NPY antagonism reduces adiposity and attenuates age-related imbalance of adipose tissue metabolism

Characterisation of neurogenic lipolytic responses in white adipose tissue ex vivo

BACKGROUND AND PURPOSE

Dysfunction of the autonomic nervous system is associated with cardiovascular dysfunction, including metabolic syndrome and obesity. Understanding mechanisms of neurogenic control of white adipose tissue is key to understanding adipose physiology and pathophysiology, though there is limited research exploring this in adipose tissue using pharmacological tools, as opposed to genetic knockout models.

EXPERIMENTAL APPROACH

Inguinal white adipose tissue from C57BL/6J mice was used in this study. We used immunocytochemistry to determine tissue innervation and glycerol release assays to quantify lipolysis in adipose tissue and isolated adipocytes. The voltage-gated Na+ channel opener veratridine was used to stimulate nervous activity in tissue ex vivo. The role of neurotransmitters and receptors mediating veratridine-evoked lipolysis in adipose tissue was pharmacologically characterised.

KEY RESULTS

Veratridine evoked glycerol release in white adipose tissue but not from isolated adipocytes. This release was abolished by tetrodotoxin and propranolol. Veratridine also induced noradrenaline release from white adipose tissue. Veratridine- and noradrenaline-evoked glycerol release was blocked by the β2-adrenoceptor antagonist ICI-118551 but not by the β1-adrenoceptor antagonist CGP 20712A. Purported β3-adrenoceptor antagonists L-748337 and SR59230A stimulated glycerol release from tissue and from isolated adipocytes. Neither L-748337 or SR59230A antagonised veratridine-evoked glycerol release but SR59230A antagonised noradrenaline-evoked glycerol release. We exclude contributions of sensory neuropeptides and the autonomic neurotransmitters neuropeptide Y and ATP.

CONCLUSION AND IMPLICATIONS

Neurogenic lipolytic responses can be measured in white adipose tissue ex vivo using veratridine to stimulate nerve activity. The lipolytic responses are mediated by β2-adrenoceptor activation. This study provides the first evidence of neurogenic lipolysis in tissue ex vivo.

Restoring neuropetide Y levels in the hypothalamus ameliorates premature aging phenotype in mice

The hypothalamus has been recognized as a regulator of whole-body aging. Neuropeptide Y (NPY), highly abundant in the central nervous system and produced by the hypothalamus, enhances autophagy in this brain region and mediates autophagy triggered by caloric restriction, suggesting a potential role as a caloric restriction mimetic and an aging regulator. Considering that hypothalamic NPY levels decline during aging, we investigated if reestablishment of NPY levels mitigate aging phenotype, using a mouse model of premature aging - Zmpste24-/- mouse. The results show that reestablishing hypothalamic NPY levels delayed aging-associated features, including lipodystrophy, alopecia, and memory. Moreover, these results suggest that strategies that promote maintenance of hypothalamic NPY levels might be relevant to counteract aging progression and age-related deteriorations.

The adipose tissue melanocortin 3 receptor is targeted by ghrelin and leptin and may be a therapeutic target in obesity

OBJECTIVE

Obesity is linked to perturbations in energy balance mechanisms, including ghrelin and leptin actions at the hypothalamic circuitry of neuropeptide Y (NPY) and melanocortin. However, information about the regulation of this system in the periphery is still scarce. Our objective was to study the regulation of the NPY/melanocortin system in the adipose tissue (AT) and evaluate its therapeutic potential for obesity and type 2 diabetes.

METHODS

The expression of the NPY/melanocortin receptors' levels was assessed in the visceral AT of individuals with obesity and altered metabolism. Protein levels of these receptors were evaluated in cultured adipocytes incubated with ghrelin (30 and 100 ng/mL) and leptin (1 and 10 nM) and in the AT of an animal model with a mutation in the leptin receptor (ZSF1 rat), to understand their regulation by leptin and ghrelin. The vertical sleeve gastrectomy animal model was used to evaluate the putative therapeutic potential of the NPY/melanocortin system.

RESULTS

In this study, we unravelled that leptin (1 nM and 10 nM) selectively reduced the levels of NPY5R and MC3R but no other NPYR/MCRs in cultured adipocytes. In turn, acylated ghrelin (100 ng/mL) significantly increased NPY1R, but the inhibition of its receptor also abrogates MC3R levels. However, in the Lepr-deficient ZSF1 rat, both NPY5R and MC3R levels were reduced, along with other NPYRs and MCRs, suggesting that leptin resistance negatively affects NPY and melanocortin signalling. In human adipose tissue, we found a downregulation of genes encoding the NPY and melanocortin receptors in the visceral AT of individuals with obesity and insulin resistance, being correlated with genes regulating metabolic activity. Additionally, diabetic obese rats submitted to vertical sleeve gastrectomy showed increased levels of NPY, melanocortin, ghrelin, and leptin receptors in the AT, including MC3R, suggesting it may constitute a therapeutic target in obesity.

CONCLUSIONS

Our results suggest that the AT NPY/melanocortin system, particularly the MC3R, may be involved in the neuroendocrine regulation of adipocyte metabolism. Altogether, our work shows MC3R is under the control of the ghrelin/leptin duo, is reduced in patients with obesity and prediabetes, and may constitute a therapeutic target in obesity.

Activity of the hypothalamic neuropeptide Y increases in adult and decreases in old rats

Middle-aged obesity and aging anorexia with muscle loss (sarcopenia) of old people present public health burden. These alterations may appear both in humans and rodents suggesting the role for regulatory alterations. Previously, we demonstrated that biphasic changes in the weight-reducing (catabolic) effects of neuropeptides of the hypothalamus-adipose tissue axis (e.g. leptin) may contribute to both trends. With regard to the anabolic effects of the hypothalamic neuropeptide Y (NPY) inhibited by leptin, we hypothesized non-linear age-related changes with shifts in the opposite directions. We investigated the orexigenic and hypometabolic effects of intracerebroventricularly administered NPY (hyperphagia induced by NPY injection or changes in food intake, body weight, heart rate, body temperature, locomotor activity during a 7-day NPY infusion), the immunoreactivity and gene expression of NPY in the hypothalamic arcuate nucleus of male Wistar rats of five age groups from young to old. The orexigenic/hypometabolic efficacy and the immunoreactivity of NPY increased in middle-aged animals preceding the peak of adiposity observed in aging rats, then decreased preceding anorexia and weight loss in old rats. These shifts may contribute to the development of both age-related obesity and aging anorexia, sarcopenia, and should be considered in future drug development targeting the NPY system.

Tissue fibrosis associated depletion of lipid-filled cells

Fibrosis is primarily described as the deposition of excessive extracellular matrix, but in many tissues it also involves a loss of lipid or lipid-filled cells. Lipid-filled cells are critical to tissue function and integrity in many tissues including the skin and lungs. Thus, loss or depletion of lipid-filled cells during fibrogenesis, has implications for tissue function. In some contexts, lipid-filled cells can impact ECM composition and stability, highlighting their importance in fibrotic transformation. Recent papers in fibrosis address this newly recognized fibrotic lipodystrophy phenomenon. Even in disparate tissues, common mechanisms are emerging to explain fibrotic lipodystrophy. These findings have implications for fibrosis in tissues composed of fibroblast and lipid-filled cell populations such as skin, lung, and liver. In this review, we will discuss the roles of lipid-containing cells, their reduction/loss during fibrotic transformation, and the mechanisms of that loss in the skin and lungs.

Mechanisms underlying retardation of aging by dietary energy restriction

Moderate restriction of dietary energy intake, referred to here as dietary restriction (DR), delays aging and extends lifespan in experimental animals compared with a diet of ad libitum feeding (AL) control animals. Basic knowledge of the mechanisms underlying the effects of DR could be applicable to extending the healthspan in humans. This review highlights the importance of forkhead box O (FoxO) transcription factors downstream of the growth hormone-insulin-like growth factor 1 signaling in the effects of DR. Our lifespan studies in mice with heterozygous Foxo1 or Foxo3 gene knockout indicated differential roles of FoxO1 and FoxO3 in the tumor-inhibiting and life-extending effects of DR. Subsequent studies suggested a critical role of FoxO3 in metabolic and mitochondrial bioenergetic adaptation to DR. Our studies also verified hypothalamic neuropeptide Y (Npy) as a vital neuropeptide showing pleiotropic and sexually dimorphic effects for extending the healthspan in the context of nutritional availability. Npy was necessary for DR to exert its effects in male and female mice; meanwhile, under AL conditions, the loss of Npy prevented obesity and insulin resistance only in female mice. Overnutrition disrupts FoxO- and Npy-associated metabolic and mitochondrial bioenergetic adaptive processes, causing the acceleration of aging and related diseases.

Four-and-a-Half LIM-Domain Protein 2 (FHL2) Induces Neuropeptide Y (NPY) in Macrophages in Visceral Adipose Tissue and Promotes Diet-Induced Obesity

Obesity is characterized by the expansion of the adipose tissue, usually accompanied by inflammation, with a prominent role of macrophages infiltrating the visceral adipose tissue (VAT). This chronic inflammation is a major driver of obesity-associated comorbidities. Four-and-a-half LIM-domain protein 2 (FHL2) is a multifunctional adaptor protein that is involved in the regulation of various biological functions and the maintenance of the homeostasis of different tissues. In this study, we aimed to gain new insights into the expression and functional role of FHL2 in VAT in diet-induced obesity. We found enhanced FHL2 expression in the VAT of mice with Western-type diet (WTD)-induced obesity and obese humans and identified macrophages as the cellular source of enhanced FHL2 expression in VAT. In mice with FHL2 deficiency (FHL2KO), WTD feeding resulted in reduced body weight gain paralleled by enhanced energy expenditure and uncoupling protein 1 (UCP1) expression, indicative of activated thermogenesis. In human VAT, FHL2 was inversely correlated with UCP1 expression. Furthermore, macrophage infiltration and the expression of the chemokine MCP-1, a known promotor of macrophage accumulation, was significantly reduced in WTD-fed FHL2KO mice compared with wild-type (wt) littermates. While FHL2 depletion did not affect the differentiation or lipid metabolism of adipocytes in vitro, FHL2 depletion in macrophages resulted in reduced expressions of MCP-1 and the neuropeptide Y (NPY). Furthermore, WTD-fed FHL2KO mice showed reduced NPY expression in VAT compared with wt littermates, and NPY expression was enhanced in VAT resident macrophages of obese individuals. Stimulation with recombinant NPY induced not only UCP1 expression and lipid accumulation but also MCP-1 expression in adipocytes. Collectively, these findings indicate that FHL2 is a positive regulator of NPY and MCP-1 expression in macrophages and herewith closely linked to the mechanism of obesity-associated lipid accumulation and inflammation in VAT. Thus, FHL2 appears as a potential novel target to interfere with the macrophage-adipocyte crosstalk in VAT for treating obesity and related metabolic disorders.

Exposure to Obesogenic Environments during Perinatal Development Modulates Offspring Energy Balance Pathways in Adipose Tissue and Liver of Rodent Models

Obesogenic environments such as Westernized diets, overnutrition, and exposure to glycation during gestation and lactation can alter peripheral neuroendocrine factors in offspring, predisposing for metabolic diseases in adulthood. Thus, we hypothesized that exposure to obesogenic environments during the perinatal period reprograms offspring energy balance mechanisms. Four rat obesogenic models were studied: maternal diet-induced obesity (DIO); early-life obesity induced by postnatal overfeeding; maternal glycation; and postnatal overfeeding combined with maternal glycation. Metabolic parameters, energy expenditure, and storage pathways in visceral adipose tissue (VAT) and the liver were analyzed. Maternal DIO increased VAT lipogenic [NPY receptor-1 (NPY1R), NPY receptor-2 (NPY2R), and ghrelin receptor], but also lipolytic/catabolic mechanisms [dopamine-1 receptor (D1R) and p-AMP-activated protein kinase (AMPK)] in male offspring, while reducing NPY1R in females. Postnatally overfed male animals only exhibited higher NPY2R levels in VAT, while females also presented NPY1R and NPY2R downregulation. Maternal glycation reduces VAT expandability by decreasing NPY2R in overfed animals. Regarding the liver, D1R was decreased in all obesogenic models, while overfeeding induced fat accumulation in both sexes and glycation the inflammatory infiltration. The VAT response to maternal DIO and overfeeding showed a sexual dysmorphism, and exposure to glycotoxins led to a thin-outside-fat-inside phenotype in overfeeding conditions and impaired energy balance, increasing the metabolic risk in adulthood.

The Bidirectional Relationship of NPY and Mitochondria in Energy Balance Regulation

Energy balance is regulated by several hormones and peptides, and neuropeptide Y is one of the most crucial in feeding and energy expenditure control. NPY is regulated by a series of peripheral nervous and humoral signals that are responsive to nutrient sensing, but its role in the energy balance is also intricately related to the energetic status, namely mitochondrial function. During fasting, mitochondrial dynamics and activity are activated in orexigenic neurons, increasing the levels of neuropeptide Y. By acting on the sympathetic nervous system, neuropeptide Y modulates thermogenesis and lipolysis, while in the peripheral sites, it triggers adipogenesis and lipogenesis instead. Moreover, both central and peripheral neuropeptide Y reduces mitochondrial activity by decreasing oxidative phosphorylation proteins and other mediators important to the uptake of fatty acids into the mitochondrial matrix, inhibiting lipid oxidation and energy expenditure. Dysregulation of the neuropeptide Y system, as occurs in metabolic diseases like obesity, may lead to mitochondrial dysfunction and, consequently, to oxidative stress and to the white adipose tissue inflammatory environment, contributing to the development of a metabolically unhealthy profile. This review focuses on the interconnection between mitochondrial function and dynamics with central and peripheral neuropeptide Y actions and discusses possible therapeutical modulations of the neuropeptide Y system as an anti-obesity tool.

Stomach secretes estrogen in response to the blood triglyceride levels

Mammals receive body energy information to maintain energy homeostasis. Ghrelin, insulin, leptin and vagal afferents transmit the status of fasting, blood glucose, body fat, and food intake, respectively. Estrogen also inhibits feeding behavior and lipogenesis, but increases body fat mass. However, how blood triglyceride levels are monitored and the physiological roles of estrogen from the perspective of lipid homeostasis remain unsettled. Here, we show that stomach secretes estrogen in response to the blood triglyceride levels. Estrogen-secreting gastric parietal cells predominantly use fatty acids as an energy source. Blood estrogen levels increase as blood triglyceride levels rise in a stomach-dependent manner. Estrogen levels in stomach tissues increase as blood triglyceride levels rise, and isolated gastric gland epithelium produces estrogen in a fatty acid-dependent manner. We therefore propose that stomach monitors and controls blood triglyceride levels using estrogen, which inhibits feeding behavior and lipogenesis, and promotes triglyceride uptake by adipocytes.

The Role of Neuropeptide Y in Adipocyte-Macrophage Crosstalk during High Fat Diet-Induced Adipose Inflammation and Liver Steatosis

Obesity is associated with an increased risk of non-alcoholic fatty liver disease (NAFLD), which is initiated by adipocyte-macrophage crosstalk. Among the possible molecules regulating this crosstalk, we focused on neuropeptide Y (NPY), which is known to be involved in hypothalamic appetite and adipose tissue inflammation and metabolism. In this study, the NPY^−/− mice showed a marked decrease in body weight and adiposity, and lower free fatty acid and adipose inflammation without food intake alteration during a high fat diet (HFD). Moreover, NPY deficiency increased the thermogenic genes expression in brown adipose tissue. Notably, NPY-mRNA expression was upregulated in macrophages from the HFD mice compared to that from the mice on a standard diet. The NPY-mRNA expression also positively correlated with the liver mass/body weight ratio. NPY deletion alleviated HFD-induced adipose inflammation and liver steatosis. Hence, our findings point toward a novel intracellular mechanism of NPY in the regulation of adipocyte-macrophage crosstalk and highlight NPY antagonism as a promising target for therapeutic approaches against obesity and NAFLD.

Skeleton interoception regulates bone and fat metabolism through hypothalamic neuroendocrine NPY

The central nervous system regulates activity of peripheral organs through interoception. In our previous study, we have demonstrated that PGE2/EP4 skeleton interception regulate bone homeostasis. Here, we show that ascending skeleton interoceptive signaling downregulates expression of hypothalamic neuropeptide Y (NPY) and induce lipolysis of adipose tissue for osteoblastic bone formation. Specifically, the ascending skeleton interoceptive signaling induces expression of small heterodimer partner-interacting leucine zipper protein (SMILE) in the hypothalamus. SMILE binds to pCREB as a transcriptional heterodimer on Npy promoters to inhibit NPY expression. Knockout of EP4 in sensory nerve increases expression of NPY causing bone catabolism and fat anabolism. Importantly, inhibition of NPY Y1 receptor (Y1R) accelerated oxidation of free fatty acids in osteoblasts and rescued bone loss in AvilCre:Ptger4fl/fl mice. Thus, downregulation of hypothalamic NPY expression lipolyzes free fatty acids for anabolic bone formation through a neuroendocrine descending interoceptive regulation.

Effect of Temperature and Selection for Growth on Intracellular Lipid Accumulation and Adipogenic Gene Expression in Turkey Pectoralis Major Muscle Satellite Cells

As multipotential stem cells, satellite cells (SCs) have the potential to express adipogenic genes resulting in lipid synthesis with thermal stress. The present study determined the effect of temperature on intracellular lipid synthesis and adipogenic gene expression in SCs isolated from the pectoralis major (p. major) muscle of 7-day-old fast-growing modern commercial (NC) turkeys compared to SCs from unselected slower-growing turkeys [Randombred Control Line 2 (RBC2)]. Since proliferating and differentiating SCs have different responses to thermal stress, three incubation strategies were used: (1) SCs proliferated at the control temperature of 38°C and differentiated at 43° or 33°C; (2) SCs proliferated at 43° or 33°C and differentiated at 38°C; or (3) SCs both proliferated and differentiated at 43°, 38°, or 33°C. During proliferation, lipid accumulation increased at 43°C and decreased at 33°C with the NC line showing greater variation than the RBC2 line. During proliferation at 43°C, peroxisome proliferator-activated receptor-γ (PPARγ) and neuropeptide-Y (NPY) expression was reduced to a greater extent in the NC line than the RBC2 line. At 33°C, expression of PPARγ, NPY, and CCAAT/enhancer-binding protein-β (C/EBPβ) was upregulated, but only in the RBC2 line. During differentiation, both lines showed greater changes in lipid accumulation and in C/EBPβ and NPY expression if the thermal challenge was initiated during proliferation. These data suggest that adipogenic gene expression is more responsive to thermal challenge in proliferating SCs than in differentiating SCs, and that growth-selection has increased temperature sensitivity of SCs, which may significantly affect breast muscle structure and composition.

Effects of Y1 receptor agonist on the pancreatic islet of diet-induced obese and diabetic mice

AIMS

Agonists of the NPY receptor might be potential in protecting pancreatic islets from injury. We aimed to characterize the role of [Leu31, Pro34]-PYY, an NPYR1 agonist, in pancreatic islets of a diet-induced obesity and insulin resistance model.

METHODS

We studied long-term high-fat diet intake as a model and selective agonist of the Y1 receptor to explore the pancreatic islet architecture and stereology, and insulin secretion in isolated islets and a whole animal model. Gene and protein expressions were assessed in isolated islets investigating the signaling cascades involved in inflammation, insulin signaling, and secretion. Also, the insulin release potential was studied in vitro.

RESULTS

Our data reveal that an infusion of NPYR1 for 14 days did not change the body mass of mice and eating behavior. NPYR1 did not modify the islet and beta-cell mass but positively impacted the inflammatory process by lowering the expressions of Tnf alpha and If gamma. Besides, NPYR1 restored the insulin signaling and the exocytose pattern by activating the PDX1/STAT3 pathway and improving the leptin signaling cascade.

CONCLUSIONS

The findings are compellingly indicating the potential effect of the NPYR1 as a target for improving the insulin resistance condition. As such, the infusion of the NPYR1 agonist would help to enhance insulin secretion by the beta-cell from the PDX1/STAT3 pathway and the improvement of the inflammatory process.

Higher Serum Neuropeptide Y Levels Are Associated with Metabolically Unhealthy Obesity in Obese Chinese Adults: A Cross-Sectional Study

Objective

Neuropeptide Y (NPY), an orexigenic peptide known to cause hyperphagia, has been involved in the occurrence and development of obesity. However, differences in the distribution of serum NPY levels in obese phenotypes (including metabolically unhealthy obesity (MUO) phenotype and metabolically healthy obesity (MHO) phenotype) and the association of NPY with MUO phenotype have not been unequivocally established. We therefore determined associations of serum NPY levels with MUO phenotype in obese Chinese adults.

Methods

A cross-sectional study was conducted from 400 obese adults in Hunan province, who underwent a health examination in the Second Xiangya Hospital, and 164 participants were finally enrolled in the study and divided into MHO and MUO groups. Serum NPY levels were examined; univariate and multivariate analyses as well as smooth curve fitting analyses were conducted to measure the association of NPY serum levels with the MUO phenotype.

Results

Serum NPY levels were significantly elevated in the MUO group compared with the MHO group ((667.69 ± 292.90) pg/mL vs. (478.89 ± 145.53) pg/mL, p < 0.001). A threshold and nonlinear association between serum NPY levels and MUO was found (p = 0.001). When serum NPY levels exceeded the turning point (471.5 pg/mL), each 10 pg/mL increment in the NPY serum level was significantly associated with an 18% increased odds ratio of MUO phenotype (OR: 1.18, 95% CI: 1.07–1.29, p = 0.0007) after adjusted for confounders.

Conclusions

Higher NPY serum levels were positively correlated with MUO phenotype in obese Chinese adults.

NPY Deficiency Prevents Postmenopausal Adiposity by Augmenting Estradiol-Mediated Browning

The orexigenic hormone neuropeptide Y (NPY) plays a pivotal role in the peripheral regulation of fat metabolism. However, the mechanisms underlying the effects of sex on NPY function have not been extensively analyzed. In this study, we examined the effects of NPY deficiency on fat metabolism in male and female mice. Body weight was slightly decreased, whereas white adipose tissue (WAT) mass was significantly decreased as the thermogenic program was upregulated in NPY-/- female mice compared with that in wild-type mice; these factors were not altered in response to NPY deficiency in male mice. Moreover, lack of NPY resulted in an increase in luteinizing hormone (LH) expression in the pituitary gland, with concomitant activation of the estradiol-mediated thermogenic program in inguinal WAT, and alleviated age-related modification of adiposity in female mice. Taken together, these data revealed a novel intracellular mechanism of NPY in the regulation of fat metabolism and highlighted the sexual dimorphism of NPY as a promising target for drug development to reduce postmenopausal adiposity.

Mechanisms of Calorie Restriction: A Review of Genes Required for the Life-Extending and Tumor-Inhibiting Effects of Calorie Restriction

This review focuses on mechanisms of calorie restriction (CR), particularly the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis as an evolutionary conserved signal that regulates aging and lifespan, underlying the effects of CR in mammals. Topics include (1) the relation of the GH-IGF-1 signal with chronic low-level inflammation as one of the possible causative factors of aging, that is, inflammaging, (2) the isoform specificity of the forkhead box protein O (FoxO) transcription factors in CR-mediated regulation of cancer and lifespan, (3) the role for FoxO1 in the tumor-inhibiting effect of CR, (4) pleiotropic roles for FoxO1 in the regulation of disorders, and (5) sirtuin (Sirt) as a molecule upstream of FoxO. From the evolutionary view, the necessity of neuropeptide Y (Npy) for the effects of CR and the pleiotropic roles for Npy in life stages are also emphasized. Genes for mediating the effects of CR and regulating aging are context-dependent, particularly depending on nutritional states.

The effect of peptide tyrosine tyrosine (PYY3–36), a selective Y2 receptor agonist on streptozotocin-induced diabetes in albino rats

Objective. The aim of the present study was to assess the effect of the PYY3–36, as a potential therapy for the type 2 diabetes mellitus (T2DM), induced by high fat diet (HFD) and an intraperitoneal (i.p.) administration of streptozotocin (STZ) in albino rats.

Methods. Forty adult male albino Wistar rats were divided into: 1) control group (C, in which the rats were fed with a standard diet and received vehicle; 2) diabetic group (D, in which T2DM was induced by feeding the rats with HFD for four weeks followed by a single i.p. injection of 35 mg/kg STZ, this group was also allowed to have HFD till the end of the study; and 3) D+PYY3–36 group (in which the diabetic rats were treated with 50 µg/kg i.p. PYY3–36 twice a day for one week). Food intake, water intake, body weight (b.w.), visceral fat weight (VFW), liver glycogen content, serum levels of glucose, insulin, and interleukin-6 (IL-6), were measured. Homeostatic-model assessment of insulin resistance (HOMA-IR) was estimated. The gene expression of the hypothalamic neuropeptide Y (NPY) and visceral nuclear factor kappa B (NF-κB) were assessed by a reverse transcription polymerase chain reaction (RT-PCR).

Results. The PYY3–36 administration to the diabetic group of rats significantly increased the serum insulin levels and liver glycogen content, decreased the body weight, VFW, food intake, water intake, serum levels of the glucose, IL-6, and HOMA-IR. It also decreased the expression of both the hypothalamic NPY and the visceral fat NF-κB.

Conclusion. With respect to the fact of improved insulin release and enhanced insulin sensitivity (an effect that may be mediated via suppressing accumulation of visceral fat and inflammatory markers), in the rats treated with PYY3–36, the PYY3–36 might be considered for the future as a promising therapeutic tool in T2DM.

Y1 receptor deficiency in β-cells leads to increased adiposity and impaired glucose metabolism

Insulin secretion from pancreatic β-cells is critical for maintaining glucose homeostasis and deregulation of circulating insulin levels is associated with the development of metabolic diseases. While many factors have been implicated in the stimulation of insulin secretion, the mechanisms that subsequently reduce insulin secretion remain largely unexplored. Here we demonstrate that mice with β-cell specific ablation of the Y1 receptor exhibit significantly upregulated serum insulin levels associated with increased body weight and adiposity. Interestingly, when challenged with a high fat diet these β-cell specific Y1-deficient mice also develop hyperglycaemia and impaired glucose tolerance. This is most likely due to enhanced hepatic lipid synthesis, resulting in an increase of lipid accumulation in the liver. Together, our study demonstrates that Y1 receptor signaling negatively regulates insulin release, and pharmacological inhibition of Y1 receptor signalling for the treatment of non-insulin dependent diabetes should be taken into careful consideration.

Stress and Obesity

Many pathways connect stress and obesity, two highly prevalent problems facing society today. First, stress interferes with cognitive processes such as executive function and self-regulation. Second, stress can affect behavior by inducing overeating and consumption of foods that are high in calories, fat, or sugar; by decreasing physical activity; and by shortening sleep. Third, stress triggers physiological changes in the hypothalamic-pituitary-adrenal axis, reward processing in the brain, and possibly the gut microbiome. Finally, stress can stimulate production of biochemical hormones and peptides such as leptin, ghrelin, and neuropeptide Y. Obesity itself can be a stressful state due to the high prevalence of weight stigma. This article therefore traces the contribution of weight stigma to stress and obesogenic processes, ultimately describing a vicious cycle of stress to obesity to stigma to stress. Current obesity prevention efforts focus solely on eating and exercise; the evidence reviewed in this article points to stress as an important but currently overlooked public policy target.

Neuropeptide Y promotes adipogenic differentiation in primary cultured human adipose-derived stem cells

Neuropeptide Y (NPY) is an important neurotransmitter in the control of energy metabolism. Several studies have shown that obesity is associated with increased levels of NPY in the hypothalamus. We hypothesized that the release of NPY has coordinated and integrated effects on energy metabolism in different tissues, such as adipocyte tissue, resulting in increased energy storage and decreased energy expenditure. Whether NPY has role in the molecular mechanism of human adipocyte tissue remains unclear. We established the model of human adipose derived stem cells (hADSCs) from human adipose tissue and differentiated it into adipocytes in the presence of NPY at different concentrations (10^-15-10^-6 mmol/L). We then assessed hADSCs proliferation and differentiation by quantifying lipid accumulation and examining the expression levels of related adipocyte markers after differentiation. Furthermore, the specific markers of white adipocyte tissue (WAT) in hADSCs were also analyzed. The results showed that low doses of NPY stimulated hADSCs proliferation (p < 0.05), while high doses of NPY inhibited hADSCs proliferation (p < 0.05). NPY significantly promoted lipid accumulation and increased the size of lipid droplets during human adipogenic differentiation; the levels of adipocyte markers PPAR-γ and C/EBPα were also increased. At the same time, NPY also increased the levels of WAT markers Cidec and RIP140 after adipocyte differentiation. The results suggested high dose NPY inhibits the proliferation of hADSCs while promotes adipocyte differentiation and increases the expression of WAT markers. This may be the reason why increased levels of NPY can lead to a rise in body weight.

Promotion of adipogenesis by neuropeptide Y during the later stages of chicken preadipocyte differentiation

Neuropeptide Y (NPY) promotes adipogenesis in both birds and mammals, although mechanisms in avians remain unclear. The objective of this study was thus to evaluate effects of NPY on chick preadipocyte proliferation and differentiation. Preadipocytes were treated with 0, 1, 10, or 100 nmol/L NPY and gene expression and cellular proliferation were evaluated at 12, 24, and 48 h. At 12 h posttreatment, mRNA abundance of topoisomerase II alpha (TOP2A), and thioredoxin-dependent peroxidase 2 was upregulated and NPY was downregulated in response to NPY (0 vs. 100 nmol/L) in preadipocytes. Cells were also treated with NPY during differentiation and harvested at 8, 10, and 12 days postinduction of differentiation. At day 8 postinduction of differentiation, there was increased lipid accumulation (0 vs. 10 and 100 nmol/L), expression of CCAAT/enhancer binding protein β and fatty acid binding protein 4 (FABP4) (0 vs. 100 nmol/L), and sterol regulatory element-binding protein (0 vs. 10 and 100 nmol/L) mRNA in NPY-treated cells. The number of proliferating cells decreased on day 8 in response to NPY (0 vs. 10 nmol/L). At day 10, FABP4 and Kruppel-like factor 7 mRNAs were downregulated (0 vs. 10 and 100 nmol/L, and 100 nmol/L, respectively), and at day 12, TOP2A mRNA was down-regulated (0 vs. 100 nmol/L) in response to NPY treatment. Activity of glycerol-3-phosphate dehydrogenase (G3PDH) was increased on days 10 and 12 in NPY-treated cells (0 vs. 100 nmol/L). Increased gene expression of proliferation markers in preadipocytes, and during differentiation increased expression of transcription factors and a fatty acid transporter, increased lipid accumulation, and increased activity of G3PDH suggest that NPY may enhance preadipocyte activity, adipogenesis, and promotes lipid accumulation throughout chicken adipocyte differentiation.

Peripheral neuropeptide Y differentially influences adipogenesis and lipolysis in chicks from lines selected for low or high body weight

Neuropeptide Y (NPY) stimulates appetite and promotes lipid deposition. We demonstrated a differential sensitivity in the food intake response to central NPY in chicks from lines selected for low (LWS) or high (HWS) body weight, but have not reported whether such differences exist in the periphery. At 5days, LWS and HWS chicks were intraperitoneally injected with 0 (vehicle), 60, or 120μg/kg BW NPY and subcutaneous adipose tissue and plasma were collected at 1, 3, 6, 12, and 24h (n=12). NPY injection increased glycerol-3-phosphate dehydrogenase (G3PDH) activity at 1 and 3h and reduced plasma non-esterified fatty acids (NEFAs) at 1 and 12h. G3PDH activity was greater in HWS than LWS while NEFAs were greater in LWS. At 1h, peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein (C/EBP)α, and microsomal triglyceride transfer protein (MTTP) mRNAs were reduced in NPY-injected chicks whereas NPY receptor 1 (NPYR1) was increased. Expression of stearoyl-CoA desaturase (SCD1) was increased by NPY at 1h in HWS but not LWS. PPARγ (3 and 6h), C/EBPβ (3h), C/EBPα (6h) and NPYR1 and 2 (24h) mRNAs were greater in NPY- than vehicle-injected chicks. At several times, adipose triglyceride lipase, MTTP, perilipin 1, NPYR1, and NPYR2 mRNAs were greater in LWS than HWS, while expression of SCD1, glycerol-3-phosphate acyltransferase 3 and lipoprotein lipase was greater in HWS than LWS. Thus, NPY promotes fat deposition and inhibits lipolysis in chicks, with line differences indicative of greater rates of lipolysis in LWS and adipogenesis in HWS.

Comparing the Effects of Melatonin with Caloric Restriction in the Hippocampus of Aging Mice: Involvement of Sirtuin1 and the FOXOs Pathway

It has been suggested that age-related neurodegeneration might be associated with neuropeptide Y (NPY); sirtuin1 (SIRT1) and forkhead box transcription factors O subfamily (FOXOs) pathways. Melatonin, a hormone mainly secreted by the pineal gland, is another anti-aging agent associated with the SIRT1-FOXOs pathway. This study aimed to compare the effects of melatonin (Mel) and caloric restriction (CR) on the expression of Sirt1, FoxO1, FoxO3a and FOXOs target genes in the aging mouse hippocampus. Neuropeptide Y-knockout (NpyKO) and wild-type (WT) male mice aged 19 months were previously treated either with food ad libitum or CR for 16 months. WT old animals were divided into four groups: control, CR, Mel and CR+Mel treated groups. The Mel and CR+Mel were treated with melatonin 10 mg/kg, daily, subcutaneously for 7 consecutive days. Mel treatment upregulated the mRNA expression of Sirt1, FOXOs (FoxO1 and FoxO3a) target genes that regulated the cell cycle [e.g., cyclin-dependent kinase inhibitor 1B (p27)], Wingless and INT-1 (Wnt1) and inducible signaling pathway protein 1 (Wisp1) in the aged mouse hippocampus. CR treatment also showed the similar actions. However, the mRNA expression of Sirt1, FoxO1, FoxO3a, p27 or Wisp1 did not alter in the CR+Mel group when compared with CR or Mel group. Melatonin could not produce any additive effect on the CR treatment group, suggesting that both treatments mimicked the effect, possibly via the same pathway. NPY which mediates physiological adaptations to energy deficits is an essential link between CR and longevity in mice. In order to focus on the role of Npy in mediating the effects of melatonin, the gene expression between NpyKO and WT male mice were compared. Our data showed that, in the absence of Npy, melatonin could not mediate effects on those gene expressions, suggesting that Npy was required for melatonin to mediate the effect, possibly, on life extension.

Neuropeptide Y resists excess loss of fat by lipolysis in calorie-restricted mice: a trait potential for the life-extending effect of calorie restriction

Neuropeptide Y (NPY) is an orexigenic peptide that plays an essential role in caloric restriction (CR)‐mediated lifespan extension. However, the mechanisms underlying the NPY‐mediated effects in CR are poorly defined. Here, we report that NPY deficiency in male mice during CR increases mortality in association with lipodystrophy. NPY^−/− mice displayed a rapid decrease in body weight and fat mass, as well as increased lipolysis during CR. These alterations in fat regulation were inhibited by the lipolysis inhibitor, acipimox, a treatment associated with reduced mortality. The lipolytic/thermogenic signaling, β3‐adrenergic receptor/hormone sensitive lipase, was markedly activated in white adipose tissue of NPY^−/− mice compared with that of NPY^+/+ mice, and thermogenesis was controlled by NPY under negative energy balance. These results demonstrate the critical role of NPY in the regulation of lipid metabolic homeostasis and survival via control of lipolysis and thermogenesis in a state of negative energy balance.

Recent advances in the understanding of how neuropeptide Y and -melanocyte stimulating hormone function in adipose physiology

Communication between the brain and the adipose tissue has been the focus of many studies in recent years, with the "brain-fat axis" identified as a system that orchestrates the assimilation and usage of energy to maintain body mass and adequate fat stores. It is now well-known that appetite-regulating peptides that were studied as neurotransmitters in the central nervous system can act both on the hypothalamus to regulate feeding behavior and also on the adipose tissue to modulate the storage of energy. Energy balance is thus partly controlled by factors that can alter both energy intake and storage/expenditure. Two such factors involved in these processes are neuropeptide Y (NPY) and α-melanocyte stimulating hormone (α-MSH). NPY, an orexigenic factor, is associated with promoting adipogenesis in both mammals and chickens, while α-MSH, an anorexigenic factor, stimulates lipolysis in rodents. There is also evidence of interaction between the 2 peptides. This review aims to summarize recent advances in the study of NPY and α-MSH regarding their role in adipose tissue physiology, with an emphasis on the cellular and molecular mechanisms. A greater understanding of the brain-fat axis and regulation of adiposity by bioactive peptides may provide insights on strategies to prevent or treat obesity and also enhance nutrient utilization efficiency in agriculturally-important species.

Neuropeptide Y mediates glucocorticoid-induced osteoporosis and marrow adiposity in mice

Increased neuropeptide Y (NPY) expression occurred in the glucocorticoid-induced osteoporotic skeleton. NPY knockout mice exhibited a minor response to the glucocorticoid-mediated exacerbation of bone accretion and fatty marrow pathogenesis. NPY deletion restored SITR1 signaling and enhanced PPARγ ubiquitination of bone tissue, an alternative strategy for ameliorating glucocorticoid-induced skeletal deterioration.

INTRODUCTION

Glucocorticoid excess is observed to worsen the pathogenesis of osteoporosis and fatty marrow. This study was undertaken to investigate the contribution of neuropeptide Y (NPY) to glucocorticoid-induced bone loss and marrow adiposity.

METHODS

NPY knockout and wild-type mice were administered methylprednisolone for four consecutive weeks. Bone mineral density, microarchitecture, and calcein-labeled mineral acquisition were quantified by μCT, dual energy X-ray absorptiometry, and histomorphometry. Expression of osteogenic and adipogenic markers and acetylation states of PPARγ were detected by RT-quantitative PCR, immunoprecipitation, and immunoblotting.

RESULTS

High NPY levels were associated with glucocorticoid-induced trabecular bone deterioration and marrow fat accumulation. Mice lacking NPY had high bone mass concomitant with spacious trabecular and cortical bone microstructure. NPY deletion shielded skeletal tissues from the glucocorticoid-induced impediment of bone mass, trabecular morphometric characteristics, mineral accretion activity, and fatty marrow development. Ex vivo, NPY deficiency sustained osteogenic differentiation capacity and curtailed the glucocorticoid-mediated escalation of adipocyte formation reactions of primary bone-marrow mesenchymal cells. NPY deletion appeared to modulate Y1 and Y2 receptors, sirtuin 1, ERK, and p38 signaling pathways, an effect that facilitated hypoacetylation and ubiquitination of adipogenic transcription factor PPARγ in the skeletal tissues exposed to glucocorticoid stress.

CONCLUSIONS

NPY mediates the glucocorticoid-induced disturbance of mineral accretion and marrow adipogenesis through post-translational modification of PPARγ. This study brings a new molecular insight into the disintegration of adipogenic and osteogenic activities within glucocorticoid-mediated osteoporotic skeletons. Control of NPY is an alternative strategy to ameliorate glucocorticoid-induced bone destruction and fatty marrow.

Neuropeptide Y gene-by-psychosocial stress interaction effect is associated with obesity in a Korean population

BACKGROUND

Chronic psychosocial stress is a crucial risk factor in the development of many diseases including obesity. Neuropeptide Y (NPY), distributed throughout the peripheral and central nervous system, is believed to pay a role in the pathophysiologic relationship between stress and obesity. Although several animal studies have investigated the impact on obesity of interactions between NPY single nucleotide polymorphisms (SNPs) and stress, the same remains to be analyzed in humans.

METHODS

To identify NPY gene-by-stress interaction effects on human obesity, we analyzed the interaction between four NPY SNPs and stress with obesity-related traits, including visceral adipose tissue (VAT). A total of 1468 adult subjects were included for this analysis.

RESULTS

In a SNP-only model without interaction with stress, no significant SNPs were found (pSNP>0.05). However, NPY SNPs-by-stress interaction effects were significantly linked to body mass index (BMI), waist circumference, and VAT (pint<0.05), even though a significant interaction effect for rs16135 on BMI was not identified. These significant interaction effects were also detected in interaction results for the binary traits of obesity. Among the obesity traits, mean changes of VAT by increased stress levels in homozygous risk allele carriers were the greatest (range of mean increases for four SNPs (min-max)=12.57cm(2)-29.86cm(2)).

CONCLUSIONS

This study suggests that common polymorphisms for NPY were associated with human obesity by interacting with psychosocial stress, emphasizing the need for stress management in obesity prevention.

Long-Term Over-Expression of Neuropeptide Y in Hypothalamic Paraventricular Nucleus Contributes to Adipose Tissue Insulin Resistance Partly via the Y5 Receptor

Intracerebroventricular injection and overexpression of Neuropeptide Y (NPY) in the paraventricular nucleus (PVN) has been shown to induce obesity and glucose metabolism disorder in rodents; however, the underlying mechanisms are still unclear. The aim of this study was to investigate the mechanism contributing to glucose metabolic disturbance induced by NPY. Recombinant lentiviral NPY vectors were injected into the PVN of rats fed a high fat (HFD) or low-fat diet. 8 weeks later, in vivo intravenous glucose tolerance tests and euglycemic-hyperinsulinemic clamp revealed that insulin resistance of adipose tissue were induced by NPY overexpression with or without HFD. NPY increased food intake, but did not change blood glucose, glycated hemoglobin A1c (HbA1c) or lipid levels. However, NPY decreased the expression of pGSK3β, PI3K p85 and pAKTSer473 in adipose tissue of rats. In vitro, 3T3-L1 adipocytes were treated with NPY, NPY Y1 and Y5 receptor antagonists. Glucose consumption and 2-deoxy-D-[3H] glucose uptake were partly inhibited by NPY, while a decrease in PI3K-AKT pathway signaling and a decreased expression of pGSK3α and pGSK3β were observed. Nevertheless, a Y5 receptor antagonist (L-152,804) reversed the effects of NPY on glucose uptake and consumption. These data suggest that long-term over-expression of NPY in PVN contributes to the establishment of adipose tissue insulin resistance, at least partly via the Y5 Receptor.

Cellular targets for neuropeptide Y-mediated control of adult neurogenesis

Neuropeptides are emerging as key regulators of stem cell niche activities in health and disease, both inside and outside the central nervous system (CNS). Among them, neuropeptide Y (NPY), one of the most abundant neuropeptides both in the nervous system and in non-neural districts, has become the focus of much attention for its involvement in a wide range of physiological and pathological conditions, including the modulation of different stem cell activities. In particular, a pro-neurogenic role of NPY has been evidenced in the neurogenic niche, where a direct effect on neural progenitors has been demonstrated, while different cellular types, including astrocytes, microglia and endothelial cells, also appear to be responsive to the peptide. The marked modulation of the NPY system during several pathological conditions that affect neurogenesis, including stress, seizures and neurodegeneration, further highlights the relevance of this peptide in the regulation of adult neurogenesis. In view of the considerable interest in understanding the mechanisms controlling neural cell fate, this review aims to summarize and discuss current data on NPY signaling in the different cellular components of the neurogenic niche in order to elucidate the complexity of the mechanisms underlying the modulatory properties of this peptide.

Soy isoflavones in nutritionally relevant amounts have varied nutrigenomic effects on adipose tissue

Soy consumption has been suggested to afford protection from cardiovascular disease (CVD). Indeed, accumulated albeit controversial evidence suggests that daily consumption of ≥25 g of soy protein with its associated phytochemicals intact can improve lipid profiles in hypercholesterolemic humans. However, the belief that soy foods and supplements positively impact human health has become increasingly controversial among the general public because of the reported estrogenic activities of soy isoflavones. In this study, we investigated the nutrigenomic actions of soy isoflavones (in nutritionally-relevant amounts) with a specific focus on the adipose tissue, due to its pivotal role in cardiometabolism. Young C57BL/6 mice were maintained for eight weeks under two different diet regimes: (1) purified control diet; or (2) purified control diet supplemented with 0.45 g% soybean dry purified extract (a genistein/daidzein mix). Soy isoflavones increased plasma total cholesterol concentrations and decreased triglyceride ones. Circulating leptin levels was also increased by soy consumption. Differentially expressed genes in adipose tissue were classified according to their role(s) in cellular or metabolic pathways. Our data show that soy isoflavones, administered in nutritionally-relevant amounts, have diverse nutrigenomic effects on adipose tissue. Taking into account the moderate average exposure to such molecules, their impact on cardiovascular health needs to be further investigated to resolve the issue of whether soy consumption does indeed increase or decrease cardiovascular risk.

Dose-dependent effects of neuropeptide Y on the regulation of preadipocyte proliferation and adipocyte lipid synthesis via the PPARγ pathways

The objective of this study was to investigate the impact of neuropeptide Y (NPY) on preadipocyte proliferation and differentiation. Preadipocytes were incubated with a range of concentrations of NPY (10(-15)M - 10(-7)M). After NPY-induced differentiation, the extent of preadipocyte adipogenesis was evaluated. The expressions levels of related adipocyte markers such as PPARγ, C/EBPα and DLK-1 were examined by real-time PCR (RT-PCR) or western blot analysis. Furthermore, the mitogen-activated protein kinase (MAPK) signaling pathway proteins were also analyzed by western blot. Our results showed that low doses of NPY stimulated preadipocyte viability and proliferation, while high NPY doses inhibited cell viability. At high concentrations of NPY significantly promoted lipid accumulation and increased the size of lipid droplets. DLK-1 mRNA expression was inhibited, but the expression levels of PPARγ and C/EBPα were increased during differentiation with the presence of high concentration of NPY. High-dose NPY also suppressed the phosphorylation of the extracellular signal-regulated kinase (ERK) 1/2 protein. We conclude that NPY has a biphasic effect on preadipocyte proliferation. A high dose inhibits the proliferation of 3T3-L1 cell while promotes adipocyte differentiation, increasing lipid accumulation especially enlarged lipid droplets' size. NPY may lead to a better understanding for drug development to prevent hyperplastic obesity and hypertrophic obesity.