was an interaction (P=0.003) between sex and aldosterone on BP response to AngII. Women also had a greater (P<0.01) increment in renal plasma flow in response to AngII than men. To assess potential mechanisms for this sex effect, we compared aldosterone responses to AngII or potassium from rat zona glomerulosa cells and observed greater aldosterone production in female than male zona glomerulosa cells basally and in response to both agonists (P<0.0001). In a rodent model of aldosterone-mediated cardiovascular disease induced by increased AngII and low NO, circulating aldosterone levels (P<0.01), myocardial damage (P<0.001), and proteinuria (P<0.05) were greater in female than male rats despite having similar BP responses. Thus, increased aldosterone production likely contributes to sex differences in cardiovascular disease, suggesting that women may be more responsive to mineralocorticoid receptor blockade than men.

Caveolin-1, cancer and therapy resistance

Resistance of solid tumors to chemo- and radiotherapy remains a major obstacle in anti-cancer treatment. Herein, the membrane protein caveolin-1 (CAV1) came into focus as it is highly expressed in many tumors and high CAV1 levels were correlated with tumor progression, invasion and metastasis, and thus a worse clinical outcome. Increasing evidence further indicates that the heterogeneous tumor microenvironment, also known as the tumor stroma, contributes to therapy resistance resulting in poor clinical outcome. Again, CAV1 seems to play an important role in modulating tumor host interactions by promoting tumor growth, metastasis, therapy resistance and cell survival. However, the mechanisms driving stroma-mediated tumor growth and radiation resistance remain to be clarified. Understanding these interactions and thus, targeting CAV1 may offer a novel strategy for preventing cancer therapy resistance and improving clinical outcomes. In this review, we will summarize the resistance-promoting effects of CAV1 in tumors, and emphasize its role in the tumor-stroma communication as well as the resulting malignant phenotype of epithelial tumors.

The Role of the Mineralocorticoid Receptor in Inflammation: Focus on Kidney and Vasculature

BACKGROUND

The remarkable success of clinical trials in mineralocorticoid receptor (MR) inhibition in heart failure has driven research on the physiological and pathological role(s) of nonepithelial MR expression. MR is widely expressed in the cardiovascular system and is a major determinant of endothelial function, smooth muscle tone, vascular remodeling, fibrosis, and blood pressure. An important new dimension is the appreciation of the role MR plays in immune cells and target organ damage in the heart, kidney and vasculature, and in the development of insulin resistance.

SUMMARY

The mechanism for MR activation in tissue injury continues to evolve with the evidence to date suggesting that activation of MR results in a complex repertoire of effects involving both macrophages and T cells. MR is an important transcriptional regulator of macrophage phenotype and function. Another important feature of MR activation is that it can occur even with normal or low aldosterone levels in pathological conditions. Tissue-specific conditional models of MR expression in myeloid cells, endothelial cells, smooth muscle cells and cardiomyocytes have been very informative and have firmly demonstrated a critical role of MR as a key pathophysiologic variable in cardiac hypertrophy, transition to heart failure, adipose inflammation, and atherosclerosis. Finally, the central nervous system activation of MR in permeable regions of the blood-brain barrier may play a role in peripheral inflammation. Key Message: Ongoing clinical trials will help clarify the role of MR blockade in conditions, such as atherosclerosis and chronic kidney disease.

Genetic variation at the microRNA binding site of CAV1 gene is associated with lung cancer susceptibility

Single nucleotide polymorphism (SNP) may influence the genesis and development of cancer in a variety of ways depending on their location. Here we conducted a study in Chinese female non-smokers to investigate the relationship between rs1049337, rs926198 and the risk or survival of lung cancer. Further, we explored whether rs1049337 could alter the binding affinity between the mRNA of CAV1 and the corresponding microRNAs. Finally, we evaluated the relationship between expression level of CAV1 and prognosis of lung cancer. The results showed that the rs1049337-C allele and rs926198-C allele were the protective alleles of lung cancer risk. Haplotype analysis indicated that the C-C haplotype (constructed by rs1049337 and rs926198) was a protective haplotype for lung cancer risk. The result of luciferase reporter assay showed that rs1049337 can affect the binding affinity of CAV1 mRNA to the corresponding microRNAs both in A549 cell line and H1299 cell line. Compared with C allele, T allele had a relatively decreased luciferase activity. Compared with paired normal adjacent tissue or normal lung tissue, lung cancer tissue showed a relatively low level of CAV1. Refer to those patients at early stage of lung cancer, the expression level of CAV1 in patients at late stage of lung cancer was relatively low. In conclusion, the results indicated that rs1049337, it's a SNP located at 3′UTR region of CAV1 may affect lung cancer risk by altering the binding affinity between the mRNA of CAV1 and the corresponding microRNAs.

Caveolin 1-related autophagy initiated by aldosterone-induced oxidation promotes liver sinusoidal endothelial cells defenestration

Aldosterone, with pro-oxidation and pro-autophagy capabilities, plays a key role in liver fibrosis. However, the mechanisms underlying aldosterone-promoted liver sinusoidal endothelial cells (LSECs) defenestration remain unknown. Caveolin 1 (Cav1) displays close links with autophagy and fenestration. Hence, we aim to investigate the role of Cav1-related autophagy in LSECs defenestration. We found the increase of aldosterone/MR (mineralocorticoid receptor) level, oxidation, autophagy, and defenestration in LSECs in the human fibrotic liver, BDL or hyperaldosteronism models; while antagonizing aldosterone or inhibiting autophagy relieved LSECs defenestration in BDL-induced fibrosis or hyperaldosteronism models. In vitro, fenestrae of primary LSECs gradually shrank, along with the down-regulation of the NO-dependent pathway and the augment of the AMPK-dependent autophagy; these effects were aggravated by rapamycin (an autophagy activator) or aldosterone treatment. Additionally, aldosterone increased oxidation mediated by Cav1, reduced ATP generation, and subsequently induced the AMPK-dependent autophagy, leading to the down-regulation of the NO-dependent pathway and LSECs defenestration. These effects were reversed by MR antagonist spironolactone, antioxidants or autophagy inhibitors. Besides, aldosterone enhanced the co-immunoprecipitation of Cav1 with p62 and ubiquitin, and induced Cav1 co-immunofluorescence staining with LC3, ubiquitin, and F-actin in the perinuclear area of LSECs. Furthermore, aldosterone treatment increased the membrane protein level of Cav1, whereas decrease the cytoplasmic protein level of Cav1, indicating that aldosterone induced Cav1-related selective autophagy and F-actin remodeling to promote defenestration. Consequently, Cav1-related selective autophagy initiated by aldosterone-induced oxidation promotes LSECs defenestration via activating the AMPK-ULK1 pathway and inhibiting the NO-dependent pathway.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: Nongenomic effects via the mineralocorticoid receptor

The mineralocorticoid receptor (MR) belongs to the steroid hormone receptor family and classically functions as a ligand-dependent transcription factor. It is involved in water-electrolyte homeostasis and blood pressure regulation but independent from these effects also furthers inflammation, fibrosis, hypertrophy and remodeling in cardiovascular tissues. Next to genomic effects, aldosterone elicits very rapid actions within minutes that do not require transcription or translation and that occur not only in classical MR epithelial target organs like kidney and colon but also in nonepithelial tissues like heart, vasculature and adipose tissue. Most of these effects can be mediated by classical MR and its crosstalk with different signaling cascades. Near the plasma membrane, the MR seems to be associated with caveolin and striatin as well as with receptor tyrosine kinases like EGFR, PDGFR and IGF1R and G protein-coupled receptors like AT1 and GPER1, which then mediate nongenomic aldosterone effects. GPER1 has also been named a putative novel MR. There is a close interaction and functional synergism between the genomic and the nongenomic signaling so that nongenomic signaling can lead to long-term effects and support genomic actions. Therefore, understanding nongenomic aldosterone/MR effects is of potential relevance for modulating genomic aldosterone effects and may provide additional targets for intervention.

Imatinib and spironolactone suppress hepcidin expression

Disorders of iron metabolism are largely attributed to an excessive or insufficient expression of hepcidin, the master regulator of systemic iron homeostasis. Here, we investigated whether drugs targeting genetic regulators of hepcidin can affect iron homeostasis. We focused our efforts on drugs approved for clinical use to enable repositioning strategies and/or to reveal iron-related side effects of widely prescribed therapeutics. To identify hepcidin-modulating therapeutics, we re-evaluated data generated by a genome-wide RNAi screen for hepcidin regulators. We identified ‘druggable’ screening hits and validated those by applying RNAi of potential drug targets and small-molecule testing in a hepatocytic cell line, in primary murine and human hepatocytes and in mice. We initially identified spironolactone, diclofenac, imatinib and Suberoylanilide hydroxamic acid (SAHA) as hepcidin modulating drugs in cellular assays. Among these, imatinib and spironolactone further suppressed liver hepcidin expression in mice. Our results demonstrate that a commonly used anti-hypertensive drug, spironolactone, which is prescribed for the treatment of heart failure, acne and female hirsutism, as well as imatinib, a first-line, lifelong therapeutic option for some frequent cancer types suppress hepcidin expression in cultured cells and in mice. We expect these results to be of relevance for patient management, which needs to be addressed in prospective clinical studies.