Biology subjects

Ragavan, M.

Publications and source records attributed to Ragavan, M..

3 recordsLinked to original sources

bioRxiv2023

Detecting altered hepatic lipid oxidation by MRI in an animal model of NAFLD

Nonalcoholic fatty liver disease (NAFLD) prevalence is increasing annually and affects over a third of U.S. adults. NAFLD can progress to nonalcoholic steatohepatitis (NASH), characterized by severe inflammation and fibrosis. NASH is predicted to become the primary cause of liver transplant by 2030. Although the etiology of NAFLD/NASH is incompletely understood, dysregulated fatty acid oxidation is implicated in disease pathogenesis. Here, we developed a method for estimating hepatic {beta}-oxidation from the metabolism of [D15]octanoate to deuterated water and detection with deuterium magnetic resonance methods. Application of this method to perfused liver from a mouse model of NAFLD revealed dysregulated hepatic {beta}-oxidation, findings that we confirmed with in vivo imaging. The high-fat diet-induced NAFLD mouse studies indicated that decreased {beta}-oxidative efficiency in the fatty liver could serve as a prognostic indicator of NAFLD progression. Furthermore, our method provides a clinically translatable imaging approach for determining hepatic {beta}-oxidation efficiency.

biochemistry↗

bioRxiv2022

In-vivo characterization of glutamine metabolism identifies therapeutic targets in clear cell renal cell carcinoma

Targeting metabolic vulnerabilities has been proposed as a therapeutic strategy in renal cell carcinoma (RCC). Here, we analyzed metabolism in patient-derived xenografts (tumorgrafts) from diverse forms of RCC. Tumorgrafts from VHL-mutant clear cell RCC (ccRCC) retained metabolic features of human ccRCC and engage in oxidative and reductive glutamine metabolism. We used several approaches to suppress glutamine metabolism and test the effect on tumor growth. Genetic silencing of isocitrate dehydrogenase-1 or -2 impaired reductive labeling of TCA cycle intermediates and suppressed tumor growth. Glutaminase inhibition resulted in modest growth suppression and variable effects on glutamine metabolism in vivo. Infusions with [amide-15N]glutamine revealed persistent amidotransferase activity during glutaminase inhibition, and blocking these activities with the amidotransferase inhibitor JHU-083 also reduced tumor growth. We conclude that ccRCC tumorgrafts catabolize glutamine via multiple pathways, perhaps explaining why it has been challenging to achieve therapeutic responses in patients by inhibiting glutaminase. TeaserGlutamine fuels the TCA cycle and amidotransferase pathways in clear cell renal cell carcinoma.

cancer biology↗

bioRxiv2020

Pioglitazone rescues mitochondrial lipid remodeling and pyruvate dehydrogenase hyperactivation in hepatic insulin resistance

Insulin resistance and altered hepatic mitochondrial function are central features of type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD), but the etiological role of these processes in disease progression remains unclear. We investigated the molecular links between insulin resistance, mitochondrial remodeling, and hepatic lipid accumulation in a rodent model of T2D / NAFLD. Livers from obese, insulin resistant mice displayed augmented mitochondrial content and increased TCA cycle and pyruvate dehydrogenase (PDH) activities. Insulin sensitization with pioglitazone mitigated pyruvate-driven TCA cycle activity and PDH activation via both covalent (PDK4 and PDP2) and allosteric (intracellular pyruvate availability) mechanisms. Interestingly, improvements in insulin sensitivity and mitochondrial function were entirely dissociated from changes in hepatic triglycerides, diacylglycerides or fatty acids. Instead, we show that the mitochondrial phospholipid cardiolipin undergoes pathological remodeling in livers from obese mice and that this is reversed by insulin sensitization. Our findings identify targetable mitochondrial features of T2D and NAFLD and highlight the benefit of insulin sensitization in managing the clinical burden of obesity-associated disease.

biochemistry↗