Protective action of aspirin and its against endothelial Nlrp3 inflammasome activation in response to LPS stimuli

OBJECTIVE Recent studies have demonstrated that the Nlrp3 inflammasome serve as a central role in the pathogenesis of cardiovascular diseases and endothelial dysfunction occurs in association with several cardiovascular risk factors.Given the demonstrated anti-inflammatory effects of aspirin,the present study was designed to test whether aspirin diminish NLRP3 inflammasome activation and prevent endothelium injury and associated coronary artery damage during LPS.METHODS Mouse carotid arterial endothelial cells(CAECs)were cultured and treated with 0.1-3 mmol·L~(-1) of aspirin in response to LPS(2μg·mL~(-1))stimuli.After 24 h,the Nlrp3 inflammasome complexes consist of varied proteins were analyzed by WB.NO and T-AOC in the supernatant was detected by ELISA.Intracellular reactive oxygen species(ROS)generation for 24 h was observed by DCF fluorescence.The mice were treated with aspirin(12.5 mg·kg~(-1) per day,62.5 mg·kg~(-1) per day,125 mg·kg~(-1) per day)and dexamethasone(0.0182 mg·kg~(-1)per day)for 7 d.The level of IL~(-1)β,IL~(-1)8 protein was detected by ELISA.RESULTS Immunofluorescence results showed the colocalization of Nlrp3 with ASC or caspase 1decrease in a concentration-dependent manner.Meanwhile,the expression of Nlrp3 and caspase 1protein was decreased with the concentration of aspirin,but no changes the expression of ASC protein.Nlrp3 protein levels in CAECs were 0.33-0.8-fold and cle-caspase 1 protein levels in CAECs were 0.48-1-fold compared to those in LPS stimulation when treated with 0.1-3 mmol·L~(-1) aspirin for 24 h(P<0.01).Aspirin significantly antagonized the effect of LPS on NO(1.22-1.91-fold that of LPS stimulation,P<0.01)and T-AOC expression(1.02-1.90-fold that of LPS stimulation,P<0.01).As the different concentration of aspirin treated,the generation of ROS was 0.51-1.10-fold that of LPS stimulation(P<0.01).In vivo data shown the level of IL~(-1)β,IL~(-1)8 protein from serum are in concordance with the level of Nlrp3 inflammasome activation.CONCLUSION We conclude that aspirin has anti-inflammatory properties,protecting CAECs fromLPS-induced injury by inhibition of NLRP3 inflammasome activation through ROS pathway.     

Nicotine improves cognitive disturbance in rodents fed with a choline-deficient diet

The effect of nicotine on learning disturbances was tested in rats. Rats were fed either a choline-enriched or a choline-deficient diet. Concentration of acetylcholine in the whole brain was significantly lower in rats fed with choline-deficient diet than rats fed with choline-enriched diet. Passive avoidance learning shows that rats on a choline-deficient diet showed significantly impaired learning compared to rats on a choline-enriched diet. Nicotine (0.04 mg/kg) administered intraperitoneally significantly potentiated learning in rats on a choline-deficient diet, as well as in rats on a choline-enriched diet. We, therefore, suggest that nicotine may potentiate learning in an acetylcholine-deprived brain.     

NLRP3 inflammasome activation is associated with PM2.5‐induced cardiac functional and pathological injury in mice

Growing evidences indicate that inflammation induced by PM_2.5 exposure has been considered as a major driving force for the development of cardiovascular diseases. However, the mechanisms underlying PM_2.5‐induced cardiac injury remain unclear. This study aims to investigate the role of NLRP3 inflammasome in PM_2.5‐induced cardiac functional and pathological injury in mice. In this study, BALB/c mice were intratracheally instilled with PM_2.5 suspension (4.0 mg/kg BW) for 5 days to set up a cardiac injury model, which was evaluated by electrocardiogram monitoring, HE and Masson staining. Then, the effects of PM_2.5 on the expression of α‐SMA, NLRP3, IL‐1β, and IL‐18 proteins and the activation of caspase‐1 and IL‐1β were investigated. The results showed that PM_2.5 exposure induced characteristic abnormal ECG changes such as the abnormality of heart rhythm, tachycardia, and T‐wave reduction. Inflammatory cell infiltration and fibrosis were observed in the heart tissues of PM_2.5‐exposed mice. Meanwhile, PM_2.5 exposure increased the expression of α‐SMA. And, NLRP3 activation‐associated proteins of NLRP3, IL‐1β, IL‐18, Cleaved caspase‐1 p10, and Cleaved IL‐1β were upregulated in heart tissue of PM_2.5‐induced mice. In summary, PM_2.5 exposure could induce cardiac functional and pathological injury, which may be associated with the activation of NLRP3 inflammasome.     

Endothelial nitric oxide synthase activation through obacunone-dependent arginase inhibition restored impaired endothelial function in ApoE-null mice

Endothelial arginase constrains the activity of endothelial nitric oxide synthase (eNOS) by substrate depletion and reduces nitric oxide bioavailability. During the screening course of arginase inhibitor, we found obacunone as an arginase inhibitor. We tested the hypothesis that obacunone regulates vascular endothelial NO production. Obacunone incubation inhibited arginase I and II activities in liver and kidney lysates, respectively, in dose-dependent manner. Obacunone reciprocally increased nitrite/nitrate (NOx) production in HUVECs. In isolated aortic rings, obacunone increased intracellular l-arginine concentration and enhanced eNOS coupling, leading to increased NO and decreased superoxide production, with no changes in protein expression. Vasoconstriction response to U46619 was attenuated in obacunone-treated aortic vessels compared to that in untreated vessels. Endothelium-dependent vasorelaxant response to acetylcholine was significantly increased in obacunone-treated vessels and was modulated by the NO-dependent signaling cascade. The dose-dependent vasorelaxant response to Ach was reduced in the aortic vessels of ApoE^?/? mice fed a high-cholesterol diet. Obacunone incubation increased vasorelaxation to the level of a WT mouse, although the endothelium-independent response to sodium nitroprusside was identical among the groups. Therefore, obacunone may help treat cardiovascular diseases derived from endothelial dysfunction and may be useful for designing pharmaceutical compounds.     

NLRP3 inflammasome activation in murine alveolar macrophages and related lung pathology is associated with MWCNT nickel contamination

Multi-walled carbon nanotubes (MWCNT) have been reported to cause lung pathologies in multiple studies. However, the mechanism responsible for the bioactivity has not been determined. This study used nine different well-characterized MWCNT and examined the outcomes in vitro and in vivo. MWCNT, from a variety of sources that differed primarily in overall purity and metal contaminants, were examined for their effects in vitro (toxicity and NLRP3 inflammasome activation using primary alveolar macrophages isolated from C57Bl/6 mice). In addition, in vivo exposures were conducted to determine the inflammatory and pathogenic potency. The particles produced a differential magnitude of responses, both in vivo and in vitro, that was associated most strongly with nickel contamination on the particle. Furthermore, the mechanism of action for the Ni-contaminated particles was in their ability to disrupt macrophage phagolysosomes, which resulted in NLRP3 activation and subsequent cytokine release associated with prolonged inflammation and lung pathology.     

Carnitine palmitoyl transferase-I inhibition is not associated with cardiac hypertrophy in rats fed a high-fat diet

1. Cardiac lipotoxicity is characterized by hypertrophy and contractile dysfunction and can be triggered by impaired mitochondrial fatty acid oxidation and lipid accumulation. The present study investigated the effect of dietary fatty acid intake alone and in combination with inhibition of mitochondrial fatty acid uptake with the carnitine palmitoyl transferase (CPT)-I inhibitor oxfenicine. Long-chain fatty acids activate peroxisome proliferator-activated receptors (PPAR), thus mRNA levels of PPAR target genes were measured. 2. Rats were untreated or given the CPT-I inhibitor oxfenicine (150 mg/kg per day) and were fed for 8 weeks with either: (i) standard low-fat chow (10% of energy from fat); (ii) a long-chain saturated fatty acid diet; (iii) a long-chain unsaturated fatty acid diet; or (iv) a medium-chain fatty acid diet (which bypasses CPT-I). High-fat diets contained 60% of energy from fat. 3. Cardiac triglyceride content was increased in the absence of oxfenicine in the saturated fat group compared with other diets. Oxfenicine treatment further increased cardiac triglyceride stores in the saturated fat group and caused a significant increase in the unsaturated fat group. Despite elevations in triglyceride stores, left ventricular mass, end diastolic volume and systolic function were unaffected. 4. The mRNA levels of PPAR-regulated genes were increased by the high saturated and unsaturated fat diets compared with standard chow or the medium chain fatty acid chow. Oxfenicine did not further upregulate PPARalpha target genes within each dietary treatment group. 5. Taken together, the data suggest that consuming a high-fat diet or inhibiting CPT-I do not result in cardiac hypertrophy or cardiac dysfunction in normal rats.     

Nicotinic acid inhibits NLRP3 inflammasome activation via SIRT1 in vascular endothelial cells

Emerging evidences indicated that NLRP3 inflammasome initiates inflammatory response involved in cardiovascular disease. Nicotinic acid (NA) has been known to possess potential anti-inflammatory property. The aim of this study was to investigate the effect of NA on the activation of NLRP3 inflammasome and the underlying mechanisms. It was found that lipopolysaccharide (LPS) and adenosine triphosphate (ATP) triggered the activation of NLRP3 inflammasome in human umbilical vein endothelial cells (HUVECs). NA inhibited NLRP3 inflammasome activation and subsequent caspase-1 cleavage as well as interleukin (IL)-1β secretion. Moreover, NA administration up-regulated SIRT1 expression in HUVECs stimulated with LPS plus ATP. Importantly, knockdown of SIRT1 reversed the inhibitory effect of NA on the activation of NLRP3 inflammasome. Further study revealed that NA also decreased the generation of reactive oxygen species (ROS) in HUVECs. In addition, NA inhibited NLRP3 inflammasome activation partly through suppression of ROS. Taken together, these findings indicate that NA is able to regulate the activation of NLRP3 inflammasome in HUVECs, which may be partly mediated by SIRT1 and ROS.     

Chronic glucokinase activation reduces glycaemia and improves glucose tolerance in high-fat diet fed mice

The present study was designed to evaluate the antinociceptive profile of caffeic acid in mice and rats. Caffeic acid (5-100 mg/kg, p.o.), in a dose dependent manner inhibited acetic acid-induced writhing and late phase of formalin-induced pain in mice, with an ED(50) of 22.38 and 10.92 mg/kg, respectively. However, caffeic acid was ineffective in the hot plate and tail flick tests. Analgesic activity was also examined in carrageenan and lipopolysaccharide (LPS)-induced mechanical hyperalgesia in rats, where locally induced myeloperoxidase (MPO), malondialdehyde (MDA) and nitrite levels in foot pad were estimated by colorimetric assay. Oral administration of caffeic acid (200mg/kg, p.o.) showed analgesic activity similar to nimesulide (4 mg/kg, p.o.) and inhibited MPO, MDA and nitrite generation in the inflamed paw. Histological examination revealed reduction in neutrophil infiltration and protection of tissue damage by caffeic acid. These results suggest that caffeic acid exhibits peripheral analgesic effect in mice and rats and could be further examined for the treatment of chronic painful episodes.     

Sesamin improves endothelial dysfunction in renovascular hypertensive rats fed with a high-fat, high-sucrose diet

Paroxonase 1 (PON1) is an antiatherogenic enzyme which is also an organophosphate hydrolyzer. It has crucial roles in detoxification of highly toxic substances and protecting LDL against oxidation. Decrease in the levels of this enzyme is a great risk for the patients with cardiovascular diseases, diabetes mellitus, chronic renal failure, rheumatoid arthritis, hyperthyroidism, and age-related macular degeneration. Therefore, inhibitors and activators of PON1 must be well-characterized, and drug studies would be a good starting point in this regard. Moreover, purification of PON1 has been a challenge for scientists due to its tight association with HDL. Here we report the purification of human serum PON1 using very simple methods and investigation of the interactions between the enzyme and some commonly used antibiotics. We purified PON1 from human serum with a high specific activity, and used the pure enzyme for inhibition studies. We observed that some antibiotics inhibit the enzyme at very low doses while some are efficient at higher doses. The antibiotics exhibited different inhibition mechanisms. We concluded that usage of these antibiotics would be very dangerous in some cases.     

Acetylase inhibitor SI-2 is a potent anti-inflammatory agent by inhibiting NLRP3 inflammasome activation

Aberrant activation of Nod-like receptor family pyrin domain-containing-3 (NLRP3) inflammasome is implicated in a variety of inflammatory diseases. Targeting NLRP3 inflammasome represents a promising therapy to cure such diseases. We and others recently demonstrated that acetylation of NLRP3 promotes the inflammasome activity and also suggested lysine acetyltransferases inhibitors could be a kind of promising agents for treating NLRP3 associated disorders. In this study, by searching for kinds of lysine acetyltransferases inhibitors, we showed that SI-2 hydrochloride (SI-2), a specific inhibitor of lysine acetyltransferase KAT13B (lysine acetyltransferases 13B), specifically blocks NLRP3 inflammasome activation both in mice in vivo and in human cells ex vivo. Intriguingly, SI-2 does not affect the acetylation of NLRP3. Instead, it disrupts the interaction between NLRP3 and adaptor apoptosis-associated speck-like protein containing CARD (ASC), then blocks the formation of ASC speck. Thus, our study identified a specific inhibitor for NLRP3 inflammasome and suggested SI-2 as a potential inhibitory agent for the therapy of NLRP3-driven diseases.     

Skeletal changes in multiparous mice fed a nutrient-sufficient diet containing cadmium

Female mice were given nutrient-sufficient, purified diets containing either 0.25, 5, or 50 ppm Cd. One-half of the females were bred for 6 consecutive 42-day rounds of pregnancy/lactation (PL mice); remaining females were non-pregnant controls (NP mice). PL mice and NP controls were sacrificed after 1, 2, 4, or 6 consecutive rounds of pregnancy/lactation. No consistent, cadmium-dependent decreases in body weight, femur calcium content, or calcium/dry weight (Ca/DW) ratio occurred among the NP mice during the 252 days of cadmium exposure. In contrast, significant, cadmium-dependent decreases in body weight (3-11%), femur calcium content (15-27%), and Ca/DW ratio (5-7%) occurred in the multiparous mice exposed to 50 vs 0.25 ppm Cd. In addition, among the PL mice, the effect of cadmium was dose-dependent, with femur calcium contents decreasing significantly as the cadmium exposure level increased from 0.25 to 5 then 50 ppm Cd (P less than 0.05). Results demonstrate that dietary cadmium exposure had a greater effect on the skeletons of dams exposed to cadmium during the stresses of pregnancy and lactation than in non-pregnant controls. The results provide evidence that the combination of cadmium exposure and multiparity may have played a role in the etiology of Itai-Itai disease in Japan.     

Kidney changes in multiparous mice fed a nutrient-sufficient diet containing cadmium

Female mice were given nutrient-sufficient, purified diets containing cadmium at either 0.25, 5, or 50 ppm, as described in the accompanying publication. One-half of the females were bred for 6 consecutive 42-day rounds of pregnancy/lactation (PL mice); remaining females were non-pregnant controls (NP mice). PL mice and NP controls were sacrificed after 1, 2, 4, or 6 consecutive rounds of pregnancy/lactation. At all levels of dietary cadmium and after all reproductive rounds, kidney cadmium concentrations were 2-5-fold higher in PL than NP mice. After 6 rounds of reproduction, the mean concentration of cadmium in the kidneys of PL mice exposed to dietary cadmium at 50 ppm was 115 micrograms Cd/g kidney, close to the critical concentration for cadmium-induced renal damage (200 micrograms/g). No consistent increases in the concentrations of amino acids, protein, or cadmium in urine were observed in the NP or PL mice in our study, indicating that cadmium-induced renal dysfunction had not yet appeared. Very small increases in kidney concentrations of zinc and copper were observed with large increases in kidney cadmium concentrations. Threshold cadmium concentrations below which the concentrations of zinc and copper were relatively constant and independent of cadmium concentration were identified; they were 7.2 micrograms Cd/g kidney for zinc and 13 micrograms Cd/g kidney for copper. In this study, cadmium-induced decreases in bone-mineral content occurred in the PL mice exposed to cadmium at 5 and 50 ppm (see accompanying publication). Data presented here indicate that the latter bone changes occurred in the absence of cadmium-induced renal dysfunction of the type that results in increased aminoaciduria/proteinuria. They suggest that the bone disease of Itai-Ital patients may also have started prior to the onset of this type of renal dysfunction.     

Effects of bezafibrate, PPAR pan-agonist, and GW501516, PPARdelta agonist, on development of steatohepatitis in mice fed a methionine- and choline-deficient diet

We evaluated the effects of bezafibrate, a peroxisome proliferator-activated receptor (PPAR) pan-agonist, and GW501516, a PPARdelta agonist, on mice fed a methionine- and choline-deficient (MCD) diet, a model of non-alcholic steatohepatitis (NASH), to investigate (a) the efficacy of bezafibrate against non-alcholic steatohepatitis and (b) the relation between non-alcholic steatohepatitis and the functional role of PPARdelta. Bezafibrate (50 or 100 mg/kg/day) and GW501516 (10 mg/kg/day) were administered by gavage once a day for 5 weeks. Hepatic lipid contents, plasma triglyceride, high density lipoprotein (HDL)-cholesterol and alanine aminotransferase (ALT) concentrations were evaluated, as were histopathological changes in the liver and hepatic mRNA expression levels. Bezafibrate and GW501516 inhibited the MCD-diet-induced elevations of hepatic triglyceride and thiobarbituric acid-reactants contents and the histopathological increases in fatty droplets within hepatocytes, liver inflammation and number of activated hepatic stellate cells. In this model, bezafibrate and GW501516 increased the levels of hepatic mRNAs associated with fatty acid beta-oxidation [acyl-CoA oxidase (ACO), carnitine palmitoyltransferase-1 (CPT-1), liver-fatty acid binding protein (L-FABP) and peroxisomal ketothiolase], and reduced the levels of those associated with inflammatory cytokines or chemokine [transforming growth factor (TGF)-beta1, interleukin (IL)-6, IL-1beta, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF) alpha and nuclear factor (NF)-kappaB1]. In addition, bezafibrate characteristically reduced the elevation in the level of plasma ALT, but enhanced that in plasma adiponectin and increased the mRNA expression levels of its receptors (adiponectin receptors 1 and 2). These results suggest that (a) bezafibrate (especially) and GW501516 might improve hepatic steatosis via an improvement in fatty acid beta-oxidation and a direct prevention of inflammation, (b) treatment with a PPARdelta agonist might improve non-alcholic steatohepatitis, (c) bezafibrate may improve non-alcholic steatohepatitis via activation not only of PPARalpha but also of PPARdelta, because bezafibrate is a PPAR pan-agonist.     

Induction of heme oxygenas-1 attenuates NLRP3 inflammasome activation in lipopolysaccharide-induced mastitis in mice

Mastitis is one of most prevalent production disease in dairy herds worldwide, and is responsible for enormous economic losses. Heme oxygenase-1 (HO-1) is a cytoprotective enzyme, which is involved in the response to oxidative stress and inflammatory response. The purpose of this study was to detect the protective effect of HO-1 on LPS-induced mastitis in mice. BALB/c mice were pretreated with hemin (HO-1 inducer) and zinc protoporphyrin (ZnPP; HO-1 inhibitor) at 2 h before LPS stimulation. The results showed that the mammary gland damage, production of inflammatory cytokines IL-1β, and MPO activity in mammary gland tissues were significantly reduced after pretreated with hemin compared with the group of LPS stimulation only. However, ZnPP reversed the effects of hemin. Furthermore, we found that the levels of ROS and NLRP3 inflammasome were increased after LPS stimulation. The increases were inhibited by hemin and the inhibition of hemin on ROS production and NLRP3 inflammasome activation were blocked by ZnPP. In addition, the results showed that hemin reduced the expression of thioredoxin-interacting protein (TXNIP) induced by LPS, and ZnPP attenuated these changes. In conclusion, the results suggested that overproduction of HO-1 may inhibit the activation of NLRP3 inflammasome and the expression of TXNIP. Induction of HO-1 may be served as a promising method against mastitis induced by LPS.     

Dexamethasone alleviate allergic airway inflammation in mice by inhibiting the activation of NLRP3 inflammasome

Dexamethasone (DEX) is the mainstay treatment for asthma, which is a common chronic airway inflammation disease. However, the mechanism of DEX resolute symptoms of asthma is not completely clear. Here, we aimed to analyze the effect of DEX on airway inflammation in OVA-induced mice and whether this effect is related to the inhibition of the activation of NLRP3 inflammasome. Female (C57BL/6) mice were used to establish the allergic airway inflammation model by inhalation OVA. The number of inflammatory cells in the bronchi alveolar lavage fluid (BALF) was counted by Swiss-Giemsa staining, and the contents of IL-1β, IL-18, IL-5 and IL-17 were detected by ELISA. The degree of inflammatory cells infiltration and mucous cells proliferation in lung tissue were separately observed by H&E and PAS staining. The proteins expression of NLRP3, pro-caspase-1, caspase-1, IL-1β, IL-6 and IL-17 in lung tissue were detected by Western blotting. We found that DEX significantly inhibited OVA-induced inflammatory cells infiltration, airway mucus secretion and goblet cell proliferation in mice. The total and classified numbers of inflammatory cells and the levels of IL-1β, IL-18, IL-5 and IL-17 in the BALF of the experimental group were significantly lower than those of the model group after DEX treatment. DEX also significantly inhibited the activity of NLRP3 inflammasome and reduced the protein contents of Pro-Caspase-1, Caspase-1, Capase-1/Pro-Caspase-1, IL-1β, IL-6 and IL-17 in lung tissues. Our study suggested that DEX alleviates allergic airway inflammation by inhibiting the activity of NLRP3 inflammasome and the levels of IL-1β and IL-18.     

Endothelial and neuronal functions in cerebral and temporal arteries from monkeys fed a high-cholesterol diet

Modifications by hyperlipidemia of endothelium-dependent and -independent relaxations were evaluated in cerebral and temporal arteries from control and hyperlipidemic (high cholesterol-fed) monkeys. Histologically atherosclerotic lesions were not observed in either group. Relaxations induced by histamine, abolished by N(G)-nitro->L-arginine (>L-NA), were significantly potentiated in the hyperlipidemic monkey cerebral arteries, compared with those in the arteries from control monkeys. Treatment with superoxide dismutase did not affect the histamine-induced relaxation. Conversely, endothelium-dependent relaxations induced by A23187, Ca2+ ionophore, in cerebral arteries did not differ between control and hyperlipidemic monkeys. In temporal arteries, relaxations by acetylcholine and A23187 did not differ between control and hyperlipidemic monkeys. Endothelium-dependent and -independent relaxations by adenosine diphosphate in cerebral and temporal arteries were not affected by hyperlipidemia. Endothelium-independent relaxations by exogenously applied nitric oxide did not differ in the arteries from control and hyperlipidemic monkeys. Nicotine-induced relaxations in cerebral arteries, which were mediated with nitric oxide released from nitroxidergic (nitrergic) nerves, and the contractions caused by nicotine in temporal and mesenteric arteries treated with >L-NA did not differ between control and hyperlipidemic monkeys. It is concluded that long exposure to hyperlipidemia did not affect endothelial functions of monkey middle cerebral and temporal arteries but enhanced nitric oxide-mediated relaxations caused by histamine, possibly due to upregulation of endothelial histamine receptor-mediated functions in the cerebral arteries. The nitroxidergic (nitrergic) and adrenergic nerve functions do not seem to be affected by hyperlipidemia.     

Nrf2 deficiency improves glucose tolerance in mice fed a high-fat diet

Nrf2, a master regulator of intracellular redox homeostasis, is indicated to participate in fatty acid metabolism in liver. However, its role in diet-induced obesity remains controversial. In the current study, genetically engineered Nrf2-null, wild-type (WT), and Nrf2-activated, Keap1-knockdown (K1-KD) mice were fed either a control or a high-fat Western diet (HFD) for 12 weeks. The results indicate that the absence or enhancement of Nrf2 activity did not prevent diet-induced obesity, had limited effects on lipid metabolism, but affected blood glucose homeostasis. Whereas the Nrf2-null mice were resistant to HFD-induced glucose intolerance, the Nrf2-activated K1-KD mice exhibited prolonged elevation of circulating glucose during a glucose tolerance test even on the control diet. Feeding a HFD did not activate the Nrf2 signaling pathway in mouse livers. Fibroblast growth factor 21 (Fgf21) is a liver-derived anti-diabetic hormone that exerts glucose- and lipid-lowering effects. Fgf21 mRNA and protein were both elevated in livers of Nrf2-null mice, and Fgf21 protein was lower in K1-KD mice than WT mice. The inverse correlation between Nrf2 activity and hepatic expression of Fgf21 might explain the improved glucose tolerance in Nrf2-null mice. Furthermore, a more oxidative cellular environment in Nrf2-null mice could affect insulin signaling in liver. For example, mRNA of insulin-like growth factor binding protein 1, a gene repressed by insulin in hepatocytes, was markedly elevated in livers of Nrf2-null mice. In conclusion, genetic alteration of Nrf2 does not prevent diet-induced obesity in mice, but deficiency of Nrf2 improves glucose homeostasis, possibly through its effects on Fgf21 and/or insulin signaling.     

Lipid profile in mice fed a high-fat diet after exogenous leptin administration

Previous studies suggest a possible link between leptin and decreased lipid levels, however, the role of leptin in high-fat diet-induced hyperlipidemia remains unclear. The aim of our study was to evaluate the effect of administering leptin on plasma and tissue lipids in mice fed a high-fat diet. Feeding a high-fat diet (2% cholesterol, 0.125% bile salts, 5% peanut oil) to four-week-old healthy mice for a period of 45 days, resulted in significantly elevated levels of plasma and tissue total cholesterol, phospholipids, free fatty acids and triglycerides as compared with those of the control mice. Subsequently after thirty days, exogenous leptin (230 microg/kg i.p.) was administered simultaneously with the daily dose of high-fat diet every alternate day for fifteen days. Leptin administration significantly reduced the levels of total cholesterol, phospholipids, free fatty acids and triglycerides in the plasma, liver, heart and kidney of both the control and high-fat diet fed mice. Moreover, leptin administration markedly reduced the levels of plasma LDL, VLDL and elevated plasma HDL and the activity of lipoprotein lipase as compared with the untreated control and high-fat diet fed mice. Thus, leptin administration was found to have a marked protective effect against hyperlipidemia and thus obesity, by virtue of its lipid lowering effects.