Interindividual differences of dietary fat-inducible Mest in white adipose tissue of C57BL/6J mice are not heritable.

Objective: Differences in white adipose tissue (WAT) expression of mesoderm-specific transcript (Mest) in C57BL6/J mice fed a high-fat diet (HFD) are concomitant with and predictive for the development of obesity. However, the basis for differences in WAT Mest among mice is unknown. This study investigated whether HFD-inducible WAT Mest, as well as susceptibility to obesity, is transmissible from parents to offspring.

Parallel control of cold-triggered adipocyte thermogenesis by UCP1 and CKB.

That uncoupling protein 1 (UCP1) is the sole mediator of adipocyte thermogenesis is a conventional viewpoint that has primarily been inferred from the attenuation of the thermogenic output of mice genetically lacking Ucp1 from birth (germline Ucp1). However, germline Ucp1 mice harbor secondary changes within brown adipose tissue. To mitigate these potentially confounding ancillary changes, we constructed mice with inducible adipocyte-selective Ucp1 disruption.

Purification of functional mouse skeletal muscle mitochondria using percoll density gradient centrifugation.

Objective: Our goal was to isolate purified mitochondria from mouse skeletal muscle using a Percoll density gradient and to assess bioenergetic function and purity via Seahorse Extracellular Flux (XF) Analyses and mass spectrometry.

Results: Mitochondria isolated from murine quadriceps femoris skeletal muscle using a Percoll density gradient method allowed for minimally contaminated preparations with time from tissue harvest to mitochondrial isolation and quantification in about 3-4 h. Percoll purification from 100 to 200 mg fresh tissue yielded ~ 200-400 ug protein.

Purification of functional mouse skeletal muscle mitochondria using Percoll density gradient centrifugation.

Objective: Our goal was to isolate purified mitochondria from mouse skeletal muscle using a Percoll density gradient and to assess bioenergetic function and purity via Seahorse Extracellular Flux (XF) Analyses and mass spectrometry.

Results: Mitochondria isolated from murine quadriceps femoris skeletal muscle using a Percoll density gradient method allowed for minimally contaminated preparations with time from tissue harvest to mitochondrial isolation and quantification in about 3-4 hours. Percoll purification from 100-200 mg fresh tissue yielded ∼200-400 ug protein.

Rapamycin/metformin co-treatment normalizes insulin sensitivity and reduces complications of metabolic syndrome in type 2 diabetic mice.

Rapamycin treatment has positive and negative effects on progression of type 2 diabetes (T2D) in a recombinant inbred polygenic mouse model, male NONcNZO10/LtJ (NcZ10). Here, we show that combination treatment with metformin ameliorates negative effects of rapamycin while maintaining its benefits. From 12 to 30 weeks of age, NcZ10 males were fed a control diet or diets supplemented with rapamycin, metformin, or a combination of both.

Social and maternal behavior in mesoderm specific transcript (Mest)-deficient mice.

Mesoderm specific transcript (Mest)/paternally expressed gene-1 (Peg1) is an imprinted gene expressed predominantly from the paternal allele. Aberrations in maternal behavior were previously reported in a Mest global knockout mouse (Mesttm1Masu). In this study, we performed in-depth social and maternal behavioral testing in a mouse model of Mest inactivation developed in our laboratory (Mesttm1.

Sprouty1 regulates gonadal white adipose tissue growth through a PDGFRα/β-Akt pathway.

Expansion of visceral white adipose tissue (vWAT) occurs in response to nutrient excess, and is a risk factor for metabolic disease. SPRY1, a feedback inhibitor of receptor tyrosine kinase (RTK) signaling, is expressed in PDGFRa+ adipocyte progenitor cells (APC) in vivo. Global deficiency of in mice results in disproportionate postnatal growth of gonadal WAT (gWAT), while iWAT and BAT were similar in size between KO and WT mice.

Protective role of ErbB3 signaling in myeloid cells during adaptation to cardiac pressure overload.

Background: Myeloid cells play an important role in a wide variety of cardiovascular disorders, including both ischemic and non-ischemic cardiomyopathies. Neuregulin-1 (NRG-1)/ErbB signaling has recently emerged as an important factor contributing to the control of inflammatory activation of myeloid cells after an ischemic injury. However, the role of ErbB signaling in myeloid cells in non-ischemic cardiomyopathy is not fully understood.

Weight Loss and Concomitant Adipose Autophagy in Methionine-Restricted Obese Mice is Not Dependent on Adiponectin or FGF21.

Objective: Identifying novel approaches to combat obesity is important to improve health span. It was hypothesized that methionine restriction (MR) will induce weight loss in obese mice by reducing adipose tissue mass caused by increased energy expenditure and reprogramming of adipose tissue homeostasis. The roles of adiponectin (ADIPOQ) and fibroblast growth factor 21 (FGF21) during weight loss in MR mice were also tested.

Cardioprotective effects of dietary rapamycin on adult female C57BLKS/J-Lepr mice.

Rapamycin (RAPA), an inhibitor of mTORC signaling, has been shown to extend life span in mice and other organisms. Recently, animal and human studies have suggested that inhibition of mTORC signaling can alleviate or prevent the development of cardiomyopathy. In view of this, we used a murine model of type 2 diabetes (T2D), BKS-Lepr , to determine whether RAPA treatment can mitigate the development of T2D-induced cardiomyopathy in adult mice.

Mesoderm-specific transcript localization in the ER and ER-lipid droplet interface supports a role in adipocyte hypertrophy.

Highly variable expression of mesoderm-specific transcript (Mest) in adipose tissue among genetically homogeneous mice fed an obesogenic diet, and its positive association with fat mass expansion, suggests that Mest is an epigenetic determinant for the development of obesity. Although the mechanisms by which MEST augments fat accumulation in adipocytes have not been elucidated, it has sequence homology and catalytic peptide motifs which suggests that it functions as an epoxide hydrolase or as a glycerol- or acylglycerol-3-phosphate acyltransferase. To better understand MEST function, detailed studies were performed to precisely define the intracellular organelle localization of MEST using immunofluorescence confocal microscopy.

Diet-induced adipose tissue expansion is mitigated in mice with a targeted inactivation of mesoderm specific transcript (Mest).

Interindividual variation of white adipose tissue (WAT) expression of mesoderm specific transcript (Mest), a paternally-expressed imprinted gene belonging to the α/β-hydrolase fold protein family, becomes apparent among genetically inbred mice fed high fat diet (HFD) and is positively associated with adipose tissue expansion (ATE). To elucidate a role for MEST in ATE, mice were developed with global and adipose tissue inactivation of Mest. Mice with homozygous (MestgKO) and paternal allelic (MestpKO) inactivation of Mest were born at expected Mendelian frequencies, showed no behavioral or physical abnormalities, and did not perturb expression of the Mest locus-derived microRNA miR-335.

Lipid Profiling of In Vitro Cell Models of Adipogenic Differentiation: Relationships With Mouse Adipose Tissues.

Our objective was to characterize lipid profiles in cell models of adipocyte differentiation in comparison to mouse adipose tissues in vivo. A novel lipid extraction strategy was combined with global lipid profiling using direct infusion and sequential precursor ion fragmentation, termed MS/MS(ALL) . Perirenal and inguinal white adipose tissue and interscapular brown adipose tissues from adult C57BL/6J mice were analyzed.

Molecular correlates of fat mass expansion in C57BL/6J mice after short-term exposure to dietary fat.

Heterogeneity of obesity within a population of inbred mice fed an obesogenic high-fat diet (HFD) is associated with changes of gene expression in white adipose tissue (WAT). One gene in particular with large variations among mice, mesoderm-specific transcript (Mest), has been shown to be highly inducible after being fed a short-term HFD, and its expression in WAT before HFD feeding is predictive for susceptibility to the development of obesity. To gain further insight into the association of Mest with rapid changes in body composition, 96 individually housed C57BL/6J mice were fed an HFD for only 2 weeks, resulting in a 12-fold and 90-fold variation in Mest mRNA in visceral epididymal and subcutaneous inguinal WAT, respectively.

Adipose tissue Mest and Sfrp5 are concomitant with variations of adiposity among inbred mouse strains fed a non-obesogenic diet.

The expression of a subset of genes including mesoderm specific transcript (Mest), secreted frizzled-related protein 5 (Sfrp5) and bone morphogenetic protein 3 (Bmp3) in adipose tissue biopsies of C57BL/6J mice before exposure to an obesogenic diet were shown to be predictive for the development of obesity in mice after feeding a high fat diet for 8 weeks. This observation led to the supposition that adipose tissue expression of this subset of genes within inbred strains of mice could be associated with their susceptibility in the development of adiposity when fed a low fat diet. The analyses of male mice from 5 inbred strains showed average bodyweights ranging from 25.

A High Fat Diet Increases Bone Marrow Adipose Tissue (MAT) But Does Not Alter Trabecular or Cortical Bone Mass in C57BL/6J Mice.

Obesity has been associated with high bone mineral density (BMD) but a greater propensity to fracture. Some obese individuals have increased marrow adipose tissue (MAT), but the impact of MAT on bone turnover remains controversial, as do changes in BMD associated with a high fat diet (HFD). In this study we hypothesized that MAT volume would increase in response to HFD but would be independent of changes in BMD.

Astrocytic leptin-receptor knockout mice show partial rescue of leptin resistance in diet-induced obesity.

To determine how astrocytic leptin signaling regulates the physiological response of mice to diet-induced obesity (DIO), we performed metabolic analyses and hypothalamic leptin signaling assays on astrocytic leptin-receptor knockout (ALKO) mice in which astrocytes lack functional leptin receptor (ObR) signaling. ALKO mice and wild-type (WT) littermate controls were studied at different stages of DIO with measurement of body wt, percent fat, metabolic activity, and biochemical parameters. When fed regular chow, the ALKO mice had similar body wt, percent fat, food intake, heat dissipation, respiratory exchange ratio, and activity as their WT littermates.

Inherent plasticity of brown adipogenesis in white fat of mice allows for recovery from effects of post-natal malnutrition.

Interscapular brown adipose tissue (iBAT) is formed during fetal development and stable for the life span of the mouse. In addition, brown adipocytes also appear in white fat depots (wBAT) between 10 and 21 days of age in mice maintained at a room temperature of 23 °C. However, this expression is transient.

Inactivation of the mitochondrial carrier SLC25A25 (ATP-Mg2+/Pi transporter) reduces physical endurance and metabolic efficiency in mice.

An ATP-Mg(2+/)P(i) inner mitochondrial membrane solute transporter (SLC25A25), which is induced during adaptation to cold stress in the skeletal muscle of mice with defective UCP1/brown adipose tissue thermogenesis, has been evaluated for its role in metabolic efficiency. SLC25A25 is thought to control ATP homeostasis by functioning as a Ca(2+)-regulated shuttle of ATP-Mg(2+) and P(i) across the inner mitochondrial membrane. Mice with an inactivated Slc25a25 gene have reduced metabolic efficiency as evidenced by enhanced resistance to diet-induced obesity and impaired exercise performance on a treadmill.

The genetics of brown adipose tissue.

Brown adipose tissue is highly differentiated and has evolved as a mechanism for heat production based upon uncoupling of mitochondrial oxidative phosphorylation. Additionally, large amounts of lipid can be stored in the cells to provide fuel necessary for heat production upon adrenergic stimulation from the central nervous system, and a highly developed vascular system evolved to rapidly deliver heat to vital organs. For unknown reasons, the development of brown adipocytes has two independent pathways: one originates from muscle progenitor cells in the fetus and leads to a fully functional cell at birth (interscapular-type brown fat), while the other transiently emerges in traditional white fat depots at weaning, regresses, and then can be induced in adult mice upon adrenergic stimulation.

The early nutritional environment of mice determines the capacity for adipose tissue expansion by modulating genes of caveolae structure.

While the phenomenon linking the early nutritional environment to disease susceptibility exists in many mammalian species, the underlying mechanisms are unknown. We hypothesized that nutritional programming is a variable quantitative state of gene expression, fixed by the state of energy balance in the neonate, that waxes and wanes in the adult animal in response to changes in energy balance. We tested this hypothesis with an experiment, based upon global gene expression, to identify networks of genes in which expression patterns in inguinal fat of mice have been altered by the nutritional environment during early post-natal development.

Inter-individual variation of dietary fat-induced mesoderm specific transcript in adipose tissue within inbred mice is not caused by altered promoter methylation.

Mesoderm specific transcript (Mest), an imprinted gene associated with fat mass expansion under conditions of positive energy balance, shows highly variable expression (approximately 80-fold) in white adipose tissue (WAT) of C57BL/6J (B6) mice fed an obesogenic diet. Since B6 mice are essentially genetically invariant and Mest is known to be regulated by CpG methylation within its immediate proximal promoter, the large variability in its expression in adipose tissue has the hallmarks of being controlled via an epigenetic mechanism. In this study, bisulfite sequencing and allelic discrimination analyses were performed to determine whether variations in CpG methylation within the Mest promoter were associated with its expression.

Identification of adropin as a secreted factor linking dietary macronutrient intake with energy homeostasis and lipid metabolism.

Obesity and nutrient homeostasis are linked by mechanisms that are not fully elucidated. Here we describe a secreted protein, adropin, encoded by a gene, Energy Homeostasis Associated (Enho), expressed in liver and brain. Liver Enho expression is regulated by nutrition: lean C57BL/6J mice fed high-fat diet (HFD) exhibited a rapid increase, while fasting reduced expression compared to controls.

Inactivation of UCP1 and the glycerol phosphate cycle synergistically increases energy expenditure to resist diet-induced obesity.

Our current paradigm for obesity assumes that reduced thermogenic capacity increases susceptibility to obesity, whereas enhanced thermogenic capacity protects against obesity. Here we report that elimination of two major thermogenic pathways encoded by the mitochondrial uncoupling protein (Ucp1) and mitochondrial glycerol-3-phosphate dehydrogenase (Gdm) result in mice with increased resistance to diet-induced obesity when housed at 28 degrees C, provided prior adaptation occurred at 20 degrees C. Obesity resistant Gdm(-/-).

Mesoderm-specific transcript is associated with fat mass expansion in response to a positive energy balance.

A 50-fold variation in mRNA and protein levels of the mesoderm-specific transcript gene (Mest) in white fat of C57BL/6J (B6) mice fed an obesogenic diet is positively correlated with expansion of fat mass. MEST protein was detected only in adipocytes, in which its induction occurred with both unsaturated and saturated dietary fat. To test the hypothesis that MEST modulates fat mass expansion, its expression was compared to that of stearoyl CoA desaturase (Scd1) in B6 mice exposed to diets and environmental temperatures that generated conditions separating the effects of food intake and adiposity.