Fetuin-B, a potential link of liver-adipose tissue cross talk during diet-induced weight loss–weight maintenance

BACKGROUND/OBJECTIVES: Numerous hepatokines are involved in inter-organ cross talk regulating tissue-specific insulin sensitivity. Adipose tissue lipolysis represents a crucial element of adipose insulin sensitivity and is substantially involved in long-term body weight regulation after dietary weight loss. Thus, we aimed to analyze the impact of the hepatokine Fetuin-B in the context of weight loss induced short- and long-term modulation of adipose insulin sensitivity. SUBJECTS/METHODS: 143 subjects (age > 18; BMI >= 27 kg/m(2)) were analyzed before (T-3) and after (T0) a standardized 12-week dietary weight reduction program. Afterward, subjects were randomized to a 12-month lifestyle intervention or a control group. After 12 months (T12) no further intervention was performed until 6 months later (T18) (Maintain-Adults trial). Tissue-specific insulin sensitivity was estimated by HOMA-IR (predominantly liver), ISIClamp (predominantly skeletal muscle), and free fatty acid suppression during hyperinsulinemic-euglycemic clamp (FFA(Supp)) (predominantly adipose tissue). Fetuin-B was measured at all concomitant time points. RESULTS: Circulating Fetuin-B levels correlated significantly with estimates of obesity, hepatic steatosis as well as HOMA-IR, ISIClamp, FFA(Supp) at baseline. Fetuin-B decreased during dietary weight loss (4.2 (3.5-4.9) vs. 3.8 (3.2-4.6) mu g/ml; p = 2.1 x 10(-5)). This change was associated with concomitant improvement of HOMA-IR (r = 0.222; p = 0.008) and FFA(Supp) (r = -0.210; p = 0.013), suggesting a particular relationship to hepatic and adipose tissue insulin sensitivity. Weight loss induced improvements of insulin resistance were almost completely preserved until months 12 and 18 and most interestingly, the short and long-term improvement of FFA(Supp) was partially predicted by baseline level of Fetuin-B. CONCLUSIONS: Our data suggest that Fetuin-B might be a potential mediator of liver-adipose cross talk involved in short- and long-term regulation of adipose insulin sensitivity, especially in the context of diet-induced weight changes

Chronic Activation of Hepatic Nrf2 Has No Major Effect on Fatty Acid and Glucose Metabolism in Adult Mice

The transcription factor NF-E2-related factor 2 (Nrf2) induces cytoprotective genes, but has also been linked to the regulation of hepatic energy metabolism. In order to assess the pharmacological potential of hepatic Nrf2 activation in metabolic disease, Nrf2 was activated over 7 weeks in mice on Western diet using two different siRNAs against kelch-like ECH-associated protein 1 (Keap1), the inhibitory protein of Nrf2. Whole genome expression analysis followed by pathway analysis demonstrated successful knock-down of Keap1 expression and induction of Nrf2-dependent genes involved in anti- oxidative stress defense and biotransformation, proving the activation of Nrf2 by the siRNAs against Keap1. Neither the expression of fatty acid- nor carbohydrate-handling proteins was regulated by Keap1 knock-down. Metabolic profiling of the animals did also not show effects on plasma and hepatic lipids, energy expenditure or glucose tolerance. The data indicate that hepatic Keap1/Nrf2 is not a major regulator of glucose or lipid metabolism in mice

Correction: Chronic Activation of Hepatic Nrf2 Has No Major Effect on Fatty Acid and Glucose Metabolism in Adult Mice.

[This corrects the article DOI: 10.1371/journal.pone.0166110.]

Sequences of siRNA molecules used in this study.

<p>Sequences of siRNA molecules used in this study.</p

Metabolic characterization of siRNA-treated mice.

<p>(A-F) 24 h average of metabolic cage analysis during light and dark phase of (A) food intake, (B) water consumption supplemented with 6% sucrose, (C) locomotor activity, (D) oxygen consumption rate, (E) energy expenditure and (F) respiratory exchange ratio (VCO₂/VO₂). (siControl* n = 9, siKeap1-1* n = 9 and siKeap1-2* n = 10). (G) Blood glucose levels (glucose: 1 mg/kg BW) during ipGTT (n = 11). Data are represented as mean ± SEM. Grey background in graphs indicates dark phase.</p

Body composition of mice during 7 weeks of WD and siRNA intervention.

<p>(A) Lean body mass, (B) free fluid and (C) fat body mass at beginning (0 weeks), in week 5 and at end of intervention (week 7) of mice treated with control and both Keap1-specific siRNAs. (D) Development of body weight under specific diet within 7 weeks. (E) Absolute body weight gain of each treatment group (* p = 0.015, one-way ANOVA with Bonferroni's mct). Data are represented as mean ± SEM. n = 11.</p

Chemical modification of Keap1-specific siRNAs improved their pharmacokinetic properties.

<p>Chemical modification of Keap1-specific siRNAs improved their pharmacokinetic properties.</p

Keap1 inhibition and Nrf2 target gene regulation by liver-selective, Keap1-specific siRNAs in mice after siRNA and WD intervention.

<p>(A) Schematic of the long-term mouse experiment. (B) Hepatic Keap1 as well as Nrf2 target genes Nqo1, Gclc and Gsr expression (n = 11). (C) Relative mRNA expression of Keap1 and Nqo1 in muscle tissue of mice (fed, n = 6). (D) Expression levels of Keap1 and Nqo1 in kidney (fed, n = 6,). Data are represented as mean ± SEM. One-way ANOVA with Bonferroni's mct. ** p < 0.01, *** p < 0.001. Black arrows: Recording of body weight and siRNA injection, Grey arrows: Experimental procedures: BC: Analysis of body composition by ¹H-nuclear magnetic resonance, EX: Sacrificing mice and organ preparation, ipGTT: intraperitoneal glucose tolerance test, MCA: Metabolic cage analysis.</p