Leptin as a Mediator of Obesity-Induced Hypertension

Molecular Mechanisms of Adiponectin-Induced Attenuation of Mechanical Stretch-Mediated Vascular Remodeling

Hypertension induces vascular hypertrophy, which changes blood vessels structurally and functionally, leading to reduced tissue perfusion and further hypertension. It is also associated with dysregulated levels of the circulating adipokines leptin and adiponectin (APN). Leptin is an obesity-associated hormone that promotes vascular smooth muscle cell (VSMC) hypertrophy. APN is a cardioprotective hormone that has been shown to attenuate hypertrophic cardiomyopathy. In this study, we investigated the molecular mechanisms of hypertension-induced VSMC remodeling and the involvement of leptin and APN in this process. To mimic hypertension, the rat portal vein (RPV) was mechanically stretched, and the protective effects of APN on mechanical stretch-induced vascular remodeling and the molecular mechanisms involved were examined by using 10 μg/ml APN. Mechanically stretching the RPV significantly decreased APN protein expression after 24 hours and APN mRNA expression in a time-dependent manner in VSMCs. The mRNA expression of the APN receptors AdipoR1, AdipoR2, and T-cadherin significantly increased after 15 hours of stretch. The ratio of APN/leptin expression in VSMCs significantly decreased after 24 hours of mechanical stretch. Stretching the RPV for 3 days increased the weight and [³H]-leucine incorporation significantly, whereas APN significantly reduced hypertrophy in mechanically stretched vessels. Stretching the RPV for 10 minutes significantly decreased phosphorylation of LKB1, AMPK, and eNOS, while APN significantly increased p-LKB1, p-AMPK, and p-eNOS in stretched vessels. Mechanical stretch significantly increased p-ERK1/2 after 10 minutes, whereas APN significantly reduced stretch-induced ERK1/2 phosphorylation. Stretching the RPV also significantly increased ROS generation after 1 hour, whereas APN significantly decreased mechanical stretch-induced ROS production. Exogenous leptin (3.1 nM) markedly increased GATA-4 nuclear translocation in VSMCs, whereas APN significantly attenuated leptin-induced GATA-4 nuclear translocation. Our results decipher molecular mechanisms of APN-induced attenuation of mechanical stretch-mediated vascular hypertrophy, with the promising potential of ultimately translating this protective hormone into the clinic.

Recent Updates on Obesity Treatments: Available Drugs and Future Directions

In the last thirty years, obesity has reached epidemic proportions and is now regarded as a major health issue in contemporary society trending to serious economic and social burdens. The latest projections of the World Health Organization are alarming. By 2030, nearly 60% of the worldwide population could be either obese or overweight, highlighting the needs to find innovative treatments. Currently, bariatric surgery is the most effective way to efficiently lower body mass. Although great improvements in terms of recovery and patient care were made in these surgical procedures, bariatric surgery remains an option for extreme forms of obesity and seems unable to tackle obesity pandemic expansion. Throughout the last century, numerous pharmacological strategies targeting either peripheral or central components of the energy balance regulatory system were designed to reduce body mass, some of them reaching sufficient levels of efficiency and safety. Nevertheless, obesity drug therapy remains quite limited on its effectiveness to actually overcome the obesogenic environment. Thus, innovative unimolecular polypharmacology strategies, able to simultaneously target multiple actors involved in the obesity initiation and expansion, were developed during the last ten years opening a new promising avenue in the pharmacological management of obesity. In this review, we first describe the clinical features of obesity-associated conditions and then focus on the outcomes of currently approved drug therapies for obesity as well as new ones expecting to reach the clinic in the near future.

Blood Pressure Indices and Associated Risk Factors in a Rural West African Adult Population: Insights from an AWI-Gen Substudy in Ghana

Systolic (SBP) and diastolic blood pressure (DBP) are commonly used for cardiovascular disease (CVD) risk prediction, and pulse pressure (PP) and mean arterial blood pressure (MAP) can provide additional information. It is therefore important to understand the factors associated with these cardiovascular risk markers. This cross-sectional study involved 1839 men and women aged 40-60 years. Data on SBP, DBP, MAP, PP, sociodemography, lifestyle, anthropometry, and lipids were collected. Gender-stratified linear regression analyses were performed to determine the association between log-transformed blood pressure indices and the study variables. Age was associated with all measured blood pressure indices (p < 0.001) among men and women. Men had higher SBP (p=0.007) and PP (p < 0.001) than women. Nankana ethnicity was associated with higher PP levels (p < 0.005) in the total population. Vendor meal consumption among women was associated with higher PP levels (p < 0.05). Fruit intake among men was associated with lower PP levels (p < 0.05). Currently unmarried women had higher SBP (p < 0.005), DBP (p < 0.05), MAP (p < 0.005), and PP (p < 0.005) than currently married women. Pesticide exposure was negatively associated with SBP (p < 0.005), DBP (p < 0.005), MAP (p < 0.005), and PP (p < 0.05) among women. Increased subcutaneous fat was associated with DBP (p < 0.005) and MAP (p < 0.05) among women. Among men, hip circumference was associated with higher DBP and MAP (p < 0.05 for both associations), subcutaneous fat associated with higher SBP (p < 0.005), DBP (p < 0.001), and MAP (p < 0.001) and visceral fat was associated with higher PP (p < 0.05). In the total population, visceral fat was associated with higher DBP (p < 0.05) and MAP (p < 0.001). High-density lipoprotein cholesterol was positively associated with SBP (p < 0.005), DBP (p < 0.005), and MAP (p < 0.001) for women and positively associated with SBP, DBP, and MAP (p < 0.001 for all three) and PP (p < 0.05) for men. The association of blood pressure indices with modifiable risk factors suggests that targeted health interventions may reduce CVD risk in this population.

Association of triglycerides to high-density lipoprotein-cholesterol ratio with risk of incident hypertension

The triglyceride to high-density lipoprotein-cholesterol (TG/HDL-C) ratio is considered a simple surrogate of insulin resistance. The aim of this study was to explore the association of the TG/HDL-C ratio with the risk of incident hypertension and whether the TG/HDL-C ratio mediates the obesity-incident hypertension association. The study analyzed 9679 participants from a rural Chinese population. Demographic and anthropometric and laboratory data were collected at baseline (2007-2008) and follow-up (2013-2014) examinations. A multivariate logistic regression model was used to analyze the association of the TG/HDL-C ratio with incident hypertension, estimating odds ratios (ORs) and 95% confidence intervals (CIs). Mediation analysis was performed to examine the contribution of the TG/HDL-C ratio to obesity-related incident hypertension. During a median follow-up of 6.00 years, hypertension developed in 1880/9679 participants (19.42%). The risk of incident hypertension was higher in the highest TG/HDL-C ratio quartile than in the lowest quartile (OR = 1.21, 95% CI = 1.02-1.42). Subgroup analyses showed that the risk of incident hypertension was increased by 30%, 36%, and 33% among women, participants < 60 years old and those with prehypertension at baseline, respectively. The TG/HDL-C ratio partially mediated the obesity-incident hypertension association (indirect effect: OR = 1.04, 95% CI: 1.01-1.07; direct effect: OR = 1.36, 95% CI: 1.16-1.62). The TG/HDL-C ratio may be a risk factor for incident hypertension, especially in women, participants < 60 years old and those with prehypertension. The TG/HDL-C ratio may also play a mediating role in obesity-related incident hypertension.

Obesity: sex and sympathetics

Obesity increases sympathetic nerve activity (SNA) in men, but not women. Here, we review current evidence suggesting that sexually dimorphic sympathoexcitatory responses to leptin and insulin may contribute. More specifically, while insulin increases SNA similarly in lean males and females, this response is markedly amplified in obese males, but is abolished in obese females. In lean female rats, leptin increases a subset of sympathetic nerves only during the high estrogen proestrus reproductive phase; thus, in obese females, because reproductive cycling can become impaired, the sporadic nature of leptin-induced sympathoexcitaton could minimize its action, despite elevated leptin levels. In contrast, in males, obesity preserves or enhances the central sympathoexcitatory response to leptin, and current evidence favors leptin’s contribution to the well-established increases in SNA induced by obesity in men. Leptin and insulin increase SNA via receptor binding in the hypothalamic arcuate nucleus and a neuropathway that includes arcuate neuropeptide Y (NPY) and proopiomelanocortin (POMC) projections to the paraventricular nucleus. These metabolic hormones normally suppress sympathoinhibitory NPY neurons and activate sympathoexcitatory POMC neurons. However, obesity appears to alter the ongoing activity and responsiveness of arcuate NPY and POMC neurons in a sexually dimorphic way, such that SNA increases in males but not females. We propose hypotheses to explain these sex differences and suggest areas of future research.

Sites and sources of sympathoexcitation in obese male rats: role of brain insulin

In males, obesity increases sympathetic nerve activity (SNA), but the mechanisms are unclear. Here, we investigate insulin, via an action in the arcuate nucleus (ArcN), and downstream neuropathways, including melanocortin receptor 3/4 (MC3/4R) in the hypothalamic paraventricular nucleus (PVN) and dorsal medial hypothalamus (DMH). We studied conscious and α-chloralose-anesthetized Sprague-Dawley rats fed a high-fat diet, which causes obesity prone (OP) rats to accrue excess fat and obesity-resistant (OR) rats to maintain fat content, similar to rats fed a standard control (CON) diet. Nonspecific blockade of the ArcN with muscimol and specific blockade of ArcN insulin receptors (InsR) decreased lumbar SNA (LSNA), heart rate (HR), and mean arterial pressure (MAP) in OP, but not OR or CON, rats, indicating that insulin supports LSNA in obese males. In conscious rats, intracerebroventricular infusion of insulin increased MAP only in OP rats and also improved HR baroreflex function from subnormal to supranormal. The brain sensitization to insulin may elucidate how insulin can drive central SNA pathways when transport of insulin across the blood-brain barrier may be impaired. Blockade of PVN, but not DMH, MC3/4R with SHU9119 decreased LSNA, HR, and, MAP in OP, but not OR or CON, rats. Interestingly, nanoinjection of the MC3/4R agonist melanotan II (MTII) into the PVN increased LSNA only in OP rats, similar to PVN MTII-induced increases in LSNA in CON rats after blockade of sympathoinhibitory neuropeptide Y Y1 receptors. ArcN InsR expression was not increased in OP rats. Collectively, these data indicate that obesity increases SNA, in part via increased InsR signaling and downstream PVN MC3/4R.

A systematic review on different models of inducing obesity in animals: Advantages and limitations

Several animals have been in the limelight of basic research associated with metabolic diseases like obesity. Obesity can be considered as a significant public health concern in the world. It raises the chances for a variety of disease conditions that includes diabetes, hypertension, liver disease, and cancers, which, in turn, decreases the overall lifespan of adult men and women. The World Health Organization has considered obesity as a global epidemic. Researchers have made several attempts to classify human obesity, but none have been successful. Animal obesity can be classified based on their etiology; however, till now, no animal model of obesity can replicate models of the human condition, they have only provided clues into the causes, aftermaths, and preventive remedy to human adiposity. Over the years, there are varieties of animal models used to induce obesity. Some of them include monogenic, polygenic, surgical, seasonal, and other models of obesity. Apart from the advantages of these models, most of them are accompanied by limitations. The primary purpose of this review is, therefore, to highlight the several models with their advantages and limitations. By knowing the benefits and limitations of animal models of obesity, researchers may be at liberty to select the appropriate one for the study of obesity.

Obesity-induced sympathoexcitation is associated with Nrf2 dysfunction in the rostral ventrolateral medulla

Increases in sympathetic nerve activity (SNA) have been implicated in obesity-induced risk for cardiovascular diseases, especially hypertension. Previous studies indicate that oxidative stress in the rostral ventrolateral medulla (RVLM), a key brain stem region that regulates sympathetic outflow to peripheral tissues, plays a pathogenic role in obesity-mediated sympathoexcitation. However, the molecular mechanisms underlying this phenomenon are not clear. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates the expression of antioxidant and anti-inflammatory genes and confers cytoprotection against oxidative stress. The present study was designed to investigate whether Nrf2 dysfunction was associated with obesity-induced oxidative stress in the RVLM and sympathoexcitation. C57BL/6J mice were fed with chow or a high-fat diet (HFD) for 16 wk. Blood pressure parameters were assessed by radiotelemeters in conscious freely moving mice. SNA was measured by heart rate variability analysis and also through assessment of depressor response to ganglionic blockade. The RVLM was microdissected for gene expression and protein analysis (Western blot analysis and activity assay) related to Nrf2 signaling. Our results showed that HFD-induced obesity resulted in significant increases in SNA, although we only observed a mild increase in mean arterial pressure. Obesity-induced oxidative stress in the RVLM was associated with impaired Nrf2 signaling marked by decreased Nrf2 activity, downregulation of Nrf2 mRNA, its target genes [NAD(P)H quinone dehyrogenase 1 (Nqo1) and superoxide dismutase 2 (Sod2)], and inflammation. Our findings suggest that obesity results in Nrf2 dysfunction, which likely causes maladaptation to oxidative stress and inflammation in the RVLM. These mechanisms could potentially contribute to obesity-induced sympathoexcitation.

Leptin-Mediated Sympathoexcitation in Obese Rats: Role for Neuron-Astrocyte Crosstalk in the Arcuate Nucleus

Introduction

Accumulated evidence indicates that obesity is associated with enhanced sympathetic activation. Hypothalamic leptin-mediated signaling may contribute to the exaggerated sympathoexcitation of obesity. The goal of this study was to investigate the "neuron-astrocyte" interaction affecting leptin-mediated sympathoexcitation within the arcuate nucleus (ARCN) of the hypothalamus in obese rats.

Methods and Results

Obesity was induced by high-fat diet (HFD, 42% of calories from fat) in Sprague Dawley rats. Twelve weeks of HFD produced hyperleptinemia, hyperlipidemia, and insulin resistance. In anesthetized rats, microinjections of leptin into the ARCN induced increases in heart rate (HR), renal sympathetic nerve activity (RSNA), and mean arterial pressure (MAP) in both control and HFD rats. However, microinjections of leptin in HFD rats elicited higher responses of RSNA and arterial pressure than control-fed rats. It also caused the inhibition of astrocytes within the ARCN using an astrocytic metabolic inhibitor, fluorocitrate, and reduced leptin-induced sympathetic activity and blood pressure responses. Moreover, the expression of the leptin receptor in the ARCN of HFD-fed rats was significantly increased compared to rats fed a control diet. Immunohistochemistry analysis revealed leptin receptor localization from both neurons and astrocytes of the ARCN. HFD rats exhibited increased protein expression of glial fibrillary acidic protein (GFAP) in the ARCN. We also found that the expression of astrocyte-specific glutamate transporters and excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2) were decreased within the ARCN of the HFD rats. In cultured astrocytic C6 cells, 24 h of leptin treatment increased the protein expression of GFAP and reduced the expression of EAAT1 and EAAT2.

Conclusion

The results suggest that central leptin signaling occurs via neuron-astrocyte interactions in the ARCN and contributing to the exaggerated sympathoexcitation observed in obese rats. The effects may be mediated by the action of leptin on regulating astrocytic glutamate transporters within the ARCN of the hypothalamus.

Risk of hypertension following perinatal adversity: IUGR and prematurity

Consistent with the paradigm shifting observations of David Barker and colleagues that revealed a powerful relationship between decreased weight through 2 years of age and adult disease, intrauterine growth restriction (IUGR) and preterm birth are independent risk factors for the development of subsequent hypertension. Animal models have been indispensable in defining the mechanisms responsible for these associations and the potential targets for therapeutic intervention. Among the modifiable risk factors, micronutrient deficiency, physical immobility, exaggerated stress hormone exposure and deficient trophic hormone production are leading candidates for targeted therapies. With the strong inverse relationship seen between gestational age at delivery and the risk of hypertension in adulthood trumping all other major cardiovascular risk factors, improvements in neonatal care are required. Unfortunately, therapeutic breakthroughs have not kept pace with rapidly improving perinatal survival, and groundbreaking bench-to-bedside studies are urgently needed to mitigate and ultimately prevent the tsunami of prematurity-related adult cardiovascular disease that may be on the horizon. This review highlights our current understanding of the developmental origins of hypertension and draws attention to the importance of increasing the availability of lactation consultants, nutritionists, pharmacists and physical therapists as critical allies in the battle that IUGR or premature infants are waging not just for survival but also for their future cardiometabolic health.

Leptin mediates the relationship between fat mass and blood pressure: The Hamamatsu School-based health study

Animal studies have shown that leptin mediates the association between obesity and hypertension. However, only a few studies have assessed this relationship in population-based epidemiological studies. This study aimed to determine whether leptin mediates the relationship between body fat and blood pressure in school-aged children.A cross-sectional survey was conducted among school-aged children in Hamamatsu, Japan. Body fat was measured using dual-energy X-ray absorptiometry. Height-normalized index of fat mass (fat mass index) was calculated by dividing fat mass by height squared. Serum leptin levels were measured by enzyme-linked immunosorbent assay. Multiple regression analysis was used to evaluate relationships between body fat, serum leptin levels, and blood pressure. The mediating effect of leptin on the association between body fat and blood pressure was assessed by causal mediation analysis and regression analysis.Both fat mass index and leptin were significantly and positively associated with blood pressure. Fat mass index was also strongly associated with serum leptin levels. Body fat and blood pressure were no longer associated after adjusting for leptin. These findings suggest that the association between body fat and blood pressure is mediated by leptin. Of the total effect of fat mass index on blood pressure, the mediating effect of leptin accounted for 78.6% (P = .03) in boys and 42.2% (P = .11) in girls.Our findings suggest that body fat is associated with blood pressure, and this association is mediated by leptin. Thus, leptin acts as a mediator that links body adiposity with blood pressure elevation in school-aged children.

Genetics of Severe Obesity

PURPOSE OF REVIEW

This review aims to present current information on genes underlying severe obesity, with the main emphasis on the three genes LEP, LEPR and MC4R.

RECENT FINDINGS

There is a substantial amount of evidence that variants in at least ten different genes are the cause of severe monogenic obesity. The majority of these are involved in the leptin-melanocortin signalling pathway. Due to the frequency of some of the identified variants, it is clear that monogenic variants also make a significant contribution to common obesity. The artificial distinction between rare monogenic obesity and common polygenic obesity is now obsolete with the identification of MC4R variants of strong effect in the general population.

Leptin, cardiovascular diseases and type 2 diabetes mellitus

Leptin, an adipokine that is implicated in the control of food intake via appetite suppression, may also stimulate oxidative stress, inflammation, thrombosis, arterial stiffness, angiogenesis and atherogenesis. These leptin-induced effects may predispose to the development of cardiovascular diseases. In the present review we discuss the evidence linking leptin levels with the presence, severity and/or prognosis of both coronary artery disease and non-cardiac vascular diseases such as stroke, carotid artery disease, peripheral artery disease (PAD) and abdominal aortic aneurysms (AAA) as well as with chronic kidney disease (CKD) and type 2 diabetes mellitus (T2DM). Leptin levels have been positively associated with the presence, severity, extent and lesion complexity of coronary atherosclerosis as well as with the presence, severity and poor clinical outcomes of both ischemic and hemorrhagic strokes. But conflicting results also exist. Furthermore, leptin was reported to independently predict common carotid intima-media thickness and carotid plaque instability. A link between hyperleptinemia and PAD has been reported, whereas limited data were available on the potential association between leptin and AAA. Elevated leptin concentrations have also been related to CKD incidence and progression as well as with insulin resistance, T2DM, micro- and macrovascular diabetic complications. Statins and antidiabetic drugs (including sitagliptin, metformin, pioglitazone, liraglutide and empagliflozin) may affect leptin levels. Further research is needed to establish the potential use (if any) of leptin as a therapeutic target in these diseases.

Leptin and Leptin receptor polymorphisms, plasma Leptin levels and obesity in Tunisian volunteers

Adipose tissue is an important endocrine organ that secretes a number of adipokines, like Leptin (LEP). The aim this study was to investigate the prevalence of single nucleotide polymorphisms in LEP gene (LEP 3'UTR A/C, -2548 G/A) and LEPR (K109R and Q223R) and their association with Leptin level and obesity. We recruited 169 non-obese (body mass index [BMI] = 24.51-3.69 kg/m² ) and 160 obese (BMI = 36-4.78 kg/m² ) patients. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism, BMI was calculated, and Leptin level was measured by ELISA. Statistical analyses were performed by spss19.0. According to LEP 3'UTR A/C polymorphism, AC and CC genotype carriers had higher Leptin levels than AA genotype carriers, respectively, 31[0.05-148.8] (P = .008) vs 41[0.05-111.6] (P = .003). The K109R polymorphism was associated with obesity (P = .025) and seems to significantly decrease the LEP levels (P < .001). Concerning LEP G2548A polymorphism, our results showed that the OR of obesity associated with 2548 AA/GG was 1.87[1.106-2.78] P = .028 vs 1.41[1.035-1.85] P = .045 for 223AA/GG polymorphism. In our haplotype analysis, one haplotype seems to be the more protective and one other seems to be the highest risk to obesity. LEP 3'UTR A/C and LEPR K109R polymorphisms were associated with Leptin level and obesity.

Disparities in Hypertension Among African-Americans: Implications of Insufficient Sleep

PURPOSE OF REVIEW

Sleep deficiency has been proposed as a potential contributor to racial disparities in cardiovascular health. We present contemporary evidence on the unequal burden of insufficient sleep in Blacks/African-Americans and the repercussions for disparate risk of hypertension.

RECENT FINDINGS

The prevalence of insufficient sleep is high and rising and has been recognized as an important cardiovascular risk factor. Presumably due to a constellation of environmental, psychosocial, and individual determinants, these risks appear exacerbated in Blacks/African-Americans, who are more likely to experience short sleep than other ethnic/racial groups. Population-based data suggest that the risk of hypertension associated with sleep deficiency is greater in those of African ancestry. However, there is a paucity of experimental evidence linking short sleep duration to blood pressure levels in African-Americans. Blacks/African-Americans may be more vulnerable to sleep deficiency and to its hypertensive effects. Future research is needed to unequivocally establish causality and determine the mechanism underlying the postulated racial inequalities in sleep adequacy and consequent cardiovascular risk.

Cardiovascular Risk in Patients with Prehypertension and the Metabolic Syndrome

Prehypertension (pHTN) and metabolic syndrome (MetS) are both lifestyle diseases that are potentiated by increased adiposity, as both disease processes are closely related to weight. In the case of pHTN, increased adiposity causes dysregulation of the renin-angiotensin-aldosterone-system (RAAS) as well as adipokine- and leptin-associated increases in adrenergic tone. In MetS, excess weight potentiates hyperglycemia and insulin resistance which causes positive feedback into the RAAS system, activates an inflammatory cascade that potentiates atherosclerosis, and causes lipid dysregulation which together contribute to cardiovascular disease, especially coronary heart disease (CHD) and heart failure (HF). The relationship with all-cause mortality is not as clear-cut in part because of some protective effects associated with the obesity paradox in chronic diseases such as CHD and HF. However, in healthy populations, the absence of excess weight and its associated effects on prehypertension and MetS are associated with a longer absolute and disease-free lifespan.

Differential contribution of POMC and AgRP neurons to the regulation of regional autonomic nerve activity by leptin

Objectives

The autonomic nervous system is critically involved in mediating the control by leptin of many physiological processes. Here, we examined the role of the leptin receptor (LepR) in proopiomelanocortin (POMC) and agouti-related peptide (AgRP) neurons in mediating the effects of leptin on regional sympathetic and parasympathetic nerve activity.

Methods

We analyzed how deletion of the LepR in POMC neurons (POMC^Cre/LepR^fl/fl mice) or AgRP neurons (AgRP^Cre/LepR^fl/fl mice) affects the ability of leptin to increase sympathetic and parasympathetic nerve activity. We also studied mice lacking the catalytic p110α or p110β subunits of phosphatidylinositol-3 kinase (PI3K) in POMC neurons.

Results

Leptin-evoked increase in sympathetic nerve activity subserving thermogenic brown adipose tissue was partially blunted in mice lacking the LepR in either POMC or AgRP neurons. On the other hand, loss of the LepR in AgRP, but not POMC, neurons interfered with leptin-induced sympathetic nerve activation to the inguinal fat depot. The increase in hepatic sympathetic traffic induced by leptin was also reduced in mice lacking the LepR in AgRP, but not POMC, neurons whereas LepR deletion in either AgRP or POMC neurons attenuated the hepatic parasympathetic nerve activation evoked by leptin. Interestingly, the renal, lumbar and splanchnic sympathetic nerve activation caused by leptin were significantly blunted in POMC^Cre/LepR^fl/fl mice, but not in AgRP^Cre/LepR^fl/fl mice. However, loss of the LepR in POMC or AgRP neurons did not interfere with the ability of leptin to increase sympathetic traffic to the adrenal gland. Furthermore, ablation of the p110α, but not the p110β, isoform of PI3K from POMC neurons eliminated the leptin-elicited renal sympathetic nerve activation.

Finally, we show trans-synaptic retrograde tracing of both POMC and AgRP neurons from the kidneys.

Conclusions

POMC and AgRP neurons are differentially involved in mediating the effects of leptin on autonomic nerve activity subserving various tissues and organs.

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Both POMC and AgRP neurons contribute to leptin-elicited increase in BAT SNA and hepatic PSNA.

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AgRP neurons mediate leptin-evoked increase in SNA subserving WAT and liver.

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Leptin-induced increase in lumbar, splanchnic and renal SNA is mediated by POMC neurons.

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The p110α, but not p110β, subunit of PI3K in POMC neurons is required for the effect of leptin on renal SNA.

BMPs as new insulin sensitizers: enhanced glucose uptake in mature 3T3-L1 adipocytes via PPARγ and GLUT4 upregulation

Insulin-resistance is the main cause of type 2 diabetes. Here we describe the identification and characterization of BMP2 and BMP6 as new insulin-sensitizing growth factors in mature adipocytes. We show that BMP2 and BMP6 lead to enhanced insulin-mediated glucose uptake in both insulin-sensitive and -insensitive adipocytes. We exclude a direct effect of BMP2 or BMP6 on translocation of GLUT4 to the plasma membrane and demonstrate that these BMPs increase GLUT4 protein levels equipotent to Rosiglitazone. BMPs induce expression of PPARγ as the crucial mediator for the insulin-sensitizing effect. A comprehensive RNA-Seq analysis in mature adipocytes revealed regulation of both BMP/Smad and PPARγ target genes. The effects of BMP2 and BMP6 are not completely redundant and include regulation of genes involved in glucose and fatty acid metabolism and adipokine expression. Collectively, these findings suggest the BMP2 and BMP6 pathway(s) as promising new drug targets to treat insulin resistance.

Obstructive sleep apnoea and polycystic ovary syndrome: A comprehensive review of clinical interactions and underlying pathophysiology

Polycystic ovary syndrome (PCOS) is the most prevalent endocrine disorder in women of reproductive age. PCOS is associated with multiple comorbidities including, obesity, insulin resistance and type 2 diabetes, as well as mood disorders and impaired quality of life (QoL). Obstructive sleep apnoea (OSA) is also a common medical condition that is often undiagnosed, particularly in women. OSA is associated with a similar spectrum of comorbidities to that observed in PCOS, including manifestations of the metabolic syndrome and impaired QoL, whilst obesity frequently constitutes a common denominator in the pathophysiology of both OSA and PCOS. Hence, it is not surprising that OSA and PCOS may coexist in women of reproductive age, and the current clinical guidelines on the management of PCOS recommend screening for OSA symptoms in overweight/obese women with PCOS. In this review, we examine the relationship between OSA and PCOS and explore the potential underlying mechanisms that link these two conditions.

Oxidative and inflammatory signals in obesity-associated vascular abnormalities

Obesity is associated with increased cardiovascular morbidity and mortality in part due to vascular abnormalities such as endothelial dysfunction and arterial stiffening. The hypertension and other health complications that arise from these vascular defects increase the risk of heart diseases and stroke. Prooxidant and proinflammatory signaling pathways as well as adipocyte-derived factors have emerged as critical mediators of obesity-associated vascular abnormalities. Designing treatments aimed specifically at improving the vascular dysfunction caused by obesity may provide an effective therapeutic approach to prevent the cardiovascular sequelae associated with excessive adiposity. In this review, we discuss the recent evidence supporting the role of oxidative stress and cytokines and inflammatory signals within the vasculature as well as the impact of the surrounding perivascular adipose tissue (PVAT) on the regulation of vascular function and arterial stiffening in obesity. In particular, we focus on the highly plastic nature of the vasculature in response to altered oxidant and inflammatory signaling and highlight how weight management can be an effective therapeutic approach to reduce the oxidative stress and inflammatory signaling and improve vascular function.

Transcriptional networks in rodent models support a role for gut-brain communication in neurogenic hypertension: a review of the evidence

Hypertension (HTN) is the most prevalent condition observed in primary health care. Hypertension shows complex etiology, and neuroinflammation, overactive sympathetic drive, and the microbiome are each associated with the disease. To obtain mechanistic perspective into neurogenic HTN, we first constructed a framework for transcriptional regulators of the disease using the Comparative Toxicogenomics Database. This approach yielded a core group of 178 transcripts that are prevalent in studies of HTN, including leptin and neuropeptide Y. We then conducted a meta-analysis for transcriptome data generated in brain tissue from HTN studies. Eight expression studies were reanalyzed, in which transcriptomics was conducted in hypertensive animal models [spontaneously hypertensive rats (SHR) and high blood pressure (BPH/2J) Schlager mice] (140 microarrays). Most strikingly, a gut-brain connection was a dominant theme in both rodent models of HTN. The transcriptomic data in the rat CNS converged on processes that included gastrointestinal motility and appetite, among others. In the mouse model, pathways converged on gastrointestinal transit. Thus, our data provide a powerful review of current molecular evidence of the interplay between gut and brain in HTN. Analyses of meta-genome data also suggested that transcriptome networks related to natriuresis, thermoregulation, reproduction (lactation and pregnancy), and vasoconstriction were associated to HTN, supporting physiological observations in independent studies by others. Lastly, we present novel transcriptome networks that may contribute to a neurogenic origin of HTN. Using this framework, new therapeutic targets can be proposed and investigated in treatment strategies.