Hyperhomocysteinemia has been identified as a risk factor for neurological disorders. To study the influence of early deficiency in nutritional determinants of hyperhomocysteinemia on the developing rat brain, dams were fed a standard diet or a diet lacking methyl groups during gestation and lactation. Homocysteinemia progressively increased in the offspring of the deficient group and at 21 days reached 13.3+/-3.7 micromol/L versus 6.8+/-0.3 micromol/L in controls. Homocysteine accumulated in both neurons and astrocytes of selective brain structures including the hippocampus, the cerebellum, the striatum, and the neurogenic subventricular zone. Most homocysteine-positive cells expressed p53 and displayed fragmented DNA indicative of apoptosis. Righting reflex and negative geotaxis revealed a delay in the onset of integration capacities in the deficient group. Between 19 and 21 days, a poorer success score was recorded in deficient animals in a locomotor coordination test. A switch to normal food after weaning allowed restoration of normal homocysteinemia. Nevertheless, at 80 days of age, the exploratory behavior in the elevated-plus maze and the learning and memory behavior in the eight-arm maze revealed that early vitamin B deprivation is associated with persistent functional disabilities, possibly resulting from the ensuing neurotoxic effects of homocysteine.

Hormones such as leptin and ghrelin can rapidly rewire hypothalamic feeding circuits when injected into rodent brains. These experimental manipulations suggest that the hypothalamus might reorganize continually in adulthood to integrate the metabolic status of the whole body. In this study, we examined whether hypothalamic plasticity occurs in naive animals according to their nutritional conditions. For this purpose, we fed mice with a short-term high-fat diet (HFD) and assessed brain remodeling through its molecular and functional signature. We found that HFD for 3 d rewired the hypothalamic arcuate nucleus, increasing the anorexigenic tone due to activated pro-opiomelanocortin (POMC) neurons. We identified the polysialic acid molecule (PSA) as a mediator of the diet-induced rewiring of arcuate POMC. Moreover, local pharmacological inhibition and genetic disruption of the PSA signaling limits the behavioral and metabolic adaptation to HFD, as treated mice failed to normalize energy intake and showed increased body weight gain after the HFD challenge. Altogether, these findings reveal the existence of physiological hypothalamic rewiring involved in the homeostatic response to dietary fat. Furthermore, defects in the hypothalamic plasticitydriven adaptive response to HFD are obesogenic and could be involved in the development of metabolic diseases.

The hypothalamus plays a crucial role in the control of the energy balance and also retains neurogenic potential into adulthood. Recent studies have reported the severe alteration of the cell turn-over in the hypothalamus of obese animals and it has been proposed that a neurogenic deficiency in the hypothalamus could be involved in the development of obesity. To explore this possibility, we examined hypothalamic cell renewal during the homeostatic response to dietary fat in mice, i.e., at the onset of diet-induced obesity. We found that switching to high-fat diet (HFD) accelerated cell renewal in the hypothalamus through a local, rapid and transient increase in cell proliferation, peaking three days after introducing the HFD. Blocking HFD-induced cell proliferation by central delivery of an antimitotic drug prevented the food intake normalization observed after HFD introduction and accelerated the onset of obesity. This result showed that HFD-induced dividing brain cells supported an adaptive anorectic function. In addition, we found that the percentage of newly generated neurons adopting a POMC-phenotype in the arcuate nucleus was increased by HFD. This observation suggested that the maturation of neurons in feeding circuits was nutritionally regulated to adjust future energy intake. Taken together, these results showed that adult cerebral cell renewal was remarkably responsive to nutritional conditions. This constituted a physiological trait required to prevent severe weight gain under HFD. Hence this report highlighted the amazing plasticity of feeding circuits and brought new insights into our understanding of the nutritional regulation of the energy balance.

Aims To assess if the inhibitory potency of nonsteroidal anti-in¯ammatory drugs (NSAIDs) on cyclooxygenase (COX) isoenzymes, when given therapeutically in humans, can be predicted from their in vitro concentration-response curves using the whole blood assay. Methods Twenty-four healthy male volunteers aged 20±27 years were recruited. Inhibition of blood COX isoenzymes was determined in vitro before any drug intake and ex vivo after single and repeated intake of either 7.5 mg meloxicam once, 400 mg ibuprofen three times daily or 75 mg diclofenac SR once, taken in a randomized cross-over design. Production of thromboxane B 2 (TXB 2 ) during clotting and of prostaglandin E 2 (PGE 2 ) during endotoxin exposure served as indicators of platelet COX-1 and monocyte COX-2 activity, respectively. Drugs were determined in plasma by h.p.l.c., with a chiral separation of ibuprofen and free fractions after equilibrium dialysis. Results Intra-subject variation for COX-1 and COX-2 at baseline was at 26t18% and 18t13% respectively, and intersubject variation at 39% and 36%, respectively. The ratios of IC 50 s and, at best, of IC 80 s revealed diclofenac and meloxicam as selective COX-2 inhibitors and ibuprofen as a preferential COX-1 inhibitor in vitro. However, after oral intake, ibuprofen inhibited ex vivo COX-2 by 80% whereas diclofenac inhibited COX-1 by 70%. Meloxicam inhibited COX-1 from 30 to 55% depending on the repetition of the dose and increase in plasma concentrations. Using in vitro dose±response curves, the in vivo inhibitory potency of diclofenac was estimated adequately from its circulating concentration ([x0.18, 0.21] for x0.03] for COX-2) but this was not the case for ibuprofen on COX-2 ([x0.14, 0.27]) and meloxicam on COX-1 ([0.31, 1.05]). The limited predictability of the system was not improved through considering the unbound fraction of the drugs or the variable chiral inversion of ibuprofen. Conclusions Assessment of COX-2 selectivity based on in vitro studies and pharmacological modelling has a limited clinical relevance. There is a need to investigate COX selectivity at therapeutic plasma concentrations of NSAIDs using the ex vivo whole blood assay.

Collectively, our results suggest that glucose-induced DRP1-dependent mitochondrial fission is an upstream regulator for mROS signaling, and consequently, a key mechanism in hypothalamic glucose sensing. Thus, for the first time, we demonstrate the involvement of DRP1 in physiological regulation of brain glucose-induced insulin secretion and food intake inhibition. Such involvement implies DRP1-dependent mROS production.

Elevated plasma homocysteine has been linked to pregnancy complications and developmental diseases. Whereas hyperhomocysteinemia is frequently observed in populations at risk of malnutrition, hypoxia may alter the remethylation of homocysteine in hepatocytes. We aimed to investigate the combined influences of early deficiency in nutritional determinants of hyperhomocysteinemia and of neonatal hypoxia on homocysteine metabolic pathways in developing rats. Dams were fed a standard diet or a diet deficient in vitamins B12, B2, folate, month, and choline from 1 mo before pregnancy until weaning of the offspring. The pups were divided into four treatment groups corresponding to "no hypoxia/standard diet," "hypoxia (100% N2 for 5 min at postnatal d 1)/standard diet," "no hypoxia/ deficiency," and "hypoxia/deficiency," and homocysteine metabolism was analyzed in their liver at postnatal d 21. Hypoxia increased plasma homocysteine in deficient pups (21.2 Ϯ 1.6 versus 13.3 Ϯ 1.2 M, p Ͻ 0.05). Whereas mRNA levels of cystathionine ␤-synthase remained unaltered, deficiency reduced the enzyme activity (48.7 Ϯ 2.9 versus 83.6 Ϯ 6.3 nmol/h/mg, p Ͻ 0.01), an effect potentiated by hypoxia (29.4 Ϯ 4.7 nmol/h/mg, p Ͻ 0.05). The decrease in methylene-tetrahydrofolate reductase activity measured in deficient pups was attenuated by hypoxia (p Ͻ 0.05), and methionine-adenosyltransferase activity was slightly reduced only in the "hypoxia/deficiency" group (p Ͻ 0.05). Finally, hypoxia enhanced the deficiency-induced drop of the S-adenosylmethionine/S-adenosylhomocysteine ratio, which is known to influence DNA methylation and gene expression. In conclusion, neonatal hypoxia may increase homocysteinemia mainly by decreasing homocysteine transsulfuration in developing rats under methyl-deficient regimen. Plasma accumulation of HCY is known to be linked to cardiovascular diseases and ageing-associated disabilities (1-3). Moderate hHCY can arise from genetic determinants (4,5) but is also frequently related to dietary deficiency in vitamins B12, B2, and folate. In newborns, the risk of hHCY is closely related to elevated maternal HCY concentrations during pregnancy, which is determined by the status of B vitamins (6 -8).A strong relationship has been documented between HCY accumulation and pregnancy complications, including recurrent miscarriages, preeclampsia, and placenta abruption (see Ref. 9 for review). In the progeny, hHCY has been associated with fetal death (10), premature birth (11), intrauterine growth retardation (12), neural tube defects (13), craniofacial anomalies (14), cardiac malformation (15), and hepatic steatosis (16).HCY production involves the demethylation of methionine, and, under normal conditions, is essentially regulated in the liver. As summarized in Figure 1, it originates from the hydrolysis of SAH, a product of transmethylation reactions through SAM, and is metabolized via two pathways of remethylation and one pathway of transsulfuration. HCY metabolism strongly depends on the nutritional intake of B vitamins,

Leptin is an adipocyte-derived hormone that controls energy balance by acting primarily in the CNS, but its action is lost in common forms of obesity due to central leptin resistance. One potential mechanism for such leptin resistance is an increased hypothalamic expression of Suppressor of cytokine signaling 3 (Socs3), a feedback inhibitor of the Jak-Stat pathway that prevents Stat3 activation. Ample studies have confirmed the important role of Socs3 in leptin resistance and obesity. However, the degree to which Socs3 participates in the regulation of energy homeostasis in nonobese conditions remains largely undetermined. In this study, using adult mice maintained under standard diet, we demonstrate that Socs3 deficiency in the mediobasal hypothalamus (MBH) reduces food intake, protects against body weight gain, and limits adiposity, suggesting that Socs3 is necessary for normal body weight maintenance. Mechanistically, MBH Socs3-deficient mice display increased hindbrain sensitivity to endogenous, meal-related satiety signals, mediated by oxytocin signaling. Thus, oxytocin signaling likely mediates the effect of hypothalamic leptin on satiety circuits of the caudal brainstem. This provides an anatomical substrate for the effect of leptin on meal size, and more generally, a mechanism for how the brain controls short-term food intake as a function of the energetic stores available in the organism to maintain energy homeostasis. Any dysfunction in this pathway could potentially lead to overeating and obesity.

The mediobasal hypothalamus (MBH) contains neurons capable of directly detecting metabolic signals such as glucose to control energy homeostasis. Among them, glucose-excited (GE) neurons increase their electrical activity when glucose rises. In view of previous work, we hypothesized that transient receptor potential canonical type 3 (TRPC3) channels are involved in hypothalamic glucose detection and the control of energy homeostasis. To investigate the role of TRPC3, we used constitutive and conditional TRPC3-deficient mouse models. Hypothalamic glucose detection was studied in vivo by measuring food intake and insulin secretion in response to increased brain glucose level. The role of TRPC3 in GE neuron response to glucose was studied by using in vitro calcium imaging on freshly dissociated MBH neurons. We found that whole-body and MBH TRPC3-deficient mice have increased body weight and food intake. The anorectic effect of intracerebroventricular glucose and the insulin secretory response to intracarotid glucose injection are blunted in TRPC3-deficient mice. TRPC3 loss of function or pharmacological inhibition blunts calcium responses to glucose in MBH neurons in vitro. Together, the results demonstrate that TRPC3 channels are required for the response to glucose of MBH GE neurons and the central effect of glucose on insulin secretion and food intake.