Non-alcoholic fatty liver disease connections with fat-free tissues: A focus on bone and skeletal muscle

Table 2 Studies exploring the association between non-alcoholic fatty liver disease and skeletal muscle mass

Ref.	Study population and sample size	Race/ethnicity	NAFLD assessment	Skeletal muscle mass assessment	Main findings: skeletal muscle
Hong et al[6], 2014	Men (n = 32) and women (n = 96) with sarcopenia vs men (n = 135) and women (n = 189) without sarcopenia	Korean	LAI	DXA:	Increased ORs of NAFLD in individuals with SMI value in the lower quartiles
				-SMI = SMM/weight (%)
Koo et al[25], 2016	Adults with NAFLD (n = 117) vs adults with NASH (n = 123) vs controls (n = 69)	Korean	Liver biopsy, Fibroscan	BIA:	Lower ASM (%) and ASM/BMI in NAFLD and NASH than controls; higher prevalence of sarcopenia in NAFLD and NASH groups than control group
				-ASM (kg)
				-ASM/weight (%)
				-ASM/BMI
Lee et al[26], 2015	Men (n = 5617) and women (n = 9515) divided into four groups: sarcopenic obese (n = 2455) vs non-sarcopenic obese subjects (n = 2198); sarcopenic non-obese (n = 2004) vs non-sarcopenic non-obese subjects (n = 8475)	Korean	For NAFLD: HSI, CNS	DXA:	Inverse correlation between all indices of NAFLD and SMI
			For fibrosis: BARD, FIB-4	-ASMI = ASM/weight (%)	Increased ORs of NAFLD and advanced fibrosis in subjects with sarcopenia
Hashimoto et al[27], 2016	Diabetic men with NAFLD (n = 58) vs controls (n = 21), and diabetic women with NAFLD (n = 39) vs controls (n = 27)	Japanese	CAP	BIA:	Negative association between CAP and SMI in men; no significant association in women
			FIB-4	-SMM (kg)
				-SMI = SMM/weight (%)
Moon et al[28], 2013	Low FLI group (men = 1641, and women, n = 1180) vs intermediate FLI group (men, n = 2600, and women, n = 2296) vs high FLI group (men, n = 1052, and women, n = 796)	Korean	FLI	BIA:	Lower SMI in the high FLI group and the intermediate FLI group than the low FLI group. Negative correlation between FLI and SMI, and between FLI and SVR. The highest SVR quartile had a lower OR for FLI ≥ 60
				-SMI = SMM/weight (%)
				-SVR = SMM/VFA
Kim et al[29], 2016	FLI ≥ 60 group (men, n = 208, and women, n = 181) vs FLI < 60 group (men, n = 976, and women, n = 2374)	Korean	FLI	DXA:	Lower SMI in the high FLI group than the low FLI group in both genders. Increased ORs for FLI-defined NAFLD in men and women with low SMI
				-ASM (kg)
				-SMI = ASM/weight (%)
Lee et al[30], 2016	Men (n = 1241) and women (n = 1520) with NFLS-based NAFLD divided into two groups: sarcopenic subjects (n = 337) v. non-sarcopenic subjects (n = 2424)	Korean	For NAFLD: NLFS, CNS,HSI;	DXA:	Higher NFS, FIB-4, and Forns index in the sarcopenic group that the non-sarcopenic group; negative association of SI with NFS, FIB-4, and Forns index
			For fibrosis: NFS, FIB-4, Forns index	-SI = ASM/BMI
Poggiogalle et al[31], 2016	Obese men (n = 81) and women (n = 346) divided into 2 groups: FLI 20 ≤ FLI < 60 (n = 61) and FLI ≥ 60 (n = 359) (FLI ≤ 20 in 7 subjects only, excluded from the analysis)	Caucasian (Italian)	FLI	DXA:	Positive association between FLI and TrFM/ASM ratio (indicating high visceral adiposity and low appendicular muscularity)
				-TrFM/ASM ratio

ASM: Appendicular skeletal mass; ASMI: Appendicular skeletal mass index; BMI: Body mass index; CAP: Controlled attenuation parameter; CNS: Comprehensive NAFLD score; CT: Computed tomography; FLI: Fatty liver index; HIS: Hepatic steatosis index; LAI: Liver attenuation index; NAFLD: Non-alcoholic fatty liver disease; NASH: Nonalcoholic steatohepatitis; NFS: NAFLD fibrosis score; SI: Sarcopenia index; NLFS: NAFLD liver fat score; SMI: Skeletal muscle index; SMM: Skeletal muscle mass; SVR: Skeletal muscle to visceral fat ratio; TrFM: Truncal fat mass; VFA: Visceral fat area.