Leptin increases lipoprotein lipase secretion by macrophages: involvement of oxidative stress and protein kinase C

Integrated approach to reducing polypharmacy in older people: exploring the role of oxidative stress and antioxidant potential therapy

Increased life expectancy, attributed to improved access to healthcare and drug development, has led to an increase in multimorbidity, a key contributor to polypharmacy. Polypharmacy is characterised by its association with a variety of adverse events in the older persons. The mechanisms involved in the development of age-related chronic diseases are largely unknown; however, altered redox homeostasis due to ageing is one of the main theories. In this context, the present review explores the development and interaction between different age-related diseases, mainly linked by oxidative stress. In addition, drug interactions in the treatment of various diseases are described, emphasising that the holistic management of older people and their pathologies should prevail over the individual treatment of each condition.

Leptin-mediated suppression of lipoprotein lipase cleavage enhances lipid uptake and facilitates lymph node metastasis in gastric cancer

BACKGROUND

Lymph node metastasis (LNM) is the primary mode of metastasis in gastric cancer (GC). However, the precise mechanisms underlying this process remain elusive. Tumor cells necessitate lipid metabolic reprogramming to facilitate metastasis, yet the role of lipoprotein lipase (LPL), a pivotal enzyme involved in exogenous lipid uptake, remains uncertain in tumor metastasis. Therefore, the aim of this study was to investigate the presence of lipid metabolic reprogramming during LNM of GC as well as the role of LPL in this process.

METHODS

Intracellular lipid levels were quantified using oil red O staining, BODIPY 493/503 staining, and flow cytometry. Lipidomics analysis was employed to identify alterations in intracellular lipid composition following LPL knockdown. Protein expression levels were assessed through immunohistochemistry, Western blotting, and enzyme-linked immunosorbent assays. The mouse popliteal LNM model was utilized to investigate differences in LNM. Immunoprecipitation and mass spectrometry were employed to examine protein associations. In vitro phosphorylation assays and Phos-tag sodium dodecyl-sulfate polyacrylamide gel electrophoresis assays were conducted to detect angiopoietin-like protein 4 (ANGPTL4) phosphorylation.

RESULTS

We identified that an elevated intracellular lipid level represents a crucial characteristic of node-positive (N+) GC and further demonstrated that a high-fat diet can expedite LNM. LPL was found to be significantly overexpressed in N+ GC tissues and shown to facilitate LNM by mediating dietary lipid uptake within GC cells. Leptin, an obesity-related hormone, intercepted the effect exerted by ANGPTL4/Furin on LPL cleavage. Circulating leptin binding to the leptin receptor could induce the activation of inositol-requiring enzyme-1 (IRE1) kinase, leading to the phosphorylation of ANGPTL4 at the serine 30 residue and subsequently reducing its binding affinity with LPL. Moreover, our research revealed that LPL disrupted lipid homeostasis by elevating intracellular levels of arachidonic acid, which then triggered the cyclooxygenase-2/prostaglandin E2 (PGE2) pathway, thereby promoting tumor lymphangiogenesis.

CONCLUSIONS

Leptin-induced phosphorylation of ANGPTL4 facilitates LPL-mediated lipid uptake and consequently stimulates the production of PGE2, ultimately facilitating LNM in GC.

Obesity, dyslipidemia, and cardiovascular disease: A joint expert review from the Obesity Medicine Association and the National Lipid Association 2024

Background

This joint expert review by the Obesity Medicine Association (OMA) and National Lipid Association (NLA) provides clinicians an overview of the pathophysiologic and clinical considerations regarding obesity, dyslipidemia, and cardiovascular disease (CVD) risk.

Methods

This joint expert review is based upon scientific evidence, clinical perspectives of the authors, and peer review by the OMA and NLA leadership.

Results

Among individuals with obesity, adipose tissue may store over 50% of the total body free cholesterol. Triglycerides may represent up to 99% of lipid species in adipose tissue. The potential for adipose tissue expansion accounts for the greatest weight variance among most individuals, with percent body fat ranging from less than 5% to over 60%. While population studies suggest a modest increase in blood low-density lipoprotein cholesterol (LDL-C) levels with excess adiposity, the adiposopathic dyslipidemia pattern most often described with an increase in adiposity includes elevated triglycerides, reduced high density lipoprotein cholesterol (HDL-C), increased non-HDL-C, elevated apolipoprotein B, increased LDL particle concentration, and increased small, dense LDL particles.

Conclusions

Obesity increases CVD risk, at least partially due to promotion of an adiposopathic, atherogenic lipid profile. Obesity also worsens other cardiometabolic risk factors. Among patients with obesity, interventions that reduce body weight and improve CVD outcomes are generally associated with improved lipid levels. Given the modest improvement in blood LDL-C with weight reduction in patients with overweight or obesity, early interventions to treat both excess adiposity and elevated atherogenic cholesterol (LDL-C and/or non-HDL-C) levels represent priorities in reducing the risk of CVD.

Obesity, dyslipidemia, and cardiovascular disease: A joint expert review from the Obesity Medicine Association and the National Lipid Association 2024

BACKGROUND

This joint expert review by the Obesity Medicine Association (OMA) and National Lipid Association (NLA) provides clinicians an overview of the pathophysiologic and clinical considerations regarding obesity, dyslipidemia, and cardiovascular disease (CVD) risk.

METHODS

This joint expert review is based upon scientific evidence, clinical perspectives of the authors, and peer review by the OMA and NLA leadership.

RESULTS

Among individuals with obesity, adipose tissue may store over 50% of the total body free cholesterol. Triglycerides may represent up to 99% of lipid species in adipose tissue. The potential for adipose tissue expansion accounts for the greatest weight variance among most individuals, with percent body fat ranging from less than 5% to over 60%. While population studies suggest a modest increase in blood low-density lipoprotein cholesterol (LDL-C) levels with excess adiposity, the adiposopathic dyslipidemia pattern most often described with an increase in adiposity includes elevated triglycerides, reduced high-density lipoprotein cholesterol (HDL-C), increased non-HDL-C, elevated apolipoprotein B, increased LDL particle concentration, and increased small, dense LDL particles.

CONCLUSIONS

Obesity increases CVD risk, at least partially due to promotion of an adiposopathic, atherogenic lipid profile. Obesity also worsens other cardiometabolic risk factors. Among patients with obesity, interventions that reduce body weight and improve CVD outcomes are generally associated with improved lipid levels. Given the modest improvement in blood LDL-C with weight reduction in patients with overweight or obesity, early interventions to treat both excess adiposity and elevated atherogenic cholesterol (LDL-C and/or non-HDL-C) levels represent priorities in reducing the risk of CVD.

Association of the oxidative balance score with obesity and body composition among young and middle-aged adults

Objective

The oxidative balance score (OBS) is important for determining the cause of obesity and its complications. We aimed to evaluate the association between OBS and obesity and other segmental body composition parameters among young and middle-aged U.S. adults.

Methods

9,998 participants from the National Health and Nutrition Examination Survey 2011-2018 were included. Lean mass percentage (LM%) and FM% were evaluated by dual-energy x-ray absorptiometry. Obesity was defined as body FM% ≥25% in men and ≥ 35% in women. The OBS was scored by 5 pro-oxidant and 21 antioxidant factors. Associations of quartiles of OBS with obesity risk were estimated using multivariable logistic regression models. Multivariable linear regression was conducted to estimate the association between OBS and segmental body composition measures including the arm LM%, leg LM%, torso LM%, whole LM%, arm FM%, leg FM%, torso FM% and total FM%.

Results

Compared to participants in the lowest quartile of OBS, those in the highest quartile of OBS were associated with a lower risk of BMI-defined obesity BMI-defined obesity [0.43 (0.36, 0.50)] and FM%-related obesity [0.43 (0.35, 0.52)]. Additionally, OBS was negatively associated with FM% of the limb and torso but positively associated with the percentage of lean mass (LM%) of the limb and trunk.

Conclusion

OBS was negatively associated with the risk of obesity and segmental FM%, but was positively associated with segmental LM% among US adults, indicating that adhering to an anti-oxidative diet and lifestyle management may be beneficial for preventing segmental obesity.

In vitro Adipocyte Differentiation Inhibition and in vivo Effects on Lipid Metabolism in High-Fat Diet-Induced Obesity of Euphorbia humifusa

Euphorbia humifusa Willd (Euphorbiaceae) is a functional raw material with various pharmacological activities. This study aimed to validate the inhibitory effect of Euphorbia humifusa extract (EHE) on adipocyte differentiation in vitro and in a high-fat-diet (HFD)-induced mouse model to evaluate the E.a humifusa as a novel anti-obesity and lipid metabolism enhancer agent. EHE effects on obesity and lipid metabolism were assessed in HFD-induced obese mice after 4-week treatments. Results were compared among four treatment groups (n = 7/group): low fat diet (LFD), high fat diet (HFD), and HFD-induced obese mice treated with either 100 or 200 mg/kg/day EHE (EHE100 and EHE200, respectively). EHE (50 to 200 μg/ml) and quercetin (50 μg/ml) significantly reduced 3T3-L1 preadipocyte differentiation (p < 0.001), in a concentration-dependent manner. EHE affected lipid metabolism, as evidenced by changes in serum lipid components. The HFD-EHE100 and HFD-EHE200 groups exhibited significantly (p < 0.05) reduced triglycerides (TG, 97.50 ± 6.56 and 82.50 ± 13.20 mg/dL, respectively) and low-density lipoprotein-cholesterol (LDL-c: 40.25 ± 4.99 and 41.25 ± 6.36 mg/dL, respectively) compared to the HFD group (TG: 129.25 ± 19.81 mg/dL; LDL-c: 51.75 ± 11.59 mg/dL). Haematoxylin and Eosin (H&E) and Oil red O staining showed that EHE markedly reduced lipid accumulation and inhibited lipogenesis in the liver. Interestingly, EHE significantly (p < 0.01) reduced the expression of adipogenic transcription factors in liver tissue. Our results indicated that EHE has the potential to be a therapeutic agent for addressing obesity and lipid metabolism.

Potential Role of Oxidative Stress in the Production of Volatile Organic Compounds in Obesity

Obesity is associated with numerous health issues such as sleep disorders, asthma, hepatic dysfunction, cancer, renal dysfunction, diabetes, cardiovascular complications, and infertility. Previous research has shown that the distribution of excess body fat, rather than excess body weight, determines obesity-related risk factors. It is widely accepted that abdominal fat is a serious risk factor for illnesses associated with obesity and the accumulation of visceral fat promotes the release of pro-oxidants, pro-inflammatory, and reactive oxygen species (ROS). The metabolic process in the human body produces several volatile organic compounds (VOCs) via urine, saliva, breath, blood, skin secretions, milk, and feces. Several studies have shown that VOCs are released by the interaction of ROS with underlying cellular components leading to increased protein oxidation, lipid peroxidation, or DNA damage. These VOCs released via oxidative stress in obese individuals may serves as a biomarker for obesity-related metabolic alterations and disease. In this review, we focus on the relationship between oxidative stress and VOCs in obesity.

Adipokines in dental pulp: physiological, pathological, and potential therapeutic roles

BACKGROUND

Hundreds of adipokines have been identified, and their extensive range of endocrine functions-regulating distant organs such as oral tissues-and local autocrine/paracrine roles have been studied. In dentistry, however, adipokines are poorly known proteins in the dental pulp; few of them have been studied despite their large number. This study reviews recent advances in the investigation of dental-pulp adipokines, with an emphasis on their roles in inflammatory processes and their potential therapeutic applications.

HIGHLIGHTS

The most recently identified adipokines in dental pulp include leptin, adiponectin, resistin, ghrelin, oncostatin, chemerin, and visfatin. They have numerous physiological and pathological functions in the pulp tissue: they are closely related to pulp inflammatory mechanisms and actively participate in cell differentiation, mineralization, angiogenesis, and immune-system modulation.

CONCLUSION

Adipokines have potential clinical applications in regenerative endodontics and as biomarkers or targets for the pharmacological management of inflammatory and degenerative processes in dental pulp. A promising direction for the development of new therapies may be the use of agonists/antagonists to modulate the expression of the most studied adipokines.

Fat regulatory mechanisms of pine nut oil based on protein interaction network analysis

BACKGROUND

Pine nut oil (PNO), a standardized and well-defined extract of Pinus koraiensis (Korean pine), has beneficial effects on wound healing, inflammatory diseases, and cancer. However, the explanation for the mechanism by which PNO reduces body fat remains uncertain. We performed a protein-protein interaction network (PPIN) analysis to explore the genes associated with pinolenic acid using the MEDILINE database from PubChem and PubMed. It was concluded through the PPIN analysis that PNO was involved in a neutral lipid biosynthetic process.

PURPOSE

This study evaluated the effects of PNO predicted by the network analysis of fat accumulation in chronic obesity mouse models established by feeding a high fat diet (HFD) to C57BL/6J mice and explored potential mechanisms.

METHODS

HFD mice were fed only HFD or HFD with PNO at 822 and 1644 mg/kg. After an oral administration of 7 weeks, several body weight and body fat-related parameters were examined, including the following: adipose weight, adipocyte size, serum lipid profiles, adipocyte expression of PPAR-γ, sterol regulatory element binding protein (SREBP)-1c, lipoprotein lipase (LPL) and leptin.

RESULTS

We showed that oral administration of PNO to HFD mice reduces body fat weight, fat in tissue, white adipose tissue weight, and adipocyte size. The serum cholesterol was improved in the HFD mice treated with PNO. Additionally, PNO has significantly attenuated the HFD-induced changes in the adipose tissue expression of PPAR-γ, SREBP-1c, LPL, and leptin.

CONCLUSIONS

The findings from this study based on the PPIN analysis suggest that PNO has potential as drug to reduce body fat through fat regulatory mechanisms by PPAR-γ and SREBP-1c.

Associations Between Antioxidant Vitamin Status, Dietary Intake, and Retinol-binding Protein 4 Levels in Prepubertal Obese Children After 3-month Weight Loss Therapy

OBJECTIVE

Adiposity is associated with increased oxidative stress, leading to changed fat-soluble vitamin concentrations. The aim of this study was to determine whether weight loss alters fat-soluble vitamin status and whether these alterations are associated with dietary intake, anthropometric parameters and adipokines in obese children.

METHODS

Vitamin A and E concentrations were measured using high-pressure liquid chromatography in 60 obese children before and after weight loss therapy. Retinol-binding protein 4 (RBP4), leptin, soluble leptin receptor (sOB-R), and high molecular weight adiponectin concentrations were determined by immunoenzymatic assays.

RESULTS

The intake of vitamin E was lower in obese children with weight loss after therapy (p=0.038). In this group, an increase was found in the vitamin A/lipids (p=0.022) and the vitamin E/lipids (p=0.008) ratios but due to the reduction in triglyceride levels. In the obese group, changes in vitamin E level were positively correlated with changes in dietary vitamin E (p=0.017) and the leptin/sOB-R ratio (p=0.046). Changes in vitamin A level were positively correlated with changes in dietary vitamin A (p=0.001) and RBP4 concentration (p=0.023). Associations between changes in RBP4 level with the changes in body mass index (BMI) (p=0.011) and total cholesterol concentration (p=0.023) but not with changes in vitamin A concentration were found in the obese after therapy.

CONCLUSION

An increased risk of vitamin E deficiency may occur in children losing weight during lifestyle intervention. Changes in BMI value may influence changes in RBP4 concentrations and consequently the vitamin A status in obese children after therapy.

Oxidative Stress, Plant Natural Antioxidants, and Obesity

Oxidative stress is important in the pathophysiology of obesity, altering regulatory factors of mitochondrial activity, modifying the concentration of inflammation mediators associated with a large number and size of adipocytes, promoting lipogenesis, stimulating differentiation of preadipocytes to mature adipocytes, and regulating the energy balance in hypothalamic neurons that control appetite. This review discusses the participation of oxidative stress in obesity and the important groups of compounds found in plants with antioxidant properties, which include (a) polyphenols such as phenolic acids, stilbenes, flavonoids (flavonols, flavanols, anthocyanins, flavanones, flavones, flavanonols, and isoflavones), and curcuminoids (b) carotenoids, (c) capsaicinoids and casinoids, (d) isothiocyanates, (e) catechins, and (f) vitamins. Examples are analyzed, such as resveratrol, quercetin, curcumin, ferulic acid, phloretin, green tea, Hibiscus Sabdariffa, and garlic. The antioxidant activities of these compounds depend on their activities as reactive oxygen species (ROS) scavengers and on their capacity to prevent the activation of NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells), and reduce the expression of target genes, including those participating in inflammation. We conclude that natural compounds have therapeutic potential for diseases mediated by oxidative stress, particularly obesity. Controlled and well-designed clinical trials are still necessary to better know the effects of these compounds.

Effect of Quercetin on Lipids Metabolism Through Modulating the Gut Microbial and AMPK/PPAR Signaling Pathway in Broilers

The present study was conducted to investigate effects and mechanism of quercetin on lipids metabolism in broilers. 480 AA broilers were randomly allotted to four treatments (0, 0.2, 0.4, and 0.6 g/kg quercetin) for 42 days. Compared with the control, 0.6 g/kg quercetin significantly decreased percentage of abdominal fat (P < 0.05); 0.2, 0.4, and 0.6 g/kg quercetin significantly decreased relative abundance of Lachnospiraceae and Desulfovibrionaceae (P < 0.05, P < 0.05, P < 0.01; P < 0.01, P < 0.01, P < 0.01); 0.2 g/kg quercetin significantly increased mRNA expression of PI3K, AMPKα1, AMPKα2, AMPKβ2, LKB1 (P < 0.01, P < 0.01, P < 0.05, P < 0.01, P < 0.05), and significantly reduced mRNA expression of SREBP1 and PPARγ (P < 0.01, P < 0.05); 0.4 g/kg quercetin significantly increased mRNA expression of LKB1 and PKB (P < 0.05, P < 0.01) and significantly reduced mRNA expression of ACC, HMGR, PPARγ, and SREBP1 (P < 0.05, P < 0.01, P < 0.01, P < 0.01); 0.6 g/kg quercetin significantly increased mRNA expression of AMPKγ, LKB1, CPT1, PPARα, PKB (P < 0.01, P < 0.01, P < 0.01, P < 0.05, P < 0.05), and significantly reduced the mRNA expression of PI3K, ACC, HMGR, PPARγ, SREBP1 (P < 0.05, P < 0.05, P < 0.01, P < 0.01, P < 0.01); 0.2 g/kg quercetin significantly increased protein expression of AMPK (P < 0.01); 0.6 g/kg quercetin significantly increased protein expression of LKB1 (P < 0.01), 0.2 and 0.6 g/kg quercetin significantly increased protein expression of PI3K, PKB, CPT1 (P < 0.05, P < 0.01, P < 0.05, P < 0.01, P < 0.01, P < 0.01), and significantly reduced protein expression of ACC and SREBP1 (P < 0.01, P < 0.01, P < 0.01, P < 0.01). In conclusion, quercetin improved lipid metabolism by modulating gut microbial and AMPK/PPAR signaling pathway in broilers.

Leptin and fractalkine: novel subcutaneous cytokines in burn injury

Burn injury is a pathology underpinned by progressive and aberrant inflammation. It is a major clinical challenge to survival and quality of life. Although the complex local and disseminating pathological processes of a burn injury ultimately stem from local tissue damage, to date relatively few studies have attempted to characterise the local inflammatory mediator profile. Here, cytokine content and associated transcriptional changes were measured in rat skin for three hours immediately following induction of a scald-type (60°C, 2 min) burn injury model. Leptin (P=0.0002) and fractalkine (P=0.0478) concentrations were significantly elevated post-burn above pre-burn and control site values, coinciding with the development of burn site oedema and differential expression of leptin mRNA (P=0.0004). Further, gene sequencing enrichment analysis indicated cytokine-cytokine receptor interaction (P=1.45×10-6). Subsequent behavioural studies demonstrated that, following subcutaneous injection into the dorsum of the paw, both leptin and fractalkine induced mechanical allodynia, heat hyperalgesia and the recruitment of macrophages. This is the first report of leptin elevation specifically at the burn site, and the first report of fractalkine elevation in any tissue post-burn which, together with the functional findings, calls for exploration of the influence of these cytokines on pain, inflammation and burn wound progression. In addition, targeting these signalling molecules represents a therapeutic potential as early formative mediators of these pathological processes.

Is melatonin, leptin or their combination more effective on oxidative stress and folliculogenesis in the obese rats?

In this study, we evaluated the effects of melatonin (Mel), leptin (Lep) or melatonin and leptin treatment on ovaries in control and obese rats. The animals were divided into control (NC), melatonin (NM), leptin (NL), melatonin-leptin (NML), obese (OC), obese-melatonin (OM), obese-leptin (OL), obese-melatonin-leptin (OML) groups. Body weights, peri-ovarian fat pads, volumetric parameters and numerical values of follicles were estimated. Also, the LH receptor (LHr) immune-positivity, catalase (CAT) and the myeloperoxidase (MPO) levels were determined. The body weight and peri-ovarian fat pads were significantly decreased following Mel (p < .05) treatment and, especially, Lep (p < .01) treatment. But, the ovarian weights were significantly increased following Lep (p < .05) and Mel (p < .01) treatment, in particular. The ovarian and cortex volume decreased in the OC group, and the cortex volume of the OC group was significantly higher than the Ob + Mel, Ob + Lep and Ob + Mel + Lep groups (p < .01). Besides, the volume of the cortex in the NL group was significantly higher than in the other groups (except for the NC group) (p < .01). Although, the total numbers of primordial and primary follicles in NC group were significantly higher than in the OC group (p < .001), the number of the primordial and primary follicles in OC group was significantly higher than in the OL (p < .05), OM (p < .05) and, especially, the OML groups (p < .001). Likewise, the number of the secondary follicles in the OML group was significantly less than that in the OC group (p < .05). The CAT and MPO activity of the OC group was significantly higher than in the NC group (p < .05) and also granulosa cell apoptosis had increased in obese rats; but it was decreased after Lep and Mel treatment. Otherwise, Lep and, in particular, Mel increased LHr positivity. We concluded that obesity could trigger abnormal ovarian function and polycystic ovary via inducing LHr apoptosis and suppressing ovarian folliculogenesis. Also, melatonin could be better for inhibition of apoptosis and modulation of folliculogenesis than leptin. These observations suggest that melatonin may act to reduce fertility in obese patients.Impact statementWhat is already known on this subject? Hormonal changes during reproductive cycle in obese women are particularly studied and there is not any study that evaluates the effects of melatonin and leptin, together.What the results of this study add? The study has shown that obese rats have increased granulosa cell apoptosis and MPO activities but melatonin and leptin reduces the apoptosis and inflammation. Moreover, the obesity decreased, but melatonin and leptin increased LHR immunoreactivity in both the granulosa and theca cells.What the implications are of these findings for clinical practice and/or further research? The results suggest that leptin and melatonin could decrease excess body weight in obese persons. Also, these hormones modulate the ovarian turn-over by regulating developing follicles. Therefore, leptin and especially melatonin could be used as a supplement to ovulation therapy.

Resistin up-regulates LPL expression through the PPARγ-dependent PI3K/AKT signaling pathway impacting lipid accumulation in RAW264.7 macrophages

Resistin is a cysteine-rich cytokine, which has been indicated as a mediator of insulin resistance and inflammation. Previous studies demonstrated that lipoprotein lipase (LPL) was an important enzyme that could mediate lipid accumulation in macrophages. Additionally, the intracellular molecules phosphatidylinositol 3-kinase (PI3K)/serine-threonine protein kinase (AKT)/peroxisome proliferator-activated receptor (PPARγ) were supposed to be involved in the lipid accumulation process in cells. However, it remains unclear whether resistin was correlated with the dysregulation of lipid metabolism in macrophages. The present study investigated that resistin could up-regulate the expression of LPL and increase the contents of intracellular triglyceride (TG) and total cholesterol (TC) in RAW264.7 macrophages. In addition, intracellular molecules PI3K, AKT and PPARγ were significantly up-regulated and activated in resitin-stimulated RAW264.7 macrophages (P < 0.05). In contrast, the effects of resistin on RAW264.7 macrophages could be abrogated by specific inhibitors for LPL (LPL-siRNA) and PI3K/AKT signaling pathway (LY294002). All together, this study demonstrated that resistin could up-regulate the expression of LPL and induce lipid accumulation in RAW264.7 macrophages. More importantly, the PPARγ-dependent PI3K/AKT signaling pathway was relevant to the lipid accumulation process in resistin-stimulated macrophages.

Adipokine Dysregulation and Insulin Resistance with Atherosclerotic Vascular Disease: Metabolic Syndrome or Independent Sequelae?

Adipokine dysregulation and insulin resistance are two hallmark sequelae attributed to the current clinical definition of metabolic syndrome (MetS) that are also linked to atherosclerotic vascular disease. Here, we critically discuss the underlying pathophysiological mechanisms and the interplay between the two sequelae. Adipokine dysregulation is involved with decreased nitric oxide, vascular inflammation, and insulin resistance in itself to promote atherosclerosis. Insulin resistance is involved with endothelial dysfunction by direct and indirect mechanisms that also promote vascular inflammation and atherosclerosis. These mechanisms are discussed in atherosclerosis irrespective of MetS, and to evaluate the possibility of synergism in MetS. High retinol-binding protein-4 (RBP-4) and low cholesterol efflux in MetS may provide evidence of possible synergism and elevated atherosclerotic risk. An adverse adipokine panel that includes fetuin-A and adiponectin can potentially assess atherosclerotic risk in even those without MetS. Genetic possibilities may exist in atherosclerotic vascular diseases secondary to insulin resistance.

Leptin Elicits LTC4 Synthesis by Eosinophils Mediated by Sequential Two-Step Autocrine Activation of CCR3 and PGD2 Receptors

Leptin is a cytokine, produced mainly by mature adipocytes, that regulates the central nervous system, mainly to suppress appetite and stimulate energy expenditure. Leptin also regulates the immune response by controlling activation of immunomodulatory cells, including eosinophils. While emerging as immune regulatory cells with roles in adipose tissue homeostasis, eosinophils have a well-established ability to synthesize pro-inflammatory molecules such as lipid mediators, a key event in several inflammatory pathologies. Here, we investigated the impact and mechanisms involved in leptin-driven activation of eicosanoid-synthesizing machinery within eosinophils. Direct in vitro activation of human or mouse eosinophils with leptin elicited synthesis of lipoxygenase as well as cyclooxygenase products. Displaying selectivity, leptin triggered synthesis of LTC₄ and PGD₂, but not PGE₂, in parallel to dose-dependent induction of lipid body/lipid droplets biogenesis. While dependent on PI3K activation, leptin-driven eosinophil activation was also sensitive to pertussis toxin, indicating the involvement of G-protein coupled receptors on leptin effects. Leptin-induced lipid body-driven LTC₄ synthesis appeared to be mediated through autocrine activation of G-coupled CCR3 receptors by eosinophil-derived CCL5, inasmuch as leptin was able to trigger rapid CCL5 secretion, and neutralizing anti-RANTES or anti-CCR3 antibodies blocked lipid body assembly and LTC₄ synthesis induced by leptin. Remarkably, autocrine activation of PGD₂ G-coupled receptors DP1 and DP2 also contributes to leptin-elicited lipid body-driven LTC₄ synthesis by eosinophils in a PGD₂-dependent fashion. Blockade of leptin-induced PGD₂ autocrine/paracrine activity by a specific synthesis inhibitor or DP1 and DP2 receptor antagonists, inhibited both lipid body biogenesis and LTC₄ synthesis induced by leptin stimulation within eosinophils. In addition, CCL5-driven CCR3 activation appears to precede PGD₂ receptor activation within eosinophils, since neutralizing anti-CCL5 or anti-CCR3 antibodies inhibited leptin-induced PGD₂ secretion, while it failed to alter PGD₂-induced LTC₄ synthesis. Altogether, sequential activation of CCR3 and then PGD₂ receptors by autocrine ligands in response to leptin stimulation of eosinophils culminates with eosinophil activation, characterized here by assembly of lipidic cytoplasmic platforms synthesis and secretion of the pleiotropic lipid mediators, PGD₂, and LTC₄.

Immunometabolic Regulation of Vascular Redox State: The Role of Adipose Tissue

SIGNIFICANCE

Vascular oxidative stress plays a crucial role in atherogenesis and cardiovascular disease (CVD). Recent evidence suggests that vascular redox state is under the control of complex pathophysiological mechanisms, ranging from inflammation to obesity and insulin resistance (IR). Recent Advances: Adipose tissue (AT) is now recognized as a dynamic endocrine and paracrine organ that secretes several bioactive molecules, called adipokines. AT has recently been shown to regulate vascular redox state in both an endocrine and a paracrine manner through the secretion of adipokines, therefore providing a mechanistic link for the association between obesity, IR, inflammation, and vascular disease. Importantly, AT behaves as a sensor of cardiovascular oxidative stress, modifying its secretory profile in response to cardiovascular oxidative injury.

CRITICAL ISSUES

The present article presents an up-to-date review of the association between AT and vascular oxidative stress. We focus on the effects of individual adipokines on modulating reactive oxygen species production and scavenging in the vascular wall. In addition, we highlight how inflammation, obesity, and IR alter the biology and secretome of AT leading to a more pro-oxidant phenotype with a particular focus on the local regulatory mechanisms of perivascular AT driven by vascular oxidation.

FUTURE DIRECTIONS

The complex and dynamic biology of AT, as well as its importance in the regulation of vascular redox state, provides numerous opportunities for the development of novel, targeted treatments in the management of CVD. Therapeutic modulation of AT biology could improve vascular redox state affecting vascular disease pathogenesis. Antioxid. Redox Signal. 29, 313-336.

Obesity, Fat Mass and Immune System: Role for Leptin

Obesity is an epidemic disease characterized by chronic low-grade inflammation associated with a dysfunctional fat mass. Adipose tissue is now considered an extremely active endocrine organ that secretes cytokine-like hormones, called adipokines, either pro- or anti-inflammatory factors bridging metabolism to the immune system. Leptin is historically one of most relevant adipokines, with important physiological roles in the central control of energy metabolism and in the regulation of metabolism-immune system interplay, being a cornerstone of the emerging field of immunometabolism. Indeed, leptin receptor is expressed throughout the immune system and leptin has been shown to regulate both innate and adaptive immune responses. This review discusses the latest data regarding the role of leptin as a mediator of immune system and metabolism, with particular emphasis on its effects on obesity-associated metabolic disorders and autoimmune and/or inflammatory rheumatic diseases.

Nutrients and Oxidative Stress: Friend or Foe?

There are different types of nutritionally mediated oxidative stress sources that trigger inflammation. Much information indicates that high intakes of macronutrients can promote oxidative stress and subsequently contribute to inflammation via nuclear factor-kappa B- (NF-κB-) mediated cell signaling pathways. Dietary carbohydrates, animal-based proteins, and fats are important to highlight here because they may contribute to the long-term consequences of nutritionally mediated inflammation. Oxidative stress is a central player of metabolic ailments associated with high-carbohydrate and animal-based protein diets and excessive fat consumption. Obesity has become an epidemic and represents the major risk factor for several chronic diseases, including diabetes, cardiovascular disease (CVD), and cancer. However, the molecular mechanisms of nutritionally mediated oxidative stress are complex and poorly understood. Therefore, this review aimed to explore how dietary choices exacerbate or dampen the oxidative stress and inflammation. We also discussed the implications of oxidative stress in the adipocyte and glucose metabolism and obesity-associated noncommunicable diseases (NCDs). Taken together, a better understanding of the role of oxidative stress in obesity and the development of obesity-related NCDs would provide a useful approach. This is because oxidative stress can be mediated by both extrinsic and intrinsic factors, hence providing a plausible means for the prevention of metabolic disorders.

Leptin Induces Sca-1+ Progenitor Cell Migration Enhancing Neointimal Lesions in Vessel-Injury Mouse Models

Supplemental Digital Content is available in the text.

Objective—

Leptin is an adipokine initially thought to be a metabolic factor. Recent publications have shown its roles in inflammation and vascular disease, to which Sca-1⁺ vascular progenitor cells within the vessel wall may contribute. We sought to elucidate the effects of leptin on Sca-1⁺ progenitor cells migration and neointimal formation and to understand the underlying mechanisms.

Approach and Results—

Sca-1⁺ progenitor cells from the vessel wall of Lepr^+/+ and Lepr^−/− mice were cultured and purified. The migration of Lepr^+/+ Sca-1⁺ progenitor cells in vitro was markedly induced by leptin. Western blotting and kinase assays revealed that leptin induced the activation of phosphorylated signal transducer and activator of transcription 3, phosphorylated extracellular signal–regulated kinases 1/2, pFAK (phosphorylated focal adhesion kinase), and Rac1 (ras-related C3 botulinum toxin substrate 1)/Cdc42 (cell division control protein 42 homolog). In a mouse femoral artery guidewire injury model, an increased expression of leptin in both injured vessels and serum was observed 24 hours post-surgery. RFP (red fluorescent protein)-Sca-1⁺ progenitor cells in Matrigel were applied to the adventitia of the injured femoral artery. RFP⁺ cells were observed in the intima 24 hours post-surgery, subsequently increasing neointimal lesions at 2 weeks when compared with the arteries without seeded cells. This increase was reduced by pre-treatment of Sca-1⁺ cells with a leptin antagonist. Guidewire injury could only induce minor neointima in Lepr^−/− mice 2 weeks post-surgery. However, transplantation of Lepr^+/+ Sca-1⁺ progenitor cells into the adventitial side of injured artery in Lepr^−/− mice significantly enhanced neointimal formation.

Conclusions—

Upregulation of leptin levels in both the vessel wall and the circulation after vessel injury promoted the migration of Sca-1⁺ progenitor cells via leptin receptor–dependent signal transducer and activator of transcription 3- Rac1/Cdc42-ERK (extracellular signal–regulated kinase)-FAK pathways, which enhanced neointimal formation.

Activation of Nrf2-Antioxidant Signaling by 1,25-Dihydroxycholecalciferol Prevents Leptin-Induced Oxidative Stress and Inflammation in Human Endothelial Cells

Background: Obesity is associated with hyperleptinemia and endothelial dysfunction. Hyperleptinemia has been reported to induce both oxidative stress and inflammation by increasing reactive oxygen species production.Objective: The objective of this study was to determine the effects of 1,25-dihydroxycholecalciferol [1,25(OH)₂D₃] against leptin-induced oxidative stress and inflammation in human endothelial cells.Methods: Small interfering RNA (siRNA) were used to knock down the expression of vitamin D receptor (VDR) in human umbilical vein endothelial cells (HUVECs). HUVECs were pretreated for 4 h with physiologic (10^-10 M) or supraphysiologic (10^-7 M) concentrations of 1,25(OH)₂D₃ and exposed to leptin (10 ng/mL). Superoxide anion production and translocation of nuclear factor (erythroid-derived 2)-like 2 (NRF2) and nuclear transcription factor κB (NF-κB) subunit p65 to the nucleus and the activation of their target genes were quantified.Results: Pretreatment of HUVECs with 1,25(OH)₂D₃ prevented the leptin-induced increase in superoxide anion production (P < 0.05). Pretreatment with 1,25(OH)₂D₃ further increased NRF2 translocation to the nucleus (by 3-fold; P < 0.05) and increased mRNA expression of superoxide dismutase 2 (SOD2; by 2-fold), glutathione peroxidase (GPX; by 3-fold), NAD(P)H dehydrogenase (quinone) 1 (NQO1; by 4-fold), and heme oxygenase 1 (HMOX1; by 2-fold) (P < 0.05). Leptin doubled the translocation of NF-κB (P < 0.05) to the nucleus and increased (P < 0.05) the upregulation of vascular inflammatory mediators such as monocyte chemoattractant protein 1 (MCP1; by 1-fold), transforming growth factor β (TGF β by 1-fold), and vascular cell adhesion molecule 1 (VCAM1; by 4-fold) (P < 0.05), which were prevented (P < 0.05) by pretreatment with 1,25(OH)₂D₃ Protective effects of 1,25(OH)₂D₃ were confirmed to be VDR dependent by using VDR siRNA.Conclusion: Pretreatment with 1,25(OH)₂D₃ in the presence of a high concentration of leptin has a beneficial effect on HUVECs through the regulation of mediators of antioxidant activity and inflammation.

Role of leptin as a link between metabolism and the immune system

Leptin is an adipocyte-derived hormone not only with an important role in the central control of energy metabolism, but also with many pleiotropic effects in different physiological systems. One of these peripheral functions of leptin is a regulatory role in the interplay between energy metabolism and the immune system, being a cornerstone of the new field of immunometabolism. Leptin receptor is expressed throughout the immune system and the regulatory effects of leptin include cells from both the innate and adaptive immune system. Leptin is one of the adipokines responsible for the inflammatory state found in obesity that predisposes not only to type 2 diabetes, metabolic syndrome and cardiovascular disease, but also to autoimmune and allergic diseases. Leptin is an important mediator of the immunosuppressive state in undernutrition status. Placenta is the second source of leptin and it may play a role in the immunomodulation during pregnancy. Finally, recent work has pointed to the participation of leptin and leptin receptor in the pathophysiology of inflammation in oral biology. Therefore, leptin and leptin receptor should be considered for investigation as a marker of inflammation and immune activation in the frontier of innate-adaptive system, and as possible targets for intervention in the immunometabolic mediated pathophysiology.

Obesity, Oxidative Stress, Adipose Tissue Dysfunction, and the Associated Health Risks: Causes and Therapeutic Strategies

Obesity is gaining acceptance as a serious primary health burden that impairs the quality of life because of its associated complications, including diabetes, cardiovascular diseases, cancer, asthma, sleep disorders, hepatic dysfunction, renal dysfunction, and infertility. It is a complex metabolic disorder with a multifactorial origin. Growing evidence suggests that oxidative stress plays a role as the critical factor linking obesity with its associated complications. Obesity per se can induce systemic oxidative stress through various biochemical mechanisms, such as superoxide generation from NADPH oxidases, oxidative phosphorylation, glyceraldehyde auto-oxidation, protein kinase C activation, and polyol and hexosamine pathways. Other factors that also contribute to oxidative stress in obesity include hyperleptinemia, low antioxidant defense, chronic inflammation, and postprandial reactive oxygen species generation. In addition, recent studies suggest that adipose tissue plays a critical role in regulating the pathophysiological mechanisms of obesity and its related co-morbidities. To establish an adequate platform for the prevention of obesity and its associated health risks, understanding the factors that contribute to the cause of obesity is necessary. The most current list of obesity determinants includes genetic factors, dietary intake, physical activity, environmental and socioeconomic factors, eating disorders, and societal influences. On the basis of the currently identified predominant determinants of obesity, a broad range of strategies have been recommended to reduce the prevalence of obesity, such as regular physical activity, ad libitum food intake limiting to certain micronutrients, increased dietary intake of fruits and vegetables, and meal replacements. This review aims to highlight recent findings regarding the role of oxidative stress in the pathogenesis of obesity and its associated risk factors, the role of dysfunctional adipose tissue in development of these risk factors, and potential strategies to regulate body weight loss/gain for better health benefits.

Better prognosis in overweight/obese coronary heart disease patients with high plasma levels of leptin

Background and aim

The involvement of leptin in atherosclerosis is very complex, including inflammation, the oxidative stress and thrombosis. Leptin has atherogenic and also antiatherogenic actions. In obesity elevated leptin levels are not sufficient to prevent disturbances of energy balance, suggesting that obese people are leptin resistant. The aim of the study was to investigate the relationship between baseline plasma levels of leptin and the incidence of new ischemic events in patients with CHD.

Methods

Plasma levels of leptin in fifty nine consecutive patients (29 men and 30 women) with CHD hospitalized in the County Emergency Clinical Hospital of Cluj-Napoca were measured using commercially available ELISA at admission. Patients with active infectious disease, neoplasia, acute coronary syndrome, stroke, hepatic or renal failure and severe heart failure were excluded The relationship between leptin levels and incident cardiovascular events (angina, nonfatal myocardial infarction or heart failure) over two years follow-up was studied using MEDCALC version 9.6.

Results

73.6% patients with CHD were overweight or suffered of obesity. There were no significant differences between women and men regarding the plasma levels of leptin, the body mass index (BMI), the number of rehospitalizations, rehospitalizations/patient, diabetes mellitus, hypertension or dyslipidemia. Only in women plasma levels of leptin are correlated with BMI. As compared with men with overweight and obesity (BMI≥25kg/m²), plasma levels of leptin were significantly higher in women with overweight and obesity (3905.97±463.91 pg/ml vs 1835.17±533.9 pg/ml) (p<0.002). Patient gender could not be demonstrated to influence prognosis. During the two years we recorded one or more readmissions in 26 patients (44%). The analysis of time till readmission using Kaplan-Meier curves, showed that leptin level (cut-off 2000 pg/ml, HR 0.38, 95% CI 0.17–0.83; p=0.01) and BMI (cut-off 28 kg/m², HR 0.3164, 95% CI 0.145–0.0689; p<0.01) were significantly associated with prognosis.

Conclusion

Patients with plasma levels of leptin >2000 pg/ml and BMI >28kg/m² had a better prognosis, suggesting a protective role of leptin in overweight/mild obesity.

RETRACTED:Betulinic acid downregulates expression of oxidative stress-induced lipoprotein lipase via the PKC/ERK/c-Fos pathway in RAW264.7 macrophages

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief. Concerns raised by Dr. Sander Kersten in PubPeer pointed out that Figures 6.1B and 6.2B of this paper were different figures but the legends and Western blots were identical; the quantification was also seen to be different between the two figures. Shortly afterwards, the authors asked to publish a corrigendum for part B of Figure 6.1, including images of western blots and associated bar plots. Subsequently, the journal conducted an investigation and found evidence that there had been improper manipulation and duplication of images in Figures 2 E, 6.2 B, 5 A and and 6.2 D, as shown by the reuse of several western blot bands with approximately 180° rotation in each case. After raising the complaint with the authors, the corresponding author agreed that the paper should be retracted. The authors apologise to the readers of the journal.

Obesity-Related Oxidative Stress: the Impact of Physical Activity and Diet Manipulation

Obesity-related oxidative stress, the imbalance between pro-oxidants and antioxidants (e.g., nitric oxide), has been linked to metabolic and cardiovascular disease, including endothelial dysfunction and atherosclerosis. Reactive oxygen species (ROS) are essential for physiological functions including gene expression, cellular growth, infection defense, and modulating endothelial function. However, elevated ROS and/or diminished antioxidant capacity leading to oxidative stress can lead to dysfunction. Physical activity also results in an acute state of oxidative stress. However, it is likely that chronic physical activity provides a stimulus for favorable oxidative adaptations and enhanced physiological performance and physical health, although distinct responses between aerobic and anaerobic activities warrant further investigation. Studies support the benefits of dietary modification as well as exercise interventions in alleviating oxidative stress susceptibility. Since obese individuals tend to demonstrate elevated markers of oxidative stress, the implications for this population are significant. Therefore, in this review our aim is to discuss (i) the role of oxidative stress and inflammation as associated with obesity-related diseases, (ii) the potential concerns and benefits of exercise-mediated oxidative stress, and (iii) the advantageous role of dietary modification, including acute or chronic caloric restriction and vitamin D supplementation.

Differential Role of Leptin and Adiponectin in Cardiovascular System

Leptin and adiponectin are differentially expressed adipokines in obesity and cardiovascular diseases. Leptin levels are directly associated with adipose tissue mass, while adiponectin levels are downregulated in obesity. Although significantly produced by adipocytes, leptin is also produced by vascular smooth muscle cells and cardiomyocytes. Plasma leptin concentrations are elevated in cases of cardiovascular diseases, such as hypertension, congestive heart failure, and myocardial infarction. As for the event of left ventricular hypertrophy, researchers have been stirring controversy about the role of leptin in this form of cardiac remodeling. In this review, we discuss how leptin has been shown to play an antihypertrophic role in the development of left ventricular hypertrophy through in vitro experiments, population-based cross-sectional studies, and longitudinal cohort studies. Conversely, we also examine how leptin may actually promote left ventricular hypertrophy using in vitro analysis and human-based univariate and multiple linear stepwise regression analysis. On the other hand, as opposed to leptin's generally detrimental effects on the cardiovascular system, adiponectin is a cardioprotective hormone that reduces left ventricular and vascular hypertrophy, oxidative stress, and inflammation. In this review, we also highlight adiponectin signaling and its protective actions on the cardiovascular system.

Differential effects of leptin and adiponectin in endothelial angiogenesis

Obesity is a major health burden with an increased risk of cardiovascular morbidity and mortality. Endothelial dysfunction is pivotal to the development of cardiovascular disease (CVD). In relation to this, adipose tissue secreted factors termed "adipokines" have been reported to modulate endothelial dysfunction. In this review, we focus on two of the most abundant circulating adipokines, that is, leptin and adiponectin, in the development of endothelial dysfunction. Leptin has been documented to influence a multitude of organ systems, that is, central nervous system (appetite regulation, satiety factor) and cardiovascular system (endothelial dysfunction leading to atherosclerosis). Adiponectin, circulating at a much higher concentration, exists in different molecular weight forms, essentially made up of the collagenous fraction and a globular domain, the latter being investigated minimally for its involvement in proinflammatory processes including activation of NF-κβ and endothelial adhesion molecules. The opposing actions of the two forms of adiponectin in endothelial cells have been recently demonstrated. Additionally, a local and systemic change to multimeric forms of adiponectin has gained importance. Thus detailed investigations on the potential interplay between these adipokines would likely result in better understanding of the missing links connecting CVD, adipokines, and obesity.

Association of plasma leptin, homocysteine and nitric oxide levels with the presence and unstability of coronary artery disease

AIM

Leptin and total homocysteine (tHcy) may participate in the pathogenesis of coronary artery disease (CAD) through nitric oxide (NO) depletion. We sought to investigate whether leptin, tHcy and NO are suitable predictors of CAD.

PATIENTS & METHODS

This study contained 50 control subjects and 50 stable and 50 unstable angina patients. Plasma leptin, tHcy and NO levels were determined using enzyme immunoassay, HPLC fluorescence and spectrophotometric methods, respectively. Other conventional risk factors were also determined.

RESULTS

Leptin and tHcy levels were highest in unstable angina patients, followed by stable angina patients and then controls (p < 0.001). Controls had significantly higher NO than patients (p <0.001). Leptin and tHcy had a positive and NO a negative association with the presence of CAD.

CONCLUSIONS

Some athrogenic effects of leptin may be mediated by affecting tHcy and NO levels. Plasma leptin, tHcy and NO levels showed significant contribution to CAD prediction and discrimination.

Imaging of atherosclerotic plaques in obesity: excessive fat accumulation, plaque progression and vulnerability

Obesity is becoming a major health issue in the world due to sedentary lifestyles and increasing intake of Western diets. Obesity is associated with metabolic abnormalities and atherosclerotic cardiovascular diseases. Adipose tissue has been increasingly considered to play a critical role in inducing metabolic disturbances and promoting atherogenesis. Arterial wall imaging permits direct visualization of atheroma burden in various vascular beds. In addition, recent advances in imaging technology help characterize components, microstructures and functional features of atherosclerotic plaques. These imaging modalities have contributed to elucidating factors associated with atherosclerosis in obese patients. Also, it provides opportunities to evaluate the effect of novel therapies on plaques in the setting of obesity. The findings of recent imaging studies and the clinical implications will be reviewed.

Leptin regulates CD16 expression on human monocytes in a sex-specific manner

Fat mass is linked mechanistically to the cardiovascular system through leptin, a 16 kDa protein produced primarily by adipocytes. In addition to increasing blood pressure via hypothalamic‐sympathetic pathways, leptin stimulates monocyte migration, cytokine secretion, and other functions that contribute to atherosclerotic plaque development. These functions are also characteristics of CD16‐positive monocytes that have been implicated in the clinical progression of atherosclerosis. This investigation sought to determine if leptin promoted the development of such CD16‐positive monocytes. Cells from 45 healthy men and women with age ranging from 20 to 59 years were analyzed. Circulating numbers of CD14⁺⁺16⁺⁺ monocytes, which are primary producers of TNFα, were positively related to plasma leptin concentrations (P < 0.0001), with a stronger correlation in men (P < 0.05 for leptin × sex interaction). In vitro, recombinant human leptin induced CD16 expression in a dose‐related manner (P = 0.02), with a stronger influence on monocytes from men (P = 0.03 for leptin × sex interaction). There were no sex‐related differences in total leptin receptor expression on any monocyte subtypes, relative expression of long versus short isoforms of the receptor, or soluble leptin receptor concentrations in the plasma. The number of circulating CD14⁺16⁺⁺ monocytes, which preferentially migrate into nascent plaques, was positively related to systolic blood pressure (R = 0.56, P = 0.0008) and intima‐media thickness (R = 0.37, P = 0.03), and negatively related to carotid compliance (R = −0.39, P = 0.02). These observations indicate that leptin promotes the development of CD16‐positive monocyte populations in a sex‐specific manner and that these subpopulations are associated with diminished vascular function.

e12177

Recombinant leptin induced CD16 expression on human monocytes in vitro in a dose‐ and sex‐specific manner. In vivo, CD16 expression on human monocytes correlated with plasma leptin concentrations in a sex‐specific manner. Blood pressure, carotid intima‐media thickness and carotid compliance were related to the number of circulating CD16‐positive monocytes.

Oxidative stress and metabolic pathologies: from an adipocentric point of view

Oxidative stress plays a pathological role in the development of various diseases including diabetes, atherosclerosis, or cancer. Systemic oxidative stress results from an imbalance between oxidants derivatives production and antioxidants defenses. Reactive oxygen species (ROS) are generally considered to be detrimental for health. However, evidences have been provided that they can act as second messengers in adaptative responses to stress. Obesity represents a major risk factor for deleterious associated pathologies such as type 2 diabetes, liver, and coronary heart diseases. Many evidences regarding obesity-induced oxidative stress accumulated over the past few years based on established correlations of biomarkers or end-products of free-radical-mediated oxidative stress with body mass index. The hypothesis that oxidative stress plays a significant role in the development of metabolic disorders, especially insulin-resistance state, is supported by several studies where treatments reducing ROS production reverse metabolic alterations, notably through improvement of insulin sensitivity, hyperlipidemia, or hepatic steatosis. In this review, we will develop the mechanistic links between oxidative stress generated by adipose tissue in the context of obesity and its impact on metabolic complications development. We will also attempt to discuss potential therapeutic approaches targeting obesity-associated oxidative stress in order to prevent associated-metabolic complications.

Localization of lipoprotein lipase and GPIHBP1 in mouse pancreas: effects of diet and leptin deficiency

BACKGROUND

Lipoprotein lipase (LPL) hydrolyzes triglycerides in plasma lipoproteins and enables uptake of lipolysis products for energy production or storage in tissues. Our aim was to study the localization of LPL and its endothelial anchoring protein glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) in mouse pancreas, and effects of diet and leptin deficiency on their expression patterns. For this, immunofluorescence microscopy was used on pancreatic tissue from C57BL/6 mouse embryos (E18), adult mice on normal or high-fat diet, and adult ob/ob-mice treated or not with leptin. The distribution of LPL and GPIHBP1 was compared to insulin, glucagon and CD31. Heparin injections were used to discriminate between intracellular and extracellular LPL.

RESULTS

In the exocrine pancreas LPL was found in capillaries, and was mostly co-localized with GPIHBP1. LPL was releasable by heparin, indicating localization on cell surfaces. Within the islets, most of the LPL was associated with beta cells and could not be released by heparin, indicating that the enzyme remained mostly within cells. Staining for LPL was found also in the glucagon-producing alpha cells, both in embryos (E18) and in adult mice. Only small amounts of LPL were found together with GPIHBP1 within the capillaries of islets. Neither a high fat diet nor fasting/re-feeding markedly altered the distribution pattern of LPL or GPIHBP1 in mouse pancreas. Islets from ob/ob mice appeared completely deficient of LPL in the beta cells, while LPL-staining was normal in alpha cells and in the exocrine pancreas. Leptin treatment of ob/ob mice for 12 days reversed this pattern, so that most of the islets expressed LPL in beta cells.

CONCLUSIONS

We conclude that both LPL and GPIHBP1 are present in mouse pancreas, and that LPL expression in beta cells is dependent on leptin.

Role of adipokines in atherosclerosis: interferences with cardiovascular complications in rheumatic diseases

Patients with rheumatic diseases have an increased risk of mortality by cardiovascular events. In fact, several rheumatic diseases such as rheumatoid arthritis, osteoarthritis, systemic lupus erythematosus, and ankylosing spondylitis are associated with a higher prevalence of cardiovascular diseases (CVDs). Although traditional cardiovascular risk factors have been involved in the pathogenesis of cardiovascular diseases in rheumatic patients, these alterations do not completely explain the enhanced cardiovascular risk in this population. Obesity and its pathologic alteration of fat mass and dysfunction, due to an altered pattern of secretion of proinflammatory adipokines, could be one of the links between cardiovascular and rheumatic diseases. Indeed, the incidence of CVDs is augmented in obese individuals with rheumatic disorders. Thus, in this paper we explore in detail the relationships among adipokines, rheumatic diseases, and cardiovascular complications by giving to the reader a holistic vision and several suggestions for future perspectives and potential clinical implications.

A potential role for the myeloid lineage in leptin-regulated bone metabolism

Leptin influences bone formation centrally through the hypothalamus and peripherally by acting on osteoblasts or their precursors. However, neither mechanism explains the divergent, gender-specific correlation between leptin and bone mineral density in humans. Although leptin is a potent regulator of pro-inflammatory immune responses, a potential role for leptin as an osteoimmunologic intermediate in bone metabolism has not been tested. Mice with myeloid-specific ablation of the long-form leptin receptor (ObRb) were generated using mice expressing cre-recombinase from the lysoszyme M promoter. At 12 weeks of age, the conditional knockout mice did not display any appreciable phenotype. However, at 52 weeks 2 changes were noted. First, there was a mild increase in liver inflammation. Second, a gender-specific, divergent bone phenotype was observed. Female mice displayed a consistent trend toward decreased trabecular bone parameters including reductions in bone volume fraction, trabecular number, and bone mineral content as well as a significant increase in marrow adipogenesis. Conversely, male mice lacked trabecular changes, but had statistically significant increases in cortical bone volume, thickness, and bone mineral density with equivalent total cortical volume. Since the year 2000, over 25 studies on more than 10,000 patients have sought to determine the correlation between leptin and bone mineral density. The results revealed a gender-specific correlation similar to that observed in our LysM transgenic animals. We hypothesize and show new evidence that regulation of myeloid lineage cells by leptin may facilitate their actions as an osteoimmunologic intermediate and contribute to leptin-regulated bone formation and metabolism in a gender-specific manner.

At the crossroad between immunity and metabolism: focus on leptin

White adipose tissue is currently considered to be an active endocrine organ that secretes a plethora of factors named adipokines, most of them proinflammatory in nature, which probably contribute to low-level systemic inflammation; a state that is often present in metabolic syndrome-associated chronic pathologies such as obesity and atherosclerosis. Leptin is historically and indisputably one of the most important adipokines secreted by fat cells, with a variety of physiological roles related to the control of metabolism, energy homeostasis and inflammatory response. One of these functions is the connection between nutritional status and immune competence. Indeed, leptin has been shown to modulate both the innate and adaptive immune responses in both normal and pathological conditions. It has been shown that conditions characterized by low leptin levels are associated with increased susceptibility to infection. Conversely, immune-mediated disorders, such as autoimmune diseases, are associated with increased secretion of leptin and the production of proinflammatory pathogenic cytokines. Thus, leptin can easily be considered a frank mediator of the inflammatory/immune response.

Redox control of protein kinase C: cell- and disease-specific aspects

Hormones, growth factors, electrical stimulation, and cell-cell interactions regulate numerous cellular processes by altering the levels of second messengers, thus influencing biochemical reactions inside the cells. The Protein Kinase C family (PKCs) is a group of serine/threonine kinases that are dependent on calcium (Ca(2+)), diacylglycerol, and phospholipids. Signaling pathways that induce variations on the levels of PKC activators have been implicated in the regulation of diverse cellular functions and, in turn, PKCs are key regulators of a plethora of cellular processes, including proliferation, differentiation, and tumorigenesis. Importantly, PKCs contain regions, both in the N-terminal regulatory domain and in the C-terminal catalytic domain, that are susceptible to redox modifications. In several pathophysiological conditions when the balance between oxidants, antioxidants, and alkylants is compromised, cells undergo redox stress. PKCs are cell-signaling proteins that are particularly sensitive to redox stress because modification of their redox-sensitive regions interferes with their activity and, thus, with their biological effects. In this review, we summarize the involvement of PKCs in health and disease and the importance of redox signaling in the regulation of this family of kinases.

Leptin administration downregulates the increased expression levels of genes related to oxidative stress and inflammation in the skeletal muscle of ob/ob mice

Obese leptin-deficient ob/ob mice exhibit a low-grade chronic inflammation together with a low muscle mass. Our aim was to analyze the changes in muscle expression levels of genes related to oxidative stress and inflammatory responses in leptin deficiency and to identify the effect of in vivo leptin administration. Ob/ob mice were divided in three groups as follows: control ob/ob, leptin-treated ob/ob (1 mg/kg/d) and leptin pair-fed ob/ob mice. Gastrocnemius weight was lower in control ob/ob than in wild type mice (P < .01) exhibiting an increase after leptin treatment compared to control and pair-fed (P < .01) ob/ob animals. Thiobarbituric acid reactive substances, markers of oxidative stress, were higher in serum (P < .01) and gastrocnemius (P = .05) of control ob/ob than in wild type mice and were significantly decreased (P < .01) by leptin treatment. Leptin deficiency altered the expression of 1,546 genes, while leptin treatment modified the regulation of 1,127 genes with 86 of them being involved in oxidative stress, immune defense and inflammatory response. Leptin administration decreased the high expression of Crybb1, Hspb3, Hspb7, Mt4, Cat, Rbm9, Serpinc1 and Serpinb1a observed in control ob/ob mice, indicating that it improves inflammation and muscle loss.

Role of leptin in the activation of immune cells

Adipose tissue is an active endocrine organ that secretes various humoral factors (adipokines), and its shift to production of proinflammatory cytokines in obesity likely contributes to the low-level systemic inflammation that may be present in metabolic syndrome-associated chronic pathologies such as atherosclerosis. Leptin is one of the most important hormones secreted by adipocytes, with a variety of physiological roles related to the control of metabolism and energy homeostasis. One of these functions is the connection between nutritional status and immune competence. The adipocyte-derived hormone leptin has been shown to regulate the immune response, innate and adaptive response, both in normal and pathological conditions. The role of leptin in regulating immune response has been assessed in vitro as well as in clinical studies. It has been shown that conditions of reduced leptin production are associated with increased infection susceptibility. Conversely, immune-mediated disorders such as autoimmune diseases are associated with increased secretion of leptin and production of proinflammatory pathogenic cytokines. Thus, leptin is a mediator of the inflammatory response.

Leptin and the clinical cardiovascular risk

Obesity is a universal health problem of increasing prevalence and represents a major public health concern. Obesity is associated with a high risk of developing cardiovascular and metabolic diseases such as hypertension, coronary atherosclerosis, myocardial hypertrophy, diabetes, dyslipidemia, and increased cardiovascular morbidity and mortality. There has been an ongoing search for mediators between obesity and cardiovascular disease. Leptin is a novel and very promising molecule of research that may link these pathologic conditions. Since its discovery in 1994, major advances have been made in the understanding of neuroendocrine mechanisms regulating appetite, metabolism, adiposity, sympathetic tone and blood pressure. In this review, we discuss the physiological and pathophysiological roles of leptin in the causation of various cardiovascular diseases.

The vasa vasorum in diseased and nondiseased arteries

The vasa vasorum form a network of microvasculature that originate primarily in the adventitial layer of large arteries. These vessels supply oxygen and nutrients to the outer layers of the arterial wall. The expansion of the vasa vasorum to the second order is associated with neovascularization related to progression of atherosclerosis. Immunohistological analysis of human plaques from autopsied aortas have defined plaque progression and show a significant correlation with vasa vasorum neovascularization. Recent technological advances in microcomputed tomography have enabled investigation of vasa vasorum structure and function in nondiseased large arteries from pigs and dogs. Smaller mammals, particularly mice with genetic modifications that enable disease development, have been used extensively to study the vasa vasorum in diseased vessels. Despite the fact that most mouse models that are used to study atherosclerosis are unable to develop plaque to the extent found in humans, studies in both humans and mice underscore the importance of angiogenic vasa vasorum in progression of atherosclerosis. Those who have examined the vasa vasorum in occluded vessels of nondiseased pigs and dogs find that inhibition of the vasa vasorum makes the animals atheroprone. Atherosclerosis is a multifactorial disease. There is increasing evidence that factors, produced in response to changes in the arterial wall, collaborate with the vasa vasorum to enhance the disease process.