Biology subjects

Yamamoto, I.

Publications and source records attributed to Yamamoto, I..

5 recordsLinked to original sources

bioRxiv2025

From Single Molecular Detail to Subcellular Dynamics: Real-Time Kinetics Study of dPA Uptake with Raman-based Spectroscopy

Real-time observation of cellular transformations at the subcellular level provides insight into the dynamic biochemical processes underlying cell function and disease. However, many challenges remain in developing methods to analyze metabolic transformations in cells quantitatively. Our study applies Raman spectroscopy (RS) and stimulated Raman scattering (SRS) to link single-molecule resolution with cellular-scale lipid turnover tracking. Using HL-60 cells as a model, we monitor the uptake kinetics of deuterated palmitic acid (dPA), a marker of de novo lipogenesis, from the first minutes to hours. SRS enables microscopic, high-temporal-resolution visualization of dPA incorporation across entire cell volumes, capturing both its distribution and uptake rate. Complementary RS measurements identify distinct metabolic phases: rapid incorporation into pre-existing lipid droplets (LDs) followed by the emergence of new, partially unsaturated LDs associated with cytochrome-linked metabolism. Statistical and spectral analyses reveal cell-to-cell heterogeneity, emphasizing the complexity of lipid metabolism at both the cellular and subcellular levels. By integrating SRS and RS data into time-dependent kinetic profiles, we establish a unified submicron-to-cellular model of fatty acid metabolism. This multi-resolution spectroscopic approach demonstrates how real-time, label-based tracking can uncover dynamic metabolic heterogeneity, advancing understanding of the fatty acid uptake and metabolism in the microscale.

cell biology↗

bioRxiv2022

Expectation for sweet taste changes peripheral glucose metabolism via basolateral amygdala

Anticipatory physiological responses to food were first reported by Ivan Pavlov a century ago but the associated neural mechanism is still ill-defined. Here, we identified two types of neurons in the basolateral amygdala (BLA), which are activated by sweetener (saccharin) or water after sucrose conditioning, representing expected sweet taste and unmet expectation, respectively. Saccharin-induced met-expectation of sweet taste enhances, while H2O-induced unmet-expectation deteriorates, glucose metabolism in peripheral tissues. Deletion of saccharin-responsive neurons in BLA impaired saccharin-induced increase in insulin sensitivity. Deletion of H2O-responsive neurons in BLA improved glucose intolerance by unmet-expectation. Saccharin- and H2O-responsive neurons had different gene expressions. Our data suggest that the gap between the expected incoming sugar and sweet taste is evaluated by distinct BLA neurons to control peripheral glucose metabolism. One-Sentence SummaryNeurons in the basolateral amygdala control blood glucose levels by comparing anticipated sugar intake and sweet taste

physiology↗

bioRxiv2020

Activation of prodynorphin neurons in the dorsomedial hypothalamus inhibits food intake and promotes positive valence

The regulation of food intake is one of the major research areas in the study of metabolic syndromes such as obesity. Gene targeting studies have clarified the roles of hypothalamic neurons in feeding behaviour. However, our understanding of neural function under physiological conditions is still limited. Immediate early genes, such as activity-regulated cytoskeleton-associated protein (Arc/Arg3.1), are useful markers of neuronal activity. Here, we investigated the role of Arc/Arg3.1 gene-expressing neurons in the hypothalamus after refeeding using the targeted recombination in active populations method. We identified refeeding-responsive prodynorphin/cholecystokinin neurons in the dorsomedial hypothalamus that project to the paraventricular hypothalamic nucleus. Chemogenetic activation of these neurons decreased food intake and promoted positive valence. Our findings provide insight into the role of newly identified hedonic neurons in the process of feeding-induced satiety.

physiology↗

bioRxiv2020

Prostaglandin in the ventromedial hypothalamus regulates peripheral glucose metabolism

The hypothalamus plays a central role in monitoring and regulating systemic glucose metabolism. The brain is enriched with phospholipids containing poly-unsaturated fatty acids, which are biologically active in physiological regulation. Here, we show that intraperitoneal glucose injection induced changes in hypothalamic distribution and amount of phospholipids, especially arachidonic-acid-containing phospholipids, that were then metabolized to produce prostaglandins. Knockdown of cytosolic phospholipase A2 (cPLA2), a key enzyme for generating arachidonic acid from phospholipids, in the hypothalamic ventromedial nucleus (VMH), lowered insulin sensitivity in muscles during regular chow diet (RCD) feeding. Conversely, the down-regulation of glucose metabolism by high fat diet (HFD) feeding was improved by knockdown of cPLA2 in the VMH through changing hepatic insulin sensitivity and hypothalamic inflammation. Our data suggest that cPLA2-mediated hypothalamic phospholipid metabolism is critical for controlling systemic glucose metabolism during RCD, while continuous activation of the same pathway to produce prostaglandins during HFD deteriorates glucose metabolism.

physiology↗

bioRxiv2019

A Single Defined Sister Chromatid Fusion Destabilizes Cell Cycle through Micronuclei Formation

Chromosome fusion is deleterious among oncogenic chromosome rearrangements, and has been proposed to cause multiple tumor-driving abnormalities. Conventional methodologies, however, lack the strictness of the experimental controls on the fusion such as the exact timing, the number and the types of fusion in a given cell. Here, we developed a human cell-based sister chromatid fusion visualization system (FuVis), in which a single defined sister chromatid fusion is induced by CRISPR/Cas9 concomitantly with mCitrine expression. Fused chromosome developed numerical and structural abnormalities, including chromosome fragmentation, an indicative of eventual chromothripsis. Live cell imaging and hierarchical Bayesian modeling indicated that micronucleus (MN) is generated in the first few cell cycle, and that cells with MN tend to possess cell cycle abnormalities. These results demonstrate that, although most cells can tolerate a single fusion, even a single sister chromatid fusion destabilizes cell cycle through MN formation.

cell biology↗