High-fat diet-induced plasma protein and liver changes in obese rats can be attenuated by melatonin supplementation

Melatonin associated with a high-fat diet during pregnancy and lactation prevents liver changes in the offspring

In the present study, we set out to determine whether melatonin combined with a high-fat diet during pregnancy and lactation can prevent liver disorders in offspring. Forty rats were divided into four groups: DC - pregnant rats submitted to the standard diet; DC + Mel - pregnant rats submitted to the standard diet combined with melatonin; HFD - pregnant rats submitted to a high-fat diet; HFD + Mel - pregnant rats submitted to a high-fat diet combined with melatonin. Morphophysiological and biochemical parameters were analyzed. Melatonin (5 mg/kg) was administered intraperitoneally. The HFD group offspring showed an increase in AST, ALT, alkaline phosphatase, cholesterol, triglycerides, LDL and glucose levels, and a reduction in HDL and lipase levels. In the liver obseved steatosis, hepatocellular ballooning, increased lobular parenchyma and reduced non-lobular parenchyma, beside reduced liver glycogen and fibrosis. These changes were not observed in the HFD + Mel group. In conclusion, melatonin combined with a high-fat diet preserves the liver architecture and function in the offspring.

Effects of maternal high-fat diet on fetal growth, placental nutrient transporters and circular RNA expression profiles

Epidemiological and experimental studies suggest that there is a strong correlation between maternal high-fat diet and fetal-placental development. The current study aims to investigate the effects of maternal high-fat diet on fetal growth, placental nutrient transporters and circular RNA expression profiles in a mouse model. Forty C57BL/6 female mice were randomly assigned to two groups, fed either a control (10% fat for energy) diet (CON) or a high-fat (60% fat for energy) diet (HFD) for 4 weeks before mating and throughout pregnancy, and were killed on day 19.5 of pregnancy. The serum glucose, total cholesterol and low-density lipoprotein, the glucolipid metabolism-related hormones, and the insulin resistance index were significantly increased. High-throughput sequencing showed that differentially expressed circRNAs (DE circRNAs) in the placenta can regulate various biological processes, cellular components, and molecular functions through various energy metabolism pathways, and mmu-let-7g-5p was found to target and bind to multiple DE circRNAs. In addition, this study also predicted that various circRNAs with protein coding functions can regulate maternal placental nutrient transport. In general, the ceRNA (circRNAs-miRNAs-mRNAs) regulatory network of maternal placental nutrient transport constructed in this study is of great significance for further understanding the effect of maternal nutrition on fetal growth in the future.

Sex Differences of Radiation Damage in High-Fat-Diet-Fed Mice and the Regulatory Effect of Melatonin

The consumption of a high-fat diet (HFD) and exposure to ionizing radiation (IR) are closely associated with many diseases. To evaluate the interaction between HFDs and IR-induced injury, we gave mice whole abdominal irradiation (WAI) to examine the extent of intestinal injury under different dietary conditions. Melatonin (MLT) is a free radical scavenger that effectively prevents hematopoietic, immune, and gastrointestinal damage induced by IR. However, its effects on WAI-induced intestinal injury in HFD-fed mice remain unclear. We demonstrated that MLT can promote intestinal structural repair following WAI and enhance the regeneration capacity of Lgr5⁺ intestinal stem cells. In addition, we investigated the effects of radiation damage on sexual dimorphism in HFD-fed mice. The results showed that the degree of IR-induced intestinal injury was more severe in the HFD-fed female mice. MLT preserved the intestinal microbiota composition of HFD-fed mice and increased the abundance of Bacteroides and Proteobacteria in male and female mice, respectively. In conclusion, MLT may reduce the negative effects of HFD and IR, thereby providing assistance in preserving the structure and function of the intestine.

Comparative secretome analysis between salinity-tolerant and control Chlamydomonas reinhardtii strains

Secretome analysis of a salt-tolerant and control Chlamydomonas reinhardtii revealed 514 differentially expressed proteins. Membrane transport and trafficking, signal transduction and channel proteins were up-regulated in the ST secretome. Salinity is a major abiotic stress that limits crop production worldwide. Multiple adverse effects have been reported in many living organisms exposed to high-saline concentrations. Chlamydomonas reinhardtii is known for secreting proteins in response to many environmental stresses. A salinity-tolerant (ST) strain of Chlamydomonas has been developed, whose cells were able to grow at 300 mM NaCl. The current study analyzed the secretomes of ST grown in TAP medium supplemented with 300 mM NaCl and the laboratory strain CC-503 grown in TAP medium without NaCl supplement. In total, 514 secreted proteins were identified of which 203 were up-regulated and 110 were down-regulated. Bioinformatic analysis predicted 168 proteins to be secreted or in the conventional secretory pathway. Out of these, 70 were up-regulated, while 51 proteins were down-regulated. Proteins involved in membrane transport and trafficking, signal transduction and channel proteins were altered in their expression in the ST secretome, suggesting the response of saline stress acts toward not only the intracellular pool of proteins but also the extracellular proteins. This also suggested that the secreted proteins might have roles in the extracellular space. Signal peptide (SP) prediction revealed that almost 40% of the predicted secreted proteins contained a signal peptide; however, a high proportion of proteins lacked an SP, suggesting that these proteins might be secreted through an unconventional protein secretion pathway.

Effect of melatonin on visceral fat deposition, lipid metabolism and hepatic lipo-metabolic gene expression in male rats

Melatonin (MT) influences lipid metabolism in animals; however, the mechanistic effect of melatonin on liver fat and abdominal adipose deposition requires further clarity. In order to study the effects of melatonin on lipid metabolism, and hepatic fat and abdominal adipose deposition in animals, twenty Sprague-Dawley (SD) rats of 6 weeks of age with similar bodyweight were randomly divided into two groups: control (CTL) and MT-treated (10 mg/kg/day). During a 60-day experiment, food intake and bodyweight were measured daily and weekly respectively. At the end of treatment, blood samples were collected to collect plasma to quantify hormones and metabolic indicators of lipid metabolism. In addition, organ and abdominal adipose depots including liver, and omental, perirenal, and epididymal fat were weighed. Liver tissue was sampled for sectioning, long-chain fatty acid (LCFA) quantification, and gene chip and Real-time quantitative PCR (qPCR) analyses. The results showed that liver weight and index (ratio of liver weight to body weight) in MT group reduced by 20.69% and 9.63% respectively; omentum weight and index reduced by 59.88% and 54.93% respectively, and epididymal fat weight reduced by 45.34% (p = 0.049), relative to CTL. Plasma lipid indices, triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL) and total cholesterol (TC) with MT treatment decreased significantly compared with the control. Fat and 8 LCFA content in liver in MT group also decreased. Gene chip and qPCR demonstrated that there were 289 genes up-regulated and 293 genes down-regulated by MT. Further analysis found that the mRNA expression of lipolysis-related genes increased, while the mRNA expression of lipogenesis-related enzymes decreased (p < 0.05) with MT. This study concluded that melatonin greatly affected fat deposition, and hepatic LCFA supply and the expression of genes associated with lipogenesis and lipolysis.

Protective role of melatonin in early-stage and end-stage liver cirrhosis

The liver is composed of hepatocytes, cholangiocytes, Kupffer cells, sinusoidal endothelial cells, hepatic stellate cells (HSCs) and dendritic cells; all these functional and interstitial cells contribute to the synthesis and secretion functions of liver tissue. However, various hepatotoxic factors including infection, chemicals, high‐fat diet consumption, surgical procedures and genetic mutations, as well as biliary tract diseases such as sclerosing cholangitis and bile duct ligation, ultimately progress into liver cirrhosis after activation of fibrogenesis. Melatonin (MT), a special hormone isolated from the pineal gland, participates in regulating multiple physiological functions including sleep promotion, circadian rhythms and neuroendocrine processes. Current evidence shows that MT protects against liver injury by inhibiting oxidation, inflammation, HSC proliferation and hepatocyte apoptosis, thereby inhibiting the progression of liver cirrhosis. In this review, we summarize the circadian rhythm of liver cirrhosis and its potential mechanisms as well as the therapeutic effects of MT on liver cirrhosis and earlier‐stage liver diseases including liver steatosis, nonalcoholic fatty liver disease and liver fibrosis. Given that MT is an antioxidative and anti‐inflammatory agent that is effective in eliminating liver injury, it is a potential agent with which to reverse liver cirrhosis in its early stage.

Melatonin Improves Fatty Liver Syndrome by Inhibiting the Lipogenesis Pathway in Hamsters with High-Fat Diet-Induced Hyperlipidemia

The aim of this study was to investigate the effect of melatonin on hepatic lipid metabolism in hamsters with high-fat diet (HFD)-induced dyslipidemia. Male Syrian hamsters were kept on either a chow control (C) or HFD for four weeks. After four weeks, animals fed the HFD were further randomly assigned to four groups: high-fat only (P), melatonin low-dosage (L), medium-dosage (M), and high-dosage (H) groups. The L, M, and H groups, respectively, received 10, 20, and 50 mg/kg/day of a melatonin solution, while the P and C groups received the ethanol vehicle. After eight weeks of the intervention, results showed that a low dose of melatonin significantly reduced HFD-induced hepatic cholesterol and triglycerides; decreased plasma cholesterol, triglycerides, and low-density lipoprotein cholesterol; and increased plasma high-density lipoprotein cholesterol (p < 0.05). In addition, melatonin markedly decreased activities of the hepatic lipogenic enzymes, acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) (p < 0.05), and elevated the relative hepatic carnitine palmitoyltransferase-1α expression in hamsters with HFD-induced hyperlipidemia. Consequently, melatonin reduced activities of the hepatic lipogenic enzymes, ACC and FAS. In summary, chronic melatonin administration improved HFD-induced dyslipidemia and hepatic lipid accumulation in Syrian hamsters with HFD-induced dyslipidemia, which might have occurred through inhibiting the lipogenesis pathway.

High-fat diet affects pregestational adiposity and glucose tolerance perturbing gestational placental macronutrient transporters culminating in an obese offspring in wild-type and glucose transporter isoform 3 heterozygous null mice

We examined the effect of a high-fat diet (HFD) vs. control diet (CD) upon pregestational and gestational wild-type (wt) and glucose transporter (glut)3 heterozygous (glut3^+/-) female mice and observed an increase in pregestational body weights, white adiposity (wt > glut3^+/-), circulating cholesterol, and high-density lipoproteins, with glucose intolerance in both genotypes. The HFD-exposed offspring displayed reduced birth weight with catch up to CD-fed in wt vs. an increased birth weight persisting as such at weaning by day 21 in glut3^+/- mice. To decipher the mechanism behind this genotype-specific difference in the HFD offspring's phenotype, we first examined placental macronutrient transporters and noted HFD-induced increase in CD36 in wt with no change in other FATPs, sodium-coupled neutral amino acid transporters and system L amino acid transporter in both genotypes. In contrast, while placental Glut1 increased in both the genotypes, only Glut3 increased in the glut3^+/- genotype in response to HFD. Hence, we next assessed glut3^+/- embryonic (ES) cells under differing stressors of low glucose, hypoxia and inhibition of oxidative phosphorylation. Reduced Glut3-mediated glucose uptake in glut3^+/- vs. wt ES cells culminated in deficient growth. We conclude that maternal HFD affects the in utero growth potential of the offspring by altering placental CD36 and Glut1 concentrations. In contrast, a differential effect on placental Glut3 concentrations between glut3^+/- and wt genotypes is evident, with an increase occurring in the glut3^+/- genotype alone. Deficient Glut3 in ES cells interferes with glucose uptake, cell survival and growth being further exaggerated with low glucose, hypoxia and inhibition of oxidative phosphorylation.

Comparison of Goto-Kakizaki rats and high fat diet-induced obese rats: Are they reliable models to study Type 2 Diabetes mellitus?

Type 2 Diabetes mellitus (T2DM) is an evident growing disease that affects different cultures throughout the world. T2DM occurs under the influence of three main factors: the genetic background, environmental and behavioral components. Obesity is strongly associated to the development of T2DM in the occident, while in the orient most of the diabetic patients are considered lean. Genetics may be a key factor in the development of T2DM in societies where obesity is not a recurrent public health problem. Herein, two different models of rats were used to understand their differences and reliability as experimental models to study the pathophysiology of T2DM, in two different approaches: the genetic (GK rats) and the environmental (HFD-induced obese rats) influences. GK rats were resistant to weight gain even though food/energy consumption (relative to body weight) was higher in this group. HFD, on the other hand, induced obesity in Wistar rats. White adipose tissue (WAT) expansion in this group was accompanied by immune cells infiltration, inflammation and insulin resistance. GK rats also presented WAT inflammation and insulin resistance; however, no immune cells infiltration was observed in the WAT of this group. Liver of HFD group presented fat accumulation without differences in inflammatory cytokines content, while liver of GK rats didn't present fat accumulation, but showed an increase of IL-6 and IL-10 content and glycogen. Also, GK rats showed increased plasma GOT and GPT. Soleus muscle of HFD presented normal insulin signaling, contrary to GK rats, which presented higher content of basal phosphorylation of GSK-3β. Our results demonstrated that HFD developed a mild insulin resistance in Wistar rats, but was not sufficient to develop T2DM. In contrast, GK rats presented all the typical hallmarks of T2DM, such as insulin resistance, defective insulin production, fasting hyperglycemia/hyperinsulinemia and lipid plasma alteration. Thus, on the given time point of this study, we may conclude that only GK rats shown to be a reliable model to study T2DM.