Hemin Improves Insulin Sensitivity and Lipid Metabolism in Cultured Hepatocytes and Mice Fed a High-Fat Diet

Heme oxygenase 2 genetic variants alter hormonal and metabolic traits in polycystic ovary syndrome

Oxidative stress and metabolic disorders are involved in the pathogenesis of polycystic ovary syndrome (PCOS). Heme oxygenase 2 (HMOX2) plays a critical role in preserving heme metabolism as well as in modulating glycolipid metabolism, oxidative stress, and inflammation. This study examined the correlation between HMOX2 G554A (rs1051308) and A-42G (rs2270363) genetic variants with the risk of PCOS and assessed the effects of these genotypes on clinical, hormonal, metabolic, and oxidative stress indices using a case-control design that included 1014 patients with PCOS and 806 control participants. We found that the allelic and genotypic frequencies of the HMOX2 G554A and A-42G polymorphisms were comparable between the PCOS and control groups in Chinese women (P > 0.05). Nevertheless, it was discovered that patients with the AA or AG genotype of A-42G polymorphism had notably elevated levels of estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), LH/FSH ratio, high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (apo)B, and/or apoB/apoA1 ratio than those with the GG genotypes (P < 0.05). Patients with the GG or AG genotype of G554A polymorphism had elevated serum levels of LH, FSH, E2, LH/FSH ratio, TC, HDL-C, LDL-C, apoB, and/or apoB/apoA1 ratio and lower 2-h glucose concentration compared with those with the AA genotype (P < 0.05). Our findings indicate a potential association between the genetic variants and endocrine abnormalities in the reproductive system and metabolic irregularities in glycolipid levels in patients, thus suggesting their potential role in the pathogenesis of PCOS.

Deficiency of lipopolysaccharide binding protein facilitates adipose browning, glucose uptake and oxygen consumption in mouse embryonic fibroblasts via activating PI3K/Akt/mTOR pathway and inhibiting autophagy

This study aimed to explore the role of lipopolysaccharide-binding protein (LBP) in adipose browning. Mouse embryonic fibroblasts (MEFs) were treated with differentiation induction reagents and Perifosine (Akt inhibitor), with the transfection of Atg5, short hairpin RNA targeting LBP (shLBP), and Atg5 (shAtg5). The expression levels of LBP, inflammatory markers , brown fat markers, lipid metabolism marker, autophagy markers, insulin signaling-related molecules , p-mTOR, mTOR, p-Akt, Akt, p-PI3K, and PI3K were quantified or determined by Western blot, qRT-PCR, and immunofluorescence assay. The formation of lipid was examined through Oil red O staining assay. The consumption of oxygen was assessed using a Seahorse XF96 analyzer, and the uptake of glucose was evaluated by [³H]-2-deoxy-D-glucose uptake assay. Deficiency of LBP promoted adipose browning, oxygen consumption, glucose uptake, and insulin sensitivity in differentiated MEFs, where it inhibited inflammation and autophagy. All of the effects above were reversed by Atg5 overexpression. Meanwhile, the knockdown of Atg5 strengthened the activation of PI3K/Akt/mTOR pathway induced by the depletion of LBP, while Perifosine partly reversed the activation of differentiated MEFs. The knockdown of LBP facilitated adipose browning, glucose uptake, and oxygen consumption in MEFs via the activation of PI3K/Akt/mTOR pathway and the inhibition of autophagy.

Stimulation of Akt Phosphorylation and Glucose Transport by Metalloporphyrins with Peroxynitrite Decomposition Catalytic Activity

Iron porphyrin molecules such as hemin and iron(III) 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (FeTBAP) have previously been shown to influence insulin signaling and glucose metabolism. We undertook this study to determine whether a catalytic action of iron porphyrin compounds would be related to their stimulation of insulin signaling and glucose uptake in C2C12 myotubes. FeTBAP did not display nitrite reductase activity or alter protein S-nitrosylation in myotubes, eliminating this as a candidate mode by which FeTBAP could act. FeTBAP displayed peroxynitrite decomposition catalytic activity in vitro. Additionally, in myotubes FeTBAP decreased protein nitration. The peroxynitrite decomposition catalyst Fe(III)5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato chloride (FeTPPS) also decreased protein nitration in myotubes, but the iron porphyrin Fe(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachlorideporphyrin pentachloride (FeTMPyP) did not. FeTBAP and FeTPPS, but not FeTMPyP, showed in vitro peroxidase activity. Further, FeTBAP and FeTPPs, but not FeTMPyP, increased Akt phosphorylation and stimulated glucose uptake in myotubes. These findings suggest that iron porphyrin compounds with both peroxynitrite decomposition activity and peroxidase activity can stimulate insulin signaling and glucose transport in skeletal muscle cells.

Transcriptomic analysis in zebrafish larvae identifies iron-dependent mitochondrial dysfunction as a possible key event of NAFLD progression induced by benzo[a]pyrene/ethanol co-exposure

Non-alcoholic fatty liver disease (NAFLD) is a worldwide epidemic for which environmental contaminants are increasingly recognized as important etiological factors. Among them, the combination of benzo[a]pyrene (B[a]P), a potent environmental carcinogen, with ethanol, was shown to induce the transition of steatosis toward steatohepatitis. However, the underlying mechanisms involved remain to be deciphered. In this context, we used high-fat diet fed zebrafish model, in which we previously observed progression of steatosis to a steatohepatitis-like state following a 7-day-co-exposure to 43 mM ethanol and 25 nM B[a]P. Transcriptomic analysis highlighted the potent role of mitochondrial dysfunction, alterations in heme and iron homeostasis, involvement of aryl hydrocarbon receptor (AhR) signaling, and oxidative stress. Most of these mRNA dysregulations were validated by RT-qPCR. Moreover, similar changes were observed using a human in vitro hepatocyte model, HepaRG cells. The mitochondria structural and functional alterations were confirmed by transmission electronic microscopy and Seahorse technology, respectively. Involvement of AhR signaling was evidenced by using in vivo an AhR antagonist, CH223191, and in vitro in AhR-knock-out HepaRG cells. Furthermore, as co-exposure was found to increase the levels of both heme and hemin, we investigated if mitochondrial iron could induce oxidative stress. We found that mitochondrial labile iron content was raised in toxicant-exposed larvae. This increase was prevented by the iron chelator, deferoxamine, which also inhibited liver co-exposure toxicity. Overall, these results suggest that the increase in mitochondrial iron content induced by B[a]P/ethanol co-exposure causes mitochondrial dysfunction that contributes to the pathological progression of NAFLD.

Whole body metabolism is improved by hemin added to high fat diet while counteracted by nitrite: a mouse model of processed meat consumption

Nitrites and nitrates are traditional food additives used as curing agents in the food industry. They inhibit the growth of microorganisms and give a typical pink color to meat. Besides the positive effects of nitrite in foods, if present at high levels in the body, may induce hypoxia and contribute to the production of pro-carcinogenic secondary N-nitrosamines. This study investigated the whole-body metabolic effects of hemin and nitrite added to a high fat diet as red and processed red meat nutritional models. Mice were fed for 11 weeks with five different diets-(1) control diet (ND), (2) high fat diet (HFD) with 60% fat, (3) HFD with hemin (HFD + H, red meat model), (4) HFD with hemin and nitrite (HFD + HN, processed meat model), and (5) HFD with hemin, nitrite, and secondary amine (HFD + HNN, N-nitrosamine generating model)-and several metabolic parameters were determined and respiratory measurements were performed. Mice fed with the HFD + H or HFD + HNN diet had a lower epididymal white adipose tissue (eWAT) : body ratio and lower fasting glucose level than those fed the HFD alone. In addition, our results demonstrated a relief in hepatosteatosis grade among the HFD + H and HFD + HNN diet fed mice. Nitrite added to the HFD impaired the ability to use fat for energy, opposite to the effect of hemin. This study shows that nitrite in addition to pro-carcinogenesis and hypoxia can impact metabolic disease progression when added to meat.

Pathophysiological changes in experimental polycystic ovary syndrome in female albino rats: Using either hemin or L-arginine

Polycystic ovary syndrome (PCOS), one of the important endocrine disorders affecting females in the reproductive age, is caused mainly by an abnormal oxidation status that subsequently causes inflammatory conditions. Thus, this study aims to examine the possible individual prophylactic effects of gasotransmitters, hemin, or L-arginine in letrozole-induced PCOS. Fifty adult female albino rats were used and separated into a control group, which received the vehicle; a letrozole-induced PCOS group (L), which received letrozole orally at a dose level of 1 mg/kg for 21 days; a letrozole+hemin (L+H) group, which received letrozole plus hemin at a dose level of 25 mg/kg injected IP twice per week for 21 days; and a letrozole+L-arginine (L+A) group, which received letrozole plus L-arginine at a dose level of 200 mg/kg orally for 21 days. During PCO induction, the body weight and Lee index were measured. Serum glucose, insulin, lipid profile, gonadotrophic hormones, testosterone, estrogen, and tumor necrosis factor alpha were assayed, while ovarian tissues were analyzed to measure the oxidative state and histopathological changes. Our results proved that either hemin or L-arginine administration could improve the oxidative state, the inflammatory reaction, the hormonal imbalance, and the metabolic disturbances in PCO rats, which was confirmed by a histopathological examination of the rats' ovaries. In conclusion, either hemin or L-arginine had protective effects against PCOS with better pathophysiological changes with hemin.