Obese women, on average, give birth to babies with high fat mass. Placental lipid metabolism alters fetal lipid delivery, potentially moderating neonatal adiposity, yet how it is affected by maternal obesity is poorly understood. We hypothesized that fatty acid (FA) accumulation (esterification) is higher and FA β-oxidation (FAO) is lower in placentas from obese, compared with lean women. We assessed acylcarnitine profiles (lipid oxidation intermediates) in mother-baby-placenta triads, in addition to lipid content, and messenger RNA (mRNA)/protein expression of key regulators of FA metabolism pathways in placentas of lean and obese women with normal glucose tolerance recruited at scheduled term Cesarean delivery. In isolated trophoblasts, we measured [3H]-palmitate metabolism. Placentas of obese women had 17.5% (95% confidence interval: 6.1, 28.7%) more lipid than placentas of lean women, and higher mRNA and protein expression of FA esterification regulators (e.g., peroxisome proliferator-activated receptor γ, acetyl-CoA carboxylase, steroyl-CoA desaturase 1, and diacylglycerol O-acyltransferase-1). [3H]-palmitate esterification rates were increased in trophoblasts from obese compared with lean women. Placentas of obese women had fewer mitochondria and a lower concentration of acylcarnitines, suggesting a decrease in mitochondrial FAO capacity. Conversely, peroxisomal FAO was greater in placentas of obese women. Altogether, these changes in placental lipid metabolism may serve to limit the amount of maternal lipid transferred to the fetus, restraining excess fetal adiposity in this population of glucose-tolerant women.

Voltage-gated potassium channels, Kv1.1, Kv1.2 and Kv1.6, were identified as PCR products from mRNA prepared from nodose ganglia. Immunocytochemical studies demonstrated expression of the proteins in all neurons from ganglia of neonatal animals (postnatal days 0-3) and in 85-90 % of the neurons from older animals (postnatal days 21-60). In voltage clamp studies, a-dendrotoxin (a-DTX), a toxin with high specificity for these members of the Kv1 family, was used to examine their contribution to K + currents of the sensory neurons. a-DTX blocked current in both A-and C-type neurons. The current had characteristics of a delayed rectifier with activation positive to _50 mV and little inactivation during 250 ms pulses. In current-clamp experiments a-DTX, used to eliminate the current, had no effect on resting membrane potential and only small effects on the amplitude and duration of the action potential of A-and C-type neurons. However, there were prominent effects on excitability. a-DTX lowered the threshold for initiation of discharge in response to depolarizing current steps, reduced spike after-hyperpolarization and increased the frequency/pattern of discharge of A-and C-type neurons at membrane potentials above threshold. Model simulations were consistent with these experimental results and demonstrated how the other major K + currents function in response to the loss of the a-DTX-sensitive current to effect these changes in action potential wave shape and discharge.

Sensory neurons express hyperpolarization-activated currents (I H ) that differ in magnitude and kinetics within the populations. We investigated the structural basis for these differences and explored the functional role of the I H channels in sensory neurons isolated from rat nodose ganglia. Immunohistochemical studies demonstrated a differential distribution of hyperpolarization-activated cyclic nucleotide-gated (HCN) protein (HCN1, HCN2, HCN4) in sensory neurons and peripheral terminals. HCN2 and HCN4 immunoreactivity was present in all nodose neurons. In contrast, only 20% of the total population expressed HCN1 immunoreactivity. HCN1 did not colocalize with IB4 (a marker for C-type neurons), and only 15% of HCN1-positive neurons colocalized with immunoreactivity for the vanilloid receptor VR1, another protein associated primarily with C-type neurons. Therefore, most HCN1-containing neurons were A-type neurons. In further support, HCN1 was present in the mechanosensitive terminals of myelinated but not unmyelinated sensory fibers, whereas HCN2 and HCN4 were present in receptor terminals of both myelinated and unmyelinated fibers. In voltage-clamp studies, cell permeant cAMP analogs shifted the activation curve for I H to depolarized potentials in C-type neurons but not A-type neurons. In current-clamp recording, CsCl, which inhibits only I H in nodose neurons, hyperpolarized the resting membrane potential from Ϫ63 Ϯ 1 to Ϫ73 Ϯ 2 mV and nearly doubled the input resistance from 1.3 to 2.2 G⍀. In addition, action potentials were initiated at lower depolarizing current injections in the presence of CsCl. At the sensory receptor terminal, CsCl decreased the threshold pressure for initiation of mechanoreceptor discharge. Therefore, elimination of the I H increases excitability of both the soma and the peripheral sensory terminals.

Background: The placentas of obese women accumulate lipids that may alter fetal lipid exposure. The long-chain omega-3 fatty acids (n-3 FAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) alter FA metabolism in hepatocytes, although their effect on the placenta is poorly understood. Objective: We aimed to investigate whether n-3 supplementation during pregnancy affects lipid metabolism in the placentas of overweight and obese women at term. Design: A secondary analysis of a double-blind randomized controlled trial was conducted in healthy overweight and obese pregnant women who were randomly assigned to DHA plus EPA (2 g/d) or placebo twice a day from early pregnancy to term. Placental FA uptake, esterification, and oxidation pathways were studied by measuring the expression of key genes in the placental tissue of women supplemented with placebo and n-3 and in vitro in isolated trophoblast cells in response to DHA and EPA treatment. Results: Total lipid content was significantly lower in the placentas of overweight and obese women supplemented with n-3 FAs than in those supplemented with placebo (14.14 6 1.03 compared with 19.63 6 1.45 mg lipid/g tissue; P , 0.05). The messenger RNA expression of placental FA synthase (FAS) and diacylglycerol O-acyltransferase 1 (DGAT1) was negatively correlated with maternal plasma enrichment in DHA and EPA (P , 0.05). The expression of placental peroxisome proliferator-activated receptor g (r = 20.39, P = 0.04) and its target genes DGAT1 (r = 20.37, P = 0.02) and PLIN2 (r = 20.38, P = 0.04) significantly decreased, with an increasing maternal n-3: n-6 ratio (representing the n-3 status) near the end of pregnancy. The expression of genes that regulate FA oxidation or uptake was not changed. Birth weight and length were significantly higher in the offspring of n-3-supplemented women than in those in the placebo group (P , 0.05), but no differences in the ponderal index were observed. Supplementation of n-3 significantly decreased FA esterification in isolated trophoblasts without affecting FA oxidation. Conclusion: Supplementing overweight and obese women with n-3 FAs during pregnancy inhibited the ability of the placenta to esterify and store lipids. This trial was registered at clinicaltrials.gov as NCT00957476.Am J Clin Nutr 2016;103:1064-72.

Mutations in the potassium channel gene Kv1.1 are associated with human episodic ataxia type 1 (EA-1) syndrome characterized by movement disorders and epilepsy. Ataxic episodes in EA-1 patients are often associated with exercise or emotional stress, which suggests a prominent role for the autonomic nervous system. Many of these alterations are reproduced in the Kv1.1-null mouse. Kv1.1 also regulates excitability of sensory neurons essential in cardiovascular and respiratory reflexes. We examined the neural control of the respiratory system of littermate wild-type (control) and Kv1.1-null mice during low O 2 (hypoxia). Immunohistochemical studies demonstrated Kv1.1 in the afferent limb of the carotid body chemoreflex (the major regulator in the response to hypoxia), consisting of the carotid body, petrosal ganglion, and nucleus of the solitary tract (NTS). Respiration was examined by plethysmography. Null mice exhibited a greater increase in respiration during hypoxia compared with controls. In vitro carotid body sensory discharge during hypoxia was greater in null than control mice. In the caudal NTS, evoked EPSCs in brainstem slices were similar between control and null mice. However, the frequency of spontaneous and miniature EPSCs was greater in null mice. Null mice also exhibited more asynchronous release after a stimulus train. These results demonstrate the important role of Kv1.1 in afferent chemosensory activity and suggest that mutations in the human Kv1.1 gene have functional consequences during stress responses that involve respiratory reflexes.

None.

The study of the TRPC cation channels as signal transducers in sensory neurons is in its infancy. Mechanoreceptors that monitor arterial pressure are prime candidates for the involvement of TRPC channels as either primary mechanical transducers or as modulators of the transduction process. Their activity patterns can be regulated by growth factors such as BDNF and by a variety of ligands that activate Gq-coupled receptors, mechanisms that have been shown in heterologous expression systems to activate TRPC channels. We investigated the distribution of TRPC1 and TRPC3-7 in nodose sensory neurons and in their peripheral axons that terminate as mechanosensitive receptors in the aortic arch of the rat. Using immunocytochemical techniques we identified these six TRPC proteins in the soma of the nodose neurons but only TRPC1 and TRPC3-5 were found to distribute to the peripheral axons and the mechanosensory terminals. TRPC1 and TRPC3 extended into the low threshold complex sensory endings with very strong labeling. In contrast, TRPC4 and TRPC5 were found primarily in major branches of the receptor but immunoreactivity was weak in the region where mechanotransduction is presumed to occur. Terminals arising from unmyelinated fibers also expressed TRPC1 and TRPC3-5 but not all fibers expressed all of the channels suggesting that specific TRPC protein may be aligned with previously described subclasses of the unmyelinated C-fibers.

The ion channels responsible for the pattern and frequency of discharge in arterial baroreceptor terminals are, with few exceptions, unknown. In this study we examined the contribution of KCNQ potassium channels that underlie the M-current to the function of the arterial baroreceptors. Labelled aortic baroreceptor neurons, immunohistochemistry and an isolated aortic arch preparation were used to demonstrate the presence and function of KCNQ2, KCNQ3 and KCNQ5 channels in aortic baroreceptors. An activator (retigabine) and an inhibitor (XE991) of the M-current were used to establish a role for these channels in setting the resting membrane potential and in regulating the response to ramp increases in arterial pressure. Retigabine raised the threshold for activation of arterial baroreceptors and shifted the pressure-response curve to higher aortic pressures. XE991, on the other hand, produced an increase in excitability as shown by an increase in discharge at elevated pressures as compared to control. We propose that KCNQ2, KCNQ3 and KCNQ5 channels provide a hyperpolarizing influence to offset the previously described depolarizing influence of the HCN channels in baroreceptor neurons and their terminals. Monitoring blood pressure is the key function of a subset of visceral sensory neurons of the nodose ganglia. A select group of nodose neurons, collectively forming the aortic depressor nerve (ADN), project to the aortic arch where they form baroreceptor terminals that respond to the stretch of the arterial wall. It is generally accepted that ion channels, activated by distortion of the sensory terminal, produce a depolarizing receptor potential that initiates action potential discharge proportional to the mechanical distortion at the ending. The information, which is essential for regulation of arterial pressure and heart rate, is relayed through the nodose ganglia to the nucleus of the solitary tract in the brainstem. The pattern of discharge initiated at the terminal region is dependent on the composite of voltage-gated ion channels expressed in the terminal. It is critical that the nerve terminals maintain a stable, negative resting level in the absence of pressure changes to ensure that the sensory information relayed to the central nervous system reflects the distortion of the terminal and not merely intrinsic discharge of the terminal. How this stability is maintained, however, has yet to be fully elucidated.We have recently demonstrated that KCNQ K + channels and the underlying M-current contribute to maintenance of the resting membrane potential in nodose neurons (Wladyka & Kunze, 2006). The aim of our current studies is to determine whether these channels are specifically present in the soma of barosensory neurons and their peripheral sensory terminals. To investigate the functional importance of the channels at the terminal regions, we also recorded unit baroreceptor discharge in the presence of KCNQ inhibitors and activators. We have demonstrated the presence of a retigabine-sensitive M-current under vol...