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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

This paper provides three easy and accessible assays for assessing lipid metabolism in mice.

Abstract

Assessing lipid metabolism is a cornerstone of evaluating metabolic function, and it is considered essential for in vivo metabolism studies. Lipids are a class of many different molecules with many pathways involved in their synthesis and metabolism. A starting point for evaluating lipid hemostasis for nutrition and obesity research is needed. This paper describes three easy and accessible methods that require little expertise or practice to master, and that can be adapted by most labs to screen for lipid-metabolism abnormalities in mice. These methods are (1) measuring several fasting serum lipid molecules using commercial kits (2) assaying for dietary lipid-handling capability through an oral intralipid tolerance test, and (3) evaluating the response to a pharmaceutical compound, CL 316,243, in mice. Together, these methods will provide a high-level overview of lipid handling capability in mice.

Introduction

Carbohydrates and lipids are two major substrates for energy metabolism. Aberrant lipid metabolism results in many human diseases, including type II diabetes, cardiovascular diseases, fatty liver diseases, and cancers. Dietary lipids, mainly triglycerides, are absorbed through the intestine into the lymphatic system and enter the venous circulation in chylomicrons near the heart1. Lipids are carried by lipoprotein particles in the bloodstream, where the fatty acid moieties are liberated by the action of lipoprotein lipase at peripheral organs such as muscle and adipose tissue2. The remaining cholesterol-rich remnant part....

Protocol

Animals are housed in standardized conditions following animal-care and experimental protocols approved by the Institutional Animal Care and Use Committee of the Baylor College of Medicine (BCM). Animals are fed a standard or special diet, water ad libitum, and kept with a 12-hour day/night cycle.

1. Measuring of fasting serum lipids

  1. Transfer mice to a new cage after 5 PM and fast with free access to water, overnight (with around 16 hours of fasting before the experiment). The over.......

Representative Results

We show with three excerpts that each assay offers valuable information about the mice's lipid metabolism. For C57BL/6J male mice, challenged by eight weeks of high-fat diet (HFD) feeding  starting at eight weeks of age, total cholesterol levels were significantly elevated, while serum triglyyceride and NEFA were not (Table 1), suggesting that triglyceride and NEFA in the blood are not predominantly regulated by a dietary fat challenge. In the second cohort of mice, C57BL/6J and C57BL6/N su.......

Discussion

The three assays described function robustly in the lab, with a few critical considerations. Overnight fasting is required for determining fasting serum lipid levels and oral intralipid tolerance test. For oral intralipid tolerance test, it is critical to spin the blood at room temperature to minimize the formation of a fat layer, especially at the 1- and 2-hour time points; it is important not to discard this fat layer if it forms. Make sure to transfer the supernatant with the lipid layer, and pipet gently to mix them .......

Acknowledgements

This work is supported by the National Institutes of Health (NIH), grant R00-DK114498, and the United States Department of Agriculture (USDA), grant CRIS: 3092-51000-062 to Y. Z.

....

Materials

NameCompanyCatalog NumberComments
20% IntralipidSigma AldrichI141
BD Slip Tip Sterile Syringes 1mlShaotongB07F1KRMYN
CL 316,243 HydrateSigma-AldrichC5976
Curved Feeding Needles (18 Gauge)Kent ScientificFNC-18-2-2
Free Glycerol ReagentSigma AldrichF6428
Glycerol Standard SolutionSigmaG7793
HR SERIES NEFA-HR(2)COLOR REAGENT AFujifilm Wako Diagnostics999-34691
HR SERIES NEFA-HR(2)COLOR REAGENT BFujifilm Wako Diagnostics991-34891
HR SERIES NEFA-HR(2)SOLVENT AFujifilm Wako Diagnostics995-34791
HR SERIES NEFA-HR(2)SOLVENT BFujifilm Wako Diagnostics993-35191
KetamineVedco50989-161-06
Matrix Plus Chemistry Reference KitVerichem9500
Micro Centrifuge TubesFisher Scientific14-222-168
Microhematrocrit Capillary Tube, Not HeparanizedFisher Scientific22-362-574
NEFA STANDARD SOLUTIONFujifilm Wako Diagnostics276-76491
Phosphate Buffered SalineBoston BioproductsBM-220
Thermo Scientific Triglycerides ReagentFisher ScientificTR22421
Total Cholesterol ReagentsThermo ScientifiTR13421
XylazineHenry Schein11695-4022-1

References

  1. Dixon, J. B. Mechanisms of chylomicron uptake into lacteals. Annals of the New York Academy of Sciences. 1207, 52-57 (2010).
  2. Nuno, J., de Oya, M. Lipoprotein lipase: review. Revista Clínica Española. 170 (3-4), 83-87 (1983....

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