Alaskan wild berry resources and human health under the cloud of climate change

Abstract

Wild berries are integral dietary components for Alaska Native people and a rich source of polyphenolic metabolites that can ameliorate metabolic disorders such as obesity and diabetes. In this study, five species of wild Alaskan berries (Vaccinium ovalifolium , Vaccinium uliginosum , Rubus chamaemorus , Rubus spectabilis , and Empetrum nigrum) were screened for bioactivity through a community-participatory research method involving three geographically distinct tribal communities. Compositional analysis by HPLC and LC-MS(2) revealed substantial site-specific variation in anthocyanins (0.01-4.39 mg/g of FW) and proanthocyanidins (0.74-6.25 mg/g of FW) and identified A-type proanthocyanidin polymers. R. spectabilis increased expression levels of preadipocyte factor 1 (182%), and proanthocyanidin-enriched fractions from other species reduced lipid accumulation in 3T3-L1 adipocytes. Selected extracts reduced serum glucose levels in C57BL/6J mice by up to 45%. Local observations provided robust insights into effects of climatic fluctuations on berry abundance and quality, and preliminary site-specific compositional and bioactivity differences were noted, suggesting the need to monitor this Alaska Native resource as climate shifts affect the region.

Figure 1

Flow chart for frozen berry extraction. Abbreviations: PRE = phenolic-rich extract (obtained after Amberlite column); ARF = anthocyanin-rich fraction (obtained after 20% methanol elution from Sephadex column); PAC = proanthocyanidin-rich fraction (obtained after 70% acetone elution from Sephadex column). Adapted from Grace et al. (2009)

Figure 2

HPLC chromatographs of phenolic-rich extracts (PRE) of 10 wild Alaskan berry samples. Chromatograms: (A)-V. ovalifolium - Akutan (VO-AK), (B)-V. ovalifolium - Seldovia (VO-SD), (C)-V. uliginosum - Akutan (VU-AK), (D)-V. uliginosum - Point Hope (VU-PH), (E)-E. nigrum - Akutan (EN-AK), (F)-E. nigrum - Point Hope (EN-PH), (G)-E. nigrum - Seldovia (EN-SD), (H)-R. chamaemorus - Point Hope (RC-PH), (I)-R. spectabilis - Akutan (RS-AK), (J)-R. spectabilis - Seldovia (RS-SD).

Figure 3

Representative LC-MS spectrum from phenolic-rich extract (PRE) of V. uliginosum - Akutan (VU-AK) showing ACs and PAC dimers through hexamers.

Figure 4

LC-MS² spectra of A-type proanthocyanidin trimers and tetramers from proanthocyanidin-rich fraction (PAC) of wild Alaskan berries. 1 - m/z 863, 2 - m/z 865, 3 - m/z 865, 4 - m/z 881, 5 - m/z 897, 6 - m/z 913, 7 - m/z 1151, 8 - m/z 1153, 9 - m/z 1169, 10 - m/z 1183.

Figure 4

LC-MS² spectra of A-type proanthocyanidin trimers and tetramers from proanthocyanidin-rich fraction (PAC) of wild Alaskan berries. 1 - m/z 863, 2 - m/z 865, 3 - m/z 865, 4 - m/z 881, 5 - m/z 897, 6 - m/z 913, 7 - m/z 1151, 8 - m/z 1153, 9 - m/z 1169, 10 - m/z 1183.

Figure 5

Western blot analysis of several representative wild Alaskan phenolic-rich extracts (PRE). (a) - pref-1 expression levels, (b)- β-actin expression levels. Protein bands are denoted by arrows. Overall pref-1 expression is calculated as the ratio between the two for each sample, compared against control. Abbreviations: AK=Akutan, SD=Seldovia, VO=V. ovalifolium, EN=E. nigrum, RS=R. spectabilis.

Figure 6

Effect of wild Alaska berry phenolic-rich extracts (PRE) on pref-1 expression levels of immature 3T3-L1 adipocytes. Run in triplicate, figure represents mean response ± SE. Asterisks denote significant activity, ** p≤0.05. Abbreviations: PRE = phenolic-rich extract, ARF = anthocyanin-rich fraction, PAC = proanthocyanidin-rich fraction, AK=Akutan, SD=Seldovia, PH=Point Hope, VO=V. ovalifolium, VU=V. uliginosum, EN=E. nigrum, RS=R. spectabilis, RC=R. chamaemorus.

Figure 7

Effects of RS-AK and RS-SD fractions on pref-1 expression levels in immature 3T3-L1 adipocytes. Run in triplicate, figure represents mean response ± SE. Asterisks denote significant activity, ** p≤0.05. Abbreviations: PRE = phenolic-rich extract, ARF = anthocyanin-rich fraction, PAC = proanthocyanidin-rich fraction, AK=Akutan, SD=Seldovia, RS=R. spectabilis.

Figure 8

Effect of phenolic-rich extracts (PRE) of Alaskan berries on lipid accumulation in mature 3T3-L1 adipocytes. Results from Red Oil O Assay given as percent lipid accumulation versus control. Run in triplicate, figure represents mean response ± SE. Asterisks denote significant activity, ** p≤0.05, *** p≤0.01. Abbreviations: PRE = phenolic-rich extract, ARF = anthocyanin-rich fraction, PAC = proanthocyanidin-rich fraction, AK=Akutan, SD=Seldovia, PH=Point Hope, VO=V. ovalifolium, VU=V. uliginosum, EN=E. nigrum, RS=R. spectabilis, RC=R. chamaemorus.

Figure 9

Effect of enriched fractions from Alaskan berries on lipid accumulation in mature 3T3-L1 adipocytes. Results from Red Oil O Assay given as percent lipid accumulation versus control. Run in triplicate, figure represents mean response ± SE. Asterisks denote significant activity, * p≤0.1, ** p≤0.05, *** p≤0.01. Abbreviations: PRE = phenolic-rich extract, ARF = anthocyanin-rich fraction, PAC = proanthocyanidin-rich fraction, AK=Akutan, SD=Seldovia, PH=Point Hope, VO=V. ovalifolium, VU=V. uliginosum, EN=E. nigrum.

Figure 10

Response of proanthocyanidin-rich fractions (PACs) on lipid accumulation in Red Oil O Assay correlated with proanthocyanidin content (in mg/g fraction). Linear correlation coefficient R²=0.896.

Figure11

Glucose levels in dietary-induced obese C57BL/6 mice at 3 and 6 h post-treatment. The experiment was repeated with similar results, figure represents mean response ± SE. Abbreviations: VU-PH=Vaccinium uliginosum from Point Hope, EN-PH= Empetrum nigrum from Point Hope, PRE=phenolic-rich extract, ARF=anthocyanin-rich fraction. Asterisks denote significant activity, ** p≤0.01 vs initial, *** p≤0.001 vs initial; letters designate significantly different treatment means at α=0.01 (n=5).