Lipoprotein lipase in mouse kidney: effects of nutritional status and high-fat diet.

Activity of lipoprotein lipase (LPL) is high in mouse kidney, but the reason is poorly understood. The aim was to characterize localization, regulation, and function of LPL in kidney of C57BL/6J mice. We found LPL mainly in proximal tubules, localized inside the tubular epithelial cells, under all conditions studied. In fed mice, some LPL colocalized with the endothelial markers CD31 and GPIHBP1 and could be removed by perfusion with heparin, indicating a vascular location. The role of angiopoietin-like protein 4 (ANGPTL4) for nutritional modulation of LPL activity was studied in wild-type and Angptl4-/- mice. In Angptl4-/- mice, kidney LPL activity remained high in fasted animals, indicating that ANGPTL4 is involved in suppression of LPL activity on fasting, like in adipose tissue. The amount of ANGPTL4 protein in kidney was low, and the protein appeared smaller in size, compared with ANGPTL4 in heart and adipose tissue. To study the influence of obesity, mice were challenged with high-fat diet for 22 wk, and LPL was studied after an overnight fast compared with fasted mice given food for 3 h. High-fat diet caused blunting of the normal adaptation of LPL activity to feeding/fasting in adipose tissue, but in kidneys this adaptation was lost only in male mice. LPL activity increases to high levels in mouse kidney after feeding, but as no difference in uptake of chylomicron triglycerides in kidneys is found between fasted and fed states, our data confirm that LPL appears to have a minor role for lipid uptake in this organ.

Angiotensin II and salt-induced decompensation in Balb/CJ mice is aggravated by fluid retention related to low oxidative stress.

Balb/CJ mice are more sensitive to treatment with angiotensin II (ANG II) and high-salt diet compared with C57BL/6J mice. Together with higher mortality, they develop edema, signs of heart failure, and acute kidney injury. The aim of the present study was to identify differences in renal gene regulation that may affect kidney function and fluid balance, which could contribute to decompensation in Balb/CJ mice after ANG II + salt treatment. Male Balb/CJ and C57BL/6J mice were divided into the following five different treatment groups: control, ANG II, salt, ANG II + salt, and ANG II + salt + N-acetylcysteine. Gene expression microarrays were used to explore differential gene expression after treatment and between the strains. Published data from the Mouse Genome Database were used to identify the associated genomic differences. The glomerular filtration rate (GFR) was measured using inulin clearance, and fluid balance was measured using metabolic cages. Gene ontology enrichment analysis of gene expression microarrays identified glutathione transferase (antioxidant system) as highly enriched among differentially expressed genes. Balb/CJ mice had similar GFR compared with C57BL/6J mice but excreted less Na+ and water, although net fluid and electrolyte balance did not differ, suggesting that Balb/CJ mice may be inherently more prone to decompensation. Interestingly, C57BL/6J mice had higher urinary oxidative stress despite their relative protection from decompensation. In addition, treatment with the antioxidant N-acetylcysteine decreased oxidative stress in C57BL/6J mice, reduced urine excretion, and increased mortality. Balb/CJ mice are more sensitive than C57BL/6J to ANG II + salt, in part mediated by lower oxidative stress, which favors fluid and Na+ retention.

Time course of decompensation after angiotensin II and high-salt diet in Balb/CJ mice suggests pulmonary hypertension-induced cardiorenal syndrome.

The genetic background of a mouse strain determines its susceptibility to disease. C57BL/6J and Balb/CJ are two widely used inbred mouse strains that we found react dramatically differently to angiotensin II and high-salt diet (ANG II + Salt). Balb/CJ show increased mortality associated with anuria and edema formation while C57BL/6J develop arterial hypertension but do not decompensate and die. Clinical symptoms of heart failure in Balb/CJ mice gave the hypothesis that ANG II + Salt impairs cardiac function and induces cardiac remodeling in male Balb/CJ but not in male C57BL/6J mice. To test this hypothesis, we measured cardiac function using echocardiography before treatment and every day for 7 days during treatment with ANG II + Salt. Interestingly, pulsed wave Doppler of pulmonary artery flow indicated increased pulmonary vascular resistance and right ventricle systolic pressure in Balb/CJ mice, already 24 h after ANG II + Salt treatment was started. In addition, Balb/CJ mice showed abnormal diastolic filling indicated by reduced early and late filling and increased isovolumic relaxation time. Furthermore, Balb/CJ exhibited lower cardiac output compared with C57BL/6J even though they retained more sodium and water, as assessed using metabolic cages. Left posterior wall thickness increased during ANG II + Salt treatment but did not differ between the strains. In conclusion, ANG II + Salt treatment causes early restriction of pulmonary flow and reduced left ventricular filling and cardiac output in Balb/CJ, which results in fluid retention and peripheral edema. This makes Balb/CJ a potential model to study the adaptive capacity of the heart for identifying new disease mechanisms and drug targets.

Cardiac hypertrophy and decreased high-density lipoprotein cholesterol in Lrig3-deficient mice.

Genetic factors confer risk for cardiovascular disease. Recently, large genome-wide population studies have shown associations between genomic loci close to LRIG3 and heart failure and plasma high-density lipoprotein (HDL) cholesterol level. Here, we ablated Lrig3 in mice and investigated the importance of Lrig3 for heart function and plasma lipid levels. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to analyze Lrig3 expression in the hearts of wild-type and Lrig3-deficient mice. In addition, molecular, physiological, and functional parameters such as organ weights, heart rate, blood pressure, heart structure and function, gene expression in the heart, and plasma insulin, glucose, and lipid levels were evaluated. The Lrig3-deficient mice were smaller than the wild-type mice but otherwise appeared grossly normal. Lrig3 was expressed at detectable but relatively low levels in adult mouse hearts. At 9 mo of age, ad libitum-fed Lrig3-deficient mice had lower insulin levels than wild-type mice. At 12 mo of age, Lrig3-deficient mice exhibited increased blood pressure, and the Lrig3-deficient female mice displayed signs of cardiac hypertrophy as assessed by echocardiography, heart-to-body weight ratio, and expression of the cardiac hypertrophy marker gene Nppa. Additionally, Lrig3-deficient mice had reduced plasma HDL cholesterol and free glycerol. These findings in mice complement the human epidemiological results and suggest that Lrig3 may influence heart function and plasma lipid levels in mice and humans.

Identification of a small molecule that stabilizes lipoprotein lipase in vitro and lowers triglycerides in vivo.

Patients at increased cardiovascular risk commonly display high levels of plasma triglycerides (TGs), elevated LDL cholesterol, small dense LDL particles and low levels of HDL-cholesterol. Many remain at high risk even after successful statin therapy, presumably because TG levels remain high. Lipoprotein lipase (LPL) maintains TG homeostasis in blood by hydrolysis of TG-rich lipoproteins. Efficient clearance of TGs is accompanied by increased levels of HDL-cholesterol and decreased levels of small dense LDL. Given the central role of LPL in lipid metabolism we sought to find small molecules that could increase LPL activity and serve as starting points for drug development efforts against cardiovascular disease. Using a small molecule screening approach we have identified small molecules that can protect LPL from inactivation by the controller protein angiopoietin-like protein 4 during incubations in vitro. One of the selected compounds, 50F10, was directly shown to preserve the active homodimer structure of LPL, as demonstrated by heparin-Sepharose chromatography. On injection to hypertriglyceridemic apolipoprotein A-V deficient mice the compound ameliorated the postprandial response after an olive oil gavage. This is a potential lead compound for the development of drugs that could reduce the residual risk associated with elevated plasma TGs in dyslipidemia.

Amphetamine-induced dopamine release in rat: Whole-brain spatiotemporal analysis with [11C]raclopride and positron emission tomography.

Whole-brain mapping of drug effects are needed to understand the neural underpinnings of drug-related behaviors. Amphetamine administration is associated with robust increases in striatal dopamine (DA) release. Dopaminergic terminals are, however, present across several associative brain regions, which may contribute to behavioral effects of amphetamine. Yet the assessment of DA release has been restricted to a few brain regions of interest. The present work employed positron emission tomography (PET) with [11C]raclopride to investigate regional and temporal characteristics of amphetamine-induced DA release across twenty sessions in adult female Sprague Dawley rats. Amphetamine was injected intravenously (2 mg/kg) to cause displacement of [11C]raclopride binding from DA D2-like receptors, assessed using temporally sensitive pharmacokinetic PET model (lp-ntPET). We show amphetamine-induced [11C]raclopride displacement in the basal ganglia, and no changes following saline injections. Peak occupancy was highest in nucleus accumbens, followed by caudate-putamen and globus pallidus. Importantly, significant amphetamine-induced displacement was also observed in several extrastriatal regions, and specifically in thalamus, insula, orbitofrontal cortex, and secondary somatosensory area. For these, peak occupancy occurred later and was lower as compared to the striatum. Collectively, these findings demonstrate distinct amphetamine-induced DA responses across the brain, and that [11C]raclopride-PET can be employed to detect such spatiotemporal differences.

Triacylglycerol-rich lipoproteins protect lipoprotein lipase from inactivation by ANGPTL3 and ANGPTL4.

Lipoprotein lipase (LPL) is important for clearance of triacylglycerols (TG) from plasma both as an enzyme and as a bridging factor between lipoproteins and receptors for endocytosis. The amount of LPL at the luminal side of the capillary endothelium determines to what extent lipids are taken up. Mechanisms to control both the activity of LPL and its transport to the endothelial sites are regulated, but poorly understood. Angiopoietin-like proteins (ANGPTLs) 3 and 4 are potential control proteins for LPL, but plasma concentrations of ANGPTLs do not correlate with plasma TG levels. We investigated the effects of recombinant human N-terminal (NT) ANGPTLs3 and 4 on LPL-mediated bridging of TG-rich lipoproteins to primary mouse hepatocytes and found that the NT-ANGPTLs, in concentrations sufficient to cause inactivation of LPL in vitro, were unable to prevent LPL-mediated lipoprotein uptake. We therefore investigated the effects of lipoproteins (chylomicrons, VLDL and LDL) on the inactivation of LPL in vitro by NT-ANGPTLs3 and 4 and found that LPL activity was protected by TG-rich lipoproteins. In vivo, postprandial TG protected LPL from inactivation by recombinant NT-ANGPTL4 injected to mice. We conclude that lipoprotein-bound LPL is stabilized against inactivation by ANGPTLs. The levels of ANGPTLs found in blood may not be sufficient to overcome this stabilization. Therefore it is likely that the prime site of action of ANGPTLs on LPL is in subendothelial compartments where TG-rich lipoprotein concentration is lower than in blood. This could explain why the plasma levels of TG and ANGPTLs do not correlate.

O304 ameliorates hyperglycemia in mice by dually promoting muscle glucose effectiveness and preserving ß-cell function.

Although insulin mediated glucose uptake in skeletal muscle is a major mechanism ensuring glucose disposal in humans, glucose effectiveness, i.e., the ability of glucose itself to stimulate its own uptake independent of insulin, accounts for roughly half of the glucose disposed during an oral glucose tolerance test. Both insulin dependent and insulin independent skeletal muscle glucose uptake are however reduced in individuals with diabetes. We here show that AMPK activator O304 stimulates insulin independent glucose uptake and utilization in skeletal muscle and heart in vivo, while preventing glycogen accumulation. Combined glucose uptake and utilization requires an increased metabolic demand and we show that O304 acts as a mitochondrial uncoupler, i.e., generates a metabolic demand. O304 averts gene expression changes associated with metabolic inflexibility in skeletal muscle and heart of diabetic mice and reverts diabetic cardiomyopathy. In Type 2 diabetes, insulin resistance elicits compensatory insulin hypersecretion, provoking ß-cell stress and eventually compensatory failure. In db/db mice O304 preserves ß-cell function by preventing decline in insulin secretion, ß-cell mass, and pancreatic insulin content. Thus, as a dual AMPK activator and mitochondrial uncoupler O304 mitigates two central defects of T2D; impaired glucose uptake/utilization and ß-cell failure, which today lack effective treatment.

Visualizing increased uptake of [18F]FDG and [18F]FTHA in kidneys from obese high-fat diet fed C57BL/6J mice using PET/CT ex vivo.

It is known that high-fat diet (HFD) and/or diabetes may influence substrate preferences and energy demands in the heart preceding diabetic cardiomyopathy. They may also induce structural glomerular changes causing diabetic nephropathy. PET/CT has been utilized to examine uptake of energy substrates, and to study metabolic changes or shifts before onset of metabolic disorders. However, conventional PET/CT scanning of organs with relatively low uptake, such as the kidney, in small animals in vivo may render technical difficulties. To address this issue, we developed a PET/CT ex vivo protocol with radiolabeled glucose and fatty acid analouges, [18F]FDG and [18F]FTHA,to study substrate uptake in mouse kidneys. We also aimed to detect a possible energy substrate shift before onset of diabetic nephropathy. The ex vivo protocol reduced interfering background as well as interindividual variances. We found increased uptake of [18F]FDG and [18F]FTHA in kidneys after HFD, compared to kidneys from young mice on standard chow. Levels of kidney triglycerides also increased on HFD. Lipoprotein lipase (LPL) activity, the enzyme responsible for release of fatty acids from circulating lipoproteins, is normally increased in postprandial mice kidneys. After long-term HFD, we found that LPL activity was suppressed, and could therefore not explain the increased levels of stored triglycerides. Suppressed LPL activity was associated with increased expression of angiopoietin-like protein4, an inhibitor of LPL. HFD did not alter the transcriptional control of some common glucose and fatty acid transporters that may mediate uptake of [18F]FDG and [18F]FTHA. Performing PET/CT ex vivo reduced interfering background and interindividual variances. Obesity and insulin resistance induced by HFD increased the uptake of [18F]FDG and [18F]FTHA and triglyceride accumulation in mouse kidneys. Increased levels of [18F]FDG and [18F]FTHA in obese insulin resistant mice could be used clinically as an indicator of poor metabolic control, and a complementary test for incipient diabetic nephropathy.

The Aged Striatum: Evidence of Molecular and Structural Changes Using a Longitudinal Multimodal Approach in Mice.

To study the aging human brain requires significant resources and time. Thus, mice models of aging can provide insight into changes in brain biological functions at a fraction of the time when compared to humans. This study aims to explore changes in dopamine D1 and D2 receptor availability and of gray matter density in striatum during aging in mice and to evaluate whether longitudinal imaging in mice may serve as a model for normal brain aging to complement cross-sectional research in humans. Mice underwent repeated structural magnetic resonance imaging (sMRI), and [11C]Raclopride and [11C]SCH23390 positron emission tomography (PET) was performed on a subset of aging mice. PET and sMRI data were analyzed by binding potential (BP ND ), voxel- and tensor-based morphometry (VBM and TBM, respectively). Longitudinal PET revealed a significant reduction in striatal BP ND for D2 receptors over time, whereas no significant change was found for D1 receptors. sMRI indicated a significant increase in modulated gray matter density (mGMD) over time in striatum, with limited clusters showing decreased mGMD. Mouse [11C]Raclopride data is compatible with previous reports in human cross-sectional studies, suggesting that a natural loss of dopaminergic D2 receptors in striatum can be assessed in mice, reflecting estimates from humans. No changes in D1 were found, which may be attributed to altered [11C]SCH23390 kinetics in anesthetized mice, suggesting that this tracer is not yet able to replicate human findings. sMRI revealed a significant increase in mGMD. Although contrary to expectations, this increase in modulated GM density may be attributed to an age-related increase in non-neuronal cells.

N-acetylcysteine decreases dopamine transporter availability in the non-lesioned striatum of the 6-OHDA hemiparkinsonian rat.

This study aimed to explore the beneficial effects of the antioxidant N-acetylcysteine (NAC) on the degenerated dopamine system. The short- and long-term regulatory mechanisms of NAC on the 6-OHDA hemiparkinsonian rat model were longitudinally investigated by performing positron emission tomography (PET) imaging using the specific dopamine transporter (DAT) radioligand [18F]FE-PE2I. The results demonstrate that after a unilateral dopamine insult NAC has a strong influence on the non-lesioned hemisphere by decreasing the levels of DAT in the striatum early after the lesion. We interpret this early and short-term decrease of DAT in the healthy striatum of NAC-treated animals as a beneficial compensatory effect induced by NAC.

Slowed relaxation and preserved maximal force in soleus muscles of mice with targeted disruption of the Serca2 gene in skeletal muscle.

Sarcoplasmic reticulum Ca(2+) ATPases (SERCAs) play a major role in muscle contractility by pumping Ca(2+) from the cytosol into the sarcoplasmic reticulum (SR) Ca(2+) store, allowing muscle relaxation and refilling of the SR with releasable Ca(2+). Decreased SERCA function has been shown to result in impaired muscle function and disease in human and animal models. In this study, we present a new mouse model with targeted disruption of the Serca2 gene in skeletal muscle (skKO) to investigate the functional consequences of reduced SERCA2 expression in skeletal muscle. SkKO mice were viable and basic muscle structure was intact. SERCA2 abundance was reduced in multiple muscles, and by as much as 95% in soleus muscle, having the highest content of slow-twitch fibres (40%). The Ca(2+) uptake rate was significantly reduced in SR vesicles in total homogenates. We did not find any compensatory increase in SERCA1 or SERCA3 abundance, or altered expression of several other Ca(2+)-handling proteins. Ultrastructural analysis revealed generally well-preserved muscle morphology, but a reduced volume of the longitudinal SR. In contracting soleus muscle in vitro preparations, skKO muscles were able to fully relax, but with a significantly slowed relaxation time compared to controls. Surprisingly, the maximal force and contraction rate were preserved, suggesting that skKO slow-twitch fibres may be able to contribute to the total muscle force despite loss of SERCA2 protein. Thus it is possible that SERCA-independent mechanisms can contribute to muscle contractile function.

AMPK activator O304 improves metabolic and cardiac function, and exercise capacity in aged mice.

Age is associated with progressively impaired, metabolic, cardiac and vascular function, as well as reduced work/exercise capacity, mobility, and hence quality of life. Exercise exhibit positive effects on age-related dysfunctions and diseases. However, for a variety of reasons many aged individuals are unable to engage in regular physical activity, making the development of pharmacological treatments that mimics the beneficial effects of exercise highly desirable. Here we show that the pan-AMPK activator O304, which is well tolerated in humans, prevented and reverted age-associated hyperinsulinemia and insulin resistance, and improved cardiac function and exercise capacity in aged mice. These results provide preclinical evidence that O304 mimics the beneficial effects of exercise. Thus, as an exercise mimetic in clinical development, AMPK activator O304 holds great potential to mitigate metabolic dysfunction, and to improve cardiac function and exercise capacity, and hence quality of life in aged individuals.

A Ketogenic Low-Carbohydrate High-Fat Diet Increases LDL Cholesterol in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial.

Ketogenic low-carbohydrate high-fat (LCHF) diets are popular among young, healthy, normal-weight individuals for various reasons. We aimed to investigate the effect of a ketogenic LCHF diet on low-density lipoprotein (LDL) cholesterol (primary outcome), LDL cholesterol subfractions and conventional cardiovascular risk factors in the blood of healthy, young, and normal-weight women. The study was a randomized, controlled, feeding trial with crossover design. Twenty-four women were assigned to a 4 week ketogenic LCHF diet (4% carbohydrates; 77% fat; 19% protein) followed by a 4 week National Food Agency recommended control diet (44% carbohydrates; 33% fat; 19% protein), or the reverse sequence due to the crossover design. Treatment periods were separated by a 15 week washout period. Seventeen women completed the study and treatment effects were evaluated using mixed models. The LCHF diet increased LDL cholesterol in every woman with a treatment effect of 1.82 mM (p < 0.001). In addition, Apolipoprotein B-100 (ApoB), small, dense LDL cholesterol as well as large, buoyant LDL cholesterol increased (p < 0.001, p < 0.01, and p < 0.001, respectively). The data suggest that feeding healthy, young, normal-weight women a ketogenic LCHF diet induces a deleterious blood lipid profile. The elevated LDL cholesterol should be a cause for concern in young, healthy, normal-weight women following this kind of LCHF diet.

Reply to Ravnskov, U. Is High Cholesterol Deleterious? An Alternative Point of View. Comment on "Burén et al. A Ketogenic Low-Carbohydrate High-Fat Diet Increases LDL Cholesterol in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial. Nutrients 2021, 13, 814".

We thank Ravnskov [...].

Lowering apolipoprotein CIII protects against high-fat diet-induced metabolic derangements.

Increased levels of apolipoprotein CIII (apoCIII), a key regulator of lipid metabolism, result in obesity-related metabolic derangements. We investigated mechanistically whether lowering or preventing high-fat diet (HFD)-induced increase in apoCIII protects against the detrimental metabolic consequences. Mice, first fed HFD for 10 weeks and thereafter also given an antisense (ASO) to lower apoCIII, already showed reduced levels of apoCIII and metabolic improvements after 4 weeks, despite maintained obesity. Prolonged ASO treatment reversed the metabolic phenotype due to increased lipase activity and receptor-mediated hepatic uptake of lipids. Fatty acids were transferred to the ketogenic pathway, and ketones were used in brown adipose tissue (BAT). This resulted in no fat accumulation and preserved morphology and function of liver and BAT. If ASO treatment started simultaneously with the HFD, mice remained lean and metabolically healthy. Thus, lowering apoCIII protects against and reverses the HFD-induced metabolic phenotype by promoting physiological insulin sensitivity.

PAN-AMPK activator O304 improves glucose homeostasis and microvascular perfusion in mice and type 2 diabetes patients.

AMPK activated protein kinase (AMPK), a master regulator of energy homeostasis, is activated in response to an energy shortage imposed by physical activity and caloric restriction. We here report on the identification of PAN-AMPK activator O304, which - in diet-induced obese mice - increased glucose uptake in skeletal muscle, reduced ß cell stress, and promoted ß cell rest. Accordingly, O304 reduced fasting plasma glucose levels and homeostasis model assessment of insulin resistance (HOMA-IR) in a proof-of-concept phase IIa clinical trial in type 2 diabetes (T2D) patients on Metformin. T2D is associated with devastating micro- and macrovascular complications, and O304 improved peripheral microvascular perfusion and reduced blood pressure both in animals and T2D patients. Moreover, like exercise, O304 activated AMPK in the heart, increased cardiac glucose uptake, reduced cardiac glycogen levels, and improved left ventricular stroke volume in mice, but it did not increase heart weight in mice or rats. Thus, O304 exhibits a great potential as a novel drug to treat T2D and associated cardiovascular complications.

Monoclonal B-cell hyperplasia and leukocyte imbalance precede development of B-cell malignancies in uracil-DNA glycosylase deficient mice.

Ung-deficient mice have reduced class switch recombination, skewed somatic hypermutation, lymphatic hyperplasia and a 22-fold increased risk of developing B-cell lymphomas. We find that lymphomas are of follicular (FL) and diffuse large B-cell type (DLBCL). All FLs and 75% of the DLBCLs were monoclonal while 25% were biclonal. Monoclonality was also observed in hyperplasia, and could represent an early stage of lymphoma development. Lymphoid hyperplasia occurs very early in otherwise healthy Ung-deficient mice, observed as a significant increase of splenic B-cells. Furthermore, loss of Ung also causes a significant reduction of T-helper cells, and 50% of the young Ung(-/-) mice investigated have no detectable NK/NKT-cell population in their spleen. The immunological imbalance is confirmed in experiments with spleen cells where the production of the cytokines interferon gamma, interleukin 6 and interleukin 2 is clearly different in wild type and in Ung-deficient mice. This suggests that Ung-proteins, directly or indirectly, have important functions in the immune system, not only in the process of antibody maturation, but also for production and functions of immunologically important cell types. The immunological imbalances shown here in the Ung-deficient mice may be central in the development of lymphomas in a background of generalised lymphoid hyperplasia.

The PPARα Agonist Fenofibrate Improves the Musculoskeletal Effects of Exercise in Ovariectomized Rats.

The musculoskeletal effects of exercise are attenuated by estrogen deficiency. The peroxisome proliferator-activated receptor-α agonist fenofibrate exerts beneficial effects in bone and muscle. We therefore examined whether fenofibrate could enhance the musculoskeletal training response during estrogen deficiency. We investigated the combined effects of 8 weeks of fenofibrate and jumping exercise in ovariectomized (OVX) Sprague Dawley rats. Female rats were allocated to a sham-operated group and four OVX groups; fenofibrate (OVX-Fen), exercise (OVX-Ex), combined fenofibrate and exercise (OVX-FenEx), and a control group (OVX-Ctr) (n = 12/group). Fenofibrate (90 mg/kg/d) or methylcellulose was given by gavage. The combination of exercise and fenofibrate resulted in enhanced femoral bone mineral density (BMD) and improved bone microarchitecture compared with fenofibrate alone as well as increased trabecular BMD compared with OVX-Ctr. These effects were not seen in the OVX-Ex group. Femoral BMD was normalized in both exercise groups relative to sham and increased more in all intervention groups compared with OVX-Ctr. A higher plasma level of the bone formation marker type 1 collagen amino propeptide was observed in the OVX-Fen and OVX-FenEx groups compared with controls. Lean mass and soleus muscle weight were higher in the OVX-FenEx group than in the OVX-Ctr group, which coincided with lower mRNA levels of Atrogin1. These results suggest that peroxisome proliferator-activated receptor-α activation improves the musculoskeletal effects of exercise during estrogen deficiency.

A low-carbohydrate high-fat diet decreases lean mass and impairs cardiac function in pair-fed female C57BL/6J mice.

BACKGROUND: Excess body fat is a major health issue and a risk factor for the development of numerous chronic diseases. Low-carbohydrate diets like the Atkins Diet are popular for rapid weight loss, but the long-term consequences remain the subject of debate. The Scandinavian low-carbohydrate high-fat (LCHF) diet, which has been popular in Scandinavian countries for about a decade, has very low carbohydrate content (~5 E %) but is rich in fat and includes a high proportion of saturated fatty acids. Here we investigated the metabolic and physiological consequences of a diet with a macronutrient composition similar to the Scandinavian LCHF diet and its effects on the organs, tissues, and metabolism of weight stable mice. METHODS: Female C57BL/6J mice were iso-energetically pair-fed for 4 weeks with standard chow or a LCHF diet. We measured body composition using echo MRI and the aerobic capacity before and after 2 and 4 weeks on diet. Cardiac function was assessed by echocardiography before and after 4 weeks on diet. The metabolic rate was measured by indirect calorimetry the fourth week of the diet. Mice were sacrificed after 4 weeks and the organ weight, triglyceride levels, and blood chemistry were analyzed, and the expression of key ketogenic, metabolic, hormonal, and inflammation genes were measured in the heart, liver, and adipose tissue depots of the mice using real-time PCR. RESULTS: The increase in body weight of mice fed a LCHF diet was similar to that in controls. However, while control mice maintained their body composition throughout the study, LCHF mice gained fat mass at the expense of lean mass after 2 weeks. The LCHF diet increased cardiac triglyceride content, impaired cardiac function, and reduced aerobic capacity. It also induced pronounced alterations in gene expression and substrate metabolism, indicating a unique metabolic state. CONCLUSIONS: Pair-fed mice eating LCHF increased their percentage of body fat at the expense of lean mass already after 2 weeks, and after 4 weeks the function of the heart deteriorated. These findings highlight the urgent need to investigate the effects of a LCHF diet on health parameters in humans.