Short-term (9 days) isocaloric fructose restriction decreased liver fat, VAT, and DNL, and improved insulin kinetics in children with obesity. These findings support efforts to reduce sugar consumption. ClinicalTrials.gov Number: NCT01200043

Compared with baseline, on day 10, liver fat decreased from a median of 7.2% (interquartile range [IQR], 2.5%−14.8%) to 3.8% (IQR, 1.7%−15.5%) (P < .001) and VAT decreased from 123 cm 3 (IQR, 85−145 cm 3 ) to 110 cm 3 (IQR, 84–134 cm 3 ) (P < .001). The DNL area under the curve decreased from 68% (IQR, 46%–83%) to 26% (IQR, 16%−37%) (P < .001). Insulin kinetics improved (P < .001). These changes occurred irrespective of baseline liver fat.

Children (9−18 years old; n = 41) had all meals provided for 9 days with the same energy and macronutrient composition as their standard diet, but with starch substituted for sugar, yielding a final fructose content of 4% of total kilocalories. Metabolic assessments were performed before and after fructose restriction. Liver fat, VAT, and subcutaneous fat were determined by magnetic resonance spectroscopy and imaging. The fractional DNL area under the curve value was measured using stable isotope tracers and gas chromatography/mass spectrometry. Insulin kinetics were calculated from oral glucose tolerance tests. Paired analyses compared change from day 0 to day 10 within each child.

Consumption of sugar is associated with obesity, type 2 diabetes mellitus, nonalcoholic fatty liver disease, and cardiovascular disease. The conversion of fructose to fat in liver (de novo lipogenesis [DNL]) may be a modifiable pathogenetic pathway. We determined the effect of 9 days of isocaloric fructose restriction on DNL, liver fat, visceral fat (VAT), subcutaneous fat, and insulin kinetics in obese Latino and African American children with habitual high sugar consumption (fructose intake >50 g/d).

See Covering the Cover synopsis on page 615 ; see editorial on page 642

The study was performed in Latino and African American children with obesity and high habitual sugar intake, comparing the effects of a fructose-reduction diet versus their habitual diet.

In children with obesity and metabolic syndrome, isocaloric substitution of starch for sugar for nine days significantly reduced de novo lipogenesis (DNL) and liver fat, while improving insulin kinetics, regardless of baseline liver fat content.

Dietary fructose has been associated with non-alcoholic fatty liver disease and type 2 diabetes, but studies have been confounded by hypercaloric feeding.

High dietary sugar consumption is associated with nonalcoholic fatty liver disease (NAFLD) and excess visceral adipose tissue (VAT),which are in turn linked to type 2 diabetes mellitus (T2DM), dyslipidemia, and cardiovascular disease in adults and children.NAFLD occurs when hepatic lipid concentration (from peripheral lipolysis or synthesis of new fat by hepatic de novo lipogenesis [DNL]) exceeds the combined rates of hepatic lipid oxidation and export.Studies have linked visceral and/or liver fat with metabolic dysfunction, including insulin resistance and T2DM,and NAFLD is a predictor of type 2 diabetes.Recently, a survey in 675 children with biopsy-proven NAFLD showed that 30% had T2DM or prediabetes.

Interrelationship between fatty liver and insulin resistance in the development of type 2 diabetes.

Sources of fatty acids stored in liver and secreted via lipoproteins in patients with nonalcoholic fatty liver disease.

The role of fructose in the pathogenesis of NAFLD and the metabolic syndrome.

Greater fructose consumption is associated with cardiometabolic risk markers and visceral adiposity in adolescents.

The link between consumption of sugar, especially fructose, and accumulation of ectopic fat is not well understood, but recent studies suggest that fructose stimulates DNL,which may drive the accumulation of liver and/or visceral fat.Fructose has been shown to specifically increase carbohydrate response element-binding protein,a transcription factor that induces 3 enzymes of DNL—adenosine triphosphate citrate lyase, acetyl-CoA carboxylase, and fatty acid synthase. We recently demonstrated that in weight-stable healthy men, high fructose intake for a 9-day period was associated with higher DNL and liver fat, compared with a diet with identical energy and macronutrient intake, but in which complex carbohydrate (starch) was substituted for sugar.We provided evidence linking fructose-driven DNL with liver fat and demonstrated that short-term reduction in fructose intake was consistently associated with lower levels of liver fat and rates of DNL, even in the absence of weight loss.

Fatty acid sources and their fluxes as they contribute to plasma triglyceride concentrations and fatty liver in humans.

In the current study, we hypothesized that short-term fructose restriction in children with obesity and metabolic syndrome who habitually consume high levels of fructose would reduce liver fat and hepatic DNL without change in energy intake or weight. We studied 41 Latino and African American children with high levels of self-reported sugar intake, feeding them diets that featured isocaloric substitution of starch for most sugar for 9 days, resulting in a reduction in total sugar content from 28% to 10%, and fructose from 12% to 4% of total energy intake. In separate publications from this study,we reported improvements in glycemia, fasting lipoproteins, blood pressure, and other clinical parameters. Here, we report the effects of isocaloric fructose restriction on liver fat, hepatic DNL, VAT, and subcutaneous adipose tissue (SAT), and their relation to changes in insulin kinetics.

Short-term isocaloric fructose restriction lowers apoC-III levels and yields less atherogenic lipoprotein profiles in children with obesity and metabolic syndrome.

The primary outcome of the study was change in liver fat, with secondary outcomes of DNL and insulin kinetics. Normal distribution was tested by box-plot, q-norm plot, and Shapiro-Wilk tests. Descriptive statistics were reported as mean ± SD for normally distributed values and as median (first quartile, third quartile) for non-normally distributed data. Outcome variables on day 0 and day 10 were compared by paired t test if distributed normally or by Kruskal-Wallis test for non-normally distributed data, including tests for effects of sex or race/ethnicity. Analysis of covariance was performed to control for weight change. As reported earlier,average weight decreased by 0.9 kg (P = .01) from day 0 to day 10, of which 0.6 kg was fat-free mass. A post-hoc sensitivity analysis was performed using data from 9 participants who did not lose weight during the dietary intervention. To determine the impact of baseline liver fat content on metabolic outcomes, we compared results within and between participants with high liver fat (fat fraction ≥5%) and those with fat fraction <5% by paired and unpaired t-tests or Mann–Whitney U test for outcomes that were not normally distributed. P values are based on 2-tailed tests. Analyses were performed using STATA software, version 12.1 (StataCorp, College Station, TX). Investigators remained blinded to key study outcomes, including MR data, DNL, dual-energy x-ray absorptiometry, insulin kinetics, and other biochemical outcomes until data collection and analysis were completed. All authors had access to the study data and reviewed and approved the final manuscript.

Samples collected during the tracer/feeding studies underwent ultracentrifugation to isolate triglyceride-rich lipoproteins (density 1.006 g/mL), and the palmitate from the triglyceride-rich lipoprotein-triglyceride fraction was analyzed by gas chromatography/mass spectrometry.Fractional DNL (percent of palmitate in circulating triglyceride that was synthesized de novo) was calculated by mass isotopomer distribution analysis.Integrated DNL-AUC was calculated during the 8-hour feeding period. Composite Insulin Sensitivity Index (CISI) and the oral glucose insulin sensitivity (OGIS) indexwere computed using insulin and glucose data from the OGTT. Insulin secretion rates (ISR) were calculated by deconvolutionand insulin clearance rates determined by dividing the ISR-AUC by the product of insulin volume of distribution (assumed to equal the C-peptide volume of distribution) and the insulin-AUC.

Calorie restriction and matched weight loss from exercise: independent and additive effects on glucoregulation and the incretin system in overweight women and men.

Effects of moderate and subsequent progressive weight loss on metabolic function and adipose tissue biology in humans with obesity.

Upon completion of the metabolic assessments on day 0, participants were discharged to home with 3 days of food and detailed instructions. They returned at 3-day intervals to pick up food for a total of 9 days. On day 10, all day 0 assessments were repeated. As described previously,the University of California, San Francisco Clinical Research Service Bionutrition Core designed individualized menus for each child and provided all food. Study diets restricted sugar and fructose intake to 10% and 4% of total energy intake, respectively, by substituting an equal number of calories from starch to match overall proportional carbohydrate consumption in each participant’s self-reported usual diet.Total energy content was estimated using Institute of Medicine formulas for weight maintenance in overweight boys and girlsand adjusted if weight changed >2% during outpatient feeding.

VAT and SAT volumes were semi-automatically generated based on either water-suppressed gradient-recalled echo images or on the fat images generated from iterative decomposition and echo asymmetry with least-squares estimation (IDEAL) MR images (10-mm-thick) at the disc between lumbar vertebrae 3 and 4. Regions of interest for VAT and SAT were determined by a single reader using a threshold-based contour mapping algorithm written in-house in IDL (Exelis Visual Information Solutions, Inc, Boulder, CO) followed by a manual alteration, as needed.

During the tracer/feeding study, participants underwent a magnetic resonance (MR) exam on a 3-Tesla scanner (GE Healthcare, Waukesha, WI) to measure liver fat, VAT, and SAT. For the liver fat measures, MR spectroscopy was obtained from a 200-mL single voxel (64 acquisitions water-suppressed, 8 acquisitions unsuppressed, with a repetition time of 2500 ms and an echo time of 30 ms), similar to prior reports.Spectra were automatically phase-, frequency-, motion-, and T2 relaxation-time−corrected (using in-house derived formulas for T2= −12.4 × L/W +31.3 ms, and T2= 23.1 × L/W + 58.5 ms; where L/W is the MR measured lipids/water at echo time = 30 ms).Quality was visually confirmed. MR liver fat fractions were calculated from the corrected MR measures of CHand CHlipids and of water as the total lipids / (total lipids + water).

Estimation of steatosis with MRS and MRI: validation with histology is confounded by differences in methodology.

Upon completion of the OGTT, an 8-hour stable isotope tracer/feeding study to measure postprandial DNL was initiated ( Figure 1 ) using liquid meals containing sodium [1-C]-acetate (Cambridge Isotope Laboratories, Cambridge, MA). After an initial double-sized meal, single-sized meals were fed every half-hour for 8 hours. Altogether, the meals provided 67% of estimated daily energy requirement (15% protein, 35% fat, 50% carbohydrate) and 5−7 g of the acetate tracer. On day 0, the fructose content of the liquid meals ranged from 12% to 18% of energy intake, depending on self-reported usual intake; on day 10, the fructose content was reduced to 4% of energy intake, but overall energy and carbohydrate content matched that of the day 0 test meals. In both cases, the remainder of carbohydrate was provided primarily as glucose polymer. Blood samples were drawn on KEDTA before the first test meal and every hour thereafter, processed, and frozen at −80°C.

Participants and their guardians were instructed to continue their usual home diets and other routines before the study. On days 0 and 10, after fasting at least 8 hours, participants underwent metabolic studies at the University of California San Francisco Pediatric Clinical Research Center ( Figure 1 ). Weight and vital signs were measured and urine pregnancy testing was performed in female participants. Body composition was measured by whole-body dual-energy x-ray absorptiometry (GE/Lunar Prodigy, Madison WI). A 2-hour 75-g oral glucose tolerance test (OGTT) was performed, with glucose, insulin, and C-peptide measurements at 0, 30, 60, 90, and 120 minutes. Fasting glucose and insulin, and their respective areas under the curve (AUC) are reported elsewhere.

Clinical research design and procedures on day 0 and day 10, depicting the time of OGTT, MR studies, and sodium [1- 13 C]-acetate administration via liquid meals (shakes) to determine rate of DNL.

Figure 1 Clinical research design and procedures on day 0 and day 10, depicting the time of OGTT, MR studies, and sodium [1- 13 C]-acetate administration via liquid meals (shakes) to determine rate of DNL.

We recruited non-diabetic African American and Latino children with obesity and metabolic syndrome who identified as high habitual sugar consumers (>15% sugar, >5% fructose) based on a food frequency questionnaire and interview by a dietitian.As described elsewhere,eligibility criteria included age 818 years, body mass index z-score ≥1.8, and at least 1 of the following: systolic blood pressure >95percentile for age and sex, fasting triglycerides >150 mg/dL, alanine aminotransferase >40 U/L, fasting glucose 100−125 mg/dL, fasting insulin >15 μIU/mL, homeostatic model assessment of insulin resistance >4.3,and severe acanthosis nigricans. This study protocol was approved by the Institutional Review Boards of the University of California, San Francisco (approval 10-03473) and Touro University-California (approval M-0609) and is registered with ClinicalTrials.gov NCT01200043 ). Informed written consent/assent were obtained before formal screening was initiated. Comprehensive metabolic assessments were performed before (day 0) and after (day 10) a 9-day dietary intervention.

At baseline, DNL-AUC did not differ significantly between those with high (≥5%) vs low liver fat (P = 0.64; Table 1 ). After 9 days of fructose restriction, DNL-AUC decreased significantly in both those with high liver fat and those with low liver fat, and the magnitude of decrease did not differ significantly between groups. However, DNL-AUC on day 10 was significantly lower in the low liver fat group compared with those with high liver fat. Liver fat and VAT also decreased significantly in both groups. Insulin secretion both during fasting and in response to OGTT decreased significantly in both groups. Insulin clearance rate increased significantly only in the high liver fat group.

Significant increases were observed in measures of insulin sensitivity (CISI, P < .001; and OGIS index, P < .001) and OGTT insulin clearance rate (P < .001) ( Table 1 ). Significant decreases were observed both in fasting ISR (P < .001), and in ISR during the OGTT (P < .001). These changes remained significant even after adjustment for weight change (P < .001).

Fractional DNL over the 8-hour tracer study decreased significantly after 9 days of fructose restriction, with the mean values for DNL at each time point continuing to diverge for the entire duration of sampling ( Figure 3 A). DNL-AUC was significantly lower on day 10 (68.4 ± 5.0 vs 29.7 ± 2.9; P < .001), decreasing in 37 of 40 participants with paired data ( Figure 3 B). Results were also statistically significant in the subset of 9 participants who did not lose weight (59.9 ± 10.1 vs 30.1 ± 7.6; P = .006; Figures 3 C and D).

Changes in postprandial fractional DNL (percent of palmitate in circulating triglyceride that was synthesized de novo) and the integrated DNL-AUC on days 0 (open circles) and 10 (closed circles) after isocaloric fructose restriction in 40 obese children (A, B) and in the subgroup of 9 children who did not lose weight (C, D) during fructose restriction. On both study days, after an overnight fast, and after the OGTT was complete, participants consumed liquid meals every 20 minutes for 6 hours, starting at 10:30 am . Blood samples were obtained hourly during this period. (A, C) Fractional DNL (mean ± SEM) for all subjects (A) and the subgroup of 9 participants who did not lose weight (C). (B, D) Individual serial measures of DNL-AUC in the group as a whole (B) and the subgroup that did not lose weight (D). Decreases in DNL-AUC were statistically significant in the group as a whole (P < .001), as well as the subgroup who did not lose weight (P = .006).

Figure 3 Changes in postprandial fractional DNL (percent of palmitate in circulating triglyceride that was synthesized de novo) and the integrated DNL-AUC on days 0 (open circles) and 10 (closed circles) after isocaloric fructose restriction in 40 obese children (A, B) and in the subgroup of 9 children who did not lose weight (C, D) during fructose restriction. On both study days, after an overnight fast, and after the OGTT was complete, participants consumed liquid meals every 20 minutes for 6 hours, starting at 10:30 am . Blood samples were obtained hourly during this period. (A, C) Fractional DNL (mean ± SEM) for all subjects (A) and the subgroup of 9 participants who did not lose weight (C). (B, D) Individual serial measures of DNL-AUC in the group as a whole (B) and the subgroup that did not lose weight (D). Decreases in DNL-AUC were statistically significant in the group as a whole (P < .001), as well as the subgroup who did not lose weight (P = .006).

At baseline, 25 participants (20 Latino, 5 African American; P = .003) had elevated liver fat (fat fraction ≥5%), and 15 (5 Latino, 10 African American) had low liver fat (fat fraction <5%; Table 1 ). Paired MR measures were available in 38 participants for liver fat and 40 for VAT and SAT. From day 0 to day 10, liver fat decreased from a median of 7.1% (IQR, 2.5%−14.8) to 3.8% (IQR, 1.7%−15.6%) (P < .001), and VAT decreased from 123 cm(IQR, 85−145 cm) to 110 cm(IQR, 84−134 cm) (P < .001), while SAT did not change significantly ( Figure 2 A). Liver fat decreased in all but 1 of the 38 participants for whom paired data were available ( Figure 2 B). The decrease in liver fat after adjustment for weight change remained statistically significant (P = .004). Among the 9 participants who did not lose weight ( Figures 2 E−H), liver fat decreased from 9.7% (IQR, 2.5%−20.1%) to 6.3% (IQR, 2.2%−17.6%) (P = .02) and VAT from 124 cm(IQR, 79−190 cm) to 91 cm(IQR, 82−154 cm) (P = .06). While males had higher liver fat and VAT on day 0 (P < .05), loss of fat did not differ significantly by sex, in either absolute or relative terms. Liver fat and VAT were higher in Latinos for both day 0 and day 10 (P < .003, Kruskal-Wallis; P < .05, t test, respectively). However, as a percent of day 0 values, the reductions in liver fat, weight-loss adjusted liver fat, VAT, and SAT were not significantly different between Latinos and African Americans.

Changes in individual fat compartments in obese children (A−D) before and after 9 days of isocaloric fructose restriction, and in the subset of 9 children who did not lose weight (E−H) during fructose restriction. (A, E) Mean ± SEM in liver fat as determined by MR, and VAT and subcutaneous SAT fat as determined by MR in the entire cohort (A) and the subgroup of 9 participants who did not lose weight (E). (B, F) Individual serial measures of liver fat in the entire cohort (B) and the subgroup of 9 participants who did not lose weight (F). (C, G) Individual serial measures of VAT. (D, H) Individual serial measures of SAT in the entire cohort (D) and the subgroup of 9 participants who did not lose weight (H). Open and closed circles to the left and right of the day 0 and day 10 individual plots depict median and IQR (B, F) or mean ± SEM (C, D, G, H). Decreases in liver fat and VAT were statistically significant in the group as a whole (P < .001 in both cases). In the subgroup who did not lose weight, change in liver fat was statistically significant (P = .02).

Figure 2 Changes in individual fat compartments in obese children (A−D) before and after 9 days of isocaloric fructose restriction, and in the subset of 9 children who did not lose weight (E−H) during fructose restriction. (A, E) Mean ± SEM in liver fat as determined by MR, and VAT and subcutaneous SAT fat as determined by MR in the entire cohort (A) and the subgroup of 9 participants who did not lose weight (E). (B, F) Individual serial measures of liver fat in the entire cohort (B) and the subgroup of 9 participants who did not lose weight (F). (C, G) Individual serial measures of VAT. (D, H) Individual serial measures of SAT in the entire cohort (D) and the subgroup of 9 participants who did not lose weight (H). Open and closed circles to the left and right of the day 0 and day 10 individual plots depict median and IQR (B, F) or mean ± SEM (C, D, G, H). Decreases in liver fat and VAT were statistically significant in the group as a whole (P < .001 in both cases). In the subgroup who did not lose weight, change in liver fat was statistically significant (P = .02).

NOTE. Parametric test when normal distribution was achieved, values are mean ± SD. Nonparametric test (Kruskal-Wallis) applied when normal distribution was not achieved, values are median (quartile 1, quartile 3).

As reported previously,52 Latino and African American children were recruited. Two were ineligible, 5 failed to show on day 0, and 2 completed day 0 testing but did not return for day 10. This article reports paired data in 41 children, of which 26 were Latino and 15 were African American; 15 were male and 26 were female, median age was 13 years (range, 9−18 years), median body mass index z-score was 2.3 (range, 1.9−3.2) and body fat was 48.6% (35.3%−55.9%). Daily intake during the 9 days of fructose restriction averaged 28 ± 6 kcal/kg with a mean ± SD macronutrient profile of 51% ± 3% carbohydrate, 16% ± 1% protein, and 33% ± 3% fat. Within the carbohydrate fraction, dietary sugar intake decreased from 28% ± 8% to 10% ± 2%, and fructose intake from 12% ± 4% to 4% ± 1%.

Discussion

31 Welsh J.A.

Karpen S.

Vos M.B. Increasing prevalence of nonalcoholic fatty liver disease among United States adolescents, 1988−1994 to 2007−2010. 32 Williams K.H.

Shackel N.A.

Gorrell M.D.

et al. Diabetes and nonalcoholic fatty liver disease: a pathogenic duo. 33 Widhalm K.

Ghods E. Nonalcoholic fatty liver disease: a challenge for pediatricians. 34 Fonvig C.E.

Chabanova E.

Andersson E.A.

et al. 1H-MRS measured ectopic fat in liver and muscle in Danish lean and obese children and adolescents. 12 Sung K.C.

Kim S.H. Interrelationship between fatty liver and insulin resistance in the development of type 2 diabetes. 7 Perry R.J.

Samuel V.T.

Petersen K.F.

et al. The role of hepatic lipids in hepatic insulin resistance and type 2 diabetes. , 8 Donnelly K.L.

Smith C.I.

Schwarzenberg S.J.

et al. Sources of fatty acids stored in liver and secreted via lipoproteins in patients with nonalcoholic fatty liver disease. , 35 Lambert J.E.

Ramos−Roman M.A.

Browning J.D.

et al. Increased de novo lipogenesis is a distinct characteristic of individuals with nonalcoholic fatty liver disease. , 36 Burgert T.S.

Taksali S.E.

Dziura J.

et al. Alanine aminotransferase levels and fatty liver in childhood obesity: associations with insulin resistance, adiponectin, and visceral fat. , 37 Byrne C.D.

Targher G. Ectopic fat, insulin resistance, and nonalcoholic fatty liver disease: implications for cardiovascular disease. , 38 Lim S.

Meigs J.B. Links between ectopic fat and vascular disease in humans. 6 Yki-Järvinen H. Non-alcoholic fatty liver disease as a cause and a consequence of metabolic syndrome. , 9 Mathieu P.

Boulanger M.C.

Després J.P. Ectopic visceral fat: a clinical and molecular perspective on the cardiometabolic risk. , 10 Fabbrini E.

Magkos F.

Mohammed B.S.

et al. Intrahepatic fat, not visceral fat, is linked with metabolic complications of obesity. , 36 Burgert T.S.

Taksali S.E.

Dziura J.

et al. Alanine aminotransferase levels and fatty liver in childhood obesity: associations with insulin resistance, adiponectin, and visceral fat. , 38 Lim S.

Meigs J.B. Links between ectopic fat and vascular disease in humans. 10 Fabbrini E.

Magkos F.

Mohammed B.S.

et al. Intrahepatic fat, not visceral fat, is linked with metabolic complications of obesity. In the past 2 decades, the prevalence of NAFLD has more than doubled in adolescentsand adults,with current estimates as high as 50% in the United States.Hepatic steatosis, as well as other ectopic fat stores, are implicated in obesity-related metabolic dysfunction that occurs in adolescentsand adultsand includes insulin resistance, dyslipidemia, diabetes, and cardiovascular disease.Multiple cross-sectional studies have linked liver fat and VAT with metabolic complications of obesity, including insulin resistance, T2DM, and cardiovascular disease.Fabbrini et al,using sensitive metabolic assessments, found that liver fat was more strongly associated with insulin resistance than was VAT. In this study, we demonstrate that as few as 9 days of isocaloric fructose restriction significantly reduced liver fat, DNL, and VAT, and improved insulin sensitivity, secretion, and clearance in children with obesity and metabolic syndrome. The improvements in these outcome measures occurred irrespective of baseline liver fat content, sex, or race/ethnicity.

39 Mager D.R.

Iñiguez I.R.

Gilmour S.

et al. The effect of a low fructose and low glycemic index/load (FRAGILE) dietary intervention on indices of liverfunction, cardiometabolic risk factors, and body composition in children and adolescents with nonalcoholic fatty liver disease (NAFLD). Others have noted that both reduction in glycemic index/load improves liver fat and metabolic function in adolescents with NAFLD.Rather, our study demonstrates that isocaloric substitution of starch for sugar, which has the end effect of increasing glycemic index, improved liver and visceral fat and insulin secretion and sensitivity within 10 days. Our data suggest that the effect of fructose on liver fat is specific and mediated through reductions in DNL.

25 Hellerstein M.K.

Christiansen M.

Kaempfer S.

et al. Measurement of de novo hepatic lipogenesis in humans using stable isotopes. 35 Lambert J.E.

Ramos−Roman M.A.

Browning J.D.

et al. Increased de novo lipogenesis is a distinct characteristic of individuals with nonalcoholic fatty liver disease. 8 Donnelly K.L.

Smith C.I.

Schwarzenberg S.J.

et al. Sources of fatty acids stored in liver and secreted via lipoproteins in patients with nonalcoholic fatty liver disease. 40 McGarry J.D. Banting Lecture 2001: Dysregulation of fatty acid metabolism in the etiology of type 2 diabetes. 4 Lim J.S.

Mietus-Snyder M.

Valente A.

et al. The role of fructose in the pathogenesis of NAFLD and the metabolic syndrome. , 41 Ouyang X.

Cirillo P.

Sautin Y.

et al. Fructose consumption as a risk factor for non-alcoholic fatty liver disease. 18 Schwarz J.M.

Noworolski S.M.

Wen M.J.

et al. Effect of a high-fructose weight-maintaining diet on lipogenesis and liver fat. 8 Donnelly K.L.

Smith C.I.

Schwarzenberg S.J.

et al. Sources of fatty acids stored in liver and secreted via lipoproteins in patients with nonalcoholic fatty liver disease. , 35 Lambert J.E.

Ramos−Roman M.A.

Browning J.D.

et al. Increased de novo lipogenesis is a distinct characteristic of individuals with nonalcoholic fatty liver disease. , 42 Savage D.B.

Choi C.S.

Samuel V.T.

et al. Reversal of diet-induced hepatic steatosis and hepatic insulin resistance by antisense oligonucleotide inhibitors of acetyl-CoA carboxylases 1 and 2. 2 Stanhope K.L.

Schwarz J.M.

Keim N.L.

et al. Consuming fructose-, not glucose-sweetened beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans. DNL was originally thought to be a minor metabolic pathway in humans.However, increased DNL has been demonstrated in adults with NAFLD.Using stable isotopes, Donnelly et alshowed that in adults with NAFLD, approximately 59% of triglyceride labeled in the liver comes from circulating fatty acids released by peripheral lipolysis, 15% from dietary fat, and 26% from DNL. If fatty acid influx is not matched by hepatic fat oxidation and export, liver fat will accumulate. DNL impacts both sides of this equation, both by generating new lipids and by suppressing hepatic fat oxidation, as the intermediate malonyl-CoA prevents fatty acid transport into mitochondria by inhibiting carnitine palmitoyl transferase-1.Fructose consumption has been proposed as a primary contributor to NAFLDby increasing DNL. We have recently shown that in healthy adults fed isocaloric diets, DNL and liver fat were higher during high-fructose feeding when compared with low-fructose feeding.Those results, taken together with those of the present study, support the hypothesis that DNL is an important mechanism in the modulation of liver fat.In addition, the increases in VAT with high-fructose feedingand the decrease in VAT observed with fructose restriction observed in the present study suggest primary links between fructose consumption, DNL, and ectopic fat. The decline of fractional DNL after 9 days of fructose restriction suggests that the process of DNL is a rational target for dietary intervention.

43 Kalia H.S.

Gaglio P.J. The prevalence and pathobiology of nonalcoholic fatty liver disease in patients of different races or ethnicities. 44 Schwarz J.M.

Chiolero R.

Revelly J.P.

et al. Effects of enteral carbohydrates on de novo lipogenesis in critically ill patients. , 45 Schwarz J.M.

Mulligan K.

Lee J.

et al. The effects of recombinant human growth hormone on hepatic lipid and carbohydrate metabolism in HIV-infected patients with fat accumulation. , 46 Schwarz J.M.

Linfoot P.

Dare D.

et al. Hepatic de novo lipogenesis in normoinsulinemic and hyperinsulinemic subjects consuming high-fat, low-carbohydrate and low-fat, high-carbohydrate isoenergetic diets. 47 Titchenell P.M.

Quinn W.J.

Lu M.

et al. Direct hepatocyte insulin signaling is required for lipogenesis but Is dispensable for the suppression of glucose production. , 48 Postic C.

Girard J. Contribution of de novo fatty acid synthesis to hepatic steatosis and insulin resistance: lessons from genetically engineered mice. Although study eligibility was not based on liver fat content, 63% of our participants had high liver fat. Consistent with other reports,high liver fat was significantly more prevalent in Latino children compared with African Americans. However, even with a habitual diet high in fructose, 37% of the children appeared to be protected against NAFLD. On day 0, the subgroup of children with low liver fat had significantly lower fasting insulin levels and higher CISI than those with high liver fat ( Table 1 ). After fructose restriction (day 10), fasting insulin levels remained significantly higher in the group with high liver fat (P = .002), despite improvements in insulin sensitivity, secretion, and clearance. We noted that both insulin secretion and clearance improved with reduction in liver fat and postprandial DNL after fructose restriction, despite calorically equivalent increases in starch consumption. We have previously shown that persons with hyperinsulinemia have high fasting DNL compared with normoinsulinemic controls.A key role of hepatic insulin signaling in stimulating DNL has been reported.Consistent with these observations, the children with high liver fat, who also had elevated fasting insulin levels, may also have had higher DNL even before feeding. These children likely had around-the-clock DNL driven by fructose in the fed state and by hyperinsulinemia in the fasting state, thus providing a potential explanation for why some obese children have elevated liver fat and others do not. Further studies are necessary to test this hypothesis and to characterize the impact of genetic factors on liver fat.

6 Yki-Järvinen H. Non-alcoholic fatty liver disease as a cause and a consequence of metabolic syndrome. , 7 Perry R.J.

Samuel V.T.

Petersen K.F.

et al. The role of hepatic lipids in hepatic insulin resistance and type 2 diabetes. , 12 Sung K.C.

Kim S.H. Interrelationship between fatty liver and insulin resistance in the development of type 2 diabetes. 19 Lustig R.H.

Mulligan K.

Noworolski S.M.

et al. Isocaloric fructose restriction and metabolic improvement in children with obesity and metabolic syndrome. 20 Gugliucci A.

Lustig R.H.

Caccavello R.

et al. Short-term isocaloric fructose restriction lowers apoC-III levels and yields less atherogenic lipoprotein profiles in children with obesity and metabolic syndrome. 7 Perry R.J.

Samuel V.T.

Petersen K.F.

et al. The role of hepatic lipids in hepatic insulin resistance and type 2 diabetes. 49 Templeman N.M.

Skovsø S.

Page M.M.

et al. A causal role for hyperinsulinemia in obesity. 50 Jia G.

DeMarco V.G.

Sowers J.R. Insulin resistance and hyperinsulinaemia in diabetic cardiomyopathy. In this article, we document improvements in liver fat, DNL, insulin kinetics, and, to a lesser extent, VAT in obese children when sugar in the diet is replaced with starch; that is, a glucose-for-fructose exchange. Liver and visceral fat are thought to play a prominent role in metabolic dysfunction.Previously published results from our study demonstrated reductions in blood pressure and levels of analytes related to prediabetes (eg, lactate, glucose, and insulin).In addition, we reported improvement in lipoprotein profiles related to atherogenicity (eg, triglyceride to high-density lipoprotein ratio, low-density lipoprotein size, and Apo-CIII concentration).All of these measures were performed in the fasting state, thus the improvements in metabolic function cannot be attributed to acute effect of fructose reduction in the liquid meals during the tracer feeding study on day 10. The improvements in metabolic, lipid, and ectopic fat parameters were accompanied by changes in homeostatic model assessment of insulin resistance and CISI, 2 measures of peripheral insulin sensitivity. By demonstrating that removal of dietary fructose (the macronutrient most closely associated with hepatic DNL) concomitantly reduces liver fat and improves insulin dynamics irrespective of calories or weight, we are able to suggest a causative mechanism of metabolic dysfunction in these children by linking DNL to both liver fat and insulin resistance. We also demonstrated that despite an increase in the glucose (starch) content of the diet, insulin secretion decreased, thus protecting against β-cell exhaustion, thought to be important in the pathogenesis of type 2 diabetes; and reducing total body insulin burden, thought to contribute to both obesityand risk for cardiovascular disease.These data also suggest an achievable dietary approach to improve metabolic dysfunction in similarly affected children who are high sugar consumers.

51 Rangan A.

Allman-Farinelli M.

Donohoe E.

et al. Misreporting of energy intake in the 2007 Australian Children's Survey: differences in the reporting of food types between plausible, under- and over-reporters of energy intake. 29 Magkos F.

Fraterrigo G.

Yoshino J.

et al. Effects of moderate and subsequent progressive weight loss on metabolic function and adipose tissue biology in humans with obesity. 19 Lustig R.H.

Mulligan K.

Noworolski S.M.

et al. Isocaloric fructose restriction and metabolic improvement in children with obesity and metabolic syndrome. , 20 Gugliucci A.

Lustig R.H.

Caccavello R.

et al. Short-term isocaloric fructose restriction lowers apoC-III levels and yields less atherogenic lipoprotein profiles in children with obesity and metabolic syndrome. 19 Lustig R.H.

Mulligan K.

Noworolski S.M.

et al. Isocaloric fructose restriction and metabolic improvement in children with obesity and metabolic syndrome. 19 Lustig R.H.

Mulligan K.

Noworolski S.M.

et al. Isocaloric fructose restriction and metabolic improvement in children with obesity and metabolic syndrome. We note the following limitations of this study. First, the study design did not include a separate external control group. However, including such a control group would have introduced new challenges. For example, studies document that dietary sugar intake by recall is consistently underestimated.Had we included an external control group, it is unlikely that we could have accurately matched their true baseline sugar intake, thus raising the possibility of over- or under-feeding sugar to the control group and potentially providing flawed results. Instead, each participant served as his/her own control, which minimized inter-participant variability. Future confirmatory studies should include a control group with specified and monitored fructose intake both before and during the experimental diet. Second, despite efforts to maintain baseline weight, overall there was a small but statistically significant weight loss (0.9 kg; 95% confidence interval, −1.3 to −0.6). While small reductions in weight could improve metabolic health,we do not believe that the salutary weight loss in these subjects mitigates our findings related to reductions in liver fat and DNL. As discussed previously,the weight loss occurred within the first 4 days and then plateaued to reach a new steady state. This result is not consistent with persistent energy deficit at the day-10 visit. As reported previously,dual-energy x-ray absorptiometry scanning documented that the weight loss occurred within the fat-free compartment (eg, water and/or muscle), the loss of either of which would not contribute substantially to improved metabolic health. In addition, the results remained statistically significant after adjusting for this weight loss using repeated measures analysis of covariance. We would be remiss in not acknowledging the possibility that slight changes in macronutrient or fiber content in the fructose-restricted dietsmay have been more satiating than their home baseline diet, which posed a challenge to the study coordinator to persuade participants to increase intake past comfort. Perhaps most importantly, sensitivity analysis documented statistically significant improvements in DNL, liver fat, and VAT in the subgroup of participants who did not lose weight ( Figures 2 E−H and 3 C and 3 D). Third, we did not measure DNL in the fasting state. While such a steady-state measurement would have yielded important information about genetic predisposition toward NAFLD and the existence of around-the-clock DNL in susceptible populations, doing so would have required changing from an outpatient to an inpatient protocol, which would have limited recruitment and retention of pediatric participants, which was already quite demanding. Lastly, we acknowledge that our study design does not allow us to speculate on benefits of fructose restriction in normal-weight children or adults, or extrapolate our results to obese individuals whose diets are low in fructose content.