Alterations in the gut microbiota composition in the obesity phenotype of heart failure with preserved ejection fraction

Introduction

Obesity is one of the most common phenotypes of heart failure with preserved ejection fraction (HFpEF). A growing body of evidence indicates that obesity is characterized by compositional alterations in the intestinal microbiota and its metabolites, collectively referred as dysbiosis.

Purpose

We sought to investigate whether the obese phenotype of HFpEF is mediated by further alterations in the microbiota and whether gut dysbiosis fuels metabolic inflammation leading to progression of HFpEF.

Methods

HFpEF was induced in C57/black mice by high-fat diet and inhibition of NO synthesis (a “2-hit-model”) (Figure 1A). High-frequency echocardiography was performed to assess diastolic function. Blood pressure (BP) was measured using CODA non-invasive tail-cuff system. For human studies, patients with obese HFpEF as well as obese and non-obese healthy individuals were prospectively recruited. Gut microbial DNA was subjected to 16S ribosomal RNA gene sequencing, and the differences in abundance and composition of bacteria were defined both in humans and mice.

Results

In mice, the 2-hit model demonstrated significantly increased BP and impaired diastolic function in the obese HFpEF group (Figure 1B). Microbiome analysis showed significant differences in the gut microbial diversity and composition in the obese HFpEF compared to the non-HFpEF obese and chow-fed mice (Figure 1C). Similarly, human microbiome sequencing showed significant gut bacterial alterations in the diversity and composition of bacteria with more profound dysbiosis observed in the obese HFpEF patients compared to the obese and lean healthy individuals (Figure 1D).

Conclusions

We provide evidence in humans as well as in a murine animal model that the obese HFpEF phenotype is associated with more pronounced gut dysbiosis compared to the non-HFpEF obesity state. Further research will elucidate the causative link between gut dysbiosis and HFpEF manifestation and the mechanistic insights into the implication of gut microbiota in HFpEF progression.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Israel science foundation

A novel mechanotronic orthosis enables symmetrical gait kinematics in a patient with a femoral nerve palsy - a case study

The usage of stance- and swing-phase control orthoses (SSCOs) is a good option in patients with neuromuscular insufficiency of the quadriceps muscle in a broad range of musculo-skeletal disorders. The subjective sensation of improved mobility in daily life and walking comfort could be objectively confirmed by the ability to walk without crutches and by harmonization of the gait patterns in hip and knee. They could also be a considered mobility device after limb salvage surgery, which may even have an impact on preoperative decision making. IMPLICATIONS FOR REHABILITATION Symmetric gate in spite of femoral nerve palsy. Early gate improvements even after hours. High patient?s motivation to use the device.

Symptoms versus neurocognition as predictors of change in life skills in schizophrenia after outpatient rehabilitation

A growing body of literature has shown that neurocognitive deficits in schizophrenia account for 20-60% of the variance in measures of outcome, and in many studies are more closely related to outcome than symptoms [Green, M.F., Kern, R.S., Braff, D.L., Mintz, J., 2000. Neurocognitive deficits and functional outcome in schizophrenia: are we measuring the "right stuff"? Schizophr. Bull. 26(1), 119-136; Green, M.F., Kern, R.S., Heaton, R.K., 2004. Longitudinal studies of cognition and functional outcome in schizophrenia: implications for MATRICS. Schizophr. Res. 72(1), 41-51]. Most of these studies have been cross-sectional, few longitudinal studies have investigated the degree to which neurocognition and symptoms predict ability to benefit from outpatient rehabilitation, and no longitudinal studies use measures of everyday life skills that are performance-based. In the current study we investigated the relationship between five measures of neurocognitive function, crystallized verbal ability, visual sustained vigilance, verbal learning, problem-solving, and processing speed, and two measures of symptoms, total positive and negative symptoms, and change on a performance-based measure of everyday life skills after a year of outpatient rehabilitation. Rehabilitation consisted of both psychosocial and cognitive interventions. Forty-six patients with schizophrenia or schizoaffective disorder were studied. Results of a linear regression model revealed that verbal learning predicted a significant amount of the variance in change in performance-based measures of everyday life skills after outpatient rehabilitation, even when variance for all other variables in the model was accounted for. Measures of crystallized verbal ability, sustained visual vigilance, problem-solving, processing speed and symptoms were not linked to functional status change. These findings emphasize the importance of verbal learning for benefiting from psychosocial and cognitive rehabilitation interventions, and suggest the development of alternative rehabilitation strategies for those who do not benefit.

Differential regulation of peroxisome proliferator activated receptor gamma1 (PPARgamma1) and PPARgamma2 messenger RNA expression in the early stages of adipogenesis

Adipocyte differentiation is driven by the expression and activation of three transcription factor families: the differentially expressed CAAT/enhancer binding proteins (C/EBPs) alpha, beta, and delta; the helix-loop-helix adipocyte differentiation and determination factor-1; and peroxisome proliferator activated receptor gamma (PPARgamma), expressed as two isoforms, PPARgamma1 and the adipocyte-specific PPARgamma2. Overexpression of PPARgamma can induce adipocyte differentiation; therefore, we analyzed the expression of the two PPARgamma isoforms during early stages of differentiation to determine whether one was preferentially induced as an early determining event. Surprisingly, in the first 24 h, a 3-6-fold increase of PPARgamma2 mRNA was observed, whereas PPARgamma1 mRNA remained unchanged. PPARgamma1 was induced 1 day later. Overexpression of C/EBPbeta has also been shown to induce adipocyte differentiation. A C/EBP site was identified only in the human PPARgamma2 promoter. Its deletion blunted the response of PPARgamma2 promoter to cotransfected C/EBPbeta or methylisobutylxanthine treatment. We hypothesize that PPARgamma2 initiates adipocyte differentiation.

Skeletal muscle peroxisome proliferator- activated receptor-gamma expression in obesity and non- insulin-dependent diabetes mellitus

The two isoforms of peroxisome proliferator-activated receptor-gamma (PPARgamma1 and PPARgamma2), are ligand-activated transcription factors that are the intracellular targets of a new class of insulin sensitizing agents, the thiazolidinediones. The observation that thiazolidinediones enhance skeletal muscle insulin sensitivity in obesity and in patients with non-insulin-dependent diabetes mellitus (NIDDM), by activating PPARgamma, and possibly by inducing its expression, suggests that PPARgamma expression in skeletal muscle plays a key role in determining tissue sensitivity to insulin, and that PPARgamma expression may be decreased in insulin resistant subjects. We used a sensitive ribonuclease protection assay, that permits simultaneous measurement of the two isoforms, to examine the effects of obesity and NIDDM, and the effects of insulin, on skeletal muscle levels of PPARgamma1 and PPARgamma2 mRNA. We studied seven patients with NIDDM (body mass index, 32+/-1 kg/m2), seven lean (24+/-1 kg/m2), and six obese (36+/-1 kg/m2) normal subjects. Biopsies from the vastus lateralis muscle were taken before and after a 5-h hyperinsulinemic (80 mU/m2 per minute) euglycemic clamp. The obese controls and NIDDM patients were insulin resistant with glucose disposal rates during the last 30 min of the clamp that were 67 and 31%, respectively, of those found in the lean controls. PPARgamma1, but not PPARgamma2 mRNA was detected in skeletal muscle at 10-15% of the level found in adipose tissue. No difference was found in PPARgamma1 levels between the three groups, and there was no change in PPARgamma1 levels after 5 h of hyperinsulinemia. In obese subjects, PPARgamma1 correlated with clamp glucose disposal rates (r = 0.92, P < 0.01). In the lean and NIDDM patients, muscle PPARgamma1 levels correlated with percentage body fat (r = 0.76 and r = 0.82, respectively, both P < 0.05) but not with body mass index.

IN CONCLUSION

(a) skeletal muscle PPARgamma1 expression does not differ between normal and diabetic subjects, and is not induced by short-term hyperinsulinemia; (b) skeletal muscle PPARgamma1 expression was higher in subjects whose percent body fat exceeded 25%, and this may be a compensatory phenomenon in an attempt to maintain normal insulin sensitivity.

The mechanism of action of steroid hormones: a new twist to an old tale

Steroid hormones, vitamins, and thyroid hormone are potent chemical messengers that exert dramatic effects on cell differentiation, homeostasis, and morphogenesis. These molecules, though diverse in structure, share a mechanistically similar mode of action. The effector molecules diffuse across cellular membranes and bind to specific high affinity receptors in the target cell nuclei. This interaction results in the conversion of an inactive receptor to one that can interact with the regulatory regions of target genes and modulate the rate of transcription of specific gene sets. The recent cloning and characterization of the functional receptors for these hormones has been enlightening as to the individual steps involved in steroid signal transduction. In addition, emerging evidence suggests that receptor function can be influenced by cell and promoter context indicating that it may be possible to develop tissue specific or tissue-restricted drugs. The concept that a single receptor can modulate gene transcription in a cell-specific manner is of great medical and pharmaceutical importance. The focus of this review is to highlight the recent developments in the steroid receptor field and to illustrate the novel approaches been undertaken to identify novel pharmaceuticals.

Induction of human growth hormone promoter activity by the adenosine 3',5'-monophosphate pathway involves a novel responsive element

Regulation of GH gene expression by GRF involves cAMP as a second messenger. We have demonstrated that a 500-basepair fragment of the human GH (hGH) gene 5' flanking region can confer cAMP inducibility upon the chloramphenicol acetyltransferase transcription unit in transient transfections of rat pituitary tumor cells treated with forskolin, an activator of adenyl cyclase. The same hGH construct is not induced by forskolin in nonpituitary-derived cells. Experiments with hGH deletion constructs reveal that binding sites for transcription factor AP-2 and the pituitary-specific factor GHF-1 are not required for forskolin stimulation, but that GHF-1 may potentiate the effect. RNA analyses reveal that forskolin also stimulates accumulation of transcripts initiated at the hGH promoter. Other agents that elevate cAMP levels also stimulate hGH expression. Since the hGH 5' flanking region contains no sequences homologous to the cAMP-responsive element of the somatostatin gene, and the AP-2 sites do not appear to be required for the forskolin response, these results suggest that a novel cAMP-responsive element exists within 82 basepairs upstream from the transcriptional start of the hGH gene and that hGH regulation by GRF may involve interaction between a tissue-specific element and a cAMP-inducible element.

Extinction of growth hormone expression in somatic cell hybrids involves repression of the specific trans-activator GHF-1

Growth hormone (GH) expression in pituitary-derived cells has been attributed to the presence of a positive trans-activator, GHF-1, which binds to two sites on the GH promoter. Somatic cell hybridization of non-GH-expressing L cells with pituitary-derived GH3 cells usually results in extinction of GH production. While previous studies showed that extinction occurs at the level of GH transcription, the exact mechanism remained elusive. We therefore characterized two parental cell lines and three hybrids, two of which extinguish GH expression and one in which GH is reexpressed after loss of mouse chromosomal material. Using in vivo transfections, in vitro transcription, DNAase I footprints, and immunoblotting experiments, no evidence for a direct repressor of GH transcription was found. Rather, extinction of GH expression in fibroblast x pituitary hybrids was accompanied by loss of GHF-1 protein and mRNA expression, suggesting that extinction occurs by repression of this trans-activator.

Tissue-specific expression of the human growth hormone gene is conferred in part by the binding of a specific trans-acting factor

The molecular basis for the pituitary-specific expression of the human growth hormone (hGH) gene was investigated, by gene transfer and protein footprinting experiments. Plasmid constructs in which CAT or Neo transcription units are fused to a 0.5 kb fragment of the hGH 5' sequences were efficiently expressed in GC and GH3 cells, derived from a pituitary tumor, but not in cell lines of other origins, indicating the presence of a tissue-specific promoter. DNaseI footprinting experiments have identified at least three factors that specifically bind to the hGH 5' region. While two of these factors were also detected in extracts of non-expressing cells, the third factor, GHF-1, was detected only in extracts of GH expressing pituitary tumor cells. Mutagenesis experiments suggest that binding of GHF-1 and some of the other more ubiquitous factors is required for optimal hGH promoter activity in vivo. Tissue specificity of the hGH promoter therefore seems to be determined by the binding of at least one tissue-specific trans-acting factor, acting in concert with several other more ubiquitous, yet specific, DNA binding proteins.

Chromosomal localization of the human c-fms oncogene

A molecular probe was prepared with specificity for the human cellular homologue of transforming sequences represented within the McDonough strain of feline sarcoma virus (v-fms). By analysis of a series of mouse-human somatic cell hybrids containing variable complements of human chromosomes it was possible to assign this human oncogene, designated c-fms, to chromosome 5. Regional localization of c-fms to band q34 on chromosome 5 was accomplished by analysis of Chinese hamster-human cell hybrids containing as their only human components, terminal and interstitial deleted forms of chromosome 5. The localization of c-fms to chromosome 5 (q34) is of interest in view of reports of a specific, apparently interstitial, deletion involving approximately two thirds of the q arm of chromosome 5 in acute myelogenous leukemia cells.

Efficient procedure for transferring specific human genes into Chinese hamster cell mutants: interspecific transfer of the human genes encoding leucyl- and asparaginyl-tRNA synthetases

We have developed a simple and efficient procedure for transferring specific human genes into mutant Chinese hamster ovary cell recipients that does not rely on using calcium phosphate-precipitated high-molecular-weight DNA. Interspecific cell hybrids between human leukocytes and temperature-sensitive Chinese hamster cell mutants with either a thermolabile leucyl-tRNA synthetase or a thermolabile asparaginyl-tRNA synthetase were used as the starting material in these experiments. These hybrids contain only one or a few human chromosomes and require expression of the appropriate human aminoacyl-tRNA synthetase gene to grow at 39 degrees C. Hybrids were exposed to very high doses of gamma-irradiation to extensively fragment the chromosomes and re-fused immediately to the original temperature-sensitive Chinese hamster mutant, and secondary hybrids were isolated at 39 degrees C. Secondary hybrids, which had retained small fragments of the human genome containing the selected gene, were subjected to another round of irradiation, refusion, and selection at 39 degrees C to reduce the amount of human DNA even further. Using this procedure, we have constructed Chinese hamster cell lines that express the human genes encoding either asparaginyl- or leucyl-tRNA synthetase, yet less than 0.1% of their DNA is derived from the human genome, as quantitated by a sensitive dot-blot nucleic acid hybridization procedure. Analysis of these cell lines with Southern blots confirmed the presence of a small number of restriction endonuclease fragments containing human DNA specifically. These cell lines represent a convenient and simple means to clone the human genomic sequences of interest.

Selective linkage disruption in human-Chinese hamster cell hybrids: deletion mapping of the leuS, hexB, emtB, and chr genes on human chromosome 5

Chinese hamster-human interspecific hybrid cells, which contain human chromosome 5 and express four genes linked on that chromosome, were subjected to selective conditions requiring them to retain one of the four linked genes, leuS (encoding leucyl-tRNA synthetase), but lose another, either emtB (encoding ribosomal protein S14) or chr. Cytogenetic and biochemical analyses of spontaneous segregants isolated by using these unique selective pressures have enabled us to determine the order and regional location of the leuS, hexB, emtB, and chr genes on human chromosome 5. These segregants arise primarily by terminal deletions of various portions of the long arm of chromosome 5. Our results indicate that the order of at least three of these genes is the same on human chromosome 5 and Chinese hamster chromosome 2. Thus, there appears to be extensive homology between Chinese hamster chromosome 2 and human chromosome 5, which represents an extreme example of the conservation of gene organization between very divergent mammalian species. In addition, these hybrids and selective conditions provide a very simple and quantitative means to assess the potency of various agents suspected of inducing gross chromosomal damage.

Linkage of the leuS, emtB, and chr genes on chromosome 5 in humans and expression of human genes encoding protein synthetic components in human--Chinese hamster hybrids

We isolated interspecific hybrids between normal human leukocytes and a Chinese hamster ovary cell line that has mutations in three genes, leuS, emtB, and chr, all of which are linked to chromosome 2. The conditionally lethal mutation in the leuS gene in this cell line affects leucyl-tRNA synthetase and renders the cell line nonviable at 39 degrees C. The mutation in the emtB locus alters ribosomal protein S14 and results in the cell line being resistant to the protein synthesis inhibitor, emetine, while the mutation in the chr locus renders the cells resistant to sodium chromate. The interspecific hybrids were selected at 39 degrees C so that they were required to retain and express the human leuS gene. Ten out of ten such heat-resistant hybrids also expressed the human emtB and chr genes. Segregants selected as having lost the human emtB gene simultaneously lost the human chr and leuS genes as well. The linkage relationship between these three genes has thus been conserved during the evolution of the human and Chinese hamster genomes. All three genes were localized to human chromosome 5. Furthermore, our results indicate that the ribosomal protein product of the human emtB gene is incorporated into functional ribosomes in place of the human corresponding Chinese hamster protein, raising several interesting questions concerning the coordinate regulation of genes encoding ribosomal proteins in mammalian cells.

Transformation of mammalian cells with an amplifiable dominant-acting gene

We have transferred a mutant hamster gene coding for an altered dihydrofolate reductase to wild-type cultured mouse cells by using total genomic DNA from methotrexate-resistant Chinese hamster ovary A29 cells as donor. By demonstrating the presence of hamster gene sequences in transformants we have provided direct evidence for gene transfer. Transformants selected for increased resistance to methotrexate contain increased amounts of the newly transferred gene. We have used this mutant dhfr gene to introduce the Escherichia coli antibiotic resistance plasmid pBR322 into animal cells. Amplification of the dhfr sequences results in amplification of the pBR322 sequences as well. The use of this gene may allow the introduction and amplification of virtually any genetic element in various new cellular environments.