A comparison of effects of lard and hydrogenated vegetable shortening on the development of high-fat diet-induced obesity in rats

Global deletion of G protein-coupled receptor 55 impairs glucose homeostasis during obesity by reducing insulin secretion and β-cell turnover

AIM

To investigate the effect of G protein-coupled receptor 55 (GPR55) deletion on glucose homeostasis and islet function following diet-induced obesity.

METHODS

GPR55-/- and wild-type (WT) mice were fed ad libitum either standard chow (SC) or a high-fat diet (HFD) for 20 weeks. Glucose and insulin tolerance tests were performed at 9/10 and 19/20 weeks of dietary intervention. Insulin secretion in vivo and dynamic insulin secretion following perifusion of isolated islets were also determined, as were islet caspase-3/7 activities and β-cell 5-bromo-20-deoxyuridine (BrdU) incorporation.

RESULTS

GPR55-/- mice fed a HFD were more susceptible to diet-induced obesity and were more glucose intolerant and insulin resistant than WT mice maintained on a HFD. Islets isolated from HFD-fed GPR55-/- mice showed impaired glucose- and pcacahorbol 12-myristate 13-acetate-stimulated insulin secretion, and they also displayed increased cytokine-induced apoptosis. While there was a 5.6 ± 1.6-fold increase in β-cell BrdU incorporation in the pancreases of WT mice fed a HFD, this compensatory increase in β-cell proliferation in response to the HFD was attenuated in GPR55-/- mice.

CONCLUSIONS

Under conditions of diet-induced obesity, GPR55-/- mice show impaired glucose handling, which is associated with reduced insulin secretory capacity, increased islet cell apoptosis and insufficient compensatory increases in β-cell proliferation. These observations support that GPR55 plays an important role in positively regulating islet function.

Dietary ingredient change induces a transient MyD88-dependent mucosal enteric glial cell response and promotes obesity

OBJECTIVE

Consumption of a modern Western-type high-fat low-fiber diet increases the risk of obesity. However, how a host responds to such a diet, especially during the early period of dietary transition from a previous low-fat and fiber-rich diet, remains poorly explored.

METHODS

Wild-type C57BL/6 mice were fed a normal chow diet or a high-fat diet. Enteric glial cell (EGC) activation was detected through quantitative real-time PCR (qRT-PCR), immunoblotting and immunohistology analysis. Fluorocitrate or genetic deletion of glial fibrillary acidic protein (GFAP)-positive glial-intrinsic myeloid differentiation factor 88 (Myd88) was used to inhibit EGC activation, and the effect of a high-fat diet on obesity was further investigated. The role of MYD88-dependent sensing of commensal products in adipocyte was observed to analyze the effect of obesity.

RESULTS

A dietary shift from a normal chow diet to a high-fat diet in mice induced a transient early-phase emergence of a GFAP-positive EGC network in the lamina propria of the ileum, accompanied with an increase in glial-derived neurotrophic factor production. Inhibition of glial cell activity blocked this response. GFAP-positive glial Myd88 knockout mice gained less body weight after high-fat diet (HFD) feeding than littermate controls. In contrast, adipocyte deletion of Myd88 in mice had no effect on weight gain but instead exacerbated glucose intolerance. Furthermore, short-term fluorocitrate intervention during HFD feeding attenuated body weight gain.

CONCLUSIONS

Our findings indicate that EGCs are early responders to intestinal ecosystem changes and the GFAP-positive glial Myd88 signaling participates in regulating obesity.

Advances in diet-induced rodent models of metabolically acquired peripheral neuropathy

Peripheral neuropathy (PN) is a severe complication that affects over 30% of prediabetic and 60% of type 2 diabetic (T2D) patients. The metabolic syndrome is increasingly recognized as a major driver of PN. However, basic and translational research is needed to understand the mechanisms that contribute to nerve damage. Rodent models of diet-induced obesity, prediabetes, T2D and PN closely resemble the human disease and have proven to be instrumental for the study of PN mechanisms. In this Perspective article, we focus on the development, neurological characterization and dietary fat considerations of diet-induced rodent models of PN. We highlight the importance of investigating sex differences and discuss some of the challenges in translation from bench to bedside, including recapitulating the progressive nature of human PN and modeling neuropathic pain. We emphasize that future research should overcome these challenges in the quest to better mimic human PN in animal models.

Intergenerational high-fat diet impairs ovarian follicular development in rodents: a systematic review and meta-analysis

CONTEXT

Excessive consumption of high-fat diets has increased in the population over time and is harmful to female fertility.

OBJECTIVE

To investigate and discuss the effects of a high-fat diet on ovarian follicles in rodents.

DATA SOURCE

A systematic literature search of PubMed, EMBASE, Web of Science, and SCOPUS was carried out.

DATA EXTRACTION

Study characteristics, including study design, population, intervention, outcome, and risk of bias were analyzed.

DATA ANALYSIS

Twenty-two articles were included in a systematic review. Given the availability of studies, a quantitative meta-analysis included 12 studies that were performed for outcomes. There was a decrease in primordial follicles in female rodents that received a high-fat diet compared with the standard diet group. The offspring of mothers exposed to a high-fat diet showed an increased number of cystic follicles and a decreased number of secondary follicles and antral follicles, compared with the control diet group. Therefore, these high-fat diet-induced follicular alterations might impair the fertility of dams and their female newborns.

CONCLUSION

The consumption of a high-fat diet causes damage to ovarian follicular development, and this commitment will persist in the next generation.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42019133865.

MUFAs in High-Fat Diets Protect against Obesity-Induced Bias of Hematopoietic Cell Lineages

SCOPE

The role of dietary fatty acids in the generation of bone marrow (BM) immune cells and their trafficking to extramedullary compartments in the obesity is not yet fully understood.

METHODS AND RESULTS

C57BL/6J mice are randomly assigned to isocaloric high-fat diets (HFDs) formulate with dietary fats rich in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) or MUFAs fortified with eicosapentaenoic and docosahexaenoic acids for 20 weeks, followed by profiling of the obese metabolic phenotype and immunophenotypic features of immune cells in blood, spleen, and BM. All HFDs induce an obese phenotype, but it becomes largely less disruptive after the HFDs are enriched in MUFAs, which also induce signs of granulopoiesis and an expansion of long-term hematopoietic stem and granulocyte-macrophage progenitor cells in BM. In contrast, a HFD enriched in SFAs disturbs the fitness of medullary lymphocytes and promotes monopoiesis in favor of pro-inflammatory activated subsets.

CONCLUSION

The reshaping of the fatty acid pools with MUFAs from the diet serves to manipulate the generation and trafficking of immune cells that are biased during obesity. These findings reveal a novel strategy by which dietary MUFAs may be instrumental in combating HFD-induced dysfunctional immune systems.

High Choline Intake during Pregnancy Reduces Characteristics of the Metabolic Syndrome in Male Wistar Rat Offspring Fed a High Fat But Not a Normal Fat Post-Weaning Diet

Maternal choline intakes are below recommendations, potentially impairing the child’s later-life metabolic health. This study aims to elucidate the interaction between the choline content of the gestational diet (GD) and fat content of the post-weaning diet (PWD) on metabolic phenotype of male Wistar rats. Pregnant Wistar rats were fed a standard rodent diet (AIN-93G) with either recommended choline (RC, 1 g/kg diet choline bitartrate) or high choline (HC, 2.5-fold). Male pups were weaned to either a normal (16%) fat (NF) or a high (45%) fat (HF) diet for 17 weeks. Body weight, visceral adiposity, food intake, energy expenditure, plasma hormones, triglycerides, and hepatic fatty acids were measured. HC-HF offspring had 7% lower body weight but not food intake, and lower adiposity, plasma triglycerides, and insulin resistance compared to RC-HF. They also had increased hepatic n-3 fatty acids and a reduced n-6/n-3 and C 18:1 n-9/C18:0 ratios. In contrast, HC-NF offspring had 6–8% higher cumulative food intake and body weight, as well as increased leptin and elevated hepatic C16:1 n-7/C16:0 ratio compared to RC-NF. Therefore, gestational choline supplementation associated with improved long-term regulation of several biomarkers of the metabolic syndrome in male Wistar rat offspring fed a HF, but not a NF, PWD.

The Effect of Tempe Gembus on High-Sensitivity C-Reactive Protein and Adiponectine Levels in Rats with Metabolic Syndrome

Metabolic syndrome can affect the inflammatory state which results in increased high-sensitivity C-reactive protein (hs CRP) and decreased adiponectin levels. Tempe gembus is a functional food that can reduce the risk of metabolic syndrome through the inflammatory pathway. This study applied a quasi experimental method, with a post-test only control group design. Sprague Dawley rats (n=30) were divided into 2 control groups (K- and K+) and 3 treatment groups (P1, P2, P3) which were given a 4-wk diet that included 2.5 g (P1), 5 g (P2), and 7.5 g (P3) of tempe gembus. Adiponectin and hs CRP levels were measured with ELISA. Statistical analysis was done with a one-way ANOVA test and a Kruskal Wallis test. It apprears that administering tempe gembus in these amounts can reduce the hs CRP levels (p=0.037) and increase adiponectin levels in rats with metabolic syndrome (p=0.008). This research has shown that a 2.5 g of tempe gembus can have a strong effect on hs CRP and 5 g of tempe gembus have a strong effect on adiponectin.

[6S]-5-Methyltetrahydrofolic Acid and Folic Acid Pregnancy Diets Differentially Program Metabolic Phenotype and Hypothalamic Gene Expression of Wistar Rat Dams Post-Birth

[6S]-5-methyltetrahydrofolic acid (MTHF) is a proposed replacement for folic acid (FA) in diets and prenatal supplements. This study compared the effects of these two forms on maternal metabolism and hypothalamic gene expression. Pregnant Wistar rats received an AIN-93G diet with recommended FA (1X, 2 mg/kg, control), 5X-FA or equimolar levels of MTHF. During lactation they received the control diet and then a high fat diet for 19-weeks post-weaning. Body weight, adiposity, food intake, energy expenditure, plasma hormones, folate, and 1-carbon metabolites were measured. RNA-sequencing of the hypothalamus was conducted at parturition. Weight-loss from weaning to 1-week post-weaning was less in dams fed either form of the 5X vs. 1X folate diets, but final weight-gain was higher in 5X-MTHF vs. 5X-FA dams. Both doses of the MTHF diets led to 8% higher food intake and associated with lower plasma leptin at parturition, but higher leptin at 19-weeks and insulin resistance at 1-week post-weaning. RNA-sequencing revealed 279 differentially expressed genes in the hypothalamus in 5X-MTHF vs. 5X-FA dams. These findings indicate that MTHF and FA differ in their programing effects on maternal phenotype, and a potential adverse role of either form when given at the higher doses.

Hippocampal-Dependent Inhibitory Learning and Memory Processes in the Control of Eating and Drug Taking

As manifestations of excessive and uncontrolled intake, obesity and drug addiction have generated much research aimed at identifying common neuroadaptations that could underlie both disorders. Much work has focused on changes in brain reward and motivational circuitry that can overexcite eating and drug-taking behaviors. We suggest that the regulation of both behaviors depends on balancing excitation produced by stimuli associated with food and drug rewards with the behavioral inhibition produced by physiological "satiety" and other stimuli that signal when those rewards are unavailable. Our main hypothesis is that dysregulated eating and drug use are consequences of diet- and drug-induced degradations in this inhibitory power. We first outline a learning and memory mechanism that could underlie the inhibition of both food and drug-intake, and we describe data that identifies the hippocampus as a brain substrate for this mechanism. We then present evidence that obesitypromoting western diets (WD) impair the operation of this process and generate pathophysiologies that disrupt hippocampal functioning. Next, we present parallel evidence that drugs of abuse also impair this same learning and memory process and generate similar hippocampal pathophysiologies. We also describe recent findings that prior WD intake elevates drug self-administration, and the implications of using drugs (i.e., glucagon-like peptide- 1 agonists) that enhance hippocampal functioning to treat both obesity and addiction are also considered. We conclude with a description of how both WD and drugs of abuse could initiate a "vicious-cycle" of hippocampal pathophysiology and impaired hippocampal-dependent behavioral inhibition.

High Fat Rodent Models of Type 2 Diabetes: From Rodent to Human

Poor dietary habits contribute to increased incidences of obesity and related co-morbidities, such as type 2 diabetes (T2D). The biological, genetic, and pathological implications of T2D, are commonly investigated using animal models induced by a dietary intervention. In spite of significant research contributions, animal models have limitations regarding the translation to human pathology, which leads to questioning their clinical relevance. Important considerations include diet-specific effects on whole organism energy balance and glucose and insulin homeostasis, as well as tissue-specific changes in insulin and glucose tolerance. This review will examine the T2D-like phenotype in rodents resulting from common diet-induced models and their relevance to the human disease state. Emphasis will be placed on the disparity in percentages and type of dietary fat, the duration of intervention, and whole organism and tissue-specific changes in rodents. An evaluation of these models will help to identify a diet-induced rodent model with the greatest clinical relevance to the human T2D pathology. We propose that a 45% high-fat diet composed of approximately one-third saturated fats and two-thirds unsaturated fats may provide a diet composition that aligns closely to average Western diet macronutrient composition, and induces metabolic alterations mirrored by clinical populations.

Systemic Insulin Resistance and Metabolic Perturbations in Chow Fed Inducible Nitric Oxide Synthase Knockout Male Mice: Partial Reversal by Nitrite Supplementation

iNOS, an important mediator of inflammation, has emerged as an important metabolic regulator. There are conflicting observations on the incidence of insulin resistance (IR) due to hyperglycemia/dyslipidemia in iNOS^−/− mice. There are reports that high fat diet (HFD) fed mice exhibited no change, protection, or enhanced susceptibility to IR. Similar observations were also reported for low fat diet (LFD) fed KO mice. In the present study chow fed iNOS^−/− mice were examined for the incidence of IR, and metabolic perturbations, and also for the effect of sodium nitrite supplementation (50 mg/L). In IR-iNOS^−/− mice, we observed significantly higher body weight, BMI, adiposity, blood glucose, HOMA-IR, serum/tissue lipids, glucose intolerance, enhanced gluconeogenesis, and disrupted insulin signaling. Expression of genes involved in hepatic and adipose tissue lipid uptake, synthesis, oxidation, and gluconeogenesis was upregulated with concomitant downregulation of genes for hepatic lipid excretion. Nitrite supplementation restored NO levels, significantly improved systemic IR, glucose tolerance, and also reduced lipid accumulation by rescuing hepatic insulin sensitivity, glucose, and lipid homeostasis. Obesity, gluconeogenesis, and adipose tissue insulin signaling were only partially reversed in nitrite supplemented iNOS^−/− mice. Our results thus demonstrate that nitrite supplementation to iNOS^−/− mice improves insulin sensitivity and metabolic homeostasis, thus further highlighting the metabolic role of iNOS.

Ethanolamides of essential α-linolenic and linoleic fatty acids suppress short-term food intake in rats

Food source has a significant impact on levels of fatty acids and their derivatives, fatty acid ethanolamides (FAEs), in the small intestine and brain. Among non-essential fatty acids, oleic acid and its FAE acutely reduce food intake. However, effects of the essential α-linolenic acid, linoleic acid, and their FAEs on appetite regulation remain undefined. This study tested the hypothesis that α-linolenic acid and linoleic acid mediate acute suppression of food intake through their corresponding FAEs, α-linolenoylethanolamide and linoleoylethanolamide, respectively. To allow for the differentiation of the effects of FAEs and their parent fatty acids, male Wistar rats were injected intraperitoneally with α-linolenic acid, linoleic acid, α-linolenoylethanolamide and linoleoylethanolamide after a 12-hour overnight fast. Short-term food intake, plasma and brain FAE status, and plasma concentrations of insulin and leptin were measured to determine whether these hormones mediate the anorectic effect of FAEs. Both ethanolamides, but not their parent fatty acids, acutely suppressed food intake up to one hour post-treatment and this effect was independent of insulin and leptin hormones. In conclusion, essential α-linolenic and linoleic fatty acids mediate acute suppression of food intake through their corresponding FAEs. These findings may aid in the further research of FAEs as potential therapeutic agents for the management and treatment of obesity.

All You Can Feed: Some Comments on Production of Mouse Diets Used in Biomedical Research with Special Emphasis on Non-Alcoholic Fatty Liver Disease Research

The laboratory mouse is the most common used mammalian research model in biomedical research. Usually these animals are maintained in germ-free, gnotobiotic, or specific-pathogen-free facilities. In these facilities, skilled staff takes care of the animals and scientists usually don’t pay much attention about the formulation and quality of diets the animals receive during normal breeding and keeping. However, mice have specific nutritional requirements that must be met to guarantee their potential to grow, reproduce and to respond to pathogens or diverse environmental stress situations evoked by handling and experimental interventions. Nowadays, mouse diets for research purposes are commercially manufactured in an industrial process, in which the safety of food products is addressed through the analysis and control of all biological and chemical materials used for the different diet formulations. Similar to human food, mouse diets must be prepared under good sanitary conditions and truthfully labeled to provide information of all ingredients. This is mandatory to guarantee reproducibility of animal studies. In this review, we summarize some information on mice research diets and general aspects of mouse nutrition including nutrient requirements of mice, leading manufacturers of diets, origin of nutrient compounds, and processing of feedstuffs for mice including dietary coloring, autoclaving and irradiation. Furthermore, we provide some critical views on the potential pitfalls that might result from faulty comparisons of grain-based diets with purified diets in the research data production resulting from confounding nutritional factors.

Rodent models of obesity

Obese or overweight people exceed one-third of the global population and obesity along with diabetes mellitus consist basic components of metabolic syndrome, both of which are known cardio-cerebrovascular risk factors with detrimental consequences. These data signify the pandemic character of obesity and the necessity for effective treatments. Substantial advances have been accomplished in preclinical research of obesity by using animal models, which mimic the human disease. In particular, rodent models have been widely used for many decades with success for the elucidation of the pathophysiology of obesity, since they share physiological and genetic components with humans and appear advantageous in their husbandry. The most representative rodents include the laboratory mouse and rat. Within this review, we attempted to consolidate the most widely used mice and rat models of obesity and highlight their strengths as well as weaknesses in a critical way. Our aim was to bridge the gap between laboratory facilities and patient's bed and help the researcher find the appropriate animal model for his/her obesity research. This tactful selection of the appropriate model of obesity may offer more translational derived results. In this regard, we included, the main diet induced models, the chemical/mechanical ones, as well as a selection of monogenic or polygenic models.

Short-Term Administration of a High-Fat Diet Impairs Wound Repair in Mice

High intake of dietary fat plays an important role in obesity development in animals and humans, and prolonged intake of high-fat diet might lead to low-grade chronic inflammation. Previous study showed that diet-induced overweight delays cutaneous wound healing in both obesity-prone and obesity-resistant animals, highlighting the importance of diet composition in the wound healing process. This study evaluated the hypothesis that a short-term administration of high-fat diet could affect cutaneous wound healing. Male mice (C57/bl6) were randomly divided into standard (10% energy from fat) or high-fat (60% energy from fat) chow groups. After 10 days of diet administration, an excisional lesion was performed and the animals were sacrificed 6 or 10 days later. There was no difference in the fasting blood glucose between groups. Ten days after wounding, high-fat chow group presented increased inflammatory infiltrate, levels of inducible nitric oxide synthase and cyclo-oxygenase-2 proteins, and lipid peroxidation. The high-fat chow group presented delayed wound closure, increased amount of myofibroblasts and vessels, and decreased deposition of type I collagen. These findings support the hypothesis that short-term administration of high-fat diet exerts negative effects on mice cutaneous wound healing, due to the interference in the inflammatory phase.

High calories but not fat content of lard-based diet contribute to impaired mitochondrial oxidative phosphorylation in C57BL/6J mice heart

Purpose

High calorie intake leads to obesity, a global socio-economic and health problem, reaching epidemic proportion in children and adolescents. Saturated and monounsaturated fatty acids from animal (lard) fat are major components of the western-pattern diet and its regular consumption leads to obesity, a risk factor for cardiovascular disease. However, no clear evidence exists whether consumption of diet rich in saturated (SFAs) and monounsaturated (MUFAs) fatty acids has detrimental effects on cardiac structure and energetics primarily due to excessive calories. We, therefore, sought to determine the impact of high calories versus fat content in diet on cardiac structure and mitochondrial energetics.

Methods

Six-week-old C57BL/6J mice were fed with high calorie, high lard fat-based diet (60% fat, HFD), high-calorie and low lard fat-based diet (10% fat, LFD), and lower-calorie and fat diet (standard chow, 12% fat, SCD) for 10 weeks.

Results

The HFD- and LFD-fed mice had higher body weight, ventricular mass and thickness of posterior and septal wall with increased cardiomyocytes diameter compared to the SCD-fed mice. These changes were associated with a reduction in the mitochondrial oxidative phosphorylation (OXPHOS) complexes I and III activity compared to the SCD-fed mice without significant differences between the HFD- and LFD-fed animals. The HFD-fed animals had higher level of malondialdehyde (MDA) than LFD and SCD-fed mice.

Conclusions

We assume that changes in cardiac morphology and selective reduction of the OXPHOS complexes activity observed in the HFD- and LFD-fed mice might be related to excessive calories with additional effect of fat content on oxidative stress.

Cardiac function and intracellular Ca2+ handling proteins are not impaired by high-saturated-fat diet-induced obesity

Obesity is often associated with changes in cardiac function; however, the mechanisms responsible for functional abnormalities have not yet been fully clarified. Considering the lack of information regarding high-saturated-fat diet-induced obesity, heart function, and the proteins involved in myocardial calcium (Ca²⁺) handling, the aim of this study was to test the hypothesis that this dietary model of obesity leads to cardiac dysfunction resulting from alterations in the regulatory proteins of intracellular Ca²⁺ homeostasis. Male Wistar rats were distributed into two groups: control (C, n=18; standard diet) and obese (Ob, n=19; high-saturated-fat diet), which were fed for 33 weeks. Cardiac structure and function were evaluated using echocardiographic and isolated papillary muscle analyses. Myocardial protein expressions of sarcoplasmic reticulum Ca²⁺-ATPase, phospholamban (PLB), PLB serine-16 phosphorylation, PLB threonine-17 phosphorylation, ryanodine receptor, calsequestrin, Na⁺/Ca²⁺ exchanger, and L-type Ca²⁺ channel were assessed by western blot. Obese rats presented 104% increase in the adiposity index (C: 4.5±1.4 vs Ob: 9.2±1.5%) and obesity-related comorbidities compared to control rats. The left atrium diameter (C: 5.0±0.4 vs Ob: 5.5±0.5 mm) and posterior wall shortening velocity (C: 36.7±3.4 vs Ob: 41.8±3.8 mm/s) were higher in the obese group than in the control. The papillary muscle function was similar between the groups at baseline and after inotropic and lusitropic maneuvers. Obesity did not lead to changes in myocardial Ca²⁺ handling proteins expression. In conclusion, the hypothesis was not confirmed, since the high-saturated-fat diet-induced obese rats did not present cardiac dysfunction or impaired intracellular Ca²⁺ handling proteins.

Cynometra cauliflora Linn. Attenuates metabolic abnormalities in high-fat diet-induced obese mice

ETHNOPHARMACOLOGICAL RELEVANCE

Cynometra cauliflora Linn. belongs to the Fabaceae family and is known locally in Malaysia as nam-nam. Traditionally, a decoction of the C. cauliflora leaves is used for treating hyperlipidemia and diabetes.

AIM OF THE STUDY

This study aims to investigate the anti-obesity and lipid lowering effects of ethanolic extract of C. cauliflora leaves and its major compound (vitexin) in C57BL/6 obese mice induced by high-fat diet (HFD), as well as to further identify the molecular mechanism underlying this action.

METHODS AND MATERIAL

Male C57BL/6 mice were fed with HFD (60% fat) for 16 weeks to become obese. The treatment started during the last 8 weeks of HFD feeding and the obese mice were treated with C. cauliflora leaf extract at 200 and 400 mg/kg/day, orlistat (10 mg/kg) and vitexin (10 mg/kg).

RESULTS

The oral administration of C. cauliflora (400 and 200 mg/kg) and vitexin significantly reduced body weight, adipose tissue and liver weight and lipid accumulation in the liver compared to control HFD group. Both doses of C. cauliflora also significantly (P ≤ 0.05) decreased serum triglyceride, LDL, lipase, IL-6, peptide YY, resistin levels, hyperglycemia, hyperinsulinemia, and hyperleptinemia compared to the control HFD group. Moreover, C. cauliflora significantly up-regulated the expression of adiponectin, Glut4, Mtor, IRS-1 and InsR genes, and significantly decreased the expression of Lepr in white adipose tissue. Furthermore, C. cauliflora significantly up-regulated the expression of hypothalamus Glut4, Mtor and NF-kB genes. GC-MS analysis of C. cauliflora leaves detected the presence of phytol, vitamin E and β-sitosterol. Besides, the phytochemical evaluation of C. cauliflora leaves showed the presence of flavonoid, saponin and phenolic compounds.

CONCLUSION

This study shows interesting outcomes of C. cauliflora against HFD-induced obesity and associated metabolic abnormalities. Therefore, the C. cauliflora extract could be a potentially effective agent for obesity management and its related metabolic disorders such as insulin resistance and hyperlipidemia.

Potential Anti-obesogenic Effects of Ginkgo biloba Observed in Epididymal White Adipose Tissue of Obese Rats

Exacerbated expansion of adipose tissue seen in diet-induced obesity leads to endocrine dysfunction and disturbance in adipokine secretion, with such abnormal profile positively associated with type 2 diabetes and other mild chronic inflammatory conditions. Ginkgo biloba extract (GbE), a mixture of polyphenols with antioxidant properties, has been recently investigated in a variety of experimental models of endocrine dysfunction, with several potentially beneficial effects identified, including improvement in insulin sensitivity in obese rats, and reduction of weight gain in ovariectomy-induced obesity and diet-induced obesity. The aim of this study was to investigate in high fat diet-induced obese male rats the effects of GbE supplementation for 2 weeks on adipocyte volume and adipose tissue lipid accumulation. GbE supplementation was effective in reducing energy intake in obese rats compared to the saline-treated placebo group. Epididymal adipocyte volume was reduced in GbE-supplemented rats, as were epididymal [1-14C]-acetate incorporation into fatty acids, perilipin (Plin 1) and fatty acid synthase (Fasn) mRNA, and FAS protein levels. Adipocyte hypertrophy in obesity is associated with insulin resistance, and in the present study we observed a reduction in the adipocyte volume of GbE-supplemented obese rats to dimensions equivalent to adipocytes from non-obese rats. GbE supplementation significantly reduced acetate accumulation and tended to reduce [3H]-oleate incorporation, into epididymal adipose tissue, suggesting a potentially anti-obesogenic effect in longer term therapies. Further studies that investigate the effects of GbE supplementation in other experimental models are required to fully elucidate its suggested beneficial effects on mild chronic inflammatory conditions.

Benefits of blended oil consumption over other sources of lipids on the cardiovascular system in obese rats

High consumption of cooking oils in modern society is believed to be the major cause of cardiovascular disease.

Comparison of Effects of Diet on Mammary Cancer: Efficacy of Various Preventive Agents and Metabolomic Changes of Different Diets and Agents

To determine the effects of diet, rats were placed on a standard diet (4% fat) or on a modified Western (high-fat diet, HFD) diet (21% fat) at 43 days of age (DOA) and administered methylnitrosourea (MNU) at 50 DOA. Rats were administered effective (tamoxifen, vorozole, and Targretin) or ineffective (metformin and Lipitor) chemopreventive agents either by daily gavage or in the diet beginning at 57 DOA and continuing until sacrifice (190 DOA). Latency period of the tumors was determined by palpation, and multiplicity and cancer weights per rat were determined at final sacrifice. Rats on the HFD versus standard diet had: (i) a 6% increase in final body weights; (ii) significant decreases in tumor latency; and (iii) significant increases in final tumor multiplicity and average tumor weight. Tamoxifen, vorozole, and Targretin were highly effective preventive agents, whereas Lipitor and metformin were ineffective in rats on either diet. Serum was collected at 78 DOA and at sacrifice (190 DOA), and metabolomics were determined to identify the metabolite changes due to diets and effective agents. Rats given the HFD had increased levels of saturated free fatty acids (including myristate) and decreased levels of 2-aminooctanoate. Furthermore, rats on the HFD diet had increased levels of 2-aminobutyrate and decreases in glycine markers previously identified as indicators of prediabetes. Targretin increased long-chain glycophospholipids (e.g., oleyl-linoleoyl-glycerophosphocholine) and decreased primary bile acids (e.g., taurocholate). Tamoxifen increased palmitoyl-linoleoyl-glycophosphocholine and decreased stearoyl-arachidonyl glycophosphocholine. Finally, increased levels of methylated nucleotides (5-methylcytidine) and decreased levels of urea cycle metabolites (N-acetylcitrulline) were associated with the presence of mammary cancers.

Impact of chronic and low cadmium exposure of rats: sex specific disruption of glucose metabolism

BACKGROUND

Several epidemiological and animal studies suggest a positive association between cadmium (Cd) exposure and incidence of type 2 diabetes, but the association remains controversial. Besides, the experimental data have mainly been obtained with relatively high levels of Cd, over various periods of time, and with artificial routes of administration.

OBJECTIVES

Do environmental exposures to Cd induce significant disruption of glucose metabolism?

METHODS

Adults Wistar rats were exposed for three months to 0, 5, 50 or 500 μg.kg^-1.d^-1 of CdCl₂ in drinking water. Relevant parameters of glucose homeostasis were measured.

RESULTS

Cd accumulated in plasma, kidney and liver of rats exposed to 50 and 500 μg.kg^-1.d^-1, without inducing signs of organ failure. In rats drinking 5 μg.kg^-1.d^-1 for 3 months, Cd exposure did not lead to any significant increase of Cd in these organs. At 50 and 500 μg.kg^-1.d^-1 of Cd, glucose and insulin tolerance were unchanged in both sexes. However, females exhibited a significant increase of both fasting and glucose-stimulated plasma insulin that was assigned to impaired hepatic insulin extraction as indicated by unaltered fasting C-peptide plasma levels.

CONCLUSIONS

Glucose homeostasis is sensitive to chronic Cd exposure in a gender-specific way. Moreover, this study proves that an environmental pollutant such as Cd can have, at low concentrations, an impact on the glucose homeostatic system and it highlights the importance of a closer scrutiny of the underlying environmental causes to understand the increased incidence of type 2 diabetes.

Why Do Mice Overeat High-Fat Diets? How High-Fat Diet Alters the Regulation of Daily Caloric Intake in Mice

OBJECTIVE

Ad libitum high-fat diets (HFDs) spontaneously increase caloric intake in rodents, which correlates positively with weight gain. However, it remains unclear why rodents overeat HFDs. This paper investigated how changing the proportion of diet that came from HFDs might alter daily caloric intake in mice.

METHODS

Mice were given 25%, 50%, or 90% of their daily caloric need from an HFD, along with ad libitum access to a low-fat rodent chow diet. Food intake was measured daily to determine how these HFD supplements impacted total daily caloric intake. Follow-up experiments addressed the timing of HFD feeding.

RESULTS

HFD supplements did not alter total caloric intake or body weight. In a follow-up experiment, mice consumed approximately 50% of their daily caloric need from an HFD in 30 minutes during the light cycle, a time when mice do not normally consume food.

CONCLUSIONS

An HFD did not disrupt regulation of total daily caloric intake, even when up to 90% of total calories came from the HFD. However, HFDs increased daily caloric intake when provided ad libitum and were readily consumed by mice outside of their normal feeding cycle. Ad libitum HFDs appear to induce overconsumption beyond the mechanisms that regulate daily caloric intake.

Modeling the Western Diet for Preclinical Investigations

Rodent models have been invaluable for biomedical research. Preclinical investigations with rodents allow researchers to investigate diseases by using study designs that are not suitable for human subjects. The primary criticism of preclinical animal models is that results are not always translatable to humans. Some of this lack of translation is due to inherent differences between species. However, rodent models have been refined over time, and translatability to humans has improved. Transgenic animals have greatly aided our understanding of interactions between genes and disease and have narrowed the translation gap between humans and model animals. Despite the technological innovations of animal models through advances in genetics, relatively little attention has been given to animal diets. Namely, developing diets that replicate what humans eat will help make animal models more relevant to human populations. This review focuses on commonly used rodent diets that are used to emulate the Western dietary pattern in preclinical studies of obesity and type 2 diabetes, nonalcoholic liver disease, maternal nutrition, and colorectal cancer.

The Antiepileptic Ketogenic Diet Alters Hippocampal Transporter Levels and Reduces Adiposity in Aged Rats

Nutritional ketosis is induced by high fat/low carbohydrate dietary regimens, which produce high levels of circulating ketone bodies, shifting metabolism away from glucose utilization. While ketogenic diets (KD) were initially introduced to suppress seizures, they are garnering attention for their potential to treat a myriad of neurodegenerative and metabolic disorders that are associated with advanced age. The feasibility and physiological impact of implementing a long-term KD in old animals, however, has not been systematically examined. In this study, young and aged rats consumed a calorically- and nutritionally-matched KD or control diet for 12 weeks. All KD-fed rats maintained higher levels of BHB and lower levels of glucose relative to controls. However, it took the aged rats longer to reach asymptotic levels of BHB compared to young animals. Moreover, KD-fed rats had significantly less visceral white and brown adipose tissue than controls without a loss of lean mass. Interestingly, the KD led to significant alterations in protein levels of hippocampal transporters for monocarboxylates, glucose, and vesicular glutamate and gamma-aminobutyric acid. Most notably, the age-related decline in vesicular glutamate transporter expression was reversed by the KD. These data demonstrate the feasibility and potential benefits of KDs for treating age-associated neural dysfunction.

Animal models of obesity and diabetes mellitus

More than one-third of the worldwide population is overweight or obese and therefore at risk of developing type 2 diabetes mellitus. In order to mitigate this pandemic, safer and more potent therapeutics are urgently required. This necessitates the continued use of animal models to discover, validate and optimize novel therapeutics for their safe use in humans. In order to improve the transition from bench to bedside, researchers must not only carefully select the appropriate model but also draw the right conclusions. In this Review, we consolidate the key information on the currently available animal models of obesity and diabetes and highlight the advantages, limitations and important caveats of each of these models.

Omega-6 and omega-3 oxylipins are implicated in soybean oil-induced obesity in mice

Soybean oil consumption is increasing worldwide and parallels a rise in obesity. Rich in unsaturated fats, especially linoleic acid, soybean oil is assumed to be healthy, and yet it induces obesity, diabetes, insulin resistance, and fatty liver in mice. Here, we show that the genetically modified soybean oil Plenish, which came on the U.S. market in 2014 and is low in linoleic acid, induces less obesity than conventional soybean oil in C57BL/6 male mice. Proteomic analysis of the liver reveals global differences in hepatic proteins when comparing diets rich in the two soybean oils, coconut oil, and a low-fat diet. Metabolomic analysis of the liver and plasma shows a positive correlation between obesity and hepatic C18 oxylipin metabolites of omega-6 (ω6) and omega-3 (ω3) fatty acids (linoleic and α-linolenic acid, respectively) in the cytochrome P450/soluble epoxide hydrolase pathway. While Plenish induced less insulin resistance than conventional soybean oil, it resulted in hepatomegaly and liver dysfunction as did olive oil, which has a similar fatty acid composition. These results implicate a new class of compounds in diet-induced obesity–C18 epoxide and diol oxylipins.

Nutritional approaches for managing obesity-associated metabolic diseases

Obesity is an ongoing pandemic and serves as a causal factor of a wide spectrum of metabolic diseases including diabetes, fatty liver disease, and cardiovascular disease. Much evidence has demonstrated that nutrient overload/overnutrition initiates or exacerbates inflammatory responses in tissues/organs involved in the regulation of systemic metabolic homeostasis. This obesity-associated inflammation is usually at a low-grade and viewed as metabolic inflammation. When it exists continuously, inflammation inappropriately alters metabolic pathways and impairs insulin signaling cascades in peripheral tissues/organs such as adipose tissue, the liver and skeletal muscles, resulting in local fat deposition and insulin resistance and systemic metabolic dysregulation. In addition, inflammatory mediators, e.g., proinflammatory cytokines, and excessive nutrients, e.g., glucose and fatty acids, act together to aggravate local insulin resistance and form a vicious cycle to further disturb the local metabolic pathways and exacerbate systemic metabolic dysregulation. Owing to the critical role of nutrient metabolism in controlling the initiation and progression of inflammation and insulin resistance, nutritional approaches have been implicated as effective tools for managing obesity and obesity-associated metabolic diseases. Based on the mounting evidence generated from both basic and clinical research, nutritional approaches are commonly used for suppressing inflammation, improving insulin sensitivity, and/or decreasing fat deposition. Consequently, the combined effects are responsible for improvement of systemic insulin sensitivity and metabolic homeostasis.