Autophagy – the process cells use to break down and recycle damaged proteins and other cellular waste – has often been described as one of the biological systems that weakens with age. A new human study suggests that this picture is too simple: autophagy changes differently depending on the cell type, the person’s sex and their level of physical function.
Published in Aging Cell, the study examined skin cells, laboratory-generated neurons and peripheral blood mononuclear cells from healthy adults aged 23 to 72. Rather than relying only on the activity of autophagy-related genes, the researchers directly measured “autophagy flux,” which reflects the movement of cellular material through the recycling pathway. This distinction was important because gene activity did not reliably indicate how quickly recycling was actually occurring.
The results showed different patterns across cells. Autophagy flux declined with age in skin cells from male participants but remained relatively stable in female skin cells. In induced neurons, it remained stable in males but increased with age in females. In blood immune cells, autophagy did not show a single age-related trend, although it became more variable among older participants and tended to be higher in people around 70 and older.
These findings challenge the idea that increasing autophagy is automatically beneficial. Among adults aged 70 and above, higher autophagy flux across the cell types studied was associated with poorer physical function. In blood cells, it was linked to lower aerobic capacity and slower walking speed; in skin cells, to higher body mass index and lower resting oxygen consumption; and in induced neurons, to lower grip strength and higher resting heart rate. The researchers caution that these are associations, not proof that increased autophagy causes declining fitness.
One possible explanation is that elevated autophagy in older adults may reflect a response to cellular stress or increased demand for waste removal rather than stronger cellular health. In younger people, higher activity may indicate robust recycling capacity, while in older individuals it may signal that cells are compensating for damage or other physiological strain. The study therefore suggests that the meaning of autophagy depends on age and biological context.
The researchers also conducted a small exercise pilot involving five adults aged 77 to 88 who completed a 12-week, mild fall-prevention programme. After the intervention, autophagy flux in blood cells decreased in four participants and moved toward the average observed in a younger healthy-aging cohort. Physical performance scores improved, although many other measures—including grip strength, blood pressure and chair-stand performance—did not change significantly. Because the pilot involved only five people and had no larger comparison group, the findings are preliminary rather than evidence that exercise can directly treat age-related autophagy changes.onlinelibrary.
The study’s broader importance lies in its caution against using a single biological marker as a universal measure of healthy aging. Autophagy-related gene expression, static measurements of cellular structures and direct measurements of recycling activity can tell different stories. The researchers say future studies will need larger groups, longer follow-up and more detailed analysis of individual immune-cell populations, lysosomal function, frailty and cognitive health.
For now, the findings do not show that autophagy is “good” or “bad” in older adults. They show that cellular recycling is a dynamic process whose effects must be interpreted in relation to the cell being studied, the person’s age and sex, and their overall physiological condition. The exercise results offer a promising direction for further research, but they do not yet establish a clinical intervention.
Source: Aging Cell
