ATM deficiency differentially affects expression of proteins related to fatty acid oxidation and oxidative stress in a sex-specific manner in response to Western-type diet prior to and following myocardial infarction.

AIMS: Published work has shown that ataxia-telangiectasia mutated kinase (ATM) deficiency is associated with cardioprotective effects in Western-type diet (WD)-fed female mice. This study assessed the expression of proteins related to fatty acid oxidation (FAO) and oxidative stress in WD-fed male and female mouse hearts, and investigated if sex-specific cardioprotective effects in WD-fed female ATM-deficient mice are maintained following myocardial infarction (MI). MAIN METHODS: Wild-type (WT) and ATM-deficient (hKO) mice (both sexes) were placed on WD for 14 weeks. Myocardial tissue from a subset of mice was used for western blot analyses, while another subset of WD-fed mice underwent MI. Heart function was analyzed by echocardiography prior to and 1 day post-MI. KEY FINDINGS: CPT1B (mitochondrial FAO enzyme) expression was lower in male hKO-WD, while it was higher in female hKO-WD vs WT-WD. WD-mediated decrease in ACOX1 (peroxisomal FAO enzyme) expression was only observed in male WT-WD. PMP70 (transports fatty acyl-CoA across peroxisomal membrane) expression was lower in male hKO-WD vs WT-WD. Catalase (antioxidant enzyme) expression was higher, while Nox4 (pro-oxidant enzyme) expression was lower in female hKO-WD vs WT-WD. Heart function was better in female hKO-WD vs WT-WD. However, post-MI heart function was not significantly different among all MI groups. Post-MI, CPT1B and catalase expression was higher in male hKO-WD-MI vs WT-WD-MI, while Nox4 expression was higher in female hKO-WD-MI vs WT-WD-MI. SIGNIFICANCE: Increased mitochondrial FAO and decreased oxidative stress contribute towards ATM deficiency-mediated cardioprotective effects in WD-fed female mice which are abolished post-MI with increased Nox4 expression.

Deficiency of ataxia-telangiectasia mutated kinase attenuates Western-type diet-induced cardiac dysfunction in female mice.

Chronic consumption of Western-type diet (WD) induces cardiac structural and functional abnormalities. Previously, we have shown that WD consumption in male ATM (ataxia-telangiectasia mutated kinase) deficient mice associates with accelerated body weight (BW) gain, cardiac systolic dysfunction with increased preload, and exacerbation of hypertrophy, apoptosis, and inflammation. This study investigated the role of ATM deficiency in WD-induced changes in functional and biochemical parameters of the heart in female mice. Six-week-old wild-type (WT) and ATM heterozygous knockout (hKO) female mice were placed on WD or NC (normal chow) for 14 weeks. BW gain, fat accumulation, and cardiac functional and biochemical parameters were measured 14 weeks post-WD. WD-induced subcutaneous and total fat contents normalized to body weight were higher in WT-WD versus hKO-WD. Heart function measured using echocardiography revealed decreased percent fractional shortening and ejection fraction, and increased LV end systolic diameter and volume in WT-WD versus WT-NC. These functional parameters remained unchanged in hKO-WD versus hKO-NC. Myocardial fibrosis, myocyte hypertrophy, and apoptosis were higher in WT-WD versus WT-NC. However, apoptosis was significantly lower and hypertrophy was significantly higher in hKO-WD versus WT-WD. MMP-9 and Bax expression, and Akt activation were higher in WT-WD versus WT-NC. PARP-1 (full-length) expression and mTOR activation were lower in WT-WD versus hKO-WD. Thus, ATM deficiency in female mice attenuates fat weight gain, preserves heart function, and associates with decreased cardiac cell apoptosis in response to WD.

Deficiency of ataxia-telangiectasia mutated kinase modulates functional and biochemical parameters of the heart in response to Western-type diet.

Ataxia-telangiectasia mutated (ATM) kinase deficiency exacerbates heart dysfunction late after myocardial infarction. Here, we hypothesized that ATM deficiency modulates Western-type diet (WD)-induced cardiac remodeling with an emphasis on functional and biochemical parameters of the heart. Weight gain was assessed in male wild-type (WT) and ATM heterozygous knockout (hKO) mice on weekly basis, whereas cardiac functional and biochemical parameters were measured 14 wk post-WD. hKO-WD mice exhibited rapid body weight gain at weeks 5, 6, 7, 8, and 10 versus WT-WD. WD decreased percent fractional shortening and ejection fraction, and increased end-systolic volumes and diameters to a similar extent in both genotypes. However, WD decreased stroke volume, cardiac output, peak velocity of early ventricular filling, and aortic ejection time and increased isovolumetric relaxation time (IVRT) and Tei index versus WT-NC (normal chow). Conversely, IVRT, isovolumetric contraction time, and Tei index were lower in hKO-WD versus hKO-NC and WT-WD. Myocyte apoptosis and hypertrophy were higher in hKO-WD versus WT-WD. WD increased fibrosis and expression of collagen-1α1, matrix metalloproteinase (MMP)-2, and MMP-9 in WT. WD enhanced AMPK activation, while decreasing mTOR activation in hKO. Akt and IKK-α/ß activation, and Bax, PARP-1, and Glut-4 expression were higher in WT-WD versus WT-NC, whereas NF-κB activation and Glut-4 expression were lower in hKO-WD versus hKO-NC. Circulating concentrations of IL-12(p70), eotaxin, IFN-γ, macrophage inflammatory protein (MIP)-1α, and MIP-1ß were higher in hKO-WD versus WT-WD. Thus, ATM deficiency accelerates weight gain, induces systolic dysfunction with increased preload, and associates with increased apoptosis, hypertrophy, and inflammation in response to WD.NEW & NOTEWORTHY Ataxia-telangiectasia mutated (ATM) kinase deficiency in humans associates with enhanced susceptibility to ischemic heart disease. Here, we provide evidence that ATM deficiency accelerates body weight gain and associates with increased cardiac preload, hypertrophy, and apoptosis in mice fed with Western-type diet (WD). Further investigations of the role of ATM deficiency in WD-induced alterations in function and biochemical parameters of the heart may provide clinically applicable information on treatment and/or nutritional counseling for patients with ATM deficiency.

Unusual augmentation of germline genome size in Cyclops kolensis (Crustacea, Copepoda): further evidence in support of a revised model of chromatin diminution.

Embryonic chromatin diminution, the selective excision of large amounts of heterochromatic DNA from presomatic cell lineages, provides an example of an unusually large augmentation of the germline genome and raises questions regarding the source of the increased amount of DNA and its relevance to the biology of the organism. DNA levels in adult germ cell nuclei of the copepod Cyclops kolensis were determined by DNA-Feulgen cytophotometry and compared with those of somatic nuclei of adults and both pre- and postdiminuted embryos from the same mothers. Almost 75 pg DNA/nucleus is excised by diminution, resulting in the return of each generation to the approximately 1 pg DNA/nucleus level found for adult soma. To account for the increase in DNA levels of germ cells observed here, we propose alternative hypotheses to the original model of chromatin diminution: (1) repetitive endocycles or (2) proliferation of genetic elements. Specific tests for these hypotheses using next-generation sequencing and quantitative cytophotometry, as well as the functional significance of germ cell DNA augmentation to the copepod, are discussed.

Heterochromatin endoreduplication prior to gametogenesis and chromatin diminution during early embryogenesis in Mesocyclops edax (Copepoda: Crustacea).

The segregation of progenitor somatic cells from those of the primordial germ cells that sequester and retain elevated levels of DNA during subsequent developmental events, poses an interesting, alternative pathway of chromosome behavior during the reproductive cycle of certain species of cyclopoid copepods and several other organisms. Separation of maternal and paternal chromosome sets during very early cleavages (gonomery) is often a feature following marked elevations of DNA levels in germ cells for some of these species. Here, we report on the accumulation of large amounts of DNA in germ line nuclei of both female and male juveniles and adults of a freshwater copepod, Mesocyclops edax (Forbes, 1890). We also report the robust uptake of 3H-thymidine by germ cells prior to gametogenesis in this species. By using cytophotometric analysis of the DNA levels in both germ line cells and somatic cells from the same specimens we demonstrate that germ cell nuclei accumulate high levels of DNA prior to the onset of gametogenesis. These elevated amounts coincide with the levels of heterochromatic DNA discarded during chromatin diminution. A new model is proposed of major cytological events accompanying the process of chromatin diminution in M. edax.

Genome size and endonuclear DNA replication in spiders.

Although genome sizes (C-values) are now available for 115 arachnid species (Gregory and Shorthouse [2003] J Hered 94:285-290), the extent of genome amplification (endonuclear DNA replication or polyploidization) accompanying tissue differentiation in this diverse and abundant class of invertebrates remains unknown. To explore this aspect of arachnid development, samples of hemolymph and other tissues were taken from wild-caught specimens as air-dried smears, stained with the Feulgen reaction for DNA, and assayed using both scanning and image analysis densitometry. Cells from midgut diverticula and Malpighian tubules of Argiope and Lycosa (=Pardosa) often showed giant nuclei with 50-100 pg of DNA per nucleus, reflecting at least four cycles of endonuclear DNA replication when compared to the DNA content of hemocytes or sperm from the same specimen. Nuclei with markedly elevated DNA levels also appeared, but far less frequently, in tissue samples from several other arachnid species (Antrodiaetus, Hypochilus, Latrodectus, Liphistus and Loxosceles), but revealed no correlation with differences in somatic cell (2C) genome sizes. Our data show that several DNA classes of polysomatic nuclei regularly arise during tissue differentiation in some species of spiders and may provide an interesting model system for further study of patterns of tissue-specific variation in DNA endoreduplication during development.