Albumin Knockout Mice Exhibit Reduced Plasma Free Fatty Acids but No Impairment in Whole Body Fat Oxidation

Objectives To improve understanding of the control of lipid metabolism, we aimed to determine whether lack of serum albumin decreases plasma free fatty acids (FFA), hepatic triacylglycerol (TAG), and whole body substrate oxidation in albumin knockout mice compared to wild type mice. Methods Male and female homozygous albumin knockout mice and C57BL/6J wild type controls, each on the 5k52 diet which contains a moderate fat content, were studied at 6–8 weeks of age. Body composition was tested by magnetic resonance. Substrate oxidation was measured by indirect calorimetry over 24 hours in metabolic cages. Plasma and tissues were collected after a 5-hour fast. Plasma FFA was measured by liquid chromatography/mass spectrometry (LC/MS). Hepatic TAG was measured by a colorimetric kit. Results In albumin knockout mice compared to the wild type mice, plasma FFA (P < 0.0001) and hepatic TAG content (P < 0.0001) were each reduced, while body fat percentage was increased (P < 0.01). In addition, female versus male showed higher hepatic TAG levels (P < 0.01). These results indicate that the lack of serum albumin decreases plasma FFA and hepatic TAG accumulation. However, the average 24-hour oxygen consumption, metabolic rate, and respiratory quotient (RQ) were not altered in albumin knockout mice, indicating that total fuel oxidation and relative contribution of lipid to whole body metabolism was not significantly unaltered. Conclusions We propose that lack of albumin reduces plasma FFA which diminishes hepatic TAG content through changes in the lipid supply to the liver. The results indicate that tissue lipid accumulation can be altered by targeting albumin without substantially disrupting whole body substrate oxidation, suggesting that metabolic control of FFA trafficking toward sites of ectopic lipid deposition and toward oxidation can be regulated independently of one another. Funding Sources McKinley Educational Initiative and the Purdue University College of Health and Human Sciences

THE EFFECTS OF EUGLVCEMIC INSULIN CLAMP ON THE METABOLISM OF 3-HYDROXVBUTYRATE AND PLASMA FREE FAHY ACIDS BY THE HIND LIMB OF LACRATING SHEEP

The effects of exogenous insulin, with euglycemia, on the concentration differences, extraction ratio and uptake of 3- hydroxybutyrate and plasma free fatty acids by the lactating sheep hind limb were studied. Generally, the results showed that with increasing plasma insulin levels, while maintaining euglycemia, the concentrations, arterio-venous concentration differences, extraction ratio and uptake of 3-hydrubutyrate and free fatty acids Were significantly (P<0.05) reduced, but Significant correlation was established between arterial concentration of 3-hydtoxvbutyrate and plasma free fatty acids and their uptake. A similar relationship was also obtained between the arterial concentrations of 3-hydroxybutyrate plasma free fatty acids.

MON-065 Prevention of 6-Mercaptopurine-Induced Hypoglycemia by Levocarnitine Replacement

Background: Symptomatic hypoglycemia has been reported in children less than 6 years of age receiving 6-Mercaptopurine for acute lymphoblastic anemia (ALL); however, the mechanism of 6-Mercaptopurine-induced hypoglycemia has been unclear. Objective: The objective was to investigate the metabolism in a 3-year-old patient with hypoglycemia induced by 6-Mercaptopurine during maintenance therapy for ALL. Methods: We reviewed test results including serum total and free carnitine levels at time of hypoglycemia in a 3-year-old child with ALL who had repeatedly low plasma glucose as a side effect of 6-Mercaptopurine. Hypoglycemia defined as plasma glucose &lt;50 mg/dL was detected using a glucose meter and each time verified in the clinical laboratory. After Levocarnitine was added to 6-Mercaptopurine therapy, the glycemic control was assessed using a glucose meter, the clinical laboratory, and a continuous glucose monitor; serum total and free carnitine levels were repeated when hypoglycemia resolved. Results: Our patient presented with fatigue, tremors and plasma glucose 39 mg/dL to 47 mg/dL, corrected with a sugary beverage. He had plasma ACTH 38 pg/mL, serum cortisol 10 mcg/dL, total carnitine 24 nmol/mL (expected 35 - 84), free carnitine 18 nmol/mL (expected 24 - 63), plasma free fatty acids 1.62 mmol/L (expected &gt;1.5), beta-hydroxybutyrate of 0.2 mmol/L to 0.7 mmol/L (expected &gt;2.0), and urine ketone bodies negative when plasma glucose was between 33 mg/dL and 39 mg/dL. Plasma insulin was undetectable at time of hypoglycemia, and serum glucose increased by less than 30 points in response to Glucagon IV. Serum IGF-1 as measure of growth hormone effect and thyroid function were normal. Hypoglycemia continued to daily recur especially during the night despite bedtime snacks high in complex carbohydrates and was prevented only by Levocarnitine 25 mg/kg/dose every 12 hours PO that raised serum total and free carnitine levels. The patient remained hypoglycemia-free one month after Levocarnitine was added to 6-Mercaptopurine therapy, in particular, he had average glucose 114 mg/dL with standard deviation 30 mg/dL, glucose 70 mg/dL to 140 mg/dL 93% of the time, and glucose &lt;55 mg/dL 0% of the time. Conclusions: Our patient had symptomatic hypoketotic hypoglycemia related to moderately reduced serum total and free carnitine, corrected with Levocarnitine replacement. Increase in plasma free fatty acids without expected increase in plasma and urine ketone bodies may be sign of impaired synthesis of carnitine, which is required for transport of fatty acids into the mitochondria to produce ketone bodies. Measuring serum total and free carnitine in hypoglycemia induced by 6-Mercaptopurine is helpful in identifying children, who may benefit from Levocarnitine replacement.