Association between neck circumference and non-alcoholic fatty liver disease: cross-sectional analysis from ELSA-Brasil

The value of neck adipose tissue as a predictor for metabolic risk in health and type 2 diabetes

Upper-body adiposity is adversely associated with metabolic health whereas the opposite is observed for the lower-body. The neck is a unique upper-body fat depot in adult humans, housing thermogenic brown adipose tissue (BAT), which is increasingly recognised to influence whole-body metabolic health. Loss of BAT, concurrent with replacement by white adipose tissue (WAT), may contribute to metabolic disease, and specific accumulation of neck fat is seen in certain conditions accompanied by adverse metabolic consequences. Yet, few studies have investigated the relationships between neck fat mass (NFM) and cardiometabolic risk, and the influence of sex and metabolic status. Typically, neck circumference (NC) is used as a proxy for neck fat, without considering other determinants of NC, including variability in neck lean mass. In this study we develop and validate novel methods to quantify NFM using dual x-ray absorptiometry (DEXA) imaging, and subsequently investigate the associations of NFM with metabolic biomarkers across approximately 7000 subjects from the Oxford BioBank. NFM correlated with systemic insulin resistance (Homeostatic Model Assessment for Insulin Resistance; HOMA-IR), low-grade inflammation (plasma high-sensitivity C-Reactive Protein; hsCRP), and metabolic markers of adipose tissue function (plasma triglycerides and non-esterified fatty acids; NEFA). NFM was higher in men than women, higher in type 2 diabetes mellitus compared with non-diabetes, after adjustment for total body fat, and also associated with overall cardiovascular disease risk (calculated QRISK3 score). This study describes the development of methods for accurate determination of NFM at scale and suggests a specific relationship between NFM and adverse metabolic health.

Predictive factors to estimate the severity of nonalcoholic fatty liver disease in candidates for Roux-en-Y gastric bypass

OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) is related to obesity, insulin resistance, dyslipidemia, and metabolic syndrome. The increasing prevalence of NAFLD results in a significant number of patients manifesting chronic liver disease over time. The aim of this study was to analyze the predictive factors to estimate NAFLD severity in patients who are candidates for Roux-en-Y gastric bypass.

METHODS

This descriptive observational study was conducted with 136 obese patients who were candidates for Roux-en-Y gastric bypass and had mild, moderate, or severe NAFLD.

RESULTS

Severe NAFLD was more prevalent among the men (P = 0.007), and mild NAFLD was more prevalent among the women (P = 0.007). Hyperferritinemia was observed in the group with severe NAFLD (P = 0.01). Neck circumference and waist-to-height ratio were associated with an increased risk when comparing the groups with mild and severe NAFLD and those with moderate and severe NAFLD (P = 0.023 and P = 0.001, respectively); the alanine aminotransferase (ALT) and aspartate aminotransferase ratio values were >1 (P = 0.002) in the same comparisons. The regression analyses showed that an increase of 1 ng/mL in vitamin D reduced the chances of severe steatosis by 10% (P = 0.043), and an increase of 1 U/L ALT increased the chances of severe steatosis by 13% (P = 0.002).

CONCLUSION

High neck circumference and low waist-to-height ratio values, male sex, hyperferritinemia, increased serum ALT values, and decreased vitamin D levels were related to the risk for severe NAFLD.

Association of neck circumference-related indices with metabolic, atherogenic and liver function biomarkers in patients with non-alcoholic fatty liver disease: a cross-sectional study

OBJECTIVE

The present study aimed to establish the association of neck circumference (NC)-related indices with metabolic, atherogenic and liver function biomarkers in patients with non-alcoholic fatty liver disease (NAFLD).

DESIGN

Cross-sectional study.

SETTING

Outpatient clinics of Tabriz University of Medical Sciences.

PARTICIPANTS

A total of 175 adult patients with NAFLD diagnosed by abdominal ultrasonography were included in this study. Sociodemographic characteristics, anthropometric measures and metabolic, atherogenic and liver function biomarkers were assessed.

RESULTS

Results on 107 women and 68 men with NAFLD showed that 52%, 45.1% and 2.9% of patients had mild, moderate and severe NAFLD, respectively. There were significant differences in most of the anthropometric indices, serum levels of ferritin, creatinine and uric acid as well as liver enzymes, and Aspartate Aminotransferase (AST) to Platelet Ratio Index (APRI) between the genders (p<0.01). However, no significant differences were found in the glycaemic, lipid profile and atherogenic biomarkers. Both NC and neck-to-height ratio (NHtR) were significantly associated with body mass index (BMI) (p=0.018, p<0.001, respectively), waist circumference (WC) (p<0.001, p=0.044, respectively) and waist-to-hip ratio (WHR) (p<0.001, p=0.026, respectively) while results showed only a significant relationship between neck-to-waist ratio (NWR) with BMI (p<0.001) and WC (p<0.001). Among metabolic factors, there were significant and positive correlations between NC and serum haemoglobin A1c (r=0.198, p<0.001), AST (r=0.300, p<0.001), alanine aminotransferase (ALT) (r=0.348, p<0.001), ferritin (r=0.403, p<0.001) and uric acid (r=0.347, p=0.003) while AST/ALT ratio was inversely related to NC (r=-0.226, p=0.003). APRI, Lipid Accumulation Product Index and also Hepatic Steatosis Index were significantly correlated with NC, NHtR and NWR (p<0.01).

CONCLUSIONS AND RELEVANCE

NC-related indices, particularly NC and NHtR, were correlated with some metabolic and liver function biomarkers (apart from lipid profile and atherogenic factors) in patients with NAFLD.