TRPC5 controls the adrenaline-mediated counter regulation of hypoglycemia.

Hypoglycemia triggers autonomic and endocrine counter-regulatory responses to restore glucose homeostasis, a response that is impaired in patients with diabetes and its long-term complication hypoglycemia-associated autonomic failure (HAAF). We show that insulin-evoked hypoglycemia is severely aggravated in mice lacking the cation channel proteins TRPC1, TRPC4, TRPC5, and TRPC6, which cannot be explained by alterations in glucagon or glucocorticoid action. By using various TRPC compound knockout mouse lines, we pinpointed the failure in sympathetic counter-regulation to the lack of the TRPC5 channel subtype in adrenal chromaffin cells, which prevents proper adrenaline rise in blood plasma. Using electrophysiological analyses, we delineate a previously unknown signaling pathway in which stimulation of PAC1 or muscarinic receptors activates TRPC5 channels in a phospholipase-C-dependent manner to induce sustained adrenaline secretion as a crucial step in the sympathetic counter response to insulin-induced hypoglycemia. By comparing metabolites in the plasma, we identified reduced taurine levels after hypoglycemia induction as a commonality in TRPC5-deficient mice and HAAF patients.

WITHDRAWN: Adipocyte Deletion of ADAM17 Leads to Insulin Resistance in Association with Age and HFD in Mice.

Withdrawal: Valeria Lopez Salazar, Rhoda Anane Karikari, Lun Li, Rabih El-Merahbi, Maria Troullinaki, Moya Wu, Tobias Wiedemann, Alina Walth, Manuel Gil Lozano, Maria Rohm, Stephan Herzig, Anastasia Georgiadi. Adipocyte Deletion of ADAM17 Leads to Insulin Resistance in Association with Age and HFD in Mice (2021). The FASEB Journal. 35:s1. doi: 10.1096/fasebj.2021.35.S1.00447. The above abstract, published online on May 14, 2021 in Wiley Online Library (wileyonlinelibrary.com), has been withdrawn by agreement between the authors, FASEB, and Wiley Periodicals Inc. The withdrawal is due to a request made by the authors prior to publication. The Publisher apologizes that this abstract was published in error.

Liver adapts mitochondrial function to insulin resistant and diabetic states in mice.

BACKGROUND & AIMS: To determine if diabetic and insulin-resistant states cause mitochondrial dysfunction in liver or if there is long term adaptation of mitochondrial function to these states, mice were (i) fed with a high-fat diet to induce obesity and T2D (HFD), (ii) had a genetic defect in insulin signaling causing whole body insulin resistance, but not full blown T2D (IR/IRS-1(+/-) mice), or (iii) were analyzed after treatment with streptozocin (STZ) to induce a T1D-like state. METHODS: Hepatic lipid levels were measured by thin layer chromatography. Mitochondrial respiratory chain (RC) levels and function were determined by Western blot, spectrophotometric, oxygen consumption and proton motive force analysis. Gene expression was analyzed by real-time PCR and microarray. RESULTS: HFD caused insulin resistance and hepatic lipid accumulation, but RC was largely unchanged. Livers from insulin resistant IR/IRS-1(+/-) mice had normal lipid contents and a normal RC, but mitochondria were less well coupled. Livers from severely hyperglycemic and hypoinsulinemic STZ mice had massively depleted lipid levels, but RC abundance was unchanged. However, liver mitochondria isolated from these animals showed increased abundance and activity of the RC, which was better coupled. CONCLUSIONS: Insulin resistance, induced either by obesity or genetic manipulation and steatosis do not cause mitochondrial dysfunction in mouse liver. Also, mitochondrial dysfunction is not a prerequisite for liver steatosis. However, severe insulin deficiency and high blood glucose levels lead to an enhanced performance and better coupling of the RC. This may represent an adaptation to fuel overload and the high energy-requirement of an unsuppressed gluconeogenesis.

Intravesical immune suppression by liposomal tacrolimus in cyclophosphamide-induced inflammatory cystitis.

AIMS: Potent immunosuppressive effect of tacrolimus has encouraged its topical application for achieving local anti-inflammatory effect. However, its poor aqueous solubility presents challenges in formulating biocompatible instillations to justify the investigation of liposomes as vehicle for tacrolimus. METHODS: Adult female Sprague-Dawley rats (N=52) divided into 4 groups were injected with cyclophosphamide (CYP) (200 mg/kg, ip) except for sham (saline injection, ip). Other three groups were instilled with either saline (1 cc, retained for 1 hr), liposome (LP- 1 cc) or liposomal encapsulated tacrolimus (LFK- 0.2 mg tacrolimus/1 ml LP). Baseline cystometrogram was performed on day 1 and day 3 prior to bladder harvest for histological staining (N=24) in all groups except sham. In addition, 4-hr baseline urine on day 1 and day 3 was collected from all groups for urine PGE2 assay and bladder harvested for PGE2 and IL2 assay on day 3 (N=28). RESULTS: Rats treated with LFK demonstrated suppression of CYP induced inflammatory reaction with reduced EP4 staining and bladder overactivity (intercontraction interval 61.0% decrease in untreated animals) as well as normalized the several fold elevation of IL 2 and PGE2 levels in tissue and urine. CYP induced effects were not suppressed in rats left untreated with tacrolimus. CONCLUSIONS: This is the first report of immunosuppression in bladder by intravesical delivery of tacrolimus using liposomes. LFK significantly inhibited CYP induced inflammatory cystitis through the modulation of IL2, PGE2, and EP4 function. These findings support investigation of local tacrolimus in cases of inflammatory cystitis refractory to conventional therapy.

Expression of E-series prostaglandin (EP) receptors and urodynamic effects of an EP4 receptor antagonist on cyclophosphamide-induced overactive bladder in rats.

OBJECTIVE: To investigate the expression of four subtypes of E-series prostaglandin (EP(1) -EP(4) ) receptors and the urodynamic effects of an EP(4) receptor antagonist (AH23848) in cyclophosphamide (CYP)-induced overactive bladder (OAB) in rats, as intravesical prostaglandin E(2) (PGE(2) ) induces OAB via activation of EP receptors and sensitization of afferent nerves. MATERIALS AND METHODS: Experimental and control rats were injected with CYP (200 mg/kg, intraperitoneally) or saline, respectively. Continuous cystometrograms (CMGs) were performed 48 h after CYP or saline injection under urethane anaesthesia. AH23848 was given intravenously at doses of 0.01 and 0.1 mg/kg. The bladder was then harvested for histology. Some bladders were harvested for analysis of EP receptors expression by Western blotting without a CMG study. CMG variables (baseline pressure; intercontraction interval [ICI], pressure threshold [PT], contraction amplitude) and histological changes were measured. RESULTS: CYP-induced up-regulation of EP(4) receptor (100% increase) accompanied by detrusor overactivity (ICI 70.5% decrease; PT, 67.7% increase). However, CYP down-regulated EP(1) receptor expression (51.9% decrease), but had no significant effects on the EP(2) and EP(3) receptors. AH23848 significantly extended the ICI in CYP-treated rats but it had no effects on other urodynamic variables or in control rats. CONCLUSIONS: Modulation of EP receptors plays a role in CYP-induced OAB. Antagonists to the EP(4) receptor may be a new target for treatment of patients with OAB.

Impact of Brain Fatty Acid Signaling on Peripheral Insulin Action in Mice.

AIMS AND METHODS: Glucose homeostasis and energy balance are under control by peripheral and brain processes. Especially insulin signaling in the brain seems to impact whole body glucose homeostasis and interacts with fatty acid signaling. In humans circulating saturated fatty acids are negatively associated with brain insulin action while animal studies suggest both positive and negative interactions of fatty acids and insulin brain action. This apparent discrepancy might reflect a difference between acute and chronic fatty acid signaling. To address this question we investigated the acute effect of an intracerebroventricular palmitic acid administration on peripheral glucose homeostasis. We developed and implemented a method for simultaneous monitoring of brain activity and peripheral insulin action in freely moving mice by combining radiotelemetry electrocorticography (ECoG) and euglycemic-hyperinsulinemic clamps. This method allowed gaining insight in the early kinetics of brain fatty acid signaling and its contemporaneous effect on liver function in vivo, which, to our knowledge, has not been assessed so far in mice. RESULTS: Insulin-induced brain activity in the theta and beta band was decreased by acute intracerebroventricular application of palmitic acid. Peripherally it amplified insulin action as demonstrated by a significant inhibition of endogenous glucose production and increased glucose infusion rate. Moreover, our results further revealed that the brain effect of peripheral insulin is modulated by palmitic acid load in the brain. CONCLUSION: These findings suggest that insulin action is amplified in the periphery and attenuated in the brain by acute palmitic acid application. Thus, our results indicate that acute palmitic acid signaling in the brain may be different from chronic effects.

PAX6 mutation alters circadian rhythm and ß cell function in mice without affecting glucose tolerance.

The transcription factor PAX6 is involved in the development of the eye and pancreatic islets, besides being associated with sleep-wake cycles. Here, we investigated a point mutation in the RED subdomain of PAX6, previously described in a human patient, to present a comprehensive study of a homozygous Pax6 mutation in the context of adult mammalian metabolism and circadian rhythm. Pax6Leca2 mice lack appropriate retinal structures for light perception and do not display normal daily rhythmic changes in energy metabolism. Despite ß cell dysfunction and decreased insulin secretion, mutant mice have normal glucose tolerance. This is associated with reduced hepatic glucose production possibly due to altered circadian variation in expression of clock and metabolic genes, thereby evading hyperglycemia. Hence, our findings show that while the RED subdomain is important for ß cell functional maturity, the Leca2 mutation impacts peripheral metabolism via loss of circadian rhythm, thus revealing pleiotropic effects of PAX6.

Type 2 diabetes risk gene Dusp8 regulates hypothalamic Jnk signaling and insulin sensitivity.

Recent genome-wide association studies (GWAS) identified DUSP8, encoding a dual-specificity phosphatase targeting mitogen-activated protein kinases, as a type 2 diabetes (T2D) risk gene. Here, we reveal that Dusp8 is a gatekeeper in the hypothalamic control of glucose homeostasis in mice and humans. Male, but not female, Dusp8 loss-of-function mice, either with global or corticotropin-releasing hormone neuron-specific deletion, had impaired systemic glucose tolerance and insulin sensitivity when exposed to high-fat diet (HFD). Mechanistically, we found impaired hypothalamic-pituitary-adrenal axis feedback, blunted sympathetic responsiveness, and chronically elevated corticosterone levels driven by hypothalamic hyperactivation of Jnk signaling. Accordingly, global Jnk1 ablation, AAV-mediated Dusp8 overexpression in the mediobasal hypothalamus, or metyrapone-induced chemical adrenalectomy rescued the impaired glucose homeostasis of obese male Dusp8-KO mice, respectively. The sex-specific role of murine Dusp8 in governing hypothalamic Jnk signaling, insulin sensitivity, and systemic glucose tolerance was consistent with functional MRI data in human volunteers that revealed an association of the DUSP8 rs2334499 risk variant with hypothalamic insulin resistance in men. Further, expression of DUSP8 was increased in the infundibular nucleus of T2D humans. In summary, our findings suggest the GWAS-identified gene Dusp8 as a novel hypothalamic factor that plays a functional role in the etiology of T2D.

Urodynamic and immunohistochemical evaluation of intravesical botulinum toxin A delivery using liposomes.

PURPOSE: Botulinum toxin A (Allergan, Irvine, California) is a high molecular weight neurotoxin used to treat hypersensitive bladder by direct injection to pass the urothelial barrier. We investigated the feasibility of intravesical botulinum toxin A delivery using liposomes (Lipella Pharmaceuticals, Pittsburgh, Pennsylvania), which are phospholipid bilayered vesicles, and evaluated the urodynamic and immunohistochemical effect on acetic acid induced bladder hyperactivity in rats. MATERIALS AND METHODS: Liposomes (1 ml), botulinum toxin A (20 U/1 ml saline) or botulinum toxin A encapsulated in liposomes (lipotoxin, that is 20 U botulinum toxin A plus 1 ml liposomes) was administered in the bladder and retained for 1 hour on day 1 after baseline cystometrogram. Continuous cystometrogram was performed on day 1 by filling the bladder with saline and on day 8 by filling the bladder with saline, followed by 0.3% acetic acid. The bladder was then harvested. Cystometrogram parameters, histology, SNAP25 and calcitonin gene-related peptide expression were measured by Western blotting or immunostaining. RESULTS: The intercontraction interval was decreased 57.2% and 56.0% after intravesical acetic acid instillation in liposome and botulinum toxin A pretreated rats, respectively. However, rats that received lipotoxin showed a significantly decreased intercontraction interval response (21.1% decrease) to acetic acid instillation but without compromised voiding function. Also, lipotoxin pretreated rats had a better decrease in the inflammatory reaction and SNAP-25 expression, and increase in calcitonin gene-related peptide immunoreactivity than those in liposome or botulinum toxin A pretreated rats. CONCLUSIONS: Intravesical lipotoxin administration cleaved SNAP-25, inhibited calcitonin gene-related peptide release from afferent nerve terminals and blocked the acetic acid induced hyperactive bladder. These results support liposomes as an efficient vehicle for delivering botulinum toxin A without injection.

Intraprostatic botulinum toxin a injection inhibits cyclooxygenase-2 expression and suppresses prostatic pain on capsaicin induced prostatitis model in rat.

PURPOSE: Cyclooxygenase-2 is a key enzyme in the conversion of arachidonic acid to prostaglandins, which are important mediators of inflammation and pain. We investigated the effect of intraprostatic botulinum toxin A administration on pain reaction and cyclooxygenase-2 expression in a capsaicin induced prostatitis model in rats. MATERIALS AND METHODS: Adult male Sprague-Dawley rats were injected with vehicle or capsaicin (10 mM, 0.1 cc) into the prostate. The nociceptive effects of capsaicin were evaluated for 30 minutes using a behavior approach. The prostate and L6 spinal cord were then removed for histology and cyclooxygenase-2 expression using Western blotting or immunostaining. A second set of animals was injected with botulinum toxin A (5 to 20 U) into the prostate 1 week before intraprostatic injection of capsaicin. RESULTS: Capsaicin induced increased pain behavior and inflammatory reaction. Botulinum toxin A 1 week before treatment dose dependently decreased inflammatory cell accumulation, cyclooxygenase-2 expression and prostatic pain. Botulinum toxin A (20 U) significantly decreased inflammatory cell accumulation, and cyclooxygenase-2 expression in the prostate, ventral horn and dorsal horn of the L6 spinal cord (93.5%, 89.4%, 90.5% and 77.5%, respectively). It decreased pain behavior for eye and locomotion scores (59.5% and 40.0%, respectively). CONCLUSIONS: Intraprostatic capsaicin injection activates cyclooxygenase-2 expression in the prostate, and spinal sensory and motor neurons, and it induces prostatic pain. Botulinum toxin A pretreatment could inhibit capsaicin induced cyclooxygenase-2 expression from the peripheral organ to the L6 spinal cord and inhibit prostatic pain and inflammation. This finding suggests a potential clinical benefit of botulinum toxin A for the treatment of nonbacterial prostatitis.

Understanding gene functions and disease mechanisms: Phenotyping pipelines in the German Mouse Clinic.

Since decades, model organisms have provided an important approach for understanding the mechanistic basis of human diseases. The German Mouse Clinic (GMC) was the first phenotyping facility that established a collaboration-based platform for phenotype characterization of mouse lines. In order to address individual projects by a tailor-made phenotyping strategy, the GMC advanced in developing a series of pipelines with tests for the analysis of specific disease areas. For a general broad analysis, there is a screening pipeline that covers the key parameters for the most relevant disease areas. For hypothesis-driven phenotypic analyses, there are thirteen additional pipelines with focus on neurological and behavioral disorders, metabolic dysfunction, respiratory system malfunctions, immune-system disorders and imaging techniques. In this article, we give an overview of the pipelines and describe the scientific rationale behind the different test combinations.

Extensive phenotypic characterization of a new transgenic mouse reveals pleiotropic perturbations in physiology due to mesenchymal hGH minigene expression.

The human growth hormone (hGH) minigene used for transgene stabilization in mice has been recently identified to be locally expressed in the tissues where transgenes are active and associated with phenotypic alterations. Here we extend these findings by analyzing the effect of the hGH minigene in TgC6hp55 transgenic mice which express the human TNFR1 under the control of the mesenchymal cell-specific CollagenVI promoter. These mice displayed a fully penetrant phenotype characterized by growth enhancement accompanied by perturbations in metabolic, skeletal, histological and other physiological parameters. Notably, this phenotype was independent of TNF-TNFR1 signaling since the genetic ablation of either Tnf or Tradd did not rescue the phenotype. Further analyses showed that the hGH minigene was expressed in several tissues, also leading to increased hGH protein levels in the serum. Pharmacological blockade of GH signaling prevented the development of the phenotype. Our results indicate that the unplanned expression of the hGH minigene in CollagenVI expressing mesenchymal cells can lead through local and/or systemic mechanisms to enhanced somatic growth followed by a plethora of primary and/or secondary effects such as hyperphagia, hypermetabolism, disturbed glucose homeostasis, altered hematological parameters, increased bone formation and lipid accumulation in metabolically critical tissues.

Epigenetic germline inheritance of diet-induced obesity and insulin resistance.

There is considerable controversy regarding epigenetic inheritance in mammalian gametes. Using in vitro fertilization to ensure exclusive inheritance via the gametes, we show that a parental high-fat diet renders offspring more susceptible to developing obesity and diabetes in a sex- and parent of origin-specific mode. The epigenetic inheritance of acquired metabolic disorders may contribute to the current obesity and diabetes pandemic.

Metformin supports the antidiabetic effect of a sodium glucose cotransporter 2 inhibitor by suppressing endogenous glucose production in diabetic mice.

Combined use of metformin and a sodium glucose cotransporter 2 inhibitor (SGLT2I) is a promising treatment strategy for type 2 diabetes. The mechanism by which combination treatment provides better glycemic control than metformin or SGLT2I monotherapy remains elusive. Therefore, we investigated the physiological mechanism by which both compounds lower blood glucose concentrations in diabetic mice. We compared the potential of metformin and the SGLT2I AVE2268 alone or in combination to mitigate hyperglycemia and modulate glucose fluxes in db/db and diabetic Tallyho/JngJ mice. SGLT2I treatment alone elicited a rapid decline in circulating blood glucose levels, which appeared to induce endogenous glucose production. Supplementation of metformin dampened this counterresponse, and therefore, combination therapy more efficiently maintained glycemic control. Finally, combination treatment blunted postprandial glucose excursions and improved HbA1c levels within 2 weeks. We conclude that coapplication of metformin enhances the glucose-lowering actions of SGLT2I by restraining endogenous glucose production, which may provide long-term improvement of glycemic control in type 2 diabetic patients.

Intravesical botulinum toxin A administration inhibits COX-2 and EP4 expression and suppresses bladder hyperactivity in cyclophosphamide-induced cystitis in rats.

BACKGROUND: Cyclooxygenase 2 (COX-2) elevation and subsequent prostaglandin E(2) (PGE(2)) production play a major role in bladder inflammation and hyperactivity. EP4 receptor, a subtype of PGE(2) receptors, mediates tissue inflammation and hypersensitivity. OBJECTIVE: To investigate the effect of intravesical botulinum toxin A (BoNT-A) on COX-2 and EP4 expression in cyclophosphamide (CYP)-induced cystitis in rats. DESIGN, SETTING, AND PARTICIPANTS: Experimental (N=40) and control animals (N=20) were injected with CYP (75 mg/kg intraperitoneally) or saline on days 1, 4, and 7. BoNT-A (1 ml, 20 unit/ml) or saline were administered into the bladder and retained for 1 h on day 2. INTERVENTION: Waking cystometrograms (CMGs) were performed. Bladder and L6 and S1 spinal cord were harvested on day 8. MEASUREMENTS: CMG parameters, histology, and COX-2 and EP4 expression by immunostaining or western blotting were measured. RESULTS AND LIMITATIONS: CYP induced increased bladder inflammatory reaction, bladder hyperactivity, and COX-2 and EP4 expression in the bladder and spinal cord. The CYP effects were suppressed by BoNT-A treatment. BoNT-A treatment decreased inflammatory reaction (56.5% decrease), COX-2 expression (77.8%, 61.7%, and 54.8% decrease for bladder, L6, and S1 spinal cord, respectively), EP4 expression (56.8%, 26.9%, and 84.2% decrease for bladder, L6, and S1 spinal cord, respectively), and suppressed bladder hyperactivity (intercontraction interval, 107% increase and contraction amplitude, 43% decrease). CONCLUSIONS: CYP injection activated COX2 and EP4 expression in the bladder and spinal cord and induced bladder inflammation and hyperactivity, which effects were suppressed by BoNT-A treatment. These findings suggest a potential benefit of EP4-targeted pharmacotherapy and BoNT-A treatment for bladder inflammatory conditions.

Intraprostatic capsaicin injection as a novel model for nonbacterial prostatitis and effects of botulinum toxin A.

OBJECTIVES: An animal model for nonbacterial prostatitis in rats was developed with the use of intraprostatic injection of capsaicin, an agent thought to excite C-afferent fibers and cause neurogenic inflammation. The analgesic and anti-inflammatory properties of botulinum toxin type A (BoNT-A) was tested in this model. METHODS: Adult male Spraque-Dawley rats were injected with varying doses of capsaicin into the prostate. The nociceptive effects of capsaicin were evaluated for 30min by using a behavior approach; then the prostate was removed for histology and cyclooxygenase (COX) 2 protein concentration measurement. Evans blue (50mg/kg) was also injected intravenously to assess for plasma protein extravasation. A second set of animals were injected with up to 20U of BoNT-A into the prostates 1 wk prior to intraprostatic injection of 1000micromol/l capsaicin. RESULTS: Capsaicin dose dependently induced modifications in pain behavior: closing of the eyes, hypolocomotion, and inflammatory changes: increase of inflammatory cell accumulation, COX2 expression, and plasma extravasation at the acute stage, but completely recovered at 1 wk. BoNT-A pretreatment dose dependently reversed pain behavior and inflammation. BoNT-A 20U significantly decreased inflammatory cell accumulation, COX2 expression, and Evans blue extraction (82.1%, 83.0%, and 50.4%, respectively), and reduced pain behavior (66.7% for eye score and 46.5% for locomotion score). CONCLUSIONS: Intraprostatic capsaicin injection induced neurogenic prostatitis and prostatic pain, and may be a useful research model. BoNT-A produced anti-inflammatory and analgesic effects, and support clinical evaluation in prostatitis.