DAF-16/FoxO directly regulates an atypical AMP-activated protein kinase gamma isoform to mediate the effects of insulin/IGF-1 signaling on aging in Caenorhabditis elegans

The DAF-16/FoxO transcription factor controls growth, metabolism and aging in Caenorhabditis elegans. The large number of genes that it regulates has been an obstacle to understanding its function. However, recent analysis of transcript and chromatin profiling implies that DAF-16 regulates relatively few genes directly, and that many of these encode other regulatory proteins. We have investigated the regulation by DAF-16 of genes encoding the AMP-activated protein kinase (AMPK), which has ?, ? and ? subunits. C. elegans has 5 genes encoding putative AMP-binding regulatory ? subunits, aakg-1-5. aakg-4 and aakg-5 are closely related, atypical isoforms, with orthologs throughout the Chromadorea class of nematodes. We report that ?75% of total ? subunit mRNA encodes these 2 divergent isoforms, which lack consensus AMP-binding residues, suggesting AMP-independent kinase activity. DAF-16 directly activates expression of aakg-4, reduction of which suppresses longevity in daf-2 insulin/IGF-1 receptor mutants. This implies that an increase in the activity of AMPK containing the AAKG-4 ? subunit caused by direct activation by DAF-16 slows aging in daf-2 mutants. Knock down of aakg-4 expression caused a transient decrease in activation of expression in multiple DAF-16 target genes. This, taken together with previous evidence that AMPK promotes DAF-16 activity, implies the action of these two metabolic regulators in a positive feedback loop that accelerates the induction of DAF-16 target gene expression. The AMPK ? subunit, aakb-1, also proved to be up-regulated by DAF-16, but had no effect on lifespan. These findings reveal key features of the architecture of the gene-regulatory network centered on DAF-16, and raise the possibility that activation of AMP-independent AMPK in nutritionally replete daf-2 mutant adults slows aging in C. elegans. Evidence of activation of AMPK subunits in mammals suggests that such FoxO-AMPK interactions may be evolutionarily conserved

An RGS-Containing Sorting Nexin Controls Drosophila Lifespan

The pursuit of eternal youth has existed for centuries and recent data indicate that fat-storing tissues control lifespan. In a D. melanogaster fat body insertional mutagenic enhancer trap screen designed to isolate genes that control longevity, we identified a regulator of G protein signaling (RGS) domain containing sorting nexin, termed snazarus (sorting nexin lazarus, snz). Flies with insertions into the 5′ UTR of snz live up to twice as long as controls. Transgenic expression of UAS-Snz from the snz Gal4 enhancer trap insertion, active in fat metabolic tissues, rescued lifespan extension. Further, the lifespan extension of snz mutants was independent of endosymbiont, e.g., Wolbachia, effects. Notably, old snz mutant flies remain active and fertile indicating that snz mutants have prolonged youthfulness, a goal of aging research. Since mammals have snz-related genes, it is possible that the functions of the snz family may be conserved to humans

Growth and Cyclin-E Expression in the Stony Coral Species Orbicella faveolata Post-Microfragmentation

Coral growth is critical to reef health, resilience under rapidly changing environmental conditions, and restoration efforts. Although fragmenting coral has been occurring for many years in an effort to restore reefs, recently it was discovered that microfragmenting, the process of cutting one piece of coral into many small pieces (about three to five polyps), induces exponential growth. Our study investigates the process by which microfragments of nine different genotypes from the stony coral species Orbicella faveolata grow and exhibit Cyclin-E expression. Microfragments were examined by using a high-powered dissecting microscope with a camera to document the precise areas of tissue exhibiting exponential growth. We found that new polyp formation occurs only on the microfragment edges and that edge polyp growth rates varied between different genotypes. We then extracted tissue from both the edge and the center of five genotypes for genetic analysis. We chose to analyze Cyclin-E expression because it is involved with stimulating mitotic division and is a conserved signaling pathway that is known to exist in Drosophila, mammals, and Cnidaria. Two primers for Cyclin-E were utilized to examine the level of expression for center and edge tissue. We found that Cyclin-E is expressed differentially between O. faveolata polyps, with a tendency for increased expression of the Cyclin-E in edge versus center tissue in each of five genotypes, although this result was not significant. Despite consistently higher levels of Cyclin-E expression within an organism's edge tissue, genotypes varied significantly in the degree of increased expression. This variation positively correlated with growth rate, suggesting the potential for molecular selection in aid of more rapid reef restoration. Future work will focus on deciphering the specific growth pathways involved in microfragmented coral growth and analyzing expression patterns in injured tissues

Adenosine nucleotide biosynthesis and AMPK regulate adult life span and mediate the longevity benefit of caloric restriction in flies

A common thread among conserved life span regulators lies within intertwined roles in metabolism and energy homeostasis. We show that heterozygous mutations of AMP biosynthetic enzymes extend Drosophila life span. The life span benefit of these mutations depends upon increased AMP:ATP and ADP:ATP ratios and adenosine monophosphate-activated protein kinase (AMPK). Transgenic expression of AMPK in adult fat body or adult muscle, key metabolic tissues, extended life span, while AMPK RNAi reduced life span. Supplementing adenine, a substrate for AMP biosynthesis, to the diet of long-lived AMP biosynthesis mutants reversed life span extension. Remarkably, this simple change in diet also blocked the prolongevity effects of dietary restriction. These data establish AMP biosynthesis, adenosine nucleotide ratios, and AMPK as determinants of adult life span; provide a mechanistic link between cellular anabolism and energy sensing pathways; and indicate that dietary adenine manipulations might alter metabolism to influence animal life span.open

Wnt Signaling Activation in Adipose Progenitors Promotes Insulin-Independent Muscle Glucose Uptake

SummaryAdipose tissues provide circulating nutrients and hormones. We present in vivo mouse studies highlighting roles for Wnt signals in both aspects of metabolism. β-catenin activation in PPARγ-expressing fat progenitors (PBCA) decreased fat mass and induced fibrotic replacement of subcutaneous fat specifically. In spite of lipodystrophy, PBCA mice did not develop the expected diabetes and hepatosteatosis, but rather exhibited improved glucose metabolism and normal insulin sensitivity. Glucose uptake was increased in muscle independently of insulin, associated with cell-surface translocation of glucose transporters and AMPK activation. Ex vivo assays showed these effects were likely secondary to blood-borne signals since PBCA sera or conditioned media from PBCA fat progenitors enhanced glucose uptake and activated AMPK in muscle cultures. Thus, adipose progenitor Wnt activation dissociates lipodystrophy from dysfunctional metabolism and highlights a fat-muscle endocrine axis, which may represent a potential therapy to lower blood glucose and improve metabolism