The brown adipose tissue glucagon receptor is functional but not essential for control of energy homeostasis in mice.

OBJECTIVE: Administration of glucagon (GCG) or GCG-containing co-agonists reduces body weight and increases energy expenditure. These actions appear to be transduced by multiple direct and indirect GCG receptor (GCGR)-dependent mechanisms. Although the canonical GCGR is expressed in brown adipose tissue (BAT) the importance of BAT GCGR activity for the physiological control of body weight, or the response to GCG agonism, has not been defined. METHODS: We studied the mechanisms linking GCG action to acute increases in oxygen consumption using wildtype (WT), Ucp1-/- and Fgf21-/- mice. The importance of basal GCGR expression within the Myf5+ domain for control of body weight, adiposity, glucose and lipid metabolism, food intake, and energy expenditure was examined in GcgrBAT-/- mice housed at room temperature or 4 °C, fed a regular chow diet (RCD) or after a prolonged exposure to high fat diet (HFD). RESULTS: Acute GCG administration induced lipolysis and increased the expression of thermogenic genes in BAT cells, whereas knockdown of Gcgr reduced expression of genes related to thermogenesis. GCG increased energy expenditure (measured by oxygen consumption) both in vivo in WT mice and ex vivo in BAT and liver explants. GCG also increased acute energy expenditure in Ucp1-/- mice, but these actions were partially blunted in Ffg21-/- mice. However, acute GCG administration also robustly increased oxygen consumption in GcgrBAT-/- mice. Moreover, body weight, glycemia, lipid metabolism, body temperature, food intake, activity, energy expenditure and adipose tissue gene expression profiles were normal in GcgrBAT-/- mice, either on RCD or HFD, whether studied at room temperature, or chronically housed at 4 °C. CONCLUSIONS: Exogenous GCG increases oxygen consumption in mice, also evident both in liver and BAT explants ex vivo, through UCP1-independent, FGF21-dependent pathways. Nevertheless, GCGR signaling within BAT is not physiologically essential for control of body weight, whole body energy expenditure, glucose homeostasis, or the adaptive metabolic response to cold or prolonged exposure to an energy dense diet.

Adiponectin modulates ventral tegmental area dopamine neuron activity and anxiety-related behavior through AdipoR1.

Adiponectin, a metabolic hormone secreted by adipocytes, can cross the blood-brain barrier to act on neurons in different brain regions, including those involved in stress-related disorders. Here we show that dopamine neurons in the ventral tegmental area (VTA) express adiponectin receptor 1 (AdipoR1). Intra-VTA infusion of adiponectin or the adiponectin mimetic AdipoRon in wild-type mice decreases basal dopamine neuron population activity and firing rate and reverses the restraint stress-induced increase in dopamine neuron activity and anxiety behavior. Adiponectin haploinsufficiency leads to increased dopamine neuron firing and anxiety behavior under basal conditions. Ablation of AdipoR1 specifically from dopamine neurons enhances neuronal and anxiogenic responses to restraint stress. The effects of intra-VTA infusion of adiponectin on neuronal activity and behavior were abolished in mice lacking AdipoR1 in dopamine neurons. These observations indicate that adiponectin can directly modulate VTA dopamine neuron activity and anxiety behavior, and that AdipoR1 is required for adiponectin-induced inhibition of dopamine neurons and anxiolytic effects. These results strengthen the idea of adiponectin as a key biological factor that links metabolic syndrome and emotional disorders.

Evaluation of maxillary sinus anatomy by cone-beam CT prior to sinus floor elevation.

PURPOSE: Surgical complications during sinus floor elevation are frequently caused by septa in the maxillary sinus. In this study, the prevalence of septa was retrospectively determined via three-dimensional imaging to assess the necessity for appropriate imaging prior to sinus floor elevation. MATERIALS AND METHODS: The cone-beam computed tomography scans of 1,029 consecutive patients were evaluated to assess the prevalence of septa, taking into account patient age and sex as well as the number and orientation of septa and their locations. If septa were present, the height was measured and the orientation was determined. RESULTS: Septa were found in 47% of patients and 33.2% of sinuses. There was no statistical difference in prevalence with respect to age, sex, or side. Most patients with septa showed one septum in one sinus (24.6%); 13.7% showed one septum in each sinus. Other combinations (up to three septa per sinus) were found in 8.7% of patients. Septa were most commonly located in the first molar region (256 septa), followed by the second molar region (225 septa), the third molar region (144), second premolar region (136), the first premolar region (44), and the canine region (5). The mean septal height was 11.7 +/- 6.08 mm for septa in a sagittal orientation (n = 206, 25.3%; maximum height of 37 mm) and 7.3 +/- 5.08 mm for those oriented transversely (n = 608, 74.7%; maximum height of 36 mm). The variance was larger for the sagittal orientation group (37.03 mm) than for transversely oriented septa (25.9 mm). CONCLUSION: Septa were found in 47% of the patients in this sample. Appropriate imaging prior to performing sinus surgery seems justified, since complications and the success rate of sinus floor elevation are clearly related to the presence of septa. Int J Oral Maxillofac Implants 2010;25:258-265.

Genetic ablation of caveolin-1 confers protection against atherosclerosis.

OBJECTIVE: The development of atherosclerosis is a process characterized by the accumulation of lipids in the form of modified lipoproteins in the subendothelial space. This initiating step is followed by the subsequent recruitment and proliferation of other cell types, including monocytes/macrophages and smooth muscle cells. Here, we evaluate the potential role of caveolae membrane domains in the pathogenesis of atherosclerosis by using apolipoprotein E-deficient (ApoE-/-) mice as a model system. METHODS AND RESULTS: Caveolin-1 (Cav-1) is a principal structural protein component of caveolae membrane domains. To directly assess the in vivo role of caveolae and Cav-1 in atherosclerosis, we interbred Cav-1-/- mice with ApoE-/- mice. Interestingly, loss of Cav-1 resulted in a dramatic >2-fold increase in non-HDL plasma cholesterol levels in the ApoE-/- background. However, despite this hypercholesterolemia, we found that loss of Cav-1 gene expression was clearly protective against the development of aortic atheromas, with up to an approximately 70% reduction in atherosclerotic lesion area. Mechanistically, we demonstrated that loss of Cav-1 resulted in the dramatic downregulation of certain proatherogenic molecules, namely, CD36 and vascular cell adhesion molecule-1. CONCLUSIONS: Taken together, our results indicate that loss of Cav-1 can counteract the detrimental effects of atherogenic lipoproteins. Thus, Cav-1 is a novel target for drug development in the pharmacologic prevention of atheroma formation. Our current data also provide the first molecular genetic evidence to support the hypothesis that caveolar transcytosis of modified lipoproteins (from the blood to the sub-endothelial space) is a critical initiating step in atherosclerosis.

Removal of visceral fat prevents insulin resistance and glucose intolerance of aging: an adipokine-mediated process?

Age-dependent changes in insulin action and body fat distribution are risk factors for the development of type 2 diabetes. To examine whether the accumulation of visceral fat (VF) could play a direct role in the pathophysiology of insulin resistance and type 2 diabetes, we monitored insulin action, glucose tolerance, and the expression of adipo-derived peptides after surgical removal of VF in aging (20-month-old) F344/Brown Norway (FBN) and in Zucker Diabetic Fatty (ZDF) rats. As expected, peripheral and hepatic insulin action were markedly impaired in aging FBN rats, and extraction of VF (accounting for approximately 18% of their total body fat) was sufficient to restore peripheral and hepatic insulin action to the levels of young rats. When examined at the mechanistic level, removal of VF in ZDF rats prevented the progressive decrease in insulin action and delayed the onset of diabetes, but VF extraction did not alter plasma free fatty acid levels. However, the expression of tumor necrosis factor-alpha and leptin in subcutaneous (SC) adipose tissue were markedly decreased after VF removal (by approximately three- and twofold, respectively). Finally, extracted VF retained approximately 15-fold higher resistin mRNA compared with SC fat. Our data suggest that insulin resistance and the development of diabetes can be significantly reduced in aging rats by preventing the age-dependent accumulation of VF. This study documents a cause-and-effect relationship between VF and major components of the metabolic syndrome.