Effects of high fat diet on the Basal activity of the hypothalamus-pituitary-adrenal axis in mice: a systematic review.

Hypothalamus-pituitary-adrenal-axis activity is suggested to be involved in the pathophysiology of the metabolic syndrome. In diet-induced obesity mouse models, features of the metabolic syndrome are induced by feeding high fat diet. However, the models reveal conflicting results with respect to the hypothalamus-pituitary-adrenal-axis activation. The aim of this review was to assess the effects of high fat feeding on the activity of the hypothalamus-pituitary-adrenal-axis in mice. PubMed, EMBASE, Web of Science, the Cochrane database, and Science Direct were electronically searched and reviewed by 2 individual researchers. We included only original mouse studies reporting parameters of the hypothalamus-pituitary-adrenal-axis after high fat feeding, and at least 1 basal corticosterone level with a proper control group. Studies with adrenalectomized mice, transgenic animals only, high fat diet for less than 2 weeks, or other interventions besides high fat diet, were excluded. 20 studies were included. The hypothalamus-pituitary-adrenal-axis evaluation was the primary research question in only 5 studies. Plasma corticosterone levels were unchanged in 40%, elevated in 30%, and decreased in 20% of the studies. The effects in the peripheral tissues and the central nervous system were also inconsistent. However, major differences were found between mouse strains, experimental conditions, and the content and duration of the diets. This systematic review demonstrates that the effects of high fat feeding on the basal activity of the hypothalamus-pituitary-adrenal-axis in mice are limited and inconclusive. Differences in experimental conditions hamper comparisons and accentuate the need for standardized evaluations to discern the effects of diet-induced obesity on the hypothalamus-pituitary-adrenal-axis.

Blocking dopamine D2 receptors by haloperidol curtails the beneficial impact of calorie restriction on the metabolic phenotype of high-fat diet induced obese mice.

Calorie restriction is the most effective way of expanding life-span and decreasing morbidity. It improves insulin sensitivity and delays the age-related loss of dopamine receptor D(2) (DRD2) expression in the brain. Conversely, high-fat feeding is associated with obesity, insulin resistance and a reduced number of DRD2 binding sites. We hypothesised that the metabolic benefit of calorie restriction involves the preservation of appropriate DRD2 transmission. The food intake of wild-type C57Bl6 male mice was restricted to 60% of ad lib. intake while they were treated with the DRD2 antagonist haloperidol or vehicle using s.c. implanted pellets. Mice with ad lib. access to food receiving vehicle treatment served as controls. All mice received high-fat food throughout the experiment. After 10 weeks, an i.p. glucose tolerance test was performed and, after 12 weeks, a hyperinsulinaemic euglycaemic clamp. Hypothalamic DRD2 binding was also determined after 12 weeks of treatment. Calorie-restricted (CR) vehicle mice were glucose tolerant and insulin sensitive compared to ad lib. (AL) fed vehicle mice. CR mice treated with haloperidol were slightly heavier than vehicle treated CR mice. Haloperidol completely abolished the beneficial impact of calorie restriction on glucose tolerance and partly reduced the insulin sensitivity observed in CR vehicle mice. The metabolic differences between AL and CR vehicle mice were not accompanied by alterations in hypothalamic DRD2 binding. In conclusion, blocking DRD2 curtails the metabolic effects of calorie restriction. Although this suggests that the dopaminergic system could be involved in the metabolic benefits of calorie restriction, restricting access to high-fat food does not increase (hypothalamic) DRD2 binding capacity, which argues against this inference.

Effects of levo- and dextrosimendan on NF-kappaB-mediated transcription, iNOS expression and NO production in response to inflammatory stimuli.

BACKGROUND AND PURPOSE: Levosimendan is used in the treatment of decompensated heart failure. It increases the contractility of the myocardium by sensitizing troponin C to calcium. In addition, levosimendan has been reported to have beneficial effects in experimental models of septic shock. Because heart failure and sepsis have been associated with excessive nitric oxide (NO) production through inducible NOS (iNOS), we investigated the effects of the simendans on NO production and iNOS expression and on generation of pro-inflammatory cytokines. EXPERIMENTAL APPROACH: Macrophages and fibroblasts were exposed to inflammatory stimuli to induce iNOS expression. Proteins were measured by western blot and mRNA expression was determined by quantitative RT-PCR. Promoter activity and nuclear factor-kappaB (NF-kappaB) and the gamma-activated site (GAS; binding site for signal transducer and activator of transcription 1; STAT1)-mediated transcription were investigated using luciferase reporter constructs. Cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured by ELISA. KEY RESULTS: Levosimendan and dextrosimendan decreased NO production in a dose-dependent manner in cells exposed to inflammatory stimuli. The simendans decreased iNOS protein and mRNA expression but did not affect iNOS mRNA decay. These compounds decreased iNOS promoter activity and inhibited NF-kappaB-mediated transcription but not that mediated by STAT1/GAS. The simendans reduced IL-6 production slightly but they had no effect on TNF-alpha synthesis. CONCLUSIONS AND IMPLICATIONS: The simendans downregulated NF-kappaB-dependent transcription and decreased iNOS promoter activity, iNOS expression and NO production. These mechanisms may contribute to their beneficial clinical effects.

Beta-lactam resistance among Escherichia coli and Klebsiella species blood culture isolates in Finnish hospitals. Finnish Study Group for Antimicrobial Resistance.

The aim of this study was to investigate beta-lactam resistance in Escherichia coli and Klebsiella spp. blood culture isolates in Finland. Special attention was given to extended-spectrum beta-lactamases. A total of 566 Escherichia coli and 108 Klebsiella spp. blood culture isolates were collected from hospitals throughout Finland and their susceptibility to beta-lactam antibiotics studied. Twenty percent of Escherichia coli and 69% of Klebsiella spp. strains were resistant to ampicillin. The mechanisms of resistance were studied by hybridization, isoelectric focusing and the clavulanate double-disk potentiation test. Of the ampicillin-resistant Escherichia coli strains, 83% produced TEM-1. Of the ampicillin-resistant Klebsiella spp. strains, 43% produced SHV-1. Only nine Escherichia coli and three Klebsiella spp. isolates were resistant to cefuroxime (MIC > or = 32 micrograms/ml), and none were resistant to third-generation cephalosporins. These data were compared with cefuroxime and third-generation cephalosporin consumption levels in Finnish hospitals. Although the use of cephalosporins is far more extensive in Finland than in other Scandinavian countries, none of the isolates produced extended-spectrum beta-lactamases. In conclusion, resistance to cefuroxime has remained rare in Finland, and cefuroxime is still an alternative to third-generation cephalosporins in the treatment of septicemia.

Comparison of central nervous system actions of taurine and N-pivaloyltaurine.

N-Acetyl, N-propionyl, and N-pivaloyl derivatives of taurine were synthesized by applying a modified Schotten-Bauman method starting from taurine and using the corresponding acid chloride or acid anhydride for direct acylation reactions. The central nervous system actions of these lipid soluble taurine derivatives, which were presumed to pass the blood-brain barrier, were studied and compared to those of taurine in mice. A large dose (15 mmol/kg) of intraperitoneally administered taurine lengthened the pentobarbitone induced sleep by 30%. N-Pivaloyltaurine was 45 times more potent but not more effective than taurine. Neither N-acetyl- nor N-propionyltaurine lengthened the pentobarbitone induced sleep in doses up to 3 mmol/kg. Intraperitoneally administered N-pivaloyltaurine depressed the locomotor activity in a smaller dose and for a longer period than taurine. However, when administered intracerebroventricularly neither N-acetyl- nor N-pivaloyltaurine altered the locomotor activity in three times larger dose than in which taurine clearly depressed it. Intraperitoneally administered N-pivaloyltaurine decreased the rectal temperature slightly more than taurine, whereas intracerebroventricularly administered taurine was clearly more potent in inducing hypothermia than its acyl derivatives. Intraperitoneally administered N-pivaloyltaurine was about three times more potent than taurine in increasing the striatal concentration of dopamine. Intraperitoneally administered N-pivaloyltaurine only in a very large dose (3 X 15 mmol/kg) slightly and transiently increased the cerebral taurine concentration. Carboxylesterase inhibition by bis-p-nitrophenyl phosphate (BNPP) did not modify this increase. Furthermore, BNPP pretreatment modified neither the hypothermic nor the striatal dopamine concentration elevating effects of N-pivaloyltaurine. Our results suggest that N-pivaloyltaurine possesses taurine-like pharmacological actions. It is not converted to taurine to produce these actions. When administered intracerebroventricularly it is less potent than taurine. However, when administered intraperitoneally it is more potent than taurine because it seems to pass the blood-brain-barrier more easily than taurine. Thus N-pivaloyltaurine could be used to study the behavioural and other central nervous system actions of taurine.