Riboflavin instability is a key factor underlying the requirement of a gut microbiota for mosquito development

We previously determined that several diets used to rear Aedes aegypti and other mosquito species support the development of larvae with a gut microbiota but do not support the development of axenic larvae. In contrast, axenic larvae have been shown to develop when fed other diets. To understand the mechanisms underlying this dichotomy, we developed a defined diet that could be manipulated in concert with microbiota composition and environmental conditions. Initial studies showed that axenic larvae could not grow under standard rearing conditions (27 °C, 16-h light: 8-h dark photoperiod) when fed a defined diet but could develop when maintained in darkness. Downstream assays identified riboflavin decay to lumichrome as the key factor that prevented axenic larvae from growing under standard conditions, while gut community members like Escherichia coli rescued development by being able to synthesize riboflavin. Earlier results showed that conventional and gnotobiotic but not axenic larvae exhibit midgut hypoxia under standard rearing conditions, which correlated with activation of several pathways with essential growth functions. In this study, axenic larvae in darkness also exhibited midgut hypoxia and activation of growth signaling but rapidly shifted to midgut normoxia and arrested growth in light, which indicated that gut hypoxia was not due to aerobic respiration by the gut microbiota but did depend on riboflavin that only resident microbes could provide under standard conditions. Overall, our results identify riboflavin provisioning as an essential function for the gut microbiota under most conditions A. aegypti larvae experience in the laboratory and field.

Diet crucially affects the health of all animals (1). Most animals have a gut microbiota that can also affect host health both positively and negatively (2–6). However, understanding of the mechanisms underlying the effects of the gut microbiota remains a major challenge. This is because animals often consume complex or variable diets, and harbor large, multimember microbial communities that can result in many interactions that hinder identification of the factors responsible for particular host responses (2, 6–11). Metaanalyses and multiomic approaches can provide inferential insights on how diet–microbe or microbe–microbe interactions affect hosts (11–18), but functional support can be difficult to generate if proposed mechanisms cannot be studied experimentally (2, 14). Thus, study systems where hosts can be reared on defined diets with or without a microbiota of known composition can significantly advance mechanistic insights by providing the means to control and manipulate dietary, microbial, and environmental variables that potentially affect a given host response (19–21).Mosquitoes are best known as insects that blood feed on humans and other vertebrates. Only adult-stage female mosquitoes blood feed, which is required for egg formation by most species (22). Blood feeding has also led to several mosquitoes evolving into vectors that can transmit disease-causing microbes between hosts (22). In contrast, the juvenile stages of all mosquitoes are aquatic, with most species feeding on detritivorous diets (22–24). Larvae hatch from eggs with no gut microbiota but quickly acquire relatively low-diversity communities from the environment by feeding (25). Most gut community members are aerobic or facultatively anaerobic bacteria in four phyla (Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria), although other microbes, such as fungi and apicomplexans, have also been identified (25–39). Gut community composition also commonly varies within and between species as a function of where larvae develop, diet, and other variables (28–30, 32, 34, 40–42).Aedes aegypti has a worldwide distribution in tropical and subtropical regions, and is the primary vector of the agents that cause yellow fever, dengue fever, and lymphatic filariasis in humans (43). Preferentially living in urban habitats, females lay eggs in water-holding containers with microbial communities, and larvae molt through four instars before pupating and emerging as adults (30, 35, 41, 43). Conventionally reared cultures with a gut microbiota are usually maintained in the laboratory under conditions that mimic natural habitats with rearing temperatures of 25 to 28 °C and a 12- to 16-h light: 8- to 12-h dark photoperiod (44–46). Most insects that require microbial partners for survival live on nutrient-poor diets where microbes provision nutrients that cannot be synthesized or produced in sufficient abundance by the host (3). Mosquito larvae can experience resource limitations in the field (23–25), but in the laboratory are reared on undefined, nutrient-rich diets, such as rodent chow, fish food flakes, or mixtures of materials like liver powder, fish meal, and yeast extract (44–46). Nonetheless, our previous studies indicated that axenic A. aegypti as well as other species consume but fail to grow beyond the first instar when fed several diets that support the development of nonsterile, conventionally reared larvae (30, 47–49). Escherichia coli and several other bacteria identified as gut community members could colonize the gut (producing monoxenic, gnotobiotic larvae) and rescue development, but feeding axenic larvae dead bacteria could not (30, 35, 47). The presence of a gut microbiota in conventional and gnotobiotic but not axenic larvae was also associated with midgut hypoxia and activation of several signaling pathways with growth functions (50, 51). Finally, our own previous results using a strain of E. coli susceptible to ampicillin (50), and more recently a method for clearing an auxotrophic strain of E. coli from gnotobiotic larvae (52), both showed that the proportion of individuals that develop into adults correlates with the duration that larvae have living bacteria in their gut.Altogether, the preceding results suggested that A. aegypti and several other mosquitoes require a gut microbiota for development. In contrast, another recent study showed that axenic A. aegypti larvae develop into adults, albeit more slowly than larvae with a gut microbiota, when fed diets comprised of autoclaved bovine liver powder (LP) and brewer’s yeast (Saccharomyces cerevisiae) extract (YE) or autoclaved LP, YE, and E. coli (EC) embedded in agar (53). This latter finding suggests the undefined dietary components used provide factors larvae require for development into adults, whereas a gut microbiota was also required to provide these factors under the conditions in which our own previous studies were conducted. The goal of this study was to identify what these factors are. Toward this end, we first assessed the growth of axenic A. aegypti when fed diets containing autoclaved LP, YE, and EC under different conditions. We then used this information to develop a defined diet that allowed us to systematically manipulate nutrient, microbial, and environmental variables. We report that the instability of riboflavin is a key factor underlying why A. aegypti larvae require a gut microbiota under most conditions experienced in the laboratory and field.     

Adipocyte signals in energy balance and digestive diseases]

For the regulation of energy balance in various internal organs including gut, pancreas and liver, visceral adipose tissue and brain perform important sensing and signaling roles via neural and endocrine pathway. Among these, adipose tissue has been known as a simple energy-storing organ, which stores excess energy in triglyceride. However, it became apparent that adipocytes have various receptors related to energy homeostasis, and secrete adipocytokines by endocrine, paracrine and autocrine mechanisms. In this review, basic roles of adipocytes in energy homeostasis and the correlation between adipocyte signals and digestive diseases are discussed.     

Chronic Q fever endocarditis.

Eight patients with chronic Q fever endocarditis were treated with tetracycline for up to 40 months. In addition, five of these patients received co-trimoxazole. Six patients had prosthetic valves. Two patients who had Q fever endocarditis on their native valves required valve replacement because of haemodynamic difficulties: in only one did the Q fever endocarditis contribute to the haemodynamic difficulty. One patient died. It is suggested that medical treatment is continued until clinically and haematologically there is no evidence of endocarditis and the Q fever phase 1 antibody titre is less than 200. No recurrence of Q fever endocarditis has been detected in three of our patients who have now stopped treatment.     

Vitamin C Deficiency of Korean Homeless Patients Visiting to Emergency Department with Acute Alcohol Intoxication

Vitamins are essential micronutrients for maintenance of tissue functions. Vitamin deficiency is one of the most serious and common health problems among both chronic alcoholics and the homeless. However, the vitamin-level statuses of such people have been little studied. We evaluated the actual vitamin statuses of alcoholic homeless patients who visited an emergency department (ED). In this study the blood levels of vitamins B1, B12, B6, and C of 217 alcoholic homeless patients were evaluated retrospectively in a single urban teaching hospital ED. Vitamin C deficiency was observed in 84.3% of the patients. The vitamin B1, B12, and B6 deficiency rates, meanwhile, were 2.3%, 2.3%, and 23.5%, respectively. Comparing the admitted patients with those who were discharged, only the vitamin C level was lower. (P=0.003) In fact, the patients'' vitamin C levels were markedly diminished, vitamin C replacement therapy for homeless patients should be considered in EDs.     

CT Findings in People Who Were Environmentally Exposed to Asbestos in Korea

Asbestos related pleuropulmonary disease has been emerging health problem for recent years. It can cause variable clinical symptoms and radiological abnormalities. However, there has been no report for their characteristics in subjects who were environmentally exposed to asbestos. We reviewed the CT images of 35 people who were environmentally exposed to asbestos in Chungnam province, Korea. The study result showed high incidence of pleural plaque and pulmonary fibrosis on chest CT (94% and 77%, respectively). The common CT findings of lung parenchymal lesions were as follows: centrilobular opacities (94%), subpleural dot-like or branching opacities (80%), interlobular septal thickening (57%), intralobular interstitial thickening (46%), parenchymal bands (43%) and subpleural curvilinear line (29%). There were no significant differences in the prevalence of pulmonary fibrosis and pleural plaques according to sex, age and duration of exposure. In conclusion, pleural plaque and pulmonary fibrosis are common asbestos-related CT finding in the exposed people. Asbestos related lung parenchymal CT findings in the participants with environmental exposure show similar to those observed in the occupational exposure.     

Noninvasive detection of multivessel disease after myocardial infarction by exercise radionuclide ventriculography

The ability of exercise radionuclide ventriculography to detect multivessel coronary artery disease in patients who survived a single myocardial infarction was assessed. Seventy-four patients who had had myocardial infarction at least 8 weeks earlier underwent cardiac catheterization and exercise radionuclide ventriculography. Thirty-eight patients had had an inferior infarction: 25 with multivessel disease and 13 with single vessel disease of the right coronary artery. Thirty-six patients had had an anterior infarction: 26 with multivessel disease and 10 with single vessel disease of the left anterior descending coronary artery.

Among patients with anterior infarction there was no significant difference between patients with single vessel disease and patients with multivessel disease with regard to resting ejection fraction, exercise ejection fraction, and the mean change from rest to exercise. Patients with single vessel disease had a decrease in ejection fraction from rest to exercise of 2.2 ± 2.7% units (mean) ± standard error [SE]), compared with a decrease of 5.4 ±1.3% units in those with multivessel disease (p = not significant [NS]). Seventeen of 26 (65%) patients with multivessel disease and 6 of 10 (60%) with single vessel disease had a decrease in ejection fraction of at least 5 percentage units (p = NS).

In patients with inferior infarction there was no difference in the mean resting ejection fraction in those with single vessel disease (53 ± 2%) compared with those with multivessel disease (50 ±2%); however, the mean exercise ejection fraction in patients with single vessel disease (57 ± 3%) was significantly higher (p < 0.005) than that in patients with multivessel disease (45 ± 2%). Sixteen of the 25 patients with multivessel disease (64%) but only 1 patient with single vessel disease (7.7%) had a decrease in ejection fraction of at least 5 percentage units (p < 0.001).

A new wall motion abnormality developed in 8 patients with anterior infarction and 11 with inferior infarction with multivessel disease and none with single vessel disease. The sensitivity and specificity in predicting multivessel disease using the criteria of the development of a new wall motion abnormality or a decrease in ejection fraction with exercise of at least 5 percentage units were 80 and 92% for the patients with inferior infarction, but only 69 and 40% for the patients with anterior infarction.

These results suggest that exercise radionuclide angiography can be used to discriminate between single and multivessel disease after inferior myocardial infarction. For patients with anterior infarction, only a new abnormality in wall motion accurately predicts multivessel disease, but this occurred in only one third of such patients.     

Electrocardiographic imaging of cardiac resynchronization therapy in heart failure: observation of variable electrophysiologic responses.

BACKGROUND: Cardiac resynchronization therapy (CRT) for congestive heart failure patients with delayed left ventricular (LV) conduction is clinically beneficial in approximately 70% of patients. Unresolved issues include patient selection, lead placement, and efficacy of LV pacing alone. Being an electrical approach, detailed electrical information during CRT is critical to resolving these issues. However, electrical data from patients have been limited because of the requirement for invasive mapping. OBJECTIVES: The purpose of this study was to provide observations and insights on the variable electrophysiologic responses of the heart to CRT using electrocardiographic imaging (ECGI). METHODS: ECGI is a novel modality for noninvasive epicardial mapping. ECGI was conducted in eight patients undergoing CRT during native rhythm and various pacing modes. RESULTS: In native rhythm (six patients), ventricular activation was heterogeneous, with latest activation in the lateral LV base in three patients and in the anterolateral, midlateral, or inferior LV in the remainder of patients. Anterior LV was susceptible to block and slow conduction. Right ventricular pacing improved electrical synchrony in two of six patients. LV pacing in three of four patients involved fusion with intrinsic excitation resulting in electrical resynchronization similar to biventricular pacing. Although generally electrical synchrony improved significantly with biventricular pacing, it was not always accompanied by clinical benefit. CONCLUSION: Results suggest that (1) when accompanied by fusion, LV pacing alone can be as effective as biventricular pacing for electrical resynchronization; (2) right ventricular pacing is not effective for resynchronization; and (3) efficacy of CRT depends strongly on the patient-specific electrophysiologic substrate.