Fat-releasing enzyme (HSL)
Hormone-Sensitive Lipase
Also searched as Hormone-Sensitive Lipase.
You want it working. Two things are worth knowing that sound contradictory and are not. First, mice bred without this enzyme are leaner, with less fat and lower blood fatty acids — which looks like an argument against raising it. Second, people born without it are not lean and well: they develop patchy fat loss in the limbs with fatty masses on the trunk, high triglycerides, fatty liver, high blood pressure, retinal deposits, and diabetes. Every one of four such people studied became diabetic, while the mice never do. The reason is that this enzyme has a second job: its products are the fat cell's own growth signal, so losing it starves fat tissue of the signal that keeps it healthy, and sick fat tissue causes diabetes. It also drags the other lipase down with it, because that one is built to order by the same signal. So the honest reading is this: raising this enzyme is about releasing fat on demand and keeping fat tissue healthy — not about having less of it. The people who publish on this propose activating it deliberately.
In depth
The lipase the adrenaline signal actually phosphorylates. It takes the second bond ten times better than the first — and it also manufactures the signal that keeps fat cells healthy.
What drives it
Lipolysis signal increases it.
'PKA, together with phosphorylated PLIN1, promote HSL translocation from the cytosol to the lipid droplet surface, inducing an acute activation of TG hydrolysis in conjunction with ATGL and MGL' (doi 10.3389/fphys.2022.826314). The kinase does two things at once: it switches this lipase on and it moves it to where its substrate is. doi 10.3389/fphys.2022.826314
Energy sensing reduces it.
Two opposite marks on one protein — the cleanest brake in the whole pathway. 'AMPK induces the inhibitory phosphorylation (Ser565) of HSL to impede active Ser563 phosphorylation by PKA, thereby inhibiting PKA-mediated activation of HSL and lipolysis' (doi 10.3389/fphys.2022.826314). The activating site and the blocking site sit two residues apart. And the loop closes on itself: 'AMPK is activated as a consequence of constitutively ongoing reesterification that consumes significant amounts of cellular ATP and generates AMP.' One qualifier, measured in humans. The sign is confirmed: 'AMP-activated protein kinase (AMPK) phosphorylates HSL on Ser565, thereby abolishing PKA-induced HSL activation.' but the magnitude in people is not: 'In human skeletal muscle, changes in AMPK activity during exercise were also associated with an increased HSL Ser565 phosphorylation, but this was not accompanied by an increased HSL activity, suggesting that AMPK can phosphorylate HSL on Ser565 but that AMPK is of minor importance as a regulator of HSL activity in human skeletal muscle during exercise' (pmc2453623). ⇒ the brake is real and may be small in people. Recorded rather than smoothed: the measurement is in muscle, not adipose, so it qualifies without overturning. doi 10.3389/fphys.2022.826314
The cell's go-signal increases it.
10.1017/S0029665109990279 — 'A rise in cAMP activates protein kinase (PK) A, which phosphorylates hormone-sensitive lipase (HSL) and LD-coating protein perilipin (PLIN) to stimulate lipolysis' (Proc Nutr Soc, Regulation of adipose tissue lipolysis revisited). Drawn as the messenger-to-lipase route that runs through the kinase. doi 10.1017/S0029665109990279
Master phosphatase reduces it.
The true off-switch. 'Strictly speaking, cAMP degradation and PKA inactivation do not per SE terminate the lipolytic cascade. Lipolysis cessation ultimately depends on the dephosphorylation of PKA targets such as HSL and perilipin by protein phosphatases' (doi 10.3389/fphys.2022.826314). Measured: 'overexpression of the PP2A regulatory subunit B (B56-alpha) significantly decreased HSL Ser660 phosphorylation... while the knockdown of B56-alpha enhanced hormone-stimulated HSL activation and lipolysis.'. doi 10.3389/fphys.2022.826314
Activated fatty acids reduces it.
'LC-CoAs, most notably OLEOYL-CoA, inhibit HSL and ATGL activity by non-competitive inhibition' (doi 10.3389/fphys.2022.826314). Conditional: 'the inhibitory effect of LC-CoA on HSL activity is dependent on the phosphorylation state of HSL and further enhanced by interactions with acyl-CoA-binding protein.'. doi 10.3389/fphys.2022.826314
The Chaperone reduces it.
'the inhibitory effect of LC-CoA on HSL activity is dependent on the phosphorylation state of HSL and further enhanced by interactions with acyl-CoA-binding protein (ACBP)' (doi 10.3389/fphys.2022.826314). It deepens an existing brake rather than applying its own. doi 10.3389/fphys.2022.826314
Nitric oxide kinase increases it.
The second road reaches the same two targets as the first — including the droplet coat. 'Les peptides natriurétiques stimulent l'activité guanylyl cyclase (GC) du récepteur NPR-A... induisent une augmentation des taux de GMPc, l'activation d'une PROTÉINE kinase G (PKG, cGK-I) puis LA phosphorylation ET L'activation DE LA PÉRILIPINE ET DE LA LHS' (Sengenes, Moro, Galitzky, Berlan, Lafontan — médecine/sciences 2005;21:61-5 — FRANÇAIS). And its power is quantified against the reference stimulant: 'Les peptides natriurétiques exercent UN PUISSANT EFFET LIPOLYTIQUE, leur effet maximal est SIMILAIRE À CELUI DE L'ISOPRÉNALINE.' Proven in living people by microdialysis: 'L'administration d'un β-bloquant NE supprime QUE TRÈS partiellement la mobilization lipidique induite par l'exercice physique alors qu'elle supprime totalement les effets d'un agoniste β-adrénergique... LA mobilization lipidique RÉSISTANT AU β-BLOQUANT EST due AUX peptides NATRIURÉTIQUES.' Blocking the epinephrine road barely dents fat mobilization during exercise, because a second road is carrying it — and under an oral beta-blocker mobilization was paradoxically improved.
The Factory Order increases it.
10.7875/first.author.2011.055 — the transcriptional master of both lipases — found only in the japanese literature. 'IRF4は脂肪細胞におけるおもなリパーゼであるATGLおよびHSLの遺伝子発現を制御することにより脂肪融解を促進し脂質生合成を抑制している' = IRF4 promotes lipolysis and suppresses lipid biosynthesis by controlling the gene expression of ATGL and HSL, the main lipases (ライフサイエンス 新着論文レビュー (first.lifesciencedb.jp/archives/2444)). Proven by deletion: adipocyte-specific IRF4 knockout suppresses lipolysis and causes an increase in whole-body fat mass. Why it matters: other routes switch the lipases on and off by phosphorylation. This one sets how much lipase exists. Drivers that raise lipase expression (theobromine, ashwagandha leaf, Moringa) act on this layer, not the activation layer. doi 10.7875/first.author.2011.055
The Phorbol-Proof Kinase increases it.
A second key that fits the same lock — and a lock the dangerous key cannot turn. 'S1P induced Thr410 phosphorylation of PKC zeta in 3T3-L1 adipocytes and activated recombinant PKC zeta in kinase assays. S1P-mediated lipolysis was dependent on hormone-sensitive lipase and relied mechanistically on PKC zeta activation of MAPK to phosphorylate HSL at Ser660' (PMC11975168 — Intracellular Sphingosine-1-Phosphate Induces Lipolysis Through Direct Activation of Protein Kinase C Zeta). Ser660 is one of the two sites the epinephrine kinase uses. This is a separate road to the same switch. And here is why it is the safe road: the kinase family splits into three groups, and 'atypical aPKCs ARE unresponsive to DAG' — the very site that irritant plant compounds occupy (PMC6465381 — Differential Regulation... via Selective Activation of Protein Kinase C Isozymes). The compound class that causes the harm physically cannot activate this kinase. It is not a safer dose of the same thing; it is a different molecule entirely. In animals the effect is real but was produced by a drug: blocking the enzyme that destroys this messenger 'reduced white gonadal adipose tissue mass and diminished adipocyte size... and increased free fatty acid in plasma' — using a vitamin-B6 antagonist, which is not a food and carries its own problems. The route is proven; a safe botanical key for it is not yet identified. PMC11975168
Lipase switch-on increases it.
The switch-on step, and the species trap underneath it. Almost all published site numbers come from rodent studies, and the numbering does not carry across: 'in vitro phosphorylation of human HSL by PKA occurs primarily on Ser649 and Ser650 (Ser659 and Ser660 in rat HSL)' (doi 10.1371/journal.pone.0003756 (pmc2582450) — Ser649 and Ser650 Are the Major Determinants of PKA-Mediated Activation of human Hormone-Sensitive Lipase). ⇒ a residue number quoted from a mouse experiment is not the same residue in a person, and the major human site is not the one most often quoted. This does not make the animal work wrong — it means the site-level precision it offers does not transfer without translation. doi 10.1371/journal.pone.0003756
What it drives
It increases Releases stored fat.
'hormone-sensitive lipase appears as the major lipase for catecholamine and natriuretic peptide-stimulated lipolysis whereas adipose triglyceride lipase mediates the hydrolysis of triglycerides during basal lipolysis' (doi 10.1016/j.biopha.2006.02.005). The human consequence of losing it is recorded: 'HSL deficiency in human patients results in impaired adipocyte development and high plasma lipid levels which eventually leads to ectopic lipid accumulation and insulin resistance' (doi 10.3389/fphys.2022.826314). My node card called this 'the second cut'. That is incomplete. 'ATGL and HSL both have the capacity to initiate TG degradation by cleaving the first ester bond, but HSL is unique in its capacity to break down the second ester bond, converting diglycerides to monoglycerides' (doi 10.1074/jbc.M109.008631 [PMC2709346]). ⇒ HSL can do both cuts; it is the only one that can do the second. And a defect in the target population that changes the product's premise: 'It is well known that expression of HSL is markedly decreased in subcutaneous adipocytes and differentiated adipocytes from obese subjects. This suggests that, at least in adipose tissue, a decreased HSL expression is a primary defect in obesity' (PMC2453623). The enzyme itself is depleted in the people this product is for — which is why the drivers that raise HSL mRNA and protein, rather than only phosphorylating what is there, matter more than they first appeared. doi 10.1016/j.biopha.2006.02.005 · PMC2709346
It increases Final fat cut.
'ATGL, considered the rate-limiting enzyme, catalyzes the first step, hydrolyzing TGs to diglycerides, which in turn are degraded by HSL into monoglycerides, with the release of a FFA in each step' (doi 10.3389/fphys.2022.826314) — the second lipase hands its product to the third. doi 10.3389/fphys.2022.826314
It increases Blocks new fat cells.
This lipase does a second job nobody expects: it manufactures the fat cell's own growth signal. In humans carrying a homozygous lipe deletion that removes the protein entirely: 'Although a defect in an enzyme that is critical for lipolysis would be expected to result in excess lipid storage, we observed the opposite, providing evidence that HSL plays a key role in maintaining adipogenesis and adipocyte function... These findings are consistent with the hypothesis that HSL deficiency in humans results in decreased production of endogenous ligands for PPAR-gamma, RXR-alpha, OR both' (doi 10.1056/NEJMoa1315496 (nejm)). And the authors draw the therapeutic conclusion themselves: 'Our results suggest that activation of HSL with consequent generation of endogenous ligands' is a route worth taking — in the same paper, in the same breath as noting that direct PPAR-gamma agonists 'can have untoward side effects'. doi 10.1056/NEJMoa1315496
It increases Fat-cell formation↓.
This lipase does a second job nobody expects: it manufactures the fat cell's own growth signal. In humans carrying a homozygous lipe deletion that removes the protein entirely: 'Although a defect in an enzyme that is critical for lipolysis would be expected to result in excess lipid storage, we observed the opposite, providing evidence that HSL plays a key role in maintaining adipogenesis and adipocyte function... These findings are consistent with the hypothesis that HSL deficiency in humans results in decreased production of endogenous ligands for PPAR-gamma, RXR-alpha, OR both' (doi 10.1056/NEJMoa1315496 (nejm)). And the authors draw the therapeutic conclusion themselves: 'Our results suggest that activation of HSL with consequent generation of endogenous ligands' is a route worth taking — in the same paper, in the same breath as noting that direct PPAR-gamma agonists 'can have untoward side effects'. doi 10.1056/NEJMoa1315496
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.