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Figure 1. Hypertrophic adipose tissue is more prone to macrophage infiltration leading to
adipokine release, inflammation, impaired lipolysis and lipogenesis. This results in ectopic
fat accumulation and lipotoxicity in various organs. Adapted from Morelli et al. [5].
Excessive fat may accumulate not only in adipocytes but also inside other organs as ectopic fat. The
liver is one of the sites where ectopic fat accumulates, thus determining NAFLD. Other sites include
the pancreas, muscle (extra- or intra-myocellular triglycerides) and heart (intramyocardial triglycerides)
[4]. Ectopic fat causes lipotoxicity, organ damage and metabolic dysfunction, often increasing the risk
of T2DM (Fig. 1).
Metabolically healthy obese (MHO), i.e. fat and fit
Not all obese subjects are insulin resistant and/or develop NAFLD. This category has been named
MHO. Their cardiometabolic risk is not as high as expected, probably because their SAT is able to
expand and to capture excess fat as has been shown in overfeeding studies [6]. It has been suggested that
MHO subjects do not significantly benefit from weight loss and lifestyle changes to the same extent as
obese patients with metabolic co-morbidities. During over-feeding these subjects are able to store excess
fat in SAT, while insulin resistant subjects tend to accumulate fat in other sites including visceral and
ectopic fat. Lipid storage is regulated by the genes DGAT2, SREBP1c, and CIDEA expressed in SAT.
In subjects that respond to overfeeding by increasing VAT, the expression of these genes is reduced [5].
For this reason, subjects with increased SAT, but low VAT are at lower risk of cardiometabolic diseases
including NAFLD [4, 5].
Adiposopathy and risk of NAFLD/NASH
The release of adipokines is limited in small adipocytes. Adipocyte dysfunction appears when they
become hypertrophic and are infiltrated by macrophages, promoting inflammation and the release of
pro-inflammatory adipokines [5, 6] (Fig. 1). This phenomenon is called adiposopathy (‘sick fat’) [6].
42 Postgraduate Course Syllabus • Metabolic Liver Disease
adipokine release, inflammation, impaired lipolysis and lipogenesis. This results in ectopic
fat accumulation and lipotoxicity in various organs. Adapted from Morelli et al. [5].
Excessive fat may accumulate not only in adipocytes but also inside other organs as ectopic fat. The
liver is one of the sites where ectopic fat accumulates, thus determining NAFLD. Other sites include
the pancreas, muscle (extra- or intra-myocellular triglycerides) and heart (intramyocardial triglycerides)
[4]. Ectopic fat causes lipotoxicity, organ damage and metabolic dysfunction, often increasing the risk
of T2DM (Fig. 1).
Metabolically healthy obese (MHO), i.e. fat and fit
Not all obese subjects are insulin resistant and/or develop NAFLD. This category has been named
MHO. Their cardiometabolic risk is not as high as expected, probably because their SAT is able to
expand and to capture excess fat as has been shown in overfeeding studies [6]. It has been suggested that
MHO subjects do not significantly benefit from weight loss and lifestyle changes to the same extent as
obese patients with metabolic co-morbidities. During over-feeding these subjects are able to store excess
fat in SAT, while insulin resistant subjects tend to accumulate fat in other sites including visceral and
ectopic fat. Lipid storage is regulated by the genes DGAT2, SREBP1c, and CIDEA expressed in SAT.
In subjects that respond to overfeeding by increasing VAT, the expression of these genes is reduced [5].
For this reason, subjects with increased SAT, but low VAT are at lower risk of cardiometabolic diseases
including NAFLD [4, 5].
Adiposopathy and risk of NAFLD/NASH
The release of adipokines is limited in small adipocytes. Adipocyte dysfunction appears when they
become hypertrophic and are infiltrated by macrophages, promoting inflammation and the release of
pro-inflammatory adipokines [5, 6] (Fig. 1). This phenomenon is called adiposopathy (‘sick fat’) [6].
42 Postgraduate Course Syllabus • Metabolic Liver Disease
