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OBJECTIVES: Obesogenic, high fat diets (HFD) increase hepatic long chain polyunsaturated fatty acid content (LCPUFA), but also lead to hepatic steatosis and insulin resistance. Fermentable fiber such as inulin (INU) may reduce these negative outcomes via a bile acid (BA)-liver signaling axis. This study tests the hypothesis that INU maintains elevated LCPUFA but reduces HFD-induced insulin resistance and fatty liver and investigates the potential relationship of bile acids. METHODS: Male mice (4 wk) were fed a low fat diet (LFD) (16% en fat) or HFD (48% en fat) containing 10% non-fermentable cellulose (CL) or 3% CL and 7% INU for 13 wks in a 2 × 2 factorial design. Tissue, plasma, and cecal contents were collected week 13. RESULTS: Intake of the HFD-CL increased hepatic LCPUFA content and steatosis and reduced insulin sensitivity vs LFD treatments. INU maintained HFD-induced LCPUFA elevation, improved insulin sensitivity, due to reductions in fasting glucose, but did not mitigate HFD-induced hepatic steatosis. When standardized to the hepatic triacylglycerol (TAG) content, LCPUFA (notably 22:6n-3) were increased by INU in the LFD only. The BAs with highest cecal concentrations were deoxycholic (DCA) and beta/omega murine cholic (B/OMCA) acids. INU increased cecal wt and decreased concentrations of DCA and B/OMCA. INU-induced B/OMCA reductions were enhanced by the HFD, but the DCA effects were independent of % en fat. The expression of multiple lipid metabolic genes was assessed. Of these, reductions in Scd1 expression occurred with both HFD and INU treatments compared to LFD-CL. SREBP1c, Fasn, Scd1, Elov5, Fads1, and Fads2 correlated with murine cholic acids and cholic acid in HFD-INU but only weakly in LFD-INU. These relationships were not evident with the CL-based diets. CONCLUSIONS: INU in an HFD provided mixed outcomes by maintaining elevated hepatic LCPUFA, reducing fasting plasma glucose concentrations but failing to reduce fasting insulin concentrations and hepatic steatosis. While cecal BAs and hepatic gene expression correlated with the INU treatments, these mechanistic changes did not mitigate HFD-induced hepatic steatosis. FUNDING SOURCES: USDA-ARS.

Time-restricted feeding (TRF) can reduce adiposity and lessen the co-morbidities of obesity. Mice consuming obesogenic high-fat (HF) diets develop insulin resistance and hepatic steatosis, but have elevated indices of long-chain polyunsaturated fatty acids (LCPUFA) that may be beneficial. While TRF impacts lipid metabolism, scant data exist regarding the impact of TRF upon lipidomic composition of tissues. We (1) tested the hypothesis that TRF of a HF diet elevates LCPUFA indices while preventing insulin resistance and hepatic steatosis and (2) determined the impact of TRF upon the lipidome in plasma, liver, and adipose tissue. For 12 weeks, male, adult mice were fed a control diet ad libitum, a HF diet ad libitum (HF-AL), or a HF diet with TRF, 12 hours during the dark phase (HF-TRF). HF-TRF prevented insulin resistance and hepatic steatosis resulting from by HF-AL treatment. TRF-blocked plasma increases in LCPUFA induced by HF-AL treatment but elevated concentrations of triacylglycerols and non-esterified saturated fatty acids. Analysis of the hepatic lipidome demonstrated that TRF did not elevate LCPUFA while reducing steatosis. However, TRF created (1) a separate hepatic lipid signature for triacylglycerols, phosphatidylcholine, and phosphatidylethanolamine species and (2) modified gene and protein expression consistent with reduced fatty acid synthesis and restoration of diurnal gene signaling. TRF increased the saturated fatty acid content in visceral adipose tissue. In summary, TRF of a HF diet alters the lipidomic profile of plasma, liver, and adipose tissue, creating a third distinct lipid metabolic state indicative of positive metabolic adaptations following HF intake.

Background/aim Time-restricted feeding (TRF) during the dark phase of the day restores metabolic homeostasis in mice. Materials and methods We performed untargeted metabolomic analysis on plasma from mice subjected to TRF that attenuates high-fat diet-enhanced spontaneous metastasis of Lewis lung carcinoma (LLC). Results Twenty-four of 152 identified metabolites differed among the four dietary groups (non-LLC-bearing mice fed the AIN93G diet and LLC-bearing mice fed the AIN93G, the high-fat diet (HFD), or TRF of the HFD). Component 1 of sparse partial least squares-discriminant analysis showed a clear separation between non-LLC-bearing and LLC-bearing mice. Major metabolites responsible for the changes were elevations in α-tocopherol, docosahexaenoic acid, cholesterol, dihydrocholestrol, isoleucine, leucine, and phenylalanine and decreases in lactic acid and pyruvic acid in LLC-bearing mice particularly those fed the HFD. Time-restricted feeding shifted the metabolic profile of LLC-bearing mice towards that of non-LLC-bearing controls. Conclusion Time-restricted feeding improves metabolic profile of LLC-bearing mice.

Secondary bile acids (BAs) and short chain fatty acids (SCFAs), two major types of bacterial metabolites in the colon, cause opposing effects on colonic inflammation at chronically high physiological levels. Primary BAs play critical roles in cholesterol metabolism, lipid digestion, and host–microbe interaction. Although BAs are reabsorbed via enterohepatic circulation, primary BAs serve as substrates for bacterial biotransformation to secondary BAs in the colon. High-fat diets increase secondary BAs, such as deoxycholic acid (DCA) and lithocholic acid (LCA), which are risk factors for colonic inflammation and cancer. In contrast, increased dietary fiber intake is associated with anti-inflammatory and anticancer effects. These effects may be due to the increased production of the SCFAs acetate, propionate, and butyrate during dietary fiber fermentation in the colon. Elucidation of the molecular events by which secondary BAs and SCFAs regulate colonic cell proliferation and inflammation will lead to a better understanding of the anticancer potential of dietary fiber in the context of high-fat diet-related colon cancer. This article reviews the current knowledge concerning the effects of secondary BAs and SCFAs on the proliferation of colon epithelial cells, inflammation, cancer, and the associated microbiome.

Increased amylose in wheat (Triticum ssp.) starch is associated with increased resistant starch, a fermentable dietary fiber. Fermentation of resistant starch in the large intestine produces short-chain fatty acids that are associated with human health benefits. Since wheat foods are an important component of the human diet, increases in amylose and resistant starch in wheat grains have the potential to deliver health benefits to a large number of people. In three replicated field trials we found that mutations in starch branching enzyme II genes (SBEIIa and SBEIIb) in both A and B genomes (SBEIIa/b-AB) of durum wheat [T. turgidum L. subsp. durum (Desf.) Husn.] resulted in large increases of amylose and resistant starch content. The presence of these four mutations was also associated with an average 5% reduction in kernel weight (P = 0.0007) and 15% reduction in grain yield (P = 0.06) compared to the wild type. Complete milling and pasta quality analysis showed that the mutant lines have an acceptable quality with positive effects on pasta firmness and negative effects on semolina extraction and pasta color. Positive fermentation responses were detected in rats (Rattus spp.) fed with diets incorporating mutant wheat flour. This study quantifies benefits and limitations associated with the deployment of the SBEIIa/b-AB mutations in durum wheat and provides the information required to develop realistic strategies to deploy durum wheat varieties with increased levels of amylose and resistant starch.

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This study was designed to determine if providing wheat, corn, and rice as whole (WG) or refined grains (RG) under free-living conditions will change parameters of health over a six-week intervention in healthy, habitual non-WG consumers. Measurements of body composition, fecal microbiota, fasting blood glucose, total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL), and triglycerides were made at baseline and post intervention. Subjects were given adequate servings of either WG or RG products based on their caloric need and asked to keep records of grain consumption, bowel movements, and GI symptoms weekly. After six weeks, subjects repeated baseline testing. Significant decreases in total, LDL, and non-HDL cholesterol were seen after the WG treatments but were not observed in the RG treatment. During Week 6, bowel movement frequency increased with increased WG consumption. No significant differences in microbiota were seen between baseline and post intervention, although, abundance of order Erysipelotrichales increased in RG subjects who ate more than 50% of the RG market basket products. Increasing consumption of WGs can alter parameters of health, but more research is needed to better elucidate the relationship between the amount consumed and the health-related outcome.

OBJECTIVES: Obesity and obesity-related disease contribute to health care costs and pose serious health risks. Rodent studies indicate that time-restricted feeding (TRF) may be effective in reducing adiposity and metabolic disease associated with obesity. However, the metabolic pathways impacted by TRF in the context of obesogenic, high-fat (HF) diets need clarity. In the present work we examined the metabolomic changes in plasma induced by TRF of a HF diet in mice compared to a HF diet eaten ad libitum (AL) vs AL intake of a low-fat (LF) control diet. METHODS: Male mice (12 weeks old) were fed a LF-AL diet (16%en fat), a HF-AL diet (48%en fat) or a HF diet restricted to feeding for 12 hours per day during the dark phase (HF-TRF). In week 9 of the study, energy expenditure data were collected. After 12 weeks, animals were fasted and plasma collected for clinical chemistries and metabolomic analysis. Multivariate analysis was used to discriminate diet treatments in untargeted metabolomic data. RESULTS: Energy expenditure measurements throughout the day showed a markedly reduced fasting respiratory exchange ratio (RER) in HF-TRF mice during the inactive (light) phase compared to AL groups. Measures of insulin resistance, while increased with HF-AL intake, were resolved in the HF-TRF group. Partial least squares discriminant analysis revealed plasma non-esterified fatty acids (NEFA) and amino acids (AA) to be important discriminators between diet treatments. TRF resulted in elevated NEFA concentrations of the saturated fatty acids (12:0 to 18:0) and the polyunsaturated fatty acids α-linolenic acid and linoleic acid compared to HF-AL. Conversely, the concentrations of aromatic and branched chain amino acids were reduced in HF-TRF mice compared to HF-AL mice. CONCLUSIONS: Alterations in plasma metabolites following TRF of a HF diet are consistent with greater lipid utilization during the inactive phase as reflected in the RER. Decreases in the aromatic and branched chain amino acid concentrations are consistent with improved insulin sensitivity in humans. FUNDING SOURCES: This work was supported by USDA-ARS project 3062-51000-053-00D. SUPPORTING TABLES, IMAGES AND/OR GRAPHS