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This paper presents an investigation that aims to: 1) explore the relations between core symptoms of adult Attention Deficit and Hyperactivity Disorder (ADHD) and several typical Internet activities, and 2) compare the predictive power of two core symptoms of ADHD- inattention and hyperactivity/impulsivity- in predicting Internet addiction. Methods: A total of 2016 Chinese college students participated in this study. The ADHD symptoms were assessed using Conners self-rating scales and DSM-5 semi-structured interviews. Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (SCID-5) was used to exclude other psychiatric disorders. Chen’s Internet addiction scale (CIAS) was used to evaluate Internet addiction. Information about Internet activities (e.g., online gaming) was collected through a self-constructed questionnaire. Results: The ratio of Internet addiction problems among individuals with ADHD symptoms is significantly higher than in ordinary individuals (48.9% vs. 14.3%). Further, each core ADHD symptom has unique relations with different types of Internet activities. Specifically, both core ADHD symptoms are negatively associated with information downloading and online learning, and positively associated with online gaming, while online shopping is only associated with hyperactivity/impulsivity. Furthermore, both core ADHD symptoms are significant predictors of Internet addiction, especially inattention. Conclusion: College students with ADHD symptoms are at a higher risk of having Internet addiction than peers without ADHD symptoms. For individuals with ADHD symptoms and excessive online gaming and/or online shopping behaviors, the probability of having Internet addiction is even higher. These findings have important implications for identifying risk factors of Internet addiction and preventing Internet addiction in Higher Education settings.

Metabolic homeostasis is one of the most exquisitely tuned systems in mammalian physiology. Metabolic homeostasis requires multiple redundant systems to cooperate to maintain blood glucose concentrations in a narrow range, despite a multitude of physiological and pathophysiological pressures. Cancer is one of the canonical pathophysiological settings in which metabolism plays a key role. In this study, we utilized REnal Gluconeogenesis Analytical Leads (REGAL), a liquid chromatography-mass spectrometry/mass spectrometry-based stable isotope tracer method that we developed to show that in conditions of metabolic stress, the fasting hepatokine fibroblast growth factor-21 (FGF-21)1, 2coordinates a liver-brain-kidney axis to promote renal gluconeogenesis. FGF-21 promotes renal gluconeogenesis by enhancing β2 adrenergic receptor (Adrb2)-driven, adipose triglyceride lipase (ATGL)-mediated intrarenal lipolysis. Further, we show that this liver-brain-kidney axis promotes gluconeogenesis in the renal parenchyma in mice and humans with renal cell carcinoma (RCC). This increased gluconeogenesis is, in turn, associated with accelerated RCC progression. We identify Adrb2 blockade as a new class of therapy for RCC in mice, with confirmatory data in human patients. In summary, these data reveal a new metabolic function of FGF-21 in driving renal gluconeogenesis, and demonstrate that inhibition of renal gluconeogenesis by FGF-21 antagonism deserves attention as a new therapeutic approach to RCC.

SummaryReprogramming metabolism is of great therapeutic interest for reducing morbidity and mortality during sepsis-induced critical illness1. Disappointing results from randomized controlled trials targeting glutamine and antioxidant metabolism in patients with sepsis have begged for both identification of new metabolic targets, and a deeper understanding of the metabolic fate of glutamine at the systemic and tissue-specific manner2–4. In critically ill patients versus elective surgical controls, skeletal muscle transcriptional metabolic reprogramming is comprised of reduced expression of genes involved in mitochondrial metabolism, electron transport, and glutamate transport, with concomitant increases in glutathione cycling, glutamine, branched chain, and aromatic amino acid transport. To analyze putative interorgan communications during sepsis, we performed systemic and tissue specific metabolic phenotyping in a murine polymicrobial sepsis model, cecal ligation and puncture. In the setting of drastically elevated inflammatory cytokines, we observed >10% body weight loss, >50% reductions in oxygen consumption and carbon dioxide production, and near full suppression of voluntary activity for the 48 hours following sepsis as compared to sham-operated controls. We found increased correlations in the metabolome between liver, kidney, and spleen, with drastic loss of correlations between the heart and quadriceps metabolome and all other organs, pointing to a shared metabolic signature within vital abdominal organs, and unique metabolic signatures for skeletal and cardiac muscle during sepsis. A lowered GSH:GSSG and elevated AMP:ATP ratio in the liver underlie the significant upregulation of isotopically labeled glutamine’s contribution to TCA anaplerosis and glutamine-derived glutathione biosynthesis; meanwhile, the skeletal muscle and spleen were the only organs where glutamine’s contribution to the TCA cycle was significantly suppressed. These results highlight tissue-specific mitochondrial reprogramming, rather than global mitochondrial dysfunction, as a mechanistic consequence of sepsis. Using a multi-omic approach, we demonstrate a model by which sepsis-induced proteolysis fuels the liver’s production of anaplerotic substrates and the antioxidant glutathione to sustain tolerance to sepsis.

In the recent years, the excessive use of internet has become frequent; it may lead to deficits in cognition and emotions. Commenting on online news is a popular way to express attitude and thoughts. It may have different impacts on the emotional state of healthy people and pathological internet users (PIUs). The impact is also related to the emotional valence of the commented text. This study aimed to explore the effect of making comments on online news and valenced text on the emotional state of PIUs. The sample included 32 undergraduate students (18 with PIU and 14 controls). The two groups commented on positive and negative online news in proper order, respectively. The emotion rating questionnaire was used to measure their emotion at different experimental stages in elicited positive and negative emotional states. The results displayed that when commenting on positive news, the emotional changes of PIU group were the same with the control group. In addition, the results indicated that when making comments on negative news, there was a difference between the PIU group and the control group for the extent of emotional changes. PIUs were rated higher than control group in “surprise” and “happiness” ways. The emotional state of PIU is easier to be affected by the act of commenting, revealing that PIUs may have poor ability of emotion management and emotional stability.

Severe hypoglycemia is the leading acute mortality risk in patients with diabetes. The counterregulatory gluconeogenic and glycogenolytic response to hypoglycemia is the primary adaptive mechanism to enable survival. To better understand the hormonal response that orchestrates hypoglycemia counterregulation, we employed the insulin tolerance test (ITT) and hyperinsulinemic-hypoglycemic clamp to mimic the two common settings in which hypoglycemia can occur in patients: postprandial insulin overdose and elevated basal insulin infusion, respectively. We found that Growth Differentiation Factor 15 (GDF15) can be induced (33.5±2.1 vs. 172.4±29.2 pg/ml, P Disclosure Z.Li: None. C.Zhang: None. R.Chang: None. J.J.Hwang: None. A.Wang: Research Support; NGM Biopharmaceuticals. R.J.Perry: None. X.Zhang: None. W.Zhu: None. Q.Xu: None. C.Yu: None. B.G.Costa lima: None. X.Li: None. K.Israni-winger: None. A.Nasiri: None. Funding National Institutes of Health (P30 DK045735) National Institutes of Health (R37 CA258271-01A1)

In this study, we identified a potential practice-changing approach, dichloroacetate (DCA), to harness metabolic adjuvant therapy to treat cancer-related fatigue (CRF). CRF is one of the most common complications in patients with multiple cancer types. Although CRF severely affects patients’ quality of life and adherence to potentially curative treatment, there have only been single symptom-relieving adjuvant therapies but no effective pharmaceutical treatment for CRF. In this study, we used YUMMER1.7 murine melanoma as the model to study CRF. Mice with late-stage YUMMER1.7 melanoma (3 weeks after tumor xenograft) have significant decreases in muscle performance, including decrease forelimb grip strength, maximum running speed, maximum oxygen consumption and motivation for movement. Dichloroacetate (DCA) has been considered as a potential therapy to slow tumor growth, based largely on its effects in vitro to halt cell division. We found that although DCA did not affect tumor growth, DCA unexpectedly preserved muscle performance in mice with late-stage compared with early-stage tumors. DCA-treated mice had significantly preserved grip strength (9.5% decrease in DCA-treated late-stage mice vs. 29% in non-treated mice), maximum running speed (13% decrease in DCA-treated mice vs. 31% in non-treated mice) and VO2 peak (no significant reduction in DCA-treated mice whereas non-treated mice decreased by 26%). The daily running distance was also significantly higher in DCA-treated mice compared with non-treated mice during the third week after tumor xenograft. Meanwhile, motivation for movement was fully reserved. Moreover, we found that DCA could relieve treatment-worsened CRF in murine YUMMER1.7 melanoma (treated with anti-PD1 immunotherapy) and MC38 colon cancer (treated with 5-fluorouracil chemotherapy) without affecting the efficacy of these treatments. An in vivo liquid chromatography-mass spectrometry/mass spectrometry-based isotope tracer study suggests that DCA treatment may postpone proteolysis in muscle of tumor-bearing mice. Concentrations of 6 free amino acids (arginine, asparagine, leucine, lysine, methionine and threonine) were increased in muscle from late-stage non-treated mice, consistent with increased proteolysis and/or less amino acid utilization in muscle tissue during advanced-stage tumor progression. Such elevation was reversed by DCA treatment. We also discovered lower concentration of serine and glycine in DCA-treated muscle tissue, which provide precursors for antioxidants to adapt to oxidative stress. The abnormal increase of muscle mitochondrial membrane potential, which may enhance reactive oxygen species production, was also reversed in DCA-treaded mice. In all, this study provides evidence for DCA as the first potential adjuvant pharmaceutical treatment to maintain physical function and motivation in cancer patients experiencing CRF. Citation Format: xinyi zhang, Won D. Lee, Brooks P. Leitner, Wanling Zhu, Zongyu Li, Rafael C. Gaspar, Alexandra A. Halberstam, Briana Robles, Joshua D. Rabinowitz, Rachel J. Perry. Dichloroacetate as a novel pharmaceutical treatment for cancer-related fatigue in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 285.

Metabolic scaling, the inverse correlation of metabolic rates to body mass, has been appreciated for more than 80 years. Studies of metabolic scaling have almost exclusively been restricted to mathematical modeling of oxygen consumption. The possibility that other metabolic processes scale with body size has not been studied. To address this gap in knowledge, we employed a systems approach spanning from transcriptomics to in vitro and in vivo tracer-based flux. Gene expression in livers of five species spanning a 30,000-fold range in mass revealed differential expression of genes related to cytosolic and mitochondrial metabolic processes, in addition to detoxication of oxidative damage. This suggests that transcriptional scaling of damage control mechanisms accommodates increased oxidative metabolism in smaller species. To determine whether flux through key implicated metabolic pathways scaled, we applied stable isotope tracer methodology to study multiple cellular compartments, tissues, and species. Comparing mice and rats, we demonstrate that while scaling of metabolic fluxes is not observed in the cell-autonomous setting, it is present in liver slices and in vivo. Together, these data reveal that metabolic scaling extends beyond oxygen consumption to numerous other metabolic pathways, and is likely regulated at the level of gene expression and substrate supply.

Increasing evidence highlights the possibility for approaches targeting metabolism as potential adjuvants to cancer therapy. Sodium-glucose transport protein 2 (SGLT2) inhibitors are the newest class of antihyperglycemic therapies, and have recently been highlighted as a novel therapeutic approach to breast cancer. To our knowledge, however, SGLT2 inhibitors have not been applied in the neoadjuvant setting as a precision medicine approach to combining metabolic therapy with standard of care therapy for this devastating disease. In this study we combine the SGLT2 inhibitor dapagliflozin with paclitaxel chemotherapy in both lean and obese mice. We show that dapagliflozin enhances the efficacy of paclitaxel, reducing tumor glucose uptake and prolonging survival in an insulin-dependent manner in some but not all breast tumors. Our data find a genetic signature for breast tumors most likely to respond to dapagliflozin in combination with paclitaxel. Tumors driven by mutations upstream of canonical insulin signaling pathways are likely to respond to such treatment, whereas tumors driven by mutations downstream of canonical insulin signaling are not. These data demonstrate that dapagliflozin enhances the response to chemotherapy in mice with breast cancer and suggest that breast cancer patients with driver mutations upstream of canonical insulin signaling may be most likely to benefit from this neoadjuvant approach. A clinical trial is currently in preparation, with an application recently submitted for Yale Human Investigations Committee approval, to test this hypothesis in breast cancer patients.One Sentence SummaryWe identify a driver mutation signature by which glucose-wasting metabolic therapy (dapagliflozin) enhances the efficacy of chemotherapy in mice with breast cancer.

Increased GABAergic output in the ventromedial hypothalamus (VMH) contributes to counterregulatory failure in recurrently hypoglycemic (RH) rats, and lactate, an alternate fuel source in the brain, contributes to this phenomenon. The current study assessed whether recurring bouts of glucose deprivation enhanced neuronal lactate uptake and, if so, whether this influenced γ-aminobutyric acid (GABA) output and the counterregulatory responses. Glucose deprivation was induced using 5-thioglucose (5TG). Control rats received an infusion of artificial extracellular fluid. These groups were compared with RH animals. Subsequently, the rats underwent a hypoglycemic clamp with microdialysis. To test whether 5TG affected neuronal lactate utilization, a subgroup of 5TG-treated rats was microinjected with a lactate transporter inhibitor [cyano-4-hydroxycinnamate (4CIN)] just before the start of the clamp. Both RH and 5TG raised VMH GABA levels, and this was associated with impaired counterregulatory responses. 4CIN reduced VMH GABA levels and restored the hormone responses in the 5TG group. We then evaluated [14C]lactate uptake in hypothalamic neuronal cultures. Recurring exposure to low glucose increased monocarboxylate transporter-2 mRNA expression and augmented lactate uptake. Taken together, our data suggest that glucose deprivation, per se, enhances lactate utilization in hypothalamic neurons, and this may contribute to suppression of the counterregulatory responses to hypoglycemia.

Activation of the adrenergic system in response to hypoglycemia is important for proper recovery from low glucose levels. However, it has been suggested that repeated adrenergic stimulation may also contribute to counterregulatory failure, but the underlying mechanisms are not known. The aim of this study was to establish whether repeated activation of noradrenergic receptors in the ventromedial hypothalamus (VMH) contributes to blunting of the counterregulatory response by enhancing local lactate production. The VMH of nondiabetic rats were infused with either artificial extracellular fluid, norepinephrine (NE), or salbutamol for 3 hours/day for 3 consecutive days before they underwent a hypoglycemic clamp with microdialysis to monitor changes in VMH lactate levels. Repeated exposure to NE or salbutamol suppressed both the glucagon and epinephrine responses to hypoglycemia compared to controls. Furthermore, antecedent NE and salbutamol treatments raised extracellular lactate levels in the VMH. To determine whether the elevated lactate levels were responsible for impairing the hormone response, we pharmacologically inhibited neuronal lactate transport in a subgroup of NE-treated rats during the clamp. Blocking neuronal lactate utilization improved the counterregulatory hormone responses in NE-treated animals, suggesting that repeated activation of VMH β2-adrenergic receptors increases local lactate levels which in turn, suppresses the counterregulatory hormone response to hypoglycemia.

Although HIV-infected men who have sex with men (MSM) constitute a newly emerged high-risk group in China, little research outside Western countries is available on effective intervention programs to enhance their well-being. The purpose of this randomized controlled trial was to evaluate the efficacy of a group intervention program designed to improve the well-being and adaptive coping strategies of 60 HIV-infected MSM in Beijing, China, randomly assigned either to the intervention group for participation in four weekly sessions or to the control group for placement on a waiting list. They all completed measurements at pre- and postintervention. Compared with the control group, the intervention group reported significantly increased problem-focused coping strategies and levels of posttraumatic growth (PTG) as well as decreased symptoms of posttraumatic stress disorder (PTSD) at the completion of the intervention. In addition, mediation analysis showed that changes in problem-focused coping strategies mediated the intervention effect on increases in PTG; however, the mediating effect of coping strategies on the association of intervention and PTSD was not significant. This study provides empirical evidence for conducting psychological intervention to promote the well-being of HIV-infected MSM. The findings also elucidate the mechanism through which intervention improved PTG.

Therapeutic strategies targeting the incretin system are effective in treating type 2 diabetes. GLP-1 receptor agonists (GLP-1RA) reduce post-prandial glucose levels by stimulating insulin and inhibiting glucagon release, but also by reducing gastric motility. Although GLP-1RA reduce gastric motility initially, their ability to sustain this over the long-term is reduced and the mechanism(s) underlying this change is not known. GLP-1R are expressed in neurons of the nucleus of the solitary tract (NTS) which play a fundamental role in regulating metabolism and gastric motility. Here, we examined whether long-term use of GLP-1RA alters GLP-1R expression in the NTS that can influence gastric motility. C57BL6 mice were treated with either saline, lixisenatide, liraglutide or exenatide ER, for 2hrs, 1d, 1wk, 2wks, 4wks or 6wks before their effects on gastric motility and NTS GLP-1R mRNA expression were evaluated. All GLP-1RA effectively slowed gastric emptying in the early stages of treatment, but within 1-2wks, their efficacy waned. By 4-6wks, no significant reduction in gastric motility was observed with any of the agonists. Of note, we observed a decline in GLP-1R mRNA expression in the NTS at 1-2wks of treatment which corresponded to the initial decline in drug efficacy. At 4wks, however, GLP-1R mRNA levels returned to pretreatment levels and suppression of gastric motility was no longer observed. To test whether the decrease in NTS GLP-1R expression contributed to attenuating the suppressive effects on gastric motility, we knocked down GLP-1R expression in the NTS using an adeno-associated viral vector to express a shRNA against the GLP-1R. Reducing NTS GLP-1R expression prevented the suppressive effects of lixisenatide on gastric motility, suggesting in mice, a decrease in NTS GLP-1R expression may contribute to the initial decrease in GLP-1RA efficacy, whereas receptor desensitization may play a more dominant role in the latter stages. Disclosure P. Wang: None. R. Mamillapalli: None. W. Zhu: None. O. Chan: None.

The objectives of this study were to understand the role of glutamatergic neurotransmission in the ventromedial hypothalamus (VMH) in response to hypoglycemia and to elucidate the effects of recurrent hypoglycemia (RH) on this neurotransmitter. We 1) measured changes in interstitial VMH glutamate levels by using microdialysis and biosensors, 2) identified the receptors that mediate glutamate’s stimulatory effects on the counterregulatory responses, 3) quantified glutamate metabolic enzyme levels in the VMH, 4) examined astrocytic glutamate reuptake mechanisms, and 5) used 1H-[13C]-nuclear magnetic resonance (NMR) spectroscopy to evaluate the effects of RH on neuronal glutamate metabolism. We demonstrated that glutamate acts through kainic acid receptors in the VMH to augment counterregulatory responses. Biosensors showed that the normal transient rise in glutamate levels in response to hypoglycemia is absent in RH animals. More importantly, RH reduced extracellular glutamate concentrations partly as a result of decreased glutaminase expression. Decreased glutamate was also associated with reduced astrocytic glutamate transport in the VMH. NMR analysis revealed a decrease in [4-13C]glutamate but unaltered [4-13C]glutamine concentrations in the VMH of RH animals. The data suggest that glutamate release is important for proper activation of the counterregulatory response to hypoglycemia and that impairment of glutamate metabolic and resynthetic pathways with RH may contribute to counterregulatory failure.

Suppression of GABAergic neurotransmission in the ventromedial hypothalamus (VMH) is crucial for full activation of counterregulatory responses to hypoglycemia, and increased γ-aminobutyric acid (GABA) output contributes to counterregulatory failure in recurrently hypoglycemic (RH) and diabetic rats. The goal of this study was to establish whether lactate contributes to raising VMH GABA levels in these two conditions. We used microdialysis to deliver artificial extracellular fluid or l-lactate into the VMH and sample for GABA. We then microinjected a GABAA receptor antagonist, an inhibitor of lactate transport (4CIN), or an inhibitor of lactate dehydrogenase, oxamate (OX), into the VMH prior to inducing hypoglycemia. To assess whether lactate contributes to raising GABA in RH and diabetes, we injected 4CIN or OX into the VMH of RH and diabetic rats before inducing hypoglycemia. l-lactate raised VMH GABA levels and suppressed counterregulatory responses to hypoglycemia. While blocking GABAA receptors did not prevent the lactate-induced rise in GABA, inhibition of lactate transport or utilization did, despite the presence of lactate. All three treatments restored the counterregulatory responses, suggesting that lactate suppresses these responses by enhancing GABA release. Both RH and diabetic rats had higher baseline GABA levels and were unable to reduce GABA levels sufficiently to fully activate counterregulatory responses during hypoglycemia. 4CIN or OX lowered VMH GABA levels in both RH and diabetic rats and restored the counterregulatory responses. Lactate likely contributes to counterregulatory failure in RH and diabetes by increasing VMH GABA levels.

AIMS/HYPOTHESIS: Roux-en-Y gastric bypass (RYGB) surgery, an effective treatment for morbid obesity, commonly leads to near complete resolution of type 2 diabetes. The underlying mechanisms, however, remain unclear and factors other than weight loss alone may be involved. METHODS: To determine whether increased hypothalamic insulin sensitivity after RYGB drives the rapid improvement in glucose metabolism, high-fat-fed rats received either an insulin receptor (IR) antisense vector or a control lentiviral vector that was microinjected into the ventromedial hypothalamus (VMH). Six weeks later, rats underwent RYGB or control gastrointestinal surgery. RESULTS: Four weeks after surgery, weight loss was comparable in RYGB and surgical controls. Nevertheless, only RYGB rats that received the control vector demonstrated both improved hepatic and peripheral insulin sensitivity. Insulin suppressed hepatic glucose production (HGP) by 50% (p

Activation of β-cell EphA5 receptors by its ligand ephrinA5 from adjacent β-cells has been reported to decrease insulin secretion during hypoglycemia. Given the similarities between islet and ventromedial hypothalamus (VMH) glucose sensing, we tested the hypothesis that the EphA5/ephrinA5 system might function within the VMH during hypoglycemia to stimulate counterregulatory hormone release as well. Counterregulatory responses and glutamine/glutamate concentrations in the VMH were assessed during a hyperinsulinemic-hypoglycemic glucose clamp study in chronically catheterized awake male Sprague-Dawley rats that received an acute VMH microinjection of ephrinA5-Fc, chronic VMH knockdown, or overexpression of ephrinA5 using an adenoassociated viral construct. Local stimulation of VMH EphA5 receptors by ephrinA5-Fc or ephrinA5 overexpression increased, whereas knockdown of VMH ephrinA5 reduced counterregulatory responses during hypoglycemia. Overexpression of VMH ephrinA5 transiently increased local glutamate concentrations, whereas ephrinA5 knockdown produced profound suppression of VMH interstitial fluid glutamine concentrations in the basal state and during hypoglycemia. Changes in ephrinA5/EphA5 interactions within the VMH, a key brain glucose-sensing region, act in concert with islets to restore glucose homeostasis during acute hypoglycemia, and its effect on counterregulation may be mediated by changes in glutamate/glutamine cycling.

OBJECTIVE Norepinephrine is locally released into the ventromedial hypothalamus (VMH), a key brain glucose-sensing region in the response to hypoglycemia. As a result, this neurotransmitter may play a role in modulating counterregulatory responses. This study examines whether norepinephrine acts to promote glucose counterregulation via specific VMH β-adrenergic receptors (BAR). RESEARCH DESIGN AND METHODS Awake male Sprague-Dawley rats received, via implanted guide cannulae, bilateral VMH microinjections of 1) artificial extracellular fluid, 2) B2AR agonist, or 3) B2AR antagonist. Subsequently, a hyperinsulinemic-hypoglycemic clamp study was performed. The same protocol was also used to assess the effect of VMH delivery of a selective B1AR or B3AR antagonist. RESULTS Despite similar insulin and glucose concentrations during the clamp, activation of B2AR in the VMH significantly lowered by 32% (P < 0.01), whereas VMH B2AR blockade raised by 27% exogenous glucose requirements during hypoglycemia (P < 0.05) compared with the control study. These changes were associated with alternations in counterregulatory hormone release. Epinephrine responses throughout hypoglycemia were significantly increased by 50% when the B2AR agonist was delivered to the VMH (P < 0.01) and suppressed by 32% with the B2AR antagonist (P < 0.05). The glucagon response was also increased by B2AR activation by 63% (P < 0.01). Neither blockade of VMH B1AR nor B3AR suppressed counterregulatory responses to hypoglycemia. Indeed, the B1AR antagonist increased rather than decreased epinephrine release (P < 0.05). CONCLUSIONS Local catecholamine release into the VMH enhances counterregulatory responses to hypoglycemia via stimulation of B2AR. These observations suggest that B2AR agonists might have therapeutic benefit in diabetic patients with defective glucose counterregulation.

Insulin is believed to regulate glucose homeostasis mainly via direct effects on the liver, muscle, and adipose tissues. The contribution of insulin's central nervous system effects to disorders of glucose metabolism has received less attention. To evaluate whether postnatal reduction of insulin receptors (IRs) within the ventromedial hypothalamus (VMH), a brain region critical for glucose sensing, contributes to disorders of peripheral glucose metabolism, we microinjected a lentiviral vector expressing an antisense sequence to knockdown IRs or a control lentiviral vector into the VMH of nonobese nondiabetic rats. After 3–4 mo, we assessed 1) glucose tolerance, 2) hepatic insulin sensitivity, and 3) insulin and glucagon secretion, using the glucose clamp technique. Knockdown of IRs locally in the VMH caused glucose intolerance without altering body weight. Increments of plasma insulin during a euglycemic clamp study failed to suppress endogenous glucose production and produced a paradoxical rise in plasma glucagon in the VMH-IR knockdown rats. Unexpectedly, these animals also displayed a 40% reduction ( P < 0.05) in insulin secretion in response to an identical hyperglycemic stimulus (∼220 mg/dl). Our data demonstrate that chronic suppression of VMH-IR gene expression is sufficient to impair glucose metabolism as well as α-cell and β-cell function in nondiabetic, nonobese rats. These data suggest that insulin resistance within the VMH may be a significant contributor to the development of type 2 diabetes.

OBJECTIVE Insulin released by the β-cell is thought to act locally to regulate glucagon secretion. The possibility that insulin might also act centrally to modulate islet glucagon secretion has received little attention. RESEARCH DESIGN AND METHODS Initially the counterregulatory response to identical hypoglycemia was compared during intravenous insulin and phloridzin infusion in awake chronically catheterized nondiabetic rats. To explore whether the disparate glucagon responses seen were in part due to changes in ventromedial hypothalamus (VMH) exposure to insulin, bilateral guide cannulas were inserted to the level of the VMH and 8 days later rats received a VMH microinjection of either 1) anti-insulin affibody, 2) control affibody, 3) artificial extracellular fluid, 4) insulin (50 μU), 5) insulin receptor antagonist (S961), or 6) anti-insulin affibody plus a γ-aminobutyric acid A (GABAA) receptor agonist muscimol, prior to a hypoglycemic clamp or under baseline conditions. RESULTS As expected, insulin-induced hypoglycemia produced a threefold increase in plasma glucagon. However, the glucagon response was fourfold to fivefold greater when circulating insulin did not increase, despite equivalent hypoglycemia and C-peptide suppression. In contrast, epinephrine responses were not altered. The phloridzin-hypoglycemia induced glucagon increase was attenuated (40%) by VMH insulin microinjection. Conversely, local VMH blockade of insulin amplified glucagon twofold to threefold during insulin-induced hypoglycemia. Furthermore, local blockade of basal insulin levels or insulin receptors within the VMH caused an immediate twofold increase in fasting glucagon levels that was prevented by coinjection to the VMH of a GABAA receptor agonist. CONCLUSIONS Together, these data suggest that insulin's inhibitory effect on α-cell glucagon release is in part mediated at the level of the VMH under both normoglycemic and hypoglycemic conditions.

The objective of this study was to determine whether the sodium-glucose transporter SGLT1 in the ventromedial hypothalamus (VMH) plays a role in glucose sensing and in regulating the counterregulatory response to hypoglycemia, and if so, whether knockdown of in the VMH can improve counterregulatory responses to hypoglycemia in diabetic rats or rats exposed to recurrent bouts of hypoglycemia (RH). Normal Sprague-Dawley rats as well as RH or streptozotocin (STZ)-diabetic rats received bilateral VMH microinjections of an adenoassociated viral vector containing either the SGLT1 short hairpin RNA (shRNA) or a scrambled RNA sequence. Subsequently, these rats underwent a hypoglycemic clamp to assess hormone responses. In a subgroup of rats, glucose kinetics was determined using tritiated glucose. The shRNA reduced VMH SGLT1 expression by 53% in nondiabetic rats, and this augmented glucagon and epinephrine responses and hepatic glucose production during hypoglycemia. Similarly, SGLT1 knockdown improved the glucagon and epinephrine responses in RH rats and restored the impaired epinephrine response to hypoglycemia in STZ-diabetic animals. These findings suggest that SGLT1 in the VMH plays a significant role in the detection and activation of counterregulatory responses to hypoglycemia. Inhibition of SGLT1 may offer a potential therapeutic target to diminish the risk of hypoglycemia in diabetes.

Defective counterregulatory responses (CRRs) to hypoglycemia are associated with a marked increase in the risk of severe hypoglycemia. The mechanisms leading to the development of defective CRRs remain largely unknown, although they are associated with antecedent hypoglycemia. Activation of AMP-activated protein kinase (AMPK) in the ventromedial hypothalamus (VMH) amplifies the counterregulatory increase in glucose production during acute hypoglycemia. To examine whether activation of AMPK in the VMH restores defective CRR, controlled hypoglycemia ( approximately 2.8 mmol/l) was induced in a group of 24 Sprague-Dawley rats, all of which had undergone a 3-day model of recurrent hypoglycemia before the clamp study. Before the acute study, rats were microinjected to the VMH with either 5-aminoimidazole-4-carboxamide (AICAR; n=12), to activate AMPK, or saline (n=12). In a subset of rats, an infusion of H(3)-glucose was additionally started to calculate glucose turnover. Stimulation of AMPK within the VMH was found to amplify hormonal CRR and increase endogenous glucose production. In addition, analysis of tissue from both whole hypothalamus and VMH showed that recurrent hypoglycemia induces an increase in the gene expression of AMPK alpha(1) and alpha(2). These findings suggest that the development of novel drugs designed to selectively activate AMPK in the VMH offer a future therapeutic potential for individuals with type 1 diabetes who have defective CRRs to hypoglycemia.

Hypoglycemia provokes a multifaceted counterregulatory response involving the sympathoadrenal system, stimulation of glucagon secretion, and the hypothalamo-pituitary-adrenal axis that is commonly impaired in diabetes. We examined whether modulation of inhibitory input from γ-aminobutyric acid (GABA) in the ventromedial hypothalamus (VMH), a major glucose-sensing region within the brain, plays a role in affecting counterregulatory responses to hypoglycemia. Normal Sprague-Dawley rats had carotid artery and jugular vein catheters chronically implanted, as well as bilateral steel microinjection guide cannulas inserted down to the level of the VMH. Seven to 10 days following surgery, the rats were microinjected with artificial extracellular fluid, the GABAA receptor agonist muscimol (1 nmol/side), or the GABAA receptor antagonist bicuculline methiodide (12.5 pmol/side) before being subjected to a hyperinsulinemic-hypoglycemic (2.5 mmol/l) glucose clamp for 90 min. Following VMH administration of bicuculline methiodide, glucose infusion rates were significantly suppressed, whereas muscimol raised glucose infusion rates significantly compared with controls. Glucagon and epinephrine responses were elevated with the antagonist and suppressed with the agonist compared with controls. Corticosterone responses, however, were unaffected by either administration of the agonist or antagonist into the VMH. These data demonstrate that modulation of the GABAergic system in the VMH alters both glucagon and sympathoadrenal, but not corticosterone, responses to hypoglycemia. Our findings are consistent with the hypothesis that GABAergic inhibitory tone within the VMH can modulate glucose counterregulatory responses.

We have previously reported that local activation of β2-adrenergic receptors (B2ARs) in the ventromedial hypothalamus (VMH) enhances hypoglycaemic counter-regulation. This study examines whether peripheral delivery of a selective B2AR agonist could also promote counter-regulatory responses and thereby has potential therapeutic value to limit hypoglycaemia risk.Conscious male Sprague-Dawley rats received an intra-arterial injection of the B2AR specific agonist, formoterol, or a control solution either before a hyperinsulinaemic-hypoglycaemic clamp study or immediately before recovery from insulin-induced hypoglycaemia. In addition, the capacity of a VMH-targeted microinjection of a B2AR antagonist to limit the anti-insulin effect of the B2AR agonist was assessed.Systemic delivery of B2AR agonist markedly reduced the exogenous glucose infusion rate (GIR) required during the hypoglycaemic clamp study. This effect was mediated by blockade of insulin's inhibitory effect on endogenous glucose production. Local blockade of B2ARs within the VMH using a specific antagonist partially diminished the effect of systemic activation of B2ARs during hypoglycaemia at least in part by diminishing the adrenaline (epinephrine) response to hypoglycaemia. Peripheral B2AR agonist injection also enhanced glucose recovery from insulin-induced hypoglycaemia.Systemic B2AR agonist administration acts to limit insulin-induced hypoglycaemia by offsetting insulin's inhibitory effect on hepatic glucose production. This effect appears to be predominately mediated via a direct effect on liver B2ARs, but a small stimulatory effect on B2ARs within the VMH cannot be excluded. Our data suggest that formoterol may have therapeutic value to limit the risk of hypoglycaemia in patients with diabetes.

OBJECTIVE Impaired glucose counterregulation during hypoglycemia is well documented in patients with type 1 diabetes; however, the molecular mechanisms underlying this defect remain uncertain. We reported that the inhibitory neurotransmitter γ-aminobutyric acid (GABA), in a crucial glucose-sensing region within the brain, the ventromedial hypothalamus (VMH), plays an important role in modulating the magnitude of the glucagon and epinephrine responses to hypoglycemia and investigated whether VMH GABAergic tone is altered in diabetes and therefore might contribute to defective counterregulatory responses. RESEARCH DESIGN AND METHODS We used immunoblots to measure GAD65 protein (a rate-limiting enzyme in GABA synthesis) and microdialysis to measure extracellular GABA levels in the VMH of two diabetic rat models, the diabetic BB rat and the streptozotocin (STZ)-induced diabetic rat, and compared them with nondiabetic controls. RESULTS Both diabetic rat models exhibited an ~50% increase in GAD65 protein as well as a twofold increase in VMH GABA levels compared with controls under baseline conditions. Moreover, during hypoglycemia, VMH GABA levels did not change in the diabetic animals, whereas they significantly declined in nondiabetic animals. As expected, glucagon responses were absent and epinephrine responses were attenuated in diabetic rats compared with their nondiabetic control counterparts. The defective counterregulatory response in STZ-diabetic animals was restored to normal with either local blockade of GABAA receptors or knockdown of GAD65 in the VMH. CONCLUSIONS These data suggest that increased VMH GABAergic inhibition is an important contributor to the absent glucagon response to hypoglycemia and the development of counterregulatory failure in type 1 diabetes.

Local delivery of glucose into a critical glucose-sensing region within the brain, the ventromedial hypothalamus (VMH), can suppress glucose counterregulatory responses to systemic hypoglycemia. Here, we investigated whether this suppression was accomplished through changes in GABA output in the VMH. Sprague-Dawley rats had catheters and guide cannulas implanted. Eight to ten days later, microdialysis-microinjection probes were inserted into the VMH, and they were dialyzed with varying concentrations of glucose from 0 to 100 mM. Two groups of rats were microdialyzed with 100 mM glucose and microinjected with either the KATP channel opener diazoxide or a GABAA receptor antagonist. These animals were then subjected to a hyperinsulinemic-hypoglycemic glucose clamp. As expected, perfusion of glucose into the VMH suppressed the counterregulatory responses. Extracellular VMH GABA levels positively correlated with the concentration of glucose in the perfusate. In turn, extracellular GABA concentrations in the VMH were inversely related to the degree of counterregulatory hormone release. Of note, microinjection of either diazoxide or the GABAA receptor antagonist reversed the suppressive effects of VMH glucose delivery on counterregulatory responses. Some GABAergic neurons in the VMH respond to changes in local glucose concentration. Glucose in the VMH dose-dependently stimulates GABA release, and this in turn dose-dependently suppresses the glucagon and epinephrine responses to hypoglycemia. These data suggest that during hypoglycemia a decrease in glucose concentration within the VMH may provide an important signal that rapidly inactivates VMH GABAergic neurons, reducing inhibitory GABAergic tone, which in turn enhances the counterregulatory responses to hypoglycemia.

OBJECTIVE—We have previously demonstrated that modulation of γ-aminobutyric acid (GABA) inhibitory tone in the ventromedial hypothalamus (VMH), an important glucose-sensing region in the brain, modulates the magnitude of glucagon and sympathoadrenal responses to hypoglycemia. In the current study, we examined whether increased VMH GABAergic tone may contribute to suppression of counterregulatory responses after recurrent hypoglycemia. RESEARCH DESIGN AND METHODS—To test this hypothesis, we quantified expression of the GABA synthetic enzyme, glutamic acid decarboxylase (GAD), in the VMH of control and recurrently hypoglycemic rats. Subsequently, we used microdialysis and microinjection techniques to assess changes in VMH GABA levels and the effects of GABAA receptor blockade on counterregulatory responses to a standardized hypoglycemic stimulus. RESULTS—Quantitative RT-PCR and immunoblots in recurrently hypoglycemic animals revealed that GAD65 mRNA and protein were increased 33 and 580%, respectively. Basal VMH GABA concentrations were more than threefold higher in recurrently hypoglycemic animals. Furthermore, whereas VMH GABA levels decreased in both control and recurrently hypoglycemic animals with the onset of hypoglycemia, the fall was not significant in recurrently hypoglycemic rats. During hypoglycemia, recurrently hypoglycemic rats exhibited a 49–63% reduction in glucagon and epinephrine release. These changes were reversed by delivery of a GABAA receptor antagonist to the VMH. CONCLUSIONS—Our data suggest that recurrent hypoglycemia increases GABAergic inhibitory tone in the VMH and that this, in turn, suppresses glucagon and sympathoadrenal responses to subsequent bouts of acute hypoglycemia. Thus, hypoglycemia-associated autonomic failure may be due in part to a relative excess of the inhibitory neurotransmitter, GABA, within the VMH.

Type 2 corticotropin-releasing factor (CRF) receptors (CRFR2) within the ventromedial hypothalamus (VMH), a key glucose-sensing region, play a major role in regulating the hormonal counterregulatory responses (CRRs) to acute hypoglycemia. The VMH expresses both subtypes of CRF receptors, CRFR1 and CRFR2. The objective of this study was to examine the role of the CRFR1 receptor in the VMH in the regulation of the CRR to acute hypoglycemia. To compare the hormonal CRR to hypoglycemia, awake and unrestrained Sprague-Dawley rats were bilaterally microinjected to the VMH with either 1) aECF, 2) CRF (1 pmol/side), 3) CRFR1 antagonist Antalarmin (500 pmol/side), or 4) CRF + Antalarmin prior to undergoing a hyperinsulinemic hypoglycemic (2.8 mM) clamp. A second series of studies also incorporated an infusion of [3H]glucose to allow the calculation of glucose dynamics. In addition the effect of CRFR1 antagonism in the paraventricular nucleus (PVN) was studied. Activation of VMH CRFR1 increased, whereas inhibition of CRFR1 suppressed hypoglycemia-induced CRRs. Inhibition of VMH CRFR1 also increased peripheral glucose utilization and reduced endogenous glucose production during hypoglycemia, whereas VMH CRF reduced peripheral glucose utilization. In contrast CRFR1 inhibition in the PVN blunted corticosterone but not epinephrine or glucagon CRR to hypoglycemia. In contrast to CRFR2 activation, CRFR1 activation within the VMH amplifies CRRs to acute hypoglycemia. The balance between these two opposing CRFRs in this key glucose-sensing region may play an important role in determining the magnitude of CRRs to acute hypoglycemia.

OBJECTIVE—To determine whether alterations in counterregulatory responses to hypoglycemia through the modulation of ATP-sensitive K+ channels (KATP channels) in the ventromedial hypothalamus (VMH) are mediated by changes in GABAergic inhibitory tone in the VMH, we examined whether opening and closing KATP channels in the VMH alter local GABA levels and whether the effects of modulating KATP channel activity within the VMH can be reversed by local modulation of GABA receptors. RESEARCH DESIGN AND METHODS—Rats were cannulated and bilateral guide cannulas inserted to the level of the VMH. Eight days later, the rats received a VMH microinjection of either 1) vehicle, 2) the KATP channel opener diazoxide, 3) the KATP channel closer glybenclamide, 4) diazoxide plus the GABAA receptor agonist muscimol, or 5) glybenclamide plus the GABAA receptor antagonist bicuculline methiodide (BIC) before performance of a hypoglycemic clamp. Throughout, VMH GABA levels were measured using microdialysis. RESULTS—As expected, diazoxide suppressed glucose infusion rates and increased glucagon and epinephrine responses, whereas glybenclamide raised glucose infusion rates in conjunction with reduced glucagon and epinephrine responses. These effects of KATP modulators were reversed by GABAA receptor agonism and antagonism, respectively. Microdialysis revealed that VMH GABA levels decreased 22% with the onset of hypoglycemia in controls. Diazoxide caused a twofold greater decrease in GABA levels, and glybenclamide increased VMH GABA levels by 57%. CONCLUSIONS—Our data suggests that KATP channels within the VMH may modulate the magnitude of counterregulatory responses by altering release of GABA within that region.

The mechanism(s) by which glucosensing neurons detect fluctuations in glucose remains largely unknown. In the pancreatic beta-cell, ATP-sensitive K+ channels (K ATP channels) play a key role in glucosensing by providing a link between neuronal metabolism and membrane potential. The present study was designed to determine in vivo whether the pharmacological opening of ventromedial hypothalamic K ATP channels during systemic hypoglycemia would amplify hormonal counterregulatory responses in normal rats and those with defective counterregulation arising from prior recurrent hypoglycemia. Controlled hypoglycemia (approximately 2.8 mmol/l) was induced in vivo using a hyperinsulinemic (20 mU x kg(-1) x min(-1)) glucose clamp technique in unrestrained, overnight-fasted, chronically catheterized Sprague-Dawley rats. Immediately before the induction of hypoglycemia, the rats received bilateral ventromedial hypothalamic microinjections of either the potassium channel openers (KCOs) diazoxide and NN414 or their respective controls. In normal rats, both KCOs amplified epinephrine and glucagon counterregulatory responses to hypoglycemia. Moreover, diazoxide also amplified the counterregulatory responses in a rat model of defective hormonal counterregulation. Taken together, our data suggest that the K ATP channel plays a key role in vivo within glucosensing neurons in the ventromedial hypothalamus in the detection of incipient hypoglycemia and the initiation of protective counterregulatory responses. We also conclude that KCOs may offer a future potential therapeutic option for individuals with insulin-treated diabetes who develop defective counterregulation.

The mechanisms by which specialized glucose-sensing neurons within the hypothalamus are able to detect a falling blood glucose remain largely unknown but may be linked to some gauge of neuronal energy status. We sought to test the hypothesis that AMP-activated protein kinase (AMPK), an intracellular kinase purported to act as a fuel sensor, plays a role in hypoglycemia sensing in the ventromedial hypothalamus (VMH) of the Sprague-Dawley rat by chemically activating AMPK in vivo through bilateral microinjection, before performing hyperinsulinemic-hypoglycemic or hyperinsulinemic-euglycemic clamp studies. In a subgroup of rats, H3-glucose was infused to determine glucose kinetics. The additional chemical activation by AICAR of AMPK in the VMH during hypoglycemia markedly reduced the amount of exogenous glucose required to maintain plasma glucose during hypoglycemia, an effect that was almost completely accounted for by a three- to fourfold increase in hepatic glucose production in comparison to controls. In contrast, no differences were seen between groups in hypoglycemia-induced rises in the principal counterregulatory hormones. In conclusion, activation of AMPK within the VMH may play an important role in hypoglycemia sensing. The combination of hypoglycemia- and AICAR-induced AMPK activity appears to result in a marked stimulus to hepatic glucose counterregulation.