Influence of NAFLD and bariatric surgery on hepatic and adipose tissue mitochondrial biogenesis and respiration.

Impaired mitochondrial oxidative phosphorylation (OXPHOS) in liver tissue has been hypothesised to contribute to the development of nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease (NAFLD). It is unknown whether OXPHOS capacities in human visceral (VAT) and subcutaneous adipose tissue (SAT) associate with NAFLD severity and how hepatic OXPHOS responds to improvement in NAFLD. In biopsies sampled from 62 patients with obesity undergoing bariatric surgery and nine control subjects without obesity we demonstrate that OXPHOS is reduced in VAT and SAT while increased in the liver in patients with obesity when compared with control subjects without obesity, but this was independent of NAFLD severity. In repeat liver biopsy sampling in 21 patients with obesity 12 months after bariatric surgery we found increased hepatic OXPHOS capacity and mitochondrial DNA/nuclear DNA content compared with baseline. In this work we show that obesity has an opposing association with mitochondrial respiration in adipose- and liver tissue with no overall association with NAFLD severity, however, bariatric surgery increases hepatic OXPHOS and mitochondrial biogenesis.

Mitochondrial adaptations to high intensity interval training in older females and males.

Introduction: High intensity interval training (HIIT) has shown to be as effective as moderate intensity endurance training to improve metabolic health. However, the current knowledge on the effect of HIIT in older individuals is limited and it is uncertain whether the adaptations are sex specific. The aim was to investigate effects of HIIT on mitochondrial respiratory capacity and mitochondrial content in older females and males. Methods: Twenty-two older sedentary males (n = 11) and females (n = 11) completed 6 weeks of supervised HIIT 3 days per week. The training consisted of 5 × 1 min cycling (124 ± 3% of max power output at session 2-6 and 135 ± 3% of max power output at session 7-20) interspersed by 1½ min recovery. Before the intervention and 72 h after last training session a muscle biopsy was obtained and mitochondrial respiratory capacity, citrate synthase activity and proteins involved in mitochondria metabolism were assessed. Furthermore, body composition and ⩒O2max were measured. Results: ⩒O2max increased and body fat percentage decreased after HIIT in both sexes (p < 0.05). In addition, CS activity and protein content of MnSOD and complex I-V increased in both sexes. Coupled and uncoupled mitochondrial respiratory capacity increased only in males. Mitochondrial respiratory capacity normalised to CS activity (intrinsic mitochondrial respiratory capacity) did not change following HIIT. Conclusion: HIIT induces favourable adaptions in skeletal muscle in older subjects by increasing mitochondrial content, which may help to maintain muscle oxidative capacity and slow down the process of sarcopenia associated with ageing.

Acetaminophen toxicity induces mitochondrial complex I inhibition in human liver tissue.

Acetaminophen (APAP) is used worldwide and is regarded as safe in therapeutic concentrations but can cause acute liver failure in higher doses. High doses of APAP have been shown to inhibit complex I and II mitochondrial respiratory capacity in mouse hepatocytes, but human studies are lacking. Here, we studied mitochondrial respiratory capacity in human hepatic tissue ex vivo with increasing doses of APAP. Hepatic biopsies were obtained from 12 obese patients who underwent a Roux-en-Y gastric bypass (RYGB) or a sleeve gastrectomy surgery. Mitochondrial respiration was measured by high-resolution respirometry. Therapeutic concentrations (≤0.13 mmol/L) of APAP did not inhibit state 3 complex I-linked respiration. APAP concentrations of ≥2.0 mmol/L in the medium significantly reduced hepatic mitochondrial respiration in a dose-dependent manner. Complex II-linked mitochondrial respiration was not inhibited by APAP. We conclude that the mitochondrial respiratory capacity is affected by a hepato-toxic effect of APAP, which involved complex I, but not complex II.

Inflammatory biomarkers in patients in Simvastatin treatment: No effect of co-enzyme Q10 supplementation.

PURPOSE: Atherosclerosis is a major risk factor for cardiovascular disease (CVD) and is known to be an inflammatory process. Statin therapy decreases both cholesterol and inflammation and is used in primary and secondary prevention of CVD. However, a statin induced decrease of plasma concentrations of the antioxidant coenzyme Q10 (CoQ10), may prevent the patients from reaching their optimal anti-inflammatory potential. Here, we studied the anti-inflammatory effect of Simvastatin therapy and CoQ10 supplementation. METHODS: 35 patients in primary prevention with Simvastatin (40 mg/day) were randomized to receive oral CoQ10 supplementation (400 mg/d) or placebo for 8 weeks. 20 patients with hypercholesterolemia who received no cholesterol-lowering treatment was a control group. Plasma concentrations of lipids and inflammatory biomarkers (interleukin-6 (IL6); -8 (IL8); -10 (IL10), tumor necrosis factor-α (TNFα); high-sensitivity C reactive protein (hsCRP)) as well as glycated hemoglobin (HbA1c) were quantified before and after the intervention. RESULTS: No significant change in inflammatory markers or lipids was observed after CoQ10 supplementation Patients in Simvastatin therapy had significantly (P < 0.05) lower baseline concentration of IL6 (0.31 ±â€¯0.03 pg/ml), IL8 (1.6 ±â€¯0.1 pg/ml) IL10 (0.16 ±â€¯0.02 pg/ml) and borderline (P = 0.053) lower TNFα (0.88 ±â€¯0.05 pg/ml), but not hsCRP (1.34 ±â€¯0.19 mg/l) compared with the control group (0.62 ±â€¯0.08, 2.6 ±â€¯0.2, 0.25 ±â€¯0.01, 1.07 ±â€¯0.09, and 1.90 ±â€¯0.35, respectively). CONCLUSIONS: Simvastatin therapy has beneficial effects on inflammatory markers in plasma, but CoQ10 supplementation seems to have no additional potentiating effect in patients in primary prevention. In contrast, glucose homeostasis may improve with CoQ10 supplementation.

Statin Treatment Decreases Mitochondrial Respiration But Muscle Coenzyme Q10 Levels Are Unaltered: The LIFESTAT Study.

BACKGROUND: Myalgia is a common adverse effect of statin therapy, but the underlying mechanism is unknown. Statins may reduce levels of coenzyme Q10 (CoQ10), which is an essential electron carrier in the mitochondrial electron transport system, thereby impairing mitochondrial respiratory function, potentially leading to myalgia. OBJECTIVES: To investigate whether statin-induced myalgia is coupled to reduced intramuscular CoQ10 concentration and impaired mitochondrial respiratory function. METHODS: Patients receiving simvastatin (i.e., statin) therapy (n = 64) were recruited, of whom 25 experienced myalgia (myalgic group) and 39 had no symptoms of myalgia (NS group). Another 20 had untreated high blood cholesterol levels (control group). Blood and muscle samples were obtained. Intramuscular CoQ10 concentration was measured, and mitochondrial respiratory function and reactive oxygen species (ROS) production were measured. Citrate synthase (CS) activity was used as a biomarker of mitochondrial content in skeletal muscle. RESULTS: Intramuscular CoQ10 concentration was comparable among groups. Mitochondrial complex II-linked respiration was reduced in the statin-myalgic and -NS groups compared with the control group. When mitochondrial respiration was normalized to CS activity, respiration rate was higher in the myalgic group compared with the NS and control groups. Maximal ROS production was similar among groups. CONCLUSION: Statin therapy appeared to impair mitochondrial complex-II-linked respiration, but the mitochondrial capacity for complex I+II-linked respiration remained intact. Myalgia was not coupled to reduced intramuscular CoQ10 levels. Intrinsic mitochondrial respiratory capacity was increased with statin-induced myalgia but not accompanied by increased ROS production.