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Central obesity with cardiometabolic syndrome (CMS) is a major global contributor to human disease, and effective therapies are needed. Here, we show that cyclic GMP-selective phosphodiesterase 9A inhibition (PDE9-I) in both male and ovariectomized female mice suppresses preestablished severe diet-induced obesity/CMS with or without superimposed mild cardiac pressure load. PDE9-I reduces total body, inguinal, hepatic, and myocardial fat; stimulates mitochondrial activity in brown and white fat; and improves CMS, without significantly altering activity or food intake. PDE9 localized at mitochondria, and its inhibition in vitro stimulated lipolysis in a PPARα-dependent manner and increased mitochondrial respiration in both adipocytes and myocytes. PPARα upregulation was required to achieve the lipolytic, antiobesity, and metabolic effects of PDE9-I. All these PDE9-I-induced changes were not observed in obese/CMS nonovariectomized females, indicating a strong sexual dimorphism. We found that PPARα chromatin binding was reoriented away from fat metabolism-regulating genes when stimulated in the presence of coactivated estrogen receptor-α, and this may underlie the dimorphism. These findings have translational relevance given that PDE9-I is already being studied in humans for indications including heart failure, and efficacy against obesity/CMS would enhance its therapeutic utility.

Negative regulation of exocytosis from secretory cells is accomplished through inhibitory signals from [G.sub.i/o] GPCRs by G[beta][gamma] subunit inhibition of 2 mechanisms: decreased calcium entry and direct interaction of G[beta][gamma] with soluble N- ethylmaleimide-sensitive factor attachment protein (SNAP) receptor (SNARE) plasma membrane fusion machinery. Previously, we disabled the second mechanism with a SNAP25 truncation (SNAP25A3) that decreased G[beta][gamma] affinity for the SNARE complex, leaving exocytotic fusion and modulation of calcium entry intact and removing GPCR-G[beta][gamma] inhibition of SNARE- mediated exocytosis. Here, we report substantial metabolic benefit in mice carrying this mutation. Snap2SA3/A3 mice exhibited enhanced insulin sensitivity and beiging of white fat. Metabolic protection was amplified in Snap2SA3/A3 mice challenged with a high-fat diet. Glucose homeostasis, whole-body insulin action, and insulin-mediated glucose uptake into white adipose tissue were improved along with resistance to diet-induced obesity. Metabolic protection in [Snap25.sup.[DELTA]3/[DELTA]3] mice occurred without compromising the physiological response to fasting or cold. All metabolic phenotypes were reversed at thermoneutrality, suggesting that basal autonomic activity was required. Direct electrode stimulation of sympathetic neuron exocytosis from [Snap25.sup.[DELTA]3/[DELTA]3] inguinal adipose depots resulted in enhanced and prolonged norepinephrine release. Thus, the G[beta][gamma]-SNARE interaction represents a cellular mechanism that deserves further exploration as an additional avenue for combating metabolic disease., Introduction Metabolic diseases, such as diabetes and obesity, have an estimated annual global economic impact in the trillions of (US) dollars (1-5). Therapeutic approaches to lower metabolic risk include augmenting [...]

A classic metabolic concept posits that insulin promotes energy storage and adipose expansion, while catecholamines stimulate release of adipose energy stores by hydrolysis of triglycerides through β-adrenergic receptor (βARs) and protein kinase A (PKA) signaling. Here, we have shown that a key hub in the insulin signaling pathway, activation of p70 ribosomal S6 kinase (S6K1) through mTORC1, is also triggered by PKA activation in both mouse and human adipocytes. Mice with mTORC1 impairment, either through adipocyte-specific deletion of Raptor or pharmacologic rapamycin treatment, were refractory to the well-known βAR-dependent increase of uncoupling protein UCP1 expression and expansion of beige/brite adipocytes (so-called browning) in white adipose tissue (WAT). Mechanistically, PKA directly phosphorylated mTOR and RAPTOR on unique serine residues, an effect that was independent of insulin/AKT signaling. Abrogation of the PKA site within RAPTOR disrupted βAR/mTORC1 activation of S6K1 without affecting mTORC1 activation by insulin. Conversely, a phosphomimetic RAPTOR augmented S6K1 activity. Together, these studies reveal a signaling pathway from βARs and PKA through mTORC1 that is required for adipose browning by catecholamines and provides potential therapeutic strategies to enhance energy expenditure and combat metabolic disease., Introduction Adipose tissue depots in both humans and rodents perform a remarkable spectrum of contrasting functions, including sequestration of excess caloric energy in the form of triglyceride in white adipose [...]

The scaffold protein p62 (sequestosome 1; SQSTM1) is an emerging key molecular link among the metabolic, immune, and proliferative processes of the cell. Here, we report that adipocyte-specific, but not [...]

The ability of mammals to resist body fat accumulation is linked to their ability to expand the number and activity of 'brown adipocytes' within white fat depots. Activation of β-adrenergic receptors (β-ARs) can induce a functional 'brown-like' adipocyte phenotype. As cardiac natriuretic peptides (NPs) and β-AR agonists are similarly potent at stimulating lipolysis in human adipocytes, we investigated whether NPs could induce human and mouse adipocytes to acquire brown adipocyte features, including a capacity for thermogenic energy expenditure mediated by uncoupling protein 1 (UCP1). In human adipocytes, atrial NP (ANP) and ventricular NP (BNP) activated PPARγ coactivator-1α (PGC-1α) and UCP1 expression, induced mitochondriogenesis, and increased uncoupled and total respiration. At low concentrations, ANP and β-AR agonists additively enhanced expression of brown fat and mitochondrial markers in a p38 MAPK-dependent manner. Mice exposed to cold temperatures had increased levels of circulating NPs as well as higher expression of NP signaling receptor and lower expression of the NP clearance receptor (Nprc) in brown adipose tissue (BAT) and white adipose tissue (WAT). NPR-C-/-mice had markedly smaller WAT and BAT depots but higher expression of thermogenic genes such as Ucp1. Infusion of BNP into mice robustly increased Ucp1 and Pgc-1α expression in WAT and BAT, with corresponding elevation of respiration and energy expenditure. These results suggest that NPs promote 'browning' of white adipocytes to increase energy expenditure, defining the heart as a central regulator of adipose tissue biology., Introduction The cardiac natriuretic peptides (NPs), atrial NP (ANP) and its ventricular companion (BNP), are key hormones in fluid and hemodynamic homeostasis. Their actions are mediated by binding to NP [...]

Rapid and efficient removal of apoptotic cells by phagocytes is important during development, tissue homeostasis and in immune responses (1-5). Efficient clearance depends on the capacity of a single phagocyte to ingest multiple apoptotic cells successively, and to process the corpse-derived cellular material (6). However, the factors that influence continued clearance by phagocytes are not known. Here we show that the mitochondrial membrane potential of the phagocyte critically controls engulfment capacity, with lower potential enhancing engulfment and vice versa. The mitochondrial membrane protein Ucp2, which acts to lower the mitochondrial membrane potential (7-9), was upregulated in phagocytes engulfing apoptotic cells. Loss of Ucp2 reduced phagocytic capacity, whereas Ucp2 overexpression enhanced engulfment. Mutational and pharmacological studies indicated a direct role for Ucp2-mediated mitochondrial function in phagocytosis. Macrophages from Ucp2-deficient mice (10,11) were impaired in phagocytosis in vitro, and Ucp2-deficient mice showed profound invivodefects in clearing dying cells in the thymus and testes. Collectively, these data indicate that mitochondrial membrane potential and Ucp2 are key molecular determinants of apoptotic cell clearance. As Ucp2 is linked to metabolic diseases and atherosclerosis (11,12), this newly discovered role for Ucp2 in apoptotic cell clearance has implications for the complex aetiology and pathogenesis ofthese diseases., When a phagocyte engulfs a dying cell it essentially doubles its cellular contents. Yet phagocytes often ingest multiple apoptotic cells sequentially, and the factors regulating the 'engulfment capacity' of a [...]