Aminoglucose-induced feeding suppression is regulated by hypothalamic neuronal histamine in rats

Identification, Characteristics and Mechanism of 1-Deoxy-N-acetylglucosamine from Deep-Sea Virgibacillus dokdonensis MCCC 1A00493

Xanthomonas oryzae pv. oryzae, which causes rice bacterial blight, is one of the most destructive pathogenic bacteria. Biological control against plant pathogens has recently received increasing interest. 1-Deoxy-N-acetylglucosamine (1-DGlcNAc) was extracted from the supernatant of Virgibacillus dokdonensis MCCC 1A00493 fermentation through antibacterial bioassay-guided isolation. Its structure was elucidated by LC/MS, NMR, chemical synthesis and time-dependent density functional theory (TD-DFT) calculations. 1-DGlcNAc specifically suppressed X. oryzae pv. oryzae PXO99A (MIC was 23.90 μg/mL), but not other common pathogens including Xanthomonas campestris pv. campestris str.8004 and Xanthomonas oryzae pv. oryzicola RS105. However, its diastereomer (2-acetamido-1,5-anhydro-2-deoxy-d-mannitol) also has no activity to X. oryzae pv. oryzae. This result suggested that activity of 1-DGlcNAc was related to the difference in the spatial conformation of the 2-acetamido moiety, which might be attributed to their different interactions with a receptor. Eighty-four unique proteins were found in X. oryzae pv. oryzae PXO99A compared with the genome of strains8004 and RS105 by blastp. There may be unique interactions between 1-DGlcNAc and one or more of these unique proteins in X. oryzae pv. oryzae. Quantitative real-time PCR and the pharmMapper server indicated that proteins involved in cell division could be the targets in PXO99A. This research suggested that specificity of active substance was based on the active group and spatial conformation selection, and these unique proteins could help to reveal the specific mechanism of action of 1-DGlcNAc against PXO99A.

Evidence for histamine involvement in the effect of histidine loads on food and water intake in rats

We examined the hypothesis that histidine is a regulator of short-term food and water intake in rats and that this control is through histidine's action as a precursor for histamine. The primary objectives were to measure food and water intake after histidine monohydrochloride monohydrate (His-HCl) given by intragastric (IG) and intraperitoneal (IP) routes of administration and to measure feeding and drinking responses to histidine when given after blockade of the histaminergic pathway by chlorpheniramine (CPA) and alpha-fluoromethylhistidine (FMH). Eight experiments were conducted using a back-to-back design. Rats were given treatment by IP or IG administration, and food and water intake was measured during time periods of 0-1, 1-2, 2-3 and 3-14 h. Histidine consistently reduced food intake with the sensitivity to IP much greater than to the IG route. The effect of histidine given by IP or IG on water intake was similar, generally causing an increase at least in the first hour. Histidine's action was not accounted for by its energy, pH or nitrogen content. Because FMH, which blocks the enzyme converting histidine to histamine, partially reversed the effect of histidine on food and water intake, these results support the hypothesis that histidine regulates food and water intake, at least in part, through its precursor control of histamine.

Hypothalamic neuronal histamine: implications of its homeostatic control of energy metabolism

In a series of studies on histaminergic functions in the hypothalamus, probes to manipulate activities of histaminergic neuron systems were applied to assess its physiologic and pathophysiologic implications using non-obese normal and Zucker obese rats, an animal model of genetic obesity. Food intake is suppressed by either activation of H1-receptor or inhibition of the H3-receptor in the ventromedial hypothalamus (VMH) or the paraventricular nucleus, each of which is involved in satiety regulation. Histamine neurons in the mesencephalic trigeminal sensory nucleus modulate masticatory functions, particularly eating speed through the mesencephalic trigeminal motor nucleus, and activation of the histamine neurons in the VMH suppress intake volume of feeding at meals. Energy deficiency in the brain, i.e., intraneuronal glucoprivation, activates neuronal histamine in the hypothalamus. Such low energy intake in turn accelerates glycogenolysis in the astrocytes to prevent the brain from energy deficit. Thus, both mastication and low energy intake act as afferent signals for activation of histaminergic nerve systems in the hypothalamus and result in enhancement of satiation. There is a rationale for efficacy of a very-low-calorie conventional Japanese diet as a therapeutic tool for weight reduction. Feeding circadian rhythm is modulated by manipulation of hypothalamic histamine neurons. Hypothalamic histamine neurons are activated by an increase in ambient temperature. Hypothalamic neuronal histamine controls adaptive behavior including a decrease in food intake and ambulation, and an increase in water intake to maintain body temperature to be normally constant. In addition, interleukin-1 beta, an endogenous pyrogen, enhanced turnover of neuronal histamine through prostaglandin E2 in the brain. Taken together, the histamine neuron system in the hypothalamus is essential for maintenance of thermoregulation through the direct and indirect control of adaptive behavior. Behavioral and metabolic abnormalities of obese Zucker rats including hyperphagia, disruption of feeding circadian rhythm, hyperlipidemia, hyperinsulinemia, and disturbance of thermoregulation are essentially derived from a defect in hypothalamic neuronal histamine. Abnormalities produced by depletion of neuronal histamine from the hypothalamus in normal rats mimic those of obese Zuckers. Grafting the lean Zucker fetal hypothalamus into the obese Zucker pups attenuates those abnormalities. These findings indicate that histamine nerve systems in the brain play a crucial role in maintaining homeostatic energy balance.

Histamine receptor and its regulation of energy metabolism

In a series of studies on brain functions of histamine, probes to manipulate activities of histaminergic neuronal systems were applied to assess histaminergic function in non-obese normal, and lean and obese Zucker rats. Food intake was suppressed by both activation of H1-receptors and inhibition of H3-receptors in the ventromedial hypothalamic nucleus (VMH) and the paraventricular nucleus, each of which is a satiety center. Feeding circadian rhythm was decreased in its amplitude through histaminergic modulation in the hypothalamus. Histamine neurons in the mesencephalic trigeminal nucleus (Me5) were involved in regulation of masticatory functions, particularly eating speed, while histamine-containing neurons in the VMH controlled intake volume of meals. Energy deficiency in the brain enhanced satiation through histaminergic activation of VMH neurons, which in turn produced glycogenolysis in the hypothalamus to maintain homoestatic control of glucose supply. A very-low-calorie conventional Japanese diet, which is a fiber rich and low energy food source, enhanced satiation by increased mastication and because of the low energy supply of the diet. Hypothalamic histamine neurons were activated by high ambient temperature and also by interleukin-1 beta, an endogenous pyrogen, to maintain homeostatic thermoregulation. Behavioral and metabolic abnormalities of Zucker obese rats were mediated by a deficit in hypothalamic neuronal histamine, and the Zucker rat was evaluated as an animal model of histamine deficiency. Transplantation of the lean fetal hypothalamus into the third cerebroventricle of host obese Zuckers attenuated the abnormalities.

A very-low-calorie conventional Japanese diet: its implications for prevention of obesity

A very-low-calorie conventional Japanese diet of 370 kcal/day has been shown to be useful for weight reduction and its long-term maintenance. Sources of the diet were mainly from chicken fillet, egg white, fish white-meat, mushroom, seaweed and low- or non-calorie fiber-rich vegetable, and contained 4.4g fat, 38.1g protein, 45.2g carbohydrate and essential minerals and vitamins. However, metabolic and neural implications of a commercial very-low-calorie liquid formula diet have rarely been investigated from the view point of food intake and appetite regulation. Animal studies have demonstrated the rationale for efficacy of the very-low calorie conventional Japanese diet as follows: (1) Increased hypothalamic histamine suppressed food intake through H1-receptors in the ventromedial hypothalamus (VMH) and paraventricular nucleus, the satiety centers. (2) Low energy intake enhanced satiety and decreased food intake through histaminergic activation of VMH neurons. (3) Mastication activated afferent signal transmission from proprioceptors in the oral cavity to the mesencephalic trigeminal nucleus(Me5). Histaminergic systems in the hypothalamus were activated by mastication and low energy supply, which was accompanied by satiation through the action of histamine in the VMH. Usefulness of the very-low-calorie conventional Japanese diet derives from utilization of conventional Japanese food stuffs as a fiber rich, low energy food source, and from enhancement of satiation by increased mastication required of the diet. The properties of the diet seemed to effect a closed positive feedback loop between histaminergic activation in hypothalamic satiety centers and behavioral changes to enhance satiation and cause feeding suppression.