Biology subjects

Kim, S. Q.

Publications and source records attributed to Kim, S. Q..

3 recordsLinked to original sources

bioRxiv2025

FGF21 signals through KLB-expressing glutamatergic neurons in the hindbrain to mediate the effects of dietary protein restriction

Animals adaptively respond to protein restriction by altering both behavior and metabolism. Previous work demonstrated that the metabolic hormone FGF21 acted in the brain to coordinate these adaptive responses, but the exact site of action remains unclear. Here, we identify a discrete population of glutamatergic, Klb-expressing neurons in the nucleus of the solitary tract (NTS), demonstrating that these neurons are key to mediating FGF21 action during protein restriction. Using a novel Klb-Flp mouse line combined with intersectional genetics, we demonstrate that these neurons are directly activated by FGF21. While previous work implicated the SCN, PVN, and VMH in FGF21 action, we find that these areas do not impact the response to protein restriction. Instead, selective ablation of NTS-KLB neurons prevents metabolic adaptations to protein restriction (food intake, food choice, and energy expenditure), while their chemogenetic activation is sufficient to drive these responses. These findings establish NTS-KLB neurons as a critical node for detecting protein status and coordinating whole-body metabolic responses, providing new insight into how the brain monitors and maintains protein homeostasis.

neuroscience↗

bioRxiv2024

FGF21 acts in the brain to drive macronutrient-specific changes in behavioral motivation and brain reward signaling

Dietary protein restriction induces adaptive changes in food preference, increasing protein consumption over carbohydrates or fat. We investigated whether motivation and reward signaling underpin these preferences. In an operant task, protein-restricted male mice responded more for liquid protein rewards, but not carbohydrate, fat, or sweet rewards compared to non-restricted mice. The protein restriction-induced increase in operant responding for protein was absent in Fgf21-KO mice and mice with neuron-specific deletion of the FGF21 co-receptor beta-Klotho (KlbCam2ka) mice. Fiber photometry recording of VTA dopamine neurons revealed that oral delivery of maltodextrin triggered a larger activation as compared to casein in control-fed mice, whereas casein triggered a larger activation in protein-restricted mice. This restriction-induced shift in nutrient-specific VTA dopamine signaling was lost in Fgf21-KO mice. These data strongly suggest that the increased FGF21 during protein restriction acts in the brain to induce a protein-specific appetite by specifically enhancing the reward value of protein-containing foods and the motivation to consume them.

neuroscience↗

bioRxiv2022

Multi-omics approach reveals dysregulation of protein phosphorylation correlated with lipid metabolism in mouse fatty liver

Obesity caused by overnutrition is a major risk factor for non-alcoholic fatty liver disease (NAFLD). Several lipid intermediates such as fatty acids, glycerophospholipids and sphingolipids are implicated in NAFLD, but detailed characterization of lipids and their functional links to proteome and phosphoproteome remain to be elucidated. To characterize this complex molecular relationship, we used multi-omics approach by conducting comparative proteomic, phoshoproteomic and lipidomic analyses of high fat (HFD) and low fat (LFD) diet fed mice livers. We quantified 2447 proteins and 1339 phosphoproteins containing 1650 class I phosphosites (with localization probability > 0.75), of which 669 phosphosites were significantly different between HFD and LFD mice livers. We detected alterations of proteins associated with cellular metabolic processes such as small molecule catabolic process, monocarboxylic acid, long- and medium-chain fatty acid, and ketone body metabolic processes, and peroxisome organization. We observed significant downregulation of protein phosphorylation in HFD fed mice liver in general. Untargeted lipidomics identified upregulation of triacylglycerols, glycerolipids and ether glycerophosphocholines and downregulation of glycerophospholipids such as lysoglycerophospholipids, as well as ceramides and acylcarnitines. Analysis of differentially regulated phosphosites revealed phosphorylation dependent deregulation of insulin signaling as well as lipogenic and lipolytic pathways during HFD induced obesity. Thus, this study reveals a molecular connection between decreased protein phosphorylation and lipolysis, as well as lipid-mediated signaling in diet-induced obesity.

systems biology↗