Evidence for the use of glomerulomegaly as a surrogate marker of glomerular damage and for alpha-linolenic acid-rich oils in the treatment of early obesity-related glomerulopathy in a diet-induced rodent model of obesity

The review of alpha-linolenic acid: Sources, metabolism, and pharmacology

α-linolenic acid (ALA, 18:3n-3) is a carboxylic acid composed of 18 carbon atoms and three cis double bonds, and is an essential fatty acid indispensable to the human body. This study aims to systematically review related studies on the dietary sources, metabolism, and pharmacological effects of ALA. Information on ALA was collected from the internet database PubMed, Elsevier, ResearchGate, Web of Science, Wiley Online Library, and Europe PMC using a combination of keywords including "pharmacology," "metabolism," "sources." The following findings are mainly contained. (a) ALA can only be ingested from food and then converted into eicosapentaenoic acid and docosahexaenoic acid in the body. (b) This conversion process is relatively limited and affected by many factors such as dose, gender, and disease. (c) Pharmacological research shows that ALA has the anti-metabolic syndrome, anticancer, antiinflammatory, anti-oxidant, anti-obesity, neuroprotection, and regulation of the intestinal flora properties. (d) There are the most studies that prove ALA has anti-metabolic syndrome effects, including experimental studies and clinical trials. (e) The therapeutic effect of ALA will be affected by the dosage. In short, ALA is expected to treat many diseases, but further high quality studies are needed to firmly establish the clinical efficacy of ALA.

Untargeted Metabolomic Analysis of the Effects and Mechanism of Nuciferine Treatment on Rats With Nonalcoholic Fatty Liver Disease

Metabolomic analysis has been used to characterize the effects and mechanisms of drugs for nonalcoholic fatty liver disease (NAFLD) at the metabolic level. Nuciferine is an active component derived from folium nelumbinis and has been demonstrated to have beneficial effects on a high-fat diet (HFD) induced hepatic steatosis model. However, the effect of the altered metabolites of nuciferine on NAFLD has not yet been elucidated. In this study, we established a NAFLD rat model using HFD and treated with nuciferine. The lipid content levels, pro-inflammatory cytokines, and oxidative stress were investigated to access the therapeutic effects of nuciferine. Additionally, the metabolic regulatory mechanisms of nuciferine on NAFLD were analyzed using untargeted metabolomics. Gene expression of the key enzymes related to the changed metabolic pathways following nuciferine intervention was also investigated. The results showed that nuciferine treatment significantly reduced the body weight, levels of lipids, and liver enzymes in the blood and improved the hepatic steatosis in the NAFLD rat model. Nuciferine treatment also increased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreased the levels of methane dicarboxylic aldehyde (MDA) in the liver. Nuciferine treatment decreased the serum levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor-alpha (TNF-α) and upregulated the gene expression of IL-6, IL-1β, and TNF-α in the liver. Metabolomic analysis indicated a metabolism disorder in the NAFLD rat model reflected in a dysfunction of the glycerophospholipid, linoleic acid, alpha-linolenic acid, arginine and proline metabolism. Conversely, treatment with nuciferine improved the metabolic disorder in the NAFLD rat model. Nuciferine treatment also regulated the gene expression of key enzymes related to the glycerophospholipid, linoleic acid, and alpha-linolenic acid metabolism pathways in the liver. In conclusion, our study demonstrated an amelioration of the metabolic disorders following nuciferine treatment in NAFLD rat model. Our study contributes to the understanding of the effects and mechanisms of drugs for complex diseases using metabolomic analysis and experimental approaches.

The Iberian pig fed with high-fat diet: a model of renal disease in obesity and metabolic syndrome

BACKGROUND

The pathogenesis of renal disease in the context of overweight/obesity, metabolic syndrome, and insulin resistance is not completely understood. This may be due to the lack of a definitive animal model of disease, which limits our understanding of obesity-induced renal damage. We evaluated the changes in renal histology and lipid deposits induced by obesity in a model of insulin resistance: the Iberian swine fed with fat-enriched food.

METHODS

Twenty-eight female sows were randomized to standard (SD) or high-fat diet (HFD: 6.8% of saturated fat) for 100 days. Weight, adiposity, analytics, oral glucose tolerance tests, and measured renal function were determined. Renal histology and lipid deposits in renal tissue were analyzed.

RESULTS

Animals on HFD developed obesity, hypertension, high levels of LDL cholesterol, triglycerides, insulin resistance, and glomerular hyperfiltration. No animal developed overt diabetes. Animals on HFD showed "diabetoid changes", including mesangial expansion [21.40% ± 4 vs.13.20% ± 4.0, p < 0.0001], nodular glomerulosclerosis [7.40% ± 7, 0.75 vs. 2.40% ± 4.7, p = 0.02], and glomerulomegaly (18% vs. 10%, p = 0.010) than those on SD. Tubular atrophy, interstitial fibrosis, inflammation, arteriolar hyalinosis, or fibrointimal thickening were mild and similar between groups. Triglyceride content in renal tissue was higher in animals on HFD than in SD (15.4% ± 0.5 vs. 12.7% ± 0.7; p < 0.01).

CONCLUSIONS

Iberian pigs fed with fat-enriched food showed diabetoid changes and glomerulomegaly as observed in obese humans making this model suitable to study obesity-induced renal disease.

Coptidis Rhizoma inhibits NLRP3 inflammasome activation and alleviates renal damage in early obesity-related glomerulopathy

BACKGROUND

Obese subjects have been considered to be in a state of chronic, low-grade systemic inflammation. Excess fat accumulation and persistent inflammation may promote renal dysfunction, to cause chronic kidney disease (CKD) and even end-stage kidney failure. Coptidis Rhizoma is a classical traditional Chinese herb well known for its hypoglycemic and hypolipidemic properties. The mechanism is partially associated with its anti-inflammatory effect. However, this effect is rarely investigated in obesity and obesity-related glomerulopathy (ORG).

PURPOSE

The current study was designed to evaluate the effect of Coptidis Rhizoma on ORG. It also aimed to determine whether this renal protection effect of Coptidis Rhizoma was related to the inhibition of NLRP3 inflammasome in ORG.

METHODS

Coptidis Rhizoma concentrated granules were prepared and the main components were identified by 3D-High Performance Liquid Chromatography (3D-HPLC) assay. The animal model of early stage ORG was established in obesity-prone (OP) rats by high protein and high fat diet feeding for 12 weeks. The treatment with Coptidis Rhizoma at different dosages was administered by intragastric infusion simultaneously. Then body weight, kidney weight, plasma lipid profiles, 24 h urine protein/albumin content and kidney histology were measured. Inflammatory biomarkers were examined both in the rat plasma and renal cortex. The gene expressions of NLRP3 inflammasome complex and NF-κB in renal tissues were also measured.

RESULTS

Coptidis Rhizoma alleviated dyslipidemia and reduced the renal weight of the rats with ORG. Meanwhile, urinary albumin to creatinine ratio and creatinine clearance rate were significantly improved. Coptidis Rhizoma also attenuated glomerular hypertrophy, mesangial hyperplasia, and effacement of podocyte foot in renal tissues of ORG rats. In addition, Coptidis Rhizoma intervention decreased the levels of proinflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) both in plasma and renal tissue. The gene expression of NLRP3 inflammasome was down-regulated and NF-κB activity was also inhibited by Coptidis Rhizoma in renal tissues of ORG rats.

CONCLUSION

Coptidis Rhizoma can ameliorate early renal damage in ORG rats and the mechanisms appear to be related to the inhibition of NLRP3 inflammasome complex.

Dietary modulation of oxylipins in cardiovascular disease and aging

Oxylipins are a group of fatty acid metabolites generated via oxygenation of polyunsaturated fatty acids and are involved in processes such as inflammation, immunity, pain, vascular tone, and coagulation. As a result, oxylipins have been implicated in many conditions characterized by these processes, including cardiovascular disease and aging. The best characterized oxylipins in relation to cardiovascular disease are derived from the ω-6 fatty acid arachidonic acid. These oxylipins generally increase inflammation, hypertension, and platelet aggregation, although not universally. Similarly, oxylipins derived from the ω-6 fatty acid linoleic acid generally have more adverse than beneficial cardiovascular effects. Alternatively, most oxylipins derived from 20- and 22-carbon ω-3 fatty acids have anti-inflammatory, antiaggregatory, and vasodilatory effects that help explain the cardioprotective effects of these fatty acids. Much less is known regarding the oxylipins derived from the 18-carbon ω-3 fatty acid α-linolenic acid, but clinical trials with flaxseed supplementation have indicated that these oxylipins can have positive effects on blood pressure. Normal aging also is associated with changes in oxylipin levels in the brain, vasculature, and other tissues, indicating that oxylipin changes with aging may be involved in age-related changes in these tissues. A small number of trials in humans and animals with interventions that contain either 18-carbon or 20- and 22-carbon ω-3 fatty acids have indicated that dietary-induced changes in oxylipins may be beneficial in slowing the changes associated with normal aging. In summary, oxylipins are an important group of molecules amenable to dietary manipulation to target cardiovascular disease and age-related degeneration.NEW & NOTEWORTHY Oxylipins are an important group of fatty acid metabolites amenable to dietary manipulation. Because of the role they play in cardiovascular disease and in age-related degeneration, oxylipins are gaining recognition as viable targets for specific dietary interventions focused on manipulating oxylipin composition to control these biological processes.

Distinct effects of dietary flax compared to fish oil, soy protein compared to casein, and sex on the renal oxylipin profile in models of polycystic kidney disease

Oxylipins are bioactive lipids derived from polyunsaturated fatty acids (PUFA) that are important regulators of kidney function and health. Targeted lipidomic analyses of renal oxylipins from four studies of rodent models of renal disease were performed to investigate the differential effects of dietary flax compared to fish oil, soy protein compared to casein, and sex. Across all studies, dietary fish oil was more effective than flax oil in reducing n-6 PUFA derived oxylipins and elevating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived oxylipins, whereas dietary flax oil resulted in higher α-linolenic acid (ALA) oxylipins. Dietary soy protein compared to casein resulted in higher linoleic acid (LA) derived oxylipins. Kidneys from females had higher levels of arachidonic acid (AA) oxylipins, but similar or lower levels of oxylipins from other PUFA. Modulation of the oxylipin profile by diet and sex may help elucidate their effects on renal physiology and health.

Specific plasma oxylipins increase the odds of cardiovascular and cerebrovascular events in patients with peripheral artery disease

Oxylipins and fatty acids may be novel therapeutic targets for cardiovascular disease. The objective was to determine if plasma oxylipins or fatty acids can influence the odds of cardiovascular/cerebrovascular events. In 98 patients (25 female, 73 male) with peripheral artery disease, the prevalence of transient ischemic attacks, cerebrovascular accidents, stable angina, and acute coronary syndrome was n = 16, 10, 16, and 24, respectively. Risk factors such as being male, diagnosed hypertension, diabetes mellitus, and hyperlipidemia were not associated with events. Plasma fatty acids and oxylipins were analyzed with gas chromatography and HPLC-MS/MS, respectively. None of 24 fatty acids quantified were associated with events. In contrast, 39 plasma oxylipins were quantified, and 8 were significantly associated with events. These 8 oxylipins are known regulators of vascular tone. For example, every 1 unit increase in Thromboxane B₂/Prostaglandin F_1α and every 1 nmol/L increase in plasma 16-hydroxyeicosatetraenoic acid, thromboxane B2, or 11,12-dihydroxyeicosatrienoic acid (DiHETrE) increased the odds of having had ≥2 events versus no event (p < 0.05). The greatest predictor was plasma 8,9-DiHETrE, which increased the odds of acute coronary syndrome by 92-fold. In conclusion, specific oxylipins were highly associated with clinical events and may represent specific biomarkers and (or) therapeutic targets of cardiovascular disease.

Mixed compared with single-source proteins in high-protein diets affect kidney structure and function differentially in obese fa/fa Zucker rats

Questions remain regarding the potential negative effects of dietary high protein (HP) on kidney health, particularly in the context of obesity in which the risk for renal disease is already increased. To examine whether some of the variability in HP effects on kidney health may be due to source of protein, obese fa/fa Zucker rats were given HP (35% of energy from protein) diets containing either casein, soy protein, or a mixed source of animal and plant proteins for 12 weeks. Control lean and obese rats were given diets containing casein at normal protein (15% of energy from protein) levels. Body weight and blood pressure were measured, and markers of renal structural changes, damage, and function were assessed. Obesity alone resulted in mild renal changes, as evidenced by higher kidney weights, proteinuria, and glomerular volumes. In obese rats, increasing the protein level using the single, but not mixed, protein sources resulted in higher renal fibrosis compared with the lean rats. The mixed-protein HP group also had lower levels of serum monocyte chemoattractant protein-1, even though this diet further increased kidney and glomerular size. Soy and mixed-protein HP diets also resulted in a small number of damaged glomeruli, while soy compared with mixed-protein HP diet delayed the increase in blood pressure over time. Since obesity itself confers added risk of renal disease, an HP diet from mixed-protein sources that enables weight loss but has fewer risks to renal health may be advantageous.