Diet-induced Obesity In Female Mice Research Articles

Increased susceptibility to diet-induced obesity in female mice impairs ovarian steroidogenesis: The role of elevated leptin signalling on nodal activity inhibition in theca cells

ObjectivesSusceptibility to obesity in humans is driven by the intricate interplay of genetic, environmental and behavioural factors. Moreover, the mechanisms linking maternal obesity to infertility remain largely understudied. In this study, we investigated how variable susceptibility to obesity in mice affects ovarian steroidogenesis, with a particular focus on the leptin-mediated dysregulation of Nodal signalling pathway in theca cells (TC). MethodsC56BL/6J (B6) and 129S1/SvlmJ (129) mice, models of maternal obesity (MO), were fed a chow diet (CD) and a high fat diet (HFD) for 16 weeks. To investigate the contrasting effects of leptin on ovarian steroidogenesis, B6 mice pharmacologically treated with leptin for 16 days on CD were used to model hyperleptinemia, while homozygous ob/ob (−/−) mice with genetic leptin deficiency, also on a CD, were used to examine the effects of obesity in the absence of leptin. Following the characterisation of the mouse phenotype, gonadal fat (GON), whole ovaries (WO), ovarian TC and granulosa cell (GC) fractions were collected for mRNA transcription and protein expression analysis. Finally, in vitro treated ovarian explants obtained from B6 mice were used to further elucidate the effects of Nodal on steroidogenesis. ResultsThe significant gain in body weight (BW) and fat mass (FM) in HFD-fed B6 mice (p < 0.05), was associated with increased mRNA transcription of the adipose tissue expansion genes Polymerase I and transcript release factor (Cavin), Secreted frizzled-related protein 5 (Sfrp5) and Mesoderm specific transcript (Mest) in GON (p < 0.05). Furthermore, the HFD-fed B6 mice presented also impaired glucose metabolism and insulin sensitivity (p < 0.05). In contrast, the HFD-fed 129 mice exhibited no changes in BW and FM, maintaining glucose and insulin metabolism. At the ovarian level, decreased protein expression of Steroidogenic Acute Regulatory Protein (StAR) in WO obtained from HFD-fed B6 mice (p = 0.05), was followed by reduced transcription of key steroidogenic genes like Star and Cytochrome P450 17a1 (Cyp17a) in TC (p < 0.05). Furthermore, the transcription of Nodal and its receptors was downregulated (p < 0.05), whereas mRNA levels of Suppressor of cytokine signalling 3 (Socs3) and SMAD family member 7 (Smad7) were upregulated in TC obtained from HFD-fed B6 mice (p < 0.05). No changes were seen in the genes regulating steroidogenesis, Nodal signalling, or Socs3 and Smad7 activity in the ovaries of HFD-fed 129 mice. Importantly, the pharmacological treatment of lean mice with leptin, upregulated the ovarian transcription of Socs3 and Smad7, while downregulating Nodal and its receptors (p < 0.05). Finally, in vitro pharmacological inhibition of Nodal signalling pathway in ovarian explants isolated from CD-fed B6 mice decreased the transcription of Star and Cyp17a in TC (p < 0.05), whereas Nodal treatment of explants obtained from HFD-fed B6 mice restored the transcription of both genes (p < 0.05). ConclusionsIncreased susceptibility to obesity in MO is associated with systemic hyperleptinemia and hypoestrogenism due to compromised ovarian steroidogenesis, largely driven by the inhibitory effects of leptin-Smad7 pathway on Nodal signalling activity in the TC compartment of ovarian follicles.

Targeted Deletion of Fibroblast Growth Factor 23 Rescues Metabolic Dysregulation of Diet-induced Obesity in Female Mice.

Fibroblast growth factor 23 (FGF23) is a bone-secreted protein widely recognized as a critical regulator of skeletal and mineral metabolism. However, little is known about the nonskeletal production of FGF23 and its role in tissues other than bone. Growing evidence indicates that circulating FGF23 levels rise with a high-fat diet (HFD) and they are positively correlated with body mass index (BMI) in humans. In the present study, we show for the first time that increased circulating FGF23 levels in obese humans correlate with increased expression of adipose Fgf23 and both positively correlate with BMI. To understand the role of adipose-derived Fgf23, we generated adipocyte-specific Fgf23 knockout mice (AdipoqFgf23Δfl/Δfl) using the adiponectin-Cre driver, which targets mature white, beige, and brown adipocytes. Our data show that targeted ablation of Fgf23 in adipocytes prevents HFD-fed female mice from gaining body weight and fat mass while preserving lean mass but has no effect on male mice, indicating the presence of sexual dimorphism. These effects are observed in the absence of changes in food and energy intake. Adipose Fgf23 inactivation also prevents dyslipidemia, hyperglycemia, and hepatic steatosis in female mice. Moreover, these changes are associated with decreased respiratory exchange ratio and increased brown fat Ucp1 expression in knockout mice compared to HFD-fed control mice (Fgf23fl/fl). In conclusion, this is the first study highlighting that targeted inactivation of Fgf23 is a promising therapeutic strategy for weight loss and lean mass preservation in humans.

LP-54 Protective effect of aryl hydrocarbon receptor (AHR) against high-fat diet-induced obesity in female mice

LP-54 Protective effect of aryl hydrocarbon receptor (AHR) against high-fat diet-induced obesity in female mice

Pubertal glyphosate-based herbicide exposure aggravates high-fat diet-induced obesity in female mice.

Glyphosate-based herbicides (GBH) are the most widely used pesticides globally. Studies have indicated that they may increase the risk of various organic dysfunctions. Herein, we verified whether exposure to GBH during puberty increases the susceptibility of male and female mice to obesity when they are fed a high-fat diet (HFD) in adulthood. From the 4th-7th weeks of age, male and female C57Bl/6 mice received water (CTL group) or 50mg GBH /kg body weight (BW; GBH group). From the 8th-21st weeks of age, the mice were fed a standard diet or a HFD. It was found that pubertal GBH exposure exacerbated BW gains and hyperphagia induced by HFD, but only in female GBH-HFD mice. These female mice also exhibited high accumulation of perigonadal and subcutaneous fat, as well as reduced lean body mass. Both male and female GBH-HFD displayed hypertrophic white adipocytes. However, only in females, pubertal GBH exposure aggravated HFD-induced fat accumulation in brown adipocytes. Furthermore, GBH increased plasma cortisol levels by 80% in GBH-HFD males, and 180% in GBH-HFD females. In conclusion, pubertal GBH exposure aggravated HFD-induced obesity, particularly in adult female mice. This study provides novel evidence that GBH misprograms lipid metabolism, accelerating the development of obesity when individuals are challenged by a second metabolic stressor, such as an obesogenic diet.

Bisphenol S induces brown adipose tissue whitening and aggravates diet-induced obesity in an estrogen-dependent manner

Bisphenol S (BPS) exposure has been implied epidemiologically to increase obesity risk, but the underlying mechanism is unclear. Here, we propose that BPS exposure at an environmentally relevant dose aggravates diet-induced obesity in female mice by inducing brown adipose tissue (BAT) whitening. We explored the underlying mechanism by which KDM5A-associated demethylation of the trimethylation of lysine 4 on histone H3 (H3K4me3) in thermogenic genes is overactivated in BAT upon BPS exposure, leading to the reduced expression of thermogenic genes. Further studies have suggested that BPS activates KDM5A transcription in BAT by binding to glucocorticoid receptor (GR) in an estrogen-dependent manner. Estrogen-estrogen receptors facilitate the accessibility of the KDM5A gene promoter to BPS-activated GR by recruiting the activator protein 1 (AP-1) complex. These results indicate that BAT is another important target of BPS and that targeting KDM5A-related signals may serve as an approach to counteract the BPS-induced susceptivity to obesity.

P31-053-23 Selenium Deficiency and Loss of Selenocysteine Lyase Activity Exacerbates Diet-Induced Obesity in Female Mice

P31-053-23 Selenium Deficiency and Loss of Selenocysteine Lyase Activity Exacerbates Diet-Induced Obesity in Female Mice

Long-term exposure to low-dose Di(2-ethylhexyl) phthalate aggravated high fat diet-induced obesity in female mice

The potential obesogenic roles of di(2-ethylhexyl) phthalate (DEHP) have attracted great attention. The current study aimed to evaluate the combined effects of chronic low-dose DEHP (0.05 mg/kg BW) and a high-fat diet (HFD) on obesity in female mice and explore the underlying mechanisms. We found that low-dose DEHP challenge for 29 weeks increased fat accumulation both in CD- and HFD-fed mice and significantly accelerated the weight gain without affecting food intake in HFD-fed mice. DEHP exposure reduced the energy metabolism, down-regulated the uncoupling protein 1 (UCP1) and total oxidative phosphorylation (OXPHOS) proteins expression in the brown adipose tissue, and up-regulated the PPARγ expression and its phosphorylation at Ser273 in white adipose tissue (WAT). Besides, the combination of DEHP and HFD drove the remodeling of gut microbiota of mice, characterized by the reduced richness and diversity and the elevated Firmicutes to Bacteroidetes (F/B) ratio. Short-chain fatty acids (SCFAs) analysis revealed that DEHP and HFD cotreatment led to a decrease in levels of acetic acid, butyric acid, and pentanoic acid. Interestingly, sodium butyrate (NaB) significantly inhibited the adipogenesis and lipid accumulation of NIH/3T3 mouse embryonic fibroblasts (PPARγ2 overexpression) and the PPARγ phosphorylation at Ser273 induced by DEHP or MEHP. These findings demonstrate that chronic low-dose DEHP challenge could prompt fat accumulation by increasing PPARγ phosphorylation at Ser273 and decreasing thermogenesis in BAT, which might be associated with the SCFAs reduction.

Diet-induced obesity alters intestinal monocyte-derived and tissue-resident macrophages and increases intestinal permeability in female mice independent of tumor necrosis factor.

Macrophages are essential for homeostatic maintenance of the anti-inflammatory and tolerogenic intestinal environment, yet monocyte-derived macrophages can promote local inflammation. Proinflammatory macrophage accumulation within the intestines may contribute to the development of systemic chronic inflammation and immunometabolic dysfunction in obesity. Using a model of high-fat diet-induced obesity in C57BL/6J female mice, we assessed intestinal paracellular permeability by in vivo and ex vivo assays and quantitated intestinal macrophages in ileum and colon tissues by multicolor flow cytometry after short (6 wk), intermediate (12 wk), and prolonged (18 wk) diet allocation. We characterized monocyte-derived CD4-TIM4- and CD4+TIM4- macrophages, as well as tissue-resident CD4+TIM4+ macrophages. Diet-induced obesity had tissue- and time-dependent effects on intestinal permeability, as well as monocyte and macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and tumor necrosis factor (TNF). We found that obese mice had increased paracellular permeability, in particular within the ileum, but this did not elicit recruitment of monocytes nor a local proinflammatory response by monocyte-derived or tissue-resident macrophages in either the ileum or colon. Proliferation of monocyte-derived and tissue-resident macrophages was also unchanged. Wild-type and TNF-/- littermate mice had similar intestinal permeability and macrophage population characteristics in response to diet-induced obesity. These data are unique from reported effects of diet-induced obesity on macrophages in metabolic tissues, as well as outcomes of acute inflammation within the intestines. These experiments also collectively indicate that TNF does not mediate effects of diet-induced obesity on paracellular permeability or intestinal monocyte-derived and tissue-resident intestinal macrophages in young female mice.NEW & NOTEWORTHY We found that diet-induced obesity in female mice has tissue- and time-dependent effects on intestinal paracellular permeability as well as monocyte-derived and tissue-resident macrophage numbers, surface marker phenotype, and intracellular production of the cytokines IL-10 and TNF. These changes were not mediated by TNF.

LBSUN132 Adipocyte-specific Ablation Of Fgf23 Attenuates Diet-induced Obesity In Female Mice

Abstract Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate homeostasis and vitamin D metabolism. In addition to its central role in mineral balance, recent findings suggested that FGF23 is associated with chronic metabolic conditions including cardiovascular disease, diabetes mellitus, and obesity. Circulating FGF23 levels are elevated in obese individuals, and they are correlated with body fat mass and abdominal obesity. Moreover, consumption of high fat diet (HFD) increases serum FGF23 levels. However, the actions of FGF23 in adipocytes and its role in lipid metabolism have not been demonstrated. To understand the role of FGF23 in adipocytes, particularly in obesity, we generated adipocyte-specific Fgf23 null mice using Cre recombinase under the control of the mouse adiponectin (Adipoq) promoter. Both male and female control (Fgf23flox/flox) and knockout (KO, AdipoqCreFgf23flox/flox) mice were fed either HFD (60%kcal fat) or normal fat diet (NFD) at 8 weeks of age for 24 weeks. Body weight measurements were taken every week and percentage of body fat was determined after longitudinally during 24 weeks of diet interventation using in vivo by an EchoMRI scannermicroCT. Serum, adipose tissue, and liver were collected upon sacrifice. After 24 weeks of HFD, male control and KO mice had comparable gain in body weight (BW) and body fat percentage. However, female KO mice had significantly lower body weight and percentage of body fat. Moreover, serum total cholesterol levels were reduced in female KO mice. Triglyceride (TG) content in the liver was significantly reduced in female KO mice, and it corresponded with downregulation of lipid droplet protein Perilipin and fatty acid transporter CD36 mRNA expression in the liver. Transcript levels of hepatic PPARγ, which is positively correlated with fat accumulation in obesity, were also suppressed in female KO mice compared to controls. Obesity is associated with low-grade chronic inflammation, and we found that hepatic mRNA expression of the inflammatory cytokine TNFα was diminished in female KO mice, suggesting that adipocytic Fgf23 modulates lipid accumulation and inflammation. In summary, our results demonstrate for the first time that adipocyte-specific ablation of Fgf23 alleviates attenuates diet-induced obesity and regulates lipid metabolism in a sex-specific manner. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Distinct Changes in Gut Microbiota Are Associated with Estradiol-Mediated Protection from Diet-Induced Obesity in Female Mice.

A decrease in ovarian estrogens in postmenopausal women increases the risk of weight gain, cardiovascular disease, type 2 diabetes, and chronic inflammation. While it is known that gut microbiota regulates energy homeostasis, it is unclear if gut microbiota is associated with estradiol regulation of metabolism. In this study, we tested if estradiol-mediated protection from high-fat diet (HFD)-induced obesity and metabolic changes are associated with longitudinal alterations in gut microbiota in female mice. Ovariectomized adult mice with vehicle or estradiol (E2) implants were fed chow for two weeks and HFD for four weeks. As reported previously, E2 increased energy expenditure, physical activity, insulin sensitivity, and whole-body glucose turnover. Interestingly, E2 decreased the tight junction protein occludin, suggesting E2 affects gut epithelial integrity. Moreover, E2 increased Akkermansia and decreased Erysipleotrichaceae and Streptococcaceae. Furthermore, Coprobacillus and Lactococcus were positively correlated, while Akkermansia was negatively correlated, with body weight and fat mass. These results suggest that changes in gut epithelial barrier and specific gut microbiota contribute to E2-mediated protection against diet-induced obesity and metabolic dysregulation. These findings provide support for the gut microbiota as a therapeutic target for treating estrogen-dependent metabolic disorders in women.

Crosstalk between the muscular estrogen receptor α and BDNF/TrkB signaling alleviates metabolic syndrome via 7,8-dihydroxyflavone in female mice

Objective7,8-Dihydroxyflavone (7,8-DHF), a small molecular mimetic of brain-derived neurotrophic factor (BDNF), alleviates high-fat diet-induced obesity in female mice in a sex-specific manner by activating muscular tropomyosin-related kinase B (TrkB). However, the underlying molecular mechanism for this sex difference is unknown. Moreover, muscular estrogen receptor α (ERα) plays a critical role in metabolic diseases. Impaired ERα action is often accompanied by metabolic syndrome (MetS) in postmenopausal women. This study investigated whether muscular ERα is involved in the metabolic effects of 7,8-DHF. MethodsFor the in vivo studies, 72 female C57BL/6J mice were given a low-fat diet or high-fat diet, and both received daily intragastric administration of vehicle or 7,8-DHF for 24 weeks. The hypothalamic-pituitary-ovarian (HPO) axis function was assessed by investigating typical sex-related serum hormones and the ovarian reserve. Indicators of menopausal MetS, including lipid metabolism, insulin sensitivity, bone density, and serum inflammatory cytokines, were also evaluated. The expression levels of ERα and other relevant signaling molecules were also examined. In vitro, the molecular mechanism involved in the interplay of ERα and TrkB receptors was verified in differentiated C2C12 myotubes using several inhibitors and a lentivirus short hairpin RNA-knockdown strategy. ResultsLong-term oral administration of 7,8-DHF acted as a protective factor for the female HPO axis function, protecting against ovarian failure, earlier menopause, and sex hormone disorders, which was paralleled by the alleviation of MetS coupled with the production of ERα-rich, TrkB-activated, and uncoupling protein 1 (UCP1) high thermogenic skeletal muscle tissues. 7,8-DHF-stimulated transactivation of ERα at serine 118 (S118) and tyrosine 537 (Y537), which was crucial to activate the BDNF/TrkB signaling cascades. In turn, activation of BDNF/TrkB signaling was also required for the ligand-independent activation of ERα, especially at the Y537 phosphorylation site. In addition, Src family kinases played a core role in the interplay of ERα and TrkB, synergistically activating the signaling pathways related to energy metabolism. ConclusionsThese findings revealed a novel role of 7,8-DHF in protecting the function of the female HPO axis and activating tissue-specific ERα, which improves our understanding of this sex difference in 7,8-DHF-mediated maintenance of metabolic homeostasis and provides new therapeutic strategies for managing MetS in women.

Estradiol regulates daily rhythms underlying diet-induced obesity in female mice.

The circadian system is a critical regulator of metabolism and obesity in males, but its role in regulating obesity in females is poorly understood. Because there are sex differences in the development of obesity and susceptibility to obesity-related disorders, we sought to determine the role of estrogens in regulating the circadian mechanisms underlying diet-induced obesity. When fed high-fat diet, C57BL/6J male mice gain weight, whereas females are resistant to diet-induced obesity. Here, we demonstrate that estradiol regulates circadian rhythms in females to confer resistance to diet-induced obesity. We found that ovariectomized females with undetectable circulating estrogens became obese and had disrupted daily rhythms of eating behavior and locomotor activity when fed a high-fat diet. The phase of the liver molecular circadian rhythm was also altered by high-fat diet feeding in ovariectomized mice. Estradiol replacement in ovariectomized females a fed high-fat diet rescued these behavioral and tissue rhythms. Additionally, restoring the daily rhythm of eating behavior in ovariectomized females with time-restricted feeding inhibited diet-induced obesity and insulin resistance. Together, these data suggest that the circadian system is a target for treating obesity and its comorbidities in women after menopause, when circulating levels of estrogens are too low to protect their circadian rhythms.

SUN-092 Distinct Changes in Gut Microbiota Are Associated with Estradiol-Mediated Protection from Diet-Induced Obesity in Female Mice

Due to an aging-associated decrease in ovarian estrogens, postmenopausal women tend to gain weight, which predisposes them to developing cardiovascular disease, type 2 diabetes, chronic inflammation, and cancer. Estradiol replacement has been shown to protect postmenopausal women and ovariectomized rodents from obesity and metabolic disorders, but the underlying mechanisms are not fully understood. In addition to estrogens, gut microbiota are also known to regulate energy homeostasis. In this study, we investigated the effects of estrogens on gut microbiota and energy metabolism in female mice on standard diet (SD) or high-fat diet (HFD). Ovariectomized adult C57BL6/J mice received implants containing estradiol (E2) or vehicle (Veh) (n=6/group). Mice were fed SD for the first two weeks and then switched to HFD for the remaining four weeks of the study. To investigate the effects of E2 and diet on gut microbiota, fresh fecal samples were collected at various times during SD and HFD for 16S rRNA gene sequencing. Using metabolic cages, the effects of E2 and HFD on energy balance were assessed longitudinally by measuring food intake, energy expenditure, and physical activity. In addition, plasma glucose, insulin, leptin, resistin and cytokines were measured during SD and HFD. Insulin sensitivity and glucose metabolism were assessed during a 2-hr hyperinsulinemic-euglycemic clamp in awake mice at the end of HFD. Our results indicate that chronic E2 treatment protected the ovariectomized mice from HFD-induced obesity, mostly due to increases in energy expenditure and physical activity. These effects were associated with altered bacterial communities; E2 increased the relative abundance of the mucin-producing microbes Akkermansia spp. (phylum Verrucomicrobia) that are responsible for the integrity of the gut epithelial barrier. Veh mice had increased the relative abundances of Erysipleotrichaceae and Streptococcaceae (family) and their lower taxa. HFD profoundly altered microbial diversity by reducing species richness, increasing evenness and altering relative abundances of multiple taxa. HFD was associated with increased Bacteriodes (phylum Bacteriodetes) and Clostridia (phylum Firmicutes), which are responsible for HFD-induced weight gain in humans. The relative abundance of Erysipleotrichi was positively correlated with HFD, but negatively correlated with E2 treatment, suggesting a potential causal relationship between this taxon and obesity. E2-treated mice were more insulin-sensitive with marked increases in whole body glucose turnover and glycogen synthesis after HFD. Taken together, these results suggest that changes in gut microbiota contribute to E2-mediated protection against diet-induced obesity and metabolic dysregulation. These findings may provide important insights for potential microbial targets for the treatment of metabolic disorders in women.

Neonatal GLP1R activation limits adult adiposity by durably altering hypothalamic architecture

ObjectiveAdult obesity risk is influenced by alterations to fetal and neonatal environments. Modifying neonatal gut or neurohormone signaling pathways can have negative metabolic consequences in adulthood. Here we characterize the effect of neonatal activation of glucagon like peptide-1 (GLP-1) receptor (GLP1R) signaling on adult adiposity and metabolism. MethodsWild type C57BL/6 mice were injected with 1 nmol/kg Exendin-4 (Ex-4), a GLP1R agonist, for 6 consecutive days after birth. Growth, body composition, serum analysis, energy expenditure, food intake, and brain and fat pad histology and gene expression were assessed at multiple time points through 42 weeks. Similar analyses were conducted in a Glp1r conditional allele crossed with a Sim1Cre deleter strain to produce Sim1Cre;Glp1rloxP/loxP mice and control littermates. ResultsNeonatal administration of Ex-4 reduced adult body weight and fat mass, increased energy expenditure, and conferred protection from diet-induced obesity in female mice. This was associated with induction of brown adipose genes and increased noradrenergic fiber density in parametrial white adipose tissue (WAT). We further observed durable alterations in orexigenic and anorexigenic projections to the paraventricular hypothalamic nucleus (PVH). Genetic deletion of Glp1r in the PVH by Sim1-Cre abrogated the impact of neonatal Ex-4 on adult body weight, WAT browning, and hypothalamic architecture. ConclusionThese observations suggest that the acute activation of GLP1R in neonates durably alters hypothalamic architecture to limit adult weight gain and adiposity, identifying GLP1R as a therapeutic target for obesity prevention.

Activation of Muscular TrkB by its Small Molecular Agonist 7,8-Dihydroxyflavone Sex-Dependently Regulates Energy Metabolism in Diet-Induced Obese Mice

Chronic activation of brain-derived neurotrophic factor (BDNF) receptor TrkB is a potential method to prevent development of obesity, but the short half-life and nonbioavailable nature of BDNF hampers validation of the hypothesis. We report here that activation of muscular TrkB by the BDNF mimetic, 7,8-dihydroxyflavone (7,8-DHF), is sufficient to protect the development of diet-induced obesity in female mice. Using in vitro and in vivo models, we found that 7,8-DHF treatment enhanced the expression of uncoupling protein 1 (UCP1) and AMP-activated protein kinase (AMPK) activity in skeletal muscle, which resulted in increased systemic energy expenditure, reduced adiposity, and improved insulin sensitivity in female mice fed a high-fat diet. This antiobesity activity of 7,8-DHF is muscular TrkB-dependent as 7,8-DHF cannot mitigate diet-induced obesity in female muscle-specific TrkB knockout mice. Hence, our data reveal that chronic activation of muscular TrkB is useful in alleviating obesity and its complications.

SIRT1 activator (SRT1720) improves the follicle reserve and prolongs the ovarian lifespan of diet-induced obesity in female mice via activating SIRT1 and suppressing mTOR signaling.

BackgroundThe prevalence of obesity is increasing worldwide and significantly affects fertility and reproduction in both men and women. Our recent study has shown that excess body fat accelerates ovarian follicle development and follicle loss in rats. The aim of the present study is to explore the effect of SIRT1 activator SRT1720 on the reserve of ovarian follicle pool and ovarian lifespan of obese mice and the underlying mechanism associated with SIRT1 and mTOR signaling.MethodsAdult female Kunming mice (n = 36) were randomly divided into three groups: the normal control (NC) group (n = 8), the caloric restriction (CR) group (fed 70% food of the NC group, n = 8) and the high-fat diet (HF) group (fed a rodent chow containing 20% fat, n = 20). After 4 months, the HF mice were further randomly divided into three groups: the control high-fat diet (CHF, n = 8) group (treated every day with an intraperitoneal injection of vehicle), the SRT1720 (SRT, n = 6) group (treated every other day with an intraperitoneal injection of SRT1720 (50 mg/kg)), the SRT1720 and nicotinamide (NAM, n = 6) group (treated every other day with an intraperitoneal injection of SRT1720 (50 mg/kg) and every day with an intraperitoneal injection of nicotinamide (100 mg/kg)). After 6 weeks of treatment, ovaries were harvested for histological and Western blotting analyses.ResultsThe body weight, ovary weight and visceral fat in the SRT group were significantly lower than those in the CHF group at the end of treatment. Histological analysis showed that the SRT mice had significantly greater number and percentage of primordial follicles, but lower number and percentage of corpora lutea and atretic follicles than the CHF mice and NAM mice. Western blot analysis demonstrated that the levels of SIRT1, SIRT6, FOXO3a and NRF-1 protein expression significantly increased in the ovaries of SRT mice, whereas those of mTORC1, p-mTOR, p-p70S6K, NFκB and p53 decreased compared to the CHF and NAM mice.ConclusionsOur study suggests that SRT1720 may improve the follicle pool reserve in HF diet-induced obese female mice via activating SIRT1 signaling and suppressing mTOR signaling, thus extending the ovarian lifespan.

Ventromedial hypothalamus-specific Ptpn1 deletion exacerbates diet-induced obesity in female mice.

Protein-tyrosine phosphatase 1B (PTP1B) regulates food intake (FI) and energy expenditure (EE) by inhibiting leptin signaling in the hypothalamus. In peripheral tissues, PTP1B regulates insulin signaling, but its effects on CNS insulin action are largely unknown. Mice harboring a whole-brain deletion of the gene encoding PTP1B (Ptpn1) are lean, leptin-hypersensitive, and resistant to high fat diet-induced (HFD-induced) obesity. Arcuate proopiomelanocortin (POMC) neuron-specific deletion of Ptpn1 causes a similar, but much milder, phenotype, suggesting that PTP1B also acts in other neurons to regulate metabolism. Steroidogenic factor-1-expressing (SF-1-expressing) neurons in the ventromedial hypothalamus (VMH) play an important role in regulating body weight, FI, and EE. Surprisingly, Ptpn1 deletion in SF-1 neurons caused an age-dependent increase in adiposity in HFD-fed female mice. Although leptin sensitivity was increased and FI was reduced in these mice, they had impaired sympathetic output and decreased EE. Immunohistochemical analysis showed enhanced leptin and insulin signaling in VMH neurons from mice lacking PTP1B in SF-1 neurons. Thus, in the VMH, leptin negatively regulates FI, promoting weight loss, whereas insulin suppresses EE, leading to weight gain. Our results establish a novel role for PTP1B in regulating insulin action in the VMH and suggest that increased insulin responsiveness in SF-1 neurons can overcome leptin hypersensitivity and enhance adiposity.

Abstract 75: Chronic Treatment With At2 Receptor Agonist Rescues High Fat Diet-induced Obesity in Female Mice.

Obesity in itself is a disease condition and a major risk factor in the development of hypertension, dyslipidemia, and hyperglycemia. Therefore, successful strategies for improving obesity and related metabolic risk factors are needed. Role of renin-angiotensin system (RAS) has been implicated in obesity and metabolic dysfunction. Recently, we have shown that AT2R knock-out in female mice caused a greater body weight gain and hyperinsulimia in response to high fat diet (HFD). In the present study, we hypothesize that AT2R activation rescues diet-induced obesity in females. To test this hypothesis, we injected AT2R non-peptide agonist C21 (0.3mg/kg/day i.p) in C57BL6 female mice on HFD for 12 weeks. C21-treatment did not affect the HFD calorie intake (HFD: 937±18 Kcal; C21HFD: 886±37 Kcal) but caused lesser body weight gain compared to control (HFD: 4.4± 0.4g; C21HFD: 3.06± 0.4g). Similar to the body weight gain pattern, gonadal fat weight and adipocyte size were decreased significantly in C21-treated mice on HFD compared to control HFD group (HFD: 4.4± 0.4 g; C21 HFD: 3.06± 0.4g) and (HFD: 6404±161.6μm2 ; C21HFD: 3874±103.2μm2 ) respectively. Moreover, the C21-treated females on HFD had lower levels of plasma insulin, improved glucose tolerance, and decreased plasma free fatty acids and hepatic triglycerides. Western blot revealed that phospho-Ser79-acetyl CoA carboxylase (p-Ser79-ACC-1) was reduced, an index of increased lipogenic activity and decreased β-oxidation process, in both adipose (Adi) and hepatic (Hep) tissues of HFD fed groups (Adi: 86% and Hep: 73% of 100% controls); C21-treatment revered the decrease in p-ser79-ACC-1 in Adi (104% of control) and caused an increase in Hep (122% of control) respectively. The HFD feeding lowered the estradiol level (ND: 38.8±2.6 vs HFD:11.3±1.2ng), which was modestly reversed by C21 treatment (C21HFD:17.4± 1.5ng) in HFD mice. Our results strongly suggest that stimulation of AT2R in female mice positively contribute, predominantly independent of estrogen, to rescue body weight gain and adipocyte size increase in response to HFD. We propose reduced lipogenesis and enhanced lipid β-oxidation as potential mechanisms linked to AT2R action in reducing obesity and its related metabolic disorders in females.

Diet-Induced Obesity in Female Mice Leads to Offspring Hyperphagia, Adiposity, Hypertension, and Insulin Resistance

Maternal obesity is increasingly prevalent and may affect the long-term health of the child. We investigated the effects of maternal diet-induced obesity in mice on offspring metabolic and cardiovascular function. Female C57BL/6J mice were fed either a standard chow (3% fat, 7% sugar) or a palatable obesogenic diet (16% fat, 33% sugar) for 6 weeks before mating and throughout pregnancy and lactation. Offspring of control (OC) and obese dams (OO) were weaned onto standard chow and studied at 3 and 6 months of age. OO were hyperphagic from 4 to 6 weeks of age compared with OC and at 3 months locomotor activity was reduced and adiposity increased (abdominal fat pad mass; P<0.01). OO were heavier than OC at 6 months (body weight, P<0.05). OO abdominal obesity was associated with adipocyte hypertrophy and altered mRNA expression of beta-adrenoceptor 2 and 3, 11 beta HSD-1, and PPAR-gamma 2. OO showed resistance artery endothelial dysfunction at 3 months, and were hypertensive, as assessed by radiotelemetry (nighttime systolic blood pressure at 6 months [mm Hg] mean+/-SEM, male OO, 134+/-1 versus OC, 124+/-2, n=8, P<0.05; female OO, 137+/-2 versus OC, 122+/-4, n=8, P<0.01). OO skeletal muscle mass (tibialis anterior) was significantly reduced (P<0.01) OO fasting insulin was raised at 3 months and by 6 months fasting plasma glucose was elevated. Exposure to the influences of maternal obesity in the developing mouse led to adult offspring adiposity and cardiovascular and metabolic dysfunction. Developmentally programmed hyperphagia, physical inactivity, and altered adipocyte metabolism may play a mechanistic role.

Resistance to diet-induced obesity in female mice lacking the pancreatic phospholipase A2 gene

Resistance to diet-induced obesity in female mice lacking the pancreatic phospholipase A2 gene