ABSTRACT
The insulin/IGF-like signalling (IIS) pathway has diverse functions in all multicellular organisms, including determination of lifespan. The seven insulin-like peptides (DILPs) in Drosophila are expressed in a stage- and tissue-specific manner. Partial ablation of the median neurosecretory cells (mNSCs) in the brain, which produce three DILPs, extends lifespan, reduces fecundity, alters lipid and carbohydrate metabolism and increases oxidative stress resistance. To determine if reduced expression of DILPs is causal in these effects, and to investigate possible functional diversification and redundancy between DILPs, we used RNA interference to lower specifically the transcript and protein levels of dilp2, the most highly expressed of the mNSC-derived DILPs. We found that DILP2 was limiting only for the increased whole-body trehalose content associated with mNSC-ablation. We observed a compensatory increase in dilp3 and 5 mRNA upon dilp2 knock down. By manipulation of dfoxo and dInR, we showed that the increase in dilp3 is regulated via autocrine insulin signaling in the mNSCs. Our study demonstrates that, despite the correlation between reduced dilp2 mRNA levels and lifespan-extension often observed, DILP2 reduction is not sufficient to extend lifespan. Nor is the increased trehalose storage associated with reduced IIS sufficient to extend lifespan. To understand the normal regulation of expression of the dilps and any functional diversification between them will require independent control of the expression of different dilps.
Subject(s)
Drosophila Proteins/metabolism , Drosophila/metabolism , Inhibitor of Apoptosis Proteins/metabolism , Longevity/genetics , Phenotype , Animals , Animals, Genetically Modified , Drosophila/genetics , Drosophila Proteins/genetics , Gene Expression Regulation , Glycogen/metabolism , Inhibitor of Apoptosis Proteins/genetics , Lipid Metabolism , Mutagenesis, Insertional , Oxidative Stress , RNA Interference , RNA, Messenger/metabolism , Signal Transduction , Trehalose/bloodABSTRACT
PURPOSE: An elevated frequency of the CCR5-Delta32 mutation in German patients with hepatitis C with viremia has been reported. The aim of the present study was to verify whether this mutation occurs in an Italian population with hepatitis C and whether it is an adverse host factor indicative of severity of liver disease and response to antiviral therapy. STUDY: The authors amplified 189-bp (wild-type) and 157-bp (Delta32 deletion) fragments of the CCR5 gene by polymerase chain reaction in 130 patients with chronic hepatitis C. Comparisons were drawn with 110 blood donors and 135 patients with primary biliary cirrhosis. RESULTS: Four (3.1%) patients with chronic hepatitis C and 1 blood donor (0.9%) were CCR5-Delta32 homozygous, whereas there was no CCR5-Delta32 homozygosity among primary biliary cirrhosis patients; the wild-type gene was present in a similar percentage in the 3 groups of patients without any significant difference (83.1% vs 90.4% vs 83.6%, respectively). Among the patients with chronic hepatitis C, no significant correlation was found between CCR5-Delta32 homozygosity and the following parameters: histologic grade/stage, hepatitis C virus genotype, viral load, serum aspartate aminotransferase, serum alanine aminotransferase, and serum gamma-glutamyltransferase. Ninety-five patients received a standard antiviral protocol with pegylated interferon (PEG Intron)+ribavirin; a sustained response was achieved in 59 patients (62.1%), and the remainder did not respond or experienced a relapse. Response to treatment was not influenced by CCR5-Delta32 deletion. CONCLUSION: No greater frequency of CCR5-Delta32 homozygosity was seen in an Italian population of patients with chronic hepatitis C. This mutation does not seem to influence either the overall severity of liver disease or the response to viral therapy.
