The mitochondrial trigger in an animal model of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading liver chronic disease featuring hepatic steatosis. Mitochondrial β-oxidation participates in the derangement of lipid metabolism at the basis of NAFLD, and mitochondrial oxidative stress contributes to the onset of the disease. We evaluated the presence and effects of mitochondrial oxidative stress in the liver from rats fed a high-fat plus fructose (HF-F) diet inducing NAFLD. Supplementation with dehydroepiandrosterone (DHEA), a multitarget antioxidant, was tested for efficacy in delaying NAFLD. A marked mitochondrial oxidative stress was originated by all diets, as demonstrated by the decrease in Superoxide Dismutase 2 (SOD2) and Peroxiredoxin III (PrxIII) amounts. All diets induced a decrease in mitochondrial DNA content and an increase in its oxidative damage. The diets negatively affected mitochondrial biogenesis as shown by decreased peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α), mitochondrial transcription factor A (TFAM), and the COX-IV subunit from the cytochrome c oxidase complex. The reduced amounts of Beclin-1 and lipidated LC3 II form of the microtubule-associated protein 1 light chain 3 (LC3) unveiled the diet-related autophagy’s decrease. The DHEA supplementation did not prevent the diet-induced changes. These results demonstrate the relevance of mitochondrial oxidative stress and the sequential dysfunction of the organelles in an obesogenic diet animal model of NAFLD

Deletion of OGG1 Results in a Differential Signature of Oxidized Purine Base Damage in mtDNA Regions

Mitochondrial oxidative stress accumulates with aging and age-related diseases and induces alterations in mitochondrial DNA (mtDNA) content. Since mtDNA qualitative alterations are also associated with aging, repair of mtDNA damage is of great importance. The most relevant form of DNA repair in this context is base excision repair (BER), which removes oxidized bases such as 8-oxoguanine (8-oxoG) and thymine glycol through the action of the mitochondrial isoform of the specific 8-oxoG DNA glycosylase/apurinic or apyrimidinic (AP) lyase (OGG1) or the endonuclease III homolog (NTH1). Mouse strains lacking OGG1 (OGG1/) or NTH1 (NTH1/) were analyzed for mtDNA alterations. Interestingly, both knockout strains presented a significant increase in mtDNA content, suggestive of a compensatory mtDNA replication. The mtDNA “common deletion” was not detected in either knockout mouse strain, likely because of the young age of the mice. Formamidopyrimidine DNA glycosylase (Fpg)-sensitive sites accumulated in mtDNA from OGG1/ but not from NTH1/ mice. Interestingly, the D-loop region was most severely aected by the absence of OGG1, suggesting that this region may be a hotspot for oxidative damage. Thus, we speculate that mtDNA alterations may send a stress message to evoke cell changes through a retrograde mitochondrial–nucleus communication

Inulin-enriched pasta improves intestinal permeability and modifies the circulating levels of zonulin and glucagon-like peptide 2 in healthy young volunteers

Apart from the intestinal environment, inulin induces physiological effects, which includes a reduction in glucose and lipid concentrations and modulation of gastrointestinal motility through the release of different peptides. We hypothesized that inulin-enriched pasta may also improve small intestine permeability in relation to zonulin and glucagon-like peptide 2 (GLP-2) levels in healthy young subjects. Twenty healthy, young male volunteers completed a randomized, double-blind crossover study consisting of a 2-week run-in period and two 5-week study periods (11% inulin-enriched or control pasta), with an 8-week washout period in between. The intestinal barrier function was assessed by lactulose-mannitol excretion in urine. Zonulin values and GLP-2 release were evaluated by enzyme-linked immunosorbent assay. In the inulin group, the urinary lactulose recovery was significantly lower than the other 2 groups. There were no significant differences in urinary mannitol levels between groups. Accordingly, the lactulose-mannitol excretion ratio was significantly decreased in the inulin-enriched pasta group compared with the other 2 groups. The inulin-enriched pasta group had significantly lower zonulin serum values and significantly higher GLP-2 basal values when compared with the baseline and control pasta groups. The dietary use of inulin-enriched pasta preserves intestinal mucosal barrier functioning and modulates circulating levels of zonulin and GLP-2, suggesting that prebiotics could be used in the prevention of gastrointestinal diseases and metabolic disorders

Differences in Liver TFAM Binding to mtDNA and mtDNA Damage between Aged and Extremely Aged Rats

While mitochondrial dysfunction is acknowledged as a major feature of aging, much less is known about the role of mitochondria in extended longevity. Livers from aged (28-month-old) and extremely aged (32-month-old) rats were analyzed for citrate synthase activity, mitochondrial transcription factor A (TFAM) amount, mitochondrial DNA (mtDNA), and 4.8 Kb “common deletion” contents. None of the assayed parameters differed significantly between age groups. TFAM-binding to mtDNA and the incidence of 8-oxo-deoxyguanosine in specific mtDNA regions, encompassing the origins of mtDNA replication (D-loop and Ori-L) and the 16-bp long direct repeat 1 (DR1) of the 4.8 Kb deletion, were determined. A decrease in TFAM binding was unveiled at all regions in extremely aged in comparison with aged rats. Reduced incidence of oxidized purines at all assayed regions was detected in 32-month-old rats compared with the 28-month-old group. A significant positive correlation between the incidence of 8-oxo-deoxoguanosine and TFAM-bound mtDNA was found at D-Loop and Ori-L regions only in 28-month-old rats. The absence of such correlation in 32-month-old rats indicates a different, fine-tuned regulation of TFAM binding in the two age groups and supports the existence of two different paces in aging and extended aging

Lipoproteins and apolipoproteins in human cerebrospinal fluid: A new role of lipoprotein(A) and apolipoprotein(A) in the neurological diseases characterized by bloodcerebrospinal fluid barrier dysfunction

The barrier between blood and CSF contributes to homeostasis of the CNS and protects it from potentially harmful substances present in the blood. Lipoproteins present in the CSF are clearly distinct from their plasma counterparts. Human CSF lipoproteins contain mainly Apo AI and Apo E, the former deriving mostly from plasma after crossing the blood–cerebrospinal fluid barrier, the latter being also produced by CNS. Apo AI and E containing lipoproteins in the brain are key players in transport and delivery of lipids, cholesterol homeostasis, and are also involved in CNS remodeling mechanisms. On the other hand, the isoform apo E4 represents the most important genetic risk factor for sporadic and familial late-onset Alzheimer’s disease and is involved in brain injury and neurodegenerative diseases. Apo B containing lipoproteins are not produced by CNS and the characterization of normal human CSF lipoproteins did not allowed the isolation of low density lipoproteins. which is characterized by a dimensional polymorphism. Lipoprotein(a) is a well known risk factor for athero-thrombosis. The pathological role of Lipoprotein(a) is strictly associated with its plasma concentrations and the size of apo(a) isoforms, with inverse relation. The pathophysiology of Lipoprotein(a) in cardio and cerebrovascular system is widely studied. Recently, we demonstrated that, in neuroinflammatory and neurodegenerative disorders, Lipoprotein(a) can cross a dysfunctional blood-CSF barrier and be found in the CSF. This chapter focuses on the physiological presence of the lipoproteins in CNS, on the pathological aspects deriving from their isoforms, and in particular on the anomalous presence in CSF of Lipoprotein(a

Correct usage of a mutated G+1 splice site and transcript quantitation in lipoprotein lipase-deficient patient

The consequence on the splice mechanism of a mutation occurring at the donor splice site of intron 1 has been studied. We demonstrate that, in spite of the change at G+1 position, this site is still utilized and can produce correctly spliced transcript. Nevertheless the mRNA is detectable only after an 'in vitro' amplification. A procedure has been developed to reveal and quantify the minute amount present in the patient. The very low mRNA level results in a total lack of enzyme, the cause of the disease. The procedure can be useful in cases of rare transcripts and when the source is limited. Furthermore we analyse the interaction between the splice consensus sequence and the small nuclear RNA, that is the necessary intermediate of the splicing mechanism. We speculate on the reasons why cryptic sites are not utilized and only the authentic site can be used, although significantly destabilized by the mutation

Non-genetic factors modify the quantitative genetic trait lipoprotein(a) and affect its pathogenicity

Lipoprotein(a) is an LDL-like lipoparticle having the distinctive multi-kringle apolipoprotein(a). Although the physiological roles of lipoprotein(a) have been somewhat elusive, its pathological effects, closely related to plasma concentrations, have been widely studied. Several variants of the LPA gene contribute to its differential expression, and to lipoprotein(a) levels and pathogenicity. Although most of the variations in lipoprotein(a) concentrations are under genetic control, a relationship between plasma levels, apolipoprotein(a) phenotypes, anthropometric and biochemical factors, and environmental-associated events has been reported in many studies. Study of transgenic animals, which bypasses the absence of lipoprotein(a) in common laboratory animals, is an excellent model to examine the function of increased plasma lipoprotein(a) in differing pathological conditions or in cases of dietary intervention. This chapter offers an overview of some of the non-genetic factors which have modest, albeit significant, effects on lipoprotein(a) levels, also assessing their possible interactions with specific apolipoprotein(a) genotypes. The effects of estrogenreplacement therapy and dietary interventions in the modulation of lipoprotein(a) levels, and the influence of age are evaluated, taking into account their implications in the atherogenic risk. Lastly, the controversial role of lipoprotein(a) as an acute phase reactant and, in particular, its possible beneficial role in surgical trauma are discussed

The Ketogenic Diet Improves Gut–Brain Axis in a Rat Model of Irritable Bowel Syndrome: Impact on 5-HT and BDNF Systems

Altered gut–brain communication can contribute to intestinal dysfunctions in the intestinal bowel syndrome. The neuroprotective high-fat, adequate-protein, low-carbohydrate ketogenic diet (KD) modulates the levels of different neurotransmitters and neurotrophins. The aim was to evaluate the effects of KD on levels of 5-HT, the receptors 5-HT3B and 5-HT4, the 5-HT transporter SERT, the neurotrophin BDNF, and its receptor TrkB in the colon and brain of a rat model of irritable bowel syndrome (IBS). Samples from Wistar rats exposed to maternal deprivation as newborns and then fed with a standard diet (IBS-Std) or KD (IBS-KD) for ten weeks were analyzed. As controls, unexposed rats (Ctrl-Std and Ctrl-KD) were studied. IBS-Std rats had a disordered enteric serotoninergic signaling shown by increased mucosal 5-HT content and reduced SERT, 5-HT3B, and 5-HT4 levels compared to controls. In the brain, these animals showed up-regulation of the BDNF receptor TrkB as a counteracting response to the stress-induced reduction of the neurotrophin. KD showed a dual effect in improving the altered 5-HT and BDNF systems. It down-regulated the increased mucosal 5-HT without affecting transporter and receptor levels. KD improved brain BDNF levels and established negative feedback, leading to a compensatory downregulation of TrkB to maintain a physiological steady state

A G->C change at the donor splice site of intron 1 causes lipoprotein lipase deficiency in a southern-Italian family

We describe a new case of lipoprotein lipase deficiency in a proband from a Southern-Italian family. Enzyme activity and mass were absent. Amplification and sequencing of individual exons, intron boundaries and the regulatory region revealed only one homozygous G→C transversion at the first nucleotide of intron 1. The single strand conformation polymorphism analysis proved to be a helpful tool for the identification of the single base mutation. Northern hybridization failed to reaveal the presence of mature lipoprotein lipase mRNA. The mutation, which destroys the conserved dinucleotide at the junction site of intron 1, causes defective mRNA splicing and it is responsible for the deficiency

The expression pattern of the AML1 gene in non-Hodgkin's B-cell lymphomas and normal B lymphocytes

We have studied the expression of the three human acute myeloid leukemia (AML) genes in primary samples of non-Hodgkin's B-cell lymphomas in which translocations involving these loci were not present. We found a widespread expression of the three AML genes in all the lymphoma samples as well as in the purified normal B-lymphocytes, Thus, the presence of the three mRNAs "per se" does not: allow the identification of the pathological status. However, AML1 showed a different transcription pattern in the neoplastic tissues with respect to the normal B-cells, The AML1b isoform proved to be peculiar to this lymphoma. Our data support the idea that qualitative and quantitative alterations of AML1 gene expression deriving from deregulating mechanisms other than translocations may be involved in this malignancy. The usage of two differently regulated promoters driving the expression of the transcripts AML1b and AML1c may be one of these mechanisms. Finally, we report the presence of a new alternatively spliced transcript in normal B-cells