Increased de novo lipogenesis is a hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD) in obesity, but the macronutrient carbon source for over half of hepatic fatty acid synthesis remains undetermined. Here, we discover that dietary protein, rather than carbohydrates or fat, is the primary nutritional risk factor for MASLD in humans. Consistently, ex vivo tracing studies identify amino acids as a major carbon supplier for the tricarboxylic acid (TCA) cycle and lipogenesis in isolated mouse hepatocytes. In vivo, dietary amino acids are twice as efficient as glucose in fueling hepatic fatty acid synthesis. The onset of obesity further drives amino acids into fatty acid synthesis through reductive carboxylation, while genetic and chemical interventions that divert amino acid carbon away from lipogenesis alleviate hepatic steatosis. Finally, low-protein diets (LPDs) not only prevent body weight gain in obese mice but also reduce hepatic lipid accumulation and liver damage. Together, this study uncovers the significant role of amino acids in hepatic lipogenesis and suggests a previously unappreciated nutritional intervention target for MASLD.

The intestine constantly encounters and adapts to the external environment shaped by diverse dietary nutrients. However, whether and how gut adaptability to dietary challenges is compromised in ulcerative colitis is incompletely understood. Here, we show that a transient high-fat diet exacerbates colitis owing to inflammation-compromised bile acid tolerance. Mechanistically, excessive tumor necrosis factor (TNF) produced at the onset of colitis interferes with bile-acid detoxification through the receptor-interacting serine/threonine-protein kinase 1/extracellular signal-regulated kinase pathway in intestinal epithelial cells, leading to bile acid overload in the endoplasmic reticulum and consequent apoptosis. In line with the synergy of bile acids and TNF in promoting gut epithelial damage, high intestinal bile acids correlate with poor infliximab response, and bile acid clearance improves infliximab efficacy in experimental colitis. This study identifies bile acids as an “opportunistic pathogenic factor” in the gut that would represent a promising target and stratification criterion for ulcerative colitis prevention/therapy.

Heat stress triggers cell membrane lipid remodeling, yet whether this signals plants to perceive high temperatures and how such physical signals are decoded into biological signals remains unclear. Here, we demonstrate that diacylglycerol kinase 7 (DGK7) responds to heat stress at the plasma membrane, converting diacylglycerol into the second messenger, phosphatidic acid (PA). Subsequently, metal-dependent phosphodiesterase (MdPDE1) senses PA, acquires its activity by binding to PA, and translocates to the nucleus to degrade another second messenger, cyclic adenosine monophosphate (cAMP). MdPDE1 then elicits transcriptional landscape changes via altering cAMP signaling. Furthermore, G protein subunit thermotolerance 2 (TT2) inhibits DGK7 activity by Ser⁴⁷⁷ dephosphorylation, blocking MdPDE1 activity and nuclear translocation. Notably, field trials demonstrated the promising applications of this mechanism that confers varying degrees of rice thermotolerance as needed. This study establishes a complete hierarchical thermo-decoding mechanism that opens opportunities for creating customized heat-tolerant crops, aiding in mitigating yield losses from global warming.

Salicylic acid (SA) is a ubiquitous plant hormone with a long history in human

civilization1,2 . Because of the central role of SA in orchestrating plant pathogen

defence, understanding SA biosynthesis is fundamental to plant immunity research

and crop improvement. Isochorismate-derived SA biosynthesis has been well

defined in Arabidopsis. However, increasing evidence suggests a crucial function for

phenylalanine-derived SA biosynthesis in many other plant species1 . Here we reveal

the phenylalanine-derived SA biosynthetic pathway in rice by identifying three

dedicated enzymes — peroxisomal benzoyl-CoA:benzyl alcohol benzoyltransferase

(BEBT), the endoplasmic reticulum-associated cytochrome P450 enzyme

benzylbenzoate hydroxylase (BBH), and cytosolic benzylsalicylate esterase (BSE)

that sequentially convert benzoyl-CoA to benzylbenzoate, benzylsalicylate and SA.

The pathogen-induced gene expression pattern and SA biosynthetic functions of this

triple-enzyme module are conserved in diverse plants. This work fills a major knowledge

gap in the biosynthesis of a key plant defence hormone, establishing a foundation for

new strategies to create disease-resistant crops.