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The objective of this study was to investigate the effect of dietary fatty acid (FA) saturation and carbon chain length on brain bile acid (BA) metabolism and neuronal number in a pig model of pediatric NAFLD. Thirty 20-day-old Iberian pigs, pair-housed in pens, were randomly assigned to receive one of three hypercaloric diets for 10 weeks: (1) lard-enriched (LAR; n = 5 pens), (2) olive-oil-enriched (OLI, n = 5), and (3) coconut-oil-enriched (COC; n = 5). Pig behavior and activity were analyzed throughout the study. All animals were euthanized on week 10 and frontal cortex (FC) samples were collected for immunohistochemistry, metabolomic, and transcriptomic analyses. Data were analyzed by multivariate and univariate statistics. No differences were observed in relative brain weight, neuronal number, or cognitive functioning between diets. Pig activity and FC levels of neuroprotective secondary BAs and betaine decreased in the COC and OLI groups compared with LAR, and paralleled the severity of NAFLD. In addition, OLI-fed pigs showed downregulation of genes involved in neurotransmission, synaptic transmission, and nervous tissue development. Similarly, COC-fed pigs showed upregulation of neurogenesis and myelin repair genes, which caused the accumulation of medium-chain acylcarnitines in brain tissue. In conclusion, our results indicate that secondary BA levels in the FCs of NAFLD pigs are affected by dietary FA composition and are associated with metabolic and transcriptomic markers of brain injury. Dietary interventions that aim to replace saturated FAs by medium-chain or monounsaturated FAs in high-fat hypercaloric diets may have a negative effect on brain health in NAFLD patients.

Borrelia burgdorferi, an agent of Lyme disease, encodes the beta(3)-chain integrin ligand P66. P66 is expressed by B. burgdorferi in the mammal, in laboratory media, and as the bacteria are acquired or transmitted by the tick, but is not expressed by the bacterium in unfed ticks. Attempts to reveal factors influencing expression revealed that P66 was expressed in all in vitro conditions investigated. Candidate regulators identified in a search of the B. burgdorferi genome for homologs to other bacterial transcription factors were cloned and introduced into E. coli carrying a p66 promoter-signal sequence-phoA (alkaline phosphatase, or AP) fusion. Three candidate transcription factors-two that decreased AP activity (Hbb and BB0527), and one that increased AP activity (BBA23)-were identified. BBA23 and BB0527 did not bind to the p66 promoter at physiologically relevant concentrations. In contrast, several promoter fragments, including p66, were bound by Hbb (BB0232), with slightly different affinities. Consistent with results from other laboratories, Hbb appears to recognize multiple DNA sequences. Changes in the expression of p66 and bb0232 in the tick at various points with respect to feeding on mice, along with the results of the reporter experiment in the surrogate host E. coli, are consistent with Hbb/BB0232 being involved in regulating p66 expression.

Borrelia burgdorferi undergoes an infectious cycle that requires adaptation to different hosts and marked differences in environment. B. burgdorferi copes with its different environments by regulating the expression of proteins required for survival in specific settings. The B. burgdorferi oligopeptide permease (Opp) is one of only a few transporters encoded by the B. burgdorferi genome. Opp proteins in other bacteria serve multiple environmental adaptation functions. B. burgdorferi appears to broaden the usage of this transporter by utilizing five different substrate binding proteins (OppA proteins) that interact with the integral membrane components of the transporter. Expression of the OppA proteins is individually regulated and may play different roles in adaptation to host environments. Very little is known about the mechanisms used by B. burgdorferi to regulate the expression of different OppA proteins. Here we show that the alternative sigma factors, RpoS and RpoN, regulate the expression of oppA5 but not that of other oppA genes. Using a reporter assay with Escherichia coli and gel shift binding assays, we also show that the B. burgdorferi BosR/Fur homologue interacts with the oppA4 promoter and that another candidate transcription factor, EbfC, interacts with the oppA5 promoter. Binding to the promoters was confirmed by gel shift assays. Expression of BosR/Fur in its different hosts does appear to parallel the expression of oppA4. A better understanding of the factors involved in gene regulation in B. burgdorferi will help to identify coregulated proteins that may cooperate to allow the organism to survive in a specific environment.