mTORC1 (Mechanistic Target of Rapamycin Complex 1) Signaling in Endothelial and Smooth Muscle Cells Is Required for Vascular Function

Inhibition of CIRBP represses the proliferation and migration of vascular smooth muscle cells via inhibiting Rheb/mTORC1 axis

The excessive migration and proliferation of vascular smooth muscle cells (VSMCs) plays a vital role in vascular intimal hyperplasia. CIRBP is involved in the proliferation of various cancer cells. This study was aimed to explore the role of CIRBP in the proliferation and migration of VSMCs. Adenovirus was used to interfere with cold-inducible RNA-binding protein (CIRBP) expression, while lentivirus was used to overexpress Ras homolog enriched in brain (Rheb). Western blotting and qRT-PCR were used to evaluate the expression of CIRBP, Rheb, and mechanistic target of rapamycin complex 1 (mTORC1) activity. The cell proliferation was determined by Ki67 immunofluorescence staining and CCK-8 assay. The wound healing assay was performed to assess cell migration. Additionally, immunohistochemistry was conducted to explore the role of CIRBP in intimal hyperplasia after vascular injury. We found that silencing CIRBP inhibited the proliferation and migration of VSMCs, decreased the expression of Rheb and mTORC1 activity. Restoration of mTORC1 activity via insulin or overexpression of Rheb via lentiviral transfection both attenuated the inhibitory effects of silencing CIRBP on the proliferation and migration of VSMCs. Moreover, Rheb overexpression abolished the inhibitory effect of silencing CIRBP on mTORC1 activity in VSMCs. CIRBP was upregulated in the injured carotid artery. Silencing CIRBP ameliorated intimal hyperplasia after vascular injury. In the summary, silencing CIRBP attenuates mTORC1 activity via reducing Rheb expression, thereby supressing the proliferation and migration of VSMCs and intimal hyperplasia after vascular injury.

Adipocyte-specific disruption of the BBSome causes metabolic and autonomic dysfunction

Obesity is a major public health issue due to its association with type 2 diabetes, hypertension, and other cardiovascular risks. The BBSome, a complex of eight conserved Bardet-Biedl syndrome (BBS) proteins, has emerged as a key regulator of energy and glucose homeostasis as well as cardiovascular function. However, the importance of adipocyte BBSome in controlling these physiological processes is not clear. Here, we show that adipocyte-specific constitutive disruption of the BBSome through selective deletion of the Bbs1 gene adiponectin (AdipoCre/Bbs1fl/fl mice) does not affect body weight under normal chow or high-fat and high-sucrose diet (HFHSD). However, constitutive BBSome deficiency caused impairment in glucose tolerance and insulin sensitivity. Similar phenotypes were observed after inducible adipocyte-specific disruption of the BBSome (AdipoCreERT2/Bbs1fl/fl mice). Interestingly, a significant increase in renal sympathetic nerve activity, measured using multifiber recording in the conscious state, was observed in AdipoCre/Bbs1fl/fl mice on both chow and HFHSD. A significant increase in tail-cuff arterial pressure was also observed in chow-fed AdipoCre/Bbs1fl/fl mice, but this was not reproduced when arterial pressure was measured by radiotelemetry. Moreover, AdipoCre/Bbs1fl/fl mice had no significant alterations in vascular reactivity. On the other hand, AdipoCre/Bbs1fl/fl mice displayed impaired baroreceptor reflex sensitivity when fed HFHSD, but not on normal chow. Taken together, these data highlight the relevance of the adipocyte BBSome for the regulation of glucose homeostasis and sympathetic traffic. The BBSome also contributes to baroreflex sensitivity under HFHSD, but not normal chow.NEW & NOTEWORTHY The current study show how genetic manipulation of fat cells impacts various functions of the body including sensitivity to the hormone insulin.

Interplay Between Plasma Glycine and Branched-Chain Amino Acids Contributes to the Development of Hypertension and Coronary Heart Disease

BACKGROUND

Higher levels of plasma glycine are linked to a reduced risk, while increased levels of total branched-chain amino acids (tBCAAs) are associated with a higher risk of essential hypertension and coronary heart disease (CHD). As these metabolic components are interconnected, analyzing the tBCAAs/glycine ratio may help to understand their interplay in the pathogenesis of cardiovascular disease.

METHODS

The Cox regression approach was combined with the development of novel genetic tools for assessments of associations between plasma metabolomic data (glycine, tBCAAs, and tBCAAs/glycine ratio) from the UK Biobank and the development of hypertension and CHD. Genome-wide association study was performed on 186 523 White UK Biobank participants to identify new independent genetic instruments for the 2-sample Mendelian randomization analyses. P-gain statistic >10 identified instruments associated with tBCAAs/glycine ratio significantly stronger compared with individual amino acids. Outcomes of genome-wide association study on hypertension and CHD were derived from the UK Biobank (nonoverlapping sample), FinnGen, and CARDIoGRAMplusC4D.

RESULTS

The tBCAAs/glycine ratio was prospectively associated with a higher risk of developing hypertension and CHD (hazard ratio quintile Q5 versus Q1, 1.196 [95% CI, 1.109-1.289] and 1.226 [95% CI, 1.160-1.296], respectively). Mendelian randomization analysis demonstrated that tBCAAs/glycine ratio (P-gain >10) was a risk factor for hypertension (meta-analyzed inverse-variance weighted causal estimate 0.45 log odds ratio/SD (95% CI, 0.26-0.64) and CHD (0.48 [95% CI, 0.29-0.67]) with an absolute effect significantly larger compared with the effect of glycine (-0.06 [95% CI, -0.1 to -0.03] and -0.08 [95% CI, -0.11 to -0.05], respectively) or tBCAAs (0.22 [95% CI, 0.09-0.34] and 0.12 [95% CI, 0.01-0.24], respectively).

CONCLUSIONS

The total BCAAs/glycine ratio is a key element of the metabolic signature contributing to hypertension and CHD, which may reflect biological pathways shared by glycine and tBCAAs.

Role of Raptor Gene Variants in Hypertension: Influence on Blood Pressure Independent of Salt Intake in White Population

BACKGROUND

The mTOR (mechanistic target of rapamycin) is an essential regulator of fundamental biological processes. mTOR forms 2 distinct complexes, mTORC1 (mTOR complex 1) when it binds with RAPTOR (Regulatory-associated Protein of mTOR) and mTORC2 (mTOR complex 2) when it associates with RICTOR (Rapamycin-insesitive companion of mTOR). Due to the previous link between the mTOR pathway, aldosterone, and blood pressure (BP), we anticipated that variants in the mTOR complex might be associated with salt-sensitive BP.

METHODS

BP and other parameters were assessed after a one-week liberal Na+ (200 mmol/d) and a one-week restricted Na+ (10 mmol/d) diet in 608 White subjects from the Hypertensive Pathotype cohort, single-nucleotide variants in MTOR, RPTOR, and RICTOR genes were obtained for candidate genes analyses.

RESULTS

The analysis revealed a significant association between a single nucleotide variants within the RPTOR gene and BP. Individuals carrying the RPTOR rs9901846 homozygous risk allele (AA) and heterozygous risk allele (GA) exhibited a 5 mm Hg increase in systolic BP on a liberal diet compared with nonrisk allele individuals (GG), but only in women. This single nucleotide variants effect was more pronounced on the restricted diet and present in both sexes, with AA carriers having a 9 mm Hg increase and GA carriers having a 5 mm Hg increase in systolic BP compared with GG. Interestingly, there were no significant associations between MTOR or RICTOR gene variants and BP.

CONCLUSIONS

The RPTOR gene variation is associated with elevated BP in White participants, regardless of salt intake, specifically in females.

Dysregulated cellular metabolism in atherosclerosis: mediators and therapeutic opportunities

Accumulating evidence over the past decades has revealed an intricate relationship between dysregulation of cellular metabolism and the progression of atherosclerotic cardiovascular disease. However, an integrated understanding of dysregulated cellular metabolism in atherosclerotic cardiovascular disease and its potential value as a therapeutic target is missing. In this Review, we (1) summarize recent advances concerning the role of metabolic dysregulation during atherosclerosis progression in lesional cells, including endothelial cells, vascular smooth muscle cells, macrophages and T cells; (2) explore the complexity of metabolic cross-talk between these lesional cells; (3) highlight emerging technologies that promise to illuminate unknown aspects of metabolism in atherosclerosis; and (4) suggest strategies for targeting these underexplored metabolic alterations to mitigate atherosclerosis progression and stabilize rupture-prone atheromas with a potential new generation of cardiovascular therapeutics.

TorS - Reframing a rational for type 2 diabetes treatment

The mammalian target of rapamycin complex 1 syndrome (Tors), paradigm implies an exhaustive cohesive disease entity driven by a hyperactive mTORC1, and which includes obesity, type 2 diabetic hyperglycemia, diabetic dyslipidemia, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, hypertension, atherosclerotic cardiovascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome, psoriasis and other. The TorS paradigm may account for the efficacy of standard-of-care treatments of type 2 diabetes (T2D) in alleviating the glycaemic and non-glycaemic diseases of TorS in T2D and non-T2D patients. The TorS paradigm may generate novel treatments for TorS diseases.

A Novel Bioactive Peptide, T14, Selectively Activates mTORC1 Signalling: Therapeutic Implications for Neurodegeneration and Other Rapamycin-Sensitive Applications

T14 modulates calcium influx via the α-7 nicotinic acetylcholine receptor to regulate cell growth. Inappropriate triggering of this process has been implicated in Alzheimer's disease (AD) and cancer, whereas T14 blockade has proven therapeutic potential in in vitro, ex vivo and in vivo models of these pathologies. Mammalian target of rapamycin complex 1 (mTORC1) is critical for growth, however its hyperactivation is implicated in AD and cancer. T14 is a product of the longer 30mer-T30. Recent work shows that T30 drives neurite growth in the human SH-SY5Y cell line via the mTOR pathway. Here, we demonstrate that T30 induces an increase in mTORC1 in PC12 cells, and ex vivo rat brain slices containing substantia nigra, but not mTORC2. The increase in mTORC1 by T30 in PC12 cells is attenuated by its blocker, NBP14. Moreover, in post-mortem human midbrain, T14 levels correlate significantly with mTORC1. Silencing mTORC1 reverses the effects of T30 on PC12 cells measured via AChE release in undifferentiated PC12 cells, whilst silencing mTORC2 does not. This suggests that T14 acts selectively via mTORC1. T14 blockade offers a preferable alternative to currently available blockers of mTOR as it would enable selective blockade of mTORC1, thereby reducing side effects associated with generalised mTOR blockade.

mTORC1 syndrome (TorS): unified paradigm for diabetes/metabolic syndrome

'Glucolipotoxicity' and 'insulin resistance' are claimed to drive type 2 diabetes (T2D) and the non-glycemic diseases of the metabolic syndrome (MetS) (obesity, dyslipidemia, hypertension). In line with that, glycemic and/or insulin control are considered to be primary goal in treating T2D/MetS. However, recent standard-of-care (SOC) treatments of T2D, initially designed to control T2D hyperglycemia, appear now to alleviate the cardio-renal and non-glycemic diseases of T2D/MetS independently of glucose lowering and insulin resistance, and in non-T2D patients altogether, calling for an alternative unifying pathophysiology/treatment paradigm for T2D/MetS. This opinion article proposes to replace the current 'glucolipotoxic/insulin-resistance' paradigm of T2D/MetS with an 'mammalian target of rapamycin complex 1 (mTORC1) syndrome' (TorS) paradigm, implying an exhaustive cohesive disease entity driven by an upstream hyperactive mTORC1, and which includes diabetic hyperglycemia, diabetic dyslipidemia, hypertension, diabetic macrovascular and microvascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome (PCOS), psoriasis, and others. The TorS paradigm may account for the insulin-resistant glycemic context of TorS, combined with response to insulin of the non-glycemic diseases of TorS. The TorS paradigm may account for the efficacy of current antidiabetic SOC treatments in diabetic and nondiabetic patients. Most importantly, the TorS paradigm may generate novel treatments for TorS.

Streptococcal arginine deiminase regulates endothelial inflammation, mTOR pathway and autophagy

Endothelial cells (EC) are active participants in the inflammation process. During the infection, the change in endothelium properties provides the leukocyte infiltrate formation and restrains pathogen dissemination due to coagulation control. Pathogenic microbes are able to change the endothelium properties and functions in order to invade the bloodstream and disseminate in the host organism. Arginine deiminase (ADI), a bacterial arginine-hydrolyzing enzyme, which causes the amino acid deficiency, important for endothelium biology. Previous research implicates altered metabolism of arginine in the development of endothelial dysfunction and inflammation. It was shown that arginine deficiency, as well as overabundance affects the balance of mechanical target of rapamycin (mTOR)/S6 kinase (S6K) pathway, arginase and endothelial nitric oxide synthase (eNOS) resulted in reactive oxygen species (ROS) production and EC activation. ADI creating a deficiency of arginine can interfere cellular arginine-dependent processes. Thus, this study was aimed at investigation of the influence of streptococcal ADI on the metabolism and inflammations of human umbilical vein endothelial cells (HUVEC). The action of ADI was studied by comparing the effect Streptococcus pyogenes M49-16 paternal strain expressing ADI and its isogenic mutant M49-16delArcA with the inactivated gene ArcA. Based on comparison of the parental and mutant strain effects, it can be concluded, that ADI suppressed mTOR signaling pathway and enhanced autophagy. The processes failed to return to the basic level with arginine supplement. Our study also demonstrates that ADI suppressed endothelial proliferation, disrupted actin cytoskeleton structure, increased phospho-NF-κB p65, CD62P, CD106, CD54, CD142 inflammatory molecules expression, IL-6 production and lymphocytes-endothelial adhesion. In spite of the ADI-mediated decrease in arginine concentration in the cell-conditioned medium, the enzyme enhanced the production of nitric oxide in endothelial cells. Arginine supplementation rescued proliferation, actin cytoskeleton structure, brought NO production to baseline and prevented EC activation. Additional evidence for the important role of arginine bioavailability in the EC biology was obtained. The results allow us to consider bacterial ADI as a pathogenicity factor that can potentially affect the functions of endothelium.

mTOR contributes to endothelium-dependent vasorelaxation by promoting eNOS expression and preventing eNOS uncoupling

Clinically used inhibitors of mammalian target of rapamycin (mTOR) negatively impacts endothelial-dependent vasodilatation (EDD) through unidentified mechanisms. Here we show that either the endothelium-specific deletion of Mtor to inhibit both mTOR complexes, or depletion of Raptor or Rictor to disrupt mTORC1 or mTORC2, causes impaired EDD, accompanied by reduced NO in the serum of mice. Consistently, inhibition of mTOR decreases NO production by human and mouse EC. Specifically, inhibition of mTORC1 suppresses eNOS gene expression, due to impairment in p70S6K-mediated posttranscriptional regulation of the transcription factor KLF2 expression. In contrast to mTORC1 inhibition, a positive-feedback between MAPK (p38 and JNK) activation and Nox2 upregulation contributes to the excessive generation of reactive oxygen species (ROS), which causes eNOS uncoupling and decreased NO bioavailability in mTORC2-inhibited EC. Adeno-associated virus-mediated EC-specific overexpression of KLF2 or suppression of Nox2 restores EDD function in endothelial mTORC1- or mTORC2-inhibited mice.

The endothelium-specific inhibition of either of mammalian target of rapamycin (mTOR) complexes impairs endothelial-dependent vasodilatation (EDD), accompanied by decreased nitric oxide bioavailability in both human and mice endothelial cells.

The causal associations of circulating amino acids with blood pressure: a Mendelian randomization study

BACKGROUND

Circulating levels of amino acids were associated with blood pressure (BP) in observational studies. However, the causation of such associations has been hypothesized but is difficult to prove in human studies. Here, we aimed to use two-sample Mendelian randomization analyses to evaluate the potential causal associations of circulating levels of amino acids with BP and risk of hypertension.

METHODS

We generated genetic instruments for circulating levels of nine amino acids by conducting meta-analyses of genome-wide association study (GWAS) in UK Biobank participants with metabolomic data (n = 98,317) and another published metabolomics GWAS (n = 24,925). Data on the associations of the genetic variants with BP and hypertension were obtained in the UK Biobank participants without metabolomic data (n = 286,390). The causal effects were estimated using inverse-variance weighted method.

RESULTS

Significant evidence consistently supported the causal effects of increased branched-chain amino acids (BCAAs, i.e., leucine, isoleucine, and valine) levels on higher BP and risk of hypertension (all P < 0.006 after Bonferroni correction except for P_{leucine-on-diastolicBP} = 0.008). For example, per standard deviation higher of genetically predicted isoleucine levels were associated with 2.71 ± 0.78 mmHg higher systolic BP and 1.24 ± 0.34 mmHg higher diastolic BP, as well as with 7% higher risk of hypertension (odds ratio: 1.07, [95% CI: 1.04-1.10]). In addition, per standard deviation higher of genetically predicted glycine level was associated with lower systolic BP (- 0.70 ± 0.17 mmHg, P = 4.04 × 10^-5) and a lower risk of hypertension (0.99 [0.98-0.99], P = 6.46 × 10^-5). In the reverse direction, genetically predicted higher systolic BP was associated with lower circulating levels of glycine (- 0.025±0.008, P = 0.001).

CONCLUSIONS

This study provides evidence for causal impacts of genetically predicted circulating BCAAs and glycine levels on BP. Meanwhile, genetically predicted higher BP was associated with lower glycine levels. Further investigations are warranted to clarify the underlying mechanisms.

Protrudin regulates FAK activation, endothelial cell migration and angiogenesis

During angiogenesis, endothelial cells form protrusive sprouts and migrate towards the angiogenic stimulus. In this study, we investigate the role of the endoplasmic reticulum (ER)-anchored protein, Protrudin, in endothelial cell protrusion, migration and angiogenesis. Our results demonstrate that Protrudin regulates angiogenic tube formation in primary endothelial cells, Human umbilical vein endothelial cells (HUVECs). Analysis of RNA sequencing data and its experimental validation revealed cell migration as a prominent cellular function affected in HUVECs subjected to Protrudin knockdown. Further, our results demonstrate that knockdown of Protrudin inhibits focal adhesion kinase (FAK) activation in HUVECs and human aortic endothelial cells (HAECs). This is associated with a loss of polarized phospho-FAK distribution upon Protrudin knockdown as compared to Protrudin expressing HUVECs. Reduction of Protrudin also results in a perinuclear accumulation of mTOR and a decrease in VEGF-mediated S6K activation. However, further experiments suggest that the observed inhibition of angiogenesis in Protrudin knockdown cells is not affected by mTOR disturbance. Therefore, our findings suggest that defects in FAK activation and its abnormal subcellular distribution upon Protrudin knockdown are associated with a detrimental effect on endothelial cell migration and angiogenesis. Furthermore, mice with global Protrudin deletion demonstrate reduced retinal vascular progression. To conclude, our results provide evidence for a novel key role of Protrudin in endothelial cell migration and angiogenesis.

mTORC1-Mediated Angiogenesis is Required for the Development of Rosacea

Although multiple evidences suggest that angiogenesis is associated with the pathophysiology of rosacea, its role is still in debate. Here, we showed that angiogenesis was enhanced in skin lesions of both rosacea patients and LL37-induced rosacea-like mice. Inhibition of angiogenesis alleviated LL37-induced rosacea-like features in mice. Mechanistically, we showed that mTORC1 was activated in the endothelial cells of the lesional skin from rosacea patients and LL37-induced rosacea-like mouse model. Inhibition of mTORC1 decreased angiogenesis and blocked the development of rosacea in mice. On the contrary, hyperactivation of mTORC1 increased angiogenesis and exacerbated rosacea-like phenotypes. Our in vitro results further demonstrated that inhibition of mTORC1 signaling significantly declined LL37-induced tube formation of human endothelial cells. Taken together, our findings revealed that mTORC1-mediated angiogenesis responding to LL37 might be essential for the development of rosacea and targeting angiogenesis might be a novel potential therapy.

Dietary modulation of large extracellular vesicles: the good and the bad for human health

Extracellular vesicles (EVs) encompassing nanovesicles derived from the endosome system and generated by plasmatic membrane shedding are of increasing interest in view of their ability to sustain cell-to-cell communication and the possibility that they could be used as surrogate biomarkers of healthy and unhealthy trajectories. Nutritional strategies have been developed to preserve health, and the impact of these strategies on circulating EVs is arousing growing interest. Data available from published studies are now sufficient for a first integration to better understand the role of EVs in the relationship between diet and health. Thus, this review focuses on human intervention studies investigating the impact of diet or its components on circulating EVs. Because of analytical bias, only large EVs have been assessed so far. The analysis highlights that poor-quality diets with elevated fat and sugar content increase levels of circulating large EVs, and these can be partly counteracted by healthy food or some food micronutrients and bioactive compounds. However, knowledge of the content and the biological functions of these diet-induced EVs is still missing. It is important to address these aspects in new research in order to state if EVs are mediators of the effects of diet on health.

Vascular effects of disrupting endothelial mTORC1 signaling in obesity

The mechanistic target of rapamycin complex 1 (mTORC1) signaling complex is emerging as a critical regulator of cardiovascular function with alterations in this pathway implicated in cardiovascular diseases. In this study, we used animal models and human tissues to examine the role of vascular mTORC1 signaling in the endothelial dysfunction associated with obesity. In mice, obesity induced by high-fat/high-sucrose diet feeding for ∼2 mo resulted in aortic endothelial dysfunction without appreciable changes in vascular mTORC1 signaling. On the other hand, chronic high-fat diet feeding (45% or 60% kcal: ∼9 mo) in mice resulted in endothelial dysfunction associated with elevated vascular mTORC1 signaling. Endothelial cells and visceral adipose vessels isolated from obese humans display a trend toward elevated mTORC1 signaling. Surprisingly, genetic disruption of endothelial mTORC1 signaling through constitutive or tamoxifen inducible deletion of endothelial Raptor (critical subunit of mTORC1) did not prevent or rescue the endothelial dysfunction associated with high-fat diet feeding in mice. Endothelial mTORC1 deficiency also failed to reverse the endothelial dysfunction evoked by a high-fat/high-sucrose diet in mice. Taken together, these data show increased vascular mTORC1 signaling in obesity, but this vascular mTORC1 activation appears not to be required for the development of endothelial impairment in obesity.