Anterior cingulate cortex and insomnia: A cingulate-striatum connection

Insomnia is an important comorbidity of chronic pain. In this issue of Neuron, Li et al. report that chronic-pain-induced insomnia is mediated by the pyramidal neurons in the anterior cingulate cortex and their dopaminergic projections to the dorsal medial striatum.

Cortical synaptic basis of consciousness

Consciousness is one of final questions for humans to tackle in neuroscience. Due to a lack of understanding of basic brain networks and mechanisms of functions, our knowledge of consciousness mainly stays at a theoretical level. Recent studies using brain imaging in humans and modern neuroscience techniques in animal studies reveal the basic brain network for consciousness. The projection from the thalamus to different cortical regions forms a network of activities to maintain consciousness in humans and animals. These feedback and feedforward circuits maintain consciousness even in certain brain injury conditions. Pterions and ion channels that contribute to these circuit neural activities are targets for drugs and manipulations that affect consciousness such as anesthetic agents. Synaptic plasticity that trains synapses during learning and information recall modified the circuits and contributes to a high level of consciousness in a certain population.

Fear memory regulation by the cAMP signaling pathway as an index of reexperiencing symptoms in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a psychiatric disorder associated with traumatic memory, yet its etiology remains unclear. Reexperiencing symptoms are specific to PTSD compared to other anxiety-related disorders. Importantly, reexperiencing can be mimicked by retrieval-related events of fear memory in animal models of traumatic memory. Recent studies revealed candidate PTSD-associated genes that were related to the cyclic adenosine monophosphate (cAMP) signaling pathway. Here, we demonstrate the tight linkage between facilitated cAMP signaling and PTSD by analyzing loss- and gain-of-cAMP signaling effects on fear memory in mice and the transcriptomes of fear memory-activated mice and female PTSD patients with reexperiencing symptoms. Pharmacological and optogenetic upregulation or downregulation of cAMP signaling transduction enhanced or impaired, respectively, the retrieval and subsequent maintenance of fear memory in mice. In line with these observations, integrative mouse and human transcriptome analysis revealed the reduced mRNA expression of phosphodiesterase 4B (PDE4B), an enzyme that degrades cAMP, in the peripheral blood of PTSD patients showing more severe reexperiencing symptoms and the mouse hippocampus after fear memory retrieval. Importantly, more severe reexperiencing symptoms and lower PDE4B mRNA levels were correlated with decreased DNA methylation of a locus within PDE4B, suggesting the involvement of methylation in the mechanism of PTSD. These findings raise the possibility that the facilitation of cAMP signaling mediating the downregulation of PDE4B expression enhances traumatic memory, thereby playing a key role in the reexperiencing symptoms of PTSD patients as a functional index of these symptoms.

Selective enhancement of fear extinction by inhibiting neuronal adenylyl cyclase 1 (AC1) in aged mice

Adenylyl cyclase 1 (AC1) is a selective subtype of ACs, which is selectively expressed in neurons. The activation of AC1 is activity-dependent, and AC1 plays an important role in cortical excitation that contributes to chronic pain and related emotional disorders. Previous studies have reported that human-used NB001 (hNB001, a selective AC1 inhibitor) produced analgesic effects in different animal models of chronic pain. However, the potential effects of hNB001 on learning and memory have been less investigated. In the present study, we found that hNB001 affected neither the induction nor the expression of trace fear, but selectively enhanced the relearning ability during the extinction in aged mice. By contrast, the same application of hNB001 did not affect recent, remote auditory fear memory, or remote fear extinction in either adult or aged mice. Furthermore, a single or consecutive 30-day oral administration of hNB001 did not affect acute nociceptive response, motor function, or anxiety-like behavior in either adult or aged mice. Our results are consistent with previous findings that inhibition of AC1 did not affect general sensory, emotional, and motor functions in adult mice, and provide strong evidence that inhibiting the activity of AC1 may be beneficial for certain forms of learning and memory in aged mice.

Long-term plasticity of NMDA GluN2B (NR2B) receptor in anterior cingulate cortical synapses

The anterior cingulate cortex (ACC) is a key cortical area for pain perception, emotional fear and anxiety. Cortical excitation is thought to be the major mechanism for chronic pain and its related emotional disorders such as anxiety and depression. GluN2B (or called NR2B) containing NMDA receptors play critical roles for such excitation. Not only does the activation of GluN2B contributes to the induction of the postsynaptic form of LTP (post-LTP), long-term upregulation of GluN2B subunits through tyrosine phosphorylation were also detected after peripheral injury. In addition, it has been reported that presynaptic NMDA receptors may contribute to the modulation of the release of glutamate from presynaptic terminals in the ACC. It is believed that inhibiting subtypes of NMDA receptors and/or downstream signaling proteins may serve as a novel therapeutic mechanism for future treatment of chronic pain, anxiety, and depression.

Single-cell RNA sequencing uncovers the cell type-dependent transcriptomic changes in the retrosplenial cortex after peripheral nerve injury

The retrosplenial cortex (RSC) is a vital area for storing remote memory and has recently been found to undergo broad changes after peripheral nerve injury. However, little is known about the role of RSC in pain regulation. Here, we examine the involvement of RSC in the pain of mice with nerve injury. Notably, reducing the activities of calcium-/calmodulin-dependent protein kinase type II-positive splenial neurons chemogenetically increases paw withdrawal threshold and extends thermal withdrawal latency in mice with nerve injury. The single-cell or single-nucleus RNA-sequencing results predict enhanced excitatory synaptic transmissions in RSC induced by nerve injury. Local infusion of 1-naphthyl acetyl spermine into RSC to decrease the excitatory synaptic transmissions relieves pain and induces conditioned place preference. Our data indicate that RSC is critical for regulating physiological and neuropathic pain. The cell type-dependent transcriptomic information would help understand the molecular basis of neuropathic pain.

Activation of the glutamatergic cingulate cortical-cortical connection facilitates pain in adult mice

The brain consists of the left and right cerebral hemispheres and both are connected by callosal projections. Less is known about the basic mechanism of this cortical-cortical connection and its functional importance. Here we investigate the cortical-cortical connection between the bilateral anterior cingulate cortex (ACC) by using the classic electrophysiological and optogenetic approach. We find that there is a direct synaptic projection from one side ACC to the contralateral ACC. Glutamate is the major excitatory transmitter for bilateral ACC connection, including projections to pyramidal cells in superficial (II/III) and deep (V/VI) layers of the ACC. Both AMPA and kainate receptors contribute to synaptic transmission. Repetitive stimulation of the projection also evoked postsynaptic Ca2+ influx in contralateral ACC pyramidal neurons. Behaviorally, light activation of the ACC-ACC connection facilitated behavioral withdrawal responses to mechanical stimuli and noxious heat. In an animal model of neuropathic pain, light inhibitory of ACC-ACC connection reduces both primary and secondary hyperalgesia. Our findings provide strong direct evidence for the excitatory or facilitatory contribution of ACC-ACC connection to pain perception, and this mechanism may provide therapeutic targets for future treatment of chronic pain and related emotional disorders.

A PRoliferation-Inducing Ligand (APRIL) in the Pathogenesis of Immunoglobulin A Nephropathy: A Review of the Evidence

A PRoliferation-Inducing Ligand (APRIL), the thirteenth member of the tumor necrosis factor superfamily, plays a key role in the regulation of activated B cells, the survival of long-lived plasma cells, and immunoglobulin (Ig) isotype class switching. Several lines of evidence have implicated APRIL in the pathogenesis of IgA nephropathy (IgAN). Globally, IgAN is the most common primary glomerulonephritis, and it can progress to end-stage kidney disease; yet, disease-modifying treatments for this condition have historically been lacking. The preliminary data in ongoing clinical trials indicate that APRIL inhibition can reduce proteinuria and slow the rate of kidney disease progression by acting at an upstream level in IgAN pathogenesis. In this review, we examine what is known about the physiologic roles of APRIL and evaluate the experimental and epidemiological evidence describing how these normal biologic processes are thought to be subverted in IgAN. The weight of the preclinical, clinical, and genetic data supporting a key role for APRIL in IgAN has galvanized pharmacologic research, and several anti-APRIL drug candidates have now entered clinical development for IgAN. Herein, we present an overview of the clinical results to date. Finally, we explore where more research and evidence are needed to transform potential therapies into clinical benefits for patients with IgAN.

High Dose Hyperfractionated Thoracic Radiotherapy vs. Standard Dose for Limited Stage Small-Cell Lung Cancer: A Multicenter, Open-Label Randomized, Phase 3 Trial

PURPOSE/OBJECTIVE(S)

Limited stage small-cell lung cancer (LS-SCLC) is associated with poor prognosis. We aimed to assess the efficacy and safety of high-dose, hyperfractionated thoracic radiotherapy of 54 Gy in 30 fractions compared with standard dose (45 Gy in 30 fractions) as a first-line treatment for LS-SCLC.

MATERIALS/METHODS

The study was an open-label, randomized, phase 3 trial, done at 16 public hospitals in China. Key inclusion criteria were patients aged 18-70 years, with previously histologically or cytologically confirmed LS-SCLC, previously untreated or received 1-2 courses of intravenous cisplatin (75 mg/m²of body-surface area, on day 1 or divided into two days of each cycle) or carboplatin (area under the curve of 5 mg/mL per min, day 1 of each cycle)and intravenous etoposide (100 mg/m²of body-surface area, on days 1-3 of each cycle), and an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.Eligible patients were randomly assigned (1:1) to receive volumetric-modulated arc radiotherapy (VMAT) of 45 Gy in 30 fractions or the simultaneous integrated boost VMAT (SIB-VMAT) of 54 Gy in 30 fractions to the primary lung tumor and lymph node metastases starting 0-42 days after the first chemotherapy course. Both groups of patients received thoracic radiotherapy twice per day and 10 fractions per week. Prophylactic cranial radiation (PCI, 25 Gy in 10 fractions) was implemented to patients with responsive disease. The primary endpoint was overall survival. Safety was analyzed in the as-treated population.

RESULTS

Between June 30, 2017, and April 6, 2021, 224 eligible patients were enrolled and randomly assigned to 54 Gy (n = 108) or 45 Gy (n = 116). Median follow-up for the primary analysis was 45 months (IQR 41-48). Median overall survival was significantly improved in the 54 Gy group (62.4 months) compared with the 45 Gy group (43.1 months; p = 0.001). Median progression-free survival was significantly improved in the 54 Gy group (30.5 months) compared with the 45 Gy group (16.7 months; p = 0.044). The most common grade 3-4 adverse events were neutropenia (30 [28%] of 108 patients in the 54 Gy group vs 27 [23%] of 116 patients in the 45 Gy group), neutropenic infections (6 [6%] vs 2 [2%]), thrombocytopenia (13 [12%] vs 12 [10%]), anemia (6 [6%] vs 4 [3%]), and esophagitis (1 [1%] vs 3 [3%]). Treatment-related serious adverse events occurred in 9 [8%] patients in the 54 Gy group and 16 [14%] patients in the 45 Gy group. There were one treatment-related deaths in 54 Gy group (myocardial infarction).

CONCLUSION

Compared with standard thoracic radiotherapy dose of 45 Gy, the high dose of 54 Gy improved overall survival and progression-free survival without increasing toxicities in patients with LS-SCLC, supporting twice-daily hyperfractionated thoracic radiotherapy of 54 Gy with concurrent chemotherapy is an alternative treatment option for LS-SCLC. This study is complete and registered with ClinicalTrials.gov, NCT03214003.

Inhibiting neuronal AC1 for treating anxiety and headache in the animal model of migraine

Migraines are a common medical condition. From a basic science point of view, the central mechanism for migraine and headache is largely unknown. In the present study, we demonstrate that cortical excitatory transmission is significantly enhanced in the anterior cingulate cortex (ACC)-a brain region which is critical for pain perception. Biochemical studies found that the phosphorylation levels of both the NMDA receptor GluN2B and AMPA receptor GluA1 were enhanced in ACC of migraine rats. Both the presynaptic release of glutamate and postsynaptic responses of AMPA receptors and NMDA receptors were enhanced. Synaptic long-term potentiation (LTP) was occluded. Furthermore, behavioral anxiety and nociceptive responses were increased, which were reversed by application of AC1 inhibitor NB001 within ACC. Our results provide strong evidence that cortical LTPs contribute to migraine-related pain and anxiety. Drugs that inhibit cortical excitation such as NB001 may serve as potential medicines for treating migraine in the future.

Risk of Acute Kidney Injury Among Older Adults With Heart Failure and With Reduced Ejection Fraction Treated With Angiotensin-Neprilysin Inhibitor vs Renin-Angiotensin System Inhibitor in Routine Clinical Care

BACKGROUND

The acute hemodynamic effects of sacubitril/valsartan, an angiotensin receptor neprilysin inhibitor (ARNI), may result in early changes in kidney function, raising concerns about acute kidney injury (AKI), particularly in those who are naïve to renin-angiotensin system inhibitors (RASis).

METHODS

We conducted a cohort study using U.S. Medicare fee-for-service claims data (2014-2017). Patients with HFrEF ≥ 65 years newly initiating ARNI or RASi, with no prior use of either drug class, were included. The primary outcome was hospitalization due to AKI as the primary discharge diagnosis, and the secondary outcome included AKI as a primary or secondary discharge diagnosis. AKI risks were described under an as-treated follow-up approach, with censoring on treatment discontinuation, switch, insurance disenrollment, death, or administrative censoring as well as an intent-to-treat approach. Propensity-score-based fine-stratification weighting was used to account for potential confounding by 81 pre-exposure characteristics. Cumulative incidence functions were used to report absolute risks, and Cox proportional hazards models were used to provide hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

We included 27,166 patients with a mean (SD) age of 73 (7.3) years, and 4155 (15.3%) were initiating ARNI. After propensity score weighting, the 180-day cumulative incidence was 2.7% (2.4%-3.1%) among RASi initiators and 2.7% (2.2%-3.5%) among ARNI initiators for the primary outcome, and it was 6.5% (6.0%-7.1%) and 6.1% (5.2%-7.1%), respectively, for the secondary outcome under as-treated follow-up. HR (95% CI) comparing ARNI with RASi were 0.91 (95% CI: 0.72-1.16) for the primary outcome and 0.92 (95% CI: 0.79-1.08) for the secondary outcome. Similar results were observed in the intent-to-treat analysis.

CONCLUSIONS

Among a large cohort of U.S. Medicare beneficiaries with HFrEF, ARNI treatment was not associated with higher rates of AKI than RASi treatment. These results provide reassurance for providers considering ARNI initiation in older patients who are RASi-naïve.

Glutamate acts as a key neurotransmitter for itch in the mammalian spinal cord

Itch sensation is one of the major sensory experiences of humans and animals. Recent studies using genetic deletion techniques have proposed that gastrin-releasing peptide (GRP) is a key neurotransmitter for itch in the spinal cord. However, these studies are mainly based on behavioral responses and lack direct electrophysiological evidence that GRP indeed mediates itch information between primary afferent fibers and spinal dorsal horn neurons. In this review, we reviewed recent studies using different experimental approaches and proposed that glutamate but not GRP acts as the key neurotransmitter in the primary afferents in the transmission of itch. GRP is more likely to serve as an itch-related neuromodulator. In the cerebral cortex, we propose that the anterior cingulate cortex (ACC) plays a significant role in both itch and pain sensations. Only behavioral measurement of itch (scratching) is not sufficient for itch measurement, since scratching the itching area also produces pleasure. Integrative experimental approaches as well as better behavioral scoring models are needed to help to understand the neuronal mechanism of itch and aid future treatment for patients with pruritic diseases.

Age-related attenuation of cortical synaptic tagging in the ACC is rescued by BDNF or a TrkB receptor agonist in both sex of mice

Long-term potentiation (LTP) is a key cellular mechanism for learning and memory, and recent studies in the hippocampus found that LTP was impaired in aged animals. Previous studies of cortical LTP have focused primarily on the homosynaptic plasticity in adult mice, while fewer studies have looked at heterosynaptic plasticity-such as synaptic tagging in aged mice. In the present study, we investigated synaptic tagging in adult and middle-aged mice's anterior cingulate cortex (ACC) using the 64-channel multielectrode dish (MED64) recording system. We found that synaptic tagging was impaired in the ACC of middle-aged male mice as compared to adult mice. Both the network late-phase LTP (L-LTP) and the recruitment of inactive responses were reduced in the ACC of middle-aged male mice. Similar results were found in female middle-aged mice, indicating that there is no gender difference. Furthermore, bath application of brain-derived neurotrophic factor (BDNF) or systemic treatment with newly developed TrkB receptor agonists R13, was shown to rescue both synaptic tagging, and L-LTP, in middle-aged mice. To determine the distribution of synaptic LTP within the ACC, a new visualization method was developed to map the Spatio-temporal variation of LTP in the ACC. Our results provide strong evidence that cortical potentiation and synaptic tagging show an age-dependent reduction, and point to the TrkB receptor as a potential drug target for the treatment of memory decline.

Multiple modulatory roles of serotonin in chronic pain and injury-related anxiety

Chronic pain is long-lasting pain that often persists during chronic diseases or after recovery from disease or injury. It often causes serious side effects, such as insomnia, anxiety, or depression which negatively impacts the patient's overall quality of life. Serotonin (5-HT) in the central nervous system (CNS) has been recognized as an important neurotransmitter and neuromodulator which regulates various physiological functions, such as pain sensation, cognition, and emotions-especially anxiety and depression. Its widespread and diverse receptors underlie the functional complexity of 5-HT in the CNS. Recent studies found that both chronic pain and anxiety are associated with synaptic plasticity in the anterior cingulate cortex (ACC), the insular cortex (IC), and the spinal cord. 5-HT exerts multiple modulations of synaptic transmission and plasticity in the ACC and the spinal cord, including activation, inhibition, and biphasic actions. In this review, we will discuss the multiple actions of the 5-HT system in both chronic pain and injury-related anxiety, and the synaptic mechanisms behind them. It is likely that the specific 5-HT receptors would be new promising therapeutic targets for the effective treatment of chronic pain and injury-related anxiety in the future.

Silent synapses in pain-related anterior cingulate cortex

Synaptic plasticity such as Long-term potentiation (LTP) is a key mechanism for learning in central synapses including the cortex. There are two least two major forms of LTPs: presynaptic LTP and postsynaptic LTP. For postsynaptic LTP, the potentiation of AMPA receptor-mediated responses through protein phosphorylation is thought to be a key mechanism. Silent synapses have been reported in the hippocampus, but it is thought to be mainly present in the cortex during early development, and may contribute to maturation of the cortical circuit. However, recent several lines of evidence demonstrate that silent synapses may exist in mature synapses of adult cortex, and they can be recruited by LTP-inducing protocols, as well as chemical-induced LTP. In pain-related cortical regions, silent synapses may not only contribute to cortical excitation after peripheral injury, but also the recruitment of new cortical circuits as well. Thus, it is proposed that silent synapses and modification of functional AMPA receptors and NMDA receptors may play important roles in chronic pain, including phantom pain.

Sound-induced analgesia cannot always be observed in adult mice

Music seems promising as an adjuvant pain treatment in humans, while its mechanism remains to be illustrated. In rodent models of chronic pain, few studies reported the analgesic effect of music. Recently, Zhou et al. stated that the analgesic effects of sound depended on a low (5 dB) signal-to-noise ratio (SNR) relative to ambient noise in mice. However, despite employing multiple behavioral analysis approaches, we were unable to extend these findings to a mice model of chronic pain listening to the 5 dB SNR.

Systematic Optimization of HPO-CPR to Boost (+)-Nootkatone Synthesis in Engineered Saccharomyces cerevisiae

As an important and expensive natural sesquiterpene compound in grapefruit, the interest in (+)-nootkatone is stimulated by its strong grapefruit-like odor and physiological activities, which induce efforts for its microbial production. However, the low catalytic efficiency of the cytochrome P450-P450 reductase (HPO-CPR) system is the main challenge. We developed a high-throughput screening (HTS) method using the principle of the color reaction between carbonyl compounds and 2,4-dinitrophenylhydrazine (DNPH), which could rapidly screen the activity of candidate HPO mutants. After optimizing the pairing of HPO and CPR and through semirational design, the optimal mutant HPO_M18 with catalytic performance 2.54 times that of the initial was obtained. An encouraging (+)-nootkatone titer of 2.39 g/L was achieved through two-stage fed-batch fermentation after metabolic engineering and endoplasmic reticulum engineering, representing the highest titer reported to date. Our findings lay the foundation for the development of an economically viable bioprocess for (+)-nootkatone.

Long-read assembly of major histocompatibility complex and killer cell immunoglobulin-like receptor genome regions in cynomolgus macaque

BACKGROUND

The major histocompatibility complex (MHC) and the killer cell immunoglobulin-like receptors (KIR) are key regulators of immune responses. The cynomolgus macaque, an Old World monkey species, can be applied as an important preclinical model for studying human diseases, including coronavirus disease 2019 (COVID-19). Several MHC-KIR combinations have been associated with either a poor or good prognosis. Therefore, macaques with a well-characterized immunogenetic profile may improve drug evaluation and speed up vaccine development. At present, a complete overview of the MHC and KIR haplotype organizations in cynomolgus macaques is lacking, and characterization by conventional techniques is hampered by the extensive expansion of the macaque MHC-B region that complicates the discrimination between genes and alleles.

METHODS

We assembled complete MHC and KIR genomic regions of cynomolgus macaque using third-generation long-read sequencing approach. We identified functional Mafa-B loci at the transcriptome level using locus-specific amplification in a cohort of 33 Vietnamese cynomolgus macaques.

RESULTS

This is the first physical mapping of complete MHC and KIR gene regions in a Vietnamese cynomolgus macaque. Furthermore, we identified four functional Mafa-B loci (B2, B3, B5, and B6) and showed that alleles of the Mafa-I*01, -B*056, -B*034, and -B*001 functional lineages, respectively, are highly frequent in the Vietnamese cynomolgus macaque population.

CONCLUSION

The insights into the MHC and KIR haplotype organizations and the level of diversity may refine the selection of animals with specific genetic markers for future medical research.

Synaptic Plasticity in the Pain-Related Cingulate and Insular Cortex

Cumulative animal and human studies have consistently demonstrated that two major cortical regions in the brain, namely the anterior cingulate cortex (ACC) and insular cortex (IC), play critical roles in pain perception and chronic pain. Neuronal synapses in these cortical regions of adult animals are highly plastic and can undergo long-term potentiation (LTP), a phenomenon that is also reported in brain areas for learning and memory (such as the hippocampus). Genetic and pharmacological studies show that inhibiting such cortical LTP can help to reduce behavioral sensitization caused by injury as well as injury-induced emotional changes. In this review, we will summarize recent progress related to synaptic mechanisms for different forms of cortical LTP and their possible contribution to behavioral pain and emotional changes.

Association of Sodium-Glucose Cotransporter-2 Inhibitors With Incident Atrial Fibrillation in Older Adults With Type 2 Diabetes

IMPORTANCE

Sodium-glucose cotransporter-2 inhibitors (SGLT-2is) have demonstrated many cardiovascular and kidney function benefits for patients with type 2 diabetes (T2D). However, the results of SGLT-2i use in primary prevention of atrial fibrillation (AF) were inconsistent in clinical trials, and incident AF was not a prespecified end point.

OBJECTIVE

To examine incident AF with initiation of an SGLT-2i compared with initiation of a dipeptidyl peptidase-4 inhibitor (DPP-4i) or a glucagonlike peptide-1 receptor agonist (GLP-1RA) among older adults (aged ≥66 years) with T2D in routine clinical practice.

DESIGN, SETTING, AND PARTICIPANTS

A population-based new-user cohort study included older adults with T2D who had no history of AF and were enrolled in Medicare fee-for-service from April 1, 2013, to December 31, 2018. Data analysis was performed from June 28 to December 1, 2021.

EXPOSURES

To control for potential confounding, new users of SGLT-2i were 1:1 propensity score (PS)-matched to new users of DPP-4is or GLP-1RAs in 2 pairwise comparisons based on 138 baseline covariates.

MAIN OUTCOMES AND MEASURES

The primary outcome was incident AF, defined as an inpatient diagnosis code for AF. Hazard ratios (HRs) and rate differences (RDs) per 1000 person-years, with their 95% CIs, were estimated in the PS-matched groups.

RESULTS

New users of SGLT-2is were 1:1 PS-matched to new users of a DPP-4i (n = 74 868) or GLP-1RA (n = 80 475). Overall, the mean (SD) age of study participants was 72 (5) years, and 165 984 were women (53.4%). The risk of incident AF was lower in the SGLT-2i group than the matched DPP-4i group (HR, 0.82; 95% CI, 0.76 to 0.89; RD, -3.7; 95% CI, -5.2 to -2.2 per 1000 person-years) or the matched GLP-1RA group (HR, 0.90; 95% CI, 0.83 to 0.98; RD, -1.8; 95% CI, -3.2 to -0.3 per 1000 person-years). Results were consistent across several sensitivity and subgroup analyses.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that the initiation of an SGLT-2i was associated with a reduced risk of incident AF compared with a DPP-4i or GLP-1RA. The results may be helpful when weighing the potential risks and benefits of various glucose level-lowering agents in older adults with T2D.

SGLT2 Inhibitors and the Risk of Acute Kidney Injury in Older Adults With Type 2 Diabetes

RATIONALE & OBJECTIVE

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have been found to have many benefits for patients with type 2 diabetes. However, whether SGLT2 inhibitors increase the risk of acute kidney injury (AKI) remains unknown. We examined the association of AKI hospitalization with prior initiation of an SGLT2 inhibitor compared with initiation of a dipeptidyl peptidase 4 (DPP-4) inhibitor or a glucagon-like peptide 1 receptor agonist (GLP-1RA) among older adults with type 2 diabetes in routine practice.

STUDY DESIGN

Population-based cohort study.

SETTING & PARTICIPANTS

Older adults aged at least 66 years with type 2 diabetes enrolled in Medicare fee-for-service and who were new users of SGLT2 inhibitor, DPP-4 inhibitor, or GLP-1RA agents in the interval from March 2013 to December 2017.

EXPOSURES

New use of an SGLT2 inhibitor versus new use of a DPP-4 inhibitor or GLP-1RA.

OUTCOME

The primary outcome was hospitalization for AKI, defined as a discharge diagnosis of AKI in the primary or secondary position.

ANALYTICAL APPROACH

New users of SGLT2 inhibitors were matched at a 1:1 ratio to new users of DPP-4 inhibitors or GLP-1RAs using propensity scores in 2 pairwise comparisons. Cox proportional hazards regression models generated hazard ratios (HRs) with 95% CIs in propensity score-matched groups.

RESULTS

Totals of 68,130 and 71,477 new users of SGLT2 inhibitors were matched to new users of DPP-4 inhibitors or GLP-1RAs, respectively. Overall, the mean age of study participants was 72 years. The risk of AKI was lower in the SGLT2 inhibitor group than in the DPP-4 inhibitor group (HR, 0.71 [95% CI, 0.65-0.76]) or the GLP-1RA group (HR, 0.81 [95% CI, 0.75-0.87]).

LIMITATIONS

Residual confounding and lack of laboratory data.

CONCLUSIONS

Among older adults with type 2 diabetes, initiation of an SGLT2 inhibitor was associated with a reduced risk of AKI compared with initiation of a DPP-4 inhibitor or a GLP-1RA.

Selective Recruitment of Presynaptic and Postsynaptic Forms of mGluR-LTD

In area CA1 of the hippocampus, long-term depression (LTD) can be induced by activating group I metabotropic glutamate receptors (mGluRs), with the selective agonist DHPG. There is evidence that mGluR-LTD can be expressed by either a decrease in the probability of neurotransmitter release [P(r)] or by a change in postsynaptic AMPA receptor number. However, what determines the locus of expression is unknown. We investigated the expression mechanisms of mGluR-LTD using either a low (30 μM) or a high (100 μM) concentration of (RS)-DHPG. We found that 30 μM DHPG generated presynaptic LTD that required the co-activation of NMDA receptors, whereas 100 μM DHPG resulted in postsynaptic LTD that was independent of the activation of NMDA receptors. We found that both forms of LTD occur at the same synapses and that these may constitute the population with the lowest basal P(r). Our results reveal an unexpected complexity to mGluR-mediated synaptic plasticity in the hippocampus.

Risk of hospitalization for heart failure in patients with hyperkalemia treated with sodium zirconium cyclosilicate versus patiromer

BACKGROUND

Sodium zirconium cyclosilicate (SZC) and patiromer were recently approved to treat hyperkalemia. Whether the initiation of SZC is associated with an increased risk of hospitalization for heart failure (HHF) compared to patiromer in routine practice remains unknown.

METHODS AND RESULTS

We conducted a new-user cohort study of non-dialysis adults who initiated SZC or patiromer using Optum's de-identified Clinformatics® Data Mart Database from May 2018 to September 2020. We performed propensity score (PS) matching in a variable ratio to match each SZC initiator with up to three patiromer initiators. The primary outcome was HHF. Cox proportional hazards regression models generated hazard ratios (HRs) with 95% confidence intervals (CIs) in the PS-matched groups. The cohort included 1,126 SZC initiators and 2,839 PS-matched patiromer initiators. The mean age was 72 years old, about 30% had a history of heart failure, and 85% had chronic kidney disease stages 3-5. The SZC group had 88 cases of HHF (incidence rate [IR] 35.8 per 100 person-years [PY]), and the patiromer group had 245 cases of HHF (IR 25.1 per 100 PY). The rate of HHF was numerically higher in the SZC initiators than patiromer initiators (HR 1.22, 95%CI 0.95, 1.56), but did not reach statistical significance. Results were consistent across sensitivity and subgroup analyses.

CONCLUSIONS

Initiation of SZC might be associated with an increased risk of hospitalization for heart failure compared to patiromer in routine practice. Larger comparative studies are needed to evaluate the safety of SZC in routine practice more precisely.

Enhancement of behavioral nociceptive responses but not itching responses by viewing mirror images in adult mice

Can mice recognize themselves in a mirror? The answer is unclear. Previous studies have reported that adult mice - when shown itch-like videos - demonstrated itch empathy. However, this was proven to be unreproducible in other studies. In the present study, we wanted to examine whether adult mice were able to recognize their mirror image. In our testing, we found that mice spent more time in the central area in an open field with mirrors surrounding the chamber than those in a normal open field. In a similar open field test with four mice placed in four directions, mice showed similar behavioral responses to those with mirrors. These results indicate that mice are able to recognize images in the mirror, however, they cannot distinguish their own mirror images from the mirror images of other mice. To repeat the experiments of itch empathy, we compared the itch responses of mice in the mirrored environment, to those without. No significant difference in itching responses was detected. Differently, in the case of chemical pain (formalin injection), animals' nociceptive responses to formalin during Phase II were significantly enhanced in the mirrored open field. A new format of heat map was developed to help the analysis of the trace of mice in the open field. Our results suggest that mice do recognize the presence of mice in the mirror, and their nociceptive - but not itch - responses are enhanced.

Whole-brain mapping of efferent projections of the anterior cingulate cortex in adult male mice

The anterior cingulate cortex (ACC) is a key cortical region that plays an important role in pain perception and emotional functions. Previous studies of the ACC projections have been collected primarily from monkeys, rabbits and rats. Due to technological advances, such as gene manipulation, recent progress has been made in our understanding of the molecular and cellular mechanisms of the ACC-related chronic pain and emotion is mainly obtained from adult mice. Few anatomic studies have examined the whole-brain projections of the ACC in adult mice. In the present study, we examined the continuous axonal outputs of the ACC in the whole brain of adult male mice. We used the virus anterograde tracing technique and an ultrahigh-speed imaging method of Volumetric Imaging with Synchronized on-the-fly-scan and Readout (VISoR). We created a three-dimensional (3D) reconstruction of mouse brains. We found that the ACC projected ipsilaterally primarily to the caudate putamen (CPu), ventral thalamic nucleus, zona incerta (ZI), periaqueductal gray (PAG), superior colliculus (SC), interpolar spinal trigeminal nucleus (Sp5I), and dorsal medullary reticular nucleus (MdD). The ACC also projected to contralateral brain regions, including the ACC, reuniens thalamic nucleus (Re), PAG, Sp5I, and MdD. Our results provide a whole-brain mapping of efferent projections from the ACC in adult male mice, and these findings are critical for future studies of the molecular and synaptic mechanisms of the ACC and its related network in mouse models of brain diseases.

Association of SGLT2 inhibitors with cardiovascular, kidney, and safety outcomes among patients with diabetic kidney disease: a meta-analysis

BACKGROUND

We conducted a systematic review and meta-analysis of the cardiovascular, kidney, and safety outcomes of sodium-glucose cotransporter 2 inhibitors (SGLT2i) among patients with diabetic kidney disease (DKD).

METHODS

We searched electronic databases for major randomized placebo-controlled clinical trials published up to September 30, 2021 and reporting on cardiovascular and kidney outcomes of SGLT2i in patients with DKD. DKD was defined as chronic kidney disease in individuals with type 2 diabetes. Random-effects meta-analysis models were used to estimate pooled hazard ratios (HR) and 95% confidence intervals (CI) for clinical outcomes including major adverse cardiovascular events (MACE: myocardial infarction [MI], stroke, and cardiovascular death), kidney composite outcomes (a combination of worsening kidney function, end-stage kidney disease, or death from renal or cardiovascular causes), hospitalizations for heart failure (HHF), deaths and safety events (mycotic infections, diabetic ketoacidosis [DKA], volume depletion, amputations, fractures, urinary tract infections [UTI], acute kidney injury [AKI], and hyperkalemia).

RESULTS

A total of 26,106 participants with DKD from 8 large-scale trials were included (median age: 65.2 years, 29.7-41.8% women, 53.2-93.2% White, median follow-up: 2.5 years). SGLT2i were associated with reduced risks of MACE (HR 0.83, 95% CI 0.75-0.93), kidney composite outcomes (HR 0.66, 95% CI 0.58-0.75), HHF (HR 0.62, 95% CI 0.55-0.71), cardiovascular death (HR 0.84, 95% CI 0.74-0.96), MI (HR 0.78, 95% CI 0.67-0.92), stroke (HR 0.76, 95% CI 0.59-0.97), and all-cause death (HR 0.86, 95% CI 0.77-0.96), with no significant heterogeneity detected. Similar results were observed among participants with reduced estimated glomerular filtration rate (eGFR: < 60 mL/min/1.73m²). The relative risks (95% CI) for adverse events were 3.89 (1.42-10.62) and 2.50 (1.32-4.72) for mycotic infections in men and women respectively, 3.54 (0.82-15.39) for DKA, and 1.29 (1.13-1.48) for volume depletion.

CONCLUSIONS

Among adults with DKD, SGLT2i were associated with reduced risks of MACE, kidney outcomes, HHF, and death. With a few exceptions of more clear safety signals, we found overall limited data on the associations between SGLT2i and safety outcomes. More research is needed on the safety profile of SGLT2i in this population.

Human safety study of a selective neuronal adenylate cyclase 1 (AC1) inhibitor NB001 which relieves the neuropathic pain and blocks ACC in adult mice

Calcium-dependent, neuronal adenylyl cyclase subtype 1 (AC1) is critical for cortical potentiation and chronic pain. NB001 is a first-in-class drug acting as a selective inhibitor against AC1. The present study delineated the pharmacokinetic (PK) properties of human-used NB001 (hNB001) formulated as immediate-release tablet. This first-in-human study was designed as randomized, double-blind, placebo-controlled trial. hNB001 showed placebo-like safety and good tolerability in healthy volunteers. A linear dose-exposure relationship was demonstrated at doses between 20 mg and 400 mg. The relatively small systemic exposure of hNB001 in human showed low bioavailability of this compound through oral administration, which can be improved through future dosage research. Food intake had minimal impact on the absorption of hNB001 tablet. Animal experiments further confirmed that hNB001 had strong analgesic effect in animal models on neuropathic pain. In brain slice prepared from the anterior cingulate cortex (ACC), bath application of hNB001 blocked the induction of LTP. These results from both rodents and human strongly suggest that hNB001 can be safely used for the future treatment of different types of chronic pain in human patients.

Mapping thalamic-anterior cingulate monosynaptic inputs in adult mice

The anterior cingulate cortex (ACC) is located in the frontal part of the cingulate cortex, and plays important roles in pain perception and emotion. The thalamocortical pathway is the major sensory input to the ACC. Previous studies have show that several different thalamic nuclei receive projection fibers from spinothalamic tract, that in turn send efferents to the ACC by using neural tracers and optical imaging methods. Most of these studies were performed in monkeys, cats, and rats, few studies were reported systematically in adult mice. Adult mice, especially genetically modified mice, have provided molecular and synaptic mechanisms for cortical plasticity and modulation in the ACC. In the present study, we utilized rabies virus-based retrograde tracing system to map thalamic-anterior cingulate monosynaptic inputs in adult mice. We also combined with a new high-throughput VISoR imaging technique to generate a three-dimensional whole-brain reconstruction, especially the thalamus. We found that cortical neurons in the ACC received direct projections from different sub-nuclei in the thalamus, including the anterior, ventral, medial, lateral, midline, and intralaminar thalamic nuclei. These findings provide key anatomic evidences for the connection between the thalamus and ACC.

The GSK-3 Inhibitor CT99021 Enhances the Acquisition of Spatial Learning and the Accuracy of Spatial Memory

Glycogen synthase kinase 3 (GSK-3) is a Ser/Thr protein kinase that regulates many cellular processes, including synaptic plasticity. Previously, we reported that inhibition of GSK-3 prevents the induction of one of the major forms of synaptic plasticity, N-methyl-D-aspartate receptor (NMDAR)-dependent long-term depression (LTD), in hippocampal slices. In the present study, we have investigated the effects of inhibiting GSK-3 on learning and memory in healthy naïve animals. Systemic administration of a highly selective GSK-3 inhibitor, CT99021, reversibly blocked NMDAR-dependent LTD in the CA1 region of the hippocampus in anesthetized adult mice. In behavioral tasks, CT99021 had no effect on locomotor activity, anxiety, hippocampus-dependent contextual fear memory, and hippocampus-dependent reversal learning. However, CT99021 facilitated the rate of learning in the Morris water maze (MWM) and T-maze and enhanced the accuracy of long-term spatial memory in the MWM. These findings suggest that GSK-3 regulates the accuracy of spatial memory acquisition and recall.

Probing the Synergistic Ratio of P450/CPR To Improve (+)-Nootkatone Production in Saccharomyces cerevisiae

(+)-Nootkatone is an expensive sesquiterpene substance found in grapefruit peels and the heartwood of yellow cedar. It can be used as a food additive, perfume, and insect repellent; therefore, its highly efficient production is greatly needed. However, the low catalytic efficiency of the membrane-anchored cytochrome P450/P450 reductase system (HPO/AtCPR) is the main challenge and limits the production of (+)-nootkatone. We developed an effective high-throughput screening system based on cell wall destruction to probe the optimal ratio of HPO/AtCPR, which achieved a twofold elevation in (+)-valencene oxidation in Saccharomyces cerevisiae. An engineered strain PK2RI-AtC/H_m6A was constructed to realize de novo (+)-nootkatone production by a series of metabolic engineering strategies. In biphasic fed-batch fermentation, maximum titers of 3.73 and 1.02 g/L for (+)-valencene and (+)-nootkatone, respectively, were achieved. The dramatically improved performance of the constructed S. cerevisiae provides an excellent approach for economical production of (+)-nootkatone from glucose.

Prescribing Patterns of Sodium-Glucose Cotransporter-2 Inhibitors in Patients with CKD: A Cross-Sectional Registry Analysis

Background

Sodium-glucose cotransporter-2 inhibitors (SGLT-2i) reduce kidney disease progression and mortality in patients with chronic kidney disease (CKD), regardless of diabetes status. However, the prescribing patterns of these novel therapeutics in the CKD population in real-world settings remain largely unknown.

Methods

This cross-sectional study included adults with stages 3-5 CKD included in the Mass General Brigham (MGB) CKD registry in March 2021. We described the adoption of SGLT-2i therapy and evaluated factors associated with SGLT-2i prescription using multivariable logistic regression models in the CKD population, with and without diabetes.

Results

A total of 72,240 patients with CKD met the inclusion criteria, 31,688 (44%) of whom were men and 61,265 (85%) White. A total of 22,653 (31%) patients were in the diabetic cohort, and 49,587 (69%) were in the nondiabetic cohort. SGLT-2i prescription was 6% in the diabetic cohort and 0.3% in the nondiabetic cohort. In multivariable analyses, younger Black men with a history of heart failure, use of cardiovascular medications, and at least one cardiologist visit in the previous year were associated with higher odds of SGLT-2i prescription in both diabetic and nondiabetic cohorts. Among patients with diabetes, advanced CKD stages were associated with lower odds of SGLT-2i prescription, whereas urine dipstick test and at least one subspecialist visit in the previous year were associated with higher odds of SGLT-2i prescription. In the nondiabetic cohort, CKD stage, urine dipstick test, and at least one nephrologist visit in the previous year were not significantly associated with SGLT-2i prescription.

Conclusions

In this registry study, prescription of SGLT-2i was low in the CKD population, particularly among patients without diabetes.

Circulating Plasma Biomarkers in Biopsy-Confirmed Kidney Disease

BACKGROUND AND OBJECTIVES

Biomarkers for noninvasive assessment of histopathology and prognosis are needed in patients with kidney disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using a proteomics assay, we measured a multimarker panel of 225 circulating plasma proteins in a prospective cohort study of 549 individuals with biopsy-confirmed kidney diseases and semiquantitative assessment of histopathology. We tested the associations of each biomarker with histopathologic lesions and the risks of kidney disease progression (defined as ≥40% decline in eGFR or initiation of KRT) and death.

RESULTS

After multivariable adjustment and correction for multiple testing, 46 different proteins were associated with histopathologic lesions. The top-performing markers positively associated with acute tubular injury and interstitial fibrosis/tubular atrophy were kidney injury molecule-1 (KIM-1) and V-set and Ig domain-containing protein 2 (VSIG2), respectively. Thirty proteins were significantly associated with kidney disease progression, and 35 were significantly associated with death. The top-performing markers for kidney disease progression were placental growth factor (hazard ratio per doubling, 5.4; 95% confidence interval, 3.4 to 8.7) and BMP and activin membrane-bound inhibitor (hazard ratio, 3.0; 95% confidence interval, 2.1 to 4.2); the top-performing markers for death were TNF-related apoptosis-inducing ligand receptor-2 (hazard ratio, 2.9; 95% confidence interval, 2.0 to 4.0) and CUB domain-containing protein-1 (hazard ratio, 2.4; 95% confidence interval, 1.8 to 3.3).

CONCLUSION

We identified several plasma protein biomarkers associated with kidney disease histopathology and adverse clinical outcomes in individuals with a diverse set of kidney diseases.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_12_28_CJN09380721.mp3.

Accuracy of identifying diagnosis of moderate to severe chronic kidney disease in administrative claims data

BACKGROUND

Prior validation studies of claims-based definitions of chronic kidney disease (CKD) using ICD-9 codes reported overall low sensitivity, high specificity, and variable but reasonable PPV. No studies to date have evaluated the accuracy of ICD-10 codes to identify a US patient population with CKD.

METHODS

We assessed the accuracy of claims-based algorithms to identify adults with CKD Stages 3-5 compared with laboratory values in a subset (~40%) of a US commercial insurance claims database (Optum's de-identified Clinformatics® Data Mart Database). We calculated the positive predictive value (PPV) of one or two ICD-9 (2012-2014) or ICD-10 (2016-2018) codes for CKD compared with a lab-based estimated glomerular filtration rate (eGFR) occurring within prespecified windows (±90 days, ±180 days, ±365 days) of the ICD-based CKD code(s).

RESULTS

The study population ranged between 104 774 and 161 305 patients (ICD-9 cohorts) and between 285 520 and 373 220 patients (ICD-10 cohorts). The mean age was 74.4 years (ICD-9) and 75.6 years (ICD-10) and the median eGFR was 48 ml/min/1.73 m² . The algorithm of two CKD codes compared with a lab value ±90 days of the first code achieved the highest PPV (PPV 86.36% [ICD-9] and 86.07% [ICD-10]). Overall, ICD-10 based codes had comparable PPVs to ICD-9 based codes and all ICD-10 based algorithms had PPVs >80%. The algorithm of one CKD code compared with laboratory value ±180 days maintained the PPV above 80% but still retained a large number of patients (PPV 80.32% [ICD-9] and 81.56% [ICD-10]).

CONCLUSION

An ICD-10-based definition of CKD identified with sufficient accuracy a patient population with CKD Stages 3-5. Our findings suggest that claims databases could be used for future real-world research studies in patients with CKD Stages 3-5.

Cortical mechanisms in migraine

Migraine is the second most prevalent disorder in the world; yet, its underlying mechanisms are still poorly understood. Cumulative studies have revealed pivotal roles of cerebral cortex in the initiation, propagation, and termination of migraine attacks as well as the interictal phase. Investigation of basic mechanisms of the cortex in migraine not only brings insight into the underlying pathophysiology but also provides the basis for designing novel treatments. We aim to summarize the current research literatures and give a brief overview of the cortex and its role in migraine, including the basic structure and function; structural, functional, and biochemical neuroimaging; migraine-related genes; and theories related to cortex in migraine pathophysiology. We propose that long-term plasticity of synaptic transmission in the cortex encodes migraine.

Medication Burden and Prescribing Patterns in Patients on Hemodialysis in the USA, 2013-2017

INTRODUCTION

The medication burden of patients with end-stage renal disease (ESRD) on hemodialysis, a patient population with a high comorbidity burden and complex care requirements, is among the highest of any of the chronic diseases. The goal of this study was to describe the medication burden and prescribing patterns in a contemporary cohort of patients with ESRD on hemodialysis in the USA.

METHODS

We used the United States Renal Data System database from January 1, 2013, and December 31, 2017, to quantify the medication burden of patients with ESRD on hemodialysis aged ≥18 years. We calculated the average number of prescription medications per patient during each respective year (January-December), number of medications within classes, including potentially harmful medications, and trends in the number of medications and classes over the 5-year study period.

RESULTS

We included a total of 163,228 to 176,133 patients from 2013 to 2017. The overall medication burden decreased slightly, from a mean of 7.4 (SD 3.8) medications in 2013 to 6.8 (SD 3.6) medications in 2017. Prescribing of potentially harmful medications decreased over time (74.0% with at least one harmful medication class in 2013-68.5% in 2017). In particular, the prescribing of non-benzodiazepine hypnotics, benzodiazepines, and opioids decreased from 2013 to 2017 (12.2%-6.3%, 23.4%-19.3%, and 60.0%-53.4%, respectively). This trend was consistent across subgroups of age, sex, race, and low-income subsidy status.

CONCLUSIONS

Patients with ESRD on hemodialysis continued to have a high overall medication burden, with a slight reduction over time accompanied by a decrease in prescribing of several classes of harmful medications. Continued emphasis on assessment of appropriateness of high medication burden in patients with ESRD is needed to avoid exposure to potentially harmful or futile medications in this patient population.

Selective inhibition of adenylyl cyclase subtype 1 reduces inflammatory pain in chicken of gouty arthritis

Lack of uricase leads to the high incidence of gout in humans and poultry, which is different from rodents. Therefore, chicken is considered to be one of the ideal animal models for the study of gout. Gout-related pain caused by the accumulation of urate in joints is one type of inflammatory pain, which causes damage to joint function. Our previous studies have demonstrated the crucial role of calcium-stimulated adenylyl cyclase subtype 1 (AC1) in inflammatory pain in rodents; however, there is no study in poultry. In the present study, we injected mono-sodium urate (MSU) into the left ankle joint of the chicken to establish a gouty arthritis model, and tested the effect of AC1 inhibitor NB001 on gouty arthritis in chickens. We found that MSU successfully induced spontaneous pain behaviors including sitting, standing on one leg, and limping after 1–3 h of injection into the left ankle of chickens. In addition, edema and mechanical pain hypersensitivity also occurred in the left ankle of chickens with gouty arthritis. After peroral administration of NB001 on chickens with gouty arthritis, both the spontaneous pain behaviors and the mechanical pain hypersensitivity were effectively relieved. The MSU-induced edema in the left ankle of chickens was not affected by NB001, suggesting a central effect of NB001. Our results provide a strong evidence that AC1 is involved in the regulation of inflammatory pain in poultry. A selective AC1 inhibitor NB001 produces an analgesic effect (not anti-inflammatory effect) on gouty pain and may be used for future treatment of gouty pain in both humans and poultry.

Synaptic potentiation of anterior cingulate cortex contributes to chronic pain of Parkinson's disease

Parkinson’s disease (PD) is a multi-system neurodegenerative disorder. Patients with PD often suffer chronic pain. In the present study, we investigated motor, sensory and emotional changes in three different PD mice models. We found that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treatment caused significant changes in all measurements. Mechanical hypersensitivity of PD model induced by MPTP peaked at 3 days and persisted for at least 14 days. Using Fos transgenic mice, we found that neurons in the anterior cingulate cortex (ACC) were activated after MPTP treatment. Inhibiting ACC by bilateral microinjection of muscimol significantly reduced mechanical hypersensitivity and anxiety-like responses. By contrast, MPTP induced motor deficit was not affected, indicating ACC activity is mostly responsible for sensory and emotional changes. We also investigated excitatory synaptic transmission and plasticity using brain slices of MPTP treated animals. While L-LTP was blocked or significantly reduced. E-LTP was not significantly affected in slices of MPTP treated animals. LTD induced by repetitive stimulation was not affected. Furthermore, we found that paired-pulse facilitation and spontaneous release of glutamate were also altered in MPTP treated animals, suggesting presynaptic enhancement of excitatory transmission in PD. Our results suggest that ACC synaptic transmission is enhanced in the animal model of PD, and cortical excitation may play important roles in PD related pain and anxiety.

The association of SBP with mortality in patients with stage 1-4 chronic kidney disease

OBJECTIVES

Hypertension is a risk factor for chronic kidney disease (CKD) progression and mortality. However, the optimal blood pressure associated with decreased mortality in each stage of CKD remains uncertain.

METHODS

In this retrospective cohort study, we included 13 414 individuals with CKD stages 1-4 from NHANES general population datasets from 1999 to 2004 followed to 31 December 2010. Multivariate analysis and Kaplan--Meier curves were used to assess SBP and risk factors associated with overall mortality in each CKD stage.

RESULTS

In these individuals with death rates of 9, 12, 30 and 54% in baseline CKD stages 1 through 4, respectively, SBP less than 100 mmHg was associated with significantly increased mortality adjusted for age, sex and race in stages 2,3,4. After excluding less than 100 mmHg, as a continuous variable, higher SBP is associated with fully adjusted increased mortality risk in those on or not on antihypertensive medication (hazard ratio 1.006, P = 0.0006 and hazard ratio 1.006 per mmHg, P < 0.0001, respectively). In those on antihypertensive medication, SBP less than 100 mmHg or in each 20 mmHg categorical group more than 120 mmHg is associated with an adjusted risk of increased mortality. Increasing age, men, smoking, diabetes and comorbidities are associated with increased mortality risk.

CONCLUSION

For patients with CKD stages 1-4, the divergence of SBP above or below 100-120 mmHg was found to be associated with higher all-cause mortality, especially in those patients on antihypertensive medication. These findings support the recent guideline of an optimal target goal SBP of 100-120 mmHg in patients with CKD stages 1-4.

Association of Sodium-Glucose Cotransporter-2 Inhibitors With Fracture Risk in Older Adults With Type 2 Diabetes

IMPORTANCE

Whether sodium-glucose cotransporter-2 inhibitors (SGLT-2i) are associated with an increased risk of fractures in older adults with type 2 diabetes (T2D) outside of clinical trials remains unknown.

OBJECTIVE

To examine the association of incident fracture among older adults with T2D with initiating an SGLT-2i compared with initiating a dipeptidyl peptidase 4 inhibitor (DPP-4i) or a glucagon-like peptide 1 receptor agonist (GLP-1RA).

DESIGN, SETTING, AND PARTICIPANTS

This is a population-based, new-user cohort study including older adults (aged ≥65 years) with T2D enrolled in Medicare fee-for-service from April 2013 to December 2017. Data analysis was performed from October 2020 to April 2021.

EXPOSURES

New users of an SGLT-2i, DPP-4i, or GLP-1RA without a previous fracture were matched in a 1:1:1 ratio using 3-way propensity score matching.

MAIN OUTCOMES AND MEASURES

The primary outcome was a composite end point of nontraumatic pelvic fracture, hip fracture requiring surgery, or humerus, radius, or ulna fracture requiring intervention within 30 days. After 3-way 1:1:1 propensity score matching, multivariable Cox proportional hazards regression models were used to generate hazard ratios (HRs) for SGLT-2i compared with DPP-4i and GLP-1RA and Kaplan-Meier curves to visualize fracture risk over time across groups.

RESULTS

Of 466 933 new initiators of study drugs, 62 454 patients were new SGLT-2i users. After 3-way matching, 45 889 (73%) new SGLT-2i users were matched to new users of DPP-4i and GLP-1RA, yielding a cohort of 137 667 patients (mean [SD] age, 72 [5] years; 64 126 men [47%]) matched 1:1:1 for analyses. There was no difference in the risk of fracture in SGLT-2i users compared with DPP-4i users (HR, 0.90; 95% CI, 0.73-1.11) or GLP-1RA users (HR, 1.00; 95% CI, 0.80-1.25). Results were consistent across categories of sex, frailty (nonfrail, prefrail, and frail), age (<75 and ≥75 years), and insulin use (baseline users and nonusers).

CONCLUSIONS AND RELEVANCE

In this nationwide Medicare cohort, initiating an SGLT-2i was not associated with an increased risk of fracture in older adults with T2D compared with initiating a DPP-4i or GLP-1RA, with consistent results across categories of frailty, age, and insulin use. These findings add to the evidence base evaluating the potential risks associated with SGLT-2i use for older adults outside of randomized clinical trials.

Brain-derived neurotrophic factor produced long-term synaptic enhancement in the anterior cingulate cortex of adult mice

Previous studies have demonstrated that brain-derived neurotrophic factor (BDNF) is one of the diffusible messengers for enhancing synaptic transmission in the hippocampus. Less information is available about the possible roles of BDNF in the anterior cingulate cortex (ACC). In the present study, we used 64-electrode array field recording system to investigate the effect of BDNF on ACC excitatory transmission. We found that BDNF enhanced synaptic responses in a dose-dependent manner in the ACC in C57/BL6 mice. The enhancement was long-lasting, and persisted for at least 3 h. In addition to the enhancement, BDNF also recruited inactive synaptic responses in the ACC. Bath application of the tropomyosin receptor kinase B (TrkB) receptor antagonist K252a blocked BDNF-induced enhancement. L-type voltage-gated calcium channels (L-VGCC), metabotropic glutamate receptors (mGluRs), but not NMDA receptors were required for BDNF-produced enhancement. Moreover, calcium-stimulated adenylyl cyclase subtype 1 (AC1) but not AC8 was essential for the enhancement. A selective AC1 inhibitor NB001 completely blocked the enhancement. Furthermore, BDNF-produced enhancement occluded theta burst stimulation (TBS) induced long-term potentiation (LTP), suggesting that they may share similar signaling mechanisms. Finally, the expression of BDNF-induced enhancement depends on postsynaptic incorporation of calcium-permeable AMPA receptors (CP-AMPARs) and protein kinase Mζ (PKMζ). Our results demonstrate that cortical BDNF may contribute to synaptic potentiation in the ACC.

FMRP acts as a key messenger for visceral pain modulation

Visceral pain is a common clinical symptom, which is caused by mechanical stretch, spasm, ischemia and inflammation. Fragile X syndrome (FXS) with lack of fragile X mental retardation protein (FMRP) protein is an inherited disorder that is characterized by moderate or severe intellectual and developmental disabilities. Previous studies reported that FXS patients have self-injurious behavior, which may be associated with deficits in nociceptive sensitization. However, the role of FMRP in visceral pain is still unclear. In this study, the FMR1 knock out (KO) mice and SH-SY5Y cell line were employed to demonstrate the role of FMRP in the regulation of visceral pain. The data showed that FMR1 KO mice were insensitive to zymosan treatment. Recording in the anterior cingulate cortex (ACC), a structure involved in pain process, showed less presynaptic glutamate release and postsynaptic responses in the FMR1 KO mice as compared to the wild type (WT) mice after zymosan injection. Zymosan treatment caused enhancements of adenylyl cyclase 1 (AC1), a pain-related enzyme, and NMDA GluN2B receptor in the ACC. However, these up-regulations were attenuated in the ACC of FMR1 KO mice. Last, we found that zymosan treatment led to increase of FMRP levels in the ACC. These results were further confirmed in SH-SY5Y cells in vitro. Our findings demonstrate that FMRP is required for NMDA GluN2B and AC1 upregulation, and GluN2B/AC1/FMRP forms a positive feedback loop to modulate visceral pain.

NMDA receptors and synaptic plasticity in the anterior cingulate cortex

The anterior cingulate cortex (ACC) plays an important role in pain modulation, and pain-related emotional disorders. In the ACC, two major forms of long-term potentiation (LTP) coexist in excitatory synapses and lay the basis of chronic pain and pain-related emotional disorders. The induction of postsynaptic LTP is dependent on the activation of postsynaptic NMDA receptors (NMDARs), while the presynaptic LTP is NMDAR-independent. Long-term depression (LTD) can also be divided into two types according to the degree of sensitivity to the inhibition of NMDARs. NMDAR heteromers containing GluN2A and GluN2B act as key molecules in both the NMDAR-dependent postsynaptic LTP and LTD. Additionally, NMDARs also exist in presynaptic terminals and modulate the evoked and spontaneous transmitter release. From a translational point of view, inhibiting subtypes of NMDARs and/or downstream signaling proteins may provide potential drug targets for chronic pain and its related emotional disorders.

21st century excitatory amino acid research: A Q & A with Jeff Watkins and Dick Evans

In 1981 Jeff Watkins and Dick Evans wrote what was to become a seminal review on excitatory amino acids (EAAs) and their receptors (Watkins and Evans, 1981). Bringing together various lines of evidence dating back over several decades on: the distribution in the nervous system of putative amino acid neurotransmitters; enzymes involved in their production and metabolism; the uptake and release of amino acids; binding of EAAs to membranes; the pharmacological action of endogenous excitatory amino acids and their synthetic analogues, and notably the actions of antagonists for the excitations caused by both nerve stimulation and exogenous agonists, often using pharmacological tools developed by Jeff and his colleagues, they provided a compelling account for EAAs, especially l-glutamate, as a bona fide neurotransmitter in the nervous system. The rest, as they say, is history, but far from being consigned to history, EAA research is in rude health well into the 21st Century as this series of Special Issues of Neuropharmacology exemplifies. With EAAs and their receptors flourishing across a wide range of disciplines and clinical conditions, we enter into a dialogue with two of the most prominent and influential figures in the early days of EAA research: Jeff Watkins and Dick Evans.

Prescribing Trends of Antidiabetes Medications in Patients With Type 2 Diabetes and Diabetic Kidney Disease, a Cohort Study

OBJECTIVE

To assess changes in antidiabetes medication class prescriptions over time among patients with diabetic kidney disease (DKD), characteristics of patients prescribed these medications, and prescribers' specialty.

RESEARCH DESIGN AND METHODS

We conducted a cohort study design using insurance claims data between 2013 and the first quarter of 2020 (2020Q1). Included are adult patients with DKD who initiated a new antidiabetes medication between 2013 and 2020Q1 (N = 160,489 patients). The primary outcome is the yearly and quarterly percent of medication initiation for each antidiabetes medication class over all antidiabetes medication initiations.

RESULTS

For patients with DKD, sodium-glucose cotransporter 2 inhibitor (SGLT2i) and glucago-like peptide 1 receptor agonist (GLP-1RA) initiations steadily increased between 2013 and 2020Q1. Internists and endocrinologists were the most frequent prescriber specialties. Patients <65 years of age had a larger percentage of all initiations that were SGLT2i or GLP-1RA, 16% and 23%, respectively, in 2019, and patients >75 years of age had a smaller percentage of all initiations that were SGLT2i or GLP-1RA, 11% and 13%, in 2019.

CONCLUSIONS

For patients with DKD, SGLT2i and GLP-1RA prescriptions have increased over time, likely reflecting evolving prescribing patterns in response to the results of recent clinical trials and new clinical guidelines.

Oxytocin in the anterior cingulate cortex attenuates neuropathic pain and emotional anxiety by inhibiting presynaptic long-term potentiation

Oxytocin is a well-known neurohypophysial hormone that plays an important role in behavioral anxiety and nociception. Two major forms of long-term potentiation, presynaptic LTP (pre-LTP) and postsynaptic LTP (post-LTP), have been characterized in the anterior cingulate cortex (ACC). Both pre-LTP and post-LTP contribute to chronic-pain-related anxiety and behavioral sensitization. The roles of oxytocin in the ACC have not been studied. Here, we find that microinjections of oxytocin into the ACC attenuate nociceptive responses and anxiety-like behavioral responses in animals with neuropathic pain. Application of oxytocin selectively blocks the maintenance of pre-LTP but not post-LTP. In addition, oxytocin enhances inhibitory transmission and excites ACC interneurons. Similar results are obtained by using selective optical stimulation of oxytocin-containing projecting terminals in the ACC in animals with neuropathic pain. Our results demonstrate that oxytocin acts on central synapses and reduces chronic-pain-induced anxiety by reducing pre-LTP.