Paternal obesity induces metabolic and sperm disturbances in male offspring that are exacerbated by their exposure to an "obesogenic" diet

 Un membre de la Garde civile espagnole sur la frontière entre l'Espagne et le Maroc à Melilla, le 17 octobre 2013. (Photo Pierre-Philippe Marcou. AFP) Un Africain est mort mardi en escaladant le triple grillage qui entoure l'enclave espagnole au Maroc. Une centaine de ses compagnons a réussi à passer en Europe. " Ultracontroversée depuis déjà une bonne dizaine d’années, le triple grillage qui sert de frontière entre le Maroc et Melilla, petite enclave espagnole du nord de l’Afrique, suscite..

Paternal obesity induces metabolic and sperm disturbances in male offspring that are exacerbated by their exposure to an "obesogenic" diet

Obesity and related comorbidities are becoming increasingly prevalent globally. In mice preconception paternal exposure to a high fat diet (HFD) impairs the metabolic and reproductive health of male offspring, despite their control diet (CD) consumption. However, offspring share lifestyle, including diet, with parents. We assessed if male offspring from HFD fathers have a heightened susceptibility to HFD-induced metabolic and reproductive derangements. This 2 × 2 design saw founder males (F0) and their offspring (F1) fed either a HFD or a nutritionally matched CD. Regardless of paternal diet, HFD fed male offspring had greater total body weight and adiposity. Offspring sired by a HFD male and fed a HFD were the heaviest, had the greatest adiposity and had the greatest concentration of serum cholesterol, triglyceride, HDL, and NEFA compared with CD sired/fed littermates. A synergistic increase in serum insulin was unmasked by both father/son HFD consumption, concomitant with increased sera glucose. Either a paternal or offspring HFD was associated with similar reductions to offspring sperm motility. Whereas sperm ROS concentrations and sperm-oocyte binding saw detrimental effects of both F0 HFD and F1 HFD with an interaction evident between both, culminating in the most impaired sperm parameters in this group. This indicates that metabolic and fertility disturbances in male offspring sired by HFD fathers are exacerbated by a "second-hit" of exposure to the same obesogenic environment postnatally. If translatable to human health, this suggests that adverse reproductive and metabolic outcomes may be amplified across generations through a shared calorie dense diet, relevant to the current worldwide obesity epidemic.Tod Fullston, Nicole O. McPherson, Julie A. Owens, Wan Xian Kang, Lauren Y. Sandeman & Michlle Lan

Paternal under-nutrition programs metabolic syndrome in offspring which can be reversed by antioxidant/vitamin food fortification in fathers

There is an ever increasing body of evidence that demonstrates that paternal over-nutrition prior to conception programs impaired metabolic health in offspring. Here we examined whether paternal under-nutrition can also program impaired health in offspring and if any detrimental health outcomes in offspring could be prevented by micronutrient supplementation (vitamins and antioxidants). We discovered that restricting the food intake of male rodents reduced their body weight, fertility, increased sperm oxidative DNA lesions and reduced global sperm methylation. Under-nourished males then sired offspring with reduced postnatal weight and growth but somewhat paradoxically increased adiposity and dyslipidaemia, despite being fed standard chow. Paternal vitamin/antioxidant food fortification during under-nutrition not only normalised founder oxidative sperm DNA lesions but also prevented early growth restriction, fat accumulation and dyslipidaemia in offspring. This demonstrates that paternal under-nutrition reduces postnatal growth but increases the risk of obesity and metabolic disease in the next generation and that micronutrient supplementation during this period of under-nutrition is capable of restoring offspring metabolic health

Obese father's metabolic state, adiposity, and reproductive capacity indicate son's reproductive health

ObjectiveTo determine whether dietary and exercise regimes in obese males can provide a novel intervention window for improving the reproductive health of the next generation.DesignExperimental animal study.SettingUniversity research facilities.Animal(s)C57BL6 male and female mice.Intervention(s)Mice were fed a control diet (6% fat) or high-fat diet (21% fat) for 9 weeks. After the initial feeding, high-fat-diet males were allocated to diet and/or exercise interventions for a further 9 weeks. After intervention males were mated with females fed standard chow (4% fat) before and during pregnancy.Main outcome measure(s)F1 sperm motility, count, morphology, capacitation, mitochondrial function, and sperm binding and weight of reproductive organs.Result(s)Our primary finding was that diet intervention alone in founders improved offspring sperm motility and mitochondrial markers of sperm health (decreased reactive oxygen species and mitochondrial membrane potential), ultimately improving sperm binding. Sperm binding and capacitation was also improved in F1 males born to a combined diet and exercise intervention in founders. Founder sperm parameters and metabolic measures as a response to diet and/or exercise (i.e., lipid/glucose homeostasis, sperm count and morphology) correlated with offspring's sperm function, independent of founder treatment. This implicates paternal metabolic and reproductive status in predicting male offspring's reproductive function.Conclusion(s)This is the first study to show that improvements to both metabolic (lipids, glucose and insulin sensitivity) and reproductive function (sperm motility and morphology) in obese fathers via diet and exercise interventions can improve subsequent reproductive health in offspring.Nicole O. McPherson, Tod Fullston, Hassan W. Bakos, Brian P. Setchell and Michelle Lan

Mutations in the nuclear localization sequence of the Aristaless related homeobox; sequestration of mutant ARX with IPO13 disrupts normal subcellular distribution of the transcription factor and retards cell division

The electronic version of this article is the complete one and can be found online at: http://www.pathogeneticsjournal.com/content/3/1/1Background: Aristaless related homeobox (ARX) is a paired-type homeobox gene. ARX function is frequently affected by naturally occurring mutations. Nonsense mutations, polyalanine tract expansions and missense mutations in ARX cause a range of intellectual disability and epilepsy phenotypes with or without additional features including hand dystonia, lissencephaly, autism or dysarthria. Severe malformation phenotypes, such as X-linked lissencephaly with ambiguous genitalia (XLAG), are frequently observed in individuals with protein truncating or missense mutations clustered in the highly conserved paired-type homeodomain. Results: We have identified two novel point mutations in the R379 residue of the ARX homeodomain; c.1135C>A, p.R379S in a patient with infantile spasms and intellectual disability and c.1136G>T, p.R379L in a patient with XLAG. We investigated these and other missense mutations (R332P, R332H, R332C, T333N: associated with XLAG and Proud syndrome) predicted to affect the nuclear localisation sequences (NLS) flanking either end of the ARX homeodomain. The NLS regions are required for correct nuclear import facilitated by Importin 13 (IPO13). We demonstrate that missense mutations in either the N- or C-terminal NLS regions of the homeodomain cause significant disruption to nuclear localisation of the ARX protein in vitro. Surprisingly, none of these mutations abolished the binding of ARX to IPO13. This was confirmed by co-immunoprecipitation and immmuno fluorescence studies. Instead, tagged and endogenous IPO13 remained bound to the mutant ARX proteins, even in the RanGTP rich nuclear environment. We also identify the microtubule protein TUBA1A as a novel interacting protein for ARX and show cells expressing mutant ARX protein accumulate in mitosis, indicating normal cell division may be disrupted. Conclusions: We show that the most likely, common pathogenic mechanism of the missense mutations in NLS regions of the ARX homeodomain is inadequate accumulation and distribution of the ARX transcription factor within the nucleus due to sequestration of ARX with IPO13.Cheryl Shoubridge, May Huey Tan, Tod Fullston, Desiree Cloosterman, David Coman, George McGillivray, Grazia M Mancini, Tjitske Kleefstra and Jozef Géc

The role of Aristaless related homeobox (ARX) gene mutations in intellectual disability.

Intellectual disability (ID) affects ~1-3% of the population, profoundly impacting the lives of affected individuals and their families. An approximate 30% excess of males with ID implicates X-chromosome genes. The most common inherited form of ID is fragile-X syndrome, affecting ~1/5,000 live male births. Another X-linked gene, the aristaless related homeobox (ARX) gene, is also frequently mutated causing X-linked ID (XLID). At least 50 pathogenic mutations spanning the ARX open reading frame (ORF) have been reported in 110 families. These mutations cause at least 10 clinically distinct pathologies, all of which include ID. These clinical entities range in severity from X-linked lissencephaly with ambiguous genitalia (XLAG) to mild ID with no other consistent clinical features. Of the known ARX mutations 60% occur in the section of the ORF that encodes for the first two tracts of uninterrupted alanine, ie polyalanine (pA) tracts. This is likely due to the extraordinarily high GC content of these regions of the gene (>97%). Two recurrent mutations (c.304ins(GCG)₇ – pA1 and c.429_452dup – pA2) arise from expansion of their respective pA tracts. The c.429_452dup mutation alone accounts for ~40% of all reported ARX mutations. To assess the frequency of ARX mutations among the intellectually disabled, genomic DNA from 613 individuals were screened for the most frequent ARX mutations. Of these, 500/613 samples were screened for mutations in the entire ARX ORF by either SSCP, dHPLC or direct Sanger sequencing. A subset of 94/500 patients were also screened for sequence variations in ultraconserved (uc) elements flanking the ARX gene, which likely act as ARX enhancers. Subsequently, using transient transfection studies we assessed the subcellular localisation of selected mutations and wildtype ARX proteins. Six different ARX mutations were detected in eight individuals (8/613; 1.3%) and potentially pathogenic sequence variations were found in uc elements in three more individuals. A total of five duplication mutations were discovered in pA2, two larger than the recurrent c.429_452dup, confirming exon 2 of ARX as a mutation ‘hot spot’. Increased aggregation was observed as a function of pA1 and pA2 length, aligning with the patient’s phenotypic severity. Three missense mutations were detected. A familial c.81G>C mutation caused a premature termination codon in exon 1, leading to Ohtahara syndrome (OS) and West syndrome (WS) in two male cousins. Although the c.81G>C mutation should truncate the ARX protein, reinitiation of translation at a down-stream methionine codon (c.121_123) likely occurs, ‘rescuing’ these patients from the otherwise severe XLAG phenotype. Two point mutations (c.1074G>T/p.R358S; c.1136G>T/ p.R379L) that alter key residues within the homeodomain were found in two individuals with brain/genital malformations and led to increased ARX protein mislocalisation. These mutations impair vital properties of ARX’s transcription factor function by perturbing its localisation into the nucleus (p.R379L) or DNA binding (p.R358S). This study confirms that ARX mutations contribute significantly to XLID and that the majority of mutations occur within exon 2, specifically within the region of pA2. Moreover, there is a correlation between the subcellular localization of the mutant protein and the clinical severity in the patients.Thesis (Ph.D.) -- University of Adelaide, School of Paediatrics and Reproductive Health, 201

Paternal obesity, interventions, and mechanistic pathways to impaired health in offspring

Background: The global rates of male overweight/obesity are rising, approaching 70% of the total adult population in Western nations. Overweight/obesity increases the risk of chronic diseases; however, there is increasing awareness that male obesity negatively impacts fertility, subsequent pregnancy, and the offspring health burden. Developmental programming is well defined in mothers; however, it is becoming increasingly evident that developmental programming can be paternally initiated and mediated through paternal obesity. Key Messages: Both human and rodent models have established that paternal obesity impairs sex hormones, basic sperm function, and molecular composition. This results in perturbed embryo development and health and an increased subsequent offspring disease burden in both sexes. The reversibility of obesity-induced parental programming has only recently received attention. Promising results in animal models utilizing diet and exercise interventions have shown improvements in sperm function and molecular composition, resulting in restorations of both embryo and fetal health and subsequent male offspring fertility. The direct mode for paternal inheritance is likely mediated via spermatozoa. We propose two main theories for the origin of male obesity-induced paternal programming: (1) accumulation of sperm DNA damage resulting in de novo mutations in the embryo and (2) changes in sperm epigenetic marks (microRNA, methylation, or acetylation) altering the access, transcription, and translation of paternally derived genes during early embryogenesis. Conclusions: Paternal overweight/obesity induces paternal programming of offspring phenotypes likely mediated through genetic and epigenetic changes in spermatozoa. These programmed changes to offspring health appear to be partially restored via diet/exercise interventions in obese fathers preconception, which have been shown to improve aspects of sperm DNA integrity. However, the majority of data surrounding paternal obesity and offspring phenotypes have come from rodent models; therefore, we contend that it will be increasingly important to study population-based data to determine the likely mode of inheritance in humans