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Cardoso S, Santos MS, Moreno A, Moreira PI. UCP2 and ANT differently modulate proton-leak in brain mitochondria of long-term hyperglycemic and recurrent hypoglycemic rats. J Bioenerg Biomembr 2013; 45:397-407. [PMID: 23504111 DOI: 10.1007/s10863-013-9503-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 02/06/2013] [Indexed: 01/20/2023]
Abstract
A growing body of evidence suggests that mitochondrial proton-leak functions as a regulator of reactive oxygen species production and its modulation may limit oxidative injury to tissues. The main purpose of this work was to characterize the proton-leak of brain cortical mitochondria from long-term hyperglycemic and insulin-induced recurrent hypoglycemic rats through the modulation of the uncoupling protein 2 (UCP2) and adenine nucleotide translocator (ANT). Streptozotocin-induced diabetic rats were treated subcutaneously with twice-daily insulin injections during 2 weeks to induce the hypoglycemic episodes. No differences in the basal proton-leak, UCP2 and ANT protein levels were observed between the experimental groups. Mitochondria from recurrent hypoglycemic rats presented a decrease in proton-leak in the presence of GDP, a specific UCP2 inhibitor, while an increase in proton-leak was observed in the presence of linoleic acid, a proton-leak activator, this effect being reverted by the simultaneous addition of GDP. Mitochondria from long-term hyperglycemic rats showed an enhanced susceptibility to ANT modulation as demonstrated by the complete inhibition of basal and linoleic acid-induced proton-leak caused by the ANT specific inhibitor carboxyatractyloside. Our results show that recurrent-hypoglycemia renders mitochondria more susceptible to UCPs modulation while the proton-leak of long-term hyperglycemic rats is mainly modulated by ANT, which suggest that brain cortical mitochondria have distinct adaptation mechanisms in face of different metabolic insults.
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Affiliation(s)
- Susana Cardoso
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517, Coimbra, Portugal
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52
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Alves MG, Martins AD, Rato L, Moreira PI, Socorro S, Oliveira PF. Molecular mechanisms beyond glucose transport in diabetes-related male infertility. Biochim Biophys Acta Mol Basis Dis 2013; 1832:626-35. [PMID: 23348098 DOI: 10.1016/j.bbadis.2013.01.011] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 01/15/2013] [Indexed: 02/06/2023]
Abstract
Diabetes mellitus (DM) is one of the greatest public health threats in modern societies. Although during a few years it was suggested that DM had no significant effect in male reproductive function, this view has been challenged in recent years. The increasing incidence of DM worldwide will inevitably result in a higher prevalence of this pathology in men of reproductive age and subfertility or infertility associated with DM is expected to dramatically rise in upcoming years. From a clinical perspective, the evaluation of semen parameters, as well as spermatozoa deoxyribonucleic acid (DNA) integrity, are often studied due to their direct implications in natural and assisted conception. Nevertheless, recent studies based on the molecular mechanisms beyond glucose transport in testicular cells provide new insights in DM-induced alterations in male reproductive health. Testicular cells have their own glucose sensing machinery that react to hormonal fluctuations and have several mechanisms to counteract hyper- and hypoglycemic events. Moreover, the metabolic cooperation between testicular cells is crucial for normal spermatogenesis. Sertoli cells (SCs), which are the main components of blood-testis barrier, are not only responsible for the physical support of germ cells but also for lactate production that is then metabolized by the developing germ cells. Any alteration in this tied metabolic cooperation may have a dramatic consequence in male fertility potential. Therefore, we present an overview of the clinical significance of DM in the male reproductive health with emphasis on the molecular mechanisms beyond glucose fluctuation and transport in testicular cells.
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Affiliation(s)
- M G Alves
- University of Beira Interior, Covilhã, Portugal.
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53
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Duarte AI, Candeias E, Correia SC, Santos RX, Carvalho C, Cardoso S, Plácido A, Santos MS, Oliveira CR, Moreira PI. Crosstalk between diabetes and brain: glucagon-like peptide-1 mimetics as a promising therapy against neurodegeneration. Biochim Biophys Acta Mol Basis Dis 2013; 1832:527-41. [PMID: 23314196 DOI: 10.1016/j.bbadis.2013.01.008] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/18/2012] [Accepted: 01/06/2013] [Indexed: 12/14/2022]
Abstract
According to World Health Organization estimates, type 2 diabetes (T2D) is an epidemic (particularly in under development countries) and a socio-economic challenge. This is even more relevant since increasing evidence points T2D as a risk factor for Alzheimer's disease (AD), supporting the hypothesis that AD is a "type 3 diabetes" or "brain insulin resistant state". Despite the limited knowledge on the molecular mechanisms and the etiological complexity of both pathologies, evidence suggests that neurodegeneration/death underlying cognitive dysfunction (and ultimately dementia) upon long-term T2D may arise from a complex interplay between T2D and brain aging. Additionally, decreased brain insulin levels/signaling and glucose metabolism in both pathologies further suggests that an effective treatment strategy for one disorder may be also beneficial in the other. In this regard, one such promising strategy is a novel successful anti-T2D class of drugs, the glucagon-like peptide-1 (GLP-1) mimetics (e.g. exendin-4 or liraglutide), whose potential neuroprotective effects have been increasingly shown in the last years. In fact, several studies showed that, besides improving peripheral (and probably brain) insulin signaling, GLP-1 analogs minimize cell loss and possibly rescue cognitive decline in models of AD, Parkinson's (PD) or Huntington's disease. Interestingly, exendin-4 is undergoing clinical trials to test its potential as an anti-PD therapy. Herewith, we aim to integrate the available data on the metabolic and neuroprotective effects of GLP-1 mimetics in the central nervous system (CNS) with the complex crosstalk between T2D-AD, as well as their potential therapeutic value against T2D-associated cognitive dysfunction.
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Affiliation(s)
- A I Duarte
- Life Sciences Department, University of Coimbra, Largo Marquês de Pombal, Coimbra, Portugal.
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Participation of antioxidant and cholinergic system in protective effect of naringenin against type-2 diabetes-induced memory dysfunction in rats. Neuroscience 2012; 226:62-72. [PMID: 22999973 DOI: 10.1016/j.neuroscience.2012.09.026] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 08/30/2012] [Accepted: 09/11/2012] [Indexed: 11/21/2022]
Abstract
Naringenin is a flavone flavonoid possessing antidiabetic, antioxidant and memory improving effects. Therefore, we studied the influence of naringenin against type-2 diabetes-induced memory dysfunction in rats. Type-2 diabetes was induced by high-fat diet and high-fat emulsion for two weeks and a low dose of streptozotocin (35 mg/kg). The memory deficit was assessed by using a novel object recognition paradigm. The changes in oxidative markers and cholinesterase (ChE) levels were evaluated in the hippocampal region. After confirmation of diabetes, naringenin (50mg/kg) treatment was given to animals as a preventive and in another set of experiments naringenin (25 and 50mg/kg) or pioglitazone (5mg/kg) or donepezil (3mg/kg) treatments were started after long-standing diabetes (4 weeks after confirmation). Both the treatment schedules show significant protection and improvement in cognitive behavior against diabetes-induced memory dysfunction and biochemical changes. Also, treatment with pioglitazone and donepezil improved memory performance in rats. Naringenin was found to decrease oxidative stress by depleting elevated lipid peroxide and nitric oxide and elevating reduced glutathione levels. Cholinergic function was improved by naringenin through the inhibition of elevated ChE activity. In conclusion, the present study suggests that naringenin acts as an antioxidant and ChE inhibitor against type-2 diabetes-induced memory dysfunction.
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55
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Cardoso S, Santos RX, Correia SC, Carvalho C, Santos MS, Baldeiras I, Oliveira CR, Moreira PI. Insulin-induced recurrent hypoglycemia exacerbates diabetic brain mitochondrial dysfunction and oxidative imbalance. Neurobiol Dis 2012; 49:1-12. [PMID: 22940631 DOI: 10.1016/j.nbd.2012.08.008] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 07/21/2012] [Accepted: 08/16/2012] [Indexed: 12/17/2022] Open
Abstract
Intensive insulin therapy can prevent or slow the progression of long-term diabetes complications but, at the same time, it increases the risk for episodes of severe hypoglycemia. In our study, we used a protocol intended to mimic the levels of blood glucose that occur in type 1 diabetic patients under an intensive insulin therapy. Streptozotocin (STZ)-induced diabetic rats were treated subcutaneously with twice-daily insulin injections for 2weeks to induce hypoglycemic episodes. Brain cortical and hippocampal mitochondria were isolated and mitochondrial bioenergetics (respiratory chain and phosphorylation system) and oxidative status parameters (malondialdehyde (MDA) levels, mitochondrial aconitase activity and enzymatic and non-enzymatic antioxidant defenses) were analyzed. The protein levels of synaptophysin, a marker of synaptic integrity, and caspase 9 activity were also evaluated in cortical and hippocampal homogenates. Brain cortical mitochondria isolated from hyper- and recurrent hypoglycemic animals presented higher levels of MDA and α-tocopherol together with an increased glutathione disulfide reductase activity, lower manganese superoxide dismutase (MnSOD) activity and glutathione-to-glutathione disulfide (GSH/GSSG) ratio. No significant alterations were found in cortical mitochondrial respiratory chain and oxidative phosphorylation system. Hippocampal mitochondria from both experimental groups presented an impaired oxidative phosphorylation system characterized by a decreased mitochondrial energization potential and ATP levels and higher repolarization lag phase. In addition, higher MDA levels and decreased GSH/GSSG, α-tocopherol levels, and aconitase, glutathione peroxidase and MnSOD activities were observed in both groups of animals. Hippocampal mitochondria from recurrent hypoglycemic animals also showed an impairment of the respiratory chain characterized by a lower state 3 of respiration, respiratory control ratio and ADP/O index, and a higher state 4 of respiration. Additionally, a non-statistically significant decrease in synaptophysin protein levels was observed in cortical homogenates from recurrent hypoglycemic rats as well as in hippocampal homogenates from hyperglycemic and recurrent hypoglycemic rats. An increase in caspase 9 activity was also observed in hippocampal homogenates from hyperglycemic and recurrent hypoglycemic animals. Our results show that mitochondrial dysfunction induced by long-term hyperglycemic effects is exacerbated by recurrent hypoglycemia, which may compromise the function and integrity of brain cells.
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Affiliation(s)
- Susana Cardoso
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
| | - Renato X Santos
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
| | - Sónia C Correia
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
| | - Cristina Carvalho
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
| | - Maria S Santos
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Department of Life Sciences, Faculty of Sciences and Technology, University of Coimbra, Portugal
| | - Inês Baldeiras
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Laboratory of Neurochemistry, Coimbra University Hospital, Portugal; Neurology Department, Faculty of Medicine, University of Coimbra, Portugal
| | - Catarina R Oliveira
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Portugal
| | - Paula I Moreira
- Center for Neuroscience and Cell Biology, University of Coimbra, Portugal; Institute of Physiology, Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal.
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56
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Russo VC, Higgins S, Werther GA, Cameron FJ. Effects of Fluctuating Glucose Levels on Neuronal Cells In Vitro. Neurochem Res 2012; 37:1768-82. [DOI: 10.1007/s11064-012-0789-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 04/12/2012] [Accepted: 04/24/2012] [Indexed: 12/29/2022]
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Duarte AI, Moreira PI, Oliveira CR. Insulin in central nervous system: more than just a peripheral hormone. J Aging Res 2012; 2012:384017. [PMID: 22500228 PMCID: PMC3303591 DOI: 10.1155/2012/384017] [Citation(s) in RCA: 179] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 10/12/2011] [Accepted: 11/23/2011] [Indexed: 12/14/2022] Open
Abstract
Insulin signaling in central nervous system (CNS) has emerged as a novel field of research since decreased brain insulin levels and/or signaling were associated to impaired learning, memory, and age-related neurodegenerative diseases. Thus, besides its well-known role in longevity, insulin may constitute a promising therapy against diabetes- and age-related neurodegenerative disorders. More interestingly, insulin has been also faced as the potential missing link between diabetes and aging in CNS, with Alzheimer's disease (AD) considered as the "brain-type diabetes." In fact, brain insulin has been shown to regulate both peripheral and central glucose metabolism, neurotransmission, learning, and memory and to be neuroprotective. And a future challenge will be to unravel the complex interactions between aging and diabetes, which, we believe, will allow the development of efficient preventive and therapeutic strategies to overcome age-related diseases and to prolong human "healthy" longevity. Herewith, we aim to integrate the metabolic, neuromodulatory, and neuroprotective roles of insulin in two age-related pathologies: diabetes and AD, both in terms of intracellular signaling and potential therapeutic approach.
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Affiliation(s)
- Ana I. Duarte
- CNC, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Paula I. Moreira
- CNC, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
- Institute of Physiology, Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal
| | - Catarina R. Oliveira
- CNC, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
- Institute of Biochemistry, Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal
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Correia SC, Santos RX, Carvalho C, Cardoso S, Candeias E, Santos MS, Oliveira CR, Moreira PI. Insulin signaling, glucose metabolism and mitochondria: major players in Alzheimer's disease and diabetes interrelation. Brain Res 2012; 1441:64-78. [PMID: 22290178 DOI: 10.1016/j.brainres.2011.12.063] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 11/07/2011] [Accepted: 12/31/2011] [Indexed: 12/24/2022]
Abstract
Many epidemiological studies have shown that diabetes, particularly type 2 diabetes, significantly increases the risk to develop Alzheimer's disease. Both diseases share several common abnormalities including impaired glucose metabolism, increased oxidative stress, insulin resistance and deposition of amyloidogenic proteins. It has been suggested that these two diseases disrupt common cellular and molecular pathways and each disease potentiates the progression of the other. This review discusses clinical and biochemical features shared by Alzheimer's disease and diabetes, giving special attention to the involvement of insulin signaling, glucose metabolism and mitochondria. Understanding the key mechanisms underlying this deleterious interaction may provide opportunities for the design of effective therapeutic strategies.
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Affiliation(s)
- Sónia C Correia
- Center for Neuroscience and Cell Biology, University of Coimbra, 3000-354 Coimbra, Portugal
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Chandrasekaran K, Swaminathan K, Kumar SM, Clemens DL, Dey A. Increased oxidative stress and toxicity in ADH and CYP2E1 overexpressing human hepatoma VL-17A cells exposed to high glucose. Integr Biol (Camb) 2012; 4:550-63. [DOI: 10.1039/c2ib00155a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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60
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Cardoso S, Santos RX, Carvalho C, Correia S, Santos MS, Moreira PI. Mitochondrial Uncoupling Proteins and Oxidative Stress: Implications for Diabetes and Neurodegeneration. ACTA ACUST UNITED AC 2011. [DOI: 10.5530/ax.2011.2.3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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61
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Silverstein JM, Musikantow D, Puente EC, Daphna-Iken D, Bree AJ, Fisher SJ. Pharmacologic amelioration of severe hypoglycemia-induced neuronal damage. Neurosci Lett 2011; 492:23-8. [PMID: 21272612 DOI: 10.1016/j.neulet.2011.01.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 01/19/2011] [Indexed: 10/18/2022]
Abstract
Hypoglycemia is a common complication for insulin treated people with diabetes. Severe hypoglycemia, which occurs in the setting of excess or ill-timed insulin administration, has been shown to cause brain damage. Previous pre-clinical studies have shown that memantine (an N-methyl-d-aspartate receptor antagonist) and erythropoietin can be neuroprotective in other models of brain injury. We hypothesized that these agents might also be neuroprotective in response to severe hypoglycemia-induced brain damage. To test this hypothesis, 9-week old, awake, male Sprague-Dawley rats underwent hyperinsulinemic (0.2 U kg(-1)min(-1)) hypoglycemic clamps to induce severe hypoglycemia (blood glucose 10-15 mg/dl for 90 min). Animals were randomized into control (vehicle) or pharmacological treatments (memantine or erythropoietin). One week after severe hypoglycemia, neuronal damage was assessed by Fluoro-Jade B and hematoxylin and eosin staining of brain sections. Treatment with both memantine and erythropoietin significantly decreased severe hypoglycemia-induced neuronal damage in the cortex by 35% and 39%, respectively (both p<0.05 vs. controls). These findings demonstrate that memantine and erythropoietin provide a protective effect against severe hypoglycemia-induced neuronal damage.
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Affiliation(s)
- Julie M Silverstein
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine,Washington University, St. Louis, MO 63110, USA
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62
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Cardoso S, Carvalho C, Santos R, Correia S, Santos MS, Seiça R, Oliveira CR, Moreira PI. Impact of STZ-induced hyperglycemia and insulin-induced hypoglycemia in plasma amino acids and cortical synaptosomal neurotransmitters. Synapse 2010; 65:457-66. [PMID: 20853444 DOI: 10.1002/syn.20863] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Accepted: 08/25/2010] [Indexed: 01/21/2023]
Abstract
In this work, we evaluated the effects of streptozotocin (STZ)-induced hyperglycemia and an acute episode of insulin-induced hypoglycemia in plasma amino acids and cortical neurotransmitters. For that purpose, we used citrate (vehicle)-treated Wistar rats, STZ-treated rats [i.p., 50 mg/kg body weight], and STZ-treated rats injected with insulin [s.c., dose adjusted with blood glucose levels] 1 h prior to sacrifice to induce an acute episode of hypoglycemia. Plasma was collected for determination of amino acids levels. In addition, cortical synaptosomal preparations were obtained and the total levels of neurotransmitters, levels of aspartate, glutamate, taurine, and GABA released by the action of KCl, iodoacetic acid (IAA), ouabain, and veratridine, membrane potential and ATP levels were evaluated. Compared with control rats, plasma from hypoglycemic rats presented increased levels of aspartate, glutamate, glutamine, and taurine whereas GABA levels were decreased in STZ and hypoglycemic rats. Similarly, glutamate and taurine levels were increased in hypoglycemic synaptosomes while GABA decreased in hypoglycemic and STZ-diabetic synaptosomes. The depolarizing agent KCl promoted an increase in aspartate, glutamate, and taurine release from hypoglycemic synaptosomes. The highest release of neurotransmitters occurred in the presence of veratridine and ouabain, two other depolarizing agents, in all groups of experimental animals. However, a higher release of glutamate was observed in the diabetic and hypoglycemic synaptosomes. No alterations were observed in synaptosomal membrane potential and ATP levels. These results show that in the presence of a metabolic insult a higher release of excitatory amino acids occurs, which may underlay the neuronal injury observed in type 1 diabetic patients under insulin therapy.
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Affiliation(s)
- Susana Cardoso
- Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
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