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Dietary Macronutrient Composition Differentially Modulates the Remodeling of Mitochondrial Oxidative Metabolism during NAFLD.

ABSTRACT: Diets rich in fats and carbohydrates aggravate non-alcoholic fatty liver disease (NAFLD), of which mitochondrial dysfunction is a central feature. It is not clear whether a high-carbohydrate driven 'lipogenic' diet differentially affects mitochondrial oxidative remodeling compared to a high-fat driven 'oxidative' environment. We hypothesized that the high-fat driven 'oxidative' environment will chronically sustain mitochondrial oxidative function, hastening metabolic dysfunction during NAFLD. Mice (C57BL/6NJ) were reared on a low-fat (LF; 10% fat calories), high-fat (HF; 60% fat calories), or high-fructose/high-fat (HFr/HF; 25% fat and 34.9% fructose calories) diet for 10 weeks. De novo lipogenesis was determined by measuring the incorporation of deuterium from D₂O into newly synthesized liver lipids using nuclear magnetic resonance (NMR) spectroscopy. Hepatic mitochondrial metabolism was profiled under fed and fasted states by the incubation of isolated mitochondria with [¹³C₃]pyruvate, targeted metabolomics of tricarboxylic acid (TCA) cycle intermediates, estimates of oxidative phosphorylation (OXPHOS), and hepatic gene and protein expression. De novo lipogenesis was higher in the HFr/HF mice compared to their HF counterparts. Contrary to our expectations, hepatic oxidative function after fasting was induced in the HFr/HF group. This differential induction of mitochondrial oxidative function by the high fructose-driven 'lipogenic' environment could influence the progressive severity of hepatic insulin resistance.

SUBMITTER: Kattapuram N

PROVIDER: S-EPMC8147090 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Carbohydrate response element binding protein (ChREBP) is a lipogenic transcription factor that is thought to be involved in the development of hepatic steatosis and insulin resistance. Increased ChREBP expression in liver results in increased hepatic steatosis, and the isoform ChREBP? in adipose tissue can predict insulin sensitivity in obese humans. As ChREBP is activated by glucose, it was postulated that the composition of diet would regulate ChREBP isoform expression in metabolically relevant tissues. We compared the effects of diets with high complex carbohydrate, high fat, or a normal chow on ChREBP expression and metabolic parameters in C57BL/6 mice. We found that diets high in fat decrease ChREBP expression in adipose tissue, but isocaloric diets high in carbohydrate have no effect. Interestingly, this decrease in adipose ChREBP was associated with increased inflammatory markers. In the same animals a high carbohydrate diet induced a robust increase in hepatic ChREBP? expression (?2-fold; p = 0.0002), but little detectable change in the more abundant ChREBP? transcript. This change was accompanied by increased expression of target genes liver pyruvate kinase (p<0.0001), acetyl-CoA carboxylase (p = 0.0191) and stearoyl-CoA desaturase-1 (p = 0.0045). This increase in ChREBP expression was associated with increased hepatic steatosis, despite no changes in body weight or body fat when compared to chow-fed mice. Unexpectedly, mice fed a high carbohydrate diet displayed enhanced sensitivity to exogenous insulin, despite having mild glucose intolerance and increased liver steatosis. In summary, we have shown the composition of diet can selectively regulate ChREBP isoform expression in a tissue specific manner. Furthermore, we have shown a high complex carbohydrate diet selectively increases hepatic ChREBP? expression, which associates with hepatic steatosis but not insulin resistance. In contrast, a high fat diet reduces adipose ChREBP, which associates with inflammation and insulin resistance.

Project description:BackgroundWe sought to characterize the effects of dietary macronutrient composition on various hormones implicated in the regulation of insulin sensitivity (IS) and energy expenditure (EE).MethodsFollowing 10-15% weight loss, 21 overweight subjects consumed 3 weight-loss maintenance diets [low fat (LF), low glycemic index (LGI) and very low carbohydrate (VLC)] in random order, each for 4 weeks. At baseline and at the end of each treatment period, fasting samples for fibroblast growth factor (FGF)-21, heme-oxygenase-1 (HO-1), chemerin, irisin, secreted frizzle-related protein (SFRP-4), total bile acids, ghrelin, gastrin inhibitory peptide (GIP), peptide-Y, and amylin; hepatic and peripheral IS; and EE were obtained. Analyses were controlled for age, gender, baseline body mass index, and diet sequence.ResultsFGF-21 decreased (P < 0.0001), with differential effect by macronutrient composition (mean change from baseline ± SEM: LF -49.4 ± 16.6, LGI -58.6 ± 16.3, VLC -76.7 ± 18.2 pg/mL, P = 0.0002). Change in FGF-21 was inversely associated with change in hepatic IS [Beta = -0.565 units/log(ng/mL), P = 0.02], but not with peripheral IS or EE. Heme-oxygenase-1 (HO-1) increased (P = 0.003), without differential effect by macronutrient composition (LF 0.40 ± 0.26, LGI 0.98 ± 0.63, VLC 0.49 ± 0.29 ng/mL, P = 0.07). Ghrelin increased (P = 0.0003), while chemerin decreased (P = 0.001) without macronutrient effect. Total bile acid, irisin, SFRP-4, GIP, peptide-Y and amylin levels did not change.ConclusionsFGF-21 levels decreased with dietary intervention in proportion to carbohydrate content, and correlated with hepatic insulin sensitivity, suggesting a pattern of improving FGF-21 resistance. HO-1 increased in response to dietary intervention, a tendency to greater increase in response to the LGI diet. Dietary intervention affected ghrelin and chemerin, independent of macronutrient composition. These findings may elucidate relationships between dietary composition, insulin sensitivity and metabolism.Trial registrationNCT00315354.

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Dietary Macronutrient Composition Differentially Modulates the Remodeling of Mitochondrial Oxidative Metabolism during NAFLD.

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