Cross-sectional association between blood cholesterol and calcium levels in genetically diverse strains of mice

Abstract

Genetically diverse outbred mice allow for the study of genetic variation in the context of high dietary and environmental control. Using a machine learning approach, we investigated clinical and morphometric factors that associate with serum cholesterol levels in 840 genetically unique Diversity Outbred mice of both sexes (n = 417 male and 423 female), and on both a control chow (% kcals in diet: protein 22%, carbohydrate 62%, fat 16%, no cholesterol) and high fat high sucrose (% kcals in diet: protein 15%, carbohydrate 41%, fat 45%, 0.05% cholesterol). We find expected elevations of cholesterol in male mice, as well as in mice with elevated serum triglycerides and/or fed a high fat high sucrose diet. The third strongest predictor was serum calcium which correlated with serum cholesterol across both diets and sexes (r = 0.39-0.48) in both Diversity Outbred (P = 3.0 × 10^-43 ) and BXD (P = 0.005) mice. This is in-line with several human cohort studies which show associations between calcium and cholesterol, and calcium as an independent predictor of cardiovascular events.

Keywords: calcium; cholesterol; cross-sectional; diversity outbred.

Fig. 1

Description of cholesterol levels in diversity outbred mice. (A) Violin plot of cholesterol levels of diversity outbred at 19 weeks, mice stratified by diet and sex. (B) Scatter plot of cholesterol levels in relation to percent fat mass at 19 weeks of age, stratified by diet and sex. (C) Pruned regression predicting cholesterol at 19 weeks. Above the box is the algorithmically generated cutoff for triglycerides (abbreviated TG in mg·dL⁻¹), calcium (Ca in mg·dL⁻¹), and body weight (BW in g). Each predictor was a phenotype measured at 19 weeks. Within each box, the value represents the average cholesterol level in that group (in mg·dL⁻¹) and the number of mice in that group (n = 840 for panel A and 818 for panel 2 as 22 mice were omitted due to missing data).

Fig. 2

Cross‐sectional associations of cholesterol with triglycerides and calcium. Sex and diet stratified scatter plots of (A) triglyceride and (B) calcium relationships with cholesterol levels at 19 weeks in diversity outbred mice (n = 840 mice and strains). (C) Cholesterol and calcium associations in male and female BXD strains (n = 326 mice from 17 female and 36 male strains; error bars represent within‐strain standard error of the mean). P‐values indicate the level of significance for the diet and sex adjusted relationship between cholesterol and triglycerides or calcium from a multivariate linear model. The lines represent independent estimates for each group.