Identification of optimal reference genes for RT-qPCR in the rat hypothalamus and intestine for the study of obesity

Evaluation of suitable reference genes for gene expression studies in the developing mouse cortex using RT-qPCR

BACKGROUND

Real-time quantitative PCR (RT-qPCR) is a widely used method to investigate gene expression in neuroscience studies. Accurate relative quantification of RT-qPCR requires the selection of reference genes that are stably expressed across the experimental conditions and tissues of interest. While RT-qPCR is often performed to investigate gene expression changes during neurodevelopment, few studies have examined the expression stability of commonly used reference genes in the developing mouse cortex.

RESULTS

Here, we evaluated the stability of five housekeeping genes, Actb, Gapdh, B2m, Rpl13a, and Hprt, in cortical tissue from mice at embryonic day 15 to postnatal day 0 to identify optimal reference genes with stable expression during late corticogenesis. The expression stability was assessed using five computational algorithms: BestKeeper, geNorm, NormFinder, DeltaCt, and RefFinder. Our results showed that B2m, Gapdh, and Hprt, or a combination of B2m/Gapdh and B2m/Hprt, were the most stably expressed genes or gene pairs. In contrast, Actb and Rpl13a were the least stably expressed.

CONCLUSION

This study identifies B2m, Gapdh, and Hprt as suitable reference genes for relative quantification in RT-qPCR-based cortical development studies spanning the period of embryonic day 15 to postnatal day 0.

Evaluation of reference genes for qPCR in human liver and kidney tissue from individuals with obesity

Given the obesity epidemic and the prevalence of comorbidities, there is an ongoing need to understand the health consequences of this disease state better. Understanding gene expression signals will facilitate the identification of mechanisms of kidney and liver dysfunction/disease often present in individuals with obesity. qPCR is the standard method for studying changes in relative gene expression. Reference genes (RGs) are obligatory for accurately normalizing mRNA transcript levels across samples. Despite the prevalence of qPCR, the reliability of the data is often compromised because RGs are still used without validation or have proven to be unstable in different tissues and various diseases. In this study, we validated seven reference genes (ACTB, B2M, RPLP0, HPRT1, GAPDH, 18S rRNA, and PPIA) using human liver tissue from 15 lean individuals and 17 individuals with a BMI ≥ 25 and human kidney tissue from 13 lean individuals and 15 individuals with a BMI ≥ 25. Cross-validation of expression stability was performed using the RefFinder platform with four algorithms: NormFinder, BestKeeper, geNorm, and the comparative ΔCt method. In obesity-related studies, the most suitable reference genes in gene expression studies are RPLP0 and HPRT1 in human kidney tissue and RPLP0 and GAPDH in the liver.

Binge Eating and Obesity Differentially Alter the Mesolimbic Endocannabinoid System in Rats

Binge eating disorder (BED) is characterized by the rapid overconsumption of palatable food in a short amount of time, often leading to obesity. The endocannabinoid system (ECS), a system involved in palatable food intake, is highly expressed in reward-related brain regions and is involved in both obesity and BED. This study investigated differences in ECS expression between these conditions using male Wistar rats exposed to specific regimen over six weeks: a non-access group (NA) with a standard diet, a continuous access group (CA) with free-choice high-fat high-sugar (fcHFHS) diet modeling obesity, and an intermittent access group (IA) with intermittent fcHFHS access modeling BED. Food intake was measured, and brain tissues from the nucleus accumbens (NAc), dorsal striatum (DS), ventral tegmental area (VTA), and rostromedial tegmental nucleus (RMTg) were analyzed for ECS expression using qPCR and mass spectrometry. We identified differential ECS expression across palatable food access groups, with variations depending on the brain region (striatal or mesencephalic). Correlation analyses revealed ECS dysregulations dependent on the type (fat or sucrose) and quantity of palatable food consumed. Comparative network analysis revealed co-regulation patterns of ECS-related genes with specific signatures associated with each eating pattern, highlighting RMTg as a key region for future research in eating behavior.

A systematic review on the selection of reference genes for gene expression studies in rodents: are the classics the best choice?

Rodents are commonly used as animal models in studies investigating various experimental conditions, often requiring gene expression analysis. Quantitative real-time reverse transcription PCR (RT-qPCR) is the most widely used tool to quantify target gene expression levels under different experimental conditions in various biological samples. Relative normalization with reference genes is a crucial step in RT-qPCR to obtain reliable quantification results. In this work, the main reference genes used in gene expression studies among the three rodents commonly employed in scientific research-hamster, rat, and mouse-are analyzed and described. An individual literature search for each rodent was conducted using specific search terms in three databases: PubMed, Scopus, and Web of Science. A total of 157 articles were selected (rats = 73, mice = 79, and hamsters = 5), identifying various reference genes. The most commonly used reference genes were analyzed according to each rodent, sample type, and experimental condition evaluated, revealing a great variability in the stability of each gene across different samples and conditions. Classic genes, which are expected to be stably expressed in both samples and conditions analyzed, demonstrated greater variability, corroborating existing concerns about the use of these genes. Therefore, this review provides important insights for researchers seeking to identify suitable reference genes for their validation studies in rodents.

Paternal high-fat diet affects weight and DNA methylation of their offspring

Obesity poses a public health threat, reaching epidemic proportions. Our hypothesis suggests that some of this epidemic stems from its transmission across generations via paternal epigenetic mechanisms. To investigate this possibility, we focused on examining the paternal transmission of CpG methylation. First-generation male Wistar rats were fed either a high-fat diet (HF) or chow and were mated with females fed chow. We collected sperm from these males. The resulting offspring were raised on a chow diet until day 35, after which they underwent a dietary challenge. Diet-induced obese (DIO) male rats passed on the obesogenic trait to both male and female offspring. We observed significant hypermethylation of the Pomc promoter in the sperm of HF-treated males and in the hypothalamic arcuate nucleus (Arc) of their offspring at weaning. However, these differences in Arc methylation decreased later in life. This hypermethylation is correlated with increased expression of DNMT3B. Further investigating genes in the Arc that might be involved in obesogenic transgenerational transmission, using reduced representation bisulfite sequencing (RRBS) we identified 77 differentially methylated regions (DMRs), highlighting pathways associated with neuronal development. These findings support paternal CpG methylation as a mechanism for transmitting obesogenic traits across generations.

Identification of adipose tissue transcriptomic memory of anorexia nervosa

BACKGROUND

Anorexia nervosa (AN) is a complex debilitating disease characterized by intense fear of weight gain and excessive exercise. It is the deadliest of any psychiatric disorder with a high rate of recidivism, yet its pathophysiology is unclear. The Activity-Based Anorexia (ABA) paradigm is a widely accepted mouse model of AN that recapitulates hypophagia and hyperactivity despite reduced body weight, however, not the chronicity.

METHODS

Here, we modified the prototypical ABA paradigm to increase the time to lose 25% of baseline body weight from less than 7 days to more than 2 weeks. We used this paradigm to identify persistently altered genes after weight restoration that represent a transcriptomic memory of under-nutrition and may contribute to AN relapse using RNA sequencing. We focused on adipose tissue as it was identified as a major location of transcriptomic memory of over-nutririon.

RESULTS

We identified 300 dysregulated genes that were refractory to weight restroration after ABA, including Calm2 and Vps13d, which could be potential global regulators of transcriptomic memory in both chronic over- and under-nutrition.

CONCLUSION

We demonstrated the presence of peristent changes in the adipose tissue transcriptome in the ABA mice after weight restoration. Despite being on the opposite spectrum of weight perturbations, majority of the transcriptomic memory genes of under- and over-nutrition did not overlap, suggestive of the different mechanisms involved in these extreme nutritional statuses.

Nuclear receptor 5A2 regulation of Agrp underlies olanzapine-induced hyperphagia

Antipsychotic (AP) drugs are efficacious treatments for various psychiatric disorders, but excessive weight gain and subsequent development of metabolic disease remain serious side effects of their use. Increased food intake leads to AP-induced weight gain, but the underlying molecular mechanisms remain unknown. In previous studies, we identified the neuropeptide Agrp and the transcription factor nuclear receptor subfamily 5 group A member 2 (Nr5a2) as significantly upregulated genes in the hypothalamus following AP-induced hyperphagia. While Agrp is expressed specifically in the arcuate nucleus of the hypothalamus and plays a critical role in appetite stimulation, Nr5a2 is expressed in both the CNS and periphery, but its role in food intake behaviors remains unknown. In this study, we investigated the role of hypothalamic Nr5a2 in AP-induced hyperphagia and weight gain. In hypothalamic cell lines, olanzapine treatment resulted in a dose-dependent increase in gene expression of Nr5a2 and Agrp. In mice, the pharmacological inhibition of NR5A2 decreased olanzapine-induced hyperphagia and weight gain, while the knockdown of Nr5a2 in the arcuate nucleus partially reversed olanzapine-induced hyperphagia. Chromatin-immunoprecipitation studies showed for the first time that NR5A2 directly binds to the Agrp promoter region. Lastly, the analysis of single-cell RNA seq data confirms that Nr5a2 and Agrp are co-expressed in a subset of neurons in the arcuate nucleus. In summary, we identify Nr5a2 as a key mechanistic driver of AP-induced food intake. These findings can inform future clinical development of APs that do not activate hyperphagia and weight gain.

The gut microbiota contributes to the pathogenesis of anorexia nervosa in humans and mice

Anorexia nervosa (AN) is an eating disorder with a high mortality. About 95% of cases are women and it has a population prevalence of about 1%, but evidence-based treatment is lacking. The pathogenesis of AN probably involves genetics and various environmental factors, and an altered gut microbiota has been observed in individuals with AN using amplicon sequencing and relatively small cohorts. Here we investigated whether a disrupted gut microbiota contributes to AN pathogenesis. Shotgun metagenomics and metabolomics were performed on faecal and serum samples, respectively, from a cohort of 77 females with AN and 70 healthy females. Multiple bacterial taxa (for example, Clostridium species) were altered in AN and correlated with estimates of eating behaviour and mental health. The gut virome was also altered in AN including a reduction in viral-bacterial interactions. Bacterial functional modules associated with the degradation of neurotransmitters were enriched in AN and various structural variants in bacteria were linked to metabolic features of AN. Serum metabolomics revealed an increase in metabolites associated with reduced food intake (for example, indole-3-propionic acid). Causal inference analyses implied that serum bacterial metabolites are potentially mediating the impact of an altered gut microbiota on AN behaviour. Further, we performed faecal microbiota transplantation from AN cases to germ-free mice under energy-restricted feeding to mirror AN eating behaviour. We found that the reduced weight gain and induced hypothalamic and adipose tissue gene expression were related to aberrant energy metabolism and eating behaviour. Our 'omics' and mechanistic studies imply that a disruptive gut microbiome may contribute to AN pathogenesis.

Chronic cold exposure modulates genes related to feeding and immune system in Nile tilapia (Oreochromis niloticus)

Nile tilapia is the fourth most produced species in the global aquiculture panorama. This species requires water temperatures higher than 16 °C to grow and survive, and so, little is known about the effects of low temperatures on genes related to food intake and inflammatory responses. This study brought insights about the modulation of genes in different tissues of Nile tilapia chronically exposed to low temperatures. Thus, sixty animals were divided in two experimental groups: a control group in which the animals remained at the optimum temperature of 24 °C; and an exposed to cold group, in which a decrease in the water temperature was applied until reaching 15 °C. These conditions were maintained for 28 days. Blood samples were collected for flow cytometry analysis, while brain, spleen, liver, and kidney tissues were collected for total RNA extraction, followed by quantitative PCR (RT-qPCR). For genes related to feeding process pathway, it was observed an upregulation in pyy and a downregulation of npy and cart gene expression. Also, pro-inflammatory cytokine genes were modulated in the spleen, kidney and liver with a higher expression of il-1b and tnfα and a reduction in the il-8 and nf-κβ gene expressions in the group exposed to 15 °C. The fish exposed to cold presented higher serum cortisol levels than the ones from control group. The blood cell analysis showed a lower level of membrane fluidity and a higher DNA fragmentation and cell disruption in the group exposed to cold. These findings suggest an important effect of a stressful situation in the tilapia organism due to cold exposure. This study brings insights on tilapia wellbeing under low temperature stress. It can be a first step to understanding the appropriate way to cope with cold impacts on aquaculture.

Antipsychotic-induced weight gain and metabolic effects show diurnal dependence and are reversible with time restricted feeding

Antipsychotic drugs (AP) are highly efficacious treatments for psychiatric disorders but are associated with significant metabolic side-effects. The circadian clock maintains metabolic homeostasis by sustaining daily rhythms in feeding, fasting and hormone regulation but how circadian rhythms interact with AP and its associated metabolic side-effects is not well-known. We hypothesized that time of AP dosing impacts the development of metabolic side-effects. Weight gain and metabolic side-effects were compared in C57Bl/6 mice and humans dosed with APs in either the morning or evening. In mice, AP dosing at the start of the light cycle/rest period (AM) resulted in significant increase in food intake and weight gain compared with equivalent dose before the onset of darkness/active period (PM). Time of AP dosing also impacted circadian gene expression, metabolic hormones and inflammatory pathways and their diurnal expression patterns. We also conducted a retrospective examination of weight and metabolic outcomes in patients who received risperidone (RIS) for the treatment of serious mental illness and observed a significant association between time of dosing and severity of RIS-induced metabolic side-effects. Time restricted feeding (TRF) has been shown in both mouse and some human studies to be an effective therapeutic intervention against obesity and metabolic disease. We demonstrate, for the first time, that TRF is an effective intervention to reduce AP-induced metabolic side effects in mice. These studies identify highly effective and translatable interventions with potential to mitigate AP-induced metabolic side effects.

Adipocytes control food intake and weight regain via Vacuolar-type H+ ATPase

Energy metabolism becomes dysregulated in individuals with obesity and many of these changes persist after weight loss and likely play a role in weight regain. In these studies, we use a mouse model of diet-induced obesity and weight loss to study the transcriptional memory of obesity. We found that the 'metabolic memory' of obesity is predominantly localized in adipocytes. Utilizing a C. elegans-based food intake assay, we identify 'metabolic memory' genes that play a role in food intake regulation. We show that expression of ATP6v0a1, a subunit of V-ATPase, is significantly induced in both obese mouse and human adipocytes that persists after weight loss. C. elegans mutants deficient in Atp6v0A1/unc32 eat less than WT controls. Adipocyte-specific Atp6v0a1 knockout mice have reduced food intake and gain less weight in response to HFD. Pharmacological disruption of V-ATPase assembly leads to decreased food intake and less weight re-gain. In summary, using a series of genetic tools from invertebrates to vertebrates, we identify ATP6v0a1 as a regulator of peripheral metabolic memory, providing a potential target for regulation of food intake, weight loss maintenance and the treatment of obesity.

Evaluation of candidate reference genes for quantitative real-time PCR analysis in a male rat model of dietary iron deficiency

BACKGROUND

Quantitative real-time polymerase chain reaction (qPCR) is a reliable and efficient method for quantitation of gene expression. Due to the increased use of qPCR in examining nutrient-gene interactions, it is important to examine, develop, and utilize standardized approaches for data analyses and interpretation. A common method used to normalize expression data involves the use of reference genes (RG) to determine relative mRNA abundance. When calculating the relative abundance, the selection of RG can influence experimental results and has the potential to skew data interpretation. Although common RG may be used for normalization, often little consideration is given to the suitability of RG selection for an experimental condition or between various tissue or cell types. In the current study, we examined the stability of gene expression using BestKeeper, comparative delta quantitation cycle, NormFinder, and RefFinder in a variety of tissues obtained from iron-deficient and pair-fed iron-replete rats to determine the optimal selection among ten candidate RG.

RESULTS

Our results suggest that several commonly used RG (e.g., Actb and Gapdh) exhibit less stability compared to other candidate RG (e.g., Rpl19 and Rps29) in both iron-deficient and iron-replete pair-fed conditions. For all evaluated RG, Tfrc expression significantly increased in iron-deficient animal livers compared to the iron-replete pair-fed controls; however, the relative induction varied nearly 4-fold between the most suitable (Rpl19) and least suitable (Gapdh) RG.

CONCLUSION

These results indicate the selection and use of RG should be empirically determined and RG selection may vary across experimental conditions and biological tissues.

Determination of the panel of reference genes for quantitative real-time PCR in fetal and adult rat intestines

In quantitative real-time PCR (qRT-PCR) detection, the stability of reference genes varies with different organs, tissue locations, sex and developmental stages. This study aimed to screen out and determine the optimal panel of reference genes of the intestine in pre- and post-natal rats of different sex. We used qRT-PCR to detect the mRNA expression of six commonly used reference genes (ACTB, GAPDH, HPRT1, B2M, RPLPO and SDHA) in rat intestines at gestational day 21 (GD21) and postnatal week 12 (PW12). Using GeNorm, BestKeeper and NormFinder software comprehensively analyzed the stability of candidate reference genes and screened out stable reference genes. Further, we used the pathological model of prenatal dexamethasone exposure (PDE) to verify the stability of the selected panel of reference genes. Based on the results of the software analysis, the optimal panel of reference genes in the fetal rat intestine was SDHA + ACTB, and the adult rat small intestine and colon were ACTB + HPRT1 and RPLP0 + GAPDH, respectively. There was no significant sex difference in the above results. Besides, in the PDE model, the results were consistent with those under physiological conditions. Therefore, the stability of intestinal reference genes in fetal rats and adult rats was different, and the intestinal reference genes of adult rats were intestinal segments-specific. The selected panel of reference genes was still stable under pathological conditions. This study determined the optimal panel of reference genes of pre- and post-natal rat intestines and provided reliable reference genes for the qRT-PCR analysis of rat intestines.

The endocannabinoid system is modulated in reward and homeostatic brain regions following diet-induced obesity in rats: a cluster analysis approach

Objectives

Increased availability of high-calorie palatable food in most countries has resulted in overconsumption of these foods, suggesting that excessive eating is driven by pleasure, rather than metabolic need. The behavior contributes to the rise in eating disorders, obesity, and associated pathologies like diabetes, cardiac disease, and cancers. The mesocorticolimbic dopamine and homeostatic circuits are interconnected and play a central role in palatable food intake. The endocannabinoid system is expressed in these circuits and represents a potent regulator of feeding, but the impact of an obesogenic diet on its expression is not fully known.

Methods

Food intake and body weight were recorded in male Wistar rats over a 6-week free-choice regimen of high fat and sugar; transcriptional regulations of the endocannabinoid system were examined post-mortem in brain reward regions (prefrontal cortex, nucleus accumbens, ventral tegmental area, and arcuate nucleus). K-means cluster analysis was used to classify animals based on individual sensitivity to obesity and palatable food intake. Endocannabinoid levels were quantified in the prefrontal cortex and nucleus accumbens. Gene expression in dopamine and homeostatic systems, including ghrelin and leptin receptors, and classical homeostatic peptides, were also investigated.

Results

The free-choice high-fat -and sugar diet induced hyperphagia and obesity in rats. Cluster analysis revealed that the propensity to develop obesity and excessive palatable food intake was differently associated with dopamine and endocannabinoid system gene expression in reward and homeostatic brain regions. CB2 receptor mRNA was increased in the nucleus accumbens of high sugar consumers, whereas CB1 receptor mRNA was decreased in obesity prone rats.

Conclusions

Transcriptional data are consistent with observations of altered dopamine function in rodents that have access to an obesogenic diet and point to cannabinoid receptors as GPCR targets involved in neuroplasticity mechanisms associated with maladaptive intake of palatable food.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02613-0.

Selar (Selar crumenophthalmus) Fish Protein Hydrolysate Has Antidiabetic Properties Possibly through GLP-1

Background :

Enzymatic hydrolysis of fish protein using protease or fish protein hydrolysate can form bioactive peptides that have antidiabetic activity. One potential mechanism of fish protein hydrolysate is reducing blood glucose through increased endogenous glucagon like peptide (GLP)-1 production. Tempeh is soy fermented food that has protease which is potential biocatalyst in producing fish protein hydrolysate.

Objective:

To evaluate the antidiabetic properties of Selar (Selar crumenophthalmus) fish protein hydrolysate using tempeh protease as biocatalyst and duodenal gene expression of GLP-1.

Methods:

Selar fish protein isolate was digested for 8 hours at 37°C using crude tempeh protease. Diabetes mellitus was induced in rats by intraperitoneal injection of streptozotosin (65 mg/kg bw) and nicotinamide (230 mg/kg bw). Fish protein isolate and hydrolysate in dose of 300 mg/bw and 500 mg/ bw were orally administered daily for 4 weeks. Blood was drawn for fasting serum glucose and lipid profile analysis. Total RNAs were isolated from duodenum and quantitative real time PCR was performed to quantify mRNA expression of GLP-1. Data were analyzed using one way ANOVA and gene expression analysis were performed using Livak.

Results and Discussion:

There is a significant difference on fasting serum glucose, total cholesterol, triglyceride, LDL-cholesterol, HDL-cholesterol and duodenal GLP-1 mRNA expression level between groups (p<0.05). The duodenal GLP-1 mRNA expression was the highest in rats who received hydrolyzed fish protein 500 mg/ bw.

Conclusion:

Hydrolysis of selar fish protein using tempeh protease has anti-diabetic properties possibly through GLP-1 production.

Binge sucrose-induced neuroadaptations: A focus on the endocannabinoid system

Binge eating, the defining feature of binge eating disorder (BED), is associated with a number of adverse health outcomes as well as a reduced quality of life. Animals, like humans, selectively binge on highly palatable food suggesting that the behaviour is driven by hedonic, rather than metabolic, signals. Given the links to both reward processing and food intake, this study examined the contribution of the endocannabinoid system (ECS) to binge-like eating in rats. Separate groups were given intermittent (12 h) or continuous (24 h) access to 10% sucrose and food over 28 days, with only the 12 h access group displaying excessive sucrose intake within a discrete period of time (i.e., binge eating). Importantly, this group also exhibited alterations in ECS transcripts and endocannabinoid levels in brain reward regions, including an increase in cannabinoid receptor 1 (CB1R) mRNA in the nucleus accumbens as well as changes in endocannabinoid levels in the prefrontal cortex and hippocampus. We then tested whether different doses (1 and 3 mg/kg) of a CB1R antagonist, Rimonabant, modify binge-like intake or the development of a conditioned place preference (CPP) to sucrose. CB1R blockade reduced binge-like intake of sucrose and blocked a sucrose CPP, but only in rats that had undergone 28 days of sucrose consumption. These findings indicate that sucrose bingeing alters the ECS in reward-related areas, modifications that exacerbate the effect of CB1R blockade on sucrose reward. Overall, our results broaden the understanding of neural alterations associated with bingeing eating and demonstrate an important role for CB1R mechanisms in reward processing. In addition, these findings have implications for understanding substance abuse, which is also characterized by excessive and maladaptive intake, pointing towards addictive-like properties of palatable food.

High-Fat Diet Alters the Expression of Reference Genes in Male Mice

Quantitative PCR (qPCR), the most accurate and sensitive technique for quantifying mRNA expression, and choice of appropriate reference genes for internal error controlling in qPCR are essential to understanding the molecular mechanisms that drive the obesity epidemic and its comorbidities. In this study, using the high-fat diet (HFD)-induced obese mouse model, we assessed the expression of 10 commonly used reference genes to validate gene-expression stability in adipose tissue, liver, and muscle across different time points (4, 8, 12, and 16 weeks after HFD feeding) during the process of obesity. The data were analyzed by the GeNorm, NormFinder, BestKeeper, and Delta-Ct method, and the results showed that the most stable reference genes were different for a specific organ or tissue in a specific time point; however, PPIA, RPLP0, and YWHAZ were the top three most stable reference genes in qPCR experiments on adipose, hepatic tissues, and muscles of mice in diet-induced obesity. In addition, the mostly used genes ACTB and GAPDH were more unstable in the fat and liver, the ACTB mRNA levels were increased in four adipose tissues, and the GAPDH mRNA levels were decreased in four adipose tissues and liver after HFD feeding. These results suggest that PPIA, RPLP0, or YWHAZ may be more appropriate to be used as reference gene than ACTB and GAPDH in the adipose tissue and liver of mice during the process of high-fat diet-induced obesity.

Alzheimer amyloid-β- peptide disrupts membrane localization of glucose transporter 1 in astrocytes: implications for glucose levels in brain and blood

Alzheimer’s disease (AD) is associated with disturbances in blood glucose regulation, and type-2 diabetes elevates the risk for dementia. A role for amyloid-β peptide (Aβ) in linking these age-related conditions has been proposed, tested primarily in transgenic mouse lines that overexpress mutated amyloid precursor protein (APP). Because APP has its own impacts on glucose regulation, we examined the BRI-Aβ42 line (“Aβ₄₂-tg”), which produces extracellular Aβ_1–42 in the CNS without elevation of APP. We also looked for interactions with diet-induced obesity (DIO) resulting from a high-fat, high-sucrose (“western”) diet. Aβ₄₂-tg mice were impaired in both spatial memory and glucose tolerance. Although DIO induced insulin resistance, Aβ_1–42 accumulation did not, and the impacts of DIO and Aβ on glucose tolerance were merely additive. Aβ₄₂-tg mice exhibited no significant differences from wild-type in insulin production, body weight, lipidemia, appetite, physical activity, respiratory quotient, an-/orexigenic factors, or inflammatory factors. These negative findings suggested that the phenotype in these mice arose from perturbation of glucose excursion in an insulin-independent tissue. To wit, cerebral cortex of Aβ₄₂-tg mice had reduced glucose utilization, similar to human patients with AD. This was associated with insufficient trafficking of glucose transporter 1 to the plasma membrane in parenchymal brain cells, a finding also documented in human AD tissue. Together, the lower cerebral metabolic rate of glucose and diminished function of parenchymal glucose transporter 1 indicate that aberrant regulation of blood glucose in AD likely reflects a central phenomenon, resulting from the effects of Aβ on cerebral parenchyma, rather than a generalized disruption of hypothalamic or peripheral endocrinology. The involvement of a specific glucose transporter in this deficit provides a new target for the design of AD therapies.

Simplified method for applying static isotropic tensile strain in cell culture experiments with identification of valid RT-qPCR reference genes for PDL fibroblasts

BACKGROUND/OBJECTIVE

Periodontal ligament fibroblasts (PDLF) play an important mediating role in orthodontic tooth movement expressing various cytokines, when exposed to compressive or tensile strain. Here, we present a simplified and easy-to-handle, but reliable and valid method for simulating static isotropic tensile strain in vitro using spherical silicone cap stamps. Furthermore, we identify appropriate reference genes for data normalization in real-time quantitative polymerase chain reaction (RT-qPCR) experiments on PDLF subjected to tensile strain.

MATERIALS AND METHODS

PDLF were cultivated on flexible bioflex membranes and exposed to static isotropic tensile strain of different magnitudes and timeframes. We determined cell number, cytotoxicity, and relative expression of proinflammatory genes cyclooxygenase-2 (COX-2) and interleukin-6 (IL-6). For normalization of RT-qPCR data, we tested the stability and validity of nine candidate reference genes with four mathematical algorithms (geNorm, NormFinder, comparative ΔCq, and BestKeeper) and ranked them based on their calculated expression stability.

RESULTS

We observed no decrease in cell number or cytotoxic effect at any of the applied magnitudes and timeframes of tensile strain. At 16 per cent and 35 per cent tensile strain for 48 hours, we detected a significant increase in COX-2 and decrease in IL-6 gene expression. Highest stability was found for TBP (TATA-box-binding protein) and PPIB (peptidylprolyl isomerase A) in reference gene validation. According to the geNorm algorithm, both genes in conjunction are sufficient for normalization. In contrast to all other candidate genes tested, gene expression normalization of target gene COX-2 to reference genes EEF1A1, RPL22, and RNA18S5 indicated no significant upregulation of COX-2 expression.

CONCLUSIONS

A strain magnitude of 16 per cent for 48 hours elicited the most distinct cellular response by PDLF subjected to static tensile isotropic strain by the presented method. TBP and PPIB in conjunction proved to be the most appropriate reference genes to normalize target gene expression in RT-qPCR studies on PDLF subjected to tensile strain.

Optimal reference genes for gene expression analysis in polyploid of Cyprinus carpio and Carassius auratus

BACKGROUND

Reference genes are usually stably expressed in various cells and tissues. However, it was reported that the expression of some reference genes may be distinct in different species. In this study, we intend to answer whether the expression of reported traditional reference genes changes or not in the polyploid fish RESULTS: By retrieving the mRNA sequencing data of three different ploidy fish from the NCBI SRA database, we selected 12 candidate reference genes, and examined their expression levels in the 10 tissues and in the four cell lines of three different ploidy fish by real-time PCR. Then, the expression profiles of these 12 candidate reference genes were systematically evaluated by using the software platforms: BestKeeper, NormFinder and geNorm.

CONCLUSION

The 28S ribosomal protein S5 gene (RPS5) and the ribosomal protein S18 gene (RPS18) are the most suitable reference genes for the polyploid of Cyprinus carpio and Carassius auratus, demonstrated by both of the tissues and the cultured cells.

Alanyl-glutamine protects the intestinal barrier function in trained rats against the impact of acute exhaustive exercise

Strenuous exercise triggers deleterious effects on the intestinal epithelium, but their mechanisms are still uncertain. Here, we investigated whether a prolonged training and an additional exhaustive training protocol alter intestinal permeability and the putative effect of alanyl-glutamine (AG) pretreatment in this condition. Rats were allocated into 5 different groups: 1) sedentary; 2 and 3) trained (50 min per day, 5 days per week for 12 weeks) with or without 6 weeks oral (1.5 g/kg) AG supplementation; 4 and 5) trained and subjected to an additional exhaustive test protocol with or without oral AG supplementation. Venous blood samples were collected to determine gasometrical indices at the end of the 12-week protocol or after exhaustive test. Lactate and glucose levels were determined before, during, and after the exhaustive test. Ileum tissue collected after all experimental procedures was used for gene expression analysis of Zonula occludens 1 (ZO-1), occludin, claudin-2, and oligopeptide transporter 1 (PepT-1). Intestinal permeability was assessed by urinary lactulose/mannitol test collected after the 12-week protocol or the exhaustive test. The exhaustive test decreased pH and base excess and increased pCO₂. Training sessions delayed exhaustion time and reduced the changes in blood glucose and lactate levels. Trained rats exhibited upregulation of PEPT-1, ZO-1, and occludin mRNA, which were partially protected by AG. Exhaustive exercise induced intestinal paracellular leakage associated with the upregulation of claudin-2, a phenomenon protected by AG treatment. Thus, AG partially prevented intestinal training adaptations but also blocked paracellular leakage during exhaustive exercise involving claudin-2 and occludin gene expression.

Monocarboxylate Transporter 6-Mediated Interactions with Prostaglandin F2α: In Vitro and In Vivo Evidence Utilizing a Knockout Mouse Model

Monocarboxylate transporter 6 (MCT6; SLC16A5) is a recently studied drug transporter that currently has no annotated endogenous function. Currently, only a handful of compounds have been characterized as substrates for MCT6 (e.g., bumetanide, nateglinide, probenecid, and prostaglandin F_2α (PGF2α)). The objective of our research was to characterize the MCT6-specific transporter kinetic parameters and MCT6-specific in vitro and in vivo interactions of PGF2α. Murine and human MCT6-mediated transport of PGF2α was assessed in MCT6-transfected oocytes. Additionally, endogenous PGF2α and a primary PGF2α metabolite (PGFM) were measured in plasma and urine in Mct6 knockout (Mct6^−/−) and wild-type (Mct6^+/+) mice. Results demonstrated that the affinity was approximately 40.1 and 246 µM respectively, for mouse and human, at pH 7.4. In vivo, plasma PGF2α concentrations in Mct6^−/− mice were significantly decreased, compared to Mct6^+/+ mice (3.3-fold). Mct6^-/- mice demonstrated a significant increase in urinary PGF2α concentrations (1.7-fold). A similar trend was observed with plasma PGFM concentrations. However, overnight fasting resulted in significantly increased plasma PGF2α concentrations, suggesting a diet-dependent role of Mct6 regulation on the homeostasis of systemic PGF2α. Overall, these results are the first to suggest the potential regulatory role of MCT6 in PGF2α homeostasis, and potentially other PGs, in distribution and metabolism.

Low-Protein Diets with Fixed Carbohydrate Content Promote Hyperphagia and Sympathetically Mediated Increase in Energy Expenditure

SCOPE

Dietary protein restriction elicits hyperphagia and increases energy expenditure; however, less is known of whether these responses are a consequence of increasing carbohydrate content. The effects of protein-diluted diets with fixed carbohydrate content on energy balance, hormones, and key markers of protein sensing and thermogenesis in tissues are determined.

METHODS AND RESULTS

Obesity-prone rats (n = 13-16 per group) are randomized to diets containing fixed carbohydrate (52% calories) and varying protein concentrations: 15% (control), 10% (mild protein restriction), 5% (moderate protein restriction) or 1% (severe protein restriction) protein calories, or protein-matched to 5% protein, for 21 days. Propranolol and ondansetron are administered to interrogate the roles of sympathetic and serotonergic systems, respectively, in diet-induced changes in energy expenditure. It is found that mild-to-moderate protein restriction promotes transient hyperphagia, whereas severe protein restriction induces hypophagia, with alterations in meal patterns. Protein restriction enhances energy expenditure that is partly attenuated by propranolol, but not ondansetron. Moderate to severe protein restriction decreases gains in body weight, lean and fat mass, decreased postprandial glucose and leptin, but increased fibroblast growth factor-21 concentrations. Protein-matching retains lean mass suggesting that intake of dietary protein, but not calories, is important for preserving lean mass. Notably, protein restriction increases the protein and/or transcript abundance of key amino acid sensing molecules in liver and intestine (PERK, eIF2α, ATF2, CHOP, 4EBP1, FGF21), and upregulated thermogenic markers (β2AR, Klotho, HADH, UCP-1) in brown adipose tissue.

CONCLUSION

Low-protein diets promote hyperphagia and sympathetically mediated increase in energy expenditure, prevent gains in tissue reserves, and concurrently upregulate hepatic and intestinal amino acid sensing intermediaries and thermogenic markers in brown adipose tissue.

Use of the REVERT® total protein stain as a loading control demonstrates significant benefits over the use of housekeeping proteins when analyzing brain homogenates by Western blot: An analysis of samples representing different gonadal hormone states

Western blot is routinely used to quantify differences in the levels of target proteins in tissues. Standard methods typically use measurements of housekeeping proteins to control for variations in loading and protein transfer. This is problematic, however, when housekeeping proteins also are affected by experimental conditions such as injury, disease, and/or gonadal hormone manipulations. Our goal was to evaluate an alternative and perhaps superior method for conducting Western blot analysis of brain tissue homogenates from rats with distinct physiologically relevant gonadal hormone states. Tissues were collected from the hippocampus, frontal cortex, and striatum of young adult female rats that either were ovariectomized to model surgical menopause, or were treated with the ovatotoxin 4-vinylcyclohexene diepoxide (VCD) to model transitional menopause. Tissues also were collected from rats with a normal estrous cycle killed at proestrus when estradiol levels are high, and at diestrus when estradiol levels are low. Western blot detection of α-tubulin, β-actin, and GAPDH was performed and were compared for sensitivity and reliability with a fluorescent total protein stain (REVERT^®). Results show that the total protein stain was much less variable across samples and had a greater linear range than α-tubulin, β-actin, or GAPDH. The stain was stable and easy to use, and did not interfere with the immunodetection or multiplexed detection of the housekeeping proteins. In addition, we show that normalization of our data to total protein, but not to GAPDH, revealed significant differences in α-tubulin expression in the hippocampus as a function of treatment, and that gel-to-gel consistency in measuring differences between paired samples run on multiple gels was significantly better when data were normalized to total protein than when normalized to GAPDH. These results demonstrate that the REVERT^® total protein stain can be used in Western blot analysis of brain tissue homogenates to control for variations in loading and protein transfer, and provides significant advantages over the use of housekeeping proteins for quantifying changes in the levels of multiple target proteins.

Evaluation of the performance of serum miRNAs as normalizers in microRNA studies focused on cardiovascular disease

Background

Few study has been done to evaluate the stability and superiority of normalizers for serum microRNA (miRNA) study in cardiovascular disease. Therefore, the aim of this study is to assess the suitability of several common normalizers (miR-16, SNOU6, 5S, miR-19b, miR-24, miR-15b, let 7i) in cardiovascular disease.

Methods

We evaluated the stability of the seven circulating miRNAs as reference genes in the blood samples from patients with cardiovascular disease [heart failure (HF) and hypertension] and healthy people. Stability was quantified by combining BestKeeper, NormFinder and comparative delta Cq analysis.

Results

A total of 62 subjects were included in this study, of which 25 patients were with HF, 10 patients were with hypertension, and 27 were healthy people. The analysis from both BestKeeper and comparative delta ct analysis demonstrated that let-7i and miR-16 showed the best performance [the standard deviations (SD) in BestKeeper for let-7i and miR-16 were 0.60 and 0.72, and the mean SD in comparative delta ct analysis for let-7i and miR-16 were 1.79 and 1.82, respectively], while SNOU6 and 5S had the highest variability. In NormFinder analysis, miR-15 show best stability (ρ=0.029), followed by miR-19b (ρ=0.037), let-7i (ρ=0.064), SNOU6 (ρ=0.064), 5S (ρ=0.064), miR-16 (ρ=0.064), while miR-24 (ρ=0.075) showed worst stability.

Conclusions

This study pointed out that in the serum studies focused on cardiovascular disease, let-7i and miR-16 had the best performance, while SNOU6 and 5S were not suitable as reference gene. This study indicate that the selection of an optimal reference genes is important to get an accurate result in serum miRNA studies, the findings are of clinical significance to guide the further miRNA studies or tests.

Bioinformatics Analysis of Genes and Pathways of CD11b+/Ly6Cintermediate Macrophages after Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI), which could induce the poor prognosis. The purpose of this study was to characterize the molecular mechanism of the functional changes of CDllb+/Ly6Cintermediate macrophages after renal IRI. The gene expression profiles of CDllb+/Ly6Cintermcdiate macrophages of the sham surgery mice, and the mice 4 h, 24 h and 9 days after renal IRI were downloaded from the Gene Expression Omnibus database. Analysis of mRNA expression profiles was conducted to identify differentially expressed genes (DEGs), biological processes and pathways by the series test of cluster. Protein-protein interaction network was constructed and analysed to discover the key genes. A total of 6738 DEGs were identified and assigned to 20 model profiles. DEGs in profile 13 were one of the predominant expression profiles, which are involved in immune cell chemotaxis and proliferation. Signet analysis showed that Atp5al, Atp5o, Cox4i, Cdc42, Rac2 and Nhp2 were the key genes involved in oxidation-reduction, apoptosis, migration, M1-M2 differentiation, and proliferation of macrophages. RPS18 may be an appreciate reference gene as it was stable in macrophages. The identified DEGs and their enriched pathways investigate factors that may participate in the functional changes of CD 1lb+Ly6Cintermediate macrophages after renal IRI. Moreover, the vital gene Nhp2 may involve the polarization of macrophages, which may be a new target to affect the process of AKI.

Valid gene expression normalization by RT-qPCR in studies on hPDL fibroblasts with focus on orthodontic tooth movement and periodontitis

Meaningful, reliable and valid mRNA expression analyses by real-time quantitative PCR (RT-qPCR) can only be achieved, if suitable reference genes are chosen for normalization and if appropriate RT-qPCR quality standards are met. Human periodontal ligament (hPDL) fibroblasts play a major mediating role in orthodontic tooth movement and periodontitis. Despite corresponding in-vitro gene expression studies being a focus of interest for many years, no information is available for hPDL fibroblasts on suitable reference genes, which are generally used in RT-qPCR experiments to normalize variability between samples. The aim of this study was to identify and validate suitable reference genes for normalization in untreated hPDL fibroblasts as well as experiments on orthodontic tooth movement or periodontitis (Aggregatibacter actinomycetemcomitans). We investigated the suitability of 13 candidate reference genes using four different algorithms (geNorm, NormFinder, comparative ΔC_q and BestKeeper) and ranked them according to their expression stability. Overall PPIB (peptidylprolyl isomerase A), TBP (TATA-box-binding protein) and RPL22 (ribosomal protein 22) were found to be most stably expressed with two genes in conjunction sufficient for reliable normalization. This study provides an accurate tool for quantitative gene expression analysis in hPDL fibroblasts according to the MIQE guidelines and shows that reference gene reliability is treatment-specific.

Validation of optimal reference genes for quantitative real time PCR in muscle and adipose tissue for obesity and diabetes research

The global incidence of obesity has led to an increasing need for understanding the molecular mechanisms that drive this epidemic and its comorbidities. Quantitative real-time RT-PCR (RT-qPCR) is the most reliable and widely used method for gene expression analysis. The selection of suitable reference genes (RGs) is critical for obtaining accurate gene expression information. The current study aimed to identify optimal RGs to perform quantitative transcriptomic analysis based on RT-qPCR for obesity and diabetes research, employing in vitro and mouse models, and human tissue samples. Using the ReFinder program we evaluated the stability of a total of 15 RGs. The impact of choosing the most suitable RGs versus less suitable RGs on RT-qPCR results was assessed. Optimal RGs differed between tissue and cell type, species, and experimental conditions. By employing different sets of RGs to normalize the mRNA expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), we show that sub-optimal RGs can markedly alter the PGC1α gene expression profile. Our study demonstrates the importance of validating RGs prior to normalizing transcriptional expression levels of target genes and identifies optimal RG pairs for reliable RT-qPCR normalization in cells and in human and murine muscle and adipose tissue for obesity/diabetes research.

Identification of suitable reference genes for real-time quantitative PCR analysis of hydrogen peroxide-treated human umbilical vein endothelial cells

Background

Oxidative stress can induce cell injury in vascular endothelial cells, which is the initial event in the development of atherosclerosis. Although quantitative real-time polymerase chain reaction (qRT-PCR) has been widely used in gene expression studies in oxidative stress injuries, using carefully validated reference genes has not received sufficient attention in related studies. The objective of this study, therefore, was to select a set of stably expressed reference genes for use in qRT-PCR normalization in oxidative stress injuries in human umbilical vein endothelial cells (HUVECs) induced by hydrogen peroxide (H₂O₂).

Results

Using geNorm analysis, we found that five stably expressed reference genes were sufficient for normalization in qRT-PCR analysis in HUVECs treated with H₂O₂. Genes with the most stable expression according to geNorm were U6, TFRC, RPLP0, GAPDH, and ACTB, and according to NormFinder were ALAS1, TFRC, U6, GAPDH, and ACTB.

Conclusion

Taken together, our study demonstrated that the expression stability of reference genes may differ according to the statistical program used. U6, TFRC, RPLP0, GAPDH, and ACTB was the optimal set of reference genes for studies on gene expression performed by qRT-PCR assays in HUVECs under oxidative stress study.

Identification of suitable reference genes for quantitative gene expression analysis in rat adipose stromal cells induced to trilineage differentiation

This study was designed to (i) identify stable reference genes for the analysis of gene expression during in vitro differentiation of rat adipose stromal cells (rASCs), (ii) recommend stable genes for individual treatment conditions, and (iii) validate these genes by comparison with normalization results from stable and unstable reference genes. On the basis of a literature review, eight genes were selected: Actb, B2m, Hprt1, Ppia, Rplp0, Rpl13a, Rpl5, and Ywhaz. Genes were ranked according to their stability under different culture conditions as assessed using GenNorm, NormFinder, and RefFinder algorithms. Although the employed algorithms returned different rankings, the most frequently top-ranked genes were: B2m and/or Ppia for all 28day treatments (ALL28); Ppia and Hprt1 (adipogenic differentiation; A28), B2m (chondrogenic differentiation; C28), Rpl5 (controls maintained in complete culture medium; CCM), Rplp0 (osteogenic differentiation for 3days; O3), Rpl13a and Actb (osteogenic differentiation for 7days; O7), Rplp0 and Ppia (osteogenic differentiation for 14days; O14), Hprt1 and Ppia (osteogenic differentiation for 28days; O28), as well as Actb (all osteogenesis time points combined; ALLOSTEO). The obtained results indicate that the performance of reference genes depends on the differentiation protocol and on the analysis time, thus providing valuable information for the design of RT-PCR experiments.

Identification of reliable reference genes for quantitative gene expression studies in oral squamous cell carcinomas compared to adjacent normal tissues in the F344 rat model

Oral squamous cell carcinomas (OSCCs) induced in F344 rats by 4-nitroquinoline-1-oxide (4-NQO) demonstrate considerable phenotypic similarity to human oral cancers and the model has been widely used for carcinogenesis and chemoprevention studies. Molecular characterization of this model needs reliable reference genes (RGs) to avoid false- positive and -negative results for proper interpretation of gene expression data between tumor and adjacent normal tissues. Microarray analysis of 11 pairs of OSCC and site-matched phenotypically normal oral tissues from 4-NQO-treated rats identified 10 stably expressed genes in OSCC compared to adjacent normal tissues (p>0.5, CV<15%) that could serve as potential RGs in this model. The commonly used 27 RGs in the rat were also analyzed based on microarray data and most of them were found unsuitable for RGs in this model. Traditional RGs such as ACTB and GAPDH were significantly altered in OSCC compared to adjacent normal tissues (p<0.01, n=11); however, the Hsp90ab1 was ranked as the best RG candidate and the combination of Hsp90ab1 and HPRT1 was identified by NormFinder to be a superior reference for gene normalization among the commonly used RGs. This result was also validated by RT-PCR based on the selected top RG candidate pool. These data suggest that there are no common RGs suitable for different models and RG(s) should be identified before gene expression analysis. We successfully identified Hsp90ab1 as a stable RG in 4-NQO-induced OSCC compared to adjacent normal tissues in F344 rats. The combination of two stably expressed genes may be a better option for gene normalization in tissue samples.

Reference genes for valid gene expression studies on rat dental, periodontal and alveolar bone tissue by means of RT-qPCR with a focus on orthodontic tooth movement and periodontitis

OBJECTIVES

To obtain valid results in relative gene/mRNA-expression analyses by RT-qPCR, a careful selection of stable reference genes is required for normalization. Currently there is little information on reference gene stability in dental, periodontal and alveolar bone tissues of the rat, especially regarding orthodontic tooth movement and periodontitis. We therefore aimed to identify the best selection and number of reference genes under these experimental as well as physiological conditions.

MATERIALS AND METHODS

In 7 male Fischer344-rats the upper left first and second molars were moved orthodontically for 2 weeks and in 7 more animals additionally subjected to an experimental periodontitis, whereas 7 animals were left untreated. Tissue samples of defined size containing both molars (without crowns) as well as the adjacent periodontal and alveolar bone tissue were retrieved and RNA extracted for RT-qPCR analyses. Nine candidate reference genes were evaluated and ranked according to their expression stability by 4 different algorithms (geNorm, NormFinder, BestKeeper, comparative ΔCq).

RESULTS

PPIB/YWHAZ were the most stabile reference genes for the combined dental, periodontal and alveolar bone tissue of the rat overall, in untreated animals and rats with additional periodontitis, whereas PPIB/B2M performed best in orthodontically treated rats with YWHAZ ranking third. Gene-stability ranking differed considerably between investigated groups. A combination of two reference genes was found to be sufficient for normalization in all cases.

CONCLUSIONS

The substantial differences in expression stability emphasize the need for valid reference genes, when aiming for meaningful results in relative gene expression analyses. Our results should enable researchers to optimize gene expression analysis in future studies by choosing the most suitable reference genes for normalization.

With Reference to Reference Genes: A Systematic Review of Endogenous Controls in Gene Expression Studies

The choice of reference genes that are stably expressed amongst treatment groups is a crucial step in real-time quantitative PCR gene expression studies. Recent guidelines have specified that a minimum of two validated reference genes should be used for normalisation. However, a quantitative review of the literature showed that the average number of reference genes used across all studies was 1.2. Thus, the vast majority of studies continue to use a single gene, with β-actin (ACTB) and/or glyceraldehyde 3-phosphate dehydrogenase (GAPDH) being commonly selected in studies of vertebrate gene expression. Few studies (15%) tested a panel of potential reference genes for stability of expression before using them to normalise data. Amongst studies specifically testing reference gene stability, few found ACTB or GAPDH to be optimal, whereby these genes were significantly less likely to be chosen when larger panels of potential reference genes were screened. Fewer reference genes were tested for stability in non-model organisms, presumably owing to a dearth of available primers in less well characterised species. Furthermore, the experimental conditions under which real-time quantitative PCR analyses were conducted had a large influence on the choice of reference genes, whereby different studies of rat brain tissue showed different reference genes to be the most stable. These results highlight the importance of validating the choice of normalising reference genes before conducting gene expression studies.

Vertical sleeve gastrectomy restores glucose homeostasis in apolipoprotein A-IV KO mice

Bariatric surgery is the most successful strategy for treating obesity, yet the mechanisms for this success are not clearly understood. Clinical literature suggests that plasma levels of apolipoprotein A-IV (apoA-IV) rise with Roux-en-Y gastric bypass (RYGB). apoA-IV is secreted from the intestine postprandially and has demonstrated benefits for both glucose and lipid homeostasis. Because of the parallels in the metabolic improvements seen with surgery and the rise in apoA-IV levels, we hypothesized that apoA-IV was necessary for obtaining the metabolic benefits of bariatric surgery. To test this hypothesis, we performed vertical sleeve gastrectomy (VSG), a surgery with clinical efficacy very similar to that for RYGB, in whole-body apoA-IV knockout (KO) mice. We found that VSG reduced body mass and improved both glucose and lipid homeostasis similarly in wild-type mice compared with apoA-IV KO mice. In fact, VSG normalized the impairment in glucose tolerance and caused a significantly greater improvement in hepatic triglyceride storage in the apoA-IV KO mice. Last, independent of surgery, apoA-IV KO mice had a significantly reduced preference for a high-fat diet. Altogether, these data suggest that apoA-IV is not necessary for the metabolic improvements shown with VSG, but also suggest an interesting role for apoA-IV in regulating macronutrient preference and hepatic triglyceride levels. Future studies are necessary to determine whether this is the case for RYGB as well.

Overweight and CpG methylation of the Pomc promoter in offspring of high-fat-diet-fed dams are not "reprogrammed" by regular chow diet in rats

This study aimed to determine whether epigenetic malprogramming induced by high-fat diet (HFD) has an obesogenic effect on nonmated and mated female rats and their offspring. Further, it aimed to reprogram offspring's epigenetic malprogramming and phenotype by providing normal diet after weaning. Body weight (BW) was measured, and plasma and hypothalamic arcuate nuclei were collected for analysis of hormones, mRNA, and DNA CpG methylation of the promoter of Pomc, a key factor in control of food intake. In nonmated females, HFD decreased Pomc/leptin ratio by ∼38%. This finding was associated with Pomc promoter hypermethylation. While heavier during pregnancy, during lactation HFD dams showed sharper BW decrease (2.5-fold) and loss of Pomc promoter hypermethylation. Moreover, their weight loss was correlated with demethylation (r=-0.707) and with gadd45b mRNA expression levels (r=0.905). Even though offspring of HFD dams ate standard chow from weaning, they displayed increased BW, Pomc promoter hypermethylation, and vulnerability to HFD challenge (3-fold kilocalorie intake increase). These findings demonstrate a long-term effect of maternal HFD on CpG methylation of the Pomc promoter in the offspring, which was not reprogrammed by standard chow from weaning. Further, the results suggest a possible mechanism of demethylation of the Pomc promoter following pregnancy and lactation.

Expression of transcripts related to intestinal ion and nutrient absorption in pregnant and lactating rats as determined by custom-designed cDNA microarray

In pregnancy and lactation, maternal adaptation for the enhancement of intestinal ion and nutrient absorption is of paramount importance for fetal development and lactogenesis. This nutrient hyperabsorption has been reported to result from upregulation of transporter gene expression, in part, under control of lactogenic hormone prolactin (PRL). Since a number of gene families are responsible for ion and nutrient transport in the rat small intestine, we herein developed a custom-designed cDNA microarray (CalGeneArray) to determine the transcriptome responses of duodenal epithelial cells during these reproductive periods, which was subsequently validated by quantitative real-time PCR. We thus designed 277 oligonucleotide probes to detect 113 transcripts related to ion/nutrient transport, bone/calcium metabolism, paracrine regulator, and cell metabolism. Pregnancy was found to upregulate the expressions of several duodenal transporters, e.g., Trpm6, Trpm7, Glut5, and Trpv6. Pregnant rats subjected to 7-day injection of bromocriptine, an inhibitor of PRL release, showed the increased levels of some other transcripts, e.g., insulin-2 and Cyp27b1, compared to untreated pregnant rats. Bromocriptine also increased the mRNA levels of insulin-2, glucose transporter-1 (Sglt1), and Cyp27b1, while decreasing those of Fgfr2c, Atp1b2, and Cldn19 in early lactation. During late lactation, the levels of eight studied transcripts (i.e., NaPi-IIb, Cyp27b1, Cldn18, Casr, Atp1b2, Xpnpep, Pept1, and Trpm7) were altered. In conclusion, the CalGeneArray was powerful to help reveal that pregnancy and lactation modulated the expression of genes related to duodenal nutrient transport and cell metabolism. Our findings supported the physiological significance of PRL in regulating nutrient absorption during pregnancy and lactation.