APOA5 and obesity due to melanocortin 4 receptor deficiency: Secondary HTG is usually caused by metabolic syndrome, diabetes, alcohol consumption, obesity, chronic renal failure, etc. [9] Primary HTG is caused by genes defects related with TG metabolism, including lipoprotein lipase (LPL), apolipoprotein C-II (APOC2), apolipoprotein A-V (APOA5), glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) and lipase maturation factor 1 (LMF1).