Full Papers

Effects of green tea on insulin sensitivity, lipid profile and expression of PPARα and PPARγ and their target genes in obese dogs

Samuel Serisier^a1a2, Veronique Leray^a2, Wilfried Poudroux^a1a2, Thierry Magot^a1, Khadija Ouguerram^a1 and Patrick Nguyen^a2 c1

^a1 INSERM U539, University Hospital, Nantes, France

^a2 Nutrition and Endocrinology Unit, National Veterinary School of Nantes, France

Abstract

As in man, canine obesity is associated with insulin resistance, dyslipidaemia and other chronic diseases. This study was designed to examine the effects of a nutritional supplement (green tea) on insulin sensitivity and plasma lipid concentrations in an obese insulin-resistant dog model. We also determined mRNA expression of two transcription factors, PPARγ and PPARα, and some of their target genes, including GLUT4, lipoprotein lipase (LPL) and adiponectin. Obese dogs were divided into two groups: a green tea group (n 6); a control group (n 4). Dogs in the green tea group were given green tea extract (80 mg/kg per d) orally, just before their single daily meal, for 12 weeks. Insulin sensitivity (using a euglycaemic–hyperinsulinaemic clamp) and concentrations of plasma TAG, total cholesterol and NEFA were assessed in each group. Gene expression was measured in visceral and subcutaneous adipose tissues and in liver and skeletal muscle, by real-time PCR. At 12 weeks in the green tea group, mean insulin sensitivity index was 60 (sem 11) % higher (P < 0·05) and TAG concentration 50 (sem 10) % lower (P < 0·001), than baseline. PPARγ, GLUT4, LPL and adiponectin expression were significantly higher in both adipose tissues, whilst PPARα and LPL expression were significantly higher in skeletal muscle, compared with baseline. These findings show that nutritional doses of green tea extract may improve insulin sensitivity and lipid profile and alter the expression of genes involved in glucose and lipid homeostasis.

(Received April 16 2007)

(Revised September 29 2007)

(Accepted October 03 2007)

(Online publication December 06 2007)

Key Words:

• Obese dogs;
• Green tea;
• Catechins;
• Insulin resistance;
• Dyslipidaemia;
• PPAR

Correspondence:

^c1 Corresponding author: Patrick Nguyen, fax +33 240 687746, email pnguyen@vet-nantes.fr

Footnotes

Abbreviations: EGCG, epigallocatechin gallate; HOMA-IR, homeostasis model of insulin resistance; LPL, lipoprotein lipase; TC, total cholesterol