Altered metabolism and DAM-signatures in female brains and microglia with aging

Despite Alzheimer's disease (AD) disproportionately affecting women, the mechanisms remain elusive. In AD, microglia undergo 'metabolic reprogramming', which contributes to microglial dysfunction and AD pathology. However, how sex and age contribute to metabolic reprogramming in microglia is understudied. Here, we use metabolic imaging, transcriptomics, and metabolic assays to probe age- and sex-associated changes in brain and microglial metabolism. Glycolytic and oxidative metabolism in the whole brain was determined using Fluorescence Lifetime Imaging Microscopy (FLIM). Young female brains appeared less glycolytic than male brains, but with aging, the female brain became 'male-like.' Transcriptomic analysis revealed increased expression of disease-associated microglia (DAM) genes (e.g., ApoE, Trem2, LPL), and genes involved in glycolysis and oxidative metabolism in microglia from aged females compared to males. To determine whether estrogen can alter the expression of these genes, BV-2 microglia-like cell lines, which abundantly express DAM genes, were supplemented with 17β-estradiol (E2). E2 supplementation resulted in reduced expression of DAM genes, reduced lipid and cholesterol transport, and substrate-dependent changes in glycolysis and oxidative metabolism. Consistent with the notion that E2 may suppress DAM-associated factors, LPL activity was elevated in the brains of aged female mice. Similarly, DAM gene and protein expression was higher in monocyte-derived microglia-like (MDMi) cells derived from middle-aged females compared to age-matched males and was responsive to E2 supplementation. FLIM analysis of MDMi from young and middle-aged females revealed reduced oxidative metabolism and FAD+ with age. Overall, our findings show that altered metabolism defines age-associated changes in female microglia and suggest that estrogen may inhibit the expression and activity of DAM-associated factors, which may contribute to increased AD risk, especially in post-menopausal women.

Altered Metabolism and DAM-signatures in Female Brains and Microglia with Aging

Despite Alzheimer's disease (AD) disproportionately affecting women, the mechanisms remain elusive. In AD, microglia undergo 'metabolic reprogramming', which contributes to microglial dysfunction and AD pathology. However, how sex and age contribute to metabolic reprogramming in microglia is understudied. Here, we use metabolic imaging, transcriptomics, and metabolic assays to probe age-and sex-associated changes in brain and microglial metabolism. Glycolytic and oxidative metabolism in the whole brain was determined using Fluorescence Lifetime Imaging Microscopy (FLIM). Young female brains appeared less glycolytic than male brains, but with aging, the female brain became 'male-like.' Transcriptomic analysis revealed increased expression of disease-associated microglia (DAM) genes (e.g., ApoE, Trem2, LPL), and genes involved in glycolysis and oxidative metabolism in microglia from aged females compared to males. To determine whether estrogen can alter the expression of these genes, BV-2 microglia-like cell lines, which abundantly express DAM genes, were supplemented with 17β-estradiol (E2). E2 supplementation resulted in reduced expression of DAM genes, reduced lipid and cholesterol transport, and substrate-dependent changes in glycolysis and oxidative metabolism. Consistent with the notion that E2 may suppress DAM-associated factors, LPL activity was elevated in the brains of aged female mice. Similarly, DAM gene and protein expression was higher in monocyte-derived microglia-like (MDMi) cells derived from middle-aged females compared to age-matched males and was responsive to E2 supplementation. FLIM analysis of MDMi from young and middle-aged females revealed reduced oxidative metabolism and FAD+ with age. Overall, our findings show that altered metabolism defines age-associated changes in female microglia and suggest that estrogen may inhibit the expression and activity of DAM-associated factors, which may contribute to increased AD risk, especially in post-menopausal women.

Emerging Alzheimer's disease therapeutics: promising insights from lipid metabolism and microglia-focused interventions

More than 55 million people suffer from dementia, with this number projected to double every 20 years. In the United States, 1 in 3 aged individuals dies from Alzheimer's disease (AD) or another type of dementia and AD kills more individuals than breast cancer and prostate cancer combined. AD is a complex and multifactorial disease involving amyloid plaque and neurofibrillary tangle formation, glial cell dysfunction, and lipid droplet accumulation (among other pathologies), ultimately leading to neurodegeneration and neuronal death. Unfortunately, the current FDA-approved therapeutics do not reverse nor halt AD. While recently approved amyloid-targeting antibodies can slow AD progression to improve outcomes for some patients, they are associated with adverse side effects, may have a narrow therapeutic window, and are expensive. In this review, we evaluate current and emerging AD therapeutics in preclinical and clinical development and provide insight into emerging strategies that target brain lipid metabolism and microglial function - an approach that may synergistically target multiple mechanisms that drive AD neuropathogenesis. Overall, we evaluate whether these disease-modifying emerging therapeutics hold promise as interventions that may be able to reverse or halt AD progression.

Human cerebrospinal fluid contains diverse lipoprotein subspecies enriched in proteins implicated in central nervous system health

Lipoproteins in cerebrospinal fluid (CSF) of the central nervous system (CNS) resemble plasma high-density lipoproteins (HDLs), which are a compositionally and structurally diverse spectrum of nanoparticles with pleiotropic functionality. Whether CSF lipoproteins (CSF-Lps) exhibit similar heterogeneity is poorly understood because they are present at 100-fold lower concentrations than plasma HDL. To investigate the diversity of CSF-Lps, we developed a sensitive fluorescent technology to characterize lipoprotein subspecies in small volumes of human CSF. We identified 10 distinctly sized populations of CSF-Lps, most of which were larger than plasma HDL. Mass spectrometric analysis identified 303 proteins across the populations, over half of which have not been reported in plasma HDL. Computational analysis revealed that CSF-Lps are enriched in proteins important for wound healing, inflammation, immune response, and both neuron generation and development. Network analysis indicated that different subpopulations of CSF-Lps contain unique combinations of these proteins. Our study demonstrates that CSF-Lp subspecies likely exist that contain compositional signatures related to CNS health.

Volanesorsen, an antisense oligonucleotide to apolipoprotein C-III, increases lipoprotein lipase activity and lowers triglycerides in partial lipodystrophy

BACKGROUND

Partial lipodystrophy (PL) syndromes involve deficiency of adipose tissue, causing severe insulin resistance and hypertriglyceridemia. Apolipoprotein C-III (apoC-III) is elevated in PL and is thought to contribute to hypertriglyceridemia by inhibiting lipoprotein lipase (LPL).

OBJECTIVE

We hypothesized that volanesorsen, an antisense oligonucleotide to apoC-III, would decrease apoC-III, increase LPL activity, and lower triglycerides in PL.

METHODS

Five adults with PL enrolled in a 16-week placebo-controlled, randomized, double blind study of volanesorsen, 300 mg weekly, followed by 1-year open label extension.

RESULTS

Within-subject effects of volanesorsen before and after 16 weeks of active drug are reported due to small sample size. From week 0 to 16, apoC-III decreased from median (25th, 75th %ile) 380 (246, 600) to 75 (26, 232) ng/mL, and triglycerides decreased from 503 (330, 1040) to 116 (86, 355) mg/dL while activation of LPL by subjects' serum increased from 21 (20, 25) to 36 (29, 42) nEq/mL*min. Although, A1c did not change, peripheral and hepatic insulin sensitivity (glucose disposal and suppression of glucose production during hyperinsulinemic clamp) increased and palmitate turnover decreased. After 32-52 weeks of volanesorsen, liver fat decreased. Common adverse events included injection site reactions and decreased platelets.

CONCLUSIONS

In PL, volanesorsen decreased apoC-III and triglycerides, in part through an LPL dependent mechanism, and may improve insulin resistance and hepatic steatosis.

Fatty acid sensing in the brain: The role of glial-neuronal metabolic crosstalk and horizontal lipid flux

The central control of energy homeostasis is a regulatory axis that involves the sensing of nutrients, signaling molecules, adipokines, and neuropeptides by neurons in the metabolic centers of the hypothalamus. However, non-neuronal glial cells are also abundant in the hypothalamus and recent findings have underscored the importance of the metabolic crosstalk and horizontal lipid flux between glia and neurons to the downstream regulation of systemic metabolism. New transgenic models and high-resolution analyses of glial phenotype and function have revealed that glia sit at the nexus between lipid metabolism and neural function, and may markedly impact the brain's response to dietary lipids or the supply of brain-derived lipids. Glia comprise the main cellular compartment involved in lipid synthesis, lipoprotein production, and lipid processing in the brain. In brief, tanycytes provide an interface between peripheral lipids and neurons, astrocytes produce lipoproteins that transport lipids to neurons and other glia, oligodendrocytes use brain-derived and dietary lipids to myelinate axons and influence neuronal function, while microglia can remove unwanted lipids in the brain and contribute to lipid re-utilization through cholesterol efflux. Here, we review recent findings regarding glial-lipid transport and highlight the specific molecular factors necessary for lipid processing in the brain, and how dysregulation of glial-neuronal metabolic crosstalk contributes to imbalanced energy homeostasis. Furthering our understanding of glial lipid metabolism will guide the design of future studies that target horizontal lipid processing in the brain to ameliorate the risk of developing obesity and metabolic disease.

Using Synthetic ApoC-II Peptides and nAngptl4 Fragments to Measure Lipoprotein Lipase Activity in Radiometric and Fluorescent Assays

Lipoprotein lipase (LPL) plays a crucial role in preventing dyslipidemia by hydrolyzing triglycerides (TGs) in packaged lipoproteins. Since hypertriglyceridemia (HTG) is a major risk factor for cardiovascular disease (CVD), the leading cause of death worldwide, methods that accurately quantify the hydrolytic activity of LPL in clinical and pre-clinical samples are much needed. To date, the methods used to determine LPL activity vary considerably in their approach, in the LPL substrates used, and in the source of LPL activators and inhibitors used to quantify LPL-specific activity, rather than other lipases, e.g., hepatic lipase (HL) or endothelial lipase (EL) activity. Here, we describe methods recently optimized in our laboratory, using a synthetic ApoC-II peptide to activate LPL, and an n-terminal Angiopoietin-Like 4 fragment (nAngptl4) to inhibit LPL, presenting a cost-effective and reproducible method to measure LPL activity in human post-heparin plasma (PHP) and in LPL-enriched heparin released (HR) fractions from LPL secreting cells. We also describe a modified version of the triolein-based assay using human serum as a source of endogenous activators and inhibitors and to determine the relative abundance of circulating factors that regulate LPL activity. Finally, we describe how an ApoC-II peptide and nAngptl4 can be applied to high-throughput measurements of LPL activity using the EnzChek™ fluorescent TG analog substrate with PHP, bovine LPL, and HR LPL enriched fractions. In summary, this manuscript assesses the current methods of measuring LPL activity and makes new recommendations for measuring LPL-mediated hydrolysis in pre-clinical and clinical samples.

Altered substrate metabolism in neurodegenerative disease: new insights from metabolic imaging

Neurodegenerative diseases (NDs), such as Alzheimer's disease (AD), Parkinson's disease (PD) and multiple sclerosis (MS), are relatively common and devastating neurological disorders. For example, there are 6 million individuals living with AD in the United States, a number that is projected to grow to 14 million by the year 2030. Importantly, AD, PD and MS are all characterized by the lack of a true disease-modifying therapy that is able to reverse or halt disease progression. In addition, the existing standard of care for most NDs only addresses the symptoms of the disease. Therefore, alternative strategies that target mechanisms underlying the neuropathogenesis of disease are much needed. Recent studies have indicated that metabolic alterations in neurons and glia are commonly observed in AD, PD and MS and lead to changes in cell function that can either precede or protect against disease onset and progression. Specifically, single-cell RNAseq studies have shown that AD progression is tightly linked to the metabolic phenotype of microglia, the key immune effector cells of the brain. However, these analyses involve removing cells from their native environment and performing measurements in vitro, influencing metabolic status. Therefore, technical approaches that can accurately assess cell-specific metabolism in situ have the potential to be transformative to our understanding of the mechanisms driving AD. Here, we review our current understanding of metabolism in both neurons and glia during homeostasis and disease. We also evaluate recent advances in metabolic imaging, and discuss how emerging modalities, such as fluorescence lifetime imaging microscopy (FLIM) have the potential to determine how metabolic perturbations may drive the progression of NDs. Finally, we propose that the temporal, regional, and cell-specific characterization of brain metabolism afforded by FLIM will be a critical first step in the rational design of metabolism-focused interventions that delay or even prevent NDs.

Exosome Isolation by Ultracentrifugation and Precipitation and Techniques for Downstream Analyses

Exosomes are 50- to 150-nm-diameter extracellular vesicles secreted by all mammalian cells except mature red blood cells and contribute to diverse physiological and pathological functions within the body. Many methods have been used to isolate and analyze exosomes, resulting in inconsistencies across experiments and raising questions about how to compare results obtained using different approaches. Questions have also been raised regarding the purity of the various preparations with regard to the sizes and types of vesicles and to the presence of lipoproteins. Thus, investigators often find it challenging to identify the optimal exosome isolation protocol for their experimental needs. Our laboratories have compared ultracentrifugation and commercial precipitation- and column-based exosome isolation kits for exosome preparation. Here, we present protocols for exosome isolation using two of the most commonly used methods, ultracentrifugation and precipitation, followed by downstream analyses. We use NanoSight nanoparticle tracking analysis and flow cytometry (Cytek^® ) to determine exosome concentrations and sizes. Imaging flow cytometry can be utilized to both size exosomes and immunophenotype surface markers on exosomes (ImageStream^® ). High-performance liquid chromatography followed by nano-flow liquid chromatography-mass spectrometry (LCMS) of the exosome fractions can be used to determine the presence of lipoproteins, with LCMS able to provide a proteomic profile of the exosome preparations. We found that the precipitation method was six times faster and resulted in a ∼2.5-fold higher concentration of exosomes per milliliter compared to ultracentrifugation. Both methods yielded extracellular vesicles in the size range of exosomes, and both preparations included apoproteins. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Pre-analytic fluid collection and processing Basic Protocol 2: Exosome isolation by ultracentrifugation Alternate Protocol 1: Exosome isolation by precipitation Basic Protocol 3: Analysis of exosomes by NanoSight nanoparticle tracking analysis Alternate Protocol 2: Analysis of exosomes by flow cytometry and imaging flow cytometry Basic Protocol 4: Downstream analysis of exosomes using high-performance liquid chromatography Basic Protocol 5: Downstream analysis of the exosome proteome using nano-flow liquid chromatography-mass spectrometry.

Lipoprotein Lipase Regulates Microglial Lipid Droplet Accumulation

Microglia become increasingly dysfunctional with aging and contribute to the onset of neurodegenerative disease (NDs) through defective phagocytosis, attenuated cholesterol efflux, and excessive secretion of pro-inflammatory cytokines. Dysfunctional microglia also accumulate lipid droplets (LDs); however, the mechanism underlying increased LD load is unknown. We have previously shown that microglia lacking lipoprotein lipase (LPL KD) are polarized to a pro-inflammatory state and have impaired lipid uptake and reduced fatty acid oxidation (FAO). Here, we also show that LPL KD microglia show excessive accumulation of LD-like structures. Moreover, LPL KD microglia display a pro-inflammatory lipidomic profile, increased cholesterol ester (CE) content, and reduced cholesterol efflux at baseline. We also show reduced expression of genes within the canonical cholesterol efflux pathway. Importantly, PPAR agonists (rosiglitazone and bezafibrate) rescued the LD-associated phenotype in LPL KD microglia. These data suggest that microglial-LPL is associated with lipid uptake, which may drive PPAR signaling and cholesterol efflux to prevent inflammatory lipid distribution and LD accumulation. Moreover, PPAR agonists can reverse LD accumulation, and therefore may be beneficial in aging and in the treatment of NDs.

Genetic Variants of Lipoprotein Lipase and Regulatory Factors Associated with Alzheimer's Disease Risk

Lipoprotein lipase (LPL) is a key enzyme in lipid and lipoprotein metabolism. The canonical role of LPL involves the hydrolysis of triglyceride-rich lipoproteins for the provision of FFAs to metabolic tissues. However, LPL may also contribute to lipoprotein uptake by acting as a molecular bridge between lipoproteins and cell surface receptors. Recent studies have shown that LPL is abundantly expressed in the brain and predominantly expressed in the macrophages and microglia of the human and murine brain. Moreover, recent findings suggest that LPL plays a direct role in microglial function, metabolism, and phagocytosis of extracellular factors such as amyloid- beta (Aβ). Although the precise function of LPL in the brain remains to be determined, several studies have implicated LPL variants in Alzheimer's disease (AD) risk. For example, while mutations shown to have a deleterious effect on LPL function and expression (e.g., N291S, HindIII, and PvuII) have been associated with increased AD risk, a mutation associated with increased bridging function (S447X) may be protective against AD. Recent studies have also shown that genetic variants in endogenous LPL activators (ApoC-II) and inhibitors (ApoC-III) can increase and decrease AD risk, respectively, consistent with the notion that LPL may play a protective role in AD pathogenesis. Here, we review recent advances in our understanding of LPL structure and function, which largely point to a protective role of functional LPL in AD neuropathogenesis.

Neuronal Lipoprotein Lipase Deficiency Alters Neuronal Function and Hepatic Metabolism

The autonomic regulation of hepatic metabolism offers a novel target for the treatment of non-alcoholic fatty liver disease (NAFLD). However, the molecular characteristics of neurons that regulate the brain-liver axis remain unclear. Since mice lacking neuronal lipoprotein lipase (LPL) develop perturbations in neuronal lipid-sensing and systemic energy balance, we reasoned that LPL might be a component of pre-autonomic neurons involved in the regulation of hepatic metabolism. Here, we show that, despite obesity, mice with reduced neuronal LPL (NEXCreLPL^flox (LPL KD)) show improved glucose tolerance and reduced hepatic lipid accumulation with aging compared to wilt type (WT) controls (LPL^flox). To determine the effect of LPL deficiency on neuronal physiology, liver-related neurons were identified in the paraventricular nucleus (PVN) of the hypothalamus using the transsynaptic retrograde tracer PRV-152. Patch-clamp studies revealed reduced inhibitory post-synaptic currents in liver-related neurons of LPL KD mice. Fluorescence lifetime imaging microscopy (FLIM) was used to visualize metabolic changes in LPL-depleted neurons. Quantification of free vs. bound nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) revealed increased glucose utilization and TCA cycle flux in LPL-depleted neurons compared to controls. Global metabolomics from hypothalamic cell lines either deficient in or over-expressing LPL recapitulated these findings. Our data suggest that LPL is a novel feature of liver-related preautonomic neurons in the PVN. Moreover, LPL loss is sufficient to cause changes in neuronal substrate utilization and function, which may precede changes in hepatic metabolism.

Lipid and Lipoprotein Metabolism in Microglia

Microglia, once viewed as static bystanders with limited homeostatic functions, are now considered key players in the development of neuroinflammatory and neurodegenerative diseases. Microglial activation is a salient feature of neuroinflammation involving a dynamic process that generates multitudinous microglial phenotypes that can respond to a variety of situational cues in the central nervous system. Recently, a flurry of single cell RNA-sequencing studies have defined microglial phenotypes in unprecedented detail, and have highlighted robust changes in the expression of genes involved in lipid and lipoprotein metabolism. Increased expression of genes such as Apolipoprotein E (ApoE), Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) and Lipoprotein Lipase (LPL) in microglia during development, damage, and disease, suggest that increased lipid metabolism is needed to fuel protective cellular functions such as phagocytosis. This review describes our current understanding of lipid and lipoprotein metabolism in microglia, and highlights microglial lipid metabolism as a modifiable target for the treatment of neurodegenerative diseases such as Alzheimer's disease and multiple sclerosis.

The small quinolone derived compound HT61 enhances the effect of tobramycin against Pseudomonas aeruginosa in vitro and in vivo

HT61 is a small quinolone-derived compound previously demonstrated to exhibit bactericidal activity against gram-positive bacteria including methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA). When combined with the classical antibiotics and antiseptics neomycin, gentamicin, mupirocin and chlorhexidine, HT61 demonstrated synergistic bactericidal activity against both MSSA and MRSA infections in vitro. In this study, we investigated the individual antimicrobial activity of HT61 alongside its capability to potentiate the efficacy of tobramycin against both a tobramycin sensitive laboratory reference strain (PAO1) and tobramycin resistant clinical isolates (RP73, NN2) of the gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa). Using broth microdilution methods, the MICs of HT61 were assessed against all strains, as well as the effect of HT61 in combination with tobramycin using both the chequerboard method and bacterial time-kill assays. A murine model of pulmonary infection was also used to evaluate the combination therapy of tobramycin and HT61 in vivo. In these studies, we demonstrated significant synergism between HT61 and tobramycin against the tobramycin resistant P. aeruginosa strains RP73 and NN2, whilst an additive/intermediate effect was observed for P. aeruginosa strain PA01 which was further confirmed using bacterial time kill analysis. In addition, the enhancement of tobramycin by HT61 was also evident in in vitro assays of biofilm eradication. Finally, in vivo studies revealed analogous effects to those observed in vitro with HT61 significantly reducing bacterial load when administered in combination with tobramycin against each of the three P. aeruginosa strains at the highest tested dose (10 mg/kg).

Lipoprotein Lipase Is a Feature of Alternatively-Activated Microglia and May Facilitate Lipid Uptake in the CNS During Demyelination

Severe demyelinating disorders of the central nervous system (CNS) such as multiple sclerosis (MS), can be devastating for many young lives. To date, the factors resulting in poor remyelination and repair are not well understood, and reparative therapies that benefit MS patients have yet to be developed. We have previously shown that the activity and abundance of Lipoprotein Lipase (LPL)—the rate-limiting enzyme in the hydrolysis of triglyceride-rich lipoproteins—is increased in Schwann cells and macrophages following nerve crush injury in the peripheral nervous system (PNS), suggesting that LPL may help scavenge myelin-derived lipids. We hypothesized that LPL may play a similar role in the CNS. To test this, mice were immunized with MOG_35–55 peptide to induce experimental allergic encephalomyelitis (EAE). LPL activity was increased (p < 0.05) in the brain at 30 days post-injection, coinciding with partial remission of clinical symptoms. Furthermore, LPL abundance and activity was up-regulated (p < 0.05) at the transition between de- and re-myelination in lysolecithin-treated ex vivo cerebellar slices. Since microglia are the key immune effector cells of the CNS we determined the role of LPL in microglia. Lipid uptake was decreased (p < 0.001) in LPL-deficient BV-2 microglial cells compared to WT. In addition, LPL-deficient cells showed dramatically reduced expression of anti-inflammatory markers, YM1 (−22 fold, p < 0.001), and arginase 1 (Arg1; −265 fold, p < 0.001) and increased expression of pro-inflammatory markers, such as iNOS compared to WT cells (+53 fold, p < 0.001). This suggests that LPL is a feature of reparative microglia, further supported by the metabolic and inflammatory profile of LPL-deficient microglia. Taken together, our data strongly suggest that LPL expression is a novel feature of a microglial phenotype that supports remyelination and repair through the clearance of lipid debris. This mechanism may be exploited to develop future reparative therapies for MS and primary neurodegenerative disorders (Alzheimer’s disease (AD) and Parkinson’s disease).

Assessment of Fatty Liver in Models of Disease Programming

Nonalcoholic fatty liver disease (NAFLD) is currently the most common cause of chronic liver disease worldwide and is present in a third of the general population and the majority of individuals with obesity and type 2 diabetes. Importantly, NAFLD can progress to severe nonalcoholic steatohepatitis (NASH), associated with liver failure and hepatocellular carcinoma. Recent research efforts have extensively focused on identifying factors contributing to the additional "hit" required to promote NALFD disease progression. The maternal diet, and in particular a high-fat diet (HFD), may be one such hit "priming" the development of severe fatty liver disease, a notion supported by the increasing incidence of NAFLD among children and adolescents in Westernized countries. In recent years, a plethora of key studies have used murine models of maternal obesity to identify fundamental mechanisms such as lipogenesis, mitochondrial function, inflammation, and fibrosis that may underlie the developmental priming of NAFLD. In this chapter, we will address key considerations for constructing experimental models and both conventional and advanced methods of quantifying NAFLD disease status.

Lipoprotein lipase in hypothalamus is a key regulator of body weight gain and glucose homeostasis in mice

AIMS/HYPOTHESIS

Regulation of energy balance involves the participation of many factors, including nutrients, among which are circulating lipids, acting as peripheral signals informing the central nervous system of the energy status of the organism. It has been shown that neuronal lipoprotein lipase (LPL) participates in the control of energy balance by hydrolysing lipid particles enriched in triacylglycerols. Here, we tested the hypothesis that LPL in the mediobasal hypothalamus (MBH), a well-known nucleus implicated in the regulation of metabolic homeostasis, could also contribute to the regulation of body weight and glucose homeostasis.

METHODS

We injected an adeno-associated virus (AAV) expressing Cre-green fluorescent protein into the MBH of Lpl-floxed mice (and wild-type mice) to specifically decrease LPL activity in the MBH. In parallel, we injected an AAV overexpressing Lpl into the MBH of wild-type mice. We then studied energy homeostasis and hypothalamic ceramide content.

RESULTS

The partial deletion of Lpl in the MBH in mice led to an increase in body weight compared with controls (37.72 ± 0.7 g vs 28.46 ± 0.12, p < 0.001) associated with a decrease in locomotor activity. These mice developed hyperinsulinaemia and glucose intolerance. This phenotype also displayed reduced expression of Cers1 in the hypothalamus as well as decreased concentration of several C18 species of ceramides and a 3-fold decrease in total ceramide intensity. Conversely, overexpression of Lpl specifically in the MBH induced a decrease in body weight.

CONCLUSIONS/INTERPRETATION

Our study shows that LPL in the MBH is an important regulator of body weight and glucose homeostasis.

Lipid Processing in the Brain: A Key Regulator of Systemic Metabolism

Metabolic disorders, particularly aberrations in lipid homeostasis, such as obesity, type 2 diabetes mellitus, and hypertriglyceridemia often manifest together as the metabolic syndrome (MetS). Despite major advances in our understanding of the pathogenesis of these disorders, the prevalence of the MetS continues to rise. It is becoming increasingly apparent that intermediary metabolism within the central nervous system is a major contributor to the regulation of systemic metabolism. In particular, lipid metabolism within the brain is tightly regulated to maintain neuronal structure and function and may signal nutrient status to modulate metabolism in key peripheral tissues such as the liver. There is now a growing body of evidence to suggest that fatty acid (FA) sensing in hypothalamic neurons via accumulation of FAs or FA metabolites may signal nutritional sufficiency and may decrease hepatic glucose production, lipogenesis, and VLDL-TG secretion. In addition, recent studies have highlighted the existence of liver-related neurons that have the potential to direct such signals through parasympathetic and sympathetic nervous system activity. However, to date whether these liver-related neurons are FA sensitive remain to be determined. The findings discussed in this review underscore the importance of the autonomic nervous system in the regulation of systemic metabolism and highlight the need for further research to determine the key features of FA neurons, which may serve as novel therapeutic targets for the treatment of metabolic disorders.

Altered cellular redox status, sirtuin abundance and clock gene expression in a mouse model of developmentally primed NASH

Background

We have previously shown that high fat (HF) feeding during pregnancy primes the development of non-alcoholic steatohepatits (NASH) in the adult offspring. However, the underlying mechanisms are unclear.

Aims

Since the endogenous molecular clock can regulate hepatic lipid metabolism, we investigated whether exposure to a HF diet during development could alter hepatic clock gene expression and contribute to NASH onset in later life.

Methods

Female mice were fed either a control (C, 7% kcal fat) or HF (45% kcal fat) diet. Offspring were fed either a C or HF diet resulting in four offspring groups: C/C, C/HF, HF/C and HF/HF. NAFLD progression, cellular redox status, sirtuin expression (Sirt1, Sirt3), and the expression of core clock genes (Clock, Bmal1, Per2, Cry2) and clock-controlled genes involved in lipid metabolism (Rev-Erbα, Rev-Erbβ, RORα, and Srebp1c) were measured in offspring livers.

Results

Offspring fed a HF diet developed NAFLD. However HF fed offspring of mothers fed a HF diet developed NASH, coupled with significantly reduced NAD⁺/NADH (p < 0.05, HF/HF vs C/C), Sirt1 (p < 0.001, HF/HF vs C/C), Sirt3 (p < 0.01, HF/HF vs C/C), perturbed clock gene expression, and elevated expression of genes involved lipid metabolism, such as Srebp1c (p < 0.05, C/HF and HF/HF vs C/C).

Conclusion

Our results suggest that exposure to excess dietary fat during early and post-natal life increases the susceptibility to develop NASH in adulthood, involving altered cellular redox status, reduced sirtuin abundance, and desynchronized clock gene expression.

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Offspring of mothers fed a high fat diet show severe fatty liver in later life.

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HF feeding is associated with altered cellular redox status and reduced sirtuin gene expression.

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HF feeding desynchronises the expression of core clock genes and lipogenic transcription factors.

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Exposure to a HF diet during development causes changes in liver metabolism that precede severe fatty liver disease.

Microbes Promote Amino Acid Harvest to Rescue Undernutrition in Drosophila

Microbes play an important role in the pathogenesis of nutritional disorders such as protein-specific malnutrition. However, the precise contribution of microbes to host energy balance during undernutrition is unclear. Here, we show that Issatchenkia orientalis, a fungal microbe isolated from field-caught Drosophila melanogaster, promotes amino acid harvest to rescue the lifespan of undernourished flies. Using radioisotope-labeled dietary components (amino acids, nucleotides, and sucrose) to quantify nutrient transfer from food to microbe to fly, we demonstrate that I. orientalis extracts amino acids directly from nutrient-poor diets and increases protein flux to the fly. This microbial association restores body mass, protein, glycerol, and ATP levels and phenocopies the metabolic profile of adequately fed flies. Our study uncovers amino acid harvest as a fundamental mechanism linking microbial and host metabolism, and highlights Drosophila as a platform for quantitative studies of host-microbe relationships.

Diet-induced maternal obesity alters ovarian morphology and gene expression in the adult mouse offspring

OBJECTIVE

To examine the effects of high-fat (HF) diet-induced maternal obesity on follicular population and gene expression in adult offspring ovaries.

DESIGN

Experimental mouse study.

SETTING

Laboratory.

ANIMAL(S)

Mice on HF diet.

INTERVENTION(S)

Female C57BL/6J mice were fed an HF or standard chow (C) diet 6 weeks before conception, through pregnancy and lactation. Offspring were fed the C or HF diet from weaning, creating the HF/HF, HF/C, C/HF, C/C offspring groups.

MAIN OUTCOME MEASURE(S)

Follicular counts and gene expression in adult offspring ovaries.

RESULT(S)

Prenatal exposure to maternal HF nutrition resulted in the reduction of primordial, antral, and Graafian follicle numbers in offspring ovaries (both HF/C and HF/HF). Expression levels of genes involved in apoptosis (FoXO3a), follicular growth and development (Gdf9), and circadian rhythms generation (Clock and Bmal1) were elevated in the ovaries of HF/C and HF/HF offspring, while expression of the circadian clock genes Cry1 and Per1 were lower in HF/HF ovaries.

CONCLUSION(S)

Maternal obesity during pregnancy has long-term deleterious consequences on follicular growth and development in the adult offspring ovaries, which may impact their reproductive potential.

Maternal and in utero determinants of type 2 diabetes risk in the young

The global prevalence of diabetes mellitus has reached epidemic proportions. In 2010, it was estimated that 6.4 % of the adult population (285 million) have diabetes. In recent years, the incidence of type 2 diabetes (T2D), a condition traditionally associated with aging, has been steadily increasing among younger individuals. It is now a well-established notion that the early-life period is a critical window of development and that influences during this period can "developmentally prime" the metabolic status of the adult. This review discusses the role of maternal and in utero influences on the developmental priming of T2D risk. Both human epidemiological studies and experimental animal models are beginning to demonstrate that early dietary challenges can accelerate the onset of age-associated metabolic disturbances, including insulin resistance, T2D, obesity, hypertension, and cardiovascular disease. These findings show that poor maternal nutrition can prime a prediabetes phenotype, often manifest as insulin resistance, by very early stages of life. Thus, the maternal diet is a critical determinant of premature T2D risk. While the mechanisms that link early nutrition to age-associated metabolic decline are currently unclear, preliminary findings suggest perturbations in a number of processes involved in cellular aging, such as changes in longevity-associated Sirtuin activity, epigenetic regulation of key metabolic genes, and mitochondrial dysfunction. Preliminary studies show that pharmacological interventions in utero and dietary supplementation in early postnatal life may alleviate insulin resistance and reduce T2D risk. However, further studies are warranted to fully understand the relationship between the early environment and long-term effects on metabolism. Such mechanistic insights will facilitate strategic interventions that prevent accelerated metabolic decline and the premature onset of T2D in the current and future generations.

High carbohydrate-low protein consumption maximizes Drosophila lifespan

Dietary restriction extends lifespan in a variety of organisms, but the key nutritional components driving this process and how they interact remain uncertain. In Drosophila, while a substantial body of research suggests that protein is the major dietary component affecting longevity, recent studies claim that carbohydrates also play a central role. To clarify how nutritional factors influence longevity, nutrient consumption and lifespan were measured on a series of diets with varying yeast and sugar content. We show that optimal lifespan requires both high carbohydrate and low protein consumption, but neither nutrient by itself entirely predicts lifespan. Increased dietary carbohydrate or protein concentration does not always result in reduced feeding-the regulation of food consumption is best described by a constant daily caloric intake target. Moreover, due to differences in food intake, increased concentration of a nutrient within the diet does not necessarily result in increased consumption of that particular nutrient. Our results shed light on the issue of dietary effects on lifespan and highlight the need for accurate measures of nutrient intake in dietary manipulation studies.

The housekeeping gene YWHAZ remains stable in a model of developmentally primed non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in Western society. Comparative gene expression studies are beginning to elucidate the molecular mechanisms underlying NAFLD progression. We have previously shown that high fat diets during early life can prime non-alcoholic steatohepatitis (NASH) in adulthood, through lipogenesis gene elevation. To generate accurate results in such studies, appropriate housekeeping genes (HKG) which are unaffected by disease processes, are used for data normalisation. However, there is little existing data to show the effects of NAFLD on HKG expression.

AIMS

To identify the HKG in a mouse model of developmentally primed NAFLD and NASH, which maintains expression stability.

METHODS

We determined the expression stability of six candidates HKG (GAPDH, YWHAZ, B2M, EIF4A2, ACTB and CYC1) in a mouse model of developmentally primed NAFLD in both the day and night, using geNORM qBasePlus software.

RESULTS

HKG expression differed across dietary groups and time of day. In the majority of treatment groups and time points the most stable gene was YWHAZ. Following high fat diet interventions CYC1 became notably unstable. Overall the effect of NAFLD and NASH on HKG expression was to maintain stability of YWHAZ, but destabilise CYC1 and EIF4A2.

CONCLUSIONS

Our data clearly shows that HKG expression is affected by NAFLD severity and time of day sampling, highlighting the importance of suitable HKG gene selection. For comparative gene expression studies investigating NAFLD we would recommend use of YWHAZ as a robust, stably expressed HKG.

Impact of antibiotic treatment for pulmonary exacerbations on bacterial diversity in cystic fibrosis

BACKGROUND

A diverse array of bacterial species is present in the CF airways, in addition to those recognised as clinically important. Here, we investigated the relative impact of antibiotics, used predominantly to target Pseudomonas aeruginosa during acute exacerbations, on other non-pseudomonal species.

METHODS

The relative abundance of viable P. aeruginosa and non-pseudomonal species was determined in sputa from 12 adult CF subjects 21, 14, and 7 days prior to antibiotics, day 3 of treatment, the final day of treatment, and 10-14 days afterwards, by T-RFLP profiling.

RESULTS

Overall, relative P. aeruginosa abundance increased during antibiotic therapy compared to other bacterial species; mean abundance pre-antibiotic 51.0±36.0% increasing to 71.3±30.4% during antibiotic (ANOVA: F(1,54)=5.16; P<0.027). Further, the number of non-pseudomonal species detected fell; pre-antibiotic 6.0±3.3 decreasing to 3.7±3.3 during treatment (ANOVA: F(1,66)=5.11; P<0.027).

CONCLUSIONS

Antibiotic treatment directed at P. aeruginosa has an additional significant impact on non-pseudomonal, co-colonising species.

Variation in stability of housekeeping genes in endometrium of healthy and polycystic ovarian syndrome women

BACKGROUND

The use of housekeeping genes (HKG) as internal controls for real-time qPCR studies of gene expression is based on the assumption of their inherent stability. However, it is unclear whether this stability is maintained in disease states. In order to test this, the present study investigated the expression of specific HKG in the endometrium of healthy and polycystic ovarian syndrome (PCOS) women.

METHODS

Endometrial tissue samples were taken from women with PCOS (n= 9) and controls (n= 10). The stability of nine candidate reference genes in the endometrial tissues were evaluated; four encode mitochondrial proteins [ATP5B, succinate dehydrogenase complex subunit A (SDHA), cytochrome c-1, glyceraldehyde-3-phosphatedehydrogenase], two encode ribosomal protein genes (18s ribosomal RNA, ribosomal protein L13A), one for cell structure (SDHA), one for cell signalling (beta actin, ACTB) and one involved in DNA repair (topoisomerase I, TOP1). The expression stability of these HKGs was calculated using geNORM qbasePLUS software, with stability defined by M-values, where higher M-value indicating less stability. In addition, changes in their cycle threshold values were analysed to determine direction of change between groups, and a Mann-Whitney U-test was used to determine statistical differences in expression.

RESULTS

The most stable HKGs observed across both PCOS endometrium were found to be YWHAZ, CYC1 and ACTB. Further TOP1 demonstrated higher gene expression in the endometrium from PCOS women compared with those from healthy women.

CONCLUSIONS

Of the nine HKGs examined, only YWHAZ, CYC1 and ACTB were stable in both control and PCOS endometrium: these should therefore be used as internal controls for quantitative reverse transcription-polymerase chain reaction analysis. Published discrepancies between endometrial gene expression studies may therefore be due in part to in the inappropriate HKG selection, and future gene expression studies should be based on HKG of known stability in both the disease and healthy states to avoid erroneous interpretation of results.

Epigenetic priming of the metabolic syndrome

The metabolic syndrome (MetS) represents a cluster of cardiometabolic risk factors, including central obesity, insulin resistance, glucose intolerance, dyslipidemia, hypertension, hyperinsulinemia and microalbuminuria, and more recently, nonalcoholic fatty liver disease (NAFLD), polycystic ovarian syndrome (PCOS) and atherosclerosis. Although the concept of the MetS is subject to debate due to lack of a unifying underlying mechanism, the prevalence of a metabolic syndrome phenotype is rapidly increasing worldwide. Moreover, it is increasingly prevalent in children and adolescents of obese mothers. Evidence from both epidemiological and experimental animal studies now demonstrates that MetS onset is increasingly likely following exposure to suboptimal nutrition during critical periods of development, as observed in maternal obesity. Thus, the developmental priming of the MetS provides a common origin for this multifactorial disorder. Consequently, the mechanisms leading to this developmental priming have recently been the subject of intensive investigation. This review discusses recent data regarding the epigenetic modifications resulting from nutrition during early development that mediate persistent changes in the expression of key metabolic genes and contribute toward an adult metabolic syndrome phenotype. In addition, this review considers the role of the endogenous molecular circadian clock system, which has the potential to act at the interface between nutrient sensing and epigenetic processing. A continued and greater understanding of these mechanisms will eventually aid in the identification of individuals at high risk of cardiovascular disease (CVD) and type 2 diabetes, and help develop therapeutic interventions, in accordance with current global government strategy.

The exclusion of dead bacterial cells is essential for accurate molecular analysis of clinical samples

The DNA-based techniques used to detect bacteria in clinical samples are unable to discriminate between live bacteria, dead bacteria, and extracellular DNA. This failure to limit analysis to viable bacterial cells represents a significant problem, leading to false-positive results, as well as a failure to resolve the impact of antimicrobial therapy. The use of propidium monoazide treatment significantly reduces the contribution of dead cells and extracellular DNA to such culture-independent analyses. Here, the increased ability to resolve the impact of antibiotic therapy on Pseudomonas aeruginosa load in cystic fibrosis respiratory samples reveals statistically significant changes that would otherwise go undetected.

Analysis of mer Gene Subclasses within Bacterial Communities in Soils and Sediments Resolved by Fluorescent-PCR-Restriction Fragment Length Polymorphism Profiling

Bacterial mer (mercury resistance) gene subclasses in mercury-polluted and pristine natural environments have been profiled by Fluorescent-PCR-restriction fragment length polymorphism (FluRFLP). For FluRFLP, PCR products were amplified from individual mer operons in mercury-resistant bacteria and from DNA isolated directly from bacteria in soil and sediment samples. The primers used to amplify DNA were designed from consensus sequences of the major subclasses of archetypal gram-negative mer operons within Tn501, Tn21, pDU1358, and pKLH2. Two independent PCRs were used to amplify two regions of different lengths (merRT(Delta)P [ca. 1 kb] and merR [ca. 0.4 kb]) starting at the same position in merR. The oligonucleotide primer common to both reactions (FluRX) was labelled at the 5(prm1) end with green (TET) fluorescent dye. Analysis of the mer sequences within databases indicated that the major subclasses could be differentiated on the basis of the length from FluRX to the first FokI restriction endonuclease site. The amplified PCR products were digested with FokI restriction endonuclease, with the restriction digest fragments resolved on an automated DNA sequencing machine which detected only those bands labelled with the fluorescent dye. For each of the individual mer operon sources examined, this single peak (in bases) position was observed in separate digests of either amplified region. These peak positions were as predicted on the basis of DNA sequence. mer PCR products amplified from DNA extracted directly from soil and sediment bacteria were studied in order to determine the profiles of the major mer subclasses present in each natural environment. In addition to peaks of the expected sizes, extra peaks were observed which were not predicted on the basis of DNA sequence. Those appearing in the restriction endonuclease digests of both study regions were presumed to be novel mer types. Genetic heterogeneity within and between mercury-polluted and pristine sites has been studied by this technique. Profiles generated were highly similar for samples taken within the same soil type. The profiles, however, changed markedly on crossing from one soil type to another, with gradients of the different groupings of mer genes identified.

Characterisation of bacteria in ascites--reporting the potential of culture-independent, molecular analysis

Spontaneous bacterial peritonitis (SBP) is a severe complication of liver disease. A significant proportion of patients have culture-negative ascites, despite having similar signs, symptoms and mortality to those with SBP. Therefore, empirical antibiotic treatment for infection is often started without knowledge of the causative organisms. Here, we investigated the potential of molecular techniques to provide rapid and accurate characterisation of the bacteria present in ascitic fluid. Ascites samples were obtained from 29 cirrhotic patients undergoing clinically indicated therapeutic paracentesis. Bacterial content was determined by terminal restriction fragment length polymorphism (T-RFLP) analysis, quantitative polymerase chain reaction (PCR) and 16S ribosomal clone sequence analysis. Bacterial signal was detected in all samples, compared to three out of ten using standard methods. Bacterial loads ranged from 5.5 x 10(2) to 5.4 x 10(7) cfu/ml, with a mean value of 1.9 x 10(6) cfu/ml (standard deviation +/- 9.6 x 10(6) cfu/ml). In all but one instance, bacterial species identified by culture were also confirmed by molecular analyses. Preliminary data presented here suggests that culture-independent, molecular analyses could provide rapid characterisation of the bacterial content of ascites fluid, providing a basis for the investigation of SBP development and allowing early and targeted antibiotic intervention.

The metabolic syndrome: common origins of a multifactorial disorder

The metabolic syndrome (MetS) represents a combination of cardiometabolic risk determinants including obesity (central adiposity), insulin resistance, glucose intolerance, dyslipidaemia, non-alcoholic fatty liver disease and hypertension. MetS is rapidly increasing in prevalence worldwide as a consequence of the continued obesity "epidemic", and as a result will have a considerable impact on the global incidence of cardiovascular disease and type 2 diabetes. Currently, there is debate concerning whether the risk of cardiovascular disease is greater in patients diagnosed with MetS than that of the sum of the individual risk factors. At present, no unifying origin that can explain the pathogenesis of MetS has been identified and therefore no unique pharmacological treatment is available. This review summarises and critically evaluates the current clinical and scientific evidence supporting the existence of MetS as a multifactorial endocrine disease, for which maternal nutrition may be a common pathogenic mechanism. In addition, we suggest that ectopic fat accumulation (such as visceral and hepatic fat accumulation) and the proinflammatory state are central to the development of the MetS.

The developmental origins, mechanisms, and implications of metabolic syndrome

Metabolic syndrome (MetS) represents a combination of cardio-metabolic risk determinants, including central obesity, insulin resistance, glucose intolerance, dyslipidemia, hypertension, hyperinsulinemia, and microalbuminuria. The prevalence of MetS is rapidly increasing worldwide, largely as a consequence of the ongoing obesity epidemic. Environmental factors during periods early in development have been shown to influence the susceptibility to develop disease in later life. In particular, there is a wealth of evidence from both epidemiological and animal studies for greater incidence of features of MetS as a result of unbalanced maternal nutrition. The mechanisms by which nutritional insults during a period of developmental plasticity result in a MetS phenotype are now beginning to receive considerable scientific interest. This review focuses on recent data regarding these mechanisms, in particular the epigenetic and transcriptional regulation of key metabolic genes in response to nutritional stimuli that mediate persistent changes and an adult MetS phenotype. A continued and greater understanding of these mechanisms will eventually allow specific interventions, with a favorable impact on the global incidence of cardiovascular disease and type 2 diabetes in the future.

Modelling the bacterial communities associated with cystic fibrosis lung infections

In many human diseases that cystic fibrosis (CF) patients suffer from, for example, lung infections, bacteria have been considered to grow as biofilms. The ability of key CF pathogens such as Pseudomonas aeruginosa to resist antibiotic therapies may be due to the poor drug penetration of these biofilms. The overall aim of this study was to develop biofilm models in vitro that resembled the bacterial species composition of CF sputa. Here, this was a step towards a longer term goal of forming multiple bacterial biofilm models in vitro that would serve, in turn, as better assays of antibiotic susceptibilities than conventionally grown cells. Biofilm models were constructed from 31 CF sputum samples, using a modified microtitre plate assay. Three forms of assessment of these biofilms were made, namely, the mass, microscopic analysis and species composition. Species composition in sputa and biofilms, characterised by terminal restriction fragment length polymorphism (T-RFLP) analysis of ribosomal gene polymerase chain reaction (PCR) products amplified from directly extracted nucleic acids, indicated that the bacterial community in sputa was well reproduced in the biofilm models. Typically, fresh sputa contained 4.6 +/- 2.3 bacterial species, with the species number decreasing to 4.0 +/- 1.6 over 5 days-this was not statistically significant (p = 0.29). This study outlines a novel methodology by which to generate and study bacterial biofilms communities. It is also hoped that the versatility of this in vitro approach, combined with its simplicity and high reproducibility, will make it an effective system to study CF sputum biofilm development and, in the longer term, serve as a means of assessing antibiotic susceptibilities.

Maternal high-fat feeding primes steatohepatitis in adult mice offspring, involving mitochondrial dysfunction and altered lipogenesis gene expression

Nonalcoholic fatty liver disease (NAFLD) describes an increasingly prevalent spectrum of liver disorders associated with obesity and metabolic syndrome. It is uncertain why steatosis occurs in some individuals, whereas nonalcoholic steatohepatitis (NASH) occurs in others. We have generated a novel mouse model to test our hypothesis: that maternal fat intake contributes to the development of NAFLD in adult offspring. Female mice were fed either a high-fat (HF) or control chow (C) diet before and during gestation and lactation. Resulting offspring were fed either a C or a HF diet after weaning, to generate four offspring groups; HF/HF, HF/C, C/HF, C/C. At 15 weeks of age, liver histology was normal in both the C/C and HF/C offspring. Kleiner scoring showed that although the C/HF offspring developed nonalcoholic fatty liver, the HF/HF offspring developed NASH. At 30 weeks, histological analysis and Kleiner scoring showed that both the HF/C and C/HF groups had NAFLD, whereas the HF/HF had a more severe form of NASH. Therefore, exposure to a HF diet in utero and during lactation contributes toward NAFLD progression. We investigated the mechanisms by which this developmental priming is mediated. At 15 weeks of age, hepatic mitochondrial electron transport chain (ETC) enzyme complex activity (I, II/III, and IV) was reduced in both groups of offspring from HF-fed mothers (HF/C and HF/HF). In addition, measurement of hepatic gene expression indicated that lipogenesis, oxidative stress, and inflammatory pathways were up-regulated in the 15-week-old HF/C and HF/HF offspring.

CONCLUSION

Maternal fat intake contributes toward the NAFLD progression in adult offspring, which is mediated through impaired hepatic mitochondrial metabolism and up-regulated hepatic lipogenesis.

Maternal high fat diet during pregnancy and lactation alters hepatic expression of insulin like growth factor-2 and key microRNAs in the adult offspring

Background

miRNAs play important roles in the regulation of gene functions. Maternal dietary modifications during pregnancy and gestation have long-term effects on the offspring, but it is not known whether a maternal high fat (HF) diet during pregnancy and lactation alters expression of key miRNAs in the offspring.

Results

We studied the effects of maternal HF diet on the adult offspring by feeding mice with either a HF or a chow diet prior to conception, during pregnancy and lactation, and all offspring were weaned onto the same chow diet until adulthood. Maternal HF fed offspring had markedly increased hepatic mRNA levels of peroxisome proliferator activated receptor-alpha (ppar-alpha) and carnitine palmitoyl transferase-1a (cpt-1a) as well as insulin like growth factor-2 (Igf2). A HF diet induced up-regulation of ppar-alpha and cpt-1a expression in the wild type but not in Igf2 knock out mice. Furthermore, hepatic expression of let-7c was also reduced in maternal HF fed offspring. Among 579 miRNAs measured with microarray, ~23 miRNA levels were reduced by ~1.5-4.9-fold. Reduced expression of miR-709 (a highly expressed miRNA), miR-122, miR-192, miR-194, miR-26a, let-7a, let7b and let-7c, miR-494 and miR-483* (reduced by ~4.9 fold) was validated by qPCR. We found that methyl-CpG binding protein 2 was the common predicted target for miR-709, miR-let7s, miR-122, miR-194 and miR-26a using our own purpose-built computer program.

Conclusion

Maternal HF feeding during pregnancy and lactation induced co-ordinated and long-lasting changes in expression of Igf2, fat metabolic genes and several important miRNAs in the offspring.

Characterization of a spirochaete isolated from a case of bovine digital dermatitis

AIMS

The aim of the study was to characterize a spirochaete isolated from the lesions of a cow with digital dermatitis (DD).

METHODS AND RESULTS

The characterization was on the basis of its light and electron microscopic appearance, enzymic profile and DNA sequence analysis of its flagellin and 16S rRNA genes. The spirochaete was 6-8-microm long and 0.2-0.3 microm in diameter, and possessed seven to eight periplasmic flagella, with three to five helical turns. The enzymic profile of the bacterium resembles, but is not identical to that of Treponema brennaborense. Its flagellin gene sequence was identical to that of Treponema phagedenis but distinct from that of an ovine spirochaete. Analysis of a 1477-bp region of the 16S rRNA genes indicated that this is a Treponema species and that it is indistinguishable from some isolates made from cases of bovine DD in the United States. Finally, electron microscopy revealed the presence of myovirus-like bacteriophage particles in all cultures of the treponeme examined.

CONCLUSIONS

The spirochaete isolate was identified as a Treponema species closely related to some isolates from the United States (by 16S rDNA) and to T. phagedenis (by flagellin gene sequence) and is associated with bacteriophage particles.

SIGNIFICANCE AND IMPACT OF THE STUDY

The fact that the isolates with the same or very similar 16S rDNA sequences have been obtained from cases of bovine DD in cattle in different countries at different times, lends further support to the hypothesis that treponemes play a role in the pathogenesis of this disease.

Use of 16S rRNA gene profiling by terminal restriction fragment length polymorphism analysis to compare bacterial communities in sputum and mouthwash samples from patients with cystic fibrosis

The bacterial communities present in the oral cavity and the lungs of 19 adult cystic fibrosis (CF) patients were compared by using terminal restriction fragment length polymorphism analysis of 16S rRNA gene PCR products amplified from nucleic acids extracted directly from bacteria in clinical samples. Sputum samples were not found to be subject to profound contamination by oral cavity bacteria. Evidence of colonization of the CF lung by certain oral bacterial species was found.

Molecular characterization of the bacteria adherent to human colorectal mucosa

AIMS

To study large intestinal mucosal bacterial communities by Denaturing Gradient Gel Electrophoresis (DGGE) profiling and sequencing of 16S rRNA gene polymerase chain reaction (PCR) products amplified from DNA extracted from colorectal biopsies taken from healthy individuals. The specific aims were to determine how similar the mucosa-associated bacterial communities are within and between individuals and also to characterize the phylogenetic origin of isolated DGGE bands.

METHODS AND RESULTS

Human colorectal biopsies were taken at routine colonoscopy from 33 patients with normal looking mucosa. The DNA was extracted directly from single biopsies and the bacterial 16S rDNA PCR amplified. The PCR products were profiled using DGGE to generate a fingerprint of the dominant members of the bacterial community associated with the biopsy. The reproducibility of this method was high (>98%). Washed and unwashed biopsies gave similar DGGE banding patterns (Median Similarity Coefficient - MSC 96%, InterQuartile Range - IQR 3.0%, n = 5). Adjacent biopsies sampled from the same patient using different forceps gave similar DGGE profiles (MSC 94%, n = 2). Two colorectal biopsies sampled at locations 2-5 cm apart, from each of 18 patients, resulted in very similar profiles (MSC 100%, IQR 2.8%). Biopsies sampled from different locations within the large intestine of the same patient also gave similar DGGE profiles (MSC 98% IQR 3.3%n = 6). Although all patients (n = 33) gave different DGGE profiles, some similarity (c. 34%) was observed between profiles obtained from 15 patients arbitrarily selected. 35 DGGE bands were excised and sequenced. Many were found to be most closely related to uncultured bacterial sequence entries in the Genbank database. Others belonged to typical gut bacterial genera including Bacteroides, Ruminococcus, Faecalibacterium and Clostridium.

CONCLUSIONS

Bacterial communities adherent to colorectal mucosa within a normal patient show little variation; in contrast, mucosal bacterial communities sampled from different patients with normal colorectal mucosa show a high degree of variation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research demonstrates that DGGE profiling of 16S rRNA gene PCR products amplified from DNA extracted directly from mucosal samples offers fresh insight into the bacterial communities that are adherent to colorectal mucosa. These findings are important with respect to further studies on the gastrointestinal tract in health and disease.

characterization of bacterial community diversity in cystic fibrosis lung infections by use of 16s ribosomal DNA terminal restriction fragment length polymorphism profiling

Progressive loss of lung function resulting from the inflammatory response to bacterial colonization is the leading cause of mortality in cystic fibrosis (CF) patients. A greater understanding of these bacterial infections is needed to improve lung disease management. As culture-based diagnoses are associated with fundamental drawbacks, we used terminal restriction fragment (T-RF) length polymorphism profiling and 16S rRNA clone data to characterize, without prior cultivation, the bacterial community in 71 sputa from 34 adult CF patients. Nineteen species from 15 genera were identified in 53 16S rRNA clones from three patients. Of these, 15 species have not previously been reported in CF lung infections and many were species requiring strict anaerobic conditions for growth. The species richness and evenness were determined from the T-RF length and volume for the 71 profiles. Species richness was on average 13.3 +/- 7.9 per sample and 13.4 +/- 6.7 per patient. On average, the T-RF bands of the lowest and highest volumes represented 0.6 and 59.2% of the total volume in each profile, respectively. The second through fifth most dominant T-RF bands represented 15.3, 7.5, 4.7, and 2.8% of the total profile volume, respectively. On average, the remaining T-RF bands represented 10.2% of the total profile volume. The T-RF band corresponding to Pseudomonas aeruginosa had the highest volume in 61.1% of the samples. However, 18 other T-RF band lengths were dominant in at least one sample. In conclusion, this reveals the enormous complexity of bacteria within the CF lung. Although their significance is yet to be determined, these findings alter our perception of CF lung infections.

Bacterial diversity in cases of lung infection in cystic fibrosis patients: 16S ribosomal DNA (rDNA) length heterogeneity PCR and 16S rDNA terminal restriction fragment length polymorphism profiling

The leading cause of morbidity and mortality in cystic fibrosis (CF) patients stems from repeated bacterial respiratory infections. Many bacterial species have been cultured from CF specimens and so are associated with lung disease. Despite this, much remains to be determined. In the present study, we characterized without prior cultivation the total bacterial community present in specimens taken from adult CF patients, extracting DNA directly from 14 bronchoscopy or sputum samples. Bacterial 16S ribosomal DNA (rRNA) gene PCR products were amplified from extracted nucleic acids, with analyses by terminal restriction fragment length polymorphism (T-RFLP), length heterogeneity PCR (LH-PCR), and sequencing of individual cloned PCR products to characterize these communities. Using the same loading of PCR products, 12 distinct T-RFLP profiles were identified that had between 3 and 32 T-RFLP bands. Nine distinct LH-PCR profiles were identified containing between one and four bands. T-RFLP bands were detected in certain samples at positions that corresponded to pathogens cultured from CF samples, e.g., Burkholderia cepacia and Haemophilus influenzae. In every sample studied, one T-RFLP band was identified that corresponded to that produced by Pseudomonas aeruginosa. A total of 103 16S rRNA gene clones were examined from five patients. P. aeruginosa was the most commonly identified species (59% of clones). Stenotrophomonas species were also common, with eight other (typically anaerobic) bacterial species identified within the remaining 17 clones. In conclusion, T-RFLP analysis coupled with 16S rRNA gene sequencing is a powerful means of analyzing the composition and diversity of the bacterial community in specimens sampled from CF patients.

Isolation and characterisation of a novel spirochaete from severe virulent ovine foot rot

A novel spirochaete was isolated from a case of severe virulent ovine foot rot (SVOFR) by immunomagnetic separation with beads coated with polyclonal anti-treponemal antisera and prolonged anaerobic broth culture. The as yet unnamed treponeme differs considerably from the only other spirochaete isolated from ovine foot rot as regards morphology, enzymic profile and 16S rDNA sequence. On the basis of 16S rDNA, it was most closely related to another unnamed spirochaete isolated from cases of bovine digital dermatitis in the USA, raising the possibility of cross-species transmission. Further information is required to establish this novel ovine spirochaete as the cause of SVOFR.

Terminal restriction fragment length polymorphism monitoring of genes amplified directly from bacterial communities in soils and sediments

Terminal Restriction Fragment Length Polymorphism (T-RFLP) or Fluorescent Polymerase Chain Reaction/Restriction Fragment Length Polymorphism (FluRFLP) have made a significant impact on the way in which PCR products amplified from mixed community DNA extracts have been assessed. Technically, these approaches are essentially the same. PCR products are generated that contain at one 5' end label, typically a fluorescent moiety, that will be detected by a DNA sequencing machine. Upon digestion using a specific restriction endonuclease, labeled and unlabeled fragments are generated. This restriction endonuclease is chosen such that following this digestion, each labeled fragment corresponds to a different sequence variant. During electrophoretic separation, the DNA sequencing machine detects only these labeled fragments and therefore detects only the sequence variants. The aim of this article is to describe the protocols and demonstrate that this profiling can be performed using different DNA sequencing machines. The analysis and applications of this approach are also discussed.

Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems

In model terrestrial ecosystems maintained for three plant generations at elevated concentrations of atmospheric carbon dioxide, increases in photosynthetically fixed carbon were allocated below ground, raising concentrations of dissolved organic carbon in soil. These effects were then transmitted up the decomposer food chain. Soil microbial biomass was unaffected, but the composition of soil fungal species changed, with increases in rates of cellulose decomposition. There were also changes in the abundance and species composition of Collembola, fungal-feeding arthropods. These results have implications for long-term feedback processes in soil ecosystems that are subject to rising global atmospheric carbon dioxide concentrations.