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Effects of Weight Loss and Long-Term Weight Maintenance With Diets Varying in Protein and Glycemic Index on Cardiovascular Risk Factors The Diet, Obesity, and Genes (DiOGenes) Study: A Randomized, Controlled Trial

Background— We sought to separately examine the effects of either weight loss or diets varying in protein content and glycemic index without further changes in body weight on cardiovascular risk factors within the Diet, Obesity, and Genes study (DiOGenes). Methods and Results— DiOGenes is a pan-European controlled dietary intervention study in 932 overweight adults who first lost body weight on an 8-week low-calorie diet and were then randomized to 1 of 5 ad libitum diets for 26 weeks. The diets were either high or low protein or high or low glycemic index in 4 combinations or control. Weight loss (−11.23 kg; 95% confidence interval, −11.54 to −10.92; P<0.001) reduced high-sensitivity C-reactive protein (−1.15 mg/L; 95% confidence interval, −1.30 to −0.41; P<0.001), low- and high-density lipoprotein cholesterol, triglycerides, and blood pressure. During the 26-week weight maintenance period in the intention-to-treat analysis, the further decrease of high-sensitivity C-reactive protein blood levels was −0.46 mg/L greater (95% confidence interval, −0.79 to −0.13) in the groups assigned to low-glycemic-index diets than in those on high-glycemic-index diets (P<0.001). Groups on low-protein diets achieved a −0.25 mg/L greater reduction in high-sensitivity C-reactive protein (95% confidence interval, −0.59 to −0.17) than those on high-protein diets (P<0.001), whereas lipid profiles and blood pressure were not differently affected. Conclusions— This large-scale intervention study clearly separates weight loss from dietary composition–related effects. Low-glycemic-index carbohydrates and, to a lesser extent, low-protein intake may specifically reduce low-grade inflammation and associated comorbidities in overweight/obese adults. Clinical Trial Registration— http://www.clinicaltrials.gov. Unique identifier: NCT00390637.

Effects of supplemented isoenergetic diets differing in cereal fiber and protein content on insulin sensitivity in overweight humans

BACKGROUND Despite their beneficial effects on weight loss and blood lipids, high-protein (HP) diets have been shown to increase insulin resistance and diabetes risk, whereas high-cereal-fiber (HCF) diets have shown the opposite effects on these outcomes. OBJECTIVE We compared the effects of isoenergetic HP and HCF diets and a diet with moderate increases in both cereal fibers and dietary protein (Mix diet) on insulin sensitivity, as measured by using euglycemic-hyperinsulinemic clamps with infusion of [6,6-(2)H(2)]glucose. DESIGN We randomly assigned 111 overweight adults with features of the metabolic syndrome to 1 of 4 two-phased, 18-wk isoenergetic diets by group-matching. Per 3-d food protocols, the percentages of energy derived from protein and carbohydrates and the intake of cereal fiber per day, respectively, were as follows-after 6 wk: 17%, 52%, and 14 g (control); 17%, 52%, and 43 g (HCF); 28%, 43%, and 13 g (HP); 23%, 44%, and 26 g (Mix); after 18 wk: 17%, 51%, and 15 g (control); 17%, 51%, and 41 g (HCF); 26%, 45%, and 14 g (HP); and 22%, 46%, and 26 g (Mix). Eighty-four participants completed the study successfully and were included in the final analyses. Adherence was supported by the provision of tailored dietary supplements twice daily in all groups. RESULTS Insulin sensitivity expressed as an M value was 25% higher after 6 wk of the HCF diet than after 6 wk of the HP diet (subgroup analysis: 4.61 ± 0.38 compared with 3.71 ± 0.36 mg · kg(-1) · min(-1), P = 0.008; treatment × time interaction: P = 0.005). Effects were attenuated after 18 wk (treatment × time interaction: P = 0.054), which was likely explained by lower adherence to the HP diet. HP intake was associated with a tendency to increased protein expression in adipose tissue of the translation initiation factor serine-kinase-6-1, which is known to mediate amino acid-induced insulin resistance. Biomarkers of protein intake indicated interference of cereal fibers with dietary protein absorption. CONCLUSION Greater changes in insulin sensitivity after intake of an isoenergetic HCF than after intake of an HP diet might help to explain the diverse effects of these diets on diabetes risk. This trial is registered at clinicaltrials.gov as NCT00579657.

WISP1 Is a Novel Adipokine Linked to Inflammation in Obesity

WISP1 (Wnt1-inducible signaling pathway protein-1, also known as CCN4) is a member of the secreted extracellular matrix–associated proteins of the CCN family and a target gene of the Wingless-type (WNT) signaling pathway. Growing evidence links the WNT signaling pathway to the regulation of adipogenesis and low-grade inflammation in obesity. We aimed to validate WISP1 as a novel adipokine. Human adipocyte differentiation was associated with increased WISP1 expression and secretion. Stimulation of human macrophages with WISP1 led to a proinflammatory response. Circulating WISP1 and WISP1 subcutaneous adipose tissue expression were regulated by weight changes in humans and mice. WISP1 expression in visceral and subcutaneous fat tissue was associated with markers of insulin resistance and inflammation in glucose-tolerant subjects. In patients with nonalcoholic fatty liver disease, we found no correlation among disease activity score, liver fat content, and WISP1 expression. Insulin regulated WISP1 expression in adipocytes in vitro but had no acute effect on WISP1 gene expression in subcutaneous fat tissue in overweight subjects who had undergone hyperinsulinemic clamp experiments. The data suggest that WISP1 may play a role in linking obesity to inflammation and insulin resistance and could be a novel therapeutic target for obesity.

Endothelin-A Receptor Blockade Prevents Left Ventricular Hypertrophy and Dysfunction in Salt-Sensitive Experimental Hypertension

Background—Salt-sensitive hypertension represents a major cause of left ventricular (LV) dysfunction. We therefore explored the potential effects of the selective endothelin-A (ETA) receptor antagonist darusentan on the development of hypertension, LV hypertrophy (LVH), and dysfunction in a genetic rat model of salt-sensitive hypertension. Methods and Results—Animals from the salt-sensitive Sabra rat strain (SBH/y) and the salt-resistant strain (SBN/y) were treated with either normal diet (SBH/y and SBN/y) or with deoxycorticosterone-acetate (DOCA) and salt (SBN/y-DOCA and SBH/y-DOCA). Additional groups were treated with 50 mg · kg−1 · d−1 of darusentan (SBH/y-DOCA-DA and SBN/y-DOCA-DA). Systolic blood pressure and LV weight increased in response to DOCA only in the SBH/y strain (+75 mm Hg and +30%;P <0.05). LV end-diastolic pressure increased and −dP/dtmax decreased in SBH/y-DOCA compared with SBH/y (P <0.05). This was paralleled by a 5-fold upregulation of LV mRNA expression of atrial natriuretic factor (ANF) and a significant reduction of sarcoplasmic reticulum (SR) Ca2+-reuptake and the SR Ca2+-ATPase to phospholamban protein ratio (−30%). Whereas treatment with darusentan in SBH/y-DOCA-DA reduced the SBP increase by 50%, LVH elevation of ANF mRNA and LV dysfunction were completely prevented (P <0.05); this was associated with a normalization of SR Ca2+-reuptake and SR Ca2+-ATPase to phospholamban ratio by darusentan (P <0.05). A moderate elevation of interstitial fibrosis in SBH/y-DOCA (P <0.05) remained unaffected by darusentan treatment. Conclusion—In the Sabra model of salt-sensitive hypertension, ETA-receptor blockade demonstrated striking effects on the prevention of LVH and LV dysfunction beyond its considerable antihypertensive effect.

GIP receptor mRNA expression in different fat tissue depots in postmenopausal non-diabetic women

AIMS Gastric inhibitory polypeptide (GIP) is an insulinotropic duodenal hormone released in response to meals. Recent studies in rodents suggested that GIP directly links overnutrition to obesity. Despite evidence for GIP effects on fat metabolism in humans, the GIP receptor (GIPR) has not been identified in fat tissues. We identified the GIPR gene in human subcutaneous and visceral fat tissues and tested the hypothesis that that the expression of this gene is influenced by central obesity and weight loss. METHODS GIPR gene mRNA expression in subcutaneous fat tissue biopsies (n=70) and in paired subcutaneous and visceral fat tissue samples (n=25) of non-diabetic postmenopausal women was studied by real-time reverse transcription polymerase chain reaction. The effect of weight reduction on GIPR gene expression in subcutaneous fat tissue was studied in a subset of 14 women. RESULTS GIPR adipose tissue gene expression was significantly lower in insulin resistant obese non-diabetic women (p=0.004). The GIPR mRNA expression was higher in the visceral fat tissue compared with subcutaneous fat (p<0.001). Despite adjustment for obesity-associated variables, waist circumference was the most significant predictor of GIPR gene expression in subcutaneous fat depot (F=4.066; beta=-0.997; p=0.0001) and, together with fasting insulin levels, in visceral fat (F=3.553; beta=-0.507 and beta=0.495; p=0.0001). Moderate weight reduction did not change gene expression levels of the GIPR gene (p=0.085). CONCLUSIONS Decreased expression of the GIPR gene in subcutaneous fat tissue is associated with signs of insulin resistance in non-diabetic women with central obesity and demonstrates that fasting hyperinsulinemia is a possible negative regulator of GIPR gene expression in subcutaneous fat. Higher GIPR gene expression levels in visceral fat vs. subcutaneous fat reflect regional differences in adipose tissue biology. Moderate weight reduction did not change gene expression levels of GIPR in subcutaneous fat.

Glucose-Dependent Insulinotropic Polypeptide Reduces Fat-Specific Expression and Activity of 11β-Hydroxysteroid Dehydrogenase Type 1 and Inhibits Release of Free Fatty Acids

Glucose-dependent insulinotropic polypeptide (GIP) has been suggested to have direct effects on nonislet tissues. GIP also reportedly increased glucose uptake and inhibition of lipolysis in adipocytes after inhibition of the intracellular cortisone-cortisol shuttle 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). We here analyzed whether GIP modifies lipid metabolism and further elucidated the relation between GIP, 11β-HSD1, and fatty acid metabolism. GIP reduced activity of 11β-HSD1 promoter constructs and the expression and activity of 11β-HSD1 in differentiated 3T3-L1 adipocytes in a time- and dose-dependent fashion. This was paralleled by a reduction of free fatty acid (FFA) release and a reduced expression of key enzymes regulating lipolysis in adipose tissue. Preinhibition of 11β-HSD1 completely abolished GIP-induced effects on FFA release. To investigate the acute effects of GIP in humans, a randomized clinical trial was performed. GIP lowered circulating FFAs compared with saline control and reduced expression and ex vivo activity of 11β-HSD1 and adipose triglyceride lipase expression in subcutaneous fat biopsies. Our data suggest that GIP reduces FFA release from adipose tissue by inhibition of lipolysis or by increased reesterification. This process appears to depend on a modification of 11β-HSD1 activity. In general, the presented data support that GIP has direct and insulin-independent effects on adipose tissue.

Increased interleukin-10 but unchanged insulin sensitivity after 4 weeks of (1, 3)(1, 6)-β-glycan consumption in overweight humans.

Obesity-induced insulin resistance has been suggested to be a systemic inflammatory condition with activation of the innate immune system. Animal studies indicate that certain dietary fibers such as (1,3)(1,6)-beta-D-glycans (BDG) have potent effects on immune activity such as increasing the antiinflammatory cytokine interleukin-10 (IL-10) and reducing the secretion of inflammatory factors. Therefore, we hypothesized that BDG consumption improves inflammatory markers and insulin sensitivity in overweight and obese subjects with moderately increased levels of C-reactive protein, indicating subclinical inflammation. We screened 180 overweight and obese subjects for moderately increased C-reactive protein levels on 2 or more occasions, in the absence of any signs of acute infection. Twelve of the subjects met all inclusion criteria and were investigated in a randomized, double-blind, placebo-controlled, crossover design for 2 x 4 weeks (washout > or =4 weeks). Subjects ingested capsules containing 3 x 0.5 g of highly purified BDG or 3 x 0.5 g of placebo (waxy maize starch) daily. Maintenance of the normal diet of the participants and the correct intake of the capsules were monitored, using 6 x 3-day food recording and counting of the provided capsules. Predefined outcome measures were BDG-induced changes in pro and antiinflammatory markers in circulating blood and gene expression in adipose tissue and peripheral insulin sensitivity expressed as M value. The BDG consumption for 4 weeks significantly increased both circulating levels and adipose tissue messenger RNA (mRNA) expression of the antiinflammatory cytokine IL-10 in overweight and obese humans. Insulin sensitivity as well as circulating levels and mRNA expression of proinflammatory cytokines were unaffected by BDG treatment. Increased IL-10 after BDG consumption might be a contributing factor to the known beneficial effects of dietary fiber intake.

Regulation of the clock gene expression in human adipose tissue by weight loss.

Background:The circadian clock coordinates numerous metabolic processes to adapt physiological responses to light–dark and feeding regimens and is itself regulated by metabolic cues. The implication of the circadian clock in the regulation of energy balance and body weight is widely studied in rodents but not in humans. Here we investigated (1) whether the expression of clock genes in human adipose tissue is changed by weight loss and (2) whether these alterations are associated with metabolic parameters.Subjects/Methods:Subcutaneous adipose tissue (SAT) samples were collected before and after 8 weeks of weight loss on an 800 kcal per day hypocaloric diet (plus 200 g per day vegetables) at the same time of the day. Fifty overweight subjects who lost at least 8% weight after 8 weeks were selected for the study. The expression of 10 clock genes and key metabolic and inflammatory genes in adipose tissue was determined by quantitative real-time PCR.Results:The expression of core clock genes PER2 and NR1D1 was increased after the weight loss. Correlations of PERIOD expression with body mass index (BMI) and serum total, high-density lipoprotein and low-density lipoprotein (LDL) cholesterol levels and of NR1D1 expression with total and LDL cholesterol were found that became non-significant after correction for multiple testing. Clock gene expression levels and their weight loss-induced changes tightly correlated with each other and with genes involved in fat metabolism (FASN, CPT1A, LPL, PPARG, PGC1A, ADIPOQ), energy metabolism (SIRT1), autophagy (LC3A, LC3B) and inflammatory response (NFKB1, NFKBIA, NLRP3, EMR1).Conclusion:Clock gene expression in human SAT is regulated by body weight changes and associated with BMI, serum cholesterol levels and the expression of metabolic and inflammatory genes. Our data confirm the tight crosstalk between molecular clock and metabolic and inflammatory pathways involved in adapting adipose tissue metabolism to changes of the energy intake in humans.

Metabolomic linkage reveals functional interaction between glucose-dependent insulinotropic polypeptide and ghrelin in humans

The gastric peptide ghrelin promotes energy storage, appetite, and food intake. Nutrient intake strongly suppresses circulating ghrelin via molecular mechanisms possibly involving insulin and gastrointestinal hormones. On the basis of the growing evidence that glucose-dependent insulinotropic polypeptide (GIP) is involved in the control of fuel metabolism, we hypothesized that GIP and/or insulin, directly or via changes in plasma metabolites, might affect circulating ghrelin. Fourteen obese subjects were infused with GIP (2.0 pmol·kg(-1)·min(-1)) or placebo in the fasting state during either euglycemic hyperinsulinemic (EC) or hyperglycemic hyperinsulinemic clamps (HC). Apart from analysis of plasma ghrelin and insulin levels, GC-TOF/MS analysis was applied to create a hormone-metabolite network for each experiment. The GIP and insulin effects on circulating ghrelin were analyzed within the framework of those networks. In the HC, ghrelin levels decreased in the absence (19.2% vs. baseline, P = 0.028) as well as in the presence of GIP (33.8%, P = 0.018). Ghrelin levels were significantly lower during HC with GIP than with placebo, despite insulin levels not differing significantly. In the GIP network combining data on GIP-infusion, EC+GIP and HC+GIP experiments, ghrelin was integrated into hormone-metabolite networks through a connection to a group of long-chain fatty acids. In contrast, ghrelin was excluded from the network of experiments without GIP. GIP decreased circulating ghrelin and might have affected the ghrelin system via modification of long-chain fatty acid pools. These observations were independent of insulin and offer potential mechanistic underpinnings for the involvement of GIP in systemic control of energy metabolism.

Effects of Weight Loss and Long-Term Weight Maintenance With Diets Varying in Protein and Glycemic Index on Cardiovascular Risk Factors

Background— We sought to separately examine the effects of either weight loss or diets varying in protein content and glycemic index without further changes in body weight on cardiovascular risk factors within the Diet, Obesity, and Genes study (DiOGenes). Methods and Results— DiOGenes is a pan-European controlled dietary intervention study in 932 overweight adults who first lost body weight on an 8-week low-calorie diet and were then randomized to 1 of 5 ad libitum diets for 26 weeks. The diets were either high or low protein or high or low glycemic index in 4 combinations or control. Weight loss (−11.23 kg; 95% confidence interval, −11.54 to −10.92; P<0.001) reduced high-sensitivity C-reactive protein (−1.15 mg/L; 95% confidence interval, −1.30 to −0.41; P<0.001), low- and high-density lipoprotein cholesterol, triglycerides, and blood pressure. During the 26-week weight maintenance period in the intention-to-treat analysis, the further decrease of high-sensitivity C-reactive protein blood levels was −0.46 mg/L greater (95% confidence interval, −0.79 to −0.13) in the groups assigned to low-glycemic-index diets than in those on high-glycemic-index diets (P<0.001). Groups on low-protein diets achieved a −0.25 mg/L greater reduction in high-sensitivity C-reactive protein (95% confidence interval, −0.59 to −0.17) than those on high-protein diets (P<0.001), whereas lipid profiles and blood pressure were not differently affected. Conclusions— This large-scale intervention study clearly separates weight loss from dietary composition–related effects. Low-glycemic-index carbohydrates and, to a lesser extent, low-protein intake may specifically reduce low-grade inflammation and associated comorbidities in overweight/obese adults. Clinical Trial Registration— http://www.clinicaltrials.gov. Unique identifier: NCT00390637.