Fasted to fed trafficking of fatty acids in human adipose tissue reveals a novel regulatory step for enhanced fat storage.

• Context: Absence or excess of adipose tissue are both associated with metabolic complications implying the importance of well-functioning adipose tissue present in normal amounts. Adipose tissue sequesters dietary fat and thus protects other tissues from excess fat exposure, especially following meals. Objective: Use of an integrative physiological technique to quantify trafficking of fatty acids (FA) in adipose tissue over a 24-h period. Methods: Adipose tissue FA handling was studied in response to three meals in eight healthy men by the combination of arterio-venous blood sampling, tissue blood flow, and specific labelling of FA tracing of exogenous and endogenous fat by stable isotope methodology. Results: The efficiency of adipose tissue FA uptake increased robustly with each meal. Chylomicron-triglyceride (TG) was the dominating source of FA. Adipose tissue fractional extraction of chylomicron-TG increased from 21+/-4 to 47+/-8% (p=0.03) between the first and last meal. Although adipose tissue lipoprotein lipase (LPL) action increased with time (2-fold), there was an even greater increase in FA re-esterification (3-fold), which led to a reduced spillover of chylomicron-derived FA, from 77+/-15 to 34+/-7% (p=0.04) comparing the end of the first and the third meal period. Increased uptake of VLDL-derived FA was observed, but spillover of VLDL-derived FA was only seen in the fasting state. Conclusion: Human adipose tissue has a significant potential to up-regulate fat storage during a normal day that goes beyond increased LPL activation. The adaptation towards increasing fat storage may provide an explanation for the beneficial properties of normal amounts of adipose tissue.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Kirurgi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Surgery (hsv//eng)

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