Lower lobe lung volume reduction surgery: a case report.

Lung volume reduction surgery (LVRS) is an option for select patients with advanced chronic obstructive pulmonary disease (COPD). Current guidelines recommend LVRS for patients with appropriate physiology and heterogeneous distribution of emphysema predominately involving upper lobes. We present an unusual case of a 72-year-old male with an advanced COPD who suffered with recurrent exacerbations despite optimal medical management. He underwent a two-stage bilateral lower lobe LVRS for heterogeneous lower lobe emphysema via video-assisted thoracoscopic (VATS) approach. This resulted in a significant subjective as well as objective improvement in his pulmonary functions, 6-min walk distance and subsequent discontinuation of supplemental oxygen.

Recent advances in the regulation of the TOR pathway by insulin and nutrients.

PURPOSE OF REVIEW: The aim of this article is to summarize recent advances in the understanding of the regulation of the target of rapamycin (TOR), a protein kinase that is regulated independently by insulin, amino acids and energy sufficiency and which participates in the control of the component of protein synthesis responsible for cell growth. RECENT FINDINGS: These have been found in two major areas: genetic studies in Drosophila followed by studies in mammalian systems have identified the components of the Tuberous Sclerosis protein complex, a heterodimer of the proteins Hamartin and Tuberin, as inhibitors of TOR signaling, and as the major targets by which the insulin/IGF-1 signal transduction pathway, through the protein kinase PKB, and the energy status of the cell, through the AMP-activated protein kinase, regulate the TOR signaling. In turn, the inhibitory action of the tuberous sclerosis protein complex has been shown to be mediated by its ability to deactivate the small, ras-like GTPase Rheb. A second advance has been achieved by the identification of the TOR-associated protein raptor, as an indispensable substrate binding sub-unit of the TOR complex, and as the site at which the inhibitory effects on TOR signaling of rapamycin and amino acid deficiency converge. SUMMARY: These findings bring us closer to the understanding of how nutrients and insulin coordinate protein synthesis to regulate anabolic cell growth.

AMP-activated protein kinase is not down-regulated in human skeletal muscle of obese females.

Obesity in humans is associated with lipid accumulation in skeletal muscle, insulin and leptin resistance, and type 2 diabetes. AMP-activated protein kinase (AMPK) is an important regulator of fatty acid (FA) metabolism in skeletal muscle. To address the hypothesis that lipid accumulation in skeletal muscle of obese subjects may be due to down-regulation of AMPK, we measured mRNA and protein levels of AMPK isoforms, AMPKalpha1 and -alpha2 activity, AMPK kinase activity, acetyl-coenzyme A carboxylase (ACCbeta) expression and phosphorylation, and FA metabolism in biopsies of rectus abdominus muscle from lean and obese women. We also examined the effect of 5-aminoimidazole-4-carboxamide riboside (AICAR) on AMPK activity and the effects of AICAR and leptin on FA metabolism. Skeletal muscle of obese subjects had increased total FA uptake and triglyceride esterification, and leptin failed to stimulate FA oxidation. However, AMPK mRNA and protein expression, AMPKalpha1 and -alpha2 activities, AMPK kinase activity, ACCbeta phosphorylation, and FA oxidation were similar in lean and obese subjects. Moreover, AICAR increased AMPKalpha2 activity, ACCbeta phosphorylation, and palmitate oxidation to a similar degree in muscle from lean and obese subjects. We conclude that the abnormal lipid metabolism and leptin resistance of skeletal muscle of obese subjects is not due to down-regulation of AMPK. In addition, the similar stimulation by AICAR of AMPK in skeletal muscle of lean and obese subjects suggests that direct pharmacological activation of AMPK may be a therapeutic approach for stimulating FA oxidation in the treatment of human obesity.

Effect of exercise intensity on skeletal muscle AMPK signaling in humans.

The effect of exercise intensity on skeletal muscle AMP-activated protein kinase (AMPK) signaling and substrate metabolism was examined in eight men cycling for 20 min at each of three sequential intensities: low (40 +/- 2% VO(2) peak), medium (59 +/- 1% VO(2) peak), and high (79 +/- 1% VO(2) peak). Muscle free AMP/ATP ratio only increased at the two higher exercise intensities (P < 0.05). AMPK alpha 1 (1.5-fold) and AMPK alpha 2 (5-fold) activities increased from low to medium intensity, with AMPK alpha 2 activity increasing further from medium to high intensity. The upstream AMPK kinase activity was substantial at rest and only increased 50% with exercise, indicating that, initially, signaling through AMPK did not require AMPK kinase posttranslational modification. Acetyl-CoA carboxylase (ACC)-beta phosphorylation was sensitive to exercise, increasing threefold from rest to low intensity, whereas neuronal NO synthase (nNOS) micro phosphorylation was only observed at the higher exercise intensities. Glucose disappearance (tracer) did not increase from rest to low intensity, but increased sequentially from low to medium to high intensity. Calculated fat oxidation increased from rest to low intensity in parallel with ACC beta phosphorylation, then declined during high intensity. These results indicate that ACC beta phosphorylation is especially sensitive to exercise and tightly coupled to AMPK signaling and that AMPK activation does not depend on AMPK kinase activation during exercise.

AMPK beta subunit targets metabolic stress sensing to glycogen.

AMP-activated protein kinase (AMPK) is a multisubstrate enzyme activated by increases in AMP during metabolic stress caused by exercise, hypoxia, lack of cell nutrients, as well as hormones, including adiponectin and leptin. Furthermore, metformin and rosiglitazone, frontline drugs used for the treatment of type II diabetes, activate AMPK. Mammalian AMPK is an alphabetagamma heterotrimer with multiple isoforms of each subunit comprising alpha1, alpha2, beta1, beta2, gamma1, gamma2, and gamma3, which have varying tissue and subcellular expression. Mutations in the AMPK gamma subunit cause glycogen storage disease in humans, but the molecular relationship between glycogen and the AMPK/Snf1p kinase subfamily has not been apparent. We show that the AMPK beta subunit contains a functional glycogen binding domain (beta-GBD) that is most closely related to isoamylase domains found in glycogen and starch branching enzymes. Mutation of key glycogen binding residues, predicted by molecular modeling, completely abolished beta-GBD binding to glycogen. AMPK binds to glycogen but retains full activity. Overexpressed AMPK beta1 localized to specific mammalian subcellular structures that corresponded with the expression pattern of glycogen phosphorylase. Glycogen binding provides an architectural link between AMPK and a major cellular energy store and juxtaposes AMPK to glycogen bound phosphatases.