Role of the Neutral Amino Acid Transporter SLC7A10 in Adipocyte Lipid Storage, Obesity and Insulin Resistance

Elucidation of mechanisms that govern lipid storage, oxidative stress, and insulin resistance may lead to improved therapeutic options for type 2 diabetes and other obesity-related diseases. Here, we find that adipose expression of the small neutral amino acid transporter SLC7A10, also known as alanine-serine-cysteine transporter-1 (ASC-1), shows strong inverse correlates with visceral adiposity, insulin resistance, and adipocyte hypertrophy across multiple cohorts. Concordantly, loss of Slc7a10 function in zebrafish in vivo accelerates diet-induced body weight gain and adipocyte enlargement. Mechanistically, SLC7A10 inhibition in human and murine adipocytes decreases adipocyte serine uptake and total glutathione levels and promotes reactive oxygen species (ROS) generation. Conversely, SLC7A10 overexpression decreases ROS generation and increases mitochondrial respiratory capacity. RNA sequencing revealed consistent changes in gene expression between human adipocytes and zebrafish visceral adipose tissue following loss of SLC7A10, e.g., upregulation of SCD (lipid storage) and downregulation of CPT1A (lipid oxidation). Interestingly, ROS scavenger reduced lipid accumulation and attenuated the lipid-storing effect of SLC7A10 inhibition. These data uncover adipocyte SLC7A10 as a novel important regulator of adipocyte resilience to nutrient and oxidative stress, in part by enhancing glutathione levels and mitochondrial respiration, conducive to decreased ROS generation, lipid accumulation, adipocyte hypertrophy, insulin resistance, and type 2 diabetes.acceptedVersio

A MicroRNA Linking Human Positive Selection and Metabolic Disorders

Postponed access: the file will be accessible after 2021-10-14Positive selection in Europeans at the 2q21.3 locus harboring the lactase gene has been attributed to selection for the ability of adults to digest milk to survive famine in ancient times. However, the 2q21.3 locus is also associated with obesity and type 2 diabetes in humans, raising the possibility that additional genetic elements in the locus may have contributed to evolutionary adaptation to famine by promoting energy storage, but which now confer susceptibility to metabolic diseases. We show here that the miR-128-1 microRNA, located at the center of the positively selected locus, represents a crucial metabolic regulator in mammals. Antisense targeting and genetic ablation of miR-128-1 in mouse metabolic disease models result in increased energy expenditure and amelioration of high-fat-diet-induced obesity and markedly improved glucose tolerance. A thrifty phenotype connected to miR-128-1-dependent energy storage may link ancient adaptation to famine and modern metabolic maladaptation associated with nutritional overabundance.acceptedVersio

A saturated map of common genetic variants associated with human height

Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions requires huge sample sizes(1). Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel(2)) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10-20% (14-24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries.A large genome-wide association study of more than 5 million individuals reveals that 12,111 single-nucleotide polymorphisms account for nearly all the heritability of height attributable to common genetic variants

A saturated map of common genetic variants associated with human height.

Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions requires huge sample sizes1. Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel2) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10-20% (14-24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries

Distribution and localisation of Gα proteins in the rostral ventrolateral medulla of normotensive and hypertensive rats : focus on catecholaminergic neurons

About 860 G-protein-coupled receptors (GPCRs) mediate their actions via heterotrimeric G-proteins. Their activation releases Gα from Gβλ subunits. The type of Gα subunit dictates the major signalling proteins involved: adenylyl cyclase, PLC and rhoGEF. The rostral ventrolateral medulla (RVLM), containing the rostral C1 (rC1) cell group, sets and maintains the tonic and reflex control of blood pressure and a plethora of inputs converge onto these neurons. We determined the relative abundance of 10 Gα subunit mRNAs, representing the four major families, within the RVLM, using quantitative RT-PCR. In situ hybridisation (ISH) combined with immunohistochemistry (IHC) was used to quantify and compare this expression in rC1 with that in the A1 and A5 cell groups. The relative abundance of Gα subunit mRNAs and a comparison of gene expression levels were quantitatively determined in normotensive and hypertensive rat strains. All 10 Gα mRNAs were detected in the RVLM of Sprague-Dawley (SD) rats with relative abundance such that Gαs > Gαi2 > Gαo > Gαq > GαL > Gα11 > Gαi3 > Gαi1 > Gα12 > Gα13. The high abundance of Gα mRNAs signalling via adenylyl cyclase indicates the importance of associated GPCRs. Within the rC1 and A1 groups similar differential Gα mRNA expression profiles were seen with Gαs being found in all rC1 cells, Gα11 absent and Gαi3 rarely expressed. Thus functionally distinct subgroups exist within the rC1 and A1 cell groups as differing distributions of Gα subunits must reflect the array of GPCRs that influence their activity. In contrast, all A5 cells expressed all Gα mRNAs suggesting a functionally homogeneous group. When the 10 Gα mRNAs of the RVLM in spontaneously hypertensive rats (SHR) were compared quantitatively to Wistar-Kyoto (WKY), only Gαs and Gα12 were significantly elevated. However when the expression in normotensive SD and WKY was compared with SHR no significant differences were evident. These findings demonstrate a range of GPCR signalling capabilities in brainstem neurons important for homeostasis and suggest a prominent role for signalling via adenylyl cyclase.15 page(s

Functional and proteomic changes which underlie differences in neuronal function in the rostral ventrolateral medulla (RVLM) of Spontaneously Hypertensive rats (SHR) compared to normotensive rats

Activity of presympathetic neurons in the RVLM contribute to sympathetic hyperactivity seen in hypertension. Voltage gated calcium channels (VGCC) underpin essential neuronal functions including excitability, neurotransmitter release and synaptic plasticity. LVA currents activate at hyperpolarized potentials and inactivate rapidly so can generate spontaneous neuronal firing and pacemaking activity, "burst firing" patterns and window currents. VGCC conductances are critical determinants of the ongoing activity of RVLM neurons. For example, Ni2+-sensitive Ca2+ currents drive bursting of RVLM neurons in response to focal hypoxia and in the absence of synaptic inputs in neonatal brain slice. We have previously shown that LVA, but not HVA conductance, in adult RVLM, is critical to maintaining sympathetic vasomotor tone in normotensive Sprague Dawley (SD) rats. The first aim was to determine functionally the role of the LVA conductance in the RVLM of SHR and normotensive Wistar Kyoto (WKY). Urethane anaesthetised (1.3 g/kg ip) ventilated animals were used. Bilateral microinjection of NiCl2 (50 nl, 50mM) were made into the RVLM of SD, WKY and SHR. In both SD (n=4) and WKY (n=5) SNA decreased immediately (peak change -56 ± 8% and -63 ± 4.5 %) as did BP (peak change -31 ± 5 and -39 ± 2 and mmHg) and HR (-33 ± 13 bpm and -57 ± 6 bpm). Vehicle had no effect. Ni2+ evoked effects were not significantly different between the two strains. In contrast injections of NiCl2 in SHR (n=6) elicited sustained increases in SNA (+54 ± 6 %), AP (+42 ± 8 mmHg) and HR (+41 ± 9 bpm). The quandary is to explain how Ni2+ could evoke this response in SHR. T-type channels can be modulated by various endogenous ligands and a number of functional and chemical differences have been individually described in the RVLM of SHR compared to WKY. In order to identify all possible candidates that could modify T-type channels we next sought to compare the protein profile in the RVLM of SHR (n=3) and WKY (n=3) by shot gun proteomics. Brains were rapidly removed under pentobarbitone anaesthesia (100mg/kg ip) and frozen before RVLM region dissection (~1mm x 1.5mm). Conventional protein preparation and digestion strategies preceded LC-MS/MS. In total 1438 proteins were identified with 168 significantly differentially expressed:70 up regulated and 98 down regulated in SHR vs WKY. Key pathways affected include: increased glutamatergic signalling (VGLUT2, EAAT, GNAO); synaptic vesicle related activity (SYN1, SYN2, SYT, SNAP25, SYNGR3, NRXN3, FLOT1, FLOT2), remodelling (MAP6, CAPZB, SEPT6, GSN, TUBB3, TUBB4, TUBB5, TUBB4B, EMS1), decreased GABAergic signalling (GAD, ABAT, GPHN), oxidative phosphorylation (ND1, NDUF6, CYTB, CYTC, ATP5G1) and altered glutathione signalling (GSS, GSTT1)

Single cells from human primary colorectal tumors exhibit polyfunctional heterogeneity in secretions of ELR plus CXC chemokines

Cancer is an inflammatory disease of tissue that is largely influenced by the interactions between multiple cell types, secreted factors, and signal transduction pathways. While single-cell sequencing continues to refine our understanding of the clonotypic heterogeneity within tumors, the complex interplay between genetic variations and non-genetic factors ultimately affects therapeutic outcome. Much has been learned through bulk studies of secreted factors in the tumor microenvironment, but the secretory behavior of single cells has been largely uncharacterized. Here we directly profiled the secretions of ELR+ CXC chemokines from thousands of single colorectal tumor and stromal cells, using an array of subnanoliter wells and a technique called microengraving to characterize both the rates of secretion of several factors at once and the numbers of cells secreting each chemokine. The ELR+ CXC chemokines are highly redundant, pro-angiogenic cytokines that signal via the CXCR1 and CXCR2 receptors, influencing tumor growth and progression. We find that human primary colorectal tumor and stromal cells exhibit polyfunctional heterogeneity in the combinations and magnitudes of secretions for these chemokines. In cell lines, we observe similar variance: phenotypes observed in bulk can be largely absent among the majority of single cells, and discordances exist between secretory states measured and gene expression for these chemokines among single cells. Together, these measures suggest secretory states among tumor cells are complex and can evolve dynamically. Most importantly, this study reveals new insight into the intratumoral phenotypic heterogeneity of human primary tumors