Table 5.
Relationships between liver and muscle fat content and FCS, insulin resistance, and adipogenesis
| Findings | FCS-liver fat corr. | FCS-muscle fat corr. | AT | N | Age | Sex | BMI | T2D | Ref. |
|---|---|---|---|---|---|---|---|---|---|
| Histology assessment of ectopic lipid content | |||||||||
| • Visceral FCS correlated with: liver injury (ALT, AST) and NAS severity (histology) | ↑ | NA | Vis. | 93 | 43 | 72 W | 52 | Unk. | (43) |
| HS | |||||||||
| • Visceral and SC FCS correlated with degree of hepatic steatosis | ↑ | NA | Abd. | 35 | 41.8 | 25 W | 49.5 | 6 | (89) |
| • Visceral FCS: predictor of liver fibrosis | HS and CD | ||||||||
| • Visceral FCS correlated with Pref-1 expression, which correlated with degree of hepatic steatosis | ↑ (?) | NA | Abd. | 29 | 42.3 | 20 W | 48.6 | Unk. | (11) |
| HS and CD | |||||||||
| Proton magnetic resonance spectroscopy assessment of ectopic lipid content | |||||||||
| • Compared to individuals with IS, individuals with IR have ↑ VAT and intrahepatic lipid | ↑ | NA | Abd. | 31 | 30-60 | 15 W | 25-35 | 0 | (127) |
| • Δ peak diameter predicted Δ intrahepatic lipid with overfeeding | OF | Mean ≈ 56 | Mean ≈ 30 | ||||||
| • FCS correlated with serum leptin, which correlated with liver fat | ↑ (?) | NA | Abd. | 34 | 24-27 | 16 W | Mean ≈ 26.8 | 0 | (29) |
| • The co-twins who was heavier had ↑ SAT, ↑ FCS, and ↑ liver fat | CD | ||||||||
| • Liver fat correlated with serum insulin | |||||||||
| • Co-twins with hypoplastic obesity: ↑ liver fat | ↑ | NA | Abd. | 40 | 28.4 | 30 W | 28 | 0 | (44) |
| • Co-twins with hypertrophic obesity: ↓ fat cell number, ↑ liver fat | CD | ||||||||
| • Δ FCS: not correlated with Δ liver fat | |||||||||
| • FCS explained 21% of liver fat variation | ↑ | NA | Abd. | 119 | 40 | 83 W | 30 | 0 | (196) |
| CD | |||||||||
| • FCS: correlated with VAT and liver fat, but not muscle fat | ↑ | — | Abd. | 46 | 37.5 | Unk. | 25-30 | 0 | (126) |
| OF | Mixed. | Mean ≈ 27.7 | |||||||
| • Participants of South Asian descent have more liver fat than those of Caucasian descent. Adjustment for FCS and fat distribution decreased the difference in liver fat | ↑ (?) | NA | Abd. | 108 | 35.5 | Unk. | Mean ≈ 27.5 | 0 | (197) |
| HS | Mixed. | ||||||||
| • No correlation between FCS and liver fat | — | NA | Abd. | 27 | 61 | 9 W | 31.4 | 27 | (199) |
| • AT adiponectin correlated negatively with liver fat | HS | ||||||||
| • Liver fat: correlated with crown-like structures and macrophages in SCAT, correlated with PAI-1 | |||||||||
| • In high visceral fat group: ↑ hepatic fat | NA | NA | Abd. | 38 | 15.1 | 14 W | 36.8 | Unk. | (124) |
| OF | |||||||||
| • FCS is not correlated with hepatic, muscle, or visceral fat | — | — | Abd. | 75 | 26.8 | 37 W | 22.9 | 0 | (123) |
| OF | |||||||||
| • No association between FCS and liver or muscle fat | — | — | Abd. | 29 | 26.8 | 0 W | 25.5 | 0 | (198) |
| OF | |||||||||
| • No difference in liver fat between T2D and control | NA | NA | Abd. | 30 | 58 | 10 W | 30.8 | 15 | (165) |
| CD | |||||||||
| • FCS: positively correlated with liver fat, but not muscle fat | ↑ | — | Abd. | 53 | 25.8 | 21 W | 35.4 | 0 | (64) |
| CD | |||||||||
| • FCS: positively correlated with liver lipids | ↑ | — | Abd. | 53 | 42 | 0 W | Unk. | 0 | (225) |
| CD | |||||||||
| CT assessment of ectopic lipid content | |||||||||
| • In high liver fat group: ↑ CD68, chemokines monocyte chemoattractant protein-1, and PAI-1, ↓ PPAR-γ and adiponectin | NA | NA | SC | 20 | Mean ≈ 40.5 | 20 W | Mean ≈ 36 | 0 | (226) |
| CD | |||||||||
| • In individuals with T2D: ↑ liver fat, ↑ muscle fat | ↑ (?) | ↑ (?) | Abd. | 102 | 58 | 59 W | Mean ≈ 33.6 | 67 | (125) |
| OF | |||||||||
| • Women with higher proportions of visceral fat have higher fat accumulation in the muscle | NA | ↑ (?) | Abd., g. | 48 | Mean ≈ 60 | 48 W | Mean ≈ 31.5 | 0 | (107) |
| CD | |||||||||
| • Liver fat: associated with IL-6 and number of macrophages in SCAT | NA | NA | Abd. | 36 | 37 | 17 W | 26 | 0 | (227) |
| HS |
Abbreviations: ↑ (in first column), increase in; ↓ (in first column): decrease in; ↑ (in second and third columns, positive correlation; Δ, change in; abd., abdominal subcutaneous; AT, adipose tissue assessment; BMI, body-mass index; CD, collagenase digestion; corr., correlation; CT, computed-tomography; FCS, fat cell size; HS, histological section; IR, insulin resistant; IS, insulin sensitive; N, number of participants; NA, not applicable or not reported; NAS, nonalcoholic steatosis; OF, osmium fixation; Ref., reference number; SAT, subcutaneous adipose tissue; Sex, number of women; T2D, type 2 diabetes; Unk., unknown; VAT, visceral adipose tissue; W, women.