Extremely rapid increase in fatty acid transport and intramyocellular lipid accumulation but markedly delayed insulin resistance after high fat feeding in rats

https://www.ncbi.nlm.nih.gov/pubmed/26197708?dopt=Citation

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Diabetologia. 2015 Oct;58(10):2381-91. doi: 10.1007/s00125-015-3691-8. Epub 2015 Jul 22.

Extremely rapid increase in fatty acid transport and intramyocellular lipid accumulation but markedly delayed insulin resistance after high fat feeding in rats.

Bonen A1Jain SS2Snook LA2Han XX2Yoshida Y2Buddo KH2Lally JS2Pask ED2Paglialunga S2Beaudoin MS2Glatz JF3Luiken JJ3Harasim E4Wright DC2Chabowski A4Holloway GP2.

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Abstract

AIMS/HYPOTHESIS: 

The mechanisms for diet-induced intramyocellular lipid accumulation and its association with insulin resistance remain contentious. In a detailed time-course study in rats, we examined whether a high-fat diet increasedintramyocellular lipid accumulation via alterations in fatty acid translocase (FAT/CD36)-mediated fatty acid transport, selected enzymes and/or fatty acid oxidation, and whether intramyocellular lipid accretion coincided with the onset of insulin resistance.

METHODS: 

We measured, daily (on days 1-7) and/or weekly (for 6 weeks), the diet-induced changes in circulating substrates, insulin, sarcolemmal substrate transporters and transport, selected enzymes, intramyocellular lipids, mitochondrial fatty acid oxidation and basal and insulin-stimulated sarcolemmal GLUT4 and glucose transport. We also examined whether upregulating fatty acid oxidation improved glucose transport in insulin-resistant muscles. Finally, in Cd36-knockout mice, we examined the role of FAT/CD36 in intramyocellular lipid accumulation, insulin sensitivity and diet-induced glucose intolerance.

RESULTS: 

Within 2-3 days, diet-induced increases occurred in insulin, sarcolemmal FAT/CD36 (but not fatty acid binding protein [FABPpm] or fatty acid transporter [FATP]1 or 4), fatty acid transport and intramyocellular triacylglycerol, diacylglycerol and ceramide, independent of enzymatic changes or muscle fatty acid oxidation. Diet-induced increases in mitochondria and mitochondrial fatty acid oxidation and impairments in insulin-stimulated glucose transport and GLUT4 translocation occurred much later (≥21 days). FAT/CD36 ablation impaired insulin-stimulated fatty acid transport and lipid accumulation, improved insulin sensitivity and prevented diet-induced glucose intolerance. Increasing fatty acid oxidation in insulin-resistant muscles improved glucose transport.

CONCLUSIONS/INTERPRETATIONS: 

High-fat feeding rapidly increases intramyocellular lipids (in 2-3 days) via insulin-mediated upregulation of sarcolemmal FAT/CD36 and fatty acid transport. The 16-19 day delay in the onset of insulin resistance suggests that additional mechanisms besides intramyocellular lipids contribute to this pathology.

KEYWORDS: 

Ceramide; Diacylglycerol; Fatty acid oxidation; GLUT4; Glucose transport; Insulin resistance; Mitochondria; Muscle; PGC-1α; Triacylglycerol

PMID: 26197708  DOI: 10.1007/s00125-015-3691-8

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