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Vue Z, Neikirk K, Vang L, Garza-Lopez E, Christensen TA, Shao J, Lam J, Beasley HK, Marshall AG, Crabtree A, Anudokem J, Rodriguez B, Kirk B, Bacevac S, Barongan T, Shao B, Stephens DC, Kabugi K, Koh HJ, Koh A, Evans CS, Taylor B, Reddy AK, Miller-Fleming T, Actkins KV, Zaganjor E, Daneshgar N, Murray SA, Mobley BC, Damo SM, Gaddy JA, Riggs B, Wanjalla C, Kirabo A, McReynolds M, Gomez JA, Phillips MA, Exil V, Dai DF, Hinton A. Three-dimensional mitochondria reconstructions of murine cardiac muscle changes in size across aging. Am J Physiol Heart Circ Physiol 2023; 325:H965-H982. [PMID: 37624101 PMCID: PMC10977873 DOI: 10.1152/ajpheart.00202.2023] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 07/26/2023] [Accepted: 08/12/2023] [Indexed: 08/26/2023]
Abstract
With sparse treatment options, cardiac disease remains a significant cause of death among humans. As a person ages, mitochondria breakdown and the heart becomes less efficient. Heart failure is linked to many mitochondria-associated processes, including endoplasmic reticulum stress, mitochondrial bioenergetics, insulin signaling, autophagy, and oxidative stress. The roles of key mitochondrial complexes that dictate the ultrastructure, such as the mitochondrial contact site and cristae organizing system (MICOS), in aging cardiac muscle are poorly understood. To better understand the cause of age-related alteration in mitochondrial structure in cardiac muscle, we used transmission electron microscopy (TEM) and serial block facing-scanning electron microscopy (SBF-SEM) to quantitatively analyze the three-dimensional (3-D) networks in cardiac muscle samples of male mice at aging intervals of 3 mo, 1 yr, and 2 yr. Here, we present the loss of cristae morphology, the inner folds of the mitochondria, across age. In conjunction with this, the three-dimensional (3-D) volume of mitochondria decreased. These findings mimicked observed phenotypes in murine cardiac fibroblasts with CRISPR/Cas9 knockout of Mitofilin, Chchd3, Chchd6 (some members of the MICOS complex), and Opa1, which showed poorer oxidative consumption rate and mitochondria with decreased mitochondrial length and volume. In combination, these data show the need to explore if loss of the MICOS complex in the heart may be involved in age-associated mitochondrial and cristae structural changes.NEW & NOTEWORTHY This article shows how mitochondria in murine cardiac changes, importantly elucidating age-related changes. It also is the first to show that the MICOS complex may play a role in outer membrane mitochondrial structure.
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Affiliation(s)
- Zer Vue
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Kit Neikirk
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Larry Vang
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Edgar Garza-Lopez
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Trace A Christensen
- Microscopy and Cell Analysis Core Facility, Mayo Clinic, Rochester, Minnesota, United States
| | - Jianqiang Shao
- Central Microscopy Research Facility, University of Iowa, Iowa City, Iowa, United States
| | - Jacob Lam
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Heather K Beasley
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Andrea G Marshall
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Amber Crabtree
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Josephs Anudokem
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Benjamin Rodriguez
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Benjamin Kirk
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Serif Bacevac
- Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Taylor Barongan
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Bryanna Shao
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Dominique C Stephens
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
- Department of Life and Physical Sciences, Fisk University, Nashville, Tennessee, United States
| | - Kinuthia Kabugi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Ho-Jin Koh
- Department of Biological Sciences, Tennessee State University, Nashville, Tennessee, United States
| | - Alice Koh
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Chantell S Evans
- Department of Cell Biology, Duke University School of Medicine, Durham, North Carolina, United States
| | - Brittany Taylor
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida, United States
| | - Anilkumar K Reddy
- Department of Medicine, Baylor College of Medicine, Houston, Texas, United States
| | - Tyne Miller-Fleming
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Ky'Era V Actkins
- Division of Genetic Medicine, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Elma Zaganjor
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
| | - Nastaran Daneshgar
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Sandra A Murray
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Bret C Mobley
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Steven M Damo
- Department of Life and Physical Sciences, Fisk University, Nashville, Tennessee, United States
| | - Jennifer A Gaddy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
- Tennessee Valley Healthcare Systems, United States Department of Veterans Affairs, Nashville, Tennessee, United States
| | - Blake Riggs
- Department of Biology at San Francisco State University, San Francisco, California, United States
| | - Celestine Wanjalla
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Annet Kirabo
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Melanie McReynolds
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, State College, Pennsylvania, United States
| | - Jose A Gomez
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, United States
| | - Mark A Phillips
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, United States
| | - Vernat Exil
- Division of Cardiology, Department of Pediatrics, St. Louis University School of Medicine, St. Louis, Missouri, United States
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Dao-Fu Dai
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Antentor Hinton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States
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Bonet J, Yadav Y, Miles J, Basu A, Cobelli C, Basu R, Dalla Man C. A new oral model of free fatty acid kinetics to assess lipolysis in subjects with and without type 2 diabetes. Am J Physiol Endocrinol Metab 2023; 325:E163-E170. [PMID: 37378622 PMCID: PMC10393336 DOI: 10.1152/ajpendo.00091.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 06/02/2023] [Accepted: 06/16/2023] [Indexed: 06/29/2023]
Abstract
Assessing free fatty acids (FFAs) kinetics and the role of insulin and glucose on FFA lipolysis and disposal may improve our understanding of the pathogenesis of type 2 diabetes (T2D). Some models have been proposed to describe FFA kinetics during an intravenous glucose tolerance test and only one during an oral glucose tolerance test. Here, we propose a model of FFA kinetics during a meal tolerance test and use it to assess possible differences in postprandial lipolysis in individuals with type 2 diabetes (T2D) and individuals with obesity without type 2 diabetes (ND). We studied 18 obese ND and 16 T2D undergoing three meal tolerance tests (MTT) on three occasions (breakfast, lunch, and dinner). We used plasma glucose, insulin, and FFA concentrations collected at breakfast to test a battery of models and selected the best one based on physiological plausibility, ability to fit the data, precision of parameter estimates, and the Akaike parsimony criterion. The best model assumes that the postprandial suppression of FFA lipolysis is proportional to the above basal insulin, while FFA disposal is proportional to FFA concentration. It was used to compare FFA kinetics in ND and T2D along the day. The maximum lipolysis suppression occurred significantly earlier in ND than T2D (39 ± 6 min vs. 102 ± 13 min, 36 ± 4 min vs. 78 ± 11 min, and 38 ± 6 min vs. 84 ± 13 min, P < 0.01, at breakfast, lunch, and dinner, respectively), making lipolysis significantly lower in ND than T2D. This is mainly attributable to the lower insulin concentration in the second group. This novel FFA model allows to assess lipolysis and insulin antilipolytic effect in postprandial conditions.NEW & NOTEWORTHY In this study, we propose a new mathematical model able to quantify postprandial FFA kinetics and adipose tissue insulin sensitivity in both subjects with obesity without type 2 diabetes (ND) and subjects with type 2 diabetes (T2D). Results show that the slower postprandial suppression of lipolysis in T2D contributes to the higher free fatty acid (FFA) concentration that, in turn, may contribute to hyperglycemia.
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Affiliation(s)
- J. Bonet
- Department of Information Engineering, University of Padova, Padova, Italy
| | - Y. Yadav
- Division of Endocrinology, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, United States
| | - J. Miles
- University of Kansas Medical Center, Kansas City, Kansas, United States
| | - A. Basu
- Division of Endocrinology, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, United States
| | - C. Cobelli
- Department of Woman and Child’s Health, University of Padova, Padova, Italy
| | - R. Basu
- Division of Endocrinology, Department of Medicine, University of Virginia School of Medicine, Charlottesville, Virginia, United States
| | - C. Dalla Man
- Department of Information Engineering, University of Padova, Padova, Italy
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Blandino-Rosano M, Scheys JO, Werneck-de-Castro JP, Louzada RA, Almaça J, Leibowitz G, Rüegg MA, Hall MN, Bernal-Mizrachi E. Novel roles of mTORC2 in regulation of insulin secretion by actin filament remodeling. Am J Physiol Endocrinol Metab 2022; 323:E133-E144. [PMID: 35723227 PMCID: PMC9291412 DOI: 10.1152/ajpendo.00076.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Mammalian target of rapamycin (mTOR) kinase is an essential hub where nutrients and growth factors converge to control cellular metabolism. mTOR interacts with different accessory proteins to form complexes 1 and 2 (mTORC), and each complex has different intracellular targets. Although mTORC1's role in β-cells has been extensively studied, less is known about mTORC2's function in β-cells. Here, we show that mice with constitutive and inducible β-cell-specific deletion of RICTOR (βRicKO and iβRicKO mice, respectively) are glucose intolerant due to impaired insulin secretion when glucose is injected intraperitoneally. Decreased insulin secretion in βRicKO islets was caused by abnormal actin polymerization. Interestingly, when glucose was administered orally, no difference in glucose homeostasis and insulin secretion were observed, suggesting that incretins are counteracting the mTORC2 deficiency. Mechanistically, glucagon-like peptide-1 (GLP-1), but not gastric inhibitory polypeptide (GIP), rescued insulin secretion in vivo and in vitro by improving actin polymerization in βRicKO islets. In conclusion, mTORC2 regulates glucose-stimulated insulin secretion by promoting actin filament remodeling.NEW & NOTEWORTHY The current studies uncover a novel mechanism linking mTORC2 signaling to glucose-stimulated insulin secretion by modulation of the actin filaments. This work also underscores the important role of GLP-1 in rescuing defects in insulin secretion by modulating actin polymerization and suggests that this effect is independent of mTORC2 signaling.
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Affiliation(s)
- Manuel Blandino-Rosano
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida
| | - Joshua O Scheys
- Medical School, Division of Metabolism, Endocrinology, and Diabetes and Brehm Center for Diabetes Research, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Joao Pedro Werneck-de-Castro
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida
| | - Ruy A Louzada
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida
| | - Joana Almaça
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida
| | - Gil Leibowitz
- Diabetes Unit and Endocrine Service, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | | | | | - Ernesto Bernal-Mizrachi
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida
- Miami VA Healthcare System, Miami, Florida
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