Role of sympathetic activity in controlling the expression of vascular endothelial growth factor in brown fat cells of lean and genetically obese rats

The nervous system and adipose tissues: a tale of dialogues

White, beige, and brown adipose tissues play a crucial role in maintaining energy homeostasis. Due to the heterogeneous and diffuse nature of fat pads, this balance requires a fine and coordinated control of many actors and therefore permanent dialogues between these tissues and the central nervous system. For about two decades, many studies have been devoted to describe the neuro-anatomical and functional complexity involved to ensure this dialogue. Thus, if it is now clearly demonstrated that there is an efferent sympathetic innervation of different fat depots controlling plasticity as well as metabolic functions of the fat pad, the crucial role of sensory innervation capable of detecting local signals informing the central nervous system of the metabolic state of the relevant pads is much more recent. The purpose of this review is to provide the current state of knowledge on this subject.

Depot- and diabetes-specific differences in norepinephrine-mediated adipose tissue angiogenesis, vascular tone, collagen deposition and morphology in obesity

AIMS

Norepinephrine (NE) is a known regulator of adipose tissue (AT) metabolism, angiogenesis, vasoconstriction and fibrosis. This may be through autocrine/paracrine effects on local resistance vessel function and morphology. The aims of this study were to investigate, in human subcutaneous and omental adipose tissue (SAT and OAT): NE synthesis, angiogenesis, NE-mediated arteriolar vasoconstriction, the induction of collagen gene expression and its deposition in non-diabetic versus diabetic obese subjects.

MATERIALS AND METHODS

SAT and OAT from obese patients were used to investigate tissue NE content, tyrosine hydroxylase (TH) density, angiogenesis including capillary density, angiogenic capacity and angiogenic gene expression, NE-mediated arteriolar vasoconstriction and collagen deposition.

KEY FINDINGS

In the non-diabetic group, NE concentration, TH immunoreactivity, angiogenesis and maximal vasoconstriction were significantly higher in OAT compared to SAT (p < 0.05). However, arterioles from OAT showed lower NE sensitivity compared to SAT (10^-8 M to 10^-7.5 M, p < 0.05). A depot-specific difference in collagen deposition was also observed, being greater in OAT than SAT. In the diabetic group, no significant depot-specific differences were seen in NE synthesis, angiogenesis, vasoconstriction or collagen deposition. SAT arterioles showed significantly lower sensitivity to NE (10^-8 M to 10^-7.5 M, p < 0.05) compared to the non-diabetic group.

SIGNIFICANCE

SAT depot in non-diabetic obese patients exhibited relatively low NE synthesis, angiogenesis, tissue fibrosis and high vasoreactivity, due to preserved NE sensitivity. The local NE synthesis in OAT and diabetes desensitizes NE-induced vasoconstriction, and may also explain the greater tissue angiogenesis and fibrosis in these depots.

The endocrine role of brown adipose tissue: An update on actors and actions

In recent years, brown adipose tissue (BAT) has been recognized not only as a main site of non-shivering thermogenesis in mammals, but also as an endocrine organ. BAT secretes a myriad of regulatory factors. These so-called batokines exert local autocrine and paracrine effects, as well as endocrine actions targeting tissues and organs at a distance. The endocrine batokines include peptide factors, such as fibroblast growth factor-21 (FGF21), neuregulin-4 (NRG4), phospholipid transfer protein (PLTP), interleukin-6, adiponectin and myostatin, and also lipids (lipokines; e.g., 12,13-dihydroxy-9Z-octadecenoic acid [12,13-diHOME]) and miRNAs (e.g., miR-99b). The liver, heart, and skeletal muscle are the most commonly reported targets of batokines. In response to BAT thermogenic activation, batokines such as NRG4 and PLTP are released and act to reduce hepatic steatosis and improve insulin sensitivity. Stress-induced interleukin-6-mediated signaling from BAT to liver favors hepatic glucose production through enhanced gluconeogenesis. Batokines may act on liver to induce the secretion of regulatory hepatokines (e.g. FGF21 and bile acids in response to miR-99b and PLTP, respectively), thereby resulting in a systemic expansion of BAT-originating signals. Batokines also target extrahepatic tissues: FGF21 and 12,13-diHOME are cardioprotective, whereas BAT-secreted myostatin and 12,13-diHOME influence skeletal muscle development and performance. Further research is needed to ascertain in humans the role of batokines, which have been identified mostly in experimental models. The endocrine role of BAT may explain the association between active BAT and a healthy metabolism in the human system, which is characterized by small amounts of BAT and a likely moderate BAT-mediated energy expenditure.

Skeletal muscle provides a pro-browning microenvironment for transplanted brown adipose tissue to maintain its effect to ameliorate obesity in ob/ob mice

Brown adipose tissue (BAT) transplantation is a promising means of increasing whole-body energy metabolism to ameliorate obesity. However, the changes in BAT following transplantation and the effects of the microenvironment of the recipient site on graft function have yet to be fully characterized. Therefore, we aimed to determine the effects of transplanting BAT from C57BL/6 mice into the dorsal subcutaneous region or deep to the quadriceps femoris muscle of leptin-deficient ob/ob mice. Subcutaneously transplanted BAT lost features of BAT and demonstrated greater inflammatory cell infiltration and more oil cysts 16 weeks following transplantation. By contrast, the sub-muscularly transplanted BAT maintained features of BAT and was more highly vascularized. Interestingly, sub-muscular BAT transplantation led to a significant increase in oxygen consumption and less inflammation in subcutaneous fat, which was associated with long-term reductions in insulin resistance and body mass gain, whereas the subcutaneous transplants failed after 16 weeks. These results demonstrate that the beneficial effects of BAT transplantation depend upon the microenvironment of the recipient site. Skeletal muscle may provide a microenvironment that maintains the inherent features of BAT grafts over a long period of time, which facilitates a reduction in obesity and improvements in glucose homeostasis.

A Differential Pattern of Batokine Expression in Perivascular Adipose Tissue Depots From Mice

Depending on its anatomical placement, perivascular adipose tissue (PVAT) has been found to possess features more (e.g., aortic thoracic) or less (e.g., aortic abdominal) similar to brown/beige adipose tissue in mice, whereas PVAT surrounding the mesenteric arteries and the caudal part of abdominal aorta is similar to white fat. PVAT is thought to influence vascular function through the effects of adipose-secreted molecules on vessels. Brown adipose tissue was recently shown to play differential secretory role via secretion of the so-called batokines but the involvement of differential batokine production in PVAT brown/beige plasticity was unclear. The current study characterizes for the first time the expression of batokines at aortic thoracic PVAT (tPVAT) and aortic abdominal PVAT (aPVAT) in comparison with typical brown and white adipose depots, in basal and thermogenically activated conditions. We found that both PVAT depots increased their expression of genes encoding the batokines bone morphogenetic protein-8b (BMP8B), fibroblast growth factor-21 (FGF21), and kininogen-2 (KNG2) in response to cold, indicating that, under cold-induced thermogenic activation, both thoracic aorta and abdominal aorta would experience intense local exposure to these PVAT-secreted batokines. In contrast, the gene expression levels of growth/differentiation factor-15 and vascular endothelial growth factor-A were induced only in tPVAT. Under short-term high-fat diet-induced thermogenic activation, the thoracic aorta would be specifically exposed to a local increase in PVAT-originating BMP8B, FGF21, and KNG2. Our data support the notion that acquisition of a brown/beige phenotype in PVAT is associated with upregulation of batokines, mainly BMP8B, FGF21, and KNG2, that can differentially target the vascular system.

Adrenoceptors in white, brown, and brite adipocytes

Adrenoceptors play an important role in adipose tissue biology and physiology that includes regulating the synthesis and storage of triglycerides (lipogenesis), the breakdown of stored triglycerides (lipolysis), thermogenesis (heat production), glucose metabolism, and the secretion of adipocyte-derived hormones that can control whole-body energy homeostasis. These processes are regulated by the sympathetic nervous system through actions at different adrenoceptor subtypes expressed in adipose tissue depots. In this review, we have highlighted the role of adrenoceptor subtypes in white, brown, and brite adipocytes in both rodents and humans and have included detailed analysis of adrenoceptor expression in human adipose tissue and clonally derived adipocytes. We discuss important considerations when investigating adrenoceptor function in adipose tissue or adipocytes. LINKED ARTICLES: This article is part of a themed section on Adrenoceptors-New Roles for Old Players. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.14/issuetoc.

Effects of tunable, 3D-bioprinted hydrogels on human brown adipocyte behavior and metabolic function

Obesity and its related health complications cause billions of dollars in healthcare costs annually in the United States, and there are yet to be safe and long-lasting anti-obesity approaches. Using brown adipose tissue (BAT) is a promising approach, as it uses fats for energy expenditure. However, the effect of the microenvironment on human thermogenic brown adipogenesis and how to generate clinically relevant sized and functioning BAT are still unknown. In our current study, we evaluated the effects of endothelial growth medium exposure on brown adipogenesis of human brown adipose progenitors (BAP). We found that pre-exposing BAP to angiogenic factors promoted brown adipogenic differentiation and metabolic activity. We further 3D bioprinted brown and white adipose progenitors within hydrogel-based bioink with controllable physicochemical properties and evaluated the cell responses in 3D bioprinted environments. We used soft, stiff, and stiff-porous constructs to encapsulate the cells. All three types had high cell viability and allowed for varying levels of function for both white and brown adipocytes. We found that the soft hydrogel constructs promoted white adipogenesis, while the stiff-porous hydrogel constructs improved both white and brown adipogenesis and were the optimal condition for promoting brown adipogenesis. Consistently, stiff-porous hydrogel constructs showed higher metabolic activities than stiff hydrogel constructs, as assessed by 2-deoxy glucose uptake (2-DOG) and oxygen consumption rate (OCR). These findings show that the physicochemical environments affect the brown adipogenesis and metabolic function, and further tuning will be able to optimize their functions. Our results also demonstrate that 3D bioprinting of brown adipose tissues with clinically relevant size and metabolic activity has the potential to be a viable option in the treatment of obesity and type 2 diabetes.

STATEMENT OF SIGNIFICANCE

One promising strategy for the treatment or prevention of obesity-mediated health complications is augmenting brown adipose tissues (BAT), which is a specialized fat that actively dissipate energy in the form of heat and maintain energy balance. In this study, we determined how pre-exposing human brown adipose progenitors (BAP) to angiogenic factors in 2D and how bioprinted microenvironments in 3D affected brown adipogenic differentiation and metabolic activity. We demonstrated that white and brown adipogenesis, and thermogenesis were regulated by tuning the bioprintable matrix stiffness and construct structure. This study not only unveils the interaction between BAP and 3D physiological microenvironments, but also presents a novel tissue engineered strategy to manage obesity and other related metabolic disorders.

Ablation of endothelial VEGFR1 improves metabolic dysfunction by inducing adipose tissue browning

Angiogenesis plays an instrumental role in the modulation of adipose tissue mass and metabolism. Targeting adipose vasculature provides an outstanding opportunity for treatment of obesity and metabolic disorders. Here, we report the physiological functions of VEGFR1 in the modulation of adipose angiogenesis, obesity, and global metabolism. Pharmacological inhibition and genetic deletion of endothelial VEGFR1 augmented adipose angiogenesis and browning of subcutaneous white adipose tissue, leading to elevated thermogenesis. In a diet-induced obesity model, endothelial-VEGFR1 deficiency demonstrated a potent anti-obesity effect by improving global metabolism. Along with metabolic changes, fatty liver and insulin sensitivity were also markedly improved in VEGFR1-deficient high fat diet (HFD)-fed mice. Together, our data indicate that targeting of VEGFR1 provides an exciting new opportunity for treatment of obesity and metabolic diseases, such as liver steatosis and type 2 diabetes.

Intermittent fasting promotes adipose thermogenesis and metabolic homeostasis via VEGF-mediated alternative activation of macrophage

Intermittent fasting (IF), a periodic energy restriction, has been shown to provide health benefits equivalent to prolonged fasting or caloric restriction. However, our understanding of the underlying mechanisms of IF-mediated metabolic benefits is limited. Here we show that isocaloric IF improves metabolic homeostasis against diet-induced obesity and metabolic dysfunction primarily through adipose thermogenesis in mice. IF-induced metabolic benefits require fasting-mediated increases of vascular endothelial growth factor (VEGF) expression in white adipose tissue (WAT). Furthermore, periodic adipose-VEGF overexpression could recapitulate the metabolic improvement of IF in non-fasted animals. Importantly, fasting and adipose-VEGF induce alternative activation of adipose macrophage, which is critical for thermogenesis. Human adipose gene analysis further revealed a positive correlation of adipose VEGF-M2 macrophage-WAT browning axis. The present study uncovers the molecular mechanism of IF-mediated metabolic benefit and suggests that isocaloric IF can be a preventive and therapeutic approach against obesity and metabolic disorders.

Quantifying Biochemical Alterations in Brown and Subcutaneous White Adipose Tissues of Mice Using Fourier Transform Infrared Widefield Imaging

Stimulating increased thermogenic activity in adipose tissue is an important biological target for obesity treatment, and label-free imaging techniques with the potential to quantify stimulation-associated biochemical changes to the adipose tissue are highly sought after. In this study, we used spatially resolved Fourier transform infrared (FTIR) imaging to quantify biochemical changes caused by cold exposure in the brown and subcutaneous white adipose tissues (BAT and s-WAT) of 6 week-old C57BL6 mice exposed to 30°C (N = 5), 24°C (N = 5), and 10°C (N = 5) conditions for 10 days. Fat exposed to colder temperatures demonstrated greater thermogenic activity as indicated by increased messenger RNA expression levels of a panel of thermogenic marker genes including uncoupling protein 1 (UCP-1) and Dio2. Protein to lipid ratio, calculated from the ratio of the integrated area from 1,600 to 1,700 cm^-1 (amide I) to the integrated area from 2,830 to 2,980 cm^-1 (saturated lipids), was elevated in 10°C BAT and s-WAT compared to 24°C (p = 0.004 and p < 0.0001) and 30°C (p = 0.0033 and p < 0.0001). Greater protein to lipid ratio was associated with greater UCP-1 expression level in the BAT (p = 0.021) and s-WAT (p = 0.032) and greater Dio2 expression in s-WAT (p = 0.033). The degree of unsaturation, calculated from the ratio of the integrated area from 2,992 to 3,020 cm^-1 (unsaturated lipids) to the integrated area from 2,830 to 2,980 cm^-1 (saturated lipids), showed stepwise decreases going from colder-exposed to warmer-exposed BAT. Complementary ¹H NMR measurements confirmed the findings from this ratio in BAT. Principal component analysis applied to FTIR spectra revealed pronounced differences in overall spectral characteristics between 30, 24, and 10°C BAT and s-WAT. Spatially resolved FTIR imaging is a promising technique to quantify cold-induced biochemical changes in BAT and s-WAT in a label-free manner.

Repurposing Drugs in Oncology (ReDO)-Propranolol as an anti-cancer agent

Propranolol (PRO) is a well-known and widely used non-selective beta-adrenergic receptor antagonist (beta-blocker), with a range of actions which are of interest in an oncological context. PRO displays effects on cellular proliferation and invasion, on the immune system, on the angiogenic cascade, and on tumour cell sensitivity to existing treatments. Both pre-clinical and clinical evidence of these effects, in multiple cancer types, is assessed and summarised and relevant mechanisms of action outlined. In particular there is evidence that PRO is effective at multiple points in the metastatic cascade, particularly in the context of the post-surgical wound response. Based on this evidence the case is made for further clinical investigation of the anticancer effects of PRO, particularly in combination with other agents. A number of trials are on-going, in different treatment settings for various cancers.

Differential Role of Adipose Tissues in Obesity and Related Metabolic and Vascular Complications

This review focuses on the contribution of white, brown, and perivascular adipose tissues to the pathophysiology of obesity and its associated metabolic and vascular complications. Weight gain in obesity generates excess of fat, usually visceral fat, and activates the inflammatory response in the adipocytes and then in other tissues such as liver. Therefore, low systemic inflammation responsible for insulin resistance contributes to atherosclerotic process. Furthermore, an inverse relationship between body mass index and brown adipose tissue activity has been described. For these reasons, in recent years, in order to combat obesity and its related complications, as a complement to conventional treatments, a new insight is focusing on the role of the thermogenic function of brown and perivascular adipose tissues as a promising therapy in humans. These lines of knowledge are focused on the design of new drugs, or other approaches, in order to increase the mass and/or activity of brown adipose tissue or the browning process of beige cells from white adipose tissue. These new treatments may contribute not only to reduce obesity but also to prevent highly prevalent complications such as type 2 diabetes and other vascular alterations, such as hypertension or atherosclerosis.

The effects of indoor and outdoor temperature on metabolic rate and adipose tissue - the Mississippi perspective on the obesity epidemic

Global warming, primarily caused by emissions of too much carbon dioxide, and climate change is a reality. This will lead to more extreme weather events with heatwaves and flooding. Some studies propose an association between thermal exposures and the prevalence of obesity with an increasing trend towards time spent in the thermal comfort zone. Longterm exposure to the thermal comfort zone can lead to a reduction of brown adipose tissue activity with an impact on energy expenditure and thermogenesis. Reduced seasonal cold exposure in combination with reduced diet-induced thermogenesis by a highly palatable high-fat and high-sugar diet and reduced physical activity contribute to the prevalence of obesity and the metabolic syndrome.

Vascular rarefaction mediates whitening of brown fat in obesity

Brown adipose tissue (BAT) is a highly vascularized organ with abundant mitochondria that produce heat through uncoupled respiration. Obesity is associated with a reduction of BAT function; however, it is unknown how obesity promotes dysfunctional BAT. Here, using a murine model of diet-induced obesity, we determined that obesity causes capillary rarefaction and functional hypoxia in BAT, leading to a BAT "whitening" phenotype that is characterized by mitochondrial dysfunction, lipid droplet accumulation, and decreased expression of Vegfa. Targeted deletion of Vegfa in adipose tissue of nonobese mice resulted in BAT whitening, supporting a role for decreased vascularity in obesity-associated BAT. Conversely, introduction of VEGF-A specifically into BAT of obese mice restored vascularity, ameliorated brown adipocyte dysfunction, and improved insulin sensitivity. The capillary rarefaction in BAT that was brought about by obesity or Vegfa ablation diminished β-adrenergic signaling, increased mitochondrial ROS production, and promoted mitophagy. These data indicate that overnutrition leads to the development of a hypoxic state in BAT, causing it to whiten through mitochondrial dysfunction and loss. Furthermore, these results link obesity-associated BAT whitening to impaired systemic glucose metabolism.

Neuronal control of metabolism through nutrient-dependent modulation of tracheal branching

During adaptive angiogenesis, a key process in the etiology and treatment of cancer and obesity, the vasculature changes to meet the metabolic needs of its target tissues. Although the cues governing vascular remodeling are not fully understood, target-derived signals are generally believed to underlie this process. Here, we identify an alternative mechanism by characterizing the previously unrecognized nutrient-dependent plasticity of the Drosophila tracheal system: a network of oxygen-delivering tubules developmentally akin to mammalian blood vessels. We find that this plasticity, particularly prominent in the intestine, drives—rather than responds to—metabolic change. Mechanistically, it is regulated by distinct populations of nutrient- and oxygen-responsive neurons that, through delivery of both local and systemic insulin- and VIP-like neuropeptides, sculpt the growth of specific tracheal subsets. Thus, we describe a novel mechanism by which nutritional cues modulate neuronal activity to give rise to organ-specific, long-lasting changes in vascular architecture.

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The Drosophila tracheal system exhibits nutrient-dependent plasticity

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Tracheal plasticity is organ specific and metabolically significant

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Nutrient- and hypoxia-responsive neurons drive adaptive tracheation

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Distinct insulin-like and Pdf neuropeptides control organ-specific tracheal branching

Brown adipose tissue derived VEGF-A modulates cold tolerance and energy expenditure

We recently reported that local overexpression of VEGF-A in white adipose tissue (WAT) protects against diet-induced obesity and metabolic dysfunction. The observation that VEGF-A induces a “brown adipose tissue (BAT)-like” phenotype in WAT prompted us to further explore the direct function of VEGF-A in BAT. We utilized a doxycycline (Dox)-inducible, brown adipocyte-specific VEGF-A transgenic overexpression model to assess direct effects of VEGF-A in BAT in vivo. We observed that BAT-specific VEGF-A expression increases vascularization and up-regulates expression of both UCP1 and PGC-1α in BAT. As a result, the transgenic mice show increased thermogenesis during chronic cold exposure. In diet-induced obese mice, introducing VEGF-A locally in BAT rescues capillary rarefaction, ameliorates brown adipocyte dysfunction, and improves deleterious effects on glucose and lipid metabolism caused by a high-fat diet challenge. These results demonstrate a direct positive role of VEGF-A in the activation and expansion of BAT.

Brown and beige fat: development, function and therapeutic potential

Adipose tissue, best known for its role in fat storage, can also suppress weight gain and metabolic disease through the action of specialized, heat-producing adipocytes. Brown adipocytes are located in dedicated depots and express constitutively high levels of thermogenic genes, whereas inducible 'brown-like' adipocytes, also known as beige cells, develop in white fat in response to various activators. The activities of brown and beige fat cells reduce metabolic disease, including obesity, in mice and correlate with leanness in humans. Many genes and pathways that regulate brown and beige adipocyte biology have now been identified, providing a variety of promising therapeutic targets for metabolic disease.

Vascular endothelial growth factor is important for brown adipose tissue development and maintenance

Vascular endothelial growth factor (VEGF) is critical for angiogenesis, but also has pleiotropic effects on several nonvascular cells. Our aim was to investigate the role of VEGF in brown adipose tissue (BAT). We show that VEGF expression increases 2.5-fold during differentiation of cultured murine brown adipocytes and that VEGF receptor-2 is phosphorylated, indicating VEGF signaling. VEGF increased proliferation in brown preadipocytes in vitro by 70%, and blockade of VEGF signaling using anti-VEGFR2 antibody DC101 increased brown adipocyte apoptosis, as determined by cell number and activation of caspase 3. Systemic VEGF neutralization in mice, accomplished by adenoviral expression of soluble Flt1, resulted in 7-fold increase in brown adipocyte apoptosis, mitochondrial degeneration, and increased mitophagy compared to control mice expressing a null adenovirus. Absence of the heparan sulfate-binding VEGF isoforms, VEGF164 and VEGF188, resulted in abnormal BAT development in mice at E15.5, with fewer brown adipocytes and lower mitochondrial protein compared to wild-type littermates. These results suggest a role for VEGF in brown adipocytes and preadipocytes to promote survival, proliferation, and normal mitochondria and development.

[Role of brown and perivascular adipose tissue in vascular complications due to obesity]

The contribution of brown and perivascular adipose tissues to the pathophysiology of metabolic and vascular complications associated with obesity are analysed in this review. To combat obesity and prevent its highly prevalent metabolic and vascular complications, a new insight on our knowledge of the role of the thermogenic function of brown adipose tissue and its promising therapeutic potential in humans is needed in addition to conventional treatments. Owing to the impact of brown adipose tissue on energy expenditure related to lipid and glucose metabolism, as well as its potential resistance against inflammation along with perivascular adipose tissue, new perspectives in the treatment of obesity treatment could be focused on the design of new drugs, or different regimens or therapies, that increase the amount and activity of brown adipose tissue. These new treatments not only may contribute to combat obesity, but also prevent complications such as type 2 diabetes and other associated metabolic and vascular changes.

Production of functional classical brown adipocytes from human pluripotent stem cells using specific hemopoietin cocktail without gene transfer

Brown adipose tissue is attracting much attention due to its antiobestic effects; however, its development and involvement in metabolic improvement remain elusive. Here we established a method for a high-efficiency (>90%) differentiation of human pluripotent stem cells (hPSCs) into functional classical brown adipocytes (BAs) using specific hemopoietin cocktail (HC) without exogenous gene transfer. BAs were not generated without HC, and lack of a component of HC induced white adipocyte (WA) marker expressions. hPSC-derived BA (hPSCdBA) showed respiratory and thermogenic activation by β-adrenergic receptor (AdrRβ) stimuli and augmented lipid and glucose tolerance, whereas human multipotent stromal cell-derived WA (hMSCdWA) improved lipid but inhibited glucose metabolism. Cotransplantation of hPSCdBA normalized hMSCdWA-induced glucose intolerance. Surprisingly, hPSCdBAs expressed various hemopoietin genes, serving as stroma for myeloid progenitors. Moreover, AdrRβ stimuli enhanced recovery from chemotherapy-induced myelosuppression. Our study enhances our understanding of BA, identifying roles in metabolic and hemogenic regulation.

The beta3 adrenoceptor agonist, amibegron (SR58611A) counteracts stress-induced behavioral and neurochemical changes

These experiments were made to study the mechanisms underlying the antidepressant-like effects of the beta(3) adrenoceptor agonist amibegron (SR58611A). To this purpose, the expression levels of the hippocampal cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), B-cell lymphoma-2 (Bcl-2) and Bax proteins were assessed, by using western blot analysis, in rats tested in the forced swim test (FST). Under basal conditions (no previous exposure to stressors), different groups of male Wistar rats received acutely or repeatedly (once/day for 7days) intraperitoneal (i.p.) injections of amibegron (1, 5 and 10mg/kg), the tricyclic antidepressant (TCA) clomipramine (50mg/kg), the selective serotonin reuptake inhibitor (SSRI) citalopram (15mg/kg) or their vehicles. The influence of stress-related conditions was studied in rats subjected to acute (4h) or repeated (4h/day for 7days) restraint stress, applied prior to the FST procedure. Compared to the control groups, both stressor procedures increased the immobility time in the FST and reduced hippocampal BDNF and Bcl-2/Bax ratio proteins expression, which were counteracted by amibegron (5 and 10mg/kg) treatment. Opposite effects were found in the CREB expression, since it was lower after acute and higher after repeated stress procedure, respectively. Again, these effects were reversed by amibegron treatment. Different results were obtained in animals treated with clomipramine or citalopram. Hence, it is likely that the observed behavioral effects of amibegron could be due, at least in part, to its action on hippocampal expression of neurotrophic and/or anti-apoptotic factors, supporting the hypothesis that beta(3) adrenoceptors may be a therapeutic target for the treatment of stress-related disorders.

Perspective: Does brown fat protect against diseases of aging?

The most commonly studied laboratory rodents possess a specialized form of fat called brown adipose tissue (BAT) that generates heat to help maintain body temperature in cold environments. In humans, BAT is abundant during embryonic and early postnatal development, but is absent or present in relatively small amounts in adults where it is located in paracervical and supraclavicular regions. BAT cells can 'burn' fatty acid energy substrates to generate heat because they possess large numbers of mitochondria in which oxidative phosphorylation is uncoupled from ATP production as a result of a transmembrane proton leak mediated by uncoupling protein 1 (UCP1). Studies of rodents in which BAT levels are either increased or decreased have revealed a role for BAT in protection against diet-induced obesity. Data suggest that individuals with low levels of BAT are prone to obesity, insulin resistance and cardiovascular disease, whereas those with higher levels of BAT maintain lower body weights and exhibit superior health as they age. BAT levels decrease during aging, and dietary energy restriction increases BAT activity and protects multiple organ systems including the nervous system against age-related dysfunction and degeneration. Future studies in which the effects of specific manipulations of BAT levels and thermogenic activity on disease processes in animal models (diabetes, cardiovascular disease, cancers, neurodegenerative diseases) are determined will establish if and how BAT affects the development and progression of age-related diseases. Data from animal studies suggest that BAT and mitochondrial uncoupling can be targeted for interventions to prevent and treat obesity and age-related diseases. Examples include: diet and lifestyle changes; specific regimens of mild intermittent stress; drugs that stimulate BAT formation and activity; induction of brown adipose cell progenitors in muscle and other tissues; and transplantation of brown adipose cells.

Spectral analysis of heart rate variability (HRV) may predict the future development of essential hypertension

Presently, essential hypertension (EH) is among the most common morbid disorders of mankind. The fundamental pathophysiology of EH is sympathetic overactivity. It has been observed that the people having common risk factors for hypertension such as obesity, insulin resistance and stress generally have increased sympathetic activity. Therefore, it is presumed that patients suffering from EH develop some degree of increased sympathetic activity much before they clinically develop hypertension. Spectral analysis of heart rate variability (HRV) has been demonstrated to accurately assess change in sympathovagal balance (autonomic activity) even when the alteration is in its minimal form. Therefore, in the present paper we hypothesize that spectral analysis of HRV could be utilized for early prediction of EH. We also suggest that the predictive knowledge of sympathovagal imbalance in the development of EH should be employed in elucidating the mechanisms for prevention of this dysfunction.

FOXC2 controls Ang-2 expression and modulates angiogenesis, vascular patterning, remodeling, and functions in adipose tissue

Adipogenesis is spatiotemporally coupled to angiogenesis throughout adult life, and the interplay between these two processes is communicated by multiple factors. Here we show that in a transgenic mouse model, increased expression of forkhead box C2 (FOXC2) in the adipose tissue affects angiogenesis, vascular patterning, and functions. White and brown adipose tissues contain a considerably high density of microvessels appearing as vascular plexuses, which show redistribution of vascular smooth muscle cells and pericytes. Dysfunction of these primitive vessels is reflected by impairment of skin wound healing. We further provide a mechanistic insight of the vascular phenotype by showing that FOXC2 controls Ang-2 expression by direct activation of its promoter in adipocytes. Remarkably, an Ang-2-specific antagonist almost completely reverses this vascular phenotype. Thus, the FOXC2-Ang-2 signaling system is crucial for controlling adipose vascular function, which is part of an adaptation to increased adipose tissue metabolism.

Expression of gLTP in sympathetic ganglia of obese Zucker rats in vivo: molecular evidence

Long-term potentiation in sympathetic ganglia (gLTP) is similar to LTP of the hippocampal area CA1 in that its expression involves similar changes in signaling molecules. We have shown previously that the stress-prone, hypertensive obese Zucker rats (OZR) expressed gLTP in sympathetic ganglia and that high blood pressure was reduced by treatment with 5-HT(3) receptor antagonists. In the present study, we present additional electrophysiological evidence for the pre-expression of gLTP in sympathetic ganglia from OZR indicated by failure of repetitive stimulation to express gLTP in isolated superior cervical ganglia (SCG) and inhibition of baseline ganglionic transmission by a 5-HT(3) receptor antagonist. We have also investigated the role of key signaling molecules in the expression of gLTP in the hypertensive OZR. Immunoblot analysis showed a significant increase in the levels of phosphorylated (P-)CaMKII and protein kinase C gamma (PKCgamma) in SCG from OZR. The ratio of P-CaMKII to the total CaMKII was markedly increased in OZR ganglia, suggesting increased phosphorylation of this molecule. Additionally, there was a significant decrease in the levels of calcineurin in ganglia. Furthermore, the neural nitric oxide synthase and hemeoxygenase II, which are essential for the expression of gLTP, were significantly elevated in OZR ganglia. The present findings confirm that ganglia from OZR have expressed gLTP and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade similar to that of LTP of the brain hippocampal area CA1.

Role of long-term potentiation of sympathetic ganglia (gLTP) in hypertension

Ganglionic long-term potentiation (gLTP) is an activity-dependent sustained increase in the synaptic efficacy of the nicotinic pathway that has been demonstrated in autonomic ganglia. Sustained enhancement in ganglionic transmission as in chronic mental stress may affect the activity of autonomic functions, including blood pressure and heart rate. An increase in sympathetic activity associated with psychosocial stress and stress-prone conditions such as obesity and aging could result in in vivo expression of gLTP leading to hypertension of a neural origin. Recent reports indicated that the prevention of the expression of gLTP in animal models of hypertension prevented or reduced high blood pressure. Although stress-induced hypertension normalizes within a few days of stress relief, prolonged mild-moderate hypertension may contribute to atherosclerotic cardiovascular diseases. The relation between hypertension and enhanced ganglionic transmission as a result of in vivo expression of gLTP is discussed in this review.

Nonhypotensive dose of β-adrenergic blocker ameliorates capillary deficits in the hearts of rats with moderate renal failure

Renal failure causes sympathetic overactivity and inadequate capillary growth in response to cardiomyocyte hypertrophy in experimental renal failure, as well as in uremic patients. In nonuremic animals, sympathetic overactivity was shown to suppress capillary growth. The purpose of this study was to examine whether blockade with alpha- and beta-adrenoblockers ameliorates the capillary deficit that was documented in the hearts of rats with moderate renal failure. Male Sprague-Dawley rats, 3 days after surgical ablation [subtotal nephrectomy (SNX)] or sham operation (sham), were treated with phenoxybenzamine, metoprolol, or a combination of both: After 12 weeks, the hearts were investigated using morphometric and stereologic techniques. The length density of myocardial capillaries was lower (p<0.05) in untreated SNX than in sham (2,786+/-372 vs 3,397+/-602 mm/mm3); the decrease was abrogated by metoprolol (3,305+/-624 mm/mm3), but not by phenoxybenzamin (2,628+/-480 mm/mm3). The intercapillary distance increased (p<0.05) in SNX (20.5+/-1.5 microm) and tended to be lower after metoprolol treatment (19.0+/-1.9 microm). The media area of intramyocardial arterioles was significantly higher in untreated SNX (1,158+/-1,343 vs 686+/-771 microm2 in sham). Metoprolol in nonhypotensive doses prevents the capillary deficit in the hearts of rats with moderate renal failure and presents an argument for an important role of sympathetic overactivity in the genesis of the capillary deficit in moderate chronic renal insufficiency.

Effects of valsartan on stress-induced changes of serum vascular endothelial growth factor and nitric oxide in mice

This study investigated the effects of renin-angiotensin system (RAS) blockade on stress-induced changes of serum vascular endothelial growth factor (VEGF) and nitric oxide (NO) in mice. Chronic stress increased the serum NO levels significantly compared to control group (p = .0172). Valsartan, an angiotensin II receptor antagonist, alone, did not make significant difference versus control group. In chronic stress + valsartan group, serum NO levels decreased nonsignificantly compared to chronic stress group. There was a nonsignificant increase in serum VEGF levels after chronic stress. Valsartan alone or with chronic stress did not significantly affect the serum VEGF levels. In conclusion, there was no correlation between NO and VEGF changes during the stress response. In this respect, there may be other mechanisms to explain the stress-induced NO increase.

Normal and neoplastic cells of brown adipose tissue express the adhesion molecule CD31

CONTEXT

CD31 (platelet-endothelial cell adhesion molecule-1; PECAM-1), an adhesion molecule involved in the process of angiogenesis, is used as a marker of normal and neoplastic vascularization. During the assessment of angiogenesis and vascular invasion in a thymic carcinoid tumor, we observed unexpected immunostaining for CD31 in perithymic brown fat nests.

OBJECTIVE

To determine whether CD31 is expressed by normal and neoplastic cells of brown fat, a tissue whose thermogenetic activity depends heavily on high perfusion.

DESIGN

Formalin-fixed, paraffin-embedded archival tissues were immunostained by the labeled avidin-biotin method using antibodies against CD31 (clones JC70A and 1A10) after retrieval of heat-induced epitopes. Archival tissues included perithymic, periadrenal, axillary, and neck adipose tissue in which were embedded nests of brown fat (n = 15), hibernoma (n = 3), lipoma (n = 6), well-differentiated liposarcoma (n = 4), and myxoid liposarcoma (n = 4).

RESULTS

Invariably, multivacuolated and univacuolated adipocytes of normal brown fat and hibernomas were intensely positive for the CD31 antigen. The immunostaining "decorated" cell membranes and the membranes of intracytoplasmic vacuoles. No expression of CD31 was found in normal adipocytes of white fat, in neoplastic cells of lipomas, or in multivacuolated lipoblasts of well-differentiated and myxoid liposarcomas.

CONCLUSIONS

The spectrum of cell types that express CD31 is expanded to include normal and neoplastic brown fat cells. We speculate that the expression of CD31 may play a role in the development and maintenance of the vascular network characterizing this specialized adipose tissue. Moreover, CD31 may inhibit the Bax-mediated apoptosis of brown fat cells. For practical purposes, CD31 may be used as an immunohistochemical marker for distinguishing between white and brown fat and for diagnosing hibernoma in paraffin sections.

Effect of SR58611A, a potent beta-3 adrenoceptor agonist, on cutaneous wound healing in diabetic and obese mice

In diabetic patients, impairment of wound healing is a serious problem which represents a significant health burden. The effect of a highly selective beta-3 adrenoceptor agonist, SR58611A, on wound healing was assessed in animal models of type II diabetes. In db/db diabetic mice, a daily oral treatment with SR58611A (1, 3 and 10 mg/kg/day for two weeks) significantly reduced hyperglycaemia from 3 mg/kg/day onwards. The compound also normalized wound healing, starting from the lowest dose tested (1 mg/kg/day). SR58611A did not affect wound healing of control (lean) mice. An oral anti-diabetic agent, devoid of affinity for beta-3 adrenoceptors, troglitazone (130 mg/kg/day p.o.), normalized glycaemia but did not improve wound healing in db/db mice. Local application of SR58611A (200 microg/day in db/db mice) did not affect wound healing. SR58611A also normalized glucose levels in ob/ob mice, but only slightly improved wound healing in this strain. Moreover, in 17-week old db/db mice (i.e. severely insulin resistant) and in streptozotocin-induced diabetic mice, SR58611A slightly decreased hyperglycaemia and did not affect wound healing. In conclusion, SR58611A improves wound healing in animal models of non-insulin-dependent diabetes. This effect is not related to its effect on glucose levels, but probably implicates systemic effects of the compound.

Neural driven angiogenesis by overexpression of nerve growth factor

Mechanisms regulating angiogenesis are crucial in adjusting tissue perfusion on metabolic demands. We demonstrate that overexpression of nerve growth factor (NGF) in brown adipose tissue (BAT) of NGF-transgenic mice elevates both mRNA and protein levels of vascular endothelial growth factor (VEGF) and VEGF-receptors. Increased vascular permeability, leukocyte-endothelial interactions (LEI), and tissue perfusion were measured using intravital microscopy. NGF-stimulation of adipocytes and endothelial cells elevates mRNA expression of VEGF and its receptors, an effect blocked by NGF neutralizing antibodies. These data suggest an activation of angiogenesis as a result of both: stimulation of adipozytes and direct mitogenic effects on endothelial cells. The increased nerve density associated with vessels strengthened our hypothesis that tissue perfusion is regulated by neural control of vessels and that the interaction between the NGF and VEGF systems is the critical driver for the activated angiogenic process. The interaction of VEGF- and NGF-systems gives new insights into neural control of organ vascularization and perfusion.

Antecedent hypoglycaemia attenuates vascular endothelial growth factor response to subsequent hypoglycaemia in healthy men

AIM

The plasma concentration of vascular endothelial growth factor (VEGF) has recently been shown to increase sharply in response to hypoglycaemia and, thus, has been proposed as having a role in hypoglycaemia counter-regulation. Many counter-regulatory hormones show a reduced response after antecedent hypoglycaemia. We therefore investigated whether this decrease in responsiveness with repetitive hypoglycaemia also pertains to VEGF.

METHODS

Three hypoglycaemic clamp experiments were performed on two consecutive days in 15 healthy men. VEGF response was assessed during the first and last hypoglycaemic period.

RESULTS

As expected, plasma VEGF concentrations rose markedly during the clamps (P < 0.001). The increase was distinctly blunted during the third (+13 +/- 8 pg/ml) as compared with the first (+54 +/- 18 pg/ml) hypoglycaemic clamp (P = 0.046).

CONCLUSION

This data confirms that circulating VEGF concentrations increase acutely during hypoglycaemia. Like the counter-regulatory hormones, the hypoglycaemia-induced rise in VEGF is attenuated after antecedent hypoglycaemia. The origin of increased systemic VEGF concentration during hypoglycaemia and its physiological role remains to be defined.

Prolactin-induced expression of vascular endothelial growth factor via Egr-1

Angiogenesis is a dynamic process regulated by both local and systemic factors. Among these is vascular endothelial growth factor (VEGF), a potent effector of angiogenesis and vascular permeability. Previously we showed that VEGF is temporally and spatially regulated in the mouse mammary gland during development and lactation. Given the functions of prolactin (PRL) during these stages and the supporting role of the vasculature, we investigated the regulation of VEGF by PRL. Treatment of HC11 mouse mammary epithelial and Nb2 rat lymphoma cells with PRL induced VEGF expression. Deletion and mutation analysis identified a GC-rich region in the proximal region of the VEGF promoter that constitutively bound Sp1 and PRL-induced Egr-1. These sites conferred PRL-responsiveness leading to increased VEGF transcription. The induction of VEGF by PRL was PRL receptor-, Jak2- and MAP kinase kinase-dependent. Our results indicate that PRL induces VEGF expression through Egr-1, and implicates VEGF as an intermediary of PRL-regulated angiogenesis.

β3-Adrenergic receptors mediate choroidal endothelial cell invasion, proliferation, and cell elongation

Beta(3)-adrenergic receptors have been reported to function primarily in adipose tissues to regulate thermogenesis. In this study, we determined if beta-adrenergic receptors are present on human choroidal endothelial cells and examined their ability to promote invasion, proliferation, and/or cell elongation. Using western blotting techniques and assays of cell invasion, cell proliferation, and endothelial cell elongation, we were able to determine that human choroidal endothelial cells do possess all three subtypes of beta-adrenergic receptors. Stimulation of the beta(3)-adrenergic receptor with BRL37344, a specific beta(3)-adrenergic receptor agonist, resulted in phosphorylation of Src, Akt, and ERK1/2. BRL37344 treatment also increased choroidal endothelial cell invasion by 103% above control values; the invasion response was inhibited by PP2 (Src inhibitor), LY294002 (PI3K inhibitor), Akt inhibitor (Akt-I), and matrix metalloproteinase 2/9 inhibitor (MMP-I). Invasion was not affected by PD98059 (mek inhibitor) or KT5823 (protein kinase G inhibitor). BRL37344 produced a significant increase in the total elongation of choroidal endothelial cells formed on Matrigel over a 24hr period. BRL37344 did significantly increase proliferation, although not to the same level as invasion. Stimulation of choroidal endothelial cells with dobutamine to activate beta(1)/beta(2)-adrenergic receptors did not affect invasion, proliferation, or endothelial cell elongation. In conclusion, beta(3)-adrenergic receptors may play a role in choroidal endothelial cell invasion and elongation, while playing a more limited function in regulation of cell proliferation.

Hypertrophic osteoarthropathy may be a marker of underlying sympathetic bias

Hypertrophic osteoarthropathy (HOA) is a condition that accompanies many seemingly unrelated diseases. It is commonly associated with various clinical conditions such as pregnancy, aging, pulmonary diseases, cancers, and other systemic illnesses. The condition has been attributed to various causes such as platelet abnormalities, hormonal disturbances, and cytokine dysfunction, but the exact underlying mechanism has been elusive. We propose a unifying hypothesis that activation of the adrenergic system is the common thread that links all of the disparate clinical associations of hypertrophic osteoarthropathy. In diseased states, autonomic stimulation may occur as a result of chemoreceptor activation in response to acidosis, hypoxia, or hypercapnia. Examples include sleep apnea, congestive heart failure, renal failure, and tumor-induced hypoxia. In this setting, clinical signs of HOA may be a marker of underlying autonomic dysfunction. Autonomic stimulation may also occur as a normal part of pregnancy or as an abnormal component of aging. The exact pathway linking adrenergic excess to HOA remains to be clarified, but a plausible scenario based on current molecular evidence is offered.

Brown adipose tissue: function and physiological significance

The function of brown adipose tissue is to transfer energy from food into heat; physiologically, both the heat produced and the resulting decrease in metabolic efficiency can be of significance. Both the acute activity of the tissue, i.e., the heat production, and the recruitment process in the tissue (that results in a higher thermogenic capacity) are under the control of norepinephrine released from sympathetic nerves. In thermoregulatory thermogenesis, brown adipose tissue is essential for classical nonshivering thermogenesis (this phenomenon does not exist in the absence of functional brown adipose tissue), as well as for the cold acclimation-recruited norepinephrine-induced thermogenesis. Heat production from brown adipose tissue is activated whenever the organism is in need of extra heat, e.g., postnatally, during entry into a febrile state, and during arousal from hibernation, and the rate of thermogenesis is centrally controlled via a pathway initiated in the hypothalamus. Feeding as such also results in activation of brown adipose tissue; a series of diets, apparently all characterized by being low in protein, result in a leptin-dependent recruitment of the tissue; this metaboloregulatory thermogenesis is also under hypothalamic control. When the tissue is active, high amounts of lipids and glucose are combusted in the tissue. The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.

Sensory but not parasympathetic nerves are required for ocular vascular remodeling following chronic sympathectomy in rat

Choroidal vascularity increases following chronic sympathetic denervation in rats. The mechanisms of this remodeling are unclear. Since both nitric oxide and substance P/CGRP have been suggested as angiogenic factors in other targets, we hypothesized that sensory or parasympathetic nerves may also participate in ocular vascular remodeling. To test this hypothesis, sympathetic denervation was accomplished by superior cervical ganglionectomy. Sensory denervation was induced by subcutaneous injections of capsaicin on postnatal days 2 and 9, and ocular parasympathetic innervation was ablated by pterygopalatine ganglion excision on postnatal day 60. Eyes were processed and sectioned for light microscopic histomorphometry. Sympathetic denervation for 6 weeks resulted in increased choroidal thickness, vascular luminal area, numbers of large venules and large arterioles, and capillaries in the outer nuclear layer. Capsaicin pretreatment prevented sympathectomy-induced increases in choroidal thickness, vascular luminal area and large venules and large arterioles, whereas pterygopalatine ganglionectomy was without effect. Both sensory and parasympathetic denervation attenuated increases in outer nuclear layer capillaries. These studies indicate that increased choroidal vascularity noted after chronic sympathectomy requires intact sensory innervation.

Protective effect of vitamin E against focal brain ischemia and neuronal death through induction of target genes of hypoxia-inducible factor-1

Vitamin E has been shown to have protective effects against cerebral ischemia, possibly due to its anti-oxidant effects. However, its non-anti-oxidant, intracellular molecular mechanism remains elusive. For in vivo experiments in rats, orally administered vitamin E significantly reduced not only the brain infarct volume but also space navigation disability after permanent middle cerebral artery (MCA) occlusion. The level of anti-oxidant after MCA occlusion was significantly increased specifically in the ipsilateral brain tissues of vitamin E-treated rats. For in vitro experiments, posttreatment with vitamin E protected primary cultured neurons from nitric oxide-induced insult. Vitamin E induced the expression of the alpha subunit of hypoxia-inducible factor-1 (HIF-1) and its target genes, including vascular endothelial growth factor (VEGF) and heme oxygenase-1. The hypoxia response element on the VEGF promoter was responsible for this vitamin E-induced transcriptional activation of VEGF gene. Taken together, these results suggest that cerebral infarction increased the permeability of vitamin E across the blood-brain barrier, and this increased vitamin E in brain tissue elicited neuroprotective effects not only through scavenging oxidants, as are previously well reported, but also by transactivating HIF-1-dependent genes, which results in protection of brains from ischemic insults.

Serum bFGF levels are reduced in Japanese overweight men and restored by a 6-month exercise education

OBJECTIVE

To investigate whether the changes in vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) concentrations before and after weight reduction in Japanese overweight men are associated with changes in body mass index (BMI), visceral, subcutaneous fat, VO(2) and work rate (WR) at ventilatory threshold (VT).

DESIGN

Cross-sectional and longitudinal clinical intervention study with exercise education.

SUBJECTS

In total, 30 Japanese overweight men (BMI, 29.0+/-2.2 kg/m(2)) and 31 normal-weight men (BMI, 22.5+/-1.6 kg/m(2)) at baseline were enrolled: 30 overweight men (BMI, 29.0+/-2.2 kg/m(2)) were further enrolled into a 6-month exercise program.

MEASUREMENTS

Fat distribution evaluated by visceral fat (V) and subcutaneous fat (S) areas measured with computed tomography scanning at umbilical levels, angiogenic peptides including VEGF and bFGF, exercise tests at baseline and after 6 months.

RESULTS

In normal-weight and overweight subjects at baseline, VEGF positively correlated with S area (r=0.350, P=0.007) but not with V area. In contrast, bFGF negatively correlated with BMI (r=-0.619, P<0.001), S (r=-0.457, P<0.001) and V areas (r=-0.466, P<0.001). By intervention with exercise education, 30 overweight subjects showed reduction in BMI (29.0+/-2.2 to 28.0+/-2.0, P<0.001), V and S areas, increase in VO(2) and WR at VT, increase in bFGF (9.21+/-5.82-21.2+/-7.04 ng/ml, P<0.001), and no change in VEGF (1.45+/-0.72-1.88+/-0.52 ng/ml, P=0.016). The stepwise multiple regression analysis revealed that DeltaBMI (beta=-6.052) and DeltaVO(2) (beta=2.806) were independently related to DeltabFGF (P<0.001) and all other variables including DeltaS area, and DeltaV area, and DeltaWR did not enter the equation at significant levels.

CONCLUSION

The present study indicated a negative correlation between serum bFGF levels and BMI at baseline as well as an association of DeltaBMI and DeltaVO(2) with DeltabFGF after exercise intervention. The exercise-induced elevation of bFGF may be beneficial in the prevention of the atherosclerosis in overweight subjects.

Reduction of elevated arterial blood pressure in obese Zucker rats by inhibition of ganglionic long-term potentiation

Sustained enhancement of the basal tone of ganglionic transmission is expected to result in an enduring increase in peripheral resistance that would lead to elevated blood pressure. Long-term potentiation of sympathetic ganglia is an activity-dependent long-lasting increase in strength of ganglionic transmission. Therefore, ganglionic long-term potentiation might be involved in the manifestation of neurogenic forms of hypertension. Expression of sympathetic ganglionic long-term potentiation is dependent on activation of 5-HT(3) receptor. We examined the possibility that elevated blood pressure in obese Zucker rat, which is reported to be stress-prone, might be partly due to a neurogenic factor resulting from expression of ganglionic long-term potentiation. Chronic treatment with the 5-HT(3) receptor antagonist ondansetron (0.5 mg/kg/day) caused a significant decrease in blood pressure of the obese Zucker rats without affecting that of normotensive lean Zucker rats. Electropysiological procedures to test for long-term potentiation in isolated ganglia suggest that ganglionic long-term potentiation has been previously expressed in vivo in ganglia from obese Zucker rat but not in those from the normotensive lean Zucker rats. The results indicate that expression of ganglionic long-term potentiation in sympathetic ganglia may be responsible for neurogenic increase in blood pressure, which contributes to the moderate hypertension often seen in the obese Zucker rats.

Vascular endothelial growth factor and social support in patients with ovarian carcinoma

BACKGROUND

The modulation of immunologic activities relevant to cancer by behavioral factors, such as stress, depression, and social support, is well documented. However, associations of behavioral factors with cytokines involved in tumor angiogenesis have not been studied. Vascular endothelial growth factor (VEGF) is a key cytokine that is capable of stimulating tumor angiogenesis, and it has been associated with poorer survival in patients with ovarian carcinoma. VEGF is modulated by a variety of behaviorally sensitive factors, including sympathetic activation. This study examined relationships of social support and depressive symptoms with VEGF levels in preoperative patients with ovarian carcinoma.

METHODS

Twenty-four women with ovarian carcinoma and 5 women with benign pelvic masses were recruited at the presurgical clinic visit, received psychosocial surveys, including the Functional Assessment of Cancer Therapy (Quality of Life) survey and the Profile of Mood States, and a blood draw. Serum VEGF levels were assessed by enzyme-linked immunosorbent assay. Analyses controlled for disease stage.

RESULTS

Women with ovarian carcinoma who reported higher levels of social well being had lower levels of VEGF (P = 0.005). Greater support from friends and neighbors (P = 0.005) and less distance from friends (P = 0.04) were facets of social well being that were associated with lower VEGF levels. Individuals who reported greater helplessness (P = 0.03) or worthlessness (P = 0.08) had higher VEGF levels, but depression as a whole (P > 0.50) was not related to VEGF levels.

CONCLUSIONS

Higher levels of social well being were correlated with lower VEGF levels in presurgical patients with ovarian carcinoma. These findings suggest a possible mechanism by which poor social support may be associated with disease progression. Further study of these relations may demonstrate novel pathways relating biobehavioral factors to tumor growth and disease progression.

Systemic vs. local cytokine and leukocyte responses to unilateral wrist flexion exercise

We hypothesized that brief exercise of a small muscle group would lead to local rather than systemic alterations in cytokines, peripheral blood mononuclear cells, and mediators of angiogenesis. Fifteen men and eight women (age range 22-36 yr old) performed 10 min of unilateral wrist flexion exercise. Blood was sampled from venous catheters in the resting and exercising arm at baseline, at the end of exercise, and at 10, 30, 60, and 120 min after exercise. Lactate was significantly elevated in the exercising arm (+276 +/- 35%; P < 0.0005) with no change in the resting arm. In contrast, increases in both arms were observed for interleukin-6 (+139 +/- 51%; P < 0.0005), growth hormone (+1,104 +/- 284%; P < 0.003), natural killer cells (+81 +/- 9%; P < 0.0005), and lymphocytes expressing CD62L, CD11a, and CD54. There were no significant differences in these increases between the resting and exercising arm. Catecholamines increased in both arms [epinephrine peak increase, +226 +/- 36% (P < 0.001); norepinephrine peak increase, +90 +/- 15% (P < 0.01)]. Fibroblast growth factor-2 initially decreased with exercise in both arms, and this was followed by a rebound increase. Vascular endothelial growth factor demonstrated a small but significant increase in both arms (+124 +/- 31%; P < 0.05). Brief, low-intensity exercise leads to a systemic rather than local response of mediators that could be involved in inflammation, repair, or angiogenic adaptation to physical activity.

Transcriptional regulation of vascular endothelial growth factor expression in epithelial and stromal cells during mouse mammary gland development

Accompanying changes in the development and function of the mammary gland is the establishment of a vascular network of critical importance for lactogenesis and tumorigenesis. A potent angiogenic and permeability factor that regulates vascular development in association with epithelial-stromal interactions is vascular endothelial growth factor (VEGF). Analysis of VEGF transcription by RT-PCR revealed mRNA for all three VEGF isoforms (VEGF120, 164, 188) within the mammary gland of nulliparous females. During pregnancy the level of VEGF188 declined and became undetectable during lactation in association with the increased abundance of VEGF120 and VEGF164 mRNAS: All three isoforms were expressed at consistent levels within the cleared mammary fat pad throughout development. Furthermore, the presence of VEGF188 mRNA in omental adipose tissue at various stages established that VEGF188 is expressed specifically in adipose tissue within the mammary gland. Using 3T3-L1 preadipocytes it was demonstrated that VEGF188 mRNA transcription occurs as a late event during lipogenesis distinct from earlier induction of VEGF120 and VEGF164 mRNA during differentiation. In contrast, HC11 mammary epithelial cells only expressed mRNA for VEGF120 and VEGF164. Localization of VEGF mRNA and protein revealed that VEGF is expressed in stromal cells of the mammary gland in nulliparous females and then undergoes a transition to epithelial expression during lactation. By contrast, mRNA for the VEGF receptors, Flk-1 and Flt-1, localized to stromal cells within the mammary fat pad during virgin and gestational development and was expressed in the interstitial tissue basal to epithelial cells during lactation. Taken together, these results support the conclusion that VEGF is differentially transcribed by specific cell types within the mammary gland, and that under hormonal regulation it functions in an autocrine/paracrine manner.

Isoform-specific regulation of vascular endothelial growth factor (VEGF) family mRNA expression in cultured mouse brown adipocytes

We have shown that brown adipose tissue (BAT), a thermogenic organ in mammals, expresses high levels of vascular endothelial growth factor (VEGF) mRNA in response to exposure to cold, which may contribute to angiogenesis associated with cold-induced hyperplasia of this tissue. In the present study, we examined mRNA expression of not only VEGF, but also VEGF-B and VEGF-C, recently cloned VEGF isoforms, in vitro using immortal brown adipocytes (HB2) isolated from mouse BAT. HB2 preadipocytes expressed detectable levels of VEGF, VEGF-B and VEGF-C mRNA, but a low level of VEGF. After HB2 cells differentiated into adipocytes, the VEGF mRNA level increased without a noticeable change in the VEGF-B and VEGF-C mRNA levels. When HB2 cells were stimulated by norepinephrine, the VEGF mRNA level increased without a change in that of VEGF-B, while the VEGF-C mRNA level decreased. A marked reduction of VEGF-C mRNA expression was also found when HB2 cells were treated with agonists of peroxisome proliferator-activated receptor gamma (PPARgamma, troglitazone), retinoic acid receptor (RAR, all-trans retinoic acid) and retinoid X receptor (RXR, 9-cis retinoic acid). These results suggest a specific adrenergic mechanism for up-regulation of VEGF expression different from those for other VEGF isoforms, and thereby the major contribution of VEGF to the cold-induced angiogenesis in BAT. In addition, the agonists of PPARgamma, RAR and RXR are suggested to be inhibitory to angiogenesis through the reduction of VEGF-C production.

Expression and distribution of heme oxygenase-1 and -2 in rat brown adipose tissue: the modulatory role of the noradrenergic system

To investigate whether brown adipose tissue (BAT) expresses the inducible (HO-1) and the constitutive (HO-2) isoform of heme oxygenase, reverse transcriptase-polymerase chain reaction, Western blotting and immunohistochemistry were performed on interscapular BAT (IBAT) from rats acclimated at environmental temperature or exposed to cold. Both HO isoforms were detected in rat IBAT. They were immunolocalized in the cytoplasm and/or nuclei of brown adipocytes, in parenchymal capillaries, arteries and in some veins and nerves. Whereas cold exposure did not affect HO-2 expression, it significantly increased the expression of HO-1, both at mRNA (about 3-fold) and protein (about 2-fold) levels, reflecting the increased expression of HO-1 in the brown adipocytes and endothelial cells of parenchymal capillaries. Western blotting of cytosolic and nuclear protein extracts from cultured differentiated brown adipocytes showed that HO-1 and HO-2 are indeed localized in the cytosol and nuclei of brown adipocytes, and that noradrenaline stimulation significantly increased their amount in cytosol but not in the nuclear fraction.

Multilocular fat cells in WAT of CL-316243-treated rats derive directly from white adipocytes

Multilocular, mitochondria-rich adipocytes appear in white adipose tissue (WAT) of rats treated with the beta3-adrenoceptor agonist, CL-316243 (CL). Objectives were to determine whether these multilocular adipocytes derived from cells that already existed in the WAT or from proliferation of precursor cells and whether new mitochondria contained in them were typical brown adipocyte mitochondria. Use of 5-bromodeoxyuridine to identify cells that had undergone mitosis during the CL treatment showed that most multilocular cells derived from cells already present in the WAT. Morphological techniques showed that at least a subpopulation of unilocular adipocytes underwent conversion to multilocular mitochondria-rich adipocytes. A small proportion of multilocular adipocytes ( approximately 8%) was positive for UCP1 by immunohistochemistry. Biochemical techniques showed that mitochondrial protein recovered from WAT increased 10-fold and protein isolated from brown adipose tissue (BAT) doubled in CL-treated rats. Stained gels showed a different protein composition of new mitochondria isolated from WAT from that of mitochondria isolated from BAT. Western blotting showed new mitochondria in WAT to contain both UCP1, but at a much lower concentration than in BAT mitochondria, and UCP3, at a higher concentration than that in BAT mitochondria. We hypothesize that multilocular adipocytes present at 7 days of CL treatment have two origins. First, most come from convertible unilocular adipocytes that become multilocular and make many mitochondria that contain UCP3. Second, some come from a cell that gives rise to more typical brown adipocytes that express UCP1.

Norepinephrine induces vascular endothelial growth factor gene expression in brown adipocytes through a beta -adrenoreceptor/cAMP/protein kinase A pathway involving Src but independently of Erk1/2

To identify the signaling pathway that mediates the adrenergic stimulation of the expression of the gene for vascular endothelial growth factor (VEGF) during physiologically induced angiogenesis, we examined mouse brown adipocytes in primary culture. The endogenous adrenergic neurotransmitter norepinephrine (NE) induced VEGF expression 3-fold, in a dose- and time-dependent manner (EC(50) approximately 90 nm). Also, the hypoxia-mimicking agent cobalt, as well as serum and phorbol ester, induced VEGF expression, but the effect of NE was additive to each of these factors, implying that a separate signaling mechanism for the NE-mediated induction was activated. The NE effect was abolished by propranolol and mimicked by isoprenaline or BRL-37344 and was thus mediated via beta-adrenoreceptors. The NE-induced VEGF expression was fully cAMP mediated, an effect which was inhibited by H-89 and thus was dependent on protein kinase A activity. Involvement of other adrenergic signaling pathways (alpha(1)-adrenoreceptors, Ca(2+), protein kinase C, alpha(2)-adrenoreceptors, and pertussis toxin-sensitive G(i)-proteins) was excluded. The specific inhibitor of Src tyrosine kinases, PP2, markedly reduced the stimulation by NE, which demonstrates that a cAMP-dependent Src-mediated pathway is positively connected to VEGF expression. However, inhibition of Erk1/2 MAP kinases by PD98059 was without effect. NE did not prolong VEGF mRNA half-life and its effect was thus transcriptional, and was independent of protein synthesis. These results demonstrate that adrenergic stimulation, through beta-adrenoreceptor/cAMP/protein kinase A signaling, recruits a pathway that branches off from the NE-activated Src-Erk1/2 cascade to enhance transcription of the VEGF gene.