Muscle, liver and appetite
The names share a conversation. Their measurements need separate columns.
Where the experiments looked
| Place | Finding | How it was studied |
|---|---|---|
| Muscle and fat | MOTS-c increased CK2 activity in muscle and suppressed it in fat | Cell-free assays and mice; muscle glucose uptake and atrophy outcomes |
| Liver | Retatrutide reduced liver fat | MRI in adults with overweight or obesity and MASLD, without type 2 diabetes |
| Appetite circuits | Semaglutide reduced intake and changed food preference | Rodent experiments involving brainstem and hypothalamic pathways |
The CK2 split gives this comparison a starting point because the tissue changes the direction of the response. The other rows ask different questions: how much fat is inside a liver, or how a medicine changes eating through neural pathways. Ranking these effects would require a shared unit that the studies never supply.
Liver fat and body weight
The retatrutide liver substudy reported a relative liver-fat change of -82.4% at 24 weeks in its highest-dose group. The separate obesity trial reported a mean body-weight change of -24.2% at 48 weeks at that trial dose. The MRI result and the body-weight result have different starting measurements, populations and time points.
Semaglutide also has whole-body weight findings. For a direct comparison, the 72-week trial of 751 adults with obesity reported mean weight change of -13.7% with semaglutide and -20.2% with tirzepatide. Retatrutide was absent from that trial. I’d resist adding its separate Phase 2 figure to the podium.
Clinical standing
| Compound | Human evidence here | Access and approval |
|---|---|---|
| MOTS-c | A dialysis biomarker cohort, alongside mouse and cell work; no completed human efficacy or safety trial of exogenous MOTS-c | No FDA approval. Research-labelled material and clinician-assessed compounded prescription care are distinct. |
| Retatrutide | Phase 2 obesity, diabetes and liver-fat studies | Investigational without FDA approval; Phase 3 studies ongoing. |
| Semaglutide | Weight, cardiovascular and kidney outcome trials | FDA-approved medicines exist. Separately compounded preparations have no FDA approval. |
A question for each place
For MOTS-c, I’m waiting for reproducible human evidence that reaches beyond a circulating biomarker. For retatrutide, the liver-fat finding leaves inflammation, scarring and long-term illness worth following. For semaglutide, human benefits already exist alongside the work of explaining how different tissues contribute.
A location can sharpen a question. It cannot choose treatment for an individual. The frequently asked questions cover the practical limits of what these papers establish.