Calorie restriction exacerbates folic acid-induced kidney fibrosis by altering mitochondria metabolism

Calorie restriction (CR) is known to confer health benefits, including longevity and disease prevention. Although CR is promising in preventing chronic kidney disease (CKD), its potential impact on the progression of kidney fibrosis from acute kidney injury (AKI) to CKD remains unclear. Here, we present evidence that CR exacerbates renal damage in a mouse model of folic acid (FA)-induced renal fibrosis by altering mitochondrial metabolism and inflammation. Mice subjected to CR (60% of ad libitum) for 3 days were subjected to high dose of FA (250 mg/kg) injection and maintained under CR for an additional week before being sacrificed. Biochemical analyses showed that CR mice exhibited increased kidney injury and fibrosis. RNA sequencing analysis demonstrated decreased electron transport and oxidative phosphorylation (OXPHOS) in CR kidneys with injury, heightened inflammatory, and fibrotic responses. Decreased CR significantly decreased OXPHOS gene and protein levels and reduced β-oxidation-associated proteins in the kidney. To determine whether defects in mitochondrial metabolism is associated with inflammation in the kidney, further in vitro experiments were performed. NRK52E kidney epithelial cells were treated with antimycin A to induce mitochondrial damage. Antimycin A treatment significantly increased chemokine expression via a STING-dependent pathway. Serum restriction in NRK49F kidney fibroblasts was observed to enhance the fibrotic response induced by TGFβ under in vitro conditions. In summary, our results indicate that CR exacerbates fibrosis and inflammatory responses in the kidney by altering mitochondrial metabolism, highlighting the importance of adequate energy supply for an effective response to AKI and fibrosis development.