Hypothalamic Pomc expression restricted to GABAergic neurons suppresses Npy overexpression and restores food intake in obese mice

Objective: Hypothalamic arcuate proopiomelanocortin (Arc-POMC) neurons are involved in different physiological processes such as the regulation of energy balance, glucose homeostasis, and stress-induced analgesia. Since these neurons heterogeneously express different biological markers and project to many hypothalamic and extrahypothalamic areas, it is proposed that Arc-POMC neurons could be classified into different subpopulations having diverse physiological roles. The aim of the present study was to characterize the contribution of the subpopulation of Arc-POMC neurons cosecreting gamma-aminobutyric acid (GABA) neurotransmitter in the control of energy balance. Methods: Arc-Pomc expression restricted to GABAergic-POMC neurons was achieved by crossing a reversible Pomc-deficient mouse line (arcPomc−) with a tamoxifen-inducible Gad2-CreER transgenic line. Pomc expression was rescued in the compound arcPomc−/−:Gad2-CreER female and male mice by tamoxifen treatment at postnatal days 25 (P25) or 60 (P60), and body weight, daily food intake, fasting glycemia, and fasting-induced hyperphagia were measured. POMC recovery was quantified by immunohistochemistry and semiquantitative RT-PCR. Neuropeptide Y (NPY) and GABAergic neurons were identified by in situ hybridization. Arc-POMC neurons projecting to the dorsomedial hypothalamic nucleus (DMH) were studied by stereotactic intracerebral injection of fluorescent retrobeads into the DMH. Results: Tamoxifen treatment of arcPomc−/−:Gad2-CreER mice at P60 resulted in Pomc expression in ∼23–25% of Arc-POMC neurons and ∼15–23% of Pomc mRNA levels, compared to Gad2-CreER control mice. Pomc rescue in GABAergic-POMC neurons at P60 normalized food intake, glycemia, and fasting-induced hyperphagia, while significantly reducing body weight. Energy balance was also improved in arcPomc−/−:Gad2-CreER mice treated with tamoxifen at P25. Distribution analysis of rescued POMC immunoreactive fibers revealed that the DMH is a major target site of GABAergic-POMC neurons. Further, the expression of the orexigenic neuropeptide Y (NPY) in the DMH was increased in arcPomc−/− obese mice but was completely restored after Pomc rescue in arcPomc−/−:Gad2-CreER mice. Finally, we found that ∼75% of Arc-POMC neurons projecting to the DMH are GABAergic. Conclusions: In the present study, we show that the expression of Pomc in the subpopulation of Arc-GABAergic-POMC neurons is sufficient to maintain normal food intake. In addition, we found that DMH-NPY expression is negatively correlated with Pomc expression in GABAergic-POMC neurons, suggesting that food intake may be regulated by an Arc-GABAergic-POMC → DMH-NPY pathway.Fil: Trotta, Milagros. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; ArgentinaFil: Bello, Estefanía Pilar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; ArgentinaFil: Alsina, Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; ArgentinaFil: Tavella, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Ferrán, José Luis. Universidad de Murcia; EspañaFil: Rubinstein, Mar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Bumaschny, Viviana Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Fisiología y Biofísica Bernardo Houssay. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Fisiología y Biofísica Bernardo Houssay; Argentin

Revelation of Expectations in Latin America (REVELA): Issue 24: September, 2012

REVELA analyzes market expectations of growth and inflation in Latin American countries. The figures analyzed represent the results of surveys of private sector actors conducted by the central banks of each country according to their own specific methodologies. They do not represent official projections by the IDB or any other official body. RES collects the results of these surveys from central banks on a monthly basis to produce a report and a set of illustrative graphs and tables.

Revelation of Expectations in Latin America (REVELA): Issue 32: June, 2013

The May 2013 surveys of expectations conducted by Central Banks with inflation targeting regimes indicate that average growth and inflation expectations have fallen slightly. The simple average inflation expectation for the region for 2013 is 4.4%, whereas average growth expectations are 4.8%. Inflation expectations fell in Paraguay (0.5%), Chile (0.3%), Guatemala (0.2%) and Uruguay (0.1%) and rose slightly only in Brazil (0.1%). Expected growth fell in Mexico (0.4%) and moderately in Chile and only increased slightly in Paraguay.

Revelation of Expectations in Latin America (REVELA): Issue 26: November, 2012

The October surveys of expectations for inflation and growth conducted by Central Banks in the region indicate increases in both growth and inflation expectations for a number of countries. Inflation expectations for 2012 have risen in Uruguay reaching 8.3%. They have also increased in Brazil currently to 5.4%, Colombia reaching 3. 1% and 2012 inflation is now expected to be 3.3% in Peru. Growth expectations have risen in Chile, Paraguay, Peru and Uruguay. Download the data from the related url.

Revelation of Expectations in Latin America (REVELA): Issue 5: January 2013

The December 2012 surveys of expectations for inflation and growth conducted by Central Banks with inflation targeting regimes continue to focus on 2012 and 2013 expectations. The weighted average expectation for regional growth for 2012, which should be close to the final figure for the year, fell to 2.5%, given the fall in expected growth in Brazil down to just 1% for the year, while for 2013 the figure rose by 0.7% compared to November's figure, to 4.7%. The average for 2012 inflation expectations is 4.9% on a GDP weighted basis and the simple average remains at 4.3%, and the respective 2013 inflation expectations are now 4.6% and 4.4%.

How Will the Food Price Shock Affect Inflation in Latin America and the Caribbean?

There is widespread concern that recent increases in international food prices may have significant effects on domestic food prices and inflation. This note assesses the impact of the recent food price shock on food, non-food and consumer inflation in the countries of Latin American and the Caribbean (LAC). Vector Autoregressive Regressions (VARs) are estimated for each country to trace the effect of international food prices, the price of oil and the value of the US dollar on domestic prices. The results are then used to calculate the potential impact of higher food prices and to project the expected rise in domestic prices to the end of 2011 and beyond, given the actual increase in food prices until February 2011. It is concluded that, due to the food price surge, increases in inflation could exceed 5 percentage points in Bolivia, Dominican Republic, Guatemala and Honduras unless additional policy actions are taken. In some countries with flexible exchange rate systems, such as Brazil, Colombia and Mexico, currencies tend to appreciate as a response to higher food prices and as a result the impact on domestic prices is muted. However, there is no simple pattern of differences between floaters and fixers; the speed and extent of pass-through is quite heterogeneous and dependent on factors such as the importance of food in the overall inflation index and local policy measures.

The fewer and the better, the better: an endogenous growth model with endogenous fertility and human capital

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A New Taxonomy of Sudden Stops: Which Sudden Stops Should Countries Be Most Concerned About?

This paper proposes a new taxonomy of Sudden Stops comprised of seven categories with definitions depending on the behavior of gross and net capital flows. The incidence of different types of Sudden Stops is tracked over time and the type of Sudden Stop related to economic performance. Sudden Stops in Net Flows associated with reductions in Gross Inflows are more disruptive than those where surges in (only) Gross Outflows dominate. The paper further discusses the mechanisms that might result in Sudden Stops in Gross Flows that are not Sudden Stops in Net Flows, such that shifts in financial assets or liabilities do not require a sharp current account adjustment. Still, it is found that Sudden Stops in Gross Inflows that do not provoke a sharp contraction in Net Flows may also be disruptive, including Sudden Stops that are driven by "other flows" -which include banking flows. The results suggest new avenues for research and future policy analysis.