Measurement of Basal and Forskolin-stimulated Lipolysis in Inguinal Adipose Fat Pads

Summary

This protocol describes the method of determining basal and forskolin-stimulated lipolysis in inguinal fat pads obtained from normal chow diet (NCD) or high fat diet (HFD) ± capsaicin fed wild type mice. As an index for lipolysis, glycerol release was measured from inguinal adipose fat pads.

Abstract

Lipolysis is a process by which the lipid stored as triglycerides in adipose tissues are hydrolyzed into glycerol and fatty acids. This article describes the method for the measurement of basal and forskolin (FSK)-stimulated lipolysis in the inguinal fat pads isolated from wild type mice fed either normal chow diet (NCD), high fat diet (HFD) or a high fat diet containing 0.01% of capsaicin (CAP; transient receptor potential vanilloid subfamily 1 (TRPV1) agonist) for 32 weeks. The method described here for performing ex vivo lipolysis is adopted from Schweiger et al.¹ We present a detailed protocol for measuring glycerol levels by UV-Visible (UV/VIS) spectrophotometry. The method described here can be used to successfully isolate inguinal fat pads for lipolysis measurements to obtain consistent results. The protocol described for inguinal fat pads can readily be extended to measure lipolysis in other tissues.

Introduction

Adipose tissues store energy as fat² and fatty acid oxidation is required for thermogenesis^3,4. Fatty acids ingested through diets are packaged along with apoproteins into chylomicrons and delivered to different tissues in the body via blood circulation. Although most cells in the body store a reserve of energy, adipose tissue stores excess energy as fat^5,6. Lipolysis in adipose tissue is regulated by complex processes and the molecular details of lipolysis still remain vague⁷.

Protocol

All protocols follow the animal care guidelines of the University of Wyoming.

1. Animal Housing and Feeding

NOTE: Adult male wild type mice (C57BL/6) (age 12 to 24 weeks) were bred in the research animal facility as per the Institutional Animal Care and Use Committee (IACUC) approved protocols.

1. Starting from week 6 of age, house mice in groups of four in separate cages and randomly assign them into feeding groups of NCD or HFD (± 0.01% CAP) until week 38 of age.
   NOTE: CAP is an agonist of TRPV1 channel protein expressed in adipose tissues^11,

Results

To evaluate the effect of CAP on basal and stimulated lipolysis, this research measured lipolysis in inguinal adipose fat pads isolated from NCD or HFD (± CAP)-fed wild type mice. The representative results for the basal and FSK-stimulated lipolysis for the inguinal fat pads are given in Table I. Basal and FSK-stimulated glycerol release in the presence of Triacsin C, which inhibits acyl coA synthetase and prevents the regeneration of TGL. As shown in

Discussion

The breakdown process of TGL into glycerol and fatty acids is catalyzed by ATGL⁹ during basal lipolysis and orchestrated by an array of proteins including the activation of adenylyl cyclase/PKA-dependent pathway during stimulated lipolysis^21,22,23. Enhancement of lipolysis increases the plasma levels of fatty acids for transportation and energy use²⁴. Fatty acids are taken up by mi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Capsaicin	Sigma, USA	M2028	TRPV1 agonist
Forskolin	Sigma, USA	F6886	Adenylyl cyclase activator
DMEM	GE healthcare and life sciences, UT, USA	SH30081.01
High fat diet	Research diets, New Brunswick, USA	D12492	Abbreviated as HFD
Tris	Amresco, USA	O497
Sodium chloride	Thermofisher Scientific	BP358-212
Sodium deoxycholate	Sigma, USA	D6750
Dithiothreitol	Sigma, USA	D9163
Sodium orthovanadate	Sigma, USA	S6508
Protease inhibitor cocktail	Sigma, USA	P8340
Free Glycerol reagent	Sigma USA	F6428
DMSO	Sigma, USA	D8779
Triacsin C	Sigma, USA	T4540	Acyl CoA transferase inhibitor
Bovine serum albumin	Sigma, USA	A7030
Chloroform	Sigma Aldrich	31998-8
Methanol	Thermofisher Scientific, USA	A412-1
Sodium hydroxide	Amresco, USA	O583
Sodium dodecyl sulfate	Sigma, USA	L3371
Bicinchoninic acid reagent	Sigma, USA	BCA1-1KT
UV-VIS Spectrophotometer	Pharmacia Biotech, NJ, USA	Ultrospec 2000
Normal chow diet	Labdiet.com	500I	abreviated as NCD
C57BL/6 mice	Jackson Laboratory, CT, USA	Stock number000664	wild type mice
Parafilm	Heathrow Scientific, USA	HS 234526A
Glycerol standard	Sigma, USA	G7793