n -3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction

Potential nutritional strategies to prevent and reverse sarcopenia in aging process: Role of fish oil-derived ω-3 polyunsaturated fatty acids, wheat oligopeptide and their combined intervention

INTRODUCTION

Nutritional support is potentially considered an essential step to prevent muscle loss and enhance physical function in older adults.

OBJECTIVES

This study aimed to assess the role of potential nutritional strategies, i.e., fish oil-derived ω-3 polyunsaturated fatty acids (PUFAs), wheat oligopeptide and their combined intervention, in preventing and reversing sarcopenia in aging process.

METHODS

One hundred 25-month-old Sprague-Dawley rats were randomly divided into 10 groups, and 10 newly purchased 6-month-old rats were included in young control group (n = 10). Fish oil (200, 400 or 800 mg/kg body weight), wheat oligopeptide (100, 200 or 400 mg/kg body weight), fish oil + wheat oligopeptide (800 + 100, 400 + 200 or 200 + 400 mg/kg body weight) or the equal volume of solvent were administered daily by gavage for 10 weeks. The effects of these interventions on natural aging rats were evaluated.

RESULTS

All intervention groups had a significant increase in muscle mass and grip strength and reduction in perirenal fat weight when compared to the aged control group (P < 0.05). The results of biochemical parameters, magnetic resonance imaging, proteomics and western blot suggested that the combination of wheat oligopeptide and fish oil-derived ω-3 PUFA, especially group WFM 2 (400 + 200 mg/kg body weight fish oil + wheat oligopeptide), was found to be more effective against aging-associated muscle loss than single intervention. Additionally, the interventions ameliorated fatty infiltration, muscle atrophy, and congestion in the intercellular matrix, and inflammatory cell infiltration in muscle tissue. The interventions also improved oxidative stress, anabolism, hormone levels, and inflammatory levels of skeletal muscle.

CONCLUSIONS

The combination of fish oil-derived ω-3 PUFA and wheat oligopeptide was found to be a promising nutritional support to prevent and reverse sarcopenia. The potential mechanism involved the promotion of protein synthesis and muscle regeneration, as well as the enhancement of muscle strength.

Fish Oil Enriched n-3 Polyunsaturated Fatty Acids Improve Ketogenic Low-Carbohydrate/High-Fat Diet-Caused Dyslipidemia, Excessive Fat Accumulation, and Weight Control in Rats

Low-carbohydrate and high-fat diets have been used for body weight (BW) control, but their adverse effects on lipid profiles have raised concern. Fish oil (FO), rich in omega-3 polyunsaturated fatty acids, has profound effects on lipid metabolism. We hypothesized that FO supplementation might improve the lipid metabolic disturbance elicited by low-carbohydrate and high-fat diets. Male SD rats were randomized into normal control diet (NC), high-fat diet (HF), and low-carbohydrate/high-fat diet (LC) groups in experiment 1, and NC, LC, LC + 5% FO (5CF), and LC + 10% FO diet (10CF) groups in experiment 2. The experimental duration was 11 weeks. In the LC group, a ketotic state was induced, and food intake was decreased; however, it did not result in BW loss compared to either the HF or NC groups. In the 5CF group, rats lost significant BW. Dyslipidemia, perirenal and epididymal fat accumulation, hepatic steatosis, and increases in triglyceride and plasma leptin levels were observed in the LC group but were attenuated by FO supplementation. These findings suggest that a ketogenic low-carbohydrate/high-fat diet with no favorable effect on body weight causes visceral and liver lipid accumulation. FO supplementation not only aids in body weight control but also improves lipid metabolism in low-carbohydrate/high-fat diet-fed rats.

Effect of dietary fish oil intake on ubiquitin ligase expression during muscle atrophy induced by sciatic nerve denervation in mice

Dietary fish oil intake improves muscle atrophy in several atrophy models however the effect on denervation-induced muscle atrophy is not clear. Thus, the aim of this study was to investigate the effects of dietary fish oil intake on muscle atrophy and the expression of muscle atrophy markers induced by sciatic nerve denervation in mice. We performed histological and quantitative mRNA expression analysis of muscle atrophy markers in mice fed with fish oil with sciatic nerve denervation. Histological analysis indicated that dietary fish oil intake slightly prevented the decrease of muscle fiber diameter induced by denervation treatment. In addition, dietary fish oil intake suppressed the MuRF1 (tripartite motif-containing 63) expression up-regulated by denervation treatment, and this was due to decreased tumor necrosis factor-alpha (TNF-α) production in skeletal muscle. We concluded that dietary fish oil intake suppressed MuRF1 expression by decreasing TNF-α production during muscle atrophy induced by sciatic nerve denervation in mice.

Natural Isotope Abundances of Carbon and Nitrogen in Tissue Proteins and Amino Acids as Biomarkers of the Decreased Carbohydrate Oxidation and Increased Amino Acid Oxidation Induced by Caloric Restriction under a Maintained Protein Intake in Obese Rats

A growing body of evidence supports a role for tissue-to-diet ¹⁵N and ¹³C discrimination factors (Δ¹⁵N and Δ¹³C), as biomarkers of metabolic adaptations to nutritional stress, but the underlying mechanisms remain poorly understood. In obese rats fed ad libitum or subjected to gradual caloric restriction (CR), under a maintained protein intake, we measured Δ¹⁵N and Δ¹³C levels in tissue proteins and their constitutive amino acids (AA) and the expression of enzymes involved in the AA metabolism. CR was found to lower protein mass in the intestine, liver, heart and, to a lesser extent, some skeletal muscles. This was accompanied by Δ¹⁵N increases in urine and the protein of the liver and plasma, but Δ¹⁵N decreases in the proteins of the heart and the skeletal muscles, alongside Δ¹³C decreases in all tissue proteins. In Lys, Δ¹⁵N levels rose in the plasma, intestine, and some muscles, but fell in the heart, while in Ala, and to a lesser extent Glx and Asx, Δ¹³C levels fell in all these tissues. In the liver, CR was associated with an increase in the expression of genes involved in AA oxidation. During CR, the parallel rises of Δ¹⁵N in urine, liver, and plasma proteins reflected an increased AA catabolism occurring at the level of the liver metabolic branch point, while Δ¹⁵N decreases in cardiac and skeletal muscle proteins indicated increased protein and AA catabolism in these tissues. Thus, an increased protein and AA catabolism results in opposite Δ¹⁵N effects in splanchnic and muscular tissues. In addition, the Δ¹³C decrease in all tissue proteins, reflects a reduction in carbohydrate (CHO) oxidation and routing towards non-indispensable AA, to achieve fuel economy.