The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 16 No. 9 • October 2013


Cardiovascular Protection

Lipid Accumulation in Vascular Endothelial Cells Induced by Palmitate, a Saturated Fatty Acid, Markedly Reduced by Green Tea Polyphenol EGCG

A new paper1 reports another potentially important beneficial effect of the major polyphenol in green tea, epigallocatechin gallate (EGCG). EGCG is shown to stimulate autophagy (a form of self-disassembly or “self-eating” that is required to maintain homeostasis) that degrades lipid droplets induced by palmitate in primary bovine aortic endothelial cells (BAEC). The accumulation of lipids in vascular endothelial cells is a major part of the process promoting atherosclerosis.

A large epidemiological study in Japan2 with an 11-year followup reported in a 2006 paper that green tea consumption was associated with reduced mortality due to cardiovascular disease but not with mortality due to cancer.

In the new study, the authors investigated whether EGCG could normalize the palmitate impairment of autophagy flux that prevents lipid accumulation in vascular endothelial cells by degrading lipid droplets and, if so, to identify the mechanism for this action. As the authors describe their findings:

“Excess intake of lipid causes obesity and ectopic lipid accumulation, which is implicated as one of the causes for cardiometabolic syndrome. Fatty acid overload increases intracellular lipid droplets, and the presence of lipid droplets in non-adipose tissue [such as muscle] plays a role in various pathophysiologies.” Their experimental results suggest, the authors say, that “the effect of EGCG in reduction of lipid droplets is mainly dependent on degradation but not inhibition of formation. These results suggest that EGCG decreases accumulation of lipid droplets through facilitation of lysosomal degradation, which may contribute to prevention of lipotoxicity [toxicity to cells by fatty acid overload] in vascular endothelial cells.”

Intensive investigation of possible mechanisms led the authors to conclude that EGCG induces autophagy through a CA2+/CaMKKbeta/AMPK mediated mechanism, which reduced palmitate-induced accumulation of lipid droplets in endothelial cells. Autophagy is a major mechanism by which old organelles (such as mitochondria) and damaged molecular debris are degraded and the basic components made available for reuse. It is also a way to regulate the turnover of supplies of resources for more efficient use. In the case of lipids, autophagy may have “important implications for human diseases with lipid over-accumulation such as those that comprise the metabolic syndrome.”4 “Decreased autophagy in the liver with ageing may contribute to hepatic [liver] lipid accumulation that occurs along with an increased incidence of the metabolic syndrome in aged humans.”4

Earlier papers that led up to this new paper1 include references #2 and #3 listed below, where two scientific groups reported an inhibitory effect of EGCG on lipid accumulation in adipocytes (fat cells). The new findings explain how autophagy plays a key role in EGCG inhibition of lipid accumulation in vascular cells which links the EGCG protection to a reduced risk of cardiovascular disease, whereas the two earlier papers reported that EGCG decreased lipid accumulation in adipocytes (fat cells), which is particularly associated with reduction of the risk of metabolic syndrome that includes obesity and insulin resistance.

Whichever way you look at it, EGCG has become something of a phenomenon if you want to maintain a healthier life (healthspan) for longer. It has earned a place as a basic component for your cabinet of medical supplies. Don’t leave home without it!

References

  1. Kim et al. Epigallocatechin gallate stimulates autophagy in vascular endothelial cells: a potential role for reducing lipid accumulation. J Biol Chem. 288:22693-705 (2013).
  2. Moon et al. Inhibitory effect of (-)-epigallocatechin-3-gallate on lipid accumulation of 3T3-L1 cells. Obesity. 15(11):2571-82 (2007).
  3. Lee et al. Inhibitory effects of green tea catechin on the lipid accumulation in 3T3-L1 adipocytes. Phytother Res. 23:1088-91 (2009).
  4. Singh et al. Autophagy regulates lipid metabolism. Nature. 458:1131-5 (2009).

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