Popular Conclusion:
1. Zinc-metalloenzymes play an important role in many aspects of cellular metabolism including DNA replication, repair and transcription.Depending on which zinc enzymes are "overvulnerable", zinc deficiency may result in accumulation of useless (or toxic) materials, malproduction of essential proteins, a neoplastic change or cell death, thus explaining the variability in aging patterns in different cell types.
2. The zinc-deficient rats in both dietary fat groups had lower levels of linoleic acid, arachidonic acid and total (n-6) fatty acids in the liver phospholipids, especially in the phosphatidylcholine, but greater concentrations of (n-3) fatty acids compared with zinc-adequate controls.
3. In general, zinc enhanced capping of lymphocytes from young individuals and suppressed from those of old individuals.
4. Cellular aging is accompanied by increased cellular permeability to zinc(II). In terms of growth inhibition, Zn(II) is more toxic to the cell than Cu(II), Mn(II), or Mg(II).
5. Dietary zinc deficiency appears to be responsible, at least in part, for the immunodeficiency that is so regularly associated with certain human cancers, such as epidermoid cancers of the head and neck region.
6. ...zinc deficiency may have a serious consequence on the oral mucosa in its tolerance...
7. Significant decrease in serum zinc concentration with advancing age were obtained in both male and female subjects.
8. ...the absence of relationship between plasma zinc and epidermal zinc. The decrease of epidermal zinc concentrations observed in elderly subjects might be due to a decrease of enzyme activities in the epidermis induced by aging; conversely, a low epidermal zinc level might induce, by itself, a fall in enzyme activities. Thus, zinc might play an important role in the development of alterations in keratinocytes with aging...
9. Zinc concentrations in the heart and lung decreased significantly with age.
10. During basal state, zinc release from red blood cells decreased with age. During zinc loading, response (defined as change from basal state) of plasma zinc concentration, urinary zinc excretion, and liver zinc increased with age, while response of fraction of zinc taken up by red blood cells decreased with age.
11. Zinc-metalloenzymes play an important role in many aspects of cellular metabolism including DNA replication, repair and transcription. 12. Cellular aging is accompanied by increased cellular permeability to zinc(II). The intrinsic zinc content of human diploid fibroblast cells increases with cell age, so that it quadruples from early to late passage, on a Zn(II) per cell or per cell volume basis, but it remains constant on a Zn(II) per protein basis. When the cells are challenged with toxic concentrations (0.2 mM) of Zn(II), both the rate of zinc incorporation into the cells and the amount of zinc incorporated at equilibrium increases considerably with age (unless measured as zinc per protein). In terms of growth inhibition, Zn(II) is more toxic to the cell than Cu(II), Mn(II), or Mg(II).
"...zinc is an essential element for growth, development and functioning
of all living cells... Zinc essentiality and the lack of a reliable index
of intracellular zinc status, formed the rationale for the zinc deficiency
hypothesis of aging. This hypothesis suggests a gradual time related zinc
deficiency occurring in each living cell, making zinc less available for
its metalloenzymes. The sum of all deleterious effects resulting from the
distorted function of different zinc enzymes, is later manifested as aging
processes. ... zinc concentration in various tissues decreases. Cadmium
may inhibit zinc activities at many stages, interfering with zinc absorption,
distribution to different tissues and transport into cells or into several
intracellular structures. Therefore, it is reasonable to assume that a
slowly developing cadmium toxicity may result in a gradual time related
zinc deficiency." (
Med Hypotheses 1994 Jun;42(6):380-4: Bin QH; Garfinkel D
The cadmium toxicity hypothesis of aging: a possible explanation for
the zinc deficiency hypothesis of aging.)
" Zinc is needed for growth and development, DNA synthesis, neurosensory
functions, and cell-mediated immunity. Their mean dietary zinc intake was
9.06 mg/day, whereas the recommended dietary allowance is 15 mg/day. Zinc
supplementation corrected zinc deficiency and normalized plasma copper
levels. Serum thymulin activity, IL-1 production, and lymphocyte ecto-5'-nucleotidase
increased significantly after supplementation. Improvement in response
to skin-test antigens and taste acuity was observed after zinc supplementation.
A mild zinc deficiency appears to be a significant clinical problem in
free-living elderly people." (
Nutrition 1993 May-Jun;9(3):218-24: Prasad AS; Fitzgerald JT;
Hess JW; Kaplan J; Pelen F; Dardenne M
Zinc deficiency in elderly patients.)
