Study of Insulin Resistance with Female Liver Androgen Receptor Knock‐Out Mice (Liv‐AKRO) on a High Fructose Diet

Abstract

Insulin resistance affects up to a third of the US adult population and polycystic ovary syndrome (PCOS) affects up to 10% of reproductive‐age adult women. The liver plays an essential component in the metabolism of insulin and androgen signaling. Hyperandrogenism in females can also increase predisposition to insulin resistance. In our study, we placed female liver androgen receptor knock‐out mice (Liv‐ARKO) on high fructose diets (HFrD) to determine if Liv‐ARKO mice demonstrated blunted insulin resistance on HFrD compared to control diet.In this study, female Liv‐ARKO mice were placed on three distinct diets: Control (Research Diets Inc) (CD), chow, and High Fructose (HFrD). The mice were sacrificed after 1 or 2 months. Some mice were given a dose of 0.5 U/kg insulin before sacrificing to investigate the effects of the diets on insulin signaling. Western blots were used to determine protein expression in tissue from the liver, skeletal muscle, white adipose tissue, ovary, and pituitary glands. BCA assays were used to standardize the protein concentration in each sample. Insulin action can be measured molecularly by examining p‐AKT. If p‐AKT levels increase in the presence of insulin, this indicates that insulin is likely functioning properly in the sample.As seen in previous studies, insulin increased p‐AKT in livers of Liv‐ARKO mice on a chow diet. In contrast, insulin did not increase p‐AKT in livers of Liv‐ARKO mice on the CD for 2 months in comparison to those not given insulin (basal). Furthermore, Liv‐ARKO mice on a HFrD for 2 months displayed an even further decrease in p‐AKT in the liver compared to Liv‐ARKO mice on a CD stimulated with insulin. Liv‐ARKO mice on the CD for 2 months showed enhanced glucose tolerance (EGT) compared to those on the CD for only 1 month. The CD increased glucose tolerance at the whole body level (GTT) and the molecular level (pAKT). Glucose tolerance also increased at 2 months in comparison to 1 month in Liv‐ARKO mice on the CD. This effect is the same and equally as significant for male and female Liv‐ARKO mice. After 2 months on the CD, Liv‐ARKO mice showed impaired insulin sensitivity (IIS) compared to 1 month on the diet. This IIS is significantly greater in female Liv‐ARKO mice compared to male.It was hypothesized that HFrD‐fed Liv‐ARKO would impair insulin action compared to the CD and chow fed mice. The Liv‐ARKO mouse model did not rescue HFrD insulin resistance. The results confirmed this hypothesis and further determined that the CD increased insulin action in comparison to the chow diet. The data suggests that the CD is reducing insulin action in the Liv‐ARKO mice. There is insulin action in Liv‐ARKO mice on the CD as pAKT is present, although at lower levels than in the basal mice. However, compared to the control, the HFrD prohibits the ability of insulin to increase pAKT, indicating complications in the early stages of the insulin signaling pathway. Further research is required into what components of the CD are prompting this difference in insulin action and if it only takes place in the Liv‐ARKO mouse model. Further investigation should be performed on the gender discrepancy in these results.