Several lines of evidence support a mitochondrial dysfunction in major psychiatric disorders. The objective of this study was to determine whether mitochondrial DNA (mtDNA) expression or content are implicated in the mitochondrial dysfunction observed in schizophrenia (SCH), bipolar disorder (BD), and major depressive disorder (MDD). MtDNA gene expression and mtDNA content (including the MT-ND4 deletion) were measured by RT-qPCR and qPCR, respectively. Post-mortem brain tissue from 60 subjects, divided evenly into four diagnostic groups (SCH, BD, MDD, and control (C)), was analyzed. MT-ND1 gene expression was significantly increased in the BD group compared with the C group. MDD and SCH patients showed a similar pattern of mtDNA expression, which was different from that in BD patients. Similarly, a larger number of MDD and SCH patients tended to have the MT-ND4 gene deleted compared with BD and C subjects. However, no other significant differences were observed in mtDNA gene expression and mtDNA content. Notably, high variability was observed in the mtDNA gene expression and content in each diagnostic group. Previous studies and the present work provide evidence for a role of mtDNA in SCH, BD and MDD. However, further studies with larger patient and control groups as well as by analyzing distinct brain regions are needed to elucidate the role of mtDNA in major psychiatric disorders.

Obesity and its comorbidities are currently considered an epidemic, and the involved pathophysiology is well studied. Hypercaloric diets are tightly related to the obesity etiology and also cause alterations in gut microbiota functionality. Diet and antibiotics are known to play crucial roles in changes in the microbiota ecosystem and the disruption of its balance; therefore, the manipulation of gut microbiota may represent an accurate strategy to understand its relationship with obesity caused by diet. Fecal microbiota transplantation, during which fecal microbiota from a healthy donor is transplanted to an obese subject, has aroused interest as an effective approach for the treatment of obesity. To determine its success, a multiomics approach was used that combined metagenomics and metaproteomics to study microbiota composition and function. To do this, a study was performed in rats that evaluated the effect of a hypercaloric diet on the gut microbiota, and this was combined with antibiotic treatment to deplete the microbiota before fecal microbiota transplantation to verify its effects on gut microbiota-host homeostasis. Our results showed that a high-fat diet induces changes in microbiota biodiversity and alters its function in the host. Moreover, we found that antibiotics depleted the microbiota enough to reduce its bacterial content. Finally, we assessed the use of fecal microbiota transplantation as a complementary obesity therapy, and we found that it reversed the effects of antibiotics and reestablished the microbiota balance, which restored normal functioning and alleviated microbiota disruption. This new approach could be implemented to support the dietary and healthy habits recommended as a first option to maintain the homeostasis of the microbiota.

Clinical conditions commonly associated with mitochondrial disorders (CAMDs) are often present in autism spectrum disorders (ASD) and intellectual disability (ID). Therefore, the mitochondrial dysfunction hypothesis has been proposed as a transversal mechanism that may function in both disorders. Here, we investigated the presence of conditions associated with mitochondrial disorders and mitochondrial DNA (mtDNA) alterations in 122 subjects who presented ASD with ID (ASD group), 115 subjects who presented ID but not ASD (ID group) and 112 healthy controls (HC group). We assessed in the three study groups the presence of the clinical conditions through a questionnaire and the mtDNA content of two mitochondrial genes, MT-ND1 and MT-ND4, by qPCR. The mtDNA sequences of 98 ASD and 95 ID subjects were obtained by mtDNA-targeted next generation sequencing and analysed through the MToolBox pipeline to identify mtDNA mutations. Subjects with ASD and ID showed higher frequencies of constipation, edema, seizures, vision alterations, strabismus and sphincter incontinence than HCs subjects. ASD and ID subjects showed significantly lower mtDNA content than HCs in both MT-ND1 and MT-ND4 genes. In addition, we identified 49 putative pathogenic variants with a heteroplasmy level higher than 60%: 8 missense, 29 rRNA and 12 tRNA variants. A total of 28.6% of ASD and 30.5% of ID subjects carried at least one putative pathogenic mtDNA mutation. The high frequency of CAMDs, the low mtDNA content and the presence of putative pathogenic mtDNA mutations observed in both ASD and ID subjects are evidence of mitochondrial dysfunction in ASD and ID.

Over the last few years, the application of high-throughput meta-omics methods has provided great progress in improving the knowledge of the gut ecosystem and linking its biodiversity to host health conditions, offering complementary support to classical microbiology. Gut microbiota plays a crucial role in relevant diseases such as obesity or cardiovascular disease (CVD), and its regulation is closely influenced by several factors, such as dietary composition. In fact, polyphenol-rich diets are the most palatable treatment to prevent hypertension associated with CVD, although the polyphenol-microbiota interactions have not been completely elucidated. For this reason, the aim of this study was to evaluate microbiota effect in obese rats supplemented by hesperidin, after being fed with cafeteria or standard diet, using a multi meta-omics approaches combining strategy of metagenomics and metaproteomics analysis. We reported that cafeteria diet induces obesity, resulting in changes in the microbiota composition, which are related to functional alterations at proteome level. In addition, hesperidin supplementation alters microbiota diversity and also proteins involved in important metabolic pathways. Overall, going deeper into strategies to integrate omics sciences is necessary to understand the complex relationships between the host, gut microbiota, and diet.

Previous studies suggest that genetic factors could be involved in mitochondrial dysfunction observed in schizophrenia (SZ), some of them claiming a role of mtDNA common variants (mtSNPs) and/or haplogroups (hgs) in developing this disorder. These studies, however, have mainly been undertaken on relatively small cohorts of patients and control individuals and most have not yet been replicated. To further analyze the role of mtSNPs in SZ risk, we have carried out the largest genotyping effort to date using two Spanish case-control samples comprising a total of 942 schizophrenic patients and 1,231 unrelated controls: 454 patients and 616 controls from Santiago de Compostela (Galicia) and 488 patients and 615 controls from Reus (Catalonia). A set of 25 mtSNPs representing main branches of the European mtDNA phylogeny were genotyped in the Galician cohort and a subset of 16 out of these 25 mtSNPs was genotyped in the Catalan cohort. These 16 common variants characterize the most common European branches of the mtDNA phylogeny. We did not observe any positive association of mtSNPs and hgs with SZ. We discuss several deficiencies of previous studies that might explain the false positive nature of previous findings, including the confounding effect of population sub-structure and deficient statistical methodologies. It is unlikely that mtSNPs defining the most common European mtDNA haplogroups are related to SZ.

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It has been reported that certain genetic factors involved in schizophrenia could be located in the mitochondrial DNA (mtDNA). Therefore, we hypothesized that mtDNA mutations and/or variants would be present in schizophrenia patients and may be related to schizophrenia characteristics and mitochondrial function. This study was performed in three steps: (1) identification of pathogenic mutations and variants in 14 schizophrenia patients with an apparent maternal inheritance of the disease by sequencing the entire mtDNA; (2) case-control association study of 23 variants identified in step 1 (16 missense, 3 rRNA, and 4 tRNA variants) in 495 patients and 615 controls, and (3) analyses of the associated variants according to the clinical, psychopathological, and neuropsychological characteristics and according to the oxidative and enzymatic activities of the mitochondrial respiratory chain. We did not identify pathogenic mtDNA mutations in the 14 sequenced patients. Two known variants were nominally associated with schizophrenia and were further studied. The MT-RNR2 1811A > G variant likely does not play a major role in schizophrenia, as it was not associated with clinical, psychopathological, or neuropsychological variables, and the MT-ATP6 9110T > C p.Ile195Thr variant did not result in differences in the oxidative and enzymatic functions of the mitochondrial respiratory chain. The patients with apparent maternal inheritance of schizophrenia did not exhibit any mutations in their mtDNA. The variants nominally associated with schizophrenia in the present study were not related either to phenotypic characteristics or to mitochondrial function. We did not find evidence pointing to a role for mtDNA sequence variation in schizophrenia.