Independent association of liver fat accumulation with insulin resistance

The correlation between hepatic controlled attenuation parameter (CAP) value and insulin resistance (IR) was stronger than that between body mass index, visceral fat area and IR

BACKGROUND

Hepatic controlled attenuation parameter (CAP) is a novel marker for quantifying hepatic fat accumulation. Insulin resistance (IR) plays a major role in the pathogenesis and natural history of hepatic steatosis. This study aimed to investigate the possible relationship between CAP value and IR.

METHODS

This study included a total of 420 patients with overweight or obesity who came to the obesity clinic at Tianjin Union Medical Center. Vibration-controlled transient elastography examination was conducted to detect CAP and liver stiffness measurement (LSM) values. Body composition, including visceral fat area (VFA), and body fat mass (BFM), was evaluated by the direct segmental multi-frequency bioelectrical impedance analysis (BIA). The associations between CAP value, body mass index (BMI), VFA, BFM and homeostasis model assessment of insulin resistance (HOMA-IR) were analyzed.

RESULTS

CAP value was positively associated with HOMA-IR (r = 0.568, P < 0.001), the strength of which was much stronger than BMI, VFA, and BFM. In multivariate linear regression, CAP value and HOMA-IR showed a significant positive association (adjusted β = 0.015, 95% CI 0.007-0.022, P < 0.001). Subgroup analysis suggested no significant interaction between CAP value and HOMA-IR across age, BMI, LSM, hypertension, and sex groups (all P for interaction > 0.05).

CONCLUSIONS

Hepatic CAP value is more remarkably than other obesity markers associated with HOMA-IR in individuals with overweight or obesity, regardless of age, BMI, LSM, hypertension, and sex.

Plant-based and Early Time-restricted Eating for Prevention and Treatment of Type 2 Diabetes in Adults: A Narrative Review

Type 2 diabetes (T2D) is a significant public health challenge for which effective lifestyle interventions are needed. A growing body of evidence supports the use of both plant-based eating patterns and early time-restricted eating (eTRE) for the prevention and treatment of T2D, but research has not yet explored the potential of these dietary strategies in combination. In this narrative review, we assessed the evidence by which plant-based diets, in conjunction with eTRE, could support T2D care. The electronic databases MEDLINE and the Web of Science were searched for relevant articles published throughout the last decade. Observational research has shown that healthy plant-based eating patterns and eTRE are associated with reductions in T2D risk. Interventional trials demonstrated that plant-based diets promote improvements in glycated hemoglobin, insulin resistance, glycemic management, and cardiometabolic risk factors. These changes may be mediated, in part, by reductions in oxidative stress, dietary acid load, and hepatocellular and intramyocellular lipids. The eTRE strategies were also shown to improve insulin resistance and glycemic management, and mechanisms of action included enhanced regulation of circadian rhythm and increased metabolic flexibility. Integrating these dietary strategies may produce additive benefits, mediated by reduced visceral adiposity and beneficial shifts in gut microbiota composition. However, potential barriers to concurrent implementation of these interventions may exist, including social challenges, scheduling constraints, and tolerance. Prospective trials are needed to examine their acceptability and clinical effects.

Dpp4+ interstitial progenitor cells contribute to basal and high fat diet-induced adipogenesis

OBJECTIVE

The capacity to generate new adipocytes from precursor cells is critical for maintaining metabolic health. Adipocyte precursor cells (APCs) constitute a heterogenous collection of cell types; however, the contribution of these various cell types to adipose tissue expansion in vivo remains unknown. The aim of the current study is to investigate the contribution of Dpp4+ progenitors to de novo adipogenesis.

METHODS

Single cell analysis has identified several transcriptionally distinct subpopulations of APCs, including Dpp4+ progenitor cells concentrated in the connective tissue surrounding many organs, including white adipose tissue (WAT). Here, we generated a Dpp4CreER mouse model for in vivo lineage tracing of these cells and their downstream progeny in the setting of basal or high fat diet (HFD)-stimulated adipogenesis.

RESULTS

Dpp4CreER mice enabled specific temporal labeling of Dpp4+ progenitor cells within their native connective tissue niche. Following a dietary chase period consisting of chow or HFD feeding for 18 weeks, Dpp4+ progenitors differentiated into mature adipocytes within the gonadal and subcutaneous WAT. HFD stimulated adipogenic contribution from Dpp4+ cells in the gonadal but not the subcutaneous depot. Flow cytometry analysis revealed that Dpp4+ progenitors give rise to DPP4(-)/ICAM1+ preadipocytes in vivo. HFD feeding did not perturb the flux of Dpp4+ cell conversion into ICAM1+ preadipocytes in gonadal WAT. Conversely, in subcutaneous WAT, HFD feeding/obesity led to an accumulation of ICAM1+ preadipocytes without a corresponding increase in mature adipocyte differentiation. Examination of non-classical murine visceral depots with relevance to humans, including omentum and retroperitoneal WAT, revealed robust contribution of Dpp4+ progenitors to de novo adipogenesis, which was further stimulated by HFD.

CONCLUSION

Our data demonstrate that Dpp4+ interstitial progenitor cells contribute to basal adipogenesis in all fat depots and are recruited to support de novo adipogenic expansion of visceral WAT in the setting of HFD-induced obesity.

Identification and study of differentially expressed miRNAs in aged NAFLD rats based on high-throughput sequencing

INTRODUCTION AND OBJECTIVES

Hepatic microRNA (miR) expression profiles were explored in aged rats with NAFLD, in order to clarify the molecular mechanisms underlying the pathophysiological processes of aging-related NAFLD.

PATIENTS OR MATERIALS AND METHODS

24 aged rats (18-month-old) and 24 young rats (2-month-old) were randomly divided into two subgroups according to diet, control group and NAFLD group. After 8 weeks of administering 45% high-fat diet or normal diet, total hepatic RNA was extracted from liver tissues of the aged rats. Differentially expressed microRNAs (DE-miRs) in aged NAFLD group were detected and screened out using high-throughput sequencing technology. The data were subjected to Gene Ontology functional enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses using a bioinformatics approach. The sequencing results were further verified by RT-qPCR.

RESULTS

Compared with the aged control liver tissues, 6 significantly upregulated miRs (miR-881-3p, miR-871-3p, miR-335, miR-223-3p, miR-155-5p, miR-146b-5p) and 4 significantly downregulated miRs (miR-182, miR-193-3p, miR-31a-5p and miR-96-5p) were identified in the aged NAFLD liver tissues. These DE-miRs were found to be involved in the regulation of cell signaling transduction and metabolism processes, probably affecting signaling pathways relevant to insulin secretion and some senile diseases. RT-qPCR results corroborated the sequencing results and demonstrated that 6 significantly upregulated miRs were not identified in the young group.

CONCLUSIONS

A total of 10 DE-miRs identified in the aged NAFLD rats were involved in some certain insulin secretion and age-related functional pathways, which may serve as novel candidate targets for the diagnosis and treatment of aging-associated NAFLD.

Association of Body Fat Percentage with Time in Range Generated by Continuous Glucose Monitoring during Continuous Subcutaneous Insulin Infusion Therapy in Type 2 Diabetes

BACKGROUND

Obesity is a crucial risk factor associated with type 2 diabetes mellitus (T2DM). Excessive accumulation of body fat may affect the glycemia control in T2DM. This study investigated the relationship between body fat percentage and time in range (TIR) assessed by continuous glucose monitoring (CGM) during short-term continuous subcutaneous insulin infusion (CSII) therapy in T2DM patients.

METHOD

A total of 85 T2DM patients were recruited in this cross-sectional study. All participants underwent 72 h CGM period during short-term CSII therapy. TIR was defined as the percentage of time spent within the target glucose range of 3.9-10.0 mmol/L. Body composition was measured using bioelectrical impedance analysis (BIA) and overfat was defined as an amount of body fat of at least 25% of total body mass for men or at least 30% for women. Multiple linear regression models were used to evaluate the independent association of body fat percentage with TIR after adjusting for confounding factors.

RESULTS

Compared with normal fat T2DM patients, individual with a higher body fat percentage exhibited lower levels of TIR (P = 0.004) and higher 72 h mean blood glucose (72 h MBG) (P = 0.001) during short-term CSII treatment. The prevalence of overfat assessed by body fat percentage decreased with the ascending TIR tertiles (P < 0.05). Multiple linear regression analysis indicated that body fat percentage was significantly associated with TIR independent of age, gender, diabetes duration, HbA1c, and BMI (P = 0.043).

CONCLUSIONS

Body fat percentage was significantly associated with TIR in T2DM during short-term CSII therapy. Reduction of body fat may be an important therapeutic target to improve glycemic control in high body fat T2DM patients, who may benefit less from intensive insulin treatment.

Effect of a Low-Fat Vegan Diet on Body Weight, Insulin Sensitivity, Postprandial Metabolism, and Intramyocellular and Hepatocellular Lipid Levels in Overweight Adults: A Randomized Clinical Trial

IMPORTANCE

Excess body weight and insulin resistance lead to type 2 diabetes and other major health problems. There is an urgent need for dietary interventions to address these conditions.

OBJECTIVE

To measure the effects of a low-fat vegan diet on body weight, insulin resistance, postprandial metabolism, and intramyocellular and hepatocellular lipid levels in overweight adults.

DESIGN, SETTING, AND PARTICIPANTS

This 16-week randomized clinical trial was conducted between January 2017 and February 2019 in Washington, DC. Of 3115 people who responded to flyers in medical offices and newspaper and radio advertisements, 244 met the participation criteria (age 25 to 75 years; body mass index of 28 to 40) after having been screened by telephone.

INTERVENTIONS

Participants were randomized in a 1:1 ratio. The intervention group (n = 122) was asked to follow a low-fat vegan diet and the control group (n = 122) to make no diet changes for 16 weeks.

MAIN OUTCOMES AND MEASURES

At weeks 0 and 16, body weight was assessed using a calibrated scale. Body composition and visceral fat were measured by dual x-ray absorptiometry. Insulin resistance was assessed with the homeostasis model assessment index and the predicted insulin sensitivity index (PREDIM). Thermic effect of food was measured by indirect calorimetry over 3 hours after a standard liquid breakfast (720 kcal). In a subset of participants (n = 44), hepatocellular and intramyocellular lipids were quantified by proton magnetic resonance spectroscopy. Repeated measure analysis of variance was used for statistical analysis.

RESULTS

Among the 244 participants in the study, 211 (87%) were female, 117 (48%) were White, and the mean (SD) age was 54.4 (11.6) years. Over the 16 weeks, body weight decreased in the intervention group by 5.9 kg (95% CI, 5.0-6.7 kg; P < .001). Thermic effect of food increased in the intervention group by 14.1% (95% CI, 6.5-20.4; P < .001). The homeostasis model assessment index decreased (-1.3; 95% CI, -2.2 to -0.3; P < .001) and PREDIM increased (0.9; 95% CI, 0.5-1.2; P < .001) in the intervention group. Hepatocellular lipid levels decreased in the intervention group by 34.4%, from a mean (SD) of 3.2% (2.9%) to 2.4% (2.2%) (P = .002), and intramyocellular lipid levels decreased by 10.4%, from a mean (SD) of 1.6 (1.1) to 1.5 (1.0) (P = .03). None of these variables changed significantly in the control group over the 16 weeks. The change in PREDIM correlated negatively with the change in body weight (r = -0.43; P < .001). Changes in hepatocellular and intramyocellular lipid levels correlated with changes in insulin resistance (both r = 0.51; P = .01).

CONCLUSIONS AND RELEVANCE

A low-fat plant-based dietary intervention reduces body weight by reducing energy intake and increasing postprandial metabolism. The changes are associated with reductions in hepatocellular and intramyocellular fat and increased insulin sensitivity.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02939638.

Association of gamma-glutamyl transferase and alanine aminotransferase with type 2 diabetes mellitus incidence in middle-aged Japanese men: 12-year follow up

AIMS/INTRODUCTION

To prospectively investigate whether simultaneous elevation of gamma-glutamyl transferase (GGT) and alanine aminotransferase (ALT) is associated with the increase of type 2 diabetes mellitus incidence independent of alcohol drinking, body mass index and triglycerides.

METHODS

A total of 2,775 Japanese male workers who had no history of type 2 diabetes mellitus were followed. High GGT and ALT were defined as the top tertiles (GGT cutpoint: 49 IU/L, ALT cutpoint: 28 IU/L). Three groups were created using these dichotomized GGT and ALT cutpoints: both low, either high or both high. Multivariable Cox proportional hazards models were carried out adjusted for potential confounding factors.

RESULTS

A total of 276 type 2 diabetes mellitus cases were identified during 12 years (27,040 person-years) of follow up. Participants with simultaneously elevated GGT and ALT had a significantly higher incidence of type 2 diabetes mellitus, even after adjustment for fasting insulin and fasting blood glucose compared with the group without GGT or ALT elevation. Similar associations were observed in non- or light-to-moderate alcohol drinkers, as well as in participants with normal weight. However, the association was weaker in participants with triglycerides <150 mg/dL. We then evaluated whether the addition of GGT and ALT would improve the prediction of type 2 diabetes mellitus incidence, and found that their inclusion significantly increased the C-statistic, net reclassification improvement and integrated discrimination improvement.

CONCLUSIONS

Simultaneous elevation of GGT and ALT was significantly associated with type 2 diabetes mellitus incidence, independent of potential confounding factors, including alcohol drinking and obesity, although the association might require concomitant elevation of triglycerides. Inclusion of GGT and ALT improved type 2 diabetes mellitus risk prediction.

Smoking results in accumulation of ectopic fat in the liver

OBJECTIVE

An association between smoking and nonalcoholic fatty liver disease has been reported. However, objective quantification of intrahepatic fat via magnetic resonance spectroscopy (MRS) in relation to smoking has rarely been performed in previous studies. Moreover, the possible pathways via which smoking could induce ectopic fat accumulation have not yet been addressed. The current study aimed to examine the association between smoking status and intrahepatic fat quantity and explore the possible mediating effects of triglycerides (TG) and adiponectin.

SUBJECTS AND METHODS

Magnetic resonance imager (MRI) spectra were analyzed to quantify intrahepatic fat in 45 men who were on average 62.3 years of age. Smoking status and alcohol intake were self-reported. Accelerometers were used to record daily total physical activity. Fasting blood TG and adiponectin levels were measured enzymatically. Differences in mean intrahepatic fat values according to smoking status were assessed using analysis of covariance.

RESULTS

A stepwise increase in mean intrahepatic fat was observed between never, former, and current smokers, respectively, independent of age, physical activity, alcohol intake, and body mass index (BMI) (P=0.005). Adjustment for TG and adiponectin significantly attenuated this association (P=0.074).

CONCLUSION

Current smoking was significantly associated with increased intrahepatic fat, which may be a result of adipocyte dysfunction, manifested as high circulating TG concentrations and low adiponectin levels.

Effect of a short-term physical activity intervention on liver fat content in obese children

Nonalcoholic fatty liver disease is the most common chronic liver disease and can present with advanced fibrosis or nonalcoholic steatohepatitis. The purpose of this study was to investigate the effect of a 7-day intense physical activity intervention on liver fat content in children with obesity. Fifty-seven obese children (mean body mass index: 26.5 ± 3.2 kg/m²; mean age: 12.0 ± 0.8 years) participated in a 7-day physical activity program. All participants were housed together, and their food intake and energy expenditure were strictly controlled. Anthropometric measurements, abdominal computerized tomography scans, and blood analyses were conducted at baseline and post-intervention. Participants lost weight by 2.53 ± 0.85 kg on average (61.0 ± 9.8 vs. 58.5 ± 9.5 kg, p < 0.05), fat mass (16.7 ± 5.1 vs. 15.7 ± 4.9 kg, p < 0.05), and serum insulin (13.7 ± 6.7 vs. 3.5 ± 2.0 μU/mL, p < 0.05). However, liver fat content was increased, presented as liver-to-spleen ratio (LSR) where lower LSR represents higher liver fat content. The intervention increased aspartate transaminase level (29.42 ± 6.78 IU/L vs. 33.50 ± 9.60 IU/L, p < 0.001). The change in liver fat content was not associated with the change in fasting insulin and liver enzymes. Short-term intense physical activity increased liver fat content independent of change in fasting insulin level and liver enzymes. This is the first human study to report increased liver fat content after physical activity-induced rapid weight loss.

Association between individual fat depots and cardio-metabolic traits in normal- and overweight children, adolescents and adults

OBJECTIVES

To determine age-related associations between fat mass (FM), regional fat depots and cardiometabolic traits in normal- and overweight children, adolescents and adults.

METHODS

Detailed body composition (regional subcutaneous and visceral adipose tissue; SAT, VAT) by whole-body magnetic resonance imaging (MRI), FM and fat-free mass by air-displacement plethysmography, systolic and diastolic blood pressure (SBP, DBP), triglycerides (TG), high-density lipoprotein cholesterol (HDL), plasma glucose and plasma insulin were measured in 433 subjects (BMI: 23.6 (21.0-27.7); 151 children and adolescents, aged 6-18 years, 150 young adults, aged 18-30 years and 132 adults, aged 30-60 years). Data were derived from pooled data of the 'Reference Center for Body Composition' in Kiel, Germany. Insulin resistance was determined by the homeostatic model assessment of insulin resistance (HOMA-IR). Partial correlations and multivariate linear regression analyses were used to evaluate the associations between body composition and cardiometabolic traits. A descriptive approach was used to demonstrate age-dependent differences in associations between body fat depots and insulin resistance, independent of BMI.

RESULTS

FM, SAT, and VAT increased from childhood to adulthood with low VAT in children and adolescents. When compared to children, TG was higher in adults. HDL and DBP did not differ between age groups. Insulin resistance was highest in male adolescents and female young adults. Associations between body fat depots and cardiometabolic traits were seen after puberty with no associations in pre- and intrapubertal children. When compared to FM, SAT and VAT had the strongest association with insulin resistance in adults. This association was independent of BMI.

CONCLUSIONS

Associations between individual body fat depots and most cardiometabolic traits became evident after puberty only. The strongest associations were observed between insulin resistance and abdominal fat in adults. The impact of VAT was independent of BMI.

Effects of a diet rich in arabinoxylan and resistant starch compared with a diet rich in refined carbohydrates on postprandial metabolism and features of the metabolic syndrome

PURPOSE

Low intake of dietary fibre is associated with the development of type 2 diabetes. Dyslipidaemia plays a key role in the pathogenesis of type 2 diabetes. Knowledge of the impact of dietary fibres on postprandial lipaemia is, however, sparse. This study aimed in subjects with metabolic syndrome to assess the impact on postprandial lipaemia and features of the metabolic syndrome of a healthy carbohydrate diet (HCD) rich in cereal fibre, arabinoxylan and resistant starch compared to a refined-carbohydrate western-style diet (WSD).

METHODS

Nineteen subjects completed the randomised, crossover study with HCD and WCD for 4-week. Postprandial metabolism was evaluated by a meal-challenge test and insulin sensitivity was assessed by HOMA-IR and Matsuda index. Furthermore, fasting cholesterols, serum-fructosamine, circulating inflammatory markers, ambulatory blood pressure and intrahepatic lipid content were measured.

RESULTS

We found no diet effects on postprandial lipaemia. However, there was a significant diet × statin interaction on total cholesterol (P = 0.02) and LDL cholesterol (P = 0.002). HCD decreased total cholesterol (-0.72 mmol/l, 95% CI (-1.29; -0.14) P = 0.03) and LDL cholesterol (-0.61 mmol/l, 95% CI (-0.86; -0.36) P = 0.002) compared with WSD in subjects on but not without statin treatment. We detected no other significant diet effects.

CONCLUSIONS

In subjects with metabolic syndrome on statins a 4-week diet rich in arabinoxylan and resistant starch improved fasting LDL and total cholesterol compared to subjects not being on statins. However, we observed no diet related impact on postprandial lipaemia or features of the metabolic syndrome. The dietary fibre x statin interaction deserves further elucidation.

Microvesicles Correlated with Components of Metabolic Syndrome in Men with Type 2 Diabetes Mellitus and Lowered Testosterone Levels But Were Unaltered by Testosterone Therapy

Aims. To investigate how circulating microvesicle phenotypes correlate with insulin sensitivity, body composition, plasma lipids, and hepatic fat accumulation. We hypothesized that changes elicited by testosterone replacement therapy are reflected in levels of microvesicles. Methods. Thirty-nine type 2 diabetic males with lowered testosterone levels were assigned to either testosterone replacement therapy or placebo and evaluated at baseline and after 24 weeks. Microvesicles were analysed by flow cytometry and defined as lactadherin-binding particles within the 0.1-1.0 μm gate. Microvesicles of platelet, monocyte, and endothelial cell origin were identified by cell-specific markers and their expression of CD36 was investigated. Results. Triglycerides correlated positively with all investigated microvesicle phenotypes in this study (p < 0.05), and indicators of hepatic fat accumulation, alanine aminotransferase, and gamma glutamyltransferase correlated with platelet and endothelial microvesicles and CD36-expressing microvesicles from platelets and monocytes (p < 0.05). BMI, waist circumference, and fat percentage correlated with CD36-expressing monocyte microvesicles (p < 0.05), while insulin sensitivity did not correlate with any microvesicle phenotypes. Microvesicle levels were unaffected by testosterone therapy. Conclusions. Metabolic syndrome components and hepatic fat accumulation correlated with microvesicle phenotypes, supporting the involvement of especially CD36 on monocytes in metabolic syndrome pathogenesis. Although testosterone therapy improved body composition measures, microvesicle phenotype levels were unaffected. This trial was registered at ClinicalTrials.gov (NCT01560546).

Correlation of body muscle/fat ratio with insulin sensitivity using hyperinsulinemic-euglycemic clamp in treatment-naïve type 2 diabetes mellitus

AIMS

Fat deposition and obesity are crucial pathological components of diabetes mellitus (DM). In clinical practice, assessment of insulin resistance is important. We hypothesized that body muscle and fat composition might be a key factor for insulin resistance in patients with type 2 DM.

METHODS

Subjects included 61 untreated DM patients. Hyperinsulinemic-euglycemic clamp examination was performed to calculate the M/I value as the insulin resistance reference indicator. Elementary body composition was measured by impedance analysis using InBody770.

RESULTS

Simple regression analysis showed that total muscle quantity/total fat quantity ratio (muscle/fat) was significantly correlated with M/I value (B=0.806, P<0.001). The regression equation was M/I value=3.6934×(muscle/fat ratio)+0.0347 (R(2)=0.6503, P<0.001). Multivariate logistic regression analysis showed that muscle/fat ratio was independently and significantly associated with insulin resistance, defined by M/I value <9 (odds ratio, 0.89; 95% confidence interval, 0.80-0.99, P=0.04). With receiver operating curve analysis, the cutoff value of muscle/fat ratio for insulin resistance was 2.40 and area under the curve was 0.87 (sensitivity 91% and specificity 76%, P<0.001), indicating that muscle/fat ratio was significantly effective for predicting insulin resistance in treatment-naïve DM. The result could provide a possible estimation of the M/I value using the regression equation M/I value=2.5438×(muscle/fat ratio)+48.6194×QUICKI-13.6522 (R(2)=0.7012).

CONCLUSION

In treatment-naïve DM, the muscle/fat ratio, assessed by InBody770 is clinically useful for evaluating the presence of insulin resistance in daily clinical practice.

Voluntary Exercise Can Ameliorate Insulin Resistance by Reducing iNOS-Mediated S-Nitrosylation of Akt in the Liver in Obese Rats

Voluntary exercise can ameliorate insulin resistance. The underlying mechanism, however, remains to be elucidated. We previously demonstrated that inducible nitric oxide synthase (iNOS) in the liver plays an important role in hepatic insulin resistance in the setting of obesity. In this study, we tried to verify our hypothesis that voluntary exercise improves insulin resistance by reducing the expression of iNOS and subsequent S-nitrosylation of key molecules of glucose metabolism in the liver. Twenty-one Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type 2 diabetes mellitus, and 18 non-diabetic control Long-Evans Tokushima Otsuka (LETO) rats were randomly assigned to a sedentary group or exercise group subjected to voluntary wheel running for 20 weeks. The voluntary exercise significantly reduced the fasting blood glucose and HOMA-IR in the OLETF rats. In addition, the exercise decreased the amount of iNOS mRNA in the liver in the OLETF rats. Moreover, exercise reduced the levels of S-nitrosylated Akt in the liver, which were increased in the OLETF rats, to those observed in the LETO rats. These findings support our hypothesis that voluntary exercise improves insulin resistance, at least partly, by suppressing the iNOS expression and subsequent S-nitrosylation of Akt, a key molecule of the signal transduction pathways in glucose metabolism in the liver.

Hepatic Steatosis as a Marker of Metabolic Dysfunction

Nonalcoholic fatty liver disease (NAFLD) is the liver manifestation of the complex metabolic derangements associated with obesity. NAFLD is characterized by excessive deposition of fat in the liver (steatosis) and develops when hepatic fatty acid availability from plasma and de novo synthesis exceeds hepatic fatty acid disposal by oxidation and triglyceride export. Hepatic steatosis is therefore the biochemical result of an imbalance between complex pathways of lipid metabolism, and is associated with an array of adverse changes in glucose, fatty acid, and lipoprotein metabolism across all tissues of the body. Intrahepatic triglyceride (IHTG) content is therefore a very good marker (and in some cases may be the cause) of the presence and the degree of multiple-organ metabolic dysfunction. These metabolic abnormalities are likely responsible for many cardiometabolic risk factors associated with NAFLD, such as insulin resistance, type 2 diabetes mellitus, and dyslipidemia. Understanding the factors involved in the pathogenesis and pathophysiology of NAFLD will lead to a better understanding of the mechanisms responsible for the metabolic complications of obesity, and hopefully to the discovery of novel effective treatments for their reversal.