Journal September 19, 2026 6 min read

What is metabolic adaptation?

Metabolic adaptation is the coordinated shift in fuel handling, hormone signalling and gene expression that follows a change in nutrient supply. This page summarises laboratory research on the pathways involved.

peptides-pro Editorial

Metabolic adaptation is the umbrella term for the coordinated set of changes in fuel handling, endocrine signalling and gene expression that a biological system makes when nutrient supply, energy demand or substrate composition changes. It is not a single molecule or a single pathway; the term covers responses as different as a liver switching its handling of amino acids when dietary protein source changes, a tumour epithelium shifting its transcriptional programme under hypoxia, and a fungus rerouting carbon into pigment biosynthesis. In the research literature the phrase is used interchangeably with terms such as metabolic remodelling, substrate switching and adaptive stress response, and it is studied across species from mice and quail to human clinical cohorts.

Because the term spans so many systems, no single identifier applies. The work described below centres on several distinct families: hepatic glutamate dehydrogenase (GDH) and its role in amino-acid-to-glucose flux, the non-classical MHC class I molecule HLA-G, the nuclear receptor REV-ERB and its mitochondrial oxidative phosphorylation targets, the mitochondria-derived peptide family (humanin, MOTS-c and the small humanin-like peptides), and fibroblast growth factor 21 (FGF21) with its obligate co-receptor β-Klotho.

Research Studies

Liver GDH and dietary protein source in mice

Control mice and Hep-Glud1^-/- mice lacking liver GDH were fed for four days on either an animal-based or a plant-based diet matched for macronutrient spectrum. Hepatic GDH was upregulated in control mice eating animal proteins relative to the plant regimen, and ad libitum-fed control mice showed lower glycemia under the plant-based diet. The authors concluded that a transition to dietary plant-based proteins requires functional liver GDH for proper control of ammonia and energy homeostasis [1].

HLA-G and tumour-intrinsic growth in clear cell renal cell carcinoma

Analysis of the Cancer Genome Atlas ccRCC cohort found that elevated HLA-G expression was associated with immunosuppressive programmes and cell populations. Interrogation of a public ccRCC single-cell RNA sequencing dataset showed that HLA-G expression within tumour epithelial clusters was associated with hypoxia-related programmes. Using integrated transcriptomic, in vitro and in vivo approaches, the authors characterised HLA-G as a tumour-intrinsic driver of growth and survival in renal cell carcinoma [2].

Hepatic proteomic recovery after refeeding in Japanese quail

Eighteen 12-week-old male quails (245.20 ± 0.213 g) were assigned to three groups (n = 6): control fed ad libitum (12.13 MJ/kg), 24 h feed deprivation followed by 6 h refeeding, and 24 h on a low metabolizable energy diet (6.30 MJ/kg) followed by 6 h refeeding. In total, 854 proteins were identified, of which 515 met the filtering criteria. The study aimed to characterise early liver protein signatures during recovery from nutritional stress [3].

Low-protein diet, gut microbiota and FGF21 in chronic kidney disease

The metabolic effects of a low-protein diet were investigated in murine models and in a randomised controlled trial in non-diabetic CKD patients, focusing on glucose homeostasis, plasma uremic toxin levels, gut microbiota remodelling and endocrine adaptations. In both experimental and clinical settings the diet improved glucose tolerance and significantly decreased circulating gut-derived uremic toxins while reducing body weight. Lactiplantibacillus plantarum WJL was reported to ameliorate chronic kidney disease by inhibiting the FGF21 adaptive stress response under low-protein diet conditions [4].

Cmpks1 and carotenoid biosynthesis in Cordyceps militaris

Cmpks1, a light-induced gene encoding a reducing type I polyketide synthase, was identified as a key regulator of pigment biosynthesis in Cordyceps militaris. Its transcription was CmWC-1-dependent and upregulated during fruiting body development. CRISPR/Cas9-mediated loss-of-function mutants showed stable albino phenotypes while retaining fruiting body differentiation; disruption of Cmpks1 abolished carotenoid biosynthesis and increased sensitivity to high-stress conditions [5].

REV-ERB agonism and sorafenib response in liver cancer

Genome-wide RNA-seq analysis of hepatocellular carcinoma identified mitochondrial oxidative phosphorylation and Hmox1 upregulation as features of the disease. The REV-ERB agonist SR9009 was reported to potentiate sorafenib efficacy in liver cancer models, framing metabolic vulnerability as a targetable axis alongside existing multikinase inhibitor therapy [6].

Mitochondria-derived peptides in hepatic metabolism

Mitochondria-derived peptides are bioactive molecules encoded by small open reading frames within mitochondrial DNA. Humanin, the first discovered, functions as a cytoprotective factor protecting cells from stress-induced apoptosis. The family also includes MOTS-c, described as a key regulator of metabolic homeostasis and stress adaptation, and the small humanin-like peptides SHLP1-6, which modulate mitochondrial bioenergetics and insulin sensitivity. These peptides are reported to maintain mitochondrial function and metabolic balance in the liver [7].

Probiotic intervention and weight regain in weight cyclers

A registered clinical study is evaluating a probiotic preparation in weight cyclers, on the premise that weight regain after caloric restriction is common and is attributed in part to metabolic adaptations. The stated rationale is that gut microbiota influence weight management and that probiotics may reduce weight regain by modulating appetite and metabolism [8].

Comparative and cross-tissue observations

Several lines of work describe adaptation at the whole-organism level. A comparative study characterised the adipokine profile of middle-aged master athletes, untrained adults and young individuals, addressing how lifelong training relates to adipose endocrine output during ageing [9]. A review examined exerkine-mediated inter-organ crosstalk in metabolic disease, arguing that the systemic benefits of exercise are not fully explained by energy expenditure, muscle glucose uptake, reduced adiposity or peripheral insulin sensitivity alone [10]. A preliminary study evaluated early postoperative changes in the energy-regulating hormones irisin and nesfatin-1 following laparoscopic sleeve gastrectomy in women with obesity [11]. Separately, adipose FGF21 signalling was reported to mediate the anti-senescence effects of protein restriction, using genetic loss-of-function models for Fgf21 and its obligate co-receptor [12].

Model or population	Intervention or comparison	Reported observation
Control and Hep-Glud1^-/- mice	4 days animal- vs plant-based diet	Hepatic GDH upregulated on animal proteins; lower glycemia on plant regimen in controls [1]
Japanese quail, 12-week-old males	24 h deprivation or low-energy diet, then 6 h refeeding	854 proteins identified, 515 passing filters [3]
Non-diabetic CKD patients and murine models	Low-protein diet	Improved glucose tolerance, reduced circulating gut-derived uremic toxins, reduced body weight [4]
ccRCC cohort and single-cell dataset	HLA-G expression analysis	Elevated HLA-G associated with immunosuppressive and hypoxia-related programmes [2]

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