Metabolic effects of a mitochondrial-targeted coenzyme Q analog in high fat fed obese mice

Abstract

We recently reported that mitoquinone (mitoQ, 500 μmol/L) added to drinking water of C57BL/6J mice attenuated weight gain, decreased food intake, increased hypothalamic orexigenic gene expression, and mitigated oxidative stress when administered from the onset of high-fat (HF) feeding. Here, we examined the effects of mitoQ on pre-existing obesity in C57BL/6J mice first made obese by 107 days of HF feeding. In contrast to our preventative study, we found that already obese mice did not tolerate mitoQ at 500 μmol/L. Within 4 days of administration, obese mice markedly decreased food and water intake and lost substantial weight necessitating a dose reduction to 250 μmol/L. Food and water intake then improved. Over the next 4 weeks, body mass of the mitoQ-treated mice increased faster than vehicle-treated controls but did not catch up. Over the subsequent 10 weeks, weights of the mitoQ-treated group remained significantly less than vehicle control, but percent fat and food intake did not differ. Although the mitoQ-treated groups continued to drink less, there was no difference in percent body fluid and no laboratory evidence of dehydration at study end. At the time of killing, hypothalamic NPY gene expression was reduced in the mitoQ-treated mice . Liver fat was markedly increased by HF feeding but did not differ between mitoQ and vehicle groups and, in contrast to our previous preventative study, there was no improvement in plasma alanine amino transferase or liver hydroperoxides. In summary, administration of mitoQ to already obese mice attenuated weight gain, but showed limited overall benefit.

Keywords: Antioxidants; Obesity; coenzyme Q; leptin; mitochondria; neuropeptide Y.

Figure 1

MitoQ structure and study protocol. (A) Structure. (B) Protocol indicating times of treatments and procedures. Mice were fed normal chow (NF) or high fat (HF) from days 1 to 107. After day 107, HF‐fed mice were either killed for baseline study or treated with mitoQ or vehicle and continued on HF until study end. NF‐fed mice were either killed or treated with vehicle and continued on NF. At baseline and study end, mice were killed over the days indicated in staggered fashion so that the average number of days treated did not vary between diet or treatment groups. Data represent mean ± SE. HF, High fat; MitoQ, mitoquinone.

Figure 2

Body mass and composition. (A) Change in body mass over time in high fat vehicle‐treated (HF veh), HF mitoQ‐treated (HF MQ), normal fed vehicle‐treated (NF veh), and in mice killed after 107 days fed normal fat (NF baseline) or high fat (HF baseline) groups. (B) Body weight at study end (day 212) in HF veh, HF MQ, and NF veh groups. (C–E) Body composition expressed in grams of fat, lean, and fluid mass, respectively, determined by NMR at day 199. (F–H) Body composition expressed as % fat, % lean, or % fluid mass determined by NMR. Data represent mean ± SE. n = 11 for HF veh and HF MQ mice, n = 6 for NF veh mice. ^a denotes P < 0.05 compared to HF veh, ^bdenotes P < 0.001 compared to HF veh and to HF MQ mice, ^cdenotes P < 0.01 compared to HF veh and to HF MQ mice by one‐way ANOVA and Tukey's multiple comparison test. HF, High fat; NMR, nuclear magnetic resonance.

Figure 3

Calorie and water intake indicated by group. (A) Caloric intake (average per cage) measured on study days indicated, beginning on day 114 and determined over intervals since prior x‐axis value. (B) Relative area under curve (AUC) (Kcal vs. time) determined from day 128 (stabilization after mitoQ dose reduction) through day 212. (C) Water intake (average per cage) measured on study days indicated beginning on day 111 and determined over intervals since prior x‐axis value. (D) Relative area under curve (AUC) (water intake versus time) determined as in panel (C). Data represent mean ± SE. n = 6 for HF veh and HF MQ mice, n = 3 for NF veh mice. *P < 0.001 compared to HF veh, ^# P < 0.001 compared to NF veh by one‐way ANOVA and Tukey's multiple comparison test. HF, High fat; MitoQ, mitoquinone.

Figure 4

Hypothalamic mRNA expression in NF veh, HF veh, and HF MQ groups. (A) neuropeptide Y; (B) leptin receptor, long form; (C) AgRP; (D) POMC; (E) cocaine and amphetamine regulated transcript. Data represent mean ± SE. *P < 0.01 compared to HF veh, ^# P < 0.01 compared to NF veh by one‐way ANOVA and Tukey's multiple comparison test. n = 6 mice per group. HF, High fat.

Figure 5

Bioenergetic effects of mitoQ and HF feeding. (A) Respiration at different concentrations of clamped ADP by liver mitochondria isolated at study end from NF veh (n = 6), HF veh (n = 11), or HF MQ mice (n = 11). (B) Inner membrane potential measured simultaneously with respiration in the mitochondria of panel A. (C) Whole body VO₂ measured prior to killing in mice used in panels A and B. (D–E) Corresponding studies of isolated mitochondria from NF (n = 4) or HF‐fed mice (n = 8) killed after 107 days of diet. (F) Whole body VO₂ measured prior to killing in mice used in panels D and E. Data represent mean ± SE. *P < 0.001 compared to NF veh by one‐way ANOVA with Tukey's multiple comparison test. #P < 0.01 compared to NF by unpaired, two‐tailed t‐test. HF, High fat.

Figure 6

Hepatic lipid, hydroperoxide, and ALT content in mice determined on liver tissue isolated at study end. (A–C) Representative Oil‐Red‐O stained histological images showing liver isolated from NF veh, HF veh, and HF MQ mice, respectively. (D) Hepatic tissue total lipid content in NF veh (n = 6), HF veh (n = 11) and HF MQ (n = 11) mice. (E) Lipid hydroperoxide content in mice of panel D. (F) Plasma ALT in mice of panel D. Data represent mean ± SE. *P < 0.001 compared to HF veh and HF MQ groups by one‐way ANOVA with Tukey's multiple comparison test. ALT, alanine aminotransferase; HF, High fat.

Figure 7

Plasma leptin and insulin concentrations. (A) Leptin in NF veh (n = 6), HF veh (n = 11), and HF MQ (n = 11) mice followed until study end and killed on days 212–230. (B) Leptin in HF and (n = 9) NF (n = 4) fed mice followed for 107 days and killed on days 107–114. (C and D) Insulin concentrations in mice corresponding to panels A and B. Data represent mean ± SE. ^a P < 0.025 compared to HF veh, ^b P < 0.001 compared to HF veh and HF MQ mice, ^c P < 0.001 compared to HF mice, ^d P < 0.025 compared to HF veh and <0.01 compared to HF MQ mice, ^e P < 0.025 compared to HF mice. Data in panels A and C were analyzed by one‐way ANOVA with Tukey's multiple comparison test. Data in panels B and D were analyzed by unpaired, two‐tailed t‐test. HF, High fat.

Figure 8

Plasma urea nitrogen, potassium, and sodium concentrations as markers of renal function and hydration. (A) Urea nitrogen in NF veh (n = 6), HF veh (n = 11), and HF MQ (n = 11) mice followed until study end and killed on days 212–230. (B) Urea nitrogen in HF (n = 9) and NF (n = 4) fed mice followed for 107 days and killed on days 107–114. (C and D) Potassium concentrations in mice corresponding to panels A and B. (E and F) Sodium concentrations in mice corresponding to panels A and B. Data represent mean ± SE. *P < 0.01 compared to NF veh, ^# P < 0.05 compared to NF mice. Data in panels A, C, and E were analyzed by one‐way ANOVA with Tukey's multiple comparison test. Data in panels B, D and F were analyzed by unpaired, two‐tailed t‐test. HF, High fat.