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Neurons of the hindbrain's dorsal motor nucleus of the vagus (DMV) in the hindbrain control key physiological functions related to diabetes, including pancreatic hormone secretion and food passage through the GI tract. Different subtypes of DMV neurons, or "functional units," are thought to mediate distinct physiological roles. However, a lack of definition and access to these subtypes has greatly limited what is known about them. Thus, there is much to learn about the nature of the DMV neurons controlling insulin release and gastric motility, how they function, and how they can be targeted to treat diabetes. To gain traction on this issue, we began by classifying DMV neuron subtypes based on their gene expression, using high-throughput single-nuclei RNA-seq in a mouse model. Our analysis revealed seven, molecularly-distinct subtypes of DMV neurons, two of which were respectively marked by their expression of the genes Calb2 and Grp. Fluorescence in situ hybridization revealed that Calb2 DMV neurons and Grp DMV neurons occupy different subregions of the DMV, suggesting they may innervate different parts of the digestive system. To investigate this, we stained the axons of Calb2 DMV neurons and Grp DMV neurons and imaged them in optically cleared stomach and pancreas from mouse. These studies revealed that Calb2 DMV neurons innervate pancreas but not stomach, whereas Grp DMV neurons innervate neither organ. To then determine whether Calb2 DMV neurons control pancreas endocrine function, we used intersectional optogenetics to stimulate Calb2 DMV neurons while assessing blood glucose levels in vivo. Preliminary data indicate that activating Calb2 DMV neurons causes a rapid and substantial decrease in blood glucose levels. Together our results not only identify Calb2 DMV neurons as pancreas afferents that can lower blood glucose, but reveal a "labeled line" logic to the organization of vagal motor neurons, in which genetically-distinct neuron subtypes innervate different digestive organs to control their function. Disclosure: N. J. Conley: None. C. Li: None. J. Campbell: None. Funding: American Diabetes Association/Pathway to Stop Diabetes (1-18-INI-14 to J.C.) [ABSTRACT FROM AUTHOR]

Background: Currently, the capacity to provide buprenorphine treatment (BT) is not sufficient to treat the growing number of people in the United States with opioid use disorder (OUD). We sought to examine participant retention in care rates of primary care delivered BT programs and to describe factors associated with retention/attrition for participants receiving BT in this setting. Objectives: A PRISMA-guided search of various databases was performed to identify the articles focusing on efficacy of BT treatment and OUD. Method: A systematic literature search identified 15 studies examining retention in care in the primary care setting between 2002 and 2020. Random effects meta-regression were used to identify retention rates across studies. Results: Retention rates decreased across time with a mean 0.52 rate at one year. Several factors were found to be related to retention, including: race, use of other drugs, receipt of counseling, and previous treatment with buprenorphine. Conclusions: While we only investigate BT through primary care, our findings indicate retention rates are equivalent to the rates reported in the specialty care literature. More work is needed to examine factors that may impact primary care delivered BT specifically and differentiate participants that may benefit from care delivered in specialty over primary care as well as the converse. [ABSTRACT FROM AUTHOR]

The article describes the use of a photoactivatable push-pull fluorophore for single- molecule imaging in live cells. According to the authors, the dicyanomethylenedihydrofuran (DCDHF) class of single-molecule cellular labels is used in which an amine donor is connected to a DCDHF acceptor via a conjugated π-bonded network. They add that photoactivation of an azide-based DCDHF fluorogen would be useful for super-resolution imaging schemes that require active control of single molecules.

In order to operate in a coordinated fashion, multisubunit enzymes use cooperative interactions intrinsic to their enzymatic cycle, but this process remains poorly understood. Accordingly, ATP number distributions in various hydrolyzed states have been obtained for single copies of the mammalian double-ring multisubunit chaperonin TRiC/CCT in free solution using the emission from chaperonin-bound fluorescent nucleotides and closed-loop feedback trapping provided by an Anti-Brownian ELectrokinetic trap. Observations of the 16-subunit complexes as ADP molecules are dissociating shows a peak in the bound ADP number distribution at 8 ADP, whose height falls over time with little shift in the position of the peak, indicating a highly cooperative ADP release process which would be difficult to observe by ensemble-averaged methods. When AlFx is added to produce ATP hydrolysis transition state mimics (ADP·AlFx) locked to the complex, the peak at 8 nucleotides dominates for all but the lowest incubation concentrations. Although ensemble averages of the single-molecule data show agreement with standard cooperativity models, surprisingly, the observed number distributions depart from standard models, illustrating the value of these single-molecule observations in constraining the mechanism of cooperativity. While a complete alternative microscopic model cannot be defined at present, the addition of subunit-occupancy-dependent cooperativity in hydrolysis yields distributions consistent with the data. [ABSTRACT FROM AUTHOR]

Neuromodulatory communication among various neurons and non-neuronal cells mediates myriad physiological and pathologic processes, yet defining regulatory and functional features of neuromodulatory transmission remains challenging because of limitations of available monitoring tools. Recently developed genetically encoded neuromodulatory transmitter sensors, when combined with superresolution and/or deconvolution microscopy, allow the first visualization of neuromodulatory transmission with nanoscale or microscale spatiotemporal resolution. In vitro and in vivo experiments have validated several high-performing sensors to have the qualities necessary for demarcating fundamental synaptic properties of neuromodulatory transmission, and initial analysis has unveiled unexpected fine control and precision of neuromodulation. These new findings underscore the importance of synaptic dynamics in synapse-, subcellular-, and circuit-specific neuromodulation, as well as the prospect of genetically encoded transmitter sensors in expanding our knowledge of various behaviors and diseases, including Alzheimer’s disease, sleeping disorders, tumorigenesis, and many others. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Genome-wide association studies have identified a single nucleotide polymorphism (SNP), rs560887, located in a G6PC2 intron that is highly correlated with variations in fasting plasma glucose (FPG). G6PC2 encodes an islet-specific glucose-6-phosphatase catalytic subunit. This study examines the contribution of two G6PC2 promoter SNPs, rs13431652 and rs573225, to the association signal. RESEARCH DESIGN AND METHODS--We genotyped 9,532 normal FPG participants (FPG <6.1 mmol/l) for three G6PC2 SNPs, rs13431652 (distal promoter), rs573225 (proximal promoter), rs560887 (3rd intron). We used regression analyses adjusted for age, sex, and BMI to assess the association with FPG and haplotype analyses to assess comparative SNP contributions. Fusion gene and gel retardation analyses characterized the effect of rs13431652 and rs573225 on G6PC2 promoter activity and transcription factor binding. RESULTS--Genetic analyses provide evidence for a strong contribution of the promoter SNPs to FPG variability at the G6PC2 locus (rs13431652: β = 0.075, P = 3.6 x 10[sup -35]; rs573225 β = 0.073 P = 3.6 x 10[sup -34]), in addition to rs560887 (β = 0.071, P = 1.2 x 10[sup -31]). The rs13431652-A and rs573225-A alleles promote increased NF-Y and Foxa2 binding, respectively. The rs13431652-A allele is associated with increased FPG and elevated promoter activity, consistent with the function of G6PC2 in pancreatic islets. In contrast, the rs573225-A allele is associated with elevated FPG but reduced promoter activity. CONCLUSIONS--Genetic and in situ functional data support a potential role for rs13431652, but not rs573225, as a causative SNP linking G6PC2 to variations in FPG, though a causative role for rs573225 in vivo cannot be ruled out. Diabetes 59:2662-2671, 2010 [ABSTRACT FROM AUTHOR]

SIM1-expressing paraventricular hypothalamus (PVH) neurons are key regulators of energy balance. Within the PVHSIM1 population, melanocortin-4 receptor-expressing (PVHMC4R) neurons are known to regulate satiety and bodyweight, yet they account for only half of PVHSIM1 neuron-mediated regulation. Here we report that PVH prodynorphin-expressing (PVHPDYN) neurons, which notably lack MC4Rs, function independently and additively with PVHMC4R neurons to account for the totality of PVHSIM1 neuron-mediated satiety. Moreover, PVHPDYN neurons are necessary for prevention of obesity in an independent but equipotent manner to PVHMC4R neurons. While PVHPDYN and PVHMC4R neurons both project to the parabrachial complex (PB), they synaptically engage distinct efferent nodes, the pre-locus coeruleus (pLC), and central lateral parabrachial nucleus (cLPBN), respectively. PB-projecting PVHPDYN neurons, like PVHMC4R neurons, receive input from interoceptive ARCAgRP neurons, respond to caloric state, and are sufficient and necessary to control food intake. This expands the CNS satiety circuitry to include two non-overlapping PVH to hindbrain circuits. • PVH neurons cause satiety, of which ∼50% is accounted for by PVHMC4R neurons • PVHPDYN neurons are identified as novel satiety neurons that prevent obesity • PVHPDYN and PVHMC4R neurons are distinct and equipotent, producing additive effects • PVHPDYN and PVHMC4R neurons use separate efferent circuits to regulate appetite Li et al. discover that PVHPDYN neurons, additively with PVHMC4R neurons, are responsible for PVH-mediated satiety. Both PVH neurons are distinct, are equipotent, and use parallel projections to different aspects of the parabrachial complex to cause satiety and prevent obesity. [ABSTRACT FROM AUTHOR]