Loss of Endothelial FTO Antagonizes Obesity-Induced Metabolic and Vascular Dysfunction.

RATIONALE: Increasing prevalence of obesity and its associated risk with cardiovascular diseases demands a better understanding of the contribution of different cell types within this complex disease for developing new treatment options. Previous studies could prove a fundamental role of FTO (fat mass and obesity-associated protein) within obesity; however, its functional role within different cell types is less understood. OBJECTIVES: We identify endothelial FTO as a previously unknown central regulator of both obesity-induced metabolic and vascular alterations. METHODS AND RESULTS: We generated endothelial Fto-deficient mice and analyzed the impact of obesity on those mice. While the loss of endothelial FTO did not influence the development of obesity and dyslipidemia, it protected mice from high-fat diet-induced glucose intolerance and insulin resistance by increasing AKT (protein kinase B) phosphorylation in endothelial cells and skeletal muscle. Furthermore, loss of endothelial FTO prevented the development of obesity-induced hypertension by preserving myogenic tone in resistance arteries. In Fto-deficient arteries, microarray analysis identified upregulation of L-Pgds with significant increases in prostaglandin D2 levels. Blockade of prostaglandin D2 synthesis inhibited the myogenic tone protection in resistance arteries of endothelial Fto-deficient mice on high-fat diet; conversely, direct addition of prostaglandin D2 rescued myogenic tone in high-fat diet-fed control mice. Myogenic tone was increased in obese human arteries with FTO inhibitors or prostaglandin D2 application. CONCLUSIONS: These data identify endothelial FTO as a previously unknown regulator in the development of obesity-induced metabolic and vascular changes, which is independent of its known function in regulation of obesity.

Coronavirus disease 2019 infection and placental histopathology in women delivering at term.

BACKGROUND: There is a paucity of data describing the effects of coronavirus disease 2019 on placental pathology, especially in asymptomatic patients. Although the pathophysiology of coronavirus disease 2019 is not completely understood, there is emerging evidence that it causes a severe systemic inflammatory response and results in a hypercoagulable state with widespread microthrombi. We hypothesized that it is plausible that a similar disease process may occur in the fetal-maternal unit. OBJECTIVE: This study aimed to determine whether coronavirus disease 2019 in term patients admitted to labor and delivery, including women without coronavirus disease 2019 symptomatology, is associated with increased placental injury compared with a cohort of coronavirus disease 2019-negative controls. STUDY DESIGN: This was a retrospective cohort study performed at NYU Winthrop Hospital between March 31, 2020, and June 17, 2020. During the study period, all women admitted to labor and delivery were routinely tested for severe acute respiratory syndrome coronavirus 2 regardless of symptomatology. The placental histopathologic findings of patients with coronavirus disease 2019 (n=77) who delivered a singleton gestation at term were compared with a control group of term patients without coronavirus disease 2019 (n=56). Controls were excluded if they had obstetrical or medical complications including fetal growth restriction, oligohydramnios, hypertension, diabetes, coagulopathy, or thrombophilia. Multivariable logistic regression models were performed for variables that were significant (P<.05) in univariable analyses. A subgroup analysis was also performed comparing asymptomatic coronavirus disease 2019 cases with negative controls. RESULTS: In univariable analyses, coronavirus disease 2019 cases were more likely to have evidence of fetal vascular malperfusion, that is, presence of avascular villi and mural fibrin deposition (32.5% [25/77] vs 3.6% [2/56], P<.0001) and villitis of unknown etiology (20.8% [16/77] vs 7.1% [4/56], P=.030). These findings persisted in a subgroup analysis of asymptomatic coronavirus disease 2019 cases compared with coronavirus disease 2019-negative controls. In a multivariable model adjusting for maternal age, race and ethnicity, mode of delivery, preeclampsia, fetal growth restriction, and oligohydramnios, the frequency of fetal vascular malperfusion abnormalities remained significantly higher in the coronavirus disease 2019 group (odds ratio, 12.63; 95% confidence interval, 2.40-66.40). Although the frequency of villitis of unknown etiology was more than double in coronavirus disease 2019 cases compared with controls, this did not reach statistical significance in a similar multivariable model (odds ratio, 2.11; 95% confidence interval, 0.50-8.97). All neonates of mothers with coronavirus disease 2019 tested negative for severe acute respiratory syndrome coronavirus 2 by polymerase chain reaction. CONCLUSION: Despite the fact that all neonates born to mothers with coronavirus disease 2019 were negative for severe acute respiratory syndrome coronavirus 2 by polymerase chain reaction, we found that coronavirus disease 2019 in term patients admitted to labor and delivery is associated with increased rates of placental histopathologic abnormalities, particularly fetal vascular malperfusion and villitis of unknown etiology. These findings seem to occur even among asymptomatic term patients.

Lipocalin-type Prostaglandin D2 Synthase appears to function as a Novel Adipokine Preventing Adipose Dysfunction in response to a High Fat Diet.

Adipose dysfunction is the primary defect in obesity that contributes to the development of dyslipidemia, insulin resistance, cardiovascular diseases, type 2 diabetes, non-alcoholic fatty liver disease (NAFLD) and some cancers. Previously, we demonstrated the development of NAFLD in lipocalin-type prostaglandin D2 synthase (L-PGDS) knockout mice regardless of diet. In the present study, we examined the role of L-PGDS in adipose in response to a high fat diet. We observed decreased expression of L-PGDS in adipose tissue and concomitant lower plasma levels in a dietary model of obesity as well as in insulin resistant 3T3-L1 adipocytes. We show reduced adiponectin expression and phosphorylation of AMPK in white adipose tissue of L-PGDS KO mice after 14 weeks on a high fat diet as compared to control C57BL/6 mice. We also observe an increased fat content in L-PGDS KO mice as demonstrated by adipocyte hypertrophy and increased expression of lipogenenic genes. We confirmed our in vivo findings in in vitro 3T3-L1 adipocytes, using an enzymatic inhibitor of L-PGDS (AT56). Rosiglitazone treatment drastically increased L-PGDS expression in insulin resistant 3T3-L1 adipocytes and increased adiponectin expression and AMPK phosphorylation in AT56 treated 3T3-L1 adipocytes. We conclude that the absence of L-PGDS has a deleterious effect on adipose tissue functioning, which further reduces insulin sensitivity in adipose tissue. Consequently, we propose L-PGDS appears to function as a potential member of the adipokine secretome involved in the regulation of the obesity-associated metabolic syndrome.

Lipocalin-type prostaglandin D2 synthase deletion induces dyslipidemia and non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is an emerging risk factor for type 2 diabetes mellitus, cardiovascular disease, and all-cause mortality. Previously, we demonstrated that lipocalin-type prostaglandin D2 synthase (L-PGDS) knockout mice show increased glucose intolerance and accelerated atherosclerosis. In the present study, we investigated the role of L-PGDS in mediating NAFLD utilizing L-PGDS knockout (KO) and control C57BL/6 mice fed either low fat (LFD) or high fat diet (HFD) for 14 weeks. Our present study demonstrates that L-PGDS KO mice remain slightly lighter in weight compared to control mice, yet develop NAFLD faster and eventually progress to the more severe non-alcoholic steatohepatitis (NASH). We found increased lipid accumulation in the liver of KO mice over time on both diets, as compared to control mice. The L-PGDS KO mice showed elevated fasting glucose and insulin levels and developed insulin resistance on both LFD and HFD. Lipogenesis marker proteins such as SREBP-1c and LXRα were increased in L-PGDS KO mice after 14 weeks on both diets, when compared to control mice. We replicated our in vivo findings in vitro using HepG2 cells treated with a combination of free fatty acids (oleic and palmitic acid) and exposure to a L-PGDS inhibitor and prostaglandin D2 receptor (DP1) antagonists. We conclude that the absence or inhibition of L-PGDS results in dyslipidemia, altered expression of lipogenesis genes and the acceleration of NAFLD to NASH, independent of diet and obesity. We propose L-PGDS KO mice as a useful model to explore the pathogenesis of NAFLD and NASH, and L-PGDS as a potential therapeutic target for treatment.

BMAL1 controls glucose uptake through paired-homeodomain transcription factor 4 in differentiated Caco-2 cells.

The transcription factor aryl hydrocarbon receptor nuclear translocator-like protein-1 (BMAL1) is an essential regulator of the circadian clock, which controls the 24-h cycle of physiological processes such as nutrient absorption. To examine the role of BMAL1 in small intestinal glucose absorption, we used differentiated human colon adenocarcinoma cells (Caco-2 cells). Here, we show that BMAL1 regulates glucose uptake in differentiated Caco-2 cells and that this process is dependent on the glucose transporter sodium-glucose cotransporter 1 (SGLT1). Mechanistic studies show that BMAL1 regulates glucose uptake by controlling the transcription of SGLT1 involving paired-homeodomain transcription factor 4 (PAX4), a transcriptional repressor. This is supported by the observation that clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated endonuclease Cas9 (Cas9) knockdown of PAX4 increases SGLT1 and glucose uptake. Chromatin immunoprecipitation (ChIP) and ChIP-quantitative PCR assays show that the knockdown or overexpression of BMAL1 decreases or increases the binding of PAX4 to the hepatocyte nuclear factor 1-α binding site of the SGLT1 promoter, respectively. These findings identify BMAL1 as a critical mediator of small intestine carbohydrate absorption and SGLT1.

Down-regulation of placental neuropilin-1 in fetal growth restriction.

BACKGROUND: Fetal growth restriction (FGR) is associated with adverse outcomes extending from fetal to adult life, and thus, constitutes a major health care challenge. Fetuses with progressive growth restriction show increasing impedance in the umbilical artery flow, which may become absent during end-diastole. Absent end-diastolic flow (AEDF) is associated with adverse perinatal outcomes including stillbirths and perinatal asphyxia. Placentas from such pregnancies demonstrate deficient fetoplacental vascular branching. Current evidence, moreover, indicates an antiangiogenic state in maternal circulation in several pregnancy complications including preeclampsia, small-for-gestational-age births, fetal death, and preterm labor. The angiogenic mediators in maternal circulation are predominantly of placental origin. Information, however, on the role of specific proangiogenic and antiangiogenic mechanisms operating at the placental level remains limited. Elucidation of these placenta-specific angiogenic mechanisms will not only extend our understanding of the causal pathway for restricted fetal growth but may also lead to the development of biomarkers that may allow early recognition of FGR. OBJECTIVE: We sought to test the hypothesis that fetoplacental angiogenic gene expression is altered in pregnancies complicated with FGR and umbilical artery Doppler AEDF. STUDY DESIGN: Placental samples were collected from FGR pregnancies complicated with umbilical artery Doppler AEDF (study group, n = 7), and from uncomplicated pregnancies (control group, n = 7), all delivered by cesarean during the last trimester of pregnancy. Angiogenic oligonucleotide microarray analysis was performed and was corroborated by quantitative real-time polymerase chain reaction, Western blot analysis, and immunohistochemistry. The Student t test with Bonferroni correction was used with P < .05 considered statistically significant. Independent groups t test was used to analyze the immunostain intensity scores with a P < .05 considered statistically significant. RESULTS: Our microarray results showed that among several differentially expressed angiogenic genes in the growth-restricted group, only the down-regulation of neuropilin (NRP)-1 was most significant (P < .0007). Quantitative real-time polymerase chain reaction confirmed a significantly lower NRP-1 gene expression in the FGR group than in the control group (mean ± SD (ˆ)cycle threshold: 0.624 ± 0.55 and 1.325 ± 0.84, respectively, P = .04). Western blot validated significantly lower NRP-1 protein expression in the FGR group than in the control group (mean ± SD NRP-1/ß-actin ratio: 0.13 ± 0.04 and 0.34 ± 0.05, respectively, P < .001). Finally, immunohistochemistry of placental villi further corroborated a significantly decreased expression of NRP-1 in the FGR group (P = .006). CONCLUSION: The study demonstrated significant down-regulation of placental NRP-1 expression in FGR pregnancies complicated with AEDF in umbilical artery. As NRP-1 is known to promote sprouting angiogenesis, its down-regulation may be involved in the deficient vascular branching observed in FGR placentas suggesting the presence of an antiangiogenic state. Further studies may elucidate such a causal role and may lead to the development of novel diagnostic and therapeutic tools.

Role of Lipocalin-type prostaglandin D2 synthase (L-PGDS) and its metabolite, prostaglandin D2, in preterm birth.

The objective of the study was to investigate the role of prostaglandin D2 during pregnancy and its mediator Lipocalin-type prostaglandin D2 synthase (L-PGDS) as a predictor of preterm birth (PTB). Transgenic L-PGDS (+/+), L-PGDS (-/-) and C57BL/6 control pregnant mice models were used to determine the effect of DP1 and DP2 receptor antagonists in lipopolysaccharide (LPS)-induced PTB mice. In addition, L-PGDS levels were measured in the cervicovaginal secretions (CVS) of 370 pregnant women using ELISA and further processed for isoform detection using 2-D gel electrophoresis. Our results found that C57BL/6 control mice (n = 26), transgenic L-PGDS (+/+) (n = 26), demonstrated an 89% and 100% preterm birth in LPS (intraperitoneal injection, 20mg/kg) induced mice model respectively. Interestingly, the incidence of PTB was significantly reduced to 40% in L-PGDS (-/-) knockout mice (n = 26). DP1 and DP2 receptor antagonists (0.264 µg/day, dose of 0.1 µg/µl with the flow of 0.11 µl/h for 28 day using Alzet pumps) were used to investigate the effect in LPS-induced PTB in C57BL/6 mice and found 3.3-fold increase in viable pups after LPS-induction. In addition, L-PGDS levels were measured in CVS samples and found that PTB women (n = 296) had two-fold higher levels compared to full term births (n = 74) and established a significant inverse correlation between levels of L-PGDS and days to expected delivery by using 370 preterm birth CVS samples. Elevated L-PGDS levels in the CVS of women may be considered as a potential biomarker for PTB in future. Secondly, the use of DP1 and DP2 receptor antagonists may represent novel tocolytic agents for the treatment of PTB.

Targeting steroid receptor coactivator 1 with antisense oligonucleotides increases insulin-stimulated skeletal muscle glucose uptake in chow-fed and high-fat-fed male rats.

The steroid receptor coactivator 1 (SRC1) regulates key metabolic pathways, including glucose homeostasis. SRC1(-/-) mice have decreased hepatic expression of gluconeogenic enzymes and a reduction in the rate of endogenous glucose production (EGP). We sought to determine whether decreasing hepatic and adipose SRC1 expression in normal adult rats would alter glucose homeostasis and insulin action. Regular chow-fed and high-fat-fed male Sprage-Dawley rats were treated with an antisense oligonucleotide (ASO) against SRC1 or a control ASO for 4 wk, followed by metabolic assessments. SRC1 ASO did not alter basal EGP or expression of gluconeogenic enzymes. Instead, SRC1 ASO increased insulin-stimulated whole body glucose disposal by ~30%, which was attributable largely to an increase in insulin-stimulated muscle glucose uptake. This was associated with an approximately sevenfold increase in adipose expression of lipocalin-type prostaglandin D2 synthase, a previously reported regulator of insulin sensitivity, and an approximately 70% increase in plasma PGD2 concentration. Muscle insulin signaling, AMPK activation, and tissue perfusion were unchanged. Although GLUT4 content was unchanged, SRC1 ASO increased the cleavage of tether-containing UBX domain for GLUT4, a regulator of GLUT4 translocation. These studies point to a novel role of adipose SRC1 as a regulator of insulin-stimulated muscle glucose uptake.

The Effect of Diet Composition on the Post-operative Outcomes of Roux-en-Y Gastric Bypass in Mice.

PURPOSE: Roux-en-Y gastric bypass (RYGB) leads to the improvement of many obesity-associated conditions. The degree to which post-operative macronutrient composition contributes to metabolic improvement after RYGB is understudied. METHODS: A mouse model of RYGB was used to examine the effects of diet on the post-operative outcomes of RYGB. Obese mice underwent either Sham or RYGB surgery and were administered either chow or HFD and then monitored for an additional 8 weeks. RESULTS: After RYGB, reductions to body weight, fat mass, and lean mass were similar regardless of diet. RYGB and HFD were independently detrimental to bone mineral density and plasma vitamin D levels. Independent of surgery, HFD accelerated hematopoietic stem and progenitor cell proliferation and differentiation and exhibited greater myeloid lineage commitment. Independent of diet, systemic iron deficiency was present after RYGB. In both Sham and RYGB groups, HFD increased energy expenditure. RYGB increased fecal energy loss, and HFD after RYGB increased fecal lipid content. RYGB lowered fasting glucose and liver glycogen levels but HFD had an opposing effect. Indices of insulin sensitivity improved independent of diet. HFD impaired improvements to dyslipidemia, NAFLD, and fibrosis. CONCLUSION: Post-operative diet plays a significant role in determining the degree to which RYGB reverses obesity-induced metabolic abnormalities such as hyperglycemia, dyslipidemia, and NAFLD. Diet composition may be targeted in order to assist in the treatment of post-RYGB bone mineral density loss and vitamin D deficiency as well as to reverse myeloid lineage commitment. HFD after RYGB continues to pose a significant multidimensional health risk.

ACTH promotes chondrogenic nodule formation and induces transient elevations in intracellular calcium in rat bone marrow cell cultures via MC2-R signaling.

Adrenocorticotropic hormone (ACTH) is among several melanocortin peptide hormones that are derived from proopiomelanocortin (POMC). ACTH has been found to enhance osteogenesis and chondrogenesis. We show that, in the presence of dexamethasone, ACTH dose-dependently increases chondrogenic nodule formation in bone marrow stromal cells (BMSC) from the Wistar Kyoto (WKY) rat. The nodules consist in condensed cells highly expressing alkaline phosphatase, Sox9 and type II collagen transcripts and a proteoglycan-rich matrix. Immunoblot analysis of crude membrane fractions has shown that these cells express three melanocortin receptors (MC-R), namely MC2-R, MC3-R and MC5-R and the melanocortin 2-receptor accessory protein (MRAP). To determine which of these receptors mediate ACTH-induced effects, we have used MC-R-specific peptides and the known agonist profiles of the receptors. Neither α-MSH, a strong agonist of MC5-R, nor γ2-MSH, a strong agonist of MC3-R, duplicates ACTH effects in rat BMSC. In addition, calcium flux has been examined as a mechanism for ACTH action at the MC2-R. Consistent with MC2-R and MRAP expression patterns in the BMSC cultures, ACTH-induced transient increases in intracellular calcium are increased with dexamethasone treatment. Neither α-MSH nor γ2-MSH affects calcium flux. Dexamethasone increases MC2-R and MRAP expression and POMC peptide expression and cleavage increasing the production of the lipolytic ß-lipotropic hormone product. Therefore, the effects of ACTH in rat BMSC enriched for mesenchymal progenitors are consistent with an MC2-R signaling mechanism, with dexamethasone being capable of regulating components of the melanocortin system in these cells.

Impaired insulin-stimulated myosin phosphatase Rho-interacting protein signaling in diabetic Goto-Kakizaki vascular smooth muscle cells.

Insulin resistance associated with Type 2 diabetes contributes to impaired vasorelaxation and therefore contributes to the enhanced incidence of hypertension observed in diabetes. In this study, we examined the role of insulin on the association of the myosin-binding subunit of myosin phosphatase (MYPT1) to myosin phosphatase Rho-interacting protein (MRIP), a relatively novel member of the myosin phosphatase complex that directly binds RhoA in vascular smooth muscle cells (VSMCs). Through a series of molecular and cellular studies, we investigated whether insulin stimulates the binding of MRIP to MYPT1 and compared the results generated from VSMCs isolated from both Wistar-Kyoto (WKY) control and Goto-Kakizaki (GK) diabetic rats. We demonstrate for the first time that insulin stimulates the binding of MRIP to MYPT1 in a dose- and time-dependent manner, as determined by immunoprecipitation, implying a regulatory role for MRIP in insulin-induced vasodilation signaling via MYPT1 interaction. VSMCs from GK model of Type 2 diabetes had impaired insulin-induced MRIP/MYPT1 binding as well as reduced MRIP expression. Adenovirus-mediated overexpression of MRIP in GK VSMCs led to significantly improved insulin-stimulated MRIP/MYPT1 binding. Finally, insulin-stimulated MRIP translocation out of stress fibers, which was observed in control VSMCs, was impaired in GK VSMCs. We believe the impaired expression of MRIP, and therefore decreased insulin-stimulated MRIP/MYPT1 association, in the GK diabetic model may contribute to the impaired insulin-mediated vasodilation observed in the diabetic vasculature and provides a novel therapeutic strategy for the treatment of Type 2 diabetes.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression.

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

Reversal of NAFLD After VSG Is Independent of Weight-Loss but RYGB Offers More Efficacy When Maintained on a High-Fat Diet.

PURPOSE: Bariatric surgery is emerging as an effective treatment for obesity and the metabolic syndrome. Recently, we demonstrated that Roux-en-Y gastric bypass (RYGB), but not vertical sleeve gastrectomy (VSG), resulted in improvements to white adipose physiology and enhanced brown adipose functioning. Since beneficial alterations to liver health are also expected after bariatric surgery, comparing the post-operative effects of RYGB and VSG on liver physiology is essential to their application in the treatment of non-alcoholic fatty liver disease (NAFLD). MATERIALS AND METHODS: The effects of RYGB and VSG on liver physiology were compared using diet induced mouse model of obesity. High-fat diet (HFD) was administered for 12 weeks after surgery and alterations to liver physiology were assessed. RESULTS: Both RYGB and VSG showed decreased liver weight as well as reductions to hepatic cholesterol and triglyceride levels. There were demonstrable improvements to NAFLD activity score (NAS) and fibrosis stage scoring after both surgeries. In RYGB, these beneficial changes to liver function resulted from the downregulation of pro-fibrotic and upregulation anti-fibrotic genes, as well as increased fatty acid oxidation and bile acid flux. For VSG, though similar alterations were observed, they were less potent. However, VSG did significantly downregulate pro-fibrotic genes and showed increased glycogen content paralleled by decreased glycogenolysis which may have contributed to the resolution of NAFLD. CONCLUSION: RYGB and VSG improve liver physiology and function, but RYGB is more efficacious. Resolutions of NAFLD in RYGB and VSG are achieved through different processes, independent of weight loss.

Microsomal triglyceride transfer protein regulates intracellular lipolysis in adipocytes independent of its lipid transfer activity.

BACKGROUND: The triglyceride (TG) transfer activity of microsomal triglyceride transfer protein (MTP) is essential for lipoprotein assembly in the liver and intestine; however, its function in adipose tissue, which does not assemble lipoproteins, is unknown. Here we have elucidated the function of MTP in adipocytes. APPROACH AND RESULTS: We demonstrated that MTP is present on lipid droplets in human adipocytes. Adipose-specific MTP deficient (A-Mttp-/-) male and female mice fed an obesogenic diet gained less weight than Mttpf/f mice, had less fat mass, smaller adipocytes and were insulin sensitive. A-Mttp-/- mice showed higher energy expenditure than Mttpf/f mice. During a cold challenge, A-Mttp-/- mice maintained higher body temperature by mobilizing more fatty acids. Biochemical studies indicated that MTP deficiency de-repressed adipose triglyceride lipase (ATGL) activity and increased TG lipolysis. Both wild type MTP and mutant MTP deficient in TG transfer activity interacted with and inhibited ATGL activity. Thus, the TG transfer activity of MTP is not required for ATGL inhibition. C-terminally truncated ATGL that retains its lipase activity interacted less efficiently than full-length ATGL. CONCLUSION: Our findings demonstrate that adipose-specific MTP deficiency increases ATGL-mediated TG lipolysis and enhances energy expenditure, thereby resisting diet-induced obesity. We speculate that the regulatory function of MTP involving protein-protein interactions might have evolved before the acquisition of TG transfer activity in vertebrates. Adipose-specific inhibition of MTP-ATGL interactions may ameliorate obesity while avoiding the adverse effects associated with inhibition of the lipid transfer activity of MTP.

RYGB Is More Effective than VSG at Protecting Mice from Prolonged High-Fat Diet Exposure: An Occasion to Roll Up Our Sleeves?

PURPOSE: Understanding the effects of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on adipose tissue physiology is important for the treatment of obesity-related metabolic disorders. By using robust mouse models of bariatric surgery that closely resemble those performed in humans, we can compare the effects of RYGB and VSG on adipose physiology in the absence of post-operative confounds such as diet and lifestyle changes. MATERIALS AND METHODS: RYGB and VSG were compared using a diet-induced mouse model of obesity. High-fat diet (HFD) was administered post-operatively and changes to white and brown adipose tissue were evaluated, along with alterations to weight, glucose homeostasis, dyslipidemia, and insulin sensitivity. RESULTS: After prolonged exposure to high-fat diet post-operatively, RYGB was effective in achieving sustained weight loss, while VSG unexpectedly accelerated weight gain rates. The resolution of obesity-related comorbidities such as glucose and insulin intolerance, dyslipidemia, and insulin sensitivity was improved after RYGB, but not for VSG. In RYGB, there were improvements to the function and health of white adipose tissue, enhanced brown adipose metabolism, and the browning of subcutaneous white adipose tissue, with no comparable changes seen for these factors after VSG. Some markers of systemic inflammation improved after both RYGB and VSG. CONCLUSION: There are significantly different effects between RYGB and VSG when HFD is administered post-operatively and robust mouse models of bariatric surgery are used. RYGB resulted in lasting physiological and metabolic changes but VSG showed little difference from that of its sham-operated, DIO counterpart.

Impaired insulin-mediated vasorelaxation in diabetic Goto-Kakizaki rats is caused by impaired Akt phosphorylation.

Insulin resistance associated with Type 2 diabetes contributes to impaired vasorelaxation. Previously, we showed the phosphorylation of myosin-bound phosphatase substrate MYPT1, a marker of the vascular smooth muscle cell (VSMC) contraction, was negatively regulated by Akt (protein kinase B) phosphorylation in response to insulin stimulation. In this study we examined the role of Akt phosphorylation on impaired insulin-induced vasodilation in the Goto-Kakizaki (GK) rat model of Type 2 diabetes. GK VSMCs had impaired basal and insulin-induced Akt phosphorylation as well as increases in basal MYPT1 phosphorylation, inducible nitric oxide synthase (iNOS) expression, and nitrite/nitrate production compared with Wistar-Kyoto controls. Both iNOS expression and the inhibition of angiotensin (ANG) II-induced MYPT1 phosphorylation were resistant to the effects of insulin in diabetic GK VSMC. We also measured the isometric tension of intact and denuded GK aorta using a myograph and observed significantly impaired insulin-induced vasodilation. Adenovirus-mediated overexpression of constitutively active Akt in GK VSMC led to significantly improved insulin sensitivity in terms of counteracting ANG II-induced contractile signaling via MYPT1, myosin light chain dephosphorylation, and reduced iNOS expression, S-nitrosylation and survivin expression. We demonstrated for the first time the presence of Akt-independent iNOS expression in the GK diabetic model and that the defective insulin-induced vasodilation observed in the diabetic vasculature can be restored by the overexpression of active Akt, which advocates a novel therapeutic strategy for treating diabetes.

Ang-II-induced Ca(2+) influx is mediated by the 1/4/5 subgroup of the transient receptor potential proteins in cultured aortic smooth muscle cells from diabetic Goto-Kakizaki rats.

Angiotensin-II (Ang-II) exerts many of its vascular effects, including the pathophysiological changes associated with type 2 diabetes, through changes in intracellular calcium concentration [Ca(2+)](i). We sought to clarify the mechanism responsible for Ang-II-induced Ca(2+) influx in cultured aortic VSMC using the Goto-Kakizaki (GK) rat model of type 2 diabetes. Ang-II-induced Ca(2+) influx was blocked by neither VDCC nor c-src inhibition but was sensitive to inositol 1,4,5-trisphosphate receptor inhibition, lanthanide and the diacylglycerol analogue, oleoyl-2-acetyl-sn-glycerol. Since transient receptor potential canonical (TRPC)-3 gene expression was undetectable in both WKY and GK VSMCs and TRPC6 gene and protein expression were significantly down-regulated in GK, we believe the 1/4/5 subgroup of TRPC proteins plays a significant role. Furthermore, in GK VSMC the elevated calcium influx observed was not attributable to increased TRPC expression, but rather an alteration of TRPC activity.

Surgical Mouse Models of Vertical Sleeve Gastrectomy and Roux-en Y Gastric Bypass: a Review.

Reviewed here are multiple mouse models of vertical sleeve gastrectomy (VSG) and Roux-en Y gastric bypass (RYGB) that have emerged over the past decade. These models use diverse approaches to both operative and perioperative procedures. Scrutinizing the benefits and pitfalls of each surgical model and what to expect in terms of post-operative outcomes will enhance our assessment of studies using mouse models, as well as advance our understanding of their translational potential. Two mouse models of bariatric surgery, VSG-lembert and RYGB-small pouch, demonstrate low mortality and most closely recapitulate the human forms of surgery. The use of liquid diets can be minimized, and in mice, RYGB demonstrates more reliable and longer lasting effects on weight loss compared to that of VSG.