The metabolic action of oxytocin has recently been intensively studied to assess the ability of the peptide to regulate energy homeostasis. Despite the obvious weight-reducing effect of oxytocin observed in experimental studies, plasma oxytocin levels were found to be unchanged or even elevated in human obesity. The aim of our study was to evaluate the changes in the oxytocin system in Zucker rats, an animal model closely mirroring morbid obesity in humans. Plasma oxytocin levels were measured in obese Zucker rats and lean controls by enzyme immunoassay after plasma extraction. The expression of oxytocin and oxytocin receptor (OXTR) was assessed at the mRNA and protein levels by quantitative real-time PCR and immunoblotting respectively. Plasma and tissue activity of oxytocinase, the main enzyme involved in oxytocin degradation, were measured by fluorometric assay using an arylamide derivate as the substrate. Obese Zucker rats displayed a marked reduction in plasma oxytocin levels. Elevated liver and adipose tissue oxytocinase activity was noticed in obese Zucker rats. Hypothalamic oxytocin gene expression was not altered by the obese phenotype. OXTR mRNA and protein levels were upregulated in the adipose tissue of obese animals in contrast to the reduced OXTR protein levels in skeletal muscle. Our results show that obesity is associated with reduced plasma oxytocin due to increased peptide degradation by liver and adipose tissue rather than changes in hormone synthesis. This study highlights the importance of the oxytocin system in the pathogenesis of obesity and suggests oxytocinase inhibition as a candidate approach in the therapy of obesity.

Background: Mitochondrial dysfunction has been shown to play an important role in the development of atherosclerosis and nonalcoholic fatty liver disease ( NAFLD ). Mitochondrial aldehyde dehydrogenase ( ALDH 2), an enzyme responsible for the detoxification of reactive aldehydes, is considered to exert protective function in mitochondria. We investigated the influence of Alda‐1, an activator of ALDH 2, on atherogenesis and on the liver steatosis in apolipoprotein E knockout (apoE ^−/− ) mice. Methods and Results: Alda‐1 caused decrease of atherosclerotic lesions approximately 25% as estimated by “en face” and “cross‐section” methods without influence on plasma lipid profile, atherosclerosis‐related markers of inflammation, and macrophage and smooth muscle content in the plaques. Plaque nitrotyrosine was not changed upon Alda‐1 treatment, and there were no changes in aortic mRNA levels of factors involved in antioxidative defense, regulation of apoptosis, mitogenesis, and autophagy. Hematoxylin/eosin staining showed decrease of steatotic changes in liver of Alda‐1‐treated apoE ^−/− mice. Alda‐1 attenuated formation of 4‐hydroxy‐2‐nonenal (4‐HNE) protein adducts and decreased triglyceride content in liver tissue. Two‐dimensional electrophoresis coupled with mass spectrometry identified 20 differentially expressed mitochondrial proteins upon Alda‐1 treatment in liver of apoE ^−/− mice, mostly proteins related to metabolism and oxidative stress. The most up‐regulated were the proteins that participated in beta oxidation of fatty acids. Conclusions: Collectively, Alda‐1 inhibited atherosclerosis and attenuated NAFLD in apoE ^−/− mice. The pattern of changes suggests a beneficial effect of Alda‐1 in NAFLD; however, the exact liver functional consequences of the revealed alterations as well as the mechanism(s) of antiatherosclerotic Alda‐1 action require further investigation.

Atherosclerosis and nonalcoholic fatty liver disease (NAFLD) are frequent causes of death in the Western countries. Recently, it has been shown that autophagy dysfunction plays an important role in the pathogenesis of both atherosclerosis and NAFLD; thus, activators of autophagy might be useful for novel therapeutic interventions. Trehalose—a naturally occuring disaccharide present in plants, bacteria, fungi, insects, and certain types of shrimps—is a known inducer of autophagy. However, according to the literature, its anti-atherosclerotic and anti-steatotic potential seem to depend on the experimental setting. The aim of our study was to comprehensively describe the influence of a prolonged treatment with orally administered trehalose on the development of atherosclerotic lesions and hepatic steatosis in apolipoprotein E knockout (apoE^−/−) mice in an experimental set up reflecting both moderate and severe proatherogenic conditions: male apoE^−/− mice on a chow diet (CD) and female apoE^−/− mice fed with a high-fat diet (HFD). We found that exogenous trehalose inhibited atherosclerosis and attenuated hepatic steatosis in apoE^−/− mice. Such effects of trehalose were not associated with changes of plasma cholesterol, low-density lipoproteins (LDL), or high-density lipoproteins (HDL). Moreover, the anti-steatotic action of trehalose in the liver was associated with the induction of autophagy. The exact molecular mechanisms of both the anti-atherosclerotic action of trehalose and its inhibitory effect on liver steatosis require further clarification.

Insulin signaling and Tau protein phosphorylation in the hippocampi of young and old obese Zucker fa/fa rats and their lean controls were assessed to determine whether obesity-induced peripheral insulin resistance and aging are risk factors for central insulin resistance and whether central insulin resistance is related to the pathologic phosphorylation of the Tau protein. Aging and obesity significantly attenuated the phosphorylation of the insulin cascade kinases Akt (protein kinase B, PKB) and GSK-3β (glycogen synthase kinase 3β) in the hippocampi of the fa/fa rats. Furthermore, the hyperphosphorylation of Tau Ser396 alone and both Tau Ser396 and Thr231 was significantly augmented by aging and obesity, respectively, in the hippocampi of these rats. Both age-induced and obesity-induced peripheral insulin resistance are associated with central insulin resistance that is linked to hyperTau phosphorylation. Peripheral hyperinsulinemia, rather than hyperglycemia, appears to promote central insulin resistance and the Tau pathology in fa/fa rats.