Counterregulatory Hormones Research Articles

Altered glucose-dependent secretion of glucagon and ACTH is associated with insulin resistance, assessed by population analysis.

This study aimed to characterize how the dysregulation of counter-regulatory hormones can contribute to insulin resistance and potentially to diabetes. Therefore, we investigated the association between insulin sensitivity and the glucose- and insulin-dependent secretion of glucagon, adrenocorticotropic hormone (ACTH), and cortisol in non-diabetic individuals using a population model analysis. Data, from hyperinsulinemic-hypoglycemic clamps, were pooled for analysis, including 52 individuals with a wide range of insulin resistance (reflected by glucose infusion rate 20-60 min; GIR20-60min). Glucagon secretion was suppressed by glucose and, to a lesser extent, insulin. The GIR20-60min and BMI were identified as predictors of the insulin effect on glucagon. At normoglycemia (5 mmol/L), a 90% suppression of glucagon was achieved at insulin concentrations of 16.3 and 43.4 µU/mL in individuals belonging to the highest and lowest quantiles of insulin sensitivity, respectively. Insulin resistance of glucagon secretion explained the elevated fasting glucagon for individuals with a low GIR20-60min. ACTH secretion was suppressed by glucose and not affected by insulin. The GIR20-60min was superior to other measures as a predictor of glucose-dependent ACTH secretion, with 90% suppression of ACTH secretion by glucose at 3.1 and 3.5 mmol/L for insulin-sensitive and insulin-resistant individuals, respectively. This difference may appear small but shifts the suppression range into normoglycemia for individuals with insulin resistance, thus, leading to earlier and greater ACTH/cortisol response when the glucose falls. Based on modeling of pooled glucose-clamp data, insulin resistance was associated with generally elevated glucagon and a potentiated cortisol-axis response to hypoglycemia, and over time both hormonal pathways may therefore contribute to dysglycemia and possibly type 2 diabetes.

Counter-regulatory responses to postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia vs surgical and non-surgical control individuals

Aims/hypothesisPost-bariatric hypoglycaemia is an increasingly recognised complication of bariatric surgery, manifesting particularly after Roux-en-Y gastric bypass. While hyperinsulinaemia is an established pathophysiological feature, the role of counter-regulation remains unclear. We aimed to assess counter-regulatory hormones and glucose fluxes during insulin-induced postprandial hypoglycaemia in patients with post-bariatric hypoglycaemia after Roux-en-Y gastric bypass vs surgical and non-surgical control individuals.MethodsIn this case–control study, 32 adults belonging to four groups with comparable age, sex and BMI (patients with post-bariatric hypoglycaemia, Roux-en-Y gastric bypass, sleeve gastrectomy and non-surgical control individuals) underwent a postprandial hypoglycaemic clamp in our clinical research unit to reach the glycaemic target of 2.5 mmol/l 150–170 min after ingesting 15 g of glucose. Glucose fluxes were assessed during the postprandial and hypoglycaemic period using a dual-tracer approach. The primary outcome was the incremental AUC of glucagon during hypoglycaemia. Catecholamines, cortisol, growth hormone, pancreatic polypeptide and endogenous glucose production were also analysed during hypoglycaemia.ResultsThe rate of glucose appearance after oral administration, as well as the rates of total glucose appearance and glucose disappearance, were higher in both Roux-en-Y gastric bypass groups vs the non-surgical control group in the early postprandial period (all p<0.05). During hypoglycaemia, glucagon exposure was significantly lower in all surgical groups vs the non-surgical control group (all p<0.01). Pancreatic polypeptide levels were significantly lower in patients with post-bariatric hypoglycaemia vs the non-surgical control group (median [IQR]: 24.7 [10.9, 38.7] pmol/l vs 238.7 [186.3, 288.9] pmol/l) (p=0.005). Other hormonal responses to hypoglycaemia and endogenous glucose production did not significantly differ between the groups.Conclusions/interpretationThe glucagon response to insulin-induced postprandial hypoglycaemia is lower in post-bariatric surgery individuals compared with non-surgical control individuals, irrespective of the surgical modality. No significant differences were found between patients with post-bariatric hypoglycaemia and surgical control individuals, suggesting that impaired counter-regulation is not a root cause of post-bariatric hypoglycaemia.Trial registrationClinicalTrials.gov NCT04334161Graphical abstract

Fibrocalculous pancreatic diabetes

Chronic Pancreatitis and the type of diabetes associated with it have been named as “Fibrocalcific Pancreatic Diabetes” (FCPD). Initially categorized by WHO in 1985 as a subtype of Malnutrition Related Diabetes Mellitus (MRDM), FCPD has subsequently been included as a disease of the exocrine pancreas under other specific forms of diabetes. Despite many years since its first description, the etiopathogenesis of FCPD remains obscure. While insulin secretion defects are definitely the crux of the problem, there is growing body of evidence to suggest that insulin resistance may play a key role in glucose metabolism in these individuals. Moreover, the role of free fatty acids, counter-regulatory hormones like glucagon and impact of hepatic and peripheral lipid distribution on the dynamics of insulin secretion remains to be explored. Other factors related to alterations in energy expenditure may compound the pathogenetic picture. In fact, not all people with Fibro calculous Pancreatitis will develop diabetes and a search for the exact triggers for hyperglycemia might provide the clue to this enigmatic disease pathophysiology.

Sex-Dimorphic Octadecaneuropeptide (ODN) Regulation of Ventromedial Hypothalamic Nucleus Glucoregulatory Neuron Function and Counterregulatory Hormone Secretion.

Central endozepinergic signaling is implicated in glucose homeostasis. Ventromedial hypothalamic nucleus (VMN) metabolic monitoring governs glucose counter-regulation. VMN glucose-stimulatory nitric oxide (NO) and glucose-inhibitory γ-aminobutyric acid (GABA) neurons express the energy gauge 5'-AMP-activated protein kinase (AMPK). Current research addresses the premise that the astrocyte glio-peptide octadecaneuropeptide (ODN) imposes sex-dimorphic control of metabolic sensor activity and neurotransmitter signaling in these neurons. The ODN G-protein coupled-receptor antagonist cyclo(1-8)[DLeu5]OP (LV-1075) was administered intracerebroventricularly (icv) to euglycemic rats of each sex; additional groups were pretreated icv with the ODN isoactive surrogate ODN11-18 (OP) before insulin-induced hypoglycemia. Western blotting of laser-catapult-microdissected VMN NO and GABA neurons showed that hypoglycemia caused OP-reversible augmentation of phospho-, e.g., activated AMPK and nitric oxide synthase (nNOS) expression in rostral (female) or middle (male) VMN segments or ODN-dependent suppression of nNOS in male caudal VMN. OP prevented hypoglycemic down-regulation of glutamate decarboxylase profiles in female rat rostral VMN, without affecting AMPK activity. LV-1075 treatment of male, not female rats elevated plasma glucagon and corticosterone concentrations. Moreover, OP attenuated hypoglycemia-associated augmentation of these hormones in males only. Results identify, for each sex, regional VMN metabolic transmitter signals that are subject to endozepinergic regulation. Directional shifts and gain-or-loss of ODN control during eu- versus hypoglycemia infer that VMN neuron receptivity to or post-receptor processing of this stimulus may be modulated by energy state. In male, counter-regulatory hormone secretion may be governed principally by ODN-sensitive neural pathways, whereas this endocrine outflow may be controlled by parallel, redundant ODN-dependent and -independent mechanisms in female.

Continuous Subcutaneous Insulin Infusions: Closing the Loop.

Continuous subcutaneous insulin infusions (CSIIs) and continuous glucose monitors (CGMs) have revolutionized the management of diabetes mellitus (DM). Over the last 2 decades the development of advanced, small, and user-friendly technology has progressed substantially, essentially closing the loop in the fasting and postabsorptive state, nearing the promise of an artificial pancreas (AP). The momentum was mostly driven by the diabetes community itself, to improve its health and quality of life. Literature regarding CSII and CGM was reviewed. Management of DM aims to regulate blood glucose to prevent long-term microvascular and macrovascular complications. CSIIs combined with CGMs provide an integrated system to maintain tight glycemic control in a safe and uninterrupted fashion, while minimizing hypoglycemic events. Recent advances have allowed to "closing of the loop" by better mimicking endogenous insulin secretion and glucose level regulation. Evidence supports sustained improvement in glycemic control with reduced episodes of hypoglycemia using these systems, while improving quality of life. Ongoing work in delivery algorithms with or without counterregulatory hormones will allow for further layers of regulation of the AP. Ongoing efforts to develop an AP have created effective tools to improve the management of DM. CSIIs and CGMs are useful in diverse populations ranging from children to older individuals, as well as in various clinical contexts. Individually and more so together, these have had a tremendous effect on the management of DM, while avoiding treatment fatigue. However, cost and accessibility are still a hindrance to its wider application.

Continuous glucose monitoring assessment in patients suffering from anorexia nervosa reveals chronic prolonged mild hypoglycemia all over the nycthemeron.

Anorexia nervosa (AN) is an eating disorder characterised by voluntary dietary restriction leading to severe undernutrition. Hypoglycaemia is mostly described through severe case reports and is always evaluated by fasting or post-meal blood glucose, showing nothing about hypoglycaemia's length or duration. The interest of continuous interstitial glucose monitoring (CGM), largely used in diabetes mellitus, has never been evaluated in AN patients. Glycaemia cycles in AN patients were assessed using CGM over 5days and then analysed according to food intake. Mean glycaemia was within normal range. 91% of the patients presented with at least one episode with glycaemia under 70mg/dl. Within the 24h, the percentage of time spent with a glycaemia under 70mg/dl was of 20.82±3.90% with a maximum of 52%. We found 2.52±0.33 hypoglycaemia events per 24h, including 21.11±3.76% at night. CGM parameters correlated with cortisol and IGF1 plasma levels. Comparison with estimated carbohydrate intakes discriminated concordant and non-concordant estimations depending on patient. AN patients display chronic prolonged mild hypoglycaemia all over the nycthemeron despite normal fasting glycaemia. Associated adaptive increased counter-regulatory hormones might protect AN patients from deeper hypoglycaemia. CGM allowed testing food intake self-estimation reliability of AN patients and could be a very useful biofeedback tool.

ISPAD Clinical Practice Consensus Guidelines 2022: Ramadan and other religious fasting by young people with diabetes.

ISPAD Clinical Practice Consensus Guidelines 2022: Ramadan and other religious fasting by young people with diabetes.

Pancreas Transplantation: Current Challenges, Considerations, and Controversies.

Pancreas transplantation (PTx) reestablishes an autoregulating source of endogenous insulin responsive to normal feedback controls. In addition to achieving complete β-cell replacement that frees the patient with diabetes from the need to monitor serum glucose and administer exogenous insulin, successful PTx provides counterregulatory hormone secretion and exocrine function. A functioning PTx mitigates glycemic variability, eliminates the daily stigma and burden of diabetes, restores normal glucose homeostasis in patients with complicated diabetes, and improves quality of life and life expectancy. The tradeoff is that it entails a major surgical procedure and requisite long-term immunosuppression. Despite the high likelihood of rendering patients euglycemic independent of exogenous insulin, PTx is considered a treatment rather than a cure. In spite of steadily improving outcomes in each successive era coupled with expansion of recipient selection criteria to include patients with a type 2 diabetes phenotype, a decline in PTx activity has occurred in the new millennium related to a number of factors including: (1) lack of a primary referral source and general acceptance by the diabetes care community; (2) absence of consensus criteria; and (3) access, education, and resource issues within the transplant community. In the author's experience, patients who present as potential candidates for PTx have felt as though they needed to circumvent the conventional diabetes care model to gain access to transplant options. PTx should be featured more prominently in the management algorithms for patients with insulin requiring diabetes who are failing exogenous insulin therapy or experiencing progressive diabetic complications regardless of diabetes type. Furthermore, all patients with diabetes and chronic kidney disease should undergo consideration for simultaneous pancreas-kidney transplantation independent of geography or location.

ODP202 Geriatric Type 1 Diabetes- unique management challenge

Abstract Case Presentation A 87 year old female with a past medical history of Type 1 Diabetes Mellitus (DM), Parkinson's disease and osteoporosis was sent from an assisted living facility to the emergency department for evaluation of elevated blood glucose levels. She had a long standing history of type 1 DM and further review revealed that she had extremely labile (brittle) blood sugars, with multiple prior hospitalizations for both hypoglycemia and hyperglycemia. Assisted living facility staff reported that her blood sugars were persistently elevated despite receiving scheduled insulin doses. On presentation, she did not have any specific complaints except for polydipsia and polyuria. She was hemodynamically stable, alert and oriented to time, place and person. Initial lab work included serum glucose 754 (70-79 mg/dL), bicarbonate 25 (21-31 mmol/L), anion gap 10 (6-14 mmol/L), ketone 0.9 (&amp;lt; 0.6 mmol/L), leukocyte count 4.7 (4-11 k/mm u) and creatinine 1. 06 (0.6-1.2 mg/dL). Urinalysis showed glycosuria and proteinuria but no evidence of infection. IVF and insulin were started. Extensive infectious work-up was negative. Her blood glucose levels stabilized with basal-bolus regimen and correctional doses of insulin. Tight glycemic control was avoided due to her history of hypoglycemic unawareness and multiple previous episodes for severe and recurrent hypoglycemia. Discussion Brittle diabetes is a disorder commonly seen in patients with Type 1 DM and is characterized by extreme swings in blood glucose levels (severe recurrent hypoglycemic and hyperglycemic episodes) without a clear cut precipitating cause requiring hospitalizations. It has been linked to autonomic dysfunction, hormonal imbalance, psychological issues, nutrient malabsorption and autoimmune conditions. Geriatric Type 1 DM presents great challenges in management as it combines micro and macro vascular complications of long standing DM with geriatric syndrome - concurrent comorbidities, cognitive losses of various degrees, vision and hearing loss, loss autonomic and hormonal counter-regulation, and progressive frailty leading to severe glycemic instability makes self management of DM near impossible. Our patient was an elderly female with osteoporosis, Parkinson's and hypoglycemic unawareness. Great care was taken to maintain her blood glucose levels in the optimal range both during and after hospitalization. Daily insulin was being administered by staff after checking blood glucose levels, avoiding the possibility of dose omission or errors. Detailed instructions on administration of the correct dose of insulin according to caloric consumption and physical activity were provided. With this case, we wish to highlight the unique challenge Brittle Diabetes in geriatric presents, and as this sector of population is growing owing to better treatment options for diabetics and longer life expectancy, there is a growing need to recognize this entity, adopt a multi-disciplinary patient centered approach and prioritize prevention of both hypoglycemia and extreme hyperglycemia over tight glycemic control. Presentation: No date and time listed

PSUN264 Insulin Edema: A rare side effect of Intensive Insulin Therapy

Abstract Insulin therapy associated generalized edema is a rare entity. The true incidence is unknown. It has been reported mostly in patients with poorly controlled diabetes mellitus started on intensive insulin regimens. The severity ranges from mild lower extremity swelling to anasarca. Management is primarily supportive with salt restrictions, diuretics and if possible, reduction of insulin doses. We present a case of a 39-year-old African American woman who developed generalized edema after initiation of insulin. She had history of gestational diabetes and presented to the endocrinology clinic to establish care after being hospitalized with Diabetic Ketoacidosis (DKA). She was diagnosed with diabetes mellitus initially during her pregnancy two years prior and was treated with insulin. After pregnancy, she was lost to follow up. She was then admitted to the hospital with severe DKA and was discharged on multiple daily injections of insulin. On the initial encounter in clinic, the patient endorsed developing abdominal distension and lower extremity swelling with insulin use previously so she was not using insulin consistently. Her physical examination was unremarkable. Lab work was significant for hemoglobin A1C of &amp;gt;15%, C-peptide 0.9 ng/mL (1.1-4.4 ng/mL), islet cell antibody 0.09 nmol/L (&amp;lt;0.02 nmol/L), glutamic acid decarboxylase antibody 0.40 nmol/L (&amp;lt;0.02 nmol/L). Her kidney and liver function were normal. She had normal thyroid function and cortisol levels. Her echocardiogram revealed normal cardiac function and she had non proliferative diabetic retinopathy on retinal exam. The patient was started on insulin and a continuous glucose monitor was placed to assess her glycemic patterns. Three days after starting insulin, she developed generalized body swelling involving face, abdomen, and lower extremities. The patient was advised to cut back on salt and started on low dose furosemide. On follow up one month later, her abdominal swelling had improved however she still had pitting lower extremity edema. On follow up two months later the edema completely resolved. Clinicians should be aware of the presentation and management of insulin induced edema. In most of the cases in literature, insulin induced edema started after starting insulin in newly diagnosed Type 1 diabetes or uncontrolled Type 2 diabetes. The pathophysiology is unclear. There is some evidence that insulin deficiency causes a catabolic state and hyperglycemia increases tissue capillary permeability. Re-introduction of insulin causes free water retention and renal excretion of sodium. This along with increased capillary permeability can lead to insulin edema. Water retention caused by the effect of counter regulatory hormones can also play a role. Insulin edema needs to be differentiated from other causes of diffuse edema. Management is generally supportive including temporarily decreasing insulin doses, salt restriction and diuretics as needed. Patient reassurance is important as well to aid in adherence to the prescribed insulin regimen. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Diabetic ketoacidosis awareness and prevention for new onset Type 1 diabetes

Diabetic ketoacidosis (DKA) is an avoidable life-threatening condition and form of metabolic acidosis that develops with a relative or absolute deficiency of circulating insulin (Cashen & Peterson, 2019). The imbalance of insulin and counterregulatory hormone levels can lead to hyperglycemia, hyperosmolality, ketosis, and acidosis which results in cerebral edema and death if not addressed quickly. The incidence of DKA hospitalizations continues to increase, and the most common cause of DKA is new-onset Type 1 diabetes (T1D).

S1720 Diabetic Ketoacidosis as a Rare Complication of Alcoholic Pancreatitis in a Previously Euglycemic Patient

Introduction: Acute alcoholic pancreatitis is an acute inflammation of the pancreas secondary to alcohol intake due to autodigestion from an increase in pancreatic enzyme release. Most commonly due to gallstones, alcohol intake, and hypertriglyceridemia, pancreatitis commonly presents with severe epigastric abdominal pain, nausea and vomiting and is managed with aggressive intravenous (IV) fluid resuscitation. Some complications include acute respiratory distress syndrome and compartment syndrome. A very rare complication of acute pancreatitis is diabetic ketoacidosis (DKA), especially in patients without a history of diabetes mellitus. Case Description/Methods: A 25-year-old female with a medical history significant for alcohol abuse presented with nausea, vomiting, and abdominal pain for 2 days. The patient reported drinking one pint of liquor per day. She was tachycardic with a heart rate of 115 and other vitals were normal. Significant laboratory studies showed a lipase of 1715, aspartate transaminase of 292, alanine transaminase of 155, glucose of 540, venous pH of 7.277, bicarbonate of 9, anion gap of 21, and beta-hydroxybutyrate of 5.1. A computed tomography scan of her abdomen and pelvis without IV contrast showed edematous and inflammatory changes in the tail of the pancreas and severe hepatic steatosis (Figure). The patient was managed with aggressive IV fluids and IV insulin infusion. Her abdominal pain and anion gap resolved on day 2 of admission and she was able to tolerate a diet. Glycated hemoglobin (HbA1c) returned a value of 4.7 and C-peptide was low at < 0.10; the subsequent pancreatic antibody panel was negative. The patient was seen in the clinic 6 months later and HbA1c at that time was 4.8. Discussion: This case illustrates DKA as a rare complication of acute pancreatitis. It provides an example of why a high level of suspicion for DKA should be present in patients presenting with alcoholic pancreatitis even in the absence of any diabetic history. Though there is no definitive mechanism of action for this presentation, it is likely from a combination of pancreatic beta-cell destruction and counter-regulatory hormone effects. Pancreatic beta-cell destruction causes impaired insulin production, leading to acute hyperglycemia. Furthermore, as acute pancreatitis can lead to severe intravascular depletion, increased secretion of counter-regulatory hormones such as cortisol and glucagon, in combination with impaired insulin secretion, can precipitate DKA in such a scenario.Figure 1.: CT abdomen without contrast demonstrating edematous and inflammatory changes in the tail of the pancreas.

Lipid biosynthesis enzyme Agpat5 in AgRP-neurons is required for insulin-induced hypoglycemia sensing and glucagon secretion

The counterregulatory response to hypoglycemia that restores normal blood glucose levels is an essential physiological function. It is initiated, in large part, by incompletely characterized brain hypoglycemia sensing neurons that trigger the secretion of counterregulatory hormones, in particular glucagon, to stimulate hepatic glucose production. In a genetic screen of recombinant inbred BXD mice we previously identified Agpat5 as a candidate regulator of hypoglycemia-induced glucagon secretion. Here, using genetic mouse models, we demonstrate that Agpat5 expressed in agouti-related peptide neurons is required for their activation by hypoglycemia, for hypoglycemia-induced vagal nerve activity, and glucagon secretion. We find that inactivation of Agpat5 leads to increased fatty acid oxidation and ATP production and that suppressing Cpt1a-dependent fatty acid import into mitochondria restores hypoglycemia sensing. Collectively, our data show that AgRP neurons are involved in the control of glucagon secretion and that Agpat5, by partitioning fatty acyl-CoAs away from mitochondrial fatty acid oxidation and ATP generation, ensures that the fall in intracellular ATP, which triggers neuronal firing, faithfully reflects changes in glycemia.

Medical Nutrition Therapy and Other Approaches to Management of Post-bariatric Hypoglycemia: A Team-Based Approach.

This manuscript provides a review of post-bariatric hypoglycemia (PBH) with a special focus on the role of the registered dietitian-nutritionist (RDN) and medical nutrition therapy (MNT) recommendations as foundational for management. As the number of bariatric surgeries rises yearly, with 256,000 performed in 2019, PBH is an increasingly encountered late complication. Following Roux-en-Y (RYGB) or vertical sleeve gastrectomy (VSG), about 1/3 of patients report symptoms suggestive of at least mild postprandial hypoglycemia, with severe and/or medically confirmed hypoglycemia in 1-10%. Anatomical alterations, changes in GLP1 and other intestinally derived hormones, excessive insulin response, reduced insulin clearance, impaired counterregulatory hormone response to hypoglycemia, and other factors contribute to PBH. MNT is the cornerstone of multidisciplinary treatment, with utilization of personal continuous glucose monitoring to improve safety when possible. While many individuals require pharmacotherapy, there are no currently approved medications for PBH. Increasing awareness and identification of individuals at risk for or with PBH is critical given the potential impact on safety, nutrition, and quality of life. A team-based approach involving the individual, the RDN, and other clinicians is essential in providing ongoing assessment and individualization of MNT in the long-term management of PBH.

Recurrent hypoglycemia increases hepatic gluconeogenesis without affecting glycogen metabolism or systemic lipolysis in rat

IntroductionRecurrent hypoglycemia (RH) impairs secretion of counterregulatory hormones. Whether and how RH affects responses within metabolically important peripheral organs to counterregulatory hormones are poorly understood. ObjectiveTo study the effects of RH on metabolic pathways associated with glucose counterregulation within liver, white adipose tissue and skeletal muscle. MethodsUsing a widely adopted rodent model of 3-day recurrent hypoglycemia, we first checked expression of counterregulatory hormone G-protein coupled receptors (GPCRs), their inhibitory regulators and downstream enzymes catalyzing glycogen metabolism, gluconeogenesis and lipolysis by qPCR and western blot. Then, we examined epinephrine-induced phosphorylation of PKA substrates to validate adrenergic sensitivity in each organ. Next, we measured hepatic and skeletal glycogen content, degree of breakdown by epinephrine and abundance of phosphorylated glycogen phosphorylase under hypoglycemia and that of phosphorylated glycogen synthase during recovery to evaluate glycogen turnover. Further, we performed pyruvate and lactate tolerance tests to assess gluconeogenesis. Additionally, we measured circulating FFA and glycerol to check lipolysis. The abovementioned studies were repeated in streptozotocin-induced diabetic rat model. Finally, we conducted epinephrine tolerance test to investigate systemic glycemic excursions to counterregulatory hormones. Saline-injected rats served as controls. ResultsRH increased counterregulatory hormone GPCR signaling in liver and epidydimal white adipose tissue (eWAT), but not in skeletal muscle. For glycogen metabolism, RH did not affect total content or epinephrine-stimulated breakdown in liver and skeletal muscle. Although RH decreased expression of phosphorylated glycogen synthase 2, it did not affect hepatic glycogen biosynthesis during recovery from hypoglycemia or after fasting-refeeding. For gluconeogenesis, RH upregulated fructose 1,6-bisphosphatase 1 and monocarboxylic acid transporter 1 that imports lactate as precursor, resulting in a lower blood lactate profile during hypoglycemia. In agreement, RH elevated fasting blood glucose and caused higher glycemic excursions during pyruvate tolerance test. For lipolysis, RH did not affect circulating levels of FFA and glycerol after overnight fasting or upon epinephrine stimulation. Interestingly, RH upregulated the trophic fatty acid transporter FATP1 and glucose transporter GLUT4 to increase lipogenesis in eWAT. These aforementioned changes of gluconeogenesis, lipolysis and lipogenesis were validated in streptozotocin-diabetic rats. Finally, RH increased insulin sensitivity to accelerate glucose disposal, which was attributable to upregulated visceral adipose GLUT4. ConclusionsRH caused metabolic adaptations related to counterregulation within peripheral organs. Specifically, adrenergic signaling was enhanced in liver and visceral fat, but not in skeletal muscle. Glycogen metabolism remained unchanged. Hepatic gluconeogenesis was augmented. Systemic lipolysis was unaffected, but visceral lipogenesis was enhanced. Insulin sensitivity was increased. These findings provided insights into mechanisms underlying clinical problems associated with intensive insulin therapy, such as high gluconeogenic flux and body weight gain.

Experimentally Induced Hypoglycemia-associated Autonomic Failure in Humans: Determinants, Designs, and Drawbacks.

ContextIatrogenic hypoglycemia remains one of the leading hindrances of optimal glycemic management in insulin-treated diabetes. Recurring hypoglycemia leads to a condition of hypoglycemia-associated autonomic failure (HAAF). HAAF refers to a combination of (i) impaired hormonal counterregulatory responses and (ii) hypoglycemia unawareness to subsequent hypoglycemia, substantially increasing the risk of severe hypoglycemia. Several studies since the 1990s have experimentally induced HAAF, yielding variable results.ObjectiveThe aim of this review was to assess the varying designs, clinical outcomes, potential assets, and drawbacks related to these studies.MethodA systemic literature search was conducted on PubMed and Embase in winter 2021 to include all human studies attempting to experimentally induce HAAF. In different combinations, the search terms used were “hypoglycemia-associated autonomic failure,” “HAAF,” “hypoglycemia,” “recurring,” “recurrent,” “repeated,” “consecutive,” and “unawareness,” yielding 1565 publications. Inclusion criteria were studies that had aimed at experimentally inducing HAAF and measuring outcomes of hormonal counterregulation and awareness of hypoglycemia.ResultsThe literature search yielded 27 eligible publications, of which 20 were successful in inducing HAAF while statistical significantly impairing both hormonal counterregulation and impairing awareness of hypoglycemia to subsequent hypoglycemia. Several factors were of significance as regards inducing HAAF: Foremost, the duration of antecedent hypoglycemia should be at least 90 minutes and blood glucose should be maintained below 3.4 mmol/L. Other important factors to consider are the type of participants, insulin dosage, and the risk of unintended hypoglycemia prior to the study.ConclusionHere we have outlined the most important factors to take into consideration when designing a study aimed at inducing HAAF, including to take into consideration other disease states susceptible to hypoglycemia, thus hopefully clarifying the field and allowing qualified studies in the future.

Primary cilia regulate adaptive responses to fasting

ObjectiveNeuronal primary cilia are known to be a required organelle for energy balance and leptin action. However, whether primary cilia directly mediate adaptive responses during starvation is yet unknown. Therefore, we investigated the counterregulatory roles of primary cilia, and their related leptin action in energy-depleted condition. MethodWe generated leptin receptor (LepR) neuron-specific primary cilia knockout (Ift88 KOLepR) mice. Leptin-mediated electrophysiological properties of the neurons in fasting condition were assessed using patch-clamp technique. Adaptive responses and neuroendocrine reflexes were measured by monitoring counterregulatory hormones. ResultsIn fasting state, the leptin-induced neuronal excitability and leptin homeostasis were impaired in Ift88 KOLepR. In addition, the Ift88 KOLepR exhibited aberrant fasting responses including lesser body weight loss, decreased energy expenditure, and lower heat generation compared to wild-type littermates. Furthermore, the primary cilia in LepR neurons are necessary for counterregulatory responses and leptin-mediated neuroendocrine adaptation to starvation. ConclusionOur results demonstrated that the neuronal primary cilia are crucial neuronal components mediating the adaptive counterregulatory responses to starvation.

Cross Talk Between Insulin and Glucagon Receptor Signaling in the Hepatocyte.

While the consumption of external energy (i.e., feeding) is essential to life, this action induces a temporary disturbance of homeostasis in an animal. A primary example of this effect is found in the regulation of glycemia. In the fasted state, stored energy is released to maintain physiological glycemic levels. Liver glycogen is liberated to glucose, glycerol and (glucogenic) amino acids are used to build new glucose molecules (i.e., gluconeogenesis), and fatty acids are oxidized to fuel long-term energetic demands. This regulation is driven primarily by the counterregulatory hormones epinephrine, growth hormone, cortisol, and glucagon. Conversely, feeding induces a rapid influx of diverse nutrients, including glucose, that disrupt homeostasis. Consistently, a host of hormonal and neural systems under the coordination of insulin are engaged in the transition from fasting to prandial states to reduce this disruption. The ultimate action of these systems is to appropriately store the newly acquired energy and to return to the homeostatic norm. Thus, at first glance it is tempting to assume that glucagon is solely antagonistic regarding the anabolic effects of insulin. We have been intrigued by the role of glucagon in the prandial transition and have attempted to delineate its role as beneficial or inhibitory to glycemic control. The following review highlights this long-known yet poorly understood hormone.

165-OR: Norepinephrine Acts on Glutamatergic Neurons in the Ventromedial Hypothalamus to Stimulate the Release of Counterregulatory Hormones

Release of glutamate in the ventromedial hypothalamus (VMH) is important for stimulating the counterregulatory hormone responses to hypoglycemia. It is currently not known whether VMH glutamatergic neurotransmission is influenced by adrenergic inputs. To address this question, we examined whether ß2-adrenergic receptors are expressed on VMH glutamatergic neurons using immunohistochemistry. Coronal brain sections collected from Sprague Dawley (SD) rats showed fairly extensive co-localization of Vglut2 (a marker of glutamatergic neurons) and ß2-adrenergic receptors. We then used local microinjection in combination with microdialysis to examine whether norepinephrine administration into the VMH stimulated the release of neurotransmitter glutamate and the counterregulatory hormones in the absence of hypoglycemia. About 7-8 rats were randomly allocated to one of two treatment groups: Controls, which received an infusion of artificial extracellular fluid, or the NE group, which received an infusion of 400 nM of norepinephrine. Our results indicate that NE administration into the VMH caused a marked increase in glutamate that was accompanied by an ∼3-fold increase in both plasma glucagon and epinephrine release (P&amp;lt;0.vs. Control) . Our data suggests that NE enhances the release of neurotransmitter glutamate in the VMH that in turn, may stimulate the release of counterregulatory hormones. Disclosure D.A.Appadurai: None. O.Chan: None. Funding NIH (DK099315)

216-LB: Hepatocyte N6-Methyladenosine mRNA Modification in Hepatic Gluconeogenesis and Diabetes

The liver produces endogenous glucose to support life during fasting. Counterregulatory hormones, including glucagon, catecholamines, and glucocorticoids, stimulate the expression of gluconeogenic enzymes in the liver, thus driving liver glucose production. In contrast, insulin suppresses hepatic gluconeogenesis, thereby restraining postprandial glucose levels. Hepatic gluconeogenesis aberrantly increases in type 2 diabetes due to an imbalance between insulin and counterregulatory hormone actions, contributing to hyperglycemia and glucose intolerance. N6-methyladenosine (m6A) RNA methylation has emerged as a critical paradigm shaping cell identities and functions. The Mettl3/Mettl14 complex catalyzes m6A on RNA and RNA-binding proteins bind to the m6A motifs and determine the fate of client mRNAs (splicing, trafficking, stability, and/or translation) . However, m6A RNA modification has not been explored in liver gluconeogenesis. Here, we identified Mettl14 as an important positive regulator of hepatic gluconeogenesis. Liver Mettl14 levels were increased in db/db mice and mice with high fat diet (HFD) -induced obesity. Hepatocyte-specific deletion of Mettl14 decreased hepatic glucose production and ameliorated HFD-induced glucose intolerance; conversely, liver-specific overexpression of Mettl14 increased liver glucose production and HFD-induced glucose intolerance. Of note, Mettl14 did not alter liver insulin actions under our experimental conditions. Remarkably, hepatic deficiency of Mettl14 profoundly blunted the ability of glucagon to stimulate gluconeogenesis in mice. Consistently, deletion of Mettl14 largely blocked glucagon-stimulated gluconeogenesis ex vivo in liver slices as well as in primary hepatocyte cultures. In contrast, overexpression of Mettl14 had the opposite effects. Collectively, these data unravel a previously unrecognized glucagon/Mettl14/gluconeogenesis axis that is involved in hyperglycemia and glucose intolerance in diabetes. Disclosure Q. Zheng: None. X. Zhong: None. D. Ren: None. L. Rui: None. Funding National Institutes of Health (RO1DK127568) , American Heart Association (831585)