Name: Nasal Insulin
Synonyms: Detemir, Levemir, Humulin, Novolin, glulisine
Therapy Type: Small Molecule (timeline), Other
Target Type: Amyloid-Related (timeline), Other (timeline)
Condition(s): Alzheimer's Disease, Mild Cognitive Impairment, Parkinson's Disease, Multiple System Atrophy
U.S. FDA Status: Alzheimer's Disease (Phase 2/3), Mild Cognitive Impairment (Phase 2), Parkinson's Disease (Phase 2), Multiple System Atrophy (Phase 2)
Approved for: Diabetes
Insulin is the peptide hormone that is standard treatment for the management of Type 1 diabetes. In a new therapeutic approach, various forms of commercially available insulin are being atomized into a spray and inhaled through the nose. The rationale behind this exploration of insulin for the treatment of cognitive impairment and dementia is twofold. First, brain areas affected in Alzheimer's disease have been shown to express insulin receptors, and insulin levels as well as insulin receptor signaling are thought to be reduced in Alzheimer's (e.g., Chiu et al., 2008; Steen et al., 2005). Second, if effective, delivery of this hormone directly into the brain along olfactory perivascular channels would sidestep the peripheral bloodstream. This would avoid the unwanted effect of increasing systemic insulin levels, which could lead to hypoglycemia or insulin resistance (e.g., Born et al., 2002).
The physiological role of insulin in the brain is incompletely understood, but it has been implicated in synaptic remodeling and glucose utilization. Insulin has also been proposed to protect against Aβ toxicity, and insulin deficits have been linked to tau pathology, neuroinflammation, and other aspects of Alzheimer's pathophysiology (De Felice et al., 2009; El Khoury et al., 2014; Zhao et al., 2009). Insulin resistance, Type 2 diabetes, obesity, and metabolic syndrome are risk factors for Alzheimer's disease (see AlzRisk Diabetes, AlzRisk Obesity).
Intranasal insulin began attracting attention in Alzheimer's research when small human studies reported improved cognition without a change in blood glucose or insulin levels in healthy volunteers (e.g., May 2002 news; Benedict et al., 2004; Benedict et al., 2007).
A single-center pilot study at the Veterans Affairs Hospital/University of Washington in Seattle reported improved verbal memory retention and attention after a three-week test of 20 international units (IU) daily of intranasal insulin compared with placebo in 24 people with amnestic memory impairment (aMCI) or mild Alzheimer's disease. The insulin was delivered with an electronic atomizer (Reger et al., 2008).
A separate small trial comparing different doses in 33 people with aMCI or early AD reported differential effects by ApoE genotype (Reger et al., 2008).
Intranasal insulin appeared safe in a subsequent four-month course of 20 or 40 IUs of intranasal insulin or placebo given to a larger group of 104 people with aMCI or mild to moderate AD. Called SNIFF-120, this single-center study reported some preservation of cognition in younger participants and some preservation of function. The study reported no change in the CSF biomarkers between the groups, but some signals on subgroup analysis (Craft et al., 2012; Jul 2010 news). Different responses by gender or ApoE genotype were also reported (Claxton et al., 2013).
In September 2013, the Alzheimer's Disease Cooperative study began enrolling for Study of Nasal Insulin in the Fight Against Forgetfulness (SNIFF), a federally funded study that delivered 20 IU of insulin or placebo after breakfast and dinner to 289 people with either aMCI or early AD. The first 49 participants used the same insulin delivery device as had been used in the previous trial; the remaining 240 used a different one. After one year of treatment, there was no cognitive or functional difference between insulin and placebo groups in the cohort of 240 who used the second delivery device. The smaller group of 48 who used the original device did show slowing of worsening in the ADAS-COG-12 subscale and activities of daily living at one year (Craft et al., 2020). A secondary analysis of MRI data from this smaller group found reduced accumulation of white-matter abnormalities in treated compared to placebo patients after one year (Kellar et al., 2021).
At AD/PD in March 2021, additional trial results were presented. Participants using the original device continued to do better than those on placebo during a six-month open-label period. There was no effect of insulin in the larger cohort using the second device. In a subsequent Phase 2 study to determine how much insulin entered the brain after nasal delivery, 19 people received 40 IU insulin or a placebo using the first device, followed by lumbar puncture. CSF insulin concentrations approximately doubled after 30 minutes. The manufacturer of the second device refused to allow its testing.
In July 2020, a Phase 2 trial of similar design began to compare three different intranasal delivery devices and two doses of insulin, 20 and 40 IU, in 30 people with no or mild cognitive impairment.
The trials of intranasal insulin vary in that some evaluate fast-acting forms of insulin as used in diabetes therapy, while others evaluate longer-acting insulin analogs. For example, two trials conducted at the University of Washington, Seattle, between 2011 and 2013 evaluated insulin detemir, a long-acting insulin analog that differs from human insulin by one amino acid. A three-week study in 60 patients with MCI or AD compared 10 and 20 IUs of detemir twice daily to placebo. The higher dose improved memory in ApoE4 carriers, worsened it in noncarriers, and did not change daily function or executive function (Claxton et al., 2015). A subsequent four-month study compared 20 IUs twice daily of insulin detemir to 20 IUs of regular insulin twice daily in 36 patients. Regular insulin, but not detemir, improved memory compared with placebo, and was associated with preserved brain volume in several regions on MRI (Craft et al., 2017). These trials did not measure exposure or target engagement.
In a small study examining glulisine, a rapid acting form of insulin, nasal delivery of 20 UI twice daily for six months failed to improve cognition, function, or mood compared to placebo in 35 people with MCI or mild probable AD (Rosenbloom et al., 2021). In pilot trials, the same investigators reported no acute improvement in cognition after a single dose of glulisine compared to placebo in nine people with AD, or 12 with Down's syndrome (Rosenbloom et al., 2014; Rosenbloom et al., 2020).
Nasal insulin is also being evaluated for neurologic conditions other than Alzheimer's. In February 2014, a trial started up at the University of Massachusetts. It evaluated the effect of 40 IUs of regular insulin on a visuospatial memory test, the Unified Parkinson's Disease Rating Scale, and other measures compared to placebo in 15 patients with Parkinson's disease. Insulin improved verbal fluency and clinical measures of PD severity compared to placebo. One patient with MSA remained stable on insulin treatment (Novak et al., 2019).
Furthermore, various trials have evaluated nasal insulin for effects on cognitive symptoms in psychiatric conditions such as schizophrenia, bipolar, and major depressive disorder.
For more trials on nasal insulin in Alzheimer's, see clinicaltrials.gov.
Last Updated: 30 Jul 2021
- Honolulu: Intranasal Insulin Trial Claims Promise in MCI, AD
- Sniff This: Therapeutic Peptides Through the Nose?
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