Sex-dimorphic neuroestradiol regulation of ventromedial hypothalamic nucleus glucoregulatory transmitter and glycogen metabolism enzyme protein expression in the rat

Polymorphism and expression of GLUD1 in relation to reproductive performance in Jining Grey goats

Understanding the molecular mechanism of mammalian reproduction (puberty and prolificacy) will play a part in improving animal reproductive performance. GLUD1 (glutamate dehydrogenase 1) is important for mammalian reproduction, as shown in previous studies; however, its roles in puberty and prolificacy have rarely been reported. In this study, we designed seven pairs of primers (P1 to P7) for cloning and sequencing genomic DNA of Jining Grey goats and Liaoning Cashmere goats. Primer 8 (P8) was designed to detect single nucleotide polymorphism (SNP) of the GLUD1 in both sexually precocious and high-fecundity breeds (Jining Grey, Nanjiang Brown and Matou goats) and sexually late-maturing and low-fecundity breeds (Liaoning Cashmere, Inner Mongolia Cashmere and Taihang goats) by PCR-RFLP (restriction fragment length polymorphism). The real-time quantitative polymerase chain reaction (RT-qPCR) technique was used to detect the expression of GLUD1 in a variety of tissues. The results showed that the A197C mutation was only found in the amplification product of P6. For this SNP locus, only two genotypes (AA and AC) were detected in Nanjiang Brown goats, while three genotypes (AA, AC and CC) were detected in the other five breeds. In Jining Grey goats, the frequency of genotypes AA, AC and CC was 0.69, 0.26 and 0.05, respectively. In Jining Grey goats, AA genotype had 0.54 (P < 0.05 ) and 0.3 (P < 0.05 ) more kids than the CC and AC genotype, respectively, and no significant difference (P > 0.05 ) was found in kidding number between the AC and CC genotype. GLUD1 was expressed in five tissues of different developmental stages. The expression level of GLUD1 in the hypothalamus was higher than that in the other four tissues except during puberty of Liaoning Cashmere goats. In puberty in goats, GLUD1 expression was significantly higher in ovaries than that in the juvenile period (P < 0.01 ). RT-qPCR results showed that the expression of GLUD1 in ovaries may relate to the puberty of goats. The present study preliminarily indicated that there might be an association between the 197 locus of GLUD1 and sexual precocity in goats, and allele A of GLUD1 was a potential DNA marker for improving kidding number in Jining Grey goats.

Sex-dependent endozepinergic regulation of ventromedial hypothalamic nucleus glucose counter-regulatory neuron aromatase protein expression in the adult rat

The hypothalamic brain cell types that produce estradiol from testosterone remain unclear. Aromatase inhibition affects ventromedial hypothalamic nucleus (VMN) glucose-stimulatory nitric oxide (NO) and glucose-inhibitory γ-aminobutyric acid (GABA) transmission during insulin (INS)-induced hypoglycemia (IIH). Pure GABA and NO nerve cell samples acquired by laser-catapult-microdissection from consecutive rostro-caudal segments of the VMN were analyzed by Western blot to investigate whether regional subpopulations of each cell type contain machinery for neuro-estradiol synthesis. Astrocyte endozepinergic signaling governs brain steroidogenesis. Pharmacological tools were used here to determine if the glio-peptide octadecaneuropeptide (ODN) controls aromatase expression in GABA and NO neurons during eu- and/or hypoglycemia. Intracerebroventricular administration of the ODN G-protein coupled-receptor antagonist cyclo(1-8)[DLeu5]OP (LV-1075) decreased (male) or enhanced (female) VMN GABAergic neuron aromatase expression, but increased or reduced this profile in nitrergic neurons in a region-specific manner in each sex. IIH suppressed aromatase levels in GABA neurons located in the middle segment of the male VMN or distributed throughout this nucleus in the female. This inhibitory response was altered by the ODN isoactive surrogate octapeptide (OP) in female, but was refractory to OP in male. NO neuron aromatase protein in hypoglycemic male (middle and caudal VMN) and female (rostral and caudal VMN) rats, but was normalized in OP- plus INS-treated rats of both sexes. Results provide novel evidence that VMN glucose-regulatory neurons may produce neuro-estradiol, and that the astrocyte endozepine transmitter ODN may impose sex-specific control of baseline and/or hypoglycemic patterns of aromatase expression in distinct subsets of nitrergic and GABAergic neurons in this neural structure.

Glycogen phosphorylase isoenzyme GPbb versus GPmm regulation of ventromedial hypothalamic nucleus glucoregulatory neurotransmitter and counter-regulatory hormone profiles during hypoglycemia: Role of L-lactate and octadecaneuropeptide

Glucose accesses the brain primarily via the astrocyte cell compartment, where it passes through the glycogen shunt before catabolism to the oxidizable fuel L-lactate. Glycogen phosphorylase (GP) isoenzymes GPbb and GPmm impose distinctive control of ventromedial hypothalamic nucleus (VMN) glucose-regulatory neurotransmission during hypoglycemia, but lactate and/or gliotransmitter involvement in those actions is unknown. Lactate or the octadecaneuropeptide receptor antagonist cyclo(1-8)[DLeu5] OP (LV-1075) did not affect gene product down-regulation caused by GPbb or GPmm siRNA, but suppressed non-targeted GP variant expression in a VMN region-specific manner. Hypoglycemic up-regulation of neuronal nitric oxide synthase was enhanced in rostral and caudal VMN by GPbb knockdown, yet attenuated by GPMM siRNA in the middle VMN; lactate or LV-1075 reversed these silencing effects. Hypoglycemic inhibition of glutamate decarboxylase65/67 was magnified by GPbb (middle and caudal VMN) or GPmm (middle VMN) knockdown, responses that were negated by lactate or LV-1075. GPbb or GPmm siRNA enlarged hypoglycemic VMN glycogen profiles in rostral and middle VMN. Lactate and LV-1075 elicited progressive rostral VMN glycogen augmentation in GPbb knockdown rats, but stepwise-diminution of rostral and middle VMN glycogen after GPmm silencing. GPbb, not GPmm, knockdown caused lactate or LV-1075 - reversible amplification of hypoglycemic hyperglucagonemia and hypercorticosteronemia. Results show that lactate and octadecaneuropeptide exert opposing control of GPbb protein in distinct VMN regions, while the latter stimulates GPmm. During hypoglycemia, GPbb and GPmm may respectively diminish (rostral, caudal VMN) or enhance (middle VMN) nitrergic transmission and each oppose GABAergic signaling (middle VMN) by lactate- and octadecaneuropeptide-dependent mechanisms.

A Novel 5-Chloro-N-phenyl-1H-indole-2-carboxamide Derivative as Brain-Type Glycogen Phosphorylase Inhibitor: Validation of Target PYGB

Brain-type glycogen phosphorylase (PYGB) inhibitors are recognized as prospective drugs for treating ischemic brain injury. We previously reported compound 1 as a novel glycogen phosphorylase inhibitor with brain-protective properties. In this study, we validated whether PYGB could be used as the therapeutic target for hypoxic-ischemic diseases and investigated whether compound 1 exerts a protective effect against astrocyte hypoxia/reoxygenation (H/R) injury by targeting PYGB. A gene-silencing strategy was initially applied to downregulate PYGB proteins in mouse astrocytes, which was followed by a series of cellular experiments with compound 1. Next, we compared relevant indicators that could prove the protective effect of compound 1 on brain injury, finding that after PYGB knockdown, compound 1 could not obviously alleviate astrocytes H/R injury, as evidenced by cell viability, which was not significantly improved, and lactate dehydrogenase (LDH) leakage rate, intracellular glucose content, and post-ischemic reactive oxygen species (ROS) level, which were not remarkably reduced. At the same time, cellular energy metabolism did not improve, and the degree of extracellular acidification was not downregulated after administration of compound 1 after PYGB knockdown. In addition, it could neither significantly increase the level of mitochondrial aerobic energy metabolism nor inhibit the expression of apoptosis-associated proteins. The above results indicate that compound 1 could target PYGB to exert its protective effect against cellular H/R injury in mouse astrocytes. Simultaneously, we further demonstrated that PYGB could be an efficient therapeutic target for ischemic-hypoxic diseases. This study provides a new reference for further in-depth study of the action mechanism of the efficacy of compound 1.

Effects of Ventromedial Hypothalamic Nucleus (VMN) Aromatase Gene Knockdown on VMN Glycogen Metabolism and Glucoregulatory Neurotransmission

The enzyme aromatase is expressed at high levels in the ventromedial hypothalamic nucleus (VMN), a principal component of the brain gluco-regulatory network. Current research utilized selective gene knockdown tools to investigate the premise that VMN neuroestradiol controls glucostasis. Intra-VMN aromatase siRNA administration decreased baseline aromatase protein expression and tissue estradiol concentrations and either reversed or attenuated the hypoglycemic regulation of these profiles in a VMN segment-specific manner. Aromatase gene repression down-regulated protein biomarkers for gluco-stimulatory (nitric oxide; NO) and -inhibitory (gamma-aminobutyric acid; GABA) neurochemical transmitters. Insulin-induced hypoglycemia (IIH) up- or down-regulated neuronal nitric oxide synthase (nNOS) and glutamate decarboxylase_65/67 (GAD), respectively, throughout the VMN. Interestingly, IIH caused divergent changes in tissue aromatase and estradiol levels in rostral (diminished) versus middle and caudal (elevated) VMN. Aromatase knockdown prevented hypoglycemic nNOS augmentation in VMN middle and caudal segments, but abolished the GAD inhibitory response to IIH throughout this nucleus. VMN nitrergic and GABAergic neurons monitor stimulus-specific glycogen breakdown. Here, glycogen synthase (GS) and phosphorylase brain- (GPbb; AMP-sensitive) and muscle- (GPmm; noradrenergic -responsive) type isoform responses to aromatase siRNA were evaluated. Aromatase repression reduced GPbb and GPmm content in euglycemic controls and prevented hypoglycemic regulation of GPmm but not GPbb expression while reversing glycogen accumulation. Aromatase siRNA elevated baseline glucagon and corticosterone secretion and abolished hypoglycemic hyperglucagonemia and hypercorticosteronemia. Outcomes document the involvement of VMN neuroestradiol signaling in brain control of glucose homeostasis. Aromatase regulation of VMN gluco-regulatory signaling of hypoglycemia-associated energy imbalance may entail, in part, control of GP variant-mediated glycogen disassembly.

Estrogenic Action in Stress-Induced Neuroendocrine Regulation of Energy Homeostasis

Estrogens are among important contributing factors to many sex differences in neuroendocrine regulation of energy homeostasis induced by stress. Research in this field is warranted since chronic stress-related psychiatric and metabolic disturbances continue to be top health concerns, and sex differences are witnessed in these aspects. For example, chronic stress disrupts energy homeostasis, leading to negative consequences in the regulation of emotion and metabolism. Females are known to be more vulnerable to the psychological consequences of stress, such as depression and anxiety, whereas males are more vulnerable to the metabolic consequences of stress. Sex differences that exist in the susceptibility to various stress-induced disorders have led researchers to hypothesize that gonadal hormones are regulatory factors that should be considered in stress studies. Further, estrogens are heavily recognized for their protective effects on metabolic dysregulation, such as anti-obesogenic and glucose-sensing effects. Perturbations to energy homeostasis using laboratory rodents, such as physiological stress or over-/under- feeding dietary regimen prevalent in today’s society, offer hints to the underlying mechanisms of estrogenic actions. Metabolic effects of estrogens primarily work through estrogen receptor α (ERα), which is differentially expressed between the sexes in hypothalamic nuclei regulating energy metabolism and in extrahypothalamic limbic regions that are not typically associated with energy homeostasis. In this review, we discuss estrogenic actions implicated in stress-induced sex-distinct metabolic disorders.

Energy metabolism measured by 31P magnetic resonance spectroscopy in the healthy human brain

BACKGROUND AND PURPOSE

Phosphorous magnetic resonance spectroscopy (31P-MRS) allows a non-invasive analysis of phosphorus-containing compounds in vivo. The present study investigated the influence of brain region, hemisphere, age, sex and brain volume on 31P-MRS metabolites in healthy adults.

MATERIALS AND METHODS

Supratentorial brain 31P-MRS spectra of 125 prospectively recruited healthy volunteers (64 female, 61 male) aged 20 to 85 years (mean: 49.4 ± 16.9 years) were examined with a 3D-31P-MRS sequence at 3T, and the compounds phosphocreatine (PCr), inorganic phosphate (Pi) and adenosine triphosphate (ATP) were measured. From this data, the metabolite ratios PCr/ATP, Pi/ATP and PCr/Pi were calculated for different brain regions. In addition, volumes of gray matter, white matter and cerebrospinal fluid were determined.

RESULTS

For all metabolite ratios significant regional differences and in several regions sex differences were found. In some brain regions and for some metabolites hemispheric differences were detected. In addition, changes with aging were found, which differed between women and men.

CONCLUSIONS

The present results indicate that 31P-MRS metabolism varies throughout the brain, with age and between sexes, and therefore have important practical implications for the design and the interpretation of future 31P-MRS studies under physiological conditions and in patients with various cerebral diseases.

Glycogen Phosphorylase Isoform Regulation of Ventromedial Hypothalamic Nucleus Gluco-Regulatory Neuron 5'-AMP-Activated Protein Kinase and Transmitter Marker Protein Expression

Brain glycogen is remodeled during metabolic homeostasis and provides oxidizable L-lactate equivalents. Brain glycogen phosphorylase (GP)-brain (GPbb; AMP-sensitive) and -muscle (GPmm; norepinephrine-sensitive) type isoforms facilitate stimulus-specific control of glycogen disassembly. Here, a whole animal model involving stereotactic-targeted delivery of GPmm or GPbb siRNA to the ventromedial hypothalamic nucleus (VMN) was used to investigate the premise that these variants impose differential control of gluco-regulatory transmission. Intra-VMN GPmm or GPbb siRNA administration inhibited glutamate decarboxylate_65/67 (GAD), a protein marker for the gluco-inhibitory transmitter γ--aminobutyric acid (GABA), in the caudal VMN. GPbb knockdown, respectively overturned or exacerbated hypoglycemia-associated GAD suppression in rostral and caudal VMN. GPmm siRNA caused a segment-specific reversal of hypoglycemic augmentation of the gluco-stimulatory transmitter indicator, neuronal nitric oxide synthase (nNOS). In both cell types, GP siRNA down-regulated 5′-AMP-activated protein kinase (AMPK) during euglycemia, but hypoglycemic suppression of AMPK was reversed by GPmm targeting. GP knockdown elevated baseline GABA neuron phosphoAMPK (pAMKP) content, and amplified hypoglycemic augmentation of pAMPK expression in each neuron type. GPbb knockdown increased corticosterone secretion in eu- and hypoglycemic rats. Outcomes validate efficacy of GP siRNA delivery for manipulation of glycogen breakdown in discrete brain structures in vivo, and document VMN GPbb control of local GPmm expression. Results document GPmm and/or -bb regulation of GABAergic and nitrergic transmission in discrete rostro-caudal VMN segments. Contrary effects of glycogenolysis on metabolic-sensory AMPK protein during eu- versus hypoglycemia may reflect energy state-specific astrocyte signaling. Amplifying effects of GPbb knockdown on hypoglycemic stimulation of pAMPK infer that glycogen mobilization by GPbb limits neuronal energy instability during hypoglycemia.

Hypoglycemic and post‑hypoglycemic patterns of glycogen phosphorylase isoform expression in the ventrolateral ventromedial hypothalamic nucleus: impact of sex and estradiol

Glycogen metabolism shapes ventromedial hypothalamic nucleus (VMN) control of glucose homeostasis. Brain glycogen mass undergoes compensatory expansion post‑recovery from insulin‑induced hypoglycemia (IIH). Current research utilized combinatory high‑resolution microdissection/high‑sensitivity Western blotting to investigate whether IIH causes residual adjustments in glycogen metabolism within the metabolic‑sensory ventrolateral VMN (VMNvl). Micropunch‑dissected tissue was collected from rostral, middle, and caudal levels of the VMNvl in each sex for analysis of glycogen synthase (GS) and glycogen phosphorylase (GP)‑muscle type (GPmm; norepinephrine‑sensitive) and GP‑brain type (GPbb; glucoprivic‑sensitive) isoform expression during and after IIH. Hypoglycemic suppression of VMNvl GS levels in males disappeared or continued after reestablishment of euglycemia, according to sampled segment. Yet, reductions in female VMNvl GS persisted after IIH. Males exhibited reductions in GPmm content in select rostro‑caudal VMNvl segments, but this protein declined in each segment post‑hypoglycemia. Females, rather, showed augmented or diminished GPmm levels during IIH, but no residual effects of IIH on this protein. In each sex, region‑specific up‑ or down‑regulation of VMNvl GPbb profiles during glucose decrements were undetected post‑recovery from IIH. Results provide novel proof of estradiol‑dependent sex‑dimorphic patterns of VMNvl GP variant expression at specific rostro‑caudal levels of this critical gluco‑regulatory structure. Sex differences in persistence of IIH‑associated GS and GPmm patterns of expression after restoration of euglycemia infer that VMNvl recovery from this metabolic stress may involve dissimilar glycogen accumulation in male versus female.