Nigel A. Calcutt is a researcher specializing in the study and treatment of peripheral nervous system disorders. His research primarily focuses on the mechanisms and therapeutics of diabetic peripheral neuropathy, including the use of muscarinic receptor antagonists to stimulate nerve repair and mitochondrial function. He has also co-authored studies evaluating diagnostic and physiological measures of neuropathy, such as rate-dependent depression of the Hoffmann reflex and nerve fiber density.
19 claims checked on air: 2 overstated 14 supported 3 unverified
"The worldwide incidence is difficult to estimate, but there've been estimates 250, 500 million people." (said at 0:06:16)
No published record matching the claim that worldwide estimates of peripheral neuropathy prevalence range from 250 million to 500 million people was located; this does not prove the claim false.
"In the US, around 30 million people suffering from some form of peripheral neuropathy." (said at 0:06:35)
Epidemiological literature on the burden of peripheral neuropathy in the United States commonly estimates that 20 to 30 million Americans are affected by some form of peripheral neuropathy across various etiologies (including diabetic neuropathy, chemotherapy-induced neuropathy, toxic/metabolic causes, and idiopathic forms). Published reviews document that peripheral neuropathies affect over 20 million individuals in the US, making the speaker's figure of 'around 30 million' an accurate approximation of the broad epidemiological range.
"Peripheral neuropathies (PNs) affect over 20 million individuals in the United States, manifesting as a wide range of sensory, motor, and autonomic nerve symptoms." (abstract, passage verified)pubmedfull study (doi)
"So, the common causes of neuropathy in the US are No. 1 is diabetes." (said at 0:06:45)
Epidemiological literature and clinical reviews consistently identify diabetes mellitus as the leading cause of peripheral neuropathy in the United States and other Western nations, accounting for more than 50% of all diagnosed peripheral neuropathy cases.
"Diabetes is the most common cause of peripheral neuropathy in the world. More than half of patients with diabetes have neuropathy, and half of patients with neuropathy have diabetes." (abstract, background, passage verified)pubmedfull study (doi)
"Diabetic neuropathy, which is often associated with both sensory symptoms, such as pain, tingling, or numbness; mild weakness; and autonomic symptoms, such as orthostatic hypotension, accounts for more than 50% of peripheral neuropathy in Western populations." (abstract, results, passage verified)pubmedfull study (doi)
"We do know that over the last 20 to 30 years in the US the rate of the progression of neuropathy has been slowed." (said at 0:08:40)
Longitudinal cohort and national surveillance data in the United States demonstrate a secular decline in the progression and rate of diabetic neuropathy and its end-stage sequelae over the past several decades. Findings from the prospective Pittsburgh Epidemiology of Diabetes Complications Study revealed a significant decreasing trend in diabetic neuropathy across successive diagnosis cohorts evaluated at 20- and 25-year diabetes durations (P < 0.05). In addition, nationwide surveillance from 1990 to 2010 documented a 51.4% reduction in lower-extremity amputations among adults with diabetes, reflecting substantial deceleration in the severe progression of neuropathic and vascular disease.
"There was a decreasing trend by diagnosis year for mortality, renal failure, and neuropathy across all time intervals (P < 0.05), with the 1950-1959 cohort having a fivefold higher mortality at 25 years than the 1970s' cohorts." (abstract, results, passage verified)pubmedfull study (doi)
"Rates of all five complications declined between 1990 and 2010, with the largest relative declines in acute myocardial infarction (-67.8%; 95% confidence interval [CI], -76.2 to -59.3) and death from hyperglycemic crisis (-64.4%; 95% CI, -68.0 to -60.9), followed by stroke and amputations, which each declined by approximately half (-52.7% and -51.4%, respectively)" (abstract, results, passage verified)pubmedfull study (doi)
"Some of them it's 80 or 90% of patients would be expected to get neuropathy." (said at 0:12:12)
Clinical and epidemiological research confirms that for specific neurotoxic chemotherapeutic agents—notably platinum compounds such as oxaliplatin and certain taxanes—the overall incidence of chemotherapy-induced peripheral neuropathy (CIPN) can reach 80% to 90% or higher during active treatment. In large observational cohorts and systematic reviews evaluating neurotoxic regimens, acute or cumulative sensory neuropathy of any grade is documented in up to 90% or more of patients receiving these agents.
"CIPN prevalence was 68.1% (57.7-78.4) when measured in the first month after chemotherapy, 60.0% (36.4-81.6) at 3months and 30.0% (6.4-53.5) at 6months or more. Different chemotherapy drugs were associated with differences in CIPN prevalence" (abstract, results, passage verified)pubmedfull study (doi)
"The primary classes of chemotherapeutic agents associated with CIPN are platinum-based drugs, taxanes, vinca alkaloids, bortezomib and thalidomide. Platinum agents are the most neurotoxic, with oxaliplatin causing the highest prevalence of CIPN." (abstract, background, passage verified)pubmedfull study (doi)
"Among 3,140 patients, 16,878 events were evaluated, with 7,187 (42.58%), 5,514 (32.67%), and 4,177 (24.75%) patients treated with cisplatin, carboplatin, or oxaliplatin, respectively. The incidence of any event of PSPN was 98.85%" (abstract, results, passage verified)pubmedfull study (doi)
"the pain had always been there. It impacts about a third to a half of the patients with neuropathy." (said at 0:21:55)
Published epidemiological literature and systematic reviews confirm that painful diabetic peripheral neuropathy (PDPN) affects approximately one-third to one-half of individuals with diabetic peripheral neuropathy. A 2025 systematic review and meta-analysis of 41 observational studies found a pooled global prevalence of painful diabetic peripheral neuropathy of 46.7% (95% CI, 41.8–51.7%) among patients with diabetic neuropathy.
"This systematic review and meta-analysis aim to determine the global prevalence of PDPN among individuals with diabetic peripheral neuropathy (DPN) and to identify associated risk factors... Of the 41 studies included, the pooled global prevalence of PDPN was 46.7 % (95 % CI, 41.8-51.7)." (abstract, results)pubmedfull study (doi)
"Pregabalin was approved, the son of gabapentin was approved for use in diabetic neuropathy, and suddenly there was a route that you could follow." (said at 0:23:25)
Pregabalin (Lyrica) received FDA approval specifically for the management of neuropathic pain associated with diabetic peripheral neuropathy (DPN), becoming one of the first oral medications approved for this indication and serving as a guideline-recommended first-line therapy.
"Duloxetine and pregabalin remain first-line therapy for neuropathic pain in DPN in all 5 of the major published guidelines by the American Association of Clinical Endocrinologists, American Academy of Neurology, European Federation of Neurological Societies, National Institute of Clinical Excellence (United Kingdom), and the American Diabetes Association, and their use has been approved by the US Food and Drug Administration." (abstract, passage verified)pubmedfull study (doi)
"Four pharmacologic options are currently approved by the US Food and Drug Administration (FDA) to treat painful DPN. These include three oral medications (duloxetine, pregabalin, and tapentadol extended release) and one topical agent (capsaicin 8% topical system)." (abstract, passage verified)pubmedfull study (doi)
"Because nothing has ever been approved to treat diabetic neuropathy, the nerve degeneration and loss, there is no route." (said at 0:23:45)
The statement is accurate. While several medications (such as pregabalin, duloxetine, and tapentadol) are FDA-approved to manage symptoms and pain associated with diabetic peripheral neuropathy, there are currently no FDA-approved disease-modifying therapies aimed at slowing, stopping, or reversing the underlying nerve degeneration and structural loss.
"There are currently no FDA-approved disease-modifying treatments for diabetic neuropathy which has been attributed to inappropriate models of the disease with limited translational capacity and major limitations of trial designs and endpoints in clinical trials." (abstract, conclusions, passage verified)pubmedfull study (doi)
"Unfortunately, currently there are no Food and Drug Administration (USA) approved disease-modifying treatments for diabetic peripheral neuropathy (DPN) as trials of putative pathogenetic treatments have failed at phase 3 clinical trial stage." (abstract, background, passage verified)pubmedfull study (doi)
"There is currently no FDA-approved disease-modifying therapy for diabetic peripheral neuropathy (DPN)." (abstract, background, passage verified)pubmedfull study (doi)
"The the the the primary observation was made by a lady named Ruth van Heyningen in the 1950s, who looked at the distribution of aldose reductase and noted that it it just happened to be present in all the organs of the body where you got diabetic complications. The eyes, the nerves, the blood vessels, the kidneys, these were all at levels with high expression of aldose reductase." (said at 0:26:45)
Biochemist Ruth van Heyningen discovered the presence of aldose reductase and the sorbitol (polyol) pathway in the ocular lens in 1959, linking polyol accumulation to the formation of sugar and diabetic cataracts. However, she did not map its distribution across the full spectrum of organs affected by diabetic complications in the 1950s. The identification of aldose reductase activity in other non-insulin-dependent tissues susceptible to diabetic complications—such as peripheral nerves, blood vessels, and the kidneys—and the broader formulation of the polyol hypothesis for systemic diabetic microvascular complications occurred in subsequent decades through work by researchers such as Kenneth Gabbay and Jin Kinoshita.
"Aldose reductase catalyzes the first step in the polyol pathway and is thought to be involved in the pathogenesis of diabetic complications." (abstract, passage verified)pubmedfull study (doi)
"Among these, the two-step sorbitol pathway has been the most extensively investigated; nevertheless, it remains controversial. To date, long-term pharmacological studies in animal models of diabetes have demonstrated that the onset and development of ocular complications that include keratopathy, retinopathy and cataract can be ameliorated by the control of excess metabolic flux through aldose reductase (AR)." (abstract, passage verified)pubmedfull study (doi)
"And aldose reductase inhibitors are perfect blockers of cataractogenesis. Um in fact, they cured most things in animals through the '60s and '70s and '80s. Um in all the animal models, they fixed pretty much everything." (said at 0:26:46)
Extensive preclinical literature from the 1960s through the 1980s and beyond demonstrates that aldose reductase inhibitors (ARIs, such as sorbinil) effectively block or reverse cataractogenesis and mitigate other diabetic complications (such as retinopathy, neuropathy, and nephropathy) in rodent and other animal models. In diabetic and galactosemic rodents, accumulation of sorbitol via the polyol pathway causes osmotic stress and tissue damage, which ARIs consistently prevented in laboratory models, despite subsequent challenges translating these robust animal results to human clinical trials.
"To date, long-term pharmacological studies in animal models of diabetes have demonstrated that the onset and development of ocular complications that include keratopathy, retinopathy and cataract can be ameliorated by the control of excess metabolic flux through aldose reductase (AR)." (abstract, results, passage verified)pubmedfull study (doi)
"Our results indicated that the aldose reductase inhibitor sorbinil, a spirohydantoin, arrested further progression and promoted a reparative process despite continuation of hyperglycemia and elevated lens glucose." (abstract, results, passage verified)pubmedfull study (doi)
"Sorbitol, formed in the presence of aldose reductase, accumulates in the lens during hyperglycemia. Dulcitol similarly accumulates in the presence of galactosemia. Cataractogenesis in both cases can be prevented by inhibitors of aldose reductase." (abstract, results, passage verified)pubmedfull study (doi)
"basically the you know, very crudely the glucose gets into the cells of the lens. They swell because they make sorbitol. I mean, the progression of aldose reductase from glucose to fructose includes an intermediate sorbitol that is a very strong osmolyte. And so, the so sorbitol accumulates in the lens, they swell, the lens fibers burst and you and you start getting cataracts with these accumulations." (said at 0:27:20)
The speaker accurately describes the classic polyol pathway (osmotic) mechanism of diabetic cataractogenesis. Under hyperglycemic conditions, aldose reductase reduces excess intracellular glucose into sorbitol. Because sorbitol is poorly permeable to cell membranes, it accumulates intracellularly and acts as an osmolyte, drawing water into the lens fibers. This osmotic swelling leads to cellular disruption, membrane damage, and lens opacification (cataract formation). While additional factors such as oxidative stress and advanced glycation end-products also contribute in human diabetic cataracts, the aldose reductase-mediated sorbitol osmotic swelling mechanism is well established.
"Aldose reductase (ALR2) is a rate-limiting component of the polyol pathway, which is essential for the NADPH-mediated conversion from glucose to sorbitol. ALR2 dysregulation has been linked to α-crystallin aggregation, increased oxidative stress, and calcium inflow, all of which contribute to a diabetic cataract." (abstract, passage verified)pubmedfull study (doi)
"The lens becomes cataractous through osmotic swelling of its cortical fibers. Sorbitol, formed in the presence of aldose reductase, accumulates in the lens during hyperglycemia." (abstract, passage verified)pubmedfull study (doi)
"pirenzepine was one of those drugs that existed that did not cross into the CNS. So, it made it purely a peripheral acting drug." (said at 0:39:28)
Pirenzepine is a selective M1 muscarinic receptor antagonist that is hydrophilic and does not effectively cross the blood-brain barrier under standard systemic administration, making its pharmacological actions predominantly restricted to the peripheral nervous system and peripheral tissues. It is widely used in pharmacological and clinical research specifically as a peripherally restricted muscarinic antagonist to distinguish central from peripheral cholinergic effects.
"Twelve patients with PD received biperiden hydrochloride (a muscarinic antagonist that crosses the blood-brain barrier), pirenzepine hydrochloride (a muscarinic antagonist that does not cross the blood-brain barrier), or placebo 2 hours before a 35% carbon dioxide-65% oxygen respiratory challenge" (abstract, methods, passage verified)pubmedfull study (doi)
"Pirenzepine, a M1 muscarinic antagonist which does not cross the blood-brain barrier, biperiden, another M1 muscarinic antagonist which is expected to penetrate into the central nervous system, or placebo was intravenously preinjected before the measurement of ventilatory responses." (abstract, methods, passage verified)pubmed
"Inhibition of muscarinic AChR restricted to the periphery may present a therapeutic advantage as it avoids adverse central cholinergic effects." (abstract, conclusions, passage verified)pubmedfull study (doi)
"pirenzepine existed and it had been used in millions of people around the world um for treating gastric ulcers. Um it was developed by a a German company, Boehringer Ingelheim. Um and you took it as an oral um pill, I believe. And it blocked acetylcholine um driven release of HCl in the stomach." (said at 0:39:58)
Pirenzepine is a selective muscarinic M1 receptor antagonist originally developed by Boehringer Ingelheim (marketed under brand names including Gastrozepin) as an oral therapeutic for peptic and gastric ulcers. Pharmacologically, it inhibits acetylcholine-mediated stimulation of gastric acid (hydrochloric acid) secretion by blocking muscarinic receptors involved in cholinergic signaling in the gastrointestinal tract.
"This mini review focuses on the closely related and commonly co-expressed M 1 R and M 3 R muscarinic acetylcholine receptor subtypes encoded respectively by CHRM1 and CHRM3 . Activated M 1 R and M 3 R signal via G q and downstream initiate phospholipid turnover, changes in cell calcium levels, and activation of protein kinases that alter gene transcription and ultimately cell function... review the pharmacology and availability for research and therapeutics of M 1 R and M 3 R-selective agonists and antagonists." (abstract, passage verified)pubmedfull study (doi)
"It had never been used in the US. Uh it was never uh approved here." (said at 0:40:40)
No published record matching the claim that pirenzepine was never approved for use in the United States by the FDA was located; this does not prove the claim false.
"When you have give too high doses systemically, you're going to start getting you know, the dry mouth, the tachycardias, the things that one associates with antimuscarinics in high doses." (said at 0:42:07)
The claim is supported by clinical literature. High systemic exposure or toxicity from antimuscarinic (parasympatholytic) agents classically produces peripheral anticholinergic manifestations, most notably dry mouth (xerostomia) and tachycardia.
"Most frequently observed clinical effect was mydriasis (53.2%), followed by confusion (40%), tachycardia (35.5%), dry mouth (35.5%), dizziness (34%), dry skin (32.5%), and delirium (31%)." (abstract, results, passage verified)pubmedfull study (doi)
"The systemic complications are those common to sympathomimetic and parasympatholytic drugs and include tachycardia, hypertension, headache, faintness. pallor, trembling, excessive sweating, palpitations, arrhythmias, confusion, hallucinations, drowsiness, ataxia, flushed skin, high fever, dysarthria, thirst, dry mouth, convulsions, disorientation, nervousness, coma, and death." (abstract, results, passage verified)pubmed
"There's also a very interesting technique called corneal confocal microscopy which takes a confocal microscope and aims it at the eye... And it has been well documented now by a colleague of ours, um Rayaz Malik, who's worked on this now and really elevated it to an art form as well as a science form, that you can use these corneal confocal microscopes to look at nerves in real time... So, you can use this to measure degeneration, apply drugs to the eye and look at regeneration, all in a human or an animal live." (said at 0:42:28)
Corneal confocal microscopy (CCM) is an established, non-invasive in vivo imaging technique used in humans and animal models to visualize sub-basal corneal nerve fibers in real time. Extensive research, notably led by Rayaz Malik and colleagues, demonstrates that CCM detects small sensory nerve fiber degeneration in neuropathies (such as diabetic peripheral neuropathy) and captures early nerve regeneration following therapeutic or surgical interventions.
"Corneal confocal microscopy (CCM) is a rapid non-invasive ophthalmic imaging technique that can image small nerve fibers in the cornea and has been utilized to show small nerve fiber loss in patients with diabetic and other neuropathies." (abstract, background, passage verified)pubmedfull study (doi)
"This meta-analysis confirms the utility of CCM to identify nerve regeneration following pharmacological and surgical interventions." (abstract, conclusions, passage verified)pubmedfull study (doi)
"The trial was completed. And I think now that I I can say that the cuz we saw efficacy. We we saw that it helped nerves regrow in the skin of diabetic patients significantly... And it could you could measure nerve regrowth in the skin of diabetic patients that didn't happen with a placebo." (said at 0:45:40)
No published record matching a clinical trial demonstrating that topical oxybutynin significantly promoted nerve regrowth in the skin of diabetic neuropathy patients compared to placebo was located; this does not prove the claim false.
"the nerve conduction studies are large fiber studies and a lot of the a lot of the problems that we've described in diabetic neuropathy are small fiber." (said at 0:50:25)
Standard nerve conduction studies evaluate myelinated, large-diameter A-alpha and A-beta nerve fibers and cannot record the activity of unmyelinated (C) or thinly myelinated (A-delta) small fibers. Because early or painful diabetic peripheral neuropathy frequently presents as small-fiber pathology, nerve conduction studies are often normal in these patients and require specialized modalities (such as skin biopsy to assess intraepidermal nerve fiber density, corneal confocal microscopy, or quantitative sensory testing) to detect small-fiber impairment.
"Nerve conduction studies only detect large fiber damage and do not capture pathology or dysfunction of small fibers. Because small nerve fiber damage is prominent in DPN, additional biomarkers of small nerve fiber function are needed." (abstract, results, passage verified)pubmedfull study (doi)
"Nerve conduction studies are useful for confirming large-fiber neuropathy and excluding alternative diagnoses, yet they may remain normal in early or predominantly small-fiber disease." (abstract, results, passage verified)pubmedfull study (doi)
"And WinSanTor, with help from Canadian government and the US government, has concluded two phase two clinical trials. Now, both of which have shown success in in showing nerve regrowth and other patient descriptors of effect." (said at 0:56:02)
The speaker claims that two Phase 2 clinical trials have concluded, both demonstrating nerve regrowth and patient-reported improvements. To date, published clinical trial data exist for only one Phase 2a randomized, double-blind, placebo-controlled trial evaluating topical 4% pirenzepine in 58 participants with diabetic peripheral neuropathy (PMID 41352124). While this trial demonstrated a statistically significant increase in lower-limb intraepidermal nerve fibre density (IENFD) over 24 weeks compared to placebo, the patient-reported outcome (Norfolk QOL-DN score) showed no significant difference in the primary modified intent-to-treat (mITT) analysis set. Improvement in QOL was observed only in a per-protocol secondary analysis, which the study authors noted requires cautious interpretation due to potential bias. Claiming that two Phase 2 trials have completed and successfully demonstrated both nerve regrowth and patient-reported benefits overstates the published evidence.
"Topical pirenzepine administered once daily for 24 weeks in patients with DPN resulted in a statistically significant growth of nerve fibres as measured by IENFD at the ankle. ... There was a 10.4-point improvement in the Norfolk QOL-DN score in the combined treatment groups over placebo (p < 0.001) in the per protocol (PP) analysis set, but no difference was observed in the modified intention-to-treat analysis, suggesting the need for cautious interpretation of the PP result due to potential bias." (abstract, results and conclusions)pubmedfull study (doi)