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The metabolism of “surplus” amino acids
For an adult in N balance, apart from small amounts of amino acids required for the synthesis of neurotransmitters, hormones, etc, an amount of amino acids almost equal to that absorbed from the diet can be considered to be “surplus” in that it will be catabolized. The higher diet-induced thermogenesis from protein than from carbohydrate or fat has generally been assumed to be due to increased protein synthesis, which is ATP expensive. To this must be added the ATP cost of protein catabolism through the ubiquitin-proteasome pathway. Amino acid catabolism will add to thermogenesis. Deamination results in net ATP formation except when serine and threonine deaminases are used, but there is the energy cost of synthesizing glutamine in extra-hepatic tissues. The synthesis of urea has a net cost of only 1·5 × ATP when the ATP yield from fumarate metabolism is offset against the ATP cost of the urea cycle, but this offset is thermogenic. In fasting and on a low carbohydrate diet as much of the amino acid carbon as possible will be used for gluconeogenesis – an ATP-expensive, and hence thermogenic, process. Complete oxidation of most amino acid carbon skeletons also involves a number of thermogenic steps in which ATP (or GTP) or reduced coenzymes are utilized. There are no such thermogenic steps in the metabolism of pyruvate, acetyl CoA or acetoacetate, but for amino acids that are metabolized by way of the citric acid cycle intermediates there is thermogenesis ranging from 1 up to 7 × ATP equivalent per mol.
Journal Article
Harper's illustrated biochemistry
Integrates detailed discussions of biochemical diseases, updated clinical information, case studies, and extensive illustrations, this classic can be used as both a text and USMLE review book. Extensively illustrated with 500+ clear, descriptive illustrations and new chapters on amino acids and peptides, structures of protein, and the Human Genome project.
Book
Psilocybin desynchronizes the human brain
A single dose of psilocybin, a psychedelic that acutely causes distortions of space–time perception and ego dissolution, produces rapid and persistent therapeutic effects in human clinical trials
1
–
4
. In animal models, psilocybin induces neuroplasticity in cortex and hippocampus
5
–
8
. It remains unclear how human brain network changes relate to subjective and lasting effects of psychedelics. Here we tracked individual-specific brain changes with longitudinal precision functional mapping (roughly 18 magnetic resonance imaging visits per participant). Healthy adults were tracked before, during and for 3 weeks after high-dose psilocybin (25 mg) and methylphenidate (40 mg), and brought back for an additional psilocybin dose 6–12 months later. Psilocybin massively disrupted functional connectivity (FC) in cortex and subcortex, acutely causing more than threefold greater change than methylphenidate. These FC changes were driven by brain desynchronization across spatial scales (areal, global), which dissolved network distinctions by reducing correlations within and anticorrelations between networks. Psilocybin-driven FC changes were strongest in the default mode network, which is connected to the anterior hippocampus and is thought to create our sense of space, time and self. Individual differences in FC changes were strongly linked to the subjective psychedelic experience. Performing a perceptual task reduced psilocybin-driven FC changes. Psilocybin caused persistent decrease in FC between the anterior hippocampus and default mode network, lasting for weeks. Persistent reduction of hippocampal-default mode network connectivity may represent a neuroanatomical and mechanistic correlate of the proplasticity and therapeutic effects of psychedelics.
Healthy adults were tracked before, during and after high doses of psilocybin and methylphenidate to assess how psychedelics can change human brain networks, and psilocybin was found to massively disrupt functional connectivity in cortex and subcortex with some changes persisting for weeks.
Journal Article
Amino Acid Metabolism
Amino Acid Metabolism, 3rd Edition covers all aspects of the biochemistry and nutritional biochemistry of the amino acids. Starting with an overview of nitrogen fixation and the incorporation of inorganic nitrogen into amino acids, the book then details other major nitrogenous compounds in micro-organisms, plants and animals. Contents include a discussion of the catabolism of amino acids and other nitrogenous compounds in animals, and the microbiological reactions involved in release of nitrogen gas back into the atmosphere. Mammalian (mainly human) protein and amino acid requirements are considered in detail, and the methods that are used to determine them.
Chapters consider individual amino acids, grouped according to their metabolic origin, and discussing their biosynthesis (in plants and micro-organisms for those that are dietary essentials for human beings), major metabolic roles (mainly in human metabolism) and catabolism (again mainly in human metabolism). There is also discussion of regulatory mechanisms for all these metabolic pathways, and of metabolic and genetic diseases affecting the (human) metabolism of amino acids.
Throughout the book the emphasis is on the nutritional importance of amino acids, integration and control of metabolism and metabolic and other disturbances of relevance to human biochemistry and health.
* Completely revised edition of this comprehensive text covering all the latest findings in amino acid metabolism research
* Written by an authority in the field
* Covers new advances in structural biology
* Clear illustrations of all structures and metabolic pathways
* Full list of recommended further reading for each chapter and bibliography of papers cited in the text
eBook
Trends in the psychedelic renaissance: applying artificial intelligence to measure media portrayal of psychedelic drugs in the 21st century
The relationship between media portrayal of psychedelic drugs, scientific research and drug policy is an area of debate.
To apply artificial intelligence technology to measure trends in media sentiment towards the therapeutic potential of psychedelic drugs.
Up to 300 of the most relevant articles from Google News searches for the term 'psychedelics' were sampled for each year from 2000 to 2025. A large language model, ChatGPT, evaluated subject matter and sentiment.
In total, 88.3% of screened URLs (3308 of 3747) were included in the analysis. The proportion of articles focusing on the therapeutic potential of psychedelics increased from 13.3% (26 of 198) from 2000 to 2009 to 85.3% (1254 of 1470) from 2020 to 2025. The average sentiment score from 2000 to 2025 for articles from all publications (
= 2168) was 78.5 ± 9.3 (mean ± s.d.) (possible range: 1-100). 1.3% (29 of 2168) of articles carried negative sentiment (<50) whereas 4.8% (103 of 2168) had extremely positive sentiment (≥90). Average sentiment reached a peak in 2020 (80.8 ± 7.0), and a statistically significant trough in sentiment was observed in 2024 relative to 2020-2023 (2020-2023, 79.2; 2024, 74.3,
< 0.00001, Mann-Whitney
-test). The proportion of negative-neutral articles (≤65) increased annually from a trough of 3.6% (8 of 267) in 2020 to a peak of 20.9% (43 of 253) in 2024. Artificial intelligence sentiment scores were correlated and concordant with average human rater scores (
= 0.88, concordance correlation coefficient 0.84).
Although most 21st-century media coverage of psychedelic drugs has been positively framed, negative and neutral coverage has increased in frequency since 2020. Researchers, clinicians, regulators and policy-makers should be mindful of the complex relationship between media portrayals of psychedelics and the results of scientific research.
Journal Article
