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

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, PPARg and PPARa, 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. PPARg, GLUT4, LPL and adiponectin expression were significantly higher in both adipose tissues, whilst PPARa 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.

Maternal green tea extract supplementation to rats fed a high-fat diet ameliorates insulin resistance in adult male offspring

“…2C). Increased mRNA expression of adiponectin in adipose tissues was also reported in GTE-supplemented obese dogs [39]. Adiponectin could increase UCP expression [40].…”

The Effect of Green Tea Extract on Fat Oxidation at Rest and during Exercise: Evidence of Efficacy and Proposed Mechanisms

“…The in vitro evidence is also supported by animal data. GTE supplementation of 4-12 wk has been shown to lead to greater PPARa and PPARg expression in the liver, adipose tissue, and skeletal muscle (89)(90)(91). However, Chen et al (80) reported no change in liver PPAR expression following 6 mo of EGCG intake in rats.…”

Conditioning causes an increase in glucose transporter-4 levels in mononuclear cells in sled dogs

“…Historically, dogs have played a critical role in our understanding and treatment of diabetes, and scientists have used dogs as a biochemical research model for studying human metabolic disorders for over a century (Catchpole et al, 2005, Serisier et al, 2008). Though there are species-specific pathologies associated with diabetes, dogs develop insulin dependent and independent forms of diabetes, and gestational diabetes akin to humans (Catchpole et al, 2005, Bergman et al, 2006, Johnson, 2008).…”