Resveratrol is a natural compound that affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here, we treated 11 healthy, obese men with placebo and 150 mg/day resveratrol (resVida) in a randomized double-blind crossover study for 30 days. Resveratrol significantly reduced sleeping and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1α protein levels, increased citrate synthase activity without change in mitochondrial content, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces metabolic changes in obese humans, mimicking the effects of calorie restriction.

Recent preclinical studies showed the potential of nicotinamide adenine dinucleotide (NAD+) precursors to increase oxidative phosphorylation and improve metabolic health, but human data are lacking. We hypothesize that the nicotinic acid derivative acipimox, an NAD+ precursor, would directly affect mitochondrial function independent of reductions in nonesterified fatty acid (NEFA) concentrations. In a multicenter randomized crossover trial, 21 patients with type 2 diabetes (age 57.7 ± 1.1 years, BMI 33.4 ± 0.8 kg/m2) received either placebo or acipimox 250 mg three times daily dosage for 2 weeks. Acipimox treatment increased plasma NEFA levels (759 ± 44 vs. 1,135 ± 97 μmol/L for placebo vs. acipimox, P < 0.01) owing to a previously described rebound effect. As a result, skeletal muscle lipid content increased and insulin sensitivity decreased. Despite the elevated plasma NEFA levels, ex vivo mitochondrial respiration in skeletal muscle increased. Subsequently, we showed that acipimox treatment resulted in a robust elevation in expression of nuclear-encoded mitochondrial gene sets and a mitonuclear protein imbalance, which may indicate activation of the mitochondrial unfolded protein response. Further studies in C2C12 myotubes confirmed a direct effect of acipimox on NAD+ levels, mitonuclear protein imbalance, and mitochondrial oxidative capacity. To the best of our knowledge, this study is the first to demonstrate that NAD+ boosters can also directly affect skeletal muscle mitochondrial function in humans.

The relationship between the age-associated decline in mitochondrial function and its effect on skeletal muscle physiology and function remain unclear. In the current study, we examined to what extent physical activity contributes to the decline in mitochondrial function and muscle health during aging and compared mitochondrial function in young and older adults, with similar habitual physical activity levels. We also studied exercise-trained older adults and physically impaired older adults. Aging was associated with a decline in mitochondrial capacity, exercise capacity and efficiency, gait stability, muscle function, and insulin sensitivity, even when maintaining an adequate daily physical activity level. Our data also suggest that a further increase in physical activity level, achieved through regular exercise training, can largely negate the effects of aging. Finally, mitochondrial capacity correlated with exercise efficiency and insulin sensitivity. Together, our data support a link between mitochondrial function and age-associated deterioration of skeletal muscle.

Elevated hepatic lipid content (IntraHepatic Lipid, IHL) increases the risk of metabolic complications. Although prolonged exercise training lowers IHL, it is unknown if acute exercise has the same effect. Furthermore, hepatic ATP content may be related to insulin resistance and IHL. We aimed to investigate if acute exercise leads to changes in IHL and whether this is accompanied by changes in hepatic ATP. Twenty-one men (age 54.8 ± 7.2 years, BMI 29.7 ± 2.2 kg/m2) performed a 2 h cycling protocol, once while staying fasted and once while ingesting glucose. IHL was determined at baseline, 30 min post-exercise and 4 h post-exercise. Additionally ATP/Total P ratio was measured at baseline and 4 h post-exercise. Compared with baseline values we did not observe any statistically significant changes in IHL within 30 min post-exercise in neither the fasted nor the glucose-supplemented condition. However, IHL was elevated 4 h post-exercise compared with baseline in the fasted condition (from 8.3 ± 1.8 to 8.7 ± 1.8%, p = 0.010), an effect that was blunted by glucose supplementation (from 8.3 ± 1.9 to 8.3 ± 1.9%, p = 0.789). Acute exercise does not decrease liver fat in overweight middle-aged men. Moreover, IHL increased 4 h post-exercise in the fasted condition, an increase that was absent in the glucose-supplemented condition. These data suggest that a single bout of exercise may not be able to lower IHL.

Cardiac lipid accumulation is associated with decreased cardiac function and energy status (PCr/ATP). It has been suggested that elevated plasma fatty acid (FA) concentrations are responsible for the cardiac lipid accumulation. Therefore, the aim of the present study was to investigate if elevating plasma FA concentrations by exercise results in an increased cardiac lipid content, and if this influences cardiac function and energy status. Eleven male subjects (age 25.4 ± 1.1 years, BMI 23.6 ± 0.8 kg/m2) performed a 2-h cycling protocol, once while staying fasted and once while ingesting glucose, to create a state of high versus low plasma FA concentrations, respectively. Cardiac lipid content was measured by proton magnetic resonance spectroscopy (1H-MRS) at baseline, directly after exercise and again 4 h post-exercise, together with systolic function (by multi-slice cine-MRI) and cardiac energy status (by 31P-MRS). Plasma FA concentrations were increased threefold during exercise and ninefold during recovery in the fasted state compared with the glucose-fed state (p < 0.01). Cardiac lipid content was elevated at the end of the fasted test day (from 0.26 ± 0.04 to 0.44 ± 0.04%, p = 0.003), while it did not change with glucose supplementation (from 0.32 ± 0.03 to 0.26 ± 0.05%, p = 0.272). Furthermore, PCr/ATP was decreased by 32% in the high plasma FA state compared with the low FA state (n = 6, p = 0.014). However, in the high FA state, the ejection fraction 4 h post-exercise was higher compared with the low FA state (63 ± 2 vs. 59 ± 2%, p = 0.018). Elevated plasma FA concentrations, induced by exercise in the fasted state, lead to increased cardiac lipid content, but do not acutely hamper systolic function. Although the lower cardiac energy status is in line with a lipotoxic action of cardiac lipid content, a causal relationship cannot be proven.

Despite a marked decrease in tissue lipid accumulation and an improvement in oxidative metabolism, no major changes were (yet) found in clinical parameters. Handgrip strength was low in NLSDM patients and did not change on bezafibrate treatment in either subject (data not presented). However, both patients did show an improvement in a leg extension test, a measure of leg muscle strength (Figure E). Although this did seem to consistently improve, the values for both patients remained low compared with age, body mass index, and sex-matched controls ( Figure E, dotted lines).Cardiac function at baseline was impaired in patient 1 and normal in patient 2 (Table). Patient 1, who is known to have frequent arrhythmias before treatment, only had 1 episode with a nonsustained ventricular tachycardia during the intervention period, as registered by the implantable cardioverter defibrillator. Still, neither the ultrasound nor the ECG could detect marked changes in cardiac function in both patients after 28 weeks of treatment (Table).Consistent with the findings in mice lacking ATGL,4 bezafibrate treatment resulted in a marked lowering of cardiac and muscle fat content and an increase in fat oxidative capacity. In healthy subjects, fibrates were shown not to affect ectopic lipid content, 7,8 suggesting that fibrates may reduce the extreme lipid accumulation that characterizes NLSDM by upregulating and normalizing oxidative metabolism. Haemmerle et al 4 showed recently that the lack of ATGL prevents liberation of fatty acids (or fatty acid intermediates) for PPAR signaling from the lipid droplet, hence resulting in an impaired fat oxidative capacity. As a consequence, oxidation of circulatory fatty acids taken up in muscle, liver, and heart is compromised, and these fatty acids will be more readily directed to storage. By providing synthetic PPAR agonists to ATGL-deficient mice, fat oxidative capacity could be increased, ectopic fat storage was blunted, and cardiac dysfunction was completely restored. The results presented here indicate that, in humans with compromised ATGL activity, PPAR treatment results in similar improvements in fat oxidation and tissue lipid storage, as in ATGL-deficient mice. However, unlike ATGL-deficient mice, the improvements in lipid accumulation and oxidative metabolism observed in our patients did not (yet) result in pronounced clinical changes. Leg muscle strength did improve but was not paralleled by a decrease/normalization of creatine kinase levels or a change in handgrip strength. Furthermore, cardiac function seemed unaltered. Whether the lack of clinical changes are attributed to the relative short duration of the treatment or the fact that treatment could only be started in patients who are in a later stage of the disease (note that ATGLdeficient mice were treated from early age onward) cannot be deduced from the present study and needs further investigation.In conclusion, our results suggest that, similar to mice lacking ATGL, NLSDM patients may also benefit from bezafibrate treatment wit...

P. (2020). Effects of a whole diet approach on metabolic flexibility, insulin sensitivity and postprandial glucose responses in overweight and obese adults -A randomized controlled trial.

Altered skeletal muscle lipid metabolism is a hallmark feature of type 2 diabetes (T2D). We investigated muscle lipid turnover in T2D versus BMI-matched control subjects (controls) and examined whether putative in vivo differences would be preserved in the myotubes. Male obese T2D individuals (n = 6) and BMI-matched controls (n = 6) underwent a hyperinsulinemic-euglycemic clamp, VO 2 max test, dual-energy X-ray absorptiometry scan, underwater weighing, and muscle biopsy of the vastus lateralis.14 C-palmitate and 14 C-oleate oxidation rates and incorporation into lipids were measured in muscle tissue as well as in primary myotubes. Palmitate oxidation (controls: 0.99 6 0.17 nmol/mg protein; T2D: 0.53 6 0.07 nmol/mg protein; P = 0.03) and incorporation of fatty acids (FAs) into triacylglycerol (TAG) (controls: 0.45 6 0.13 nmol/mg protein; T2D: 0.11 6 0.02 nmol/mg protein; P = 0.047) were significantly reduced in muscle homogenates of T2D. These reductions were not retained for palmitate oxidation in primary myotubes (P = 0.38); however, incorporation of FAs into TAG was lower in T2D (P = 0.03 for oleate and P = 0.11 for palmitate), with a strong correlation of TAG incorporation between muscle tissue and primary myotubes (r = 0.848, P = 0.008). The data indicate that the ability to incorporate FAs into TAG is an intrinsic feature of human muscle cells that is reduced in individuals with T2D.