Ketogenic diet in combination with voluntary exercise impacts markers of hepatic metabolism and oxidative stress in male and female Wistar rats

Abstract

Ketogenic diets (KDs) are shown to benefit hepatic metabolism; however, their effect on the liver when combined with exercise is unknown. We investigated the effects of a KD versus a “western” diet (WD) on markers of hepatic lipid metabolism and oxidative stress in exercising rats. Male and female Wistar rats with access to voluntary running wheels were randomized to 3 groups (n = 8–14 per group): standard chow (SC; 17% fat), WD (42% fat), or KD (90.5% fat) for 7 weeks. Body fat percentage (BF%) was increased in WD and KD versus SC, although KD females displayed lower BF% versus WD (p ≤ 0.05). Liver triglycerides were higher in KD and WD versus SC but were attenuated in KD females versus WD (p ≤ 0.05). KD suppressed hepatic markers of de novo lipogenesis (fatty acid synthase, acetyl coenzyme A carboxylase) and increased markers of mitochondrial biogenesis/content (peroxisome proliferator activated receptor-1α, mitochondrial transcription factor A (TFAM), and citrate synthase activity). KD also increased hepatic glutathione peroxidase 1 and lowered oxidized glutathione. Female rats exhibited elevated hepatic markers of mitochondrial biogenesis (TFAM), mitophagy (light chain 3 II/I ratio, autophagy-related protein 12:5), and cellular energy homeostasis (phosphorylated 5′AMP-activated protein kinase/5′AMP-activated protein kinase) versus males. These data highlight that KD and exercise beneficially impacts hepatic metabolism and oxidative stress and merits further investigation. Novelty KD feeding combined with exercise improved hepatic oxidative stress, suppressed markers of de novo lipogenesis, and increased markers of mitochondrial content versus WD feeding. Males and females responded similarly to combined KD feeding and exercise. Female rats exhibited elevated hepatic markers of autophagy/mitophagy and energy homeostasis compared with male rats.

The role of hepatocellular eNOS in NAFLD development and hepatic mitochondrial adaptations to exercise

“…However, this appears to be driven by the males, with female mice showing similar histological scoring across genotypes, and not surprising lower steatosis compared to males. This is consistent with previous findings, as female rodents are protected against hepatic steatosis and NAFLD development versus their male counterparts (66)(67)(68)(69)(70). Importantly, EX resolved inflammation and NAS score in eNOS hep-/mice, suggesting hepatocellular eNOS is dispensable for EX-induced histological improvements in the liver, at least on a low-fat diet.…”

“…3.5A), suggesting that hepatocytes from these mice have an impaired energy sensing ability compared to eNOS fl/fl mice. Similar to our previous work (66,67), females exhibited marked elevation in TFAM protein compared to males, regardless of EX or genotype (Fig. 3.5C).…”

“…As we have published previously (66,67), male mice had elevated hepatic steatosis compared to female mice regardless of other conditions, with no effect of sex on inflammation and NAS (Fig. 3.1A-B).…”

“…Our group has demonstrated that female rodents are not only protected from hepatic steatosis compared to male mice, but also displayed elevated markers of hepatic mitochondrial biogenesis and mitophagy (66,67). Additionally, female mice possessed elevated hepatic mitochondrial content, respiratory capacity, and lower reactive oxygen species emission compared to male mice, regardless of physical activity status (68)(69)(70).…”

Branched chain amino acids and carbohydrate restriction exacerbate ketogenesis and hepatic mitochondrial oxidative dysfunction during NAFLD

“…12,38 While several benefits of ketogenic diets have been documented in humans and mice models with NAFLD, there is ambiguity about these diets long-term impacts on hepato-cellular function. 11,17,[19][20][21]39 Biochemically, ketogenesis is the reflection of surplus acetyl-CoA from FFA oxidation, getting diverted away from complete oxidation through the TCA cycle, toward the synthesis of ketones. In other words, the ketogenic environment upregulates components of mitochondrial oxidative machinery in the liver (eg, β-oxidation, ketone synthesis).…”