Regulation of Hepatic Follistatin Expression at Rest and during Exercise in Mice.

INTRODUCTION: Follistatin (FST) is a protein with numerous biological roles and was recently identified as an exercise-inducible hepatokine; however, the signals that regulate this are not well understood. The purpose of this study was to delineate potential endocrine factors that may regulate hepatic FST at rest and during exercise. METHODS: This study used four experiments. First, male and female C57BL/6J mice remained sedentary or were subjected to a single bout of exercise at moderate or exhaustive intensity with liver collected immediately post. Second, mice were injected with glucagon (1 mg·kg, 60 min), epinephrine (2 mg·kg, 30 min), glucagon then epinephrine, or saline. Third, mice were pretreated with propranolol (20-60 mg·kg, 30 min) before epinephrine injection. Fourth, glucagon receptor wild type (Gcgr) or knockout (Gcgr) mice were pretreated with saline or propranolol (20 mg·kg, 30 min) and were subjected to a single bout of exhaustive exercise with liver collected immediately post or after 2 h recovery. In all experiments liver FST mRNA expression was measured, and in experiment four FST protein content was measured. RESULTS: A single bout of treadmill exercise performed at an exhaustive but not moderate-intensity increased FST expression, as did injection of glucagon or epinephrine alone and when combined. Pretreatment of mice with propranolol attenuated the epinephrine-induced increase in FST expression. The exercise-induced increase in FST expression was attenuated in Gcgr mice, with no effect of propranolol. Gcgr mice had higher protein content of FST, but there was no effect of exercise or propranolol. CONCLUSIONS: These data suggest that both glucagon and epinephrine regulate hepatic FST expression at rest; however, only glucagon is required for the exercise-induced increase.

Glucagon receptor knockout mice are protected against acute olanzapine-induced hyperglycemia.

OBJECTIVES: To determine if glucagon is involved in mediating the increase in blood glucose levels caused by the second-generation antipsychotic drug olanzapine. MATERIALS AND METHODS: Whole body glucagon receptor deficient mice (Gcgr-/-) or WT littermate controls were injected with olanzapine (5mg/kg BW IP) and changes in blood glucose measured over the following 120min. Separate cohorts of mice were treated with olanzapine and changes in pyruvate tolerance, insulin tolerance and whole body substrate oxidation were determined. RESULTS: Olanzapine treatment increased serum glucagon and lead to rapid increases in blood glucose concentrations in WT mice. Gcgr-/- mice were protected against olanzapine-induced increases in blood glucose but this was not explained by differences in terminal serum insulin concentrations, enhanced AKT phosphorylation in skeletal muscle, adipose tissue or liver or differences in RER. In both genotypes olanzapine induced an equivalent degree of insulin resistance as measured using an insulin tolerance test. Olanzapine treatment led to an exaggerated glucose response to a pyruvate challenge in WT but not Gcgr-/- mice and this was paralleled by reductions in the protein content of PEPCK and G6Pase in livers from Gcgr-/- mice. CONCLUSIONS: Gcgr-/- mice are protected against olanzapine-induced increases in blood glucose. This is likely a result of reductions in liver glucose output, perhaps secondary to decreases in PEPCK and G6Pase protein content. Our findings highlight the central role of the liver in mediating olanzapine-induced disturbances in glucose homeostasis.

Imaging Neurons within Thick Brain Sections Using the Golgi-Cox Method.

The Golgi-Cox method of neuron staining has been employed for more than two hundred years to advance our understanding of neuron morphology within histological brain samples. While it is preferable from a practical perspective to prepare brain sections at the greatest thickness possible, in order to increase the probability of identifying stained neurons that are fully contained within single sections, this approach is limited from a technical perspective by the working distance of high-magnification microscope objectives. We report here a protocol to stain neurons using the Golgi-Cox method in mouse brain sections that are cut at 500 µm thickness, and to visualize neurons throughout the depth of these sections using an upright microscope fitted with a high-resolution 30X 1.05 N.A. silicone oil-immersion objective that has an 800 µm working distance. We also report two useful variants of this protocol that may be employed to counterstain the surface of mounted brain sections with the cresyl violet Nissl stain, or to freeze whole brains for long-term storage prior to sectioning and final processing. The main protocol and its two variants produce stained thick brain sections, throughout which full neuron dendritic trees and dendrite spines may be reliably visualized and quantified.

Voluntary wheel running attenuates lipopolysaccharide-induced liver inflammation in mice.

Sepsis induces an acute inflammatory response in the liver, which can lead to organ failure and death. Given the anti-inflammatory effects of exercise, we hypothesized that habitual physical activity could protect against acute sepsis-induced liver inflammation via mechanisms, including heat shock protein (HSP) 70/72. Male C57BL/6J mice (n = 80, ∼8 wk of age) engaged in physical activity via voluntary wheel running (VWR) or cage control (SED) for 10 wk. To induce sepsis, we injected (2 mg/kg ip) LPS or sterile saline (SAL), and liver was harvested 6 or 12 h later. VWR attenuated increases in body and epididymal adipose tissue mass, improved glucose tolerance, and increased liver protein content of PEPCK (P < 0.05). VWR attenuated increases in LPS-induced IL-6 signaling and mRNA expression of other inflammatory markers (TNF-α, chemokine C-C motif ligand 2, inducible nitric oxide synthase, IL-10, IL-1ß) in the liver; however, this was not reflected at the whole body level, as systemic markers of inflammation were similar between SED and VWR. Insulin tolerance was greater in VWR compared with SED at 6 but not 12 h after LPS. The protective effect of VWR occurred in parallel with increases in the liver protein content of HSP70/72, a molecular chaperone that can protect against inflammatory challenges. This study provides novel evidence that physical activity protects against the inflammatory cascade induced by LPS in the liver and that these effects may be mediated via HSP70/72.