A low-protein, high-carbohydrate diet increases browning in perirenal adipose tissue but not in inguinal adipose tissue

Nutrition. 2017 Oct;42:37-45. doi: 10.1016/j.nut.2017.05.007. Epub 2017 May 31.

Abstract

Objective: The aim of this study was to evaluate the browning and origin of fatty acids (FAs) in the maintenance of triacylglycerol (TG) storage and/or as fuel for thermogenesis in perirenal adipose tissue (periWAT) and inguinal adipose tissue (ingWAT) of rats fed a low-protein, high-carbohydrate (LPHC) diet.

Methods: LPHC (6% protein, 74% carbohydrate) or control (C; 17% protein, 63% carbohydrate) diets were administered to rats for 15 d. The tissues were stained with hematoxylin and eosin for histologic analysis. The content of uncoupling protein 1 (UCP1) was determined by immunofluorescence. Levels of T-box transcription factor (TBX1), PR domain containing 16 (PRDM16), adipose triacylglycerol lipase (ATGL), hormone-sensitive lipase, lipoprotein lipase (LPL), glycerokinase, phosphoenolpyruvate carboxykinase (PEPCK), glucose transporter 4, β3-adrenergic receptor (AR), β1-AR, protein kinase A (PKA), adenosine-monophosphate-activated protein kinase (AMPK), and phospho-AMPK were determined by immunoblotting. Serum fibroblast growth factor 21 (FGF21) was measured using a commercial kit (Student's t tests, P < 0.05).

Results: The LPHC diet increased FGF21 levels by 150-fold. The presence of multilocular adipocytes, combined with the increased contents of UCP1, TBX1, and PRDM16 in periWAT of LPHC-fed rats, suggested the occurrence of browning. The contents of β1-AR and LPL were increased in the periWAT. The ingWAT showed higher ATGL and PEPCK levels, phospho-AMPK/AMPK ratio, and reduced β3-AR and PKA levels.

Conclusion: These findings suggest that browning occurred only in the periWAT and that higher utilization of FAs from blood lipoproteins acted as fuel for thermogenesis. Increased glycerol 3-phosphate generation by glyceroneogenesis increased FAs reesterification from lipolysis, explaining the increased TG storage in the ingWAT.

Keywords: Brite; Energy expenditure; High-carbohydrate diet; Low-protein; Protein restriction; White adipose tissue.

MeSH terms

  • Adipose Tissue, Brown / drug effects
  • Adipose Tissue, Brown / metabolism*
  • Animals
  • Diet / methods
  • Diet, Protein-Restricted / methods*
  • Dietary Carbohydrates / administration & dosage*
  • Fibroblast Growth Factors / blood
  • Fluorescent Antibody Technique
  • Inguinal Canal
  • Kidney / drug effects
  • Kidney / metabolism*
  • Male
  • Models, Animal
  • Rats
  • Rats, Wistar

Substances

  • Dietary Carbohydrates
  • fibroblast growth factor 21
  • Fibroblast Growth Factors