Friedreich's ataxia (FRDA) is an autosomal recessive, degenerative disease that involves the central and peripheral nervous systems and the heart. A gene, X25, was identified in the critical region for the FRDA locus on chromosome 9q13. This gene encodes a 210-amino acid protein, frataxin, that has homologs in distant species such as Caenorhabditis elegans and yeast. A few FRDA patients were found to have point mutations in X25, but the majority were homozygous for an unstable GAA trinucleotide expansion in the first X25 intron.

Friedreich's ataxia is due to loss of function mutations in the gene encoding frataxin (FRDA). Frataxin is a protein of unknown function. In situ hybridization analyses revealed that mouse frataxin expression correlates well with the main site of neurodegeneration, but the expression pattern is broader than expected from the pathology of the disease. Frataxin mRNA is predominantly expressed in tissues with a high metabolic rate, including liver, kidney, brown fat and heart. We found that mouse and yeast frataxin homologues contain a potential mitochondrial targeting sequence in their N-terminal domains and that disruption of the yeast gene results in mitochondrial dysfunction. Finally, tagging experiments demonstrate that human frataxin co-localizes with a mitochondrial protein. Friedreich's ataxia is therefore a mitochondrial disease caused by a mutation in the nuclear genome.

SUMMARY Metabolic homeostasis is achieved by complex molecular and cellular networks that differ significantly among individuals and are difficult to model with genetically engineered lines of mice optimized to study single gene function. Here, we systematically acquired metabolic phenotypes by using the EUMODIC EMPReSS protocols across a large panel of isogenic but diverse strains of mice (BXD type) to study the genetic control of metabolism. We generated and analyzed 140 classical phenotypes and deposited these in an open-access web service for systems genetics (www.genenetwork.org). Heritability, influence of sex, and genetic modifiers of traits were examined singly and jointly by using quantitative-trait locus (QTL) and expression QTL-mapping methods. Traits and networks were linked to loci encompassing both known variants and novel candidate genes, including alkaline phosphatase (ALPL), here linked to hypophosphatasia. The assembled and curated phenotypes provide key resources and exemplars that can be used to dissect complex metabolic traits and disorders.

Friedreich ataxia (FRDA), the most common autosomal recessive ataxia, is caused in almost all cases by homozygous intronic expansions resulting in the loss of frataxin, a mitochondrial protein conserved through evolution, and involved in mitochondrial iron homeostasis. Yeast knockout models, and histological and biochemical data from patient heart biopsies or autopsies indicate that the frataxin defect causes a specific iron-sulfur protein deficiency and mitochondrial iron accumulation leading to the pathological changes. Affected human tissues are rarely available to further examine this hypothesis. To study the mechanism of the disease, we generated a mouse model by deletion of exon 4 leading to inactivation of the Frda gene product. We show that homozygous deletions cause embryonic lethality a few days after implantation, demonstrating an important role for frataxin during early development. These results suggest that the milder phenotype in humans is due to residual frataxin expression associated with the expansion mutations. Surprisingly, in the frataxin knockout mouse, no iron accumulation was observed during embryonic resorption, suggesting that cell death could be due to a mechanism independent of iron accumulation.

ObjectiveTo systematically review the effect of oral intake of bacterial probiotics on 15 variables related to obesity, diabetes and non-alcoholic fatty liver disease.DesignSystematic review and meta-analysis.Data sourcesMedline, EMBASE and COCHRANE from 1990 to June 2018.Eligibility criteriaRandomised controlled trials (≥14 days) excluding hypercholesterolaemia, alcoholic liver disease, polycystic ovary syndrome and children <3 years.ResultsOne hundred and five articles met inclusion criteria, representing 6826 subjects. In overweight but not obese subjects, probiotics induced improvements in: body weight (k=25 trials, d=−0.94 kg mean difference, 95% CI −1.17 to −0.70, I²=0.0%), body mass index (k=32, d=−0.55 kg/m², 95% CI −0.86 to −0.23, I²=91.9%), waist circumference (k=13, d=−1.31 cm, 95% CI −1.79 to −0.83, I²=14.5%), body fat mass (k=11, d=−0.96 kg, 95% CI −1.21 to −0.71, I²=0.0%) and visceral adipose tissue mass (k=5, d=−6.30 cm², 95% CI −9.05 to −3.56, I²=0.0%). In type 2 diabetics, probiotics reduced fasting glucose (k=19, d=−0.66 mmol/L, 95% CI −1.00 to −0.31, I²=27.7%), glycated haemoglobin (k=13, d=−0.28 pp, 95% CI −0.46 to −0.11, I²=54.1%), insulin (k=13, d=−1.66 mU/L, 95% CI −2.70 to −0.61, I²=37.8%) and homeostatic model of insulin resistance (k=10, d=−1.05 pp, 95% CI −1.48 to −0.61, I²=18.2%). In subjects with fatty liver diseases, probiotics reduced alanine (k=12, d=−10.2 U/L, 95% CI −14.3 to −6.0, I²=93.50%) and aspartate aminotransferases (k=10, d=−9.9 U/L, 95% CI −14.1 to -5.8, I²=96.1%). These improvements were mostly observed with bifidobacteria (Bifidobacterium breve, B. longum), Streptococcus salivarius subsp. thermophilus and lactobacilli (Lactobacillus acidophilus, L. casei, L. delbrueckii) containing mixtures and influenced by trials conducted in one country.ConclusionsThe intake of probiotics resulted in minor but consistent improvements in several metabolic risk factors in subjects with metabolic diseases.Trial registration numberCRD42016033273.

Peroxisome proliferator-activated receptor ␥ (PPAR␥) is a nuclear receptor, which controls adipocyte differentiation. We targeted with homologous recombination the PPAR␥2-specific exon B, resulting in a white adipose tissue knockdown of PPAR␥. Although homozygous (PPAR␥ hyp/hyp ) mice are born with similar weight as the WT mice, the PPAR␥ hyp/hyp animals become growth retarded and develop severe lipodystrophy and hyperlipidemia. Almost half of these PPAR␥ hyp/hyp mice die before adulthood, whereas the surviving PPAR␥ hyp/hyp animals overcome the growth retardation, yet remain lipodystrophic. In contrast to most lipodystrophic models, the adult PPAR␥ hyp/hyp mice only have mild glucose intolerance and do not have a fatty liver. These metabolic consequences of the lipodystrophy are relatively benign because of the induction of a compensatory gene expression program in the muscle that enables efficient oxidation of excess lipids. The PPAR␥ hyp/hyp mice unequivocally demonstrate that PPAR␥ is the master regulator of adipogenesis in vivo and establish that lipid and glucose homeostasis can be relatively well maintained in the absence of white adipose tissue.T he peroxisome proliferator-activated receptor ␥ (PPAR␥) is a nuclear receptor that acts as a lipid sensor, integrating the control of energy, lipid, and glucose homeostasis (1). The actions of PPAR␥ are mediated by two protein isoforms, the widely expressed PPAR␥1 and adipose tissue-restricted PPAR␥2 with an additional 28 aa in the NH 2 terminus (2-4). PPAR␥ is the master regulator of differentiation and energy storage by adipocytes (5-8). Despite undisputed arguments that support a pivotal role of PPAR␥ in adipocyte differentiation in vitro, the PPAR␥ field has been slowed by the absence of good animal models for PPAR␥ deficiency, because homozygous PPAR␥-deficient animals are embryonic lethal (8). This has had a restrictive impact on studies aimed at unraveling the pleiotropic roles of PPAR␥ in adult homeostasis. We therefore generated, by homologous recombination, mice that carry a hypomorphic mutation at the PPAR␥2 locus and characterized the molecular and metabolic phenotype of these mice. MethodsHomologous Recombination. The main features of our targeting strategy are shown in Fig. 1A. The loxP sites were inserted in reverse orientation at position Ϫ45 of the PPAR␥2 gene, 445 bp downstream of the exon B splice site and at the 3Ј end of the frt-PGKneo-frt cassette. The Pro-12-Ala mutation that was introduced in the B exon was flanked by an EcoRI site. Chimeric animals were generated from two independently targeted embryonic stem (ES) cell clones (nos. 84 and 73). Heterozygous animals, derived from the two ES cell clones, were backcrossed for seven generations to mice with either a SV129 or a C5S7BL͞6J background and then intercrossed to generate PPAR␥ hyp/hyp mice for analysis. The Pro-12-Ala knock-in PPAR␥ Ala12Ala animals were generated by intercrossing PPAR␥ hyp/hyp mice with mice that expressed the FLP recombinase under the control of a cytomegalovirus ...

In a systematic search for peroxisome proliferatoractivated receptor-␥ (PPAR-␥) target genes, we identified S3-12 and perilipin as novel direct PPAR-␥ target genes. Together with adipophilin and tail-interacting protein of 47 kDa, these genes are lipid droplet-associating proteins with distinct expression pattern but overlapping expression in adipose tissue. The expression of S3-12 and perilipin is tightly correlated to the expression and activation of PPAR-␥ in adipocytes, and promoter characterization revealed that the S3-12 and the perilipin promoters contain three and one evolutionarily conserved PPAR response elements, respectively. We furthermore demonstrate that the expression of S3-12 and perilipin is reduced in obese compared with lean Zucker rats, whereas the expression of adipophilin is increased. Others have shown that perilipin is an essential factor in the hormonal regulation of lipolysis of stored triglycerides within adipose tissue. The direct regulation of perilipin and S3-12 by PPAR-␥ therefore is likely to be an important mediator of the in vivo effects of prolonged treatment with PPAR-␥ activators: insulin sensitization, fatty acid trapping in adipose tissue, reduced basal adipose lipolysis, and weight gain. Diabetes 53:1243-1252, 2004 T oday's western lifestyle, which involves a highcalorie diet and a lack of exercise, has led to an epidemic of obesity, which often is associated with type 2 diabetes, hypertension, hyperlipidemia, and cardiovascular disease. Increased energy intake results in an imbalance between fat synthesis and degradation, leading to an increase in circulating fatty acids (FAs) and accumulation of lipids in white adipose tissue (WAT). Whereas most tissues store triacylglycerol (TAG), cholesterol esters (CEs), or lipids in relatively small (Ͻ1 m diameter) droplets that can be used as an energy source or for membrane biogenesis, WAT stores most of the body's TAG reservoir in droplets that can exceed 50 m in diameter (1). Although the interior of those lipid droplets consists largely of neutral lipids, a number of proteins associate with the droplet surface. These include P 200 , caveolins, vimentin (1,2), mouse adipose differentiation-related protein (ADRP)/human adipophilin (hereafter referred to as adipophilin) (3), perilipin (4,5), S3-12 (6), and tail-interacting protein of 47 kDa (TIP-47) (7).Perilipin, adipophilin, and TIP-47 exhibit high sequence identity within an NH 2 -terminal motif termed PAT-1 (after perilipin, adipophilin, and TIP-47) and a more distally located PAT-2 domain (8,9). A fourth protein, S3-12, has been described along with these PAT family members. S3-12 contains a repeated 33-amino acid motif also found in adipophilin (10), and it shares protein sequence identity to both adipophilin and TIP-47 in the COOH terminus, but not to perilipin (8).At present, the lipid droplet-associating properties have been thoroughly studied only for adipophilin and perilipin (11,12). Adipophilin associates with smaller neutral lipid storage droplets located within most...

Parkinson's disease (PD) is a severe neurological disorder, characterized by the progressive degeneration of the dopaminergic nigrostriatal pathway and the presence of Lewy bodies (LBs). The discovery of genes responsible for familial forms of the disease has provided insights into its pathogenesis. Mutations in the parkin gene, which encodes an E3 ubiquitin-protein ligase involved in the ubiquitylation and proteasomal degradation of specific protein substrates, have been found in nearly 50% of patients with autosomal-recessive early-onset parkinsonism. The abnormal accumulation of substrates due to loss of Parkin function may be the cause of neurodegeneration in parkin-related parkinsonism. Here, we demonstrate that Parkin interacts with, ubiquitylates and promotes the degradation of p38, a key structural component of the mammalian aminoacyl-tRNA synthetase complex. We found that the ubiquitylation of p38 is abrogated by truncated variants of Parkin lacking essential functional domains, but not by the pathogenic Lys161Asn point mutant. Expression of p38 in COS7 cells resulted in the formation of aggresome-like inclusions in which Parkin was systematically sequestered. In the human dopaminergic neuroblastoma-derived SH-SY5Y cell line, Parkin promoted the formation of ubiquitylated p38-positive inclusions. Moreover, the overexpression of p38 in SH-SY5Y cells caused significant cell death against which Parkin provided protection. Analysis of p38 expression in the human adult midbrain revealed strong immunoreactivity in normal dopaminergic neurons and the labeling of LBs in idiopathic PD. This suggests that p38 plays a role in the pathogenesis of PD, opening the way for a detailed examination of its potential non-canonical role in neurodegeneration.