Elsevier

Neuropeptides

Volume 58, August 2016, Pages 73-81
Neuropeptides

Insulin and IGF-1 regularize energy metabolites in neural cells expressing full-length mutant huntingtin

https://doi.org/10.1016/j.npep.2016.01.009Get rights and content

Highlights

  • HD cortical and striatal cells exhibit decreased ATP/ADP ratio.

  • HD cortical and striatal cells present PDH-related metabolic dysfunction.

  • IGF-1 ameliorates the anomalous pyruvate levels in HD striatal cells.

  • Insulin and IGF-1 rescue energy deficits in YAC128 cortical cells.

Abstract

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder linked to the expression of mutant huntingtin. Bioenergetic dysfunction has been described to contribute to HD pathogenesis. Thus, treatment paradigms aimed to ameliorate energy deficits appear to be suitable candidates in HD. In previous studies, we observed protective effects of insulin growth factor-1 (IGF-1) in YAC128 and R6/2 mice, two HD mouse models, whereas IGF-1 and/or insulin halted mitochondrial-driven oxidative stress in mutant striatal cells and mitochondrial dysfunction in HD human lymphoblasts. Here, we analyzed the effect of IGF-1 versus insulin on energy metabolic parameters using striatal cells derived from HD knock-in mice and primary cortical cultures from YAC128 mice. STHdhQ111/Q111 cells exhibited decreased ATP/ADP ratio and increased phosphocreatine levels. Moreover, pyruvate levels were increased in mutant cells, most probably in consequence of a decrease in pyruvate dehydrogenase (PDH) protein expression and increased PDH phosphorylation, reflecting its inactivation. Insulin and IGF-1 treatment significantly decreased phosphocreatine levels, whereas IGF-1 only decreased pyruvate levels in mutant cells. In a different scenario, primary cortical cultures derived from YAC128 mice also displayed energetic abnormalities. We observed a decrease in both ATP/ADP and phosphocreatine levels, which were prevented following exposure to insulin or IGF-1. Furthermore, decreased lactate levels in YAC128 cultures occurred concomitantly with a decline in lactate dehydrogenase activity, which was ameliorated with both insulin and IGF-1. These data demonstrate differential HD-associated metabolic dysfunction in striatal cell lines and primary cortical cultures, both of which being alleviated by insulin and IGF-1.

Introduction

Huntington's disease (HD) in an autosomal dominant neurodegenerative disorder caused by an abnormal expansion of CAG triplets in the HTT gene, encoding for mutant huntingtin (mHTT in humans, or mHtt in mice). HD clinical symptoms include involuntary movements, dementia, dramatic weight loss, and eventually death. Neuropathologically, HD is characterized by selective dysfunction and death of GABAergic projection medium spiny neurons in the striatum. Moreover, the degree of striatal atrophy correlates with the degeneration of cerebral cortex during the latest stages (Gil and Rego, 2008). Although striatal death underlies many symptoms in advanced stages of the disease (Vonsattel and DiFiglia, 1998), early deficits, which seem to occur years before the evident movement disorder, are more likely associated with neuronal and synaptic dysfunction in the cortex (e.g. Rosas et al., 2005). An expansion of more than 39 CAG repeats in the HTT gene underlies several mechanisms of neurodegeneration, such as oxidative stress, mitochondrial dysfunction, and deficits in energy metabolism (Naia et al., 2011). In particular, mHTT impairs mitochondrial respiration and ATP production (Milakovic and Johnson, 2005, Seong et al., 2005, Silva et al., 2013). Elevated levels of lactate were also detected in the striatum and cerebral cortex of HD patients (Koroshetz et al., 1997, Jenkins et al., 1998), as well as decreased ATP and phosphocreatine (PCr) levels following glycolysis inhibition in HD cybrids, exhibiting bioenergetically dysfunctional mitochondria (Ferreira et al., 2011). Additionally, a diversity of metabolic enzymes are altered in HD, namely, pyruvate dehydrogenase (PDH) (Perluigi et al., 2005, Ferreira et al., 2011), pyruvate carboxylase (PC) (Butterworth, 1986, Lee et al., 2013), glucose-6-phosphate dehydrogenase (Ferreira et al., 2011), aconitase (Tabrizi et al., 2000), and aspartate aminotransferase (Perluigi et al., 2005).

During the last few years, our group analyzed the effects of insulin and insulin-like growth factor 1 (IGF-1) in HD, from peripheral to neural cells and also in in vivo models. The insulin/IGF-1 signaling has been studied for many years in several neurodegenerative disorders linked to toxic protein aggregation, but it has generated conflicting results. While some studies demonstrated that IGF-1 modulates the clearance of brain aggregation-prone proteins, such as amyloid-β peptide (Carro et al., 2002) or mHTT (Humbert et al., 2002), other authors claimed that reduced insulin/IGF-1 signaling regulate disaggregation of amyloid-β peptide, ataxin-3, and other polyglutamine proteins to promote cell survival (Morley et al., 2002, Cohen et al., 2006, Kapperler et al., 2008, Teixeira-Castro et al., 2011). Indeed, IGF-1 signaling was described to be deleterious in the regulation of lifespan in nematodes (Kenyon et al., 1993) and mouse models (Holzenberger et al., 2003); however, the ablation of IGF-1 or its receptor promoted brain growth retardation (D'Ercole et al., 2002), indicating that IGF-1 may stimulate neuronal development. A more recent study found no measurable effect between the inhibition of insulin/IGF-1 pathway and the decreased mHTT aggregation (Jakubik et al., 2014). Even so, IGF-1 plasma levels were shown to be increased in YAC128 mice (expressing human full-length mHTT), correlating with increased body weight (Pouladi et al., 2010), and high IGF-1 levels were associated with cognitive decline in HD patients (Saleh et al., 2010).

Counterweighting the previous data, recent findings in our group showed that peripheral administration of IGF-1 prevented metabolic abnormalities in a hemizygous R6/2 mouse model of HD, such as impaired glucose tolerance and age-related decrease in body weight by enriching blood insulin and IGF-1 levels (Duarte et al., 2011). Indeed, both insulin and IGF-1 may activate insulin/IGF-1 receptor (IR/IGF-1R), stimulating PI-3K/Akt signaling pathways, through direct phosphorylation of HTT by Akt at serine 421 (Humbert et al., 2002), which appears to promote mitochondrial function and modulate the expression of proteins involved in glucose metabolism and anti-apoptotic mechanisms (Duarte et al., 2008, Naia et al., 2015). The activation of the same pathway also counteracted the increase in lactate/pyruvate ratio in both YAC128 mice (Lopes et al., 2014) and HD human lymphoblasts (Naia et al., 2015). In addition, we showed that the activation of IGF-1/insulin signaling pathways in striatal cells expressing 111 glutamines precludes mitochondrial generation of reactive oxygen species and mitochondrial dysfunction, largely reducing apoptotic and senescent cells induced by mHtt expression (Ribeiro et al., 2014). Nevertheless, it remained unknown whether the improvement in mitochondrial function would also be linked to an improvement in cell bioenergetics. Therefore, we hypothesized that insulin or IGF-1 treatment could ameliorate metabolic function in the context of HD. Here, we show that both insulin and IGF-1 can rescue energy deficits in YAC128 primary cortical cells by ameliorating ATP, PCr, and lactate levels, the later involving modified lactate dehydrogenase (LDH) activity. Furthermore, IGF-1 alleviates anomalous pyruvate levels in homozygous STHdhQ111/Q111 striatal cells derived from HD knock-in mice.

Section snippets

Materials

Fetal bovine serum (FBS), B27 supplement and penicillin/streptomycin were from Gibco (Paisley, Scotland, UK). Insulin from porcine pancreas, DMEM medium, trypsin-type IX-S from porcine pancreas, IGF-1, glucose-6-phosphate, deoxy-d-glucose (DG), l-glutamine, poly-l-lysine, fatty acid free bovine serum albumin (BSA), trypan blue (0.4%), resazurin, adenine dinucleotide phosphate hydrate (NADP), nicotinamide adenine dinucleotide hydrate (NAD), ADP, glucose 6 phosphate dehydrogenase (G6P-DH),

Insulin and IGF-1 restore energy metabolic parameters in primary cortical cultures derived from YAC128 mice

We started by characterizing the energy levels in YAC128 versus wild-type mice primary cortical cells exhibiting similar levels of HTT protein (Supplementary Fig. S1). In these cells, we found a significant decrease in ATP/ADP ratio (Fig. 1A) that was accompanied by an increase in AMP levels (data not shown). Decreased ATP/ADP ratio was restored after insulin or IGF-1 (1 nM) exposure (Fig. 1A). Importantly, due to structural homology, insulin and IGF-1 can bind and activate both IR and IGF-1R,

Discussion

Under a great controversy (Carro et al., 2002, Morley et al., 2002, Cohen et al., 2006, Kapperler et al., 2008), insulin and IGF-1 have demonstrated important effects in the central nervous system, including neuronal survival, learning and memory, and animal life span (D'Ercole et al., 2002, Zemva and Schubert, 2014). Moreover, these peptides have been previously described to stimulate glucose uptake and intracellular metabolism in peripheral tissues (Andreassen et al., 2002, Duarte et al., 2011

Conflict of interest

The authors declare that there are no conflict of interests regarding this study.

Acknowledgements

This work was supported by “Fundação para a Ciência e Tecnologia” (FCT), Portugal, grant referencePTDC/SAU-FCF/66421/2006 and PTDC/SAU-FCF/108056/2008, and co-financed by COMPETE-“Programa Operacional Factores de Competitividade”, QREN, and the European Union (FEDER-“Fundo Europeu de Desenvolvimento Regional”). CNC was supported by project PEst-C/SAU/LA0001/2013-2014. L. Naia, M. Ribeiro, and C. Lopes are/were supported by Ph.D. fellowships from FCT (SFRH/BD/86655/2012, SFRH/BD/41285/899/2007,

References (52)

  • F. Mochel et al.

    Early alterations of brain cellular energy homeostasis in Huntington's disease models

    J. Biol. Chem.

    (2012)
  • M. Perluigi et al.

    Proteomic analysis of protein expression and oxidative modification in R6/2 transgenic mice: a model of Huntington disease

    Mol. Cell. Proteomics

    (2005)
  • M. Ribeiro et al.

    Insulin and IGF-1 improve mitochondrial function in a PI-3K/Akt-dependent manner and reduce mitochondrial generation of reactive oxygen species in Huntington's disease knock-in striatal cells

    Free Radic. Biol. Med.

    (2014)
  • H. Ryu et al.

    The therapeutic role of creatine in Huntington's disease

    Pharmacol. Ther.

    (2005)
  • A.C. Silva et al.

    Mitochondrial respiratory chain complex activity and bioenergetic alterations in human platelets derived from pre-symptomatic and symptomatic Huntington's disease carriers

    Mitochondrion

    (2013)
  • V. Stocchi et al.

    Simultaneous extraction and reverse-phase high-performance liquid chromatographic determination of adenine and pyridine nucleotides in human red blood cells

    Anal. Biochem.

    (1985)
  • J. Butterworth

    Changes in nine enzyme markers for neurons, glia, and endothelial cells in agonal state and Huntington's disease caudate nucleus

    J. Neurochem.

    (1986)
  • E. Carro et al.

    Serum insulin-like growth factor I regulates brain amyloid-beta levels

    Nat. Med.

    (2002)
  • E. Cohen et al.

    Opposing activities protect against age-onset proteotoxicity

    Science

    (2006 Sep 15)
  • A. Dedeoglu et al.

    Creatine therapy provides neuroprotection after onset of clinical symptoms in Huntington's disease transgenic mice

    J. Neurochem.

    (2002)
  • A.J. D'Ercole et al.

    Mutant mouse models of insulin-like growth factor actions in the central nervous system

    Neuropeptides

    (2002)
  • M. Gårseth et al.

    Proton magnetic resonance spectroscopy of cerebrospinal fluid in neurodegenerative disease: indication of glial energy impairment in Huntington chorea, but not Parkinson disease

    J. Neurosci. Res.

    (2000)
  • J.M. Gil et al.

    Mechanisms of neurodegeneration in Huntington's disease

    Eur. J. Neurosci.

    (2008)
  • S. Gines et al.

    Specific progressive cAMP reduction implicates energy deficit in presymptomatic Huntington's disease knock-in mice

    Hum. Mol. Genet.

    (2003)
  • M. Holzenberger et al.

    IGF-1 receptor regulates lifespan and resistance to oxidative stress in mice

    Nature

    (2003)
  • B.G. Jenkins et al.

    Evidence for impairment of energy metabolism in vivo in Huntington's disease using localized 1 H NMR spectroscopy

    Neurology

    (1993)
  • Cited by (27)

    • Autonomous regulation of retinal insulin biosynthesis in diabetes

      2022, Neuropeptides
      Citation Excerpt :

      Although insulin is involved in glucose metabolism, the brain was considered an insulin insensitive organ. It is now argued that insulin facilitates critical brain functions like metabolism, cognition and motivated behaviors in the CNS, along with being a potent mitogenic and neurotrophic factor (Ferrario and Reagan, 2018; Mielke and Wang, 2005; Abbott et al., 1999; Wu et al., 2004; Naia et al., 2016). Anatomically and developmentally, the retina is known as an extension of the CNS; it consists of retinal ganglion cells, the axons of which form the optic nerve, whose fibers are, in effect, CNS axons (London et al., 2013).

    • Insulin-like growth factor 1 signaling in motor neuron and polyglutamine diseases: From molecular pathogenesis to therapeutic perspectives

      2020, Frontiers in Neuroendocrinology
      Citation Excerpt :

      Both insulin and IGF-I restored phosphocreatine levels, whereas only IGF-I decreased pyruvate levels. The reduction in ATP/ADP and phosphocreatine levels were rescued after exposure to insulin or IGF-I (Naia et al., 2016). The effect of IGF-I in different HD models seems to be protective, suggesting therapeutic potential for IGF-I also in this fatal polyQ disease.

    • Intranasal insulin treatment modulates the neurotropic, inflammatory, and oxidant mechanisms in the cortex and hippocampus in a low-grade inflammation model

      2020, Peptides
      Citation Excerpt :

      Microglia cells can also enhance the release of neurotrophic factors, such as insulin-like growth factor 1, and anti-inflammatory interleukins (IL-4 and IL-10) to assist the inflammation resolution and promote neuron survival [11,12]. Insulin has important regulatory effects in the CNS, including metabolic [13], cognitive [14], and electrophysiological [15], and normalizes the brain function in neurological disease models [16]. Insulin has been shown to act on all brain cell types, including neurons, astrocytes, oligodendrocytes, and microglia, which all express insulin receptors [17].

    • Insulin-like growth factor-1 activates AMPK to augment mitochondrial function and correct neuronal metabolism in sensory neurons in type 1 diabetes

      2019, Molecular Metabolism
      Citation Excerpt :

      A well-characterized upstream activator of AMPK is Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ) [31]. A small range of studies have demonstrated that IGF-1 can regulate cellular metabolism and bioenergetics in neurons and astrocytes and protect against Huntington's disease [32–35]. In human tissues derived from persons with diabetes there is down-regulation of the AMPK/PGC-1α pathway [36,37].

    • Alterations in the metabolic and cardiorespiratory response to exercise in Huntington's Disease

      2018, Parkinsonism and Related Disorders
      Citation Excerpt :

      A comprehensive large-scale study is required to unpick medication effects, with the metabolic consequences of drugs in the same sub-class varying substantially due to differences in receptor pharmacology. Metabolic deficits observed in animal models and cell cultures of HD suggest that observed effects are not purely driven by medication [27,28], however they may account for some variability in exercise prescription responses. Overall, we have demonstrated that metabolic and cardiorespiratory deficits contribute towards a reduced exercise performance and affects recovery in HD.

    View all citing articles on Scopus
    1

    The authors contributed equally for this work.

    View full text