Blueberries improve glucose tolerance without altering body composition in obese postmenopausal mice

Abstract

Objective: Metabolic syndrome (MetS) risk increases significantly during menopause and remains elevated postmenopause. Several botanicals, including blueberries (BB), have been shown to delay MetS progression, but few studies have been conducted in postmenopausal animal models. Here, the effects of BB supplementation on obese postmenopausal mice using a chemically induced menopause model were examined.

Methods: After induction of menopause, mice were fed a high-fat diet or the same diet supplemented with 4% BB powder for 12 weeks. Body weight and body composition were measured, and mice were subjected to glucose and insulin tolerance tests. Serum triglycerides and adiponectin were measured, and liver histology and hepatic gene expression were assessed.

Results: Menopausal and BB-supplemented mice had significantly higher body weights and fat mass than control mice, while menopausal mice had impaired glucose tolerance and higher serum triglycerides when compared with control and BB-supplemented mice. Menopausal mice also had hepatic steatosis that was prevented by BB supplementation and correlated with expression of genes involved in hepatic fatty acid oxidation.

Conclusions: BB supplementation prevents the glucose intolerance and hepatic steatosis that occur in obese postmenopausal mice, and these effects are independent of body weight.

Conflict of interest statement

CONFLICTS OF INTEREST STATEMENT

Competing interests: the authors have no competing interests.

© 2015 The Obesity Society.

Figures

Figure 1. Menopause-induced changes in body weight and body composition are not altered by BB supplementation

A) Body weights for all animals throughout study duration. Body weights of VCD-injected mice and BB-supplemented VCD-injected mice were not significantly different from each other, but were significantly different from those of control mice from weeks 8–20 of the study. B) Mean body composition data for various groups at study end (20 weeks). Control mice had significantly less fat mass than V or VB mice, but no changes in fat free mass or fluid were noted. *p

Figure 2. BB supplementation does not improve insulin tolerance, but does improve glucose tolerance, in obese postmenopausal mice

A) Graphical depiction of insulin tolerance time following an i.p. insulin injection. At baseline, V mice had higher blood glucose levels than VB or C groups; however, no changes in blood glucose levels over time were noted among any of the groups in response to an insulin injection. B) Graphical depiction of glucose tolerance over time following an i.p. bolus of glucose. V mice demonstrated impaired glucose tolerance at 30, 45, 60, and 90 minutes post-injection. C) GTT results expressed as area under the curve *p

Figure 3. BB supplementation improves serum triglycerides in obese postmenopausal mice

A) Serum triglyceride levels at study end. B) Serum adiponectin levels at study end. *p

Figure 4. BB supplementation prevents hepatic steatosis in obese postmenopausal mice

Representative photomicrographs of H&E-stained liver sections at 100x magnifications. Scale bars = 50 um. The livers of V mice (panel B) had more severe lipid deposition than C mice (panel A), and BB supplementation prevented the lipid deposition seen in the menopausal liver (panel C). These qualitative histologic results were verified with a quantitative method for tissue triglyceride measurement; results appear in D. *p

Figure 5. Menopause decreases expression of genes associated with hepatic fatty acid oxidation and BB supplementation prevents these changes

Relative expression levels of hepatic A) CD36, B) Cs, and C) Hadha in livers after 12 weeks of HFD or HFD supplemented with BB . **p<0.01, ****p<0.0001 vs. V group. C = cycling HFD control group, V = HFD+VCD, VB = HFD+BB+VCD, Cd36 = fatty acid translocase/CD36, Cs = citrate synthase, and Hadha = long-chain hydroxyacyl-CoA dehydrogenase.