Comparative aspects of lipid metabolism: impact on contemporary research and use of animal models

Insights into the interplay between gut microbiota and lipid metabolism in the obesity management of canines and felines

Obesity is a prevalent chronic disease that has significant negative impacts on humans and our companion animals, including dogs and cats. Obesity occurs with multiple comorbidities, such as diabetes, hypertension, heart disease and osteoarthritis in dogs and cats. A direct link between lipid metabolism dysregulation and obesity-associated diseases has been implicated. However, the understanding of such pathophysiology in companion animals is limited. This review aims to address the role of lipid metabolism in various metabolic disorders associated with obesity, emphasizing the involvement of the gut microbiota. Furthermore, we also discuss the management of obesity, including approaches like nutritional interventions, thus providing novel insights into obesity prevention and treatment for canines and felines.

Development of fatty liver disease model using high cholesterol and low choline diet in white leghorn chickens

Nonalcoholic fatty liver disease (NAFLD), which shows similar symptoms as fatty liver hemorrhage syndrome (FLHS) in chickens, is the most common cause of chronic liver disease and cancer in humans. NAFLD patients and FLHS in chickens have demonstrated severe liver disorders when infected by emerging strains of human hepatitis E virus (HEV) and avian HEV, respectively. We sought to develop a fatty liver disease chicken model by altering the diet of 3-week-old white leghorn chickens. The high cholesterol, and low choline (HCLC) diet included 7.6% fat with additional 2% cholesterol and 800 mg/kg choline in comparison to 5.3% fat, and 1,300 mg/kg choline in the regular diet. Our diet induced fatty liver avian model successfully recapitulates the clinical features seen during NAFLD in humans and FLHS in chickens, including hyperlipidemia and hepatic steatosis, as indicated by significantly higher serum triglycerides, serum cholesterol, liver triglycerides, cholesterol, and fatty acids. By developing this chicken model, we expect to provide a platform to explore the role of lipids in the liver pathology linked with viral infections and contribute to the development of prophylactic interventions.

Gene co-expression network analysis for porcine intramuscular fatty acid composition

In pigs, meat quality depends markedly on the fatty acid (FA) content and composition of the intramuscular fat, which is partly determined by the gene expression in this tissue. The aim of this work was to identify the link between muscle gene expression and its FA composition. In an (Iberian × Duroc) × Duroc backcrossed pig population, we identified modules of co-expressed genes, and correlation analyses were performed for each of them versus the phenotypes, finding four relevant modules. Two of the modules were positively correlated with saturated FAs (SFAs) and monounsaturated FAs (MUFAs), while negatively correlated with polyunsaturated FAs (PUFAs) and the omega-6/omega-3 ratio. The gene-enrichment analysis showed that these modules had over-representation of pathways related with the biosynthesis of unsaturated FAs, the Peroxisome proliferator-activated receptor signalling pathway and FA elongation. The two other relevant modules were positively correlated with PUFA and the n-6/n-3 ratio, but negatively correlated with SFA and MUFA. In this case, they had an over-representation of pathways related with fatty and amino acid degradation, and with oxidative phosphorylation. Using a graphical Gaussian model, we inferred a network of connections between the genes within each module. The first module had 52 genes with 87 connections, and the most connected genes were ADIPOQ, which is related with FA oxidation, and ELOVL6 and FABP4, both involved in FA metabolism. The second module showed 196 genes connected by 263 edges, being FN1 and MAP3K11 the most connected genes. On the other hand, the third module had 161 genes connected by 251 edges and ATG13 was the top neighbouring gene, while the fourth module had 224 genes and 655 connections, and its most connected genes were related with mitochondrial pathways. Overall, this work successfully identified relevant muscle gene networks and modules linked with FA composition, providing further insights on how the physiology of the pigs influences FA composition.

The Long Non-Coding RNA Obesity-Related (Obr) Contributes To Lipid Metabolism Through Epigenetic Regulation

Obesity is a multifactorial disease that is part of today's epidemic and also increases the risk of other metabolic diseases. Long noncoding RNAs (lncRNAs) provide one tier of regulatory mechanisms to maintain metabolic homeostasis. Although lncRNAs are a significant constituent of the mammalian genome, studies aimed at their metabolic significance, including obesity, are only beginning to be addressed. Here, a developmentally regulated lncRNA, termed as obesity related (Obr), whose expression in metabolically relevant tissues such as skeletal muscle, liver, and pancreas is altered in diet-induced obesity, is identified. The Clone 9 cell line and high-fat diet-induced obese Wistar rats are used as a model system to verify the function of Obr. By using stable expression and antisense oligonucleotide-mediated downregulation of the expression of Obr followed by different molecular biology experiments, its role in lipid metabolism is verified. It is shown that Obr associates with the cAMP response element-binding protein (Creb) and activates different transcription factors involved in lipid metabolism. Its association with the Creb histone acetyltransferase complex, which includes the cAMP response element-binding protein (CBP) and p300, positively regulates the transcription of genes involved in lipid metabolism. In addition, Obr is regulated by Pparγ in response to lipid accumulation.

Incremental supply of fat, lactose, or protein influences the diurnal pattern of heat production and substrate oxidation in pre-weaning calves

Increasing nutrient supply to dairy calves has well known benefits; however, the effects of milk replacer (MR) composition when supplied in higher amounts are not fully understood, particularly in the first weeks of life. To better understand the metabolism of macronutrient supply in young calves (21 d old), we investigated diurnal patterns of heat production and substrate oxidation in young calves fed MR with an incremental supply of fat, lactose, or protein. Thirty-two groups of 3 mixed-sex Holstein-Friesian newborn calves (3.4 ± 1.6 d of age), were randomly assigned to one of 4 dietary treatments and studied for 21 d. Diets consisted of a basal MR (23.3% CP, 21.2% EE, and 48.8% lactose of DM) fed at 550 kJ/kg BW0.85 per day (CON; n = 24), or the basal MR incrementally supplied with 126 kJ of DE/BW0.85 per day as milk fat (+FAT; n = 23), lactose (+LAC; n = 24), or milk protein (+PRO; n = 23). Calves were fed MR in 2 daily meals and had ad libitum access to water, but were not supplied with any calf starter nor forage. After 2 weeks of adaptation to the diets, groups of 3 calves were placed for 1 week in an open-circuit respiration chamber for nitrogen and energy balance measurements (lasting 7 d). On d 3, glucose oxidation kinetics was estimated by using [U-13C]glucose. Measurements included total heat production (total energy [HP], activity [Hact] expenditure, resting metabolic rate [RMR]), respiration quotient (RQ), carbohydrate (COX) and fat oxidation (FOX) in 10 min. intervals and averaging these values per hour over days. Incremental supply of lactose and fat increased body fat deposition, with observed patterns in RMR indicating that this increase occurred primarily after the meals. Specifically, the average daily RMR was highest in the +PRO group and lowest in the CON treatment. The HP was higher in the +PRO group and throughout the day, hourly means of HP were higher in this treatment mainly caused by an increase in Hact. The recovery of 13CO2 from oral pulse-dosed [U-13C]glucose was high (77%), and not significantly different between treatments, indicating that ingested lactose was oxidized to a similar extent across treatments. Increasing lactose supply in young calves increased fat retention by reduction in fatty oxidation. Calves fed a MR with additional protein or fat raised RMR persistently throughout the day, while extra lactose supply only affects RMR after the meal. Dietary glucose was almost completely oxidized (77% based on (13C) glucose measurement) regardless of nutrient supplementation. Extra protein supply increased HP and FOX compared with similar intakes of fat and lactose. Fasting heat production (FHP) of young, group-housed calves is comparable to literature values and unaffected by energy intake. Overall, these findings deepen our understanding of how different nutrients impact metabolic processes, fat retention, and energy expenditure in young dairy calves.

Metabolic remodelling in atrial fibrillation: manifestations, mechanisms and clinical implications

Atrial fibrillation (AF) is a continually growing health-care burden that often presents together with metabolic disorders, including diabetes mellitus and obesity. Current treatments often fall short of preventing AF and its adverse outcomes. Accumulating evidence suggests that metabolic disturbances can promote the development of AF through structural and electrophysiological remodelling, but the underlying mechanisms that predispose an individual to AF are aetiology-dependent, thus emphasizing the need for tailored therapeutic strategies to treat AF that target an individual's metabolic profile. AF itself can induce changes in glucose, lipid and ketone metabolism, mitochondrial function and myofibrillar energetics (as part of a process referred to as 'metabolic remodelling'), which can all contribute to atrial dysfunction. In this Review, we discuss our current understanding of AF in the setting of metabolic disorders, as well as changes in atrial metabolism that are relevant to the development of AF. We also describe the potential of available and emerging treatment strategies to target metabolic remodelling in the setting of AF and highlight key questions and challenges that need to be addressed to improve outcomes in these patients.

Effects of diets containing fish oils or fish oil concentrates with high cetoleic acid content on the circulating cholesterol concentration in rodents. A systematic review and meta-analysis

Hypercholesterolaemia is a major risk factor for CVD. Fish intake is associated with lower risk of CVD, whereas supplementation with n-3 long-chain PUFA (LC-PUFA) has little effect on the cholesterol concentration. We therefore investigated if cetoleic acid (CA), a long-chain MUFA (LC-MUFA) found especially in pelagic fish species, could lower the circulating total cholesterol (TC) concentration in rodents. A systematic literature search was performed using the databases PubMed, Web of Science and Embase, structured around the population (rodents), intervention (CA-rich fish oils or concentrates), comparator (diets not containing CA) and the primary outcome (circulating TC). Articles were assessed for risk of bias using the SYRCLE's tool. A meta-analysis was conducted in Review Manager v. 5.4.1 (the Cochrane Collaboration) to determine the effectiveness of consuming diets containing CA-rich fish oils or concentrates on the circulating TC concentration. Twelve articles were included in the systematic review and meta-analysis, with data from 288 rodents. Consumption of CA-rich fish oils and concentrates resulted in a significantly lower circulating TC concentration relative to comparator groups (mean difference -0·65 mmol/l, 95 % CI (-0·93, -0·37), P < 0·00001), with high statistical heterogeneity (I2 = 87 %). The risk of bias is unclear since few of the entries in the SYRCLE's tool were addressed. To conclude, intake of CA-rich fish oils and concentrates prevents high cholesterol concentration in rodents and should be further investigated as functional dietary ingredients or supplements to reduce the risk for developing CVD in humans.

Upregulated hepatic lipogenesis from dietary sugars in response to low palmitate feeding supplies brain palmitate

Palmitic acid (PAM) can be provided in the diet or synthesized via de novo lipogenesis (DNL), primarily, from glucose. Preclinical work on the origin of brain PAM during development is scarce and contrasts results in adults. In this work, we use naturally occurring carbon isotope ratios (13C/12C; δ13C) to uncover the origin of brain PAM at postnatal days 0, 10, 21 and 35, and RNA sequencing to identify the pathways involved in maintaining brain PAM, at day 35, in mice fed diets with low, medium, and high PAM from birth. Here we show that DNL from dietary sugars maintains the majority of brain PAM during development and is augmented in mice fed low PAM. Importantly, the upregulation of hepatic DNL genes, in response to low PAM at day 35, demonstrates the presence of a compensatory mechanism to maintain total brain PAM pools compared to the liver; suggesting the importance of brain PAM regulation.

Tumor lipid metabolism: a mechanistic link between diet and cancer progression

The potential for 'anti-cancer' diets to markedly alter cancer risk and prognosis has captured the imagination of patients, physicians, and researchers alike, but many of these dietary recommendations come from correlative studies that attribute certain diets to altered cancer risk. While provocative, little is known about the molecular mechanisms behind how these dietary interventions impact cancer progression. Within this context, however, changes in tumor lipid metabolism are emerging as a key contributor. In this review, we examine the current understanding of lipid metabolism in the tumor microenvironment (TME), suggesting how diet-induced changes in lipid composition may regulate tumor progression and therapeutic efficacy. By dissecting various cellular pathways involved in lipid metabolism, we highlight how diet modulates the balance between saturated and unsaturated fatty acid (FA) species in tumors to impact cancer cell and stromal cell function. Finally, we describe how current cancer therapies may synergize with diet to improve therapeutic efficacy.

Fibroblast Growth Factor 21 Has a Diverse Role in Energetic and Reproductive Physiological Functions of Female Beef Cattle

Fibroblast growth factor 21 (FGF21) has been identified in multiple mammalian species as a molecular marker of energy metabolism while also providing negative feedback to the gonads. However, the role of FGF21 in regulating the energetic and reproductive physiology of beef heifers and cows has yet to be characterized. Herein, we investigated the temporal concentrations of FGF21 in female beef cattle from the prepubertal period to early lactation. Circulating concentrations of FGF21, non-esterified fatty acids, plasma urea nitrogen, glucose, and progesterone were assessed. Ultrasonography was employed to determine the onset of puberty and resumption of postpartum ovarian cyclicity as well as to measure backfat thickness. Finally, cows and calves underwent the weigh-suckle-weigh technique to estimate rate of milk production. We have revealed that FGF21 has an expansive role in the physiology of female beef cattle, including pubertal onset, adaptation to nutritional transition, rate of body weight gain, circulating markers of metabolism, and rate of milk production. In conclusion, FGF21 plays a role in physiological functions in beef cattle that can be applied to advance the understanding of basic scientific processes governing the nutritional regulation of reproductive function but also provides a novel means for beef cattle producers to select parameters of financial interest.

Effects of uni and bilateral castration on growth performance and lipid metabolism in yellow cattle

This study was conducted to examine the influence of uni and bilateral castration on growth performance and lipid metabolism in yellow cattle. Eighteen 9-month-old healthy yellow cattle (average body weight 184.03 ± 4.09 kg) were selected and divided into three groups: The uncastrated cattle (C), half castrated cattle (HC) and full castrated cattle (FC). The results showed that the growth rate of FC group was significantly reduced as compared to HC and C group, while the feed to gain ratio exhibited an opposite trend. The concentrations of triglycerides (TG), low-density lipoprotein cholesterol (LDL) and high-density lipoprotein (HDL) were increased significantly in FC group from day 60 to the end of the trial compared to HC and control groups. Serum testosterone concentration of FC group cattle was decreased from day 60 to 120 d of the trial compared to HC and control groups. The concentration of the lauric acid in FC cattle was significantly increased from the HC and control groups. In the FC group, the acetyl-CoA carboxylase alpha (ACACA), ACC and fatty acid synthase (FAS) gene expression levels were significantly higher compared to control and HC groups. Our results of this study suggest that bilateral castration increased the lipid metabolism and fatty acid composition compared to unilateral castrated and un-castrated cattle.HighlightsBilateral castration alters the growth performance in yellow cattle.Bilateral castration alters hormones levels and lipid metabolites levels in serum.Bilateral castration improves the lipid metabolism and fatty acid profile.

Nonhuman primate genetic models for the study of rare diseases

Pre-clinical research and development relies heavily upon translationally valid models of disease. A major difficulty in understanding the biology of, and developing treatments for, rare disease is the lack of animal models. It is important that these models not only recapitulate the presentation of the disease in humans, but also that they share functionally equivalent underlying genetic causes. Nonhuman primates share physiological, anatomical, and behavioral similarities with humans resulting from close evolutionary relationships and high genetic homology. As the post-genomic era develops and next generation sequencing allows for the resequencing and screening of large populations of research animals, naturally occurring genetic variation in nonhuman primates with clinically relevant phenotypes is regularly emerging. Here we review nonhuman primate models of multiple rare genetic diseases with a focus on the similarities and differences in manifestation and etiologies across species. We discuss how these models are being developed and how they can offer new tools and opportunities for researchers interested in exploring novel therapeutics for these and other genetic diseases. Modeling human genetic diseases in translationally relevant nonhuman primates presents new prospects for development of therapeutics and a better understanding of rare diseases. The post-genomic era offers the opportunity for the discovery and further development of more models like those discussed here.

Biochemical Activation and Regulatory Functions of Trans-Regulatory KLF14 and Its Association with Genetic Polymorphisms

Krüpple-Like family of transcription factor-14 (KLF14) is a master trans-regulatory gene that has multiple biological regulatory functions and is involved in many pathological mechanisms. It controls the expressions of several other genes which are involved in multiple regulatory functions. KLF14 plays a significant role in lipid metabolism, glucose regulation and insulin sensitivity. Cell apoptosis, proliferation, and differentiation are regulated by the KLF14 gene, and up-regulation of KLF14 prevents cancer progression. KLF14 has been used as an epigenetic biomarker for the estimation of chronological age due to the presence of different age-related CpG sites on genes that become methylated with age. Different genome-wide association studies have identified several KLF14 variants in adipose tissues. These single nucleotide polymorphisms in KLF14 have been associated with dyslipidemia, insulin resistance, and glucose intolerance. Moreover, the prevalence of genetic polymorphism is different in different populations due to ethnic differences and epigenetic modifications. In addition, environmental and physiological factors such as diet, age, gender, and obesity are also responsible for genetic mutations in KLF14.

Efficacy and safety of metabolic interventions for the treatment of severe COVID-19: in vitro, observational, and non-randomized open-label interventional study

Background

Viral infection is associated with a significant rewire of the host metabolic pathways, presenting attractive metabolic targets for intervention.

Methods

We chart the metabolic response of lung epithelial cells to SARS-CoV-2 infection in primary cultures and COVID-19 patient samples and perform in vitro metabolism-focused drug screen on primary lung epithelial cells infected with different strains of the virus. We perform observational analysis of Israeli patients hospitalized due to COVID-19 and comparative epidemiological analysis from cohorts in Italy and the Veteran's Health Administration in the United States. In addition, we perform a prospective non-randomized interventional open-label study in which 15 patients hospitalized with severe COVID-19 were given 145 mg/day of nanocrystallized fenofibrate added to the standard of care.

Results

SARS-CoV-2 infection produced transcriptional changes associated with increased glycolysis and lipid accumulation. Metabolism-focused drug screen showed that fenofibrate reversed lipid accumulation and blocked SARS-CoV-2 replication through a PPARα-dependent mechanism in both alpha and delta variants. Analysis of 3233 Israeli patients hospitalized due to COVID-19 supported in vitro findings. Patients taking fibrates showed significantly lower markers of immunoinflammation and faster recovery. Additional corroboration was received by comparative epidemiological analysis from cohorts in Europe and the United States. A subsequent prospective non-randomized interventional open-label study was carried out on 15 patients hospitalized with severe COVID-19. The patients were treated with 145 mg/day of nanocrystallized fenofibrate in addition to standard-of-care. Patients receiving fenofibrate demonstrated a rapid reduction in inflammation and a significantly faster recovery compared to patients admitted during the same period.

Conclusions

Taken together, our data suggest that pharmacological modulation of PPARα should be strongly considered as a potential therapeutic approach for SARS-CoV-2 infection and emphasizes the need to complete the study of fenofibrate in large randomized controlled clinical trials.

Funding

Funding was provided by European Research Council Consolidator Grants OCLD (project no. 681870) and generous gifts from the Nikoh Foundation and the Sam and Rina Frankel Foundation (YN). The interventional study was supported by Abbott (project FENOC0003).

Clinical trial number

NCT04661930.

The impact of moderate endurance exercise on cardiac telomeres and cardiovascular remodeling in obese rats

Introduction

Hypercaloric nutrition and physical inactivity cause obesity, a potential driver of myocardial apoptosis and senescence that may accelerate cardiac aging. Although physical activity reduces mortality, its impact on myocardial aging is insufficiently understood. Here we investigated the effects of a hypercaloric high-fat diet (HFD) and regular exercise training on cardiac cells telomeres and histomorphometric indices of cardiac aging.

Methods

Ninety-six 4-months old female Sprague-Dawley rats were fed for 10 months normal (ND) or a HFD diet. Half of the animals in each group performed 30 min treadmill-running sessions on 5 consecutive days per week. At study end, cardiomyocyte cross-sectional area (CSA), interstitial collagen content, vascular density, apoptotic and senescent cells, relative telomere length (RTL), and expression of telomerase-reverse transcriptase (Tert) as marker of telomere-related senescence and apoptosis were analyzed.

Results

Compared to ND, the HFD group developed obesity, higher CSA, lower capillary density and tended to have more apoptotic cardiomyocytes and interstitials cells. Myocardial RTL and the expression of Terf-1 and Terf-2 were comparable in sedentary HFD and ND animals. In the HFD group, regular moderate endurance exercise improved myocardial vascularization, but had no effect on CSA or apoptosis. Notably, the combination of exercise and HFD increased senescence when compared to sedentary ND or HFD, and reduced RTL when compared to exercise ND animals. Exercising HFD animals also showed a trend toward higher Tert expression compared to all other groups. In addition, exercise reduced Terf-1 expression regardless of diet.

Conclusion

HFD-induced obesity showed no effects on myocardial telomeres and induced only mild morphologic alterations. Summarized, long-term moderate endurance exercise partially reverses HFD-induced effects but may even trigger cardiac remodeling in the context of obesity.

Graduate Student Literature Review: A scoping review on the impact of consumption of dairy products on phosphatidylcholine and lysophosphatidylcholine in circulation and the liver in human studies and animal models

Dairy consumption is inversely related to the risk of developing type 2 diabetes in epidemiological research. One proposed hypothesis is that phospholipid (PL) species associated with dairy consumption mediate this relationship. This scoping review aimed to identify the existing literature in animal and human trials investigating the impact of dairy products, including milk, yogurt, and cheese as well as dairy-derived PL supplementation on PL and its species in the circulation, summarizing the characteristics of these studies and identifying research gaps. A systematic search was conducted across 3 databases (PubMed, Scopus, and Web of Science) in March 2021. Of 2,427 identified references, 15 studies (7 humans and 8 animal studies) met the eligibility criteria and were included in the final narrative synthesis. The evidence base was heterogeneous, involving a variety of clinical and preclinical studies, metabolically healthy or obese/diabetic participants or animal models, and displayed mixed findings. Circulating postprandial concentrations of total PL were elevated acutely but unchanged after longer intervention with dairy products. The PL concentration remained stable even after a high dosage of milk supplemented with dairy-derived PL, which may be related to increased fecal excretion; however, certain phosphatidylcholine (PC) or lysophosphatidylcholine species were increased in circulation by interventions. These include several PC species with 32 to 38 total carbons in addition to the dairy biomarkers C15:0 and C17:0. The results of this scoping review demonstrate a small body of literature indicating that dairy products can influence blood concentrations of PC and lysophosphatidylcholine species in both rodents and humans without alteration of total PL and PC. There is a lack of well-designed trials in humans and animals that explore the potential differences between individual dairy foods on PL species. In addition, trials to understand the bioactive properties of PC and lysophosphatidylcholine species on cardiometabolic risk are needed.

Effects of diets containing proteins from fish muscles or fish by-products on the circulating cholesterol concentration in rodents: a systematic review and meta-analysis

A high circulating cholesterol concentration is considered an important risk factor for the development of CVD. Since lean fish intake and fish protein supplementation have been associated with lower cholesterol concentration in some but not all clinical studies, the main aim of this study was to investigate the effect of diets containing proteins from fish muscles and fish by-products on the serum/plasma total cholesterol (TC) concentration in rodents. A systematic literature search was performed using the databases PubMed, Web of Science and Embase, structured around the population (rodents), intervention (type of fish and fraction, protein dose and duration), comparator (casein) and the primary outcome (circulating TC). Articles were assessed for risk of bias using the SYRCLE's tool. A meta-analysis was conducted in Review Manager v. 5·4·1 (the Cochrane Collaboration) to determine the effectiveness of proteins from fish on the circulating TC concentration. Thirty-nine articles were included in the systematic review and meta-analysis, with data from 935 rodents. The risk of bias is unclear since few of the entries in the SYRCLE's tool were addressed. Consumption of proteins from fish resulted in a significantly lower circulating TC concentration when compared with control groups (mean difference -0·24 mmol/l, 95 % CI - 0·34, -0·15, P < 0·00001), with high statistical heterogeneity (I² = 71 %). To conclude, proteins from fish muscles and by-products show promise as a functional dietary ingredient or supplement by preventing high cholesterol concentration in rodents, thus reducing one of the most important risk factors for developing CVD.

Nutritional Characterization, Antioxidant, and Lipid-Lowering Effects of Yellow Mombin (Spondias mombin) Supplemented to Rats Fed a High-Fat Diet

The aim of this study was to evaluate the effects of supplementing yellow mombin (YM) on the oxidative, somatic, and lipid parameters in rats fed a high-fat diet. A total of 24 adult Wistar rats were randomized into three groups: normal-fat diet (NF), high-fat diet (HF), and high-fat diet with YM supplementation (HFYM). Diets were administered for four weeks, and YM (400 mg/kg) was supplemented via gavage in the last two weeks of the experiment. After the four-week period, the somatic, serum biochemical, and liver oxidative parameters were evaluated. YM has a high antioxidant activity and significant amounts of phenolic compounds, carotenoids, vitamin C, dietary fibre, and minerals. The HFYM group had the lowest body weight (18.75%), body mass index (17.74%), and adiposity (31.63%) compared with the HF group. YM supplementation reduced low-density lipoprotein by 43.05% and increased high-density lipoprotein by 25.73%, but did not improve the triglyceride levels in the serum. YM treatment improved glucose tolerance and lipid peroxidation, and also enhanced the antioxidant capacity, superoxide dismutase, and glutathione peroxidase activities in the liver. These results indicate the lipid-lowering property and potential antioxidant activity of YM against liver oxidative damage caused by a high-fat diet intake, which may be associated with the bioactive compounds present in this fruit.

Crossbred Sows Fed a Western Diet during Pre-Gestation, Gestation, Lactation, and Post-Lactation Periods Develop Signs of Lean Metabolic Syndrome That Are Partially Attenuated by Spirulina Supplementation

Excessive dietary intake of fats and sugars (“Western diet”, WD) is one of the leading causes of obesity. The consumption of the microalga Arthrospira platensis (spirulina, Sp) is increasing due to its presumed health benefits. Both WD and Sp are also consumed by pregnant and breastfeeding women. This study investigated if gestating and lactating domestic pigs are an appropriate model for WD-induced metabolic disturbances similar to those observed in humans and if Sp supplementation may attenuate any of these adverse effects. Pigs were fed a WD high in fat, sugars, and cholesterol or a control diet. Half of the animals per diet group were supplemented with 20 g Sp per day. The WD did not increase body weight or adipose tissue accumulation but led to metabolic impairments such as higher cholesterol concentration in plasma, lower IGF1 plasma levels, and signs of hepatic damage compared to the control group. Spirulina supplementation could not reduce all the metabolic impairments observed in WD-fed animals. These findings indicate limited suitability of gestating and lactating domestic pigs as a model for WD but a certain potential of low-dose Sp supplementation to partially attenuate negative WD effects.

Insulin sensitivity is associated with the observed variation of de novo lipid synthesis and body composition in finishing pigs

Variations in body composition among pigs can be associated with insulin sensitivity given the insulin anabolic effect. The study objectives were to characterize this association and to compare de novo lipogenesis and the gene expression in the adipose tissue of pigs of the same genetic background. Thirty 30-95 kg of body weight (BW) pigs, catheterized in the jugular vein participated into an oral glucose tolerance test (OGTT; 1.75 g glucose/kg of BW) to calculate insulin-related indexes. The 8 fattest and the 8 leanest pigs were used to determine the relative mRNA abundance of studied genes. The rate of lipogenesis was assessed by incorporation of [U-¹³C]glucose into lipids. The QUICKI and Matsuda indexes negatively correlated with total body lipids (r =  - 0.67 and r =  - 0.59; P < 0.01) and de novo lipogenesis (r =  - 0.58; P < 0.01). Fat pigs had a higher expression level of lipogenic enzymes (ACACA, ACLY; P < 0.05) than lean pigs. The reduced insulin sensitivity in fat pigs was associated with a higher expression level of glucose-6-phosphate dehydrogenase (G6PD) and a lower expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ). In conclusion, pigs with increased body lipids have lower insulin sensitivity which is associated with increased de novo lipogenesis.

L-Arginine increases AMPK phosphorylation and the oxidation of energy substrates in hepatocytes, skeletal muscle cells, and adipocytes

Previous work has shown that dietary L-arginine (Arg) supplementation reduced white fat mass in obese rats. The present study was conducted with cell models to define direct effects of Arg on energy-substrate oxidation in hepatocytes, skeletal muscle cells, and adipocytes. BNL CL.2 mouse hepatocytes, C2C12 mouse myotubes, and 3T3-L1 mouse adipocytes were treated with different extracellular concentrations of Arg (0, 15, 50, 100 and 400 µM) or 400 µM Arg + 0.5 mM N^G-nitro-L-arginine methyl ester (L-NAME; an NOS inhibitor) for 48 h. Increasing Arg concentrations in culture medium dose-dependently enhanced (P < 0.05) the oxidation of glucose and oleic acid to CO₂ in all three cell types, lactate release from C2C12 cells, and the incorporation of oleic acid into esterified lipids in BNL CL.2 and 3T3-L1 cells. Arg at 400 µM also stimulated (P < 0.05) the phosphorylation of AMP-activated protein kinase (AMPK) in all three cell types and increased (P < 0.05) NO production in C2C12 and BNL CL.2 cells. The inhibition of NOS by L-NAME moderately reduced (P < 0.05) glucose and oleic acid oxidation, lactate release, and the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) in BNL CL.2 cells, but had no effect (P > 0.05) on these variables in C2C12 or 3T3-L1 cells. Collectively, these results indicate that Arg increased AMPK activity and energy-substrate oxidation in BNL CL.2, C2C12, and 3T3-L1 cells through both NO-dependent and NO-independent mechanisms.

Dietary L-arginine supplementation increases the hepatic expression of AMP-activated protein kinase in rats

The goal of this study was to elucidate the molecular mechanisms responsible for the anti-obesity effect of L-arginine supplementation in diet-induced obese rats. Male Sprague-Dawley rats were fed either a low-fat or high-fat diet for 15 weeks. Thereafter, lean or obese rats were pair-fed their same respective diets and received drinking water containing either 1.51% L-arginine-HCl or 2.55% L-alanine (isonitrogenous control) for 12 weeks. Gene and protein expression of key enzymes in the metabolism of energy substrates were determined using real-time polymerase-chain reaction and western blotting techniques. The mRNA levels of hepatic fatty acid synthase and stearoyl-CoA desaturase were reduced (P < 0.05) but those of hepatic AMP-activated protein kinase-α (AMPKα), peroxisome proliferator activator receptor γ coactivator-1α, and carnitine palmitoyltransferase I (CPT-I), as well as skeletal muscle CPT-I were increased (P < 0.05) by L-arginine treatment. The protein expression and activity of hepatic AMPKα markedly increased (P < 0.05) but the activity of hepatic acetyl-CoA carboxylase (ACC) decreased (P < 0.05) in response to dietary L-arginine supplementation. Collectively, our results indicate that liver is the major target for the action of dietary L-arginine supplementation on reducing white-fat mass in diet-induced obese rats by inhibiting fatty acid synthesis and increasing fatty acid oxidation via the AMPK-ACC signaling pathway. Additionally, increased CPT-I expression in skeletal muscle may also contribute to the enhanced oxidation of long-chain fatty acids in L-arginine-supplemented rats.

Effect of arginine supplementation on the production of milk fat in dairy cows

Arginine, one of the conditionally essential AA, has been reported to affect fat synthesis and metabolism in nonruminant animals by influencing adenosine monophosphate activated protein kinase (AMPK) in some organs. In dairy cows, the effect of Arg on milk fat production is not clear, and any potential mechanism that underlies the effect is unknown. We tested the hypothesis that Arg infusion would improve the production of milk fat, and explored possible mechanism that might underlie any effect. We used 6 healthy lactating cows at 20 ± 2 d in milk, in fourth parity, with a body weight of 508 ± 14 kg, body condition score of 3.0 ± 0, and a milk yield of 30.6 ± 1.8 kg/d (mean ± standard deviation). The cows were blocked by days in milk and milk yield and each cow received 3 treatments in a replicated 3 × 3 Latin square design, with each of the experimental periods lasting 7 d with a 14-d washout between each period. The treatments, delivered in random order, were (1) infusion of saline (control); (2) infusion of 0.216 mol/d of l-Arg in saline (Arg); (3) infusion of 0.868 mol/d of l-Ala in saline (the Arg and Ala treatments were iso-nitrogenous) through a jugular vein. On the last day of each experimental period, blood was sampled to measure insulin, nitric oxide, glucose, and nonesterified fatty acid, and the liver and mammary gland were biopsied to measure the expression of genes. Milk yield was recorded, and milk fat percentage was measured daily during each of the experimental periods. The yield and composition of fatty acid (FA) in milk was measured daily on the last 3 d during each of the experimental periods. The data were analyzed using a mixed model with treatment as a fixed factor, and cow, period, and block as random factors. The daily milk yield and milk fat yield when the cows were infused with Arg were 2.2 kg and 76 g, respectively, higher than that in control, and 1.8 kg and 111 g, respectively, higher than that in Ala. When the cows were infused with Arg they had higher concentration and yield of de novo synthesized FA, than when they received the control or Ala infusions, although milk fat percentage, daily feed intake, and the digestibility of nutrients were not affected by treatment. The serum concentration of nitric oxide and insulin were higher during Arg than during control or Ala, with no difference between control and Ala. In the liver, the expression of the genes coding for AMPK (PRKAA1, PRKAB1, and PRKAG1) and genes related to the oxidation of FA were higher during Arg than during control or Ala, whereas in the mammary gland the expression PRKAB1 was lowest, and the expression of genes involved in the synthesis of milk fat were highest, during Arg infusion. The results suggest the intravenous infusion of Arg enhanced the production of milk fat by promoting the de novo synthesis of FA and increasing milk yield.

Effects of Anthocyanin-rich Berries on the Risk of Metabolic Syndrome: A Systematic Review and Meta-analysis

OBJECTIVE: Metabolic syndrome (MetS) can lead to fatal complications, including cardiovascular disease. Emerging evidence suggests has emerged that increased fruit and vegetable intake and decreased intake of saturated fats, simple sugars, and processed foods can improve cardiovascular health. Anthocyanins (color pigments) have anti-inflammatory and antioxidant capacities but are of low bioavailability. In this systematic review and metaanalysis, we investigate the possible beneficial effects of the intake of berries high in anthocyanins on MetS risk factors. We also investigate the influences of high-density lipoprotein (HDL), lowdensity lipoprotein (LDL), triglycerides (TG), and total cholesterol (TC). METHODS: We identified 2,274 articles from PUBMED and EMBASE following a search input designed to include studies of interest of these, 21 met inclusion criteria. RESULTS: The studies showed an overall reduction in low-density lipoprotein (p=0.04). Increases in HDL were found with cranberry and freeze-dried berry intake during a 4-6-week intervention. No statistically significant findings were detected for fasting glucose, Hb1Ac, insulin levels, blood pressure, oxidized LDL (OX-LDL), BMI, and overall HDL. CONCLUSIONS: We conclude from this systematic review and meta-analysis that increased berry intake improves MetS key risk factors and reduces the risk of cardiovascular disease. Pronounced effects were apparent for concentrated berry products, such as freeze-dried strawberries.

De novo lipogenesis in non-alcoholic fatty liver disease: Quantification with stable isotope tracers

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is characterized as an abnormal accumulation of triglyceride in hepatocytes. Hepatic de novo lipogenesis may play an important role in the accumulation of lipids in the liver during NAFLD. Due to the importance of lipid biosynthetic fluxes in NAFLD and T2D, tracer methodologies have been developed for their study and quantification. Here, we address novel approaches to measure and quantify DNL using stable isotope tracers. Deuterated water is a widely used tracer for quantifying DNL rates in both animal models and humans. Enrichment of lipid hydrogens from ² H2O can be resolved and quantified by ² H NMR and MS spectroscopy of isolated lipids. NMR provides a much higher level of positional enrichment information compared with MS which yields a more detailed picture of lipid biosynthetic. It can also be used to quantify low levels of lipid ¹³ C enrichment from a second tracer such as [U-¹³ C]sugar with minimal interference of one tracer with the other.

CONCLUSIONS

Despite the clear association between elevated DNL activity and increased hepatic triglyceride levels, implementation of non-destructive and novel methods to quantify DNL and its contribution to NAFLD are also of huge interest.

The potential effect mechanism of high-fat and high-carbohydrate diet-induced obesity on anxiety and offspring of zebrafish

Anxiety and obesity are two current phenomena. They are among the important public health problems with increasing prevalence worldwide. Although it is claimed that there are strong relations between them, the mechanism of this relationship has not been fully clarified yet. On the other hand, the effect of this relationship on the offspring has been another research subject. In this study, obese zebrafish were obtained by feeding two different diets, one containing high amount of lipid (HF) and the other containing high amount of carbohydrate (HK), and their anxiety levels were evaluated. To establish a relationship between these two phenomena, in addition to histopathological and immunohistochemical analysis in the brain tissues of fish, the transcription levels of some genes related to lipid and carbohydrate metabolisms were determined. In addition, offspring were taken from obese zebrafish and studied to examine the effect of parental obesity on offspring. As a result, it was observed that the HC diet, causing more weight increase than the HF diet, showed an anxiolytic while the HF diet an anxiogenic effect. It was suggested that the probable cause of this situation may be the regulatory effect on the appetite-related genes depending on the upregulation severity of the PPAR gene family based on the diet content. In addition, it was also suggested that it may have contributed to this process in neuron degenerations caused by oxidative stress. Regarding effects on offspring, it can be concluded that HF diet-induced obesity has more negative effects on the next generation than the HC diet.Level of evidenceNo Level of evidence: animal study.

Perspectives on scaling production of adipose tissue for food applications

With rising global demand for food proteins and significant environmental impact associated with conventional animal agriculture, it is important to develop sustainable alternatives to supplement existing meat production. Since fat is an important contributor to meat flavor, recapitulating this component in meat alternatives such as plant based and cell cultured meats is important. Here, we discuss the topic of cell cultured or tissue engineered fat, growing adipocytes in vitro that could imbue meat alternatives with the complex flavor and aromas of animal meat. We outline potential paths for the large scale production of in vitro cultured fat, including adipogenic precursors during cell proliferation, methods to adipogenically differentiate cells at scale, as well as strategies for converting differentiated adipocytes into 3D cultured fat tissues. We showcase the maturation of knowledge and technology behind cell sourcing and scaled proliferation, while also highlighting that adipogenic differentiation and 3D adipose tissue formation at scale need further research. We also provide some potential solutions for achieving adipose cell differentiation and tissue formation at scale based on contemporary research and the state of the field.

The Anti-Obesity Potential of Cyperus rotundus Extract Containing Piceatannol, Scirpusin A and Scirpusin B from Rhizomes: Preclinical and Clinical Evaluations

PURPOSE

Obesity is a complex medical problem that increases the risk of other diseases like diabetes, cardiovascular diseases, and fatty liver disease. The present study evaluated the efficacy and safety of Cyperus rotundus rhizome extract (CRE), standardized to contain Piceatannol, Scirpusin A, and Scirpusin B (5% total Stilbenoids) in overweight individuals. The mechanism of activity was evaluated in a diet-induced mice model of obesity and adipocytes in vitro.

MATERIALS AND METHODS

The efficacy, safety, and tolerability of CRE were evaluated in 30 obese individuals with a BMI of 30 to 40 kg/m² for 90 days in a randomized, double-blind, parallel-group, placebo-controlled study. In vitro studies were carried out in differentiated 3T3 L1 adipocytes, and the therapeutic efficacy was evaluated in high-fat diet-induced obese mice.

RESULTS

The pilot clinical study showed a reduction in body weight with a significant decrease in waist circumference and BMI. The serum lipid profile showed a significant improvement in CRE-treated individuals. The extract was well tolerated, and no adverse effects were reported at the end of the study. CRE showed a dose-dependent adipogenesis reduction in vitro with an IC₅₀ value of 9.39 μg/mL, while oral administration of CRE reduced weight gain in diet-induced obese mice. The efficacy in mice was associated with reduced levels of leptin, corticosteroids, and serum lipid levels, with no adverse effects.

CONCLUSION

CRE has anti-adipogenic properties, is safe for human consumption, and effectively manages weight and hypercholesterolemia in overweight individuals.

Pigs (Sus Scrofa) in Biomedical Research

Much of biomedical oriented research is conducted with animal models. Over the years, rodents (primarily rats and mice) have emerged as the preferred species for basic biochemistry, cell biology, physiology and nutrition studies. In the past, dogs have been used for the evaluation of dietary protein quality and other aspects of animal nitrogen metabolism and physiology, cardiovascular and endocrine research. At an increasing rate, pigs have also been used as a model species in biomedical research. Pigs are readily available in various mature sizes and genotypic/phenotypic traits, and there are many anatomic, nutritional and physiologic similarities between human beings and pigs. Many notable reviews summarizing the role of pigs in biomedical studies have already been published and these are cited below. The present review focuses on characteristics that make pigs an excellent biomedical animal model in particular in obesity, diabetes and cardiovascular research. To procure an animal model for obesity, irrespective of species used, these animals must be fed a dense caloric diet (high fat) to achieve an experimental working model within a reasonable period. This review also focuses on a putative role of gastrointestinal microbiota in obesity as obese animals exhibit a shift in the distribution of gastrointestinal microbial phyla from lean animals. But to date such results have not pinpointed a treatable cause for obesity. Sometimes, the choice of sampling sites for microbial assessment in many reports can be questioned as the microbial content and phyla distribution in easily collected fecal samples may differ from those obtained directly from the small intestine and upper colon. While pigs are still utilized in many countries for medical surgery practice, this has been discontinued in US medical schools.

Targeting Lipid Metabolism for the Treatment of Age-Related Macular Degeneration: Insights from Preclinical Mouse Models

Age-related macular degeneration (AMD) is a major leading cause of irreversible visual impairment in the world with limited therapeutic interventions. Histological, biochemical, genetic, and epidemiological studies strongly implicate dysregulated lipid metabolism in the retinal pigmented epithelium (RPE) in AMD pathobiology. However, effective therapies targeting lipid metabolism still need to be identified and developed for this blinding disease. To test lipid metabolism-targeting therapies, preclinical AMD mouse models are needed to establish therapeutic efficacy and the role of lipid metabolism in the development of AMD-like pathology. In this review, we provide a comprehensive overview of current AMD mouse models available to researchers that could be used to provide preclinical evidence supporting therapies targeting lipid metabolism for AMD. Based on previous studies of AMD mouse models, we discuss strategies to modulate lipid metabolism as well as examples of studies evaluating lipid-targeting therapeutics to restore lipid processing in the RPE. The use of AMD mouse models may lead to worthy lipid-targeting candidate therapies for clinical trials to prevent the blindness caused by AMD.

The Majority of Brain Palmitic Acid is Maintained by Lipogenesis from Dietary Sugars and is Augmented in Mice fed Low Palmitic Acid Levels from Birth

Previously, results from studies investigating if brain palmitic acid (16:0; PAM) was maintained by either dietary uptake or lipogenesis de novo (DNL) varied. Here, we utilize naturally occurring carbon isotope ratios (¹³ C/¹² C; δ¹³ C) to uncover the origin of brain PAM. Additionally, we explored brain and liver fatty acid concentration, total brain metabolomic profile, and behaviour. BALB/c dams were equilibrated onto either a low PAM diet (LP; <2%) or high PAM diet (HP; >95%) prior to producing one generation of offspring. Offspring stayed on the respective diet of the dam until 15-weeks of age, at which time the Open Field test was conducted in the offspring, prior to euthanasia and tissue lipid extraction. Although liver PAM was lower in offspring fed the LP diet, as well as female offspring, brain PAM was not affected by diet or sex. Across offspring of either sex on both diets, brain ¹³ C-PAM revealed compared to dietary uptake, DNL from dietary sugars contributed 68.8%-79.5% and 46.6%-58.0% to the total brain PAM pool by both peripheral and local brain DNL, and local brain DNL alone, respectively. DNL was augmented in offspring fed the LP diet, and the ability to upregulate DNL in the liver or the brain depended on sex. Anxiety-like behaviours were decreased in offspring fed the LP diet and were correlated with markers of LP diet consumption including increased liver ¹³ C-PAM, warranting further investigation. Altogether, our results indicate that DNL from dietary sugars is a compensatory mechanism to maintain brain PAM in response to a LP diet.

Intravenous administration of three multiwalled carbon nanotubes to female rats and their effect on urinary biochemical profile

This study was conducted to investigate the influence of outer diameter (OD) and length (L) of multiwalled carbon nanotubes (MWCNTs) on biodistribution and the perturbation of endogenous metabolite profiles. Three different-sized carboxylated MWCNTs (NIEHS-12-2: L 0.5-2 μm, OD 10-20 nm, NIEHS-13-2: L 0.5-2 μm, OD 30-50 nm, and NIEHS-14-2: L 10-30 μm, OD 10-20 nm) in water were administered to female Sprague-Dawley rats as a single intravenous dose of 1 mg/kg MWCNTs. Biodistribution in liver, lung, spleen, and lymph nodes was evaluated in tissue sections at 1 and 7 days' post-dosing using enhanced darkfield microscopy and hyperspectral imaging. Nuclear magnetic resonance (NMR) analysis was used for biochemical profiling and pathway mapping of endogenous metabolites in urine collected at 24-h intervals prior to dosing, at Day 1 and Day 7. At Day 1 and Day 7, all three MWCNTs were observed in liver. NIEHS-12-2 was observed in spleen, whereas NIEHS-13-2 and NIEHS-14-2 were not. All three MWCNTs were observed in lymph nodes and lung at Day 7. The urinary biochemical profile showed the highest positive fold change (FC) at Day 7 for the metabolites acetate, alanine, and lactate, whereas 1-methylnicotinamide, 2-oxoglutarate, and hippurate had some of the lowest FCs for all three MWCNTs. This study demonstrates that the observed tissue location of MWCNTs is size dependent. Overlaps in the perturbation of endogenous metabolite profiles were found regardless of their size, and the biochemical responses were more profound at Day 7 compared with Day 1, indicating a delayed biological response to MWCNTs.

Rho-Kinase as a Therapeutic Target for Nonalcoholic Fatty Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) is a major public health problem and the most common form of chronic liver disease, affecting 25% of the global population. Although NAFLD is closely linked with obesity, insulin resistance, and type 2 diabetes mellitus, knowledge on its pathogenesis remains incomplete. Emerging data have underscored the importance of Rho-kinase (Rho-associated coiled-coil-containing kinase [ROCK]) action in the maintenance of normal hepatic lipid homeostasis. In particular, pharmacological blockade of ROCK in hepatocytes or hepatic stellate cells prevents the progression of liver diseases such as NAFLD and fibrosis. Moreover, mice lacking hepatic ROCK1 are protected against obesity-induced fatty liver diseases by suppressing hepatic de novo lipogenesis. Here we review the roles of ROCK as an indispensable regulator of obesity-induced fatty liver disease and highlight the key cellular pathway governing hepatic lipid accumulation, with focus on de novo lipogenesis and its impact on therapeutic potential. Consequently, a comprehensive understanding of the metabolic milieu linking to liver dysfunction triggered by ROCK activation may help identify new targets for treating fatty liver diseases such as NAFLD.

Metformin acts to suppress β-hydroxybutyric acid-mediated inflammatory responses through activation of AMPK signaling in bovine hepatocytes

The occurrence of bovine ketosis involves the accumulation of β-hydroxybutyric acid (BHBA), which contributes to the initiation and acceleration of hepatic metabolic stress and inflammation. Metformin has other beneficial effects apart from its medical intervention for diabetes, such as prevention of laminitis and hyper-triglyceridemic. AMPK maintains energy homeostasis and is the intracellular target of metformin action. This study aims to uncover the role of metformin in modulating BHBA-induced inflammatory responses through the activation of AMPK signaling. The hepatocytes were isolated from the liver tissue of mid-lactation multiparous Holstein cows (~160 d postpartum). Treatments were conducted as follows: treated with PBS for 18 h (control); pretreated with PBS for 12 h followed by treatment of 1.2 mM BHBA for 6 h (BHBA); pretreated with 1.5 mM or 3 mM metformin for 12 h followed by the BHBA treatment (1.2 mM) for 6 h (M(1.5)+B; M(3)+B). The inhibitor of AMPK, Compound C, at a concentration of 10 μM, was applied to substantiate the AMPK-dependent responses. RT-qPCR were applied for the mRNA expression while Western-blots and immunofluorescence were conducted for the target proteins expression. Among dose-dependent assays for BHBA, the concentration of BHBA at 1.2 mM activated NF-κB signaling by upregulating the expression of phosphorylated NF-κB and pro-inflammatory cytokines compared with the control cells (P < 0.05). Along with the upregulation of phosphorylated AMPKα and ACCα, metformin at 1.5 and 3 mM inactivated NF-κB signaling components (p65 and IκBα) and the inflammatory genes (TNFA, IL6, IL1B and COX-2) which were activated by BHBA. Additionally, BHBA inhibited cells staining intensity in EdU assay were increased by pretreatment with metformin. The activation of AMPK resulted in the increased gene and protein expression of SIRT1, along with the deacetylation of H3K9 and H3K14. However, the AMPK inhibitor compound C blocked this effect. Compared with BHBA treated cells, the protein expression of COX-2 and IL-1β were decreased by the pretreatment with metformin, and the inhibitory effect of metformin was released by compound C. The bound of NF-κB onto IL1B promoter displayed higher in BHBA group and this was suppressed by pretreatment with metformin (P < 0.05). Altogether, metformin attenuates the BHBA-induced inflammation through the inactivation of NF-κB as a target for AMPK/SIRT1 signaling in bovine hepatocytes.

CD8+ T Cells Involved in Metabolic Inflammation in Visceral Adipose Tissue and Liver of Transgenic Pigs

Anti-inflammatory therapies have the potential to become an effective treatment for obesity-related diseases. However, the huge gap of immune system between human and rodent leads to limitations of drug discovery. This work aims at constructing a transgenic pig model with higher risk of metabolic diseases and outlining the immune responses at the early stage of metaflammation by transcriptomic strategy. We used CRISPR/Cas9 techniques to targeted knock-in three humanized disease risk genes, GIPR^dn , hIAPP and PNPLA3^I148M . Transgenic effect increased the risk of metabolic disorders. Triple-transgenic pigs with short-term diet intervention showed early symptoms of type 2 diabetes, including glucose intolerance, pancreatic lipid infiltration, islet hypertrophy, hepatic lobular inflammation and adipose tissue inflammation. Molecular pathways related to CD8⁺ T cell function were significantly activated in the liver and visceral adipose samples from triple-transgenic pigs, including antigen processing and presentation, T-cell receptor signaling, co-stimulation, cytotoxicity, and cytokine and chemokine secretion. The similar pro-inflammatory signaling in liver and visceral adipose tissue indicated that there might be a potential immune crosstalk between the two tissues. Moreover, genes that functionally related to liver antioxidant activity, mitochondrial function and extracellular matrix showed distinct expression between the two groups, indicating metabolic stress in transgenic pigs' liver samples. We confirmed that triple-transgenic pigs had high coincidence with human metabolic diseases, especially in the scope of inflammatory signaling at early stage metaflammation. Taken together, this study provides a valuable large animal model for the clinical study of metaflammation and metabolic diseases.

Validation of an adipose-liver human-on-a-chip model of NAFLD for preclinical therapeutic efficacy evaluation

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease and strongly correlates with the growing incidence of obesity and type II diabetes. We have developed a human-on-a-chip model composed of human hepatocytes and adipose tissue chambers capable of modeling the metabolic factors that contribute to liver disease development and progression, and evaluation of the therapeutic metformin. This model uses a serum-free, recirculating medium tailored to represent different human metabolic conditions over a 14-day period. The system validated the indirect influence of adipocyte physiology on hepatocytes that modeled important aspects of NAFLD progression, including insulin resistant biomarkers, differential adipokine signaling in different media and increased TNF-α-induced steatosis observed only in the two-tissue model. This model provides a simple but unique platform to evaluate aspects of an individual factor's contribution to NAFLD development and mechanisms as well as evaluate preclinical drug efficacy and reassess human dosing regimens.

Cholesterol metabolism: a new molecular switch to control inflammation

The immune system protects the body against harm by inducing inflammation. During the immune response, cells of the immune system get activated, divided and differentiated in order to eliminate the danger signal. This process relies on the metabolic reprogramming of both catabolic and anabolic pathways not only to produce energy in the form of ATP but also to generate metabolites that exert key functions in controlling the response. Equally important to mounting an appropriate effector response is the process of immune resolution, as uncontrolled inflammation is implicated in the pathogenesis of many human diseases, including allergy, chronic inflammation and cancer. In this review, we aim to introduce the reader to the field of cholesterol immunometabolism and discuss how both metabolites arising from the pathway and cholesterol homeostasis are able to impact innate and adaptive immune cells, staging cholesterol homeostasis at the centre of an adequate immune response. We also review evidence that demonstrates the clear impact that cholesterol metabolism has in both the induction and the resolution of the inflammatory response. Finally, we propose that emerging data in this field not only increase our understanding of immunometabolism but also provide new tools for monitoring and intervening in human diseases, where controlling and/or modifying inflammation is desirable.

The Effect of High Fat Diet on Cerebrovascular Health and Pathology: A Species Comparative Review

In both humans and animal models, consumption of a high-saturated-fat diet has been linked to vascular dysfunction and cognitive impairments. Laboratory animals provide excellent models for more invasive high-fat-diet-related research. However, the physiological differences between humans and common animal models in terms of how they react metabolically to high-fat diets need to be considered. Here, we review the factors that may affect the translatability of mechanistic research in animal models, paying special attention to the effects of a high-fat diet on vascular outcomes. We draw attention to the dissociation between metabolic syndrome and dyslipidemia in rodents, unlike the state in humans, where the two commonly occur. We also discuss the differential vulnerability between species to the metabolic and vascular effects of macronutrients in the diet. Findings from animal studies are better interpreted as modeling specific aspects of dysfunction. We conclude that the differences between species provide an opportunity to explore why some species are protected from the detrimental aspects of high-fat-diet-induced dysfunction, and to translate these findings into benefits for human health.

Technical Note: In vivo estimation of lipogenesis using a bolus injection of [U-13C]glucose in pigs

The use of radioactive isotopes to measure de novo lipogenesis in pigs has been well established. Different from radioactive isotopes, stable isotopes present little or no risk to human and animal subjects. Therefore, the objective of this study was to adapt the method of bolus injection of radioactive glucose (14C) to use 13C-labeled glucose to estimate de novo lipogenesis in finishing pigs. Five vein-catheterized gilts received 3.0 kg/d of a commercial diet for 2 wk. On the last day, the pigs received a bolus injection of [U-13C]glucose (12 mg/kg body weight). A serial of blood samples was taken for 4 h to determine the glucose rate of disappearance (Rd) from plasma glucose isotopic enrichment (IE). The 13C IE of lipids was determined from adipose tissue biopsies collected at 1, 2, and 3 h after the bolus injection and from adipose tissue collected after pig euthanasia 4 h after the bolus. Lipogenesis was estimated from the incorporation of 13C from glucose into adipose tissue lipids. Glucose Rd, estimated using a double-exponential function, averaged 5.4 ± 1.4 mmol/min. The IE of lipids increased linearly during the 4 h following the bolus injection (P < 0.05). The rate of incorporation of glucose into lipids, estimating lipogenesis, averaged 9.0 µg glucose/(min × g of lipids) 4 h after the bolus injection. In conclusion, the in vivo method using a bolus injection of [U-13C]glucose allows a successful estimation of de novo lipogenesis in finishing pigs.

Diet Rich in Lard Promotes a Metabolic Environment Favorable to Trypanosoma cruzi Growth

Background: Trypanosoma cruzi is a protozoan parasite that causes Chagas disease and affects 6-7 million people mainly in Latin America and worldwide. Here, we investigated the effects of hyperlipidic diets, mainly composed of olive oil or lard on experimental T. cruzi infection. C57BL/6 mice were fed two different dietary types in which the main sources of fatty acids were either monounsaturated (olive oil diet) or saturated (lard diet). Methods: After 60 days on the diet, mice were infected with 50 trypomastigote forms of T. cruzi Colombian strain. We evaluated the systemic and tissue parasitism, tissue inflammation, and the redox status of mice after 30 days of infection. Results: Lipid levels in the liver of mice fed with the lard diet increased compared with that of the mice fed with olive oil or normolipidic diets. The lard diet group presented with an increased parasitic load in the heart and adipose tissues following infection as well as an increased expression of Tlr2 and Tlr9 in the heart. However, no changes were seen in the survival rates across the dietary groups. Infected mice receiving all diets presented comparable levels of recruited inflammatory cells at 30 days post-infection but, at this time, we observed lard diet inducing an overproduction of CCL2 in the cardiac tissue and its inhibition in the adipose tissue. T. cruzi infection altered liver antioxidant levels in mice, with the lard diet group demonstrating decreased catalase (CAT) activity compared with that of other dietary groups. Conclusions: Our data demonstrated that T. cruzi growth is more favorable on tissue of mice subjected to the lard diet. Our findings supported our hypothesis of a relationship between the source of dietary lipids and parasite-induced immunopathology.

Obesity Development and Signs of Metabolic Abnormalities in Young Göttingen Minipigs Consuming Energy Dense Diets Varying in Carbohydrate Quality

Consumption of fructose has been associated with a higher risk of developing obesity and metabolic syndrome (MetS). The aim of this study was to examine the long-term effects of fructose compared to starch from high-amylose maize starch (HiMaize) at ad libitum feeding in a juvenile Göttingen Minipig model with 20% of the diet provided as fructose as a high-risk diet (HR, n = 15) and 20% as HiMaize as a lower-risk control diet (LR, n = 15). The intake of metabolizable energy was on average similar (p = 0.11) among diets despite increased levels of the satiety hormone PYY measured in plasma (p = 0.0005) of the LR pigs. However, after over 20 weeks of ad libitum feeding, no difference between diets was observed in daily weight gain (p = 0.103), and a difference in BW was observed only at the end of the experiment. The ad libitum feeding promoted an obese phenotype over time in both groups with increased plasma levels of glucose (p = 0.005), fructosamine (p < 0.001), insulin (p = 0.03), and HOMA-IR (p = 0.02), whereas the clinical markers of dyslipidemia were unaffected. When compared to the LR diet, fructose did not accelerate the progression of MetS associated parameters and largely failed to change markers that indicate a stimulated de novo lipogenesis.

Lipid Receptor G2A-Mediated Signal Pathway Plays a Critical Role in Inflammatory Response by Promoting Classical Macrophage Activation

Macrophage polarization is a dynamic and integral process in tissue inflammation and remodeling. In this study, we describe that lipoprotein-associated phospholipase A₂ (Lp-PLA₂) plays an important role in controlling inflammatory macrophage (M1) polarization in rodent experimental autoimmune encephalomyelitis (EAE) and in monocytes from multiple sclerosis (MS) patients. Specific inhibition of Lp-PLA₂ led to an ameliorated EAE via markedly decreased inflammatory and demyelinating property of M1. The effects of Lp-PLA₂ on M1 function were mediated by lysophosphatidylcholine, a bioactive product of oxidized lipids hydrolyzed by Lp-PLA₂ through JAK2-independent activation of STAT5 and upregulation of IRF5. This process was directed by the G2A receptor, which was only found in differentiated M1 or monocytes from MS patients. M1 polarization could be inhibited by a G2A neutralizing Ab, which led to an inhibited disease in rat EAE. In addition, G2A-deficient rats showed an ameliorated EAE and an inhibited autoimmune response. This study has revealed a mechanism by which lipid metabolites control macrophage activation and function, modification of which could lead to a new therapeutic approach for MS and other inflammatory disorders.

Systemic PFOS and PFOA exposure and disturbed lipid homeostasis in humans: what do we know and what not?

Associations between per- and polyfluoroalkyl substances (PFASs) and increased blood lipids have been repeatedly observed in humans, but a causal relation has been debated. Rodent studies show reverse effects, i.e. decreased blood cholesterol and triglycerides, occurring however at PFAS serum levels at least 100-fold higher than those in humans. This paper aims to present the main issues regarding the modulation of lipid homeostasis by the two most common PFASs, PFOS and PFOA, with emphasis on the underlying mechanisms relevant for humans. Overall, the apparent contrast between human and animal data may be an artifact of dose, with different molecular pathways coming into play upon exposure to PFASs at very low versus high levels. Altogether, the interpretation of existing rodent data on PFOS/PFOA-induced lipid perturbations with respect to the human situation is complex. From a mechanistic perspective, research on human liver cells shows that PFOS/PFOA activate the PPARα pathway, whereas studies on the involvement of other nuclear receptors, like PXR, are less conclusive. Other data indicate that suppression of the nuclear receptor HNF4α signaling pathway, as well as perturbations of bile acid metabolism and transport might be important cellular events that require further investigation. Future studies with human-relevant test systems would help to obtain more insight into the mechanistic pathways pertinent for humans. These studies shall be designed with a careful consideration of appropriate dosing and toxicokinetics, so as to enable biologically plausible quantitative extrapolations. Such research will increase the understanding of possible perturbed lipid homeostasis related to PFOS/ PFOA exposure and the potential implications for human health.

Liver organoids in domestic animals: an expected promise for metabolic studies

The liver is one of the most important organs, both in terms of the different metabolic processes (energy, lipid, ferric, uric, etc.) and of its central role in the processes of detoxification of substances of food origin or noxious substances (alcohol, drugs, antibiotics, etc.). The development of a relevant model that reproduces some of the functions of this tissue has become a challenge, in particular for human medicine. Thus, in recent years, most studies aimed at producing hepatocytes in vitro with the goal of developing hepatic 3D structures have been carried out in the human model. However, the tools and protocols developed using this unique model can also be considered to address physiological questions specific to this tissue in other species, such as the pig, chicken, and duck. Different strategies are presently being considered to carry out in vitro studies of the hepatic metabolism of these agronomic species.

Research Note: Potential usage of DF-1 cell line as a new cell model for avian adipogenesis

Current research of avian adipogenesis has been dependent on primary preadipocytes culture due to the lack of commercially available immortal preadipocyte cell lines in avian species. In addition to primary stromal vascular cells, primary chicken embryonic fibroblasts (CEF) were suggested as new in vitro models for adipogenesis study, because CEF can be differentiated into adipocytes by a combination of fatty acids and insulin (FI), or all-trans retinoic acid (atRA) alone in the media containing chicken serum (CS). However, there are decreases in differentiation of primary cells due to diverse population of cell types and low adipogenic potential of cells after passages. In the present study, adipogenic differentiation of DF-1 cells, immortal fibroblasts derived from an embryonic chicken, was tested with 4 different medium; 10% fetal bovine serum (FBS), 10% CS, 10% CS with FI, and 10% CS with FI and atRA. Lipid droplets stained with Oil Red O were not shown in DF-1 cells under 10% FBS, appeared with very small sizes under 10% CS, significantly increased under 10% CS with FI, and most significantly accumulated under 10% CS with FI and atRA. In addition, expressions of markers for adipogenesis (Znf423, C/ebpβ, Pparγ, and Fabp4), fatty acid uptake (CD36), triglyceride synthesis (Gpd1, Dgat2), and lipid droplet stabilization (Plin1) were significantly upregulated by supplementation of 10% CS with FI and atRA. Morphological evidence for formation of lipid droplets and dramatic induction of adipogenic marker genes support the adipogenic potential of DF-1 cells, offering DF-1 cells as a new cell model to investigate various research studies involving avian adipogenesis.

High-fructose feeding does not induce steatosis or non-alcoholic fatty liver disease in pigs

Non-alcoholic fatty liver disease (NAFLD) is an increasingly prevalent condition that has been linked to high-fructose corn syrup consumption with induction of hepatic de novo lipogenesis (DNL) as the suggested central mechanism. Feeding diets very high in fructose (> 60%) rapidly induce several features of NAFLD in rodents, but similar diets have not yet been applied in larger animals, such as pigs. With the aim to develop a large animal NAFLD model, we analysed the effects of feeding a high-fructose (HF, 60% w/w) diet for four weeks to castrated male Danish Landrace-York-Duroc pigs. HF feeding upregulated expression of hepatic DNL proteins, but levels were low compared with adipose tissue. No steatosis or hepatocellular ballooning was seen on histopathological examination, and plasma levels of transaminases were similar between groups. Inflammatory infiltrates and the amount of connective tissue was slightly elevated in liver sections from fructose-fed pigs, which was corroborated by up-regulation of macrophage marker expression in liver homogenates. Supported by RNA-profiling, quantitative protein analysis, histopathological examination, and biochemistry, our data suggest that pigs, contrary to rodents and humans, are protected against fructose-induced steatosis by relying on adipose tissue rather than liver for DNL.

Role of Corticosterone in Lipid Metabolism in Broiler Chick White Adipose Tissue

Excessive accumulation of body fat in broiler chickens has become a serious problem in the poultry industry. However, the molecular mechanism of triglyceride accumulation in chicken white adipose tissue (WAT) has not been elucidated. In the present study, we investigated the physiological importance of the catabolic hormone corticosterone, the major glucocorticoid in chickens, in the regulation of chicken WAT lipid metabolism. We first examined the effects of fasting on the mRNA levels of lipid metabolism-related genes associated with WAT, plasma corticosterone, and non-esterified fatty acid (NEFA). We then examined the effects of corticosterone on the expression of these genes in vivo and in vitro. In 10-day-old chicks, 3 h of fasting significantly decreased mRNA levels of lipoprotein lipase (LPL) in WAT and significantly elevated plasma concentrations of NEFA. Six hours of fasting significantly increased mRNA levels of adipose triglyceride lipase (ATGL) in WAT and significantly elevated plasma concentrations of corticosterone. On the other hand, fasting significantly reduced mRNA levels of LPL in WAT and elevated plasma concentrations of NEFA in 29-day-old chicks without affecting mRNA levels of ATGL in WAT or plasma corticosterone concentrations. Oral administration of corticosterone significantly reduced mRNA levels of LPL and significantly increased the mRNA levels of ATGL in WAT in 29-day-old chicks without affecting plasma NEFA concentrations. The addition of corticosterone to primary chicken adipocytes significantly increased mRNA levels of ATGL, whereas mRNA levels of LPL tended to decrease. NEFA concentrations in the culture medium were not influenced by corticosterone levels. These results suggest that plasma corticosterone partly regulates the gene expression of lipid metabolism-related genes in chicken WAT and this regulation is different from the acute elevation of plasma NEFA due to short-term fasting.

In Vitro and In Vivo Models of Non-Alcoholic Fatty Liver Disease: A Critical Appraisal

Non-alcoholic fatty liver disease (NAFLD), including non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), represents the hepatic manifestation of obesity and metabolic syndrome. Due to the spread of the obesity epidemic, NAFLD is becoming the most common chronic liver disease and one of the principal indications for liver transplantation. However, no pharmacological treatment is currently approved to prevent the outbreak of NASH, which leads to fibrosis and cirrhosis. Preclinical research is required to improve our knowledge of NAFLD physiopathology and to identify new therapeutic targets. In the present review, we summarize advances in NAFLD preclinical models from cellular models, including new bioengineered platforms, to in vivo models, with a particular focus on genetic and dietary mouse models. We aim to discuss the advantages and limits of these different models.