Loss of Free Fatty Acid Receptor 2 leads to impaired islet mass and beta cell survival

The regulation of pancreatic β cell mass is a critical factor to help maintain normoglycemia during insulin resistance. Nutrient-sensing G protein-coupled receptors (GPCR) contribute to aspects of β cell function, including regulation of β cell mass. Nutrients such as free fatty acids (FFAs) contribute to precise regulation of β cell mass by signaling through cognate GPCRs, and considerable evidence suggests that circulating FFAs promote β cell expansion by direct and indirect mechanisms. Free Fatty Acid Receptor 2 (FFA2) is a β cell-expressed GPCR that is activated by short chain fatty acids, particularly acetate. Recent studies of FFA2 suggest that it may act as a regulator of β cell function. Here, we set out to explore what role FFA2 may play in regulation of β cell mass. Interestingly, Ffar2(-/-) mice exhibit diminished β cell mass at birth and throughout adulthood, and increased β cell death at adolescent time points, suggesting a role for FFA2 in establishment and maintenance of β cell mass. Additionally, activation of FFA2 with Gαq/11-biased agonists substantially increased β cell proliferation in in vitro and ex vivo proliferation assays. Collectively, these data suggest that FFA2 may be a novel therapeutic target to stimulate β cell growth and proliferation

ADRA1A-Gα_q signalling potentiates adipocyte thermogenesis through CKB and TNAP

Noradrenaline (NA) regulates cold-stimulated adipocyte thermogenesis(1). Aside from cAMP signalling downstream of β-adrenergic receptor activation, how NA promotes thermogenic output is still not fully understood. Here, we show that coordinated α(1)-adrenergic receptor (AR) and β(3)-AR signalling induces the expression of thermogenic genes of the futile creatine cycle(2,3), and that early B cell factors, oestrogen-related receptors and PGC1α are required for this response in vivo. NA triggers physical and functional coupling between the α(1)-AR subtype (ADRA1A) and Gα(q) to promote adipocyte thermogenesis in a manner that is dependent on the effector proteins of the futile creatine cycle, creatine kinase B and tissue-non-specific alkaline phosphatase. Combined Gα(q) and Gα(s) signalling selectively in adipocytes promotes a continual rise in whole-body energy expenditure, and creatine kinase B is required for this effect. Thus, the ADRA1A–Gα(q)–futile creatine cycle axis is a key regulator of facultative and adaptive thermogenesis

Transcriptional Control and Development of Energy Burning Adipocytes

Obesity is a major driver of medical morbidity worldwide by promoting the pathogenesis of diabetes mellitus, cardiovascular disease and nonalcoholic fatty liver disease. Obesity is fundamentally a disorder of energy balance with energy intake chronically exceeding energy expenditure. There exists an urgent need to understand pathways in vivo that can be coopted to increase energy expenditure in a specific manner. One organ in small mammals and humans that expends large amounts of energy is thermogenic adipose tissue. Genetic models in rodents and environmental perturbations in humans have identified an important role for this tissue in controlling insulin sensitivity and energy expenditure. Thermogenic adipocytes develop during stereotyped periods during embryogenesis are their activity is controlled postnatally by environmental factors such as cold exposure. This thesis work is comprised of two studies that sought to determine how transcription factors that control thermogenic adipocyte development to facilitate environmental responsiveness and what specific cells develop into thermogenic adipocytes in vivo. In the first study we used in vivo genetic loss of function studies, metabolic phenotyping, and transcription factor reporter assays to identify that activity of Early B Cell Factors are required for the basal and cold-stimulated thermogenic program in brown adipose tissue by controlling the activity and expression of cold-induced transcription factors. This study linked regulators that had traditionally been studied in the development of thermogenic adipocytes to the factors that control the cold-induced thermogenic program. In the second study, we determined the developmental and maintenance structure of perivascular adipose tissue, a thermogenic adipose depot present in small mammals and humans. We discovered that this lineage initially develops from a fibroblastic lineage and identified a novel adipogenic adventitial smooth muscle cell present in adulthood that has the capacity to generate adipocytes in vitro and in vivo. Taken together, these two studies have identified the key factors required for controlling thermogenic gene transcription in brown adipocytes and the precise progenitor cells for making thermogenic adipocytes in vivo

ADRA1A-Gα signalling potentiates adipocyte thermogenesis through CKB and TNAP

Noradrenaline (NA) regulates cold-stimulated adipocyte thermogenesis. Aside from cAMP signalling downstream of β-adrenergic receptor activation, how NA promotes thermogenic output is still not fully understood. Here, we show that coordinated α-adrenergic receptor (AR) and β-AR signalling induces the expression of thermogenic genes of the futile creatine cycle, and that early B cell factors, oestrogen-related receptors and PGC1α are required for this response in vivo. NA triggers physical and functional coupling between the α-AR subtype (ADRA1A) and Gα to promote adipocyte thermogenesis in a manner that is dependent on the effector proteins of the futile creatine cycle, creatine kinase B and tissue-non-specific alkaline phosphatase. Combined Gα and Gα signalling selectively in adipocytes promotes a continual rise in whole-body energy expenditure, and creatine kinase B is required for this effect. Thus, the ADRA1A-Gα-futile creatine cycle axis is a key regulator of facultative and adaptive thermogenesis

Genome-wide association study of thoracic aortic aneurysm and dissection in the Million Veteran Program.

Acknowledgements: This work was supported by funding from the Department of VA Office of Research and Development, MVP grant MVP000 and the Department of Veterans, I01-BX003362 (P.S.T.), IK2-CX001780 (S.M.D.), IK2BX005759-01 (D.K.). This publication does not represent the views of the Department of VA or the United States Government. This project was partially supported by the Baszucki Research Initiative provided to Stanford Vascular Surgery in 2022 (D.K.). S.A.L., Y.L. and Y.H.S. are supported by grants from the American Heart Association Vascular Diseases Strategically Focused Research Networks (AHA18SFRN33960114). S.A.L. is supported in part by the Jimmy and Roberta Howell Professorship in Cardiovascular Surgery at Baylor College of Medicine. P.N. is supported by grants from the National Heart, Lung, and Blood Institute (R01HL142711, R01HL148050, R01HL151283, R01HL127564, R01HL151152) and the National Human Genome Research Institute (U01HG011719). K.G.A. is supported by grants from the National Institutes of Health (NIH; 1K08HL153937) and the American Heart Association (862032). K.P. is supported by a grant from the National Heart, Lung, and Blood Institute (5-T32HL007208-43). A.R.A. is supported by award number F30-DK120062. D.M.M. is supported by the National Heart, Lung, and Blood Institute (RO1HL62594) and the John Ritter and Remembrin’ Benjamin foundations. M.G.L. is supported by the Institute for Translational Medicine and Therapeutics of the Perelman School of Medicine at the University of Pennsylvania, the NIH–NHLBI National Research Service Award postdoctoral fellowship (T32HL007843) and the Measey Foundation. R.D. is supported by the National Institute of General Medical Sciences of the NIH (R35-GM124836) and the National Heart, Lung, and Blood Institute of the NIH (R01-HL139865 and R01-HL155915). J.P.P. is supported by a grant from the NIH (K08HL159346). S.B. is supported by the Wellcome Trust (225790/Z/22/Z) and the United Kingdom Research and Innovation Medical Research Council (MC_UU_00002/7). D.M.M. is supported by a grant from the NIH (R01HL109942). C.J.W. was supported by a grant from the NIH (R01HL109946). P.T.E. is supported by grants from the NIH (1RO1HL092577, 1R01HL157635, 5R01HL139731), from the American Heart Association Strategically Focused Research Networks (18SFRN34110082) and from the European Union (MAESTRIA 965286).The current understanding of the genetic determinants of thoracic aortic aneurysms and dissections (TAAD) has largely been informed through studies of rare, Mendelian forms of disease. Here, we conducted a genome-wide association study (GWAS) of TAAD, testing ~25 million DNA sequence variants in 8,626 participants with and 453,043 participants without TAAD in the Million Veteran Program, with replication in an independent sample of 4,459 individuals with and 512,463 without TAAD from six cohorts. We identified 21 TAAD risk loci, 17 of which have not been previously reported. We leverage multiple downstream analytic methods to identify causal TAAD risk genes and cell types and provide human genetic evidence that TAAD is a non-atherosclerotic aortic disorder distinct from other forms of vascular disease. Our results demonstrate that the genetic architecture of TAAD mirrors that of other complex traits and that it is not solely inherited through protein-altering variants of large effect size

Genome-wide association study of thoracic aortic aneurysm and dissection in the Million Veteran Program

The current understanding of the genetic determinants of thoracic aortic aneurysms and dissections (TAAD) has largely been informed through studies of rare, Mendelian forms of disease. Here, we conducted a genome-wide association study (GWAS) of TAAD, testing ~25 million DNA sequence variants in 8,626 participants with and 453,043 participants without TAAD in the Million Veteran Program, with replication in an independent sample of 4,459 individuals with and 512,463 without TAAD from six cohorts. We identified 21 TAAD risk loci, 17 of which have not been previously reported. We leverage multiple downstream analytic methods to identify causal TAAD risk genes and cell types and provide human genetic evidence that TAAD is a non-atherosclerotic aortic disorder distinct from other forms of vascular disease. Our results demonstrate that the genetic architecture of TAAD mirrors that of other complex traits and that it is not solely inherited through protein-altering variants of large effect size

Genome-wide association study of thoracic aortic aneurysm and dissection in the Million Veteran Program.

The current understanding of the genetic determinants of thoracic aortic aneurysms and dissections (TAAD) has largely been informed through studies of rare, Mendelian forms of disease. Here, we conducted a genome-wide association study (GWAS) of TAAD, testing ~25 million DNA sequence variants in 8,626 participants with and 453,043 participants without TAAD in the Million Veteran Program, with replication in an independent sample of 4,459 individuals with and 512,463 without TAAD from six cohorts. We identified 21 TAAD risk loci, 17 of which have not been previously reported. We leverage multiple downstream analytic methods to identify causal TAAD risk genes and cell types and provide human genetic evidence that TAAD is a non-atherosclerotic aortic disorder distinct from other forms of vascular disease. Our results demonstrate that the genetic architecture of TAAD mirrors that of other complex traits and that it is not solely inherited through protein-altering variants of large effect size