Reduced phosphorylation of brain insulin receptor substrate and Akt proteins in apolipoprotein-E4 targeted replacement mice

10.1038/srep03754Scientific Reports4

Regulatory RNAs and chromatin modification in dosage compensation: A continuous path from flies to humans?

Chromosomal sex determination is a widely distributed strategy in nature. In the most classic scenario, one sex is characterized by a homologue pair of sex chromosomes, while the other includes two morphologically and functionally distinct gonosomes. In mammalian diploid cells, the female is characterized by the presence of two identical X chromosomes, while the male features an XY pair, with the Y bearing the major genetic determinant of sex, i.e. the SRY gene. In other species, such as the fruitfly, sex is determined by the ratio of autosomes to X chromosomes. Regardless of the exact mechanism, however, all these animals would exhibit a sex-specific gene expression inequality, due to the different number of X chromosomes, a phenomenon inhibited by a series of genetic and epigenetic regulatory events described as "dosage compensation". Since adequate available data is currently restricted to worms, flies and mammals, while for other groups of animals, such as reptiles, fish and birds it is very limited, it is not yet clear whether this is an evolutionary conserved mechanism. However certain striking similarities have already been observed among evolutionary distant species, such as Drosophila melanogaster and Mus musculus. These mainly refer to a) the need for a counting mechanism, to determine the chromosomal content of the cell, i.e. the ratio of autosomes to gonosomes (a process well understood in flies, but still hypothesized in mammals), b) the implication of non-translated, sex-specific, regulatory RNAs (roX and Xist, respectively) as key elements in this process and the location of similar mediators in the Z chromosome of chicken c) the inclusion of a chromatin modification epigenetic final step, which ensures that gene expression remains stably regulated throughout the affected area of the gonosome. This review summarizes these points and proposes a possible role for comparative genetics, as they seem to constitute proof of maintained cell economy (by using the same basic regulatory elements in various different scenarios) throughout numerous centuries of evolutionary history

Sequentially appearing erythema nodosum, erythema multiforme and Henoch-Schönlein purpura in a patient with <it>Mycoplasma pneumoniae</it> infection: a case report

<p>Abstract</p> <p>Introduction</p> <p>A wide variety of skin manifestations are associated with <it>Mycoplasma pneumoniae</it> infection. However, the precise mechanisms by which <it>M. pneumoniae</it> infection is able to produce a variety of cutaneous manifestations are poorly understood.</p> <p>Case presentation</p> <p>An 8-year-old Japanese girl presented with sequential skin manifestations, including erythema nodosum, erythema multiforme and Henoch-Schönlein purpura. Although a chest radiograph showed no significant lung abnormalities, serological examinations revealed that these skin manifestations were associated with <it>M. pneumoniae</it> infection.</p> <p>Conclusion</p> <p>It has been reported that the variations in cutaneous manifestations of <it>M. pneumoniae</it> infection can be attributed to the immaturity of the adaptive immunity of a host. However, the case presented herein indicates that skin manifestations might not be specific for each individual. An awareness of the varied patterns of cutaneous disease is essential for the early diagnosis and treatment of patients with manifestations of <it>M. pneumoniae</it> infection.</p

Attenuated mTOR Signaling and Enhanced Autophagy in Adipocytes from Obese Patients with Type 2 Diabetes

Type 2 diabetes (T2D) is strongly linked to obesity and an adipose tissue unresponsive to insulin. The insulin resistance is due to defective insulin signaling, but details remain largely unknown. We examined insulin signaling in adipocytes from T2D patients, and contrary to findings in animal studies, we observed attenuation of insulin activation of mammalian target of rapamycin (mTOR) in complex with raptor (mTORC1). As a consequence, mTORC1 downstream effects were also affected in T2D: feedback signaling by insulin to signal-mediator insulin receptor substrate-1 (IRS1) was attenuated, mitochondria were impaired and autophagy was strongly upregulated. There was concomitant autophagic destruction of mitochondria and lipofuscin particles, and a dependence on autophagy for ATP production. Conversely, mitochondrial dysfunction attenuated insulin activation of mTORC1, enhanced autophagy and attenuated feedback to IRS1. The overactive autophagy was associated with large numbers of cytosolic lipid droplets, a subset with colocalization of perlipin and the autophagy protein LC3/atg8, which can contribute to excessive fatty acid release. Patients with diagnoses of T2D and overweight were consecutively recruited from elective surgery, whereas controls did not have T2D. Results were validated in a cohort of patients without diabetes who exhibited a wide range of insulin sensitivities. Because mitochondrial dysfunction, inflammation, endoplasmic-reticulum stress and hypoxia all inactivate mTORC1, our results may suggest a unifying mechanism for the pathogenesis of insulin resistance in T2D, although the underlying causes might differ