Can prokineticin prevent obesity and insulin resistance?

Intracerebroventricular prokineticin 2 infusion may play a role on the hypothalamus-pituitary-thyroid axis and energy metabolism

AIM

The hypothesis of this study is to determine the effects of intracerebroventricular (icv) prokineticin 2 infusion on food consumption and body weight and to elucidate whether it has effects on energy expenditure via the hypothalamus-pituitary-thyroid (HPT) axis in adipose tissue.

MATERIAL AND METHODS

A total of 40 rats were used in the study and 4 groups were established: Control, Sham, Prokineticin 1.5 and Prokineticin 4.5 (n=10). Except for the Control group, rats were treated intracerebroventricularly via osmotic minipumps, the Sham group was infused with aCSF (vehicle), and the Prokineticin 1.5 and Prokineticin 4.5 groups were infused with 1.5 nMol and 4.5 nMol prokineticin 2, respectively. Food and water consumption and body weight were monitored during 7-day infusion in all groups. At the end of the infusion, the rats were decapitated and serum TSH, fT4 and fT3 levels were determined by ELISA. In addition, PGC-1α and UCP1 gene expression levels in white adipose tissue (WAT) and brown adipose tissue (BAT), TRH from rat hypothalamic tissue were determined by real-time PCR.

RESULTS

Icv prokineticin 2 (4.5 nMol) infusion had no effect on water consumption but reduced daily food consumption and body weight (p<0.05). Icv prokineticin 2 (4.5 nMol) infusion significantly increased serum TSH, fT4 and fT3 levels when compared to Control and Sham groups (p<0.05). Also, icv prokineticin 2 (4.5 nMol) infusion increased the expression of TRH in the hypothalamus tissue and expression of PGC-1α UCP1 in the WAT and BAT (p<0.05).

CONCLUSION

Icv prokineticin 2 (4.5 nMol) infusion may suppress food consumption via its receptors in the hypothalamus and reduce body weight by stimulating energy expenditure and thermogenesis in adipose tissue through the HPT axis.

MRAP2a Binds and Modulates Activity and Localisation of Prokineticin Receptor 1 in Zebrafish

The prokineticin system plays a role in hypothalamic neurons in the control of energy homeostasis. Prokineticin receptors (PKR1 and PKR2), like other G-protein-coupled receptors (GPCRs) are involved in the regulation of energy intake and expenditure and are modulated by the accessory membrane protein 2 of the melanocortin receptor (MRAP2). The aim of this work is to characterise the interaction and regulation of the non-melanocortin receptor PKR1 by MRAP2a in zebrafish (zMRAP2a) in order to use zebrafish as a model for the development of drugs targeting accessory proteins that can alter the localisation and activity of GPCRs. To this end, we first showed that zebrafish PKR1 (zPKR1) is able to interact with both zMRAP2a and human MRAP2 (hMRAP2). This interaction occurs between the N-terminal region of zPKR1 and the C-terminal domain of zMRAP2a, which shows high sequence identity with hMRAP2 and a similar propensity for dimer formation. Moreover, we demonstrated that in Chinese hamster ovary (CHO) cells, zMRAP2a or hMRAP2 are able to modulate zPKR1 activation induced by zebrafish PK2 (zPK2) resulting in an impaired ERK and STAT3 activation.

Therapeutic Potential of Targeting Prokineticin Receptors in Diseases

The prokineticins (PKs) were discovered approximately 20 years ago as small peptides inducing gut contractility. Today, they are established as angiogenic, anorectic, and proinflammatory cytokines, chemokines, hormones, and neuropeptides involved in variety of physiologic and pathophysiological pathways. Their altered expression or mutations implicated in several diseases make them a potential biomarker. Their G-protein coupled receptors, PKR1 and PKR2, have divergent roles that can be therapeutic target for treatment of cardiovascular, metabolic, and neural diseases as well as pain and cancer. This article reviews and summarizes our current knowledge of PK family functions from development of heart and brain to regulation of homeostasis in health and diseases. Finally, the review summarizes the established roles of the endogenous peptides, synthetic peptides and the selective ligands of PKR1 and PKR2, and nonpeptide orthostatic and allosteric modulator of the receptors in preclinical disease models. The present review emphasizes the ambiguous aspects and gaps in our knowledge of functions of PKR ligands and elucidates future perspectives for PK research. SIGNIFICANCE STATEMENT: This review provides an in-depth view of the prokineticin family and PK receptors that can be active without their endogenous ligand and exhibits "constitutive" activity in diseases. Their non- peptide ligands display promising effects in several preclinical disease models. PKs can be the diagnostic biomarker of several diseases. A thorough understanding of the role of prokineticin family and their receptor types in health and diseases is critical to develop novel therapeutic strategies with safety concerns.

The balance of concentration between Prokineticin 2β and Prokineticin 2 modulates the food intake by STAT3 signaling

The secreted bioactive peptide prokineticin 2 (PK2) is a potent adipokine and its central and peripheral administration reduces food intake in rodents. The pk2 gene has two splice variants, PK2 and PK2L (PK2 long form), which is cleaved into an active peptide, PK2β, that preferentially binds prokineticin receptor 1 (PKR1). We investigated the role of PK2β in the regulation of food intake. We demonstrated that intraperitoneal injection of PK2β, in contrast to PK2, did not reduce food intake in mice. Exposure of hypotalamic explants to PK2, but not PK2β, induced phosphorylation of STAT3 and ERK. We also evidenced that in adipocytes from PKR1 knock-out mice, a model of obesity, there were higher PK2β levels than PK2 inducing a decreased activation of STAT3 and ERK. Our results suggest that variations in PK2 and PK2β levels, due to modulation of pk2 gene splicing processes, affect food intake in mice.

Prokineticin signaling in heart-brain developmental axis: Therapeutic options for heart and brain injuries

Heart and brain development occur simultaneously during the embryogenesis, and both organ development and injuries are interconnected. Early neuronal and cardiac injuries share mutual cellular events, such as angiogenesis and plasticity that could either delay disease progression or, in the long run, result in detrimental health effects. For this reason, the common mechanisms provide a new and previously undervalued window of opportunity for intervention. Because angiogenesis, cardiogenesis and neurogenesis are essential for the development and regeneration of the heart and brain, we discuss therein the role of prokineticin as an angiogenic neuropeptide in heart-brain development and injuries. We focus on the role of prokineticin signaling and the effect of drugs targeting prokineticin receptors in neuroprotection and cardioprotection, with a special emphasis on heart failure, neurodegenerativParkinson's disease and ischemic heart and brain injuries. Indeed, prokineticin triggers common pro-survival signaling pathway in heart and brain. Our review aims at stimulating researchers and clinicians in neurocardiology to focus on the role of prokineticin signaling in the reciprocal interaction between heart and brain. We hope to facilitate the discovery of new treatment strategies, acting in both heart and brain degenerative diseases.

Targeting GPCRs Against Cardiotoxicity Induced by Anticancer Treatments

Novel anticancer medicines, including targeted therapies and immune checkpoint inhibitors, have greatly improved the management of cancers. However, both conventional and new anticancer treatments induce cardiac adverse effects, which remain a critical issue in clinic. Cardiotoxicity induced by anti-cancer treatments compromise vasospastic and thromboembolic ischemia, dysrhythmia, hypertension, myocarditis, and cardiac dysfunction that can result in heart failure. Importantly, none of the strategies to prevent cardiotoxicity from anticancer therapies is completely safe and satisfactory. Certain clinically used cardioprotective drugs can even contribute to cancer induction. Since G protein coupled receptors (GPCRs) are target of forty percent of clinically used drugs, here we discuss the newly identified cardioprotective agents that bind GPCRs of adrenalin, adenosine, melatonin, ghrelin, galanin, apelin, prokineticin and cannabidiol. We hope to provoke further drug development studies considering these GPCRs as potential targets to be translated to treatment of human heart failure induced by anticancer drugs.

New roles for prokineticin 2 in feeding behavior, insulin resistance and type 2 diabetes: Studies in mice and humans

Objective

Prokineticin 2 (PROK2) is a hypothalamic neuropeptide that plays a critical role in the rhythmicity of physiological functions and inhibits food intake. PROK2 is also expressed in the main olfactory bulb (MOB) as an essential factor for neuro-and morphogenesis. Since the MOB was shown to be strongly involved in eating behavior, we hypothesized that PROK2 could be a new target in the regulation of food intake and energy homeostasis, through its effects in the MOB. We also asked whether PROK2 could be associated with the pathophysiology of obesity, the metabolic syndrome (MetS), and type 2 diabetes (T2D) in humans.

Methods

We assessed in wild type mice whether the expression of Prok2 in the MOB is dependent on the nutritional status. We measured the effect of human recombinant PROK2 (rPROK2) acute injection in the MOB on food intake and olfactory behavior. Then, using a lentivirus expressing Prok2-shRNA, we studied the effects of Prok2 underexpression in the MOB on feeding behavior and glucose metabolism. Metabolic parameters and meal pattern were determined using calorimetric cages. In vivo 2-deoxyglucose uptake measurements were performed in mice after intraperitoneally insulin injection. Plasmatic PROK2 dosages and genetic associations studies were carried out respectively on 148 and more than 4000 participants from the D.E.S.I.R. (Data from an Epidemiologic Study on the Insulin Resistance Syndrome) cohort.

Results

Our findings showed that fasting in mice reduced Prok2 expression in the MOB. Acute injection of rPROK2 in the MOB significantly decreased food intake whereas Prok2-shRNA injection resulted in a higher dietary consumption characterized by increased feeding frequency and decreased meal size. Additionally, Prok2 underexpression in the MOB induced insulin resistance compared to scrambled shRNA-injected mice. In the human D.E.S.I.R. cohort, we found a significantly lower mean concentration of plasma PROK2 in people with T2D than in those with normoglycemia. Interestingly, this decrease was no longer significant when adjusted for Body Mass Index (BMI) or calorie intake, suggesting that the association between plasma PROK2 and diabetes is mediated, at least partly, by BMI and feeding behavior in humans. Moreover, common Single Nucleotide Polymorphisms (SNPs) in PROK2 gene were genotyped and associated with incident T2D or impaired fasting glycemia (IFG), MetS, and obesity.

Conclusions

Our data highlight PROK2 as a new target in the MOB that links olfaction with eating behavior and energy homeostasis. In humans, plasma PROK2 is negatively correlated with T2D, BMI, and energy intake, and PROK2 genetic variants are associated with incident hyperglycemia (T2D/IFG), the MetS and obesity.

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Fasting alters prokineticin 2 (Prok2) expression in the main olfactory bulb (MOB).

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Acute injection of PROK2 into the MOB diminishes food intake.

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Partial deletion of MOB-Prok2 affects meal pattern and induces insulin resistance.

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Type 2 diabetes (T2D) in humans is correlated with lower plasma PROK2 level.

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Polymorphisms of PROK2 gene associate with incident T2D and the metabolic syndrome.

Visceral white adipose tissue and serum proteomic alternations in metabolically healthy obese patients undergoing bariatric surgery

Metabolically healthy obesity is characterized as a comorbidity-free obesity status, however the exact pathogenetic mechanisms implicated in its transition to unhealthy obesity have not yet been unveiled. Our aim was to investigate the effect of metabolic health on the proteomic profile both in serum and visceral fat of morbidly obese subjects. 28 patients undergoing bariatric surgery were prospectively enrolled. They were divided into two groups: metabolically healthy (MHO, n = 18) and unhealthy (MUO, n = 10) obese patients. 30 biomarkers were measured in serum and visceral adipose tissue with the use of targeted proteomic analysis (Luminex assays). TNF weak inducer of apoptosis (TWEAK) (p = 0.043), TNF related apoptosis inducing ligand (TRAIL) (p = 0.037), Growth differentiation factor-15 (GDF-15) (p = 0.04), Resistin (RETN) (p = 0.047), Matrix metalloproteinase-9 (MMP-9) (p = 0.011) and C-terminal telopeptide (ICTP) (p = 0.022) were up-regulated in the MUO group in the visceral white adipose tissue. Moreover, C-C motif ligand-3 (CCL-3) (p = 0.056), Interleukin-20 (IL-20) (p = 0.04), Prokineticin-1 (PROK-1) (p = 0.028) and TWEAK (p = 0.016) were found to be suppressed in the serum of MHO group. Significant correlations between serum and adipose tissue levels of certain cytokines were also observed, while 16 biomarkers were associated with BMI. Our results indicate metabolic health substantially attenuates the expression of TWEAK, TRAIL, GDF-15, RETN, MMP-9 and ICTP expression locally, in the visceral white adipose tissue, and the expression of CCL-3, IL-20, PROK-1 and TWEAK in the peripheral blood. Intriguingly, different cytokines -except for TWEAK- are up-regulated in each site, suggesting that obesity is not a homogenous but a multi-dimensional disease.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

Prokineticin receptor-1-dependent paracrine and autocrine pathways control cardiac tcf21+ fibroblast progenitor cell transformation into adipocytes and vascular cells

Cardiac fat tissue volume and vascular dysfunction are strongly associated, accounting for overall body mass. Despite its pathophysiological significance, the origin and autocrine/paracrine pathways that regulate cardiac fat tissue and vascular network formation are unclear. We hypothesize that adipocytes and vasculogenic cells in adult mice hearts may share a common cardiac cells that could transform into adipocytes or vascular lineages, depending on the paracrine and autocrine stimuli. In this study utilizing transgenic mice overexpressing prokineticin receptor (PKR1) in cardiomyocytes, and tcf21ERT-cre^TM-derived cardiac fibroblast progenitor (CFP)-specific PKR1 knockout mice (PKR1^tcf−/−), as well as FACS-isolated CFPs, we showed that adipogenesis and vasculogenesis share a common CFPs originating from the tcf21⁺ epithelial lineage. We found that prokineticin-2 is a cardiomyocyte secretome that controls CFP transformation into adipocytes and vasculogenic cells in vivo and in vitro. Upon HFD exposure, PKR1^tcf−/− mice displayed excessive fat deposition in the atrioventricular groove, perivascular area, and pericardium, which was accompanied by an impaired vascular network and cardiac dysfunction. This study contributes to the cardio-obesity field by demonstrating that PKR1 via autocrine/paracrine pathways controls CFP–vasculogenic- and CFP-adipocyte-transformation in adult heart. Our study may open up new possibilities for the treatment of metabolic cardiac diseases and atherosclerosis.

Prokineticin Is a New Linker between Obesity and Cardiovascular Diseases

Obesity is a fast growing epidemic event worldwide. Fatness is associated with a number of comorbidities, including cardiovascular diseases (CVDs). Although obesity can be heredity in 30–70% cases, the environmental contributions also play an important role in the increasing prevalence of obesity. The relationship between development of obesity and CVD is poorly characterized. Obesity and CVD can also be resulted from a common mechanism such as metabolic, inflammatory, and neurohormonal changes. Prokineticins are defined as cytokines (immunoregulatory proteins), adipokines (adipocyte-secreted hormone), angiogenic (increasing vessel formation), or aneroxic (lowering food intake) hormones. Prokineticin-mediated signaling plays a key role in the development of obesity and CVD. Two forms of prokineticins exist in circulation and in various tissues including the brain, heart, kidney, and adipose. Prokineticins act on the two G protein-coupled receptors, namely, PKR1 and PKR2. Prokineticin-2 (PK2) via PKR1 receptor controls food intake and prevents adipose tissue expansion. The anti-adipocyte effect of PKR1 signaling is due to suppression of preadipocyte proliferation and differentiation capacity into adipocytes. PK2/PKR1 signaling promotes transcapillary passages of insulin and increases insulin sensitivity. It also plays an important role in the heart and kidney development and functions. Here, we discuss PK2 as a new adipocytokine in the association between obesity and CVD. We also highlight targeting PKR1 can be a new approach to treat obesity and CVD.

Effect of ezetimibe on plasma adipokines: a systematic review and meta-analysis

AIMS

Statins are known to influence the status of adipokines, which play a key role in the pathophysiology of cardiometabolic diseases. As the effect of ezetimibe as an add-on to statin therapy on the impact of statins on plasma adipokines levels is currently unclear, the aim of the present study was to investigate this through a meta-analysis of controlled trials.

METHODS

A systematic review was performed, followed by a bibliographic search in PubMed, Medline, SCOPUS, Web of Science and Google Scholar databases. Quantitative data synthesis was performed using a fixed- or random-effects model (based on the level of interstudy heterogeneity) and the generic inverse variance weighting method. Effect sizes were expressed as standardized mean difference (SMD) and 95% confidence interval (CI).

RESULTS

Meta-analysis of 23 controlled trials did not suggest any significant effect of adding ezetimibe on top of statin therapy on plasma concentrations of adiponectin (SMD 0.34, 95% CI -0.28, 0.96; P = 0.288), leptin (SMD -0.75, 95% CI: -2.35, 0.85; P = 0.360), plasminogen activator inhibitor 1 (SMD -1.06, 95% CI: -2.81, 0.69; P = 0.236) and interleukin 6 (SMD 0.30, 95% CI: -0.08, 0.67; P = 0.124). However, significantly greater reductions in plasma concentrations of tumour necrosis factor α (TNF-α) (SMD -0.48, 95% CI -0.87, -0.08; P = 0.018) were achieved with ezetimibe/statin combination therapy.

CONCLUSIONS

The results suggested that ezetimibe add-on to statin therapy is associated with an enhanced TNF-α-lowering effect compared with statin monotherapy. Owing to the emerging role of TNF-α in the pathogenesis of metabolic disorders, further investigations are required to unveil the translational relevance of this TNF-α-lowering effect.

Ranking factors involved in diabetes remission after bariatric surgery using machine-learning integrating clinical and genomic biomarkers

As weight-loss surgery is an effective treatment for the glycaemic control of type 2 diabetes in obese patients, yet not all patients benefit, it is valuable to find predictive factors for this diabetic remission. This will help elucidating possible mechanistic insights and form the basis for prioritising obese patients with dysregulated diabetes for surgery where diabetes remission is of interest. In this study, we combine both clinical and genomic factors using heuristic methods, informed by prior biological knowledge in order to rank factors that would have a role in predicting diabetes remission, and indeed in identifying patients who may have low likelihood in responding to bariatric surgery for improved glycaemic control. Genetic variants from the Illumina CardioMetaboChip were prioritised through single-association tests and then seeded a larger selection from protein-protein interaction networks. Artificial neural networks allowing nonlinear correlations were trained to discriminate patients with and without surgery-induced diabetes remission, and the importance of each clinical and genetic parameter was evaluated. The approach highlighted insulin treatment, baseline HbA1c levels, use of insulin-sensitising agents and baseline serum insulin levels, as the most informative variables with a decent internal validation performance (74% accuracy, area under the curve (AUC) 0.81). Adding information for the eight top-ranked single nucleotide polymorphisms (SNPs) significantly boosted classification performance to 84% accuracy (AUC 0.92). The eight SNPs mapped to eight genes - ABCA1, ARHGEF12, CTNNBL1, GLI3, PROK2, RYBP, SMUG1 and STXBP5 - three of which are known to have a role in insulin secretion, insulin sensitivity or obesity, but have not been indicated for diabetes remission after bariatric surgery before.