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Heni M. The insulin resistant brain: impact on whole-body metabolism and body fat distribution. Diabetologia 2024; 67:1181-1191. [PMID: 38363340 PMCID: PMC11153284 DOI: 10.1007/s00125-024-06104-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 12/19/2023] [Indexed: 02/17/2024]
Abstract
Insulin exerts its actions not only on peripheral organs but is also transported into the brain where it performs distinct functions in various brain regions. This review highlights recent advancements in our understanding of insulin's actions within the brain, with a specific emphasis on investigations in humans. It summarises current knowledge on the transport of insulin into the brain. Subsequently, it showcases robust evidence demonstrating the existence and physiological consequences of brain insulin action, while also introducing the presence of brain insulin resistance in humans. This pathophysiological condition goes along with an impaired acute modulation of peripheral metabolism in response to brain insulin action, particularly in the postprandial state. Furthermore, brain insulin resistance has been associated with long-term adiposity and an unfavourable adipose tissue distribution, thus implicating it in the pathogenesis of subgroups of obesity and (pre)diabetes that are characterised by distinct patterns of body fat distribution. Encouragingly, emerging evidence suggests that brain insulin resistance could represent a treatable entity, thereby opening up novel therapeutic avenues to improve systemic metabolism and enhance brain functions, including cognition. The review closes with an outlook towards prospective research directions aimed at further elucidating the clinical implications of brain insulin resistance. It emphasises the critical need to establish feasible diagnostic measures and effective therapeutic interventions.
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Affiliation(s)
- Martin Heni
- Division of Endocrinology and Diabetology, Department of Internal Medicine 1, University Hospital Ulm, Ulm, Germany.
- Department for Diagnostic Laboratory Medicine, Institute for Clinical Chemistry and Pathobiochemistry, University Hospital of Tübingen, Tübingen, Germany.
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Rebelos E, Latva-Rasku A, Koskensalo K, Pekkarinen L, Saukko E, Ihalainen J, Honka MJ, Tuisku J, Bucci M, Laurila S, Rajander J, Salminen P, Nummenmaa L, Jansen JFA, Ferrannini E, Nuutila P. Insulin-stimulated brain glucose uptake correlates with brain metabolites in severe obesity: A combined neuroimaging study. J Cereb Blood Flow Metab 2024; 44:407-418. [PMID: 37824728 PMCID: PMC10870965 DOI: 10.1177/0271678x231207114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 08/30/2023] [Accepted: 09/15/2023] [Indexed: 10/14/2023]
Abstract
The human brain undergoes metabolic adaptations in obesity, but the underlying mechanisms have remained largely unknown. We compared concentrations of often reported brain metabolites measured with magnetic resonance spectroscopy (1H-MRS, 3 T MRI) in the occipital lobe in subjects with obesity and lean controls under different metabolic conditions (fasting, insulin clamp, following weight loss). Brain glucose uptake (BGU) quantified with 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET)) was also performed in a subset of subjects during clamp. In dataset A, 48 participants were studied during fasting with brain 1H-MRS, while in dataset B 21 participants underwent paired brain 1H-MRS acquisitions under fasting and clamp conditions. In dataset C 16 subjects underwent brain 18F-FDG-PET and 1H-MRS during clamp. In the fasting state, total N-acetylaspartate was lower in subjects with obesity, while brain myo-inositol increased in response to hyperinsulinemia similarly in both lean participants and subjects with obesity. During clamp, BGU correlated positively with brain glutamine/glutamate, total choline, and total creatine levels. Following weight loss, brain creatine levels were increased, whereas increases in other metabolites remained not significant. To conclude, insulin signaling and glucose metabolism are significantly coupled with several of the changes in brain metabolites that occur in obesity.
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Affiliation(s)
- Eleni Rebelos
- Turku PET Centre, University of Turku, Turku, Finland
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Aino Latva-Rasku
- Turku PET Centre, University of Turku, Turku, Finland
- Department of Endocrinology, Turku University Hospital, Turku, Finland
| | - Kalle Koskensalo
- Department of Medical Physics, Turku University Hospital, Turku, Finland
| | - Laura Pekkarinen
- Turku PET Centre, University of Turku, Turku, Finland
- Department of Endocrinology, Turku University Hospital, Turku, Finland
| | - Ekaterina Saukko
- Department of Radiology, Turku University Hospital, Turku, Finland
| | - Jukka Ihalainen
- Turku PET Centre, Accelerator Laboratory, Åbo Akademi University, Turku, Finland
| | | | - Jouni Tuisku
- Turku PET Centre, University of Turku, Turku, Finland
| | - Marco Bucci
- Turku PET Centre, University of Turku, Turku, Finland
- Theme Inflammation and Aging, Karolinska University Hospital, Stockholm, Sweden
- Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Stockholm, Sweden
| | - Sanna Laurila
- Turku PET Centre, University of Turku, Turku, Finland
| | - Johan Rajander
- Turku PET Centre, Accelerator Laboratory, Åbo Akademi University, Turku, Finland
| | - Paulina Salminen
- Department of Digestive Surgery and Urology, Turku University Hospital, Turku, Finland
- Department of Surgery, University of Turku, Turku, Finland
| | - Lauri Nummenmaa
- Turku PET Centre, University of Turku, Turku, Finland
- Department of Psychology University of Turku, Turku, Finland
| | - Jacobus FA Jansen
- Department of Radiology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ele Ferrannini
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku, Turku, Finland
- Department of Endocrinology, Turku University Hospital, Turku, Finland
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Ruegsegger GN, Ekholm ER, Monroe CE, Rappaport CI, Huppert RD, Anton CR, Ferguson MJ. Glucose tolerance status associates with improvements in cognitive function following high-intensity exercise in adults with obesity. Physiol Behav 2023; 272:114389. [PMID: 37890604 DOI: 10.1016/j.physbeh.2023.114389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 09/28/2023] [Accepted: 10/24/2023] [Indexed: 10/29/2023]
Abstract
PURPOSE Obesity, insulin resistance (IR), and proinflammatory cytokines associate with cognitive decline. Numerous studies document cognitive benefits of acute exercise bouts in lean individuals. However, how co-morbidities such as obesity and IR influence cognitive changes induced by acute exercise is unclear. We examined the effects of acute high-intensity aerobic exercise on cognitive function in age-matched and BMI-matched obese adults with normal glucose tolerance (NGT) or impaired glucose tolerance (IGT) and in lean, NGT adults. METHODS 49 adults (15 Lean, 18 Obese-NGT, 16 Obese-IGT) performed one session of high-intensity interval exercise (four cycles of 4-min at 75% Wmax with 3-min rest). Cognitive function testing and blood sampling were performed pre- and post-exercise. RESULTS Following exercise, measurements of executive function and working memory were improved in Lean and Obese-NGT (p < 0.05), but not Obese-IGT. Changes in cognitive function following exercise negatively correlated with 2-hr glucose during an OGTT after controlling for body weight and body composition (rp = -0.40, p = 0.007). Serum levels of inflammatory cytokines IL-6 and CRP remained increased 60-minutes post-exercise in Obese-IGT, but not in Lean or Obese-NGT, which positively associated with 2-hr glucose during an OGTT (p < 0.01) and negatively with changes in cognitive function following exercise (p < 0.01). Greater insulin levels in Obese-IGT post-exercise also negatively correlated with changes in cognitive function following exercise (p < 0.01). CONCLUSION Improvements in cognition following acute high-intensity exercise positively associate with glucose tolerance, independent of body weight and body composition. Further, poorer changes in cognitive performance following exercise associate with persistent peripheral inflammation.
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Affiliation(s)
- Gregory N Ruegsegger
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States.
| | - Emily R Ekholm
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
| | - Chandler E Monroe
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
| | - Chapin I Rappaport
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
| | - Rocco D Huppert
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
| | - Caleb R Anton
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
| | - Mia J Ferguson
- Department of Health and Human Performance, University of Wisconsin-River Falls, A173 Falcon Center, 410 S. 3rd St., River Falls, WI, 54022, United States
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Rebelos E, Malloggi E, Parenti M, Dardano A, Tura A, Daniele G. Near-Infrared Spectroscopy: A Free-Living Neuroscience Tool to Better Understand Diabetes and Obesity. Metabolites 2023; 13:814. [PMID: 37512521 PMCID: PMC10384622 DOI: 10.3390/metabo13070814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 06/25/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023] Open
Abstract
The human brain is the least accessible of all organs and attempts to study it in vivo rely predominantly on neuroimaging. Functional near-infrared spectroscopy (fNIRS) allows for the study of cortical neural activity in a non-invasive manner that may resemble free-living conditions. Moreover, compared to other neuroimaging tools, fNIRS is less expensive, it does not require the use of ionizing radiation, and can be applied to all study populations (patients suffering from claustrophobia, or neonates). In this narrative review, we provide an overview of the available research performed using fNIRS in patients with diabetes and obesity. The few studies conducted to date have presented controversial results regarding patients with diabetes, some reporting a greater hemodynamic response and others reporting a reduced hemodynamic response compared to the controls, with an unclear distinction between types 1 and 2. Subjects with obesity or a binge eating disorder have reduced prefrontal activation in response to inhibitory food or non-food stimuli; however, following an intervention, such as cognitive treatment, prefrontal activation is restored. Moreover, we discuss the potential of future applications of fNIRS for a better understanding of cortical neural activity in the context of metabolic disorders.
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Affiliation(s)
- Eleni Rebelos
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Eleonora Malloggi
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Martina Parenti
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
| | - Angela Dardano
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
- CISUP, Center for Instrument Sharing, University of Pisa, 56124 Pisa, Italy
| | - Andrea Tura
- CNR Institute of Neuroscience, 35131 Padova, Italy
| | - Giuseppe Daniele
- Department of Clinical and Experimental Medicine, University of Pisa, 56126 Pisa, Italy
- CISUP, Center for Instrument Sharing, University of Pisa, 56124 Pisa, Italy
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Insulin Resistance and the Brain–Novel Insights Combining Metabolic Research and Neuroscience. Metabolites 2022; 12:metabo12090780. [PMID: 36144185 PMCID: PMC9503398 DOI: 10.3390/metabo12090780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 08/22/2022] [Indexed: 11/23/2022] Open
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Circulating N-Acetylaspartate does not track brain NAA concentrations, cognitive function or features of small vessel disease in humans. Sci Rep 2022; 12:11530. [PMID: 35798828 PMCID: PMC9262942 DOI: 10.1038/s41598-022-15670-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 04/15/2022] [Indexed: 01/07/2023] Open
Abstract
N-acetylaspartate (NAA) is the second most abundant metabolite in the human brain; although it is assumed to be a proxy for a neuronal marker, its function is not fully elucidated. NAA is also detectable in plasma, but its relation to cerebral NAA levels, cognitive performance, or features of cerebral disease has not been investigated. To study whether circulating NAA tracks cerebral NAA levels, and whether circulating NAA correlates with cognitive function and features of cerebral small vessel disease (SVD). Two datasets were analyzed. In dataset 1, structural MRI was acquired in 533 subjects to assess four features of cerebral SVD. Cognitive function was evaluated with standardized test scores (N = 824). In dataset 2, brain 1H-MRS from the occipital region was acquired (N = 49). In all subjects, fasting circulating NAA was measured with mass spectrometry. Dataset 1: in univariate and adjusted for confounders models, we found no correlation between circulating NAA and the examined features of cerebral SVD. In univariate analysis, circulating NAA levels were associated inversely with the speed in information processing and the executive function score, however these associations were lost after accounting for confounders. In line with the negative findings of dataset 1, in dataset 2 there was no correlation between circulating and central NAA or total NAA levels. This study indicates that circulating NAA levels do not reflect central (occipital) NAA levels, cognitive function, or cerebral small vessel disease in man.
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Rebelos E, Rinne JO, Nuutila P, Ekblad LL. Brain Glucose Metabolism in Health, Obesity, and Cognitive Decline-Does Insulin Have Anything to Do with It? A Narrative Review. J Clin Med 2021; 10:jcm10071532. [PMID: 33917464 PMCID: PMC8038699 DOI: 10.3390/jcm10071532] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/01/2021] [Accepted: 04/02/2021] [Indexed: 12/13/2022] Open
Abstract
Imaging brain glucose metabolism with fluorine-labelled fluorodeoxyglucose ([18F]-FDG) positron emission tomography (PET) has long been utilized to aid the diagnosis of memory disorders, in particular in differentiating Alzheimer’s disease (AD) from other neurological conditions causing cognitive decline. The interest for studying brain glucose metabolism in the context of metabolic disorders has arisen more recently. Obesity and type 2 diabetes—two diseases characterized by systemic insulin resistance—are associated with an increased risk for AD. Along with the well-defined patterns of fasting [18F]-FDG-PET changes that occur in AD, recent evidence has shown alterations in fasting and insulin-stimulated brain glucose metabolism also in obesity and systemic insulin resistance. Thus, it is important to clarify whether changes in brain glucose metabolism are just an epiphenomenon of the pathophysiology of the metabolic and neurologic disorders, or a crucial determinant of their pathophysiologic cascade. In this review, we discuss the current knowledge regarding alterations in brain glucose metabolism, studied with [18F]-FDG-PET from metabolic disorders to AD, with a special focus on how manipulation of insulin levels affects brain glucose metabolism in health and in systemic insulin resistance. A better understanding of alterations in brain glucose metabolism in health, obesity, and neurodegeneration, and the relationships between insulin resistance and central nervous system glucose metabolism may be an important step for the battle against metabolic and cognitive disorders.
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Affiliation(s)
- Eleni Rebelos
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
| | - Juha O. Rinne
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
- Department of Endocrinology, Turku University Hospital, 20520 Turku, Finland
| | - Laura L. Ekblad
- Turku PET Centre, University of Turku and Turku University Hospital, 20520 Turku, Finland; (E.R.); (J.O.R.); (P.N.)
- Correspondence: ; Tel.: +358-2-3138721
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Rebelos E, Honka MJ, Ekblad L, Bucci M, Hannukainen JC, Fernandes Silva L, Virtanen KA, Nummenmaa L, Nuutila P. The Obesity Risk SNP (rs17782313) near the MC4R Gene Is Not Associated with Brain Glucose Uptake during Insulin Clamp-A Study in Finns. J Clin Med 2021; 10:jcm10061312. [PMID: 33806715 PMCID: PMC8004974 DOI: 10.3390/jcm10061312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/18/2021] [Accepted: 03/18/2021] [Indexed: 12/03/2022] Open
Abstract
The melanocortin system is involved in the control of adiposity through modulation of food intake and energy expenditure. The single nucleotide polymorphism (SNP) rs17782313 near the MC4R gene has been linked to obesity, and a previous study using magnetoencephalography has shown that carriers of the mutant allele have decreased cerebrocortical response to insulin. Thus, in this study, we addressed whether rs17782313 associates with brain glucose uptake (BGU). Here, [18F]-fluorodeoxyglucose positron emission tomography (PET) data from 113 Finnish subjects scanned under insulin clamp conditions who also had the rs17782313 determined were compiled from a single-center cohort. BGU was quantified by the fractional uptake rate. Statistical analysis was performed with statistical parametric mapping. There was no difference in age, BMI, and insulin sensitivity as indexed by the M value between the rs17782313-C allele carriers and non-carriers. Brain glucose uptake during insulin clamp was not different by gene allele, and it correlated with the M value, in both the rs17782313-C allele carriers and non-carriers. The obesity risk SNP rs17782313 near the MC4R gene is not associated with brain glucose uptake during insulin clamp in humans, and this frequent mutation cannot explain the enhanced brain glucose metabolic rates in insulin resistance.
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Affiliation(s)
- Eleni Rebelos
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
- Correspondence: (E.R.); (P.N.); Tel.: +39-3488454140 (E.R.); +358-2313-1868 (P.N.)
| | | | - Laura Ekblad
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
| | - Marco Bucci
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
- Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Jarna C. Hannukainen
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
| | - Lilian Fernandes Silva
- Institute of Clinical Medicine, Internal Medicine, University of Eastern Finland, 70210 Kuopio, Finland;
| | - Kirsi A. Virtanen
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
| | - Lauri Nummenmaa
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
- Department of Psychology, University of Turku, 20520 Turku, Finland
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku, 20520 Turku, Finland; (L.E.); (M.B.); (J.C.H.); (K.A.V.); (L.N.)
- Department of Endocrinology, Turku University Hospital, 20521 Turku, Finland
- Correspondence: (E.R.); (P.N.); Tel.: +39-3488454140 (E.R.); +358-2313-1868 (P.N.)
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