Age-related loss of ovarian function promotes adiposity and insulin resistance in women. Estrogen (E(2)) directly enhances insulin sensitivity and suppresses lipogenesis in peripheral tissues. ...Recently, the central actions of E(2) in the regulation of energy homeostasis are becoming clearer; however, the functional relevance and degree of contribution of the central vs. peripheral actions of E(2) are currently unknown. Therefore, we prepared and analyzed four groups of mice. 1) CONTROL: sham-operated mice fed a regular diet, 2) OVX-HF: ovariectomized (OVX) mice fed a 60% high-fat diet (HF), 3) E2-SC: OVX-HF mice subcutaneously treated with E(2), and 4) E2-ICV: OVX-HF mice treated with E(2) intracerebroventricularly. OVX-HF mice showed increased body weight with both visceral and subcutaneous fat volume enlargement, glucose intolerance, and insulin resistance. Both E2-SC and E2-ICV equally ameliorated these abnormalities. Although the size of adipocytes and number of CD11c-positive macrophages in perigonadal fat in OVX-HF were reduced by both E(2) treatments, peripherally administered E(2) decreased the expression of TNFα, lipoprotein lipase, and fatty acid synthase in the white adipose tissue (WAT) of OVX-HF. In contrast, centrally administered E(2) increased hormone-sensitive lipase in WAT, decreased the hepatic expression of gluconeogenic enzymes, and elevated core body temperature and energy expenditure with marked upregulation of uncoupling proteins in the brown adipose tissue. These results suggest that central and peripheral actions of E(2) regulate insulin sensitivity and glucose metabolism via different mechanisms, and their coordinated effects may be important to prevent the development of obesity and insulin resistance in postmenopausal women.
Aims/hypothesis
The imbalance between maternal insulin resistance and a relative lack of insulin secretion underlies the pathogenesis of gestational diabetes mellitus (GDM). Alterations in T cell ...subtypes and increased levels of circulating proinflammatory cytokines have been proposed as potential mechanisms underlying the pathophysiology of insulin resistance in GDM. Since oestrogen modulates T cell immunity, we hypothesised that oestrogen plays a homeostatic role in visceral adipose tissue by coordinating T cell immunity through oestrogen receptor α (ERα) in T cells to prevent GDM.
Methods
Female CD4-cre ERα
fl/fl
(KO) mice on a C57BL/6 background with ERα ablation specifically in T cells, and ERα
fl/fl
(ERα-floxed FL) mice were fed 60 kJ% high-fat diet (HFD) for 4 weeks. Female mice mated with male BALB/c mice to achieve allogenic pregnancy and were maintained on an HFD to generate the GDM model. Mice were divided into four experimental groups: non-pregnant FL, non-pregnant KO, pregnant FL (FL-GDM) and pregnant KO (KO-GDM). GTTs and ITTs were performed on day 12.5 or 13.5 and 16.5 after breeding, respectively. On day 18.5 after breeding, mice were killed and T cell subsets in the gonadal white adipose tissue (gWAT) and spleen were analysed using flow cytometry. Histological examination was also conducted and proinflammatory gene expression in gWAT and the liver was evaluated.
Results
KO mice that mated with BALB/c mice showed normal fertility rates and fetal weights as compared with FL mice. Body and tissue weights were similar between FL and KO mice. When compared with FL-GDM mice, KO-GDM mice showed decreased insulin secretion (serum insulin concentration 15 min after glucose loading: 137.3 ± 18.3 pmol/l and 40.1 ± 36.5 pmol/l, respectively;
p
< 0.05), impaired glucose tolerance (glucose AUC in GTT: 2308.3 ± 54.0 mmol/l × min and 2620.9 ± 122.1 mmol/l × min, respectively;
p
< 0.05) and increased numbers of T helper (Th)17 cells in gWAT (0.4 ± 0.0% vs 0.8 ± 0.1%;
p
< 0.05). However, the contents of Th1 and regulatory T cells (Tregs) in gWAT remained similar between FL-GDM and KO-GDM. Glucose-stimulated insulin secretion was similar between isolated islets derived from FL and KO mice, but was reduced by IL-17A treatment. Moreover, the levels of proinflammatory gene expression, including expression of
Emr1
and
Tnfa
in gWAT, were significantly higher in KO-GDM mice than in FL-GDM mice (5.1-fold and 2.7-fold, respectively;
p
< 0.01 for both). Furthermore, KO-GDM mice showed increased expression of genes encoding hepatokines,
Ahsg
and
Fgf21
(both were 2.4-fold higher vs FL-GDM mice;
p
< 0.05 and
p
= 0.09, respectively), with no changes in inflammatory gene expression (e.g.,
Tnfa
and
Ifng
) in the liver compared with FL-GDM mice.
Conclusions/interpretation
Deletion of ERα in T cells caused impaired maternal adaptation of insulin secretion, changes in hepatokine profiles, and enhanced chronic inflammation in gWAT alongside an abnormal increase in Th17 cells. These results suggest that the ERα-mediated oestrogen signalling effects in T cells regulate T cell immunity and contribute to glucose homeostasis in pregnancy.
Graphical abstract
Circadian rhythm is crucial for preventing hepatic insulin resistance, although the mechanism remains uncovered. Here we report that the wake-active hypothalamic orexin system plays a key role in ...this regulation. Wild-type mice showed that a daily rhythm in blood glucose levels peaked at the awake period; however, the glucose rhythm disappeared in orexin knockout mice despite normal feeding rhythm. Central administration of orexin A during nighttime awake period acutely elevated blood glucose levels but subsequently lowered daytime glucose levels in normal and diabetic db/db mice. The glucose-elevating and -lowering effects of orexin A were suppressed by adrenergic antagonists and hepatic parasympathectomy, respectively. Moreover, the expression levels of hepatic gluconeogenic genes, including Pepck, were increased and decreased by orexin A at nanomolar and femtomolar doses, respectively. These results indicate that orexin can bidirectionally regulate hepatic gluconeogenesis via control of autonomic balance, leading to generation of the daily blood glucose oscillation. Furthermore, during aging, orexin deficiency enhanced endoplasmic reticulum (ER) stress in the liver and caused impairment of hepatic insulin signaling and abnormal gluconeogenic activity in pyruvate tolerance test. Collectively, the daily glucose rhythm under control of orexin appears to be important for maintaining ER homeostasis, thereby preventing insulin resistance in the liver.
Platelet-derived growth factor-B (PDGF-B) is a main factor to promote adipose tissue angiogenesis, which is responsible for the tissue expansion in obesity. In this process, PDGF-B induces the ...dissociation of pericytes from blood vessels; however, its regulatory mechanism remains unclear. In the present study, we found that stromal cell-derived factor 1 (SDF1) plays an essential role in this regulatory mechanism. SDF1 mRNA was increased in epididymal white adipose tissue (eWAT) of obese mice. E
x vivo
pharmacological analyses using cultured adipose tissue demonstrated that physiological concentrations (1–100 pg/mL) of SDF1 inhibited the PDGF-B-induced pericyte dissociation from vessels via two cognate SDF1 receptors, CXCR4 and CXCR7. In contrast, higher concentrations (> 1 ng/mL) of SDF1 alone caused the dissociation of pericytes via CXCR4, and this effect disappeared in the cultured tissues from PDGF receptor β (PDGFRβ) knockout mice. To investigate the role of SDF1 in angiogenesis in vivo, the effects of anagliptin, an inhibitor of dipeptidyl peptidase 4 (DPP4) that degrades SDF1, were examined in mice fed a high-fat diet. Anagliptin increased the SDF1 levels in the serum and eWAT. These changes were associated with a reduction of pericyte dissociation and fat accumulation in eWAT. AMD3100, a CXCR4 antagonist, cancelled these anagliptin effects. In flow-cytometry analysis, anagliptin increased and decreased the PDGF-B expression in endothelial cells and macrophages, respectively, whereas anagliptin reduced the PDGFRβ expression in pericytes of eWAT. These results suggest that SDF1 negatively regulates the adipose tissue angiogenesis in obesity by altering the reactivity of pericytes to PDGF-B.
Non-alcoholic steatohepatitis (NASH) occasionally occurs under obesity; however, factors modulating the natural history of fatty liver disease remain unknown. Since hypothalamic orexin that regulates ...physical activity and autonomic balance prevents obesity, we investigate its role in NASH development. Male orexin-deficient mice fed a high-fat diet (HFD) show severe obesity and progression of NASH with fibrosis in the liver. Hepatic fibrosis also develops in ovariectomized orexin-deficient females fed an HFD but not ovariectomized wild-type controls. Moreover, long-term HFD feeding causes hepatocellular carcinoma (HCC) in orexin-deficient mice. Intracerebroventricular injection of orexin A or pharmacogenetic activation of orexin neurons acutely activates hepatic mTOR-sXbp1 pathway to prevent endoplasmic reticulum (ER) stress, a NASH-causing factor. Daily supplementation of orexin A attenuates hepatic ER stress and inflammation in orexin-deficient mice fed an HFD, and autonomic ganglionic blocker suppresses the orexin actions. These results suggest that hypothalamic orexin is an essential factor for preventing NASH and associated HCC under obesity.
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•Orexin deficiency exacerbates diet-induced obesity and hepatic steatosis•Orexin deficiency triggers the progression from steatosis to NASH and HCC•Orexin improves hepatic ER homeostasis through the autonomic nervous system•Daily administration with orexin prevents NASH-causing inflammatory events
Tsuneki et al. reveal that central actions of orexin are required for preventing NASH and hepatocellular carcinoma (HCC) under diet-induced obese conditions. In this process, orexin attenuates hepatic endoplasmic reticulum (ER) stress-associated inflammation via the autonomic nervous system in addition to causing the anti-obese effect via promotion of physical activity.
MC903 is a synthetic derivative of vitamin D3 that has been designed to diminish its impact on calcium metabolism and is clinically used as a transdermal reagent for psoriasis. Animal studies showed ...that an oral or intraperitoneal vitamin D3 treatment prevented the development of obesity. In contrast, the bioavailability of orally administered vitamin D3 is reported to be low in obese patients. In the current study, we aimed to investigate the impact of a transdermal treatment with MC903 in established obese mice. We further studied the underlying mechanisms of MC903-mediated metabolic improvement.
Male C57BL/6 J mice were fed standard chow or a 60% high-fat diet (HFD) for 7 weeks, and a transdermal treatment with MC903 on the ear auricle was initiated thereafter. The metabolic profiles of mice were analyzed during 4 weeks of treatment, and mice were dissected for histological and gene expression analyses. The direct impacts of MC903 and vitamin D3 were investigated using 3T3-L1 adipocytes and C2C12 myotubes in vitro.
HFD-fed mice showed significant increases in body and epididymal white adipose tissue (eWAT) weights with enlarged adipocytes. They exhibited glucose intolerance, decreased oxygen consumption, and chronic inflammation in eWAT. The transdermal treatment with MC903 significantly ameliorated these metabolic abnormalities in HFD-fed mice without affecting food consumption. In accordance with enhanced energy metabolism, myofiber diameters and the expression of uncoupling protein 3 (UCP3) in the gastrocnemius and soleus muscle were significantly increased in MC903-treated HFD mice. In addition, vitamin D3 and MC903 both suppressed adipogenic differentiation and enhanced lipolysis in 3T3-L1 adipocytes, and increased UCP3 expression in cultured C2C12 myotubes. Furthermore, MC903 increased oxygen consumption and UCP3 knockdown significantly decreased them in C2C12 myotubes.
A transdermal treatment with MC903 increased myofiber diameter and energy metabolism and decreased visceral fat accumulation, thereby improving obesity and glucose intolerance in mice.
Serum aldosterone level is clinically known to correlate with body weight and insulin resistance. Because the underlying molecular mechanism is largely unknown, we examined the effect of aldosterone ...on insulin-induced metabolic signaling leading to glucose uptake in 3T3-L1 adipocytes. Aldosterone reduced the amounts of insulin receptor substrate (IRS) 1 and IRS2 in a time- and dose-dependent manner. As a result, insulin-induced phosphorylation of Akt-1 and -2, and subsequent uptake of 2-deoxyglucose were decreased. Degradation of IRSs was effectively prevented by a glucocorticoid receptor antagonist and antioxidant N-acetylcysteine, but not by a mineralocorticoid receptor antagonist. Because aldosterone induced phosphorylation of IRS1 at Ser307, responsible kinases were investigated, and we revealed that rapamycin and BMS345541, but neither SP600125 nor calphostin C, conferred for degradation of IRSs. Although lactacystin prevented the degradation of IRSs, glucose uptake was not preserved. Importantly, sucrose-gradient-sediment intracellular fraction analysis revealed that lactacystin did not effectively restore the reduction of IRS1 in the low-density microsome fraction, important for the transduction of insulin’s metabolic signaling. These results indicate that aldosterone deteriorates metabolic action of insulin by facilitating the degradation of IRS1 and IRS2 via glucocorticoid receptor-mediated production of reactive oxygen species, and activation of IκB Kinase β and target of rapamycin complex 1. Thus, aldosterone appears to be a novel key factor in the development of insulin resistance in visceral obesity.
Aldosterone appears to be a key factor in the development of insulin resistance in visceral obesity.
Adipose tissue macrophages (ATMs) play a central role in tissue remodeling and homeostasis. However, whether ATMs promote adipose angiogenesis in obesity remains unclear. We examined the impact of ...ATMs deletion on adipose angiogenesis and tissue expansion in the epididymal white adipose tissue (eWAT) of high-fat diet (HFD)-fed mice by using liposome-encapsulated clodronate. We further elucidated the induction mechanisms of platelet-derived growth factor (PDGF)-B in macrophages in response to obesity-associated metabolic stresses, since it plays a significant role in the regulation of pericyte behavior for the initiation of neoangiogenesis during tissue expansion. ATM depletion prevented adipose tissue expansion in HFD-fed mice by inhibiting pericyte detachment from vessels, resulting in less vasculature in eWAT. The lipopolysaccharide (LPS) stimulation and high glucose concentration augmented glucose incorporation and glycolytic capacity with the induction of Pdgfb mRNA. This effect was mediated through extracellular signal-regulated kinase (ERK) among mitogen-activated protein kinases coupled with glycolysis in RAW264.7 macrophages. The Pdgfb induction system was distinct from that of inflammatory cytokines mediated by mechanistic target of rapamycin complex 1 (mTORC1) and NFκB signaling. Thus, obesity-associated hyperglycemia and chronic inflammation fuels ERK signaling coupled with glycolysis in pro-inflammatory macrophages, which contribute to the expansion of eWAT through PDGF-B-dependent vascular remodeling.
Brain-derived neurotrophic factor (BDNF), an essential factor for maintaining brain functions, has been reported to be reduced in various neurological diseases, including Alzheimer's disease and ...major depression. Therefore, new drugs to increase the BDNF expression need to be developed. Since phosphatidylinositol (3,4,5)-trisphosphate, a membrane signaling molecule produced by phosphoinositide 3 (PI3)-kinase in the BDNF signaling, is a candidate target of SH2 domain-containing inositol 5′ phosphatase 2 (SHIP2, a 5′-lipid phosphatase), the present study examined the effect of a SHIP2 inhibitor AS1949490 on Bdnf expression in cultured cortical neurons. BDNF increased its own mRNA levels, and AS1949490 enhanced this positive feedback regulation. The effects of BDNF in combination with AS1949490 on the Bdnf mRNA levels were blocked by inhibitors of mitogen-activated protein kinase kinase (U0126), PI3-kinase (LY294002), phospholipase Cγ (U73122), and protein kinase C (bisindolylmaleimide I), whereas the effect of BDNF alone was inhibited only by U0126. The mRNA stability assay using actinomycin D demonstrated that AS1949490 reduced degradation of the self-amplified Bdnf mRNA levels, and this effect was disappeared in the presence of bisindolylmaleimide I. These results suggest that BDNF promoted the Bdnf mRNA stabilization in a protein kinase C-dependent manner only in the presence of AS1949490, thereby enhancing Bdnf expression. Furthermore, behavioral analyses indicated that central administration of AS1949490 caused memory-improving and anti-depressant effects in passive avoidance test and forced swim test, respectively. Therefore, inhibition of SHIP2 appears to be valuable therapeutic strategy against neurological disorders associated with insufficient BDNF functions.
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Sensor-augmented insulin pump therapy with a predictive low glucose suspend (SAP-PLGS) feature is a remarkably progressed modality for the glycemic management of patients with type 1 diabetes. This ...technology avoids nocturnal hypoglycemia and severe hypoglycemia. A Brazilian woman developed type 1 diabetes at age 11 and was treated with multiple daily insulin injections. At age 20, she was admitted to our internal medicine department for her first pregnancy. Her HbA1c was 7.9% in the 6 weeks of gestation. Although the combination of continuous subcutaneous insulin infusion and a sensor-augmented pump was introduced, she had a miscarriage in the next week. After 6 months, she became pregnant again. Despite an HbA1c of 7.2%, she had another miscarriage. Thereafter, she returned to multiple daily insulin injections and began using intermittently scanned continuous glycemic monitoring. At age 22, she had her third pregnancy. Her HbA1c was 7.3%. SAP-PLGS was then introduced, which reduced her frequent hypoglycemic events and blood glucose fluctuations. She gave birth to a 4137 g boy at 39 weeks without significant complications. Successful delivery can be obtained in women with type 1 diabetes following repeated miscarriages after introducing SAP-PLGS. We hypothesize that the modality might contributed to our patient’s miscarriage avoidance by reducing her glycemic fluctuations.
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