Biology subjects

Hakeem-Sanni, M. F.

Publications and source records attributed to Hakeem-Sanni, M. F..

4 recordsLinked to original sources

bioRxiv2024

Fatty acids are not a significant contributor to the TCA cycle in cancer cell lines: evidence of incomplete fatty acid oxidation.

Upregulated fatty acid oxidation (FAO) is a hallmark of many aggressive cancers and is widely presumed to fuel the tricarboxylic acid (TCA) cycle for ATP production. However, the quantitative relationship between FAO capacity and its contribution to mitochondrial metabolism relative to other fuels remains unclear. Here, we combined parallel stable-isotope tracing with metabolic phenotyping across a diverse panel of 27 cancer cell lines to reveal a fundamental capacity-contribution paradox. Despite exhibiting FAO rates that varied over eight-fold, exogenous long-chain fatty acids consistently contributed minimally (<10%) to TCA cycle intermediates in all cancer cell lines. We demonstrated that FAO functions as a compensatory source of acetyl-CoA in cells with limited glucose-derived acetyl-CoA synthesis, rather than acting as a primary fuel source. In this context, high FAO rates do not primarily result from FAO-mediated suppression of glucose oxidation, but instead reflect the recruitment of fatty acid- and glutamine-derived carbons via a malic enzyme-dependent shunt to sustain the mitochondrial acetyl-CoA pool while preserving glucose-derived anaplerotic flux. These findings challenge the prevailing view that FAO serves as a primary bioenergetic fuel in cancer, instead identifying it as a compensatory rheostat that supplements acetyl-CoA supply in glucose-limited settings by working together with glutamine-driven, malic enzyme-dependent anaplerosis, providing a mechanistic framework to reinterpret the efficacy of FAO inhibitors beyond simple caloric starvation.

cancer biology↗

bioRxiv2024

Pathway metabolite ratios reveal distinctive glutamine metabolism in a subset of proliferating cells

Large-scale metabolomic analyses of pan-cancer cell line panels have provided significant insights into the relationships between metabolism and cancer cell biology. Here, we took a pathway-centric approach by transforming targeted metabolomic data into ratios to study associations between reactant and product metabolites in a panel of cancer and non-cancer cell lines. We identified five clusters of cells from various tissue origins. Of these, cells in Cluster 4 had high ratios of TCA cycle metabolites relative to pyruvate, produced more lactate yet consumed less glucose and glutamine, and greater OXPHOS activity compared to Cluster 3 cells with low TCA cycle metabolite ratios. This was due to more glutamine cataplerotic efflux and not glycolysis in cells of Cluster 4. In silico analyses of loss-of-function and drug sensitivity screens showed that Cluster 4 cells were more susceptible to gene deletion and drug targeting of lactate and glutamine metabolism, and OXPHOS than cells in Cluster 3. Our results highlight the potential of pathway-centric approaches to reveal new aspects of cellular metabolism from metabolomic data.

cancer biology↗

bioRxiv2024

CPT1a regulates the delivery of extracellular fatty acids for cardiolipin turnover in prostate cancer cells.

Mitochondrial fatty acid oxidation (FAO) has been proposed to be a major bioenergetic pathway in prostate cancer. However, this concept fails to consider FAO relative to other mitochondrial substrates. Here, we found extracellular long-chain fatty acids (LCFAs), including palmitate, stearate, oleate, linoleate, linolenate, are minor sources of carbon entering the TCA cycle compared to glucose and glutamine in prostate cancer cells, despite being assimilated in the mitochondria as acyl-carnitines. In contrast, cardiolipins were a prominent LCFAs sink, with some species achieving greater than 50% 13C-labelling within 6 hours, suggesting high cardiolipin turnover using extracellular LCFAs. Knockdown of CPT1a, the rate-limiting enzyme of LCFA entry into mitochondria, reduced the incorporation of extracellular linoleate into cardiolipins. These results demonstrate that FAO is not a major input for the TCA cycle and provide evidence for an underappreciated role for CPT1a in regulating LCFAs entry into mitochondria for cardiolipin remodelling.

cancer biology↗

bioRxiv2023

Hepatic Lipid Droplet-Associated Proteome Changes Distinguish Dietary-Induced Fatty Liver from Insulin Resistance in Male Mice.

Fatty liver is characterised by the expansion of lipid droplets and is associated with the development of many metabolic diseases, including insulin resistance, dyslipidaemia and cardiovascular disease. We assessed the morphology of hepatic lipid droplets and performed quantitative proteomics in lean, glucose-tolerant mice compared to high-fat diet (HFD) fed mice that displayed hepatic steatosis and glucose intolerance as well as high-starch diet (HStD) fed mice who exhibited similar levels of hepatic steatosis but remained glucose tolerant. Both HFD and HStD-fed mice had more and larger lipid droplets than Chow-fed animals. We observed striking differences in liver lipid droplet proteomes of HFD and HStD-fed mice compared to Chow-fed mice, with fewer differences between HFD and HStD. Taking advantage of our diet strategy, we identified a fatty liver lipid droplet proteome consisting of proteins common in HFD- and HStD-fed mice. Likewise, a proteome associated with glucose tolerance that included proteins common in Chow and HStD but not HFD-fed mice was identified. Notably, glucose intolerance was associated with changes in the ratio of adipose triglyceride lipase (ATGL) to perilipin 5 (PLIN5) in the lipid droplet proteome, suggesting dysregulation of neutral lipid homeostasis in glucose-intolerant fatty liver, which supports bioactive lipid synthesis and impairs hepatic insulin action. We conclude that our novel dietary approach uncouples ectopic lipid burden from insulin resistance-associated changes in the hepatic lipid droplet proteome.

cell biology↗