HPLC analysis of brain and plasma for octanoic and decanoic acids.

Abstract

Two methods are described for determination of octanoic and decanoic acids in plasma and brain homogenate by "high-performance" liquid chromatography with ultraviolet detection. Analysis of the underivatized acids had a detection limit of only 50 mg/L, but formation of the p-bromophenacyl ester increased the sensitivity by 100-fold, to a detection limit of 0.5 mg/L. The latter procedure gave interassay coefficients of variation of 4.1% and 4.8% for octanoic and decanoic acids, respectively. The corresponding intra-assay values were 3.95% and 4.7% (n = 6). The derivative method, applied to samples of plasma from children receiving a medium-chain triglyceride (MCT) diet, gave values in agreement with results by gas-liquid chromatography. Results have also been obtained for samples from mice, either treated with the medium-chain triglyceride diet or given infusions of sodium octanoate.

Medium‐chain fatty acids inhibit mitochondrial metabolism in astrocytes promoting astrocyte‐neuron lactate and ketone body shuttle systems

“…Concentrations of MCFAs causing net oxidation in astrocytes are probably close to physiologic. In individuals consuming an MCT diet, C8 and C10 measured in the blood plasma (22) were higher than the concentrations found in our study to cause net oxidation in astrocytes. Elevated concentrations of C8 have also been observed in the CNS of mice after intravenous infusion of this MCFA (22).…”

“…In individuals consuming an MCT diet, C8 and C10 measured in the blood plasma (22) were higher than the concentrations found in our study to cause net oxidation in astrocytes. Elevated concentrations of C8 have also been observed in the CNS of mice after intravenous infusion of this MCFA (22). Direct measurements of C8 and C10 in the brain will be necessary to determine whether the concentration shown in our study to alter astrocyte metabolism can be reached in animals receiving an MCT diet.…”

“…A rationale for conducting this study was to elucidate whether, in addition to the promotion of liver ketogenesis, MCFAs could act directly on energy metabolism in the CNS. In support of this hypothesis, MCFAs can reach the brain where they are rapidly metabolized (15,22). We tested whether MCFAs modulate mitochondrial function in human astrocytes and neurons.…”

Octanoate oxidation measured by13C-NMR spectroscopy in rat skeletal muscle, heart, and liver

“…Contribution of octanoate to the oxidative metabolism of the major sites of fatty acid oxidation (heart, liver, and resting and contracting skeletal muscle) was assessed in the intact rat with 13 C-NMR spectroscopy. Under inhalation anesthesia, [2,4,6,[8][9][10][11][12][13] C4]octanoate was infused into the jugular vein and the sciatic nerve of one limb was stimulated for 1 h. Octanoate was a principal contributor to the acetyl-CoA pool in all tissues examined, with highest oxidation occurring in heart and soleus muscle followed by predominantly red portion of gastrocnemius muscle (RG), liver, and then white portion of gastrocnemius muscle (WG). Fractional contribution of 13 C-labeled octanoate to the acetyl-CoA pool (Fc2) was 0.563 Ϯ 0.066 for heart and 0.367 Ϯ 0.054 for liver.…”

“…We postulated that octanoate utilization would increase with contraction and be reflected in a similar or higher fractional contribution of 13 C-labeled octanoate to oxidative metabolism in contracted vs. resting muscles. [2,4,6,[8][9][10][11][12][13] C4]octanoate was infused into the jugular vein of an intact rat over the course of 1 h, and the contribution of octanoate to the oxidative metabolism of heart, liver, and rested and contracted gastrocnemius and soleus muscle was determined. Blood and plasma samples were analyzed to quantitate levels of [ 13 C]octanoate, metabolite concentrations, as well as the conversion of [ 13 C]octanoate into other labeled substrates.…”