The effect of an intracerebroventricular injection of metformin or AICAR on the plasma concentrations of melatonin in the ewe: potential involvement of AMPK?

<p>Abstract</p> <p>Background</p> <p>It is now widely accepted that AMP-activated protein kinase (AMPK) is a critical regulator of energy homeostasis. Recently, it has been shown to regulate circadian clocks. In seasonal breeding species such as sheep, the circadian clock controls the secretion of an endogenous rhythm of melatonin and, as a consequence, is probably involved in the generation of seasonal rhythms of reproduction. Considering this, we identified the presence of the subunits of AMPK in different hypothalamic nuclei involved in the pre- and post-pineal pathways that control seasonality of reproduction in the ewe and we investigated if the intracerebroventricular (i.c.v.) injection of two activators of AMPK, metformin and AICAR, affected the circadian rhythm of melatonin in ewes that were housed in constant darkness. In parallel the secretion of insulin was monitored as a peripheral metabolic marker. We also investigated the effects of i.c.v. AICAR on the phosphorylation of AMPK and acetyl-CoA carboxylase (ACC), a downstream target of AMPK, in brain structures along the photoneuroendocrine pathway to the pineal gland.</p> <p>Results</p> <p>All the subunits of AMPK that we studied were identified in all brain areas that were dissected but with some differences in their level of expression among structures. Metformin and AICAR both reduced (p < 0.001 and p < 0.01 respectively) the amplitude of the circadian rhythm of melatonin secretion independently of insulin secretion. The i.c.v. injection of AICAR only tended (p = 0.1) to increase the levels of phosphorylated AMPK in the paraventricular nucleus but significantly increased the levels of phosphorylated ACC in the paraventricular nucleus (p < 0.001) and in the pineal gland (p < 0.05).</p> <p>Conclusions</p> <p>Taken together, these results suggest a potential role for AMPK on the secretion of melatonin probably acting trough the paraventricular nucleus and/or directly in the pineal gland. We conclude that AMPK may act as a metabolic cue to modulate the rhythm of melatonin secretion.</p

Hemodialysis vascular access: everything you always wanted to know about it (but were afraid to ask)

Vascular accesses are essential for effective dialysis treatment. Arteriovenous fistulas, grafts and central venous catheters are the options available to the nephrologist, but they all have their pros and cons. All of the 3 types of vascular access share the same complications but at different rates, and their costs vary enormously, with on balance the arteriovenous fistula being the best choice. Nevertheless, recently the number of incident patients starting dialysis treatment with a venous catheter as vascular access has been steadily increasing. This is true even for more advanced countries such as the United States, where despite the efforts made to promote the use of fistulas, their prevalence is still low compared with Europe. Moreover, nowadays nephrologists are required to master technical skills that once were those of surgeons and to perform interventions to preserve the patency of the access. The aim of this paper is to review the prevalence, benefits and complications of the different vascular accesses in light of the most recent finding

Hemodialysis vascular access: everything you always wanted to know about it (but were afraid to ask)

Vascular accesses are essential for effective dialysis treatment. Arteriovenous fistulas, grafts and central venous catheters are the options available to the nephrologist, but they all have their pros and cons. All of the 3 types of vascular access share the same complications but at different rates, and their costs vary enormously, with on balance the arteriovenous fistula being the best choice. Nevertheless, recently the number of incident patients starting dialysis treatment with a venous catheter as vascular access has been steadily increasing. This is true even for more advanced countries such as the United States, where despite the efforts made to promote the use of fistulas, their prevalence is still low compared with Europe. Moreover, nowadays nephrologists are required to master technical skills that once were those of surgeons and to perform interventions to preserve the patency of the access. The aim of this paper is to review the prevalence, benefits and complications of the different vascular accesses in light of the most recent finding

Effects of continuous erythropoietin receptor activator (CERA) in kidney transplant recipients

Erythropoietin-stimulating agents (ESAs) are commonly used to treat anemia in kidney transplant recipients (KTRs). Since 2007, continuous erythropoietin receptor activator (CERA) has been one of the newest recombinant ESAs to treat anemia in dialysis and nondialysis patients with chronic kidney disease. The efficacy of CERA to manage anemia has not been extensively evaluated in KTRs. We evaluated safety, efficacy, and satisfaction among KTRs treated with CERA. We enrolled 19 anemic KTRs (60 ± 9.3 y) who were treated with short-acting ESA for ≥24 weeks. They were shifted to the equivalent dose of CERA and followed for 24 weeks. We measured serum hemoglobin, hematocrit, creatinine, iron, ferritin, and transferrin. To investigate tolerance to and satisfaction with short-acting ESA and CERA, questionnaires were administered to the patients before shifting to CERA and at the end of the follow-up. After 6 months, CERA induced an increase in hemoglobin levels (12.3 ± 0.8 vs 11.2 ± 1.1 g/dL; P = .002, CERA vs short-acting ESA, respectively). In 2 patients treatment was discontinued because the hemoglobin increased to >13 g/dL. No significant differences were observed in serum iron and creatinine between short-acting ESA and CERA throughout the study. The questionnaires showed better compliance to CERA treatment with reduced pain at the injection site, which led subjects to prefer CERA to short-acting ESA. In summary, CERA showed better control of anemia compared with short-acting ESA. It was preferred by the majority of patients, mainly because of the reduced number of monthly injections. Our results demonstrated CERA to be effective, safe, and well tolerated in the management of anemia in KTR

Unlearned and learned effects of intra-hypothalamic cyclic AMP injection on feeding

INJECTIONS of adrenergic drugs into the hypothalamus of the rat have a wide variety of effects on feeding. Depending on site of injection, dosage, the rat's hunger state, and the drugs' peripheral alpha or beta characteristics, food intake may be elicited1–7 or suppressed7–9, or reactions to particular tastes may be modified either directly10–12 or by associative learning13. Such effects have been thought to result from the action of the injected drugs on synaptic receptors that normally respond to endogenous catecholamines. Adrenergic drugs can have marked effects on brain glycogen, however, varying widely in time course and direction between drugs and doses14–17. Drug-induced glycogenolysis might appreciably increase or decrease the supply of glucose to neurones affected. The firing rates of some neurones in both the ventromedial and lateral regions of the rat hypothalamus are influenced by the local concentration of glucose18,19. Furthermore, many of these glucosensitive units are affected by amphetamine19, which increases the amount of noradrenaline at the synapse20, inhibits feeding when injected into the hypothalamus9, and facilitates feeding when injected either with propranolol into the lateral hypothalamus or by itself into the ventromedial hypothalamus6. Although it has yet to be proved that hypothalamic glucose-sensitive neurones control normal feeding, the question arises whether any of the effects of hypothalamic injection of adrenergic drugs on feeding arise from metabolic rather than synaptic action

MHD and confinement during pellet injection on FTU

The study sets out to investigate the parts of the FTU operating space over which pellet injection effects performance improvement and to elucidate the phenomena which hinder it. In this respect the behaviour of the q=1 resonance is found to play the most relevant role