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Inflammation has a critical role in the development of insulin resistance. Recent evidence points to a contribution by the central nervous system in the modulation of peripheral inflammation through the anti-inflammatory reflex. However, the importance of this phenomenon remains elusive in type 2 diabetes pathogenesis. Here we show that rat insulin-2 promoter (Rip)mediated deletion of Pten, a gene encoding a negative regulator of PI3K signaling, led to activation of the cholinergic antiinflammatory pathway that is mediated by M2 activated macrophages in peripheral tissues. As such, [Rip-cre.sup.+] [Pten.sup.flox/flox] mice showed lower systemic inflammation and greater insulin sensitivity under basal conditions compared to littermate controls, which were abolished when the mice were treated with an acetylcholine receptor antagonist or when macrophages were depleted. After feeding with a high-fat diet, the Pten-deleted mice remained markedly insulin sensitive, which correlated with massive subcutaneous fat expansion. They also exhibited more adipogenesis with M2 macrophage infiltration, both of which were abolished after disruption of the anti-inflammatory efferent pathway by left vagotomy. In summary, we show that Pten expression in [Rip.sup.+] neurons has a critical role in diabetes pathogenesis through mediating the anti-inflammatory reflex., Inflammation is an integral component of insulin resistance and type 2 diabetes (1-3), and activation of both circulating monocytes and tissue-resident macrophages is necessary for the development of peripheral insulin [...]

TSC1 is a tumor suppressor that associates with TSC2 to inactivate Rheb, thereby inhibiting signaling by the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). mTORC1 stimulates cell growth by promoting anabolic cellular processes, such as translation, in response to growth factors and nutrient signals. To test roles for TSC1 and mTORC1 in [beta]-cell function, we utilized Rip2/Cre to generate mice lacking Tsc1 in pancreatic [beta]-cells (Rip-Tsc1cKO mice). Although obesity developed due to hypothalamic Tsc1 excision in older Rip-Tsc1cKO animals, young animals displayed a prominent gain-of-function [beta]-cell phenotype prior to the onset of obesity. The young Rip-Tsc1cKO animals displayed improved glycemic control due to mTOR-mediated enhancement of [beta]-cell size, mass, and insulin production but not determinants of [beta]-cell number (proliferation and apoptosis), consistent with an important anabolic role for mTOR in [beta]-cell function. Furthermore, mTOR mediated these effects in the face of impaired Akt signaling in [beta]-cells. Thus, mTOR promulgates a dominant signal to promote [beta]-cell/islet size and insulin production, and this pathway is crucial for [beta]-cell function and glycemic control. tuberous sclerosis complex; mammalian target of rapamycin; pancreatic [beta]-cell; conditional knockout mice; rat insulin promoter 2 doi: 10.1152/ajpendo.00262.2009.

Leptin acts via its receptor (LepRb) to regulate neural circuits in concert with body energy stores. In addition to acting on a number of hypothalamic structures, leptin modulates the mesolimbic dopamine (DA) system. To determine the sites at which LepRb neurons might directly influence the mesolimbic DA system, we examined the distribution of LepRb neurons and their projections within mesolimbic brain regions. Although the ventral tegmental area (VTA) containsDALepRb neurons, LepRb neurons are absent from the amygdala and striatum. Also, LepRb-EGFPf mice (which label projections from LepRb neurons throughout the brain) reveal that few LepRb neurons project to the nucleus accumbens (NAc). In contrast, the central amygdala (CeA) and its rostral extension receive copious projections from LepRb neurons. Indeed, LepRb-specific anterograde tracing demonstrates (and retrograde tracing confirms) that VTA LepRb neurons project to the extended CeA (extCeA) but not the NAc. Consistently, leptin promotes cAMP response element-binding protein phosphorylation in the extCeA, but not NAc, of leptin-deficient animals. Furthermore, transgenic mice expressing the trans-synaptic tracer wheat germ agglutinin in LepRb neurons reveal the innervation of CeA cocaine- and amphetamine-regulated transcript (CART) neurons by LepRb neurons, and leptin suppresses the increased CeA CART expression of leptin-deficient animals. Thus, LepRb VTA neurons represent a subclass of VTA DA neurons that specifically innervates and controls the extCeA; we hypothesize that these neurons primarily modulate CeA-directed behaviors. [ABSTRACT FROM AUTHOR]

Protein kinase C (PKC) and angiotensin II (AngII) can regulate cardiac function in pathological conditions such as in diabetes or ischemic heart disease. We have reported that expression of connective tissue growth factor (CTGF) is increased in the myocardium of diabetic mice. Now we showed that the increase in CTGF expression in cardiac tissues of streptozotocin-induced diabetic rats was reversed by captopril and islet cell transplantation. Infusion of AngII in rats increased CTGF mRNA expression by 15-fold, which was completely inhibited by co-infusion with AT1 receptor antagonist, candesartan. Similarly, incubation of cultured cardiomyocytes with AngII increased CTGF mRNA expression by 2-fold, which was blocked by candesartan and a general PKC inhibitor, GF109203X. The role of PKC isoform-dependent action was further studied using adenoviral vector-mediated gene transfer of dominant negative (dn) PKC or wild type PKC isoforms. Expression of dnPKCα, -∈, and -ζ isoforms suppressed AngII-induced CTGF expression in cardiomyocytes. In contrast, expression of dominant negative PKCδ significantly increased AngII-induced CTGF expression, whereas expression of wild type PKCδ inhibited this induction. This inhibitory effect was further confirmed in the myocardium of transgenic mice with cardiomyocyte-specific overexpression of PKCδ (δTg mice). Thus, AngII can regulate CTGF expression in cardiomyocytes through a PKC activation-mediated pathway in an isoform-selective manner both in physiological and diabetic states and may contribute to the development of cardiac fibrosis in diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Objective: Conditional gene targeting has been extensively used for in vivo analysis of gene function in β-cell biology. The objective of this study was to examine whether mouse transgenic Cre lines, used to mediate β-cell- or pancreas-specific recombination, also drive Cre expression in the brain., Research Design and Methods: Transgenic Cre lines driven by Ins1, Ins2, and Pdx1 promoters were bred to R26R reporter strains. Cre activity was assessed by β-galactosidase or yellow fluorescent protein expression in the pancreas and the brain. Endogenous Pdx1 gene expression was monitored using Pdx1(tm1Cvw) lacZ knock-in mice. Cre expression in β-cells and co-localization of Cre activity with orexin-expressing and leptin-responsive neurons within the brain was assessed by immunohistochemistry., Results: All transgenic Cre lines examined that used the Ins2 promoter to drive Cre expression showed widespread Cre activity in the brain, whereas Cre lines that used Pdx1 promoter fragments showed more restricted Cre activity primarily within the hypothalamus. Immunohistochemical analysis of the hypothalamus from Tg(Pdx1-cre)(89.1Dam) mice revealed Cre activity in neurons expressing orexin and in neurons activated by leptin. Tg(Ins1-Cre/ERT)(1Lphi) mice were the only line that lacked Cre activity in the brain., Conclusions: Cre-mediated gene manipulation using transgenic lines that express Cre under the control of the Ins2 and Pdx1 promoters are likely to alter gene expression in nutrient-sensing neurons. Therefore, data arising from the use of these transgenic Cre lines must be interpreted carefully to assess whether the resultant phenotype is solely attributable to alterations in the islet β-cells.

TSC1 is a tumor suppressor that associates with TSC2 to inactivate Rheb, thereby inhibiting signaling by the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). mTORC1 stimulates cell growth by promoting anabolic cellular processes, such as translation, in response to growth factors and nutrient signals. To test roles for TSC1 and mTORC1 in β-cell function, we utilized Rip2/Cre to generate mice lacking Tsc1 in pancreatic β-cells (Rip-Tsc1cKO mice). Although obesity developed due to hypothalamic Tsc1 excision in older Rip-Tsc1cKO animals, young animals displayed a prominent gain-of-function β-cell phenotype prior to the onset of obesity. The young Rip-Tsc1cKO animals displayed improved glycemic control due to mTOR-mediated enhancement of β-cell size, mass, and insulin production but not determinants of β-cell number (proliferation and apoptosis), consistent with an important anabolic role for mTOR in β-cell function. Furthermore, mTOR mediated these effects in the face of impaired Akt signaling in β-cells. Thus, mTOR promulgates a dominant signal to promote β-cell/islet size and insulin production, and this pathway is crucial for β-cell function and glycemic control.