Which are characteristics of a high-fat diet fed mouse?...
1. hyperleptinemia
2. pancreatic Beta-cell death
3. 1 & 2

http://www.obesity-news.com/abs02-01.htm

Obesity-induced diabetes involves an accumulation
of triglycerides within pancreatic beta-cells.
This accumulation leads to apoptosis (cell death)
of the islets by increasing ceramide formation and
enhancing nitric oxide production. 


http://nutrition.ucdavis.edu/InfoSheets/fat.htm

References:

7 Dube MG, et al., Central leptin gene therapy blocks
high-fat diet-induced weight gain, hyperleptinemia,
and hyperinsulinemia - Increase in serum ghrelin
levels. Diabetes; 2002; 51(6); pp. 1729-36.


So it appears that:

3. 1 & 2

is the correct answer.