Physiological insights gained from gene expression analysis in obesity and diabetes

Effects of mitochondrial dysfunction on cellular function: Role in atherosclerosis

Atherosclerosis, an immunoinflammatory disease of medium and large arteries, is associated with life-threatening clinical events, such as acute coronary syndromes and stroke. Chronic inflammation and impaired lipoprotein metabolism are considered to be among the leading causes of atherosclerosis, while numerous risk factors, including arterial hypertension, diabetes mellitus, obesity, and aging, can contribute to the development of the disease. In recent years, emerging evidence has underlined the key role of mitochondrial dysfunction in the pathogenesis of atherosclerosis. Mitochondrial dysfunction is believed to result in an increase in reactive oxygen species, leading to oxidative stress, chronic inflammation, and intracellular lipid deposition, all of which can contribute to the pathogenesis of atherosclerosis. Critical cells, including endothelial cells, vascular smooth muscle cells, and macrophages, play an important role in atherosclerosis. Mitochondrial function is also involved in maintaining the normal function of these cells. To better understand the relationship between mitochondrial dysfunction and atherosclerosis, this review summarizes the findings of recent studies and discusses the role of mitochondrial dysfunction in the risk factors and critical cells of atherosclerosis. FACTS: OPEN QUESTIONS.

The effects of quinoa bran dietary fiber on glucose and lipid metabolism and hepatic transcriptome in obese rats

BACKGROUND

As a complex chronic metabolic disease, obesity not only affects the quality of human life but also increases the risk of various other diseases. Therefore, it is important to investigate the molecular mechanisms and therapeutic effects of dietary interventions that counteract obesity.

RESULTS

In this study, we extracted soluble (SDF) and insoluble dietary fiber (IDF) from quinoa bran using an enzymatic method and further investigated their effects on lipid metabolism and blood lipid levels in obese rats. Quinoa bran dietary fiber showed significantly reduced body weight, blood glucose level, total cholesterol, triglyceride, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels compared to those in the model group of obese rats. Aspartate aminotransferase and alanine aminotransferase levels were significantly lower in the IDF group, demonstrating that IDF improved liver injury more significantly than SDF, which was consistent with the analysis of liver tissue sections. IDF supplementation significantly improved the oxidation resistance of obese rats by decreasing malondialdehyde and increasing superoxide dismutase and glutathione peroxidase levels compared to the high-fat diet group levels. Transcriptome analysis showed that IDF caused hepatic changes in genes (Ehhadh, PPARα, FADS, CPT1, CPT2, SCD-1, Acadm, and CYP7A1) related to fatty acid degradation, and this result coincided with that of the gene expression validation result.

CONCLUSION

Overall, our research offers crucial data for the logical development of dietary fiber from quinoa bran with nutritional purposes. © 2023 Society of Chemical Industry.

A mathematically rigorous algorithm to define, compute and assess relevance of the probable dissociation constants in characterizing a biochemical network

Metabolism results from enzymatic- and non-enzymatic interactions of several molecules, is easily parameterized with the dissociation constant and occurs via biochemical networks. The dissociation constant is an empirically determined parameter and cannot be used directly to investigate in silico models of biochemical networks. Here, we develop and present an algorithm to define, compute and assess the relevance of the probable dissociation constant for every reaction of a biochemical network. The reactants and reactions of this network are modelled by a stoichiometry number matrix. The algorithm computes the null space and then serially generates subspaces by combinatorially summing the spanning vectors that are non-trivial and unique. This is done until the terms of each row either monotonically diverge or form an alternating sequence whose terms can be partitioned into subsets with almost the same number of oppositely signed terms. For a selected null space-generated subspace the algorithm utilizes several statistical and mathematical descriptors to select and bin terms from each row into distinct outcome-specific subsets. The terms of each subset are summed, mapped to the real-valued open interval [Formula: see text] and used to populate a reaction-specific outcome vector. The p1-norm for this vector is then the probable dissociation constant for this reaction. These steps are continued until every reaction of a modelled network is unambiguously annotated. The assertions presented are complemented by computational studies of a biochemical network for aerobic glycolysis. The fundamental premise of this work is that every row of a null space-generated subspace is a valid reaction and can therefore, be modelled as a reaction-specific sequence vector with a dimension that corresponds to the cardinality of the subspace after excluding all trivial- and redundant-vectors. A major finding of this study is that the row-wise sum or the sum of the terms contained in each reaction-specific sequence vector is mapped unambiguously to a positive real number. This means that the probable dissociation constants, for all reactions, can be directly computed from the stoichiometry number matrix and are suitable indicators of outcome for every reaction of the modelled biochemical network. Additionally, we find that the unambiguous annotation for a biochemical network will require a minimum number of iterations and will determine computational complexity.

ReDirection: an R-package to compute the probable dissociation constant for every reaction of a user-defined biochemical network

Biochemical networks integrate enzyme-mediated substrate conversions with non-enzymatic complex formation and disassembly to accomplish complex biochemical and physiological functions. The choice of parameters and constraints used in most of these studies is numerically motivated and network-specific. Although sound in theory, the outcomes that result depart significantly from the intracellular milieu and are less likely to retain relevance in a clinical setting. There is a need for a computational tool which is biochemically relevant, mathematically rigorous, and unbiased, and can ascribe functionality to and generate potentially testable hypotheses for a user-defined biochemical network. Here, we present "ReDirection," an R-package which computes the probable dissociation constant for every reaction of a biochemical network directly from a null space-generated subspace of the stoichiometry number matrix of the modeled network. "ReDirection" delineates this subspace by excluding all trivial and redundant or duplicate occurrences of non-trivial vectors, combinatorially summing the vectors that remain and verifying that the upper or lower bounds of the sequence of terms formed by each row of this subspace belong to the open real-valued intervals - ∞ , - 1 or 1 , ∞ or whether the number of terms that are differently signed are almost equal. "ReDirection" iterates these steps until these bounds are consistent and unambiguous for all reactions of the modeled biochemical network. Thereafter, "ReDirection" filters the terms from each row of this subspace, bins them to outcome-specific subsets, sums and maps this to an outcome-specific reaction vector, and computes the p1-norm, which is the probable dissociation constant for a reaction. "ReDirection" works on first principles, does not discriminate between enzymatic and non-enzymatic reactions, offers a biochemically relevant and mathematically rigorous environment to explore user-defined biochemical networks under baseline and perturbed conditions, and can be used to address empirically intractable biochemical problems. The utility and relevance of "ReDirection" are highlighted by numerical studies on stoichiometric number models of biochemical networks of galactose metabolism and heme and cholesterol biosynthesis. "ReDirection" is freely available and accessible from the comprehensive R archive network (CRAN) with the URL (https://cran.r-project.org/package=ReDirection).

Mitochondrial Methionyl-tRNA Formyltransferase Deficiency Alleviates Metaflammation by Modulating Mitochondrial Activity in Mice

Various studies have revealed the association of metabolic diseases with inflammation. Mitochondria are key organelles involved in metabolic regulation and important drivers of inflammation. However, it is uncertain whether the inhibition of mitochondrial protein translation results in the development of metabolic diseases, such that the metabolic benefits related to the inhibition of mitochondrial activity remain unclear. Mitochondrial methionyl-tRNA formyltransferase (Mtfmt) functions in the early stages of mitochondrial translation. In this study, we reveal that feeding with a high-fat diet led to the upregulation of Mtfmt in the livers of mice and that a negative correlation existed between hepatic Mtfmt gene expression and fasting blood glucose levels. A knockout mouse model of Mtfmt was generated to explore its possible role in metabolic diseases and its underlying molecular mechanisms. Homozygous knockout mice experienced embryonic lethality, but heterozygous knockout mice showed a global reduction in Mtfmt expression and activity. Moreover, heterozygous mice showed increased glucose tolerance and reduced inflammation, which effects were induced by the high-fat diet. The cellular assays showed that Mtfmt deficiency reduced mitochondrial activity and the production of mitochondrial reactive oxygen species and blunted nuclear factor-κB activation, which, in turn, downregulated inflammation in macrophages. The results of this study indicate that targeting Mtfmt-mediated mitochondrial protein translation to regulate inflammation might provide a potential therapeutic strategy for metabolic diseases.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Mitochondrial Dynamics and Mitophagy in Cardiometabolic Disease

Mitochondria play a key role in cellular metabolism. Mitochondrial dynamics (fusion and fission) and mitophagy, are critical to mitochondrial function. Fusion allows organelles to share metabolites, proteins, and mitochondrial DNA, promoting complementarity between damaged mitochondria. Fission increases the number of mitochondria to ensure that they are passed on to their offspring during mitosis. Mitophagy is a process of selective removal of excess or damaged mitochondria that helps improve energy metabolism. Cardiometabolic disease is characterized by mitochondrial dysfunction, high production of reactive oxygen species, increased inflammatory response, and low levels of ATP. Cardiometabolic disease is closely related to mitochondrial dynamics and mitophagy. This paper reviewed the mechanisms of mitochondrial dynamics and mitophagy (focus on MFN1, MFN2, OPA1, DRP1, and PINK1 proteins) and their roles in diabetic cardiomyopathy, myocardial infarction, cardiac hypertrophy, heart failure, atherosclerosis, and obesity.

A comprehensive review on high fat diet-induced diabetes mellitus: An epigenetic view

Modern lifestyle, genetics, nutritional overload through high-fat diet attributed prevalence and diabetes outcomes with various complications primarily due to obesity in which energy-dense diets frequently affect metabolic health. One possible issue usually associated with elevated chronic fat intake is insulin resistance, and hyperglycaemia constitutes an important function in altering the carbohydrates and lipids metabolism. Similarly, in assessing human susceptibility to weight gain and obesity, genetic variations play a central role, contributing to keen interest in identifying the possible role of epigenetics as a mediator of gene-environmental interactions influencing the production of type 2 diabetes mellitus and its related concerns. Epigenetic modifications associated with the acceptance of a sedentary lifestyle and environmental stress factors in response to energy intake and expenditure imbalances complement genetic alterations and lead to the production and advancement of metabolic disorders such as diabetes and obesity. Methylation of DNA, histone modifications and increases in the expression of non-coding RNAs can result in reduced transcriptional activity of key β-cell genes thus creating insulin resistance. Epigenetics contribute to changes in the expression of the underlying insulin resistance and insufficiency gene networks, along with low-grade obesity-related inflammation, increased ROS generation and DNA damage in multi organs. This review focused on epigenetic mechanisms and metabolic regulations associated with high fat diet (HFD)-induced diabetes mellitus.

Mitophagy-mediated adipose inflammation contributes to type 2 diabetes with hepatic insulin resistance

White adipose tissues (WAT) play crucial roles in maintaining whole-body energy homeostasis, and their dysfunction can contribute to hepatic insulin resistance and type 2 diabetes mellitus (T2DM). However, the mechanisms underlying these alterations remain unknown. By analyzing the transcriptome landscape in human adipocytes based on available RNA-seq datasets from lean, obese, and T2DM patients, we reveal elevated mitochondrial reactive oxygen species (ROS) pathway and NF-κB signaling with altered fatty acid metabolism in T2DM adipocytes. Mice with adipose-specific deletion of mitochondrial redox Trx2 develop hyperglycemia, hepatic insulin resistance, and hepatic steatosis. Trx2-deficient WAT exhibited excessive mitophagy, increased inflammation, and lipolysis. Mechanistically, mitophagy was induced through increasing ROS generation and NF-κB-dependent accumulation of autophagy receptor p62/SQSTM1, which recruits damaged mitochondria with polyubiquitin chains. Importantly, administration of ROS scavenger or NF-κB inhibitor ameliorates glucose and lipid metabolic disorders and T2DM progression in mice. Taken together, this study reveals a previously unrecognized mechanism linking mitophagy-mediated adipose inflammation to T2DM with hepatic insulin resistance.

Subcutaneous Adipose Tissue and Systemic Inflammation Are Associated With Peripheral but Not Hepatic Insulin Resistance in Humans

Obesity-related insulin resistance (IR) may develop in multiple organs, representing various etiologies for cardiometabolic diseases. We identified abdominal subcutaneous adipose tissue (ScAT) transcriptome profiles in liver or muscle IR by means of RNA sequencing in overweight or obese participants of the Diet, Obesity, and Genes (DiOGenes) (NCT00390637, ClinicalTrials.gov) cohort (n = 368). Tissue-specific IR phenotypes were derived from a 5-point oral glucose tolerance test. Hepatic and muscle IR were characterized by distinct abdominal ScAT transcriptome profiles. Genes related to extracellular remodeling were upregulated in individuals with primarily hepatic IR, while genes related to inflammation were upregulated in individuals with primarily muscle IR. In line with this, in two independent cohorts, the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) (n = 325) and the Maastricht Study (n = 685), an increased systemic low-grade inflammation profile was specifically related to muscle IR but not to liver IR. We propose that increased ScAT inflammatory gene expression may translate into an increased systemic inflammatory profile, linking ScAT inflammation to the muscle IR phenotype. These distinct IR phenotypes may provide leads for more personalized prevention of cardiometabolic diseases.

Emerging Therapeutic Targets for Metabolic Syndrome: Lessons from Animal Models

Background:

Metabolic syndrome is a cluster of medical conditions that synergistically increase the risk of heart diseases and diabetes. The current treatment strategy for metabolic syndrome focuses on treating its individual components. A highly effective agent for metabolic syndrome has yet to be developed. To develop a target for metabolic syndrome, the mechanism encompassing different organs - nervous system, pancreas, skeletal muscle, liver and adipose tissue - needs to be understood. Many animal models have been developed to understand the pathophysiology of metabolic syndrome. Promising molecular targets have emerged while characterizing these animals. Modulating these targets is expected to treat some components of metabolic syndrome.

Objective:

o discuss the emerging molecular targets in an animal model of metabolic syndrome.

Methods:

A literature search was performed for the retrieval of relevant articles.

Conclusion:

Multiple genes/pathways that play important role in the development of Metabolic Syndrome are discussed.

Impact of high-fat diet on vasoconstrictor reactivity of white and brown adipose tissue resistance arteries

Blood flow regulation is a critical factor for tissue oxygenation and substrate supply. Increased reactivity of arteries to vasoconstrictors may increase vascular resistance, resulting in reduced blood flow. We aimed to investigate the effect of a high-fat (HF) diet on stiffness and vasoconstrictor reactivity of white adipose tissue (WAT) and brown adipose tissue (BAT) resistance arteries and also investigated the interconversion of both adipose depots in the setting of a HF diet. Vasoconstrictor reactivity and passive morphology and mechanical properties of arteries from B6D2F1 mice (5 mo old) fed normal chow (NC) or a HF diet (8 wk) were measured using pressure myography. Receptor gene expression in WAT and BAT arteries and markers of WAT and BAT were assessed in whole tissue lysates by real-time RT-PCR. Despite greater receptor-independent vasoconstriction (in response to KCl, P < 0.01), vasoconstriction in response to angiotensin II ( P < 0.01) was lower in NC-BAT than NC-WAT arteries and similar in response to endothelin-1 ( P = 0.07) and norepinephrine ( P = 0.11) in NC-BAT and NC-WAT arteries. With the exception of BAT artery reactivity to endothelin-1 and angiotensin II, the HF diet tended to attenuate reactivity in arteries from both adipose depots and increased expression of adipose markers in BAT. No significant differences in morphology or passive mechanical properties were found between adipose types or diet conditions. Alterations in gene expression of adipose markers after the HF diet suggest beiging of BAT. An increase in brown adipocytes in the absence of increased BAT mass may be a compensatory mechanism to dissipate excess energy from a HF diet. NEW & NOTEWORTHY Despite no differences in passive mechanical properties and greater receptor-independent vasoconstriction, receptor-mediated vasoconstriction was either lower in brown than white adipose tissue arteries or similar in brown and white adipose tissue arteries. A high-fat diet has a greater impact on vasoconstrictor responses in white adipose tissue but leads to altered adipose tissue gene expression consistent with beiging of the brown adipose tissue.

Environmental Pollutants Effect on Brown Adipose Tissue

Brown adipose tissue (BAT) with its thermogenic function due to the presence of the mitochondrial uncoupling protein 1 (UCP1), has been positively associated with improved resistance to obesity and metabolic diseases. During recent years, the potential influence of environmental pollutants on energetic homoeostasis and obesity development has drawn increased attention. The purpose of this review is to discuss how regulation of BAT function could be involved in the environmental pollutant effect on body energy metabolism. We mainly focused in reviewing studies on animal models, which provide a better insight into the cellular mechanisms involved in this effect on body energy metabolism. The current literature supports the hypothesis that some environmental pollutants, acting as endocrine disruptors (EDCs), such as dichlorodiphenyltrichoroethane (DDT) and its metabolite dichlorodiphenylethylene (DDE) as well as some, traffic pollutants, are associated with increased obesity risk, whereas some other chemicals, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), had a reverse association with obesity. Noteworthy, the EDCs associated with obesity and metabolic disorders impaired BAT mass and function. Perinatal exposure to DDT impaired BAT thermogenesis and substrate utilization, increasing susceptibility to metabolic syndrome. Ambient particulate air pollutions induced insulin resistance associated with BAT mitochondrial dysfunction. On the other hand, the environmental pollutants (PFOS/PFOA) elicited a reduction in body weight and adipose mass associated with upregulation of UCP1 and increased oxidative capacity in brown-fat mitochondria. Further research is needed to better understand the physiological role of BAT in response to exposure to both obesogenic and anti-obesogenic pollutants and to confirm the same role in humans.

High Fat With High Sucrose Diet Leads to Obesity and Induces Myodegeneration

Skeletal muscle utilizes both free fatty acids (FFAs) and glucose that circulate in the blood stream. When blood glucose levels acutely increase, insulin stimulates muscle glucose uptake, oxidation, and glycogen synthesis. Under these conditions, skeletal muscle preferentially oxidizes glucose while the oxidation of fatty acids (FAs) oxidation is reciprocally decreased. In metabolic disorders associated with insulin resistance, such as diabetes and obesity, both glucose uptake, and utilization muscle are significantly reduced causing FA oxidation to provide the majority of ATP for metabolic processes and contraction. Although the causes of this metabolic inflexibility or disrupted "glucose-fatty acid cycle" are largely unknown, a diet high in fat and sugar (HFS) may be a contributing factor. This metabolic inflexibility observed in models of obesity or with HFS feeding is detrimental because high rates of FA oxidation in skeletal muscle can lead to the buildup of toxic metabolites of fat metabolism and the accumulation of pro-inflammatory cytokines, which further exacerbate the insulin resistance. Further, HFS leads to skeletal muscle atrophy with a decrease in myofibrillar proteins and phenotypically characterized by loss of muscle mass and strength. Overactivation of ubiquitin proteasome pathway, oxidative stress, myonuclear apoptosis, and mitochondrial dysfunction are some of the mechanisms involved in muscle atrophy induced by obesity or in mice fed with HFS. In this review, we will discuss how HFS diet negatively impacts the various physiological and metabolic mechanisms in skeletal muscle.

Depot-specific differences in fat mass expansion in WT and ob/ob mice

The study was designed to investigate the cellular mechanisms underlying the differential fat expansion in different fat depots in wild type (WT) and ob/ob (OB) mice. At 6 weeks old, no differences in fat mass were found between SAT and VAT in WT mice, while O-SAT showed significantly higher weight than that of O-VAT. The average adipocyte size of SAT (~ 4133.47 μm2) was smaller than that of VAT (~ 7438.91 μm2) in OB mice. O-SAT preadipocytes gained higher triglyceride contents and higher levels of PPARγ and C/EBPα than did O-VAT preadipocytes upon in vitro differentiation. W-SAT and W-VAT displayed no significant differences in fatty acid uptake, while 1.36 fold significantly higher fatty acid uptake was found in O-SAT compared to O-VAT. Approximately 52% of the radioactivity recovered in cellular lipids was found in TAG in O-SAT, which was significantly higher than the other three adipocyte types. Significantly more radiolabelled oleic acid was β-oxidized to CO2 in adipocytes from O-VAT than that from O-SAT. ATP production was significantly lower in W-SAT compared with W-VAT, whereas no significantly ATP level was observed between O-SAT and O-VAT. Expression of UCP-1 in SAT from either WT or OB mice was significantly higher than the counterpart of VAT, which demonstrated higher uncoupled respiration and lower oxidative phosphorylation in SAT. Together, a combined increase in adipogenesis and FA uptake, and decreases in β-oxidation and ATP production, contributed to greater expansion of SAT compared to VAT in obese mice.

Transcriptional Regulatory Mechanisms in Adipose and Muscle Tissue Associated with Composite Glucometabolic Phenotypes

OBJECTIVE

Tissue-specific gene expression is associated with individual metabolic measures. However, these measures may not reflect the true but latent underlying biological phenotype. This study reports gene expression associations with multidimensional glucometabolic characterizations of obesity, glucose homeostasis, and lipid traits.

METHODS

Factor analysis was computed by using orthogonal rotation to construct composite phenotypes (CPs) from 23 traits in 256 African Americans without diabetes. Genome-wide transcript expression data from adipose and muscle were tested for association with CPs, and expression quantitative trait loci (eQTLs) were identified by associations between cis-acting single-nucleotide polymorphisms (SNPs) and gene expression.

RESULTS

The factor analysis identified six CPs. CPs 1 through 6 individually explained 34%, 12%, 9%, 8%, 6%, and 5% of the variation in 23 glucometabolic traits studied. There were 3,994 and 929 CP-associated transcripts identified in adipose and muscle tissue, respectively; CP2 had the largest number of associated transcripts. Pathway analysis identified multiple canonical pathways from the CP-associated transcripts. In adipose and muscle, significant cis-eQTLs were identified for 558 and 164 CP-associated transcripts (q-value < 0.01), respectively.

CONCLUSIONS

Adipose and muscle transcripts comprehensively define pathways involved in regulating glucometabolic disorders. Cis-eQTLs for CP-associated genes may act as primary causal determinants of glucometabolic phenotypes by regulating transcription of key genes.

Obesity Associated Modulation of miRNA and Co-Regulated Target Transcripts in Human Adipose Tissue of Non-Diabetic Subjects

OBJECTIVE

Micro RNAs (miRNAs) are a class of non-coding regulatory RNAs. We performed a transcriptome-wide analysis of subcutaneous adipose tissue and in vitro studies to identify miRNAs and co-regulated target transcripts associated with insulin sensitivity (SI) and obesity in human.

METHODS

We selected 20 insulin-resistant (IR, SI=2.0±0.7) and 20 insulin-sensitive (IS, SI=7.2±2.3) subjects from a cohort of 117 metabolically characterized non-diabetic Caucasians for comparison.

RESULTS

After global profiling, 3 miRNAs had marginally different expressions between IR and IS subjects. A total of 14 miRNAs were significantly correlated with %fat mass, body mass index (BMI), or SI. The qRT-PCR validated the correlation of miR-148a-3p with BMI (r=-0.70, P=2.73X10(-6)). MiRNA target filtering analysis identified DNA methyltransferase 1 (DNMT1) as one of the target genes of miR-148a-3p. DNMT1 expression in adipose tissue was positively correlated with BMI (r=0.47, p=8.42X10(-7)) and was inversely correlated with miR-148a-3p (r=-0.34). Differentiation of SGBS preadipocytes showed up-regulation of miR-148a-3p and down-regulation of DNMT1 in differentiated adipocytes. After transfecting miR-148a-3p mimics into HeLa-S3 cells, DNMT1 was down-regulated, while transfection of adipose stem cells with miR-148a-3p inhibitor up-regulated DNMT1.

CONCLUSIONS

Our results indicate that miR-148a-3pmediated regulation of DNMT1 expression may play a mechanistic role in obesity.

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

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

Gene expression profiles in whole blood and associations with metabolic dysregulation in obesity

BACKGROUND

Gene expression data provides one tool to gain further insight into the complex biological interactions linking obesity and metabolic disease. This study examined associations between blood gene expression profiles and metabolic disease in obesity.

METHODS

Whole blood gene expression profiles, performed using the Illumina HT-12v4 Human Expression Beadchip, were compared between (i) individuals with obesity (O) or lean (L) individuals (n=21 each), (ii) individuals with (M) or without (H) Metabolic Syndrome (n=11 each) matched on age and gender. Enrichment of differentially expressed genes (DEG) into biological pathways was assessed using Ingenuity Pathway Analysis. Association between sets of genes from biological pathways considered functionally relevant and Metabolic Syndrome were further assessed using an area under the curve (AUC) and cross-validated classification rate (CR).

RESULTS

For OvL, only 50 genes were significantly differentially expressed based on the selected differential expression threshold (1.2-fold, p<0.05). For MvH, 582 genes were significantly differentially expressed (1.2-fold, p<0.05) and pathway analysis revealed enrichment of DEG into a diverse set of pathways including immune/inflammatory control, insulin signalling and mitochondrial function pathways. Gene sets from the mTOR signalling pathways demonstrated the strongest association with Metabolic Syndrome (p=8.1×10^-8; AUC: 0.909, CR: 72.7%).

CONCLUSIONS

These results support the use of expression profiling in whole blood in the absence of more specific tissue types for investigations of metabolic disease. Using a pathway analysis approach it was possible to identify an enrichment of DEG into biological pathways that could be targeted for in vitro follow-up.

A fish oil diet induces mitochondrial uncoupling and mitochondrial unfolded protein response in epididymal white adipose tissue of mice

White adipose tissue (WAT) mitochondrial dysfunction is linked to the pathogenesis of obesity driven insulin resistance. Dietary conditions that alter fat mass are known to affect white adipocyte mitochondrial function, however, the impact of high calorie diets on white adipocyte mitochondria is not fully understood. The aim of this study is to assess the effect of a diet rich in saturated or polyunsaturated fat on mitochondrial unfolded protein response (UPR^mt), a retrograde signaling response that maintains mitochondrial homeostasis, in epididymal WAT (eWAT). Mice were fed a low fat diet (LFD), saturated fat diet (SFD) or fish oil (unsaturated fat diet, UFD) and assessed changes in eWAT mitochondria. Compared to mice fed a LFD, SFD-fed mice have reduced mitochondrial biogenesis markers, mitochondrial fatty acid oxidation enzymes and TCA cycle enzymes, suggesting an impaired mitochondrial function that could contribute to increased fat mass. In contrast, isocaloric UFD-fed mice have increased expression of mitochondrial uncoupling protein 1 (UCP1) and peroxisomal fatty acid oxidation enzymes suggesting that elevated mitochondrial uncoupling and peroxisomal fatty acid oxidation could contribute to the reduction in fat mass. Interestingly, expression of UPR^mt-associated proteins caseinolytic peptidase (ClpP) and heat shock protein 60 (Hsp60) are induced by UFD, whereas SFD reduced the expression of ClpP. Based on our data, we propose that induction of UPR^mt helps to preserve a functional mitochondria and efficient utilization of fat by UFD whereas a dampened UPR^mt response might impair mitochondrial function and promote fat accumulation by SFD. Thus, our findings suggest a potential role of UPR^mt in mediating the beneficial effects of fish oil.

Targeting the NO/superoxide ratio in adipose tissue: relevance to obesity and diabetes management

Insulin sensitivity and metabolic homeostasis depend on the capacity of adipose tissue to take up and utilize excess glucose and fatty acids. The key aspects that determine the fuel-buffering capacity of adipose tissue depend on the physiological levels of the small redox molecule, nitric oxide (NO). In addition to impairment of NO synthesis, excessive formation of the superoxide anion (О2•- ) in adipose tissue may be an important interfering factor diverting the signalling of NO and other reactive oxygen and nitrogen species in obesity, resulting in metabolic dysfunction of adipose tissue over time. Besides its role in relief from superoxide burst, enhanced NO signalling may be responsible for the therapeutic benefits of different superoxide dismutase mimetics, in obesity and experimental diabetes models. This review summarizes the role of NO in adipose tissue and highlights the effects of NO/О2•- ratio 'teetering' as a promising pharmacological target in the metabolic syndrome.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Metabolic Effect of an Oriental Herbal Medicine on Obesity and Its Comorbidities with Transcriptional Responses in Diet-Induced Obese Mice

Taeeumjowuitang (TJ) is an alternative herbal medicine that has been used to treat obesity in Korea. The molecular mechanisms involved in TJ-induced anti-obesity effects have not yet been determined. The aim of the current study was to elucidate the effects of TJ on obesity and metabolic syndrome, by analyzing the transcriptional and metabolic responses to TJ treatment. C57BL/6J mice were fed a high-fat or high-fat + 3% (w/w) TJ diet for 12 weeks. Their phenotypic characteristics were measured and the anti-obesity mechanism was elucidated, based on the RNA sequencing (RNA-seq) transcriptomic profiles in an animal model of obesity. TJ treatment ameliorated insulin resistance, dyslipidemia, and hepatic steatosis in high-fat diet-induced obese mice, with a simultaneous reduction in body weight gain by enhancing energy expenditure and suppressing adiposity. An analysis of the global transcriptional changes by RNA-seq revealed that TJ upregulated mitochondrial oxidative phosphorylation-associated genes in epididymal white adipose tissue (eWAT), suggesting an enhanced mitochondrial function after TJ treatment. Moreover, TJ effectively attenuated the high-fat diet-induced inflammatory response through transcriptional changes in eWAT. Our findings provide some mechanistic insights into the effects of TJ, an alternative oriental medicine, in the treatment of obesity and its comorbidities. They demonstrate that metabolic and transcriptional responses to diet-induced obesity with TJ treatment were desirable in adipose tissue metabolism.

Modulation of IL-27 in adipocytes during inflammatory stress

OBJECTIVE

While it is well established that adipose tissue-derived inflammation plays an important role in the pathogenic mechanisms linking obesity with metabolic dysfunction, the inflammatory mediators involved have not been fully elucidated. Here, we explored IL-12 family cytokines with a focus on IL-27 during obesity-induced inflammation in mice and cultured adipocytes (ADs) following exposure to inflammatory stimuli.

METHODS

Relative mRNA abundance of IL-12 cytokines was assessed by reverse transcription polymerase chain reaction (RT-PCR) in genetically obese B6-ob/ob mice as well as C57BL/6J mice fed a high-fat diet and in ADs following exposure to inflammatory stimuli. Protein secretion of cytokines into culture media was assessed by ELISA, and the biological outcome of IL-27 stimulation was assessed by RT-PCR and immunoblotting.

RESULTS

Heterodimeric subunits constituting IL-27 were significantly induced in obese mice. While all IL-12 genes were markedly induced by inflammatory stress in cultured ADs, IL-27 protein was the only cytokine secreted into culture media in response to inflammatory stress. Cultured ADs also responded to IL-27 stimulation with divergent outcomes that were dependent on the inflammatory milieu of target cells.

CONCLUSIONS

These findings support the premise of autocrine/paracrine mechanisms involving IL-27 in ADs under conditions of inflammatory stress that may link obesity with inflammatory diseases.

Red light activated “caged” reagents for microRNA research

“Caged” reagents for miRNA research were prepared. It was demonstrated that these reagents can be activated by non-toxic to cells red light both in cells and in cell free settings.

Effects of High Fat Feeding on Adipose Tissue Gene Expression in Diabetic Goto-Kakizaki Rats

Development and progression of type 2 diabetes is a complex interaction between genetics and environmental influences. High dietary fat is one environmental factor that is conducive to the development of insulin-resistant diabetes. In the present report, we compare the responses of lean poly-genic, diabetic Goto-Kakizaki (GK) rats to those of control Wistar-Kyoto (WKY) rats fed a high fat diet from weaning to 20 weeks of age. This comparison included a wide array of physiological measurements along with gene expression profiling of abdominal adipose tissue using Affymetrix gene array chips. Animals of both strains fed a high fat diet or a normal diet were sacrificed at 4, 8, 12, 16, and 20 weeks for this comparison. The microarray analysis revealed that the two strains developed different adaptations to increased dietary fat. WKY rats decrease fatty acid synthesis and lipogenic processes whereas GK rats increase lipid elimination. However, on both diets the major differences between the two strains remained essentially the same. Specifically relative to the WKY strain, the GK strain showed lipoatrophy, chronic inflammation, and insulin resistance.

The cell biology of fat expansion

Adipose tissue is a complex, multicellular organ that profoundly influences the function of nearly all other organ systems through its diverse metabolite and adipokine secretome. Adipocytes are the primary cell type of adipose tissue and play a key role in maintaining energy homeostasis. The efficiency with which adipose tissue responds to whole-body energetic demands reflects the ability of adipocytes to adapt to an altered nutrient environment, and has profound systemic implications. Deciphering adipocyte cell biology is an important component of understanding how the aberrant physiology of expanding adipose tissue contributes to the metabolic dysregulation associated with obesity.

Integrative network analysis reveals different pathophysiological mechanisms of insulin resistance among Caucasians and African Americans

Background

African Americans (AA) have more pronounced insulin resistance and higher insulin secretion than European Americans (Caucasians or CA) when matched for age, gender, and body mass index (BMI). We hypothesize that physiological differences (including insulin sensitivity [S_I]) between CAs and AAs can be explained by co-regulated gene networks in tissues involved in glucose homeostasis.

Methods

We performed integrative gene network analyses of transcriptomic data in subcutaneous adipose tissue of 99 CA and 37 AA subjects metabolically characterized as non-diabetic, with a range of S_I and BMI values.

Results

Transcripts negatively correlated with S_I in only the CA or AA subjects were enriched for inflammatory response genes and integrin-signaling genes, respectively. A sub-network (module) with TYROBP as a hub enriched for genes involved in inflammatory response (corrected p = 1.7E-26) was negatively correlated with S_I (r = −0.426, p = 4.95E-04) in CA subjects. S_I was positively correlated with transcript modules enriched for mitochondrial metabolism in both groups. Several S_I-associated co-expressed modules were enriched for genes differentially expressed between groups. Two modules involved in immune response to viral infections and function of adherens junction, are significantly correlated with S_I only in CAs. Five modules involved in drug/intracellular transport and oxidoreductase activity, among other activities, are correlated with S_I only in AAs. Furthermore, we identified driver genes of these race-specific S_I-associated modules.

Conclusions

S_I-associated transcriptional networks that were deranged predominantly in one ethnic group may explain the distinctive physiological features of glucose homeostasis among AA subjects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0078-0) contains supplementary material, which is available to authorized users.

Impaired adipose tissue expandability and lipogenic capacities as ones of the main causes of metabolic disorders

Obesity is considered a major health problem. However, mechanisms involved and its comorbidities are not elucidated. Recent theories concerning the causes of obesity have focused on a limit to the functional capacity of adipose tissue, comparing it with other vital organs. This assumption has been the central point of interest in our laboratory. We proposed that the failure of adipose tissue is initiated by the difficulty of this tissue to increase its cellularity due to excess in fat contribution, owing to genetic or environmental factors. Nevertheless, why the adipose tissue reduces its capacity to make new adipocytes via mesenchymal cells of the stroma has not yet been elucidated. Thus, we suggest that this tissue ceases fulfilling its main function, the storage of excess fat, thereby affecting some of the key factors involved in lipogenesis, some of which are reviewed in this paper (PPARγ, ROR1, FASN, SCD1, Rab18, BrCa1, ZAG, and FABP4). On the other hand, mechanisms involved in adipose tissue expandability are also impaired, predominating hypertrophy via an increase in apoptosis and a decrease in adipogenesis and angiogenesis. However, adipose tissue failure is only part of this great orchestra, only a chapter of this nightmare.

Adipose tissue gene expression and metabolic health of obese adults

Obese subjects with a similar body mass index (BMI) exhibit substantial heterogeneity in gluco- and cardiometabolic heath phenotypes. However, defining genes that underlie the heterogeneity of metabolic features among obese individuals and determining metabolically healthy and unhealthy phenotypes remain challenging. We conducted unsupervised hierarchical clustering analysis of subcutaneous adipose tissue transcripts from 30 obese men and women ⩾40 years old. Despite similar BMIs in all subjects, we found two distinct subgroups, one metabolically healthy (group 1) and one metabolically unhealthy (group 2). Subjects in group 2 showed significantly higher total cholesterol (P=0.005), low-density lipoprotein cholesterol (P=0.006), 2-h insulin during oral glucose tolerance test (P=0.015) and lower insulin sensitivity (SI, P=0.029) compared with group 1. We identified significant upregulation of 141 genes (for example, MMP9 and SPP1) and downregulation of 17 genes (for example, NDRG4 and GINS3) in group 2 subjects. Intriguingly, these differentially expressed transcripts were enriched for genes involved in cardiovascular disease-related processes (P=2.81 × 10(-11)-3.74 × 10(-02)) and pathways involved in immune and inflammatory response (P=8.32 × 10(-5)-0.04). Two downregulated genes, NDRG4 and GINS3, have been located in a genomic interval associated with cardiac repolarization in published GWASs and zebra fish knockout models. Our study provides evidence that perturbations in the adipose tissue gene expression network are important in defining metabolic health in obese subjects.

Adipose tissue CIDEA is associated, independently of weight variation, to change in insulin resistance during a longitudinal weight control dietary program in obese individuals

AIM

Weight loss reduces risk factors associated with obesity. However, long-term metabolic improvement remains a challenge. We investigated quantitative gene expression of subcutaneous adipose tissue in obese individuals and its relationship with low calorie diet and long term weight maintenance induced changes in insulin resistance.

RESEARCH DESIGN

Three hundred eleven overweight and obese individuals followed a dietary protocol consisting of an 8-week low calorie diet followed by a 6-month ad libitum weight-maintenance diet. Individuals were clustered according to insulin resistance trajectories assessed using homeostasis model assessment of insulin resistance (HOMA-IR) index. Adipose tissue mRNA levels of 267 genes selected for regulation according to obesity, metabolic status and response to dieting was assessed using high throughput RT-qPCR. A combination of discriminant analyses was used to identify genes with regulation according to insulin resistance trajectories. Partial correlation was used to control for change in body mass index.

RESULTS

Three different HOMA-IR profile groups were determined. HOMA-IR improved during low calorie diet in the 3 groups. At the end of the 6-month follow-up, groups A and B had reduced HOMA-IR by 50%. In group C, HOMA-IR had returned to baseline values. Genes were differentially expressed in the adipose tissue of individuals according to groups but a single gene, CIDEA, was common to all phases of the dietary intervention. Changes in adipose tissue CIDEA mRNA levels paralleled variations in insulin sensitivity independently of change in body mass index. Overall, CIDEA was up-regulated in adipose tissue of individuals with successful long term insulin resistance relapse and not in adipose tissue of unsuccessful individuals.

CONCLUSION

The concomitant change in adipose tissue CIDEA mRNA levels and insulin sensitivity suggests a beneficial role of adipose tissue CIDEA in long term glucose homeostasis, independently of weight variation.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00390637.

Hepatic Monoacylglycerol O-acyltransferase 1 as a Promising Therapeutic Target for Steatosis, Obesity, and Type 2 Diabetes

Over the past decade, considerable advances have been made in the discovery of gene targets in metabolic diseases. However, in vivo studies based on molecular biological technologies such as the generation of knockout mice and the construction of short hairpin RNA vectors require considerable effort and time, which is a major limitation for in vivo functional analysis. Here, we introduce a liver-specific nonviral small interfering RNA (siRNA) delivery system into rapid and efficient characterization of hepatic gene targets in metabolic disease mice. The comparative transcriptome analysis in liver between KKAy diabetic and normal control mice demonstrated that the expression of monoacylglycerol O-acyltransferase 1 (Mogat1), an enzyme involved in triglyceride synthesis and storage, was highly elevated during the disease progression. The upregulation of Mogat1 expression in liver was also found in other genetic (db/db) and diet-induced obese mice. The silencing of hepatic Mogat1 via a liver-specific siRNA delivery system resulted in a dramatic improvement in blood glucose levels and hepatic steatosis as well as overweight with no apparent overall toxicities, indicating that hepatic Mogat1 is a promising therapeutic target for metabolic diseases. The integrated approach with transcriptomics and nonviral siRNA delivery system provides a blueprint for rapid drug discovery and development.

Systems genetics approaches to understand complex traits

Systems genetics is an approach to understand the flow of biological information that underlies complex traits. It uses a range of experimental and statistical methods to quantitate and integrate intermediate phenotypes, such as transcript, protein or metabolite levels, in populations that vary for traits of interest. Systems genetics studies have provided the first global view of the molecular architecture of complex traits and are useful for the identification of genes, pathways and networks that underlie common human diseases. Given the urgent need to understand how the thousands of loci that have been identified in genome-wide association studies contribute to disease susceptibility, systems genetics is likely to become an increasingly important approach to understanding both biology and disease.

Characterization of the peripheral blood transcriptome in a repeated measures design using a panel of healthy individuals

A repeated measures microarray design with 22 healthy, non-smoking volunteers (aging 32±5years) was set up to study transcriptome profiles in whole blood samples. The results indicate that repeatable data can be obtained with high within-subject correlation. Probes that could discriminate between individuals are associated with immune and inflammatory functions. When investigating possible time trends in the microarray data, we have found no differential expression within a sampling period (within-season effect). Differential expression was observed between sampling seasons and the data suggest a weak response of genes related to immune system functioning. Finally, a high number of probes showed significant season-specific expression variability within subjects. Expression variability increased in springtime and there was an association of the probe list with immune system functioning. Our study suggests that the blood transcriptome of healthy individuals is reproducible over a time period of several months.

Molecular sources of residual cardiovascular risk, clinical signals, and innovative solutions: relationship with subclinical disease, undertreatment, and poor adherence: implications of new evidence upon optimizing cardiovascular patient outcomes

Residual risk, the ongoing appreciable risk of major cardiovascular events (MCVE) in statin-treated patients who have achieved evidence-based lipid goals, remains a concern among cardiologists. Factors that contribute to this continuing risk are atherogenic non-low-density lipoprotein (LDL) particles and atherogenic processes unrelated to LDL cholesterol, including other risk factors, the inherent properties of statin drugs, and patient characteristics, ie, genetics and behaviors. In addition, providers, health care systems, the community, public policies, and the environment play a role. Major statin studies suggest an average 28% reduction in LDL cholesterol and a 31% reduction in relative risk, leaving a residual risk of about 69%. Incomplete reductions in risk, and failure to improve conditions that create risk, may result in ongoing progression of atherosclerosis, with new and recurring lesions in original and distant culprit sites, remodeling, arrhythmias, rehospitalizations, invasive procedures, and terminal disability. As a result, identification of additional agents to reduce residual risk, particularly administered together with statin drugs, has been an ongoing quest. The current model of atherosclerosis involves many steps during which disease may progress independently of guideline-defined elevations in LDL cholesterol. Differences in genetic responsiveness to statin therapy, differences in ability of the endothelium to regenerate and repair, and differences in susceptibility to nonlipid risk factors, such as tobacco smoking, hypertension, and molecular changes associated with obesity and diabetes, may all create residual risk. A large number of inflammatory and metabolic processes may also provide eventual therapeutic targets to lower residual risk. Classically, epidemiologic and other evidence suggested that raising high-density lipoprotein (HDL) cholesterol would be cardioprotective. When LDL cholesterol is aggressively lowered to targets, low HDL cholesterol levels are still inversely related to MCVE. The efflux capacity, or ability to relocate cholesterol out of macrophages, is believed to be a major antiatherogenic mechanism responsible for reduction in MCVE mediated in part by healthy HDL. HDL cholesterol is a complex molecule with antioxidative, anti-inflammatory, anti-thrombotic, antiplatelet, and vasodilatory properties, among which is protection of LDL from oxidation. HDL-associated paraoxonase-1 has a major effect on endothelial function. Further, HDL promotes endothelial repair and progenitor cell health, and supports production of nitric oxide. HDL from patients with cardiovascular disease, diabetes, and autoimmune disease may fail to protect or even become proinflammatory or pro-oxidant. Mendelian randomization and other clinical studies in which raising HDL cholesterol has not been beneficial suggest that high plasma levels do not necessarily reduce cardiovascular risk. These data, coupled with extensive preclinical information about the functional heterogeneity of HDL, challenge the "HDL hypothesis", ie, raising HDL cholesterol per se will reduce MCVE. After the equivocal AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides: Impact on Global Health Outcomes) study and withdrawal of two major cholesteryl ester transfer protein compounds, one for off-target adverse effects and the other for lack of efficacy, development continues for two other agents, ie, anacetrapib and evacetrapib, both of which lower LDL cholesterol substantially. The negative but controversial HPS2-THRIVE (the Heart Protection Study 2-Treatment of HDL to Reduce the Incidence of Vascular Events) trial casts further doubt on the HDL cholesterol hypothesis. The growing impression that HDL functionality, rather than abundance, is clinically important is supported by experimental evidence highlighting the conditional pleiotropic actions of HDL. Non-HDL cholesterol reflects the cholesterol in all atherogenic particles containing apolipoprotein B, and has outperformed LDL cholesterol as a lipid marker of cardiovascular risk and future mortality. In addition to including a measure of residual risk, the advantages of using non-HDL cholesterol as a primary lipid target are now compelling. Reinterpretation of data from the Treating to New Targets study suggests that better control of smoking, body weight, hypertension, and diabetes will help lower residual risk. Although much improved, control of risk factors other than LDL cholesterol currently remains inadequate due to shortfalls in compliance with guidelines and poor patient adherence. More efficient and greater use of proven simple therapies, such as aspirin, beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, combined with statin therapy, may be more fruitful in improving outcomes than using other complex therapies. Comprehensive, intensive, multimechanistic, global, and national programs using primordial, primary, and secondary prevention to lower the total level of cardiovascular risk are necessary.

Deriving at candidate genes of metabolic stress from pancreas of WNIN/GR-Ob mutant rats

Development of appropriate animal model systems have greatly helped our understanding of the basic mechanism(s) of several degenerative diseases. WNIN/GR-Ob?a mutant rat strain developed at the National Center for Laboratory Animal Sciences facility of National Institute of Nutrition, is a new animal model ideal to study the metabolic syndrome since it is obese with impaired glucose tolerance and also exhibits several secondary complications. The present study was performed in the pancreas of this mutant model to assess the global gene expression (microarray) to assess the transcriptome level changes in situ depicting inflammation, obesity, insulin resistance, and diabetes in these animals. Our findings suggest an interplay of several confounding factors in pancreas which include inflammation /macrophage infiltration/apoptosis/oxidative and endoplasmic reticulum stress, all contributing for the shift toward pro-inflammation. We were able to phenotypically correlate the metabolic alterations vis-a-vis candidate genes (array analyses) compared between mutants and its age matched, parental controls. We advocate that the data reported here would provide a suitable insight in to the pathophysiology of metabolic syndrome .

The systems genetics resource: a web application to mine global data for complex disease traits

The Systems Genetics Resource (SGR) (http://systems.genetics.ucla.edu) is a new open-access web application and database that contains genotypes and clinical and intermediate phenotypes from both human and mouse studies. The mouse data include studies using crosses between specific inbred strains and studies using the Hybrid Mouse Diversity Panel. SGR is designed to assist researchers studying genes and pathways contributing to complex disease traits, including obesity, diabetes, atherosclerosis, heart failure, osteoporosis, and lipoprotein metabolism. Over the next few years, we hope to add data relevant to deafness, addiction, hepatic steatosis, toxin responses, and vascular injury. The intermediate phenotypes include expression array data for a variety of tissues and cultured cells, metabolite levels, and protein levels. Pre-computed tables of genetic loci controlling intermediate and clinical phenotypes, as well as phenotype correlations, are accessed via a user-friendly web interface. The web site includes detailed protocols for all of the studies. Data from published studies are freely available; unpublished studies have restricted access during their embargo period.

Short-term, high fat feeding-induced changes in white adipose tissue gene expression are highly predictive for long-term changes

SCOPE

We aimed to evaluate the predictability of short-term (5 days) changes in epididymal white adipose tissue (eWAT) gene expression for long-term (12 weeks) changes induced by high-fat diet (HFD) feeding.

METHODS AND RESULTS

Mice were fed semisynthetic diets containing 10 (low-fat diet) or 40 (HFD) energy% of fat. Global gene expression in eWAT was analyzed using microarrays and confirmed by quantitative PCR. As expected, HFD feeding resulted in increased body fat accumulation and reduced glucose tolerance after 12 weeks. A total of 4678 transcripts were significantly changed by HFD after 12 weeks and 973 after 5 days, with an overlap of 764 transcripts encoding 549 genes. Of these, 79% were downregulated and 21% were upregulated by HFD, all in the same direction and highly correlated (r(2) = 0.90) between the time points. Pathway analysis showed downregulation of the main identified processes: lipid metabolism, carbohydrate metabolism, and oxidative phosphorylation. Mest (mesoderm-specific transcript) was highly upregulated, confirming its role as an early marker of fat cell expansion.

CONCLUSION

The high predictive value of short-term gene expression changes for long-term effects of high fat feeding is a promising step to establish robust early biomarkers that could shorten animal trials to assess health-promoting food compounds.

Novel genes underlying beta cell survival in metabolic stress

Relative insulin deficiency, in response to increased metabolic demand (obesity, genetic insulin resistance, pregnancy and aging) lead to Type2 diabetes. Susceptibility of the type 2 diabetes has a genetic basis, as a subset of people with risk factors (obesity, Insulin Resistance, pregnancy), develop Type2 Diabetes. We aimed to identify 'cluster' of overexpressed genes, underlying increased beta cell survival in diabetes resistant C57BL/6J ob/ob mice (compared to diabetes susceptible BTBR ob/ob mice). We used 'consensus' overexpression status to identify 'cluster' of 11 genes consisting of Aldh18a1, Rfc4, Dynlt3, Prom1, H13, Psen1, Ssr4, Dad1, Anpep, Fam111a and Plk1. Information (biological processes, molecular functions, cellular components, protein-protein interactions/associations, gene deletion/knockout/inhibition studies) of all the genes in 'cluster' were collected by text mining using different literature search tools, gene information databases and protein-protein interaction databases. Beta cell specific function of these genes were also inferred using meta analysis tool of Beta Cell Biology Consortium, by studying the expression pattern of these genes in microarray studies related to beta-cell stimulation/injury, pancreas development and growth and cell differentiation. In the 'clusters', 6 genes (Dad1, Psen1, Ssr4, Rfc4, H13, Plk1) have a role in cell survival. Only Psen1 was previously identified to have role in successful beta cell compensation. We advocate these genes to be potentially involved in successful beta cell compensation and prevent T2D in humans, by conferring protection against diabetogenic insults.

Adipose-specific deletion of TFAM increases mitochondrial oxidation and protects mice against obesity and insulin resistance

Obesity and type 2 diabetes are associated with mitochondrial dysfunction in adipose tissue, but the role for adipose tissue mitochondria in the development of these disorders is currently unknown. To understand the impact of adipose tissue mitochondria on whole-body metabolism, we have generated a mouse model with disruption of the mitochondrial transcription factor A (TFAM) specifically in fat. F-TFKO adipose tissue exhibit decreased mtDNA copy number, altered levels of proteins of the electron transport chain, and perturbed mitochondrial function with decreased complex I activity and greater oxygen consumption and uncoupling. As a result, F-TFKO mice exhibit higher energy expenditure and are protected from age- and diet-induced obesity, insulin resistance, and hepatosteatosis, despite a greater food intake. Thus, TFAM deletion in the adipose tissue increases mitochondrial oxidation that has positive metabolic effects, suggesting that regulation of adipose tissue mitochondria may be a potential therapeutic target for the treatment of obesity.

Unmasking the janus faces of autophagy in obesity-associated insulin resistance and cardiac dysfunction

Autophagy is an intracellular, lysosomal-dependent process involved in the turnover of long-lived proteins, damaged organelles and other subcellular structures. The autophagic process is known to play an essential role in the maintenance of cellular homeostasis. Results from recent studies also indicate an important role for the autophagic process in the pathogenesis of human diseases, including cancer, cardiovascular diseases, obesity, diabetes mellitus and ageing. Because of the pivotal role of autophagy in the regulation of adipogenesis, obesity and insulin sensitization, research efforts have focused on elucidating the role of autophagy in metabolic syndrome. Mammalian target of rapamycin (mTOR) is a key regulator of cell growth and is characterized by a complex signalling mechanism that affects protein synthesis and autophagy. Results from experimental and clinical studies reveal some interesting, but conflicting, findings regarding the mTOR signalling pathway and autophagy in adipocytes in metabolic syndrome. Although the pivotal role of autophagy in obesity and other metabolic diseases has been established, its involvement in obesity-induced cardiac dysfunction remains unknown, as do the upstream signalling regulators of autophagy. The present minireview discusses the molecular mechanisms of autophagy in the regulation of cardiac function in overweight and obesity. Further studies using appropriate models are needed to better unravel the complex intracellular mechanisms involved in the regulation of autophagy in obesity-induced cardiac dysfunction.

Mitochondrial dysfunction in white adipose tissue

Although mitochondria in brown adipose tissue and their role in non-shivering thermogenesis have been widely studied, we have only a limited understanding of the relevance of mitochondria in white adipose tissue (WAT) for cellular homeostasis of the adipocyte and their impact upon systemic energy homeostasis. A better understanding of the regulatory role that white adipocyte mitochondria play in the regulation of whole-body physiology becomes increasingly important. WAT mitochondrial biogenesis can effectively be induced pharmacologically using a number of agents, including PPARγ agonists. Through their ability to influence key biochemical processes central to the adipocyte, such as fatty acid (FA) esterification and lipogenesis, as well as their impact upon the production and release of key adipokines, mitochondria play a crucial role in determining systemic insulin sensitivity.

Impact of obesity on IL-12 family gene expression in insulin responsive tissues

Mounting evidence has established a role for chronic inflammation in the development of obesity-induced insulin resistance, as genetic ablation of pro-inflammatory cytokines and chemokines elevated in obesity improves insulin signaling in vitro and in vivo. Recent evidence further highlights interleukin (IL)-12 family cytokines as prospective inflammatory mediators linking obesity to insulin resistance. In this study, we present empirical evidence demonstrating that IL-12 family related genes are expressed and regulated in insulin-responsive tissues under conditions of obesity. First, we report that respective mRNAs for each of the known members of this cytokine family are expressed within detectable ranges in WAT, skeletal muscle, liver and heart. Second, we show that these cytokines and their cognate receptors are divergently regulated with genetic obesity in a tissue-specific manner. Third, we demonstrate that select IL-12 family cytokines are regulated in WAT in a manner that is dependent on the developmental stage of obesity as well as the inflammatory progression associated with obesity. Fourth, we report that respective mRNAs for IL-12 cytokines and receptors are also expressed and divergently regulated in cultured adipocytes under conditions of inflammatory stress. To our knowledge, this report is the first study to systemically evaluated mRNA expression of all IL-12 family cytokines and receptors in any tissue under conditions of obesity highlighting select family members as potential mediators linking excess nutrient intake to metabolic diseases such as insulin resistance, diabetes and heart disease.

Angiotensinogen gene polymorphisms and food-intake behavior in young, normal female subjects in Japan

OBJECTIVE

We examined whether angiotensinogen (AGT) gene polymorphisms are associated with food preferences in young, normal female subjects.

METHODS

Fifty-two young, normal female subjects (21-22 y old) were recruited. After a 12-h fast, blood samples were obtained to examine the AGT gene polymorphisms (rs699 and rs7079), angiotensin-converting enzyme (ACE) insertion (I)/deletion (D), and adrenergic β3 receptor (ADRB3) gene polymorphisms (rs4994). A trained dietitian interviewed the participants to determine the portion size and frequency of food eaten for 1 wk by using the established questionnaire FFQg 3.0.

RESULTS

The genotypes of the AGT Met235Thr polymorphisms were TT:TC:CC = 2:19:31 (T:C = 0.22:0.78). The genotypes of AGT rs7079 were CC:CA:AA = 26:21:5 (C:A = 0.70:0.30), and those of ACE were DD:DI:II = 5:28:19 (D/I = 0.37:0.63). The genotypes of ADRB3 Trp64Arg were TT:TC:CC = 38:11:3 (T:C = 0.84:0.16). The total caloric intake was greater for those with the MM/MT genotype of AGT Met235Thr than for those with the TT genotype (1993 versus 1698 kcal/d, P < 0.05). The consumption of total lipids, cholesterol, and unsaturated free fatty acids was also higher in those with the MM/MT genotype of AGT Met235Thr than in those with the TT genotype. However, the AGT polymorphism (rs7079) and the ACE I/D were not associated with food preferences. In contrast, the subjects with ADRB3 Trp64 tended to show a high energy intake and preferences for proteins and lipids including fatty acids and cholesterol. They ate more fish and meat. Multiple regression analysis showed that the energy intake in subjects with the MM/MT genotype was independently determined by total lipids (B = 11.7, P < 0.0001) and carbohydrates (B = 4.6, P < 0.0001).

CONCLUSIONS

The AGT Met235Thr polymorphism was significantly associated with a higher caloric intake owing to total fat and carbohydrate consumption.

Network analysis of adipose tissue gene expression highlights altered metabolic and regulatory transcriptomic activity in high-fat-diet-fed IL-1RI knockout mice

A subacute inflammatory phenotype is implicated in the pathology of insulin resistance (IR) and type 2 diabetes mellitus. Interleukin (IL)-1α and IL-1β are produced by innate immune cells, including macrophages, and mediate their inflammatory response through the IL-1 type I receptor (IL-IRI). This study sought to understand the transcriptomic signature of adipose tissue in obese IL-1RI(-/-) mice. Following dietary intervention, markers of insulin sensitivity and inflammation in adipose tissue were determined, and gene expression was assessed with microarrays. IL-1RI(-/-) mice fed a high-fat diet (HFD) had significantly lower plasma inflammatory cytokine concentrations than wild-type mice. Metabolic network analysis of transcriptomic effects identified up-regulation and co-expression of genes involved in lipolysis, lipogenesis and tricarboxylic acid (TCA) cycle. Further assessment of gene expression in a network of protein interactions related to innate immunity highlighted Stat3 as a potential transcriptional regulator of IL-1 signalling. The complex, downstream effects of IL-1 signalling through the IL-1RI receptor remain poorly defined. Using network-based analyses of transcriptomic signatures in IL-1RI(-/-) mice, we have identified expression changes in genes involved in lipid cycling and TCA cycle, which may be more broadly indicative of a restoration of mitochondrial function in the context of HFD. Our results also highlight a potential role for Stat3 in linking IL-1 signalling to adipogenesis and IR.

Differential gene expression in adipose tissue from obese human subjects during weight loss and weight maintenance

BACKGROUND

Differential gene expression in adipose tissue during diet-induced weight loss followed by a weight stability period is poorly characterized. Markers of these processes may provide a deeper understanding of underlying mechanisms.

OBJECTIVE

We aimed to identify differentially expressed genes in human adipose tissue during weight loss and weight maintenance after weight loss.

DESIGN

RNA from subcutaneous abdominal adipose tissue from 9 obese subjects was analyzed by using a complementary DNA microarray at baseline after weight loss on a low-calorie diet and after weight maintenance.

RESULTS

Subjects lost 18.8 ± 1.8% of weight and maintained this loss during weight maintenance (1.1 ± 2.1%; range: -9.3 to 10.6%). Most differentially expressed genes exhibited a reciprocal regulation and returned to baseline after weight loss (2163 genes) and weight maintenance (3175 genes). CETP and ABCG1, both of which participate in the HDL-mediated reverse cholesterol transport (RCT), were among the most upregulated of the 750 genes that were differentially expressed after both processes. Several genes involved in inflammation were downregulated. The use of real-time polymerase chain reaction confirmed or partially confirmed the previously implicated genes TNMD and MMP9 (both downregulated), PNPLA3 (upregulated), and CIDEA and SCD (both reciprocally regulated).

CONCLUSIONS

The beneficial effects of weight loss should be investigated after long-term weight maintenance. The processes of weight loss and weight maintenance should be viewed as biologically distinct. CETP and ABCG1 may be important mediators of these effects through HDL-mediated RCT.

Systems-based approaches to cardiovascular disease

Common cardiovascular diseases, such as atherosclerosis and congestive heart failure, are exceptionally complex, involving a multitude of environmental and genetic factors that often show nonlinear interactions as well as being highly dependent on sex, age, and even the maternal environment. Although focused, reductionistic approaches have led to progress in elucidating the pathophysiology of cardiovascular diseases, such approaches are poorly powered to address complex interactions. Over the past decade, technological advances have made it possible to interrogate biological systems on a global level, raising hopes that, in combination with computational approaches, it may be possible to more fully address the complexities of cardiovascular diseases. In this Review, we provide an overview of such systems-based approaches to cardiovascular disease and discuss their translational implications.

Systems biology approach for new target and biomarker identification

The pharmaceutical industry is spending increasingly large amounts of money on the discovery and development of novel medicines, but this investment is not adequately paying off in an increased rate of newly approved drugs by the FDA. The post-genomic era has provided a wealth of novel approaches for generating large, high-dimensional genetic and transcriptomic data sets from large cohorts of preclinical species as well as normal and diseased individuals. This systems biology approach to understanding disease-related biology is revolutionizing our understanding of the cellular pathways and gene networks underlying the onset of disease, and the mechanisms of pharmacological treatments that ameliorate disease phenotypes. In this article, we review a number of approaches being used by pharmaceutical and biotechnology companies, e.g., high-throughput DNA genotyping, sequencing, and genome-wide gene expression profiling, to enable drug discovery and development through the identification of new drug targets and biomarkers of disease progression, drug pharmacodynamics, and predictive markers for selecting the patients most likely to respond to therapy.