Cognitive and behavioral improvement in adults with fragile X syndrome treated with metformin-two cases

State-of-the-art therapies for fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by a full mutation (> 200 CGG repeats) in the FMR1 gene. FXS is the leading cause of inherited intellectual disabilities and the most commonly known genetic cause of autism spectrum disorder. Children with FXS experience behavioral and sleep problems, anxiety, inattention, learning difficulties, and speech and language delays. There are no approved medications for FXS; however, there are several interventions and treatments aimed at managing the symptoms and improving the quality of life of individuals with FXS. A combination of non-pharmacological therapies and pharmacotherapy is currently the most effective treatment for FXS. Currently, several targeted treatments, such as metformin, sertraline, and cannabidiol, can be used by clinicians to treat FXS. Gene therapy is rapidly developing and holds potential as a prospective treatment option. Soon its efficacy and safety in patients with FXS will be demonstrated. WHAT THIS PAPER ADDS: Targeted treatment of fragile X syndrome (FXS) is the best current therapeutic approach. Gene therapy holds potential as a prospective treatment for FXS in the future.

Longitudinal follow-up of metformin treatment in Fragile X Syndrome

Introduction

Metformin has been used as a targeted treatment to potentially improve cognition and slow the typical IQ decline that occurs during development among individuals with fragile X syndrome (FXS). In this follow-up study, we are following the trajectory of IQ and adaptive behavior changes over 1 to 3 years in individuals with FXS who are clinically treated with metformin in an open label trial.

Method

Individuals with FXS ages 6 to 25 years (mean 13.15 ± 5.50) and nonverbal IQ mean 57.69 (±15.46) were treated for 1-3 years (1.88 ± 0.63). They all had a baseline IQ test using the Leiter-III non-verbal cognitive assessment and the Vineland-III adaptive behavior assessment before the start of metformin. Repeat Leiter-III and Vineland-III were completed after at least 1 year of metformin (500-1,000 mg/dose given twice a day).

Result

There were no significant changes in non-verbal IQ or in the adaptive behavior measurements at FDR < 0.05. The findings thus far indicate that both IQ and adaptive behavior are stable over time, and we did not see a significant decline in either measure.

Conclusion

Overall, the small sample size and short follow-up duration limit the interpretation of the effects of metformin on cognitive development and adaptive functioning. There is individual variability but overall for the group there was no significant decline in IQ or adaptive behavior.

A Comprehensive Review of Fragile X Syndrome and Fragile X Premutation Associated Conditions in Africa

Fragile X syndrome (FXS) is a genetic disorder caused by a mutation in the fragile X messenger ribonucleoprotein 1 (FMR1) gene and known to be a leading cause of inherited intellectual disability globally. It results in a range of intellectual, developmental, and behavioral problems. Fragile X premutation-associated conditions (FXPAC), caused by a smaller CGG expansion (55 to 200 CGG repeats) in the FMR1 gene, are linked to other conditions that increase morbidity and mortality for affected persons. Limited research has been conducted on the burden, characteristics, diagnosis, and management of these conditions in Africa. This comprehensive review provides an overview of the current literature on FXS and FXPAC in Africa. The issues addressed include epidemiology, clinical features, discrimination against affected persons, limited awareness and research, and poor access to resources, including genetic services and treatment programs. This paper provides an in-depth analysis of the existing worldwide data for the diagnosis and treatment of fragile X disorders. This review will improve the understanding of FXS and FXPAC in Africa by incorporating existing knowledge, identifying research gaps, and potential topics for future research to enhance the well-being of individuals and families affected by FXS and FXPAC.

An Update on Psychopharmacological Treatment of Autism Spectrum Disorder

While behavioral interventions remain the mainstay of treatment of autism spectrum disorder (ASD), several potential targeted treatments addressing the underlying neurophysiology of ASD have emerged in the last few years. These are promising for the potential to, in future, become part of the mainstay treatment in addressing the core symptoms of ASD. Although it is likely that the development of future targeted treatments will be influenced by the underlying heterogeneity in etiology, associated genetic mechanisms influencing ASD are likely to be the first targets of treatments and even gene therapy in the future for ASD. In this article, we provide a review of current psychopharmacological treatment in ASD including those used to address common comorbidities of the condition and upcoming new targeted approaches in autism management. Medications including metformin, arbaclofen, cannabidiol, oxytocin, bumetanide, lovastatin, trofinetide, and dietary supplements including sulforophane and N-acetylcysteine are discussed. Commonly used medications to address the comorbidities associated with ASD including atypical antipsychotics, serotoninergic agents, alpha-2 agonists, and stimulant medications are also reviewed. Targeted treatments in Fragile X syndrome (FXS), the most common genetic disorder leading to ASD, provide a model for new treatments that may be helpful for other forms of ASD. Appeared originally in Neurotherapeutics 2022; 19:248-262.

Off-label psychopharmacological interventions for autism spectrum disorders: strategic pathways for clinicians

The prevalence of autism spectrum disorder (ASD) continues to see a trend upward with a noticeable increase to 1 in 36 children less than 8 years of age in the recent MMWR. There are many factors linked to the substantially increased burden of seeking mental health services, and clinically these individuals are likely to present for impairments associated with co-occurring conditions. The advances in cutting-edge research and the understanding of co-occurring conditions in addition to psychosocial interventions have provided a window of opportunity for psychopharmacological interventions given the limited availability of therapeutics for core symptomatology. The off-label psychopharmacological treatments for these co-occurring conditions are central to clinical practice. However, the scattered evidence remains an impediment for practitioners to systematically utilize these options. The review collates the crucial scientific literature to provide stepwise treatment alternatives for individuals with ASD; with an aim to lead practitioners in making informed and shared decisions. There are many questions about the safety and tolerability of off-label medications; however, it is considered the best practice to utilize the available empirical data in providing psychoeducation for patients, families, and caregivers. The review also covers experimental medications and theoretical underpinnings to enhance further experimental studies. In summary, amidst the growing clinical needs for individuals with ASD and the lack of approved clinical treatments, the review addresses these gaps with a practical guide to appraise the risk and benefits of off-label medications.

Fragile X Syndrome in children

Fragile X syndrome is caused by the expansion of CGG triplets in the FMR1 gene, which generates epigenetic changes that silence its expression. The absence of the protein coded by this gene, FMRP, causes cellular dysfunction, leading to impaired brain development and functional abnormalities. The physical and neurologic manifestations of the disease appear early in life and may suggest the diagnosis. However, it must be confirmed by molecular tests. It affects multiple areas of daily living and greatly burdens the affected individuals and their families. Fragile X syndrome is the most common monogenic cause of intellectual disability and autism spectrum disorder; the diagnosis should be suspected in every patient with neurodevelopmental delay. Early interventions could improve the functional prognosis of patients with Fragile X syndrome, significantly impacting their quality of life and daily functioning. Therefore, healthcare for children with Fragile X syndrome should include a multidisciplinary approach.

Drosophila melanogaster as a Model to Study Fragile X-Associated Disorders

Fragile X syndrome (FXS) is a global neurodevelopmental disorder caused by the expansion of CGG trinucleotide repeats (≥200) in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene. FXS is the hallmark of Fragile X-associated disorders (FXD) and the most common monogenic cause of inherited intellectual disability and autism spectrum disorder. There are several animal models used to study FXS. In the FXS model of Drosophila, the only ortholog of FMR1, dfmr1, is mutated so that its protein is missing. This model has several relevant phenotypes, including defects in the circadian output pathway, sleep problems, memory deficits in the conditioned courtship and olfactory conditioning paradigms, deficits in social interaction, and deficits in neuronal development. In addition to FXS, a model of another FXD, Fragile X-associated tremor/ataxia syndrome (FXTAS), has also been established in Drosophila. This review summarizes many years of research on FXD in Drosophila models.

Light in the Rational Treatment of Autism? Effects of Metformin on Steroid Hormones in a Patient with Polycystic Ovarian Syndrome (PCOS)

Background: Metformin is an effective treatment option for type 2 diabetes mellitus, and it is, to this day, the most prescribed oral antiglycaemic drug. Besides its effects mainly on mitochondrial activity, an off-label use came up as a pharmaceutical for subjects with a diagnosis of polycystic ovarian syndrome (PCOS) along with altered steroid hormone homeostasis. Besides these effects, even an influence on mood and social behavior was described, leading to the aim of this case report to elucidate the effects before versus after treatment with metformin on steroid hormones and social behavior. Methods: A female patient with diagnosed PCOS was analyzed three times for steroid hormone levels. The first analysis was performed before treatment; the second, after a period of 71 days with metformin at 2 × 500 mg; and the third, after a total of 144 days with metformin at 2 × 500 mg. Spot urine probes were taken in the morning for a combined gas chromatography−mass spectrometry (GC-MS), and the steroid levels were adjusted for creatinine excretion. A questionnaire on social behavior (Autism Spectrum Questionnaire) was administered before treatment and after 71 days. Results: A decrease in all the steroid hormones measured was detected after 71 and 144 days of treatment with metformin, being more pronounced after 144 days of treatment and highly significant (p < 0.001). Furthermore, in the untreated state, the class of corticosterone metabolites showed increased values compared to the female reference values for TH-11-DH-corticosterone, TH-corticosterone, and 5a-TH-corticosterone. In the class of estrogen metabolites, increased values compared to the reference values were detected for 17b-estradiol; in the class of 11-deoxycortisol metabolites, an increase in TH-11-deoxycortisol was detected. For the class of cortisol metabolites, increased values compared to the reference values were detected for cortisone, TH-cortisone, a-cortolone, b-cortolone, 20b-dihydrocortisone, cortisol, TH-cortisol, 5a-TH-cortisol, a-cortol, 20b-dihydrocortisol, and 6b-OH-cortisol. No increases in androgen metabolites were detected. Interestingly, weight decreased from 93.4 kg to 91.3 kg after 71 days and fell to 82.7 kg after 144 days of treatment. The skeletal muscle mass was 30.1 kg at the first visit, decreasing to 29.9 kg and to 27.5 kg. No significant difference in the social behavior score from baseline to after 71 days of treatment was detected. Discussion: Metformin improved the steroid hormone profiles from levels above the upper reference values to the middle of the reference values after 71 days and to the lower ends of the reference values after 144 days of treatment. This implies not only that metformin has an effect on steroid hormone levels, but in addition that the efficacy of the pharmaceutical seems to depend on the time interval from intake. To summarize, in this patient, steroid hormones were affected but social behavior was not. If no effect of metformin on social behavior exists, this must be supported by further cases.

ADGRL3 genomic variation implicated in neurogenesis and ADHD links functional effects to the incretin polypeptide GIP

Attention deficit/hyperactivity disorder (ADHD) is the most common childhood neurodevelopmental disorder. Single nucleotide polymorphisms (SNPs) in the Adhesion G Protein-Coupled Receptor L3 (ADGRL3) gene are associated with increased susceptibility to developing ADHD worldwide. However, the effect of ADGRL3 non-synonymous SNPs (nsSNPs) on the ADGRL3 protein function is vastly unknown. Using several bioinformatics tools to evaluate the impact of mutations, we found that nsSNPs rs35106420, rs61747658, and rs734644, previously reported to be associated and in linkage with ADHD in disparate populations from the world over, are predicted as pathogenic variants. Docking analysis of rs35106420, harbored in the ADGLR3-hormone receptor domain (HRM, a common extracellular domain of the secretin-like GPCRs family), showed that HRM interacts with the Glucose-dependent insulinotropic polypeptide (GIP), part of the incretin hormones family. GIP has been linked to the pathogenesis of diabetes mellitus, and our analyses suggest a potential link to ADHD. Overall, the comprehensive application of bioinformatics tools showed that functional mutations in the ADGLR3 gene disrupt the standard and wild ADGRL3 structure, most likely affecting its metabolic regulation. Further in vitro experiments are granted to evaluate these in silico predictions of the ADGRL3-GIP interaction and dissect the complexity underlying the development of ADHD.

Dysregulation of BMP, Wnt, and Insulin Signaling in Fragile X Syndrome

Drosophila models of neurological disease contribute tremendously to research progress due to the high conservation of human disease genes, the powerful and sophisticated genetic toolkit, and the rapid generation time. Fragile X syndrome (FXS) is the most prevalent heritable cause of intellectual disability and autism spectrum disorders, and the Drosophila FXS disease model has been critical for the genetic screening discovery of new intercellular secretion mechanisms. Here, we focus on the roles of three major signaling pathways: BMP, Wnt, and insulin-like peptides. We present Drosophila FXS model defects compared to mouse models in stem cells/embryos, the glutamatergic neuromuscular junction (NMJ) synapse model, and the developing adult brain. All three of these secreted signaling pathways are strikingly altered in FXS disease models, giving new mechanistic insights into impaired cellular outcomes and neurological phenotypes. Drosophila provides a powerful genetic screening platform to expand understanding of these secretory mechanisms and to test cellular roles in both peripheral and central nervous systems. The studies demonstrate the importance of exploring broad genetic interactions and unexpected regulatory mechanisms. We discuss a number of research avenues to pursue BMP, Wnt, and insulin signaling in future FXS investigations and the development of potential therapeutics.

Metformin-Treatment Option for Social Impairment? An Open Clinical Trial to Elucidate the Effects of Metformin Treatment on Steroid Hormones and Social Behavior

BACKGROUND

Social behavior is mediated by steroid hormones, whereby various lines of evidence indicate that metformin might improve the symptoms of social withdrawal. This directly yields to the aim of the study to correlate the impact of metformin treatment on the potential alterations in steroid hormone homeostasis, which is ultimately impacting social behavior. Therefore, urinary samples of patients before and after treatment with metformin will be correlated to social behavior to elucidate potential changes in steroid hormone profiles and social behavior.

MATERIAL AND METHODS

An observational study in healthy adults with a new indication for metformin. Steroid hormone analysis, including the most prominent androgen, estrogen, progesterone, aldosterone, corticosterone, cortisone and cortisol metabolites analyzed with gas chromatography-mass spectrometry and a questionnaire on social behavior (Autism Spectrum Questionnaire (AQ)) will be administered prior to and after around a 12-week phase of metformin treatment.

DISCUSSION

It is likely that due to different pathophysiological mechanisms such as an effect on the respiratory chain in mitochondria or via AMP-activated protein kinase, a general alteration of steroid hormone levels can be detected prior to post treatment. The encompassing measurement of steroid hormones shall give hints concerning the involvement of specific cascades yielding potential pharmacological targets for future research.

Fragile X Syndrome: From Molecular Aspect to Clinical Treatment

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by the full mutation as well as highly localized methylation of the fragile X mental retardation 1 (FMR1) gene on the long arm of the X chromosome. Children with FXS are commonly co-diagnosed with Autism Spectrum Disorder, attention and learning problems, anxiety, aggressive behavior and sleep disorder, and early interventions have improved many behavior symptoms associated with FXS. In this review, we performed a literature search of original and review articles data of clinical trials and book chapters using MEDLINE (1990-2021) and ClinicalTrials.gov. While we have reviewed the biological importance of the fragile X mental retardation protein (FMRP), the FXS phenotype, and current diagnosis techniques, the emphasis of this review is on clinical interventions. Early non-pharmacological interventions in combination with pharmacotherapy and targeted treatments aiming to reverse dysregulated brain pathways are the mainstream of treatment in FXS. Overall, early diagnosis and interventions are fundamental to achieve optimal clinical outcomes in FXS.

An Update on Psychopharmacological Treatment of Autism Spectrum Disorder

While behavioral interventions remain the mainstay of treatment of autism spectrum disorder (ASD), several potential targeted treatments addressing the underlying neurophysiology of ASD have emerged in the last few years. These are promising for the potential to, in future, become part of the mainstay treatment in addressing the core symptoms of ASD. Although it is likely that the development of future targeted treatments will be influenced by the underlying heterogeneity in etiology, associated genetic mechanisms influencing ASD are likely to be the first targets of treatments and even gene therapy in the future for ASD. In this article, we provide a review of current psychopharmacological treatment in ASD including those used to address common comorbidities of the condition and upcoming new targeted approaches in autism management. Medications including metformin, arbaclofen, cannabidiol, oxytocin, bumetanide, lovastatin, trofinetide, and dietary supplements including sulforophane and N-acetylcysteine are discussed. Commonly used medications to address the comorbidities associated with ASD including atypical antipsychotics, serotoninergic agents, alpha-2 agonists, and stimulant medications are also reviewed. Targeted treatments in Fragile X syndrome (FXS), the most common genetic disorder leading to ASD, provide a model for new treatments that may be helpful for other forms of ASD.

The Use of Peptides in the Treatment of Fragile X Syndrome: Challenges and Opportunities

Fragile X Syndrome (FXS) is the most frequent cause of inherited intellectual disabilities and autism spectrum disorders, characterized by cognitive deficits and autistic behaviors. The silencing of the Fmr1 gene and consequent lack of FMRP protein, is the major contribution to FXS pathophysiology. FMRP is an RNA binding protein involved in the maturation and plasticity of synapses and its absence culminates in a range of morphological, synaptic and behavioral phenotypes. Currently, there are no approved medications for the treatment of FXS, with the approaches under study being fairly specific and unsatisfying in human trials. Here we propose peptides/peptidomimetics as candidates in the pharmacotherapy of FXS; in the last years this class of molecules has catalyzed the attention of pharmaceutical research, being highly selective and well-tolerated. Thanks to their ability to target protein-protein interactions (PPIs), they are already being tested for a wide range of diseases, including cancer, diabetes, inflammation, Alzheimer's disease, but this approach has never been applied to FXS. As FXS is at the forefront of efforts to develop new drugs and approaches, we discuss opportunities, challenges and potential issues of peptides/peptidomimetics in FXS drug design and development.

Transcriptional Regulation of MECP2E1-E2 Isoforms and BDNF by Metformin and Simvastatin through Analyzing Nascent RNA Synthesis in a Human Brain Cell Line

Methyl CpG binding protein 2 (MeCP2) is the main DNA methyl-binding protein in the brain that binds to 5-methylcytosine and 5-hydroxymethyl cytosine. MECP2 gene mutations are the main origin of Rett Syndrome (RTT), a neurodevelopmental disorder in young females. The disease has no existing cure, however, metabolic drugs such as metformin and statins have recently emerged as potential therapeutic candidates. In addition, induced MECP2-BDNF homeostasis regulation has been suggested as a therapy avenue. Here, we analyzed nascent RNA synthesis versus steady state total cellular RNA to study the transcriptional effects of metformin (an anti-diabetic drug) on MECP2 isoforms (E1 and E2) and BNDF in a human brain cell line. Additionally, we investigated the impact of simvastatin (a cholesterol lowering drug) on transcriptional regulation of MECP2E1/E2-BDNF. Metformin was capable of post-transcriptionally inducing BDNF and/or MECP2E1, while transcriptionally inhibiting MECP2E2. In contrast simvastatin significantly inhibited BDNF transcription without significantly impacting MECP2E2 transcripts. Further analysis of ribosomal RNA transcripts confirmed that the drug neither individually nor in combination affected these fundamentally important transcripts. Experimental analysis was completed in conditions of the presence or absence of serum starvation that showed minimal impact for serum deprival, although significant inhibition of steady state MECP2E1 by simvastatin was only detected in non-serum starved cells. Taken together, our results suggest that metformin controls MECP2E1/E2-BDNF transcriptionally and/or post-transcriptionally, and that simvastatin is a potent transcriptional inhibitor of BDNF. The transcriptional effect of these drugs on MECP2E1/E2-BDNF were not additive under these tested conditions, however, either drug may have potential application for related disorders.

Metformin Ameliorates Lipopolysaccharide-Induced Depressive-Like Behaviors and Abnormal Glutamatergic Transmission

Simple Summary

Metformin is a promising drug for diabetes and has been reported to have antidepressant effects in depression patients or patients with comorbid depression and other diseases. However, it is largely unclear how metformin ameliorates depressive-like behaviors. To this end, we injected mice with a bacterial endotoxin (lipopolysaccharide) to induce depressive-like behaviors such as increased immobility in the forced swimming test and tail suspension test. In this depression mouse model, metformin administration ameliorated depressive-like behaviors. Glutamate is a major excitatory signal for the communications between neurons in the brain. Dysfunction of glutamatergic neurotransmission is implicated in the pathogenesis of depression. Glutamatergic transmission was elevated in our depression mouse model. Metformin administration also recovered the glutamatergic transmission deficit in the model. Taken together, our results suggest metformin had antidepressant effects and can correct abnormal glutamatergic transmission in the lipopolysaccharide-induced depression mouse model. These findings provide new insights into the underlying mechanism by which metformin acts against depression.

Abstract

Metformin, a first-line drug for type 2 diabetes mellitus (T2DM), has been found to reduce depressive symptoms in patients with comorbid depression and other diseases. However, it is largely unclear how metformin ameliorates depressive-like behaviors. Here, we used lipopolysaccharide (LPS) to induce depressive-like behaviors in mice and found that LPS-treated mice exhibited increased immobility in the forced swimming test (FST) and tail suspension test (TST), as well as increased glutamatergic transmission. Furthermore, metformin administration in the LPS-treated mice ameliorated depressive-like behaviors and elevated glutamatergic transmission. Our results suggest that metformin has antidepressant effects and can correct abnormal glutamatergic transmission, providing an insight into the underlying mechanism by which metformin acts against depression.

Metformin Enhances Excitatory Synaptic Transmission onto Hippocampal CA1 Pyramidal Neurons

Metformin (Met) is a first-line drug for type 2 diabetes mellitus (T2DM). Numerous studies have shown that Met exerts beneficial effects on a variety of neurological disorders, including Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). However, it is still largely unclear how Met acts on neurons. Here, by treating acute hippocampal slices with Met (1 μM and 10 μM) and recording synaptic transmission as well as neuronal excitability of CA1 pyramidal neurons, we found that Met treatments significantly increased the frequency of miniature excitatory postsynaptic currents (mEPSCs), but not amplitude. Neither frequency nor amplitude of miniature inhibitory postsynaptic currents (mIPSCs) were changed with Met treatments. Analysis of paired-pulse ratios (PPR) demonstrates that enhanced presynaptic glutamate release from terminals innervating CA1 hippocampal pyramidal neurons, while excitability of CA1 pyramidal neurons was not altered. Our results suggest that Met preferentially increases glutamatergic rather than GABAergic transmission in hippocampal CA1, providing a new insight on how Met acts on neurons.

Pharmacological Treatments for Fragile X Syndrome Based on Synaptic Dysfunction

BACKGROUND

Fragile X syndrome (FXS) is the most common form of monogenic hereditary cognitive impairment, including intellectual disability, autism, hyperactivity, and epilepsy.

METHODS

This article reviews the literature pertaining to the role of synaptic dysfunction in FXS.

RESULTS

In FXS, synaptic dysfunction alters the excitation-inhibition ratio, dysregulating molecular and cellular processes underlying cognition, learning, memory, and social behavior. Decades of research have yielded important hypotheses that could explain, at least in part, the development of these neurological disorders in FXS patients. However, the main goal of translating lab research in animal models to pharmacological treatments in the clinic has been so far largely unsuccessful, leaving FXS a still incurable disease.

CONCLUSION

In this concise review, we summarize and analyze the main hypotheses proposed to explain synaptic dysregulation in FXS, by reviewing the scientific evidence that led to pharmaceutical clinical trials and their outcome.

Elevated de novo protein synthesis in FMRP-deficient human neurons and its correction by metformin treatment

FXS is the most common genetic cause of intellectual (ID) and autism spectrum disorders (ASD). FXS is caused by loss of FMRP, an RNA-binding protein involved in the translational regulation of a large number of neuronal mRNAs. Absence of FMRP has been shown to lead to elevated protein synthesis and is thought to be a major cause of the synaptic plasticity and behavioural deficits in FXS. The increase in protein synthesis results in part from abnormal activation of key protein translation pathways downstream of ERK1/2 and mTOR signalling. Pharmacological and genetic interventions that attenuate hyperactivation of these pathways can normalize levels of protein synthesis and improve phenotypic outcomes in animal models of FXS. Several efforts are currently underway to trial this strategy in patients with FXS. To date, elevated global protein synthesis as a result of FMRP loss has not been validated in the context of human neurons. Here, using an isogenic human stem cell-based model, we show that de novo protein synthesis is elevated in FMRP-deficient neural cells. We further show that this increase is associated with elevated ERK1/2 and Akt signalling and can be rescued by metformin treatment. Finally, we examined the effect of normalizing protein synthesis on phenotypic abnormalities in FMRP-deficient neural cells. We find that treatment with metformin attenuates the increase in proliferation of FMRP-deficient neural progenitor cells but not the neuronal deficits in neurite outgrowth. The elevated level of protein synthesis and the normalization of neural progenitor proliferation by metformin treatment were validated in additional control and FXS patient-derived hiPSC lines. Overall, our results validate that loss of FMRP results in elevated de novo protein synthesis in human neurons and suggest that approaches targeting this abnormality are likely to be of partial therapeutic benefit in FXS.

Could metformin be therapeutically useful in Huntington's disease?

Emerging evidence suggest that dimethylbiguanide (metformin), a first-line drug for type 2 diabetes mellitus, could be neuroprotective in a range of brain pathologies, which include neurodegenerative diseases and brain injury. However, there are also contraindications that associate metformin treatment with cognitive impairment as well as adverse outcomes in Alzheimer's disease and Parkinson's disease animal models. Recently, a beneficial effect of metformin in animal models of Huntington's disease (HD) has been strengthened by multiple reports. In this brief review, the findings associated with the effects of metformin in attenuating neurodegenerative diseases are discussed, focusing on HD-associated pathology and the potential underlying mechanisms highlighted by these studies. The mechanism of action of metformin is complex, and its therapeutic efficacy is therefore expected to be dependent on the disease context. The key metabolic pathways that are effectively affected by metformin, such as AMP-activated protein kinase activation, may be altered in the later decades of the human lifespan. In this regard, metformin may nonetheless be therapeutically useful for neurological diseases with early pathological onsets, such as HD.

Metformin and cognition from the perspectives of sex, age, and disease

Metformin is the safest and the most widely prescribed first-line therapy for managing hyperglycemia due to different underlying causes, primarily type 2 diabetes mellitus. In addition to its euglycemic properties, metformin has stimulated a wave of clinical trials to investigate benefits on aging-related diseases and longevity. Such an impact on the lifespan extension would undoubtedly expand the therapeutic utility of metformin regardless of glycemic status. However, there is a scarcity of studies evaluating whether metformin has differential cognitive effects across age, sex, glycemic status, metformin dose, and duration of metformin treatment and associated pathological conditions. By scrutinizing the available literature on animal and human studies for metformin and brain function, we expect to shed light on the potential impact of metformin on cognition across age, sex, and pathological conditions. This review aims to provide readers with a broader insight of (a) how metformin differentially affects cognition and (b) why there is a need for more translational and clinical studies examining multifactorial interactions. The outcomes of such comprehensive studies will streamline precision medicine practices, avoiding "fit for all" approach, and optimizing metformin use for longevity benefit irrespective of hyperglycemia.

Cognitive and behavioral improvement in adults with fragile X syndrome treated with metformin-two cases

BACKGROUND

The majority of individuals with fragile X syndrome (FXS) have intellectual disability, behavioral problems, autism, and language deficits. IQ typically declines with age in boys with the full mutation. The results of preclinical studies demonstrated that metformin, a biguanide used to treat type 2 diabetes, rescues multiple phenotypes of FXS in both Drosophila and mouse models. Preliminary studies of patients with FXS demonstrated improvements in behavior.

METHODS

Here, we present two cases of individuals who have been treated with metformin clinically for one year.

RESULTS

Both patients demonstrated significant cognitive and behavioral improvements. They also improved eating habits and normalization of their weight percentiles.

CONCLUSION

Metformin may be a candidate drug for treatment of several types of symptoms in individuals with FXS.