Hypothalamic mTORC1 signaling controls sympathetic nerve activity and arterial pressure and mediates leptin effects

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.

mTORC1 in energy expenditure: consequences for obesity

In eukaryotic cells, the mammalian target of rapamycin complex 1 (sometimes referred to as the mechanistic target of rapamycin complex 1; mTORC1) orchestrates cellular metabolism in response to environmental energy availability. As a result, at the organismal level, mTORC1 signalling regulates the intake, storage and use of energy by acting as a hub for the actions of nutrients and hormones, such as leptin and insulin, in different cell types. It is therefore unsurprising that deregulated mTORC1 signalling is associated with obesity. Strategies that increase energy expenditure offer therapeutic promise for the treatment of obesity. Here we review current evidence illustrating the critical role of mTORC1 signalling in the regulation of energy expenditure and adaptive thermogenesis through its various effects in neuronal circuits, adipose tissue and skeletal muscle. Understanding how mTORC1 signalling in one organ and cell type affects responses in other organs and cell types could be key to developing better, safer treatments targeting this pathway in obesity.

Contribution of serum elements to blood pressure during pregnancy by impacting gut microbiota: A prospective cohort study

Exposure to environmental elements can alter gut microbiota, further affecting host health. Exploring the interrelationships among element exposure, gut microbiota and blood pressure (BP) during pregnancy, as well as the mediating roles of gut microbiota, is warranted, which holds implications for maternal and offspring health. In a prospective cohort study between 2017-2018, 733 pregnant women were included. The serum elements and gut microbiota during the second trimester were assessed, and BP was collected during the second and third trimester and before delivery. Fourteen associations were identified between serum elements and BP, including positive associations of zinc (Zn) and thallium (Tl) with systolic BP during the second trimester. Rubidium (Rb) showed a positive association with Pielou's evenness. Serum elements, such as Tl and Rb, were significantly associated with the relative abundance of bacteria and co-abundance groups (CAGs). Alpha diversity was negatively associated with BP levels and trajectories. Moreover, 15 associations between gut microbiota and BP were shown. Finally, mediation analysis confirmed that CAG2 and Pielou's evenness mediated the associations of Tl and Rb with BP, respectively. We concluded that serum elements can contribute to BP changes during pregnancy through gut microbiota, suggesting gut microbiota-targeted approach as a potential intervention.

Amino acid profiles: exploring their diagnostic and pathophysiological significance in hypertension

Hypertension, a major contributor to cardiovascular morbidity, is closely linked to amino acid metabolism. Amino acids, particularly branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs), may play pivotal roles in the pathogenesis and potential management of hypertension. This review investigated the relationships between amino acid profiles, specifically BCAAs and AAAs, and hypertension, and examined their potential as diagnostic and therapeutic targets. An in-depth analysis was conducted on studies highlighting the associations of specific amino acids such as arginine, glycine, proline, glutamine, and the BCAAs and AAAs with hypertension. BCAAs and AAAs, alongside other amino acids like arginine, glycine, and proline, showed significant correlations with hypertension. These amino acids influence multiple pathways including nitric oxide synthesis, vascular remodeling, and neurotransmitter production, among others. Distinct amino acid profiles were discerned between hypertensive and non-hypertensive individuals. Amino acid profiling, particularly the levels of BCAAs and AAAs, offers promising avenues in the diagnostic and therapeutic strategies for hypertension. Future studies are crucial to confirm these findings and to delineate amino acid-based interventions for hypertension treatment.

Leptin promotes proliferation of human undifferentiated spermatogonia by activating the PI3K/AKT/mTOR pathway

BACKGROUND

Male infertility is a common disease affecting male reproductive health. Leptin is an important hormone that regulates various physiological processes, including reproductive function. However, few experimental studies have been carried out to elucidate the mechanism of leptin's effects on male reproductive function.

OBJECTIVE

The purpose of this study was to investigate the effects of leptin on testicular spermatogenesis and its mechanism, so as to provide potential targets for the treatment of patients with spermatogenic dysfunction.

METHODS

Testicular tissues were collected from eight prostate cancer patients undergoing surgical castration. GPR125-positive spermatogonia were isolated by two consecutive magnetic activated cell sorting (MACS), followed by incubation with conditioned medium. To identify the signaling pathway(s) involved in the effects of leptin, undifferentiated spermatogonia were treated with different concentrations of leptin and antagonists of leptin-related pathways. The proliferative effect of leptin was evaluated by cell counting using a hemocytometer. Expressions of p-AKT, p-ERK, p-STAT, and p-S6K were determined by western blotting analysis.

RESULTS

Leptin promoted the growth of human GPR125-positive spermatogonia in a concentration-dependent manner. The most significant proliferative effect was observed using 100 ng/mL leptin after 6 days of culture. Leptin significantly increased the phosphorylation of STAT3, AKT, and ERK in undifferentiated spermatogonia. Phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 inhibited the leptin-induced activation of AKT, ERK, and downstream S6K. Treatment with the mammalian target of rapamycin (mTOR) inhibitor rapamycin also inhibited S6K phosphorylation. Moreover, both LY294002 and rapamycin were found to inhibit the leptin-induced proliferation of undifferentiated spermatogonia. These results suggested that the leptin-induced proliferation of GPR125-positive spermatogonia was dependent on the PI3K/AKT/mTOR pathway. Further exploration of proliferation and apoptotic markers suggested that leptin may alleviate cell apoptosis by regulating the expression of Bax and FasL.

CONCLUSIONS

A certain concentration of leptin (25∼100 ng/mL) could promote proliferation of undifferentiated spermatogonia, which was mediated by PI3K/AKT/mTOR pathway.

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.

Leptin signaling and its central role in energy homeostasis

Leptin plays a critical role in regulating appetite, energy expenditure and body weight, making it a key factor in maintaining a healthy balance. Despite numerous efforts to develop therapeutic interventions targeting leptin signaling, their effectiveness has been limited, underscoring the importance of gaining a better understanding of the mechanisms through which leptin exerts its functions. While the hypothalamus is widely recognized as the primary site responsible for the appetite-suppressing and weight-reducing effects of leptin, other brain regions have also been increasingly investigated for their involvement in mediating leptin's action. In this review, we summarize leptin signaling pathways and the neural networks that mediate the effects of leptin, with a specific emphasis on energy homeostasis.

Neuronal atg1 Coordinates Autophagy Induction and Physiological Adaptations to Balance mTORC1 Signalling

The mTORC1 nutrient-sensing pathway integrates metabolic and endocrine signals into the brain to evoke physiological responses to food deprivation, such as autophagy. Nevertheless, the impact of neuronal mTORC1 activity on neuronal circuits and organismal metabolism remains obscure. Here, we show that mTORC1 inhibition acutely perturbs serotonergic neurotransmission via proteostatic alterations evoked by the autophagy inducer atg1. Neuronal ATG1 alters the intracellular localization of the serotonin transporter, which increases the extracellular serotonin and stimulates the 5HTR7 postsynaptic receptor. 5HTR7 enhances food-searching behaviour and ecdysone-induced catabolism in Drosophila. Along similar lines, the pharmacological inhibition of mTORC1 in zebrafish also stimulates food-searching behaviour via serotonergic activity. These effects occur in parallel with neuronal autophagy induction, irrespective of the autophagic activity and the protein synthesis reduction. In addition, ectopic neuronal atg1 expression enhances catabolism via insulin pathway downregulation, impedes peptidergic secretion, and activates non-cell autonomous cAMP/PKA. The above exert diverse systemic effects on organismal metabolism, development, melanisation, and longevity. We conclude that neuronal atg1 aligns neuronal autophagy induction with distinct physiological modulations, to orchestrate a coordinated physiological response against reduced mTORC1 activity.

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.

Effects of Hesperidin Consumption on the Cardiovascular System in Pre- and Stage 1 Hypertensive Subjects: Targeted and Non-Targeted Metabolomic Approaches (CITRUS Study)

SCOPE

The aim of the present work is to determine new biomarkers of the biological effects of hesperidin in orange juice (OJ) applying a non-targeted metabolomics approach validated by targeted metabolomics analyses of compliance biomarkers.

METHODS AND RESULTS

Plasma/serum and urine targeted (HPLC-MS/MS) and untargeted (¹ H-NMR) metabolomics signatures are explored in a subsample with pre- and stage-1 hypertension subjects of the CITRUS study (N = 159). Volunteers received 500 mL day^-1 of control drink, OJ, or hesperidin-enriched OJ (EOJ) for 12-weeks. A 6-h postprandrial study is performed at baseline. Targeted analyses reveals plasma and urine hesperetin 7-O-β-d-glucuronide as the only metabolite differing between OJ and EOJ groups after 12-weeks consumption, and in urine is correlated with a decreased systolic blood pressure level. The non-targeted approach shows that after single dose and 12-weeks consumption of OJ and EOJ change several metabolites related with an anti-inflammatory and antioxidant actions, lower blood pressure levels and uremic toxins.

CONCLUSIONS

Hesperetin 7-O-β-d-glucuronide can be a candidate marker for distinguishing between the consumption of different hesperidin doses at 12-weeks consumption as well as a potential agent mediating blood pressure reduction. Moreover, changes in different endogenous metabolites can explain the mechanisms of action and the biological effects of hesperidin consumption.

Central and peripheral leptin resistance in obesity and improvements of exercise

Obesity is strongly related to leptin resistance that refers to the state in which leptin fails to inhibit appetite, enhance energy expenditure and regulate glycolipid metabolism, whereas decreasing leptin resistance is important for obesity treatment. Leptin resistance that develops in brain and also directly in peripheral tissues is considered as central and peripheral leptin resistance, respectively. The mechanism of central leptin resistance is the focus of intensive studies but still not totally clarified. A challenged notion about the effect of impaired leptin BBB transport emerges and a concept of "selective leptin resistance" is discussed. Peripheral leptin resistance, especially leptin resistance in muscle, has drawn more attention recently, while its mechanism remains unclear. Exercise is an effective way to reduce obesity, which is at least in part due to the alleviation of leptin resistance. Here, we summarized newly discovered data about the associated factors of central leptin resistance and peripheral leptin resistance, and the actions of exercise on leptin resistance, which is important to understand the mechanisms of leptin resistance and exercise-induced alleviation of leptin resistance, and to facilitate clinical application of leptin in obesity treatment.

Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism

The discovery of leptin was intrinsically associated with its ability to regulate body weight. However, the effects of leptin are more far-reaching and include profound glucose-lowering and anti-lipogenic effects, independent of leptin's regulation of body weight. Regulation of glucose metabolism by leptin is mediated both centrally and via peripheral tissues and is influenced by the activation status of insulin signaling pathways. Ectopic fat accumulation is diminished by both central and peripheral leptin, an effect that is beneficial in obesity-associated disorders. The magnitude of leptin action depends upon the tissue, sex, and context being examined. Peripheral tissues that are of particular relevance include the endocrine pancreas, liver, skeletal muscle, adipose tissues, immune cells, and the cardiovascular system. As a result of its potent metabolic activity, leptin is used to control hyperglycemia in patients with lipodystrophy and is being explored as an adjunct to insulin in patients with type 1 diabetes. To fully understand the role of leptin in physiology and to maximize its therapeutic potential, the mechanisms of leptin action in these tissues needs to be further explored.

An Overview of Similarities and Differences in Metabolic Actions and Effects of Central Nervous System Between Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs) and Sodium Glucose Co-Transporter-2 Inhibitors (SGLT-2is)

GLP-1 receptor agonists (GLP-1RAs) and SGLT-2 inhibitors (SGLT-2is) are novel antidiabetic medications associated with considerable cardiovascular benefits therapying treatment of diabetic patients. GLP-1 exhibits atherosclerosis resistance, whereas SGLT-2i acts to ameliorate the neuroendocrine state in the patients with chronic heart failure. Despite their distinct modes of action, both factors share pathways by regulating the central nervous system (CNS). While numerous preclinical and clinical studies have demonstrated that GLP-1 can access various nuclei associated with energy homeostasis and hedonic eating in the CNS via blood-brain barrier (BBB), research on the activity of SGLT-2is remains limited. In our previous studies, we demonstrated that both GLP-1 receptor agonists (GLP-1RAs) liraglutide and exenatide, as well as an SGLT-2i, dapagliflozin, could activate various nuclei and pathways in the CNS of Sprague Dawley (SD) rats and C57BL/6 mice, respectively. Moreover, our results revealed similarities and differences in neural pathways, which possibly regulated different metabolic effects of GLP-1RA and SGLT-2i via sympathetic and parasympathetic systems in the CNS, such as feeding, blood glucose regulation and cardiovascular activities (arterial blood pressure and heart rate control). In the present article, we extensively discuss recent preclinical studies on the effects of GLP-1RAs and SGLT-2is on the CNS actions, with the aim of providing a theoretical explanation on their mechanism of action in improvement of the macro-cardiovascular risk and reducing incidence of diabetic complications. Overall, these findings are expected to guide future drug design approaches.

Type 2 diabetes - unmet need, unresolved pathogenesis, mTORC1-centric paradigm

The current paradigm of type 2 diabetes (T2D) is gluco-centric, being exclusively categorized by glycemic characteristics. The gluco-centric paradigm views hyperglycemia as the primary target, being driven by resistance to insulin combined with progressive beta cells failure, and considers glycemic control its ultimate treatment goal. Most importantly, the gluco-centric paradigm considers the non-glycemic diseases associated with T2D, e.g., obesity, dyslipidemia, hypertension, macrovascular disease, microvascular disease and fatty liver as 'risk factors' and/or 'outcomes' and/or 'comorbidities', rather than primary inherent disease aspects of T2D. That is in spite of their high prevalence (60-90%) and major role in profiling T2D morbidity and mortality. Moreover, the gluco-centric paradigm fails to realize that the non-glycemic diseases of T2D are driven by insulin and, except for glycemic control, response to insulin in T2D is essentially the rule rather than the exception. Failure of the gluco-centric paradigm to offer an exhaustive unifying view of the glycemic and non-glycemic diseases of T2D may have contributed to T2D being still an unmet need. An mTORC1-centric paradigm maintains that hyperactive mTORC1 drives the glycemic and non-glycemic disease aspects of T2D. Hyperactive mTORC1 is proposed to act as double-edged agent, namely, to interfere with glycemic control by disrupting the insulin receptor-Akt transduction pathway, while concomitantly driving the non-glycemic diseases of T2D. The mTORC1-centric paradigm may offer a novel perspective for T2D in terms of pathogenesis, clinical focus and treatment strategy.

Insulin potentiates essential amino acids effects on mechanistic target of rapamycin complex 1 signaling in MAC-T cells

Different models of lactation offer conflicting evidence as to whether insulin signaling is required for AA to stimulate mechanistic target of rapamycin complex 1 (mTORC1) activity. We hypothesized that insulin potentiates essential AA stimulation of mTORC1 activity in the MAC-T mammary epithelial cell line. Here, our objective was to assess mTORC1 signaling activity in response to insulin and individual or grouped essential AA. Insulin and essential AA concentrations in the treatment medium ranged from normo- to supraphysiological, with insulin at 0, 1, 10, or 100 nmol/L and essential AA at approximately 0, 0.01, 0.05, 0.1, 1, or 3× reference plasma levels. Effects and interaction of insulin and total essential AA were tested in a 3 × 5 factorial design (n = 3 replicates/treatment); insulin and the individual AA Leu, Met, Ile, and Arg were likewise tested in 3 × 4 factorials (n = 4). As the remaining individual AA His, Lys, Phe, Thr, Trp, and Val were expected to not affect mTORC1, these were tested only at the highest insulin level, 100 nmol/L (n = 4). For all of these, linear and quadratic effects of total and individual AA were evaluated. Essential AA were subsequently grouped by their positive (Leu, Met, Ile, Arg, and Thr; TOR-AA) or absent-to-negative effects (His, Lys, Phe, Trp, and Val; NTOR-AA), and tested for interaction in a 2 × 2 factorial design (n = 4), with each AA at its respective 1× plasma level, and insulin held at 100 nmol/L. All experiments consisted of 1 h treatment incubation, followed by Western blotting of cell lysates to measure phosphorylation and abundance of the mTORC1 pathway proteins Akt (Ser473); ribosomal protein S6 kinase p70 (S6K1, Thr389); eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Ser65); and ribosomal protein S6 (S6, Ser240/244). The Akt phosphorylation was overall increased by insulin, with a possible negative interaction with both total essential AA and the individual AA Leu. Total essential AA also increased S6K1 and 4E-BP1 phosphorylation in an insulin-dependent manner. The individual AA Leu, Met, Ile, and Arg increased S6K1 phosphorylation in an insulin-dependent manner. Similarly, Met and Arg increased 4E-BP1 phosphorylation in an insulin-dependent manner. Histidine, Lys, Trp, and Val did not affect S6K1 phosphorylation. However, S6K1 phosphorylation was linearly increased by Thr and quadratically decreased by Phe. Relative to the phosphorylation of S6K1 when cells were incubated with no essential AA, the NTOR-AA group had no effect, whereas the TOR-AA increased phosphorylation to the same degree observed with all 10 essential AA. Overall, we have found that insulin is required for essential AA to stimulate mTORC1 activity in MAC-T cells. In addition, the AA responsible for the bulk of mTORC1 activation in MAC-T are limited to Leu, Met, Ile, Arg, and Thr.

Leptin, Obesity, and Hypertension: A Review of Pathogenetic Mechanisms

The adipokine leptin is expressed at higher concentrations in obese subjects, who also incidentally have a higher prevalence of hypertension. The pathogenesis of this obesity-related hypertension is controversial and is believed to be related to many factors including increased sympathetic activity, abnormalities of the renin-angiotensin system, sodium retention, and an endotheliopathy acting independently or in concert with increased circulating leptin. This review discusses the potential mechanisms through which changes in leptin signal transduction pathways in tissues with the leptin receptor, especially the hypothalamus, mediate the pathogenetic relationships between obesity and hypertension. The hypothesis is explored that leptin effects on blood pressure (BP) are meditated by the downstream effects of hypothalamic leptin signaling and ultimately result in activation of specific melanocortin receptors located on sympathetic neurons in the spinal cord. The physiological consequences of this sympathetic activation of the heart and kidney are activation of the renin-angiotensin system, sodium retention and circulatory expansion and finally, elevated BP. This sequence of events has been elegantly demonstrated with leptin infusion and gene knockout studies in animal models but has not been convincingly reproducibly confirmed in humans. Further studies in human subjects on the specific roles of hypothalamic leptin in essential hypertension are indicated as elucidation of the signaling pathways should provide better understanding of the role of weight loss in BP control and afford an additional mechanism for pharmacologic control of BP in adults and children at risk of cardiovascular disease.

Mechanistic Target of Rapamycin Complex 1 Signaling Modulates Vascular Endothelial Function Through Reactive Oxygen Species

Background

The mechanistic target of rapamycin complex 1 (mTORC1) is an important intracellular energy sensor that regulates gene expression and protein synthesis through its downstream signaling components, the S6‐kinase and the ribosomal S6 protein. Recently, signaling arising from mTORC1 has been implicated in regulation of the cardiovascular system with implications for disease. Here, we examined the contribution of mTORC1 signaling to the regulation of vascular function.

Methods and Results

Activation of mTORC1 pathway in aortic rings with leucine or an adenoviral vector expressing a constitutively active S6‐kinase reduces endothelial‐dependent vasorelaxation in an mTORC1‐dependent manner without affecting smooth muscle relaxation responses. Moreover, activation of mTORC1 signaling in endothelial cells increases reactive oxygen species (ROS) generation and ROS gene expression resulting in a pro‐oxidant gene environment. Blockade of ROS signaling with Tempol restores endothelial function in vascular rings with increased mTORC1 activity indicating a crucial interaction between mTORC1 and ROS signaling. We then tested the role of nuclear factor‐κB transcriptional complex in connecting mTORC1 and ROS signaling in endothelial cells. Blockade of inhibitor of nuclear factor κ‐B kinase subunit β activity with BMS‐345541 prevented the increased ROS generation associated with increased mTORC1 activity in endothelial cells but did not improve vascular endothelial function in aortic rings with increased mTORC1 and ROS signaling.

Conclusions

These results implicate mTORC1 as a critical molecular signaling hub in the vascular endothelium in mediating vascular endothelial function through modulation of ROS signaling.

A role for sodium glucose cotransporter 2 inhibitors (SGLT2is) in the treatment of Alzheimer's disease?

With the lack of success and increasing urgency for therapies capable of impacting Alzheimer's disease (AD) and its progression, there are increasing efforts to expand testing of new mechanistic hypotheses to attack the disease from different angles. Three such hypotheses are the "Mitochondrial Cascade (MC)" hypothesis, the "Endo-Lysosomal Dysfunction (ELD)" hypothesis and the "Type 3 Diabetes (T3D)" hypothesis. These hypotheses provide a rationale for new pharmacological approaches to address the mitochondrial, endo-lysosomal and metabolic dysfunction associated with AD. It is increasingly evident that there is critical interplay between the metabolic dysfunction associated with obesity/metabolic syndrome/type 2 diabetes mellitus (T2DM) and patient susceptibility to AD development. A candidate for a common mechanism linking these metabolically-driven disease states is chronically-activated mechanistic target of rapamycin (mTOR) signaling. Unrestrained chronic mTOR activation may be responsible for sustaining metabolic, lysosomal and mitochondrial dysfunction in AD, driving both the breakdown of the blood-brain barrier via endothelial cell dysfunction and hyperphosphorylation of tau and formation of amyloid plaques in the brain. It is hypothesized that sodium glucose cotransporter 2 (SGLT2) inhibition, mediated by sustained glucose loss, restores mTOR cycling through nutrient-driven, nightly periods of transient mTOR inhibition (and restoration of catabolic cellular housekeeping processes) interspersed by daily periods of transient mTOR activation (and anabolism) accompanying eating. In this way, a flexible mTOR dynamic is restored, thereby preventing or even reducing the progress of AD pathology. The first study to investigate the effect of SGLT2 inhibition in patients with AD is ongoing and focuses on the impact on energy metabolism in the brain following treatment with the SGLT2 inhibitor dapagliflozin.

Leucine Potentiates Glucose-mediated 18F-FDG Uptake in Brown Adipose Tissue via β-Adrenergic Activation

Significant depots of brown adipose tissue (BAT) have been identified in many adult humans through positron emission tomography (PET), with the amount of BAT being inversely correlated with obesity. As dietary activation of BAT has implications for whole body glucose metabolism, leucine was used in the present study to determine its ability to promote BAT activation resulting in increased glucose uptake. In order to assess this, 2-deoxy-2-(fluorine-18)fluoro-d-glucose (¹⁸F-FDG) uptake was measured in C57BL/6 mice using microPET after treatment with leucine, glucose, or both in interscapular BAT (IBAT). Pretreatment with propranolol (PRP) was used to determine the role of β-adrenergic activation in glucose and leucine-mediated ¹⁸F-FDG uptake. Analysis of maximum standardized uptake values (SUV_MAX) determined that glucose administration increased ¹⁸F-FDG uptake in IBAT by 25.3%. While leucine did not promote ¹⁸F-FDG uptake alone, it did potentiate glucose-mediated ¹⁸F-FDG uptake, increasing ¹⁸F-FDG uptake in IBAT by 22.5%, compared to glucose alone. Pretreatment with PRP prevented the increase in IBAT ¹⁸F-FDG uptake following the combination of glucose and leucine administration. These data suggest that leucine is effective in promoting BAT ¹⁸F-FDG uptake through β-adrenergic activation in combination with glucose.

Central nesfatin-1 activates lipid mobilization in adipose tissue and fatty acid oxidation in muscle via the sympathetic nervous system

Little is known about the influence of central nesfatin-1 on lipid metabolism under diabetic conditions. The main objective of this study was to characterize the mechanisms by which central nesfatin-1 regulates lipid metabolism in streptozotocin (STZ)-induced type 2 diabetes mellitus (T2DM) and whether the sympathetic nervous system is involved. Male Kunming mice were fed high-fat diets (HFDs) and were treated twice with low-dose STZ (100 mg/kg, intraperitoneal [IP]) to generate the T2DM model. Pharmacological adrenergic blockage (phentolamine 10 mg/kg, propranolol 0.017 mmol) and surgical denervation of sympathetic nervous system of the hindlimb and inguinal fat were used to block nerve conduction to determine whether the effect of central nesfatin-1 required the hypothalamic-sympathetic nervous system axis. Plasma free fatty acid (FFA) and insulin levels were measured. AMP-activated protein kinase (AMPK) levels in skeletal muscle and hormone-sensitive lipase and adipose triglycerides lipase (HSL/ATGL) levels in white adipose tissue (WAT) were measured using western blot. mRNA expression of AMPK was measured. We found that there were significantly fewer NUCB2/nesfatin-1 immunoreactive neurons in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) in T2DM mice. Central nesfatin-1 administration decreased levels of plasma FFA significantly and activated AMPK to enhance fatty-acid oxidation in skeletal muscle in T2DM mice. In addition, HSL and ATGL were significantly activated during triglyceride mobilization in WAT triggered by central nesfatin-1 administration. Adrenergic blockade and morphological denervation of the sciatic and femoral nerves reduced these changes. Taken together, these data suggest that central nesfatin-1 regulates peripheral lipid metabolism in type 2 diabetes via the sympathetic nervous system.

Sex specific effect of ATPase inhibitory factor 1 on body weight: studies in high fat diet induced obese mice and genetic association studies in humans

BACKGROUND

Based on the metabolic effect of exogenous ATPase inhibitory factor 1 (IF1) on glucose metabolism, we tested whether IF1 treatment is effective in ameliorating weight gain and whether its effects are sex specific.

METHODS

HFD-fed C57BL/6 mice were treated with IF1 (5 mg/kg body weight, injected intraperitoneally). The underlying mechanisms of effect of IF1 on body weight were investigated in vitro and in vivo. Associations between genotypes of IF1 and obesity and relevant phenotype were further tested at the population level.

RESULTS

Chronic treatment with IF1 significantly decreased body weight gain by regulating food intake of HFD-fed male mice. IF1 activated the AKT/mTORC pathway and modulated the expression of appetite genes in the hypothalamus of HFD-fed male mice and its effect was confirmed in hypothalamic cell lines as well as hypothalamic primary cells. This required the interaction of IF1 with β-F1-ATPase on the plasma membrane of hypothalamic cells, which led to an increase in extracellular ATP production. In addition, IF1 treatment showed sympathetic nerve activation as measured by serum norepinephrine levels and UCP-1 expression in the subcutaneous fat of HFD-fed male mice. Notably, administration of recombinant IF1 to HFD-fed ovariectomized female mice showed remarkable reductions in food intake as well as body weight, which was not observed in wild-type 5-week female mice. Lastly, sex-specific genotype associations of IF1 with obesity prevalence and metabolic traits were demonstrated at the population level in humans. IF1 genetic variant (rs3767303) was significantly associated with lower prevalence of obesity and lower levels of body mass index, waist circumference, hemoglobin A1c, and glucose response area only in male participants.

CONCLUSION

IF1 is involved in weight regulation by controlling food intake and potentially sympathetic nerve activation in a sex-specific manner.

Leptin receptor-expressing neuron Sh2b1 supports sympathetic nervous system and protects against obesity and metabolic disease

Leptin stimulates the sympathetic nervous system (SNS), energy expenditure, and weight loss; however, the underlying molecular mechanism remains elusive. Here, we uncover Sh2b1 in leptin receptor (LepR) neurons as a critical component of a SNS/brown adipose tissue (BAT)/thermogenesis axis. LepR neuron-specific deletion of Sh2b1 abrogates leptin-stimulated sympathetic nerve activation and impairs BAT thermogenic programs, leading to reduced core body temperature and cold intolerance. The adipose SNS degenerates progressively in mutant mice after 8 weeks of age. Adult-onset ablation of Sh2b1 in the mediobasal hypothalamus also impairs the SNS/BAT/thermogenesis axis; conversely, hypothalamic overexpression of human SH2B1 has the opposite effects. Mice with either LepR neuron-specific or adult-onset, hypothalamus-specific ablation of Sh2b1 develop obesity, insulin resistance, and liver steatosis. In contrast, hypothalamic overexpression of SH2B1 protects against high fat diet-induced obesity and metabolic syndromes. Our results unravel an unrecognized LepR neuron Sh2b1/SNS/BAT/thermogenesis axis that combats obesity and metabolic disease.

Establishment of the circadian metabolic phenotype strategy in spontaneously hypertensive rats: a dynamic metabolomics study

BACKGROUND

Circadian rhythms play a fundamental role in the progression of cardiovascular events. Almost all cardiovascular diseases have a circadian misalignment usually characterized by changes in metabolites. This study aimed to dynamically monitor rhythmic biomarkers, to elucidate the metabolic pathways that are potentially under circadian control in spontaneously hypertensive rats (SHRs), and to eventually establish a circadian metabolic phenotype strategy based on metabolomics.

METHODS

In this study, an untargeted metabolomics technology was used to dynamically monitor changes in serum metabolites between SHR model group and WKY control group. Liquid chromatography-mass spectrometry (LC-MS) combined with multivariate statistical analysis was applied to identify markers of hypertension rhythm imbalance. The concentrations of amino acids and their metabolites identified as markers were quantified by a subsequent targeted metabolomics analysis. Overall, these approaches comprehensively explored the rhythm mechanism and established a circadian metabolic phenotype strategy.

RESULTS

The metabolic profile revealed a disorder in the diurnal metabolism pattern in SHRs. Moreover, multivariate statistical analysis revealed metabolic markers of rhythm homeostasis, such as arginine, proline, phenylalanine, citric acid, L-malic acid, succinic acid, etc., accompanied by an imbalance in hypertension. The key metabolic pathways related to rhythm imbalance in hypertension were found by enrichment analysis, including amino acid metabolism, and the tricarboxylic acid cycle (TCA). In addition, the quantitative analysis of amino acids and their metabolites showed that the changes in leucine, isoleucine, valine, taurine, serine, and glycine were the most obvious.

CONCLUSIONS

In summary, this study illustrated the relationship between metabolites and the pathways across time on hypertension. These results may provide a theoretical basis for personalized treatment programmes and timing for hypertension.

Metabolomics Elucidates Dose-Dependent Molecular Beneficial Effects of Hesperidin Supplementation in Rats Fed an Obesogenic Diet

Metabolic syndrome (MetS) is a global epidemic concern. Polyphenols are proposed as good candidates for its prevention, although their mechanisms are not fully understood. The gut microbiota seems to play a key role in polyphenol beneficial effects. Here, we assessed the effects of the citrus polyphenol hesperidin combining an untargeted metabolomics approach, which has an inherent potential to elucidate the host-microbiome interplay, with extensive anthropometric and biochemical characterizations and integrating metabolomics results with our previous 16S rRNA bacterial sequencing data. The rats were fed either a standard or an obesogenic cafeteria diet (CAF) for 17 weeks. After nine weeks, rats were supplemented with vehicle; low- (H1), or high- (H2) hesperidin doses. CAF animals developed MetS features. Hesperidin supplementation in CAF rats decreased the total cholesterol, LDL-C, and free fatty acids. The highest hesperidin dose also ameliorated blood pressure, insulin sensitivity, and decreased markers of arterial stiffness and inflammation. Metabolomics revealed an improvement of the lipidomic profile, decreases in circulating amino acids, and lower excretions of inflammation- and oxidative stress-related metabolites. Bacteroidaceae increases in the CAF-H2 group paralleled higher excretions of microbial-derived metabolites. Overall, our results provide detailed insights into the molecular effects of hesperidin on MetS and suggest that it is a promising prebiotic for the treatment of MetS and related conditions.

Treatment of Primary Aldosteronism With mTORC1 Inhibitors

CONTEXT

Mammalian target of rapamycin complex 1 (mTORC1) activity is often increased in the adrenal cortex of patients with primary aldosteronism (PA), and mTORC1 inhibition decreases aldosterone production in adrenocortical cells, suggesting the mTORC1 pathway as a target for treatment of PA.

OBJECTIVE

To investigate the effect of mTORC1 inhibition on adrenal steroid hormones and hemodynamic parameters in mice and in patients with PA.

DESIGN

(i) Plasma aldosterone, corticosterone, and angiotensin II (Ang II) were measured in mice treated for 24 hours with vehicle or rapamycin. (ii) Plasma aldosterone levels after a saline infusion test, plasma renin, and 24-hour urine steroid hormone metabolome and hemodynamic parameters were measured during an open-label study in 12 patients with PA, before and after 2 weeks of treatment with everolimus and after a 2-week washout.

MAIN OUTCOME MEASURES

(i) Change in plasma aldosterone levels. (ii) Change in other steroid hormones, renin, Ang II, and hemodynamic parameters.

RESULTS

Treatment of mice with rapamycin significantly decreased plasma aldosterone levels (P = 0.007). Overall, treatment of PA patients with everolimus significantly decreased blood pressure (P < 0.05) and increased renin levels (P = 0.001) but did not decrease aldosterone levels significantly. However, prominent reduction of aldosterone levels upon everolimus treatment was observed in four patients.

CONCLUSION

In mice, mTORC1 inhibition was associated with reduced plasma aldosterone levels. In patients with PA, mTORC1 inhibition was associated with improved blood pressure and renin suppression. In addition, mTORC1 inhibition appeared to reduce plasma aldosterone in a subset of patients.

Dairy Products: Is There an Impact on Promotion of Prostate Cancer? A Review of the Literature

This review of the literature aims to study potential associations between high consumption of milk and/or dairy products and prostate cancer (PC). Literature is scarce, yet there is a direct relationship between mTORC1 activation and PC; several ingredients in milk/dairy products, when in high concentrations, increase signaling of the mTORC1 pathway. However, there are no studies showing an unequivocal relationship between milk products PC initiation and/or progression. Three different reviews were conducted with articles published in the last 5 years: (M1) PC and intake of dairy products, taking into account the possible mTORC1signaling mechanism; (M2) Intake of milk products and incidence/promotion of PC; (M3) mTORC1 activation signaling pathway, levels of IGF-1 and PC; (M4) mTORC pathway and dairy products. Of the 32 reviews identified, only 21 met the inclusion criteria and were analyzed. There is little scientific evidence that directly link the three factors: incidence/promotion of PC, intake of dairy products and PC, and PC and increased mTORC1 signaling. Persistent hyper-activation of mTORC1 is associated with PC promotion. The activity of exosomal mRNA in cellular communication may lead to different impacts of different types of milk and whether or not mammalian milks will have their own characteristics within each species. Based on this review of the literature, it is possible to establish a relationship between the consumption of milk products and the progression of PC; we also found a possible association with PC initiation, hence it is likely that the intake of dairy products should be reduced or minimized in mens' diet.

Endospanin 1 Determines the Balance of Leptin-Regulated Hypothalamic Functions

Endospanin 1 (Endo1), a protein encoded in humans by the same gene than the leptin receptor (ObR), and increased by diet-induced obesity, is an important regulator of ObR trafficking and cell surface exposure, determining leptin signaling strength. Defective intracellular trafficking of the leptin receptor to the neuronal plasma membrane has been proposed as a mechanism underlying the development of leptin resistance observed in human obesity. More recently, Endo1 has emerged as a mediator of "selective leptin resistance." The underlying mechanisms of the latter are not completely understood, but the possibility of differential activation of leptin signaling pathways was suggested among others. In this respect, the expression level of Endo1 is crucial for the appropriate balance between different leptin signaling pathways and leptin functions in the hypothalamus and is likely participating in selective leptin resistance for the control of energy and glucose homeostasis.

Diseases of Civilization - Cancer, Diabetes, Obesity and Acne - the Implication of Milk, IGF-1 and mTORC1

Nutrition and food are one of the most complex aspects of human lives, being influenced by biochemical, psychological, social and cultural factors. The Western diet is the prototype of modern dietary pattern and is mainly characterized by the intake of large amounts of red meat, dairy products, refined grains and sugar. Large amounts of scientific evidence positively correlate Western diet to acne, obesity, diabetes, heart disease and cancer, the so-called "diseases of civilization". The pathophysiological common ground of all these pathologies is the IGF-1 and mTORC pathways, which will be disscussed further in this paper.

Hypothalamic Dysfunction in Obesity and Metabolic Disorders

The hypothalamus is the brain region responsible for the maintenance of energetic homeostasis. The regulation of this process arises from the ability of the hypothalamus to orchestrate complex physiological responses such as food intake and energy expenditure, circadian rhythm, stress response, and fertility. Metabolic alterations such as obesity can compromise these hypothalamic regulatory functions. Alterations in circadian rhythm, stress response, and fertility further contribute to aggravate the metabolic dysfunction of obesity and contribute to the development of chronic disorders such as depression and infertility.At cellular level, obesity caused by overnutrition can damage the hypothalamus promoting inflammation and impairing hypothalamic neurogenesis. Furthermore, hypothalamic neurons suffer apoptosis and impairment in synaptic plasticity that can compromise the proper functioning of the hypothalamus. Several factors contribute to these phenomena such as ER stress, oxidative stress, and impairments in autophagy. All these observations occur at the same time and it is still difficult to discern whether inflammatory processes are the main drivers of these cellular dysfunctions or if the hypothalamic hormone resistance (insulin, leptin, and ghrelin) can be pinpointed as the source of several of these events.Understanding the mechanisms that underlie the pathophysiology of obesity in the hypothalamus is crucial for the development of strategies that can prevent or attenuate the deleterious effects of obesity.

Leptin: role over central nervous system in epilepsy

Adipose tissue is a dynamic organ with different effects on the body. Many of these effects are mediated by leptin, a hormone strongly involved in regulation of feeding and energy metabolism. It has an important role as a mediator of neuronal excitatory activity and higher brain functions. The aim of this study was to review the association between leptin and cerebral neuronal function, in particular its anticonvulsant or convulsant effects and the possible therapeutic role for treating epilepsy. For this purpose, the databases Pubmed, Science Direct, Elsevier, ResearchGate and Scielo were searched to identify experimental studies, reviews and systematic review articles, published in English, Spanish or Portuguese. Experimental studies and the presence of leptin receptors in nervous system sites other than the hypothalamus suggest an influence on higher brain functions. Indeed several animal studies have demonstrated a role of these channels in epileptiform activity as both anticonvulsive and convulsive effects have been found. The reason for these discrepancies is unclear but provides clear evidence of a potential role of leptin and leptin therapy in epileptiform activity. The association between leptin and brain function demonstrates the importance of peripheral metabolic hormones on central nervous system and opens a new way for the development of novel therapeutic interventions in diseases like epilepsy. Nevertheless further investigations are important to clarify the dynamics and diverse actions of leptin on excitatory regulation in the brain.

Plasma Leptin Concentration and Sympathetic Nervous Activity in Older Adults With Physical Dysfunction

Context

Previous research has shown a positive relationship between plasma leptin and sympathetic nervous activity. High plasma leptin activate inflammatory cytokines and lead to muscle wasting. However, studies have detected low sympathetic nervous activity and high plasma leptin in older adults with muscle wasting, sarcopenia, and frailty. High plasma leptin do not seem to correlate with high sympathetic nervous activity. However, their relationship in older adults remains unclear.

Objective

We investigated the relationship between plasma leptin and sympathetic nervous activity in older adults.

Design, Setting, and Participants

We conducted a cross-sectional study and analyzed the results from 69 participants aged ≥75 years. Sympathetic nervous activity was measured by heart rate variability, obtained from 24-hour Holter monitoring. A functional independence measure (FIM) and Barthel index were used to assess physical function.

Results

The plasma leptin was higher in women (men, 3.4 ± 2.8 ng/mL; women, 6.6 ± 6.5 ng/mL; P = 0.024). Plasma leptin was negatively and substantially related to the FIM (β = −0.233; P = 0.049) and Barthel index (β = −0.298, P = 0.018) after adjustment for covariates. However, the data showed no relationship between the plasma leptin and sympathetic nervous activity.

Conclusions

We could not detect an association between sympathetic nervous activity and plasma leptin in older adults. This might suggest a failure of the feedback system of the sympathetic nervous system, leading to muscle wasting in older adults.

Astragaloside IV Prevents Obesity-Associated Hypertension by Improving Pro-Inflammatory Reaction and Leptin Resistance

Low-grade pro-inflammatory state and leptin resistance are important underlying mechanisms that contribute to obesity-associated hypertension. We tested the hypothesis that Astragaloside IV (As IV), known to counteract obesity and hypertension, could prevent obesity-associated hypertension by inhibiting pro-inflammatory reaction and leptin resistance. High-fat diet (HFD) induced obese rats were randomly assigned to three groups: the HFD control group (HF con group), As IV group, and the As IV + α-bungaratoxin (α-BGT) group (As IV+α-BGT group). As IV (20 mg·Kg-1·d-1) was administrated to rats for 6 weeks via daily oral gavage. Body weight and blood pressure were continuously measured, and NE levels in the plasma and renal cortex was evaluated to reflect the sympathetic activity. The expressions of leptin receptor (LepRb) mRNA, phosphorylated signal transducer and activator of transcription-3 (p-STAT3), phosphorylated phosphatidylinositol 3-kinase (p-PI3K), suppressor of cytokine signaling 3 (SOCS3) mRNA, and protein-tyrosine phosphatase 1B (PTP1B) mRNA, pro-opiomelanocortin (POMC) mRNA and neuropeptide Y (NPY) mRNA were measured by Western blot or qRT-PCR to evaluate the hypothalamic leptin sensitivity. Additionally, we measured the protein or mRNA levels of α7nAChR, inhibitor of nuclear factor κB kinase subunit β/ nuclear factor κB (IKKβ/NF-KB) and pro-inflammatory cytokines (IL-1β and TNF-α) in hypothalamus and adipose tissue to reflect the anti-inflammatory effects of As IV through upregulating expression of α7nAChR. We found that As IV prevented body weight gain and adipose accumulation, and also improved metabolic disorders in HFD rats. Furthermore, As IV decreased BP and HR, as well as NE levels in blood and renal tissue. In the hypothalamus, As IV alleviated leptin resistance as evidenced by the increased p-STAT3, LepRb mRNA and POMC mRNA, and decreased p-PI3K, SOCS3 mRNA, and PTP1B mRNA. The effects of As IV on leptin sensitivity were related in part to the up-regulated α7nAchR and suppressed IKKβ/NF-KB signaling and pro-inflammatory cytokines in the hypothalamus and adipose tissue, since co-administration of α7nAChR selective antagonist α-BGT could weaken the improved effect of As IV on central leptin resistance. Our study suggested that As IV could efficiently prevent obesity-associated hypertension through inhibiting inflammatory reaction and improving leptin resistance; furthermore, these effects of As IV was partly related to the increased α7nAchR expression.

Leptin and brain-adipose crosstalks

Interactions between the brain and distinct adipose depots have a key role in maintaining energy balance, thereby promoting survival in response to metabolic challenges such as cold exposure and starvation. Recently, there has been renewed interest in the specific central neuronal circuits that regulate adipose depots. Here, we review anatomical, genetic and pharmacological studies on the neural regulation of adipose function, including lipolysis, non-shivering thermogenesis, browning and leptin secretion. In particular, we emphasize the role of leptin-sensitive neurons and the sympathetic nervous system in modulating the activity of brown, white and beige adipose tissues. We provide an overview of advances in the understanding of the heterogeneity of the brain regulation of adipose tissues and offer a perspective on the challenges and paradoxes that the community is facing regarding the actions of leptin on this system.

Rapamycin Exacerbates Cardiovascular Dysfunction after Complete High-Thoracic Spinal Cord Injury

Autonomic dysreflexia (AD) is a potentially life-threatening syndrome in individuals with spinal cord injury (SCI) above the T6 spinal level that is characterized by episodic hypertension in response to noxious stimuli below the lesion. Maladaptive intraspinal plasticity is thought to contribute to the temporal development of AD, and experimental approaches that reduce such plasticity mitigate the severity of AD. The mammalian target of rapamycin (mTOR) has gained interest as a mediator of plasticity, regeneration, and nociceptor hypersensitivity in the injured spinal cord. Based on our preliminary data that prolonged rapamycin (RAP) treatment markedly reduces mTOR activity in the cord weeks after high-thoracic (T4) spinal transection, we sought to determine whether RAP could modulate AD development by impeding intraspinal plasticity. Naïve and injured rats were administered RAP or vehicle every other day, beginning immediately after injury for four weeks, and hemodynamic monitoring was conducted to analyze the frequency of spontaneously occurring AD, as well as the severity of colorectal distention (CRD) induced AD. Results showed that after SCI, RAP significantly exacerbated sustained body weight loss and caused a marked elevation in resting blood pressure, with average daily blood pressure rising above even normal naïve levels within one week after injury. Moreover, RAP significantly increased the frequency of daily spontaneous AD and increased the absolute blood pressure induced by CRD at three weeks post-injury. These dynamic cardiovascular effects were not, however, correlated with changes in the density of nociceptive c-fibers or c-Fos+ neurons throughout the spinal cord, indicating that intraspinal plasticity associated with AD was not altered by treatment. These findings caution against the use of RAP as a therapeutic intervention for SCI because it evokes toxic weight loss and exacerbates cardiovascular dysfunction perhaps mediated by increased peripheral nociceptor sensitivity and/or vascular resistance.

Factors Responsible for Obesity-Related Hypertension

PURPOSE OF REVIEW

The major health issue of being overweight or obese relates to the development of hypertension, insulin resistance and diabetic complications. One of the major underlying factors influencing the elevated blood pressure in obesity is increased activity of the sympathetic nerves to particular organs such as the kidney.

RECENT FINDINGS

There is now convincing evidence from animal studies that major signals such as leptin and insulin have a sympathoexcitatory action in the hypothalamus to cause hypertension. Recent studies suggest that this may involve 'neural plasticity' within hypothalamic signalling driven by central actions of leptin mediated via activation of melanocortin receptor signalling and activation of brain neurotrophic factors. This review describes the evidence to support the contribution of the SNS to obesity related hypertension and the major metabolic and adipokine signals.

Inhibition of Mammalian Target of Rapamycin Complex 1 Attenuates Salt-Induced Hypertension and Kidney Injury in Dahl Salt-Sensitive Rats

The goal of the present study was to explore the protective effects of mTORC1 (mammalian target of rapamycin complex 1) inhibition by rapamycin on salt-induced hypertension and kidney injury in Dahl salt-sensitive (SS) rats. We have previously demonstrated that H₂O₂ is elevated in the kidneys of SS rats. The present study showed a significant upregulation of renal mTORC1 activity in the SS rats fed a 4.0% NaCl for 3 days. In addition, renal interstitial infusion of H₂O₂ into salt-resistant Sprague Dawley rats for 3 days was also found to stimulate mTORC1 activity independent of a rise of arterial blood pressure. Together, these data indicate that the salt-induced increases of renal H₂O₂ in SS rats activated the mTORC1 pathway. Daily administration of rapamycin (IP, 1.5 mg/kg per day) for 21 days reduced salt-induced hypertension from 176.0±9.0 to 153.0±12.0 mm Hg in SS rats but had no effect on blood pressure salt sensitivity in Sprague Dawley treated rats. Compared with vehicle, rapamycin reduced albumin excretion rate in SS rats from 190.0±35.0 to 37.0±5.0 mg/d and reduced the renal infiltration of T lymphocytes (CD3⁺) and macrophages (ED1⁺) in the cortex and medulla. Renal hypertrophy and cell proliferation were also reduced in rapamycin-treated SS rats. We conclude that enhancement of intrarenal H₂O₂ with a 4.0% NaCl diet stimulates the mTORC1 pathway that is necessary for the full development of the salt-induced hypertension and kidney injury in the SS rat.

Recent Advances in Neurogenic Hypertension: Dietary Salt, Obesity, and Inflammation

Neurally-mediated hypertension results from a dysregulation of sympathetic and/or neuroendocrine mechanisms to increase ABP. Multiple factors may exert multiple central effects to alter neural circuits and produce unique sympathetic signatures and elevate ABP. In this brief review, we have discussed novel observations regarding three contributing factors: dietary salt intake, obesity, and inflammation. However, the interaction among these and other factors is likely much more complex; recent studies suggest a prior exposure to one stimulus may sensitize the response to a subsequent hypertensive stimulus. Insight into the central mechanisms by which these factors selectively alter SNA or cooperatively interact to impact hypertension may represent a platform for novel therapeutic treatment strategies.

Hypothalamic and inflammatory basis of hypertension

Hypertension is a major health problem with great consequences for public health. Despite its role as the primary cause of significant morbidity and mortality associated with cardiovascular disease, the pathogenesis of essential hypertension remains largely unknown. The central nervous system (CNS) in general, and the hypothalamus in particular, are intricately involved in the development and maintenance of hypertension. Over the last several decades, the understanding of the brain's role in the development of hypertension has dramatically increased. This brief review is to summarize the neural mechanisms of hypertension with a focus on neuroendocrine and neurotransmitter involvement, highlighting recent findings that suggest that hypothalamic inflammation disrupts key signalling pathways to affect the central control of blood pressure, and therefore suggesting future development of interventional strategies that exploit recent findings pertaining to the hypothalamic control of blood pressure as well as the inflammatory-sympathetic mechanisms involved in hypertension.

The cellular and molecular bases of leptin and ghrelin resistance in obesity

Obesity, a major risk factor for the development of diabetes mellitus, cardiovascular diseases and certain types of cancer, arises from a chronic positive energy balance that is often due to unlimited access to food and an increasingly sedentary lifestyle on the background of a genetic and epigenetic vulnerability. Our understanding of the humoral and neuronal systems that mediate the control of energy homeostasis has improved dramatically in the past few decades. However, our ability to develop effective strategies to slow the current epidemic of obesity has been hampered, largely owing to the limited knowledge of the mechanisms underlying resistance to the action of metabolic hormones such as leptin and ghrelin. The development of resistance to leptin and ghrelin, hormones that are crucial for the neuroendocrine control of energy homeostasis, is a hallmark of obesity. Intensive research over the past several years has yielded tremendous progress in our understanding of the cellular pathways that disrupt the action of leptin and ghrelin. In this Review, we discuss the molecular mechanisms underpinning resistance to leptin and ghrelin and how they can be exploited as targets for pharmacological management of obesity.

Obesity-associated extracellular mtDNA activates central TGFβ pathway to cause blood pressure increase

Hypothalamic inflammation was recently found to mediate obesity-related hypertension, but the responsible upstream mediators remain unexplored. In this study, we show that dietary obesity is associated with extracellular release of mitochondrial DNA (mtDNA) into the cerebrospinal fluid and that central delivery of mtDNA mimics transforming growth factor-β (TGFβ) excess to activate downstream signaling pathways. Physiological study reveals that central administration of mtDNA or TGFβ is sufficient to cause hypertension in mice. Knockout of the TGFβ receptor in proopiomelanocortin neurons counteracts the hypertensive effect of not only TGFβ but also mtDNA excess, while the hypertensive action of central mtDNA can be blocked pharmacologically by a TGFβ receptor antagonist or genetically by TGFβ receptor knockout. Finally, we confirm that obesity-induced hypertension can be reversed through central treatment with TGFβ receptor antagonist. In conclusion, circulating mtDNA in the brain employs neural TGFβ pathway to mediate a central inflammatory mechanism of obesity-related hypertension.

Leptin as a Mediator of Obesity-Induced Hypertension

Hypertension and associated cardiovascular diseases represent the most common health complication of obesity and the leading cause of morbidity and mortality in overweight and obese patients. Emerging evidence suggests a critical role for the central nervous system particularly the brain action of the adipocyte-derived hormone leptin in linking obesity and hypertension. The preserved ability of leptin to cause cardiovascular sympathetic nerve activation despite the resistance to the metabolic actions of the hormone appears essential in this pathological process. This review describes the evidence supporting the neurogenic bases for obesity-associated hypertension with a particular focus on the neuronal and molecular signaling pathways underlying leptin's effects on sympathetic nerve activity and blood pressure.

Developmental Origins of Cardiometabolic Diseases: Role of the Maternal Diet

Developmental origins of cardiometabolic diseases have been related to maternal nutritional conditions. In this context, the rising incidence of arterial hypertension, diabetes type II, and dyslipidemia has been attributed to genetic programming. Besides, environmental conditions during perinatal development such as maternal undernutrition or overnutrition can program changes in the integration among physiological systems leading to cardiometabolic diseases. This phenomenon can be understood in the context of the phenotypic plasticity and refers to the adjustment of a phenotype in response to environmental input without genetic change, following a novel, or unusual input during development. Experimental studies indicate that fetal exposure to an adverse maternal environment may alter the morphology and physiology that contribute to the development of cardiometabolic diseases. It has been shown that both maternal protein restriction and overnutrition alter the central and peripheral control of arterial pressure and metabolism. This review will address the new concepts on the maternal diet induced-cardiometabolic diseases that include the potential role of the perinatal malnutrition.

Contribution of adaptive thermogenesis to the hypothalamic regulation of energy balance

Obesity and its related disorders are among the most pervasive diseases in contemporary societies, and there is an urgent need for new therapies and preventive approaches. Given (i) our poor social capacity to correct unhealthy habits, and (ii) our evolutionarily genetic predisposition to store excess energy as fat, the current environment of caloric surplus makes the treatment of obesity extremely difficult. During the last few decades, an increasing number of methodological approaches have increased our knowledge of the neuroanatomical basis of the control of energy balance. Compelling evidence underlines the role of the hypothalamus as a homeostatic integrator of metabolic information and its ability to adjust energy balance. A greater understanding of the neural basis of the hypothalamic regulation of energy balance might indeed pave the way for new therapeutic targets. In this regard, it has been shown that several important peripheral signals, such as leptin, thyroid hormones, oestrogens and bone morphogenetic protein 8B, converge on common energy sensors, such as AMP-activated protein kinase to modulate sympathetic tone on brown adipose tissue. This knowledge may open new ways to counteract the chronic imbalance underlying obesity. Here, we review the current state of the art on the role of hypothalamus in the regulation of energy balance with particular focus on thermogenesis.

Neural Control of Non-vasomotor Organs in Hypertension

Hypertension affects over 25 % of the population with the incidence continuing to rise, due in part to the growing obesity epidemic. Chronic elevations in sympathetic nerve activity (SNA) are a hallmark of the disease and contribute to elevations in blood pressure through influences on the vasculature, kidney, and heart (i.e., neurogenic hypertension). In this regard, a number of central nervous system mechanisms and neural pathways have emerged as crucial in chronically elevating SNA. However, it is important to consider that "sympathetic signatures" are present, with differential increases in SNA to regional organs that are dependent upon the disease progression. Here, we discuss recent findings on the central nervous system mechanisms and autonomic regulatory networks involved in neurogenic hypertension, in both non-obesity- and obesity-associated hypertension, with an emphasis on angiotensin-II, salt, oxidative and endoplasmic reticulum stress, inflammation, and the adipokine leptin.

mTORC1 Signaling Contributes to Drinking But Not Blood Pressure Responses to Brain Angiotensin II

Mechanistic target of rapamycin complex 1 (mTORC1) is a molecular node that couples extracellular cues to a wide range of cellular events controlling various physiological processes. Here, we identified mTORC1 signaling as a critical mediator of angiotensin II (Ang II) action in the brain. In neuronal GT1-7 cells, we show that Ang II stimulates neuronal mTORC1 signaling in an Ang II type 1 receptor-dependent manner. In mice, a single intracerebroventricular (ICV) injection or chronic sc infusion of Ang II activated mTORC1 signaling in the subfornical organ, a critical brain region in cardiovascular control and fluid balance. Moreover, transgenic sRA mice with brain-specific overproduction of Ang II displayed increased mTORC1 signaling in the subfornical organ. To test the functional role of brain mTORC1 in mediating the action of Ang II, we examined the consequence of mTORC1 inhibition with rapamycin on Ang II-induced increase in water intake and arterial pressure. ICV pretreatment with rapamycin blocked ICV Ang II-mediated increases in the frequency, duration, and amount of water intake but did not interfere with the pressor response evoked by Ang II. In addition, ICV delivery of rapamycin significantly reduced polydipsia, but not hypertension, of sRA mice. These results demonstrate that mTORC1 is a novel downstream pathway of Ang II type 1 receptor signaling in the brain and selectively mediates the effect of Ang II on drinking behavior.

Long-term leucine supplementation aggravates prolonged strenuous exercise-induced cardiovascular changes in trained rats

NEW FINDINGS

What is the central question of this study? Can long-term leucine supplementation prevent prolonged strenuous endurance exercise induced cardiac injury? What is the main finding and its importance? Prolonged endurance exercise does not seem to exceed cardiac energetic capacity, hence it does not represent an energy threat to this organ, at least in trained subjects. However, it may induce, in susceptible individuals, a state of cardiac electrical instability, which has been associated with ventricular arrhythmias and sudden cardiac death. This situation might be worsened when combined with leucine supplementation, which leads to increased blood pressure and cardiac injury. Leucine supplementation failed to prevent cardiac fatigue symptoms and may aggravate prolonged strenuous exercise-induced cardiovascular disturbances in trained rats. Observational studies have raised concerns that prolonged strenuous exercise training may be associated with increased risk of cardiac arrhythmia and even primary cardiac arrest or sudden death. It has been demonstrated that leucine can reduce prolonged exercise-induced muscle damage and accelerate the recovery process. The aim of this study was to investigate the effects of prolonged strenuous endurance exercise on cardiovascular parameters and biomarkers of cardiac injury in trained adult male rats and assess the use of leucine as an auxiliary substance to prevent the likely cardiac adverse effects caused by strenuous exercise. Twenty-four male Wistar rats were randomly allocated to receive a balanced control diet (18% protein) or a leucine-rich diet (15% protein plus 3% leucine) for 6 weeks. The rats were submitted to 1 h of exercise, 5 days per week for 6 weeks. Three days after the training period, the rats were submitted to swimming exercise until exhaustion, and cardiac parameters were assessed. Exercising until exhaustion significantly increased cardiac biomarker levels, cytokines and glycogen content inhibited protein synthesis signalling and led to cardiac electrical disturbances. When combined with exercise, leucine supplementation led to greater increases in the aforementioned parameters and also a significant increase in blood pressure and protein degradation signalling. We report, for the first time, that leucine supplementation not only fails to prevent cardiac fatigue symptoms, but may also aggravate prolonged strenuous exercise-induced cardiovascular disturbances in trained rats. Furthermore, we find that exercising until exhaustion can cause cardiac electrical disturbances and damage cardiac myocytes.

Hypothalamic roles of mTOR complex I: integration of nutrient and hormone signals to regulate energy homeostasis

Mammalian or mechanistic target of rapamycin (mTOR) senses nutrient, energy, and hormone signals to regulate metabolism and energy homeostasis. mTOR activity in the hypothalamus, which is associated with changes in energy status, plays a critical role in the regulation of food intake and body weight. mTOR integrates signals from a variety of "energy balancing" hormones such as leptin, insulin, and ghrelin, although its action varies in response to these distinct hormonal stimuli as well as across different neuronal populations. In this review, we summarize and highlight recent findings regarding the functional roles of mTOR complex 1 (mTORC1) in the hypothalamus specifically in its regulation of body weight, energy expenditure, and glucose/lipid homeostasis. Understanding the role and underlying mechanisms behind mTOR-related signaling in the brain will undoubtedly pave new avenues for future therapeutics and interventions that can combat obesity, insulin resistance, and diabetes.

The use of pupillometry as monitoring of intraoperative analgesia in the consumption of analgesics during the first 12 hours after surgery

INTRODUCTION

Intraoperative evaluation of analgesia remains today often based on heart rate and arterial pressure fluctuations. None of these parameters is specific. Incorrect handling during this process may increase surgical morbi-mortality of the patients and their acute postoperative pain. The aim of this study was to evaluate the impact of intraoperative analgesia controlled by pupillometry on postoperative analgesic consumption and the pain intensity in the first 12h in the hospital room, after major gynecological surgery.

PATIENTS AND METHODS

A prospective, cohort study with allocation of groups of sequentially according to programming of operating room was designed. ASA I-III patients scheduled for elective surgery of abdominal hysterectomy by laparotomy or laparoscopy through intravenous general anesthesia were included. Patients were divided into 2 groups: pupillometry group (P-1), in which intraoperative analgesia was guided by pupillometry, and hemodynamic group (H-2) according to values of blood pressure and heart rate. In the hospitalization room the values of visual analogue scale (VAS) were routinely registered with 3 courts for the study: 3, 8 and 12h of the postoperative period. Postoperative analgesia was standardized as follows: NSAIDs was administered if VAS was ≥ 3 or if the patient expressly requested an analgesic. After this, the efficacy of treatment was assessed. If the patient had pain, the next scheduled drug was given up to an VAS<3. Data for total analgesic consumption administered in the hospital room, VAS and adverse effects were collected within 12h postoperatively.

RESULTS

A total of 59 patients, 30 group P-1 and 29 group H-2, were included. Group P-1 experienced less pain than group H-2, with statistical significance in each phase (VAS 3h, VAS 8h and VAS 12h). These data are consistent with the consumption of analgesics for patients. There was a statistically significant reduction (p<0.001) in the group P-1 (1.80 [DE 0.99]; medium 2, 95% confidence interval 1.43-2.17) compared with group H-2 (5.66 [1.58]; medium 6, 95% confidence interval 5.05-6.26).

CONCLUSIONS

Monitoring of the intraoperative analgesia by pupillometry was able to reduce the intensity of the acute postoperative pain and analgesic consumption in the first 12h in the hospital room after major gynecological surgery.