Leptin down-regulates peroxisome proliferator-activated receptor gamma (PPAR-gamma) mRNA levels in primary human monocyte-derived macrophages

Immunometabolism mRNA expression phenotypes and reprogramming of CD14 in T2DM with or without CVD

BACKGROUND/AIM

Type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD) have a significant impact on the expression of genes in peripheral blood mononuclear cells (PBMCs). The primary objective of this study was to investigate the role of two signaling pathways, STAT1/6, and two important modulators of immunometabolism, leptin and PPARs, in the development of T2DM with and without CVD. Furthermore, the study aimed to assess the correlation between these factors and the dynamics of CD14 in PBMCs. This research was conducted within the context of a growing body of literature on the complex pathophysiology of T2DM and its association with CVD. Prior studies have indicated that T2DM is characterized by an imbalance in immunometabolism and the involvement of various signaling pathways.

MATERIALS AND METHODS

Blood samples were collected from a total of 47 subjects, including 7 healthy volunteers, 20 individuals diagnosed with diabetes and cardiovascular disease (D.CVD) and another 20 individuals diagnosed with diabetes only (D). PBMCs were isolated from these samples, and the expression levels of leptin, PPARγ, PPARα, and CD14 genes were measured using Real-Time PCR.

RESULTS

The most relevant result showed that diabetic patients with CVD had significantly higher levels of leptin expression, which was positively correlated with STAT1 (r = 0.7497, p = 0.0001). On the other hand, diabetic patients without CVD had elevated PPARγ expression, which was strongly correlated with STAT6 (r = 0.8437, p = 0.0001). Interestingly, we found a significant increase in the PPARγ/ PPARα ratio in the D.CVD group compared to the D group (4.273 ± 0.9531; 7.52 ± 3.556, p = 0.0479). Moreover, CD14 expression was significantly reduced in this group compared to diabetic patients without CVD.

CONCLUSION

These findings suggested that the immunometabolic imbalance in T2DM was driven by a STAT1/Leptin phenotype in diabetic patients with CVD and by a STAT6/PPARγ phenotype in diabetic patients without CVD. Taking into account STAT1/Leptin and STAT6/PPARγ profiling could help clinicians identify novel therapeutic targets for T2DM and other related diseases.

Leptin signaling in breast cancer and its crosstalk with peroxisome proliferator-activated receptors α and γ

Obesity may create a mitogenic microenvironment that influences tumor initiation and progression. The obesity-associated adipokine, leptin regulates energy metabolism and has been implicated in cancer development. It has been shown that some cell types other than adipocytes can express leptin and leptin receptors in tumor microenvironments. It has been shown that peroxisome proliferator-activated receptors (PPAR) agonists can affect leptin levels and vice versa leptin can affect PPARs. Activation of PPARs affects the expression of several genes involved in aspects of lipid metabolism. In addition, PPARs regulate cancer cell progression through their action on the tumor cell proliferation, metabolism, and cellular environment. Some studies have shown an association between obesity and several types of cancer, including breast cancer. There is some evidence that suggests that there is crosstalk between PPARs and leptin during the development of breast cancer. Through a systematic review of previous studies, we have reviewed the published relevant articles regarding leptin signaling in breast cancer and its crosstalk with peroxisome proliferator-activated receptors α and γ.

The Role of Adipokines in Inflammatory Mechanisms of Obesity

Adipokines are currently widely studied cellular signaling proteins produced by adipose tissue and involved in various processes, including inflammation; energy and appetite modulation; lipid and glucose metabolism; insulin sensitivity; endothelial cell functioning; angiogenesis; the regulation of blood pressure; and hemostasis. The current review attempted to highlight the key functions of adipokines in the inflammatory mechanisms of obesity, its complications, and its associated diseases. An extensive search for materials on the role of adipokines in the pathogenesis of obesity was conducted online using the PubMed and Scopus databases until October 2022.

Ferulic Acid Mediates Metabolic Syndrome via the Regulation of Hepatic Glucose and Lipid Metabolisms and the Insulin/IGF-1 Receptor/PI3K/AKT Pathway in Palmitate-Treated HepG2 Cells

Ferulic acid (FA) is one of the most abundant bound phenolics in whole grains, partly contributing to its preventive effects on metabolic syndrome (MetS). The study aims to investigate if FA mediates MetS through the regulation of hepatic metabolisms and the insulin receptor related pathways in the palmitate-treated HepG2 cells (MetS model). We found that FA (50, 100, and 200 μM) dramatically ameliorated the lipid accumulation in the MetS model. FA significantly decreased the activities of the gluconeogenic enzymes, G6Pase and PEPCK, downregulated the lipogenic enzyme FAS-1, and upregulated the lipolytic enzyme CPT-1 by regulating a series of transcriptional factors including HNF4α, FOXO-1, SREBP-1c, and PPAR-γ. Notably, we found that FA's ability to alleviate MetS is achieved by activating the insulin receptor/PI3K/AKT pathway. Our results validated the effects of FA on mediating the metabolic disorders of lipid and glucose pathways and unveiled its potential intracellular mechanisms for the prevention of MetS.

The Complex Relationship Between Microbiota, Immune Response and Creeping Fat in Crohn's Disease

In the last decade, there has been growing interest in the pathological involvement of hypertrophic mesenteric fat attached to the serosa of the inflamed intestinal segments involved in Crohn's disease [CD], known as creeping fat. In spite of its protective nature, creeping fat harbours an aberrant inflammatory activity which, in an already inflamed intestine, may explain why creeping fat is associated with a greater severity of CD. The transmural inflammation of CD facilitates the interaction of mesenteric fat with translocated intestinal microorganisms, contributing to activation of the immune response. This may be not the only way in which microorganisms alter the homeostasis of this fatty tissue: intestinal dysbiosis may also impair xenobiotic metabolism. All these CD-related alterations have a functional impact on nuclear receptors such as the farnesoid X receptor or the peroxisome proliferator-activated receptor γ, which are implicated in regulation of the immune response, adipogenesis and the maintenance of barrier function, as well as on creeping fat production of inflammatory-associated cells such as adipokines. The dysfunction of creeping fat worsens the inflammatory course of CD and may favour intestinal fibrosis and fistulizing complications. However, our current knowledge of the pathophysiology and pathogenic role of creeping fat is controversial and a better understanding might provide new therapeutic targets for CD. Here we aim to review and update the key cellular and molecular alterations involved in this inflammatory process that link the pathological components of CD with the development of creeping fat.

Itaconate and leptin affecting PPARγ in M2 macrophages: A potential link to early-onset colorectal cancer

BACKGROUND

Along with the rising incidence of obesity, there has been an increase in patients diagnosed with early-onset colorectal cancer (<50 years old). In colorectal cancer, worse patient survival is associated with certain cytokine expression and downregulation of peroxisome proliferator activated receptor gamma expression. The effects of the obesity hormone leptin and macrophage-specific metabolite itaconate on these mechanisms are poorly understood. We investigated their impact on peroxisome proliferator activated receptor gamma and macrophage cytokine expression in vitro.

METHODS

M2-like macrophages were treated with either leptin, 4-octyl itaconate, or dimethyl itaconate in a dose- and time-dependent manner. Gene expression after treatment with 4 doses (D1-4) of each compound was analyzed at 4 time points (3, 6, 18, and 24 hours).

RESULTS

Peroxisome proliferator activated receptor gamma was downregulated after 4-octyl itaconate treatment at 18 hours (FC -32.67, P ≤ .001). Interleukin-8 was upregulated after leptin and dimethyl itaconate treatment at 6 hours (FC 26.35 at D4, P ≤ .001, and FC 23.26 at D3, P = .006). Dimethyl itaconate upregulated IL-1β at 24 hours (FC 18.00 at D4, P ≤ .001). Tumor necrosis factor-α showed maximum downregulation after 4-octyl itaconate at 18 hours (FC -103.25 at D4, P ≤ .001).

CONCLUSIONS

Itaconate downregulates peroxisome proliferator activated receptor gamma as a tumor-suppressing factor and upregulates anti-inflammatory cytokines in M2-like macrophages. Itaconate provides a link between obesity and colorectal cancer and may be a key regulator in early-onset colorectal cancer.

PPARγ2 Pro12Ala Polymorphism is Associated in Children With Traits Related to Susceptibility to Type 2 Diabetes

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear receptor that regulates glucose and lipid metabolism. Pharmacological activators of PPARγ are being used as a treatment of obesity related disorders such as dyslipidaemia and type 2 diabetes, but questions remain open regarding the effects of PPARγ on traits related to the development of type 2 diabetes. In our study, we have analyzed the relationship of the common variant Pro12Ala in the human PPARγ2 gene with the presence of obesity and with insulin, HOMA and lipid profile in a representative sample of 6-to 8-year-old children free from the confounding factors associated with adults. We found that Ala12Ala genotype was significantly more frequent in females with obesity than in those without obesity, with Ala12Ala carriers having significantly higher weight and body mass index (BMI), however the association disappeared when adjusting by leptin concentrations. The Ala12Ala genotype was associated with significantly higher HDL-cholesterol and apoA-I levels in males but not in females, independently of BMI. In a recessive model, in females, leptin levels appeared higher in Ala12Ala carriers. Although no apparent differences were observed in any sex when analyzing insulin levels and HOMA among genotypes without adjusting, lower insulin levels and lower HOMA appeared associated with Ala12Ala carriers when adjusting for BMI and leptin levels. In summary, our data showed that leptin seems to be having an effect on the association between the PPARγ2 Pro12Ala and BMI. Besides, after controlling for BMI and leptin, a protective effect of the Ala12Ala variant of the PPARγ2 Pro12Ala polymorphism on insulin sensitivity is evident already in prepubertal children.

Prolonged Chronic Consumption of a High Fat with Sucrose Diet Alters the Morphology of the Small Intestine

(1) The high-fat diet (HFD) of western countries has dramatic effect on the health of several organs, including the digestive tract, leading to the accumulation of fats that can also trigger a chronic inflammatory process, such as that which occurs in non-alcohol steatohepatitis. The effects of a HFD on the small intestine, the organ involved in the absorption of this class of nutrients, are still poorly investigated. (2) To address this aspect, we administered a combined HFD with sucrose (HFD w/Suc, fat: 58% Kcal) regimen (18 months) to mice and investigated the morphological and molecular changes that occurred in the wall of proximal tract of the small intestine compared to the intestine of mice fed with a standard diet (SD) (fat: 18% Kcal). (3) We found an accumulation of lipid droplets in the mucosa of HFD w/Suc-fed mice that led to a disarrangement of mucosa architecture. Furthermore, we assessed the expression of several key players involved in lipid metabolism and inflammation, such as perilipin, leptin, leptin receptor, PI3K, p-mTOR, p-Akt, and TNF-α. All these molecules were increased in HFD mice compared to the SD group. We also evaluated anti-inflammatory molecules like adiponectin, adiponectin receptor, and PPAR-γ, and observed their significant reduction in the HFD w/Suc group compared to the control. Our data are in line with the knowledge that improper eating habits present a primary harmful assault on the bowel and the entire body's health. (4) These results represent a promising starting point for future studies, helping to better understand the complex and not fully elucidated spectrum of intestinal alterations induced by the overconsumption of fat.

Leptin in Atherosclerosis: Focus on Macrophages, Endothelial and Smooth Muscle Cells

Increasing adipose tissue mass in obesity directly correlates with elevated circulating leptin levels. Leptin is an adipokine known to play a role in numerous biological processes including regulation of energy homeostasis, inflammation, vascular function and angiogenesis. While physiological concentrations of leptin may exhibit multiple beneficial effects, chronically elevated pathophysiological levels or hyperleptinemia, characteristic of obesity and diabetes, is a major risk factor for development of atherosclerosis. Hyperleptinemia results in a state of selective leptin resistance such that while beneficial metabolic effects of leptin are dampened, deleterious vascular effects of leptin are conserved attributing to vascular dysfunction. Leptin exerts potent proatherogenic effects on multiple vascular cell types including macrophages, endothelial cells and smooth muscle cells; these effects are mediated via an interaction of leptin with the long form of leptin receptor, abundantly expressed in atherosclerotic plaques. This review provides a summary of recent in vivo and in vitro studies that highlight a role of leptin in the pathogenesis of atherosclerotic complications associated with obesity and diabetes.

Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism

The discovery of leptin was intrinsically associated with its ability to regulate body weight. However, the effects of leptin are more far-reaching and include profound glucose-lowering and anti-lipogenic effects, independent of leptin's regulation of body weight. Regulation of glucose metabolism by leptin is mediated both centrally and via peripheral tissues and is influenced by the activation status of insulin signaling pathways. Ectopic fat accumulation is diminished by both central and peripheral leptin, an effect that is beneficial in obesity-associated disorders. The magnitude of leptin action depends upon the tissue, sex, and context being examined. Peripheral tissues that are of particular relevance include the endocrine pancreas, liver, skeletal muscle, adipose tissues, immune cells, and the cardiovascular system. As a result of its potent metabolic activity, leptin is used to control hyperglycemia in patients with lipodystrophy and is being explored as an adjunct to insulin in patients with type 1 diabetes. To fully understand the role of leptin in physiology and to maximize its therapeutic potential, the mechanisms of leptin action in these tissues needs to be further explored.

Role of Leptin in Acute Ischemic Stroke

Purpose

Leptin has been implicated as a pathogenetic contributor to atherosclerosis. We aimed to investigate the association of leptin level with ischemic stroke.

Materials and Methods

We prospectively enrolled 52 patients with acute ischemic stroke and measured leptin levels and compared with age- and sex-matched healthy controls. Risk factors, body mass index (BMI), biochemical parameters, intima-media thickness (IMT) on carotid vertebral Doppler and neuroimaging was done. Data were entered into MS-Excel and appropriate statistical analysis was done using SPSS software version 21.0. P = 0.05 was considered statistically significant.

Results

Serum leptin was significantly elevated in stroke patients (6598.1 ± 1035.1) compared to controls (3090.7 ± 698.86) (P < 0.01). Patients had higher BMI (26.9 ± 1.7) than controls (26.9 ± 1.7) (P < 0.00). BMI, total cholesterol, low-density lipoprotein (LDL) cholesterol, white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and C reactive protein (CRP) were significantly elevated in stroke patients than controls. Correlation analysis among patient group showed that serum leptin positively correlated with CRP (r - 0.41, P - <0.05), WBCs (r - 0.28, P - <0.05), ESR (r - 0.429, P - <0.01) total cholesterol (r - 0.31, P - <0.05), LDL-cholesterol (r - 0.19, P - <0.05), and IMT (r - 0.714, P - <0.001).

Conclusion

Our study showed high leptin levels in patients with stroke. Stroke patients with high leptin had higher BMI and inflammatory markers. The results of our study indicate that leptin may have a role in atherosclerosis mediated through inflammation. Future research should be directed toward understanding the role of leptin in the pathogenesis of cerebrovascular diseases and its potential role in preventive treatment of ischemic stroke.

Fetal programming by androgen excess in rats affects ovarian fuel sensors and steroidogenesis

Fetal programming by androgen excess is hypothesized as one of the main factors contributing to the development of polycystic ovary syndrome (PCOS). PCOS is more than a reproductive disorder, as women with PCOS also show metabolic and other endocrine alterations. Since both ovarian and reproductive functions depend on energy balance, the alterations in metabolism may be related to reproductive alterations. The present study aimed to evaluate the effect of androgen excess during prenatal life on ovarian fuel sensors and its consequences on steroidogenesis. To this end, pregnant rats were hyperandrogenized with testosterone and the following parameters were evaluated in their female offspring: follicular development, PPARG levels, adipokines (including leptin, adiponectin, and chemerin as ovarian fuel sensors), serum gonadotropins (LH and FSH), the mRNA of their ovarian receptors, and the expression of steroidogenic mediators. At 60 days of age, the prenatally hyperandrogenized (PH) female offspring displayed both an irregular ovulatory phenotype and an anovulatory phenotype with altered follicular development and the presence of cysts. Both PH groups showed altered levels of both proteins and mRNA of PPARG and a different expression pattern of the adipokines studied. Although serum gonadotropins were not impaired, there were alterations in the mRNA levels of their ovarian receptors. The steroidogenic mediators Star, Cyp11a1, Cyp17a1, and Cyp19a1 were altered differently in each of the PH groups. We concluded that androgen excess during prenatal life leads to developmental programming effects that affect ovarian fuel sensors and steroidogenesis in a phenotype-specific way.

The role of adipokines in systemic sclerosis: a missing link?

Systemic sclerosis is a multiorgan autoimmune disease characterized by vasculopathy and tissue fibrosis of unknown etiology. Recently, adipokines (cell signaling proteins secreted by adipose tissue) have attracted much attention as a cytokine family contributing to the various pathological processes of systemic sclerosis. Adipokines, such as leptin, adiponectin, resistin, adipsin, visfatin or chemerin are a heterogenic group of molecules. Adiponectin exhibits anti-fibrotic features and affects inflammatory reactions. Leptin promotes fibrosis and inflammation. Resistin was linked to vascular involvement in systemic sclerosis. Visfatin was associated with regression of skin lesions in late-stage systemic sclerosis. Chemerin appears as a marker of increased risk of impaired renal function and development of skin sclerosis in the early stage of systemic sclerosis. Vaspin was indicated to have a protective role in digital ulcers development. Novel adipokines-adipsin, apelin, omentin and CTRP-3-are emerging as molecules potentially involved in SSc pathogenesis. Serum adipokine levels may be used as predictive and diagnostic factors in systemic sclerosis. However, further investigations are required to establish firm correlations between distinct adipokines and systemic sclerosis.

Antifibrotics in liver disease: are we getting closer to clinical use?

The process of wound healing in response to chronic liver injury leads to the development of liver fibrosis. Regardless of etiology, the profound impact of the degree of liver fibrosis on the prognosis of chronic liver diseases has been well demonstrated. While disease-specific therapy, such as treatments for viral hepatitis, has been shown to reverse liver fibrosis and cirrhosis in both clinical trials and real-life practice, subsets of patients do not demonstrate fibrosis regression. Moreover, where disease-specific therapies are not available, the need for antifibrotics exists. Increased understanding into the pathogenesis of liver fibrosis sets the stage to focus on antifibrotic therapies attempting to: (1) Minimize liver injury and inflammation; (2) Inhibit liver fibrogenesis by enhancing or inhibiting target receptor-ligand interactions or intracellular signaling pathways; and (3) Promote fibrosis resolution. While no antifibrotic therapies are currently available, a number are now being evaluated in clinical trials, and their use is becoming closer to reality for select subsets of patients.

Intrauterine programming mechanism for hypercholesterolemia in prenatal caffeine-exposed female adult rat offspring

Clinical and animal studies have indicated that hypercholesterolemia and its associated diseases have intrauterine developmental origins. Our previous studies showed that prenatal caffeine exposure (PCE) led to fetal overexposure to maternal glucocorticoids (GCs) and increased serum total cholesterol levels in adult rat offspring. This study further confirms the intrauterine programming of PCE-induced hypercholesterolemia in female adult rat offspring. Pregnant Wistar rats were intragastrically administered caffeine (30, 60, and 120 mg/kg/d) from gestational day (GD)9 to 20. Female rat offspring were euthanized at GD20 and postnatal wk 12; several adult rat offspring were additionally subjected to ice-water swimming stimulation to induce chronic stress prior to death. The effects of GCs on cholesterol metabolism and epigenetic regulation were verified using the L02 cell line. The results showed that PCE induced hypercholesterolemia in adult offspring, which manifested as significantly higher levels of serum total cholesterol and LDL cholesterol (LDL-C) as well as higher ratios of LDL-C/HDL cholesterol. We further found that the cholesterol levels were increased in fetal livers but were decreased in fetal blood, accompanied by increased maternal blood cholesterol levels and reduced placental cholesterol transport. Furthermore, analysis of PCE offspring in the uterus and in a postnatal basal/chronic stress state and the results of in vitro experiments showed that hepatic cholesterol metabolism underwent GC-dependent changes and was associated with cholesterol synthase via abnormalities in 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) histone acetylation. We concluded that, to compensate for intrauterine placentally derived decreases in fetal blood cholesterol levels, high intrauterine GC levels activated fetal hepatic CCAAT enhancer binding protein α signaling and down-regulated Sirtuin1 expression, which mediated the high levels of histone acetylation ( via H3K9ac and H3K14ac) and expression of HMGCR. This GC-dependent cholesterol metabolism programming effect was sustained through adulthood, leading to the occurrence of hypercholesterolemia.-Xu, D., Luo, H. W., Hu, W., Hu, S. W., Yuan, C., Wang, G. H., Zhang, L., Yu, H., Magdalou, J., Chen, L. B., Wang, H. Intrauterine programming mechanism for hypercholesterolemia in prenatal caffeine-exposed female adult rat offspring.

Light-triggered methylcellulose gold nanoparticle hydrogels for leptin release to inhibit fat stores in adipocytes

Leptin is released in response to increased triglyceride storage in adipocytes and impacts body weight, but has drawbacks such as poor therapeutic effect and side effects when delivered systemically. Leptin also modifies adipocyte sensitivity to insulin to inhibit lipid accumulation. Here, light-triggered degradation of hydrogels was used to improve accuracy and effectiveness for sustained and controllable release. In our approach, leptin was entrapped within methylcellulose (MC)-based hydrogels, with incorporation of gold nanoparticles (NP). The incorporation of gold NP into MC hydrogels led to a tunable light irradiation response that dictated the hydrogel release rate of leptin. This manuscript demonstrates feasibility in designing tunable thermosensitive hydrogels for loading multimodality therapeutic agents to enhance the bioactivity of leptin for obesity therapy.

Differential expression of sirtuin 2 and adipocyte maturation restriction: an adaptation process during hypoxia in fish

Sirtuins have received widespread attention due to their diverse physiological role in metabolism. Among sirtuins, SIRT2 is more abundant in adipocytes and exerts effects on adipocyte differentiation, a process which involves conversion of preadipocytes to mature adipocytes orchestrated by adipokines and adipogenic transcription factors. Grey mullet (Mugil cephalus) was chosen as a study organism due to its excellent service as a biomonitor. Adipocytes isolated from natural field conditions were termed as field-hypoxic (Ennore) and -normoxic (Kovalam) based on dissolved oxygen (DO) level in the estuary. A previous study portrayed the hypoxic instance of Ennore estuary (low DO) and grey mullet [HIF1α in adipocytes, brain endothelial cell (EC) and hepatocytes] inhabiting this estuary ( Padmini et al., 2016a, b; Padmini and Tharani, 2015). In this context, fish adipocytes of both conditions were subjected to in vitro hypoxia for 1 h (in the pre/trigassed incubator with the supply of 1% O₂; 94% N₂; 5% CO₂) and were analysed for the expression of adipokines, adipogenic transcription factors and anti-adipogenic markers in fish adipocytes. Elevation of asymmetric dimethylarginine (ADMA), TNFα and leptin along with decreased adiponectin, adipogenic transcription factors and altering sirtuins were observed in test adipocytes and in control adipocytes on in vitro hypoxia. This suggests that adipocytes may follow internal caloric restriction as portrayed from cytomorphological/ultrastructural analysis, limiting adipocyte maturation process, one of the adaptive mechanisms triggered by adipocyte of fish surviving in Ennore estuary. Prolonged exposure to hypoxia (test on in vitro hypoxia for 1 h) showed a drastic alteration in these components leading to both structural and biological fluctuation when compared to limited hypoxic condition (field-hypoxic and control on in vitro hypoxia). Our study concludes that hypoxia may serve as the chief molecular cue in eliciting adipocyte maturation restriction though metabolic reprogramming and it also shows the significance of adipocyte maturation restriction in imparting survival mechanism.

Summary: Adipocyte maturation restriction is tightly regulated by SIRT2 activation which downregulates preadipocytes from the maturation process as adaptation strategy in fish surviving in the polluted (hypoxic) environment.

High post-natal mortality associated with defects in lung maturation and reduced adiposity in mice with gestational exposure to high fat and N-acetylcysteine

Studies have demonstrated that maternal consumption of a high fat diet (HFD) increases offspring susceptibility to metabolic disease. This study was initiated to identify the mechanistic contribution of oxidative stress on this phenomenon. Two weeks prior to mating, dams were fed either HFD or Control diet with or without supplementation with the anti-oxidant N-acetylcysteine (NAC). Pups born to HFD dams had reduced crown rump length (CRL) at birth and higher neonatal mortality compared to pups from Control dams. Supplementation with NAC normalized CRL in pups from HFD dams, but notably increased mortality. Histological examination of the lungs postnatally and prenatally, revealed normal branching morphogenesis but delayed alveolarization in pups from dams fed HFD+NAC. Discontinuation of NAC at ED17.5 with re-introduction at PD3 improved offspring survival and lung maturation. Additionally, interscapular brown adipose tissue (BAT) was reduced in ED18.5 embryos from HFD dams. These findings suggest that increased mortality in offspring from dams fed HFD+NAC during pregnancy may in part be the result of delayed pulmonary alveolarization and decreased BAT.

Unexploited Antineoplastic Effects of Commercially Available Anti-Diabetic Drugs

The development of efficacious antitumor compounds with minimal toxicity is a hot research topic. Numerous cancer cell targeted agents are evaluated daily in laboratories for their antitumorigenicity at the pre-clinical level, but the process of their introduction into the market is costly and time-consuming. More importantly, even if these new antitumor agents manage to gain approval, clinicians have no former experience with them. Accruing evidence supports the idea that several medications already used to treat pathologies other than cancer display pleiotropic effects, exhibiting multi-level anti-cancer activity and chemosensitizing properties. This review aims to present the anticancer properties of marketed drugs (i.e., metformin and pioglitazone) used for the management of diabetes mellitus (DM) type II. Mode of action, pre-clinical in vitro and in vivo or clinical data as well as clinical applicability are discussed here. Given the precious multi-year clinical experience with these non-antineoplastic drugs their repurposing in oncology is a challenging alternative that would aid towards the development of therapeutic schemes with less toxicity than those of conventional chemotherapeutic agents. More importantly, harnessing the antitumor function of these agents would save precious time from bench to bedside to aid the fight in the arena of cancer.

Genetic associations of leptin-related polymorphisms with systemic lupus erythematosus

Leptin is abnormally elevated in the plasma of patients with systemic lupus erythematosus (SLE), where it is thought to promote and/or sustain pro-inflammatory responses. Whether this association could reflect an increased genetic susceptibility to develop SLE is not known, and studies of genetic associations with leptin-related polymorphisms in SLE patients have been so far inconclusive. Here we genotyped DNA samples from 15,706 SLE patients and healthy matched controls from four different ancestral groups, to correlate polymorphisms of genes of the leptin pathway to risk for SLE. It was found that although several SNPs showed weak associations, those associations did not remain significant after correction for multiple testing. These data do not support associations between defined leptin-related polymorphisms and increased susceptibility to develop SLE.

The effects of perfluorinated chemicals on adipocyte differentiation in vitro

The 3T3-L1 preadipocyte culture system has been used to examine numerous compounds that influence adipocyte differentiation or function. The perfluoroalkyl acids (PFAAs), used as surfactants in a variety of industrial applications, are of concern as environmental contaminants that are detected worldwide in human serum and animal tissues. This study was designed to evaluate the potential for PFAAs to affect adipocyte differentiation and lipid accumulation using mouse 3T3-L1 cells. Cells were treated with perfluorooctanoic acid (PFOA) (5-100 µM), perfluorononanoic acid (PFNA) (5-100 µM), perfluorooctane sulfonate (PFOS) (50-300 µM), perfluorohexane sulfonate (PFHxS) (40-250 µM), the peroxisome proliferator activated receptor (PPAR) PPARα agonist Wyeth-14,643 (WY-14,643), and the PPARγ agonist rosiglitazone. The PPARγ agonist was included as a positive control as this pathway is critical to adipocyte differentiation. The PPARα agonist was included as the PFAA compounds are known activators of this pathway. Cells were assessed morphometrically and biochemically for number, size, and lipid content. RNA was extracted for qPCR analysis of 13 genes selected for their importance in adipocyte differentiation and lipid metabolism. There was a significant concentration-related increase in cell number and decreased cell size after exposure to PFOA, PFHxS, PFOS, and PFNA. All four PFAA treatments produced a concentration-related decrease in the calculated average area occupied by lipid per cell. However, total triglyceride levels per well increased with a concentration-related trend for all compounds, likely due to the increased cell number. Expression of mRNA for the selected genes was affected by all exposures and the specific impacts depended on the particular compound and concentration. Acox1 and Gapdh were upregulated by all six compounds. The strongest overall effect was a nearly 10-fold induction of Scd1 by PFHxS. The sulfonated PFAAs produced numerous, strong changes in gene expression similar to the effects after treatment with the PPARγ agonist rosiglitazone. By comparison, the effects on gene expression were muted for the carboxylated PFAAs and for the PPARα agonist WY-14,643. In summary, all perfluorinated compounds increased cell number, decreased cell size, increased total triglyceride, and altered expression of genes associated with adipocyte differentiation and lipid metabolism.

Regulation effects of TZQ-F on adipocyte differentiation and insulin action

ETHNOPHARMACOLOGICAL RELEVANCE

TZQ has been used in traditional Chineses medicine for treating diabetes. Based on the recipe of traditional anti-diabetic formula TZQ, we have developed TZQ-F which has been in phase 2 clinical trails. To study the mechanisms by which TZQ-F ameliorates diabetes, we examined whether treatment with TZQ-F improves hyperinsulinemia, hyperglycemia and obesity in type 2 diabetic KKA(y) mice and whether this is associated with an improvement of adipocyte differentiation and insulin action.

METHODS

TZQ-F, fenofibrate, rosiglitazone or distilled water was administered to 7-week-old diabetic KKA(y) and nondiabetic C57BL/6J mice for 8 weeks. Insulin resistance index, body weight and levels of serum blood glucose, leptin, insulin and adiponectin were evaluated. The expression of peroxisome proliferator-activated receptor γ (PPARγ) in skeletal muscle and liver tissues were determined with real-time PCR and western boltting. The mRNA expressions of insulin receptor (InsR), insulin receptor substrate-1 (IRS-1), insulin receptor substrate-2 (IRS-2), glucose transporter-1 (Glut-1) and Phosphoenolpyruvate 3-kinases (PI3K) in skeletal muscle and liver tissues were determined with real-time PCR. Histopathology of liver has been observed.

RESULTS

Treatment of TZQ-F for 8 weeks ameliorated hyperglycemia, hyperinsulinemia, hyperleptinemia and hypoadiponectinemia in KKA(y) mice. TZQ-F also up-regulated expression of PPARγ in liver tissue. However, it had no effect on regulation of expression of PPARγ in muscle tissue. In addition, TZQ-F upregulates InsR, IRS-1, IRS-2, Glut-1, and PI3K mRNA expression. Consistent with the in vivo results, histology study demonstrated that TZQ-F alleviated pathologic changes of the liver induced by high-fat diet.

CONCLUSIONS

These results first indicate that TZQ-F can be beneficial for reducing hyperinsulinemia, hyperglycemia and obesity through its potency of regulating adipocyte differentiation and insulin action.

Increased expression of fatty acid binding protein 4 and leptin in resident macrophages characterises atherosclerotic plaque rupture

OBJECTIVE

Resident macrophages play an important role in atheromatous plaque rupture. The macrophage gene expression signature associated with plaque rupture is incompletely defined due to the complex cellular heterogeneity in the plaque. We aimed to characterise differential gene expression in resident plaque macrophages from ruptured and stable human atheromatous lesions.

METHODS AND RESULTS

We performed genome-wide expression analyses of isolated macrophage-rich regions of stable and ruptured human atherosclerotic plaques. Plaques present in carotid endarterectomy specimens were designated as stable or ruptured using clinical, radiological and histopathological criteria. Macrophage-rich regions were excised from 5 ruptured and 6 stable plaques by laser micro-dissection. Transcriptional profiling was performed using Affymetrix microarrays. The profiles were characteristic of activated macrophages. At a false discovery rate of 10%, 914 genes were differentially expressed between stable and ruptured plaques. The findings were confirmed in fourteen further stable and ruptured samples for a subset of eleven genes with the highest expression differences (p < 0.05). Pathway analysis revealed that components of the PPAR/Adipocytokine signaling pathway were the most significantly upregulated in ruptured compared to stable plaques (p = 5.4 × 10(-7)). Two key components of the pathway, fatty-acid binding-protein 4 (FABP4) and leptin, showed nine-fold (p = 0.0086) and five-fold (p = 0.0012) greater expression respectively in macrophages from ruptured plaques.

CONCLUSIONS

We found differences in gene expression signatures between macrophages isolated from stable and ruptured human atheromatous plaques. Our findings indicate the involvement of FABP4 and leptin in the progression of atherosclerosis and plaque rupture, and suggest that down-regulation of PPAR/adipocytokine signaling within plaques may have therapeutic potential.

Peroxisome proliferator-activated receptor-gamma expression in the lung tissue of obese rats

PURPOSE

Obesity is a risk factor for asthma and type II diabetes. Peroxisome proliferator- activated receptor (PPAR)-γ has been suggested to regulate inflammatory responses in diabetes and asthma. We investigated whether PPAR-α, PPAR-γ, adiponectin receptors (AdipoR1, AdipoR2), leptin, and tumor necrosis factor (TNF)-α are expressed in rat lung tissues and whether the expression differs between obese Otsuka Long-Evans Tokushima Fatty (OLETF) and lean Long Evans Tokushima Otsuka (LETO) rats.

MATERIALS AND METHODS

Obese and lean rats were given with a high fat diet or a 30% restricted diet for 32 weeks, and their blood glucose levels and weights were monitored. After 32 weeks, mRNA levels of PPAR-α, PPAR-γ, AdipoR1, AdipoR2, leptin, and TNF-α in lung tissues were measured using real time PCR.

RESULTS

PPAR-α, PPAR-γ, AdipoR1, AdipoR2, leptin, and TNF-α were expressed in both obese and lean rat lung tissues. Increased serum glucose levels on intraperitoneal glucose tolerance testing and a higher weight gain at 32 weeks were observed in OLETF control rats compared to OLETF diet restricted rats. PPAR-γ expression was markedly elevated in obese control and diet restricted rats compared to lean rats, although PPAR-γ expression in obese rats was not affected by diet restriction. Leptin was highly expressed in OLETF rats compared to LETO rats. TNF-α expression was enhanced in OLETF control rats compared LETO diet restricted rats, and decreased by diet restriction. PPAR-α, AdipoR1, and AdipoR2 expression were not significantly different between obese and lean rats.

CONCLUSION

PPAR-γ was highly expressed in the lung tissues of obese rats and may be a novel treatment target for regulating lung inflammation associated with obesity.

Recurrent miscarriage: current concepts in diagnosis and treatment

Although recurrent miscarriage (RM) affects only 1-3% of couples, it has a major influence on the wellbeing and psychosocial status of patients. Therefore, research into improved diagnosis and development of new treatment strategies is essential. In this review, we summarize current concepts on diagnosis and treatment in RM, drawing upon research reports and international guidelines to provide insights into the pathophysiology of pregnancy disrupted by repeated miscarriage. Anatomical malformations, infectious diseases, endocrine disorders, autoimmune defects as well as acquired and inherited thrombophilia are established risk factors in RM. In addition, our recent findings indicate an impact on miscarriage incidence of glycoproteins such as glycodelin, and nuclear hormone receptors such as the peroxisome proliferator-activated receptors (PPARs). Significantly reduced glycodelin expression is associated with miscarriage, whereas up-regulation of PPARs appears to compensate for either the activated immune response or the disturbed cytotrophoblast differentiation in RM patients. There is also evidence that circulating placental microparticles are increased in a subgroup of RM patients, indicating an acquired procoagulant state even outside pregnancy. Treatment strategies like aspirin and low molecular weight heparin (LMWH) are standard medications in RM, although only a few placebo-controlled trials have proven their benefit in respect to live birth rate. There is emerging evidence that new treatment options, including drugs like TNFalpha inhibitors and granulocyte colony-stimulating factor (G-CSF) might be beneficial in some cases of RM. However, larger clinical trials must be completed to further prove or disprove benefits of these drugs in the treatment of RM patients.

PI-3 K/AKT and ERK signaling pathways mediate leptin-induced inhibition of PPARgamma gene expression in primary rat hepatic stellate cells

Compelling evidence indicates the pro-fibrogenic action of leptin in liver. Peroxisome proliferator-activated receptor-gamma (PPARgamma) can reverse hepatic stellate cell (HSC) activation and maintain HSC quiescence. HSC activation, a key step in the development of liver fibrosis, is coupled with the up-expression of leptin and the dramatic down-expression of PPARgamma. The present study is aimed to assess the effect of leptin on PPARgamma gene expression in primary cultured rat HSCs and investigate the related mechanisms by using Western blotting analysis, real-time PCR, transient transfection approach, and cell growth analysis. The results suggest that leptin negatively regulates PPARgamma gene expression at mRNA level, protein level and PPARgamma gene promoter activity level in HSCs. The inhibitory effect of leptin on PPARgamma gene expression contributes to cell growth of activated HSCs in vitro. Phosphatidylinositol 3-kinase/AKT (PI-3 K/AKT) and extracellular signal-regulated kinase (ERK) signaling pathways mediate the leptin-induced inhibition of PPARgamma gene expression. In summary, these findings suggest that leptin down-regulates PPARgamma gene expression through activation of PI-3 K/AKT or ERK signaling pathway in primary cultured rat HSCs. Our results might provide novel insights into the mechanisms for the pro-fibrogenic action of leptin in liver.

Effect of niacin on adipocyte leptin in hypercholesterolemic rabbits

BACKGROUND

Leptin may play an important role in the development of atherosclerosis. Several transcription genes [including peroxisome proliferator-activated receptor gamma (PPARgamma) and CD36] involved in lipid and glucose metabolism and inflammatory processes may correlate to leptin expression. The aim of this study was to investigate the effect of niacin on serum leptin levels in hypercholesterolemic rabbits and the expression of leptin, PPARgamma, and CD36 in adipocytes from hypercholesterolemic rabbits.

METHODS

Eighteen rabbits fed with high-cholesterol diet for 8 weeks were randomly divided into two groups: (a) high-cholesterol group (n=6), which is maintained on high-cholesterol diet for 6 weeks, and (b) niacin group (n=6), which receives the same cholesterol diet plus niacin (200 mg/kg/day) for 6 weeks. The control group (n=6) was fed with normal diet for 14 weeks. Subcutaneous adipose was collected for RNA analysis. The direct effect of niacin on leptin release was assayed in hypercholesterolemic rabbit adipocytes. Leptin levels in serum and adipocyte culture supernatant were measured via enzyme-linked immunosorbent assay. RT-PCR was used to evaluate leptin, PPARgamma, and CD36 mRNA expression in adipose and adipocytes.

RESULTS

Compared with the control group, rabbits fed with high-cholesterol diets showed higher levels of serum total cholesterol, low-density lipoprotein cholesterol, and leptin, all of which were significantly reduced by niacin treatment. After 6 weeks of treatment with niacin, the leptin level was significantly decreased by 21.8% (6.87+/-1.58 vs. 8.79+/-1.45, P<.05) and leptin mRNA expression of adipose was significantly lower in rabbits treated with niacin than in those fed with high-cholesterol diet continuously (0.58+/-0.11 vs. 0.73+/-0.15, P<.05). Niacin dose-dependently inhibited leptin secretion and increased CD36 and PPARgamma expression in cultured adipocytes. The reduction of leptin mRNA expression of hypercholesterolemic rabbits by niacin was negatively correlated with the up-regulation of PPARgamma and CD36 mRNA expression by niacin (r=-.69 and r=-.63, respectively, P<.01).

CONCLUSION

Niacin can reduce serum level and adipose mRNA expression of leptin and up-regulate PPARgamma and CD36 mRNA expression in hypercholesterolemic rabbits.

The role of macrophage leptin receptor in aortic root lesion formation

Plasma leptin is often elevated in obese individuals, and previous studies have suggested leptin as a factor that links obesity and atherosclerosis. Because macrophages play a key role in atherogenesis and are responsive to leptin, we hypothesized that leptin increases aortic root lesion formation, in part, through macrophage leptin receptor (LepR). Three different bone marrow transplantation studies were conducted in which bone marrow, with or without LepR, was transplanted into lethally irradiated 1) LDL receptor-deficient (LDLR(-/-)) mice with moderate hyperleptinemia due to Western diet (WD) feeding, 2) LDLR(-/-) mice with WD feeding plus pharmacologically induced hyperleptinemia (daily injection of 125 microg leptin), or 3) obese, hyperleptinemic, LepR-deficient LDLR(-/-) (LepR(db/db);LDLR(-/-)) mice. Minor differences in plasma parameters such as cholesterol, triglycerides, and insulin were observed in some groups; however, a consistent trend for the role of LepR on these parameters was not detected. In each of the studies, macrophage LepR expression did not have an effect on aortic root atherosclerotic lesion formation. These results suggest that nonhematopoietic cells may have a more significant role than macrophages in leptin-mediated effects on aortic root lesion formation.

The peroxisome proliferator activated receptor gamma (PPARgamma) ligand rosiglitazone modulates bronchoalveolar lavage levels of leptin, adiponectin, and inflammatory cytokines in lean and obese mice

Obese mice that lack leptin receptor (db (-) /db (-)) have been shown to have innate bronchial hyperresponsiveness (BHR). It has been proposed that the obesity-mediated BHR may involve a combination of increased leptin and reduced systemic adiponectin levels. The aim of this study was to determine if obesity modifies the airway concentration of leptin and adiponectin and whether treatment with a synthetic peroxisome proliferator-activated receptor gamma (PPARgamma) ligand can reduce airway leptin and increase airway adiponectin. In this study, obese, leptin receptor-deficient (db (-) /db (-)), or lean (db ( + ) /db (-)) mice were treated with rosiglitazone (3 mg/kg/day) or vehicle by gavage daily for 1 week. Bronchioalveolar lavage (BAL) was subsequently performed to determine levels of leptin, adiponectin, and inflammatory cytokines. Treatment with rosiglitazone increased BAL adiponectin levels in lean (p = 0.04) and to a lesser extent in obese mice (p = 0.07). Rosiglitazone treatment lowered leptin levels in lean mice, but increased leptin levels in BAL fluid of obese mice (p < 0.01). The BAL levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) were lower in the lean rosiglitazone-treated group compared with the obese vehicle-treated group and lower in the obese rosiglitazone-treated group compared with the obese vehicle-treated group. These results demonstrate that obesity is associated with alterations in adipokine and cytokine levels in the airways that can be modulated by treatment with roziglitazone.

Either integrin subunit beta1 or beta3 is involved in mediating monocyte adhesion, IL-1beta protein and mRNA expression in response to surfaces functionalized with fibronectin-derived peptides

We synthesized gelatin-based, interpenetrating network (IPN) scaffolds immobilized with fibronectin (FN)-derived peptides to assess monocyte-biomaterial interaction. Human primary monocytes were seeded onto peptide-grafted IPN or tissue-culture polystyrene (TCPS) pre-adsorbed with FN or FN-derived peptides. Monocyte cell density on both TCPS and IPN surfaces was higher in the presence of the arginine-glycine-aspartic acid (RGD) peptide. Pretreatment with anti-integrin beta1 or beta3 antibody decreased monocyte density on all ligand-modified TCPS and IPN. Interleukin-1 beta (IL-1beta) protein levels of cells on modified TCPS decreased over time. IL-1beta expression of monocytes in the presence of IPNs peaked at 24 h and then decreased through 168 h. Ligand identity did not affect IL-1beta expression in either TCPS or IPN samples. Pretreatment with anti-integrin beta1 or beta3 antibody reduced IL-1beta levels from both TCPS and IPN samples in a ligand-independent manner, particularly at 24 h. Monocytic IL-1beta mRNA expression in IPN samples without antibody pretreatment was highest at 2 h and decreased over time. IL-1beta mRNA expression in cells with anti-integrin beta1 or beta3 antibody pretreatment was similar to those without antibody pretreatment, except for methoxygrafted IPN samples. The change in IL-1beta mRNA expression did not correlate with changes in protein expression. The results indicate that monocyte adhesion was affected by the substrate and the RGD sequence and beta1 or beta3 containing integrin receptors. beta1- or beta3-containing integrin receptors were also involved in IL-1beta gene and protein expression in monocytes adhered to gelatin-based biomaterial surfaces.

Peroxisome proliferator-activated receptor-gamma is expressed by rat peritoneal mesothelial cells: its potential role in peritoneal cavity local defense

BACKGROUND/AIMS

Peritoneal mesothelial cells (PMCs) play an important role in peritoneal inflammatory and immune response. It was reported that the peroxisomal proliferator-activated receptor-gamma (PPARgamma) ligand could effectively reduce inflammatory processes. However, the expression and function of PPARgamma in PMCs has not been reported. This study was to investigate the expression of PPARgamma in rat PMCs and the effect of PPARgamma activation on the production of CD40 and ICAM-1 induced by lipopolysaccharide (LPS).

METHODS

Rat PMCs (RPMCs) were harvested from the peritoneal cavity of Sprague-Dawley rats and maintained under defined in vitro conditions. The cells were treated separately with LPS, 15d-PGJ(2), and ciglitazone at different time points. The mRNA and protein expression of PPARgamma, CD40 and ICAM-1 were detected by RT-PCR and Western blot, respectively. The intracellular distribution of PPARgamma was detected by immunocytochemistry.

RESULTS

RPMCs expressed PPARgamma both at the mRNA and protein level. The specific signals for PPARgamma were mainly localized in the nucleus with weak staining in the cytoplasm. Stimulation of RPMCs with LPS resulted in a time-dependent increase in the expression of PPARgamma with the peak of mRNA at 3 h and protein at 12 h. Thereafter the expression of PPARgamma gradually attenuated. The mRNA expressions for CD40, ICAM-1 and protein expression of ICAM-1 were significantly upregulated following stimulation with LPS. Both 15d-PGJ(2) and ciglitazone decreased the expression of CD40 mRNA and ICAM-1 protein. However, ciglitazone was less effective than 15d-PGJ(2).

CONCLUSIONS

There is constitutive expression of PPARgamma in cultured RPMCs and PPARgamma ligands which strongly inhibit LPS-induced CD40 and ICAM-1 production in RPMCs. It suggested that PPARgamma might play a part in the local defense of the peritoneal cavity by downregulating inflammatory mediators, which may play a potential role in preventing peritoneal fibrosis induced by peritonitis. Further in vivo study is needed to demonstrate the long-term effects.

Is there an estrogenic component in the metabolic syndrome?

One of the major upcoming concerns leading to health related problems in the industrialized societies is the metabolic syndrome which is characterized by central obesity, hypertension, raised fasting glucose and triglyceride levels. The focus of this review is on a potential estrogenic linkage between the metabolic mechanisms involved into the development of this disease cluster and specific estrogen related regulatory pattern. The candidate molecules for this link are insulin and insulin-like growthfactor, C-reactive protein, peroxisome-proliferation-activatingreceptorgamma, and leptin which all seem to interact with each other and show a responsiveness to changing estrogen levels. From this perspective they might also represent target molecules for a phytochemical intervention with phytoestrogens.