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Blood-brain barrier as a dynamic interface allowing selective passage of nutrients, peptides, and gut hormones.

TOPICS DISCUSSED:

• Blood-Brain Barrier Structure: Capillary endothelial cells with tight junctions, absent fenestrae, and minimal vesicles create a selective interface; supported by astrocytes and pericytes.
• Crossing Mechanisms: Lipid-soluble small molecules diffuse passively; glucose, amino acids, and regulatory peptides use saturable transporters whose rates vary by need.
• Peptide Transport: Many peptides cross via lipid solubility or specific transporters; rate, not all-or-none presence, determines biological relevance; efflux systems remove some (e.g. certain enkephalins).
• Dynamic Regulation: Transporters for leptin and insulin are modulated by epinephrine, triglycerides, and brain demand; changes occur in aging and Alzheimer’s (reduced glucose uptake, impaired Aβ efflux).
• Circumventricular Organs: Leaky capillary regions allow rapid sampling of blood signals while tanycytes limit spread to surrounding brain tissue.
• Drug Delivery Challenges: Small lipid-soluble drugs, barrier disruption (e.g. focused ultrasound), and “Trojan-horse” strategies each have limitations; intranasal delivery shows rapid brain distribution.
• Peptides & Brain Effects: Gut peptides like GLP-1 analogs, insulin, and ghrelin influence cognition and memory; brain entry predicts central effects.

GUEST: William Banks, MD is a physician-scientist and leading researcher on the blood-brain barrier. He has focused on humoral brain-body communication, peptide transport, and the barrier’s role in health and disease.

RELATED CONTENT:

• M&M 298 | GLP-1s & Novel Peptides in Obesity, Diabetes & Metabolic Health | Katrin Svensson

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Ferroptosis, an iron-dependent cell death pathway driven by lipid peroxidation; chronoferoptosis, in which chronic stress sensitizes neurons gradually.

TOPICS DISCUSSED:

• Cell Death Pathways: Apoptosis proceeds through regulated steps with surface “eat me” signals that enable non-inflammatory clearance by phagocytes, whereas ferroptosis and related pathways release cellular contents that can amplify local damage and inflammation.
• Ferroptosis Discovery: Work on glutamate toxicity in neuronal cell lines first identified a glutathione-depletion pathway termed oxytosis; parallel studies in cancer cells renamed and generalized it as ferroptosis to highlight iron’s catalytic role.
• Lipid Peroxidation: Polyunsaturated fatty acids in membranes are oxidized non-enzymatically when ferrous iron reacts with hydrogen peroxide in the Fenton reaction, generating hydroxyl radicals that produce toxic lipid peroxides and reactive carbonyls that modify proteins.
• GPX4 & Glutathione: Glutathione peroxidase-4 is an enzyme that reduces lipid peroxides within membranes and requires glutathione as cofactor; depletion of either component removes this critical line of defense.
• Chronoferoptosis: Nine-day treatment of differentiated neuronal cells with chronic iron or glutathione synthesis inhibitor reduced GPX4 protein, raised basal lipid peroxidation, and increased cell death after addition of otherwise sublethal secondary stressors.
• Protective Compounds: Screening identified flavonoids such as fisetin and sterubin plus synthetic molecules J-147 and CMS-121 that block lipid peroxidation directly or indirectly and, in several cases, also raise glutathione levels.
• Human Disease Evidence: Postmortem brain tissue from Alzheimer’s and Parkinson’s patients shows elevated lipid peroxidation markers and altered iron handling in vulnerable regions; similar changes appear in animal models of multiple diseases.
• Dietary & NRF2 Links: Compounds that activate the NRF2 transcription factor, including sulforaphane from broccoli and certain flavonoids, upregulate antioxidant enzymes including GPX4 and may support long-term cellular resilience.

ABOUT THE GUEST: Pamela Maher, PhD is a research professor at the Salk Institute for Biological Studies in La Jolla, California. Her laboratory studies ferroptosis mechanisms in neurodegenerative diseases and works to identify compounds that inhibit iron-dependent lipid peroxidation. 

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Endogenous peptide diversity, GLP-1 drugs, and methods for novel peptide discovery.

TOPICS DISCUSSED:

• Peptide Structure & Production: Short amino acid chains (3-50 residues) cleaved from larger precursors by PCSK enzymes, stored in dense-core vesicles, and released upon stimuli rather than acting as folded enzymes like proteins.
• Tissue-Specific Processing: The same precursor yields different peptides by tissue; preproglucagon produces glucagon in pancreas but GLP-1 in gut L-cells due to distinct cleavage patterns.
• Signaling Timescales: Peptides act over minutes via GPCRs and can drive longer transcriptional changes such as FOS expression, yet are cleared rapidly by proteases and kidneys.
• Endogenous GLP-1: Meal-stimulated incretin from gut that boosts insulin secretion with a half-life of only minutes, limiting primary action to periphery rather than deep brain structures.
• GLP-1 Engineering for Brain Access: DPP4 site mutations plus lipid conjugation enable albumin binding, extend half-life, and raise brain exposure.
• Dose-Dependent Effects: Low GLP-1 doses mainly lower blood glucose via pancreas; higher doses engage hindbrain and hypothalamic neurons to suppress appetite and alter food preference.
• Novel Peptide Discovery: Computational scans across the genome flag hundreds of uncharacterized precursors, facilitating new peptide discovery.
• BRP Peptide: This newly discovered brain-derived peptide suppresses feeding in GLP-1 receptor knockout mice, activates non-overlapping neurons, and does not slow gastric emptying.

ABOUT THE GUEST: Katrin Svensson, PhD, is a biochemist and physiologist who leads a laboratory at Stanford University focused on peptide hormone physiology and the regulation of energy balance.

PRACTICAL TAKEAWAYS:

• GLP-1 drugs require higher doses to engage brain satiety circuits for meaningful weight loss; lower doses primarily improve glucose control with little effect on appetite.
• Response varies widely across individuals, with some losing over 25% body weight while others see minimal change.
• Emerging peptides under study may suppress appetite via brain pathways that avoid the gastric slowing responsible for common GI side effects of current GLP-1 drugs.
• Research peptides purchased online frequently show variable purity below pharmaceutical standards and may contain unsafe formulation components or aggregates.

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The possible role of deuterium (heavy isotope of hydrogen) in regulating cell division, mitochondrial metabolism & cancer.

TOPICS DISCUSSED:

• Deuterium Basics: Deuterium is twice as massive as regular hydrogen; natural water contains ~150 ppm, with stronger oxygen-deuterium bonds slowing reactions compared to oxygen-hydrogen.
• Mitochondrial Role: Healthy mitochondria produce deuterium-depleted metabolic water (~110 ppm from fat oxidation vs. ~150 ppm from carbs), helping maintain low cellular D:H ratios.
• Cell Growth Regulation: Lower deuterium slows cell division in vitro; cells sense small D:H changes, with higher levels (near/above 150 ppm) promoting growth.
• In Vitro Evidence: DDW (e.g., 25-125 ppm) can reduce proliferation and alters cancer-related gene expression.
• Animal Models: DDW caused tumor regression in mice with transplanted human cancers and showed possible efficacy in veterinary use for dogs and cats.
• Human Prostate Cancer: Phase 2 randomized study showed greater Prostate-Specific Antigen (PSA) reduction, tumor shrinkage, and better 1-year survival with DDW plus standard therapy vs. placebo.
• Dietary Modulation: Ketogenic/high-fat diets lower body deuterium from lipid oxidation.
• Broader Implications: Potential in neurodegeneration models; larger trials needed for registration as adjunct cancer therapy.

ABOUT THE GUEST: Gábor Somlyai, PhD is a molecular biologist who pioneered deuterium depletion studies at the National Institute of Oncology in Hungary. His primary work focuses on the role of deuterium in living organisms and the development of deuterium-depleted water for cancer therapy.

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New research finds that excess antioxidants can support tumor growth in preexisting cancers.

TOPICS DISCUSSED:

• Oxidative Stress: Reactive oxygen species (ROS) generated by mitochondrial metabolism cause damage; context determines whether they promote or suppress cancer.
• Glutathione Biology: Primary cellular antioxidant made from cysteine, glycine, and glutamate; works with peroxidase enzymes to protect against ROS.
• Antioxidant Paradox: Clinical trials (SELECT vitamin E, beta-carotene) showed supplements increased cancer rather than preventing it.
• Cancer Antioxidant Hijacking: Tumors ramp up antioxidant systems to handle high metabolic rates and survive stress including metastasis.
• Extracellular Glutathione Catabolism: Cancer cells break down external glutathione into amino acids, particularly cysteine, to fuel growth (new findings).
• Therapeutic Window: Blocking glutathione breakdown slows tumors in models while sparing normal cells.
• Diet vs Supplements: Balanced diets support glutathione needs; excess isolated antioxidants may enrich the tumor microenvironment.

ABOUT THE GUEST: Isaac Harris, PhD is a biologist working on the role of antioxidants in health, disease, and cancer metabolism.

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Fructose survival hypothesis: how fructose metabolism in the liver triggers ATP depletion, uric acid production, oxidative stress, lipogenesis & leptin resistance.

TOPICS DISCUSSED:

• Glucose vs Fructose Metabolism: Fructose is rapidly metabolized in the liver by fructokinase without feedback, causing ATP depletion and uric acid production, unlike glucose metabolism.
• Liver Effects: Fructose induces uric acid production, NADPH oxidase activation, mitochondrial oxidative stress, and de novo lipogenesis even under caloric restriction.
• Fructose Survival Hypothesis: Fructose signaling promotes fat storage, leptin resistance, foraging behavior, and metabolic syndrome as adaptations for hibernation or starvation, including metabolic water production.
• Brain Impacts: Endogenous fructose production from glucose (polyol pathway) triggered by high glucose, salt, or stress leads to insulin resistance, mitochondrial damage, and neuroinflammation in Alzheimer’s-vulnerable regions.
• Evolutionary Context: Human uricase mutation ~12 million years ago enhanced fructose effects for fat storage during seasonal starvation but increases vulnerability today.
• Modern Triggers: Added sugars, high fructose corn syrup, salt-sugar combinations, and omega-6 fats synergize with fructose to amplify inflammation, appetite, and disease risk.
• Alzheimer’s Link: Fructose-driven brain changes mirror Alzheimer’s pathology, with high brain fructose in patients and potential for fructokinase inhibitors as therapy.

ABOUT THE GUEST: Richard Johnson MD, is a professor of medicine who has conducted clinical practice and NIH-funded research on sugar metabolism since the late 1990s. His work focuses on the role of fructose in metabolic syndrome, obesity, and related diseases.

RELATED CONTENT:

• Article | Dietary Fructose & Metabolic Health: An Evolutionary Perspective
• M&M 249: Fructose, Microglia, Anxiety & Brain Development | Justin Perry | 249

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Deep-dive into a 2026 cardiology review paper claiming seed oils reduce inflammation, exposing misrepresentations of cited clinical trials, and detailing how oxidized Ω-6 fats trigger inflammation.

Companion article: Click HERE

TOPICS DISCUSSED:

• Seed Oil Profiles: Typical seed oils like sunflower are high in linoleic acid (omega-6 PUFA), while canola is higher in monounsaturated fats and resembles olive oil.
• Review Paper Critique: The 2026 JACC review falsely claims sunflower oil reduce inflammation like olive oil, citing an RCT that showed benefits only for canola and olive.
• RCT Analysis: In Iranian women with metabolic issues, switching to canola or olive oil lowered CRP by increasing MUFA and decreasing PUFA intake; sunflower oil produced no change.
• CRP Biology: CRP responds to oxidized lipids and cellular damage patterns, rising with exercise or infection and marking oxidized Ω-6 metabolites in modern diets.
• Oxidized Lipids: Ω-6 fats in LDL and cardiolipin oxidize easily, generating 4-HNE, MDA, and other signals that trigger immune clearance, similar to bacterial threats.
• Sterile Inflammation: High dietary linoleic acid causes chronic immune activation without pathogens, potentially contributing to metabolic and cardiovascular issues.

PRACTICAL TAKEAWAYS:

• Prioritize monounsaturated fats from olive or avocado oil over high-linoleic seed oils like standard sunflower or soybean for lower oxidative stress potential.
• Check labels for high-oleic versions of sunflower oil, which shift the profile toward monounsaturated fats.
• Evaluate nutrition claims by examining original studies and fatty acid compositions rather than accepting review summaries at face value.

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Human genetic variation in dietary fat metabolism and its implications for health & disease.

TOPICS DISCUSSED:

• Linoleic Acid Rise: Linoleic acid now comprises 6-8% or more of energy in Western diets.
• Metabolic Pathways: Omega-6 linoleic acid converts to arachidonic acid and pro-inflammatory oxylipins; omega-3 ALA converts via shared enzymes to EPA/DHA with anti-inflammatory effects.
• FADS Genetic Variants: Ancestry-linked haplotypes in the FADS cluster create large “pipe” size differences, altering fatty acid by up to 40% between ancestral and derived versions.
• Population Differences: African ancestry populations often have high-conversion “big pipe” genotypes; Indigenous American ancestry populations have low-conversion “small pipe” genotypes; European ancestry comes with a mix of both.
• Omega-3 Deficiency: High linoleic intake suppresses EPA production, especially in small-pipe populations, contributing to hypertriglyceridemia and fatty liver in Mexican cohorts.
• Clinical Evidence: Reanalysis of VITAL trial showed 83% reduction in myocardial infarction with omega-3 supplementation in African Americans; Mexican data link low EPA to unique diabetes forms.
• Methodological Issues: Compositional data (from GC-FID measurements) versus absolute concentration measurements can flip relationships between linoleic acid and key biomarkers.

ABOUT THE GUEST: Floyd Chilton PhD is Professor and Director of the Center for Precision Nutrition and Wellness at the University of Arizona. His research focuses on functional genomics, fatty acid metabolism, and precision nutrition, particularly how genetic ancestry influences responses to dietary fats.

RELATED EPISODE:

• M&M 291: Omega Polyunsaturated Fats & Inflammation | Philip Calder

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Pregnenolone, a neurosteroid derived from cholesterol, affects brain activity and shows promise for treating mood and substance abuse disorders.

TOPICS DISCUSSED:

• Steroid Biosynthesis: Cholesterol converted to pregnenolone, the precursor for all steroid hormones including cortisol, aldosterone, and sex hormones.
• Corticosteroids: Synthetic versions like prednisone primarily target glucocorticoid receptors for anti-inflammatory uses but can impact mood and cognition.
• Pregnenolone Mechanisms: Positive allosteric modulator of NMDA receptors for cognition and negative allosteric modulator of CB1 cannabinoid receptors.
• Allopregnanolone: GABAergic derivative of pregnenolone; its IV form Brexanolone is FDA-approved for postpartum depression.
• Clinical Trials: Pregnenolone at 100-500 mg improved depressive symptoms in placebo-controlled studies of bipolar disorder patients.
• Cannabis Interaction: THC robustly induces brain pregnenolone production; supplementation may reduce cannabis and alcohol use.
• Corticosteroid Brain Impact: Prednisone use associated with smaller hippocampal volumes and memory deficits.

ABOUT THE GUEST: Sherwood Brown, MD, PhD is Vice Chair for Clinical Research in the Department of Psychiatry at the University of Texas Southwestern Medical Center in Dallas. With a background in chemistry, his research focuses on steroids and comorbidities in people with mood disorders.

RELATED EPISODE:

• M&M 124: Hormonal Contraception, Sex Hormones, Menstruation, Pregnancy, Puberty, Estrogens, Androgens, Effects of Birth Control on Cognition | Adriene Beltz

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How omega-3 fats in human health, including dietary intake needs, supplements, & omega fat testing.

TOPICS DISCUSSED:

• ω-3 chemistry: EPA and DHA differ from plant ALA in chain length and double-bond count, making them structurally and biologically distinct — and largely irreplaceable by ALA conversion.
• ALA-to-EPA/DHA conversion: A small percentage of dietary ALA converts to EPA, and conversion to DHA is even lower; vegans rely on this inefficient pathway for all long-chain omega-3s.
• Cardiovascular mechanisms: ω-3s lower triglycerides, reduce platelet stickiness, improve endothelial function, and slow resting heart rate, reducing cardiovascular risk.
• ω-3 Index: Defined as red blood cell EPA+DHA as a percent of total fatty acids; 8–12% is the target range, while most Americans sit around 4–5%.
• Brain & dementia risk: Higher DHA blood levels are associated with significantly lower risk of dementia and Alzheimer’s in large cohorts including the UK Biobank and Framingham.
• Linoleic acid nuance: Higher blood levels of dietary linoleic acid (omega-6) associate with lower dementia and cardiovascular risk; downstream omega-6 metabolites — not linoleic acid itself — associate with adverse outcomes.
• Supplementation practicalities: Most people need 1–2 g/day of EPA+DHA to reach an ω-3 Index >8%; oxidation concerns with fish oil supplements may be overstated.

ABOUT THE GUEST: Bill Harris, PhD is founder of both OmegaQuant Laboratory and the Fatty Acid Research Institute (Sioux Falls, SD), where his work centers on blood fatty acid biomarkers as predictors of disease risk in large population cohort studies.

KNOW YOURSELF:

• OmegaQuant: At-home blood testing to see fatty acid profiles, including omega-3 fatty acids. Use link to see options and support M&M.

RELATED EPISODE:

• M&M 134: Omega Fats, Vegetable & Seed Oils, Sugar, Processed Food, Metabolic Health & Dietary Origins of Chronic Inflammatory Disease | Artemis Simopoulos

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