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Hepowit NL, Moon B, Ebert AC, Dickson RC, MacGurn JA. Art2 mediates selective endocytosis of methionine transporters during adaptation to sphingolipid depletion. J Cell Sci 2023; 136:jcs260675. [PMID: 37337792 PMCID: PMC10399987 DOI: 10.1242/jcs.260675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 06/01/2023] [Indexed: 06/21/2023] Open
Abstract
Accumulating evidence in several model organisms indicates that reduced sphingolipid biosynthesis promotes longevity, although underlying mechanisms remain unclear. In yeast, sphingolipid depletion induces a state resembling amino acid restriction, which we hypothesized might be due to altered stability of amino acid transporters at the plasma membrane. To test this, we measured surface abundance for a diverse panel of membrane proteins in the presence of myriocin, a sphingolipid biosynthesis inhibitor, in Saccharomyces cerevisiae. Unexpectedly, we found that surface levels of most proteins examined were either unaffected or increased during myriocin treatment, consistent with an observed decrease in bulk endocytosis. In contrast, sphingolipid depletion triggered selective endocytosis of the methionine transporter Mup1. Unlike methionine-induced Mup1 endocytosis, myriocin triggered Mup1 endocytosis that required the Rsp5 adaptor Art2, C-terminal lysine residues of Mup1 and the formation of K63-linked ubiquitin polymers. These findings reveal cellular adaptation to sphingolipid depletion by ubiquitin-mediated remodeling of nutrient transporter composition at the cell surface.
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Affiliation(s)
- Nathaniel L. Hepowit
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Bradley Moon
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Adam C. Ebert
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Robert C. Dickson
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
| | - Jason A. MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
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2
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Handy RM, Holloway GP. Insights into the development of insulin resistance: Unraveling the interaction of physical inactivity, lipid metabolism and mitochondrial biology. Front Physiol 2023; 14:1151389. [PMID: 37153211 PMCID: PMC10157178 DOI: 10.3389/fphys.2023.1151389] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 04/07/2023] [Indexed: 05/09/2023] Open
Abstract
While impairments in peripheral tissue insulin signalling have a well-characterized role in the development of insulin resistance and type 2 diabetes (T2D), the specific mechanisms that contribute to these impairments remain debatable. Nonetheless, a prominent hypothesis implicates the presence of a high-lipid environment, resulting in both reactive lipid accumulation and increased mitochondrial reactive oxygen species (ROS) production in the induction of peripheral tissue insulin resistance. While the etiology of insulin resistance in a high lipid environment is rapid and well documented, physical inactivity promotes insulin resistance in the absence of redox stress/lipid-mediated mechanisms, suggesting alternative mechanisms-of-action. One possible mechanism is a reduction in protein synthesis and the resultant decrease in key metabolic proteins, including canonical insulin signaling and mitochondrial proteins. While reductions in mitochondrial content associated with physical inactivity are not required for the induction of insulin resistance, this could predispose individuals to the detrimental effects of a high-lipid environment. Conversely, exercise-training induced mitochondrial biogenesis has been implicated in the protective effects of exercise. Given mitochondrial biology may represent a point of convergence linking impaired insulin sensitivity in both scenarios of chronic overfeeding and physical inactivity, this review aims to describe the interaction between mitochondrial biology, physical (in)activity and lipid metabolism within the context of insulin signalling.
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The Role of Mitochondrial Quality Control in Cognitive Dysfunction in Diabetes. Neurochem Res 2022; 47:2158-2172. [PMID: 35661963 PMCID: PMC9352619 DOI: 10.1007/s11064-022-03631-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 05/05/2022] [Accepted: 05/07/2022] [Indexed: 12/26/2022]
Abstract
Type 2 diabetes (T2DM) is a well known risk factor for Alzheimer’s disease. Mitochondria are the center of intracellular energy metabolism and the main source of reactive oxygen species. Mitochondrial dysfunction has been identified as a key factor in diabetes-associated brain alterations contributing to neurodegenerative events. Defective insulin signaling may act in concert with neurodegenerative mechanisms leading to abnormalities in mitochondrial structure and function. Mitochondrial dysfunction triggers neuronal energy exhaustion and oxidative stress, leading to brain neuronal damage and cognitive impairment. The normality of mitochondrial function is basically maintained by mitochondrial quality control mechanisms. In T2DM, defects in the mitochondrial quality control pathway in the brain have been found to lead to mitochondrial dysfunction and cognitive impairment. Here, we discuss the association of mitochondrial dysfunction with T2DM and cognitive impairment. We also review the molecular mechanisms of mitochondrial quality control and impacts of mitochondrial quality control on the progression of cognitive impairment in T2DM.
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Lovell AJ, Hoecht EM, Hucik B, Cervone DT, Dyck DJ. The effects of diet and chronic exercise on skeletal muscle ghrelin response. Metabol Open 2022; 14:100182. [PMID: 35340718 PMCID: PMC8942827 DOI: 10.1016/j.metop.2022.100182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 11/20/2022] Open
Abstract
Background Recent findings indicate that ghrelin, particularly the unacylated form (UnAG), acutely stimulates skeletal muscle fatty acid oxidation (FAO) and can preserve insulin signaling and insulin-stimulated glucose uptake in the presence of high concentrations of saturated fatty acids. However, we recently reported that the stimulatory effect of ghrelin on FAO and subsequent ability to protect insulin stimulated glucose uptake was lost following 6-weeks (6w) of chronic high fat feeding. In the current study we examined the effects of both short-term 5 day (5d) and chronic 6w high-fat diet (HFD) on muscle ghrelin response, and whether exercise training could prevent the development of muscle ghrelin resistance with 6w of HFD Methods and Results Soleus muscle strips were isolated from male rats to determine the direct effects of acylated (AG) and UnAG isoforms on FAO and glucose uptake. A 5d HFD did not alter the response of soleus muscle to AG or UnAG. Conversely, 6w of HFD was associated with a loss of ghrelin's ability to stimulate FAO and protect insulin stimulated glucose uptake. Muscle response to UnAG remained intact following the 6w HFD with chronic exercise training. Unexpectedly, muscle response to both AG and UnAG was also lost after 6w of low-fat diet (LFD) consumption. Protein content of the classic ghrelin receptor, GHS-R1a, was not affected by diet or training. Corticotropin-releasing hormone receptor-2 (CRF-2R) content, a putative receptor for ghrelin in muscle, was significantly decreased in soleus from 6w HFD-fed animals and increased following exercise training. This may explain the protection of UnAG response with training in HFD-fed rats but does not explain why ghrelin response was also lost in LFD-fed animals. Conclusions UnAG protects muscle glucose uptake during acute lipid oversupply, likely due to its ability to stimulate FAO. This effect is lost in 6w HFD-fed animals but protected with exercise training. Unexpectedly, ghrelin response was lost in 6w LFD-fed animals. The loss of ghrelin response in muscle with a LFD cannot be explained by a change in putative ghrelin receptor content. We believe that the sedentary nature of the animals is a major factor in the development of muscle ghrelin resistance and warrants further research. Ghrelin stimulates fatty acid oxidation in skeletal muscle. This stimulation is strongly associated with protection from acute fat overload. Prolonged sedentary behaviour and a high fat diet impair ghrelin's ability to stimulate fatty acid oxidation. Exercise training preserves ghrelin's positive effects on skeletal muscle.
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Yaribeygi H, Maleki M, Sathyapalan T, Jamialahmadi T, Sahebkar A. Pathophysiology of Physical Inactivity-Dependent Insulin Resistance: A Theoretical Mechanistic Review Emphasizing Clinical Evidence. J Diabetes Res 2021; 2021:7796727. [PMID: 34660812 PMCID: PMC8516544 DOI: 10.1155/2021/7796727] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 12/17/2022] Open
Abstract
The modern lifestyle has a negative impact on health. It is usually accompanied by increased stress levels and lower physical activity, which interferes with body homeostasis. Diabetes mellitus is a relatively common metabolic disorder with increasing prevalence globally, associated with various risk factors, including lower physical activity and a sedentary lifestyle. It has been shown that sedentary behavior increases the risk of insulin resistance, but the intermediate molecular mechanisms are not fully understood. In this mechanistic review, we explore the possible interactions between physical inactivity and insulin resistance to help better understand the pathophysiology of physical inactivity-dependent insulin resistance and finding novel interventions against these deleterious pathways.
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Affiliation(s)
- Habib Yaribeygi
- Research Center of Physiology, Semnan University of Medical Sciences, Semnan, Iran
| | - Mina Maleki
- Urology and Nephrology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Thozhukat Sathyapalan
- Academic Diabetes, Endocrinology and Metabolism, Hull York Medical School, University of Hull, UK
| | - Tannaz Jamialahmadi
- Department of Food Science and Technology, Quchan Branch, Islamic Azad University, Quchan, Iran
- Department of Nutrition, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Amirhossein Sahebkar
- Biotechnology Research Center, Pharmaceutical Technology Institute, Mashhad University of Medical Sciences, Mashhad, Iran
- Applied Biomedical Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
- School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran
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Hepowit NL, Macedo JKA, Young LEA, Liu K, Sun RC, MacGurn JA, Dickson RC. Enhancing lifespan of budding yeast by pharmacological lowering of amino acid pools. Aging (Albany NY) 2021; 13:7846-7871. [PMID: 33744865 PMCID: PMC8034917 DOI: 10.18632/aging.202849] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Accepted: 01/21/2021] [Indexed: 04/20/2023]
Abstract
The increasing prevalence of age-related diseases and resulting healthcare insecurity and emotional burden require novel treatment approaches. Several promising strategies seek to limit nutrients and promote healthy aging. Unfortunately, the human desire to consume food means this strategy is not practical for most people but pharmacological approaches might be a viable alternative. We previously showed that myriocin, which impairs sphingolipid synthesis, increases lifespan in Saccharomyces cerevisiae by modulating signaling pathways including the target of rapamycin complex 1 (TORC1). Since TORC1 senses cellular amino acids, we analyzed amino acid pools and identified 17 that are lowered by myriocin treatment. Studying the methionine transporter, Mup1, we found that newly synthesized Mup1 traffics to the plasma membrane and is stable for several hours but is inactive in drug-treated cells. Activity can be restored by adding phytosphingosine to culture medium thereby bypassing drug inhibition, thus confirming a sphingolipid requirement for Mup1 activity. Importantly, genetic analysis of myriocin-induced longevity revealed a requirement for the Gtr1/2 (mammalian Rags) and Vps34-Pib2 amino acid sensing pathways upstream of TORC1, consistent with a mechanism of action involving decreased amino acid availability. These studies demonstrate the feasibility of pharmacologically inducing a state resembling amino acid restriction to promote healthy aging.
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Affiliation(s)
- Nathaniel L. Hepowit
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Jessica K. A. Macedo
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - Lyndsay E. A. Young
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
| | - Ke Liu
- Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, Sichuan University, Chengdu 610000, Sichuan, P. R. China
| | - Ramon C. Sun
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
- Department of Neuroscience, University of Kentucky, Lexington, KY 40536, USA
| | - Jason A. MacGurn
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Robert C. Dickson
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536, USA
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Methnani J, Amor D, Yousfi N, Bouslama A, Omezzine A, Bouhlel E. Sedentary behavior, exercise and COVID-19: immune and metabolic implications in obesity and its comorbidities. J Sports Med Phys Fitness 2020; 61:1538-1547. [PMID: 33305550 DOI: 10.23736/s0022-4707.20.11898-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Many reports showed a dramatic decrease in the levels of physical activity during the current pandemic of SARS-CoV-2. This has substantial immune and metabolic implications, especially in those at risk or with metabolic diseases including individuals with obesity and Type 2 diabetes. In this study we discussed the route from physical inactivity to immune and metabolic aberrancies; focusing on how insulin resistance could represent an adaptive mechanism to the low physical activity levels and on how such an adaptive mechanism could shift to a pathognomonic feature of metabolic diseases, creating a vicious circle of immune and metabolic aberrancies. We provide a theoretical framework to the severe immunopathology of COVID-19 in patients with metabolic diseases. We finally discuss the idea of exercise as a potential adjuvant against COVID-19 and emphasize how even interrupting prolonged periods of sitting with short time breaks of very light activity could be a feasible strategy to limit the deleterious effects of the outbreak.
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Affiliation(s)
- Jabeur Methnani
- University of Manouba, High Institute of Sport and Physical Education, Ksar Said, Tunis, Tunisia - .,Department of Biochemistry, LR12SP11, Sahloul University Hospital, Sousse, Tunisia - .,Laboratory of Exercise Physiology and Physiopathology: from Integrated to Molecular Biology, Medicine and Health, LR19ES09, Faculty of Medicine of Sousse, Sousse, Tunisia -
| | - Dorra Amor
- Department of Biochemistry, LR12SP11, Sahloul University Hospital, Sousse, Tunisia.,University of Monastir, Faculty of Pharmacy of Monastir, Monastir, Tunisia
| | - Nariman Yousfi
- University of Manouba, High Institute of Sport and Physical Education, Ksar Said, Tunis, Tunisia.,Research Laboratory of "Sport Performance Optimization, " National Center of Medicine and Sport Sciences, Tunis, Tunisia
| | - Ali Bouslama
- Department of Biochemistry, LR12SP11, Sahloul University Hospital, Sousse, Tunisia.,University of Monastir, Faculty of Pharmacy of Monastir, Monastir, Tunisia
| | - Asma Omezzine
- Department of Biochemistry, LR12SP11, Sahloul University Hospital, Sousse, Tunisia.,University of Monastir, Faculty of Pharmacy of Monastir, Monastir, Tunisia
| | - Ezdine Bouhlel
- University of Manouba, High Institute of Sport and Physical Education, Ksar Said, Tunis, Tunisia.,Laboratory of Exercise Physiology and Physiopathology: from Integrated to Molecular Biology, Medicine and Health, LR19ES09, Faculty of Medicine of Sousse, Sousse, Tunisia
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Dirks ML, Wall BT, Stephens FB. Rebuttal from Marlou L. Dirks, Benjamin T. Wall and Francis B. Stephens. J Physiol 2020; 598:3813-3814. [PMID: 32643203 DOI: 10.1113/jp279715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Marlou L Dirks
- Department of Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Benjamin T Wall
- Department of Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Francis B Stephens
- Department of Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
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McKenzie AI, Reidy PT, Nelson DS, Mulvey JL, Yonemura NM, Petrocelli JJ, Mahmassani ZS, Tippetts TS, Summers SA, Funai K, Drummond MJ. Pharmacological inhibition of TLR4 ameliorates muscle and liver ceramide content after disuse in previously physically active mice. Am J Physiol Regul Integr Comp Physiol 2020; 318:R503-R511. [PMID: 31994900 PMCID: PMC7099462 DOI: 10.1152/ajpregu.00330.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 01/07/2020] [Accepted: 01/21/2020] [Indexed: 12/19/2022]
Abstract
Toll-like receptor 4 (TLR4) is a proposed mediator of ceramide accumulation, muscle atrophy, and insulin resistance in skeletal muscle. It is currently unknown whether pharmacological inhibition of TLR4, using the TLR4-specific inhibitor TAK-242 during muscle disuse, is able to prevent changes in intracellular ceramide species and consequently preserve muscle size and insulin sensitivity in physically active mice. To address this question, we subjected running wheel-conditioned C57BL/6 male mice (13 wk old; ∼10/group) to 7 days of hindlimb suspension (HS), 7 days of continued wheel running (WR), or daily injections of TAK-242 during HS (HS + TAK242) for 7 days. We measured hindlimb muscle morphology, intramuscular and liver ceramide content, HOMA-IR, mRNA proxies of ceramide turnover and lipid trafficking, and muscle fatty acid and glycerolipid content. As a result, soleus and liver ceramide abundance was greater (P < 0.05) in HS vs. WR but was reduced with TLR4 inhibition (HS + TAK-242 vs. HS). Muscle mass declined (P < 0.01) with HS (vs. WR), but TLR4 inhibition did not prevent this loss (soleus: P = 0.08; HS vs. HS + TAK-242). HOMA-IR was impaired (P < 0.01) in HS versus WR mice, but only fasting blood glucose was reduced with TLR4 inhibition (HS + TAK-242 vs HS, P < 0.05). Robust decreases in muscle Spt2 and Cd36 mRNA and muscle lipidomic trafficking may partially explain reductions in ceramides with TLR4 inhibition. In conclusion, pharmacological TLR4 inhibition in wheel-conditioned mice prevented ceramide accumulation during the early phase of hindlimb suspension (7 days) but had little effect on muscle size and insulin sensitivity.
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Affiliation(s)
- Alec I McKenzie
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Paul T Reidy
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Daniel S Nelson
- University of Utah Department of Nutrition and Integrated Physiology, Salt Lake City, Utah
| | - Jade L Mulvey
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Nikol M Yonemura
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Jonathan J Petrocelli
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Ziad S Mahmassani
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Trevor S Tippetts
- University of Utah Department of Nutrition and Integrated Physiology, Salt Lake City, Utah
| | - Scott A Summers
- University of Utah Department of Nutrition and Integrated Physiology, Salt Lake City, Utah
| | - Katsuhiko Funai
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
| | - Micah J Drummond
- University of Utah Department of Physical Therapy and Athletic Training, Salt Lake City, Utah
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