The Ketogenic Diet Impairs Mitochondrial Function in Hearts of Male and Female Mice

Abstract

Ketone bodies have been identified as an important fuel source during physiological and pathological stress. During exercise, augmenting ketone body metabolism in the skeletal muscle may enhance exercise performance while targeting ketone body metabolism in cardiac disease may improve cardiac function. These provocative, yet still debated, findings may promote the consumption of the ketogenic diet (KD) as a method to increase ketone body availability. Since the KD is a high‐fat, low carbohydrate diet, this dietary strategy has the potential to have untoward effects on the heart. Therefore, the purpose of this study was to evaluate the effects of short‐term consumption of the KD on cardiac mitochondrial function. A secondary objective was to evaluate potential sex differences in response to the KD. Male (n=9) and female (n=11) mice at four‐months of age were randomly assigned to a standard chow or KD (90% fat, 9% protein, 1% carbohydrates) group for 6 weeks. Body weight (BW) was obtained weekly. Glucose and ketone bodies were measured at the end of the dietary intervention via hand‐held meters. After 6 weeks, mitochondria were isolated from all hearts and respiration was assessed with an oxygen electrode system. During the first week, Male‐KD lost 2.5±1.5% of initial BW compared to an increase of 0.3±1.5% of initial BW for Male‐Chow. By the third week, both Male‐KD and Male‐Chow gained BW at a similar rate until the end of the study. In contrast, Female‐KD mice gained BW throughout the 6 weeks and the relative increased compared to baseline was approximately 1.7‐2.0‐fold greater than Female‐chow. Serum ketone bodies were significantly increased in both Male‐KD and Female‐KD mice compared to chow fed groups (Male‐chow, 0.33±0.05 vs. Male‐KD, 0.66±0.10 mM, P<0.05; Female‐chow, 0.33±0.02 vs. Female‐KD, 0.66±0.11 mM, P<0.05). There were no significant sex differences in serum ketone bodies or glucose. State 3 respiration with succinate + ADP was ~35% lower in both male and female KD groups (Male‐chow, 236±14 vs. Male‐KD, 148±11 nmol/min/mg, P<0.05; Female‐chow, 186±22 vs. Female‐KD, 133±10 nmol/min/mg, P=0.08). State 3 respiration with pyruvate/malate + ADP were ~30% lower in both Male and female KD groups (Male‐chow, 157±18 vs. Male‐KD, 105±10 nmol/min/mg, P=NS; Female‐chow, 138±22 vs. Female‐KD, 81±8 nmol/min/mg, P=0.06). No statistically significant sex differences in mitochondria function were noted. In summary, 6‐weeks of KD results in sex differences in patterns of weight gain as male mice experience a transient weight loss and females gain weight throughout the study period. Despite the difference in weight gain, hearts from both males and females fed the KD have similar decrements in mitochondrial function. In conclusion, these findings suggest that the KD may negatively affect cardiac mitochondria and caution against the short‐term use of KD.