Biology subjects

Shimobayashi, M.

Publications and source records attributed to Shimobayashi, M..

7 recordsLinked to original sources

bioRxiv2026

Generation of functional adipoids from human induced pluripotent stem cells

Human adipose tissue models are lacking although essential for metabolic research. Traditional primary cell cultures are poorly scalable and unsuitable for drug screening or modeling of genetic disease. Conventional two-dimensional adipocyte cultures cannot withstand the long-term treatment required to mimic chronic conditions such as obesity and insulin resistance. To overcome these limitations, we developed an accessible protocol to produce three-dimensional human induced pluripotent stem cell (hiPSC)-derived adipocyte microtissues, termed adipoids. hiPSC-derived adipoids display long-term stability and viability. Single-nucleus RNA sequencing revealed that adipoids contain mature adipocytes and adipocyte stem/progenitor cells, similar to human adipose tissue. Furthermore, hiPSC-derived adipoids contain unilocular adipocytes, exhibit stimulated lipolysis, and secrete adipokines. Thus, hiPSC-derived adipoids provide a functional, scalable and genetically tractable model to perform large-scale pharmacological screens and to investigate human metabolic disease.

molecular biology↗

bioRxiv2025

A dietary intervention following incretin analog treatment restores adipose tissue functions in diet-induced obese mice

Obesity affects more than 15% of the world population and is associated with the development of glucose intolerance and type 2 diabetes. In recent years, incretin analogs are prescribed at a high rate for treatment of obesity and diabetes due to their potent effects on lowering bodyweight and improving glucose homeostasis. However, recent studies suggest that many patients do not stay on incretin analog therapy and thereby rapidly regain bodyweight. The non-compliance of patients to incretin analog therapy is not only due to drug shortage but also insufficient knowledge on the long-term effects of the therapy. To address this knowledge gap and provide a long-term therapy strategy for obesity, we examined the effects of incretin analog treatment and withdrawal on adipose tissue functions in diet-induced obese mice. Our transcriptome data suggest that incretin analog treatment restored most of obesity-mediated deregulated gene expression in adipose tissue. However, genes encoding lipogenic enzymes, downregulated by diet-induced obesity, were not restored by incretin analog treatment. Upon therapy withdrawal, mice displayed rapid bodyweight regain, impaired adipose tissue function, and glucose intolerance. In contrast, a dietary intervention following incretin analog therapy withdrawal restored lipogenic gene expression in adipose tissue, maintained glucose homeostasis, increased lean mass and minimized body weight regain. Our findings revealed the effects of incretin analog therapy and therapy withdrawal on adipose tissue and highlight the importance of a dietary intervention following incretin analog therapy, which may contribute to the development of long-term therapy guidelines of incretin analog therapy for patients with obesity.

physiology↗

bioRxiv2024

MLX phosphorylation stabilizes the ChREBP-MLX heterotetramer on tandem E-boxes to control carbohydrate and lipid metabolism

The heterodimeric ChREBP-MLX transcription factor complex is a key mediator that couples intracellular sugar levels to carbohydrate and lipid metabolism. To promote the expression of target genes, two ChREBP-MLX heterodimers form a heterotetramer to bind a tandem element with two adjacent E-boxes, called Carbohydrate Responsive Element (ChoRE). How the ChREBP-MLX hetero-tetramerization is achieved and regulated, remains poorly understood. Here we show that MLX phosphorylation on an evolutionarily conserved motif is necessary for the heterotetramer formation on the ChoRE and the transcriptional activity of the ChREBP-MLX complex. We identified CK2 and GSK3 as MLX kinases that coordinately phosphorylate MLX. High intracellular glucose-6-phosphate accumulation inhibits MLX phosphorylation and heterotetramer formation on the ChoRE, impairing ChREBP-MLX activity. Physiologically, MLX phosphorylation is necessary in Drosophila to maintain sugar tolerance and lipid homeostasis. Our findings suggest that MLX phosphorylation is a key mechanism for the ChREBP-MLX heterotetramer formation to regulate carbohydrate and lipid metabolism.

cell biology↗

bioRxiv2022

Hepatic mTORC2 compensates for loss of adipose mTORC2 in mediating energy storage and glucose homeostasis

Mammalian target of rapamycin complex 2 (mTORC2) is a protein kinase complex that plays an important role in energy homeostasis. Loss of adipose mTORC2 reduces lipogenic enzyme expression and de novo lipogenesis in adipose tissue. Adipose-specific mTORC2 knockout mice also displays triglyceride accumulation in the liver. However, the mechanism and physiological role of hepatic triglyceride accumulation upon loss of adipose mTORC2 are unknown. Here, we show that loss of adipose mTORC2 increases expression of de novo lipogenic enzymes in the liver, thereby causing accumulation of hepatic triglyceride and hypertriglyceridemia. Simultaneous inhibition of lipogenic enzymes in adipose tissue and liver by ablating mTORC2 in both tissues prevented accumulation of hepatic triglycerides and hypertriglyceridemia. However, loss of adipose and hepatic mTORC2 caused severe insulin resistance and glucose intolerance. Thus, our findings suggest that increased hepatic lipogenesis is a compensatory mechanism to cope with loss of lipogenesis in adipose tissue, and further suggest that mTORC2 in adipose tissue and liver plays a crucial role in maintaining whole-body energy homeostasis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/521172v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@904812org.highwire.dtl.DTLVardef@6b9f43org.highwire.dtl.DTLVardef@1a507b9org.highwire.dtl.DTLVardef@19e08a7_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2022

Adipose mTORC2 is essential for arborization of sensory neurons in white adipose tissue and whole-body energy homeostasis

Adipose tissue, via sympathetic and sensory neurons, communicates with the central nervous system (CNS) to mediate energy homeostasis. In contrast to the sympathetic nervous system, the morphology, role and regulation of the sensory nervous system in adipose tissue is poorly characterized. Taking advantage of recent progress in whole-mount three-dimensional imaging of adipose tissue, we identified a neuronal network of calcitonin gene-related protein (CGRP)-positive sensory neurons in white adipose tissue (WAT). Furthermore, we show that adipose mammalian target of rapamycin complex 2 (mTORC2), a major component of the insulin signaling pathway, mediates sensory innervation in WAT. Based on visualization of neuronal networks, mTORC2-deficient WAT displayed reduced arborization of (CGRP)-positive sensory neurons, while sympathetic neurons were unaffected. This selective loss of sensory innervation followed reduced expression of growth-associated protein 43 (GAP43) in CGRP-positive sensory neurons. Finally, we found that loss of sensory innervation in WAT correlated with systemic insulin resistance. Our findings suggest that adipose mTORC2 is necessary for sensory innervation in WAT which likely contributes to WAT-to-CNS communication.

physiology↗

bioRxiv2020

The 3.2A resolution structure of human mTORC2

The protein kinase mammalian target of rapamycin (mTOR) is the central regulator of cell growth. Aberrant mTOR signaling is linked to cancer, diabetes and neurological disorders. mTOR exerts its functions in two distinct multiprotein complexes, mTORC1 and mTORC2. Here we report a 3.2 [A] resolution cryo-EM reconstruction of mTORC2. It reveals entangled folds of the defining Rictor and the substrate-binding SIN1 subunits, identifies the C-terminal domain of Rictor as the source of the rapamycin insensitivity of mTORC2, and resolves mechanisms for mTORC2 regulation by complex destabilization. Two novel small molecule binding sites are visualized, an inositol hexakisphosphate (InsP6) pocket in mTOR and an mTORC2-specific nucleotide binding site in Rictor which also forms a zinc finger. Structural and biochemical analyses suggest that InsP6 and nucleotide binding do not control mTORC2 activity directly but rather have roles in folding or ternary interactions. These insights provide a firm basis for studying mTORC2 signaling and for developing mTORC2-specific inhibitors.

biochemistry↗

bioRxiv2019

Diet-induced loss of adipose Hexokinase 2 triggers hyperglycemia

Chronically high blood glucose (hyperglycemia) leads to diabetes, fatty liver disease, and cardiovascular disease. Obesity is a major risk factor for hyperglycemia, but the underlying mechanism is unknown. Here we show that a high fat diet (HFD) in mice causes early loss of expression of the glycolytic enzyme Hexokinase 2 (HK2) specifically in adipose tissue. Adipose-specific knockout of Hk2 caused enhanced gluconeogenesis and lipogenesis in liver, a condition known as selective insulin resistance, leading to glucose intolerance. Furthermore, we observed reduced hexokinase activity in adipose tissue of obese and diabetic patients, and identified a loss-of-function mutation in the hk2 gene of naturally hyperglycemic Mexican cavefish. Mechanistically, HFD in mice led to loss of HK2 by inhibiting translation of Hk2 mRNA. Our findings identify adipose HK2 as a critical mediator of systemic glucose homeostasis, and suggest that obesity-induced loss of adipose HK2 is an evolutionarily conserved, non-cell-autonomous mechanism for the development of hyperglycemia. One Sentence SummaryLoss of the glycolytic enzyme Hexokinase 2 in adipose tissue is a mechanism underlying high blood glucose levels.

physiology↗