Effect of saturated or monounsaturated fatty acids on bone and calcium absorption in older mice

Abstract

A high fat diet (HFD) and obesity have been shown to reduce bone mineral density (BMD) and Ca absorption (Ca‐abs). However, previous experiments have not examined the effect of HFD in the absence of obesity or addressed the type of fatty acids. In this study, we examined 28 eight‐month old female C57BL/6J mice that were pair‐fed one of three diets. The HFD (45% fat) was either enriched with monounsaturated fatty acids (MUFA) or with saturated fatty acids (SFA) and was compared to a low fat diet (LFD; 10% fat). Mice were analyzed for BMD (dual energy x‐ray absorptiometry), intestinal Ca‐abs, and the mRNA expression of Ca transporters. In vivo fractional Ca‐abs was measured using 45Ca (5‐d measurement). After 8wk, there was no significant different in body weight between groups, but fat was greater in the MUFA than LFD mice (p<0.05). Total body, femur and humerus BMD of mice fed SFA were lower than LFD or MUFA (P<0.001). There tended to be a rise in 45Ca–abs only in the HFD groups (p<0.06), but the change did not differ between groups. Intestinal Ca transporter, calbindin‐D9k mRNA expression, was higher in MUFA mice and both MUFA and SFA showed lower renal Ca transporter expression, TRPV5, compared to LFD (p<0.05). It is concluded that the detrimental effects of a HFD on BMD occurs due to a deleterious effect of SFA, and this occurs in the absence of excess caloric intake and of a significant contribution from intestinal or renal Ca transport.